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Sample records for drive neutralization escape

  1. Flexibility in Surface-Exposed Loops in a Virus Capsid Mediates Escape from Antibody Neutralization

    PubMed Central

    Kolawole, Abimbola O.; Li, Ming; Xia, Chunsheng; Fischer, Audrey E.; Giacobbi, Nicholas S.; Rippinger, Christine M.; Proescher, Jody B. G.; Wu, Susan K.; Bessling, Seneca L.; Gamez, Monica; Yu, Chenchen; Zhang, Rebecca; Mehoke, Thomas S.; Pipas, James M.; Wolfe, Joshua T.; Lin, Jeffrey S.; Feldman, Andrew B.

    2014-01-01

    the antibody structure into the virion/antibody complex identifies two conformations of the antibody binding domain of the viral capsid: one with a superior fit and the other with an inferior fit to the antibody. These data suggest a unique mode of antibody neutralization. In contrast to other viruses that largely escape antibody neutralization through direct disruption of the antibody-virus interface, we identify mutations that acted indirectly by limiting the conformation of the antibody binding loop in the viral capsid and drive the antibody binding domain into the conformation unable to be bound by the antibody. PMID:24501415

  2. Escape from neutralization by the respiratory syncytial virus-specific neutralizing monoclonal antibody palivizumab is driven by changes in on-rate of binding to the fusion protein

    SciTech Connect

    Bates, John T.; Keefer, Christopher J.; Slaughter, James C.; Kulp, Daniel W.; Schief, William R.

    2014-04-15

    The role of binding kinetics in determining neutralizing potency for antiviral antibodies is poorly understood. While it is believed that increased steady-state affinity correlates positively with increased virus-neutralizing activity, the relationship between association or dissociation rate and neutralization potency is unclear. We investigated the effect of naturally-occurring antibody resistance mutations in the RSV F protein on the kinetics of binding to palivizumab. Escape from palivizumab-mediated neutralization of RSV occurred with reduced association rate (K{sub on}) for binding to RSV F protein, while alteration of dissociation rate (K{sub off}) did not significantly affect neutralizing activity. Interestingly, linkage of reduced K{sub on} with reduced potency mirrored the effect of increased K{sub on} found in a high-affinity enhanced potency palivizumab variant (motavizumab). These data suggest that association rate is the dominant factor driving neutralization potency for antibodies to RSV F protein antigenic site A and determines the potency of antibody somatic variants or efficiency of escape of viral glycoprotein variants. - Highlights: • The relationship of affinity to neutralization for virus antibodies is uncertain. • Palivizumab binds to RSV escape mutant fusion proteins, but with reduced affinity. • Association rate (K{sub on}) correlated well with the potency of neutralization.

  3. Immune escape by human immunodeficiency virus type 1 from neutralizing antibodies: evidence for multiple pathways.

    PubMed Central

    Watkins, B A; Reitz, M S; Wilson, C A; Aldrich, K; Davis, A E; Robert-Guroff, M

    1993-01-01

    Sera from many HIV-1-infected individuals contain broadly reactive, specific neutralizing antibodies. Despite their broad reactivity, variant viruses, resistant to neutralization, can be selected in vitro in the presence of such antisera. We have previously shown that neutralization resistance of an escape mutant with an amino acid substitution in the transmembrane protein (A582T) occurs because of alteration of a conformational epitope that is recognized by neutralizing antibodies directed against the CD4 binding site. In this report we demonstrate that immune escape via a single-amino-acid substitution (A281V) within a conserved region of the envelope glycoprotein gp120 confers neutralization resistance against a broadly reactive neutralizing antiserum from a seropositive individual. We show this alteration affects V3 and additional regions unrelated to V3 or the CD4 binding site. Together with previous studies on escape mutants selected in vitro, our findings suggest that immune-selective pressure can arise by multiple pathways. PMID:7693973

  4. Two Escape Mechanisms of Influenza A Virus to a Broadly Neutralizing Stalk-Binding Antibody

    PubMed Central

    Chai, Ning; Swem, Lee R.; Reichelt, Mike; Chen-Harris, Haiyin; Luis, Elizabeth; Park, Summer; Fouts, Ashley; Lupardus, Patrick; Wu, Thomas D.; Li, Olga; McBride, Jacqueline; Lawrence, Michael; Xu, Min; Tan, Man-Wah

    2016-01-01

    Broadly neutralizing antibodies targeting the stalk region of influenza A virus (IAV) hemagglutinin (HA) are effective in blocking virus infection both in vitro and in vivo. The highly conserved epitopes recognized by these antibodies are critical for the membrane fusion function of HA and therefore less likely to be permissive for virus mutational escape. Here we report three resistant viruses of the A/Perth/16/2009 strain that were selected in the presence of a broadly neutralizing stalk-binding antibody. The three resistant viruses harbor three different mutations in the HA stalk: (1) Gln387Lys; (2) Asp391Tyr; (3) Asp391Gly. The Gln387Lys mutation completely abolishes binding of the antibody to the HA stalk epitope. The other two mutations, Asp391Tyr and Asp391Gly, do not affect antibody binding at neutral pH and only slightly reduce binding at low pH. Interestingly, they enhance the fusion ability of the HA, representing a novel mechanism that allows productive membrane fusion even in the presence of antibody and hence virus escape from antibody neutralization. Therefore, these mutations illustrate two different resistance mechanisms used by IAV to escape broadly neutralizing stalk-binding antibodies. Compared to the wild type virus, the resistant viruses release fewer progeny viral particles during replication and are more sensitive to Tamiflu, suggesting reduced viral fitness. PMID:27351973

  5. Two Escape Mechanisms of Influenza A Virus to a Broadly Neutralizing Stalk-Binding Antibody.

    PubMed

    Chai, Ning; Swem, Lee R; Reichelt, Mike; Chen-Harris, Haiyin; Luis, Elizabeth; Park, Summer; Fouts, Ashley; Lupardus, Patrick; Wu, Thomas D; Li, Olga; McBride, Jacqueline; Lawrence, Michael; Xu, Min; Tan, Man-Wah

    2016-06-01

    Broadly neutralizing antibodies targeting the stalk region of influenza A virus (IAV) hemagglutinin (HA) are effective in blocking virus infection both in vitro and in vivo. The highly conserved epitopes recognized by these antibodies are critical for the membrane fusion function of HA and therefore less likely to be permissive for virus mutational escape. Here we report three resistant viruses of the A/Perth/16/2009 strain that were selected in the presence of a broadly neutralizing stalk-binding antibody. The three resistant viruses harbor three different mutations in the HA stalk: (1) Gln387Lys; (2) Asp391Tyr; (3) Asp391Gly. The Gln387Lys mutation completely abolishes binding of the antibody to the HA stalk epitope. The other two mutations, Asp391Tyr and Asp391Gly, do not affect antibody binding at neutral pH and only slightly reduce binding at low pH. Interestingly, they enhance the fusion ability of the HA, representing a novel mechanism that allows productive membrane fusion even in the presence of antibody and hence virus escape from antibody neutralization. Therefore, these mutations illustrate two different resistance mechanisms used by IAV to escape broadly neutralizing stalk-binding antibodies. Compared to the wild type virus, the resistant viruses release fewer progeny viral particles during replication and are more sensitive to Tamiflu, suggesting reduced viral fitness. PMID:27351973

  6. Analysis of anisotropic suprathermal ion distributions using multidirectional measurements of escaping neutral atom fluxes

    SciTech Connect

    Goncharov, P. R.; Ozaki, T.; Veshchev, E. A.; Sudo, S.

    2008-10-15

    A feasible approach in obtaining experimental data on the angular dependence of the ion distribution function in a fusion plasma is to perform angle-resolved measurements of kinetic energy spectra of escaping neutral atoms. A general calculation scheme has been developed and realized as a FORTRAN code that has a predictive force to simulate the experimentally measurable anisotropic distributions and random samples of escaping neutral atom kinetic energies for any given angle-dependent ion distribution law, electron density, and temperature profiles, plasma composition, magnetic surface structure, and experiment geometry on any toroidal plasma device with magnetic confinement. As a particular application of the method to a specific experiment, measured signals for all 20 channels of the angle-resolved multisightline neutral particle analyzer on Large Helical Device have been numerically simulated for certain predefined model fast ion distribution functions.

  7. Analysis of anisotropic suprathermal ion distributions using multidirectional measurements of escaping neutral atom fluxes.

    PubMed

    Goncharov, P R; Ozaki, T; Veshchev, E A; Sudo, S

    2008-10-01

    A feasible approach in obtaining experimental data on the angular dependence of the ion distribution function in a fusion plasma is to perform angle-resolved measurements of kinetic energy spectra of escaping neutral atoms. A general calculation scheme has been developed and realized as a FORTRAN code that has a predictive force to simulate the experimentally measurable anisotropic distributions and random samples of escaping neutral atom kinetic energies for any given angle-dependent ion distribution law, electron density, and temperature profiles, plasma composition, magnetic surface structure, and experiment geometry on any toroidal plasma device with magnetic confinement. As a particular application of the method to a specific experiment, measured signals for all 20 channels of the angle-resolved multisightline neutral particle analyzer on Large Helical Device have been numerically simulated for certain predefined model fast ion distribution functions. PMID:19044624

  8. HIV-1 resistance to neutralizing antibodies: Determination of antibody concentrations leading to escape mutant evolution.

    PubMed

    Magnus, Carsten; Reh, Lucia; Trkola, Alexandra

    2016-06-15

    Broadly neutralizing antibodies against human immunodeficiency virus type 1 (HIV-1) are considered vital components of novel therapeutics and blueprints for vaccine research. Yet escape to even the most potent of these antibodies is imminent in natural infection. Measures to define antibody efficacy and prevent mutant selection are thus urgently needed. Here, we derive a mathematical framework to predict the concentration ranges for which antibody escape variants can outcompete their viral ancestors, referred to as mutant selection window (MSW). When determining the MSW, we focus on the differential efficacy of neutralizing antibodies against HIV-1 in two canonical infection routes, free-virus infection and cell-cell transmission. The latter has proven highly effective in vitro suggesting its importance for both in vivo spread as well as for escaping targeted intervention strategies. We observed a range of MSW patterns that highlight the potential of mutants to arise in both transmission pathways and over wide concentration ranges. Most importantly, we found that only when the arising mutant has both, residual sensitivity to the neutralizing antibody and reduced infectivity compared to the parental virus, antibody dosing outside of the MSW to restrict mutant selection is possible. Emergence of mutants that provide complete escape and have no considerable fitness loss cannot be prevented by adjusting antibody doses. The latter may in part explain the ubiquitous resistance to neutralizing antibodies observed in natural infection and antibody treatment. Based on our findings, combinations of antibodies targeting different epitopes should be favored for antibody-based interventions as this may render complete resistance less likely to occur and also increase chances that multiple escapes result in severe fitness loss of the virus making longer-term antibody treatment more feasible. PMID:26494166

  9. Requirements for neutral beam current drive in tokamaks

    SciTech Connect

    Dory, R.A.

    1988-01-01

    This paper contains viewgraphs on the use of neutral beam current drive in future tokamaks. Current profiles, slowing down distributions, beam destabilization of alfven waves and plasma parameters are some items covered in this paper. (DWL)

  10. Neutralization escape mutants define a dominant immunogenic neutralization site on hepatitis A virus

    SciTech Connect

    Stapleton, J.T.; Lemon, S.M.

    1987-02-01

    Hepatitis A virus is an hepatotrophic human picornavirus which demonstrates little antigenic variability. To topologically map immunogenic sites on hepatitis A virus which elicit neutralizing antibodies, eight neutralizing monoclonal antibodies were evaluated in competition immunoassays employing radiolabeled monoclonal antibodies and HM-175 virus. Whereas two antibodies (K3-4C8 and K3-2F2) bound to intimately overlapping epitopes, the epitope bound by a third antibody (B5-B3) was distinctly different as evidenced by a lack of competition between antibodies for binding to the virus. The other five antibodies variably blocked the binding of both K3-4C8-K3-2F2 and B5-B3, suggesting that these epitopes are closely spaced and perhaps part of a single neutralization immunogenic site. Several combinations of monoclonal antibodies blocked the binding of polyclonal human convalescent antibody by greater than 96%, indicating that the neutralization epitopes bound by these antibodies are immunodominant in humans. Spontaneously arising HM-175 mutants were selected for resistance to monoclonal antibody-mediated neutralization. Neutralization resistance was associated with reduced antibody binding. These results suggest that hepatitis A virus may differ from poliovirus in possessing a single, dominant neutralization immunogenic site and therefore may be a better candidate for synthetic peptide or antiidiotype vaccine development.

  11. Precipitation of energetic neutral atoms and induced non-thermal escape fluxes from the Martian atmosphere

    SciTech Connect

    Lewkow, N. R.; Kharchenko, V.

    2014-08-01

    The precipitation of energetic neutral atoms, produced through charge exchange collisions between solar wind ions and thermal atmospheric gases, is investigated for the Martian atmosphere. Connections between parameters of precipitating fast ions and resulting escape fluxes, altitude-dependent energy distributions of fast atoms and their coefficients of reflection from the Mars atmosphere, are established using accurate cross sections in Monte Carlo (MC) simulations. Distributions of secondary hot (SH) atoms and molecules, induced by precipitating particles, have been obtained and applied for computations of the non-thermal escape fluxes. A new collisional database on accurate energy-angular-dependent cross sections, required for description of the energy-momentum transfer in collisions of precipitating particles and production of non-thermal atmospheric atoms and molecules, is reported with analytic fitting equations. Three-dimensional MC simulations with accurate energy-angular-dependent cross sections have been carried out to track large ensembles of energetic atoms in a time-dependent manner as they propagate into the Martian atmosphere and transfer their energy to the ambient atoms and molecules. Results of the MC simulations on the energy-deposition altitude profiles, reflection coefficients, and time-dependent atmospheric heating, obtained for the isotropic hard sphere and anisotropic quantum cross sections, are compared. Atmospheric heating rates, thermalization depths, altitude profiles of production rates, energy distributions of SH atoms and molecules, and induced escape fluxes have been determined.

  12. Envelope-chimeric Entry-targeted Measles Virus Escapes Neutralization and Achieves Oncolysis

    PubMed Central

    Miest, Tanner S; Yaiw, Koon-Chu; Frenzke, Marie; Lampe, Johanna; Hudacek, Andrew W; Springfeld, Christoph; von Messling, Veronika; Ungerechts, Guy; Cattaneo, Roberto

    2011-01-01

    Measles virus (MV) is a promising vector for cancer therapy and multivalent vaccination, but high prevalence of pre-existing neutralizing antibodies may reduce therapeutic efficacy, particularly following systemic administration. MV has only one serotype, but here we show that its envelope glycoproteins can be exchanged with those of the closely related canine distemper virus (CDV), generating a chimeric virus capable of escaping neutralization. To target its entry, we displayed on the CDV attachment protein a single-chain antibody specific for a designated receptor. To enhance oncolytic efficacy we armed the virus with a prodrug convertase gene capable of locally activating chemotherapeutic prodrugs. The new virus achieved high titers, was genetically stable, and was resistant to neutralization by sera from both MV-immunized mice and MV-immune humans. The new virus targeted syngeneic murine tumor cells expressing the designated receptor implanted in immunocompetent mice, and synergized with a chemotherapeutic prodrug in a model of oncolysis. Importantly, the chimeric MV remained oncolytic when administered systemically even in the presence of anti-MV antibodies capable of abrogating the therapeutic efficacy of the parental, nonshielded MV. This work shows that targeting, arming, and shielding can be combined to generate a tumor-specific, neutralization-resistant virus that can synergize with chemotherapeutics. PMID:21610701

  13. Subgroup J avian leukosis virus neutralizing antibody escape variants contribute to viral persistence in meat-type chickens.

    PubMed

    Pandiri, A R; Mays, J K; Silva, R F; Hunt, H D; Reed, W M; Fadly, A M

    2010-06-01

    We have previously demonstrated a high incidence of chickens with persistent viremia even in the presence of neutralizing antibodies (V+A+) against the inoculated parental virus in commercial meat-type chickens inoculated at hatch with subgroup J avian leukosis virus (ALV J) field isolates. In this study, we used an ALV J molecular clone, ADOL pR5-4, to determine the role of neutralizing antibody (NAb) escape mutants in maintaining a high incidence of viral persistence, namely, V+A+ infection profile in commercial meat-type chickens. Chickens were housed as a flock in a pen or housed in isolation in solitary Horsfall-Bauer units for testing for NAb escape variants. The emergence of NAb escape variants was evaluated by sequential autologous virus neutralization (VN) (between virus and antibody from the same sampling period) and heterologous VN (between virus and antibody from preceding and succeeding sampling periods). Sequential virus isolates and corresponding antisera from 18 chickens were examined by VN matrix. In all chickens, autologous virus isolates were not neutralized by corresponding antisera. However, some of these resilient autologous virus isolates were neutralized by antibodies from subsequent sampling intervals. Nucleotide sequence analysis of consecutive isolates from three individually housed chickens with V+A+ infection profile revealed distinct changes within the envelope region, suggesting viral evolution to escape the host immune response. These results demonstrate that the emergence of antibody escape variants in commercial meat-type chickens contributes to ALV J persistence. PMID:20608529

  14. Neutral Beam Current Drive in Spheromak plasma and plasma stability

    NASA Astrophysics Data System (ADS)

    Pearlstein, L. D.; Jayakumar, R. J.; Hudson, B.; Hill, D. N.; Lodestro, L. L.; McLean, H. S.; Fowler, T. K.; Casper, T. A.

    2007-11-01

    A key question for the Sustained Spheromak Physics Experiment (SSPX) is understanding how spheromaks can be sustained by other current drive tools such as neutral beam current drive. Another question is whether the present relationship between current and maximum spheromak magnetic field (plasma beta) is related to Alcator-like ohmic confinement limit or is a stability limit. Using the code CORSICA, the fraction of neutral beam current drive that can be achieved has been calculated for different injection angles with a fixed equilibrium. It is seen that relaxing the equilibrium with this drive simply drives the core safety factor to low values. Other equilibria where the NBI may give aligned current drive are being explored. Free-boundary equilibria calculations are underway to see what hyper-resistivity model gives the observed sustained SSPX performance and include that in the NBI calculations. Work performed under the auspices of the US DOE by University of California Lawrence Livermore National Laboratory under contract W-7405-ENG-48.

  15. Direct activation of the Mauthner cell by electric field pulses drives ultrarapid escape responses.

    PubMed

    Tabor, Kathryn M; Bergeron, Sadie A; Horstick, Eric J; Jordan, Diana C; Aho, Vilma; Porkka-Heiskanen, Tarja; Haspel, Gal; Burgess, Harold A

    2014-08-15

    Rapid escape swims in fish are initiated by the Mauthner cells, giant reticulospinal neurons with unique specializations for swift responses. The Mauthner cells directly activate motoneurons and facilitate predator detection by integrating acoustic, mechanosensory, and visual stimuli. In addition, larval fish show well-coordinated escape responses when exposed to electric field pulses (EFPs). Sensitization of the Mauthner cell by genetic overexpression of the voltage-gated sodium channel SCN5 increased EFP responsiveness, whereas Mauthner ablation with an engineered variant of nitroreductase with increased activity (epNTR) eliminated the response. The reaction time to EFPs is extremely short, with many responses initiated within 2 ms of the EFP. Large neurons, such as Mauthner cells, show heightened sensitivity to extracellular voltage gradients. We therefore tested whether the rapid response to EFPs was due to direct activation of the Mauthner cells, bypassing delays imposed by stimulus detection and transmission by sensory cells. Consistent with this, calcium imaging indicated that EFPs robustly activated the Mauthner cell but only rarely fired other reticulospinal neurons. Further supporting this idea, pharmacological blockade of synaptic transmission in zebrafish did not affect Mauthner cell activity in response to EFPs. Moreover, Mauthner cells transgenically expressing a tetrodotoxin (TTX)-resistant voltage-gated sodium channel retained responses to EFPs despite TTX suppression of action potentials in the rest of the brain. We propose that EFPs directly activate Mauthner cells because of their large size, thereby driving ultrarapid escape responses in fish. PMID:24848468

  16. Direct activation of the Mauthner cell by electric field pulses drives ultrarapid escape responses

    PubMed Central

    Tabor, Kathryn M.; Bergeron, Sadie A.; Horstick, Eric J.; Jordan, Diana C.; Aho, Vilma; Porkka-Heiskanen, Tarja; Haspel, Gal

    2014-01-01

    Rapid escape swims in fish are initiated by the Mauthner cells, giant reticulospinal neurons with unique specializations for swift responses. The Mauthner cells directly activate motoneurons and facilitate predator detection by integrating acoustic, mechanosensory, and visual stimuli. In addition, larval fish show well-coordinated escape responses when exposed to electric field pulses (EFPs). Sensitization of the Mauthner cell by genetic overexpression of the voltage-gated sodium channel SCN5 increased EFP responsiveness, whereas Mauthner ablation with an engineered variant of nitroreductase with increased activity (epNTR) eliminated the response. The reaction time to EFPs is extremely short, with many responses initiated within 2 ms of the EFP. Large neurons, such as Mauthner cells, show heightened sensitivity to extracellular voltage gradients. We therefore tested whether the rapid response to EFPs was due to direct activation of the Mauthner cells, bypassing delays imposed by stimulus detection and transmission by sensory cells. Consistent with this, calcium imaging indicated that EFPs robustly activated the Mauthner cell but only rarely fired other reticulospinal neurons. Further supporting this idea, pharmacological blockade of synaptic transmission in zebrafish did not affect Mauthner cell activity in response to EFPs. Moreover, Mauthner cells transgenically expressing a tetrodotoxin (TTX)-resistant voltage-gated sodium channel retained responses to EFPs despite TTX suppression of action potentials in the rest of the brain. We propose that EFPs directly activate Mauthner cells because of their large size, thereby driving ultrarapid escape responses in fish. PMID:24848468

  17. Characterization of Poliovirus Neutralization Escape Mutants of Single-Domain Antibody Fragments (VHHs)

    PubMed Central

    Schotte, Lise; Thys, Bert; Strauss, Mike; Filman, David J.; Rombaut, Bart

    2015-01-01

    To complete the eradication of poliovirus and to protect unvaccinated people subsequently, the development of one or more antiviral drugs will be necessary. A set of five single-domain antibody fragments (variable parts of the heavy chain of a heavy-chain antibody [VHHs]) with an in vitro neutralizing activity against poliovirus type 1 was developed previously (B. Thys, L. Schotte, S. Muyldermans, U. Wernery, G. Hassanzadeh-Ghassabeh, and B. Rombaut, Antiviral Res 87:257–264, 2010, http://dx.doi.org/10.1016/j.antiviral.2010.05.012), and their mechanisms of action have been studied (L. Schotte, M. Strauss, B. Thys, H. Halewyck, D. J. Filman, M. Bostina, J. M. Hogle, and B. Rombaut, J Virol 88:4403–4413, 2014, http://dx.doi.org/10.1128/JVI.03402-13). In this study, neutralization escape mutants were selected for each VHH. Sequencing of the P1 region of the genome showed that amino acid substitutions are found in the four viral proteins of the capsid and that they are located both in proximity to the binding sites of the VHHs and in regions further away from the canyon and hidden beneath the surface. Characterization of the mutants demonstrated that they have single-cycle replication kinetics that are similar to those of their parental strain and that they are all drug (VHH) independent. Their resistant phenotypes are stable, as they do not regain full susceptibility to the VHH after passage over HeLa cells in the absence of VHH. They are all at least as stable as the parental strain against heat inactivation at 44°C, and three of them are even significantly (P < 0.05) more resistant to heat inactivation. The resistant variants all still can be neutralized by at least two other VHHs and retain full susceptibility to pirodavir and 35-1F4. PMID:26014941

  18. Novel Rabies Virus-Neutralizing Epitope Recognized by Human Monoclonal Antibody: Fine Mapping and Escape Mutant Analysis†

    PubMed Central

    Marissen, Wilfred E.; Kramer, R. Arjen; Rice, Amy; Weldon, William C.; Niezgoda, Michael; Faber, Milosz; Slootstra, Jerry W.; Meloen, Rob H.; Clijsters-van der Horst, Marieke; Visser, Therese J.; Jongeneelen, Mandy; Thijsse, Sandra; Throsby, Mark; de Kruif, John; Rupprecht, Charles E.; Dietzschold, Bernhard; Goudsmit, Jaap; Bakker, Alexander B. H.

    2005-01-01

    Anti-rabies virus immunoglobulin combined with rabies vaccine protects humans from lethal rabies infections. For cost and safety reasons, replacement of the human or equine polyclonal immunoglobulin is advocated, and the use of rabies virus-specific monoclonal antibodies (MAbs) is recommended. We produced two previously described potent rabies virus-neutralizing human MAbs, CR57 and CRJB, in human PER.C6 cells. The two MAbs competed for binding to rabies virus glycoprotein. Using CR57 and a set of 15-mer overlapping peptides covering the glycoprotein ectodomain, a neutralization domain was identified between amino acids (aa) 218 and 240. The minimal binding region was identified as KLCGVL (aa 226 to 231), with key residues K-CGV- identified by alanine replacement scanning. The critical binding region of this novel nonconformational rabies virus epitope is highly conserved within rabies viruses of genotype 1. Subsequently, we generated six rabies virus variants escaping neutralization by CR57 and six variants escaping CRJB. The CR57 escape mutants were only partially covered by CRJB, and all CRJB-resistant variants completely escaped neutralization by CR57. Without exception, the CR57-resistant variants showed a mutation at key residues within the defined minimal binding region, while the CRJB escape viruses showed a single mutation distant from the CR57 epitope (N182D) combined with mutations in the CR57 epitope. The competition between CR57 and CRJB, the in vitro escape profile, and the apparent overlap between the recognized epitopes argues against including both CR57 and CRJB in a MAb cocktail aimed at replacing classical immunoglobulin preparations. PMID:15795253

  19. Neutral and Selective Processes Drive Population Differentiation for Iris hexagona.

    PubMed

    Hamlin, Jennafer A P; Arnold, Michael L

    2015-01-01

    Gene flow among widespread populations can be reduced by geographical distance or by divergent selection resulting from local adaptation. In this study, we tested for the divergence of phenotypes and genotypes among 8 populations of Iris hexagona. Using a genotyping-by-sequencing approach, we generated a panel of 750 single nucleotide polymorphisms (SNPs) and used population genetic analyses to determine what may affect patterns of divergence across I. hexagona populations. Specifically, genetic differentiation was compared between populations at neutral and nonneutral SNPs and detected significant differences between the 2 types of markers. We then asked whether loci with the strongest degree of population genetic differentiation were also the loci with the strongest association to morphology or climate differences, allowing us to test if pollinators or climate drive population differentiation or some combination of both. We found 2 markers that were associated with morphology and 1 marker associated with 2 of the environmental variables, which were also identified in the outlier analysis. We then show that the SNPs putatively under selection were positively correlated with both geographic distance and phenotypic distance, albeit weakly to phenotypic distance. Moreover, neutral SNPs were only correlated with geographic distance and thus isolation-by-distance was observed for neutral SNPs. Our data suggest that both deterministic and neutral processes have contributed to the evolutionary trajectory of I. hexagona populations. PMID:26163584

  20. A transmission/escape probabilities model for neutral particle transport in the outer regions of a diverted tokamak

    SciTech Connect

    Stacey, W.M.

    1992-12-01

    A new computational model for neutral particle transport in the outer regions of a diverted tokamak plasma chamber is presented. The model is based on the calculation of transmission and escape probabilities using first-flight integral transport theory and the balancing of fluxes across the surfaces bounding the various regions. The geometrical complexity of the problem is included in precomputed probabilities which depend only on the mean free path of the region.

  1. Effects of MHD instabilities on neutral beam current drive

    SciTech Connect

    Podestà, M.; Gorelenkova, M.; Darrow, D. S.; Fredrickson, E. D.; Gerhardt, S. P.; White, R. B.

    2015-04-17

    One of the primary tools foreseen for heating, current drive (CD) and q-profile control in future fusion reactors such as ITER and a Fusion Nuclear Science Facility is the neutral beam injection (NBI). However, fast ions from NBI may also provide the drive for energetic particle-driven instabilities (e.g. Alfvénic modes (AEs)), which in turn redistribute fast ions in both space and energy, thus hampering the control capabilities and overall efficiency of NB-driven current. Based on experiments on the NSTX tokamak (M. Ono et al 2000 Nucl. Fusion 40 557), the effects of AEs and other low-frequency magneto-hydrodynamic instabilities on NB-CD efficiency are investigated. When looking at the new fast ion transport model, which accounts for particle transport in phase space as required for resonant AE perturbations, is utilized to obtain consistent simulations of NB-CD through the tokamak transport code TRANSP. It is found that instabilities do indeed reduce the NB-driven current density over most of the plasma radius by up to ~50%. Moreover, the details of the current profile evolution are sensitive to the specific model used to mimic the interaction between NB ions and instabilities. Finally, implications for fast ion transport modeling in integrated tokamak simulations are briefly discussed.

  2. Effects of MHD instabilities on neutral beam current drive

    DOE PAGESBeta

    Podestà, M.; Gorelenkova, M.; Darrow, D. S.; Fredrickson, E. D.; Gerhardt, S. P.; White, R. B.

    2015-04-17

    One of the primary tools foreseen for heating, current drive (CD) and q-profile control in future fusion reactors such as ITER and a Fusion Nuclear Science Facility is the neutral beam injection (NBI). However, fast ions from NBI may also provide the drive for energetic particle-driven instabilities (e.g. Alfvénic modes (AEs)), which in turn redistribute fast ions in both space and energy, thus hampering the control capabilities and overall efficiency of NB-driven current. Based on experiments on the NSTX tokamak (M. Ono et al 2000 Nucl. Fusion 40 557), the effects of AEs and other low-frequency magneto-hydrodynamic instabilities on NB-CDmore » efficiency are investigated. When looking at the new fast ion transport model, which accounts for particle transport in phase space as required for resonant AE perturbations, is utilized to obtain consistent simulations of NB-CD through the tokamak transport code TRANSP. It is found that instabilities do indeed reduce the NB-driven current density over most of the plasma radius by up to ~50%. Moreover, the details of the current profile evolution are sensitive to the specific model used to mimic the interaction between NB ions and instabilities. Finally, implications for fast ion transport modeling in integrated tokamak simulations are briefly discussed.« less

  3. Highly Pathogenic Avian Influenza Virus Subtype H5N1 Escaping Neutralization: More than HA Variation

    PubMed Central

    Höper, Dirk; Kalthoff, Donata; Hoffmann, Bernd

    2012-01-01

    Influenza A viruses are one of the major threats in modern health care. Novel viruses arise due to antigenic drift and antigenic shift, leading to escape from the immune system and resulting in a serious problem for disease control. In order to investigate the escape process and to enable predictions of escape, we serially passaged influenza A H5N1 virus in vitro 100 times under immune pressure. The generated escape viruses were characterized phenotypically and in detail by full-genome deep sequencing. Mutations already found in natural isolates were detected, evidencing the in vivo relevance of the in vitro-induced amino acid substitutions. Additionally, several novel alterations were triggered. Altogether, the results imply that our in vitro system is suitable to study influenza A virus evolution and that it might even be possible to predict antigenic changes of influenza A viruses circulating in vaccinated populations. PMID:22090121

  4. Temporal analysis of HIV envelope sequence evolution and antibody escape in a subtype A-infected individual with a broad neutralizing antibody response

    PubMed Central

    Bosch, Katherine A.; Rainwater, Stephanie; Jaoko, Walter; Overbaugh, Julie

    2010-01-01

    The origin of broadly neutralizing HIV-specific antibodies and their relation to HIV evolution are not well defined. Here we examined virus evolution and neutralizing antibody escape in a subtype A infected individual with a broad, cross subtype, antibody response. The majority of envelope variants isolated over the first ~ 5 years post-infection were poorly neutralized by contemporaneous plasma that neutralized variants from earlier in infection, consistent with a dynamic process of escape. The majority of variants could be neutralized by later plasma, suggesting these evolving variants may have contributed to the elicitation of new antibody responses. However, some variants from later in infection were recognized by plasma from earlier in infection, including one notably neutralization-sensitive variant that was sensitive due to a proline at position 199 in V2. These studies suggest a complex pattern of virus evolution in this individual with a broad NAb response, including persistence of neutralization-sensitive viruses. PMID:20034648

  5. HIV-1 clade C escapes broadly neutralizing autologous antibodies with N332 glycan specificity by distinct mechanisms.

    PubMed

    Deshpande, Suprit; Patil, Shilpa; Kumar, Rajesh; Hermanus, Tandile; Murugavel, Kailapuri G; Srikrishnan, Aylur K; Solomon, Suniti; Morris, Lynn; Bhattacharya, Jayanta

    2016-01-01

    The glycan supersite centered on N332 in the V3 base of the HIV-1 envelope (Env) is a target for broadly neutralizing antibodies (bnAbs) such as PGT121 and PGT128. In this study, we examined the basis of resistance of HIV-1 clade C Envs obtained from broadly cross neutralizing (BCN) plasma of an Indian donor with N332 specificity. Pseudotyped viruses expressing autologous envs were found to be resistant to autologous BCN plasma as well as to PGT121 and PGT128 mAbs despite the majority of Envs containing an intact N332 residue. While resistance of one of the Envs to neutralization by autologous plasma antibodies with shorter V1 loop length was found to be correlated with a N332S mutation, resistance to neutralization of rest of the Envs was found to be associated with longer V1 loop length and acquisition of protective N-glycans. In summary, we show evidence of escape of circulating HIV-1 clade C in an individual from autologous BCN antibodies by three distinct mechanisms. PMID:27576440

  6. Calculation of low-Z impurity pellet induced fluxes of charge exchange neutral particles escaping from magnetically confined toroidal plasmas.

    PubMed

    Goncharov, P R; Ozaki, T; Sudo, S; Tamura, N; Tolstikhina, I Yu; Sergeev, V Yu

    2008-10-01

    Measurements of energy- and time-resolved neutral hydrogen and helium fluxes from an impurity pellet ablation cloud, referred to as pellet charge exchange or PCX experiments, can be used to study local fast ion energy distributions in fusion plasmas. The estimation of the local distribution function f(i)(E) of fast ions entering the cloud requires knowledge of both the fraction F(0)(E) of incident ions exiting the cloud as neutral atoms and the attenuation factor A(E,rho) describing the loss of fast atoms in the plasma. Determination of A(E,rho), in turn, requires the total stopping cross section sigma(loss) of neutral atoms in the plasma and the Jacobian reflecting the measurement geometry and the magnetic surface shape. The obtained functions F(0)(E) and A(E,rho) enter multiplicatively into the probability density for escaping neutral particle kinetic energy. A general calculation scheme has been developed and realized as a FORTRAN code, which is to be applied for the calculation of f(i)(E) from PCX experimental results obtained with low-Z impurity pellets. PMID:19044625

  7. Europa's atmospheric neutral escape: Importance of symmetrical O2 charge exchange

    NASA Astrophysics Data System (ADS)

    Dols, Vincent J.; Bagenal, Fran; Cassidy, Timothy A.; Crary, Frank J.; Delamere, Peter A.

    2016-01-01

    We model the interaction of the jovian magnetospheric plasma with the atmosphere of Europa using a multi-species chemistry model where the atmospheric distributions of H2 and O2 are prescribed. The plasma flow is idealized as an incompressible flow around a conducting obstacle. We compute changes in plasma composition resulting from this interaction as well as the reaction rates integrated over the simulation domain for several upstream plasma conditions (ion density, ion temperature and flow velocity). We show that for all cases, the main atmospheric loss process is a cascade of symmetrical charge exchanges on O2, which results in the ejection of neutrals. The production rate of ejected neutrals is about an order of magnitude larger than the production of ions. This conclusion is relevant to future missions to Europa that aim to detect fast neutrals. The neutral ejection resulting from this charge exchange creates an oxygen cloud around the orbit of the moon that is very extended radially but also very tenuous, and has not yet been directly detected.

  8. The Lyman Alpha Reference Sample. V. The Impact of Neutral ISM Kinematics and Geometry on Lyα Escape

    NASA Astrophysics Data System (ADS)

    Rivera-Thorsen, Thøger E.; Hayes, Matthew; Östlin, Göran; Duval, Florent; Orlitová, Ivana; Verhamme, Anne; Mas-Hesse, J. Miguel; Schaerer, Daniel; Cannon, John M.; Otí-Floranes, Héctor; Sandberg, Andreas; Guaita, Lucia; Adamo, Angela; Atek, Hakim; Herenz, E. Christian; Kunth, Daniel; Laursen, Peter; Melinder, Jens

    2015-05-01

    We present high-resolution far-UV spectroscopy of the 14 galaxies of the Lyα Reference Sample; a sample of strongly star-forming galaxies at low redshifts (0.028 < z < 0.18). We compare the derived properties to global properties derived from multi-band imaging and 21 cm H i interferometry and single-dish observations, as well as archival optical SDSS spectra. Besides the Lyα line, the spectra contain a number of metal absorption features allowing us to probe the kinematics of the neutral ISM and evaluate the optical depth and and covering fraction of the neutral medium as a function of line of sight velocity. Furthermore, we show how this, in combination with the precise determination of systemic velocity and good Lyα spectra, can be used to distinguish a model in which separate clumps together fully cover the background source, from the “picket fence” model named by Heckman et al. We find that no one single effect dominates in governing Lyα radiative transfer and escape. Lyα escape in our sample coincides with a maximum velocity-binned covering fraction of ≲0.9 and bulk outflow velocities of ≳50 km s-1, although a number of galaxies show these characteristics and yet little or no Lyα escape. We find that Lyα peak velocities, where available, are not consistent with a strong backscattered component, but rather with a simpler model of an intrinsic emission line overlaid by a blueshifted absorption profile from the outflowing wind. Finally, we find a strong anticorrelation between Hα equivalent width and maximum velocity-binned covering factor, and propose a heuristic explanatory model. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs GO 11522, GO 11727, GO 12027, and GO 12583.

  9. Transmission and accumulation of CTL escape variants drive negative associations between HIV polymorphisms and HLA.

    PubMed

    Leslie, Alasdair; Kavanagh, Daniel; Honeyborne, Isobella; Pfafferott, Katja; Edwards, Charles; Pillay, Tilly; Hilton, Louise; Thobakgale, Christina; Ramduth, Danni; Draenert, Rika; Le Gall, Sylvie; Luzzi, Graz; Edwards, Anne; Brander, Christian; Sewell, Andrew K; Moore, Sarah; Mullins, James; Moore, Corey; Mallal, Simon; Bhardwaj, Nina; Yusim, Karina; Phillips, Rodney; Klenerman, Paul; Korber, Bette; Kiepiela, Photini; Walker, Bruce; Goulder, Philip

    2005-03-21

    Human immunodeficiency virus (HIV)-1 amino acid sequence polymorphisms associated with expression of specific human histocompatibility leukocyte antigen (HLA) class I alleles suggest sites of cytotoxic T lymphocyte (CTL)-mediated selection pressure and immune escape. The associations most frequently observed are between expression of an HLA class I molecule and variation from the consensus sequence. However, a substantial number of sites have been identified in which particular HLA class I allele expression is associated with preservation of the consensus sequence. The mechanism behind this is so far unexplained. The current studies, focusing on two examples of "negatively associated" or apparently preserved epitopes, suggest an explanation for this phenomenon: negative associations can arise as a result of positive selection of an escape mutation, which is stable on transmission and therefore accumulates in the population to the point at which it defines the consensus sequence. Such negative associations may only be in evidence transiently, because the statistical power to detect them diminishes as the mutations accumulate. If an escape variant reaches fixation in the population, the epitope will be lost as a potential target to the immune system. These data help to explain how HIV is evolving at a population level. Understanding the direction of HIV evolution has important implications for vaccine development. PMID:15781581

  10. Off-axis Neutral Beam Current Drive for Advanced Scenario Development in DIII-D

    SciTech Connect

    Murakami, M; Park, J; Petty, C; Luce, T; Heidbrink, W; Osborne, T; Wade, M; Austin, M; Brooks, N; Budny, R; Challis, C; DeBoo, J; deGrassie, J; Ferron, J; Gohil, P; Hobirk, J; Holcomb, C; Hollmann, E; Hong, R; Hyatt, A; Lohr, J; Lanctot, M; Makowski, M; McCune, D; Politzer, P; Prater, R; John, H S; Suzuki, T; West, W; Unterberg, E; Van Zeeland, M; Yu, J

    2008-10-13

    Modification of the two existing DIII-D neutral beam lines is proposed to allow vertical steering to provide off-axis neutral beam current drive (NBCD) as far off-axis as half the plasma radius. New calculations indicate very good current drive with good localization off-axis as long as the toroidal magnetic field, B{sub T}, and the plasma current, I{sub p}, are in the same direction (for a beam steered downward). The effects of helicity can be large: e.g., ITER off-axis NBCD can be increased by more than 20% if the B{sub T} direction is reversed. This prediction has been tested by an off-axis NBCD experiment using reduced size plasmas that are vertically shifted with the existing NBI on DIII-D. The existence of off-axis NBCD is evident in sawtooth and internal inductance behavior. By shifting the plasma upward or downward, or by changing the sign of the toroidal field, measured off-axis NBCD profiles, determined from MSE data, are consistent with predicted differences (40%-45%) arising from the NBI orientation with respect to the magnetic field lines. Modification of the DIII-D NB system will strongly support scenario development for ITER and future tokamaks as well as providing flexible scientific tools for understanding transport, energetic particles and heating and current drive.

  11. Identifying possible sites for antibody neutralization escape: Implications for unique functional properties of the C-terminal tail of Human Immunodeficiency Virus Type 1 gp41.

    PubMed

    Lu, Zhifeng; Huang, Yushen; Tan, Yue; Yu, Yang; Wang, Junyi; Chen, Ying-Hua

    2016-07-01

    A previous amino acid sequence analyses from our laboratory reported nine potential sites in gp41 glycoprotein of HIV-1 that may contribute to virus escape from antibody neutralization. Besides four sites found outside the membrane of HIV-1 virus, five located in the C-terminal tail of gp41 specifically in the lentivirus lytic peptides motifs (LLPs). To further study the bioinformatical results, the virus infectivity assay and the standard neutralization assay were conducted on conservatively mutated virus. Two sites in the LLP3 domain stood out with the ability to alter the resistance of HIV-1 virus to certain broadly neutralizing antibodies (bNAbs). While the glycoprotein incorporation on the viral membrane and the interaction of the LLP3 domain with the lipid membrane remained unaltered, the increase in neutralization resistance of the mutant virus was associated with the changes on Env conformation. Our findings demonstrate different sensibility of bNAbs to mutations in the C-terminal tail and indicate an unrecognized potential role for even minor sequence variation in the C-terminal tail in modulating the antigenicity of the ectodomain of HIV-1 envelope glycoprotein complex. PMID:27157128

  12. Continuous viral escape and selection by autologous neutralizing antibodies in drug-naive human immunodeficiency virus controllers.

    PubMed

    Mahalanabis, Madhumita; Jayaraman, Pushpa; Miura, Toshiyuki; Pereyra, Florencia; Chester, E Michael; Richardson, Barbra; Walker, Bruce; Haigwood, Nancy L

    2009-01-01

    We assessed differences in the character and specificity of autologous neutralizing antibodies (ANAbs) against individual viral variants of the quasispecies in a cohort of drug-naïve subjects with long-term controlled human immunodeficiency virus type 1 (HIV-1) infection and moderate levels of broad heterologous neutralizing antibodies (HNAb). Functional plasma virus showed continuous env evolution despite a short time frame and low levels of viral replication. Neutralization-sensitive variants dominated in subjects with intermittent viral blips, while neutralization-resistant variants predominated in elite controllers. By sequence analysis of this panel of autologous variants with various sensitivities to neutralization, we identified more than 30 residues in envelope proteins (Env) associated with resistance or sensitivity to ANAbs. The appearance of new sensitive variants is consistent with a model of continuous selection and turnover. Strong ANAb responses directed against autologous Env variants are present in long-term chronically infected individuals, suggesting a role for these responses in contributing to the durable control of HIV replication. PMID:18987151

  13. Continuous Viral Escape and Selection by Autologous Neutralizing Antibodies in Drug-Naïve Human Immunodeficiency Virus Controllers▿

    PubMed Central

    Mahalanabis, Madhumita; Jayaraman, Pushpa; Miura, Toshiyuki; Pereyra, Florencia; Chester, E. Michael; Richardson, Barbra; Walker, Bruce; Haigwood, Nancy L.

    2009-01-01

    We assessed differences in the character and specificity of autologous neutralizing antibodies (ANAbs) against individual viral variants of the quasispecies in a cohort of drug-naïve subjects with long-term controlled human immunodeficiency virus type 1 (HIV-1) infection and moderate levels of broad heterologous neutralizing antibodies (HNAb). Functional plasma virus showed continuous env evolution despite a short time frame and low levels of viral replication. Neutralization-sensitive variants dominated in subjects with intermittent viral blips, while neutralization-resistant variants predominated in elite controllers. By sequence analysis of this panel of autologous variants with various sensitivities to neutralization, we identified more than 30 residues in envelope proteins (Env) associated with resistance or sensitivity to ANAbs. The appearance of new sensitive variants is consistent with a model of continuous selection and turnover. Strong ANAb responses directed against autologous Env variants are present in long-term chronically infected individuals, suggesting a role for these responses in contributing to the durable control of HIV replication. PMID:18987151

  14. Subgroup J Avian Leukosis Virus Neutralizing Antibody Escape Variants Contribute to Viral Persistence in Meat-Type Chickens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We have previously demonstrated a high incidence of chickens with persistent viremia even in the presence of neutralizing antibodies (NAb) against the inoculated parental virus (V+A+) in commercial meat-type chickens inoculated at hatch with Subgroup J avian leukosis virus (ALV J) field isolates. I...

  15. Fast wave current drive in neutral beam heated plasmas on DIII-D

    SciTech Connect

    Petty, C.C.; Forest, C.B.; Pinsker, R.I.

    1997-04-01

    The physics of non-inductive current drive and current profile control using the fast magnetosonic wave has been demonstrated on the DIII-D tokamak. In non-sawtoothing discharges formed by neutral beam injection (NBI), the radial profile of the fast wave current drive (FWCD) was determined by the response of the loop voltage profile to co, counter, and symmetric antenna phasings, and was found to be in good agreement with theoretical models. The application of counter FWCD increased the magnetic shear reversal of the plasma and delayed the onset of sawteeth, compared to co FWCD. The partial absorption of fast waves by energetic beam ions at high harmonics of the ion cyclotron frequency was also evident from a build up of fast particle pressure near the magnetic axis and a correlated increase in the neutron rate. The anomalous fast particle pressure and neutron rate increased with increasing NBI power and peaked when a harmonic of the deuterium cyclotron frequency passed through the center of the plasma. The experimental FWCD efficiency was highest at 2 T where the interaction between the fast waves and the beam ions was weakest; as the magnetic field strength was lowered, the FWCD efficiency decreased to approximately half of the maximum theoretical value.

  16. Current drive with fast waves, electron cyclotron waves, and neutral injection in the DIII-D tokamak

    SciTech Connect

    Prater, R.; Petty, C.C.; Pinsker, R.I.; Chiu, S.C.; deGrassie, J.S.; Harvey, R.W.; Ikel, H.; Lin-Liu, Y.R.; Luce, T.C. ); James, R.A. ); Porkolab, M. ); Baity, F.W.; Goulding, R.H.; Hoffmann, D.J. ); Kawash

    1992-09-01

    Current drive experiments have been performed on the DIII-D tokamak using fast waves, electron cyclotron waves, and neutral injection. Fast wave experiments were performed using a 4-strap antenna with 1 MW of power at 60 MHz. These experiments showed effective heating of electrons, with a global heating efficiency equivalent to that of neutral injection even when the single pass damping was calculated to be as small as 5%. The damping was probably due to the effect of multiple passes of the wave through the plasma. Fast wave current drive experiments were performed with a toroidally directional phasing of the antenna straps. Currents driven by fast wave current drive (FWCD) in the direction of the main plasma current of up to 100 kA were found, not including a calculated 40 kA of bootstrap current. Experiments with FWCD in the counter current direction showed little current drive. In both cases, changes in the sawtooth behavior and the internal inductance qualitatively support the measurement of FWCD. Experiments on electron cyclotron current drive have shown that 100 kA of current can be driven by 1 MW of power at 60 GHz. Calculations with a Fokker-Planck code show that electron cyclotron current drive (ECCD) can be well predicted when the effects of electron trapping and of the residual electric field are included. Experiments on driving current with neutral injection showed that effective current drive could be obtained and discharges with full current drive were demonstrated. Interestingly, all of these methods of current drive had about the same efficiency, 0.015 {times} 10{sup 20} MA/MW/m{sup 2}.

