bluuebunny/crossref_metadata_2025 huggingface dataset:
Zero Leakage: Results of an Advanced Lip Seal Technology
Authors: Dega R. L.
Published: September 2011

The advent of the “Helixseal,” a type of hydrodynamic sealing element, to the automotive industry has provided a means for greatly reducing sealing problems with very little increase in production cost. A new sealing technology, developed during a 10-year program at the General Motors Research Laboratories, has involved detailed studies to optimize the basic sealing parameters of radial lip-type seals. Although all elements of a conventional lip seal design can be optimized, the frequency of seal failure is still intolerable due to the large number of production variables which affect leakage. Consequently, it was necessary to explore and develop a means of complementing the lip seal, whereby increased reliability could be assured. The Helixseal is based upon hydrodynamic principles which allow the generation of controlled fluid forces. It consists of angular pumping vanes, applied to the seal face to provide a viscous shear force that opposes leakage of the fluid film. Optimized design of the Helixseal can assure zero leakage in seal applications.
Pressure, Frictional Resistance, and Flow Characteristics of the Partially Wetted Rotating Disk
Authors: Ketola H. N. , McGrew J. M.
Published: September 2011

A theory of the partially wetted rotating disk is described and experimental data presented which verify the application of this theory in practical applications. Four different flow regimes may be identified according to the value of the disk Reynolds number and the spacing ratio between the disk and stationary wall. The analytical expressions for prediction of the pressure gradient developed and the frictional resistance are uniquely determined by the disk Reynolds number, spacing ratio, and the degree of wetting of the disk.
Performance of a Modified Packed-Gland Seal
Authors: Allen C. M. , Rieder W. G.
Published: September 2011

An experimental investigation of the mechanics of hydrodynamic lubrication and heat generation and dissipation of packed-gland rotary shaft seals was performed on a somewhat novel design. The design differs from conventional stuffing-box seals in that the packing was inverted so that it rotated with the shaft. It was also skewed so as to enhance heat transfer and lubrication. Further, the gland was loaded hydraulically so that the axial pressure applied to the packing was readily controllable. These modifications proved to be successful in that much improved stability of operation was obtained through lowered coefficients of friction (with water as the sealed fluid) and interface temperature which prolonged seal life without serious detriment to leakage. Some rheological data on Teflon-asbestos packing is presented as well as kinetic coefficients of friction. Motion picture frame photographic sequences of the packing interface showing packing deterioration and lubricant film cavitation are included also.
Viscoelasticity and Its Application to Lubrication
Authors: Philippoff W.
Published: September 2011

Polymer solutions such as polymer-containing (VI-improved) oils show a variety of mechanical effects in flow that differ qualitatively from the ones observable under the same conditions in Newtonian liquids. This has, of course, been realized for a long time but the reason for their occurring has been traced to different sources. The point of view that the author has supported for a number of years, actually his idea for this happening, is that polymer solutions become elastic in steady flow. This thesis can be supported beginning with molecular theory through the mechanics of observable effects down to tests by a large variety of experimental methods. This point of view is by no means universally accepted in the rheological community. This elasticity causes “normal stresses” that may influence the load-carrying ability of journal bearings. However, the great problem is measuring their properties at the rates of shear occurring in practice (in the millions sec−1) and the existing eccentric geometry.
Some Measurements of High Pressure Lubricant Rheology
Authors: Novak J. D. , Winer W. O.
Published: September 2011

The advancement of the fields of elastohydrodynamic lubrication and high pressure metal forming in the past few years has focused attention on the need for reliable data of the variation of viscosity with pressure, temperature, and shear stress in well-defined fluids. This paper describes an investigation in which these effects were observed. The equipment used was a high pressure capillary-type viscometer which made possible the continuous variation of shear stress over a wide range at pressures up to 80,000 psi. Well-defined paraffinic and naphthenic base oils and several polymer blends of these oils were investigated as well as a polybutene, a diester, and two silicone fluids.
Gas-Bearing Turbomachinery
Authors: Sternlicht B.
Published: September 2011

The paper presents gas bearing turbomachinery developments for the past decade. With the aid of examples of eight different requirements, it answers the question: “Why Gas-Bearing Turbomachinery?” These examples cover: No Contamination, high efficiency, low temperature, high temperature, radiation damage, reliability and long life, high speed and long life, and simplification. The paper points out the parameters and design procedures that are important to gas bearing turbomachinery designers. A table which enables selection of gas bearings and one which compares rotor weights for motor and turbine drives are included. Several remaining problem areas are identified and an example of bearing distortion, resulting from friction, is given.
Design of One-Piece Jet-Engine Compressor End Seals
Authors: Winn L. W. , Thorkildsen R. L. , Wilcock D. F.
Published: September 2011

Performance of advanced air-breathing propulsion systems can be significantly improved through the utilization of effective sealing devices. One of the areas in which immediate benefits are realizable from improvements in sealing efficiency is the high-pressure compressor end area. This paper describes the design of a face-type flexible seal and a face-type rigid seal for a compressor end seal based upon the cruise conditions expected in one version of the supersonic transport (SST) jet engine. The seals, non-contacting during operation, operate on air films achieved through the employment of hybrid gas-bearing geometries on the seal faces. The design procedure discussed consists primarily of the selection of the most applicable seal-face geometries force and moment balance, determination of seal tracking capability, establishment of leakage characteristics, thermal gradients, and stress and deflection calculations. The design results indicate that satisfactory seal performance can be obtained with either of the two configurations. Leakage reductions of an order of magnitude compared to that encountered with labyrinth seals commonly used in existing jet-engine systems can be achieved.
A Step-Bearing Accelerometer With Pneumatic Signal Output
Authors: Sidell R. S. , Richardson H. H.
Published: September 2011

