bluuebunny/crossref_metadata_2025 huggingface dataset:
In-Cylinder Injection of Oxygen-Enriched Air to Reduce Diesel Exhaust Emissions
Authors: Longman Douglas E. , Cole Roger L. , Aggarwal Suresh K.
Published: September 2008

The long time challenge for diesel engine manufacturers has been to reduce both particulate matter (PM) and NOx emissions simultaneously without sacrificing engine performance. One technique for reducing PM has been to inject air or oxygen-enriched air directly into the combustion chamber. Previous studies using the KIVA-3V computational fluid dynamics (CFD) model have shown benefits and the importance of the gas injection’s characteristics on the technique’s effectiveness in reducing emissions. Using a Caterpillar 3401E single cylinder engine, an experimental investigation has been conducted to demonstrate the effectiveness of an oxygen-enriched air injection system and fuel injection timing retard in reducing the NOx and the PM emissions in terms of both the particulate size and concentration. The gaseous emissions were measured using a Pierburg AMA 2000 gaseous emissions bench which included a chemiluminescent analyzer for NOx volumetric measurements, non-dispersive infrared (NDIR) analyzer for CO and CO2 measurements, and a parametric fuel cell for O2 measurements. PM emissions (i.e., soot particle concentration and size distribution) were measured using a TSI Model 3936 Scanning Mobility Particle Sizer (SMPS). The experimental observations regarding the effects of oxygen-enriched air injection on NOx and PM emissions were in accord with the previously reported results for late-cycle gas injection from a KIVA-3V model. The air injection technique additionally provided a low level of oxygen-enrichment during the compression cycle, with results similar to previous intake air oxygen-enrichment studies. A simultaneous reduction of NOx and particulates was demonstrated when the fuel injection timing characteristics were optimized in conjunction with the oxygen-enriched air injection. The experimental PM emissions were analyzed for number and size distributions and also found to be consistent with previously reported trends.
Magnetron sputtered Si–B–C–N films with high oxidation resistance and thermal stability in air at temperatures above 1500 °C
Authors: Vlček Jaroslav , Hřeben Stanislav , Kalaš Jiří , Čapek Jiří , Zeman Petr , Čerstvý Radomír , Peřina Vratislav , Setsuhara Yuichi
Published: September 2008

Novel quaternary Si–B–C–N materials are becoming increasingly attractive because of their possible high-temperature and harsh-environment applications. In the present work, amorphous Si–B–C–N films were deposited on Si and SiC substrates by reactive dc magnetron cosputtering using a single C–Si–B or B4C–Si target in nitrogen-argon gas mixtures. A fixed 75% Si fraction in the target erosion areas, a rf induced negative substrate bias voltage of −100 V, a substrate temperature of 350 °C, and a total pressure of 0.5 Pa were used in the depositions. The corresponding discharge and deposition characteristics (such as the ion-to-film-forming particle flux ratio, ion energy per deposited atom, and deposition rate) are presented to understand complex relationships between process parameters and film characteristics. Films deposited under optimized conditions (B4C–Si target, 50% N2+50% Ar gas mixture), possessing a composition (in at. %) Si32–34B9–10C2–4N49–51 with a low (less than 5 at. %) total content of hydrogen and oxygen, exhibited extremely high oxidation resistance in air at elevated temperatures (even above 1500 °C). Formation of protective surface layers (mainly composed of Si and O) was proved by high-resolution transmission electron microscopy, Rutherford backscattering spectrometry, and x-ray diffraction measurements after oxidization. Amorphous structure of the Si–B–C–N films was maintained under the oxidized surface layers after annealing in air up to 1700 °C (a limit imposed by thermogravimetric analysis in oxidative atmospheres).
Silane injection in a high-density low-pressure plasma system and its influence on the deposition kinetics and material properties of SiO2
Authors: Botha R. , Haj Ibrahim B. , Bulkin P. , Drévillon B.
Published: September 2008

High-rate, low temperature deposition is an essential requirement for industrial fabrication technology to be suitable for the deposition of optical and protective coatings. High-density, low-pressure plasmas have received significant attention for such applications due to their ability to create large and controllable ion fluxes onto the substrate. In this study, the high-rate deposition of silica films from a silane and oxygen gas mixture in a high-density plasma system based on a matrix distributed electron cyclotron resonance (MDECR) plasma source is investigated using directional jet injection of undiluted silane. The influence of process parameters such as the microwave power, radio frequency biasing of the substrate holder, and gas flows on the OH content of the oxide films is studied using phase-modulated spectroscopic ellipsometry (SE), Fourier transform infrared (FTIR) spectroscopy, and transmission measurements. The results of the measurements, taken at various points across the wafer, show a decrease in the thickness-normalized OH concentration in the areas of higher deposition rates. The corresponding gas phase composition is investigated using optical emission spectroscopy and compared to the FTIR, transmission and SE measurement results in order to validate our findings and ultimately optimize the deposition process. It is found that the primary silane flux onto the surface, which depends on the positioning of the jet injection point and gas flow rate, plays an important role not only on the deposition rate but also on the OH content of the films. The authors conclude that high-density plasma deposition systems such as the MDECR plasma enhanced chemical vapor deposition system cannot be considered as well mixed for gases with dissociation products that have high sticking coefficients, contrary to the accepted paradigm.
Structure and mechanical properties of diamondlike carbon films produced by hollow-cathode plasma deposition
Authors: Jiang H. F. , Tian X. B. , Yang S. Q. , Fu R. K. Y. , Chu P. K.
Published: September 2008