  17. Viral variants that initiate and drive maturation of V1V2-directed HIV-1 broadly neutralizing antibodies

    PubMed Central

    Bhiman, Jinal N.; Anthony, Colin; Doria-Rose, Nicole A.; Karimanzira, Owen; Schramm, Chaim A.; Khoza, Thandeka; Kitchin, Dale; Botha, Gordon; Gorman, Jason; Garrett, Nigel J.; Abdool Karim, Salim S.; Shapiro, Lawrence; Williamson, Carolyn; Kwong, Peter D.; Mascola, John R.; Morris, Lynn; Moore, Penny L.

    2015-01-01

    The elicitation of broadly neutralizing antibodies (bNAbs) is likely to be essential for a preventative HIV-1 vaccine, but this has not yet been achieved by immunization. In contrast some HIV-1-infected individuals naturally mount bNAb responses during chronic infection, suggesting that years of maturation are required for breadth1-6. Recent studies have shown that viral diversification precedes the emergence of bNAbs but the significance of this observation is unknown7,8. Here, we delineate the key viral events that drove neutralization breadth within the CAP256-VRC26 family of 33 monoclonal antibodies (mAbs) isolated from a superinfected individual. First, we identified minority viral variants that were distinct from both transmitted/founder (T/F) viruses and efficiently engaged the bNAb precursor, termed bNAb-initiating envelopes. Second, deep sequencing revealed a pool of diverse epitope variants (immunotypes) that were preferentially neutralized by broader members of the antibody lineage. In contrast, a “dead-end” antibody sublineage unable to neutralize these immunotypes showed limited evolution and failed to develop breadth. Thus, early viral escape at key antibody-virus contact sites selects for sublineages that can tolerate these changes, providing a new mechanism for the generation of neutralization breadth within a developing antibody lineage. PMID:26457756

  18. Addition of a Single gp120 Glycan Confers Increased Binding to Dendritic Cell-Specific ICAM-3-Grabbing Nonintegrin and Neutralization Escape to Human Immunodeficiency Virus Type 1

    PubMed Central

    Lue, James; Hsu, Mayla; Yang, David; Marx, Preston; Chen, Zhiwei; Cheng-Mayer, Cecilia

    2002-01-01

    The potential role of dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) binding in human immunodeficiency virus transmission across the mucosal barrier was investigated by assessing the ability of simian-human immunodeficiency chimeric viruses (SHIVs) showing varying degrees of mucosal transmissibility to bind the DC-SIGN expressed on the surface of transfected cells. We found that gp120 of the highly transmissible, pathogenic CCR5-tropic SHIVSF162P3 bound human and rhesus DC-SIGN with an efficiency threefold or greater than that of gp120 of the nonpathogenic, poorly transmissible parental SHIVSF162, and this increase in binding to the DC-SIGN of the SHIVSF162P3 envelope gp120 translated into an enhancement of T-cell infection in trans. The presence of an additional glycan at the N-terminal base of the V2 loop of SHIVSF162P3 gp120 compared to that of the parental virus was shown to be responsible for the increase in binding to DC-SIGN. Interestingly, this glycan also conferred escape from autologous neutralization, raising the possibility that the modification occurred as a result of immune selection. Our data suggest that more-efficient binding of envelope gp120 to DC-SIGN could be relevant to the enhanced mucosal transmissibility of SHIVSF162P3 compared to that of parental SHIVSF162. PMID:12239306

  19. Dust escape from Io

    NASA Astrophysics Data System (ADS)

    Flandes, Alberto

    2004-08-01

    The Dust ballerina skirt is a set of well defined streams composed of nanometric sized dust particles that escape from the Jovian system and may be accelerated up to >=200 km/s. The source of this dust is Jupiter's moon Io, the most volcanically active body in the Solar system. The escape of dust grains from Jupiter requires first the escape of these grains from Io. This work is basically devoted to explain this escape given that the driving of dust particles to great heights and later injection into the ionosphere of Io may give the particles an equilibrium potential that allow the magnetic field to accelerate them away from Io. The grain sizes obtained through this study match very well to the values required for the particles to escape from the Jovian system.

  20. Resistance of a human serum-selected human immunodeficiency virus type 1 escape mutant to neutralization by CD4 binding site monoclonal antibodies is conferred by a single amino acid change in gp120.

    PubMed Central

    McKeating, J A; Bennett, J; Zolla-Pazner, S; Schutten, M; Ashelford, S; Brown, A L; Balfe, P

    1993-01-01

    We have selected an HXB2 variant which can replicate in the presence of a neutralizing human serum. Sequencing of the gp120 region of the env gene from the variant and parental viruses identified a single amino acid substitution in the third conserved region of gp120 at residue 375 (AGT-->AAT, Ser-->Asn; designated 375 S/N). The escape mutant was found to be resistant to neutralization by soluble CD4 (sCD4) and four monoclonal antibodies (MAbs), 39.13g, 1.5e, G13, and 448, binding to epitopes overlapping that of the CD4 binding site (CD4 b.s.). Introduction of the 375 S/N mutation into HXB2 by site-directed mutagenesis confirmed that this mutation is responsible for the neutralization-resistant phenotype. Both sCD4 and three of the CD4 b.s. MAbs (39.13g, 1.5e, and G13) demonstrated reduced binding to the native 375 S/N mutant gp120. The ability to select for an escape variant resistant to multiple independent CD4 b.s. MAbs by a human serum confirms the reports that antibodies to the discontinuous CD4 b.s. are a major component of the group-specific neutralizing activity in human sera. PMID:7688820

  1. EMERGENCE OF SUBGROUP J AVIAN LEUKOSIS VIRUS NEUTRALIZING ANTIBODY ESCAPE VARIANTS IN MEAT-TYPE CHICKENS INFECTED WITH VIRUS AT HATCH

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Infection of meat-type chickens at hatch with field isolates of Subgroup J avian leukosis virus (ALV J) results in a high incidence of chickens with persistent viremia even in the presence of neutralizing antibodies (NAb) against the inoculated parental virus (V+A+). The purpose of this study was t...

  2. MAVEN Measurements of the Ion Escape Rate from Mars

    NASA Astrophysics Data System (ADS)

    Brain, Dave; Dong, Yaxue; Fortier, Kier; Fang, Xiaohua; McFadden, James; Halekas, Jasper; Connerney, Jack; Eparvier, Frank; Dong, Chuanfei; Bougher, Stephen; Ma, Yingjuan; Modolo, Ronan; Lillis, Rob; Luhmann, Janet; Curry, Shannon; Seki, Kanako; Jakosky, Bruce

    2015-04-01

    The loss of atmospheric particles (neutral atoms, neutral molecules, ions) to space is thought to have played a role in the evolution of Martian climate over the past ~4 billion years. Due to the lack of a global magnetic field on Mars, the solar wind has direct access to the upper layers of the Martian atmosphere, and can drive non-thermal escape of charged particles (ions) from the atmosphere. Two spacecraft (Phobos 2 and Mars Express) have previously measured escaping ions at Mars. The recently arrived MAVEN spacecraft is equipped with instruments to measure escaping ions with high time cadence and high energy and mass resolution, as well as instruments to provide contextual information about what controls the variation in escape rates. We report on the total escape rate of heavy planetary ions from the Martian atmosphere measured by MAVEN. Heavy ions are identified in data from the SupraThermal And Thermal Ion Composition (STATIC) instrument. Rudimentary estimates of ion escape rate are obtained by summing the measured ion fluxes over a surface downstream from Mars with respect to the solar wind flow. This estimate can then be refined to account for the limited field of view of the instrument (investigation of measured particle distributions) and the limited spatial coverage of the spacecraft orbit trajectory. Variability in measured escape rates can also be grouped according to upstream conditions and the orientation of Mars (and its crustal magnetic fields) with respect to the solar wind. Important upstream drivers include the solar Extreme Ultraviolet (EUV) flux, solar wind pressure, and the interplanetary magnetic field strength and direction. These drivers are measured directly by MAVEN's EUV, SWIA, and MAG instruments. We will provide an initial estimate of ion escape rates based on the first several months of MAVEN data. We will then report on progress to refine these estimates to correct for instrument field of view and spacecraft coverage effects, as

  3. Mechanisms of Ionospheric Mass Escape

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Khazanov, G. V.

    2010-01-01

    The dependence of ionospheric O+ escape flux on electromagnetic energy flux and electron precipitation into the ionosphere is derived for a hypothetical ambipolar pick-up process, powered the relative motion of plasmas and neutral upper atmosphere, and by electron precipitation, at heights where the ions are magnetized but influenced by photo-ionization, collisions with gas atoms, ambipolar and centrifugal acceleration. Ion pick-up by the convection electric field produces "ring-beam" or toroidal velocity distributions, as inferred from direct plasma measurements, from observations of the associated waves, and from the spectra of incoherent radar echoes. Ring-beams are unstable to plasma wave growth, resulting in rapid relaxation via transverse velocity diffusion, into transversely accelerated ion populations. Ion escape is substantially facilitated by the ambipolar potential, but is only weakly affected by centrifugal acceleration. If, as cited simulations suggest, ion ring beams relax into non-thermal velocity distributions with characteristic speed equal to the local ion-neutral flow speed, a generalized "Jeans escape" calculation shows that the escape flux of ionospheric O+ increases with Poynting flux and with precipitating electron density in rough agreement with observations.

  4. Observational Constraints on a Pluto Torus of Circumsolar Neutral Gas

    NASA Astrophysics Data System (ADS)

    Hill, M. E.; Kollmann, P.; McNutt, R. L., Jr.; Smith, H. T.; Bagenal, F.; Brown, L. E.; Elliott, H. A.; Haggerty, D. K.; Horanyi, M.; Krimigis, S. M.; Kusterer, M. B.; Lisse, C. M.; McComas, D. J.; Piquette, M. R.; Sidrow, E. J.; Strobel, D. F.; Szalay, J.; Vandegriff, J. D.; Zirnstein, E.; Ennico Smith, K.; Olkin, C.; Weaver, H. A., Jr.; Young, L. A.; Stern, S. A.

    2015-12-01

    We present the concept of a neutral gas torus surrounding the Sun, aligned with Pluto's orbit, and place observational constraints based primarily on comparison of New Horizons (NH) measurements with a 3-D Monte Carlo model adapted from analogous satellite tori surrounding Saturn and Jupiter. Such a torus, or perhaps partial torus, should result from neutral N2 escaping from Pluto's exosphere. Unlike other more massive planets closer to the Sun, neutrals escape Pluto readily owing, e.g., to the high thermal speed relative to the escape velocity. Importantly, escaped neutrals have a long lifetime due to the great distance from the Sun, ~100 years for photoionization of N2 and ~180 years for photoionization of N, which results from disassociated N2. Despite the lengthy 248-year orbit, these long e-folding lifetimes may allow an enhanced neutral population to form an extended gas cloud that modifies the N2 spatial profile near Pluto. These neutrals are not directly observable by NH but once ionized N2+ or N+ are picked up by the solar wind, reaching ~50 keV, making these pickup ions (PUIs) detectable by NH's Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument. PEPSSI observations analyzed to date may constrain the N2 density; the remaining ~95% of the encounter data, scheduled for downlink in August along with similarly anticipated data from the Solar Wind Around Pluto (SWAP) experiment, should help determine the Pluto outgassing rates. Measurements from SWAP include the solar wind speed, a quantity that greatly enhances PUI studies by enabling us to directly account for the PUI distribution's sensitive dependence on plasma speed. Note that anomalous cosmic ray Si observed at Voyager is overabundant by a factor of ~3000 relative to interstellar composition. This might be related to "outer source" PUIs, but the fact that N2 and Si are indistinguishable in many instruments could mean that N2 is actually driving this apparent Si discrepancy.

  5. The great escape

    PubMed Central

    Sin, Ho-Su; Namekawa, Satoshi H

    2013-01-01

    Epigenetic mechanisms precisely regulate sex chromosome inactivation as well as genes that escape the silencing process. In male germ cells, DNA damage response factor RNF8 establishes active epigenetic modifications on the silent sex chromosomes during meiosis, and activates escape genes during a state of sex chromosome-wide silencing in postmeiotic spermatids. During the course of evolution, the gene content of escape genes in postmeiotic spermatids recently diverged on the sex chromosomes. This evolutionary feature mirrors the epigenetic processes of sex chromosomes in germ cells. In this article, we describe how epigenetic processes have helped to shape the evolution of sex chromosome-linked genes. Furthermore, we compare features of escape genes on sex chromosomes in male germ cells to escape genes located on the single X chromosome silenced during X-inactivation in females, clarifying the distinct evolutionary implications between male and female escape genes. PMID:23880818

  6. Crew Escape Certification Test

    NASA Technical Reports Server (NTRS)

    1988-01-01

    This video tape shows the Shuttle hatch jettison test at Rockwell facilities. The video also shows a Shuttle escape pole deployment test from a NASA aircraft, and an emergency egress test performed by a volunteer Navy parachutist using the pole and a parachute escape system.

  7. MAVEN measurements of photochemical escape of oxygen from the Martian atmosphere

    NASA Astrophysics Data System (ADS)

    Lillis, R. J.; Deighan, J.; Fox, J. L.; Bougher, S. W.; Cravens, T. E.; Lee, Y.; Mahaffy, P. R.; Benna, M.; Elrod, M. K.; Andersson, L.; McFadden, J.

    2015-10-01

    One of the primary goals of the Mars Atmosphere and Volatile Evolution Mission (MAVEN) mission is to characterize rates of atmospheric escape at the present epoch and relate those escape rates to solar drivers [1]. One of the major escape processes is known as photochemical escape, which is broadly defined as a process by which a) an exothermic reaction in the atmosphere/ionosphere results in an upward-traveling neutral particle whose velocity exceeds planetary escape velocity and b) the particle is not prevented from escaping through any subsequent collisions[2].At Mars, photochemical escape of oxygen is expected to be a significant channel for atmospheric escape, particularly in the early solar system when extreme ultraviolet (EUV) fluxes were much higher[3]. Thus characterizing this escape process is central to understanding the role escape to space has played in Mars' climate evolution.

  8. Structured Observations Reveal Slow HIV-1 CTL Escape

    PubMed Central

    Roberts, Hannah E.; Hurst, Jacob; Robinson, Nicola; Brown, Helen; Flanagan, Peter; Vass, Laura; Fidler, Sarah; Weber, Jonathan; Babiker, Abdel; Phillips, Rodney E.; McLean, Angela R.; Frater, John

    2015-01-01

    The existence of viral variants that escape from the selection pressures imposed by cytotoxic T-lymphocytes (CTLs) in HIV-1 infection is well documented, but it is unclear when they arise, with reported measures of the time to escape in individuals ranging from days to years. A study of participants enrolled in the SPARTAC (Short Pulse Anti-Retroviral Therapy at HIV Seroconversion) clinical trial allowed direct observation of the evolution of CTL escape variants in 125 adults with primary HIV-1 infection observed for up to three years. Patient HLA-type, longitudinal CD8+ T-cell responses measured by IFN-γ ELISpot and longitudinal HIV-1 gag, pol, and nef sequence data were used to study the timing and prevalence of CTL escape in the participants whilst untreated. Results showed that sequence variation within CTL epitopes at the first time point (within six months of the estimated date of seroconversion) was consistent with most mutations being transmitted in the infecting viral strain rather than with escape arising within the first few weeks of infection. Escape arose throughout the first three years of infection, but slowly and steadily. Approximately one third of patients did not drive any new escape in an HLA-restricted epitope in just under two years. Patients driving several escape mutations during these two years were rare and the median and modal numbers of new escape events in each patient were one and zero respectively. Survival analysis of time to escape found that possession of a protective HLA type significantly reduced time to first escape in a patient (p = 0.01), and epitopes escaped faster in the face of a measurable CD8+ ELISpot response (p = 0.001). However, even in an HLA matched host who mounted a measurable, specific, CD8+ response the average time before the targeted epitope evolved an escape mutation was longer than two years. PMID:25642847

  9. THERMALLY DRIVEN ATMOSPHERIC ESCAPE

    SciTech Connect

    Johnson, Robert E.

    2010-06-20

    Accurately determining the escape rate from a planet's atmosphere is critical for determining its evolution. A large amount of Cassini data is now available for Titan's upper atmosphere and a wealth of data is expected within the next decade on escape from Pluto, Mars, and extra-solar planets. Escape can be driven by upward thermal conduction of energy deposited well below the exobase, as well as by nonthermal processes produced by energy deposited in the exobase region. Recent applications of a model for escape driven by upward thermal conduction, called the slow hydrodynamic escape model, have resulted in surprisingly large loss rates for the atmosphere of Titan, Saturn's largest moon. Based on a molecular kinetic simulation of the exobase region, these rates appear to be orders of magnitude too large. Therefore, the slow hydrodynamic model is evaluated here. It is shown that such a model cannot give a reliable description of the atmospheric temperature profile unless it is coupled to a molecular kinetic description of the exobase region. Therefore, the present escape rates for Titan and Pluto must be re-evaluated using the atmospheric model described here.

  10. The Aeronomy of Mars: Characterization by MAVEN of the Upper Atmosphere Reservoir That Regulates Volatile Escape

    NASA Astrophysics Data System (ADS)

    Bougher, S. W.; Cravens, T. E.; Grebowsky, J.; Luhmann, J.

    2015-12-01

    The Mars thermosphere-ionosphere-exosphere (TIE) system constitutes the atmospheric reservoir (i.e. available cold and hot planetary neutral and thermal ion species) that regulates present day escape processes from the planet. The characterization of this TIE system, including its spatial and temporal (e.g., solar cycle, seasonal, diurnal, episodic) variability is needed to determine present day escape rates. Without knowledge of the physics and chemistry creating this TIE region and driving its variations, it is not possible to constrain either the short term or long term histories of atmosphere escape from Mars. MAVEN (Mars Atmosphere and Volatile Evolution Mission) will make both in-situ and remote measurements of the state variables of the Martian TIE system. A full characterization of the thermosphere (˜100-250 km) and ionosphere (˜100-400 km) structure (and its variability) will be conducted with the collection of spacecraft in-situ measurements that systematically span most local times and latitudes, over a regular sampling of Mars seasons, and throughout the bottom half of the solar cycle. Such sampling will far surpass that available from existing spacecraft and ground-based datasets. In addition, remote measurements will provide a systematic mapping of the composition and structure of Mars neutral upper atmosphere and coronae (e.g. H, C, N, O), as well as probe lower altitudes. Such a detailed characterization is a necessary first step toward answering MAVEN's three main science questions (see Jakosky et al. 2014, this issue). This information will be used to determine present day escape rates from Mars, and provide an estimate of integrated loss to space throughout Mars history.

  11. Escape behaviors in insects.

    PubMed

    Card, Gwyneth M

    2012-04-01

    Escape behaviors are, by necessity, fast and robust, making them excellent systems with which to study the neural basis of behavior. This is especially true in insects, which have comparatively tractable nervous systems and members who are amenable to manipulation with genetic tools. Recent technical developments in high-speed video reveal that, despite their short duration, insect escape behaviors are more complex than previously appreciated. For example, before initiating an escape jump, a fly performs sophisticated posture and stimulus-dependent preparatory leg movements that enable it to jump away from a looming threat. This newfound flexibility raises the question of how the nervous system generates a behavior that is both rapid and flexible. Recordings from the cricket nervous system suggest that synchrony between the activity of specific interneuron pairs may provide a rapid cue for the cricket to detect the direction of an approaching predator and thus which direction it should run. Technical advances make possible wireless recording from neurons while locusts escape from a looming threat, enabling, for the first time, a direct correlation between the activity of multiple neurons and the time-course of an insect escape behavior. PMID:22226514

  12. Escape and rescue model

    NASA Astrophysics Data System (ADS)

    Alvord, D.; Nelson, H. E.

    The Escape and Rescue model is a discrete-event simulation program written in Simscript. It was developed to simulate the emergency movement involved in escape and/or rescue of people from a Board and Care Home housing a group of persons with varying degrees of physical or mental disabilities along with a small live-in staff. It may, however, be used in a much more general setting. It can reasonably handle a building with up to 100 residents and 100 rooms.

  13. Natural selection and neutral evolution jointly drive population divergence between alpine and lowland ecotypes of the allopolyploid plant Anemone multifida (Ranunculaceae).

    PubMed

    McEwen, Jamie R; Vamosi, Jana C; Rogers, Sean M

    2013-01-01

    Population differentiation can be driven in large part by natural selection, but selectively neutral evolution can play a prominent role in shaping patters of population divergence. The decomposition of the evolutionary history of populations into the relative effects of natural selection and selectively neutral evolution enables an understanding of the causes of population divergence and adaptation. In this study, we examined heterogeneous genomic divergence between alpine and lowland ecotypes of the allopolyploid plant, Anemone multifida. Using peak height and dominant AFLP data, we quantified population differentiation at non-outlier (neutral) and outlier loci to determine the potential contribution of natural selection and selectively neutral evolution to population divergence. We found 13 candidate loci, corresponding to 2.7% of loci, with signatures of divergent natural selection between alpine and lowland populations and between alpine populations (Fst  = 0.074-0.445 at outlier loci), but neutral population differentiation was also evident between alpine populations (FST  = 0.041-0.095 at neutral loci). By examining population structure at both neutral and outlier loci, we determined that the combined effects of selection and neutral evolution are associated with the divergence of alpine populations, which may be linked to extreme abiotic conditions and isolation between alpine sites. The presence of outlier levels of genetic variation in structured populations underscores the importance of separately analyzing neutral and outlier loci to infer the relative role of divergent natural selection and neutral evolution in population divergence. PMID:23874801

  14. Natural Selection and Neutral Evolution Jointly Drive Population Divergence between Alpine and Lowland Ecotypes of the Allopolyploid Plant Anemone multifida (Ranunculaceae)

    PubMed Central

    McEwen, Jamie R.; Vamosi, Jana C.; Rogers, Sean M.

    2013-01-01

    Population differentiation can be driven in large part by natural selection, but selectively neutral evolution can play a prominent role in shaping patters of population divergence. The decomposition of the evolutionary history of populations into the relative effects of natural selection and selectively neutral evolution enables an understanding of the causes of population divergence and adaptation. In this study, we examined heterogeneous genomic divergence between alpine and lowland ecotypes of the allopolyploid plant, Anemone multifida. Using peak height and dominant AFLP data, we quantified population differentiation at non-outlier (neutral) and outlier loci to determine the potential contribution of natural selection and selectively neutral evolution to population divergence. We found 13 candidate loci, corresponding to 2.7% of loci, with signatures of divergent natural selection between alpine and lowland populations and between alpine populations (Fst  = 0.074–0.445 at outlier loci), but neutral population differentiation was also evident between alpine populations (FST  = 0.041–0.095 at neutral loci). By examining population structure at both neutral and outlier loci, we determined that the combined effects of selection and neutral evolution are associated with the divergence of alpine populations, which may be linked to extreme abiotic conditions and isolation between alpine sites. The presence of outlier levels of genetic variation in structured populations underscores the importance of separately analyzing neutral and outlier loci to infer the relative role of divergent natural selection and neutral evolution in population divergence. PMID:23874801

  15. MEMO: Mars Escape and Magnetic Orbiter

    NASA Astrophysics Data System (ADS)

    Chassefiere, E.; Langlais, B.; Leblanc, F.; Sotin, C.; Barabash, S.; Dehant, V.; Dougherty, M.; Lammer, H.; Mandea, M.; Vennerstrom, S.

    There are several reasons to believe that Mars could have become an Earth like planet rather than the present dry and cold planet. In particular, many elements suggest the presence of liquid water at the Martian surface during a relatively short period at an early stage of its history. Since liquid water may have been the birthplace for life on Earth, the fate of Martian water is one of the major key and yet unanswered question to be solved. Mars Escape and Magnetic Orbiter (MEMO) is a low periapsis orbiter of Mars devoted to the measurement of present escape and the characterization of the fossil magnetic field of Mars. The use of a low periapsis altitude orbit (120-150 km) is required to detect and quantify all populations of atoms and molecules involved in escape. It is also required to measure the magnetic field of Mars with an unprecedented spatial resolution that would allow getting a more precise timing of the dynamo and its disappearance. Achieving a full characterization of atmospheric escape, and extrapolating it back to the past requires: (i) to measure escape fluxes of neutral and ion species, and characterize the dynamics and chemistry of the regions of the atmosphere where escape occurs (thermosphere, ionosphere, exosphere), as well as their responses to solar activity, and (ii) to characterize the lateral variations of the magnetic field of lithospheric origin, and by extension, the timing of the Martian dynamo. Of particular interest is the extinction of the dynamo that is thought to have enhanced the atmospheric escape processes still operating today. The proposed low-periapsis orbiter will consist of the following elements: • An "Escape Package" to characterize by both in-situ and remote measurements the thermosphere, ionosphere, exosphere and solar wind interaction regions (from one hundred to several thousand km), including thermal, suprathermal 1 and energetic particles. • A "Magnetic Field Package", to characterize the magnetization of the

  16. Spacecraft Escape Capsule

    NASA Technical Reports Server (NTRS)

    Robertson, Edward A.; Charles, Dingell W.; Bufkin, Ann L.; Rodriggs, Liana M.; Peterson, Wayne; Cuthbert, Peter; Lee, David E.; Westhelle, Carlos

    2006-01-01

    A report discusses the Gumdrop capsule a conceptual spacecraft that would enable the crew to escape safely in the event of a major equipment failure at any time from launch through atmospheric re-entry. The scaleable Gumdrop capsule would comprise a command module (CM), a service module (SM), and a crew escape system (CES). The CM would contain a pressurized crew environment that would include avionic, life-support, thermal control, propulsive attitude control, and recovery systems. The SM would provide the primary propulsion and would also supply electrical power, life-support resources, and active thermal control to the CM. The CES would include a solid rocket motor, embedded within the SM, for pushing the CM away from the SM in the event of a critical thermal-protection-system failure or loss of control. The CM and SM would normally remain integrated with each other from launch through recovery, but could be separated using the CES, if necessary, to enable the safe recovery of the crew in the CM. The crew escape motor could be used, alternatively, as a redundant means of de-orbit propulsion for the CM in the event of a major system failure in the SM.

  17. Advanced Crew Escape Suit.

    PubMed

    1995-09-01

    Design of the S1032 Launch Entry Suit (LES) began following the Challenger loss and NASA's decision to incorporate a Shuttle crew escape system. The LES (see Figure 1) has successfully supported Shuttle missions since NASA's Return to Flight with STS-26 in September 1988. In 1990, engineers began developing the S1035 Advanced Crew Escape Suit (ACES) to serve as a replacement for the LES. The ACES was designed to be a simplified, lightweight, low-bulk pressure suit which aided self donning/doffing, provided improved comfort, and enhanced overall performance to reduce crew member stress and fatigue. Favorable crew member evaluations of a prototype led to full-scale development and qualification of the S1035 ACES between 1990 and 1992. Production of the S1035 ACES began in February 1993, with the first unit delivered to NASA in May 1994. The S1035 ACES first flew aboard STS-68 in August 1994 and will become the primary crew escape suit when the S1032 LES ends its service life in late 1995. The primary goal of the S1035 development program was to provide improved performance over that of the S1032 to minimize the stress and fatigue typically experienced by crew members. To achieve this, five fundamental design objectives were established, resulting in various material/configuration changes. PMID:11540717

  18. [Escape mutants of hepatitis B virus].

    PubMed

    Jaramillo, Carlos Mario; Navas, María-Cristina

    2015-04-01

    The hepatitis B virus (HBV) infection is a public health problem worldwide. Considering HBV morbidity and mortality and the economic consequences .of this infection, policies and strategies to control it have been implemented, especially in regions where HBV infection is endemic, with high rates of vertical and horizontal infection. One of these strategies is the development of the recombinant vaccine. A 92% of the countries in the world have implemented the vaccine with a global coverage of 69%. The escape variants of HBV correspond to isolates with mutations in the sequence coding for the "a" determinant; these mutations result in changes in the amino acid sequence of the surface antigen (HBsAg) that prevent neutralization of viral particles by antibodies generated in response to vaccination or infection. The escape variants can infect vaccinated individuals and have been identified in the population of countries with different epidemiological patterns. PMID:26065452

  19. Orbiter escape pole

    NASA Technical Reports Server (NTRS)

    Goodrich, Winston D. (Inventor); Wesselski, Clarence J. (Inventor); Pelischek, Timothy E. (Inventor); Becker, Bruce H. (Inventor); Kahn, Jon B. (Inventor); Grimaldi, Margaret E. (Inventor); McManamen, John P. (Inventor); Castro, Edgar O. (Inventor)

    1989-01-01

    A Shuttle type of aircraft (10) with an escape hatch (12) has an arcuately shaped pole housing (16) attachable to an interior wall and ceiling with its open end adjacent to the escape hatch. The pole housing 16 contains a telescopically arranged and arcuately shaped primary pole member (22) and extension pole member (23) which are guided by roller assemblies (30,35). The extension pole member (23) is slidable and extendable relative to the primary pole member (22). For actuation, a spring actuated system includes a spring (52) in the pole housing. A locking member (90) engages both pole members (22,23) through notch portions (85,86) in the pole members. The locking member selectively releases the extension pole member (23) and the primary pole member (22). An internal one-way clutch or anti-return mechanism prevents retraction of the extension pole member from an extended position. Shock absorbers (54)(150,152) are for absoring the energy of the springs. A manual backup deployment system is provided which includes a canted ring (104) biased by a spring member (108). A lever member (100) with a slot and pin connection (102) permits the mechanical manipulation of the canted ring to move the primary pole member. The ring (104) also prevents retraction of the main pole. The crew escape mechanism includes a magazine (60) and a number of lanyards (62), each lanyard being mounted by a roller loop (68) over the primary pole member (22). The strap on the roller loop has stitching for controlled release, a protection sheath (74) to prevent tangling and a hook member (69) for attachment to a crew harness.

  20. Lyman-Werner UV escape fractions from primordial haloes

    NASA Astrophysics Data System (ADS)

    Schauer, Anna T. P.; Whalen, Daniel J.; Glover, Simon C. O.; Klessen, Ralf S.

    2015-12-01

    Population III (Pop III) stars can regulate star formation in the primordial Universe in several ways. They can ionize nearby haloes, and even if their ionizing photons are trapped by their own haloes, their Lyman-Werner (LW) photons can still escape and destroy H2 in other haloes, preventing them from cooling and forming stars. LW escape fractions are thus a key parameter in cosmological simulations of early reionization and star formation but have not yet been parametrized for realistic haloes by halo or stellar mass. To do so, we perform radiation hydrodynamical simulations of LW UV escape from 9-120 M⊙ Pop III stars in 105-107 M⊙ haloes with ZEUS-MP. We find that photons in the LW lines (i.e. those responsible for destroying H2 in nearby systems) have escape fractions ranging from 0 to 85 per cent. No LW photons escape the most massive halo in our sample, even from the most massive star. Escape fractions for photons elsewhere in the 11.18-13.6 eV energy range, which can be redshifted into the LW lines at cosmological distances, are generally much higher, being above 60 per cent for all but the least massive stars in the most massive haloes. We find that shielding of H2 by neutral hydrogen, which has been neglected in most studies to date, produces escape fractions that are up to a factor of 3 smaller than those predicted by H2 self-shielding alone.

  1. Physical Processes for Driving Ionospheric Outflows in Global Simulations

    NASA Technical Reports Server (NTRS)

    Moore, Thomas Earle; Strangeway, Robert J.

    2009-01-01

    We review and assess the importance of processes thought to drive ionospheric outflows, linking them as appropriate to the solar wind and interplanetary magnetic field, and to the spatial and temporal distribution of their magnetospheric internal responses. These begin with the diffuse effects of photoionization and thermal equilibrium of the ionospheric topside, enhancing Jeans' escape, with ambipolar diffusion and acceleration. Auroral outflows begin with dayside reconnexion and resultant field-aligned currents and driven convection. These produce plasmaspheric plumes, collisional heating and wave-particle interactions, centrifugal acceleration, and auroral acceleration by parallel electric fields, including enhanced ambipolar fields from electron heating by precipitating particles. Observations and simulations show that solar wind energy dissipation into the atmosphere is concentrated by the geomagnetic field into auroral regions with an amplification factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Internal plasmas thus enable electromagnetic driving via coupling to the plasma, neutral gas and by extension, the entire body " We assess the Importance of each of these processes in terms of local escape flux production as well as global outflow, and suggest methods for their implementation within multispecies global simulation codes. We complete 'he survey with an assessment of outstanding obstacles to this objective.

  2. Modeling Neutral Densities Downstream of a Gridded Ion Thruster

    NASA Technical Reports Server (NTRS)

    Soulas, George C.

    2010-01-01

    The details of a model for determining the neutral density downstream of a gridded ion thruster are presented. An investigation of the possible sources of neutrals emanating from and surrounding a NEXT ion thruster determined that the most significant contributors to the downstream neutral density include discharge chamber neutrals escaping through the perforated grids, neutrals escaping from the neutralizer, and vacuum facility background neutrals. For the neutral flux through the grids, near- and far-field equations are presented for rigorously determining the neutral density downstream of a cylindrical aperture. These equations are integrated into a spherically-domed convex grid geometry with a hexagonal array of apertures for determining neutral densities downstream of the ion thruster grids. The neutrals escaping from an off-center neutralizer are also modeled assuming diffuse neutral emission from the neutralizer keeper orifice. Finally, the effect of the surrounding vacuum facility neutrals is included and assumed to be constant. The model is used to predict the neutral density downstream of a NEXT ion thruster with and without neutralizer flow and a vacuum facility background pressure. The impacts of past simplifying assumptions for predicting downstream neutral densities are also examined for a NEXT ion thruster.

  3. Reconstructing the Alcatraz escape

    NASA Astrophysics Data System (ADS)

    Baart, F.; Hoes, O.; Hut, R.; Donchyts, G.; van Leeuwen, E.

    2014-12-01

    In the night of June 12, 1962 three inmates used a raft made of raincoatsto escaped the ultimate maximum security prison island Alcatraz in SanFrancisco, United States. History is unclear about what happened tothe escapees. At what time did they step into the water, did theysurvive, if so, where did they reach land? The fate of the escapees has been the subject of much debate: did theymake landfall on Angel Island, or did the current sweep them out ofthe bay and into the cold pacific ocean? In this presentation, we try to shed light on this historic case using avisualization of a high-resolution hydrodynamic simulation of the San Francisco Bay, combined with historical tidal records. By reconstructing the hydrodynamic conditions and using a particle based simulation of the escapees we show possible scenarios. The interactive model is visualized using both a 3D photorealistic and web based visualization. The "Escape from Alcatraz" scenario demonstrates the capabilities of the 3Di platform. This platform is normally used for overland flooding (1D/2D). The model engine uses a quad tree structure, resulting in an order of magnitude speedup. The subgrid approach takes detailed bathymetry information into account. The inter-model variability is tested by comparing the results with the DFlow Flexible Mesh (DFlowFM) San Francisco Bay model. Interactivity is implemented by converting the models from static programs to interactive libraries, adhering to the Basic ModelInterface (BMI). Interactive models are more suitable for answeringexploratory research questions such as this reconstruction effort. Although these hydrodynamic simulations only provide circumstantialevidence for solving the mystery of what happened during the foggy darknight of June 12, 1962, it can be used as a guidance and provides aninteresting testcase to apply interactive modelling.

  4. Neutral Gas and Low-Redshift Starbursts: From Infall to Ionization

    NASA Astrophysics Data System (ADS)

    Jaskot, Anne; Oey, M. S.; Salzer, J. J.; Van Sistine, A.; Haynes, M. P.

    2014-01-01

    The interplay of gas inflows, star formation, and feedback drives galaxy evolution, and starburst galaxies provide important laboratories for probing these processes at their most extreme. With two samples of low-redshift starburst galaxies, we examine the conversion of neutral gas into stars and the subsequent effects of stellar feedback on the neutral interstellar medium (ISM). The ALFALFA Hα survey represents a complete, volume-limited sample of HI-selected galaxies with 21 cm spectra and Hα and R-band imaging. By contrasting the starburst galaxies with the rest of the gas-rich galaxy population, we investigate the roles of galaxy morphology, HI kinematics, and the atomic gas supply in triggering extreme levels of star formation. Both an elevated HI gas supply and an external disturbance are necessary to drive the starbursts. While neutral gas may fuel a starburst, it may also increase starbursts' optical depths and hinder the transport of ionizing radiation. In contrast to the expectations for high-redshift star-forming galaxies, neutral gas appears to effectively bar the escape of ionizing radiation in most low-redshift starbursts. To evaluate the impact of radiative feedback in extreme starbursts, we analyze optical spectra of the Green Pea galaxies, a low-redshift sample selected by their intense [O III] λ5007 emission and compact sizes. We use nebular photoionization and stellar population models to constrain the Peas' burst ages, ionizing sources, and optical depths and find that the Peas are likely optically thin to Lyman continuum (LyC) radiation. These young starbursts still generate substantial ionizing radiation, while recent supernovae may have carved holes in the ISM that enhance LyC photon escape into the intergalactic medium. While the ALFALFA survey demonstrates the role of external processes in triggering starbursts, the Green Peas show that starbursts' radiation can escape to affect their external environment.

  5. HIV Evolution and Escape.

    PubMed Central

    Richman, Douglas D.; Little, Susan J.; Smith, Davey M.; Wrin, Terri; Petropoulos, Christos; Wong, Joseph K.

    2004-01-01

    Human immunodeficiency virus (HIV) exemplifies the principles of Darwinian evolution with a telescoped chronology. Because of its high mutation rate and remarkably high rates of replication, evolution can be appreciated over periods of days in contrast to the durations conceived of by Darwin. Certain selective pressures that drive the evolution of HIV include chemotherapy, anatomic compartmentalization and the immune response. Examples of these selective forces on HIV evolution are described. Images Fig. 5 PMID:17060974

  6. THERMALLY DRIVEN ATMOSPHERIC ESCAPE: TRANSITION FROM HYDRODYNAMIC TO JEANS ESCAPE

    SciTech Connect

    Volkov, Alexey N.; Johnson, Robert E.; Tucker, Orenthal J.; Erwin, Justin T.

    2011-03-10

    Thermally driven escape from planetary atmospheres changes in nature from an organized outflow (hydrodynamic escape) to escape on a molecule-by-molecule basis (Jeans escape) with increasing Jeans parameter, {lambda}, the ratio of the gravitational to thermal energy of the atmospheric molecules. This change is described here for the first time using the direct simulation Monte Carlo method. When heating is predominantly below the lower boundary of the simulation region, R{sub 0}, and well below the exobase of a single-component atmosphere, the nature of the escape process changes over a surprisingly narrow range of Jeans parameters, {lambda}{sub 0}, evaluated at R{sub 0}. For an atomic gas, the transition occurs over {lambda}{sub 0} {approx} 2-3, where the lower bound, {lambda}{sub 0} {approx} 2.1, corresponds to the upper limit for isentropic, supersonic outflow. For {lambda}{sub 0} > 3 escape occurs on a molecule-by-molecule basis and we show that, contrary to earlier suggestions, for {lambda}{sub 0} > {approx}6 the escape rate does not deviate significantly from the familiar Jeans rate. In a gas composed of diatomic molecules, the transition shifts to {lambda}{sub 0} {approx} 2.4-3.6 and at {lambda}{sub 0} > {approx}4 the escape rate increases a few tens of percent over that for the monatomic gas. Scaling by the Jeans parameter and the Knudsen number, these results can be applied to thermally induced escape of the major species from solar and extrasolar planets.

  7. Escape from Vela X

    SciTech Connect

    Hinton, J.; Funk, S.; Parsons, R.D.; Ohm, S.; /Leicester U. /Leeds U.

    2012-02-15

    While the Vela pulsar and its associated nebula are often considered as the archetype of a system powered by a {approx} 10{sup 4} year old isolated neutron star, many features of the spectral energy distribution of this pulsar wind nebula are both puzzling and unusual. Here we develop a model that for the first time relates the main structures in the system, the extended radio nebula (ERN) and the X-ray cocoon through continuous injection of particles with a fixed spectral shape. We argue that diffusive escape of particles from the ERN can explain the steep Fermi-LAT spectrum. In this scenario Vela X should produce a distinct feature in the locally-measured cosmic ray electron spectrum at very high energies. This prediction can be tested in the future using the Cherenkov Telescope Array (CTA). If particles are indeed released early in the evolution of PWNe and can avoid severe adiabatic losses, PWN provide a natural explanation for the rising positron fraction in the local CR spectrum.

  8. Xenon Fractionation, Hydrogen Escape, and the Oxidation of the Earth

    NASA Astrophysics Data System (ADS)

    Zahnle, K. J.; Catling, D. C.

    2014-12-01

    Xenon in Earth's atmosphere is severely mass fractionated and depleted compared to any plausible solar system source material, yet Kr is unfractionated. These observations seem to imply that Xe has escaped from Earth. Vigorous hydrodynamic hydrogen escape can produce mass fractionation in heavy gases. The required hydrogen flux is very high but within the range permitted by solar EUV heating when Earth was 100 Myrs old or younger. However this model cannot explain why Xe escapes but Kr does not. Recently, what appears to be ancient atmospheric xenon has been recovered from several very ancient (3-3.5 Ga) terrestrial hydrothermal barites and cherts (Pujol 2011, 2013). What is eye-catching about this ancient Xe is that it is less fractionated that Xe in modern air. In other words, it appears that a process was active on Earth some 3 to 3.5 billion years ago that caused xenon to fractionate. By this time the Sun was no longer the EUV source that it used to be. If xenon was being fractionated by escape — currently the only viable hypothesis — it had to be in Earth's Archean atmosphere and under rather modest levels of EUV forcing. It should be possible for Xe, but not Kr, to escape from Earth as an ion. In a hydrodynamically escaping hydrogen wind the hydrogen is partially ionized. The key concepts are that ions are much more strongly coupled to the escaping flow than are neutrals (so that a relatively modest flow of H and H+ to space could carry Xe+ along with it, the flux can be small enough to be consistent with diffusion-limited flux), and that Xe alone among the noble gases is more easily ionized than hydrogen. This sort of escape is possible along the polar field lines, although a weak or absent magnetic field would likely work as well. The extended history of hydrogen escape implicit in Xe escape in the Archean is consistent with other suggestions that hydrogen escape in the Archean was considerable. Hydrogen escape plausibly played the key role in creating

  9. An escape from crowding.

    PubMed

    Freeman, Jeremy; Pelli, Denis G

    2007-01-01

    Crowding occurs when nearby flankers jumble the appearance of a target object, making it hard to identify. Crowding is feature integration over an inappropriately large region. What determines the size of that region? According to bottom-up proposals, the size is that of an anatomically determined isolation field. According to top-down proposals, the size is that of the spotlight of attention. Intriligator and Cavanagh (2001) proposed the latter, but we show that their conclusion rests on an implausible assumption. Here we investigate the role of attention in crowding using the change blindness paradigm. We measure capacity for widely and narrowly spaced letters during a change detection task, both with and without an interstimulus cue. We find that standard crowding manipulations-reducing spacing and adding flankers-severely impair uncued change detection but have no effect on cued change detection. Because crowded letters look less familiar, we must use longer internal descriptions (less compact representations) to remember them. Thus, fewer fit into working memory. The memory limit does not apply to the cued condition because the observer need remember only the cued letter. Cued performance escapes the effects of crowding, as predicted by a top-down account. However, our most parsimonious account of the results is bottom-up: Cued change detection is so easy that the observer can tolerate feature degradation and letter distortion, making the observer immune to crowding. The change detection task enhances the classic partial report paradigm by making the test easier (same/different instead of identifying one of many possible targets), which increases its sensitivity, so it can reveal degraded memory traces. PMID:18217837

  10. Photochemical escape of oxygen from the Martian atmosphere: first results from MAVEN

    NASA Astrophysics Data System (ADS)

    Lillis, Rob; Deigan, Justin; Fox, Jane; Bougher, Steve; Lee, Yuni; Cravens, Thomas; Rahmati, Ali; Jakosky, Bruce

    2015-04-01

    One of the primary goals of the MAVEN mission is to characterize rates of atmospheric escape at the present epoch and relate those escape rates to solar drivers. One of the major escape processes is known as photochemical escape, which is broadly defined as a process by which a) an exothermic reaction in the atmosphere results in an upward-traveling neutral particle whose velocity exceeds planetary escape velocity and b) the particle is not prevented from escaping through any subsequent collisions. At Mars, photochemical escape of oxygen is expected to be a significant channel for atmospheric escape, particularly in the early solar system when extreme ultraviolet (EUV) fluxes were much higher. Thus characterizing this escape process is central to understanding the role escape to space has played in Mars' climate evolution. Because escaping hot atoms cannot easily be directly measured, models of production and transport (through the atmosphere) of such atoms must be used to constrain escape rates. These models require altitude profiles of neutral densities and electron and ion densities and temperatures, as well as compositional information. All the relevant quantities upon which photochemical escape depends will be measured by MAVEN at the relevant altitudes (150-250 km). LPW will measure electron density and temperature, NGIMS will measure neutral and ion density and STATIC will measure ion density and temperature. 4 separate calculations must be made for every altitude profile: Profiles of O2+dissociative recombination (DR) rates will be calculated straightforwardly from electron temperature, electron density and O2+density. Profiles of rotational and vibrational distributions of O2+ ions will be calculated from profiles of CO2, O, O2, O+, CO2+ and CO+ via a lookup table from an empirical model. Profiles of energy distributions of hot O atoms will be calculated from the results of step 2 and from profiles of electron and ion temperatures. Profiles of all neutral

  11. Suicide as Escape from Self.

    ERIC Educational Resources Information Center

    Baumeister, Roy F.

    1990-01-01

    Suicide is analyzed as a motivation to escape from adversive self-awareness. The causal chain is traced from initial failures that are attributed internally because of a cognitively deconstructed state. (SLD)

  12. Automatic fluid separator supplies own driving power

    NASA Technical Reports Server (NTRS)

    Decker, M. S.; Majneri, L. A.; Spulgis, I. S.

    1966-01-01

    Centrifugal separator suspended in the fuel tank of a space vehicle selects and vents gas vapor at zero gravity. Escaping vapor is used to drive an expander turbine that is magnetically coupled to the separator.

  13. Structural acid-base chemistry in the metallic state: how μ3-neutralization drives interfaces and helices in Ti21Mn25.

    PubMed

    Stacey, Timothy E; Fredrickson, Daniel C

    2013-08-01

    Intermetallic phases remain a large class of compounds whose vast structural diversity is unaccounted for by chemical theory. A recent resurgence of interest in intermetallics, due to their potential in such applications as catalysis and thermoelectricity, has intensified the need for models connecting their compositions to their structures and stability. In this Article, we illustrate how the μ3-acidity model, an extension of the acid/base concept based on the Method of Moments, offers intuitive explanations for puzzling structural progressions occurring in intermetallics formed between transition metals. Simple CsCl-type structures are frequently observed for phases with near 1:1 ratios of transition metals. However, in two compounds, TiCu and Ti21Mn25, structures are adopted which deviate from this norm. μ3-Acidity analysis shows that the formation of CsCl-type phases in these exceptional systems would yield an imbalance in the acid/base strength pairing, resulting in overneutralization of the weaker partner and thus instability. Intriguing geometrical features emerge in response, which serve to improve the neutralization of the constituent elements. In both TiCu and Ti21Mn25, part of the structure shields weaker acids or bases from their stronger partners by enhancing homoatomic bonding in the sublattice of the weaker acid or base. In TiCu, this protection is accomplished by developing doubled layers of Ti atoms to reduce their heteroatomic contacts. In Ti21Mn25 the structural response is more extreme: Ti-poor TiMn2 domains are formed to guard Mn from the Ti atoms, while the remaining Ti segregates to regions between the TiMn2 domains. The geometrical details of this arrangement fine-tune the acid/base interactions for an even greater level of stability. The most striking of these occurs in the Ti-rich region, where a paucity of Mn neighbors leads to difficulty in achieving strong neutralization. The Ti atoms arrange themselves in helical tubes, maximizing

  14. Orbital Effects on Mercury's Escaping Sodium Exosphere

    NASA Technical Reports Server (NTRS)

    Schmidt, Carl A.; Wilson, Jody K.; Baumgardner, Jeffrey; Mendillo, Michael

    2009-01-01

    We present results from coronagraphic imaging of Mercury's sodium tail over a 7 deg field of view. Several sets of observations made at the McDonald Observatory since May 2007 show a tail of neutral sodium atoms stretching more than 1000 Mercury radii (R(sub m)) in length, or a full degree of sky. However, no tail was observed extending beyond 120 R(sub m) during the January 2008 MESSENGER Fly-by period, or during a similar orbital phase of Mercury in July 2008. Large changes in Mercury's heliocentric radial velocity cause Doppler shifts about the Fraunhofer absorption features; the resultant change in solar flux and radiation pressure is the primary cause of the observed variation in tail brightness. Smaller fluctuations in brightness may exist due to changing source rates at the surface, but we have no explicit evidence for such changes in this data set. The effects of radiation pressure on Mercury's escaping atmosphere are investigated using seven observations spanning different orbital phases. Total escape rates of atmospheric sodium are estimated to be between 5 and 13 x 10(exp 23) atoms/s and show a correlation to radiation pressure. Candidate sources of Mercury's sodium exosphere include desorption by UV sunlight, thermal desorption, solar wind channeled along Mercury's magnetic field lines, and micro-meteor impacts. Wide-angle observations of the full extent of Mercury's sodium tail offer opportunities to enhance our understanding of the time histories of these source rates.

