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Search Results: 1 - 10 of 1895 matches for " Heather Brockway "
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The CSN/COP9 Signalosome Regulates Synaptonemal Complex Assembly during Meiotic Prophase I of Caenorhabditis elegans
Heather Brockway,Nathan Balukoff,Martha Dean,Benjamin Alleva,Sarit Smolikove
PLOS Genetics , 2014, DOI: doi/10.1371/journal.pgen.1004757
Abstract: The synaptonemal complex (SC) is a conserved protein structure that holds homologous chromosome pairs together throughout much of meiotic prophase I. It is essential for the formation of crossovers, which are required for the proper segregation of chromosomes into gametes. The assembly of the SC is likely to be regulated by post-translational modifications. The CSN/COP9 signalosome has been shown to act in many pathways, mainly via the ubiquitin degradation/proteasome pathway. Here we examine the role of the CSN/COP9 signalosome in SC assembly in the model organism C. elegans. Our work shows that mutants in three subunits of the CSN/COP9 signalosome fail to properly assemble the SC. In these mutants, SC proteins aggregate, leading to a decrease in proper pairing between homologous chromosomes. The reduction in homolog pairing also results in an accumulation of recombination intermediates and defects in repair of meiotic DSBs to form the designated crossovers. The effect of the CSN/COP9 signalosome mutants on synapsis and crossover formation is due to increased neddylation, as reducing neddylation in these mutants can partially suppress their phenotypes. We also find a marked increase in apoptosis in csn mutants that specifically eliminates nuclei with aggregated SC proteins. csn mutants exhibit defects in germline proliferation, and an almost complete pachytene arrest due to an inability to activate the MAPK pathway. The work described here supports a previously unknown role for the CSN/COP9 signalosome in chromosome behavior during meiotic prophase I.
An information-theoretic analog of a result of Perelman
Brockway McMillan
Mathematics , 2007,
Abstract: Each compact manifold M of finite dimension k is differentiable and supports an intrinsic probability measure. There then exists a measurable transformation of M to the k-dimensional "surface" of the (k+1)-dimensional ball.
Computing the unknotting numbers of certain pretzel knots
Seph Shewell Brockway
Mathematics , 2013,
Abstract: We compute the unknotting number of two infinite families of pretzel knots, $P(3,1,\dots,1,b)$ (with $b$ positive and odd and an odd number of 1s) and $P(3,3,3c)$ (with $c$ positive and odd). To do this, we extend a technique of Owens using Donaldson's diagonalization theorem, and one of Traczyk using the Jones polynomial, building on work of Lickorish and Millett.
HIV Prevention in Papua New Guinea: Is It Working or Not?  [PDF]
Heather Worth
World Journal of AIDS (WJA) , 2012, DOI: 10.4236/wja.2012.23016
Abstract: Introduction: There is a global call for structural approaches to HIV that go beyond awareness and HIV testing to approach prevention work via the social and economic drivers of the epidemic. Papua New Guinea is the epicentre of the HIV epidemic in the Pacific, with an adult prevalence rate of 0.9%. Since 2004, there has been a concerted response to HIV, with vastly increased rates of HIV testing and roll-out of antiretroviral therapy, and considerable funding for HIV prevention. Objectives: While incidence is slowing there are still a considerable number of new infections each year and many commentators are worried that HIV prevention is not working in that country. This article aims to critically examine HIV prevention programs in Papua New Guinea to show whether HIV prevention is effectiveness in reaching those most vulnerable to infection. Methods: Using data from HIV prevention programs and behavioural surveys this article will assess how HIV prevention has been carried out and the effectiveness of those programs. Results: There is little evidence to indicate that HIV prevention in Papua New Guinea, particularly among those most at risk of HIV has been successful. Conclusion: there is a dearth of HIV prevention interventions in Papua New Guinea that go beyond awareness-raising to deal with the structural drivers of the epidemic.
SN 1987A Gamma-Ray Limits on the Conversion of Pseudoscalars
J. W. Brockway,E. D. Carlson,G. G. Raffelt
Physics , 1996, DOI: 10.1016/0370-2693(96)00778-2
Abstract: Pseudoscalar particles $\phi$ usually couple electromagnetically by an interaction of the form $\frc14 g \phi F {\widetilde F}$, allowing them to convert to photons in the presence of magnetic fields. Notably, new low-mass pseudoscalars emitted from supernova (SN) 1987A would have been converted to $\gamma$-rays in the intervening magnetic field of the galaxy. Therefore, measurements by the Solar Maximum Mission (SMM) Gamma-Ray Spectrometer (GRS) can limit the inverse coupling constant to $g^{-1}>1{\times}10^{11}\,\rm GeV$, assuming the pseudoscalar is massless. This is an improvement over other astrophysical limits of a factor of about 2.5.
The Effect of Tick Size on Testing for Nonlinearity in Financial Markets Data  [PDF]
Heather Mitchell, Michael McKenzie
Journal of Mathematical Finance (JMF) , 2011, DOI: 10.4236/jmf.2011.11001
Abstract: The discrete nature of financial markets time-series data may prejudice the BDS and Close Returns test for nonlinearity. Our estimation results suggest that a tick/volatility ratio threshold exists, beyond which the test results are biased. Further, tick/volatility ratios that exceed these thresholds are frequently observed in financial markets data, which suggests that the results of the BDS and CR test must be interpreted with caution.
Calculation of Start-Oscillation-Current for Lossy Gyrotron Traveling-Wave Tube (Gyro-TWT) Using Linear Traveling-Wave Tube (TWT) Parameter Conversions  [PDF]
Heather H. Song
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2013, DOI: 10.4236/jemaa.2013.51001