A novel pneumatic acceleration sensor utilizing a single gas-bearing supported element is described. System damping and pneumatic signal output are obtained by reverse-flow flapper-nozzle valves which act as negative springs with respect to the inertial mass. Approximate design relationships for the static and dynamic performance of a two-axis accelerometer are presented. A prototype unit built to verify feasibility is described and experimental results are presented and compared with the analysis.
Calculation of Stiffness and Damping Properties of Gas Bearings
Authors: Lund J. W.
Published: September 2011

The dynamic characteristics of a gas bearing can be represented by a set of spring and damping coefficients (impedances) which are functions of the static load on the bearing, the rotating speed and the whirl frequency of the journal. For a rotor supported in gas bearings, these coefficients can be used directly in a critical speed calculation or an unbalance response calculation. In addition, the coefficients can be employed in a stability investigation. The paper gives the computational method for obtaining the spring and damping coefficients and, also, describes how they are used in rotor calculations and stability studies. Numerical results are given in graphical and tabular form for a tilting pad journal bearing and a three-lobe journal bearing.
Some Problems in High-Temperature Bearing Materials
Authors: Stoloff N. S.
Published: September 2011

Bearings which are lubricated by process fluids are being considered for application at temperatures exceeding 1000 deg F. Although under static conditions, nickel-base alloys offer an excellent combination of strength and surface stability, these alloys may change dimensions during long-time bearing applications. It is shown that if creep strength is inadequate, high shaft speeds can lead to significant radial growth. Dimensional stability is also affected by precipitation. A detailed study of Hastelloy X heated in the temperature range 1100–1400 deg F reveals that precipitation occurs even after many hundreds of hours exposure, resulting in dimensional changes of up to 3 microin. per hr of exposure. Means of alleviating these problems are discussed.
Component Hardness Differences and Their Effect on Bearing Fatigue
Authors: Zaretsky E. V. , Parker R. J. , Anderson W. J.
Published: September 2011

The five-ball fatigue tester and full-scale rolling-element bearings were used to determine the effect of component hardness differences of SAE 52100 steel on bearing fatigue and load capacity. Maximum fatigue life and load capacity are achieved when the rolling elements of a bearing are one to two points (Rockwell C) harder than the races. There appears to be an interrelation among compressive residual stresses induced in the races during operation, differences in component hardness, and fatigue life. Differences in contact temperature and plastically deformed profile radii could not account for differences in fatigue life.
An Approximate Method of Solution of Reynolds’ Equation: The Laplace Approximation
Authors: Donaldson R. R.
Published: September 2011

An approximation technique which combines the regions of accuracy of the short bearing and small eccentricity ratio approximations is presented and discussed by means of a sample problem.
Derivation of Governing Equations For Self-Acting Foil Bearings
Authors: Barlow E. J.
Published: September 2011

Contained is the derivation of the equations for the self-acting foil bearing. These equations include the effects of bending stiffness of the tape and of compressibility of the lubricant. They are nonlinear, and the boundary conditions are divided equally between the two ends of the tape. These complications even make obtaining numerical solutions difficult. Linearized solutions are derived for large wrap angles neglecting the bending stiffness of the tape.
Stability of a Squeeze-Film Journal Bearing
Authors: Beck J. V. , Strodtman C. L.
Published: September 2011

An investigation is made of the regions of stability for a compressible fluid, squeeze-film journal bearing of infinite length. Motion along one axis considered and the resulting dynamic equation is solved two ways: by variational techniques and by numerical techniques. The solution from the variational analysis can be approximated by a Mathieu equation thus showing that instability can occur at one-half the driving frequency. The numerical analysis shows the stability limits in terms of the load, drive amplitude, and dimensionless “mass.” The stability analysis is significant as there appears to be a rather large number of combinations of the parameters for which the squeeze-film journal is not stable. The stability characteristics of a squeeze-film bearing should, therefore, be examined carefully before application.
The Steady-State and Dynamic Characteristics of the Tilting-Pad Journal Bearing in Laminar and Turbulent Flow Regimes
Authors: Orcutt F. K.
Published: September 2011

Calculated steady-state and dynamic characteristics are given for the four-pad, tilting-pad journal bearing with preload coefficients of 0 and 0.5 and for mean Reynolds up to 12,000. The calculated characteristics are compared with experimental measurements over the same range of operating parameters. Correlation is good, leading to the conclusion that the calculated data are effective for design analysis of rotor-bearing systems using tilting-pad bearings.
Experiments on an Ultrastable Gas Journal Bearing
Authors: Malanoski S. B.
Published: September 2011