Diamondlike carbon (DLC) films are deposited on AISI 304 stainless-steel substrates using hollow-cathode chemical vapor deposition. The effects of the substrate bias on the structural and mechanical properties of the films are studied. X-ray photoelectron spectroscopy reveals the existence of CC (sp2) and C–C (sp3) functional groups in the films, and Raman spectra show that the ratio of the G (graphite) peak to the D (disorder) peak depends on the sample bias. The DLC film deposited at −50V bias has the highest sp3 content, and this is consistent with the G-band position and D-band full width at half maximum as a result of substrate biasing. The sample bias also has a critical influence on the thickness and hardness of the deposited films. The largest thickness (1700nm) and highest hardness (HV1099) are achieved at a bias voltage of −50V. All the films show low friction coefficients, and the sample treated at −200V gives rise to the lowest friction coefficient.
Wafer heating mechanisms in a molecular gas, inductively coupled plasma: in situ, real time wafer surface measurements and three-dimensional thermal modeling
Authors: Titus M. J. , Graves D. B.
Published: September 2008

The authors report measurements and modeling of wafer heating mechanisms in an Ar∕O2 inductively coupled plasma (ICP). The authors employed a commercially available on-wafer sensor system (PlasmaTemp™ developed by KLA-Tencor) consisting of an on-board electronics module housing battery power and data storage with 30 temperature sensors embedded onto the wafer at different radial positions. This system allows for real time, in situ wafer temperature measurements. Wafer heating mechanisms were investigated by combining temperature measurements from the PlasmaTemp™ sensor wafer with a three-dimensional heat transfer model of the wafer and a model of the ICP. Comparisons between pure Ar and Ar∕O2 discharges demonstrated that two additional wafer heating mechanisms can be important in molecular gas plasmas compared to atomic gas discharges. The two mechanisms are heating from the gas phase and O-atom surface recombination. These mechanisms were shown to contribute as much as 60% to wafer heating under conditions of low bias power. This study demonstrated how the “on-wafer” temperature sensor not only yields a temperature profile distribution across the wafer, but can be used to help determine plasma characteristics, such as ion flux profiles or plasma processing temperatures.
Growth and interface of HfO2 films on H-terminated Si from a TDMAH and H2O atomic layer deposition process
Authors: Hackley Justin C. , Demaree J. Derek , Gougousi Theodosia
Published: September 2008

Hf O 2 thin films have been deposited by an atomic layer deposition (ALD) process using alternating pulses of tetrakis(dimethyl)amino hafnium and H2O precursors at a substrate temperature of 200–325°C. The initial stage of film growth on OH- and H-terminated Si(100) surfaces is investigated using Rutherford backscattering spectrometry (RBS), x-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). The authors observe an initial growth barrier on the Si–H surface for the first approximately four process cycles, where film growth is more efficient on the OH-terminated surface. Both starting surfaces require about 15cycles to reach a steady growth rate per cycle, with the OH-terminated surface displaying a slightly higher growth rate of 2.7×1014Hf∕cm2 compared to 2.4×1014Hf∕cm2 for Si–H. Combining the RBS and SE data we conclude that the films deposited on the OH-terminated surface are denser than those deposited on the Si–H surface. Angle-resolved XPS measurements reveal the formation of an ∼8Å interfacial layer after four ALD cycles on the H-terminated surface for a deposition temperature of 250°C, and transmission electron microscopy verifies that the thickness of the interfacial layer does not change substantially between the 4th and the 25th process cycles. The interfacial layer appears to depend weakly on the deposition temperature from 200to325°C, ranging from 6.9to8.4Å.
Enhanced chemical immunity for negative electron affinity GaAs photoemitters
Authors: Mulhollan G. A. , Bierman J. C.
Published: September 2008

Negative electron affinity GaAs photoemitters require ultrahigh vacuum conditions to achieve the best performance and to maintain the quantum yield. This limits their utility in applications where the background pressure is high. The authors have developed an activation procedure by which the reactivity to CO2, a principal cause of yield decay, is greatly reduced. The use of a second alkali in the activation process is responsible for the increased immunity of the activated surface. The best immunity was obtained by using a combination of Cs and Li without any loss in near band gap yield.
Enhancement of metal oxide deposition rate and quality using pulsed plasma-enhanced chemical vapor deposition at low frequency
Authors: Seman Michael T. , Richards David N. , Rowlette Pieter C. , Kubala Nicholas G. , Wolden Colin A.
Published: September 2008

The deposition rate and quality of alumina thin films fabricated by plasma-enhanced chemical vapor deposition (PECVD) increased significantly when square wave power modulation was applied at low frequency (∼1Hz). The pulsed PECVD rate was enhanced by a factor of ∼3 relative to continuous wave operation, and the quantity of impurities was dramatically attenuated. Deposition experiments on trenches with aspect ratios ranging from 4 to infinity demonstrated that the technique achieves a high degree of conformality. Important reactor design and operating considerations are described. Pulsed PECVD produced similar quality improvements for Ta2O5, TiO2, and ZnO, suggesting that the approach has widespread potential for metal oxide synthesis.
Effect of negative bias voltage on CrN films deposited by arc ion plating. I. Macroparticles filtration and film-growth characteristics
Authors: Wang Qi Min , Kim Kwang Ho
Published: September 2008

