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"Roger, Nathan"
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Ancient Biomolecules from Deep Ice Cores Reveal a Forested Southern Greenland
It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections.
Journal Article
The Impact of Service-Oriented Undergraduate Research on an Ongoing Participatory Community Action Research Project at Homeless Shelters
This article provides (a) a brief description of an ongoing research project at homeless shelters, (a) an example of an undergraduate student’s independent (and unique) contributions to the Project; and (c) the student’s reflection on civic-related and professional-related development associated with the work.
Journal Article
Paleo-Eskimo mtDNA Genome Reveals Matrilineal Discontinuity in Greenland
The Paleo-Eskimo Saqqaq and Independence I cultures, documented from archaeological remains in Northern Canada and Greenland, represent the earliest human expansion into the New World's northern extremes. However, their origin and genetic relationship to later cultures are unknown. We sequenced a mitochondrial genome from a Paleo-Eskimo human by using 3400-to 4500-year-old frozen hair excavated from an early Greenlandic Saqqaq settlement. The sample is distinct from modern Native Americans and Neo-Eskimos, falling within haplogroup D2a1, a group previously observed among modern Aleuts and Siberian Sireniki Yuit. This result suggests that the earliest migrants into the New World's northern extremes derived from populations in the Bering Sea area and were not directly related to Native Americans or the later Neo-Eskimos that replaced them.
Journal Article
AKT Signaling Regulates Agrin-Mediated Acetylcholine Receptor Surface Density
Background and Objectives: Acetylcholine receptors (AChRs) are ligand-gated ion channels concentrated at the postsynaptic membrane of skeletal muscle fibers, where their abundance is essential for efficient neuromuscular transmission. The serine/threonine kinase AKT is a central signaling node in muscle homeostasis, regulating metabolism, growth, and survival. However, its role in the Agrin-mediated regulation of postsynaptic AChRs remains incompletely defined. Here, we demonstrate a novel role of AKT in regulating Agrin-induced AChR accumulation in differentiated C2C12 myotubes. Materials and Methods: Differentiated C2C12 myotubes were stimulated with Agrin in the presence or absence of the AKT inhibitor MK2206 during either the formation or maintenance phase. AChR clustering was quantified using α-bungarotoxin labeling. Expression of AChR subunits and neuromuscular junction-associated genes was assessed. Proteasome involvement was examined using the inhibitor MG132. Results: Pharmacological inhibition of AKT using MK2206 during either the formation or maintenance phase of Agrin stimulation significantly reduced α-bungarotoxin-labeled AChR intensity. AKT inhibition also attenuated Agrin-induced expression of multiple AChR subunits and neuromuscular junction-associated genes. Importantly, inhibition of proteasome activity with MG132 restored AChR intensity in the presence of AKT inhibition, suggesting that AKT signaling limits proteasome-dependent AChR loss. Conclusions: these findings identify AKT as a regulator of Agrin-mediated AChR accumulation and maintenance in vitro. These findings identify AKT as a critical integrator of metabolic and synaptic signaling required for postsynaptic receptor stability, with implications for neuromuscular disorders and muscle atrophy.
Journal Article
Enhanced Access to Early Visual Processing of Perceptual Simultaneity in Autism Spectrum Disorders
We compared judgements of the simultaneity or asynchrony of visual stimuli in individuals with autism spectrum disorders (ASD) and typically-developing controls using Magnetoencephalography (MEG). Two vertical bars were presented simultaneously or non-simultaneously with two different stimulus onset delays. Participants with ASD distinguished significantly better between real simultaneity (0 ms delay between two stimuli) and apparent simultaneity (17 ms delay between two stimuli) than controls. In line with the increased sensitivity, event-related MEG activity showed increased differential responses for simultaneity versus apparent simultaneity. The strongest evoked potentials, observed over occipital cortices at about 130 ms, were correlated with performance differences in the ASD group only. Superior access to early visual brain processes in ASD might underlie increased resolution of visual events in perception.