  15. Role of detergents in driving complex structural arrangements in colloidal suspensions of Photosystem I (PS I) via charge stabilization and neutralization

    NASA Astrophysics Data System (ADS)

    Niroomand, Hanieh; Mukherjee, Dibyendu; Khomami, Bamin

    2012-02-01

    Specific concentrations of detergents such as DM (n-Dodecyl-β-D-Maltoside) and Triton X-100 (TX-100) used for Photosystem I (PS I) stabilization in buffer solutions play significant roles in controlling the solution-phase protein-protein interactions. Such control on PS I-PS I interactions facilitates uniform monolayer deposition of PS I on self-assembled monolayer (SAM)/Au substrates, a critical step for their future incorporation into bio-hybrid photovoltaic devices. Moreover, electric-field assisted assembly from PS I solutions with TX-100 as the detergent facilitates the formation of uniform PS I monolayer. But, the same phenomenon is not observed for PS I suspensions with DM as the detergent. To explain the underlying colloidal physics of these systems, in-situ dynamic light scattering experiments under various incubation times and applied voltages reveal the role of DM in charge neutralization and in turn, significant reduction of the PS I dipole moment in solution. Furthermore, small angle X-ray scattering measurements provide the much-needed structural information for a detailed understanding of the protein-detergent complexation process. These detailed investigations point towards the use of random sequential adsorption techniques in creating systematic dense monolayers of PS I.

  16. Characterizing Atmospheric Escape from Mars Today and Through Time, with MAVEN

    NASA Astrophysics Data System (ADS)

    Lillis, R. J.; Brain, D. A.; Bougher, S. W.; Leblanc, F.; Luhmann, J. G.; Jakosky, B. M.; Modolo, R.; Fox, J.; Deighan, J.; Fang, X.; Wang, Y. C.; Lee, Y.; Dong, C.; Ma, Y.; Cravens, T.; Andersson, L.; Curry, S. M.; Schneider, N.; Combi, M.; Stewart, I.; Clarke, J.; Grebowsky, J.; Mitchell, D. L.; Yelle, R.; Nagy, A. F.; Baker, D.; Lin, R. P.

    2015-12-01

    Two of the primary goals of the MAVEN mission are to determine how the rate of escape of Martian atmospheric gas to space at the current epoch depends upon solar influences and planetary parameters and to estimate the total mass of atmosphere lost to space over the history of the planet. Along with MAVEN's suite of nine science instruments, a collection of complementary models of the neutral and plasma environments of Mars' upper atmosphere and near-space environment are an indispensable part of the MAVEN toolkit, for three primary reasons. First, escaping neutrals will not be directly measured by MAVEN and so neutral escape rates must be derived, via models, from in situ measurements of plasma temperatures and neutral and plasma densities and by remote measurements of the extended exosphere. Second, although escaping ions will be directly measured, all MAVEN measurements are limited in spatial coverage, so global models are needed for intelligent interpolation over spherical surfaces to calculate global escape rates. Third, MAVEN measurements will lead to multidimensional parameterizations of global escape rates for a range of solar and planetary parameters, but further global models informed by MAVEN data will be required to extend these parameterizations to the more extreme conditions that likely prevailed in the early solar system, which is essential for determining total integrated atmospheric loss. We describe these modeling tools and the strategies for using them in concert with MAVEN measurements to greater constrain the history of atmospheric loss on Mars.

  17. Photochemical escape of oxygen from the Martian atmosphere: new insights from MAVEN

    NASA Astrophysics Data System (ADS)

    Lillis, R. J.; Deighan, J.; Bougher, S. W.; Cravens, T.; Fox, J. L.; Lee, Y.; Rahmati, A.; McFadden, J. P.; Benna, M.; Mahaffy, P. R.; Elrod, M. K.; Andersson, L.; Fowler, C. M.; Curry, S.; Gröller, H.; Jakosky, B. M.

    2015-12-01

    One of the primary goals of the MAVEN mission is to characterize rates of atmospheric escape from Mars at the present epoch and relate those escape rates to solar drivers. One of the known escape processes is photochemical escape, where a) an exothermic chemical reaction in the atmosphere results in an upward-traveling neutral particle whose velocity exceeds planetary escape velocity and b) the particle is not prevented from escaping through any subsequent collisions. Because escaping hot atoms are not directly measured, models of production and transport (through the atmosphere) of such atoms must be used to constrain photochemical escape rates. These models require altitude profiles of neutral densities and electron and ion densities and temperatures, as well as compositional information, all of which are measured by MAVEN instruments at the relevant altitudes (150-300 km). For every altitude profile: Profiles of O2+ dissociative recombination (DR) rates will be calculated from electron temperature, electron density and O2+ density. Profiles of energy distributions of hot O atoms will be calculated from profiles of electron and ion temperatures. Profiles of all neutral densities will be input into models of hot O transport in order to calculate photochemical escape fluxes from DR of O2+. We will present photochemical escape fluxes as a function of several factors, in particular solar zenith angle and EUV flux. This, combined with further simulations with progressively higher EUV fluxes, will eventually enable a total integrated loss estimate over the course of Martian history and hence a determination of the impact of this loss process on the evolution of the Martian climate.

  18. Neutralizer optimization

    NASA Technical Reports Server (NTRS)

    Patterson, Michael J.; Mohajeri, Kayhan

    1991-01-01

    The preliminary results of a test program to optimize a neutralizer design for 30 cm xenon ion thrusters are discussed. The impact of neutralizer geometry, neutralizer axial location, and local magnetic fields on neutralizer performance is discussed. The effect of neutralizer performance on overall thruster performance is quantified, for thruster operation in the 0.5-3.2 kW power range. Additionally, these data are compared to data published for other north-south stationkeeping (NSSK) and primary propulsion xenon ion thruster neutralizers.

  19. Plasma Escape from Unmagnetized Bodies

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Grebowsky, J. M.; Intriligator, D. S.

    1998-01-01

    A considerable fraction of atmospheric loss at Venus and Titan is in the form of plasma escape. This is due in part to the fact that the ionospheres of these unmagnetized bodies interact directly with the high speed plasmas flowing around them. The similarities of the interactions help reinforce interpretations of measurements made at each body, especially when instruments and measurement sites differ. For example, it is well established through this method that ions born in the exospheres above the ionopauses are picked up and carried away by the solar wind at Venus and the rotating plasma in Saturn's magnetosphere. On the other hand, it is more difficult to relate the observations associated with escape of cooler ionospheric plasma down the ionotails of each body. A clear example of ionospheric plasma escaping Titan was observed as it flowed down its ionotail (1). Measurements at Venus have not as yet clearly distinguished between ionospheric and pickup ion escape in the ionotail; however, cold ions detected in the distant wake at 1 AU by the CELIAS/CTOF instrument on SOHO have been interpreted as ionospheric in origin (2). An algorithm to determine ionospheric flow from Pioneer Venus aeronomical measurements is used to show that escape of cold ionospheric plasma is likely to occur. These results along with plasma flow measurements made in the ionotail of Venus are combined and compared to the corresponding flow at Titan.

  20. Viral escape from antisense RNA.

    PubMed

    Bull, J J; Jacobson, A; Badgett, M R; Molineux, I J

    1998-05-01

    RNA coliphage SP was propagated for several generations on a host expressing an inhibitory antisense RNA complementary to bases 31-270 of the positive-stranded genome. Phages evolved that escaped inhibition. Typically, these escape mutants contained 3-4 base substitutions, but different sequences were observed among different isolates. The mutations were located within three different types of structural features within the predicted secondary structure of SP genomic RNA: (i) hairpin loops; (ii) hairpin stems; and (iii) the 5' region of the phage genome complementary to the antisense molecule. Computer modelling of the mutant genomic RNAs showed that all of the substitutions within hairpin stems improved the Watson-Crick pairing of the stem. No major structural rearrangements were predicted for any of the mutant genomes, and most substitutions in coding regions did not alter the amino acid sequence. Although the evolved phage populations were polymorphic for substitutions, many substitutions appeared independently in two selected lines. The creation of a new, perfect, antisense RNA against an escape mutant resulted in the inhibition of that mutant but not of other escape mutants nor of the ancestral, unevolved phage. Thus, at least in this system, a population of viruses that evolved to escape from a single antisense RNA would require a cocktail of several antisense RNAs for inhibition. PMID:9643550

  1. MAVEN in situ measurements of photochemical escape of oxygen from Mars

    NASA Astrophysics Data System (ADS)

    Lillis, Robert; Deighan, Justin; Fox, Jane; Bougher, Stephen; Lee, Yuni; Cravens, Thomas; Rahmati, Ali; Mahaffy, Paul; Benna, Mehdi; Groller, Hannes; Jakosky, Bruce

    2016-04-01

    One of the primary goals of the MAVEN mission is to characterize rates of atmospheric escape from Mars at the present epoch and relate those escape rates to solar drivers. One of the known escape processes is photochemical escape, where a) an exothermic chemical reaction in the atmosphere results in an upward-traveling neutral particle whose velocity exceeds planetary escape velocity and b) the particle is not prevented from escaping through subsequent collisions. At Mars, photochemical escape of oxygen is expected to be a significant channel for atmospheric escape, particularly in the early solar system when extreme ultraviolet (EUV) fluxes were much higher. Thus characterizing this escape process and its variability with solar drivers is central to understanding the role escape to space has played in Mars' climate evolution. We use near-periapsis (<400 km altitude) data from three MAVEN instruments: the Langmuir Probe and Waves (LPW) instrument measures electron density and temperature, the Suprathermal And Thermal Ion Composition (STATIC) experiment measures ion temperature and the Neutral Gas and Ion Mass Spectrometer (NGIMS) measures neutral and ion densities. For each profile of in situ measurements, we make several calculations, each as a function of altitude. The first uses electron and temperatures and simulates the dissociative recombination of both O2+ and CO2+ to calculate the probability distribution for the initial energies of the resulting hot oxygen atoms. The second is a Monte Carlo hot atom transport model that takes that distribution of initial O energies and the measured neutral density profiles and calculates the probability that a hot atom born at that altitude will escape. The third takes the measured electron and ion densities and electron temperatures and calculates the production rate of hot O atoms. We then multiply together the profiles of hot atom production and escape probability to get profiles of the production rate of escaping atoms

  2. On the hydrodynamic model of thermal escape from planetary atmospheres and its comparison with kinetic simulations

    NASA Astrophysics Data System (ADS)

    Volkov, A. N.

    2016-06-01

    Parkers' model of thermal escape implies the search of solutions of one-dimensional hydrodynamic equations for an inviscid but thermally conducting gas with a critical point and vanishing temperature far from the source. The properties of solutions of this model are studied for neutral mon- and diatomic gases with the viscosity index varying from 1/2 to 1. The domains of existence and uniqueness of solutions in terms of the source Jeans escape parameter and Knudsen number are established. The solutions are found to exist only in a narrow range of the critical point Jeans parameter. The lower and upper limits of this range correspond to solutions that are dominated by either heat conduction or adiabatic expansion. Thermal escape described by Parker's model occurs in two asymptotic regimes: the low-density (LD) regime, when escape is dominated by heat conduction, and the high-density (HD) regime, when escape is dominated by adiabatic expansion. Expressions for the mass and energy escape rates in these regimes are found theoretically. The comparison of results of hydrodynamic and kinetic simulations performed in identical conditions shows that Parker's model is capable of describing thermal escape only in the HD regime, providing decent agreement with the kinetic model in terms of the atmospheric structure below the exobase and the mass and energy escape rates. In the LD regime, Parker's model predicts a much faster drop in atmospheric temperature and less extended atmospheres, and can both over- and underestimate the escape rates in orders of magnitude.

  3. Collective Predation and Escape Strategies

    NASA Astrophysics Data System (ADS)

    Angelani, Luca

    2012-09-01

    The phenomenon of collective predation is analyzed by using a simple individual-based model reproducing spatial animal movements. Two groups of self-propelled organisms are simulated by using Vicseklike models including steric intragroup repulsion. Chase and escape are described by intergroups interactions, attraction (for predators) or repulsion (for preys) from nearest particles of the opposite group. The quantitative analysis of some relevant quantities (total catch time, lifetime distribution, predation rate) allows us to characterize many aspects of the predation phenomenon and gives insights into the study of efficient escape strategies. The reported findings could be of relevance for many basic and applied disciplines, from statistical physics, to ecology, and robotics.

  4. Automated Escape Guidance Algorithms for An Escape Vehicle

    NASA Technical Reports Server (NTRS)

    Flanary, Ronald; Hammen, David; Ito, Daigoro; Rabalais, Bruce; Rishikof, Brian; Siebold, Karl

    2002-01-01

    An escape vehicle was designed to provide an emergency evacuation for crew members living on a space station. For maximum escape capability, the escape vehicle needs to have the ability to safely evacuate a station in a contingency scenario such as an uncontrolled (e.g., tumbling) station. This emergency escape sequence will typically be divided into three events: The fust separation event (SEP1), the navigation reconstruction event, and the second separation event (SEP2). SEP1 is responsible for taking the spacecraft from its docking port to a distance greater than the maximum radius of the rotating station. The navigation reconstruction event takes place prior to the SEP2 event and establishes the orbital state to within the tolerance limits necessary for SEP2. The SEP2 event calculates and performs an avoidance burn to prevent station recontact during the next several orbits. This paper presents the tools and results for the whole separation sequence with an emphasis on the two separation events. The fust challenge includes collision avoidance during the escape sequence while the station is in an uncontrolled rotational state, with rotation rates of up to 2 degrees per second. The task of avoiding a collision may require the use of the Vehicle's de-orbit propulsion system for maximum thrust and minimum dwell time within the vicinity of the station vicinity. The thrust of the propulsion system is in a single direction, and can be controlled only by the attitude of the spacecraft. Escape algorithms based on a look-up table or analytical guidance can be implemented since the rotation rate and the angular momentum vector can be sensed onboard and a-priori knowledge of the position and relative orientation are available. In addition, crew intervention has been provided for in the event of unforeseen obstacles in the escape path. The purpose of the SEP2 burn is to avoid re-contact with the station over an extended period of time. Performing this maneuver properly

  5. In situ and remote measurements of ions escaping from Venus

    NASA Astrophysics Data System (ADS)

    Kollmann, P.; Brandt, P. C.

    2013-12-01

    Venus is thought to lose a large fraction of its atmosphere in the form ions, mainly via pickup. The relative loss rate of the exosphere as neutrals or ions is not known, nor is the flux of escaping ions well constrained. Knowledge of these processes will shed light on the role an intrinsic magnetic field has in atmospheric erosion. We use the complementary in-situ plasma and energetic neutral atom (ENA) measurements from the Venus Express (VEx) spacecraft in order to constrain the ion escape. VEx completed about 2500 orbits to date and reached altitudes as low as 200km. The ASPERA/IMA instrument measured directional proton and oxygen ion spectra in the 10eV to 40keV range. We bin the data accumulated over the mission in space and bulk flow direction, yielding a direct measure of the local ion escape flux. While such in-situ measurements provide data without ambiguity, they are limited by the orbital coverage. This is why we include remote ENA measurements from the ASPERA/NPD (100eV to 10keV) instrument to our study. ENAs are created when escaping ions charge exchange with the high atmosphere atoms or molecules. We have done an exhaustive analysis of the data, excluding time periods of instrument contamination. Most ENA emission originates from low altitudes above Venus' limb. These measurements will be compared with the in-situ data, which allows constraining the atmospheric density at high altitudes. Interestingly, there are also ENA emissions from other directions, which were not sampled in-situ. This allows us to put a lower limit to the escape from these regions.

  6. Numerical study of beam propagation and plasma properties in the neutralizer and the E-RID of the ITER Neutral Beam Injector

    NASA Astrophysics Data System (ADS)

    Lifschitz, A. F.; Revel, A.; Caillault, L.; Minea, T.

    2014-04-01

    Non-ohmic heating will be used in the experimental nuclear fusion reactor ITER to reach thermonuclear temperatures. Two heating mechanism will be implemented, i.e. microwaves resonant with ion and electron cyclotron frequencies and energetic neutral beam injection, which contributes also to the current drive. Each one of the two neutral beam injector planned for ITER will deliver 16 MW of 1 MeV D0 beam. In the injector, negative ions D- coming from a 40 A negative ion source are electrostatically accelerated to 1 MeV, and stripped of their extra electron by collision with a target gas in a structure known as the neutralizer. Residual charged particles are deflected after the neutralizer in an electrostatic ion dump (E-RID). The ionization of the deuterium buffer gas filling the neutralizer induced by the D- beam creates a rarefied plasma which is expected to efficiently screens the Coulomb repulsion of the beam. Moreover, this plasma can eventually escape from the neutralizer and move back in the accelerator, towards the accelerating grids and the negative ion source. The transport of the beam through the neutralizer and the RID and the related plasma properties were studied using a 3D electrostatic particle-in-cell code called OBI-3 (Orsay Beam Injector 3 dimensional). Particle-particle and particle-wall collisions are treated using the Monte Carlo collision approach. Simulations show that the secondary plasma effectively screens the beam space charge preventing beam transverse expansion. Plasma ions created in the neutralizer form an upstream current with a magnitude of ˜0.5% of the negative ion current. Gas breakdown leading to arc formation in the RID was not observed. Finally, results for the propagation of non-ideal beams coming from simulations of the extraction and consecutive acceleration taken from Revel et al 2013 Nucl. Fusion 53 073027 are presented.

  7. 42 CFR 84.51 - Entry and escape, or escape only; classification.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... during entry into a hazardous atmosphere, and for escape from a hazardous atmosphere; or (b) Escape only. Respirators designed and approved for use only during escape from a hazardous atmosphere....

  8. 42 CFR 84.51 - Entry and escape, or escape only; classification.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... during entry into a hazardous atmosphere, and for escape from a hazardous atmosphere; or (b) Escape only. Respirators designed and approved for use only during escape from a hazardous atmosphere....

  9. 42 CFR 84.51 - Entry and escape, or escape only; classification.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... during entry into a hazardous atmosphere, and for escape from a hazardous atmosphere; or (b) Escape only. Respirators designed and approved for use only during escape from a hazardous atmosphere....

  10. 42 CFR 84.51 - Entry and escape, or escape only; classification.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... during entry into a hazardous atmosphere, and for escape from a hazardous atmosphere; or (b) Escape only. Respirators designed and approved for use only during escape from a hazardous atmosphere....

  11. 42 CFR 84.51 - Entry and escape, or escape only; classification.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... during entry into a hazardous atmosphere, and for escape from a hazardous atmosphere; or (b) Escape only. Respirators designed and approved for use only during escape from a hazardous atmosphere....

  12. Lise Meitner's escape from Germany

    NASA Astrophysics Data System (ADS)

    Sime, Ruth Lewin

    1990-03-01

    Lise Meitner (1878-1968) achieved prominence as a nuclear physicist in Germany; although of Jewish origin, her Austrian citizenship exempted her from Nazi racial laws until the annexation of Austria in 1938 precipitated her dismissal. Forbidden to emigrate, she narrowly escaped to the Netherlands with the help of concerned friends in the international physics community.

  13. Lunar escape systems feasibility study

    NASA Technical Reports Server (NTRS)

    Matzenauer, J. O.

    1976-01-01

    Results are presented for a study conducted to determine the feasibility of simple lunar escape system concepts, to develop a spectrum of operational data, and to identify techniques and configurations suitable for the emergency escape mission. The study demonstrated the feasibility of the lunar emergency escape-to-orbit system (LESS) designed to provide a means for the two-man crew of a lunar module (LM) or extended-stay LM (ELM) to escape from the lunar surface in the event that the LM/ELM ascent stage becomes unsafe or is otherwise unable to take off. The LESS is to carry the two astronauts to a safe lunar orbit, where the Apollo command and service modules (CSM) are to be used for rendezvous and rescue, all within the lifetime of the backpack life support system (about 4 hr). It is concluded that simple manual control modes are sufficient, that simple boost profiles are acceptable, and that one man can deploy and set up the LESS. Initial guidance data can be calculated for the LESS by Mission Control and transmitted via the LM/ELM uplink.

  14. Io's neutral clouds: From the atmosphere to the plasma torus

    NASA Astrophysics Data System (ADS)

    Burger, Matthew Howard

    2003-10-01

    Since the discovery of sodium thirty years ago, observations of Io's neutral features have provided essential insight into understanding the relationship between the Io's atmosphere and the Io torus, a ring of plasma encircling Jupiter. In this thesis I use observations and models of lo's corona, extended neutral clouds, and fast sodium jet to probe the interactions between the atmosphere, torus, and neutral clouds. A corona and neutral cloud model, based on the model of Wilson and Schneider (1999), has been developed to study neutral loss from Io. Neutrals are ejected from Io's exobase and their trajectories followed under the influence of gravity until lost into the plasma torus. I also developed description of the plasma torus based on Voyager and ground-based observations to accurately determine neutral lifetimes. Mutual eclipsing events between Galilean satellites were used to measure the shape of lo's sodium corona, revealing a corona that is only approximately spherically symmetric around Io. I discovered a previously undetected asymmetry: the sub-Jupiter corona is denser than the anti-Jupiter corona. Modeling implies that sodium source from the sub-Jupiter hemisphere must be twice as large as from the anti-Jupiter hemisphere. The Galileo spacecraft has imaged a remarkable atmospheric escape process occurring in Io's ionosphere. Electrodynamic consequences of Io's motion through Jupiter's magnetosphere drive mega-amp currents through lo's ionosphere; some sodium ions carrying this current are neutralized as they leave the atmosphere. The Galileo images show that the resulting fast sodium jet removes ˜5 × 1025 atoms sec-1 from Io's atmosphere. The source region of the jet is much smaller than Io itself implying that the ionosphere is densest near Io's equator. A model-based comparison of the neutral oxygen and sodium clouds details differences in the morphologies and spatial extent of each: sodium extends only 1/4 the way around Jupiter while oxygen forms a

  15. Identification of human neutralizing antibodies against MERS-CoV and their role in virus adaptive evolution

    PubMed Central

    Tang, Xian-Chun; Agnihothram, Sudhakar S.; Jiao, Yongjun; Stanhope, Jeremy; Graham, Rachel L.; Peterson, Eric C.; Avnir, Yuval; Tallarico, Aimee St. Clair; Sheehan, Jared; Zhu, Quan; Baric, Ralph S.; Marasco, Wayne A.

    2014-01-01

    The newly emerging Middle East Respiratory Syndrome coronavirus (MERS-CoV) causes a Severe Acute Respiratory Syndrome-like disease with ∼43% mortality. Given the recent detection of virus in dromedary camels, zoonotic transfer of MERS-CoV to humans is suspected. In addition, little is known about the role of human neutralizing Ab (nAb) pressure as a driving force in MERS-CoV adaptive evolution. Here, we used a well-characterized nonimmune human Ab-phage library and a panning strategy with proteoliposomes and cells to identify seven human nAbs against the receptor-binding domain (RBD) of the MERS-CoV Spike protein. These nAbs bind to three different epitopes in the RBD and human dipeptidyl peptidase 4 (hDPP4) interface with subnanomolar/nanomolar binding affinities and block the binding of MERS-CoV Spike protein with its hDPP4 receptor. Escape mutant assays identified five amino acid residues that are critical for neutralization escape. Despite the close proximity of the three epitopes on the RBD interface, escape from one epitope did not have a major impact on neutralization with Abs directed to a different epitope. Importantly, the majority of escape mutations had negative impacts on hDPP4 receptor binding and viral fitness. To our knowledge, these results provide the first report on human nAbs against MERS-CoV that may contribute to MERS-CoV clearance and evolution. Moreover, in the absence of a licensed vaccine or antiviral for MERS, this panel of nAbs offers the possibility of developing human mAb-based immunotherapy, especially for health-care workers. PMID:24778221

  16. Magnetic buoyancy and the escape of magnetic fields from stars

    NASA Astrophysics Data System (ADS)

    Parker, E. N.

    1984-06-01

    Magnetic buoyancy causes the azimuthal magnetic fields of stars to rise rapidly to the surface, from where they are generally assumed to escape freely into space. However, a closer look at the problem reveals the simple fact that disengagement of the field from the gas, and escape into space, require a convoluted field configuration, producing neutral point reconnection of the flux in the tenuous gas above the surface of the star. Only that flux which reconnects can escape. Recent observations of the magnetic fields emerging through the surface of the Sun show that even at sunspot maximum the gaps in longitude between bipolar magnetic regions are so wide as to limit severely the reconnection between regions. We suggest from the observations that no more than perhaps 3% of the flux that is observed to emerge through the surface is able to reconnect and escape. Hence the surface of the Sun approximates to an impenetrable barrier rather than an open surface, with quantitative consequences for theoretical dynamo models. Recent observations of the retraction of bipolar fields at the end of their appearance at the surface suggest active dynamical control by the convection beneath the surface.

  17. Blue Origin Conducts Pad Escape Test

    NASA Video Gallery

    Blue Origin conducted a successful pad escape test Oct. 19 at the company's West Texas launch site, firing its pusher escape motor and launching a full-scale suborbital crew capsule from a simulate...

  18. Genetic Algorithms with Local Minimum Escaping Technique

    NASA Astrophysics Data System (ADS)

    Tamura, Hiroki; Sakata, Kenichiro; Tang, Zheng; Ishii, Masahiro

    In this paper, we propose a genetic algorithm(GA) with local minimum escaping technique. This proposed method uses the local minimum escaping techique. It can escape from the local minimum by correcting parameters when genetic algorithm falls into a local minimum. Simulations are performed to scheduling problem without buffer capacity using this proposed method, and its validity is shown.

  19. [Escape Behaviors and Its Underlying Neuronal Circuits].

    PubMed

    Oda, Yoichi

    2015-10-01

    Escape behaviors are crucial to survive predator encounters or aversive stimuli. The neural circuits mediating escape behaviors of different animal species have a common framework to trigger extremely fast and robust movement with minimum delay. Thus, the neuronal escape circuits possibly represent functional architectures that perform the most efficient sensory-motor processing in the brain. Here, I review the escape behaviors and underlying neuronal circuits of several invertebrates and fish by focusing on the Mauthner cells, a pair of giant reticulospinal neurons in the hindbrain, that trigger fast escape behavior in goldfish and zebrafish. PMID:26450070

  20. Neutral particle beams for space defense

    NASA Astrophysics Data System (ADS)

    Botwin, Robert; Favale, Anthony

    Neutral particle beam (NPB) weapons direct highly focused high energy streams of electrically neutral atomic particles traveling at nearly the speed of light, escaping deflection from the earth's magnetic field and acting on the subatomic structure of a target, destroying it from within. The beam's brief contact with a reentry vehicle produces a nuclear reaction in the latter that yields particle emissions; by detecting and identifying those particles, it becomes possible to effectively distinguish warheads from decoys. Attention is given to the NPB program roles to be played by the Beam Experiment Aboard Rocket and Neutral Particle Beam Integrated Space Experiment projects.

  1. Escape of a driven particle from a metastable state: A semiclassical approach.

    PubMed

    Ghosh, Pradipta; Shit, Anindita; Chattopadhyay, Sudip; Chaudhuri, Jyotipratim Ray

    2010-06-28

    In this article we explore the dynamics of escape of a particle in the semiclassical regime by driving the particle externally. We demonstrate that under suitable approximations the semiclassical escape rate essentially assumes the structure of classical Kramers rate. Both internal (due to thermal bath) as well as external noises (due to driving) are being considered. The noises are stationary, Gaussian, and are characterized by arbitrary decaying memory kernel. Finally, we subject our formulation to rigorous numerical test under variedly changing conditions of the parameters. PMID:20590205

  2. On ion escape from Venus

    NASA Astrophysics Data System (ADS)

    Jarvinen, Riku

    2011-04-01

    This doctoral thesis is about the solar wind influence on the atmosphere of the planet Venus. A numerical plasma simulation model was developed for the interaction between Venus and the solar wind to study the erosion of charged particles from the Venus upper atmosphere. The developed model is a hybrid simulation where ions are treated as particles and electrons are modelled as a fluid. The simulation was used to study the solar wind induced ion escape from Venus as observed by the European Space Agency's Venus Express and NASA's Pioneer Venus Orbiter spacecraft. Especially, observations made by the ASPERA-4 particle instrument onboard Venus Express were studied. The thesis consists of an introductory part and four peer-reviewed articles published in scientific journals. In the introduction Venus is presented as one of the terrestrial planets in the Solar System and the main findings of the work are discussed within the wider context of planetary physics. Venus is the closest neighbouring planet to the Earth and the most earthlike planet in its size and mass orbiting the Sun. Whereas the atmosphere of the Earth consists mainly of nitrogen and oxygen, Venus has a hot carbon dioxide atmosphere, which is dominated by the greenhouse effect. Venus has all of its water in the atmosphere, which is only a fraction of the Earth's total water supply. Since planets developed presumably in similar conditions in the young Solar System, why Venus and Earth became so different in many respects? One important feature of Venus is that the planet does not have an intrinsic magnetic field. This makes it possible for the solar wind, a continuous stream of charged particles from the Sun, to flow close to Venus and to pick up ions from the planet's upper atmosphere. The strong intrinsic magnetic field of the Earth dominates the terrestrial magnetosphere and deflects the solar wind flow far away from the atmosphere. The region around Venus where the planet's atmosphere interacts with the

  3. On ion escape from Venus

    NASA Astrophysics Data System (ADS)

    Jarvinen, R.

    2011-04-01

    This doctoral thesis is about the solar wind influence on the atmosphere of the planet Venus. A numerical plasma simulation model was developed for the interaction between Venus and the solar wind to study the erosion of charged particles from the Venus upper atmosphere. The developed model is a hybrid simulation where ions are treated as particles and electrons are modelled as a fluid. The simulation was used to study the solar wind induced ion escape from Venus as observed by the European Space Agency's Venus Express and NASA's Pioneer Venus Orbiter spacecraft. Especially, observations made by the ASPERA-4 particle instrument onboard Venus Express were studied. The thesis consists of an introductory part and four peer-reviewed articles published in scientific journals. In the introduction Venus is presented as one of the terrestrial planets in the Solar System and the main findings of the work are discussed within the wider context of planetary physics.Venus is the closest neighbouring planet to the Earth and the most earthlike planet in its size and mass orbiting the Sun. Whereas the atmosphere of the Earth consists mainly of nitrogen and oxygen, Venus has a hot carbon dioxide atmosphere, which is dominated by the greenhouse effect. Venus has all of its water in the atmosphere, which is only a fraction of the Earth's total water supply. Since planets developed presumably in similar conditions in the young Solar System, why Venus and Earth became so different in many respects?One important feature of Venus is that the planet does not have an intrinsic magnetic field. This makes it possible for the solar wind, a continuous stream of charged particles from the Sun, to flow close to Venus and to pick up ions from the planet's upper atmosphere. The strong intrinsic magnetic field of the Earth dominates the terrestrial magnetosphere and deflects the solar wind flow far away from the atmosphere. The region around Venus where the planet's atmosphere interacts with the

  4. Escape Dynamics in Quasihomogeneous Fields

    NASA Astrophysics Data System (ADS)

    Mioc, Vasile; Stavinschi, Magda

    The escape in the two-body problem associated to a quasihomogeneous potential (a sum of homogeneous potentials) is being tackled. The basic equations of the problem are put in a form for which the infinity is a singularity, then they are regularized via McGehee-type transformations. The singularity is replaced by a manifold pasted on the phase space, and the flow on this manifold is described; it is identical with the analogous flows corresponding to already studied concrete astronomical and physical situations.

  5. Helium escape from the Earth's atmosphere - The charge exchange mechanism revisited

    NASA Technical Reports Server (NTRS)

    Lie-Svendsen, O.; Rees, M. H.; Stamnes, K.

    1992-01-01

    We have studied the escape of neutral helium from the terrestrial atmosphere through exothermic charge exchange reactions between He(+) ions and the major atmospheric constituents N2, O2 and O. Elastic collisions with the neutral background particles were treated quantitatively using a recently developed kinetic theory approach. An interhemispheric plasma transport model was employed to provide a global distribution of He(+) ions as a function of altitude, latitude and local solar time and for different levels of solar ionization. Combining these ion densities with neutral densities from an MSIS model and best estimates for the reaction rate coefficients of the charge exchange reactions, we computed the global distribution of the neutral He escape flux. The escape rates show large diurnal and latitudinal variations, while the global average does not vary by more than a factor of three over a solar cycle. We find that this escape mechanism is potentially important for the overall balance of helium in the Earth's atmosphere. However, more accurate values for the reaction rate coefficients of the charge exchange reactions are required to make a definitive assessment of its importance.

  6. Wind Enhanced Escape, Ion Pickup and the Evolution of Water on Mars

    NASA Technical Reports Server (NTRS)

    Hartle, Richard

    1999-01-01

    Preferential loss of hydrogen over deuterium from Mars has produced a deuterium rich atmosphere possessing a D/B ratio 5.2 times that of terrestrial water. Rayleigh fractionation is applied, constrained by the deuterium enrichment factor, to determine the magnitudes of ancient and present water reservoirs on the planet. The dominant lose mechanisms of R and D from the current atmosphere are thought to be thermal escape and solar wind ion pickup of the neutral and ion forms of theme constituents, respectively. During an earlier martian epoch, only thermal escape was significant because Mars had a terrestrial sized magnetosphere that protected the atmosphere from solar wind scavenging processes. The magnitudes of present and ancient water reservoirs are estimated when thermal escape is considered alone and subsequently when the effects of ion pickup are added. The escape fluxes of R and D are significantly increased above the respective Jeans fluxes when the effects of thermospheric winds and planetary rotation are accounted for at the exobase. Such wind enhanced escape also increases as the mass of an escaping constituent increases; thus, the increase in the escape flux of D is greater than that of H. When the fractionation process is also constrained by the D/H ratio observed in hydrous minerals of SNC meteorites, an ancient crustal reservoir of Martian water in derived, tens of meters in global-equivalent depth, considerably exceeding that obtained with no winds. The reservoir becomes even larger when ion pickup processes are added.

  7. Mars atmosphere evolution: Escape to space

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.

    1992-01-01

    The loss mechanisms and the rates of escape, to space, of Martian atmosphere constituents have changed throughout the history of the solar system. For the first billion years, Mars' atmosphere escape was probably dominated by impact erosion related to the presence of debris left over from the accretionary phase. This loss was further augmented by hydrodynamic outflows related to the presence of an early denser atmosphere and a sun that was brighter in the EUV wavelengths. Following this initial 'catastrophic' phase, during which a large fraction of the original atmosphere was lost but then replaced by volcanism and cometary impact, the 'modern' loss mechanisms which still operate today would have taken over. Those mechanisms that now contribute to escape to space consist of classical thermal or Jeans escape, nonthermal escape due to chemical reaction in the atmosphere, and solar wind-related losses. Both the loss mechanisms and the rates of escape are discussed.

  8. Wind-Induced Atmospheric Escape: Titan

    NASA Technical Reports Server (NTRS)

    Hartle, Richard; Johnson, Robert; Sittler, Edward, Jr.; Sarantos, Menelaos; Simpson, David

    2012-01-01

    Rapid thermospheric flows can significantly enhance the estimates of the atmospheric loss rate and the structure of the atmospheric corona of a planetary body. In particular, rapid horizontal flow at the exobase can increase the corresponding constituent escape rate. Here we show that such corrections, for both thermal and non-thermal escape, cannot be ignored when calculating the escape of methane from Titan, for which drastically different rates have been proposed. Such enhancements are also relevant to Pluto and exoplanets.

  9. Escape nightmares and postescape stressful events.

    PubMed

    Cernovsky, Z Z

    1988-04-01

    Correlation matrix based on questionnaire item responses by 38 Czechoslovak refugees suggested that "escape nightmares" (recurrent nightmares about being back in the exhomeland, wanting to or trying to re-escape to the free world) are unrelated to postescape incidence of various stressful events (e.g., illness, job difficulties, financial problems). However, refugees who reported a greater number of the stressful events also reported a somewhat higher incidence of nightmares on themes other than escape from homeland (r = .34). PMID:3399334

  10. Model of a mechanical clock escapement

    NASA Astrophysics Data System (ADS)

    Moline, David; Wagner, John; Volk, Eugene

    2012-07-01

    The mechanical tower clock originated in Europe during the 14th century to sound hourly bells and later display hands on a dial. An important innovation was the escapement mechanism, which converts stored energy into oscillatory motion for fixed time intervals through the pendulum swing. Previous work has modeled the escapement mechanism in terms of inelastic and elastic collisions. We derive and experimentally verify a theoretical model in terms of impulsive differential equations for the Graham escapement mechanism in a Seth Thomas tower clock. The model offers insight into the clock's mechanical behavior and the functionality of the deadbeat escapement mechanism.

  11. Electronic Escape Trails for Firefighters

    NASA Technical Reports Server (NTRS)

    Jorgensen, Charles; Schipper, John; Betts, Bradley

    2008-01-01

    A proposed wireless-communication and data-processing system would exploit recent advances in radio-frequency identification devices (RFIDs) and software to establish information lifelines between firefighters in a burning building and a fire chief at a control station near but outside the building. The system would enable identification of trails that firefighters and others could follow to escape from the building, including identification of new trails should previously established trails become blocked. The system would include a transceiver unit and a computer at the control station, portable transceiver units carried by the firefighters in the building, and RFID tags that the firefighters would place at multiple locations as they move into and through the building (see figure). Each RFID tag, having a size of the order of a few centimeters, would include at least standard RFID circuitry and possibly sensors for measuring such other relevant environmental parameters as temperature, levels of light and sound, concentration of oxygen, concentrations of hazardous chemicals in smoke, and/or levels of nuclear radiation. The RFID tags would be activated and interrogated by the firefighters and control-station transceivers. Preferably, RFID tags would be configured to communicate with each other and with the firefighters units and the control station in an ordered sequence, with built-in redundancy. In a typical scenario, as firefighters moved through a building, they would scatter many RFID tags into smoke-obscured areas by use of a compressed-air gun. Alternatively or in addition, they would mark escape trails by dropping RFID tags at such points of interest as mantraps, hot spots, and trail waypoints. The RFID tags could be of different types, operating at different frequencies to identify their functions, and possibly responding by emitting audible beeps when activated by signals transmitted by transceiver units carried by nearby firefighters.

  12. iDriving (Intelligent Driving)

    Energy Science and Technology Software Center (ESTSC)

    2012-09-17

    iDriving identifies the driving style factors that have a major impact on fuel economy. An optimization framework is used with the aim of optimizing a driving style with respect to these driving factors. A set of polynomial metamodels is constructed to reflect the responses produced in fuel economy by changing the driving factors. The optimization framework is used to develop a real-time feedback system, including visual instructions, to enable drivers to alter their driving stylesmore » in responses to actual driving conditions to improve fuel efficiency.« less

  13. iDriving (Intelligent Driving)

    SciTech Connect

    Malikopoulos, Andreas

    2012-09-17

    iDriving identifies the driving style factors that have a major impact on fuel economy. An optimization framework is used with the aim of optimizing a driving style with respect to these driving factors. A set of polynomial metamodels is constructed to reflect the responses produced in fuel economy by changing the driving factors. The optimization framework is used to develop a real-time feedback system, including visual instructions, to enable drivers to alter their driving styles in responses to actual driving conditions to improve fuel efficiency.

  14. Career development. The great escape.

    PubMed

    Clews, Graham

    2006-03-23

    The healthcare outside hospitals white paper is part of a continuing drive to involve non-NHS bodies in patient care. This means an unfamiliar working environment for migrating managers; with different motivations, less job security and increased entrepreneurial freedom. Managers in Partnership has called on managers to develop self-marketing skills to suit the new job market. PMID:16618075

  15. Alternative end joining, clonal evolution, and escape from a telomere-driven crisis

    PubMed Central

    Hendrickson, Eric A; Baird, Duncan M

    2015-01-01

    Telomere dysfunction and fusion play key roles in driving genomic instability and clonal evolution in many tumor types. We have recently described a role for DNA ligase III (LIG3) in facilitating the escape of cells from crisis induced by telomere dysfunction. Our data indicate that LIG3-mediated telomere fusion is important in facilitating clonal evolution. PMID:27308409

  16. Escape as Reinforcement and Escape Extinction in the Treatment of Feeding Problems

    ERIC Educational Resources Information Center

    LaRue, Robert H.; Stewart, Victoria; Piazza, Cathleen C.; Volkert, Valerie M.; Patel, Meeta R.; Zeleny, Jason

    2011-01-01

    Given the effectiveness of putative escape extinction as treatment for feeding problems, it is surprising that little is known about the effects of escape as reinforcement for appropriate eating during treatment. In the current investigation, we examined the effectiveness of escape as reinforcement for mouth clean (a product measure of…

  17. Generalized Jeans' Escape of Pick-Up Ions in Quasi-Linear Relaxation

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Khazanov, G. V.

    2011-01-01

    Jeans escape is a well-validated formulation of upper atmospheric escape that we have generalized to estimate plasma escape from ionospheres. It involves the computation of the parts of particle velocity space that are unbound by the gravitational potential at the exobase, followed by a calculation of the flux carried by such unbound particles as they escape from the potential well. To generalize this approach for ions, we superposed an electrostatic ambipolar potential and a centrifugal potential, for motions across and along a divergent magnetic field. We then considered how the presence of superthermal electrons, produced by precipitating auroral primary electrons, controls the ambipolar potential. We also showed that the centrifugal potential plays a small role in controlling the mass escape flux from the terrestrial ionosphere. We then applied the transverse ion velocity distribution produced when ions, picked up by supersonic (i.e., auroral) ionospheric convection, relax via quasi-linear diffusion, as estimated for cometary comas [1]. The results provide a theoretical basis for observed ion escape response to electromagnetic and kinetic energy sources. They also suggest that super-sonic but sub-Alfvenic flow, with ion pick-up, is a unique and important regime of ion-neutral coupling, in which plasma wave-particle interactions are driven by ion-neutral collisions at densities for which the collision frequency falls near or below the gyro-frequency. As another possible illustration of this process, the heliopause ribbon discovered by the IBEX mission involves interactions between the solar wind ions and the interstellar neutral gas, in a regime that may be analogous [2].

  18. MEMO: Mars Escape and Magnetic Orbiter

    NASA Astrophysics Data System (ADS)

    Leblanc, F.; Langlais, B.; Chassefiere, E.; Sotin, C.; Barabash, S.; Dehant, V.; Dougherty, M.; Lammer, H.; Mandea, M.; Vennerstrom, S.

    2007-03-01

    MEMO is a new orbiter devoted to the characterization of present atmospheric escape and of the fossile magnetic field. The low periapsis (~130 km) is required to detect and quantify atoms and molecules involved in the escape, and to measure the magnetic f

  19. Escaping Homelessness: Anticipated and Perceived Facilitators

    ERIC Educational Resources Information Center

    Patterson, Allisha; Tweed, Roger

    2009-01-01

    One study with two distinct sections was conducted to identify factors facilitating escape from homelessness. In Section 1, 58 homeless individuals rated possible facilitators of escape (factors they believed would help them become more independent and self-sufficient). In Section 2, 80 participants who had already exited homelessness rated the…

  20. Submarine 'safe to escape' studies in man.

    PubMed

    Jurd, K M; Seddon, F M; Thacker, J C; Blogg, S L; Stansfield, M R D; White, M G; Loveman, G A M

    2014-01-01

    The Royal Navy requires reliable advice on the safe limits of escape from a distressed submarine (DISSUB). Flooding in a DISSUB may cause a rise in ambient pressure, increasing the risk of decompression sickness (DCS) and decreasing the maximum depth from which it is safe to escape. The aim of this study was to investigate the pressure/depth limits to escape following saturation at raised ambient pressure. Exposure to saturation pressures up to 1.6 bar (a) (160 kPa) (n = 38); escapes from depths down to 120 meters of sea water (msw) (n = 254) and a combination of saturation followed by escape (n = 90) was carried out in the QinetiQ Submarine Escape Simulator, Alverstoke, United Kingdom. Doppler ultrasound monitoring was used to judge the severity of decompression stress. The trials confirmed the previously untested advice, in the Guardbook, that if a DISSUB was lying at a depth of 90 msw, then it was safe to escape when the pressure in the DISSUB was 1.5 bar (a), but also indicated that this advice may be overly conservative. This study demonstrated that the upper DISSUB saturation pressure limit to safe escape from 90 msw was 1.6 bar (a), resulting in two cases of DCS. PMID:25109084

  1. Atmospheric escape, redox evolution, and planetary habitability

    NASA Astrophysics Data System (ADS)

    Catling, D. C.; Zahnle, K. J.

    2011-12-01

    Through the greenhouse effect, the presence and composition of an atmosphere is critical for defining a (conventional) circumstellar habitable zone in terms of planetary surface temperatures suitable for liquid water. Lack of knowledge of planetary atmospheres is likely to frustrate attempts to say with any certainty whether detected terrestrial-sized exoplanets may or may not be habitable. Perhaps an underappreciated role in such considerations is the evolutionary effect of atmospheric escape for determining atmospheric composition or whether an atmosphere exists in the first place. Whether atmospheres exist at all on planets is demonstrably connected to the effect of integrated atmospheric escape. When we observe our own Solar System and transiting exoplanets, the existence of an atmosphere is clearly delineated by a relative vulnerability to thermal escape and impact erosion. The prevalence of thermal escape as a key evolutionary determinant for the presence of planetary atmosphere is shown by a relationship between the relative solar (or stellar) heating and the escape velocity. Those bodies with too much stellar heating and too smaller escape velocity end up devoid of atmospheres. Impact erosion is evident in the relationship between impact velocity and escape velocity. Escape due to impacts is particularly important for understanding the large differences in the atmospheres of giant planet moons, such as Ganymede versus Titan. It is also significant for Mars-sized planets. The oxidation state of atmospheres is important for some theories of the origin of life (where an early reducing atmosphere is helpful for organic synthesis) and the evolution of advanced life (where free molecular oxygen is the best source of high energy metabolism). Surfaces on some relatively small planets and moons are observed to have evolved to an oxidized state, which theory and observation can explain through atmospheric escape. There are several examples in the Solar System where a

  2. Impaired Driving

    MedlinePlus

    ... Risk Factors BAC Effects Prevention Additional Resources How big is the problem? In 2014, 9,967 people ... Driving: A Threat to Everyone (October 2011) Additional Data Drunk Driving State Data and Maps Motor Vehicle ...

  3. Drugged Driving

    MedlinePlus

    ... Infographics » Drugged Driving Drugged Driving Email Facebook Twitter Text Description of Infographic Top Right Figure : In 2009, ... crash than those who don't smoke. Bottom Text: Develop Social Strategies Offer to be a designated ...

  4. Light weight escape capsule for fighter aircraft

    NASA Technical Reports Server (NTRS)

    Robert, James A.

    1988-01-01

    Emergency crew escape capabilities have been less than adequate for fighter aircraft since before WW II. From the over-the-side bailout of those days through the current ejection seat with a rocket catapult, escaping from a disabled aircraft has been risky at best. Current efforts are underway toward developing a high-tech, smart ejection seat that will give fighter pilots more room to live in the sky, but an escape capsule is needed to meet current and future fighter envelopes. Escape capsules have a bad reputation due to past examples of high weight, poor performance and great complexity. However, the advantages available demand that a capsule be developed. This capsule concept will minimize the inherent disavantages and incorporate the benefits while integrating all aspects of crew station design. The resulting design is appropriate for a crew station of the year 2010 and includes improved combat acceleration protection, chemical or biological combat capability, improved aircraft to escape system interaction, and the highest level of escape performance achievable. The capsule is compact, which can allow a reduced aircraft size and weighs only 1200 lb. The escape system weight penalty is only 120 lb higher than that for the next ejection seat and the capsule has a corresponding increase in performance.

