Extracellular Stress and Lipopolysaccharide Modulate Acinetobacter baumannii Surface-Associated Motility

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.

High‐Performance n‐Channel Thin‐Film Field‐Effect Transistors Based on a Nanowire‐Forming Polymer

Hahm, Suk Gyu,Rho, Yecheol,Jung, Jungwoon,Kim, Se Hyun,Sajoto, Tissa,Kim, Felix S.,Barlow, Stephen,Park, Chan Eon,Jenekhe, Samson A.,Marder, Seth R.,Ree, Moonhor WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.16

<P><B>Abstract</B></P><P>A new electrontransport polymer, poly{[<I>N,N′</I>‐dioctylperylene‐3,4,9,10‐bis(dicarboximide)‐1,7(6)‐diyl]‐<I>alt</I>‐[(2,5‐bis(2‐ethyl‐hexyl)‐1,4‐phenylene)bis(ethyn‐2,1‐diyl]} (PDIC8‐EB), is synthesized. In chloroform, the polymer undergoes self‐assembly, forming a nanowire suspension. The nanowire's optical and electrochemical properties, morphological structure, and field‐effect transistor (FET) characteristics are investigated. Thin films fabricated from a PDIC8‐EB nanowire suspension are composed of ordered nanowires and ordered and amorphous non‐nanowire phases, whereas films prepared from a homogeneous PDIC8‐EB solution consist of only the ordered and amorphous non‐nanowire phases. X‐ray scattering experiments suggest that in both nanowires and ordered phases, the PDIC8 units are laterally stacked in an edge‐on manner with respect to the film plane, with full interdigitation of the octyl chains, and with the polymer backbones preferentially oriented within the film plane. The ordering and orientations are significantly enhanced through thermal annealing at 200 °C under inert conditions. The polymer film with high degree of structural ordering and strong orientation yields a high electron mobility (0.10 ± 0.05 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>), with a high on/off ratio (3.7 × 10<SUP>6</SUP>), a low threshold voltage (8 V), and negligible hysteresis (0.5 V). This study demonstrates that the polymer in the nanowire suspension provides a suitable material for fabricating the active layers of high‐performance n‐channel FET devices via a solution coating process.</P>

RF plasma functionalized carbon surfaces for supporting sensor architectures

J.S. Quinton,A. Deslandes,A. Barlow,J.G. Shapter,C. Fairman,J.J. Gooding,D.B. Hibbert 한국물리학회 2008 Current Applied Physics Vol.8 No.3,4

Carbon has a number of properties that make it ideal for use in sensor and electrical applications. Using radio frequency plasma with different precursor gases and operating plasma conditions, it is possible to pre-treat a variety of carbon surfaces in preparation for further molecular attachment, or surface functionalization. Research in our laboratory involves studies on highly ordered pyrolytic graphite (HOPG) as a model carbon substrate and pyrolysed photoresist films (PPF). Plasma treated surfaces have been characterised using a variety of surface sensitive techniques. We will report on results obtained using X-ray photoelectron spectroscopy to probe the chemical nature of the treated surfaces, and hence the extent of treatment. Time of flight secondary-ion mass spectrometry (ToFSIMS) has been utilised to determine the extent of hydrogenation after plasma treatment. Scanning tunnelling microscopy (STM) measurements provide morphological information about the treated surfaces, in particular damage and a severe change in surface structures that may be caused by various plasma treatments. Etching and/or nucleation and growth features are also observed and will be discussed, with the types of features and their distribution strongly dependent on the precursor gas that is used to support the plasma. Carbon has a number of properties that make it ideal for use in sensor and electrical applications. Using radio frequency plasma with different precursor gases and operating plasma conditions, it is possible to pre-treat a variety of carbon surfaces in preparation for further molecular attachment, or surface functionalization. Research in our laboratory involves studies on highly ordered pyrolytic graphite (HOPG) as a model carbon substrate and pyrolysed photoresist films (PPF). Plasma treated surfaces have been characterised using a variety of surface sensitive techniques. We will report on results obtained using X-ray photoelectron spectroscopy to probe the chemical nature of the treated surfaces, and hence the extent of treatment. Time of flight secondary-ion mass spectrometry (ToFSIMS) has been utilised to determine the extent of hydrogenation after plasma treatment. Scanning tunnelling microscopy (STM) measurements provide morphological information about the treated surfaces, in particular damage and a severe change in surface structures that may be caused by various plasma treatments. Etching and/or nucleation and growth features are also observed and will be discussed, with the types of features and their distribution strongly dependent on the precursor gas that is used to support the plasma.

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.