Chromium nitride (CrN) films were deposited on Si wafers by arc ion plating (AIP) at various negative bias voltages and several groups of N2∕Ar gas flux ratios and chamber gas pressures. The authors systematically investigated the influence of negative bias voltage on the synthesis, composition, microstructure, and properties of the AIP CrN films. In this part (Part I), the investigations were mainly focused on the macroparticle distributions and film-growth characteristics. The results showed that macroparticle densities on the film surfaces decreased greatly by applying negative bias voltage, which can be affected by partial pressure of N2 and Ar gases. From the statistical analysis of the experimental results, they proposed a new hybrid mechanism of ion bombardment and electrical repulsion. Also, the growth of the AIP CrN films was greatly altered by applying negative bias voltage. By increasing the bias voltage, the film surfaces became much smoother and the films evolved from apparent columnar microstructures to an equiaxed microstructure. The impinging high-energy Cr ions accelerated by negative bias voltages were deemed the inherent reason for the evolution of growth characteristics.
Effect of negative bias voltage on CrN films deposited by arc ion plating. II. Film composition, structure, and properties
Authors: Wang Qi Min , Kim Kwang Ho
Published: September 2008

Chromium nitride (CrN) films were deposited on Si wafers by arc ion plating at various negative bias voltages and several groups of N2∕Ar gas flux ratios and chamber gas pressures. The authors systematically investigated the influence of negative bias voltage on the synthesis, composition, microstructure, and properties of the arc ion plating (AIP) CrN films. In this article, the authors investigated the influence of negative bias voltage on the chemical composition, structure, and mechanical properties of the CrN films. The results showed that the chemical composition and phase structure of the AIP CrN films were greatly altered by application of negative bias voltage. Due to the selective resputtering effect, substoichiometric CrN films were obtained. With increase in bias voltages, the main phases in the films transformed from Cr+CrN to Cr2N at low N2∕Ar flow ratios, whereas the films at high N2∕Ar flow ratios retained the CrN phase structure. The CrN films experienced texture transformation from CrN (200) to CrN (220), and Cr2N (300) to Cr2N(300)+Cr2N(110). Increase in negative bias voltage also resulted in microstructure evolution of coarse columnar grains→fine columnar grains→quasiamorphous microstructure→recrystallized structures. From the experimental results, the authors proposed a new structure zone model based on enhanced bombardment of incident ions by application of negative bias voltage. The influence of negative bias voltage on the microhardness and residual stresses of the films and the inherent mechanisms were also explored.
Origin of hydrogen desorption during friction of stainless steel by alumina in ultrahigh vacuum
Authors: Nevshupa R. A. , Roman E. , de Segovia J. L.
Published: September 2008

A study of the tribodesorption of hydrogen stimulated by the friction of an alumina pin on stainless steel in ultrahigh vacuum at room temperature is presented. A special two-chamber ultrahigh-vacuum system separated by a well-defined orifice of low conductance is used to determine minute amounts of desorbed gases. The friction cell allows the control of the normal force of the alumina pin on the stainless-steel surface, the frequency of sweeping, as well as the dwell, i.e., the time between consecutive strokes. The profile of the p(H2)-t desorption curve shows a near-exponential increase in pressure to a stable value; then, after the friction cessation, the pressure decreases back to the initial value. The desorption curve presents an oscillating signal over the continuous one that corresponds with the sweeping frequency. An important aspect of the present research has been to elucidate the origin of the desorbed hydrogen: bulk or surface of materials. In this respect, the amount of tribodesorbed hydrogen is compared with the amount of adsorbed hydrogen at dwell times from 0.5to4s. This adsorption is 50 and 5 times lower than the desorbed hydrogen at normal forces of 0.072 and 0.218N, respectively, and a dwell time of 4s. An important finding is that the amount of desorbed hydrogen is irrespective of the dwell time, and the desorption rate increases linearly with sweeping frequency. The authors conclude that the origin of the desorbed hydrogen is in the bulk.
Increased O(D1) metastable flux with Ar and Kr diluted oxygen plasmas and improved film properties of grown SiO2 film
Authors: Kitajima Takeshi , Nakano Toshiki , Makabe Toshiaki
Published: September 2008

Metastable O(D1) atoms produced in rare gas diluted O2 plasmas are believed to be the key of high quality SiO2 film formation at low substrate temperatures. The authors diagnosed the behavior of the O(D1) density in highly rare gas diluted O2 plasma and applied the increased O(D1) flux to the formation of thin SiO2 films on Si(100) substrate. O(D1) flux increases 4.5 times with Kr (97%) dilution of O2 plasma while it increases 2.8 times for the case of Ar (97%). X-ray photoelectron spectroscopy spectrum showed Si–Si bond in the grown film was decreased by rare gas diluted plasmas. The stoichiometry of the film is improved by Ar and Kr dilution and corresponds to the increase in O(D1) flux to the surface. Electrical breakdown field measured by atomic force microscopy was 1.5 times higher for Kr/O2 plasma grown film compared to the pure O2 case and supports the quality of the film.
Real-time scanning tunneling microscopy observations of the oxidation of a Ti∕Pt(111)-(2×2) surface alloy using O2 and NO2
Authors: Hsieh Shuchen , Liu G. F. , Koel Bruce E.
Published: September 2008