The start-oscillation-current of a gyro-TWT (gyrotron traveling-wave tube) determines the stable operating current level of the device. The amplifier is susceptible to oscillations when the operating current level is higher than the start-oscillation current. There are several ways of calculating the start-oscillation current, including using the linear and nonlinear theory of a gyro-TWT. In this paper, a simple way of determining the start-oscillation current of lossy gyro-TWT is introduced. The linear TWT parameters that include the effects of synchronism, loss, and gain, were converted to gyro-TWT parameters to calculate the start-oscillation-current. The dependence on magnetic field, loss, and beam alpha was investigated. Calculations were carried out for a V-band gyro-TWT for both operating and competing modes. The proposed method of calculating the start-oscillation current provides a simple and fast way to estimate the oscillation conditions and can be used for the design process of a gyro-TWT.

A Novel Compact Microstrip Elliptical Patch Resonator Filter with Tunable Bandwidth  [PDF]
Ruwaybih Alsulami, Heather Song
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2013, DOI: 10.4236/jemaa.2013.52012

A novel elliptical patch resonator for a compact bandpass filter with tunable bandwidth is presented. This bandpass filter has the advantage of great flexibility in which the center frequency can be changed easily. The bandwidth of this filter can be modified by simply changing one variable, and this makes the proposed design unique. The order of the elliptical patch resonator can be increased, and three types of different orders of the same design are compared. The proposed filter can be used for future compact advanced wireless communication systems.

Broadband Miniaturized Bandpass Filter with Circular Stubs for Compact Wireless and Mobile Communication Systems  [PDF]
Yulan Zhang, Heather Song
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2013, DOI: 10.4236/jemaa.2013.53018

A miniaturized square resonator bandpass filter with circular stubs is designed, fabricated, and characterized. Analytical calculations were carried out to determine the critical filter parameters and the design was optimized using a 3D electromagnetic finite-element solver. The measured results were in good agreement with the designed results. The proposed filter exhibits significant improvement in bandwidth compared to the conventional square resonator bandpass filters.

Double-Sided Microstrip Circular Antenna Array for WLAN/WiMAX Applications  [PDF]
Ruwaybih Alsulami, Heather Song
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2013, DOI: 10.4236/jemaa.2013.54029

The design, fabrication, and characterization of the microstrip circular antenna arrays were presented. The proposed antennas were designed for single band at 2.45 GHz and dual bands at 3.3 - 3.6 and 5.0 - 6.0 GHz to support WLAN/WiMAX applications. The proposed single and dual band antennas showed omnidirectional radiation pattern with the gain values of 3.5 dBi at 2.45 GHz, 4.0 dBi at 3.45 GHz, and 3.3 dBi at 5.5 GHz. The dual band antenna array was placed on both top and bottom layers to obtain the desired antenna characteristics. The proposed double-sided dual band antenna provides omnidirectional radiation pattern with high gain.

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