Shallow grooving in a herringbone pattern has been proposed to enhance the stability of both gas and liquid-lubricated journal bearings. It has been shown theoretically that this possibility is particularly advantageous for unloaded journal bearings. This paper describes corroborating experiments. The experiments included the running of an unloaded bearing up to speeds of 60,000 rpm and the collection of steady-state load-displacement, attitude angle data at intermediate speeds up to and including 60,000 rpm. No sign of bearing whirl instability was detected. There was good correlation between theoretical and experimental data. Design data for the partially grooved journal bearing is included for future designs.
Numerical Analysis of the Gas-Lubricated Spiral-Groove Thrust Bearing-Compressor
Authors: James D. D. , Potter A. F.
Published: September 2011

The isothermal Reynolds differential equation of gas film lubrication is written in finite-difference form for numerical analysis of the pressure distribution within spiral-groove thrust bearings and compressors. Appropriate jump equations are presented which provide flow continuity at the land-to-groove interfaces. Gas flow, load support, static stiffness, power consumption, and compressor efficiency are computed and theoretical performance curves are presented for this device. Agreement between computed data and experiment is discussed and presented in graphical form.
Transient Dynamics of a Tilting Pad Gas Bearing System
Authors: Castelli V. , McCabe J. T.
Published: September 2011

A method for obtaining the performance characteristics of a rotor-tilting pad gas lubricated journal bearing system by solving the appropriate dynamics equations together with the time-transient Reynolds’ equation is outlined. Results for a 4 degree of freedom and an 18 degree of freedom system are given. Comparison with steady-state and experimental results are also discussed.
Large area microcorrals and cavity formation on cantilevers using a focused ion beam
Authors: Saraf Laxmikant V. , Britt David W.
Published: September 2011

The authors utilize a focused ion beam (FIB) to explore various sputtering parameters in order to form large area microcorrals and cavities on cantilevers. Microcorrals were rapidly created by modifying ion beam blur and overlaps. Modifications of the FIB sputtering parameters affect the periodicity and shape of the corral microstructure. Cantilever deflections show ion beam amorphization effects as a function of the sputtered area and cantilever base cavities with or without side walls. The FIB sputtering parameters address a method for the rapid creation of a cantilever tensiometer with integrated fluid storage and delivery.
The Genome and Metabolome Collide
Authors: Damani Samir
Published: September 2011

A study of genomic variants and myriad metabolite concentrations reveals insights into disease biology and novel therapeutic targets.
Ankyring the Heart Rhythm
Authors: Lin Richard J.
Published: September 2011

Mutations in a membrane-targeting adaptor protein illuminate a molecular pathway in a common cardiac arrhythmia.
DNA Vaccination Elicits Protective Immune Responses against Pandemic and Classic Swine Influenza Viruses in Pigs
Authors: Gorres J. Patrick , Lager Kelly M. , Kong Wing-Pui , Royals Michael , Todd John-Paul , Vincent Amy L. , Wei Chih-Jen , Loving Crystal L. , Zanella Eraldo L. , Janke Bruce , Kehrli Marcus E. , Nabel Gary J. , Rao Srinivas S.
Published: September 2011

Swine influenza is a highly contagious viral infection in pigs that significantly impacts the pork industry due to weight loss and secondary infections. There is also the potential of a significant threat to public health, as was seen in 2009 when the pandemic H1N1 influenza virus strain emerged from reassortment events among avian, swine, and human influenza viruses within pigs. As classic and pandemic H1N1 strains now circulate in swine, an effective vaccine may be the best strategy to protect the pork industry and public health. Current inactivated-virus vaccines available for swine influenza protect only against viral strains closely related to the vaccine strain, and egg-based production of these vaccines is insufficient to respond to large outbreaks. DNA vaccines are a promising alternative since they can potentially induce broad-based protection with more efficient production methods. In this study we evaluated the potentials of monovalent and trivalent DNA vaccine constructs to (i) elicit both humoral and gamma interferon (IFN-γ) responses and (ii) protect pigs against viral shedding and lung disease after challenge with pandemic H1N1 or classic swine H1N1 influenza virus. We also compared the efficiency of a needle-free vaccine delivery method to that of a conventional needle/syringe injection. We report that DNA vaccination elicits robust serum antibody and cellular responses after three immunizations and confers significant protection against influenza virus challenge. Needle-free delivery elicited improved antibody responses with the same efficiency as conventional injection and should be considered for development as a practical alternative for vaccine administration.
National Prevalence Estimates for Cytomegalovirus IgM and IgG Avidity and Association between High IgM Antibody Titer and Low IgG Avidity
Authors: Dollard Sheila C. , Staras Stephanie A. S. , Amin Minal M. , Schmid D. Scott , Cannon Michael J.
Published: September 2011

Primary cytomegalovirus (CMV) infection of the mother during pregnancy presents risk of CMV infection of the fetus with resulting permanent disability. CMV IgM antibody is generated following primary CMV infection but also can appear during nonprimary CMV infection and is thus of limited diagnostic use by itself. In contrast, the presence of low CMV IgG avidity has been shown to be a unique and reliable serologic indicator of primary CMV infection. We measured CMV IgG and IgM antibody levels and IgG avidity in sera from a population sample of 6,067 U.S. women aged 12 to 49 years from NHANES (National Health and Nutrition Examination Survey). The CMV IgG prevalence was 58% overall and increased strongly with age. The CMV IgM prevalence was 3.0% overall and remained relatively flat across age groups. The prevalence of low IgG avidity was 2.0% overall, decreased sharply with age, and was seen mainly among IgM-positive sera. Fourteen to 18% of the CMV IgM-positive sera were low IgG avidity, presumably representing primary CMV infection. High CMV IgM antibody titer was a strong predictor of low IgG avidity. The ability to reliably identify primary CMV infection during pregnancy is important for management of the pregnancy, including possible treatment options for the fetus. Both IgM and IgG avidity measurements provide useful clinical information for evaluating primary CMV infection, although commercial tests for CMV IgG avidity are not yet widely available in the United States.
Use of Inactivated Escherichia coli Enterotoxins To Enhance Respiratory Mucosal Adjuvanticity during Vaccination in Swine
Authors: Barrette Roger W. , Szczepanek Steven M. , Rood Debra , Challa Sreerupa , Avery Naomi , Vajdy Michael , Kramer Ed , Rodriguez Luis , Silbart Lawrence K.
Published: September 2011