The authors have used scanning tunneling microscopy (STM), low energy electron diffraction (LEED), and Auger electron spectroscopy (AES) to study the nascent oxidation of an ordered Ti∕Pt(111)-(2×2) surface alloy exposed to oxygen (O2) or nitrogen dioxide (NO2) under ultrahigh vacuum conditions. The Ti∕Pt(111)-(2×2) surface alloy was formed by depositing an ultrathin Ti film on Pt(111) and annealing to 1050K. This produces an alloy film in which the surface layer is pure Pt and the second layer contains Ti atoms in a (2×2) structure, which causes the pattern observed by STM and LEED. Real-time imaging of the surface at 300K was carried out by continuously scanning with the STM while either O2 or NO2 was introduced into the chamber. O2 exposures did not cause any gross structural changes; however oxygen was detected on the surface afterward using AES. Annealing this surface to 950K resulted in the formation of an ordered TiOx overlayer as characterized by both LEED and STM. In contrast, NO2 exposures caused definite changes in the surface morphology at 300K, and the root-mean-square roughness increased from 3.5to7.1Å after a large NO2 exposure. No ordered structures were produced by this treatment, but annealing the surface to 950K formed an ordered pattern in LEED and corresponding clear, well-resolved structures in STM images. We account for these observations on the disruption or reconstruction of the Ti∕Pt(111)-(2×2) surface alloy by arguments recalling that Ti oxidation is an activated process. The energetic barrier to TiOx formation cannot be surmounted at room temperature at low oxygen coverages, and annealing the surface was necessary to initiate this reaction. However, the higher oxygen coverages obtained using the more reactive oxidant NO2 lowered the chemical potential in the system sufficiently to overcome the activation barrier to extract Ti from the alloy at room temperature and form a disordered TiOx film. These results illustrate the importance of the surface oxygen coverage in nucleating the room temperature oxidation of the Pt–Ti surface alloys and further show the ability of NO2 in ultrahigh vacuum studies for probing the chemistry that will occur at higher O2 pressure.
Enhanced Sensitivity of Photodetection via Quantum Illumination
Authors: Lloyd Seth
Published: September 2008

The use of quantum-mechanically entangled light to illuminate objects can provide substantial enhancements over unentangled light for detecting and imaging those objects in the presence of high levels of noise and loss. Each signal sent out is entangled with an ancilla, which is retained. Detection takes place via an entangling measurement on the returning signal together with the ancilla. This paper shows that for photodetection, quantum illumination with
m
bits of entanglement can in principle increase the effective signal-to-noise ratio by a factor of 2

m

, an exponential improvement over unentangled illumination. The enhancement persists even when noise and loss are so great that no entanglement survives at the detector.
Atmospheric CO
2
and Climate on Millennial Time Scales During the Last Glacial Period
Authors: Ahn Jinho , Brook Edward J.
Published: September 2008

Reconstructions of ancient atmospheric carbon dioxide (CO
2
) variations help us better understand how the global carbon cycle and climate are linked. We compared CO
2
variations on millennial time scales between 20,000 and 90,000 years ago with an Antarctic temperature proxy and records of abrupt climate change in the Northern Hemisphere. CO
2
concentration and Antarctic temperature were positively correlated over millennial-scale climate cycles, implying a strong connection to Southern Ocean processes. Evidence from marine sediment proxies indicates that CO
2
concentration rose most rapidly when North Atlantic Deep Water shoaled and stratification in the Southern Ocean was reduced. These increases in CO
2
concentration occurred during stadial (cold) periods in the Northern Hemisphere, several thousand years before abrupt warming events in Greenland.
Species-Specific Transcription in Mice Carrying Human Chromosome 21
Authors: Wilson Michael D. , Barbosa-Morais Nuno L. , Schmidt Dominic , Conboy Caitlin M. , Vanes Lesley , Tybulewicz Victor L. J. , Fisher Elizabeth M. C. , Tavaré Simon , Odom Duncan T.
Published: September 2008

Homologous sets of transcription factors direct conserved tissue-specific gene expression, yet transcription factor–binding events diverge rapidly between closely related species. We used hepatocytes from an aneuploid mouse strain carrying human chromosome 21 to determine, on a chromosomal scale, whether interspecies differences in transcriptional regulation are primarily directed by human genetic sequence or mouse nuclear environment. Virtually all transcription factor–binding locations, landmarks of transcription initiation, and the resulting gene expression observed in human hepatocytes were recapitulated across the entire human chromosome 21 in the mouse hepatocyte nucleus. Thus, in homologous tissues, genetic sequence is largely responsible for directing transcriptional programs; interspecies differences in epigenetic machinery, cellular environment, and transcription factors themselves play secondary roles.
Superiority, Competition, and Opportunism in the Evolutionary Radiation of Dinosaurs
Authors: Brusatte Stephen L. , Benton Michael J. , Ruta Marcello , Lloyd Graeme T.
Published: September 2008

The rise and diversification of the dinosaurs in the Late Triassic, from 230 to 200 million years ago, is a classic example of an evolutionary radiation with supposed competitive replacement. A comparison of evolutionary rates and morphological disparity of basal dinosaurs and their chief “competitors,” the crurotarsan archosaurs, shows that dinosaurs exhibited lower disparity and an indistinguishable rate of character evolution. The radiation of Triassic archosaurs as a whole is characterized by declining evolutionary rates and increasing disparity, suggesting a decoupling of character evolution from body plan variety. The results strongly suggest that historical contingency, rather than prolonged competition or general “superiority,” was the primary factor in the rise of dinosaurs.
Cavity Optomechanics with a Bose-Einstein Condensate
Authors: Brennecke Ferdinand , Ritter Stephan , Donner Tobias , Esslinger Tilman
Published: September 2008