  5. High torque bellows seal rotary drive

    NASA Technical Reports Server (NTRS)

    Diaguila, A. J.; Macomber, J. W.; Adams, D. W.

    1972-01-01

    Bellows seal rotary drive device was developed which allows high torque transmission through sealed compartments. Bearing friction which would normally be carried by sealing bellows in comparable devices is absorbed by universal-gimbal joint. It can be used to transmit high torque, low speed, rotary motion through sealed barriers to prevent contamination or escape of fluids.

  6. Apollo experience report: Launch escape propulsion subsystem

    NASA Technical Reports Server (NTRS)

    Townsend, N. A.

    1973-01-01

    The Apollo launch escape propulsion subsystem contained three solid rocket motors. The general design, development, and qualification of the solid-propellant pitch-control, tower-jettison, and launch-escape motors of the Apollo launch escape propulsion subsystem were completed during years 1961 to 1966. The launch escape system components are described in general terms, and the sequence of events through the ground-based test programs and flight-test programs is discussed. The initial ground rules established for this system were that it should use existing technology and designs as much as possible. The practicality of this decision is proved by the minimum number of problems that were encountered during the development and qualification program.

  7. Wind enhanced planetary escape: Collisional modifications

    NASA Technical Reports Server (NTRS)

    Curtis, S. A.; Hartle, R. E.

    1976-01-01

    The problem of thermal escape is considered in which both the effects of thermospheric winds at the exobase and collisions below the exobase are included in a Monte Carlo calculation. The collisions are included by means of a collisional relaxation layer of a background gas which models the transition region between the exosphere and the thermosphere. The wind effects are considered in the limiting cases of vertical and horizontal flows. Two species are considered: terrestrial hydrogen and terrestrial helium. In the cases of terrestrial hydrogen the escape fluxes were found to be strongly filtered or throttled by collisions at high exospheric temperatures. The model is applied to molecular hydrogen diffusing through a methane relaxation layer under conditions possible on Titan. The results are similar to the case of terrestrial hydrogen with wind enhanced escape being strongly suppressed by collisions. It is concluded that wind enhanced escape is not an important process on Titan.

  8. Biogeochemistry: Nocturnal escape route for marsh gas

    NASA Astrophysics Data System (ADS)

    Anthony, Katey Walter; MacIntyre, Sally

    2016-07-01

    A field study of methane emissions from wetlands reveals that more of the gas escapes through diffusive processes than was thought, mostly at night. Because methane is a greenhouse gas, the findings have implications for global warming.

  9. Stellar wind interaction and pick-up ion escape of the Kepler-11 "super-Earths"

    NASA Astrophysics Data System (ADS)

    Kislyakova, Kristina; Johnstone, Colin; Odert, Petra; Erkaev, Nikolai; Lammer, Helmut; Lüftinger, Theresa; Holmstöm, Mats; Khodachenko, Maxim; Güdel, Manuel

    2014-05-01

    We present the results of modeling of the interactions between stellar wind and the extended hydrogen-dominated upper atmospheres of planets and estimate the resulting escape of planetary pick-up ions from the 5 «super-Earths» in the compact Kepler-11 system. We compare the escape rates with the efficiency of the thermal escape of neutral hydrogen atoms. Assuming the stellar wind of Kepler-11 is similar to the solar wind, we used a polytropic 1D hydrodynamic wind model to estimate the wind properties at the planetary orbits. We applied a Direct Simulation Monte Carlo Model to model the hydrogen coronae and the stellar wind plasma interaction around Kepler-11b-f planets within a realistic expected heating efficiency range of 15-40%. The same model was used to estimate the ion pick-up escape from the XUV heated and hydrodynamically extended upper atmospheres of Kepler-11b-f. Modeling clarifies the influence of possible magnetic moments on escape processes and allows to estimate the charge exchange and photoionization production rates of planetary ions as well as the loss rates of pick-up H+ ions for all five planets. This study presents also the comparison of the results between the five 'super-Earths' and in a more general sense also with the thermal escape rates of the neutral planetary hydrogen atoms. Our results show that for all Kepler-11b-f exoplanets, a huge neutral hydrogen corona is formed around the planet. The non-symmetric form of the corona changes from planet to planet and is defined mostly by radiation pressure, charge-exchange and gravitational effects. According to our estimates, nonthermal escape rates of pick-up ionized hydrogen atoms for Kepler-11 «super-Earths» vary between ~ 6.4 × 1030 s-1 and ~ 4.1 × 1031 s-1 depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of ~ 1.07 × 107 g·s-1 and ~ 6.8 × 107 g·s-1 respectively, which is a few percent of the thermal

  10. Pile Driving

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Machine-oriented structural engineering firm TERA, Inc. is engaged in a project to evaluate the reliability of offshore pile driving prediction methods to eventually predict the best pile driving technique for each new offshore oil platform. Phase I Pile driving records of 48 offshore platforms including such information as blow counts, soil composition and pertinent construction details were digitized. In Phase II, pile driving records were statistically compared with current methods of prediction. Result was development of modular software, the CRIPS80 Software Design Analyzer System, that companies can use to evaluate other prediction procedures or other data bases.

  11. Polymer escape from a confining potential

    SciTech Connect

    Mökkönen, Harri; Ikonen, Timo; Jónsson, Hannes; Ala-Nissila, Tapio

    2014-02-07

    The rate of escape of polymers from a two-dimensionally confining potential well has been evaluated using self-avoiding as well as ideal chain representations of varying length, up to 80 beads. Long timescale Langevin trajectories were calculated using the path integral hyperdynamics method to evaluate the escape rate. A minimum is found in the rate for self-avoiding polymers of intermediate length while the escape rate decreases monotonically with polymer length for ideal polymers. The increase in the rate for long, self-avoiding polymers is ascribed to crowding in the potential well which reduces the free energy escape barrier. An effective potential curve obtained using the centroid as an independent variable was evaluated by thermodynamic averaging and Kramers rate theory then applied to estimate the escape rate. While the qualitative features are well reproduced by this approach, it significantly overestimates the rate, especially for the longer polymers. The reason for this is illustrated by constructing a two-dimensional effective energy surface using the radius of gyration as well as the centroid as controlled variables. This shows that the description of a transition state dividing surface using only the centroid fails to confine the system to the region corresponding to the free energy barrier and this problem becomes more pronounced the longer the polymer is. A proper definition of a transition state for polymer escape needs to take into account the shape as well as the location of the polymer.

  12. Polymer escape from a confining potential

    NASA Astrophysics Data System (ADS)

    Mökkönen, Harri; Ikonen, Timo; Jónsson, Hannes; Ala-Nissila, Tapio

    2014-02-01

    The rate of escape of polymers from a two-dimensionally confining potential well has been evaluated using self-avoiding as well as ideal chain representations of varying length, up to 80 beads. Long timescale Langevin trajectories were calculated using the path integral hyperdynamics method to evaluate the escape rate. A minimum is found in the rate for self-avoiding polymers of intermediate length while the escape rate decreases monotonically with polymer length for ideal polymers. The increase in the rate for long, self-avoiding polymers is ascribed to crowding in the potential well which reduces the free energy escape barrier. An effective potential curve obtained using the centroid as an independent variable was evaluated by thermodynamic averaging and Kramers rate theory then applied to estimate the escape rate. While the qualitative features are well reproduced by this approach, it significantly overestimates the rate, especially for the longer polymers. The reason for this is illustrated by constructing a two-dimensional effective energy surface using the radius of gyration as well as the centroid as controlled variables. This shows that the description of a transition state dividing surface using only the centroid fails to confine the system to the region corresponding to the free energy barrier and this problem becomes more pronounced the longer the polymer is. A proper definition of a transition state for polymer escape needs to take into account the shape as well as the location of the polymer.

  13. Submarine tower escape decompression sickness risk estimation.

    PubMed

    Loveman, G A M; Seddon, E M; Thacker, J C; Stansfield, M R; Jurd, K M

    2014-01-01

    Actions to enhance survival in a distressed submarine (DISSUB) scenario may be guided in part by knowledge of the likely risk of decompression sickness (DCS) should the crew attempt tower escape. A mathematical model for DCS risk estimation has been calibrated against DCS outcome data from 3,738 exposures of either men or goats to raised pressure. Body mass was used to scale DCS risk. The calibration data included more than 1,000 actual or simulated submarine escape exposures and no exposures with substantial staged decompression. Cases of pulmonary barotrauma were removed from the calibration data. The calibrated model was used to estimate the likelihood of DCS occurrence following submarine escape from the United Kingdom Royal Navy tower escape system. Where internal DISSUB pressure remains at - 0.1 MPa, escape from DISSUB depths < 200 meters is estimated to have DCS risk < 6%. Saturation at raised DISSUB pressure markedly increases risk, with > 60% DCS risk predicted for a 200-meter escape from saturation at 0.21 MPa. Using the calibrated model to predict DCS for direct ascent from saturation gives similar risk estimates to other published models. PMID:25109085

  14. Atomic hydrogen escape rate due to charge exchange with hot plasmaspheric ions

    NASA Technical Reports Server (NTRS)

    Maher, L. J.; Tinsley, B. A.

    1977-01-01

    Data on ion and electron temperatures and concentrations to several thousand kilometers of altitude were obtained from the Atmosphere Explorer C satellite for 1974 and to 850 km from Arecibo incoherent scatter radar measurements. These data were used to normalize diffusive equilibrium profiles. From these profiles and by using the neutral atmospheric model of Jacchia (1971) and a new hydrogen model, the charge-exchange-induced neutral hydrogen escape fluxes for equatorial and middle latitudes were calculated. The data confirm earlier estimates that the charge exchange loss is more important than Jeans escape for the earth. It is also found that inside the plasmapause this charge exchange process with hot plasmapheric ions is the major production and loss process for the satellite population in the hydrogen geocorona.

  15. Simulations of neutralized final focus

    SciTech Connect

    Welch, D.R.; Rose, D.V.; Genoni, T.C.; Yu, S.S.; Barnard, J.J.

    2005-01-18

    In order to drive an inertial fusion target or study high energy density physics with heavy ion beams, the beam radius must be focused to < 3 mm and the pulse length must be compressed to < 10 ns. The conventional scheme for temporal pulse compression makes use of an increasing ion velocity to compress the beam as it drifts and beam space charge to stagnate the compression before final focus. Beam compression in a neutralizing plasma does not require stagnation of the compression, enabling a more robust method. The final pulse shape at the target can be programmed by an applied velocity tilt. In this paper, neutralized drift compression is investigated. The sensitivity of the compression and focusing to beam momentum spread, plasma, and magnetic field conditions is studied with realistic driver examples. Using the 3D particle-in-cell code, we examine issues associated with self-field generation, stability, and vacuum-neutralized transport transition and focusing.

  16. Escape of a mesoscopic particle from a modulated optical trap

    NASA Astrophysics Data System (ADS)

    Kruse, J. R.; Dykman, M. I.; Golding, B.

    2003-03-01

    We describe experiments on noise-induced escape of a mesoscopic particle from a bistable potential well. The potential is created by the interaction of two focused laser beams with a glass sphere of diameter ˜ 1 μm. The trapping potential is mapped quantitatively in 3-dimensions by a statistical method [1]. The dynamics of the particle can be varied from highly overdamped to underdamped by tuning the density of the surrounding environment. The eigenfrequencies of the trapped particle, as well as over-barrier transition rates W, have been directly measured as a function of damping. When the potential is modulated, the escape probability of the particle over the potential barrier becomes synchronized with the driving field. At large modulation amplitude, we find that the system approaches a saddle-node bifurcation. We have measured the critical exponent that describes the amplitude dependence of ln W as the bifurcation point is approached. By varying the modulation frequency, it is possible to probe the non-adiabatic region where the critical exponent has been predicted to change, with results in agreement with theory and numerical simulations. [1] L.I. McCann, M.I. Dykman, and B. Golding, Nature 402, 785 (1999).

  17. 46 CFR 28.390 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 1 2011-10-01 2011-10-01 false Means of escape. 28.390 Section 28.390 Shipping COAST... Operate With More Than 16 Individuals on Board § 28.390 Means of escape. (a) Each space which is used by... two widely separated means of escape. At least one of the means of escape must be independent...

  18. 46 CFR 28.390 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 1 2013-10-01 2013-10-01 false Means of escape. 28.390 Section 28.390 Shipping COAST... Operate With More Than 16 Individuals on Board § 28.390 Means of escape. (a) Each space which is used by... two widely separated means of escape. At least one of the means of escape must be independent...

  19. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Means of escape. 177.500 Section 177.500 Shipping COAST...) CONSTRUCTION AND ARRANGEMENT Escape Requirements § 177.500 Means of escape. (a) Except as otherwise provided in... least two means of escape, one of which must not be a watertight door. (b) The two required means...

  20. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Means of escape. 177.500 Section 177.500 Shipping COAST...) CONSTRUCTION AND ARRANGEMENT Escape Requirements § 177.500 Means of escape. (a) Except as otherwise provided in... least two means of escape, one of which must not be a watertight door. (b) The two required means...

  1. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Means of escape. 177.500 Section 177.500 Shipping COAST...) CONSTRUCTION AND ARRANGEMENT Escape Requirements § 177.500 Means of escape. (a) Except as otherwise provided in... least two means of escape, one of which must not be a watertight door. (b) The two required means...

  2. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Means of escape. 177.500 Section 177.500 Shipping COAST...) CONSTRUCTION AND ARRANGEMENT Escape Requirements § 177.500 Means of escape. (a) Except as otherwise provided in... least two means of escape, one of which must not be a watertight door. (b) The two required means...

  3. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Means of escape. 177.500 Section 177.500 Shipping COAST...) CONSTRUCTION AND ARRANGEMENT Escape Requirements § 177.500 Means of escape. (a) Except as otherwise provided in... least two means of escape, one of which must not be a watertight door. (b) The two required means...

  4. 46 CFR 28.390 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 1 2012-10-01 2012-10-01 false Means of escape. 28.390 Section 28.390 Shipping COAST... Operate With More Than 16 Individuals on Board § 28.390 Means of escape. (a) Each space which is used by... two widely separated means of escape. At least one of the means of escape must be independent...

  5. HST study of Lyman-alpha emission in star-forming galaxies: the effect of neutral gas flows

    NASA Astrophysics Data System (ADS)

    Kunth, Daniel; Mas-Hesse, J. M.; Terlevich, E.; Terlevich, R.; Lequeux, J.; Fall, S. Michael

    1998-06-01

    We present high dispersion HST GHRS UV spectroscopic observations of 8 H II galaxies covering a wide range of metallicities and physical properties. We have found Lyalpha \\ emission in 4 galaxies with blueshifted absorption features, leading to P Cygni like profiles in 3 of them. In all these objects the O I and Si II absorption lines are also blueshifted with respect to the ionized gas, indicating that the neutral gas is outflowing in these galaxies with velocities up to 200 km s(-1) or more. The rest of the sample shows broad damped Lyalpha \\ absorption profiles centered at the wavelength corresponding to the redshift of the H II emitting gas. We therefore find that the velocity structure of the neutral gas in these galaxies is the driving factor that determines the detectability of Lyalpha \\ in emission. Relatively small column densities of neutral gas with even very small dust content would destroy the Lyalpha \\ emission if this gas is static with respect to the ionized region where Lyalpha \\ photons originate. The situation changes dramatically when most of the neutral gas is velocity-shifted with respect to the ionized regions because resonant scattering by neutral hydrogen will be most efficient at wavelengths shorter than the Lyalpha \\ emission, allowing the Lyalpha \\ photons to escape (at least partially). This mechanism complements the effect of porosity in the neutral interstellar medium discussed by other authors, which allows to explain the escape of Lyalpha \\ photons in regions surrounded by static neutral gas, but with only partial covering factors. The anisotropy of these gas flows and their dependence on the intrinsic properties of the violent star-forming episodes taking place in these objects (age, strength, gas geometry,...) might explain (in part) the apparent lack of correlation between other properties (like metallicity) and the frequency of occurence and strength of Lyalpha \\ emission in star-forming galaxies. Attempts to derive the

  6. Hydrogen Escape from early Earth and Mars

    NASA Astrophysics Data System (ADS)

    Zugger, M. E.; Ramirez, R. M.; Kasting, J. F.

    2012-12-01

    A controversy regarding hydrodynamic escape rates arose when Tian et al. (2005) published transonic escape rates for an atmosphere composed of pure H2. Tian et al. concluded that the hydrogen escape rate from early Earth would have been a factor of 20 or more slower than the diffusion limit, even if the solar EUV (extreme ultraviolet) flux was enhanced by a factor of 5 relative to today. This conclusion was challenged by Catling (2006), who pointed out that solar EUV fluxes could have been much higher than this so that plenty of energy should have been available to power escape. This controversy has remained unresolved to date. Hydrogen escape from early Mars is also of interest. As discussed in this session in a complementary paper by Ramirez et al., collision-induced absorption by molecular hydrogen could have helped to warm early Mars, perhaps explaining the formation of valleys and valley networks. Ramirez et al. have shown that a mixture of 90% CO2 and 10% H2 is capable raising early Mars' surface temperature above the freezing point of water, for surface pressures exceeding ~3 bar. However, we need to understand whether H2 mixing ratios of 10% are physically plausible. The H2 partial pressure in Mars' early atmosphere would have been determined by the balance between volcanic outgassing and escape to space. The 10% mixing ratio is high compared to the value of ~10-3 typically assumed for early Earth. But Mars' early atmosphere may have been more reduced than Earth's (Wadwha, 2001); if the hydrogen escape rate on Mars was also slower than on Earth, then additional increases in atmospheric hydrogen concentration are possible. To answer these questions about the early atmospheres of Earth and Mars, we have modified an existing model of hydrodynamic escape, developed by F. Tian, J. Kasting, and others, to converge for atmospheres with a wide range of hydrogen mixing ratios. The model finds subsonic solutions to the hydrodynamic equations; these can be shown to

  7. Compensatory escape mechanism at low Reynolds number

    PubMed Central

    Gemmell, Brad J.; Sheng, Jian; Buskey, Edward J.

    2013-01-01

    Despite high predation pressure, planktonic copepods remain one of the most abundant groups on the planet. Their escape response provides one of most effective mechanisms to maximize evolutionary fitness. Owing to their small size (100 µm) compared with their predators (>1 mm), increasing viscosity is believed to have detrimental effects on copepods’ fitness at lower temperature. Using high-speed digital holography we acquire 3D kinematics of the nauplius escape including both location and detailed appendage motion. By independently varying temperature and viscosity we demonstrate that at natural thermal extremes, contrary to conventional views, nauplii achieve equivalent escape distance while maintaining optimal velocity. Using experimental results and kinematic simulations from a resistive force theory propulsion model, we demonstrate that a shift in appendage timing creates an increase in power stroke duration relative to recovery stroke duration. This change allows the nauplius to limit losses in velocity and maintain distance during escapes at the lower bound of its natural thermal range. The shift in power stroke duration relative to recovery stroke duration is found to be regulated by the temperature dependence of swimming appendage muscle groups, not a dynamic response to viscosity change. These results show that copepod nauplii have natural adaptive mechanisms to compensate for viscosity variations with temperature but not in situations in which viscosity varies independent of temperature, such as in some phytoplankton blooms. Understanding the robustness of escapes in the wake of environmental changes such as temperature and viscosity has implications in assessing the future health of performance compensation. PMID:23487740

  8. Cerebrospinal Fluid HIV Escape from Antiretroviral Therapy.

    PubMed

    Ferretti, Francesca; Gisslen, Magnus; Cinque, Paola; Price, Richard W

    2015-06-01

    CNS infection is a nearly constant facet of systemic CNS infection and is generally well controlled by suppressive systemic antiretroviral therapy (ART). However, there are instances when HIV can be detected in the cerebrospinal fluid (CSF) despite suppression of plasma viruses below the clinical limits of measurement. We review three types of CSF viral escape: asymptomatic, neuro-symptomatic, and secondary. The first, asymptomatic CSF escape, is seemingly benign and characterized by lack of discernable neurological deterioration or subsequent CNS disease progression. Neuro-symptomatic CSF escape is an uncommon, but important, entity characterized by new or progressive CNS disease that is critical to recognize clinically because of its management implications. Finally, secondary CSF escape, which may be even more uncommon, is defined by an increase of CSF HIV replication in association with a concomitant non-HIV infection, as a consequence of the local inflammatory response. Understanding these CSF escape settings not only is important for clinical diagnosis and management but also may provide insight into the CNS HIV reservoir. PMID:25860317

  9. Stellar wind interaction and pick-up ion escape of the Kepler-11 "super-Earths"

    NASA Astrophysics Data System (ADS)

    Kislyakova, K. G.; Johnstone, C. P.; Odert, P.; Erkaev, N. V.; Lammer, H.; Lüftinger, T.; Holmström, M.; Khodachenko, M. L.; Güdel, M.

    2014-02-01

    Aims: We study the interactions between stellar winds and the extended hydrogen-dominated upper atmospheres of planets. We estimate the resulting escape of planetary pick-up ions from the five "super-Earths" in the compact Kepler-11 system and compare the escape rates with the efficiency of the thermal escape of neutral hydrogen atoms. Methods: Assuming the stellar wind of Kepler-11 is similar to the solar wind, we use a polytropic 1D hydrodynamic wind model to estimate the wind properties at the planetary orbits. We apply a direct simulation Monte Carlo model to model the hydrogen coronae and the stellar wind plasma interaction around Kepler-11b-f within a realistic expected heating efficiency range of 15-40%. The same model is used to estimate the ion pick-up escape from the XUV heated and hydrodynamically extended upper atmospheres of Kepler-11b-f. From the interaction model, we study the influence of possible magnetic moments, calculate the charge exchange and photoionization production rates of planetary ions, and estimate the loss rates of pick-up H+ ions for all five planets. We compare the results between the five "super-Earths" and the thermal escape rates of the neutral planetary hydrogen atoms. Results: Our results show that a huge neutral hydrogen corona is formed around the planet for all Kepler-11b-f exoplanets. The non-symmetric form of the corona changes from planet to planet and is defined mostly by radiation pressure and gravitational effects. Non-thermal escape rates of pick-up ionized hydrogen atoms for Kepler-11 "super-Earths" vary between ~6.4 × 1030 s-1 and ~4.1 × 1031 s-1, depending on the planet's orbital location and assumed heating efficiency. These values correspond to non-thermal mass loss rates of ~1.07 × 107 g s-1 and ~6.8 × 107 g s-1 respectively, which is a few percent of the thermal escape rates.

  10. Comparative pick-up ion distributions at Mars and Venus: Consequences for atmospheric deposition and escape

    NASA Astrophysics Data System (ADS)

    Curry, Shannon M.; Luhmann, Janet; Ma, Yingjuan; Liemohn, Michael; Dong, Chuanfei; Hara, Takuya

    2015-09-01

    Without the shielding of a substantial intrinsic dipole magnetic field, the atmospheres of Mars and Venus are particularly susceptible to similar atmospheric ion energization and scavenging processes. However, each planet has different attributes and external conditions controlling its high altitude planetary ion spatial and energy distributions. This paper describes analogous test particle simulations in background MHD fields that allow us to compare the properties and fates, precipitation or escape, of the mainly O+ atmospheric pick-up ions at Mars and Venus. The goal is to illustrate how atmospheric and planetary scales affect the upper atmospheres and space environments of our terrestrial planet neighbors. The results show the expected convection electric field-related hemispheric asymmetries in both precipitation and escape, where the degree of asymmetry at each planet is determined by the planetary scale and local interplanetary field strength. At Venus, the kinetic treatment of O+ reveals a strong nightside source of precipitation while Mars' crustal fields complicate the simple asymmetry in ion precipitation and drive a dayside source of precipitation. The pickup O+ escape pattern at both Venus and Mars exhibits low energy tailward escape, but Mars exhibits a prominent, high energy 'polar plume' feature in the hemisphere of the upward convection electric field while the Venus ion wake shows only a modest poleward concentration. The overall escape is larger at Venus than Mars (2.1 ×1025 and 4.3 ×1024 at solar maximum, respectively), but the efficiency (likelihood) of O+ escaping is 2-3 times higher at Mars. The consequences of these comparisons for pickup ion related atmospheric energy deposition, loss rates, and detection on spacecraft including PVO, VEX, MEX and MAVEN are considered. In particular, both O+ precipitation and escape show electric field controlled asymmetries that grow with energy, while the O+ fluxes and energy spectra at selected spatial

  11. Radiative equilibrium and escape of Pluto's atmosphere

    NASA Astrophysics Data System (ADS)

    Erwin, Justin; Koskinen, Tommi T.; Yelle, Roger V.

    2015-11-01

    Observations of Pluto’s extend atmosphere by the New Horizons spacecraft motivate an update to our modeling effort on Pluto’s atmosphere. New Horizons observations have already improved our constraints on planet radius and surface pressure, which are key to modeling the atmospheric structure. We model the radiative conductive equilibrium in the lower atmosphere combined with the UV driven escape model of the upper atmosphere. The non-LTE radiative transfer model in the lower atmosphere include heating and cooling by CH4, CO, and HCN. The escape model of the upper atmosphere is updated to include diffusion and escape of each molecular component. These results will be used to aid in the analysis and better understanding of the full atmospheric structure.

  12. Thermal escape from extrasolar giant planets.

    PubMed

    Koskinen, Tommi T; Lavvas, Panayotis; Harris, Matthew J; Yelle, Roger V

    2014-04-28

    The detection of hot atomic hydrogen and heavy atoms and ions at high altitudes around close-in extrasolar giant planets (EGPs) such as HD209458b implies that these planets have hot and rapidly escaping atmospheres that extend to several planetary radii. These characteristics, however, cannot be generalized to all close-in EGPs. The thermal escape mechanism and mass loss rate from EGPs depend on a complex interplay between photochemistry and radiative transfer driven by the stellar UV radiation. In this study, we explore how these processes change under different levels of irradiation on giant planets with different characteristics. We confirm that there are two distinct regimes of thermal escape from EGPs, and that the transition between these regimes is relatively sharp. Our results have implications for thermal mass loss rates from different EGPs that we discuss in the context of currently known planets and the detectability of their upper atmospheres. PMID:24664923

  13. Thermal escape from extrasolar giant planets

    PubMed Central

    Koskinen, Tommi T.; Lavvas, Panayotis; Harris, Matthew J.; Yelle, Roger V.

    2014-01-01

    The detection of hot atomic hydrogen and heavy atoms and ions at high altitudes around close-in extrasolar giant planets (EGPs) such as HD209458b implies that these planets have hot and rapidly escaping atmospheres that extend to several planetary radii. These characteristics, however, cannot be generalized to all close-in EGPs. The thermal escape mechanism and mass loss rate from EGPs depend on a complex interplay between photochemistry and radiative transfer driven by the stellar UV radiation. In this study, we explore how these processes change under different levels of irradiation on giant planets with different characteristics. We confirm that there are two distinct regimes of thermal escape from EGPs, and that the transition between these regimes is relatively sharp. Our results have implications for thermal mass loss rates from different EGPs that we discuss in the context of currently known planets and the detectability of their upper atmospheres. PMID:24664923

  14. Broadening of neutralization activity to directly block a dominant antibody-driven SARS-coronavirus evolution pathway.

    PubMed

    Sui, Jianhua; Aird, Daniel R; Tamin, Azaibi; Murakami, Akikazu; Yan, Meiying; Yammanuru, Anuradha; Jing, Huaiqi; Kan, Biao; Liu, Xin; Zhu, Quan; Yuan, Qing-An; Adams, Gregory P; Bellini, William J; Xu, Jianguo; Anderson, Larry J; Marasco, Wayne A

    2008-11-01

    Phylogenetic analyses have provided strong evidence that amino acid changes in spike (S) protein of animal and human SARS coronaviruses (SARS-CoVs) during and between two zoonotic transfers (2002/03 and 2003/04) are the result of positive selection. While several studies support that some amino acid changes between animal and human viruses are the result of inter-species adaptation, the role of neutralizing antibodies (nAbs) in driving SARS-CoV evolution, particularly during intra-species transmission, is unknown. A detailed examination of SARS-CoV infected animal and human convalescent sera could provide evidence of nAb pressure which, if found, may lead to strategies to effectively block virus evolution pathways by broadening the activity of nAbs. Here we show, by focusing on a dominant neutralization epitope, that contemporaneous- and cross-strain nAb responses against SARS-CoV spike protein exist during natural infection. In vitro immune pressure on this epitope using 2002/03 strain-specific nAb 80R recapitulated a dominant escape mutation that was present in all 2003/04 animal and human viruses. Strategies to block this nAb escape/naturally occurring evolution pathway by generating broad nAbs (BnAbs) with activity against 80R escape mutants and both 2002/03 and 2003/04 strains were explored. Structure-based amino acid changes in an activation-induced cytidine deaminase (AID) "hot spot" in a light chain CDR (complementarity determining region) alone, introduced through shuffling of naturally occurring non-immune human VL chain repertoire or by targeted mutagenesis, were successful in generating these BnAbs. These results demonstrate that nAb-mediated immune pressure is likely a driving force for positive selection during intra-species transmission of SARS-CoV. Somatic hypermutation (SHM) of a single VL CDR can markedly broaden the activity of a strain-specific nAb. The strategies investigated in this study, in particular the use of structural information in

  15. Distracted Driving

    MedlinePlus

    ... combines all three types of distraction. 3 How big is the problem? Deaths In 2013, 3,154 ... European countries. More A CDC study analyzed 2011 data on distracted driving, including talking on a cell ...

  16. Distracted driving

    MedlinePlus

    ... stay safe with a cell phone in the car. ... for Disease Control and Prevention Injury Prevention & Control. Motor Vehicle Safety. www.cdc.gov/motorvehiclesafety/distracted_driving . Accessed May ...

  17. Driving Safely

    MedlinePlus

    ... drivers’ flexibility and coordination, and reduced driving errors. S l Hand grip strengthening to help you hold on to the steering wheel l Shoulder and upper arm flexibility exercises to make ...

  18. Statistical theory of asteroid escape rates.

    PubMed

    Jaffé, Charles; Ross, Shane D; Lo, Martin W; Marsden, Jerrold; Farrelly, David; Uzer, T

    2002-07-01

    Transition states in phase space are identified and shown to regulate the rate of escape of asteroids temporarily captured in circumplanetary orbits. The transition states, similar to those occurring in chemical reaction dynamics, are then used to develop a statistical semianalytical theory for the rate of escape of asteroids temporarily captured by Mars. Theory and numerical simulations are found to agree to better than 1%. These calculations suggest that further development of transition state theory in celestial mechanics, as an alternative to large-scale numerical simulations, will be a fruitful approach to mass transport calculations. PMID:12097024

  19. Martian Atmospheric and Ionospheric plasma Escape

    NASA Astrophysics Data System (ADS)

    Lundin, Rickard

    2016-04-01

    Solar forcing is responsible for the heating, ionization, photochemistry, and erosion processes in the upper atmosphere throughout the lifetime of the terrestrial planets. Of the four terrestrial planets, the Earth is the only one with a fully developed biosphere, while our kin Venus and Mars have evolved into arid inhabitable planets. As for Mars, there are ample evidences for an early Noachian, water rich period on Mars. The question is, what made Mars evolve so differently compared to the Earth? Various hydrosphere and atmospheric evolution scenarios for Mars have been forwarded based on surface morphology, chemical composition, simulations, semi-empiric (in-situ data) models, and the long-term evolution of the Sun. Progress has been made, but the case is still open regarding the changes that led to the present arid surface and tenuous atmosphere at Mars. This presentation addresses the long-term variability of the Sun, the solar forcing impact on the Martian atmosphere, and its interaction with the space environment - an electromagnetic wave and particle interaction with the upper atmosphere that has implications for its photochemistry, composition, and energization that governs thermal and non-thermal escape. Non-thermal escape implies an electromagnetic upward energization of planetary ions and molecules to velocities above escape velocity, a process governed by a combination of solar EUV radiation (ionization), and energy and momentum transfer by the solar wind. The ion escape issue dates back to the early Soviet and US-missions to Mars, but the first more accurate estimates of escape rates came with the Phobos-2 mission in 1989. Better-quality ion composition measurement results of atmospheric/ionospheric ion escape from Mars, obtained from ESA Mars Express (MEX) instruments, have improved our understanding of the ion escape mechanism. With the NASA MAVEN spacecraft orbiting Mars since Sept. 2014, dual in-situ measurement with plasma instruments are now

  20. Enhanced HIV-1 neutralization by antibody heteroligation

    PubMed Central

    Mouquet, Hugo; Warncke, Malte; Scheid, Johannes F.; Seaman, Michael S.; Nussenzweig, Michel C.

    2012-01-01

    Passive transfer of broadly neutralizing human antibodies against HIV-1 protects macaques against infection. However, HIV-1 uses several strategies to escape antibody neutralization, including mutation of the gp160 viral surface spike, a glycan shield to block antibody access to the spike, and expression of a limited number of viral surface spikes, which interferes with bivalent antibody binding. The latter is thought to decrease antibody apparent affinity or avidity, thereby interfering with neutralizing activity. To test the idea that increasing apparent affinity might enhance neutralizing activity, we engineered bispecific anti–HIV-1 antibodies (BiAbs) that can bind bivalently by virtue of one scFv arm that binds to gp120 and a second arm to the gp41 subunit of gp160. The individual arms of the BiAbs preserved the binding specificities of the original anti-HIV IgG antibodies and together bound simultaneously to gp120 and gp41. Heterotypic bivalent binding enhanced neutralization compared with the parental antibodies. We conclude that antibody recognition and viral neutralization of HIV can be improved by heteroligation. PMID:22219363

  1. Constraining the Metallicity and Escape Fraction of Two z≈3.1 Lyman-Alpha Emitting Galaxies

    NASA Astrophysics Data System (ADS)

    Richardson, Mark L. A.; McLinden, E. M.; Malhotra, S.; Rhoads, J. E.; Levesque, E. M.

    2012-05-01

    We observed two z≈3.1 Lyman-α emitting galaxies (LAE) using the Near-infrared Integral Field Spectrometer (NIFS) at Gemini North, specifically looking for [OIII] 4960 & 5008Å, [OII] 3727Å, and H-β 4863Å. We detected the [OIII] doublet in both objects, determined upper limits for [OII] for both objects, and determined upper limits for H-β for one object. With the detections and upper limits we use the [OIII]/[OII] and R23 line diagnostic to attempt to constrain the metallicity and escape fraction of Ly-α. These metallicity constraints are needed to explore the behaviour of the Mass-Metallicty relation in the low-mass regime and also give insight into the star formation histories of LAE which are known to host young stellar populations. The escape fraction, when combined with an extinction correction, gives insight into the presence of neutral gas. This neutral gas is responsible for resonantly scattering any escaped Ly-α photons, increasing its optical depth to dust. For one object we constrain the metallicity to be Z≤ 0.4Z⊙ and constrain the escape fraction of Ly-α to be Fesc ≤ 30%. For the second object we are only able to constrain its escape fraction, finding 6% ≤ Fesc ≤ 40%. We would like to thank the Natural Sciences and Engineering Research Council of Canada for their financial support through a post-graduate fellowship.

  2. Centrifugally Stimulated Exospheric Ion Escape at Mercury

    NASA Technical Reports Server (NTRS)

    Delcourt, Dominique; Seki, K.; Terada, N.; Moore, Thomas E.

    2012-01-01

    We investigate the transport of ions in the low-altitude magnetosphere magnetosphere of Mercury. We show that, because of small spatial scales, the centrifugal effect due to curvature of the E B drift paths can lead to significant particle energization in the parallel direction. We demonstrate that because of this effect, ions with initial speed smaller than the escape speed such as those produced via thermal desorption can overcome gravity and escape into the magnetosphere. The escape route of this low-energy exosphere originating material is largely controlled by the magnetospheric convection rate. This escape route spreads over a narrower range of altitudes when the convection rate increases. Bulk transport of low-energy planetary material thus occurs within a limited region of space once moderate magnetospheric convection is established. These results suggest that, via release of material otherwise gravitationally trapped, the E B related centrifugal acceleration is an important mechanism for the net supply of plasma to the magnetosphere of Mercury.

  3. Developing the E-Scape Software System

    ERIC Educational Resources Information Center

    Derrick, Karim

    2012-01-01

    Most innovations have contextual pre-cursors that prompt new ways of thinking and in their turn help to give form to the new reality. This was the case with the e-scape software development process. The origins of the system existed in software components and ideas that we had developed through previous projects, but the ultimate direction we took…

  4. Nociception and escape behavior in planarians

    NASA Astrophysics Data System (ADS)

    Schoetz Collins, Eva-Maria

    2015-03-01

    Planarians are famous and widely studied for their regenerative capabilities. When a moving planarian is cut through the middle, the resulting head and tail pieces instantaneously retract and exhibit a characteristic escape response that differs from normal locomotion. In asexual animals, a similar reaction is observed when the planarian undergoes fission, suggesting that reproduction through self-tearing is a rather traumatic event for the animal. Using a multiscale approach, we unravel the dynamics, mechanics, and functional aspects of the planarian escape response. This musculature-driven gait was found to be a dominating response that supersedes the urge to feed or reproduce and quantitatively differs from other modes of planarian locomotion (gliding, peristalsis). We show that this escape gait constitutes the animal's pain response mediated by TRP like receptors and the neurotransmitter histamine, and that it can be induced through adverse thermal, mechanical, electrical or chemical stimuli. Ultimately, we will examine the neuronal subpopulations involved in mediating escape reflexes in planarians and how they are functionally restored during regeneration, thereby gaining mechanistic insight into the neuronal circuits required for specific behaviors. Supported by BWF CASI and Sloan Foundation.

  5. Animal escapology II: escape trajectory case studies

    PubMed Central

    Domenici, Paolo; Blagburn, Jonathan M.; Bacon, Jonathan P.

    2011-01-01

    Summary Escape trajectories (ETs; measured as the angle relative to the direction of the threat) have been studied in many taxa using a variety of methodologies and definitions. Here, we provide a review of methodological issues followed by a survey of ET studies across animal taxa, including insects, crustaceans, molluscs, lizards, fish, amphibians, birds and mammals. Variability in ETs is examined in terms of ecological significance and morpho-physiological constraints. The survey shows that certain escape strategies (single ETs and highly variable ETs within a limited angular sector) are found in most taxa reviewed here, suggesting that at least some of these ET distributions are the result of convergent evolution. High variability in ETs is found to be associated with multiple preferred trajectories in species from all taxa, and is suggested to provide unpredictability in the escape response. Random ETs are relatively rare and may be related to constraints in the manoeuvrability of the prey. Similarly, reports of the effect of refuges in the immediate environment are relatively uncommon, and mainly confined to lizards and mammals. This may be related to the fact that work on ETs carried out in laboratory settings has rarely provided shelters. Although there are a relatively large number of examples in the literature that suggest trends in the distribution of ETs, our understanding of animal escape strategies would benefit from a standardization of the analytical approach in the study of ETs, using circular statistics and related tests, in addition to the generation of large data sets. PMID:21753040

  6. Evolution: Escaping the Inevitability of Ageing.

    PubMed

    Archer, C Ruth; Hosken, David J

    2016-03-01

    William Hamilton argued that even species inhabiting the farthest flung corners of the universe should age. However, a recent study shows that to find a species that escapes ageing, you only need to look as far as your local pond. PMID:26954440

  7. THE EFFECT OF GALACTIC PROPERTIES ON THE ESCAPE FRACTION OF IONIZING PHOTONS

    SciTech Connect

    Fernandez, Elizabeth R.; Shull, J. Michael E-mail: michael.shull@colorado.edu

    2011-04-10

    The escape fraction, f{sub esc}, of ionizing photons from early galaxies is a crucial parameter for determining whether the observed galaxies at z {>=} 6 are able to reionize the high-redshift intergalactic medium. Previous attempts to measure f{sub esc} have found a wide range of values, varying from less than 0.01 to nearly 1. Rather than finding a single value of f{sub esc}, we clarify through modeling how internal properties of galaxies affect f{sub esc} through the density and distribution of neutral hydrogen within the galaxy, along with the rate of ionizing photons' production. We find that the escape fraction depends sensitively on the covering factor of clumps, along with the density of the clumped and interclump medium. One must therefore be cautious when dealing with an inhomogeneous medium. Fewer high-density clumps lead to a greater escape fraction than more numerous low-density clumps. When more ionizing photons are produced in a starburst, f{sub esc} increases, as photons escape more readily from the gas layers. Large variations in the predicted escape fraction, caused by differences in the hydrogen distribution, may explain the large observed differences in f{sub esc} among galaxies. Values of f{sub esc} must also be consistent with the reionization history. High-mass galaxies alone are unable to reionize the universe, because f{sub esc} >1 would be required. Small galaxies are needed to achieve reionization, with greater mean escape fraction in the past.

  8. Oxygen Pickup Ions at Mars: Model Comparisons with MAVEN Data and Implications for Oxygen Escape

    NASA Astrophysics Data System (ADS)

    Cravens, Tom; Rahmati, Ali; Larsen, Davin; Lillis, Rob; Connerney, Jack; Halekas, Jasper; Bougher, Stephen W.

    2015-04-01

    A major source of atmospheric escape on Mars is the dissociative recombination of O2+ in the ionosphere, which creates oxygen atoms with energies exceeding the escape energy. These atoms are the source of the hot oxygen exosphere of Mars, which extends to tens of Martian radii. Direct measurement of the distant oxygen exosphere, which is mainly populated with escaping neutral oxygen atoms, is difficult due to the very low densities at these distances. However, ionization of these atoms creates pickup ions that are accelerated by the solar wind convective electric field to high energies, allowing them to be measured by the SEP (Solar Energetic Particle) instrument onboard the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft.We modeled the hot oxygen at Mars and its interaction with the solar wind using Monte Carlo and test particle methods and using densities and temperatures from the MTGCM (Mars Thermospheric General Circulation Model). The distribution function of hot oxygen atoms at 300 km is calculated using a two-stream method, and the Liouville theorem extends this distribution for the gravitationally bound and escaping parts to high altitudes. We determined the O+ flux upstream of Mars as a function of energy, and separate it into parts due both the gravitationally bound and the escaping oxygen. Significant fluxes of O+ ions are predicted for energies greater than 60 keV and have been observed by the SEP instrument, even when MAVEN was several Martian radii away from the planet. These data-model comparisons will be presented and then interpreted in terms of the escape of oxygen from Mars.

  9. Antibody neutralization of retargeted measles viruses.

    PubMed

    Lech, Patrycja J; Pappoe, Roland; Nakamura, Takafumi; Tobin, Gregory J; Nara, Peter L; Russell, Stephen J

    2014-04-01

    The measles virus (MV) vaccine lineage is a promising oncolytic but prior exposure to the measles vaccine or wild-type MV strains limits treatment utility due to the presence of anti-measles antibodies. MV entry can be redirected by displaying a polypeptide ligand on the Hemagglutinin (H) C-terminus. We hypothesized that retargeted MV would escape neutralization by monoclonal antibodies (mAbs) recognizing the H receptor-binding surface and be less susceptible to neutralization by human antisera. Using chimeric H proteins, with and without mutations that ablate MV receptor binding, we show that retargeted MVs escape mAbs that target the H receptor-binding surface by virtue of mutations that ablate infection via SLAM and CD46. However, C-terminally displayed domains do not mediate virus entry in the presence of human antibodies that bind to the underlying H domain. In conclusion, utility of retargeted oncolytic measles viruses does not extend to evasion of human serum neutralization. PMID:24725950

  10. Exploring potential Pluto-generated neutral tori

    NASA Astrophysics Data System (ADS)

    Smith, Howard T.; Hill, Matthew; KollMann, Peter; McHutt, Ralph

    2015-11-01

    The NASA New Horizons mission to Pluto is providing unprecedented insight into this mysterious outer solar system body. Escaping molecular nitrogen is of particular interest and possibly analogous to similar features observed at moons of Saturn and Jupiter. Such escaping N2 has the potential of creating molecular nitrogen and N (as a result of molecular dissociation) tori or partial toroidal extended particle distributions. The presence of these features would present the first confirmation of an extended toroidal neutral feature on a planetary scale in our solar system. While escape velocities are anticipated to be lower than those at Enceladus, Io or even Europa, particle lifetimes are much longer in Pluto’s orbit because as a result of much weaker solar interaction processes along Pluto’s orbit (on the order of tens of years). Thus, with a ~248 year orbit, Pluto may in fact be generating an extended toroidal feature along it orbit.For this work, we modify and apply our 3-D Monte Carlo neutral torus model (previously used at Saturn, Jupiter and Mercury) to study/analyze the theoretical possibility and scope of potential Pluto-generated neutral tori. Our model injects weighted particles and tracks their trajectories under the influence of all gravitational fields with interactions with other particles, solar photons and Pluto collisions. We present anticipated N2 and N tori based on current estimates of source characterization and environmental conditions. We also present an analysis of sensitivity to assumed initial conditions. Such results can provide insight into the Pluto system as well as valuable interpretation of New Horizon’s observational data.

  11. Simulating the one-dimensional structure of Titan's upper atmosphere: 3. Mechanisms determining methane escape

    NASA Astrophysics Data System (ADS)

    Bell, Jared M.; Bougher, Stephen W.; Waite, J. Hunter, Jr.; Ridley, Aaron J.; Magee, Brian A.; Mandt, Kathleen E.; Westlake, Joseph; DeJong, Anna D.; Bar-Nun, Akiva; Jacovi, Ronen; Toth, Gabor; De La Haye, Virginie; Gell, David; Fletcher, Gregory

    2011-11-01

    This investigation extends the work presented by Bell et al. (2010a, 2010b). Using the one-dimensional (1-D) configuration of the Titan Global Ionosphere-Thermosphere Model (T-GITM), we quantify the relative importance of the different dynamical and chemical mechanisms that determine the CH4 escape rates calculated by T-GITM. Moreover, we consider the implications of updated Huygens Gas Chromatograph Mass Spectrometer (GCMS) determinations of both the 40Ar mixing ratios and 15N/14N isotopic ratios in work by Niemann et al. (2010). Combining the GCMS constraints in the lower atmosphere with the Ion Neutral Mass Spectrometer (INMS) measurements in work by Magee et al. (2009), our simulation results suggest that the optimal CH4 homopause altitude is located at 1000 km. Using this homopause altitude, we conclude that topside escape rates of 1.0 × 1010 CH4 m-2 s-1 (referred to the surface) are sufficient to reproduce the INMS methane measurements in work by Magee et al. (2009). These escape rates of methane are consistent with the upper limits to methane escape (1.11 × 1011 CH4 m-2 s-1) established by both the Cassini Plasma Spectrometer (CAPS) and Magnetosphere Imaging Instrument (MIMI) measurements of Carbon-group ions in the near Titan magnetosphere.

  12. Launch Pad Escape System Design (Human Spaceflight)

    NASA Technical Reports Server (NTRS)

    Maloney, Kelli

    2011-01-01

    A launch pad escape system for human spaceflight is one of those things that everyone hopes they will never need but is critical for every manned space program. Since men were first put into space in the early 1960s, the need for such an Emergency Escape System (EES) has become apparent. The National Aeronautics and Space Administration (NASA) has made use of various types of these EESs over the past 50 years. Early programs, like Mercury and Gemini, did not have an official launch pad escape system. Rather, they relied on a Launch Escape System (LES) of a separate solid rocket motor attached to the manned capsule that could pull the astronauts to safety in the event of an emergency. This could only occur after hatch closure at the launch pad or during the first stage of flight. A version of a LES, now called a Launch Abort System (LAS) is still used today for all manned capsule type launch vehicles. However, this system is very limited in that it can only be used after hatch closure and it is for flight crew only. In addition, the forces necessary for the LES/LAS to get the capsule away from a rocket during the first stage of flight are quite high and can cause injury to the crew. These shortcomings led to the development of a ground based EES for the flight crew and ground support personnel as well. This way, a much less dangerous mode of egress is available for any flight or ground personnel up to a few seconds before launch. The early EESs were fairly simple, gravity-powered systems to use when thing's go bad. And things can go bad very quickly and catastrophically when dealing with a flight vehicle fueled with millions of pounds of hazardous propellant. With this in mind, early EES designers saw such a passive/unpowered system as a must for last minute escapes. This and other design requirements had to be derived for an EES, and this section will take a look at the safety design requirements had to be derived for an EES, and this section will take a look at

  13. 33 CFR 143.101 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Officer in Charge, Marine Inspection, one or more “secondary means of escape.” (d) Unmanned OCS facilities... board, unmanned facilities shall also be provided with one or more “secondary means of escape,” but...

