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Search Results: 1 - 10 of 211797 matches for " Christopher P. Loo "
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Intrusion Detection for Routing Attacks in Sensor Networks
Chong Eik Loo,Mun Yong Ng,Christopher Leckie,Marimuthu Palaniswami
International Journal of Distributed Sensor Networks , 2006, DOI: 10.1080/15501320600692044
Abstract: Security is a critical challenge for creating robust and reliable sensor networks. For example, routing attacks have the ability to disconnect a sensor network from its central base station. In this paper, we present a method for intrusion detection in wireless sensor networks. Our intrusion detection scheme uses a clustering algorithm to build a model of normal traffic behavior, and then uses this model of normal traffic to detect abnormal traffic patterns. A key advantage of our approach is that it is able to detect attacks that have not previously been seen. Moreover, our detection scheme is based on a set of traffic features that can potentially be applied to a wide range of routing attacks. In order to evaluate our intrusion detection scheme, we have extended a sensor network simulator to generate routing attacks in wireless sensor networks. We demonstrate that our intrusion detection scheme is able to achieve high detection accuracy with a low false positive rate for a variety of simulated routing attacks.
Strong HIV-1-Specific T Cell Responses in HIV-1-Exposed Uninfected Infants and Neonates Revealed after Regulatory T Cell Removal
Fatema A. Legrand, Douglas F. Nixon, Christopher P. Loo, Erika Ono, Joan M. Chapman, Maristela Miyamoto, Ricardo S. Diaz, Amélia M.N. Santos, Regina C.M. Succi, Jacob Abadi, Michael G. Rosenberg, Maria Isabel de Moraes-Pinto, Esper G. Kallas
PLOS ONE , 2006, DOI: 10.1371/journal.pone.0000102
Abstract: Background In utero transmission of HIV-1 occurs on average in only 3%–15% of HIV-1-exposed neonates born to mothers not on antiretroviral drug therapy. Thus, despite potential exposure, the majority of infants remain uninfected. Weak HIV-1-specific T-cell responses have been detected in children exposed to HIV-1, and potentially contribute to protection against infection. We, and others, have recently shown that the removal of CD4+CD25+ T-regulatory (Treg) cells can reveal strong HIV-1 specific T-cell responses in some HIV-1 infected adults. Here, we hypothesized that Treg cells could suppress HIV-1-specific immune responses in young children. Methodology/Principal Findings We studied two cohorts of children. The first group included HIV-1-exposed-uninfected (EU) as well as unexposed (UNEX) neonates. The second group comprised HIV-1-infected and HIV-1-EU children. We quantified the frequency of Treg cells, T-cell activation, and cell-mediated immune responses. We detected high levels of CD4+CD25+CD127? Treg cells and low levels of CD4+ and CD8+ T cell activation in the cord blood of the EU neonates. We observed HIV-1-specific T cell immune responses in all of the children exposed to the virus. These T-cell responses were not seen in the cord blood of control HIV-1 unexposed neonates. Moreover, the depletion of CD4+CD25+ Treg cells from the cord blood of EU newborns strikingly augmented both CD4+ and CD8+ HIV-1-specific immune responses. Conclusions/Significance This study provides new evidence that EU infants can mount strong HIV-1-specific T cell responses, and that in utero CD4+CD25+ T-regulatory cells may be contributing to the lack of vertical transmission by reducing T cell activation.
Decision Making in International Tertiary Education: The Role of National Image  [PDF]
Jing Cai, Theresa Loo
Advances in Journalism and Communication (AJC) , 2014, DOI: 10.4236/ajc.2014.23012
Abstract: The purpose of this paper is to explore the influence of the national image on the image of its tertiary education among non-nationals and on their choice of location for study. We present a conceptual model of how the image of the nation impacts on the image of tertiary education based upon Ajzen & Fishbein’s (1980) “theory of reasoned action”. With data from China & India, a model is developed from a calibration sample and tested against a validation sample using structural equation modelling. The model fits the data well and shows that a national image for Chic (prestigious, refined, elegant) and Enterprise (innovative, cool, trendy) has a positive influence on the beliefs about, attitudes towards and propensity to consume tertiary education offered by the UK. Our work indicates that there will be mileage in investing not just on the image of education itself, but on the image of the nation in the promotion of international tertiary education.