In order to augment responses to respiratory vaccines in swine, various adjuvants were intranasally coadministered with a foot-and-mouth disease virus (FMDV) antigen to pigs. Detoxified
Escherichia coli
enterotoxins LTK63 and LTR72 enhanced antigen-specific mucosal and systemic immunity, demonstrating their efficacy as adjuvants for nonreplicating antigens upon intranasal immunization in swine.
Molecular and Epidemiological Evaluation of Strain Replacement in Patients Previously Harboring Gentamicin-Resistant MRSA
Authors: De Angelis Giulia , Francois Patrice , Lee Andie , Schrenzel Jacques , Renzi Gesuele , Girard Myriam , Pittet Didier , Harbarth Stephan
Published: September 2011

Gentamicin-susceptible methicillin-resistant
Staphylococcus aureus
(GS-MRSA) clones have gradually replaced gentamicin-resistant MRSA (GR-MRSA) clones in many European countries. We studied molecular and epidemiological aspects of MRSA strain replacement in individual patients. All patients from whom at least 2 MRSA strains showing different gentamicin susceptibility patterns were isolated between 1996 and 2008 were retrospectively identified. Staphylococcal cassette chromosome
mec
(SCC
mec
) type and clonality between isolates were determined using molecular methods. Risk factors for individual GR-MRSA SCC
mec
I (prevalent clone) strain replacement with GS-MRSA non-SCC
mec
I types were studied in a nested case-crossover study (
n
= 55 patients). MRSA strain replacement was observed in 127 patients, 85 (67%) of whom were initially colonized with GR-MRSA replaced subsequently by GS-MRSA. Most GS-MRSA replacement strains (50; 59%) possessed SCC
mec
IV. All MRSA isolate pairs from the same patient that consisted of different gentamicin susceptibility and SCC
mec
types were also genotypically different. Exposure to domiciliary nursing assistance (odds ratio [OR], 8.1; 95% confidence interval [CI], 1.2 to 53.7) and high Charlson scores (OR, 7.1; 95% CI, 1.1 to 46.8) were associated with individual strain replacement. In individual patients, exogenous acquisition of a different MRSA strain was responsible for strain replacement in most cases. Domiciliary nursing assistance could be a target for specific control measures to prevent transmission of GS-MRSA in our setting.
Laboratory-Confirmed Case of Yaws in a 10-Year-Old Boy from the Republic of the Congo
Authors: Pillay Allan , Chen Cheng-Yen , Reynolds Mary G. , Mombouli Jean V. , Castro Arnold C. , Louvouezo Davy , Steiner Bret , Ballard Ronald C.
Published: September 2011

We report a case of yaws in a patient with puritic cutaneous eruption who was initially suspected of infection with monkeypox. The diagnosis was established by real-time PCR and sequencing of specific treponemal DNA sequences. This is the first report describing the use of DNA sequencing to identify
Treponema pallidum
subsp.
pertenue
-specific sequences in a patient with active yaws.
Bartonella Species Bacteremia in Two Patients with Epithelioid Hemangioendothelioma
Authors: Mascarelli Patricia E. , Iredell Jonathan R. , Maggi Ricardo G. , Weinberg Guy , Breitschwerdt Edward B.
Published: September 2011

Bartonella henselaeandB. koehleraebacteremia was documented in two epithelioid hemangioendothelioma patients andB. koehleraebacteremia in an asymptomatic partner of one of the patients. Considering the biology and clinically variable natural history of epithelioid hemangioendothelioma, these results suggest that chronicBartonellainfection could have a role in the development of this vascular neoplasm.Bartonellaspp. are known to induce vasoproliferative tumors in immunocompromised patients and may play a role in the development of epithelioid hemangioendothelioma in immunocompetent patients.
Stabilization of Influenza Virus Replication Intermediates Is Dependent on the RNA-Binding but Not the Homo-Oligomerization Activity of the Viral Nucleoprotein
Authors: Vreede Frank T. , Ng Andy Ka-Leung , Shaw Pang-Chui , Fodor Ervin
Published: September 2011