  14. 33 CFR 143.101 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Officer in Charge, Marine Inspection, one or more “secondary means of escape.” (d) Unmanned OCS facilities... board, unmanned facilities shall also be provided with one or more “secondary means of escape,” but...

  15. 33 CFR 143.101 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Officer in Charge, Marine Inspection, one or more “secondary means of escape.” (d) Unmanned OCS facilities... board, unmanned facilities shall also be provided with one or more “secondary means of escape,” but...

  16. 17. VIEW OF ESCAPE TRAINING TANK, SHOWING ENCLOSED PASSAGEWAY FROM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. VIEW OF ESCAPE TRAINING TANK, SHOWING ENCLOSED PASSAGEWAY FROM ELEVATOR TO 18-FOOT LOCK, LOOKING EAST - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  17. 14. DETAIL VIEW OF ESCAPE TRAINING TANK, SHOWING HOLDDOWN RODS, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. DETAIL VIEW OF ESCAPE TRAINING TANK, SHOWING HOLD-DOWN RODS, LOOKING SOUTH - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  18. 15. VIEW OF ESCAPE TRAINING TANK, LOOKING EAST ACROSS MEZZANINE, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. VIEW OF ESCAPE TRAINING TANK, LOOKING EAST ACROSS MEZZANINE, SHOWING ENTRANCE TO SUBMARINE SECTION AT 110-FOOT LEVEL - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  19. 34. VIEW OF SUBMARINE ESCAPE TRAINING TANK PRIOR TO ADDITION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    34. VIEW OF SUBMARINE ESCAPE TRAINING TANK PRIOR TO ADDITION OF BLISTERS IN 1959, LOOKING SOUTHEAST - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  20. 21. VIEW OF ESCAPE TRAINING TANK, SHOWING INTERIOR OF CUPOLA ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    21. VIEW OF ESCAPE TRAINING TANK, SHOWING INTERIOR OF CUPOLA AND TOP OF THE TANK, LOOKING NORTHEAST - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  1. 18. VIEW OF ESCAPE TRAINING TANK, SHOWING ENCLOSED PASSAGEWAY FROM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. VIEW OF ESCAPE TRAINING TANK, SHOWING ENCLOSED PASSAGEWAY FROM 50-FOOT LOCK TO ELEVATOR, LOOKING WEST - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  2. 23. VIEW OF ESCAPE TRAINING TANK, LOOKING NORTHWEST, SHOWING TWOLOCK ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. VIEW OF ESCAPE TRAINING TANK, LOOKING NORTHWEST, SHOWING TWO-LOCK RECOMPRESSION CHAMBER IN PASSAGEWAY FROM ELEVATOR TO CUPOLA - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  3. Structural basis of influenza virus neutralization

    PubMed Central

    Han, Thomas; Marasco, Wayne A.

    2010-01-01

    Although seasonal influenza vaccines play a valuable role in reducing the spread of the virus at the population level, ongoing viral evolution to evade immune responses remains problematic. No current vaccines are likely to elicit enduring protection in the face of emerging and re-emerging influenza viruses that rapidly undergoing antigenic drift. Eliciting broadly cross-neutralizing antibody responses against influenza virus is a crucial goal for seasonal and pandemic influenza vaccine preparation. Recent three-dimensional structure information obtained from crystallization of influenza antigens in complex with neutralizing antibodies (nAbs) have provided a framework for interpreting antibody-based viral neutralization that should aid in the design of vaccine immunogens. Here, we will review current knowledge of the structure-based mechanisms contributing to the neutralization and neutralization escape of influenza viruses. We will also explore the potential for this structure-based approach to overcome the challenge of obtaining the highly desired “universal” influenza vaccine. PMID:21251008

  4. Escape of atmospheres and loss of water

    NASA Technical Reports Server (NTRS)

    Hunten, D. M.; Donahue, T. M.; Walker, J. C. G.; Kasting, J. F.

    1989-01-01

    The properties and limitations of several loss processes for atmospheric gases are presented and discussed. They include thermal loss (Jeans and hydrodynamic); nonthermal loss (all processes involve charged particles); and impact erosion, including thermal escape from a molten body heated by rapid accretion. Hydrodynamic escape, or 'blowoff', is of particular interest because it offers the prospect of processing large quantities of gas and enriching the remainder in heavy elements and isotopes. In a second part, the water budgets and likely evolutionary histories of Venus, Earth and Mars are assessed. Although it is tempting to associate the great D/H enrichment on Venus with loss of a large initial endowment, a steady state with juvenile water (perhaps from comets) is equally probable.

  5. Endosomal escape: a bottleneck in intracellular delivery.

    PubMed

    Shete, Harshad K; Prabhu, Rashmi H; Patravale, Vandana B

    2014-01-01

    With advances in therapeutic science, apart from drugs, newer bioactive moieties like oligonucleotides, proteins, peptides, enzymes and antibodies are constantly being introduced for the betterment of therapeutic efficacy. These moieties have intracellular components of the cells like cytoplasm and nucleus as one of their pharmacological sites for exhibiting therapeutic activity. Despite their promising efficacy, their intracellular bioavailability has been critically hampered leading to failure in the treatment of numerous diseases and disorders. The endosomal uptake pathway is known to be a rate-limiting barrier for such systems. Bioactive molecules get trapped in the endosomal vesicles and degraded in the lysosomal compartment, necessitating the need for effective strategies that facilitate the endosomal escape and enhance the cytosolic bioavailability of bioactives. Microbes like viruses and bacteria have developed their innate mechanistic tactics to translocate their genome and toxins by efficiently penetrating the host cell membrane. Understanding this mechanism and exploring it further for intracellular delivery has opened new avenues to surmount the endosomal barrier. These strategies include membrane fusion, pore formation and proton sponge effects. On the other hand, progress in designing a novel smart polymeric carrier system that triggers endosomal escape by undergoing modulations in the intracellular milieu has further led to an improvement in intracellular delivery. These comprise pH, enzyme and temperature-induced modulators, synthetic cationic lipids and photo-induced physical disruption. Each of the aforementioned strategies has its own unique mechanism to escape the endosome. This review recapitulates the numerous strategies designed to surmount the bottleneck of endosomal escape and thereby achieve successful intracellular uptake of bioactives. PMID:24730275

  6. Cold ion escape from the Martian ionosphere

    NASA Astrophysics Data System (ADS)

    Fränz, M.; Dubinin, E.; Andrews, D.; Barabash, S.; Nilsson, H.; Fedorov, A.

    2015-12-01

    We here report on new measurements of the escape flux of oxygen ions from Mars by combining the observations of the ASPERA-3 and MARSIS experiments on board the European Mars Express spacecraft. We show that in previous estimates of the total heavy ion escape flow the contribution of the cold ionospheric outflow with energies below 10 eV has been underestimated. Both case studies and the derived flow pattern indicate that the cold plasma observed by MARSIS and the superthermal plasma observed by ASPERA-3 move with the same bulk speed in most regions of the Martian tail. We determine maps of the tailside heavy ion flux distribution derived from mean ion velocity distributions sampled over 7 years. If we assume that the superthermal bulk speed derived from these long time averages of the ion distribution function represent the total plasma bulk speed we derive the total tailside plasma flux. Assuming cylindrical symmetry we determine the mean total escape rate for the years 2007-2014 at 2.8 ± 0.4 ×1025 atoms / s which is in good agreement with model estimates. A possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside.

  7. Cold Ion Escape from the Martian Ionosphere

    NASA Astrophysics Data System (ADS)

    Fränz, M.; Dubinin, E.; Andrews, D.; Nilsson, H.; Barabash, S.; Fedorov, A.

    2015-10-01

    We here report on new measurements of the escape flux of oxygen ions from Mars by combining the observations of the ASPERA-3 and MARSIS experiments on board the European Mars Express spacecraft. We show that in previous estimates of the total heavy ion escape flow the contribution of the coldionospheric outflow with energies below 10 eV has been underestimated. Both case studies and the derived flow pattern indicate that the cold plasma observed by MARSIS and the superthermal plasma observed by ASPERA-3 move with the same bulk speed in most regions of the Martian tail. We determine maps of the tailside heavy ion flux distribution derived from mean ion velocity distributions sampled over 7 years. If we assume that the superthermal bulk speed derived from these long time averages of the ion distribution function represent the total plasma bulk speed we derive the total tailside plasma flux. Assuming cylindrical symmetry we determine the mean total escape rate for the years 2007 to 2014 at 2.9±0.2×10 25 atoms/s which is in good agreement with model estimates. In this talk we will also try to compare these results with more recent observations by the MAVEN spacecraft. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

  8. Scrunching: a novel escape gait in planarians

    NASA Astrophysics Data System (ADS)

    Cochet-Escartin, Olivier; Mickolajczyk, Keith J.; Collins, Eva-Maria S.

    2015-10-01

    The ability to escape a predator or other life-threatening situations is central to animal survival. Different species have evolved unique strategies under anatomical and environmental constraints. In this study, we describe a novel musculature-driven escape gait in planarians, ‘scrunching’, which is quantitatively different from other planarian gaits, such as gliding and peristalsis. We show that scrunching is a conserved gait among different flatworm species, underlying its importance as an escape mechanism. We further demonstrate that it can be induced by a variety of physical stimuli, including amputation, high temperature, electric shock and low pH. We discuss the functional basis for scrunching as the preferential gait when gliding is impaired due to a disruption of mucus production. Finally, we show that the key mechanical features of scrunching are adequately captured by a simple biomechanical model that is solely based on experimental data from traction force microscopy and tissue rheology without fit parameters. Together, our results form a complete description of this novel form of planarian locomotion. Because scrunching has distinct dynamics, this gait can serve as a robust behavioral readout for studies of motor neuron and muscular functions in planarians and in particular the restoration of these functions during regeneration.

  9. Scrunching: a novel escape gait in planarians.

    PubMed

    Cochet-Escartin, Olivier; Mickolajczyk, Keith J; Collins, Eva-Maria S

    2015-10-01

    The ability to escape a predator or other life-threatening situations is central to animal survival. Different species have evolved unique strategies under anatomical and environmental constraints. In this study, we describe a novel musculature-driven escape gait in planarians, 'scrunching', which is quantitatively different from other planarian gaits, such as gliding and peristalsis. We show that scrunching is a conserved gait among different flatworm species, underlying its importance as an escape mechanism. We further demonstrate that it can be induced by a variety of physical stimuli, including amputation, high temperature, electric shock and low pH. We discuss the functional basis for scrunching as the preferential gait when gliding is impaired due to a disruption of mucus production. Finally, we show that the key mechanical features of scrunching are adequately captured by a simple biomechanical model that is solely based on experimental data from traction force microscopy and tissue rheology without fit parameters. Together, our results form a complete description of this novel form of planarian locomotion. Because scrunching has distinct dynamics, this gait can serve as a robust behavioral readout for studies of motor neuron and muscular functions in planarians and in particular the restoration of these functions during regeneration. PMID:26356147

  10. Xenon Fractionation and Archean Hydrogen Escape

    NASA Technical Reports Server (NTRS)

    Zahnle, K. J.

    2015-01-01

    Xenon is the heaviest gas found in significant quantities in natural planetary atmospheres. It would seem the least likely to escape. Yet there is more evidence for xenon escape from Earth than for any element other than helium and perhaps neon. The most straightforward evidence is that most of the radiogenic Xe from the decay of (129)I (half-life 15.7 Myr) and (244)Pu (half-life 81 Myr) that is Earth's birthright is missing. The missing xenon is often attributed to the impact erosion of early atmospheres of Earth and its ancestors. It is obvious that if most of the radiogenic xenon were driven off by impacts, most of the rest of the atmophiles fared the same fate. The other line of evidence is in the nonradiogenic isotopes of xenon and its silent partner, krypton. Atmospheric xenon is strongly mass fractionated (at about 4% per amu) compared to any known solar system source (Figure 1). This is in stark contrast to krypton, which may not be fractionated at all: atmospheric Kr is slightly heavier than solar Kr (at about 0.5% per amu), but it is the same as in carbonaceous chondrites. Nonradiogenic xenon is also under abundant relative to krypton (the so-called "missing xenon" problem). Together these observations imply that xenon has been subject to fractionating escape and krypton not.

  11. CRV Escape Trajectories from the ISS

    NASA Technical Reports Server (NTRS)

    Foti, Tony M.

    1999-01-01

    The Crew Return Vehicle (CRV) slated for use on the International Space Station (ISS) provides a safe return for up to seven crew members under various emergency conditions. One of the most demanding situations for executing the escape involves separating from a tumbling ISS Current requirements specify a maximum Root Sum Square (RSS) tumble rate of 2 degrees/second, with the additional requirement for an expedited departure from any ISS attitude. The design of a trajectory that ensures no re-contact with the ISS poses many challenges on the Guidance, Navigation, and Control (GN&C) system of the vehicle. To ensure no re-contact the trajectory design employs a two burn sequence, with the first burn preventing near-term collision and the second burn preventing far-field re-contact This presentation describes the approach used to design and to evaluate trajectories for CRV departure from the baselined location on the ISS Node 3 starboard. This approach involved performing a parametric search of selected control variables vital in escaping the tumbling ISS The presentation provides a candidate targeting methodology for escape using minimal information from available navigation devices, and presents the quantitative results from the analysis.

  12. 30 CFR 77.1101 - Escape and evacuation; plan.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Fire Protection § 77.1101 Escape and evacuation; plan. (a) Before September 30, 1971, each operator of... event of a fire. (b) All employees shall be instructed on current escape and evacuation plans, fire alarm signals, and applicable procedures to be followed in case of fire. (c) Plans for escape...

  13. 30 CFR 77.1101 - Escape and evacuation; plan.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Fire Protection § 77.1101 Escape and evacuation; plan. (a) Before September 30, 1971, each operator of... event of a fire. (b) All employees shall be instructed on current escape and evacuation plans, fire alarm signals, and applicable procedures to be followed in case of fire. (c) Plans for escape...

  14. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... controls. (b) Every mechanical escape facility with a platform, cage, or other device shall be equipped with brakes that can stop the fully loaded platform, cage, or other device. (c) Mechanical escape... cages, platforms, or elevators. (e) Mechanical escape facilities shall have rated capacities...

  15. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... controls. (b) Every mechanical escape facility with a platform, cage, or other device shall be equipped with brakes that can stop the fully loaded platform, cage, or other device. (c) Mechanical escape... cages, platforms, or elevators. (e) Mechanical escape facilities shall have rated capacities...

  16. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... controls. (b) Every mechanical escape facility with a platform, cage, or other device shall be equipped with brakes that can stop the fully loaded platform, cage, or other device. (c) Mechanical escape... cages, platforms, or elevators. (e) Mechanical escape facilities shall have rated capacities...

  17. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... controls. (b) Every mechanical escape facility with a platform, cage, or other device shall be equipped with brakes that can stop the fully loaded platform, cage, or other device. (c) Mechanical escape... cages, platforms, or elevators. (e) Mechanical escape facilities shall have rated capacities...

  18. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... controls. (b) Every mechanical escape facility with a platform, cage, or other device shall be equipped with brakes that can stop the fully loaded platform, cage, or other device. (c) Mechanical escape... cages, platforms, or elevators. (e) Mechanical escape facilities shall have rated capacities...

  19. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Means of escape. 169.313 Section 169.313 Shipping COAST... and Arrangement Hull Structure § 169.313 Means of escape. (a) Except as provided by paragraph (f) of this section, there must be at least two means of escape from all areas generally accessible to...

  20. 46 CFR 127.240 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Means of escape. 127.240 Section 127.240 Shipping COAST... Particular Construction and Arrangements § 127.240 Means of escape. (a) Except as provided by paragraphs (l) and (m) of this section, there must be at least two means of escape, exclusive of windows...

  1. 46 CFR 127.240 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Means of escape. 127.240 Section 127.240 Shipping COAST... Particular Construction and Arrangements § 127.240 Means of escape. (a) Except as provided by paragraphs (l) and (m) of this section, there must be at least two means of escape, exclusive of windows...

  2. 46 CFR 127.240 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Means of escape. 127.240 Section 127.240 Shipping COAST... Particular Construction and Arrangements § 127.240 Means of escape. (a) Except as provided by paragraphs (l) and (m) of this section, there must be at least two means of escape, exclusive of windows...

  3. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Means of escape. 169.313 Section 169.313 Shipping COAST... and Arrangement Hull Structure § 169.313 Means of escape. (a) Except as provided by paragraph (f) of this section, there must be at least two means of escape from all areas generally accessible to...

  4. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Means of escape. 116.500 Section 116.500 Shipping COAST... and Embarkation Station Requirements § 116.500 Means of escape. (a) Except as otherwise provided in... least two means of escape, one of which must not be a watertight door. (b) The two required means...

  5. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Means of escape. 169.313 Section 169.313 Shipping COAST... and Arrangement Hull Structure § 169.313 Means of escape. (a) Except as provided by paragraph (f) of this section, there must be at least two means of escape from all areas generally accessible to...

  6. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Means of escape. 116.500 Section 116.500 Shipping COAST... and Embarkation Station Requirements § 116.500 Means of escape. (a) Except as otherwise provided in... least two means of escape, one of which must not be a watertight door. (b) The two required means...

  7. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Means of escape. 169.313 Section 169.313 Shipping COAST... and Arrangement Hull Structure § 169.313 Means of escape. (a) Except as provided by paragraph (f) of this section, there must be at least two means of escape from all areas generally accessible to...

  8. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Means of escape. 116.500 Section 116.500 Shipping COAST... and Embarkation Station Requirements § 116.500 Means of escape. (a) Except as otherwise provided in... least two means of escape, one of which must not be a watertight door. (b) The two required means...

  9. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Means of escape. 169.313 Section 169.313 Shipping COAST... and Arrangement Hull Structure § 169.313 Means of escape. (a) Except as provided by paragraph (f) of this section, there must be at least two means of escape from all areas generally accessible to...

  10. Methane in the lunar exosphere: Implications for solar wind carbon escape

    NASA Astrophysics Data System (ADS)

    Hodges, , R. Richard

    2016-07-01

    A positive identification of methane in the lunar exosphere has been made in data from the neutral mass spectrometer on the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft. Like argon-40, methane is adsorbed on the lunar surface during nighttime. However, higher activation energies for methane delay its desorption at sunrise by about an hour local time, creating a postsunrise bulge with peak concentration of approximately 400-450 molecules cm-3 at a reference altitude of 12 km, which is just above the highest topographic feature on the Moon. The rate of escape of carbon as methane derived from the LADEE data is estimated to be in the range 1.5-4.5 × 1021 s-1. A lower bound for solar carbon escape derived separately from Apollo sample analyses is 3.4 × 1021 s-1.

  11. Autonomous Soft Robotic Fish Capable of Escape Maneuvers Using Fluidic Elastomer Actuators

    PubMed Central

    Onal, Cagdas D.; Rus, Daniela

    2014-01-01

    Abstract In this work we describe an autonomous soft-bodied robot that is both self-contained and capable of rapid, continuum-body motion. We detail the design, modeling, fabrication, and control of the soft fish, focusing on enabling the robot to perform rapid escape responses. The robot employs a compliant body with embedded actuators emulating the slender anatomical form of a fish. In addition, the robot has a novel fluidic actuation system that drives body motion and has all the subsystems of a traditional robot onboard: power, actuation, processing, and control. At the core of the fish's soft body is an array of fluidic elastomer actuators. We design the fish to emulate escape responses in addition to forward swimming because such maneuvers require rapid body accelerations and continuum-body motion. These maneuvers showcase the performance capabilities of this self-contained robot. The kinematics and controllability of the robot during simulated escape response maneuvers are analyzed and compared with studies on biological fish. We show that during escape responses, the soft-bodied robot has similar input–output relationships to those observed in biological fish. The major implication of this work is that we show soft robots can be both self-contained and capable of rapid body motion.

  12. Cold Ion Escape from the Martian Ionosphere

    NASA Astrophysics Data System (ADS)

    Fraenz, M.; Dubinin, E.; Wei, Y.; Woch, J. G.; Morgan, D. D.; Barabash, S. V.; Lundin, R. N.; Fedorov, A.

    2012-12-01

    It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. We first use support from the MARSIS radar experiment for some orbits with fortunate observation geometry. Here we have observed a transterminator flow of O+ and O2+ ions with a super-sonic velocity of around 5km/s and fluxes of 0.8x10^9/cm^2s. If we assume a symmetric flux around the terminator this corresponds to an ion flow of 3.1x10^25/s half of which is expected to escape from Mars (Fraenz et al, 2010). This escape flux is significantly higher than previously observed on the tailside of Mars, we discuss possible reasons for the difference. Since 2008 the MARSIS radar does nightside local plasma density measurement which often coincide with ASPERA-3 measurements. In a new analysis of the combined nightside datasets (Fig. 1) we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of about 0.5 R_M the flux settles at a constant value (Fig. 2) which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvenic regime.; Median oxygen ion flux reconstructed by combining ion velocity observations of the Mars Express ASPERA-3 IMA sensor and local plasma density observations by the MARSIS radar. Each bin value is the median from observations on about 3000 orbits between May 2007 and July 2011. Horizontal axis is MSO X-axis (Sun towards the left), vertical axis is vertical distance from MSO X-axis. ; Ring median flux of cylindrical ring regions of all bins shown in previous figure. The different colors show median fluxes

  13. Basin Explosions and Escape Phenomena in the Twin-Well Duffing Oscillator: Compound Global Bifurcations Organizing Behaviour

    NASA Astrophysics Data System (ADS)

    Ueda, Y.; Yoshida, S.; Stewart, H. B.; Thompson, J. M. T.

    1990-07-01

    The sinusoidally drive, twin-well Duffing oscillator has become a central archetypal model for studies of chaos and fractal basin boundaries in the nonlinear dynamics of dissipative ordinary differential equations. It can also be used to illustrate and elucidate universal features of the escape from a potential well, the jumps from one-well to cross-well motions displaying similar characteristics to those recently charted for the cubic one-well potential. We identify here some new codimension-two global bifurcations which serve to organize the bifurcation set and structure the related basin explosions and escape phenomena.

  14. Hydrodynamical Modeling of Hydrogen Escape from Rocky Planets

    NASA Astrophysics Data System (ADS)

    Barringer, Daniel; Zugger, M.; Kasting, J.

    2013-01-01

    Hydrogen escape affects both the composition of primitive atmospheres of terrestrial planets and the planet’s state of oxidation. On Mars, hydrogen escape played a critical role in how long the planet remained in a warm wet state amenable to life. For both solar and extrasolar planets, hydrogen-rich atmospheres are better candidates for originating life by way of Miller-Urey-type prebiotic synthesis. However, calculating the rate of atmospheric hydrogen escape is difficult, for a number of reasons. First, the escape can be controlled either by diffusion through the homopause or by conditions in the upper atmosphere, whichever is slower. Second, both thermal and non-thermal escape mechanisms are typically important. Third, thermal escape itself can be subdivided into Jeans escape (thin upper atmosphere), and hydrodynamic escape, and hydrodynamic escape can be further subdivided into transonic escape and slower subsonic escape, depending on whether the exobase occurs above or below the sonic point. Additionally, the rate of escape for real terrestrial planet atmospheres, which are not 100% hydrogen, depends upon the concentration of infrared coolants, and upon heating and photochemistry driven largely by extreme ultraviolet (EUV) radiation. We have modified an existing 1-D model of hydrodynamic escape (F. Tian et al., JGR, 2008) to work in the high- hydrogen regime. Calculations are underway to determine hydrogen escape rates as a function of atmospheric H2 mixing ratio and the solar EUV flux. We will compare these rates with the estimated upper limit on the escape rate based on diffusion. Initial results for early Earth and Mars will later be extended to rocky exoplanets.

  15. Risks incurred by hydrogen escaping from containers and conduits

    SciTech Connect

    Swain, M.R.; Grilliot, E.S.; Swain, M.N.

    1998-08-01

    This paper is a discussion of a method for hydrogen leak classification. Leaks are classified as; gas escapes into enclosed spaces, gas escapes into partially enclosed spaces (vented), and gas escapes into unenclosed spaces. Each of the three enclosure classifications is further divided into two subclasses; total volume of hydrogen escaped and flow rate of escaping hydrogen. A method to aid in risk assessment determination in partially enclosed spaces is proposed and verified for several enclosure geometries. Examples are discussed for additional enclosure geometries.

  16. Restricting HIV-1 pathways for escape using rationally designed anti–HIV-1 antibodies

    PubMed Central

    Klein, Florian; Horwitz, Joshua A.; Halper-Stromberg, Ariel; Sather, D. Noah; Marcovecchio, Paola M.; Lee, Terri; West, Anthony P.; Gao, Han; Seaman, Michael S.; Stamatatos, Leonidas; Nussenzweig, Michel C.; Bjorkman, Pamela J.

    2013-01-01

    Recently identified broadly neutralizing antibodies (bNAbs) that potently neutralize most HIV-1 strains are key to potential antibody-based therapeutic approaches to combat HIV/AIDS in the absence of an effective vaccine. Increasing bNAb potencies and resistance to common routes of HIV-1 escape through mutation would facilitate their use as therapeutics. We previously used structure-based design to create the bNAb NIH45-46G54W, which exhibits superior potency and/or breadth compared with other bNAbs. We report new, more effective NIH45-46G54W variants designed using analyses of the NIH45-46–gp120 complex structure and sequences of NIH45-46G54W–resistant HIV-1 strains. One variant, 45-46m2, neutralizes 96% of HIV-1 strains in a cross-clade panel and viruses isolated from an HIV-infected individual that are resistant to all other known bNAbs, making it the single most broad and potent anti–HIV-1 antibody to date. A description of its mechanism is presented based on a 45-46m2–gp120 crystal structure. A second variant, 45-46m7, designed to thwart HIV-1 resistance to NIH45-46G54W arising from mutations in a gp120 consensus sequence, targets a common route of HIV-1 escape. In combination, 45-46m2 and 45-46m7 reduce the possible routes for the evolution of fit viral escape mutants in HIV-1YU-2–infected humanized mice, with viremic control exhibited when a third antibody, 10–1074, was added to the combination. PMID:23712429

  17. Escape process in systems characterized by stable noises and position-dependent resting times

    NASA Astrophysics Data System (ADS)

    Srokowski, Tomasz

    2016-06-01

    Stochastic systems characterized by a random driving in a form of the general stable noise are considered. The particle experiences long rests due to the traps the density of which is position dependent and obeys a power-law form attributed to the underlying self-similar structure. Both the one- and two-dimensional cases are analyzed. The random walk description involves a position-dependent waiting time distribution. On the other hand, the stochastic dynamics is formulated in terms of the subordination technique where the random time generator is position dependent. The first passage time problem is addressed by evaluating a first passage time density distribution and an escape rate. The influence of the medium nonhomogeneity on those quantities is demonstrated; moreover, the dependence of the escape rate on the stability index and the memory parameter is evaluated. Results indicate essential differences between the Gaussian case and the case involving Lévy flights.

  18. Global analysis of fungal morphology exposes mechanisms of host cell escape

    PubMed Central

    O’Meara, Teresa R.; Veri, Amanda O.; Ketela, Troy; Jiang, Bo; Roemer, Terry; Cowen, Leah E.

    2015-01-01

    Developmental transitions between single-cell yeast and multicellular filaments underpin virulence of diverse fungal pathogens. For the leading human fungal pathogen Candida albicans, filamentation is thought to be required for immune cell escape via induction of an inflammatory programmed cell death. Here we perform a genome-scale analysis of C. albicans morphogenesis and identify 102 negative morphogenetic regulators and 872 positive regulators, highlighting key roles for ergosterol biosynthesis and N-linked glycosylation. We demonstrate that C. albicans filamentation is not required for escape from host immune cells; instead, macrophage pyroptosis is driven by fungal cell-wall remodelling and exposure of glycosylated proteins in response to the macrophage phagosome. The capacity of killed, previously phagocytized cells to drive macrophage lysis is also observed with the distantly related fungal pathogen Cryptococcus neoformans. This study provides a global view of morphogenetic circuitry governing a key virulence trait, and illuminates a new mechanism by which fungi trigger host cell death. PMID:25824284

  19. Escape process in systems characterized by stable noises and position-dependent resting times.

    PubMed

    Srokowski, Tomasz

    2016-06-01

    Stochastic systems characterized by a random driving in a form of the general stable noise are considered. The particle experiences long rests due to the traps the density of which is position dependent and obeys a power-law form attributed to the underlying self-similar structure. Both the one- and two-dimensional cases are analyzed. The random walk description involves a position-dependent waiting time distribution. On the other hand, the stochastic dynamics is formulated in terms of the subordination technique where the random time generator is position dependent. The first passage time problem is addressed by evaluating a first passage time density distribution and an escape rate. The influence of the medium nonhomogeneity on those quantities is demonstrated; moreover, the dependence of the escape rate on the stability index and the memory parameter is evaluated. Results indicate essential differences between the Gaussian case and the case involving Lévy flights. PMID:27415243

  20. Scintillator probe diagnostic for high energy particles escaped from Large Helical Device

    SciTech Connect

    Nishiura, M.; Isobe, M.; Saida, T.; Sasao, M.; Darrow, D.S.

    2004-10-01

    A scintillator probe for escaping fast ion diagnostics has been developed in the Large Helical Device. This probe is capable of traveling across a divertor leg and sweeping the aperture angle rotationally with respect to the axis of the probe shaft. Pitch angle and gyro radius resolutions are estimated numerically by using a Monte Carlo orbit simulation. The result shows that the detector has sufficient resolution in pitch angle and gyro radius for our target plasmas. Under the neutral beam injected plasma, a signal derived from fast ions was obtained on the scintillator plate and analyzed by using the recorded camera image.

  1. Cold Ion Escape from the Martian Ionosphere

    NASA Astrophysics Data System (ADS)

    Fränz, Markus; Dubinin, Eduard; Andrews, David; Nilsson, Hans; Fedorov, Andrei

    2014-05-01

    It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. The ion sensor IMA of this experiment has in principle a low-energy cut-off at 10eV but in negative spacecraft charging cold ions are lifted into the range of measurement but the field of view is restricted to about 4x360 deg. In a recent paper Nilsson et al. (Earth Planets Space, 64, 135, 2012) tried to use the method of long-time averaged distribution functions to overcome these constraints. In this paper we first use the same method to show that we get results consistent with this when using ASPERA-3 observations only. But then we can show that these results are inconsistent with observations of the local plasma density by the MARSIS radar instrument on board Mars Express. We demonstrate that the method of averaged distribution function can deliver the mean flow speed of the plasma but the low-energy cut-off does usually not allow to reconstruct the density. We then combine measurements of the cold ion flow speed with the plasma density observations of MARSIS to derive the cold ion flux. In an analysis of the combined nightside datasets we show that the main escape channel is along the shadow boundary on the tailside of Mars. At a distance of about 0.5 Martian radii the flux settles at a constant value which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

  2. X-chromosome inactivation and escape

    PubMed Central

    DISTECHE, CHRISTINE M.; BERLETCH, JOEL B.

    2016-01-01

    X-chromosome inactivation, which was discovered by Mary Lyon in 1961 results in random silencing of one X chromosome in female mammals. This review is dedicated to Mary Lyon, who passed away last year. She predicted many of the features of X inactivation, for e.g., the existence of an X inactivation center, the role of L1 elements in spreading of silencing and the existence of genes that escape X inactivation. Starting from her published work here we summarize advances in the field. PMID:26690513

  3. Suicide as escape from psychotic panic.

    PubMed

    Goldblatt, Mark J; Ronningstam, Elsa; Schechter, Mark; Herbstman, Benjamin; Maltsberger, John T

    2016-01-01

    Suicides of patients in states of acute persecutory panic may be provoked by a subjective experience of helpless terror threatening imminent annihilation or dismemberment. These patients are literally scared to death and try to run away. They imagine suicide is survivable and desperately attempt to escape from imaginary enemies. These states of terror occur in a wide range of psychotic illnesses and are often associated with command hallucinations and delusions. In this article, the authors consider the subjective experience of persecutory panic and the suicide response as an attempt to flee from danger. PMID:27294586

  4. Serial Escape System For Aircraft Crews

    NASA Technical Reports Server (NTRS)

    Wood, Kenneth E.

    1990-01-01

    Emergency escape system for aircraft and aerospace vehicles ejects up to seven crewmembers, one by one, within 120 s. Intended for emergencies in which disabled craft still in stable flight at no more than 220 kn (113 m/s) equivalent airspeed and sinking no faster than 110 ft/s (33.5 m/s) at altitudes up to 50,000 ft (15.2 km). Ejection rockets load themselves from magazine after each crewmember ejected. Jumpmaster queues other crewmembers and helps them position themselves on egress ramp. Rockets pull crewmembers clear of aircraft structure. Provides orderly, controlled exit and avoids ditching at sea or landing in rough terrain.

  5. Escape Artists of the X Chromosome.

    PubMed

    Balaton, Bradley P; Brown, Carolyn J

    2016-06-01

    Inactivation of one X chromosome in mammalian females achieves dosage compensation between XX females and XY males; however, over 15% of human X-linked genes continue to be expressed from the inactive X chromosome. New genomic methodologies have improved our identification and characterization of these escape genes, revealing the importance of DNA sequence, chromatin structure, and chromosome ultrastructure in regulating expression from an otherwise inactive chromosome. Study of these exceptions to the rule of silencing highlights the interconnectedness of chromatin and chromosome structure in X-chromosome inactivation (XCI). Recent advances also demonstrate the importance of these genes in sexually dimorphic disease risk, particularly cancer. PMID:27103486

  6. Quantum and classical resonant escapes of a strongly driven Josephson junction

    NASA Astrophysics Data System (ADS)

    Yu, H. F.; Zhu, X. B.; Peng, Z. H.; Cao, W. H.; Cui, D. J.; Tian, Ye; Chen, G. H.; Zheng, D. N.; Jing, X. N.; Lu, Li; Zhao, S. P.; Han, Siyuan

    2010-04-01

    The properties of phase escape in a dc superconducting quantum interference device (SQUID) at 25 mK, which is well below quantum-to-classical crossover temperature Tcr , in the presence of strong resonant ac driving have been investigated. The SQUID contains two Nb/Al-AlOx/Nb tunnel junctions with Josephson inductance much larger than the loop inductance so it can be viewed as a single junction having adjustable critical current. We find that with increasing microwave power W and at certain frequencies ν and ν/2 , the single primary peak in the switching current distribution, which is the result of macroscopic quantum tunneling of the phase across the junction, first shifts toward lower bias current I and then a resonant peak develops. These results are explained by quantum resonant phase escape involving single and two photons with microwave-suppressed potential barrier. As W further increases, the primary peak gradually disappears and the resonant peak grows into a single one while shifting further to lower I . At certain W , a second resonant peak appears, which can locate at very low I depending on the value of ν . Analysis based on the classical equation of motion shows that such resonant peak can arise from the resonant escape of the phase particle with extremely large oscillation amplitude resulting from bifurcation of the nonlinear system. Our experimental result and theoretical analysis demonstrate that at T≪Tcr , escape of the phase particle could be dominated by classical process, such as dynamical bifurcation of nonlinear systems under strong ac driving.

  7. Perceiving object dangerousness: an escape from pain?

    PubMed

    Anelli, Filomena; Ranzini, Mariagrazia; Nicoletti, Roberto; Borghi, Anna M

    2013-08-01

    A variety of studies showed that participants are facilitated when responding to graspable objects, while it has not been fully investigated what happens during interactions with graspable objects that are potentially dangerous. The present study focuses on the mechanisms underlying the processing of dangerous objects. In two experiments, we adopted a paradigm that has never been employed in this context, a bisection task. The line was flanked by objects belonging to different categories. We explored the sensitivity to the distinction between neutral and dangerous objects, by measuring whether the performance was biased toward a specific object category. In Experiment 1 both teenagers and adults bisected lines flanked by dangerous and neutral graspable objects, and they misperceived the line midpoint toward the neutral graspable object or, stated differently, on the opposite side of the dangerous graspable object. In Experiment 2 adults bisected lines flanked by dangerous and neutral objects matched on graspability (both graspable and ungraspable, Experiment 2a), or by graspable and ungraspable objects matched on dangerousness (both neutral and dangerous, Experiment 2b). Results confirmed the finding of Experiment 1, but also indicated that participants misperceived the line midpoint toward the ungraspable object when it was presented, being it dangerous or not. This evidence demonstrated sensitivity to object dangerousness maintained across lifespan. The emergence of aversive affordances evoked by dangerous graspable objects strenghtens the importance to consider graspability in the investigation of dangerous objects. Possible neural mechanisms involved in the processing of dangerous graspable objects are discussed. PMID:23743714

  8. Neutral beam monitoring

    DOEpatents

    Fink, Joel H.

    1981-08-18

    Method and apparatus for monitoring characteristics of a high energy neutral beam. A neutral beam is generated by passing accelerated ions through a walled cell containing a low energy neutral gas, such that charge exchange neutralizes the high energy ion beam. The neutral beam is monitored by detecting the current flowing through the cell wall produced by low energy ions which drift to the wall after the charge exchange. By segmenting the wall into radial and longitudinal segments various beam conditions are further identified.

  9. Energy distributions of sputtered copper neutrals and ions

    NASA Technical Reports Server (NTRS)

    Lundquist, T. R.

    1978-01-01

    Direct quantitative analysis of surfaces by secondary ion mass spectrometry will depend on an understanding of the yield ratio of ions to neutrals. This ratio as a function of the energy of the sputtered particles has been obtained for a clean polycrystalline copper surface sputtered by 1000-3000 eV Ar(+). The energy distributions of both neutral and ionized copper were measured with a retarding potential analyzer using potential modulation differentiation and signal averaging. The maximum for both distributions is identical and occurs near 2.5 eV. The energy distributions of neutrals is more sharply peaked than that of the ions, presumably as a consequence of more efficient nutralization of slow escaping ions by the mobile electrons of copper. The ion-neutral ratio is compared with results from various ionization models.

  10. The effects of steady swimming on fish escape performance.

    PubMed

    Anwar, Sanam B; Cathcart, Kelsey; Darakananda, Karin; Gaing, Ashley N; Shin, Seo Yim; Vronay, Xena; Wright, Dania N; Ellerby, David J

    2016-06-01

    Escape maneuvers are essential to the survival and fitness of many animals. Escapes are frequently initiated when an animal is already in motion. This may introduce constraints that alter the escape performance. In fish, escape maneuvers and steady, body caudal fin (BCF) swimming are driven by distinct patterns of curvature of the body axis. Pre-existing muscle activity may therefore delay or diminish a response. To quantify the performance consequences of escaping in flow, escape behavior was examined in bluegill sunfish (Lepomis macrochirus) in both still-water and during steady swimming. Escapes executed during swimming were kinematically less variable than those made in still-water. Swimming escapes also had increased response latencies and lower peak velocities and accelerations than those made in still-water. Performance was also lower for escapes made up rather than down-stream, and a preference for down-stream escapes may be associated with maximizing performance. The constraints imposed by pre-existing motion and flow, therefore, have the potential to shape predator-prey interactions under field conditions by shifting the optimal strategies for both predators and prey. PMID:27161016

  11. Escape from X Inactivation Varies in Mouse Tissues

    PubMed Central

    Yang, Fan; Shendure, Jay; Noble, William S.; Disteche, Christine M.; Deng, Xinxian

    2015-01-01

    X chromosome inactivation (XCI) silences most genes on one X chromosome in female mammals, but some genes escape XCI. To identify escape genes in vivo and to explore molecular mechanisms that regulate this process we analyzed the allele-specific expression and chromatin structure of X-linked genes in mouse tissues and cells with skewed XCI and distinguishable alleles based on single nucleotide polymorphisms. Using a binomial model to assess allelic expression, we demonstrate a continuum between complete silencing and expression from the inactive X (Xi). The validity of the RNA-seq approach was verified using RT-PCR with species-specific primers or Sanger sequencing. Both common escape genes and genes with significant differences in XCI status between tissues were identified. Such genes may be candidates for tissue-specific sex differences. Overall, few genes (3–7%) escape XCI in any of the mouse tissues examined, suggesting stringent silencing and escape controls. In contrast, an in vitro system represented by the embryonic-kidney-derived Patski cell line showed a higher density of escape genes (21%), representing both kidney-specific escape genes and cell-line specific escape genes. Allele-specific RNA polymerase II occupancy and DNase I hypersensitivity at the promoter of genes on the Xi correlated well with levels of escape, consistent with an open chromatin structure at escape genes. Allele-specific CTCF binding on the Xi clustered at escape genes and was denser in brain compared to the Patski cell line, possibly contributing to a more compartmentalized structure of the Xi and fewer escape genes in brain compared to the cell line where larger domains of escape were observed. PMID:25785854

  12. The escape model for Galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Giacinti, G.; Kachelrieß, M.; Semikoz, D. V.

    2015-08-01

    The escape model explains the cosmic ray (CR) knee by energy-dependent CR leakage from the Milky Way, with an excellent fit to all existing data. We test this model calculating the trajectories of individual CRs in the Galactic magnetic field. We find that the CR escape time τesc(E) exhibits a knee-like structure around E/Z = few × 1015 eV for small coherence lengths and strengths of the turbulent magnetic field. The resulting intensities for different groups of nuclei are consistent with the ones determined by KASCADE and KASCADE-Grande, using simple power-laws as injection spectra. The transition from Galactic to extragalactic CRs happens in this model at low energies and is terminated below ≈ 3 × 1018 eV. The intermediate energy region up to the ankle is populated by CRs accelerated in starburst galaxies. This model provides a good fit to ln(A) data, while the estimated CR dipole anisotropy is close to, or below, upper limits in the energy range 1017 - 1018 eV. The phase of the dipole is expected to change between 1 × 1017 and 3 × 1018 eV.

  13. A New Maneuver for Escape Trajectories

    NASA Technical Reports Server (NTRS)

    Adams, Robert B.

    2008-01-01

    This presentation put forth a new maneuver for escape trajectories and specifically sought to find an analytical approximation for medium thrust trajectories. In most low thrust derivations the idea is that escape velocity is best achieved by accelerating along the velocity vector. The reason for this is that change in specific orbital energy is a function of velocity and acceleration. However, Levin (1952) suggested that while this is a locally optimal solution it might not be a globally optimal one. Turning acceleration inward would drop periapse giving a higher velocity later in the trajectory. Acceleration at that point would be dotted against a higher magnitude V giving a greater rate of change of mechanical energy. The author then hypothesized that decelerating from the initial orbit and then accelerating at periapse would not lead to a gain in greater specific orbital energy--however, the hypothesis was incorrect. After considerable derivation it was determined that this new maneuver outperforms a direct burn when the overall DeltaV budget exceeds the initial orbital velocity (the author has termed this the Heinlein maneuver). The author provides a physical explanation for this maneuver and presents optimization analyses.

  14. Escape mechanisms of dust in Io

    NASA Astrophysics Data System (ADS)

    Flandes, A.

    The injection of material into the jovian magnetosphere through Io's volcanic activity makes possible the formation of structures such as the plasma torus and the dust ballerina skirt. Io's high temperature volcanism produces spectacular plumes, but even the tallest plumes, as those of Pelen Patera, will not produce enough energy to defeat the gravitational attraction of Io. The fact is that dust escapes from Io, which implies that a second mechanism is acting on the grains. Grains brought to the top of the highest plumes by the volcanic forces are still under Io's gravitational pull, but need only a minimum charge (~10-1 4 C) so that the Lorentz force due to the Jovian magnetic field equilibrates this attraction. In the volcanic vents, the escape velocity of the ejected material and its own density produces enough collisions to create charges. On top of the highest plumes (~500km) charged grains are exposed to the plasma torus that co-rotates rigidly with Jupiter and, due to the relative velocity among Io and the torus, the grains will be dragged away from Io. As it is well known, these dust grains will also be dragged away from Jupiter.

  15. Escape dynamics of many hard disks.

    PubMed

    Taniguchi, Tooru; Murata, Hiroki; Sawada, Shin-Ichi

    2014-11-01

    Many-particle effects in escapes of hard disks from a square box via a hole are discussed in a viewpoint of dynamical systems. Starting from N disks in the box at the initial time, we calculate the probability P_{n}(t) for at least n disks to remain inside the box at time t for n=1,2,...,N. At early times, the probabilities P_{n}(t),n=2,3,...,N-1, are described by superpositions of exponential decay functions. On the other hand, after a long time the probability P_{n}(t) shows a power-law decay ∼t^{-2n} for n≠1, in contrast to the fact that it decays with a different power law ∼t^{-n} for cases without any disk-disk collision. Chaotic or nonchaotic properties of the escape systems are discussed by the dynamics of a finite-time largest Lyapunov exponent, whose decay properties are related with those of the probability P_{n}(t). PMID:25493874

  16. How some T cells escape tolerance induction.

    PubMed

    Gammon, G; Sercarz, E

    1989-11-01

    A feature common to many animal models of autoimmune disease, for example, experimental allergic encephalomyelitis, experimental autoimmune myasthenia gravis and collagen-induced arthritis, is the presence of self-reactive T cells in healthy animals, which are activated to produce disease by immunization with exogenous antigen. It is unclear why these T cells are not deleted during ontogeny in the thymus and, having escaped tolerance induction, why they are not spontaneously activated by self-antigen. To investigate these questions, we have examined an experimental model in which mice are tolerant to an antigen despite the presence of antigen-reactive T cells. We find that the T cells that escape tolerance induction are specific for minor determinants on the antigen. We propose that these T cells evade tolerance induction because some minor determinants are only available in relatively low amounts after in vivo processing of the whole antigen. For the same reason, these T cells are not normally activated but can be stimulated under special circumstances to circumvent tolerance. PMID:2478888

  17. F111 Crew Escape Module pilot parachute

    SciTech Connect

    Tadios, E.L.

    1991-01-01

    A successfully deployment of a parachute system highly depends on the efficiency of the deployment device and/or method. There are several existing methods and devices that may be considered for a deployment system. For the F111 Crew Escape Module (CEM), the recovery parachute system deployment is initiated by the firing of a catapult that ejects the complete system from the CEM. At first motion of the pack, a drogue gun is fired, which deploys the pilot parachute system. The pilot parachute system then deploys the main parachute system, which consists of a cluster of three 49-ft diameter parachutes. The pilot parachute system which extracts the F111 Crew Escape Module recovery parachute system must provide reasonable bag strip velocities throughout the flight envelope (10 psf to 300 psf). The pilot parachute system must, therefore, have sufficient drag area at the lower dynamic pressures and a reduced drag area at the high end of the flight envelope. The final design that was developed was a dual parachute system which consists of a 5-ft diameter guide surface parachute tethered inside a 10-ft diameter flat circular parachute. The high drag area is sustained at the low dynamic pressures by keeping both parachutes intact. The drag area is reduced at the higher extreme by allowing the 10-ft parachute attachment to fail. The discussions to follow describe in detail how the system was developed. 4 refs., 10 figs., 2 tabs.

  18. Dementia and driving

    MedlinePlus

    ... not drive at times of the day when traffic is heaviest. Do not drive when the weather is bad. Do not drive long distances. Drive only on roads the person is used to. Caregivers should try to lessen ...

  19. Strong Constraint on Human Genes Escaping X-Inactivation Is Modulated by their Expression Level and Breadth in Both Sexes.

