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Christin N. McQueary,Benjamin C. Kirkup,Yuanzheng Si,Miriam Barlow,Luis A. Actis,David W. Craft,Daniel V. Zurawski 한국미생물학회 2012 The journal of microbiology Vol.50 No.3
Acinetobacter baumannii is a nosocomial bacterial pathogen, and infections attributed to this species are further complicated by a remarkable ability to acquire antimicrobial resistance genes and to survive in a desiccated state. While the antibiotic resistance and biofilm formation of A. baumannii is well-documented, less is known about the virulence attributes of this organism. Recent studies reported A. baumannii strains display a motility phenotype, which appears to be partially dependent upon Type IV pili, autoinducer molecules, and the response to blue light. In this study, we wanted to determine the prevalence of this trait in genetically diverse clinical isolates, and any additional required factors, and environmental cues that regulate motility. When strains are subjected to a wide array of stress conditions, A. baumannii motility is significantly reduced. In contrast, when extracellular iron is provided or salinity is reduced, motility is significantly enhanced. We further investigated whether the genes required for the production of lipopolysaccharide (lpsB) and K1 capsule (epsA/ptk) are required for motility as demonstrated in other Gram-negative bacteria. Transposon mutagenesis resulted in reduced motility by the insertion derivatives of each of these genes. The presence of the parental allele provided in trans, in the insertion mutant background, could only restore motility in the lpsB mutant. The production of core LPS directly contributes to the motility phenotype, while capsular polysaccharide may have an indirect effect. Further, the data suggest motility is regulated by extracellular conditions, indicating that A. baumannii is actively sensing the environment and responding accordingly.
Traffic Engineering Based on Local States in Internet Protocol-Based Radio Access Networks
Barlow David A.,Vassiliou Vasos,Krasser Sven,Owen Henry L.,Grimminger Jochen,Huth Hans-Peter,Sokol Joachim The Korea Institute of Information and Commucation 2005 Journal of communications and networks Vol.7 No.3
The purpose of this research is to develop and evaluate a traffic engineering architecture that uses local state information. This architecture is applied to an Internet protocol radio access network (RAN) that uses multi-protocol label switching (MPLS) and differentiated services to support mobile hosts. We assume mobility support is provided by a protocol such as the hierarchical mobile Internet protocol. The traffic engineering architecture is router based-meaning that routers on the edges of the network make the decisions onto which paths to place admitted traffic. We propose an algorithm that supports the architecture and uses local network state in order to function. The goal of the architecture is to provide an inexpensive and fast method to reduce network congestion while increasing the quality of service (QoS) level when compared to traditional routing and traffic engineering techniques. We use a number of different mobility scenarios and a mix of different types of traffic to evaluate our architecture and algorithm. We use the network simulator ns-2 as the core of our simulation environment. Around this core we built a system of pre-simulation, during simulation, and post-processing software that enabled us to simulate our traffic engineering architecture with only very minimal changes to the core ns-2 software. Our simulation environment supports a number of different mobility scenarios and a mix of different types of traffic to evaluate our architecture and algorithm.
Thilker, David A.,Bianchi, Luciana,Schiminovich, David,Gil de Paz, Armando,Seibert, Mark,Madore, Barry F.,Wyder, Ted,Rich, R. Michael,Yi, Sukyoung,Barlow, Tom,Conrow, Tim,Forster, Karl,Friedman, Peter IOP Publishing 2010 ASTROPHYSICAL JOURNAL LETTERS - Vol.714 No.1
<P>We have discovered recent star formation in the outermost portion ((1-4) x R(25)) of the nearby lenticular (S0) galaxy NGC 404 using Galaxy Evolution Explorer UV imaging. FUV-bright sources are strongly concentrated within the galaxy's Hi ring (formed by a merger event according to del Rio et al.), even though the average gas density is dynamically subcritical. Archival Hubble Space Telescope imaging reveals resolved upper main-sequence stars and conclusively demonstrates that the UV light originates from recent star formation activity. We present FUV, NUV radial surface brightness profiles, and integrated magnitudes for NGC 404. Within the ring, the average star formation rate (SFR) surface density (Sigma(SFR)) is similar to 2.2 x 10(-5) M(circle dot) yr(-1) kpc(-2). Of the total FUV flux, 70% comes from the H I ring which is forming stars at a rate of 2.5 x 10(-3) M(circle dot) yr(-1). The gas consumption timescale, assuming a constant SFR and no gas recycling, is several times the age of the universe. In the context of the UV-optical galaxy color-magnitude diagram, the presence of the star-forming Hi ring places NGC 404 in the green valley separating the red and blue sequences. The rejuvenated lenticular galaxy has experienced a merger-induced, disk-building excursion away from the red sequence toward bluer colors, where it may evolve quiescently or (if appropriately triggered) experience a burst capable of placing it on the blue/star-forming sequence for up to similar to 1 Gyr. The green valley galaxy population is heterogeneous, with most systems transitioning from blue to red but others evolving in the opposite sense due to acquisition of fresh gas through various channels.</P>
A Spray-Processable, Low Bandgap, and Ambipolar Donor−Acceptor Conjugated Polymer
Steckler, Timothy T.,Zhang, Xuan,Hwang, Jungseek,Honeyager, Ryan,Ohira, Shino,Zhang, Xiao-Hong,Grant, Adrian,Ellinger, Stefan,Odom, Susan A.,Sweat, Daniel,Tanner, David B.,Rinzler, Andrew G.,Barlow, S American Chemical Society 2009 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.131 No.8
STUDYING LARGE- AND SMALL-SCALE ENVIRONMENTS OF ULTRAVIOLET LUMINOUS GALAXIES
Basu-Zych, Antara R.,Schiminovich, David,Heinis, Sebastien,Overzier, Roderik,Heckman, Tim,Zamojski, Michel,Ilbert, Olivier,Koekemoer, Anton M.,Barlow, Tom A.,Bianchi, Luciana,Conrow, Tim,Donas, Jose,F IOP Publishing 2009 The Astrophysical journal Vol.699 No.2
THE STAR FORMATION LAW AT LOW SURFACE DENSITY
Wyder, Ted K.,Martin, D. Christopher,Barlow, Tom A.,Foster, Karl,Friedman, Peter G.,Morrissey, Patrick,Neff, Susan G.,Neill, James D.,Schiminovich, David,Seibert, Mark,Bianchi, Luciana,Donas, Jos&eacu IOP Publishing 2009 The Astrophysical journal Vol.696 No.2