Cavity optomechanics studies the coupling between a mechanical oscillator and the electromagnetic field in a cavity. We report on a cavity optomechanical system in which a collective density excitation of a Bose-Einstein condensate serves as the mechanical oscillator coupled to the cavity field. A few photons inside the ultrahigh-finesse cavity trigger strongly driven back-action dynamics, in quantitative agreement with a cavity optomechanical model. We approach the strong coupling regime of cavity optomechanics, where a single excitation of the mechanical oscillator substantially influences the cavity field. The results open up new directions for investigating mechanical oscillators in the quantum regime and the border between classical and quantum physics.
The Measles Virus Fusion Protein Transmembrane Region Modulates Availability of an Active Glycoprotein Complex and Fusion Efficiency
Authors: Mühlebach Michael D. , Leonard Vincent H. J. , Cattaneo Roberto
Published: September 2008

The glycoprotein complex of paramyxoviruses mediates receptor binding and membrane fusion. In particular, the measles virus (MV) fusion (F) protein executes membrane fusion, after receptor binding by the hemagglutinin (H) protein. Structures and single amino acids influencing fusion function have been identified in the F-protein ectodomain and cytoplasmic tail, but not in its transmembrane (TM) region. Since this region influences function of the envelope proteins of other viruses, we examined its role in the MV F protein. Alanine-scanning mutagenesis revealed that an F protein with a single mutation of a central TM region leucine (L507A) was more fusogenic than the unmodified F protein while retaining similar kinetics of proteolytic processing. In contrast, substitution of residues located near the edges of the lipid bilayer reduced fusion activity. This was true not only when the mutated F proteins were coexpressed with H but also in the context of infections with recombinant viruses. Analysis of the H-F complexes with reduced fusion activities revealed that more precursor (F
0
) than activated (F
1+2
) protein coprecipitated with H. In contrast, in complexes with enhanced fusion activity, including H-F
L507A
, the F
0
/F
1+2
ratio shifted toward F
1+2
. Thus, fusion activity correlated with an active F-H protein complex, and the MV F protein TM region modulated availability of this complex.
Localization of Herpes Simplex Virus Type 1 UL37 in the Golgi Complex Requires UL36 but Not Capsid Structures
Authors: Desai Prashant , Sexton Gerry L. , Huang Eugene , Person Stanley
Published: September 2008

The herpes simplex virus type 1 (HSV-1) UL37 gene encodes a 120-kDa polypeptide which resides in the tegument structure of the virion and is important for morphogenesis. The goal of this study was to use green fluorescent protein (GFP) to follow the fate of UL37 within cells during the normal course of virus replication. GFP was inserted in frame at the C terminus of UL37 to generate a fluorescent-protein-tagged UL37 polypeptide. A virus designated K37eGFP, which replicated normally on Vero cells, was isolated and was shown to express the fusion polypeptide. When cells infected with this virus were examined by confocal microscopy, the fluorescence was observed to be predominantly cytoplasmic. As the infection progressed, fluorescence began to accumulate in a juxtanuclear structure. Mannosidase II and giantin were observed to colocalize with UL37eGFP at these structures, as judged by immunofluorescence assays. Therefore, UL37 traffics to the Golgi complex during infection. A VP26mRFP marker (red fluorescent protein fused to VP26) was recombined into K37eGFP, and when cells infected with this “dual-color” virus were examined, colocalization of the red (capsid) and green (UL37) fluorescence in the Golgi structure was observed. Null mutations in VP5 (ΔVP5), which abolished capsid assembly, and in UL36 (Δ36) were recombined into the K37eGFP virus genome. In cells infected with K37eGFP/ΔVP5, localization of UL37eGFP to the Golgi complex was similar to that for the parental virus (K37eGFP), indicating that trafficking of UL37eGFP to the Golgi complex did not require capsid structures. Confocal analysis of cells infected with K37eGFP/Δ36 showed that, in the absence of UL36, accumulation of UL37eGFP at the Golgi complex was not evident. This indicates an interaction between these two proteins that is important for localization of UL37 in the Golgi complex and thus possibly for cytoplasmic envelopment of the capsid. This is the first demonstration of a functional role for UL36:UL37 interaction in HSV-1-infected cells.
Role of Cellular Glycosaminoglycans and Charged Regions of Viral G Protein in Human Metapneumovirus Infection
Authors: Thammawat Sutthiwan , Sadlon Tania A. , Hallsworth Peter G. , Gordon David L.
Published: September 2008

Human metapneumovirus (hMPV) is an important cause of lower respiratory tract disease, particularly in infants and young children. hMPV has two major glycoproteins, G and F, which are responsible for virus attachment and membrane fusion, respectively. We investigated the role of cellular glycosaminoglycans (GAGs) and G protein in hMPV infection. The pretreatment of hMPV with soluble heparin markedly inhibited the infection of HEp-2 cells. Recombinant G protein, comprising the extracellular domain of G, bound to heparin-agarose columns and also to HEp-2 cells. hMPV infection and G protein binding to HEp-2 cells was inhibited by other soluble GAGs, including chondroitin sulfates, by the enzymatic removal of cell surface GAGs with GAG lyases or by the pretreatment of cells with basic fibroblast growth factor. The role of cellular GAGs was confirmed by the binding of G protein to wild-type CHO cells but not to GAG-deficient CHO-pgsA745 cells. An analysis of the G protein sequence revealed two adjacent clusters of positively charged amino acids (
149
EKKKTRA
155
and
159
QRRGKGKE
166
). Truncated G fragments were expressed, and only the fragment containing these putative heparin binding domains retained heparin binding. The alanine mutagenesis of charged residues in either of these regions resulted in the loss of binding to heparin and to HEp-2 cells, suggesting that both sites are likely to be required for hMPV attachment. These results, taken together with the inhibition of hMPV infection by soluble G protein, indicate an important role for G protein and cellular GAGs in hMPV infection.
Engineered Expression of the TLR5 Ligand Flagellin Enhances Paramyxovirus Activation of Human Dendritic Cell Function
Authors: Arimilli Subhashini , Johnson John B. , Clark Kimberly M. , Graff Aaron H. , Alexander-Miller Martha A. , Mizel Steven B. , Parks Griffith D.
Published: September 2008