    PubMed

    Slavney, Andrea; Arbiza, Leonardo; Clark, Andrew G; Keinan, Alon

    2016-02-01

    In eutherian mammals, X-linked gene expression is normalized between XX females and XY males through the process of X chromosome inactivation (XCI). XCI results in silencing of transcription from one ChrX homolog per female cell. However, approximately 25% of human ChrX genes escape XCI to some extent and exhibit biallelic expression in females. The evolutionary basis of this phenomenon is not entirely clear, but high sequence conservation of XCI escapers suggests that purifying selection may directly or indirectly drive XCI escape at these loci. One hypothesis is that this signal results from contributions to developmental and physiological sex differences, but presently there is limited evidence supporting this model in humans. Another potential driver of this signal is selection for high and/or broad gene expression in both sexes, which are strong predictors of reduced nucleotide substitution rates in mammalian genes. Here, we compared purifying selection and gene expression patterns of human XCI escapers with those of X-inactivated genes in both sexes. When we accounted for the functional status of each ChrX gene's Y-linked homolog (or "gametolog"), we observed that XCI escapers exhibit greater degrees of purifying selection in the human lineage than X-inactivated genes, as well as higher and broader gene expression than X-inactivated genes across tissues in both sexes. These results highlight a significant role for gene expression in both sexes in driving purifying selection on XCI escapers, and emphasize these genes' potential importance in human disease. PMID:26494842

  20. Investigating the Consequences of Interference between Multiple CD8+ T Cell Escape Mutations in Early HIV Infection.

    PubMed

    Garcia, Victor; Feldman, Marcus W; Regoes, Roland R

    2016-02-01

    During early human immunodeficiency virus (HIV) infection multiple CD8+ T cell responses are elicited almost simultaneously. These responses exert strong selective pressures on different parts of HIV's genome, and select for mutations that escape recognition and are thus beneficial to the virus. Some studies reveal that the later these escape mutations emerge, the more slowly they go to fixation. This pattern of escape rate decrease(ERD) can arise by distinct mechanisms. In particular, in large populations with high beneficial mutation rates interference among different escape strains--an effect that can emerge in evolution with asexual reproduction and results in delayed fixation times of beneficial mutations compared to sexual reproduction--could significantly impact the escape rates of mutations. In this paper, we investigated how interference between these concurrent escape mutations affects their escape rates in systems with multiple epitopes, and whether it could be a source of the ERD pattern. To address these issues, we developed a multilocus Wright-Fisher model of HIV dynamics with selection, mutation and recombination, serving as a null-model for interference. We also derived an interference-free null model assuming initial neutral evolution before immune response elicitation. We found that interference between several equally selectively advantageous mutations can generate the observed ERD pattern. We also found that the number of loci, as well as recombination rates substantially affect ERD. These effects can be explained by the underexponential decline of escape rates over time. Lastly, we found that the observed ERD pattern in HIV infected individuals is consistent with both independent, interference-free mutations as well as interference effects. Our results confirm that interference effects should be considered when analyzing HIV escape mutations. The challenge in estimating escape rates and mutation-associated selective coefficients posed by

  1. Investigating the Consequences of Interference between Multiple CD8+ T Cell Escape Mutations in Early HIV Infection

    PubMed Central

    Garcia, Victor; Feldman, Marcus W.; Regoes, Roland R.

    2016-01-01

    During early human immunodeficiency virus (HIV) infection multiple CD8+ T cell responses are elicited almost simultaneously. These responses exert strong selective pressures on different parts of HIV’s genome, and select for mutations that escape recognition and are thus beneficial to the virus. Some studies reveal that the later these escape mutations emerge, the more slowly they go to fixation. This pattern of escape rate decrease(ERD) can arise by distinct mechanisms. In particular, in large populations with high beneficial mutation rates interference among different escape strains –an effect that can emerge in evolution with asexual reproduction and results in delayed fixation times of beneficial mutations compared to sexual reproduction– could significantly impact the escape rates of mutations. In this paper, we investigated how interference between these concurrent escape mutations affects their escape rates in systems with multiple epitopes, and whether it could be a source of the ERD pattern. To address these issues, we developed a multilocus Wright-Fisher model of HIV dynamics with selection, mutation and recombination, serving as a null-model for interference. We also derived an interference-free null model assuming initial neutral evolution before immune response elicitation. We found that interference between several equally selectively advantageous mutations can generate the observed ERD pattern. We also found that the number of loci, as well as recombination rates substantially affect ERD. These effects can be explained by the underexponential decline of escape rates over time. Lastly, we found that the observed ERD pattern in HIV infected individuals is consistent with both independent, interference-free mutations as well as interference effects. Our results confirm that interference effects should be considered when analyzing HIV escape mutations. The challenge in estimating escape rates and mutation-associated selective coefficients posed by

  2. Synthesizing within-host and population-level selective pressures on viral populations: the impact of adaptive immunity on viral immune escape

    PubMed Central

    Volkov, Igor; Pepin, Kim M.; Lloyd-Smith, James O.; Banavar, Jayanth R.; Grenfell, Bryan T.

    2010-01-01

    The evolution of viruses to escape prevailing host immunity involves selection at multiple integrative scales, from within-host viral and immune kinetics to the host population level. In order to understand how viral immune escape occurs, we develop an analytical framework that links the dynamical nature of immunity and viral variation across these scales. Our epidemiological model incorporates within-host viral evolutionary dynamics for a virus that causes acute infections (e.g. influenza and norovirus) with changes in host immunity in response to genetic changes in the virus population. We use a deterministic description of the within-host replication dynamics of the virus, the pool of susceptible host cells and the host adaptive immune response. We find that viral immune escape is most effective at intermediate values of immune strength. At very low levels of immunity, selection is too weak to drive immune escape in recovered hosts, while very high levels of immunity impose such strong selection that viral subpopulations go extinct before acquiring enough genetic diversity to escape host immunity. This result echoes the predictions of simpler models, but our formulation allows us to dissect the combination of within-host and transmission-level processes that drive immune escape. PMID:20335194

  3. Plasma heating with multi-MeV neutral atom beams

    SciTech Connect

    Grisham, L.R.; Post, D.E.; Mikkelsen, D.R.; Eubank, H.P.

    1981-10-01

    We explore the utility and feasibility of neutral beams of greater than or equal to 6 AMU formed from negative ions, and also of D/sup 0/ formed from D/sup -/. The negative ions would be accelerated to approx. 1 to 2 MeV/AMU and neutralized, whereupon the neutral atoms would be used to heat and, perhaps, to drive current in magnetically confined plasmas. Such beams appear feasible and offer the promise of significant advantages relative to conventional neutral beams based on positive deuterium ions at approx. 150 keV.

  4. A Single Amino Acid Deletion in the Matrix Protein of Porcine Reproductive and Respiratory Syndrome Virus Confers Resistance to a Polyclonal Swine Antibody with Broadly Neutralizing Activity

    PubMed Central

    Popescu, Luca N.; Monday, Nicholas; Calvert, Jay G.; Rowland, Raymond R. R.

    2015-01-01

    Assessment of virus neutralization (VN) activity in 176 pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV) identified one pig with broadly neutralizing activity. A Tyr-10 deletion in the matrix protein provided escape from broad neutralization without affecting homologous neutralizing activity. The role of the Tyr-10 deletion was confirmed through an infectious clone with a Tyr-10 deletion. The results demonstrate differences in the properties and specificities of VN responses elicited during PRRSV infection. PMID:25855739

  5. Characterization of epitopes on the rabies virus glycoprotein by selection and analysis of escape mutants.

    PubMed

    Fallahi, Firouzeh; Wandeler, Alexander I; Nadin-Davis, Susan A

    2016-07-15

    The glycoprotein (G) is the only surface protein of the lyssavirus particle and the only viral product known to be capable of eliciting the production of neutralizing antibodies. In this study, the isolation of escape mutants resistant to monoclonal antibody (Mab) neutralization was attempted by a selection strategy employing four distinct rabies virus strains: the extensively passaged Evelyn Rokitnicki Abelseth (ERA) strain and three field isolates representing two bat-associated variants and the Western Canada skunk variant (WSKV). No escape mutants were generated from either of the bat-associated viral variants but two neutralization mutants were derived from the WSKV isolate. Seven independent ERA mutants were recovered using Mabs directed against antigenic sites I (four mutants) and IIIa (three mutants) of the glycoprotein. The cross-neutralization patterns of these viral mutants were used to determine the precise location and nature of the G protein epitopes recognized by these Mabs. Nucleotide sequencing of the G gene indicated that those mutants derived using Mabs directed to antigenic site (AS) III all contained amino acid substitutions in this site. However, of the four mutants selected with AS I Mabs, two bore mutations within AS I as expected while the remaining two carried mutations in AS II. WSKV mutants exhibited mutations at the sites appropriate for the Mabs used in their selection. All ERA mutant preparations were more cytopathogenic than the parental virus when propagated in cell culture; when in vivo pathogenicity in mice was examined, three of these mutants exhibited reduced pathogenicity while the remaining four mutants exhibited comparable pathogenic properties to those of the parent virus. PMID:27132040

  6. Quantum stochastic dynamics in the presence of a time-periodic rapidly oscillating potential: nonadiabatic escape rate.

    PubMed

    Shit, Anindita; Chattopadhyay, Sudip; Chaudhuri, Jyotipratim Ray

    2013-09-12

    Escape from a metastable state in the presence of a high-frequency field (where the driving becomes nonadiabatic) underlies a broad range of phenomena of physics and chemistry, and thus its understanding is of paramount importance. We study the problem of intermediate-to-high-damping escape from a metastable state of a dissipative system driven by a rapidly oscillating field, one of the most important classes of nonequilibrium systems, in a broad range of field driving frequencies (ω) and amplitudes (a). We construct a Langevin equation using quantum gauge transformation in the light of Floquet theorem and exploiting a systematic perturbative expansion in powers of 1/ω using "Kapitza-Landau time window". The quantum dynamics in a high-frequency field are found to be described by an effective time-independent potential. The temperature dependence of escape rate and the change of its form with varying parameters of the field have been analyzed. It may decrease upon increasing the temperature which is contingent on the effects of intricate interplay between external modulation and dissipation. The crossover temperature between tunnelling and thermal hopping increases with an increase in external modulation so that quantum effects in the escape are relevant at higher temperatures. These observations are uncommon and counterintuitive and, therefore, of considerable interest. Our results might be valuable for the exploration of the dynamics of cold atoms in electromagnetic fields. PMID:23627350

  7. Immunogenetic Mechanisms Driving Norovirus GII.4 Antigenic Variation

    PubMed Central

    Donaldson, Eric F.; Corti, Davide; Swanstrom, Jesica; Debbink, Kari; Lanzavecchia, Antonio; Baric, Ralph S.

    2012-01-01

    Noroviruses are the principal cause of epidemic gastroenteritis worldwide with GII.4 strains accounting for 80% of infections. The major capsid protein of GII.4 strains is evolving rapidly, resulting in new epidemic strains with altered antigenic potentials. To test if antigenic drift may contribute to GII.4 persistence, human memory B cells were immortalized and the resulting human monoclonal antibodies (mAbs) characterized for reactivity to a panel of time-ordered GII.4 virus-like particles (VLPs). Reflecting the complex exposure history of the volunteer, human anti-GII.4 mAbs grouped into three VLP reactivity patterns; ancestral (1987–1997), contemporary (2004–2009), and broad (1987–2009). NVB 114 reacted exclusively to the earliest GII.4 VLPs by EIA and blockade. NVB 97 specifically bound and blocked only contemporary GII.4 VLPs, while NBV 111 and 43.9 exclusively reacted with and blocked variants of the GII.4.2006 Minerva strain. Three mAbs had broad GII.4 reactivity. Two, NVB 37.10 and 61.3, also detected other genogroup II VLPs by EIA but did not block any VLP interactions with carbohydrate ligands. NVB 71.4 cross-neutralized the panel of time-ordered GII.4 VLPs, as measured by VLP-carbohydrate blockade assays. Using mutant VLPs designed to alter predicted antigenic epitopes, two evolving, GII.4-specific, blockade epitopes were mapped. Amino acids 294–298 and 368–372 were required for binding NVB 114, 111 and 43.9 mAbs. Amino acids 393–395 were essential for binding NVB 97, supporting earlier correlations between antibody blockade escape and carbohydrate binding variation. These data inform VLP vaccine design, provide a strategy for expanding the cross-blockade potential of chimeric VLP vaccines, and identify an antibody with broadly neutralizing therapeutic potential for the treatment of human disease. Moreover, these data support the hypothesis that GII.4 norovirus evolution is heavily influenced by antigenic variation of neutralizing epitopes

  8. New Analysis of Hydrogen and Deuterium Escape from Venus

    NASA Astrophysics Data System (ADS)

    Donahue, Thomas M.

    1999-10-01

    This paper is concerned with the time required for escape of hydrogen and deuterium to produce the present D/ H ratio in Venus water, the sizes of the original hydrogen reservoirs and their sensitivity to the magnitude of the present escape fluxes, the characteristics of exogenous and endogenous hydrogen sources, and the D/ H ratio for primordial Venus hydrogen. The procedure followed allowed the H escape flux to vary over a large range, the ratio of input to escape flux to vary from 0 to 1, and the fractionation factor, which expresses the relative efficiency of D and H escape, to vary between 0.02 and 0.5. It was found that, unless deuterium escape is very efficient, the present H escape flux (averaged over a solar cycle) cannot be larger than about 10 7 cm -2 s -1 if today's water is to be the remnant of water deposited eons ago. On the other hand if the escape flux is as large as large as 3×10 7 cm -2 s -1, today's water would be the remnant of water outgassed only about 500 million years ago. These conclusions are relatively insensitive to factors other than the magnitude of the escape flux. Since recent analysis of escape fluxes indicates that the H escape fluxes may be in the neighborhood of 3×10 7 cm -2 s -1 and the fractionation factor may be 0.14 or larger, the suggestion of Grinspoon (1993, Nature 363, 1702-1704) that the water now on Venus was created during a recent massive resurfacing event is credible. However, since it is still possible that the average escape flux is as small as 7×10 6 cm -2 s -1, the choice between 4 and 0.5 Gyr must await a resolution of this conflict by reanalysis of Pioneer Venus Lyman α data (Paxton, L., D. E. Anderson, and A. I. F. Stewart 1988, J. Geophys. Res. 93, 1766-1772).

  9. The atmospheric escape at Mars: complementing the scenario

    NASA Astrophysics Data System (ADS)

    Lilensten, Jean; Simon, Cyril; Barthélémy, Mathieu; Thissen, Roland; Ehrenreich, David; Gronoff, Guillaume; Witasse, Olivier

    2013-04-01

    In the recent years, the presence of dications in the atmospheres of Mars, Venus, Earth and Titan has been modeled and assessed. These studies also suggested that these ions could participate to the escape of the planetary atmospheres because a large fraction of them is unstable and highly ener- getic. When they dissociate, their internal energy is transformed into kinetic energy which may be larger than the escape energy. This study assesses the impact of the doubly-charged ions in the escape of CO2-dominated planetary atmospheres and to compare it to the escape of thermal photo-ions.We solve a Boltzmann transport equation at daytime taking into account the dissociative states of CO++ for a simplified single constituent atmosphere of a 2 case-study planet. We compute the escape of fast ions using a Beer-Lambert approach. We study three test-cases. On a Mars-analog planet in today's conditions, we retrieve the measured electron escape flux. When comparing the two mechanisms (i.e. excluding solar wind effects, sputtering ...), the escape due to the fast ions issuing from the dissociation of dications may account for up to 6% of the total and the escape of thermal ions for the remaining. We show that these two mechanisms cannot explain the escape of the atmosphere since the magnetic field vanished but complement the other processes and allow writing the scenario of the Mars escape. We show that the atmosphere of a Mars analog planet would empty in another giga years and a half. At Venus orbit, the contribution of the dications in the escape rate is negligible.When simulating the hot Jupiter HD209458b, the two processes cannot explain the measured escape flux of C+.

  10. Indirect Evidence for Escaping Ionizing Photons in Local Lyman Break Galaxy Analogs

    NASA Astrophysics Data System (ADS)

    Alexandroff, Rachael M.; Heckman, Timothy M.; Borthakur, Sanchayeeta; Overzier, Roderik; Leitherer, Claus

    2015-09-01

    A population of early star-forming galaxies is the leading candidate for the re-ionization of the universe. It is still unclear, however, what conditions and physical processes would enable a significant fraction of the ionizing (Lyman continuum) photons to escape from these gas-rich galaxies. In this paper we present the results of the analysis of Hubble Space Telescope Cosmic Origins Spectrograph far-UV (FUV) spectroscopy plus ancillary multi-waveband data of a sample of 22 low-redshift galaxies that are good analogs to typical star-forming galaxies at high redshift. We measure three parameters that provide indirect evidence of the escape of ionizing radiation (leakiness): (1) the residual intensity in the cores of saturated interstellar low-ionization absorption lines, which indicates incomplete covering by that gas in the galaxy; (2) the relative amount of blueshifted Lyα line emission, which can indicate the existence of holes in the neutral hydrogen on the front-side of the galaxy outflow, and (3) the relative weakness of the [S ii] optical emission lines that trace matter-bounded H ii regions. We show that our residual intensity measures are only negligibly affected by infilling from resonance emission lines. We find all three diagnostics agree well with one another. We use these diagnostics to rank-order our sample in terms of likely leakiness, noting that a direct measure of escaping Lyman continuum has recently been made for one of the leakiest members of our sample. We then examine the correlations between our ranking and other proposed diagnostics of leakiness. We find a good correlation with the equivalent width of the Lyα emission line, but no significant correlations with either the flux ratio of the [O iii]/[O ii] emission lines or the ratio of star-formation rates derived from the (dust-corrected) FUV and Hα luminosities. Turning to galaxy properties, we find the strongest correlations with leakiness are with the compactness of the star

  11. Wind and Rotation Enhanced Escape From the Early Terrestrial Atmospheres

    NASA Astrophysics Data System (ADS)

    Hartle, R. E.

    2001-05-01

    The earliest atmospheres of the terrestrial planets are thought to have been hotter, have stronger winds and rotate faster than atmospheres of today. Since these primitive atmospheres were weakly bound, they evolved rapidly because atmospheric escape was very strong, often referred to as "blowoff." Such escape has been treated as hydrodynamic, transonic flow, similar to solar wind flow dynamics. However, in many cases the outward flow is hydrodynamic at low altitudes only to become collisionless at higher altitudes, well before sonic speeds are ever attained. Recent models dealing with such transition from fluid to kinetic flow have applied the Jeans escape flux at the exobase. This approach has lead to escape rates that are too low due to the fact that thermospheric winds and planetary rotation increase escape fluxes considerably over the corresponding Jeans fluxes (1). In particular, for a given density and temperature at the exobase, the escape flux increases as the wind speed and/or the rotation rate increase. Also, for a given wind speed and rotation rate, the escape flux enhancement over the Jeans flux increases as the mass of an escaping constituent increases, an important factor in isotope fractionation, especially the enrichment of deuterium on Mars. Accounting for a range of possible temperatures, thermospheric wind speeds and planetary rotation rates in the primitive atmospheres of the terrestrial planets, estimates are made of light constituent escape flux increases over the corresponding Jeans fluxes. (1) Hartle, R. E. and H. G. Mayr, J. Geophys. Res., 81, 1207, 1976.

  12. Wind and Rotation Enhanced Escape from the Early Terrestrial Atmospheres

    NASA Technical Reports Server (NTRS)

    Hartle, Richard E.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    The earliest atmospheres of the terrestrial planets are thought to have been hotter, have stronger winds and rotate faster than atmospheres of today. Since these primitive atmospheres were weakly bound, they evolved rapidly because atmospheric escape was very strong, often referred to as "blowoff." Such escape has been treated as hydrodynamic, transonic flow; similar to solar wind flow dynamics. However, in many cases, although the outward flow is hydrodynamic at low altitudes, it becomes collisionless at higher altitudes, before sonic speeds are ever attained. Recent models dealing with the transition from fluid to kinetic flow have applied the Jeans escape flux at the exobase. This approach leads to escape rates that are too low, because thermospheric winds and planetary rotation are known to increase the escape flux above the corresponding Jeans flux. In particular, for a given density and temperature at the exobase, the escape flux increases as the wind speed and/or the rotation rate increase. Also, for a given wind speed and rotation rate, the escape flux enhancement over the Jeans flux increases as the mass of an escaping constituent increases, an important factor in isotope fractionation, especially the enrichment of deuterium on Mars. Accounting for a range of possible temperatures, thermospheric wind speeds and planetary rotation rates in the primitive atmospheres of the terrestrial planets, estimates are made of light constituent escape flux increases over the corresponding Jeans fluxes.

  13. Chaotic Scattering and Escape Times of Marginally Trapped Ultracold Neutrons

    PubMed Central

    Coakley, K. J.; Doyle, J. M.; Dzhosyuk, S. N.; Yang, L.; Huffman, P. R.

    2005-01-01

    We compute classical trajectories of Ultracold neutrons (UCNs) in a superconducting Ioffe-type magnetic trap using a symplectic integration method. We find that the computed escape time for a particular set of initial conditions (momentum and position) does not generally stabilize as the time step parameter is reduced unless the escape time is short (less than approximately 10 s). For energy intervals where more than half of the escape times computed for UCN realizations are numerically well determined, we predict the median escape time as a function of the midpoint of the interval. PMID:27308152

  14. The polarization of escaping terrestrial continuum radiation

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Calvert, W.; Huff, R. L.; Jones, D.; Sugiura, M.

    1988-01-01

    The polarization of an escaping terrestrial continuum radiation event that occurred on March 2, 1982, was determined using plasma wave measurements from the DE-1 spacecraft. The source of the radiation was determined to be located near the magnetic equator on the nightside of the earth at a radial distance of about 2.8-3.5 earth radii. Two meridional beams were detected, one directed north at an angle of about 20-30 deg with respect to the magnetic equator, and the other directed south at a comparable angle. Polarization measurements indicated that the radiation is right-hand polarized with respect to an outward directed E plane normal in the Northern Hemisphere and left-hand polarized in the Southern Hemisphere.

  15. Escape of Black Holes from the Brane

    SciTech Connect

    Flachi, Antonino; Tanaka, Takahiro

    2005-10-14

    TeV-scale gravity theories allow the possibility of producing small black holes at energies that soon will be explored at the CERN LHC or at the Auger observatory. One of the expected signatures is the detection of Hawking radiation that might eventually terminate if the black hole, once perturbed, leaves the brane. Here, we study how the 'black hole plus brane' system evolves once the black hole is given an initial velocity that mimics, for instance, the recoil due to the emission of a graviton. The results of our dynamical analysis show that the brane bends around the black hole, suggesting that the black hole eventually escapes into the extra dimensions once two portions of the brane come in contact and reconnect. This gives a dynamical mechanism for the creation of baby branes.

  16. Gated narrow escape time for molecular signaling.

    PubMed

    Reingruber, Jürgen; Holcman, David

    2009-10-01

    The mean time for a diffusing ligand to activate a target protein located on the surface of a microdomain can regulate cellular signaling. When the ligand switches between various states induced by chemical interactions or conformational changes, while target activation occurs in only one state, this activation time is affected. We investigate this dynamics using new equations for the sojourn times spent in each state. For two states, we obtain exact solutions in dimension one, and asymptotic ones confirmed by Brownian simulations in dimension 3. We find that the activation time is quite sensitive to changes of the switching rates, which can be used to modulate signaling. Interestingly, our analysis reveals that activation can be fast although the ligand spends most of the time "hidden" in the nonactivating state. Finally, we obtain a new formula for the narrow escape time in the presence of switching. PMID:19905605

  17. On neutral plasma oscillations

    SciTech Connect

    Shadwick, B.A.; Morrison, P.J.

    1993-06-01

    We examine the conditions for the existence of spectrally stable neutral modes in a Vlasov-Poisson plasma and show that for stable equilibria of systems that have unbounded spatial domain, the only possible neutral modes are those with phase velocities that correspond to stationary inflection points of the equilibrium distribution function. It is seen that these neutral modes can possess positive or negative free energy.

  18. ALEX neutral beam probe

    SciTech Connect

    Pourrezaei, K.

    1982-01-01

    A neutral beam probe capable of measuring plasma space potential in a fully 3-dimensional magnetic field geometry has been developed. This neutral beam was successfully used to measure an arc target plasma contained within the ALEX baseball magnetic coil. A computer simulation of the experiment was performed to refine the experimental design and to develop a numerical model for scaling the ALEX neutral beam probe to other cases of fully 3-dimensional magnetic field. Based on this scaling a 30 to 50 keV neutral cesium beam probe capable of measuring space potential in the thermal barrier region of TMX Upgrade was designed.

  19. The escape of Lyman photons from a young starburst: the case of Haro11†

    NASA Astrophysics Data System (ADS)

    Hayes, Matthew; Östlin, Göran; Atek, Hakim; Kunth, Daniel; Mas-Hesse, J. Miguel; Leitherer, Claus; Jiménez-Bailón, Elena; Adamo, Angela

    2007-12-01

    Lyman α (Lyα) is one of the dominant tools used to probe the star-forming galaxy population at high redshift (z). However, astrophysical interpretations of data drawn from Lyα alone hinge on the Lyα escape fraction which, due to the complex radiative transport, may vary greatly. Here, we map the Lyα emission from the local luminous blue compact galaxy Haro11, a known emitter of Lyα and the only known candidate for low-z Lyman continuum emission. To aid in the interpretation, we perform a detailed ultraviolet and optical multiwavelength analysis and model the stellar population, dust distribution, ionizing photon budget, and star-cluster population. We use archival X-ray observations to further constrain properties of the starburst and estimate the neutral hydrogen column density. The Lyα morphology is found to be largely symmetric around a single young star-forming knot and is strongly decoupled from other wavelengths. From general surface photometry, only very slight correlation is found between Lyα and Hα, E(B - V), and the age of the stellar population. Only around the central Lyα bright cluster do we find the Lyα/Hα ratio at values predicted by the recombination theory. The total Lyα escape fraction is found to be just 3 per cent. We compute that ~90 per cent of the Lyα photons that escape do so after undergoing multiple resonance scattering events, masking their point of origin. This leads to a largely symmetric distribution and, by increasing the distance that photons must travel to escape, decreases the escape probability significantly. While dust must ultimately be responsible for the destruction of Lyα, it plays a little role in governing the observed morphology, which is regulated more by interstellar medium kinematics and geometry. We find tentative evidence for local Lyα equivalent width in the immediate vicinity of star clusters being a function of cluster age, consistent with hydrodynamic studies. We estimate the intrinsic production

  20. Lyman Continuum Escape Fraction of Star-forming Dwarf Galaxies at z ˜ 1

    NASA Astrophysics Data System (ADS)

    Rutkowski, Michael J.; Scarlata, Claudia; Haardt, Francesco; Siana, Brian; Henry, Alaina; Rafelski, Marc; Hayes, Matthew; Salvato, Mara; Pahl, Anthony J.; Mehta, Vihang; Beck, Melanie; Malkan, Matthew; Teplitz, Harry I.

    2016-03-01

    To date, no direct detection of Lyman continuum emission has been measured for intermediate-redshift (z˜ 1) star-forming galaxies. We combine Hubble Space Telescope grism spectroscopy with GALEX UV and ground-based optical imaging to extend the search for escaping Lyman continuum to a large (˜600) sample of z˜ 1 low-mass ({log}(\\bar{M}) ≃ 9.3{M}⊙ ), moderately star-forming (\\bar{{{\\Psi }}} ≲ 10{M}⊙ yr-1) galaxies selected initially on Hα emission. The characteristic escape fraction of LyC from star-forming galaxies (SFGs) that populate this parameter space remains weakly constrained by previous surveys, but these faint (sub-L⋆) SFGs are assumed to play a significant role in the reionization of neutral hydrogen in the intergalactic medium (IGM) at high redshift z\\gt 6. We do not make an unambiguous detection of escaping LyC radiation from this z˜ 1 sample, individual non-detections to constrain the absolute Lyman continuum escape fraction, {f}{esc} \\lt 2.1% (3σ). We measure an upper limit of {f}{esc} \\lt 9.6% from a sample of SFGs selected on high Hα equivalent width (EW \\gt 200 {{\\mathringA }}), which are thought to be close analogs of high redshift sources of reionization. For reference, we also present an emissivity-weighted escape fraction that is useful for measuring the general contribution SFGs to the ionizing UV background. In the discussion, we consider the implications of these intermediate redshift constraints for the reionization of hydrogen in the IGM at high (z\\gt 6) redshift. If we assume our z˜ 1 SFGs, for which we measure this emissivity-weighted {f}{esc}, are analogs to the high redshift sources of reionization, we find it is difficult to reconcile reionization by faint ({M}{UV}≲ -13) SFGs with a low escape fraction ({f}{esc} \\lt 3%), with constraints from independent high redshift observations. If {f}{esc} evolves with redshift, reionization by SFGs may be consistent with observations from Planck.

  1. Pickup ions near Mars associated with escaping oxygen atoms

    NASA Astrophysics Data System (ADS)

    Cravens, T. E.; Hoppe, A.; Ledvina, S. A.; McKenna-Lawlor, S.

    2002-08-01

    Ions produced by ionization of Martian neutral atoms or molecules and picked up by the solar wind flow are expected to be an important ingredient of the Martian plasma environment. Significant fluxes of energetic (55-72 keV) oxygen ions were recorded in the wake of Mars and near the bow shock by the solar low-energy detector (SLED) charged particle detector onboard the Phobos 2 spacecraft. Also, copious fluxes of oxygen ions in the ranges 0.5-25 and 0.01-6 keV/q were detected in the Martian wake by the Automatic Space Plasma Experiment with Rotating Analyzer (ASPERA) instrument on Phobos 2. This paper provides a quantitative analysis of the SLED energetic ion data using a test particle model in which one million ion trajectories were numerically calculated. These trajectories were used to determine the ion flux as a function of energy in the vicinity of Mars for conditions appropriate for Circular Orbit 42 of Phobos 2. The electric and magnetic fields required by the test particle model were taken from a three-dimensional magnetohydrodynamic (MHD) model of the solar wind interaction with Mars. The ions were started at rest with a probability proportional to the density expected for exospheric hot oxygen. The test particle model supports the identification of the ions observed in channel 1 of the SLED instrument as pick-up oxygen ions that are created by the ionization of oxygen atoms in the distant part of the exosphere. The flux of 55-72 keV oxygen ions near the orbit of the Phobos 2 should be proportional to the oxygen density at radial distances from Mars of about 10 Rm (Martian radii) and hence proportional to the direct oxygen escape rate from Mars that is an important part of the overall oxygen loss rate at Mars. The modeled energetic oxygen fluxes also exhibit a spin modulation as did the SLED fluxes during Circular Orbit 42.

  2. Energy-limited escape revised. The transition from strong planetary winds to stable thermospheres

    NASA Astrophysics Data System (ADS)

    Salz, M.; Schneider, P. C.; Czesla, S.; Schmitt, J. H. M. M.

    2016-01-01

    Gas planets in close proximity to their host stars experience photoevaporative mass loss. The energy-limited escape concept is generally used to derive estimates for the planetary mass-loss rates. Our photoionization hydrodynamics simulations of the thermospheres of hot gas planets show that the energy-limited escape concept is valid only for planets with a gravitational potential lower than log 10(-ΦG)< 13.11 erg g-1 because in these planets the radiative energy input is efficiently used to drive the planetary wind. Massive and compact planets with log 10(-ΦG) ≳ 13.6 erg g-1 exhibit more tightly bound atmospheres in which the complete radiative energy input is re-emitted through hydrogen Lyα and free-free emission. These planets therefore host hydrodynamically stable thermospheres. Between these two extremes the strength of the planetary winds rapidly declines as a result of a decreasing heating efficiency. Small planets undergo enhanced evaporation because they host expanded atmospheres that expose a larger surface to the stellar irradiation. We present scaling laws for the heating efficiency and the expansion radius that depend on the gravitational potential and irradiation level of the planet. The resulting revised energy-limited escape concept can be used to derive estimates for the mass-loss rates of super-Earth-sized planets as well as massive hot Jupiters with hydrogen-dominated atmospheres.

  3. Energy Release, Acceleration, and Escape of Solar Energetic Ions

    NASA Astrophysics Data System (ADS)

    de Nolfo, G. A.; Ireland, J.; Ryan, J. M.; Young, C. A.

    2013-12-01

    Solar flares are prodigious producers of energetic particles, and thus a rich laboratory for studying particle acceleration. The acceleration occurs through the release of magnetic energy, a significant fraction of which can go into the acceleration of particles. Coronal mass ejections (CMEs) certainly produce shocks that both accelerate particles and provide a mechanism for escape into the interplanetary medium (IP). What is less well understood is whether accelerated particles produced from the flare reconnection process escape, and if so, how these same particles are related to solar energetic particles (SEPs) detected in-situ. Energetic electron SEPs have been shown to be correlated with Type III radio bursts, hard X-ray emission, and EUV jets, making a very strong case for the connection between acceleration at the flare and escape along open magnetic field lines. Because there has not been a clear signature of ion escape, as is the case with the Type III radio emission for electrons, sorting out the avenues of escape for accelerated flare ions and the possible origin of the impulsive SEPs continues to be a major challenge. The key to building a clear picture of particle escape relies on the ability to map signatures of escape such as EUV jets at the Sun and to follow the progression of these escape signatures as they evolve in time. Furthermore, nuclear γ-ray emissions provide critical context relating ion acceleration to that of escape. With the advent observations from Fermi as well as RHESSI and the Solar Dynamics Observatory (SDO), the challenge of ion escape from the Sun can now be addressed. We present a preliminary study of the relationship of EUV jets with nuclear γ-ray emission and Type III radio observations and discuss the implications for possible magnetic topologies that allow for ion escape from deep inside the corona to the interplanetary medium.

  4. Imaging space plasmas in energetic neutral atoms

    NASA Astrophysics Data System (ADS)

    Roelof, E. C.; Demajistre, R.; Mitchell, D. G.; C:Son Brandt, P.

    2004-11-01

    Many space plasmas contain energetic singly-charged ions immersed in a cold gas of neutral atoms and molecules. When the energetic ions undergo charge-exchange collisions with the background cold neutrals, they become energetic neutral atoms (ENAs). Thus the space plasma Â"glowsÂ" in the ENAs which escape the plasma on straight-line trajectories. Properly designed 2-dimentsional particle telescopes that deflect ions using electro-static fields become ENA Â"camerasÂ". Such cameras are now operating on the NASA IMAGE spacecraft in orbit around Earth and the NASA/ESA Cassini spacecraft in orbit around Saturn. They are providing all-sky global images of the singly-charged trapped ion populations of these planets with time resolution of a few minutes. Each pixel contains an energy spectra from 10 to 200 keV/nucleon of the major singly-charged ions (protons and O^+), thus providing a quantitative diagnostic of energetic ion injection, acceleration, and transport. ENA imaging has now taken its place as a fundamental tool in magnetospheric research, and new missions are moving forward to apply ENA imaging to the heliosphere itself (the domain of the solar wind) and its termination ˜100 AU from the Sun where it interacts with the local interstellar gas.

  5. Neutrality in Language Policy

    ERIC Educational Resources Information Center

    Wee, Lionel

    2010-01-01

    The unavoidability of language makes it critical that language policies appeal to some notion of language neutrality as part of their rationale, in order to assuage concerns that the policies might otherwise be unduly discriminatory. However, the idea of language neutrality is deeply ideological in nature, since it is not only an attempt to treat…

  6. How to Escape a Home Fire (Take This Safety Quiz).

    ERIC Educational Resources Information Center

    PTA Today, 1994

    1994-01-01

    A checklist/safety quiz from the National Fire Protection Association examines individual knowledge of how to escape if a home fire breaks out. The organization recommends that every household develop a fire escape plan and practice it at least twice a year. (SM)

  7. 33 CFR 143.101 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Means of escape. 143.101 Section 143.101 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES DESIGN AND EQUIPMENT OCS Facilities § 143.101 Means of escape. (a) “Primary...

  8. Green Pea Galaxies Reveal Secrets of Lyα Escape

    NASA Astrophysics Data System (ADS)

    Yang, Huan; Malhotra, Sangeeta; Gronke, Max; Rhoads, James E.; Dijkstra, Mark; Jaskot, Anne; Zheng, Zhenya; Wang, Junxian

    2016-04-01

    We analyze archival Lyα spectra of 12 “Green Pea” galaxies observed with the Hubble Space Telescope, model their Lyα profiles with radiative transfer models, and explore the dependence of the Lyα escape fraction on various properties. Green Pea galaxies are nearby compact starburst galaxies with [O iii] λ5007 equivalent widths (EWs) of hundreds of Å. All 12 Green Pea galaxies in our sample show Lyα lines in emission, with an Lyα EW distribution similar to high-redshift Lyα emitters. Combining the optical and UV spectra of Green Pea galaxies, we estimate their Lyα escape fractions and find correlations between Lyα escape fraction and kinematic features of Lyα profiles. The escape fraction of Lyα in these galaxies ranges from 1.4% to 67%. We also find that the Lyα escape fraction depends strongly on metallicity and moderately on dust extinction. We compare their high-quality Lyα profiles with single H i shell radiative transfer models and find that the Lyα escape fraction anticorrelates with the derived H i column densities. Single-shell models fit most Lyα profiles well, but not the ones with the highest escape fractions of Lyα. Our results suggest that low H i column density and low metallicity are essential for Lyα escape and make a galaxy an Lyα emitter.

  9. [Examination of the escape phenomenon in disease modifying antirheumatic drugs].

    PubMed

    Kawasaki, Yoichi; Moriyama, Masahiro; Shibata, Kazuhiko; Gomita, Yutaka

    2005-03-01

    Although disease-modifying antirheumatic drugs (DMARDs) are used in the treatment of rheumatoid arthritis (RA), the selection of agents in the case of relapse (escape phenomenon) lacks clear-cut standards. Therefore we investigated the rate and conditions of escape as well as the agents used after escapes had occurred. Outpatients of the Matsubara Mayflower Hospital with a history of DMARD administration during the 4 years prior to May 2003 were studied. Those receiving salazosulfapyridine (SASP) had a high escape rate and those receiving methotrexate (MTX) and bucillamine (BC) had a low rate. The continuous duration of administration was long for MTX and BC, but short for sodium aurothiomalate (GST). BC and Actarit (AR) gradually elevated C-reactive protein (CRP) levels and the erythrocyte sedimentation rate (ESR). In patients receiving SASP and MTX, a high level of CRP and high ESR was seen 2 months prior to the occurrence of escape and remained unchanged after escape. With respect to the agents used after escape, SASP and BC were substituted with other DMARDs. A combination with other DMARDs was usually administered to patients who had been receiving MTX. Taken together, the present results clarified the characteristics of DMARD escape and will contribute to the appropriate pharmacotherapy for RA. PMID:15738628

  10. The Origins and Underpinning Principles of E-Scape

    ERIC Educational Resources Information Center

    Kimbell, Richard

    2012-01-01

    In this article I describe the context within which we developed project e-scape and the early work that laid the foundations of the project. E-scape (e-solutions for creative assessment in portfolio environments) is centred on two innovations. The first concerns a web-based approach to portfolio building; allowing learners to build their…

  11. Fire Won't Wait--Plan Your Escape!

    ERIC Educational Resources Information Center

    PTA Today, 1991

    1991-01-01

    Discusses the importance of home fire escape drills, detailing fire safety plans. Early detection and warning (smoke detectors) coupled with well-rehearsed escape plans help prevent serious injury. Children need to be taught about fire safety beginning at a very early age. (SM)

  12. 46 CFR 108.445 - Alarm and means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Alarm and means of escape. 108.445 Section 108.445 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Fire Extinguishing Systems Fixed Carbon Dioxide Fire Extinguishing Systems § 108.445 Alarm and means of escape. (a) Each CO2...

  13. 35. INTERIOR VIEW OF EQUIPMENT HOUSE, SUBMARINE ESCAPE TRAINING TANK, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    35. INTERIOR VIEW OF EQUIPMENT HOUSE, SUBMARINE ESCAPE TRAINING TANK, PRIOR TO ENLARGEMENT OF ROOM AND INSTALLATION OF TRIPLE-LOCK RECOMPRESSION CHAMBER IN 1957 - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  14. 29. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION AT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION AT POINT JUST ABOVE THE SUBMARINE SECTION AT THE 110-FOOT LEVEL 1929-1930 - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  15. 36. VIEW OF CUPOLA, SUBMARINE ESCAPE TRAINING TANK, SHOWING ROVING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    36. VIEW OF CUPOLA, SUBMARINE ESCAPE TRAINING TANK, SHOWING ROVING RESCUE BELL SUSPENDED ABOVE TANK, WITH TWO-LOCK RECOMPRESSION CHAMBER AT REAR, LOOKING WEST. Photo taken after installation of recompression chamber in 1956. - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  16. 22. VIEW OF ESCAPE TRAINING TANK, LOOKING WEST FROM EAST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. VIEW OF ESCAPE TRAINING TANK, LOOKING WEST FROM EAST SIDE OF CUPOLA TOWARD ELEVATOR. TWO-LOCK RECOMPRESSION CHAMBER AT REAR - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  17. 31. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    31. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION OF THE ELEVATOR AND PASSAGEWAYS TO THE 18- AND 50-FOOT LOCKS AND CUPOLA 1932 - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  18. 7. VIEW OF ESCAPE TRAINING TANK, LOOKING UP SOUTH SIDE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. VIEW OF ESCAPE TRAINING TANK, LOOKING UP SOUTH SIDE FROM 50-FOOT PASSAGEWAY, SHOWING 25-FOOT BLISTER AT LEFT, 18-FOOT PASSAGEWAY AND PLATFORM AT RIGHT - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  19. Teachers Offering Healthy Escape Options for Teenagers in Pain

    ERIC Educational Resources Information Center

    Kaywell, Joan F.

    2005-01-01

    "[T]wenty-five percent of today's teenagers have inordinate emotional baggage beyond the normal angst of adolescence." This burden can lead to unhealthy escapes, including substance abuse, sexual activity, violence, eating disorders, and suicide. One healthy escape, however, lies in books, where students can read about teenagers living in painful…

  20. Spatial calibration of a tokamak neutral beam diagnostic using in situ neutral beam emission.

    PubMed

    Chrystal, C; Burrell, K H; Grierson, B A; Pace, D C

    2015-10-01

    Neutral beam injection is used in tokamaks to heat, apply torque, drive non-inductive current, and diagnose plasmas. Neutral beam diagnostics need accurate spatial calibrations to benefit from the measurement localization provided by the neutral beam. A new technique has been developed that uses in situ measurements of neutral beam emission to determine the spatial location of the beam and the associated diagnostic views. This technique was developed to improve the charge exchange recombination (CER) diagnostic at the DIII-D tokamak and uses measurements of the Doppler shift and Stark splitting of neutral beam emission made by that diagnostic. These measurements contain information about the geometric relation between the diagnostic views and the neutral beams when they are injecting power. This information is combined with standard spatial calibration measurements to create an integrated spatial calibration that provides a more complete description of the neutral beam-CER system. The integrated spatial calibration results are very similar to the standard calibration results and derived quantities from CER measurements are unchanged within their measurement errors. The methods developed to perform the integrated spatial calibration could be useful for tokamaks with limited physical access. PMID:26520957

  1. Spatial calibration of a tokamak neutral beam diagnostic using in situ neutral beam emission

    SciTech Connect

    Chrystal, C.; Burrell, K. H.; Pace, D. C.; Grierson, B. A.

    2015-10-15

    Neutral beam injection is used in tokamaks to heat, apply torque, drive non-inductive current, and diagnose plasmas. Neutral beam diagnostics need accurate spatial calibrations to benefit from the measurement localization provided by the neutral beam. A new technique has been developed that uses in situ measurements of neutral beam emission to determine the spatial location of the beam and the associated diagnostic views. This technique was developed to improve the charge exchange recombination (CER) diagnostic at the DIII-D tokamak and uses measurements of the Doppler shift and Stark splitting of neutral beam emission made by that diagnostic. These measurements contain information about the geometric relation between the diagnostic views and the neutral beams when they are injecting power. This information is combined with standard spatial calibration measurements to create an integrated spatial calibration that provides a more complete description of the neutral beam-CER system. The integrated spatial calibration results are very similar to the standard calibration results and derived quantities from CER measurements are unchanged within their measurement errors. The methods developed to perform the integrated spatial calibration could be useful for tokamaks with limited physical access.

  2. Spatial calibration of a tokamak neutral beam diagnostic using in situ neutral beam emission

    NASA Astrophysics Data System (ADS)

    Chrystal, C.; Burrell, K. H.; Grierson, B. A.; Pace, D. C.

    2015-10-01

    Neutral beam injection is used in tokamaks to heat, apply torque, drive non-inductive current, and diagnose plasmas. Neutral beam diagnostics need accurate spatial calibrations to benefit from the measurement localization provided by the neutral beam. A new technique has been developed that uses in situ measurements of neutral beam emission to determine the spatial location of the beam and the associated diagnostic views. This technique was developed to improve the charge exchange recombination (CER) diagnostic at the DIII-D tokamak and uses measurements of the Doppler shift and Stark splitting of neutral beam emission made by that diagnostic. These measurements contain information about the geometric relation between the diagnostic views and the neutral beams when they are injecting power. This information is combined with standard spatial calibration measurements to create an integrated spatial calibration that provides a more complete description of the neutral beam-CER system. The integrated spatial calibration results are very similar to the standard calibration results and derived quantities from CER measurements are unchanged within their measurement errors. The methods developed to perform the integrated spatial calibration could be useful for tokamaks with limited physical access.

  3. Strain-Specific V3 and CD4 Binding Site Autologous HIV-1 Neutralizing Antibodies Select Neutralization-Resistant Viruses

    SciTech Connect

    Moody, M.  Anthony; Gao, Feng; Gurley, Thaddeus  C.; Amos, Joshua  D.; Kumar, Amit; Hora, Bhavna; Marshall, Dawn  J.; Whitesides, John  F.; Xia, Shi-Mao; Parks, Robert; Lloyd, Krissey  E.; Hwang, Kwan-Ki; Lu, Xiaozhi; Bonsignori, Mattia; Finzi, Andrés; Vandergrift, Nathan  A.; Alam, S.  Munir; Ferrari, Guido; Shen, Xiaoying; Tomaras, Georgia  D.; Kamanga, Gift; Cohen, Myron  S.; Sam, Noel  E.; Kapiga, Saidi; Gray, Elin S.; Tumba, Nancy  L.; Morris, Lynn; Zolla-Pazner, Susan; Gorny, Miroslaw  K.; Mascola, John  R.; Hahn, Beatrice H.; Shaw, George  M.; Sodroski, Joseph  G.; Liao, Hua-Xin; Montefiori, David C.; Hraber, Peter T.; Korber, Bette T.; Haynes, Barton F.

    2015-09-09

    The third variable (V3) loop and the CD4 binding site (CD4bs) of the viral envelope are frequently targeted by neutralizing antibodies (nAbs) in HIV-1-infected individuals. In chronic infection, virus escape mutants repopulate the plasma and V3 and CD4bs nAbs emerge that can neutralize heterologous tier 1 easy-to-neutralize, but not tier 2 difficult-to-neutralize HIV-1 isolates. However, neutralization sensitivity of autologous plasma viruses to this type of nAb response has not been studied. We describe the development and evolution in vivo of antibodies distinguished by their target specificity for V3and CD4bs epitopes on autologous tier 2 viruses but not on heterologous tier 2 viruses. A surprisingly high fraction of autologous circulating viruses was sensitive to these antibodies. These findings demonstrate a role for V3 and CD4bs antibodies in constraining the native envelope trimer in vivo to a neutralization-resistant phenotype, explaining why HIV-1 transmission generally occurs by tier 2 neutralization-resistant viruses.

  4. Strain-Specific V3 and CD4 Binding Site Autologous HIV-1 Neutralizing Antibodies Select Neutralization-Resistant Viruses

    DOE PAGESBeta

    Moody, M.  Anthony; Gao, Feng; Gurley, Thaddeus  C.; Amos, Joshua  D.; Kumar, Amit; Hora, Bhavna; Marshall, Dawn  J.; Whitesides, John  F.; Xia, Shi-Mao; Parks, Robert; et al

    2015-09-09

    The third variable (V3) loop and the CD4 binding site (CD4bs) of the viral envelope are frequently targeted by neutralizing antibodies (nAbs) in HIV-1-infected individuals. In chronic infection, virus escape mutants repopulate the plasma and V3 and CD4bs nAbs emerge that can neutralize heterologous tier 1 easy-to-neutralize, but not tier 2 difficult-to-neutralize HIV-1 isolates. However, neutralization sensitivity of autologous plasma viruses to this type of nAb response has not been studied. We describe the development and evolution in vivo of antibodies distinguished by their target specificity for V3and CD4bs epitopes on autologous tier 2 viruses but not on heterologous tiermore » 2 viruses. A surprisingly high fraction of autologous circulating viruses was sensitive to these antibodies. These findings demonstrate a role for V3 and CD4bs antibodies in constraining the native envelope trimer in vivo to a neutralization-resistant phenotype, explaining why HIV-1 transmission generally occurs by tier 2 neutralization-resistant viruses.« less

  5. Structural basis of hepatitis C virus neutralization by broadly neutralizing antibody HCV1

    SciTech Connect

    Kong, Leopold; Giang, Erick; Robbins, Justin B.; Stanfield, Robyn L.; Burton, Dennis R.; Wilson, Ian A.; Law, Mansun

    2012-10-29

    Hepatitis C virus (HCV) infects more than 2% of the global population and is a leading cause of liver cirrhosis, hepatocellular carcinoma, and end-stage liver diseases. Circulating HCV is genetically diverse, and therefore a broadly effective vaccine must target conserved T- and B-cell epitopes of the virus. Human mAb HCV1 has broad neutralizing activity against HCV isolates from at least four major genotypes and protects in the chimpanzee model from primary HCV challenge. The antibody targets a conserved antigenic site (residues 412-423) on the virus E2 envelope glycoprotein. Two crystal structures of HCV1 Fab in complex with an epitope peptide at 1.8-{angstrom} resolution reveal that the epitope is a {beta}-hairpin displaying a hydrophilic face and a hydrophobic face on opposing sides of the hairpin. The antibody predominantly interacts with E2 residues Leu{sup 413} and Trp{sup 420} on the hydrophobic face of the epitope, thus providing an explanation for how HCV isolates bearing mutations at Asn{sup 415} on the same binding face escape neutralization by this antibody. The results provide structural information for a neutralizing epitope on the HCV E2 glycoprotein and should help guide rational design of HCV immunogens to elicit similar broadly neutralizing antibodies through vaccination.