The influenza virus nucleoprotein (NP) is believed to play a central role in directing a switch from RNA genome transcription to replication by the viral RNA polymerase. However, this role has recently been disputed with the proposal of alternative regulatory mechanisms. It has been suggested that the expression of viral polymerase and NP allows genome replication by stabilization of cRNA replication intermediates and complementary ribonucleoprotein (cRNP) assembly. Here, we demonstrate that the RNA-binding activity of NP is necessary for stabilization of cRNA, whereas, surprisingly, homo-oligomerization of NP is not essential. However, both RNA binding and homo-oligomerization activities are essential for genome replication.
The Reovirus σ1s Protein Is a Determinant of Hematogenous but Not Neural Virus Dissemination in Mice
Authors: Boehme Karl W. , Frierson Johnna M. , Konopka Jennifer L. , Kobayashi Takeshi , Dermody Terence S.
Published: September 2011

Nonstructural protein σ1s is a critical determinant of hematogenous dissemination by type 1 reoviruses, which reach the central nervous system (CNS) by a strictly blood-borne route. However, it is not known whether σ1s contributes to neuropathogenesis of type 3 reoviruses, which disseminate by both vascular and neural pathways. Using isogenic type 3 viruses that vary only in σ1s expression, we observed that mice survived at a higher frequency following hind-limb inoculation with σ1s-null virus than when inoculated with wild-type virus. This finding suggests that σ1s is essential for reovirus virulence when inoculated at a site that requires systemic spread to cause disease. Wild-type and σ1s-null viruses produced comparable titers in the spinal cord, suggesting that σ1s is dispensable for invasion of the CNS. Although the two viruses ultimately achieved similar peak titers in the brain, loads of wild-type virus were substantially greater than those of the σ1s-null mutant at early times after inoculation. In contrast, wild-type virus produced substantially higher titers than the σ1s-null virus in peripheral organs to which reovirus spreads via the blood, including the heart, intestine, liver, and spleen. Concordantly, viral titers in the blood were higher following infection with wild-type virus than following infection with the σ1s-null mutant. These results suggest that differences in viral brain titers at early time points postinfection are due to limited virus delivery to the brain by hematogenous pathways. Transection of the sciatic nerve prior to hind-limb inoculation diminished viral spread to the spinal cord. However, wild-type virus retained the capacity to disseminate to the brain following sciatic nerve transection, indicating that wild-type reovirus can spread to the brain by the blood. Together, these results indicate that σ1s is not required for reovirus spread by neural mechanisms. Instead, σ1s mediates hematogenous dissemination within the infected host, which is required for full reovirus neurovirulence.
The SI Strain of Measles Virus Derived from a Patient with Subacute Sclerosing Panencephalitis Possesses Typical Genome Alterations and Unique Amino Acid Changes That Modulate Receptor Specificity and Reduce Membrane Fusion Activity
Authors: Seki Fumio , Yamada Kentaro , Nakatsu Yuichiro , Okamura Koji , Yanagi Yusuke , Nakayama Tetsuo , Komase Katsuhiro , Takeda Makoto
Published: September 2011

Subacute sclerosing panencephalitis (SSPE) is a fatal sequela associated with measles and is caused by persistent infection of the brain with measles virus (MV). The SI strain was isolated in 1976 from a patient with SSPE and shows neurovirulence in animals. Genome nucleotide sequence analyses showed that the SI strain genome possesses typical genome alterations for SSPE-derived strains, namely, accumulated amino acid substitutions in the M protein and cytoplasmic tail truncation of the F protein. Through the establishment of an efficient reverse genetics system, a recombinant SI strain expressing a green fluorescent protein (rSI-AcGFP) was generated. The infection of various cell types with rSI-AcGFP was evaluated by fluorescence microscopy. rSI-AcGFP exhibited limited syncytium-forming activity and spread poorly in cells. Analyses using a recombinant MV possessing a chimeric genome between those of the SI strain and a wild-type MV strain indicated that the membrane-associated protein genes (M, F, and H) were responsible for the altered growth phenotype of the SI strain. Functional analyses of viral glycoproteins showed that the F protein of the SI strain exhibited reduced fusion activity because of an E300G substitution and that the H protein of the SI strain used CD46 efficiently but used the original MV receptors on immune and epithelial cells poorly because of L482F, S546G, and F555L substitutions. The data obtained in the present study provide a new platform for analyses of SSPE-derived strains as well as a clear example of an SSPE-derived strain that exhibits altered receptor specificity and limited fusion activity.
Sequences in Gibbon Ape Leukemia Virus Envelope That Confer Sensitivity to HIV-1 Accessory Protein Vpu
Authors: Janaka Sanath Kumar , Lucas Tiffany M. , Johnson Marc C.
Published: September 2011

HIV-1 efficiently forms pseudotyped particles with many gammaretrovirus glycoproteins, such as Friend murine leukemia virus (F-MLV) Env, but not with the related gibbon ape leukemia virus (GaLV) Env or with a chimeric F-MLV Env with a GaLV cytoplasmic tail domain (CTD). This incompatibility is modulated by the HIV-1 accessory protein Vpu. Because the GaLV Env CTD does not resemble tetherin or CD4, the well-studied targets of Vpu, we sought to characterize the modular sequence in the GaLV Env CTD required for this restriction in the presence of Vpu. Using a systematic mutagenesis scan, we determined that the motif that makes GaLV Env sensitive to Vpu is INxxIxxVKxxVxRxK. This region in the CTD of GaLV Env is predicted to form a helix. Mutations in the CTD that would break this helix abolish sensitivity to Vpu. Although many of these positions can be replaced with amino acids with similar biophysical properties without disrupting the Vpu sensitivity, the final lysine residue is required. This Vpu sensitivity sequence appears to be modular, as the unrelated Rous sarcoma virus (RSV) Env can be made Vpu sensitive by replacing its CTD with the GaLV Env CTD. In addition, F-MLV Env can be made Vpu sensitive by mutating two amino acids in its cytoplasmic tail to make it resemble more closely the Vpu sensitivity motif. Surprisingly, the core components of this Vpu sensitivity sequence are also present in the host surface protein CD4, which is also targeted by Vpu through its CTD.
Comparative Analysis of Poxvirus Orthologues of the Vaccinia Virus E3 Protein: Modulation of Protein Kinase R Activity, Cytokine Responses, and Virus Pathogenicity
Authors: Myskiw Chad , Arsenio Janilyn , Hammett Craig , van Bruggen Rebekah , Deschambault Yvon , Beausoleil Nicole , Babiuk Shawn , Cao Jingxin
Published: September 2011