The paramyxovirus simian virus 5 (SV5) is a poor activator of human dendritic cell (DC) maturation pathways in vitro, and infected DC do not upregulate cell surface costimulatory proteins or secretion of immunomodulatory cytokines. We evaluated the hypothesis that activation of SV5-infected DC would be enhanced by engineering SV5 to express a Toll-like-receptor (TLR) ligand. To test this hypothesis, a novel virus was engineered such that the gene encoding an intracellular form of the TLR5 ligand flagellin was expressed from the genome of wild-type (WT) SV5 (SV5-flagellin). Cells infected in vitro with the flagellin-expressing virus released low levels of biologically active flagellin, which was capable of stimulating TLR5 signaling. Infection of human peripheral blood mononuclear cell-derived immature DC with SV5-flagellin resulted in enhanced levels of interleukin-6 (IL-6) and IL-12 compared to infection with DC with the parental virus, WT SV5. In contrast to cytokine induction, the flagellin-expressing virus did not appreciably increase DC surface expression of the costimulatory molecule CD80 or CD86 above the level seen with WT SV5 alone. In mixed-culture assays, DC infected with the flagellin-expressing virus were more effective at activating gamma interferon secretion from both CD8+and CD4+allogeneic T cells than DC infected with WT SV5. Our results with SV5-directed intracellular expression of flagellin may be applicable to other vectors or pathogenic viruses where overcoming impairment of DC activation could contribute to the development of safer and more effective vaccines.
Molecular Basis of the Interaction between Complement Receptor Type 2 (CR2/CD21) and Epstein-Barr Virus Glycoprotein gp350
Authors: Young Kendra A. , Herbert Andrew P. , Barlow Paul N. , Holers V. Michael , Hannan Jonathan P.
Published: September 2008

The binding of the Epstein-Barr virus glycoprotein gp350 by complement receptor type 2 (CR2) is critical for viral attachment to B lymphocytes. We set out to test hypotheses regarding the molecular nature of this interaction by developing an enzyme-linked immunosorbent assay (ELISA) for the efficient analysis of the gp350-CR2 interaction by utilizing wild-type and mutant forms of recombinant gp350 and also of the CR2 N-terminal domains SCR1 and SCR2 (designated CR2 SCR1-2). To delineate the CR2-binding site on gp350, we generated 17 gp350 single-site substitutions targeting an area of gp350 that has been broadly implicated in the binding of both CR2 and the major inhibitory anti-gp350 monoclonal antibody (MAb) 72A1. These site-directed mutations identified a novel negatively charged CR2-binding surface described by residues Glu-21, Asp-22, Glu-155, Asp-208, Glu-210, and Asp-296. We also identified gp350 amino acid residues involved in non-charge-dependent interactions with CR2, including Tyr-151, Ile-160, and Trp-162. These data were supported by experiments in which phycoerythrin-conjugated wild-type and mutant forms of gp350 were incubated with CR2-expressing K562 cells and binding was assessed by flow cytometry. The ELISA was further utilized to identify several positively charged residues (Arg-13, Arg-28, Arg-36, Lys-41, Lys-57, Lys-67, Arg-83, and Arg-89) within SCR1-2 of CR2 that are involved in the binding interaction with gp350. These experiments allowed a comparison of those CR2 residues that are important for binding gp350 to those that define the epitope for an effective inhibitory anti-CR2 MAb, 171 (Asn-11, Arg-13, Ser-32, Thr-34, Arg-36, and Tyr-64). The mutagenesis data were used to calculate a model of the CR2-gp350 complex using the soft-docking program HADDOCK.
Numerical simulation of the dynamics of fluid oscillations in a gravitationally unstable, compositionally stratified fissure
Authors: Longo Antonella , Barbato David , Papale Paolo , Saccorotti Gilberto , Barsanti Michele
Published: September 2008

We have simulated the dynamics of convection, mixing and ascent of two basaltic magmas differing in their volatile and crystal content, giving rise to a gravitationally unstable configuration along a dyke or fissure. Numerical simulations are performed by a recently developed code which describes the transient 2D dynamics of multicomponent fluids from the incompressible to the compressible regime, and the initial and boundary conditions are inspired to the paroxysmal eruption which occurred at Stromboli in 2003 (

D'Auria
et al.
2006

). Multicomponent (H
2
O+CO
2
) saturation is accounted for by modelling the non-ideal equilibrium between the gas phase and the melt. The numerical results show the formation of a rising bulge of light magma, and the sink of discrete batches of dense magma towards deep fissure regions. Such dynamics are associated with a complex evolution of the pressure field, which shows variations occurring over a wide spectrum of frequencies. A first order analysis of the propagation of such pressure disturbances through the country rocks shows that the pre-eruptive fissure dynamics are able to produce mm-size, mainly radial deformation of the volcano, and a detectable seismic signal with spectral peaks at periods of about 50 s.
Trends in activity at Pu'u 'O'o during 2001–2003: insights from the continuous thermal record
Authors: Marchetti Emanuele , Harris Andrew J. L.
Published: September 2008