  6. Routes to formation of highly excited neutral atoms in the break-up of strongly driven hydrogen molecule

    NASA Astrophysics Data System (ADS)

    Emmanouilidou, Agapi

    2012-06-01

    We present a theoretical quasiclassical treatment of the formation, during Coulomb explosion, of highly excited neutral H atoms for strongly-driven hydrogen molecule. This process, where after the laser field is turned off, one electron escapes to the continuum while the other occupies a Rydberg state, was recently reported in an experimental study in Phys. Rev. Lett 102, 113002 (2009). We find that two-electron effects are important in order to correctly account for all pathways leading to highly excited neutral hydrogen formation [1]. We identify two pathways where the electron that escapes to the continuum does so either very quickly or after remaining bound for a few periods of the laser field. These two pathways of highly excited neutral H formation have distinct traces in the probability distribution of the escaping electron momentum components. [4pt] [1] A. Emmanouilidou, C. Lazarou, A. Staudte and U. Eichmann, Phys. Rev. A (Rapid) 85 011402 (2012).

  7. Prediction of anti-angiogenesis escape.

    PubMed

    Mitamura, Takashi; Gourley, Charlie; Sood, Anil K

    2016-04-01

    Many clinical trials have demonstrated the benefit of anti-angiogenesis therapy in the treatment of gynecologic cancer. However, these benefits have often been in terms of progression-free rather than overall survival and in some cases, the magnitude of benefit demonstrated in the pivotal phase 3 trials has been disappointing when compared with the percentage of patients who responded in earlier phase 2 trials. Two potential explanations for this are the current inability to stratify patients according to chance of benefit and the development of resistance mechanisms within the tumor. In this article, we review the prediction of response and the proposed resistance and escape mechanisms involved in anti-angiogenesis therapy, including the up-regulation of alternative proangiogenic pathways, vascular co-option, and resistance to hypoxia. These insights may offer a personalized strategy for anti-angiogenesis therapy and help us to consider the best selection of other therapies that should be combined with anti-angiogenesis therapy to improve the outcome of patients with gynecologic cancer. PMID:26748214

  8. WANDERING STARS: AN ORIGIN OF ESCAPED POPULATIONS

    SciTech Connect

    Teyssier, Maureen; Johnston, Kathryn V.; Shara, Michael M.

    2009-12-10

    We demonstrate that stars beyond the virial radii of galaxies may be generated by the gravitational impulse received by a satellite as it passes through the pericenter of its orbit around its parent. These stars may become energetically unbound (escaped stars), or may travel to further than a few virial radii for longer than a few Gyr, but still remain energetically bound to the system (wandering stars). Larger satellites (10%-100% the mass of the parent), and satellites on more radial orbits are responsible for the majority of this ejected population. Wandering stars could be observable on Mpc scales via classical novae, and on 100 Mpc scales via Type Ia supernova. The existence of such stars would imply a corresponding population of barely bound, old, high-velocity stars orbiting the Milky Way, generated by the same physical mechanism during the Galaxy's formation epoch. Sizes and properties of these combined populations should place some constraints on the orbits and masses of the progenitor objects from which they came, providing insight into the merging histories of galaxies in general and the Milky Way in particular.

  9. Escaping the resource curse in China.

    PubMed

    Cao, Shixiong; Li, Shurong; Ma, Hua; Sun, Yutong

    2015-02-01

    Many societies face an income gap between rich regions with access to advanced technology and regions that are rich in natural resources but poorer in technology. This "resource curse" can lead to a Kuznets trap, in which economic inequalities between the rich and the poor increase during the process of socioeconomic development. This can also lead to depletion of natural resources, environmental degradation, social instability, and declining socioeconomic development. These problems will jeopardize China's achievements if the current path continues to be pursued without intervention by the government to solve the problems. To mitigate the socioeconomic development gap between western and eastern China, the government implemented its Western Development Program in 2000. However, recent data suggest that this program has instead worsened the resource curse. Because each region has its own unique strengths and weaknesses, China must escape the resource curse by accounting for this difference; in western China, this can be done by improving education, promoting high-tech industry, adjusting its economic strategy to balance regional development, and seeking more sustainable approaches to socioeconomic development. PMID:24973055

  10. Dications and thermal ions in planetary atmospheric escape

    NASA Astrophysics Data System (ADS)

    Lilensten, J.; Simon Wedlund, C.; Barthélémy, M.; Thissen, R.; Ehrenreich, D.; Gronoff, G.; Witasse, O.

    2013-01-01

    In the recent years, the presence of dications in the atmospheres of Mars, Venus, Earth and Titan has been modeled and assessed. These studies also suggested that these ions could participate to the escape of the planetary atmospheres because a large fraction of them is unstable and highly energetic. When they dissociate, their internal energy is transformed into kinetic energy which may be larger than the escape energy. The goal of this study is to assess the impact of the doubly-charged ions in the escape of CO2-dominated planetary atmospheres and to compare it to the escape of thermal photo-ions. We solve a Boltzmann transport equation at daytime taking into account the dissociative states of CO2++ for a simplified single constituent atmosphere of a case-study planet. We compute the escape of fast ions using a Beer-Lambert approach. We study three test-cases. On a Mars-analog planet in today's conditions, we retrieve the measured electron escape flux. When comparing the two mechanisms (i.e. excluding solar wind effects, sputtering, etc.), the escape due to the fast ions issuing from the dissociation of dications may account for up to 6% of the total and the escape of thermal ions for the remaining. We show that these two mechanisms cannot explain the escape of the atmosphere since the magnetic field vanished and even contribute only marginally to this loss. We show that with these two mechanisms, the atmosphere of a Mars analog planet would empty in another giga years and a half. At Venus orbit, the contribution of the dications in the escape rate is negligible. When simulating the hot Jupiter HD 209458 b, the two processes cannot explain the measured escape flux of C+. This study shows that the dications may constitute a source of the escape of planetary atmospheres which had not been taken into account until now. This source, although marginal, is not negligible. The influence of the photoionization is of course large, but cannot explain alone the loss of Mars

  11. Species ages in neutral biodiversity models.

    PubMed

    Chisholm, Ryan A; O'Dwyer, James P

    2014-05-01

    Biogeography seeks to understand the mechanisms that drive biodiversity across long temporal and large spatial scales. Theoretical models of biogeography can be tested by comparing their predictions of quantities such as species ages against empirical estimates. It has previously been claimed that the neutral theory of biodiversity and biogeography predicts species ages that are unrealistically long. Any improved theory of biodiversity must rectify this problem, but first it is necessary to quantify the problem precisely. Here we provide analytical expressions for species ages in neutral biodiversity communities. We analyse a spatially implicit metacommunity model and solve for both the zero-sum and non-zero-sum cases. We explain why our new expressions are, in the context of biodiversity, usually more appropriate than those previously imported from neutral molecular evolution. Because of the time symmetry of the spatially implicit neutral model, our expressions also lead directly to formulas for species persistence times and species lifetimes. We use our new expressions to estimate species ages of forest trees under a neutral model and find that they are about an order of magnitude shorter than those predicted previously but still unrealistically long. In light of our results, we discuss different models of biogeography that may solve the problem of species ages. PMID:24530891

  12. Equivalent Neutral Wind

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy; Tang, Wenqing

    1996-01-01

    The definition of equivalent neutral wind and the rationale for using it as the geophysical product of a spaceborne scatterometer are reviewed. The differences between equivalent neutral wind and actual wind, which are caused by atmospheric density stratification, are demonstrated with measurements at selected locations. A method of computing this parameter from ship and buoy measurements is described and some common fallacies in accounting for the effects of atmospheric stratification on wind shear are discussed. The computer code for the model to derive equivalent neutral wind is provided.

  13. Conceptual Design of Neutral Beam Injection System for EAST

    NASA Astrophysics Data System (ADS)

    Hu, Chundong; NBI Team

    2012-06-01

    Neutral beam injection (NBI) system with two neutral beam injections will be constructed on the Experimental Advanced Superconducting Tokamak (EAST) in two stages for high power auxiliary plasmas heating and non-inductive current drive. Each NBI can deliver 2~4 MW beam power with 50~80 keV beam energy in 10~100 s pulse length. Each elements of the NBI system are presented in this contribution.

  14. Nonlinear response of a linear chain to weak driving

    NASA Astrophysics Data System (ADS)

    Hennig, D.; Mulhern, C.; Burbanks, A. D.; Schimansky-Geier, L.

    2014-01-01

    We study the escape of a chain of coupled units over the barrier of a metastable potential. It is demonstrated that a very weak external driving field with a suitably chosen frequency suffices to accomplish speedy escape. The latter requires passage through a transition state, the formation of which is triggered by permanent feeding of energy from a phonon background into humps of localized energy and elastic interaction of the arising breather solutions. In fact, cooperativity between the units of the chain entailing coordinated energy transfer is shown to be crucial for enhancing the rate of escape in an extremely effective and low-energy cost way where the effects of entropic localization and breather coalescence conspire.

  15. Studies on Neutral Beam Injection into the SSPX Spheromak Plasma

    SciTech Connect

    Jayakumar, R; Pearlstein, L D; Casper, T A; Fowler, T K; Hill, D N; Hudson, B; McLean, H; Moller, J

    2007-10-19

    In the Sustained Spheromak Physics Experiment, (SSPX) ['Improved operation of the SSPX spheromak', R.D. Wood, D.N. Hill, E.B. Hooper, S. Woodruff1, H.S. McLean and B.W. Stallard, Nucl. Fusion 45 1582-1588 (2005)], plasmas with core electron temperatures reaching up to 500 eV at densities of 10{sup 20}/m{sup 3} have been sustained for several milliseconds, making them suitable as targets for neutral beam injection. High performance and further progress in understanding Spheromak plasma physics are expected if neutral beams are injected into the plasma. This paper presents the results of numerical 1.5 D modeling of the plasma to calculate neutral beam current drive and ion and electron heating. The results are presented for varying initial conditions of density, temperatures and profiles and beam energy, injection angle and power. Current drive efficiency (Ampere/Watt of absorbed power) of up to 0.08 can be achieved with best performance SSPX shots as target. Analyses of neutral beam heating indicate that ion temperatures of up to 1.5 keV and electron temperatures of up to 750 eV can be obtained with injection of about 1 MW of neutral beam for 5-10 ms and with diffusivities typically observed in SSPX. Injection targeting near the magnetic axis appears to be the best for heating and current drive. Effect of the current drive and evolution of SSPX equilibrium are discussed.

  16. Evolutionary escape on complex genotype-phenotype networks.

    PubMed

    Ibáñez-Marcelo, Esther; Alarcón, Tomás

    2016-04-01

    We study the problem of evolutionary escape that is the process whereby a population under sudden changes in the selective pressures acting upon it try to evade extinction by evolving from previously well-adapted phenotypes to those that are favoured by the new selective pressure. We perform a comparative analysis between results obtained by modelling genotype space as a regular hypercube (H-graphs), which is the scenario considered in previous work on the subject, to those corresponding to a complex genotype-phenotype network (B-graphs). In order to analyse the properties of the escape process on both these graphs, we apply a general theory based on multi-type branching processes to compute the evolutionary dynamics and probability of escape. We show that the distribution of distances between phenotypes in B-graphs exhibits a much larger degree of heterogeneity than in H-graphs. This property, one of the main structural differences between both types of graphs, causes heterogeneous behaviour in all results associated to the escape problem. We further show that, due to the heterogeneity characterising escape on B-graphs, escape probability can be underestimated by assuming a regular hypercube genotype network, even if we compare phenotypes at the same distance in H-graphs. Similarly, it appears that the complex structure of B-graphs slows down the rate of escape. PMID:26802479

  17. Efficiently estimating salmon escapement uncertainty using systematically sampled data

    USGS Publications Warehouse

    Reynolds, Joel H.; Woody, Carol Ann; Gove, Nancy E.; Fair, Lowell F.

    2007-01-01

    Fish escapement is generally monitored using nonreplicated systematic sampling designs (e.g., via visual counts from towers or hydroacoustic counts). These sampling designs support a variety of methods for estimating the variance of the total escapement. Unfortunately, all the methods give biased results, with the magnitude of the bias being determined by the underlying process patterns. Fish escapement commonly exhibits positive autocorrelation and nonlinear patterns, such as diurnal and seasonal patterns. For these patterns, poor choice of variance estimator can needlessly increase the uncertainty managers have to deal with in sustaining fish populations. We illustrate the effect of sampling design and variance estimator choice on variance estimates of total escapement for anadromous salmonids from systematic samples of fish passage. Using simulated tower counts of sockeye salmon Oncorhynchus nerka escapement on the Kvichak River, Alaska, five variance estimators for nonreplicated systematic samples were compared to determine the least biased. Using the least biased variance estimator, four confidence interval estimators were compared for expected coverage and mean interval width. Finally, five systematic sampling designs were compared to determine the design giving the smallest average variance estimate for total annual escapement. For nonreplicated systematic samples of fish escapement, all variance estimators were positively biased. Compared to the other estimators, the least biased estimator reduced bias by, on average, from 12% to 98%. All confidence intervals gave effectively identical results. Replicated systematic sampling designs consistently provided the smallest average estimated variance among those compared.

  18. Solar Neutral Particles

    NASA Video Gallery

    This animation shows a neutral solar particle's path leaving the sun, following the magnetic field lines out to the heliosheath. The solar particle hits a hydrogen atom, stealing its electron, and ...

  19. A niche for neutrality.

    PubMed

    Adler, Peter B; Hillerislambers, Janneke; Levine, Jonathan M

    2007-02-01

    Ecologists now recognize that controversy over the relative importance of niches and neutrality cannot be resolved by analyzing species abundance patterns. Here, we use classical coexistence theory to reframe the debate in terms of stabilizing mechanisms (niches) and fitness equivalence (neutrality). The neutral model is a special case where stabilizing mechanisms are absent and species have equivalent fitness. Instead of asking whether niches or neutral processes structure communities, we advocate determining the degree to which observed diversity reflects strong stabilizing mechanisms overcoming large fitness differences or weak stabilization operating on species of similar fitness. To answer this question, we propose combining data on per capita growth rates with models to: (i) quantify the strength of stabilizing processes; (ii) quantify fitness inequality and compare it with stabilization; and (iii) manipulate frequency dependence in growth to test the consequences of stabilization and fitness equivalence for coexistence. PMID:17257097

  20. Is dispersal neutral?

    PubMed

    Lowe, Winsor H; McPeek, Mark A

    2014-08-01

    Dispersal is difficult to quantify and often treated as purely stochastic and extrinsically controlled. Consequently, there remains uncertainty about how individual traits mediate dispersal and its ecological effects. Addressing this uncertainty is crucial for distinguishing neutral versus non-neutral drivers of community assembly. Neutral theory assumes that dispersal is stochastic and equivalent among species. This assumption can be rejected on principle, but common research approaches tacitly support the 'neutral dispersal' assumption. Theory and empirical evidence that dispersal traits are under selection should be broadly integrated in community-level research, stimulating greater scrutiny of this assumption. A tighter empirical connection between the ecological and evolutionary forces that shape dispersal will enable richer understanding of this fundamental process and its role in community assembly. PMID:24962790

  1. Extended Driving Impairs Nocturnal Driving Performances

    PubMed Central

    Sagaspe, Patricia; Taillard, Jacques; Åkerstedt, Torbjorn; Bayon, Virginie; Espié, Stéphane; Chaumet, Guillaume; Bioulac, Bernard; Philip, Pierre

    2008-01-01

    Though fatigue and sleepiness at the wheel are well-known risk factors for traffic accidents, many drivers combine extended driving and sleep deprivation. Fatigue-related accidents occur mainly at night but there is no experimental data available to determine if the duration of prior driving affects driving performance at night. Participants drove in 3 nocturnal driving sessions (3–5am, 1–5am and 9pm–5am) on open highway. Fourteen young healthy men (mean age [±SD] = 23.4 [±1.7] years) participated Inappropriate line crossings (ILC) in the last hour of driving of each session, sleep variables, self-perceived fatigue and sleepiness were measured. Compared to the short (3–5am) driving session, the incidence rate ratio of inappropriate line crossings increased by 2.6 (95% CI, 1.1 to 6.0; P<.05) for the intermediate (1–5am) driving session and by 4.0 (CI, 1.7 to 9.4; P<.001) for the long (9pm–5am) driving session. Compared to the reference session (9–10pm), the incidence rate ratio of inappropriate line crossings were 6.0 (95% CI, 2.3 to 15.5; P<.001), 15.4 (CI, 4.6 to 51.5; P<.001) and 24.3 (CI, 7.4 to 79.5; P<.001), respectively, for the three different durations of driving. Self-rated fatigue and sleepiness scores were both positively correlated to driving impairment in the intermediate and long duration sessions (P<.05) and increased significantly during the nocturnal driving sessions compared to the reference session (P<.01). At night, extended driving impairs driving performances and therefore should be limited. PMID:18941525

  2. 16. INTERIOR VIEW OF SUBMARINE SECTION AT 110FOOT LEVEL, ESCAPE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    16. INTERIOR VIEW OF SUBMARINE SECTION AT 110-FOOT LEVEL, ESCAPE TRAINING TANK, SHOWING LADDER TO ESCAPE TANK, LOOKING SOUTH - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  3. Escape of Pluto's Atmosphere: In Situ Measurements from New Horizons and Remote Observations from Chandra

    NASA Astrophysics Data System (ADS)

    McNutt, R. L., Jr.; Hill, M. E.; Kollmann, P.; Krimigis, S. M.; Brown, L. E.; Kusterer, M. B.; Lisse, C. M.; Mitchell, D. G.; Vandegriff, J. D.; McComas, D. J.; Bagenal, F.; Elliott, H. A.; Ennico Smith, K.; Horanyi, M.; Olkin, C.; Piquette, M. R.; Stern, A.; Strobel, D. F.; Szalay, J.; Valek, P. W.; Weaver, H. A., Jr.; Weidner, S.; Young, L. A.; Zirnstein, E.; Wolk, S. J.

    2015-12-01

    The escape rate of Pluto's atmosphere is of significant scientific interest. It is a Group 1 science goal of the New Horizons mission. In addition, a Group 3 science goal of the mission has been to characterize the energetic particle environment of the Pluto system. The Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) is a compact, energy by time-of-flight (TOF) instrument developed to address both of these science goals. Pluto is known to have an atmosphere, and current models postulate a majority N2 composition with free escape of up to ~1028 molecules/sec. This is very similar to the physical situation of a variety comets observed in the inner heliosphere. However, the gravitational field of Pluto exerts a significant effect on the escaping neutrals, unlike at a comet. The ionization of neutrals emitted from comets results in heavy ions, which are accelerated by the convective solar-wind electric field. The expected major ionization product near Pluto is singly ionized N2 molecules with pickup energies sufficient to be measured with PEPSSI. In the process of measuring the local energetic particle environment, such measurements will also provide constraints on the local density of Pluto's extended atmosphere, which, along with plasma measurements from the Solar Wind Around Pluto (SWAP) instrument also on New Horizons should allow the inference of the strengh and extent of mass-loading of the solar wind due to Pluto's atmosphere. Pluto's neutral atmosphere also provides a source population for charge exchange of highly ionized, minor ions in the solar wind, such as O, C, and N. This process allows these ions to capture one electron and be left in an excited state. That state, in turn decays with the emission of a low-energy (100 eV to 1 keV) X-ray, which can be detected at Earth. Such observations have been made of comets since the X-ray emission discovery in 1996 and used to infer cometary outgassing rates. Similar observatins have been made

  4. Electrical drive for automobile

    SciTech Connect

    Fobbs, H.

    1980-09-16

    Electrical apparatus for driving an automobile is described that is comprised of a dc motor operationally connected to the rear axle through a drive shaft with the motor energized from storage batteries and recharged from alternators coupled to the drive shaft adjacent a clutch at the rear end of the automobile through an auxiliary drive shaft.

  5. Coaxial Redundant Drives

    NASA Technical Reports Server (NTRS)

    Brissette, R.

    1983-01-01

    Harmonic drives allow redundancy and high out put torque in small package. If main drive fails, standby drive takes over and produces torque along same axis as main drive. Uses include power units in robot for internal pipeline inspection, manipulators in deep submersible probes or other applications in which redundancy protects against costly failures.

  6. Calculation of the resonance escape factor of magnesium spectral line shapes in the case of a MgCl{sub 2}--water plasma

    SciTech Connect

    Hannachi, R.; Cressault, Y.; Teulet, Ph.; Gleizes, A.; Ben Lakhdar, Z.; Taieeb, G.

    2007-09-19

    The resonance escape factors for the lines emitted by a neutral magnesium atom MgI at 285.2127 nm (3 {sup 1}S-3 {sup 1}P) and of ionic magnesium MgII at 279.5528 nm (3 {sup 2}S-3 {sup 2}P) are calculated assuming a Voigt profile and in the case of MgCl{sub 2}-water plasma. The dependence of the escape factor on the optical thickness {tau}{sub 0} from the line center which itself depends on the two main spectral line shape broadening mechanisms (pressure and Doppler effects) are considered. The variation of the resonance escape factors with the temperature and the MgCl{sub 2} molar proportion are also investigated. This calculation is useful for the application of laser induced breakdown spectroscopy in the quantitative analysis of elemental composition.

  7. Monitoring the Escape of DNA from a Nanopore Using an Alternating Current Signal

    PubMed Central

    Lathrop, Daniel K.; Ervin, Eric N.; Barrall, Geoffrey A.; Keehan, Michael G.; Kawano, Ryuji; Krupka, Michael A.; White, Henry S.; Hibbs, Andrew H.

    2010-01-01

    We present the use of an alternating current (AC) signal as a means to monitor the conductance of an α-hemolysin (αHL) pore as a DNA hairpin with a polydeoxyadenosine tail is driven into and released from the pore. Specifically, a 12 base pair DNA hairpin attached to a 50-nucleotide poly-A tail (HP-A50) is threaded into an αHL channel using a DC driving voltage. Once the HP-A50 molecule is trapped within the αHL channel, the DC driving voltage is turned off and the conductance of the channel is monitored using an AC voltage. The escape time, defined as the time it takes the HP-A50 molecule to transport out of the αHL channel, is then measured. This escape time has been monitored as a function of AC amplitude (20 to 250 mVac), AC frequency (60–200 kHz), DC drive voltage (0 to 100 mVdc), and temperature (−10 to 20 °C), in order to determine their effect on the predominantly diffusive motion of the DNA through the nanopore. The applied AC voltage used to monitor the conductance of the nanopore has been found to play a significant role in the DNA/nanopore interaction. The experimental results are described by a one-dimensional asymmetric periodic potential model that includes the influence of the AC voltage. An activation enthalpy barrier of 1.74 × 10−19 J and a periodic potential asymmetry parameter of 0.575 are obtained for the diffusion at zero electrical bias of a single nucleotide through αHL. PMID:20099878

  8. Solar array drive system

    NASA Technical Reports Server (NTRS)

    Berkopec, F. D.; Sturman, J. C.; Stanhouse, R. W.

    1976-01-01

    A solar array drive system consisting of a solar array drive mechanism and the corresponding solar array drive electronics is being developed. The principal feature of the solar array drive mechanism is its bidirectional capability which enables its use in mechanical redundancy. The solar array drive system is of a widely applicable design. This configuration will be tested to determine its acceptability for generic mission sets. Foremost of the testing to be performed is the testing for extended duration.

  9. Prey escaping wolves, Canis lupus, despite close proximity

    USGS Publications Warehouse

    Nelson, M.E.; Mech, L.D.

    1993-01-01

    We describe attacks by wolf (Canis lupus) packs in Minnesota on a white-tailed deer (Odocoileus virginianus) and a moose (Alces alces) in which wolves were within contact distance of the prey but in which the prey escaped.

  10. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... wearing life jackets. There must be no protrusions in means of escape that could cause injury, ensnare clothing, or damage life jackets. (f) The minimum clear opening of a door or passageway used as a means...

  11. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... wearing life jackets. There must be no protrusions in means of escape that could cause injury, ensnare clothing, or damage life jackets. (f) The minimum clear opening of a door or passageway used as a means...

  12. 40. Launch Area, Underground Missile Storage Structure, detail of escape ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    40. Launch Area, Underground Missile Storage Structure, detail of escape hatch and decontamination shower VIEW WEST - NIKE Missile Battery PR-79, Launch Area, East Windsor Road south of State Route 101, Foster, Providence County, RI

  13. 10. VIEW OF SILO DOORS, AIR VENTS, AND ESCAPE HATCH, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. VIEW OF SILO DOORS, AIR VENTS, AND ESCAPE HATCH, LOOKING EAST. WHITE STRUCTURES BELONG TO CURRENT OCCUPANTS Everett Weinreb, photographer, April 1988 - Los Pinetos Nike Missile Site, Santa Clara Road, Los Angeles National Forest, Sylmar, Los Angeles County, CA

  14. 3. VIEW OF ESCAPE TUNNEL IN NORTH FACE OF LAUNCH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. VIEW OF ESCAPE TUNNEL IN NORTH FACE OF LAUNCH OPERATIONS BUILDING. BUNKER PERISCOPE VISIBLE ABOVE RIGHT CORNER OF TUNNEL. - Vandenberg Air Force Base, Space Launch Complex 3, Launch Operations Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  15. 14. View inside Building 802, the "Escape Hatch" at the ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. View inside Building 802, the "Escape Hatch" at the rear of the "Sleeping Quarters", facing south. - Naval Air Station Fallon, 100-man Fallout Shelter, 800 Complex, off Carson Road near intersection of Pasture & Berney Roads, Fallon, Churchill County, NV

  16. 61. View of exhaust air vent (foreground), escape hatch, and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    61. View of exhaust air vent (foreground), escape hatch, and elevator doors at launch pad "A" with building 157, sentry control box on right, looking southwest - Nike Missile Battery MS-40, County Road No. 260, Farmington, Dakota County, MN

  17. Survey of space escape/rescue/survivability capabilities.

    NASA Technical Reports Server (NTRS)

    Fleisig, R.; Bolger, P. H.; Heath, G. W.

    1971-01-01

    Discussion of preventive or remedial systems to achieve safer space flight operations. Escape, rescue, and survival systems are defined by categories: on board, prepositioned aid, and earth-launched concepts. The survey considers separable escape or survival capsules; standby escape or rescue systems; and earth-launched manned and unmanned rescue systems. Reports covering such systems are listed, and the contents are classified as to scope of investigation, space mission, and design approach. Mission classes considered are earth orbit, lunar, and interplanetary. Results of the space escape, rescue, and survivability investigations are summarized in terms of system features and performance, including apparent voids or limitations in rescue capability. Recovery requirements and resources for space rescue are discussed.

  18. The thermodynamics of endosomal escape and DNA release from lipoplexes.

    PubMed

    Avital, Yotam Y; Grønbech-Jensen, Niels; Farago, Oded

    2016-01-28

    Complexes of cationic and neutral lipids and DNA (lipoplexes) are emerging as promising vectors for gene therapy applications. Their appeal stems from their non pathogenic nature and the fact that they self-assemble under conditions of thermal equilibrium. Lipoplex adhesion to the cell plasma membrane initiates a three-stage process termed transfection, consisting of (i) endocytosis, (ii) lipoplex breakdown, and (iii) DNA release followed by gene expression. As successful transfection requires lipoplex degradation, it tends to be hindered by the lipoplex thermodynamic stability; nevertheless, it is known that the transfection process may proceed spontaneously. Here, we use a simple model to study the thermodynamic driving forces governing transfection. We demonstrate that after endocytosis [stage (i)], the lipoplex becomes inherently unstable. This instability, which is triggered by interactions between the cationic lipids of the lipoplex and the anionic lipids of the enveloping plasma membrane, is entropically controlled involving both remixing of the lipids and counterions release. Our detailed calculation shows that the free energy gain during stage (ii) is approximately linear in Φ+, the mole fraction of cationic lipids in the lipoplex. This free energy gain, ΔF, reduces the barrier for fusion between the enveloping and the lipoplex bilayers, which produces a hole allowing for DNA release [stage (iii)]. The linear relationship between ΔF and the fraction of cationic lipids explains the experimentally observed exponential increase of transfection efficiency with Φ+ in lamellar lipoplexes. PMID:26700879

  19. Pioneer Venus Orbiter (PVO) Ionosphere Evidence for Atmospheric Escape

    NASA Astrophysics Data System (ADS)

    Grebowsky, J. M.; Hoegy, W. R.

    2009-12-01

    An early estimate of escape of H2O from Venus [McElroy et al., 1982] using observed hot oxygen densities inferred by Nagy et al. [1981] from PVO OUVS 1304 Å dayglow and using ionization rates from photoionization and electron impact. This resulted in an estimated oxygen ionization rate planet-wide above the plasmapause of 3x1025 atoms/s. Based on the energetic O+ being swept up and removed by solar wind, McElroy et al. [1982] gave an estimate of a loss rate for O of 6x106 atoms/cm2/s. Using a different method of estimating escape based data in the ionotail of Venus, Brace et al. [1987] estimated a total planetary O+ escape rate of 5x1025 ions/s. Their estimate was based on PVO measurements of superthermal O+ (energy range 9-16 eV) in the tail ray plasma between 2000 and 3000 km. Their estimated global mean flux was 107 atoms/cm2/s. The two escape rates are remarkably close considering all the errors involved in such estimates of escape. A study of escape by Luhmann et al. [2008] using VEX observations at low solar activity finds modest escape rates, prompting the authors to reconsider the evidence from both PVO and VEX of the possibility of enhanced escape during extreme interplanetary conditions. We reexamine the variation of escape under different solar wind conditions using ion densities and plasma content in the dayside and nightside of Venus using PVO ionosphere density during times of high solar activity. Citations: Brace, L.H., W. T. Kasprzak, H.A. Taylor, R. F. Theis, C. T. Russess, A. Barnes, J. D. Mihalov, and D. M. Hunten, "The Ionotail of Venus: Its Configuration and Evidence for Ion Escape", J. Geophys. Res. 92, 15-26, 1987. Luhmann, J.G., A. Fedorov, S. Barabash, E. Carlsson, Y. Futaana, T.L. Zhang, C.T. Russell, J.G. Lyon, S.A. Ledvina, and D.A. Brain, “Venus Express observations of atmospheric oxygen escape during the passage of several coronal mass ejections”, J. Geophys. Res., 113, 2008. McElroy, M. B., M. J. Prather, J. M. Rodiquez, " Loss

  20. Photoelectron escape fluxes over the equatorial and midlatitude regions

    NASA Technical Reports Server (NTRS)

    Narasingarao, B. C.; Singh, R. N.; Maier, E. J.

    1972-01-01

    Satellite measurements of photoelectron escape flux around noontime made by Explorer 31 in 600-800 km altitude range are reported for the equatorial and midlatitude regions. The pitch angle distributions and the spectral distributions are derived from the data. Analyzed data show that the flux for equatorial regions is lower by a factor 2 to 3 in comparison to that of midlatitude regions. Theoretical calculations are also made to compare with observed escape fluxes.

  1. Impact of immune escape mutations on HIV-1 fitness in the context of the cognate transmitted/founder genome

    PubMed Central

    2012-01-01

    Background A modest change in HIV-1 fitness can have a significant impact on viral quasispecies evolution and viral pathogenesis, transmission and disease progression. To determine the impact of immune escape mutations selected by cytotoxic T lymphocytes (CTL) on viral fitness in the context of the cognate transmitted/founder (T/F) genome, we developed a new competitive fitness assay using molecular clones of T/F genomes lacking exogenous genetic markers and a highly sensitive and precise parallel allele-specific sequencing (PASS) method. Results The T/F and mutant viruses were competed in CD4+ T-cell enriched cultures, relative proportions of viruses were assayed after repeated cell-free passage, and fitness costs were estimated by mathematical modeling. Naturally occurring HLA B57-restricted mutations involving the TW10 epitope in Gag and two epitopes in Tat/Rev and Env were assessed independently and together. Compensatory mutations which restored viral replication fitness were also assessed. A principal TW10 escape mutation, T242N, led to a 42% reduction in replication fitness but V247I and G248A mutations in the same epitope restored fitness to wild-type levels. No fitness difference was observed between the T/F and a naturally selected variant carrying the early CTL escape mutation (R355K) in Env and a reversion mutation in the Tat/Rev overlapping region. Conclusions These findings reveal a broad spectrum of fitness costs to CTL escape mutations in T/F viral genomes, similar to recent findings reported for neutralizing antibody escape mutations, and highlight the extraordinary plasticity and adaptive potential of the HIV-1 genome. Analysis of T/F genomes and their evolved progeny is a powerful approach for assessing the impact of composite mutational events on viral fitness. PMID:23110705

  2. The Lyman continuum escape fraction of low mass star-forming galaxies at z~1.

    NASA Astrophysics Data System (ADS)

    Rutkowski, Michael J.; Scarlata, Claudia; Haardt, Francesco; Siana, Brian D.; Rafelski, Marc; Henry, Alaina L.; Hayes, Matthew; Salvato, Mara; Pahl, Anthony; Mehta, Vihang; Beck, Melanie; Malkan, Matthew Arnold; Teplitz, Harry I.

    2016-01-01

    Star-forming galaxies (SFGs) in the high redshift universe (z>6) are believed to ionize neutral hydrogen in the intergalactic medium during the epoch of reionization. We tested this assumption by studying likely analogs of these SFGs in archival HST grism spectroscopy with GALEX UV and ground-based optical images at the redshift range in which we can directly measure the rest-frame Lyman continuum (λ<912Å, LyC) emission. We selected ~1400 SFGs for study on the presence of strong Hα emission and strongly selected against those SFGs whose GALEX FUV photometry could be contaminated by low redshift interlopers along the line of sight to produce a sample of ~600 z~1 SFGs. We made no unambiguous detection of escaping Lyman continuum radiation in individual galaxies in this sample, and stacked the individual non-detections in order to constrain the absolute Lyman continuum escape fraction, fesc<2% (3σ). We sub-divided this sample and stacked SFGs to measure upper limits to fesc with respect to stellar mass,luminosity and relative orientation. For z~1 high Hα equivalent width (EW>200Å) SFGs, we found for the first time an upper limit to fesc<9%. We discuss the implications of these limits for the ionizing emissivity of high redshift SFGs during the epoch of reionization. We conclude that reionization by SFGs is only marginally consistent with independent Planck observations of the CMB electron scattering opacity unless the LyC escape fraction of SFGs increases with redshift and an unobserved population of faint (MUV<-13 AB) SFGs contributes significantly to the UV background.

  3. Initiation and spread of escape waves within animal groups

    PubMed Central

    Herbert-Read, James E.; Buhl, Jerome; Hu, Feng; Ward, Ashley J. W.; Sumpter, David J. T.

    2015-01-01

    The exceptional reactivity of animal collectives to predatory attacks is thought to be owing to rapid, but local, transfer of information between group members. These groups turn together in unison and produce escape waves. However, it is not clear how escape waves are created from local interactions, nor is it understood how these patterns are shaped by natural selection. By startling schools of fish with a simulated attack in an experimental arena, we demonstrate that changes in the direction and speed by a small percentage of individuals that detect the danger initiate an escape wave. This escape wave consists of a densely packed band of individuals that causes other school members to change direction. In the majority of cases, this wave passes through the entire group. We use a simulation model to demonstrate that this mechanism can, through local interactions alone, produce arbitrarily large escape waves. In the model, when we set the group density to that seen in real fish schools, we find that the risk to the members at the edge of the group is roughly equal to the risk of those within the group. Our experiments and modelling results provide a plausible explanation for how escape waves propagate in nature without centralized control. PMID:26064630

  4. Some Possible Cases of Escape Mimicry in Neotropical Butterflies.

    PubMed

    Pinheiro, C E G; Freitas, A V L

    2014-10-01

    The possibility that escape or evasive mimicry evolved in butterflies and other prey insects in a similar fashion to classical Batesian and Müllerian mimicry has long been advanced in the literature. However, there is a general disagreement among lepidopterists and evolutionary biologists on whether or not escape mimicry exists, as well as in which mimicry rings this form of mimicry has evolved. Here, we review some purported cases of escape mimicry in Neotropical butterflies and suggest new mimicry rings involving several species of Archaeoprepona, Prepona, and Doxocopa (the "bright blue bands" ring) and species of Colobura and Hypna (the "creamy bands" ring) where the palatability of butterflies, their ability to escape predator attacks, geographic distribution, relative abundance, and co-occurrence in the same habitats strongly suggest that escape mimicry is involved. In addition, we also indicate other butterfly taxa whose similarities of coloration patterns could be due to escape mimicry and would constitute important case studies for future investigation. PMID:27193948

  5. Foraging behavior delays mechanically-stimulated escape responses in fish.

    PubMed

    Bohórquez-Herrera, Jimena; Kawano, Sandy M; Domenici, Paolo

    2013-11-01

    Foraging and the evasion of predators are fundamental for the survival of organisms, but they impose contrasting demands that can influence performance in each behavior. Previous studies suggested that foraging organisms may experience decreased vigilance to attacks by predators; however, little is known about the effect of foraging on escape performance with respect to the kinematics and the timing of the response. This study tested the hypothesis that engaging in foraging activities affected escape performance by comparing fast-start escape responses of silver-spotted sculpins Blepsias cirrhosus under three conditions: (1) control (no foraging involved), (2) while targeting prey, and (3) immediately after capture of prey. Escape response variables (non-locomotor and locomotor) were analyzed from high-speed videos. Responsiveness was lower immediately after capturing a prey item compared with the other two treatments, and latency of performance was higher in the control treatment than in the other two. Locomotor variables such as maximum speed, maximum acceleration, and turning rates did not show statistical differences among the three groups. Our results demonstrate that foraging can negatively affect two fundamental components of the escape response: (1) responsiveness and (2) latency of escape, suggesting that engaging in foraging may decrease an individual's ability to successfully evade predators. PMID:23624863

  6. Optimal escapement in stage-structured fisheries with environmental stochasticity.

    PubMed

    Holden, Matthew H; Conrad, Jon M

    2015-11-01

    Stage-structured population models are commonly used to understand fish population dynamics and additionally for stock assessment. Unfortunately, there is little theory on the optimal harvest of stage-structured populations, especially in the presence of stochastic fluctuations. In this paper, we find closed form optimal equilibrium escapement policies for a three-dimensional, discrete-time, stage-structured population model with linear growth, post-harvest nonlinear recruitment, and stage-specific pricing and extend the analytic results to structured populations with environmental stochasticity. When only fishing reproductive adults, stochasticity does not affect optimal escapement policies. However, when harvesting immature fish, the addition of stochasticity can increase or decrease optimal escapement depending on the second and third derivative of the recruitment function. For logistic recruitment, stochasticity reduces optimal immature escapement by a multiplicative factor of one over one plus the variance of the environmental noise. Using hard clam, Mercenaria mercenaria, as an example and assuming Beverton-Holt recruitment, we show that optimal fishing of hard clam targets the immature stage class exclusively and that environmental stochasticity increases optimal escapement for low discount rates and decreases optimal escapement for high discount rates. PMID:26362229

  7. Ion Neutral Mass Spectrometer Measurements from Titan

    NASA Technical Reports Server (NTRS)

    Waite, J. H., Jr.; Niemann, H.; Yelle, R. V.; Kasprzak, W.; Cravens, T.; Luhmann, J.; McNutt, R.; Ip, W.-H.; Gell, D.; Muller-Wordag, I. C. F.

    2005-01-01

    Introduction: The Ion Neutral Mass Spectrometer (INMS) aboard the Cassini orbiter has obtained the first in situ composition measurements of the neutral densities of molecular nitrogen, methane, argon, and a host of stable carbon-nitrile compounds in its first flyby of Titan. The bulk composition and thermal structure of the moon s upper atmosphere do not appear to be changed since the Voyager flyby in 1979. However, the more sensitive techniques provided by modern in-situ mass spectrometry also give evidence for large-spatial-scale large-amplitude atmospheric waves in the upper atmosphere and for a plethora of stable carbon-nitrile compounds above 1174 km. Furthermore, they allow the first direct measurements of isotopes of nitrogen, carbon, and argon, which provide interesting clues about the evolution of the atmosphere. The atmosphere was first accreted as ammonia and ammonia ices from the Saturn sub-nebula. Subsequent photochemistry likely converted the atmosphere into molecular nitrogen. The early atmosphere was 1.5 to 5 times more substantial and was lost via escape over the intervening 4.5 billion years due to the reduced gravity associated with the relatively small mass of Titan. Carbon in the form of methane has continued to outgas over time from the interior with much of it being deposited in the form of complex hydrocarbons on the surface and some of it also being lost to space.

  8. On geometric factors for neutral particle analyzers

    SciTech Connect

    Stagner, L.; Heidbrink, W. W.

    2014-11-15

    Neutral particle analyzers (NPA) detect neutralized energetic particles that escape from plasmas. Geometric factors relate the counting rate of the detectors to the intensity of the particle source. Accurate geometric factors enable quick simulation of geometric effects without the need to resort to slower Monte Carlo methods. Previously derived expressions [G. R. Thomas and D. M. Willis, “Analytical derivation of the geometric factor of a particle detector having circular or rectangular geometry,” J. Phys. E: Sci. Instrum. 5(3), 260 (1972); J. D. Sullivan, “Geometric factor and directional response of single and multi-element particle telescopes,” Nucl. Instrum. Methods 95(1), 5–11 (1971)] for the geometric factor implicitly assume that the particle source is very far away from the detector (far-field); this excludes applications close to the detector (near-field). The far-field assumption does not hold in most fusion applications of NPA detectors. We derive, from probability theory, a generalized framework for deriving geometric factors that are valid for both near and far-field applications as well as for non-isotropic sources and nonlinear particle trajectories.

  9. Ion precipitation in planetary upper atmospheres: test particle simulations and implications for escape

    NASA Astrophysics Data System (ADS)

    Parkinson, Christopher; Liemohn; Fang, Xiaohua

    A 3-D Monte Carlo energetic particle transport model has been developed and successfully applied to ion precipitation into planetary upper atmospheres in our solar system (viz., Earth, Mars, Jupiter, and Saturn), and can be readily be extended using a full Lorentz motion formu-lation in the absence of strong dipole planetary magnetic fields. This model can be used with a variety of other models to assess the influence of hot ion precipitation on the thermosphere and exosphere of planetary atmospheres and the subsequent sputtering and escape. For instance in the case of Mars, a pick-up ion transport model already exists to allow for particle acceleration exerted by the convection electric field used in conjunction with existing model results from the Mars Thermosphere General Circulation Model (MTGCM) and the BATS-R-US global MHD model. The loss of exospheric neutrals through ionization, in which they become pick-up ions in the solar wind, can be calculated to examine the relative contribution of the various ionization processes. Solar wind protons as well as pick-up ions from a planetary exosphere routinely enter and alter their upper atmosphere. A study of the pick-up ion escape, sputtering, ion-ization, excitation, and energy deposition will be reviewed and discussed, resulting in a robust examination of the influence of energetic ion transport on planetary upper atmospheres.

  10. Glutamate Utilization Couples Oxidative Stress Defense and the Tricarboxylic Acid Cycle in Francisella Phagosomal Escape

    PubMed Central

    Ramond, Elodie; Gesbert, Gael; Rigard, Mélanie; Dairou, Julien; Dupuis, Marion; Dubail, Iharilalao; Meibom, Karin; Henry, Thomas; Barel, Monique; Charbit, Alain

    2014-01-01

    Intracellular bacterial pathogens have developed a variety of strategies to avoid degradation by the host innate immune defense mechanisms triggered upon phagocytocis. Upon infection of mammalian host cells, the intracellular pathogen Francisella replicates exclusively in the cytosolic compartment. Hence, its ability to escape rapidly from the phagosomal compartment is critical for its pathogenicity. Here, we show for the first time that a glutamate transporter of Francisella (here designated GadC) is critical for oxidative stress defense in the phagosome, thus impairing intra-macrophage multiplication and virulence in the mouse model. The gadC mutant failed to efficiently neutralize the production of reactive oxygen species. Remarkably, virulence of the gadC mutant was partially restored in mice defective in NADPH oxidase activity. The data presented highlight links between glutamate uptake, oxidative stress defense, the tricarboxylic acid cycle and phagosomal escape. This is the first report establishing the role of an amino acid transporter in the early stage of the Francisella intracellular lifecycle. PMID:24453979

  11. Trade-offs between performance and variability in the escape responses of bluegill sunfish (Lepomis macrochirus)

    PubMed Central

    Hitchcock, Amanda C.; Chen, Tiffany; Connolly, Erin; Darakananda, Karin; Jeong, Janet; Quist, Arbor; Robbins, Allison; Ellerby, David J.

    2015-01-01

    Successful predator evasion is essential to the fitness of many animals. Variation in escape behaviour may be adaptive as it reduces predictability, enhancing escape success. High escape velocities and accelerations also increase escape success, but biomechanical factors likely constrain the behavioural range over which performance can be maximized. There may therefore be a trade-off between variation and performance during escape responses. We have used bluegill sunfish (Lepomis macrochirus) escape responses to examine this potential trade-off, determining the full repertoire of escape behaviour for individual bluegill sunfish and linking this to performance as indicated by escape velocity and acceleration. Fish escapes involve an initial C-bend of the body axis, followed by variable steering movements. These generate thrust and establish the escape direction. Directional changes during the initial C-bend were less variable than the final escape angle, and the most frequent directions were associated with high escape velocity. Significant inter-individual differences in escape angles magnified the overall variation, maintaining unpredictability from a predator perspective. Steering in the latter stages of the escape to establish the final escape trajectory also affected performance, with turns away from the stimulus associated with reduced velocity. This suggests that modulation of escape behaviour by steering may also have an associated performance cost. This has important implications for understanding the scope and control of intra- and inter-individual variation in escape behaviour and the associated costs and benefits. PMID:25910940

  12. Trade-offs between performance and variability in the escape responses of bluegill sunfish (Lepomis macrochirus).

    PubMed

    Hitchcock, Amanda C; Chen, Tiffany; Connolly, Erin; Darakananda, Karin; Jeong, Janet; Quist, Arbor; Robbins, Allison; Ellerby, David J

    2015-01-01

    Successful predator evasion is essential to the fitness of many animals. Variation in escape behaviour may be adaptive as it reduces predictability, enhancing escape success. High escape velocities and accelerations also increase escape success, but biomechanical factors likely constrain the behavioural range over which performance can be maximized. There may therefore be a trade-off between variation and performance during escape responses. We have used bluegill sunfish (Lepomis macrochirus) escape responses to examine this potential trade-off, determining the full repertoire of escape behaviour for individual bluegill sunfish and linking this to performance as indicated by escape velocity and acceleration. Fish escapes involve an initial C-bend of the body axis, followed by variable steering movements. These generate thrust and establish the escape direction. Directional changes during the initial C-bend were less variable than the final escape angle, and the most frequent directions were associated with high escape velocity. Significant inter-individual differences in escape angles magnified the overall variation, maintaining unpredictability from a predator perspective. Steering in the latter stages of the escape to establish the final escape trajectory also affected performance, with turns away from the stimulus associated with reduced velocity. This suggests that modulation of escape behaviour by steering may also have an associated performance cost. This has important implications for understanding the scope and control of intra- and inter-individual variation in escape behaviour and the associated costs and benefits. PMID:25910940

  13. Neutral particle lithography

    NASA Astrophysics Data System (ADS)

    Craver, Barry Paul

    Neutral particle lithography (NPL) is a high resolution, proximity exposure technique where a broad beam of energetic neutral particles floods a stencil mask and transmitted beamlets transfer the mask pattern to resist on a substrate, such that each feature is printed in parallel, rather than in the serial manner of electron beam lithography. It preserves the advantages of ion beam lithography (IBL), including extremely large depth-of-field, sub-5 nm resist scattering, and the near absence of diffraction, yet is intrinsically immune to charge-related artifacts including line-edge roughness and pattern placement errors due to charge accumulation on the mask and substrate. In our experiments, a neutral particle beam is formed by passing an ion beam (e.g., 30 keV He+) through a high pressure helium gas cell (e.g., 100 mTorr) to convert the ions to energetic neutrals through charge transfer scattering. The resolution of NPL is generally superior to that of IBL for applications involving insulating substrates, large proximity gaps, and ultra-small features. High accuracy stepped exposures with energetic neutral particles, where magnetic or electrostatic deflection is impossible, have been obtained by clamping the mask to the wafer, setting the proximity gap with a suitable spacer, and mechanically inclining the mask/wafer stack relative to the beam. This approach is remarkably insensitive to vibration and thermal drift; nanometer scale image offsets have been obtained with +/-2 nm placement accuracy for experiments lasting over one hour. Using this nanostepping technique, linewidth versus dose curves were obtained, from which the NPL lithographic blur was determined as 4.4+/-1.4 nm (1sigma), which is 2-3 times smaller than the blur of electron beam lithography. Neutral particle lithography has the potential to form high density, periodic patterns with sub-10 nm resolution.