Comparison of Small Modular Reactor and Large Nuclear Reactor Fuel Cost  [PDF]
Christopher P. Pannier, Radek Skoda
Energy and Power Engineering (EPE) , 2014, DOI: 10.4236/epe.2014.65009
Abstract:

Small modular reactors (SMRs) offer simple, standardized, and safe modular designs for new nuclear reactor construction. They are factory built, requiring smaller initial capital investment and facilitating shorter construction times. SMRs also promise competitive economy when compared with the current reactor fleet. Construction cost of a majority of the projects, which are mostly in their design stages, is not publicly available, but variable costs can be determined from fuel enrichment, average burn-up, and plant thermal efficiency, which are public parameters for many near-term SMR projects. The fuel cost of electricity generation for selected SMRs and large reactors is simulated, including calculation of optimal tails assay in the uranium enrichment process. The results are compared between one another and with current generation large reactor designs providing a rough comparison of the long-term economics of a new nuclear reactor project. SMRs are predicted to have higher fuel costs than large reactors. Particularly, integral pressurized water reactors (iPWRs) are shown to have from 15% to 70% higher fuel costs than large light water reactors using 2014 nuclear fuels market data. Fuel cost sensitivities to reactor design parameters are presented.

Hardware/Software Codesign in a Compact Ion Mobility Spectrometer Sensor System for Subsurface Contaminant Detection
Sin Ming Loo,Jonathan P. Cole,Molly M. Gribb
EURASIP Journal on Embedded Systems , 2008, DOI: 10.1155/2008/137295
Abstract: A field-programmable-gate-array-(FPGA-) based data acquisition and control system was designed in a hardware/software codesign environment using an embedded Xilinx Microblaze soft-core processor for use with a subsurface ion mobility spectrometer (IMS) system, designed for detection of gaseous volatile organic compounds (VOCs). An FPGA is used to accelerate the digital signal processing algorithms and provide accurate timing and control. An embedded soft-core processor is used to ease development by implementing nontime critical portions of the design in software. The design was successfully implemented using a low-cost, off-the-shelf Xilinx Spartan-III FPGA and supporting digital and analog electronics.
Chemokine Co-Receptor CCR5/CXCR4-Dependent Modulation of Kv2.1 Channel Confers Acute Neuroprotection to HIV-1 Glycoprotein gp120 Exposure
Andrew J. Shepherd, Lipin Loo, Durga P. Mohapatra
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0076698
Abstract: Infection with human immunodeficiency virus-1 (HIV-1) within the brain has long been known to be associated with neurodegeneration and neurocognitive disorder (referred as HAND), a condition characterized in its early stages by declining cognitive function and behavioral disturbances. Mechanistically, the HIV-1 coat glycoprotein 120 (gp120) has been suggested to be a critical factor inducing apoptotic cell death in neurons via the activation of p38 mitogen-activated protein kinase (MAPK), upon chronic exposure to the virus. Here we show that acute exposure of neurons to HIV-1 gp120 elicits a homeostatic response, which provides protection against non-apoptotic cell death, involving the major somatodendritic voltage-gated K+ (Kv) channel Kv2.1 as the key mediator. The Kv2.1 channel has recently been shown to provide homeostatic control of neuronal excitability under conditions of seizures, ischemia and neuromodulation/neuroinflammation. Following acute exposure to gp120, cultured rat hippocampal neurons show rapid dephosphorylation of the Kv2.1 protein, which ultimately leads to changes in specific sub-cellular localization and voltage-dependent channel activation properties of Kv2.1. Such modifications in Kv2.1 are dependent on the activation of the chemokine co-receptors CCR5 and CXCR4, and subsequent activation of the protein phosphatase calcineurin. This leads to the overall suppression of neuronal excitability and provides neurons with a homeostatic protective mechanism. Specific blockade of calcineurin and Kv2.1 channel activity led to significant enhancement of non-apoptotic neuronal death upon acute gp120 treatment. These observations shed new light on the intrinsic homeostatic mechanisms of neuronal resilience during the acute stages of neuro-HIV infections.
Identification of the Major Expressed S-Layer and Cell Surface-Layer-Related Proteins in the Model Methanogenic Archaea: Methanosarcina barkeri Fusaro and Methanosarcina acetivorans C2A
Lars Rohlin,Deborah R. Leon,Unmi Kim,Joseph A. Loo,Rachel R. Ogorzalek Loo,Robert P. Gunsalus
Archaea , 2012, DOI: 10.1155/2012/873589
Abstract: Many archaeal cell envelopes contain a protein coat or sheath composed of one or more surface exposed proteins. These surface layer (S-layer) proteins contribute structural integrity and protect the lipid membrane from environmental challenges. To explore the species diversity of these layers in the Methanosarcinaceae, the major S-layer protein in Methanosarcina barkeri strain Fusaro was identified using proteomics. The Mbar_A1758 gene product was present in multiple forms with apparent sizes of 130, 120, and 100 kDa, consistent with post-translational modifications including signal peptide excision and protein glycosylation. A protein with features related to the surface layer proteins found in Methanosarcina acetivorans C2A and Methanosarcina mazei Goel was identified in the M. barkeri genome. These data reveal a distinct conserved protein signature with features and implied cell surface architecture in the Methanosarcinaceae that is absent in other archaea. Paralogous gene expression patterns in two Methanosarcina species revealed abundant expression of a single S-layer paralog in each strain. Respective promoter elements were identified and shown to be conserved in mRNA coding and upstream untranslated regions. Prior M. acetivorans genome annotations assigned S-layer or surface layer associated roles of eighty genes: however, of 68 examined none was significantly expressed relative to the experimentally determined S-layer gene.