A permanent thermal monitoring system deployed on the north rim of Pu'u 'O'o crater (Kilauea, Hawaii) provided an 811-day-long data-set spanning March 2001–December 2003. These data allowed us to characterize three emission styles from vents on the crater floor: lava flows, sustained degassing and gas-piston events. Lava flows were recorded as sudden increases in temperature followed by smooth and relatively long-lasting decreases as the lava cooled. Sustained degassing was associated with persistently high levels of thermal signal and was the most common signal type. Finally, gas-piston events were all preceded by marked reductions in temperature (due to diminished degassing) and were marked by abrupt increases (due to the arrival of a gas jet) followed by 50–300 second waning phases. Lava flow occurrence, maximum temperature recorded during degassing, gas-piston thermal amplitude, occurrence and waveform all showed coupled, systematic changes through time. This implies modification of a common source process, and may be a result of a slight change in the magma level beneath the crater so as to modify the conduit geometry/primary degassing pathways, and hence gas collection and release processes, as well as slug ascent dynamics.
From Strombolian explosions to fire fountains at Etna Volcano (Italy): what do we learn from acoustic measurements?
Authors: Vergniolle S. , Ripepe M.
Published: September 2008

The 2001 eruption of Etna volcano, prior to the flank eruption, was marked by 16 episodes separated from one another by few days of quiescence. Insights into fire fountain formation are provided by a close comparison of the sound produced by an episode solely involving a series of Strombolian explosions (4 July) and one also showing a transition to a fire fountain (12 July). The best fit between measured and synthetic waveforms gives the temporal evolution of the bubble length, 8–100 m, and overpressure, 0.2 MPa. Both episodes result from the coalescence of a foam layer trapped at the top of the reservoir. At the transition towards a fire fountain, the number of explosions and the bubble length increase simultaneously, suggesting that the foam destabilization is more efficient when a fire fountain is produced. Acoustic records give access to the gas volume trapped within the foam, called ‘active’ degassing, while the height of fire fountains also includes the gas from passive degassing. The small bubbles from passive degassing are carried to the surface via the wake of the slugs, coming from the depth of the reservoir. The proportion between active and total gas volume represents 38–48%.
Epoxyeicosatrienoic acids are part of the VEGF-activated signaling cascade leading to angiogenesis
Authors: Webler Anke C. , Michaelis U. Ruth , Popp Rüdiger , Barbosa-Sicard Eduardo , Murugan Andiappan , Falck John R. , Fisslthaler Beate , Fleming Ingrid
Published: September 2008

Cytochrome P-450 (CYP) epoxygenases metabolize arachidonic acid to epoxyeicosatrienoic acid (EET) regioisomers, which activate several signaling pathways to promote endothelial cell proliferation, migration, and angiogenesis. Since vascular endothelial growth factor (VEGF) plays a key role in angiogenesis, we assessed a possible role of EETs in the VEGF-activated signal transduction cascade. Stimulation with VEGF increased CYP2C promoter activity in endothelial cells and enhanced CYP2C8 mRNA and protein expression resulting in increased intracellular EET levels. VEGF-induced endothelial cell tube formation was inhibited by the EET antagonist 14,15-epoxyeicosa-5( Z)-enoicacid (14,15-EEZE), which did not affect the VEGF-induced phosphorylation of its receptor or basic fibroblast growth factor (bFGF)-stimulated tube formation. Moreover, VEGF-stimulated endothelial cell sprouting in a modified spheroid assay was reduced by CYP2C antisense oligonucleotides. Mechanistically, VEGF stimulated the phosphorylation of the AMP-activated protein kinase (AMPK), which has also been linked to CYP induction, and the overexpression of a constitutively active AMPK mutant increased CYP2C expression. On the other hand, a dominant-negative AMPK mutant prevented the VEGF-induced increase in CYP2C RNA and protein expression in human endothelial cells. In vivo (Matrigel plug assay) in mice, endothelial cells were recruited into VEGF-impregnated plugs; an effect that was sensitive to 14,15-EEZE and the inclusion of small interfering RNA directed against the AMPK. The EET antagonist did not affect responses observed in plugs containing bFGF. Taken together, our data indicate that CYP2C-derived EETs participate as second messengers in the angiogenic response initiated by VEGF and that preventing the increase in CYP expression curtails the angiogenic response to VEGF.
AIF-1 expression regulates endothelial cell activation, signal transduction, and vasculogenesis
Authors: Tian Ying , Jain Surbhi , Kelemen Sheri E. , Autieri Michael V.
Published: September 2008

Endothelial cell (EC) activation plays a key role in vascular inflammation, thrombosis, and angiogenesis. Allograft inflammatory factor-1 (AIF-1) is a cytoplasmic, calcium-binding, inflammation-responsive scaffold protein that has been implicated in the regulation of inflammation. The expression and function of AIF-1 in EC is uncharacterized, and the purpose of this study was to characterize AIF-1 expression and function in ECs. AIF-1 expression colocalized with CD31-positive ECs in neointima of inflamed human arteries but not normal arteries. AIF-1 is detected at low levels in unstimulated EC, but expression can be increased in response to serum and soluble factors. Stable transfection of AIF-1 small interfering RNA (siRNA) in ECs reduced AIF-1 protein expression by 73% and significantly reduced EC proliferation and migration ( P < 0.05 and 0.001). Rescue of AIF-1 expression restored both proliferation and migration of siRNA-expressing ECs, and AIF-1 overexpression enhanced both of these activities, suggesting a strong association between AIF-1 expression and EC activation. Activation of mitogen-activated protein kinase p44/42 and PAK1 was significantly reduced in siRNA ECs challenged with inflammatory stimuli. Reduction of AIF-1 expression did not decrease EC tube-like structure or microvessel formation from aortic rings, but overexpression of AIF-1 did significantly increase the number and complexity of these structures. These data indicate that AIF-1 expression plays an important role in signal transduction and activation of ECs and may also participate in new vessel formation.
Age-dependent FOXO regulation of p27Kip1 expression via a conserved binding motif in rat muscle precursor cells
Authors: Lees Simon J. , Childs Tom E. , Booth Frank W.
Published: September 2008