NGC 404: A REJUVENATED LENTICULAR GALAXY ON A MERGER-INDUCED, BLUEWARD EXCURSION INTO THE GREEN VALLEY

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>

TIDAL DWARF GALAXIES AROUND A POST-MERGER GALAXY, NGC 4922

Sheen, Yun-Kyeong,Jeong, Hyunjin,Yi, Sukyoung K.,Ferreras, Ignacio,Lotz, Jennifer M.,Olsen, Knut A. G.,Dickinson, Mark,Barnes, Sydney,Park, Jang-Hyun,Ree, Chang H.,Madore, Barry F.,Barlow, Tom A.,Conr American Institute of Physics 2009 The Astronomical journal Vol.138 No.6

<P>One possible channel for the formation of dwarf galaxies involves birth in the tidal tails of interacting galaxies. We report the detection of a bright UV tidal tail and several young tidal dwarf galaxy (TDG) candidates in the post-merger galaxy NGC 4922 in the Coma cluster. Based on a two-component population model (combining young and old stellar populations), we find that the light of tidal tail predominantly comes from young stars (a few Myr old). The Galaxy Evolution Explorer ultraviolet data played a critical role in the parameter (age and mass) estimation. Our stellar mass estimates of the TDG candidates are ~10<SUP>6–7</SUP> M<SUB>☉</SUB>, typical for dwarf galaxies.</P>

The <i>UV</i>–optical colour dependence of galaxy clustering in the local universe

Loh, Yeong-Shang,Rich, R. Michael,Heinis, Sé,bastien,Scranton, Ryan,Mallery, Ryan P.,Salim, Samir,Martin, D. Christopher,Wyder, Ted,Arnouts, Sté,phane,Barlow, Tom A.,Forster, Karl,Friedman Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.407 No.1

<P>ABSTRACT</P><P>We measure the UV-optical colour dependence of galaxy clustering in the local Universe. Using the clean separation of the red and blue sequences made possible by the <I>NUV</I>−<I>r</I> colour–magnitude diagram, we segregate the galaxies into red, blue and intermediate ‘green’ classes. We explore the clustering as a function of this segregation by removing the dependence on luminosity and by excluding edge-on galaxies as a means of a non-model dependent veto of highly extincted galaxies. We find that ξ(<I>r</I><SUB>p</SUB>, π) for both red and green galaxies shows strong redshift-space distortion on small scales – the ‘finger-of-God’ effect, with green galaxies having a lower amplitude than is seen for the red sequence, and the blue sequence showing almost no distortion. On large scales, ξ(<I>r</I><SUB>p</SUB>, π) for all three samples show the effect of large-scale streaming from coherent infall. On scales of 1 <I>h</I><SUP>−1</SUP> Mpc < <I>r</I><SUB>p</SUB> < 10 <I>h</I><SUP>−1</SUP> Mpc, the projected auto-correlation function <I>w</I><SUB>p</SUB>(<I>r</I><SUB>p</SUB>) for red and green galaxies fits a power law with slope γ∼ 1.93 and amplitude <I>r</I><SUB>0</SUB>∼ 7.5 and 5.3, compared with γ∼ 1.75 and <I>r</I><SUB>0</SUB>∼ 3.9 <I>h</I><SUP>−1</SUP> Mpc for blue sequence galaxies. Compared to the clustering of a fiducial <I>L</I>* galaxy, the red, green and blue have a relative bias of 1.5, 1.1 and 0.9, respectively. The <I>w</I><SUB>p</SUB>(<I>r</I><SUB>p</SUB>) for blue galaxies display an increase in convexity at ∼ 1 <I>h</I><SUP>−1</SUP> Mpc, with an excess of large-scale clustering. Our results suggest that the majority of blue galaxies are likely central galaxies in less massive haloes, while red and green galaxies have larger satellite fractions, and preferentially reside in virialized structures. If blue sequence galaxies migrate to the red sequence via processes like mergers or quenching that take them through the green valley, such a transformation may be accompanied by a change in environment in addition to any change in luminosity and colour.</P>

A search for doubly charged Higgs production in Z⁰ decays

OPAL Collaboration,Acton, P.D.,Alexander, G.,Allison, J.,Allport, P.P.,Anderson, K.J.,Arcelli, S.,Astbury, A.,Axen, D.,Azuelos, G.,Bahan, G.A.,Baines, J.T.M.,Ball, A.H.,Banks, J.,Barlow, R.J.,Barnett, North-Holland Pub. Co 1992 Physics letters. Section B Vol.295 No.3

A search for the decay of the Z<SUP>0</SUP> into doubly charged Higgs bosons (H<SUP>+/-+/-</SUP>) decaying to same-sign lepton pairs is presented using data collected with the OPAL detector at LEP, with an integrated luminosity of 6.8 pb<SUP>-</SUP>. Four-track final states from prompt decays, and events with at least one highly ionizing track from long-lived H<SUP>+/-+/-</SUP> were sought. H<SUP>+/-+/-</SUP> are excluded in the mass range from zero to 45.6 GeV/c<SUP>2</SUP> and for a coupling constant range that extends down to zero.

Resilient Reduced-State Resource Reservation

D. A. Barlow,V. Vassiliou,S. Krasser,H. L. Owen,A. Csaszar,A. Takacs,R. Szabo,T. Henk 한국통신학회 2005 Journal of communications and networks Vol.7 No.4

Traffic Engineering Based on Local States in Internet Protocol-Based Radio Access Networks

D. A. Barlow,V. Vassiliou,S. Krasser,H. L. Owen,J. Grimminger,H.-P. Huth,J. Sokol 한국통신학회 2005 Journal of communications and networks Vol.7 No.3