Poxviruses are important human and animal pathogens that have evolved elaborate strategies for antagonizing host innate and adaptive immunity. The E3 protein of vaccinia virus, the prototypic member of the orthopoxviruses, functions as an inhibitor of innate immune signaling and is essential for vaccinia virus replication in vivo and in many human cell culture systems. However, the function of orthologues of E3 expressed by poxviruses of other genera with different host specificity remains largely unknown. In the present study, we characterized the E3 orthologues from sheeppox virus, yaba monkey tumor virus, swinepox virus, and myxoma virus for their ability to modulate protein kinase R (PKR) function, cytokine responses and virus pathogenicity. We found that the E3 orthologues of myxoma virus and swinepox virus could suppress PKR activation and interferon (IFN)-induced antiviral activities and restore the host range function of E3 in HeLa cells. In contrast, the E3 orthologues from sheeppox virus and yaba monkey tumor virus were unable to inhibit PKR activation. While the sheeppox orthologue was unable to restore the host range function of E3, the yaba monkey tumor virus orthologue partially restored E3-deficient vaccinia virus replication in HeLa cells, correlated with its ability to suppress IFN-induced antiviral activities. Moreover, poxvirus E3 orthologues show varying ability to inhibit the induction of antiviral and proinflammatory cytokines. Despite these
in vitro
results, none of the E3 orthologues tested was capable of restoring pathogenicity to E3-deficient vaccinia virus
in vivo
.
Analysis of Influenza Virus Hemagglutinin Receptor Binding Mutants with Limited Receptor Recognition Properties and Conditional Replication Characteristics
Authors: Bradley Konrad C. , Galloway Summer E. , Lasanajak Yi , Song Xuezheng , Heimburg-Molinaro Jamie , Yu Hai , Chen Xi , Talekar Ganesh R. , Smith David F. , Cummings Richard D. , Steinhauer David A.
Published: September 2011

To examine the range of selective processes that potentially operate when poorly binding influenza viruses adapt to replicate more efficiently in alternative environments, we passaged a virus containing an attenuating mutation in the hemagglutinin (HA) receptor binding site in mice and characterized the resulting mutants with respect to the structural locations of mutations selected, the replication phenotypes of the viruses, and their binding properties on glycan microarrays. The initial attenuated virus had a tyrosine-to-phenylalanine mutation at HA1 position 98 (Y98F), located in the receptor binding pocket, but viruses that were selected contained second-site pseudoreversion mutations in various structural locations that revealed a range of molecular mechanisms for modulating receptor binding that go beyond the scope that is generally mapped using receptor specificity mutants. A comparison of virus titers in the mouse respiratory tract versus MDCK cells in culture showed that the mutants displayed distinctive replication properties depending on the system, but all were less attenuated in mice than the Y98F virus. An analysis of receptor binding properties confirmed that the initial Y98F virus bound poorly to several different species of erythrocytes, while all mutants reacquired various degrees of hemagglutination activity. Interestingly, both the Y98F virus and pseudoreversion mutants were shown to bind very inefficiently to standard glycan microarrays containing an abundance of binding substrates for most influenza viruses that have been characterized to date, provided by the Consortium for Functional Glycomics. The viruses were also examined on a recently developed microarray containing glycans terminating in sialic acid derivatives, and limited binding to a potentially interesting subset of glycans was revealed. The results are discussed with respect to mechanisms for HA-mediated receptor binding, as well as regarding the species of molecules that may act as receptors for influenza virus on host cell surfaces.
The Interaction between Bamboo Mosaic Virus Replication Protein and Coat Protein Is Critical for Virus Movement in Plant Hosts
Authors: Lee Cheng-Cheng , Ho Yuan-Ning , Hu Rei-Hsing , Yen Yu-Ting , Wang Zheng-Cheng , Lee Ya-Chien , Hsu Yau-Heiu , Meng Menghsiao
Published: September 2011