Journal Article
Image warfare in the war on terror: Image munitions and the continuation of war and politics by other means
This thesis argues that the image as circulated within society has changed from what is broadly conceived of as a mass media society to that of an information society or a rhizomatic condition. This discontinuity is linked to changes that have taken place both within technology and the 'communications systems' that make up the media. This is theorized as a move from the 'mobilization of images' to the 'weaponization of images' and it takes the following form: the mobilization of images is connected to a twentieth century notion of propaganda and the rise of a mass society; whereas the weaponizing of images is understood as emerging through a networked/rhizomatic society connected with new media. It has also resulted in a paradigm shift from techno-war to image warfare. More specifically, this thesis is about exploring how American and British governments and militaries are failing to manage image warfare because they are operating with an outdated understanding that it is possible to 'control' images; whereas Al Qaeda appears to be understanding image warfare better. What I seek to show in this thesis is the disjuncture between this outdated idea of 'controlling' images (which Western governments and media continue to use) and a more dispersed or deterritorialized idea about how images operate in a rhizomatic condition. I explore this via my three conceptual terms: 'image munitions', 'counter-image munitions', 'remediation battles', with specific reference to the war on terror and specifically through four thematic case studies - political communications, suicides, executions and abuses - which allow exploration of different parts of this new theatre of war. In the conclusion I reflect on the implications of this analysis for understandings of contemporary and future warfare.
Dissertation
Image warfare in the war on terror: image munitions and the continuation of war and politics by other means
This thesis argues that the image as circulated within society has changed from what is broadly conceived of as a mass media society to that of an information society or a rhizomatic condition. This discontinuity is linked to changes that have taken place both within technology and the 'communications systems' that make up the media. This is theorized as a move from the 'mobilization of images' to the 'weaponization of images' and it takes the following form: the mobilization of images is connected to a twentieth century notion of propaganda and the rise of a mass society; whereas the weaponizing of images is understood as emerging through a networked/rhizomatic society connected with new media. It has also resulted in a paradigm shift from techno-war to image warfare. More specifically, this thesis is about exploring how American and British governments and militaries are failing to manage image warfare because they are operating with an outdated understanding that it is possible to 'control' images; whereas Al Qaeda appears to be understanding image warfare better. What I seek to show in this thesis is the disjuncture between this outdated idea of 'controlling' images (which Western governments and media continue to use) and a more dispersed or deterritorialized idea about how images operate in a rhizomatic condition. I explore this via my three conceptual terms: 'image munitions', 'counter-image munitions', 'remediation battles', with specific reference to the war on terror and specifically through four thematic case studies - political communications, suicides, executions and abuses - which allow exploration of different parts of this new theatre of war. In the conclusion I reflect on the implications of this analysis for understandings of contemporary and future warfare.
Dissertation
Numerical modelling of environmental dose rate and its application to trapped-charge dating
Accurate estimation of environmental dose rate is essential for high-resolution trapped-charge dating. Beta and gamma emissions from simulated sediments containing radioactive uranium, thorium and potassium are modelled in contexts that are spatially heterogeneous. Dose rate was modelled using Monte Carlo radiation transport codes MCNP and PENELOPE. A number of key issues that affect dose rate evaluation are examined and updated corrections are calculated. Granular structures used for geometrical input into the models were simulated using randomly packed ellipsoids. The pair correlation function and chord length distributions were derived. The effects of water content on dose rate were modelled and compared with cavity theory. Apart from activity dilution, the variation of grain size or water content was shown to be significant for gamma radiations due to the transition from charged particle equilibrium. The standard correction for beta dose rate due to grain size was found to be satisfactory although sensitivity to grain shape and material should be taken into account. Dose rate modeling was applied to three dating studies of early human fossils: Skhul V, Israel skull; Hofmeyr, South Africa skull and the Forbes’ Quarry, Gibraltar skull. The spatial modelling was implemented using computerised tomographic (CT) images and dose rate found to be modified significantly by the presence of the skull in the sediment. Time evolution of the dose rate was examined for the latter two skulls and dates of 36±3ka (Hofmeyr) and 55-95ka (Forbes’ Quarry) were calculated.
Dissertation