Previously, we have demonstrated that forkhead box O3a (FOXO3a) overexpression increased p27Kip1 promoter activity and protein expression, whereas it decreased proliferation in muscle precursor cells (MPCs). The objectives of the present study were to 1) locate and identify FOXO regulatory elements in the rat p27Kip1 promoter using deletion analysis of a promoter/reporter construct and 2) determine if age-related differences exist in FOXO-induced p27Kip1 expression. The full-length (−4.0/+0.4 kb) rat p27Kip1 promoter construct revealed that both FOXO1 and FOXO3a induced an increase in transcriptional activity. Interestingly, MPCs isolated from old animals exhibited an increased FOXO3a-induced p27Kip1 promoter activity compared with MPCs isolated from young animals. Deletion of a 253-bp portion of the 5′-untranslated region (UTR) resulted in a significant decrease in FOXO-induced p27Kip1 promoter expression. Site-specific mutation of a daf-16 family protein-binding element (DBE) within this 253-bp portion of the 5′-UTR also demonstrated a decrease in FOXO-induced p27Kip1 promoter expression. These data suggest that a putative FOXO regulatory element located in the 5′-UTR of the rat p27 Kip1 gene plays a role in the age-dependent differences in FOXO3a-dependent p27Kip1 promoter expression. These findings have implications for developing treatment strategies aimed at increasing the proliferation of MPCs and regenerative capacity of aged skeletal muscle.
Extracellular nucleotides stimulate Cl−currents in biliary epithelia through receptor-mediated IP3 and Ca2+release
Authors: Dutta Amal K. , Woo Kangmee , Doctor R. Brian , Fitz J. Gregory , Feranchak Andrew P.
Published: September 2008

Extracellular ATP regulates bile formation by binding to P2 receptors on cholangiocytes and stimulating transepithelial Cl−secretion. However, the specific signaling pathways linking receptor binding to Cl−channel activation are not known. Consequently, the aim of these studies in human Mz-Cha-1 biliary cells and normal rat cholangiocyte monolayers was to assess the intracellular pathways responsible for ATP-stimulated increases in intracellular Ca2+concentration ([Ca2+]i) and membrane Cl−permeability. Exposure of cells to ATP resulted in a rapid increase in [Ca2+]iand activation of membrane Cl−currents; both responses were abolished by prior depletion of intracellular Ca2+. ATP-stimulated Cl−currents demonstrated mild outward rectification, reversal at ECl−, and a single-channel conductance of ∼17 pS, where E is the equilibrium potential. The conductance response to ATP was inhibited by the Cl−channel inhibitors NPPB and DIDS but not the CFTR inhibitor CFTRinh-172. Both ATP-stimulated increases in [Ca2+]iand Cl−channel activity were inhibited by the P2Y receptor antagonist suramin. The PLC inhibitor U73122 and the inositol 1,4,5-triphosphate (IP3) receptor inhibitor 2-APB both blocked the ATP-stimulated increase in [Ca2+]iand membrane Cl−currents. Intracellular dialysis with purified IP3 activated Cl−currents with identical properties to those activated by ATP. Exposure of normal rat cholangiocyte monolayers to ATP increased short-circuit currents ( Isc), reflecting transepithelial secretion. The Iscwas unaffected by CFTRinh-172 but was significantly inhibited by U73122 or 2-APB. In summary, these findings indicate that the apical P2Y-IP3 receptor signaling complex is a dominant pathway mediating biliary epithelial Cl−transport and, therefore, may represent a potential target for increasing secretion in the treatment of cholestatic liver disease.
Canalicular Mrp2 localization is reversibly regulated by the intracellular redox status
Authors: Sekine Shuichi , Ito Kousei , Horie Toshiharu
Published: September 2008

Oxidative stress is known to be a common feature of cholestatic syndrome. We have described the internalization of multidrug resistance-associated protein 2 (Mrp2), a biliary transporter involved in bile salt-independent bile flow, under acute oxidative stress, and a series of signaling pathways finally leading to the activation of novel protein kinase C were involved in this mechanism; however, it has been unclear whether the internalized Mrp2 localization was relocalized to the canalicular membrane when the intracellular redox status was recovered from oxidative stress. In this study, we demonstrated that decreased canalicular expression of Mrp2 induced by tertiary-butyl hydroperoxide (t-BHP) was recovered to the canalicular membrane by the replenishment of GSH by GSH-ethyl ester, a cell-permeable form of GSH. Moreover, pretreatment of isolated rat hepatocytes with colchicine and PKA inhibitor did not affect the t-BHP-induced Mrp2 internalization process but did prevent the Mrp2 recycling process induced by GSH replenishment. Moreover, intracellular cAMP concentration similarly changed with the change of intracellular GSH content. Taken together, our data clearly indicate that the redox-sensitive balance of PKA/PKC activation regulates the reversible Mrp2 localization in two different pathways, the microtubule-independent internalization pathway and -dependent recycling pathway of Mrp2.