Bamboo mosaic virus
(BaMV) is a positive-sense RNA virus belonging to the genus
Potexvirus
. Open reading frame 1 (ORF1) encodes the viral replication protein that consists of a capping enzyme domain, a helicase-like domain (HLD), and an RNA-dependent RNA polymerase domain from the N to C terminus. ORF5 encodes the viral coat protein (CP) required for genome encapsidation and the virus movement in plants. In this study, application of a yeast-two hybrid assay detected an interaction between the viral HLD and CP. However, the interaction did not affect the NTPase activity of the HLD. To identify the critical amino acids of CP interacting with the HLD, a random mutational library of CP was created using error-prone PCR, and the mutations adversely affecting the interaction were screened by a bacterial two-hybrid system. As a result, the mutations A209G and N210S in CP were found to weaken the interaction. To determine the significance of the interaction, the mutations were introduced into a BaMV infectious clone, and the mutational effects on viral replication, movement, and genome encapsidation were investigated. There was no effect on accumulations of BaMV CP and genomic RNAs within protoplasts; however, the virus cell-to-cell movement in plants was restricted. Sequence alignment revealed that A209 of BaMV CP is conserved in many potexviruses. Mutation of the corresponding residue in
Foxtail mosaic virus
CP also reduced the viral HLD-CP interaction and restricted the virus movement, suggesting that interaction between CP and a widely conserved HLD in the potexviral replication protein is crucial for viral trafficking through plasmodesmata.
Solution Properties of Murine Leukemia Virus Gag Protein: Differences from HIV-1 Gag
Authors: Datta Siddhartha A. K. , Zuo Xiaobing , Clark Patrick K. , Campbell Stephen J. , Wang Yun-Xing , Rein Alan
Published: September 2011

Immature retrovirus particles are assembled from the multidomain Gag protein. In these particles, the Gag proteins are arranged radially as elongated rods. We have previously characterized the properties of HIV-1 Gag in solution. In the absence of nucleic acid, HIV-1 Gag displays moderately weak interprotein interactions, existing in monomer-dimer equilibrium. Neutron scattering and hydrodynamic studies suggest that the protein is compact, and biochemical studies indicate that the two ends can approach close in three-dimensional space, implying the need for a significant conformational change during assembly. We now describe the properties of the Gag protein of Moloney murine leukemia virus (MLV), a gammaretrovirus. We found that this protein is very different from HIV-1 Gag: it has much weaker protein-protein interaction and is predominantly monomeric in solution. This has allowed us to study the protein by small-angle X-ray scattering and to build a low-resolution molecular envelope for the protein. We found that MLV Gag is extended in solution, with an axial ratio of ∼7, comparable to its dimensions in immature particles. Mutational analysis suggests that runs of prolines in its matrix and p12 domains and the highly charged stretch at the C terminus of its capsid domain all contribute to this extended conformation. These differences between MLV Gag and HIV-1 Gag and their implications for retroviral assembly are discussed.
013 Resuscitation feedback and targeted education improves quality of pre-hospital resuscitation in Scotland
Authors: Clarke S , Lyon R M , Milligan D J , Clegg G R
Published: September 2011

Objectives and Backgrounds

Out-of-hospital cardiac arrest is a leading cause of mortality and neurological morbidity in the UK. Cardiopulmonary resuscitation is vital to maintaining cerebral and cardiac perfusion until return of spontaneous circulation. Recent studies have demonstrated the adverse physiological consequences of poor resuscitation technique and that quality of Cardiopulmonary resuscitation is a critical determinant of outcome. Analysis of the defibrillator transthoracic impedance (TTI) trace gives an objective measure of pre-hospital resuscitation quality. This study aims to analyse the impact of targeted resuscitation feedback and training on quality of pre-hospital resuscitation.

Methods

Single centre, prospective cohort study over 13 months (1st December 2009–31st December 2010). Modems were fitted to the defibrillators on vehicles from Edinburgh City ambulance station (n=40). Resuscitation events were collected by telemetry and analysed. Outcome measures were: resuscitation time spent performing chest compressions, compression rate, hands-off time required to deliver a shock and use of automatic or manual defibrillator mode. Baseline data were gathered over a 3-month period. Monthly resuscitation classes and personalised written feedback following each resuscitation attempt were then introduced for 6 months. Resuscitation quality was again measured and compared to baseline data.

Results

Analysis of 111 downloads showed hands-on-chest time improved significantly following feedback and targeted resuscitation training (73.0% vs 79.3%, p=0.007). Compression rate was unchanged (Abstract 013 figures 1 and 2). There was a significant reduction in median time-to-shock interval from 20.25 s (IQR 15.50–25.50 s) to 13.45 s (IQR 2.25–22.00 s) (p=0.006). Use of automatic rhythm recognition fell from 50% to 28.6% (p=0.03).

Abstract 013 Figure 1

Frequency histogram showing the distribution of compression rates around the “ideal” 90–110/min (2005 Guidelines: shaded area) during the baseline data collection period.

Abstract 013 Figure 2

Frequency histogram showing the distribution of compression rates around the “ideal” 90–110/min (2005 Guidelines: shaded area) following implementation of feedback and resuscitation training.

Conclusions

TTI trace analysis following Out-of-hospital cardiac arrest allows objective evaluation of resuscitation quality. Targeted training and feedback improves the quality of pre-hospital resuscitation. Further studies are required to establish improvement in survival as a result of this approach.
031 Delivering safety net advice and the Emergency Department Clinical Quality Indicator of unplanned re-attendance in children
Authors: Roland D , Geliot T , Patel A
Published: September 2011

Objectives and Background

A Department of Health study has shown parents of children presenting with fever who did not receive safety net advice were more likely to unnecessarily re-attend. This work aimed to improve the proportion of safety net advice given by junior doctors at the outset of their attachment. In 2009, an audit of feverish children who presented to our Emergency Department found the number of junior doctors providing safety net advice to parents fell from 70.9% in July to 55.9% when a new cohort commenced in August.