Identification of the Major Expressed S-Layer and Cell Surface-Layer-Related Proteins in the Model Methanogenic Archaea: Methanosarcina barkeri Fusaro and Methanosarcina acetivorans C2A
Lars Rohlin,Deborah R. Leon,Unmi Kim,Joseph A. Loo,Rachel R. Ogorzalek Loo,Robert P. Gunsalus
Archaea , 2012, DOI: 10.1155/2012/873589
Abstract: Many archaeal cell envelopes contain a protein coat or sheath composed of one or more surface exposed proteins. These surface layer (S-layer) proteins contribute structural integrity and protect the lipid membrane from environmental challenges. To explore the species diversity of these layers in the Methanosarcinaceae, the major S-layer protein in Methanosarcina barkeri strain Fusaro was identified using proteomics. The Mbar_A1758 gene product was present in multiple forms with apparent sizes of 130, 120, and 100 kDa, consistent with post-translational modifications including signal peptide excision and protein glycosylation. A protein with features related to the surface layer proteins found in Methanosarcina acetivorans C2A and Methanosarcina mazei Goel was identified in the M. barkeri genome. These data reveal a distinct conserved protein signature with features and implied cell surface architecture in the Methanosarcinaceae that is absent in other archaea. Paralogous gene expression patterns in two Methanosarcina species revealed abundant expression of a single S-layer paralog in each strain. Respective promoter elements were identified and shown to be conserved in mRNA coding and upstream untranslated regions. Prior M. acetivorans genome annotations assigned S-layer or surface layer associated roles of eighty genes: however, of 68 examined none was significantly expressed relative to the experimentally determined S-layer gene. 1. Introduction Like cell envelopes of other archaeal species as well as gram-positive and gram-negative bacteria, the envelopes of methanogenic archaea have essential roles in protecting the cell from environmental challenges [1–3]. For example, envelopes resist attacks directed at the cytoplasmic membrane by extracellular enzymes, small lipophilic or chaotrophic molecules, and other toxic agents. The envelopes also aid in resisting osmotic stress and dehydration while allowing transit of small molecular weight nutrients and waste products [4]. However, relatively little is known about the cell envelopes of the Methanosarcinaceae, which include highly studied model organisms Methanosarcina acetivorans C2A, Methanosarcina mazei Goe1, and Methanosarcina barkeri Fusaro. Prior electron microscopy studies reveal the presence of a typical S-layer surrounding the cytoplasmic membrane [5, 6]. Bioinformatic studies have predicted surface-layer and surface-layer-related proteins for these methanogenic strains. For example, the genome annotations of M. acetivorans list 81 ORFs with these assigned functions [7], while over 14 and 52
Considerations for Implementing OGC WMS and WFS Specifications in a Desktop GIS  [PDF]
Christopher D. Michaelis, Daniel P. Ames
Journal of Geographic Information System (JGIS) , 2012, DOI: 10.4236/jgis.2012.42021
Abstract: An implementation of the Open Geospatial Consortium Web Feature Service (WFS) and Web Map Service (WMS) specifications in an open source desktop GIS is presented together with a discussion of considerations for improving the use of web services data in desktop applications. In our implementation, WFS and WMS services are consumed by a plug-in to MapWindow GIS [1], allowing the end user to view WFS, WMS and ArcIMS data, including data from the ESRI Geography Network, in a transparent manner that can be configured for either data analysis and modeling, or data visualization. This implementation in an open source GIS allows for others to view and use the code, improve it, and otherwise implement the suggested considerations in other GIS platforms. Specific considerations proposed here include: pre-fetching through envelope optimization, tile display, and feature complexity reduction. These strategies improve the speed and responsiveness with which data can be viewed and analyzed. Comparisons made with other web-based data access implementations are used to evaluate whether these techniques provide performance benefits, and under which circumstances.
Peripheral Nerve Blockade in a Patient with Mastocytosis  [PDF]
Christopher H. Bailey, Kent P. Weinmeister
Open Journal of Anesthesiology (OJAnes) , 2015, DOI: 10.4236/ojanes.2015.53010
Abstract: Mastocytosis is a rare group of disorders with chronic and episodic mast cell release of mediators which can have systemic and cutaneous manifestations. Triggers of anaphylaxis include commonly used medications for anesthesia, analgesia, and muscle relaxation. There is little in the literature regarding local anesthesia in emergent surgery for patients with mastocytosis. This case details the use of a peripheral nerve blockade for multiple surgeries and pain control in a patient with biopsy-proven mastocytosis.
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