Methods

A key slide set was introduced into the paediatric induction lecture (given during the Emergency Department's internal programme) regarding safety net advice in August 2010.

Results

Following this awareness campaign, an audit involving 457 case notes revealed safety net advice increased significantly from 76.0% in July 2010 to 89.5% in the August cohort. In 2009 there were 41 medically related re-attendances in July (39.0% subsequently admitted) and 48 in August (41.7% admitted). These “return to be admitted” rates were not significantly different (Z value 0.037, p>0.05). In 2010 there were 50 medically related representations in July (40.0% admitted) and 54 in August (27.8% admitted). These “return to be admitted” rates were not significantly different (Z value 1.11, p>0.05). In children aged 16 and over the total number of re-attendees increased from 6.5% to 7.2% between July and August 2010 with the August result significantly higher than the year total (Z value 2.655, p<0.01) although August had the highest re-attendance amount of the year. In children under 16 re-attendees fell from 3.9% to 3.6% between July and August with the August result not being significantly different from the year total (Z value 1.502, p>0.05).

Conclusion

The provision of improved safety net advice did not increase the Clinical Quality Indicator of unplanned re-attendance. Induction programmes have an important role to play in promoting evidence-based practice and improving quality.
009 No more “admit for 12 h trop”? Cardiac markers point of care testing in patients with suspected low to moderate risk ACS
Authors: Robinson D , Choudhry T , Nisar S , Barker M , Lee G
Published: September 2011

Objectives and Backgrounds

Current diagnostic strategies using cardiac markers in the assessment of suspected acute coronary syndrome (ACS) involve the measurement of serum troponin 10–12 h after the onset of chest pain. We evaluated the potential impact of a multimarker strategy using point of care (POC) measurement of myoglobin, creatine kinase (CK)-MB and troponin I to exclude MI in ≤90 min.

Methods

Patients presenting to the Emergency Department with suspected ACS with non-diagnostic ECGs were included. We measured myoglobin, CK-MB and troponin I with a POC device at presentation and at 90 min. Standard laboratory testing of troponin I was performed at 12 h. Sensitivity, specificity and likelihood ratios for the POC triple cardiac marker strategy were calculated. We also calculated time to decision point for POC testing vs laboratory testing.

Results

Complete data were available for 109 patients. 73 patients had negative POC testing and normal laboratory troponin. POC markers were positive in 36 patients, of which 19 had positive 12 h laboratory troponin I. Sensitivity of POC cardiac markers was 100% (95% CI 0.79% to 1.0%), specificity 81% (95% CI 0.71% to 0.88%), negative likelihood ratio <0.001 and positive likelihood ratio 5.29. Mean time to decision point was 700 min earlier for POC testing vs laboratory troponin measurement. We estimate that implementation of the triple cardiac markers POC pathway in our institution would save 3 beds per day.

Conclusions

Triple cardiac marker POC testing at 90 min can be used to reliably exclude acute myocardial infarction in patients with low to moderate risk ACS, and has the potential to reduce inpatient medical bed occupancy.
CALCULATION OF THE PHOTOLUMINESCENCE SPECTRA FORYb3+-DOPEDCuInS2CRYSTAL
Authors: SU PING , ZHENG WEN-CHEN , LIU HONG-GANG
Published: September 2011

Six crystal field energy levels obtained from the photoluminescence spectra of Yb3+-doped CuInS2semiconductor crystal are calculated from the diagonalization (of energy matrix) method. The root-mean-square (r.m.s) deviation σ is 4.5 cm-1and so the calculated results are in good agreement with the experimental values. The local tetragonal distortion angle θ for the Yb3+center in CuInS2(which is different from the corresponding angle θhin the host crystal) is obtained from the calculation.
THE INTERSUBBAND TRANSITIONS AND BINDING ENERGY OF SHALLOW DONOR IMPURITIES IN DIFFERENT SHAPED QUANTUM WELLS UNDER THE MAGNETIC FIELD
Authors: YESILGUL U. , UNGAN F. , KASAPOGLU E. , SARI H. , SÖKMEN I.
Published: September 2011

The intersubband transitions and impurity binding energy in differently shaped semiconductor quantum wells under a magnetic field are calculated using a variational method within the effective mass approximation. Our calculations have revealed the dependence of the intersubband transitions and impurity binding energy on the magnetic field strength and the shape of the quantum wells.
CRITICAL ACTIVATION PARAMETERS FOR LaFeAsO-BASED SUPERCONDUCTORS
Authors: CHU ZOTIN KWANG-HUA
Published: September 2011

The occurrence of high-Tc superconductivity in the iron pnictides shares a similar amorphous characteristic with that of high-Tc superconducting cuprates. Here we show that nearly frictionless (electric-field-driven) transport of condensed electrons in amorphous superconductors could happen after using the Eyring's transition-rate approach which has been successfully adopted to study the critical transport of other superconductors as well as supersolid helium in very low temperature environment. The critical temperatures related to the nearly frictionless transport of electrons were found to be directly relevant to the superconducting temperature of high-temperature superconductors (like La [ O 1-x F x] FeAs (x = 0.11-0.12)) after selecting specific activation energies and activation volumes.