  14. Neutral particle dynamics in the Alcator C-Mod tokamak

    SciTech Connect

    Niemczewski, A.P.

    1995-08-01

    This thesis presents an experimental study of neutral particle dynamics in the Alcator C-Mod tokamak. The primary diagnostic used is a set of six neutral pressure gauges, including special-purpose gauges built for in situ tokamak operation. While a low main chamber neutral pressure coincides with high plasma confinement regimes, high divertor pressure is required for heat and particle flux dispersion in future devices such as ITER. Thus we examine conditions that optimize divertor compression, defined here as a divertor-to-midplane pressure ratio. We find both pressures depend primarily on the edge plasma regimes defined by the scrape-off-layer heat transport. While the maximum divertor pressure is achieved at high core plasma densities corresponding to the detached divertor state, the maximum compression is achieved in the high-recycling regime. Variations in the divertor geometry have a weaker effect on the neutral pressures. For otherwise similar plasmas the divertor pressure and compression are maximum when the strike point is at the bottom of the vertical target plate. We introduce a simple flux balance model, which allows us to explain the divertor neutral pressure across a wide range of plasma densities. In particular, high pressure sustained in the detached divertor (despite a considerable drop in the recycling source) can be explained by scattering of neutrals off the cold plasma plugging the divertor throat. Because neutrals are confined in the divertor through scattering and ionization processes (provided the mean-free-paths are much shorter than a typical escape distance) tight mechanical baffling is unnecessary. The analysis suggests that two simple structural modifications may increase the divertor compression in Alcator C-Mod by a factor of about 5. Widening the divertor throat would increase the divertor recycling source, while closing leaks in the divertor structure would eliminate a significant neutral loss mechanism. 146 refs., 82 figs., 14 tabs.

  15. Ultracold neutral plasmas.

    PubMed

    Killian, Thomas C

    2007-05-01

    Ultracold neutral plasmas occupy an exotic regime of plasma physics in which electrons form a swarming, neutralizing background for ions that sluggishly move in a correlated manner. Strong interactions between the charged particles give rise to surprising dynamics such as oscillations of the average kinetic energy during equilibration and extremely fast recombination. Such phenomena offer stimulating and challenging problems for computational scientists, and the physics can be applied to other environments, such as the interior of gas giant planets and plasmas created by short-pulse laser irradiation of solid, liquid, and cluster targets. PMID:17478712

  16. Neutral beam development plan

    SciTech Connect

    Staten, H S

    1980-08-01

    The national plan is presented for developing advanced injection systems for use on upgrades of existing experiments, and use on future facilities such as ETF, to be built in the late 1980's or early 90's where power production from magnetic fusion will move closer to a reality. Not only must higher power and longer pulse length systems be developed , but they must operate reliably; they must be a tool for the experimenter, not the experiment itself. Neutral beam systems handle large amounts of energy and as such, they often are as complicated as the plasma physics experiment itself. This presents a significant challenge to the neutral beam developer.

  17. Heating and current drive systems for TPX

    SciTech Connect

    Swain, D.; Goranson, P.; Halle, A. von; Bernabei, S.; Greenough, N.

    1994-05-24

    The heating and current drive (H and CD) system proposed for the TPX tokamak will consist of ion cyclotron, neutral beam, and lower hybrid systems. It will have 17.5 MW of installed H and CD power initially, and can be upgraded to 45 MW. It will be used to explore advanced confinement and fully current-driven plasma regimes with pulse lengths of up to 1,000 s.

  18. Structure of Rotavirus Outer-Layer Protein VP7 Bound with a Neutralizing Fab

    SciTech Connect

    Aoki, Scott T.; Settembre, Ethan C.; Trask, Shane D.; Greenberg, Harry B.; Harrison, Stephen C.; Dormitzer, Philip R.

    2009-06-17

    Rotavirus outer-layer protein VP7 is a principal target of protective antibodies. Removal of free calcium ions (Ca{sup 2+}) dissociates VP7 trimers into monomers, releasing VP7 from the virion, and initiates penetration-inducing conformational changes in the other outer-layer protein, VP4. We report the crystal structure at 3.4 angstrom resolution of VP7 bound with the Fab fragment of a neutralizing monoclonal antibody. The Fab binds across the outer surface of the intersubunit contact, which contains two Ca{sup 2+} sites. Mutations that escape neutralization by other antibodies suggest that the same region bears the epitopes of most neutralizing antibodies. The monovalent Fab is sufficient to neutralize infectivity. We propose that neutralizing antibodies against VP7 act by stabilizing the trimer, thereby inhibiting the uncoating trigger for VP4 rearrangement. A disulfide-linked trimer is a potential subunit immunogen.

  19. Nitrogen and Oxygen Budget ExpLoration (NOBEL) for ESA M5-call: Measurement requirements to understand the atmospheric escape/budget

    NASA Astrophysics Data System (ADS)

    Yamauchi, Masatoshi; Dandouras, Iannis; Rème, Henri; Marghitu, Octav

    2016-04-01

    The NOBEL mission aims to study the thermal and non-thermal escape of major atmospheric components (nitrogen, oxygen, and their isotopes) from the Earth, a magnetized planet. This requires the first-time exploration of the Earth's entire exosphere as well as the first-time examination of isotope ratios in an extended altitude range from the upper ionosphere (800 km high) up to the magnetosphere. The measurement quality should allow connecting the various types of escape from the Earth to the different gravity mass-filtering and chemical reactions on a geological time scale, such that the result will be used as a good reference to understand the atmospheric/ionospheric evolution of magnetized planets based on their 17,18O/16O isotope ratio and N/O ratio. Since the solar EUV and solar wind conditions during solar maximum at present are comparable to the solar minimum conditions 1-2 billion years ago, the escaping amount and the isotope and N/O ratios should be obtained as a function of external forcing (solar and geomagnetic conditions) to allow a scaling to the past. To achieve these goals, the ion measurements in this mission should be able to separate nitrogen species (N, N2, N+ and N2+) from oxygen (O, O+), near the exobase, in the exosphere (for modelling thermal escape, hydrodynamics escape, and the pre-acceleration amount of non-thermal escape) and up in the magnetosphere (for modelling non-thermal escape and circulation of all ions). Furthermore, these aims require the capability to measure isotope ratios of cold oxygen ions and neutrals. We briefly discuss why we focus on the exosphere, on isotope ratios, and nitrogen measurements, and finally describe the current idea of a mission profile using a spinning satellite in a 500 km × 33000 km altitude high-inclination orbit.

  20. Stars on the run: escaping from stellar clusters

    NASA Astrophysics Data System (ADS)

    Moyano Loyola, Guido R. I.; Hurley, Jarrod R.

    2013-09-01

    A significant proportion of Milky Way stars are born in stellar clusters, which dissolve over time so that the members become part of the disc and halo populations of the Galaxy. In this work, we will assume that these young stellar clusters live mainly within the disc of the Galaxy and that they can have primordial binary percentages ranging from 0 per cent to as high as 70 per cent. We have evolved models of such clusters to an age of 4 Gyr through N-body simulations, paying attention to the stars and binaries that escape in the process. We have quantified the contribution of these escaping stars to the Galaxy population by analysing their escape velocity and evolutionary stage at the moment of escape. In this way, we could analyse the mechanisms that produced these escapers, whether evaporation through weak two-body encounters, energetic close encounters or stellar evolution events, e.g. supernovae. In our models, we found that the percentage of primordial binaries in a star cluster does not produce significant variations in the velocities of the stars that escape in the velocity range of 0-20 km s-1. However, in the high-velocity 20-100 km s-1 range the number of escapers increased markedly as the primordial binary percentage increased. We could also infer that dissolving stellar clusters such as those that we have modelled can populate the Galactic halo with giant stars for which the progenitors were stars of up to 2.4 M⊙. Furthermore, choices made for the velocity kicks of remnants do influence the production of hyper-velocity stars - and to a lesser extent stars in the high-velocity range - but once again the difference for the 99 per cent of stars in the 0-20 km s-1 range is not significant.

  1. Green Pea Galaxies Reveal Secrets of Lyα Escape

    NASA Astrophysics Data System (ADS)

    Yang, Huan; Malhotra, Sangeeta; Gronke, Max; Rhoads, James E.; Jaskot, Anne; Zheng, Zhenya; Dijkstra, Mark; Wang, JunXian

    2016-01-01

    In star-forming galaxies, a lot of Lyα photons were generated in HII regions surrounding massive stars. The escape of Lyα photons from galaxies is a key issue in studying high redshift galaxies and probing cosmic reionization with Lyα. To understand Lyα escape, it is valuable to study high quality Lyα profiles in Lyα emitters. However, such studies are rare due to the faintness of high-z Lyα emitters and the lack of local analogs with high Lyα equivalent width. Here we show that "Green Pea" galaxies are the best local analogs of high-z Lyα emitters and their high quality Lyα profiles demonstrate low HI column density is the key to Lyα escape. The Lyα escape fraction shows correlations with the ratio of Lyα blue peak velocity to Hα line width, the normalized flux density at valley of Lyα profile, and a few other features of Lyα profiles. We compared the Lyα profiles with outflowing HI shell radiative transfer model and found that the best-fit HI column density is anti-correlated with the Lyα escape fraction. We also found an anti-correlation between Lyα escape fraction and galactic metallicity. Our results support that LAEs with high Lyα escape fraction have low metallicity, low HI column density, and mild HI gas outflow.

  2. Neutral gas outflows in nearby [U]LIRGs via optical NaD feature

    NASA Astrophysics Data System (ADS)

    Cazzoli, S.; Arribas, S.; Maiolino, R.; Colina, L.

    2016-05-01

    We studied the properties of the neutral gas in a sample of 38 local luminous and ultra luminous infrared galaxies ([U]LIRGs, 51 individual galaxies at z ≤ 0.09), which mainly covers the less explored LIRG luminosity range. This study is based on the analysis of the spatially integrated and spatially resolved spectra of the NaDλλ 5890, 5896 Å feature obtained with the integral field unit (IFU) of VIMOS at the Very Large Telescope. Analyzing spatially integrated spectra, we find that the contribution of the stars to the observed NaD equivalent width is small (<35%) for about half of the sample, and therefore this feature is dominated by inter stellar medium (ISM) absorption. After subtracting the stellar contribution, we find that the pure-ISM integrated spectra generally show blueshifted NaD profiles, indicating neutral gas outflow velocities, V, in the range 65-260 km s-1. Excluding the galaxies with powerful AGNs, V shows a dependency with the star formation rate (SFR) of the type V ∝ SFR0.15, which is in rather good agreement with previous results. The spatially resolved analysis could be performed for 40 galaxies, 22 of which have neutral gas velocity fields dominated by noncircular motions with signatures of cone-like winds. However, a large number of targets (11/40) show disk rotation signatures. Based on a simple model, we found that the wind masses are in the range 0.4-7.5 × 108 M⊙, reaching up to ~3% of the dynamical mass of the host. The mass rates are typically only ~0.2-0.4 times the corresponding global SFR indicating that, in general, the mass loss is too small to slow down the star formation significantly. In the majority of cases, the velocity of the outflowing gas is not sufficient to escape the host potential well and, therefore, most of the gas rains back into the galaxy disk. On average V/vesc is higher in less massive galaxies, confirming that the galaxy mass has a primary role in shaping the recycling of gas and metals. The

  3. CO2-Neutral Fuels

    NASA Astrophysics Data System (ADS)

    Goede, Adelbert; van de Sanden, Richard

    2016-06-01

    Mimicking the biogeochemical cycle of System Earth, synthetic hydrocarbon fuels are produced from recycled CO2 and H2O powered by renewable energy. Recapturing CO2 after use closes the carbon cycle, rendering the fuel cycle CO2 neutral. Non-equilibrium molecular CO2 vibrations are key to high energy efficiency.

  4. Bleach Neutralizes Mold Allergens

    ERIC Educational Resources Information Center

    Science Teacher, 2005

    2005-01-01

    Researchers at National Jewish Medical and Research Center have demonstrated that dilute bleach not only kills common household mold, but may also neutralize the mold allergens that cause most mold-related health complaints. The study, published in the Journal of Allergy and Clinical Immunology, is the first to test the effect on allergic…

  5. Dynamics of ion beam charge neutralization by ferroelectric plasma sources

    NASA Astrophysics Data System (ADS)

    Stepanov, Anton D.; Gilson, Erik P.; Grisham, Larry R.; Kaganovich, Igor D.; Davidson, Ronald C.

    2016-04-01

    Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams, as has been demonstrated on the Neutralized Drift Compression Experiment NDCX-I and NDCX-II. This article presents experimental results on charge neutralization of a high-perveance 38 keV Ar+ beam by a plasma produced in a FEPS discharge. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable with sufficiently dense FEPS plasma. The transverse electrostatic potential of the ion beam is reduced from 15 V before neutralization to 0.3 V, implying that the energy of the neutralizing electrons is below 0.3 eV. Measurements of the time-evolution of beam radius show that near-complete charge neutralization is established ˜5 μs after the driving pulse is applied to the FEPS and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub-μs surface discharge. Measurements of current flow in the driving circuit of the FEPS show the existence of electron emission into vacuum, which lasts for tens of μs after the high voltage pulse is applied. It is argued that the beam is neutralized by the plasma produced by this process and not by a surface discharge plasma that is produced at the instant the high-voltage pulse is applied.

  6. Dynamics of ion beam charge neutralization by ferroelectric plasma sources

    DOE PAGESBeta

    Stepanov, Anton D.; Gilson, Erik P.; Grisham, Larry R.; Kaganovich, Igor D.; Davidson, Ronald C.

    2016-04-27

    Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams, as has been demonstrated on the Neutralized Drift Compression Experiment NDCX-I and NDCX-II. This article presents experimental results on charge neutralization of a high-perveance 38 keV Ar+ beam by a plasma produced in a FEPS discharge. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable with sufficiently dense FEPS plasma. The transverse electrostatic potential of the ion beam is reduced from 15V before neutralization to 0.3 V,more » implying that the energy of the neutralizing electrons is below 0.3 eV. Measurements of the time-evolution of beam radius show that near-complete charge neutralization is established similar to –5 μs after the driving pulse is applied to the FEPS and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub-mu s surface discharge. Measurements of current flow in the driving circuit of the FEPS show the existence of electron emission into vacuum, which lasts for tens of mu s after the high voltage pulse is applied. Lastly, it is argued that the beam is neutralized by the plasma produced by this process and not by a surface discharge plasma that is produced at the instant the high-voltage pulse is applied.« less

  7. Driving and neurodegenerative diseases.

    PubMed

    Uc, Ergun Y; Rizzo, Matthew

    2008-09-01

    The proportion of elderly people in the general population is rising, resulting in greater numbers of drivers with neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. These neurodegenerative disorders impair cognition, visual perception, and motor function, leading to reduced driver fitness and greater crash risk. Yet neither medical diagnosis nor age alone is reliable enough to predict driver safety or crashes or to revoke the driving privileges of these individuals. Driving research utilizes tools such as questionnaires about driving habits and history, driving simulators, standardized road tests utilizing instrumented vehicles, and state driving records. Research challenges include outlining the evolution of driving safety, understanding the mechanisms of driving impairment, and developing a reliable and efficient standardized test battery for prediction of driver safety in neurodegenerative disorders. This information will enable healthcare providers to advise their patients with neurodegenerative disorders with more certainty, affect policy, and help develop rehabilitative measures for driving. PMID:18713573

  8. Modeling thermospheric neutral density

    NASA Astrophysics Data System (ADS)

    Qian, Liying

    Satellite drag prediction requires determination of thermospheric neutral density. The NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) and the global-mean Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM) were used to quantify thermospheric neutral density and its variations, focusing on annual/semiannual variation, the effect of using measured solar irradiance on model calculations of solar-cycle variation, and global change in the thermosphere. Satellite drag data and the MSIS00 empirical model were utilized to compare to the TIEGCM simulations. The TIEGCM simulations indicated that eddy diffusion and its annual/semiannual variation is a mechanism for annual/semiannual density variation in the thermosphere. It was found that eddy diffusion near the turbopause can effectively influence thermospheric neutral density. Eddy diffusion, together with annual insolation variation and large-scale circulation, generated global annual/semiannual density variation observed by satellite drag. Using measured solar irradiance as solar input for the TIEGCM improved the solar-cycle dependency of the density calculation shown in F10.7 -based thermospheric empirical models. It has been found that the empirical models overestimate density at low solar activity. The TIEGCM simulations did not show such solar-cycle dependency. Using historic measurements of CO2 and F 10.7, simulations of the global-mean TIMEGCM showed that thermospheric neutral density at 400 km had an average long-term decrease of 1.7% per decade from 1970 to 2000. A forecast of density decrease for solar cycle 24 suggested that thermospheric density will decrease at 400 km from present to the end of solar cycle 24 at a rate of 2.7% per decade. Reduction in thermospheric density causes less atmospheric drag on earth-orbiting space objects. The implication of this long-term decrease of thermospheric neutral density is that it will increase the

  9. Does a threat appeal moderate reckless driving? A terror management theory perspective.

    PubMed

    Ben-Ari, O T; Florian, V; Mikulincer, M

    2000-01-01

    A series of two studies examined the effects of threat appeals on reckless driving from a terror management theory perspective. In both studies, all the participants (N = 109) reported on the relevance of driving to their self-esteem, and, then, half of them were exposed to a road trauma film and the remaining to a neutral film. In Study 1, the dependent variable was the self-report of intentions to drive recklessly in hypothetical scenarios. In Study 2, the dependent variable was actual behavior (driving speed) in a driving simulator. Findings indicated that a road trauma film led to less reported intentions of reckless driving, but to higher driving speed than a neutral film. These effects were only found among participants who perceived driving as relevant to their self-esteem. The discussion emphasized the self-enhancing mechanisms proposed by the terror management theory. PMID:10576671

  10. Gear bearing drive

    NASA Technical Reports Server (NTRS)

    Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)

    2011-01-01

    A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.

  11. Magnetic drive coupling

    NASA Technical Reports Server (NTRS)

    Carter, Edward L. (Inventor)

    1987-01-01

    The driving and driven members of a magnetic drive are separated by en enlarged gap to provide clearance for a conduit or other member. Flux pins in the gap maintain the torque transmitting capability of the drive. The spacing between two of the flux pins is increased to provide space for the conduit.

  12. Magnetic drive coupling

    NASA Technical Reports Server (NTRS)

    Carter, Edward L. (Inventor)

    1989-01-01

    The driving (30) and driven (32) members of a magnetic drive (20) are separated by an enlarged gap (35) to provide clearance for a conduit (23) or other member. Flux pins (40) in the gap (35) maintain the torque transmitting capability of the drive (20). The spacing between two of the flux pins is increased to provide space for the conduit (23).

  13. Sequential Dependencies in Driving

    ERIC Educational Resources Information Center

    Doshi, Anup; Tran, Cuong; Wilder, Matthew H.; Mozer, Michael C.; Trivedi, Mohan M.

    2012-01-01

    The effect of recent experience on current behavior has been studied extensively in simple laboratory tasks. We explore the nature of sequential effects in the more naturalistic setting of automobile driving. Driving is a safety-critical task in which delayed response times may have severe consequences. Using a realistic driving simulator, we find…

  14. Grieving while Driving

    ERIC Educational Resources Information Center

    Rosenblatt, Paul C.

    2004-01-01

    Secondary analysis of data from 84 people in 2 interview studies shows that some bereaved people grieve actively while driving. The grief can be intense, even years after a death. Grief while driving may erupt spontaneously or be set off by a wide range of reminders. Some bereaved people seem to save their grieving for times when they drive,…

  15. Rare HLA Drive Additional HIV Evolution Compared to More Frequent Alleles

    PubMed Central

    Lockhart, David W.; Listgarten, Jennifer; Maley, Stephen N.; Kadie, Carl; Learn, Gerald H.; Nickle, David C.; Heckerman, David E.; Deng, Wenjie; Brander, Christian; Ndung'u, Thumbi; Coovadia, Hoosen; Goulder, Philip J.R.; Korber, Bette T.; Walker, Bruce D.; Mullins, James I.

    2009-01-01

    Abstract HIV-1 can evolve HLA-specific escape variants in response to HLA-mediated cellular immunity. HLA alleles that are common in the host population may increase the frequency of such escape variants at the population level. When loss of viral fitness is caused by immune escape variation, these variants may revert upon infection of a new host who does not have the corresponding HLA allele. Furthermore, additional escape variants may appear in response to the nonconcordant HLA alleles. Because individuals with rare HLA alleles are less likely to be infected by a partner with concordant HLA alleles, viral populations infecting hosts with rare HLA alleles may undergo a greater amount of evolution than those infecting hosts with common alleles due to the loss of preexisting escape variants followed by new immune escape. This hypothesis was evaluated using maximum likelihood phylogenetic trees of each gene from 272 full-length HIV-1 sequences. Recent viral evolution, as measured by the external branch length, was found to be inversely associated with HLA frequency in nef (p < 0.02), env (p < 0.03), and pol (p ≤ 0.05), suggesting that rare HLA alleles provide a disproportionate force driving viral evolution compared to common alleles, likely due to the loss of preexisting escape variants during early stages postinfection. PMID:19327049

  16. Verge and Foliot Clock Escapement: A Simple Dynamical System

    NASA Astrophysics Data System (ADS)

    Denny, Mark

    2010-09-01

    The earliest mechanical clocks appeared in Europe in the 13th century. From about 1250 CE to 1670 CE, these simple clocks consisted of a weight suspended from a rope or chain that was wrapped around a horizontal axle. To tell time, the weight must fall with a slow uniform speed, but, under the action of gravity alone, such a suspended weight would accelerate. To prevent this acceleration, an escapement mechanism was required. The best such escapement mechanism was called the verge and foliot escapement, and it was so successful that it lasted until about 1800 CE. These simple weight-driven clocks with verge and foliot escapements were accurate enough to mark the hours but not minutes or seconds. From 1670, significant improvements were made (principally by introducing pendulums and the newly invented anchor escapement) that justified the introduction of hands to mark minutes, and then seconds. By the end of the era of mechanical clocks, in the first half of the 20th century, these much-studied and much-refined machines were accurate to a millisecond a day.

  17. Enhancing endosomal escape for nanoparticle mediated siRNA delivery

    NASA Astrophysics Data System (ADS)

    Ma, Da

    2014-05-01

    Gene therapy with siRNA is a promising biotechnology to treat cancer and other diseases. To realize siRNA-based gene therapy, a safe and efficient delivery method is essential. Nanoparticle mediated siRNA delivery is of great importance to overcome biological barriers for systemic delivery in vivo. Based on recent discoveries, endosomal escape is a critical biological barrier to be overcome for siRNA delivery. This feature article focuses on endosomal escape strategies used for nanoparticle mediated siRNA delivery, including cationic polymers, pH sensitive polymers, calcium phosphate, and cell penetrating peptides. Work has been done to develop different endosomal escape strategies based on nanoparticle types, administration routes, and target organ/cell types. Also, enhancement of endosomal escape has been considered along with other aspects of siRNA delivery to ensure target specific accumulation, high cell uptake, and low toxicity. By enhancing endosomal escape and overcoming other biological barriers, great progress has been achieved in nanoparticle mediated siRNA delivery.

  18. THE ESCAPE FRACTION OF IONIZING RADIATION FROM GALAXIES

    SciTech Connect

    Benson, Andrew; Venkatesan, Aparna; Shull, J. Michael E-mail: avenkatesan@usfca.edu

    2013-06-10

    The escape of ionizing radiation from galaxies plays a critical role in the evolution of gas in galaxies, and the heating and ionization history of the intergalactic medium. We present semi-analytic calculations of the escape fraction of ionizing radiation for both hydrogen and helium from galaxies ranging from primordial systems to disk-type galaxies that are not heavily dust-obscured. We consider variations in the galaxy density profile, source type, location, and spectrum, and gas overdensity/distribution factors. For sufficiently hard first-light sources, the helium ionization fronts closely track or advance beyond that of hydrogen. Key new results in this work include calculations of the escape fractions for He I and He II ionizing radiation, and the impact of partial ionization from X-rays from early active galactic nuclei or stellar clusters on the escape fractions from galaxy halos. When factoring in frequency-dependent effects, we find that X-rays play an important role in boosting the escape fractions for both hydrogen and helium, but especially for He II. We briefly discuss the implications of these results for recent observations of the He II reionization epoch at low redshifts, as well as the UV data and emission-line signatures from early galaxies anticipated from future satellite missions.

  19. Single-File Escape of Colloidal Particles from Microfluidic Channels.

    PubMed

    Locatelli, Emanuele; Pierno, Matteo; Baldovin, Fulvio; Orlandini, Enzo; Tan, Yizhou; Pagliara, Stefano

    2016-07-15

    Single-file diffusion is a ubiquitous physical process exploited by living and synthetic systems to exchange molecules with their environment. It is paramount to quantify the escape time needed for single files of particles to exit from constraining synthetic channels and biological pores. This quantity depends on complex cooperative effects, whose predominance can only be established through a strict comparison between theory and experiments. By using colloidal particles, optical manipulation, microfluidics, digital microscopy, and theoretical analysis we uncover the self-similar character of the escape process and provide closed-formula evaluations of the escape time. We find that the escape time scales inversely with the diffusion coefficient of the last particle to leave the channel. Importantly, we find that at the investigated microscale, bias forces as tiny as 10^{-15}  N determine the magnitude of the escape time by drastically reducing interparticle collisions. Our findings provide crucial guidelines to optimize the design of micro- and nanodevices for a variety of applications including drug delivery, particle filtering, and transport in geometrical constrictions. PMID:27472142

  20. Folding and escape of nascent proteins at ribosomal exit tunnel

    NASA Astrophysics Data System (ADS)

    Bui, Phuong Thuy; Hoang, Trinh Xuan

    2016-03-01

    We investigate the interplay between post-translational folding and escape of two small single-domain proteins at the ribosomal exit tunnel by using Langevin dynamics with coarse-grained models. It is shown that at temperatures lower or near the temperature of the fastest folding, folding proceeds concomitantly with the escape process, resulting in vectorial folding and enhancement of foldability of nascent proteins. The concomitance between the two processes, however, deteriorates as temperature increases. Our folding simulations as well as free energy calculation by using umbrella sampling show that, at low temperatures, folding at the tunnel follows one or two specific pathways without kinetic traps. It is shown that the escape time can be mapped to a one-dimensional diffusion model with two different regimes for temperatures above and below the folding transition temperature. Attractive interactions between amino acids and attractive sites on the tunnel wall lead to a free energy barrier along the escape route of the protein. It is suggested that this barrier slows down the escape process and consequently promotes correct folding of the released nascent protein.

  1. Folding and escape of nascent proteins at ribosomal exit tunnel.

    PubMed

    Bui, Phuong Thuy; Hoang, Trinh Xuan

    2016-03-01

    We investigate the interplay between post-translational folding and escape of two small single-domain proteins at the ribosomal exit tunnel by using Langevin dynamics with coarse-grained models. It is shown that at temperatures lower or near the temperature of the fastest folding, folding proceeds concomitantly with the escape process, resulting in vectorial folding and enhancement of foldability of nascent proteins. The concomitance between the two processes, however, deteriorates as temperature increases. Our folding simulations as well as free energy calculation by using umbrella sampling show that, at low temperatures, folding at the tunnel follows one or two specific pathways without kinetic traps. It is shown that the escape time can be mapped to a one-dimensional diffusion model with two different regimes for temperatures above and below the folding transition temperature. Attractive interactions between amino acids and attractive sites on the tunnel wall lead to a free energy barrier along the escape route of the protein. It is suggested that this barrier slows down the escape process and consequently promotes correct folding of the released nascent protein. PMID:26957181

  2. History of oxygen and carbon escape from the Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.; Zhang, M. H. G.; Johnson, R. E.; Bougher, S. W.; Nagy, A. F.

    1992-01-01

    A fraction of the oxygen in the Martian atmosphere continually escapes to space because dissociative recombination of the O2(+) ions in the ionosphere can impart sufficient energy to the product O atoms. In addition, ionization of the extended atomic oxygen corona resulting from the above process adds to escape since the solar wind can carry away O(+) ions born above a few hundred km altitude. A further by-product of this ion-pickup by the solar wind is an additional population of escaping oxygen atoms that are sputtered from the atmosphere near the exobase by pickup ions that are on reentry rather than escaping trajectories. This sputtering process can also remove carbon in the form of intact or dissociated CO2 since all atoms and molecules in the 'target' gas are subject to the collisional energy transfer that characterizes sputtering. We have estimated the present rates of escape of oxygen and carbon due to these mechanisms, as well as the rates at several epochs in the history of the solar system.

  3. Enhancing Endosomal Escape for Intracellular Delivery of Macromolecular Biologic Therapeutics.

    PubMed

    Lönn, Peter; Kacsinta, Apollo D; Cui, Xian-Shu; Hamil, Alexander S; Kaulich, Manuel; Gogoi, Khirud; Dowdy, Steven F

    2016-01-01

    Bioactive macromolecular peptides and oligonucleotides have significant therapeutic potential. However, due to their size, they have no ability to enter the cytoplasm of cells. Peptide/Protein transduction domains (PTDs), also called cell-penetrating peptides (CPPs), can promote uptake of macromolecules via endocytosis. However, overcoming the rate-limiting step of endosomal escape into the cytoplasm remains a major challenge. Hydrophobic amino acid R groups are known to play a vital role in viral escape from endosomes. Here we utilize a real-time, quantitative live cell split-GFP fluorescence complementation phenotypic assay to systematically analyze and optimize a series of synthetic endosomal escape domains (EEDs). By conjugating EEDs to a TAT-PTD/CPP spilt-GFP peptide complementation assay, we were able to quantitatively measure endosomal escape into the cytoplasm of live cells via restoration of GFP fluorescence by intracellular molecular complementation. We found that EEDs containing two aromatic indole rings or one indole ring and two aromatic phenyl groups at a fixed distance of six polyethylene glycol (PEG) units from the TAT-PTD-cargo significantly enhanced cytoplasmic delivery in the absence of cytotoxicity. EEDs address the critical rate-limiting step of endosomal escape in delivery of macromolecular biologic peptide, protein and siRNA therapeutics into cells. PMID:27604151

  4. Enhancing Endosomal Escape for Intracellular Delivery of Macromolecular Biologic Therapeutics

    PubMed Central

    Lönn, Peter; Kacsinta, Apollo D.; Cui, Xian-Shu; Hamil, Alexander S.; Kaulich, Manuel; Gogoi, Khirud; Dowdy, Steven F.

    2016-01-01

    Bioactive macromolecular peptides and oligonucleotides have significant therapeutic potential. However, due to their size, they have no ability to enter the cytoplasm of cells. Peptide/Protein transduction domains (PTDs), also called cell-penetrating peptides (CPPs), can promote uptake of macromolecules via endocytosis. However, overcoming the rate-limiting step of endosomal escape into the cytoplasm remains a major challenge. Hydrophobic amino acid R groups are known to play a vital role in viral escape from endosomes. Here we utilize a real-time, quantitative live cell split-GFP fluorescence complementation phenotypic assay to systematically analyze and optimize a series of synthetic endosomal escape domains (EEDs). By conjugating EEDs to a TAT-PTD/CPP spilt-GFP peptide complementation assay, we were able to quantitatively measure endosomal escape into the cytoplasm of live cells via restoration of GFP fluorescence by intracellular molecular complementation. We found that EEDs containing two aromatic indole rings or one indole ring and two aromatic phenyl groups at a fixed distance of six polyethylene glycol (PEG) units from the TAT-PTD-cargo significantly enhanced cytoplasmic delivery in the absence of cytotoxicity. EEDs address the critical rate-limiting step of endosomal escape in delivery of macromolecular biologic peptide, protein and siRNA therapeutics into cells. PMID:27604151

  5. Loss of water from Venus. I - Hydrodynamic escape of hydrogen

    NASA Technical Reports Server (NTRS)

    Kasting, J. F.; Pollack, J. B.

    1983-01-01

    A one-dimensional photochemical-dynamic model is used to study hydrodynamic loss of hydrogen from a primitive, water-rich atmosphere on Venus. The escape flux is calculated as a function of the H2O mixing ratio at the atmospheric cold trap. The cold trap mixing ratio is then related in an approximate fashion to the H2O concentration in the lower atmosphere. Hydrodynamic escape should have been the dominant loss process for hydroogen when the H2O mass mixing ratio in the lower atmosphere exceeded approximately 0.1. The escape rate would have depended upon the magnitude of the solar ultraviolet flux and the atmospheric EUV heating efficiency and, to a lesser extent, on the O2 content of the atmosphere. The time required for Venus to have lost the bulk of a terrestrial ocean of water is on the order of a billion years. Deuterium would have been swept away along with hydrogen if the escape rate was high enough, but some D/H enrichment should have occurred as the escape rate slowed down.

  6. Escape Rates in a Stochastic Environment with Multiple Scales

    NASA Astrophysics Data System (ADS)

    Forgoston, Eric; Schwartz, Ira B.

    2009-01-01

    We consider a stochastic environment with two time scales and outline a general theory that compares two methods to reduce the dimension of the original system. The first method involves the computation of the underlying deterministic center manifold followed by a naive replacement of the stochastic term. The second method allows one to more accurately describe the stochastic effects and involves the derivation of a normal form coordinate transform that is used to find the stochastic center manifold. The results of both methods are used along with the path integral formalism of large fluctuation theory to predict the escape rate from one basin of attraction to another. The general theory is applied to the example of a surface flow described by a generic, singularly perturbed, damped, nonlinear oscillator with additive, Gaussian noise. We show how both nonlinear reduction methods compare in escape rate scaling. Additionally, the center manifolds are shown to predict high prehistory probability regions of escape. The theoretical results are confirmed using numerical computation of the mean escape time and escape prehistory, and we briefly discuss the extension of the theory to stochastic control.

  7. Mars atmospheric escape constrained using MAVEN IUVS coronal observations

    NASA Astrophysics Data System (ADS)

    Chaffin, Michael S.; Deighan, Justin; Chaufray, Jean-Yves; Jain, Sonal; Stewart, Ian; McClintock, Bill; Crismani, Matteo; Stiepen, Arnaud; Holsclaw, Greg; Clarke, John; Montmessin, Franck; Eparvier, Frank; Thiemann, Ed; Chamberlain, Phil; Schneider, Nick; Jakosky, Bruce

    2015-11-01

    Every planetary atmosphere is capped by a corona: an extended, extremely tenuous region where collisions are negligible and particles follow ballistic trajectories. At Mars, the corona is especially extended due to the low gravity of the planet, and a large number of coronal particles are on escaping trajectories. Such escape has played a critical role in the history of the Mars system, likely removing a substantial fraction of the water initially present on the planet, but the mechanism and magnitude of this escape remains poorly constrained. Currently in orbit at Mars, MAVEN's Imaging Ultraviolet Spectrograph (IUVS) is mapping the distribution of oxygen and hydrogen above 200 km at a high spatial and temporal cadence, revealing a dynamic corona in unprecedented detail. Results will be presented demonstrating that the H in the corona is not spherically symmetric in its distribution, and can potentially be used as a tracer of thermospheric general circulation; and that non-thermal "hot" O (in contrast with more spatially confined "cold" thermal O) is ionospherically sourced with a characteristic energy of 1.1 eV and responds to solar EUV forcing. These results will be interpreted in terms of their impact on our current understanding of how atmospheric escape operates today. We will also discuss how these processes may have acted in the past to deplete Mars' initial water inventory, potentially altering the redox balance of the planet and atmosphere through differential escape of H and O.

  8. Immunosuppressive cells in tumor immune escape and metastasis.

    PubMed

    Liu, Yang; Cao, Xuetao

    2016-05-01

    Tumor immune escape and the initiation of metastasis are critical steps in malignant progression of tumors and have been implicated in the failure of some clinical cancer immunotherapy. Tumors develop numerous strategies to escape immune surveillance or metastasize: Tumors not only modulate the recruitment and expansion of immunosuppressive cell populations to develop the tumor microenvironment or pre-metastatic niche but also switch the phenotype and function of normal immune cells from a potentially tumor-reactive state to a tumor-promoting state. Immunosuppressive cells facilitate tumor immune escape by inhibiting antitumor immune responses and furthermore promote tumor metastasis by inducing immunosuppression, promoting tumor cell invasion and intravasation, establishing a pre-metastatic niche, facilitating epithelial-mesenchymal transition, and inducing angiogenesis at primary tumor or metastatic sites. Numerous translational studies indicate that it is possible to inhibit tumor immune escape and prevent tumor metastasis by blocking immunosuppressive cells and eliminating immunosuppressive mechanisms that are induced by either immunosuppressive cells or tumor cells. Furthermore, many clinical trials targeting immunosuppressive cells have also achieved good outcome. In this review, we focus on the underlying mechanisms of immunosuppressive cells in promoting tumor immune escape and metastasis, discuss our current understanding of the interactions between immunosuppressive cells and tumor cells in the tumor microenvironment, and suggest future research directions as well as potential clinical strategies in cancer immunotherapy. PMID:26689709

  9. Single-File Escape of Colloidal Particles from Microfluidic Channels

    NASA Astrophysics Data System (ADS)

    Locatelli, Emanuele; Pierno, Matteo; Baldovin, Fulvio; Orlandini, Enzo; Tan, Yizhou; Pagliara, Stefano

    2016-07-01

    Single-file diffusion is a ubiquitous physical process exploited by living and synthetic systems to exchange molecules with their environment. It is paramount to quantify the escape time needed for single files of particles to exit from constraining synthetic channels and biological pores. This quantity depends on complex cooperative effects, whose predominance can only be established through a strict comparison between theory and experiments. By using colloidal particles, optical manipulation, microfluidics, digital microscopy, and theoretical analysis we uncover the self-similar character of the escape process and provide closed-formula evaluations of the escape time. We find that the escape time scales inversely with the diffusion coefficient of the last particle to leave the channel. Importantly, we find that at the investigated microscale, bias forces as tiny as 10-15 N determine the magnitude of the escape time by drastically reducing interparticle collisions. Our findings provide crucial guidelines to optimize the design of micro- and nanodevices for a variety of applications including drug delivery, particle filtering, and transport in geometrical constrictions.

  10. Electric versus hydraulic drives

    SciTech Connect

    Not Available

    1983-01-01

    This volume records the proceedings of a conference organised by the Engineering Manufacturing Industries Division of the Institution of Mechanical Engineers. Topics considered include high performance position control - a review of the current state of developments; hydrostatic drives - present and future; electric drives - present and future trends; electrical and hydraulic drives for heavy industrial robots; the development of an electro-mechanical tilt system for the advanced passenger train; industrial hydraulic ring mains - effective or efficient. the comparison of performance of servo feed-drive systems; overhead crane drives; the future of d.c. servodrives; the choice of actuator for military systems; linear electro-hydraulic actuators; and actuation for industrial robots.

  11. Coexisting chaotic and periodic dynamics in clock escapements.

    PubMed

    Moon, Francis C; Stiefel, Preston D

    2006-09-15

    This paper addresses the nature of noise in machines. As a concrete example, we examine the dynamics of clock escapements from experimental, historical and analytical points of view. Experiments on two escapement mechanisms from the Reuleaux kinematic collection at Cornell University are used to illustrate chaotic-like noise in clocks. These vibrations coexist with the periodic dynamics of the balance wheel or pendulum. A mathematical model is presented that shows how self-generated chaos in clocks can break the dry friction in the gear train. This model is shown to exhibit a strange attractor in the structural vibration of the clock. The internal feedback between the oscillator and the escapement structure is similar to anti-control of chaos models. PMID:16893802

  12. Neural Circuits Underlying Visually Evoked Escapes in Larval Zebrafish.

    PubMed

    Dunn, Timothy W; Gebhardt, Christoph; Naumann, Eva A; Riegler, Clemens; Ahrens, Misha B; Engert, Florian; Del Bene, Filippo

    2016-02-01

    Escape behaviors deliver organisms away from imminent catastrophe. Here, we characterize behavioral responses of freely swimming larval zebrafish to looming visual stimuli simulating predators. We report that the visual system alone can recruit lateralized, rapid escape motor programs, similar to those elicited by mechanosensory modalities. Two-photon calcium imaging of retino-recipient midbrain regions isolated the optic tectum as an important center processing looming stimuli, with ensemble activity encoding the critical image size determining escape latency. Furthermore, we describe activity in retinal ganglion cell terminals and superficial inhibitory interneurons in the tectum during looming and propose a model for how temporal dynamics in tectal periventricular neurons might arise from computations between these two fundamental constituents. Finally, laser ablations of hindbrain circuitry confirmed that visual and mechanosensory modalities share the same premotor output network. We establish a circuit for the processing of aversive stimuli in the context of an innate visual behavior. PMID:26804997

  13. Fractal templates in the escape dynamics of trapped ultracold atoms

    SciTech Connect

    Mitchell, Kevin A.; Steck, Daniel A.

    2007-09-15

    We consider the dynamic escape of a small packet of ultracold atoms launched from within an optical dipole trap. Based on a theoretical analysis of the underlying nonlinear dynamics, we predict that fractal behavior can be seen in experimental escape data. These data can be collected by measuring the time-dependent escape rate for packets launched over a range of angles. This fractal pattern is particularly well resolved below the Bose-Einstein transition temperature - a direct result of the extreme phase-space localization of the condensate. We predict that several self-similar layers of this novel fractal should be measurable, and we explain how this fractal pattern can be predicted and analyzed with recently developed techniques in symbolic dynamics.

  14. Leaflet escape in a revised Edwards-Duromedics mitral prosthesis.

    PubMed

    Mert, Murat; Ozkara, Ahmet; Hatemi, AliCan

    2003-07-01

    The original Duromedics-Edwards bileaflet valve was withdrawn from the market in 1988 after 12 reports of leaflet escape. The leaflet was modified by the manufacturer, and the revised Edwards-Duromedics and Edwards TEKNA valves were introduced in 1990 and 1993, respectively. However, problems of leaflet escape have now been reported with the new models. A case is reported of sudden leaflet fracture of a revised Duromedics mitral valve 86 months after implantation; this was managed successfully by emergency replacement with a St. Jude Medical mechanical prosthesis. The fracture had occurred transversely, with the two fragments embolizing bilaterally to the right common iliac and left external iliac arteries. In the absence of an exact diagnosis, but with a high index of suspicion, the key to survival of patients with leaflet escape is immediate reoperation. PMID:12918855

  15. Group nightmares about escape from ex-homeland.

    PubMed

    Cernovsky, Z

    1990-09-01

    Escape nightmares (recurrent nightmares about re-escaping ex-homeland) were studied via a 79-item questionnaire administered to 83 Czechoslovak refugees who were living in Switzerland. The key features of the nightmare were not related significantly to the refugees' age, gender, occupation, or educational level. Further analyses dealt with mutual relationships of the various reported aspects of the escape nightmares. The reports of dreaming about arrival in the ex-homeland by a "mistake," such as boarding a wrong airplane (i.e., a Freudian parapraxis), were associated with higher levels of (subsequent) dream anxiety, with waking up due to mounting dream tension, and with the dreamer not knowing at first upon awakening whether he was now in the free world or elsewhere. PMID:2246363

  16. Behavior of Ants Escaping from a Single-Exit Room

    PubMed Central

    Wang, Shujie; Lv, Wei; Song, Weiguo

    2015-01-01

    To study the rules of ant behavior and group-formation phenomena, we examined the behaviors of Camponotus japonicus, a species of large ant, in a range of situations. For these experiments, ants were placed inside a rectangular chamber with a single exit that also contained a filter paper soaked in citronella oil, a powerful repellent. The ants formed several groups as they moved toward the exit to escape. We measured the time intervals between individual escapes in six versions of the experiment, each containing an exit of a different width, to quantify the movement of the groups. As the ants exited the chamber, the time intervals between individual escapes changed and the frequency distribution of the time intervals exhibited exponential decay. We also investigated the relationship between the number of ants in a group and the group flow rate. PMID:26125191

  17. Kramers escape of a self-propelled particle

    NASA Astrophysics Data System (ADS)

    Geiseler, Alexander; Hänggi, Peter; Schmid, Gerhard

    2016-08-01

    We investigate the escape rate of an overdamped, self-propelled spherical Brownian particle on a surface from a metastable potential well. Within a modeling in terms of a 1D constant speed of the particle's active dynamics we consider the associated rate using both numerical and analytical approaches. Regarding the properties of the stationary state in the potential well, two major timescales exist, each governing the translational and the rotational dynamics of the particle, respectively. The particle radius is identified to present the essential quantity in charge of regulating the ratio between those timescales. For very small and very large particle radii, approximate analytic expressions for the particle's escape rate can be derived, which, within their respective range of validity, compare favorably with the precise escape numerics of the underlying full two-dimensional Fokker-Planck description.

  18. Neutral particle beam intensity controller

    DOEpatents

    Dagenhart, William K.

    1986-01-01

    A neutral beam intensity controller is provided for a neutral beam generator in which a neutral beam is established by accelerating ions from an ion source into a gas neutralizer. An amplitude modulated, rotating magnetic field is applied to the accelerated ion beam in the gas neutralizer to defocus the resultant neutral beam in a controlled manner to achieve intensity control of the neutral beam along the beam axis at constant beam energy. The rotating magnetic field alters the orbits of ions in the gas neutralizer before they are neutralized, thereby controlling the fraction of neutral particles transmitted out of the neutralizer along the central beam axis to a fusion device or the like. The altered path or defocused neutral particles are sprayed onto an actively cooled beam dump disposed perpendicular to the neutral beam axis and having a central open for passage of the focused beam at the central axis of the beamline. Virtually zero therough 100% intensity control is achieved by varying the magnetic field strength without altering the ion source beam intensity or its species yield.

  19. Between detection and neutralization.

    SciTech Connect

    Snell, Mark Kamerer; Green, Mary Wilson; Adams, Douglas Glenn; Pritchard, Daniel Allison

    2005-08-01

    Security system analytical performance analysis is generally based on the probability of system effectiveness. The probability of effectiveness is a function of the probabilities of interruption and neutralization. Interruption occurs if the response forces are notified in sufficient time to engage the adversary. Neutralization occurs if the adversary attack is defeated after the security forces have actively engaged the adversary. Both depend upon communications of data. This paper explores details of embedded communications functions that are often assumed to be inconsequential. It is the intent of the authors to bring focus to an issue in security system modeling that, if not well understood, has the potential to be a deciding factor in the overall system failure or effectiveness.

  20. Recombination Drives Vertebrate Genome Contraction

    PubMed Central

    Nam, Kiwoong; Ellegren, Hans

    2012-01-01

    Selective and/or neutral processes may govern variation in DNA content and, ultimately, genome size. The observation in several organisms of a negative correlation between recombination rate and intron size could be compatible with a neutral model in which recombination is mutagenic for length changes. We used whole-genome data on small insertions and deletions within transposable elements from chicken and zebra finch to demonstrate clear links between recombination rate and a number of attributes of reduced DNA content. Recombination rate was negatively correlated with the length of introns, transposable elements, and intergenic spacer and with the rate of short insertions. Importantly, it was positively correlated with gene density, the rate of short deletions, the deletion bias, and the net change in sequence length. All these observations point at a pattern of more condensed genome structure in regions of high recombination. Based on the observed rates of small insertions and deletions and assuming that these rates are representative for the whole genome, we estimate that the genome of the most recent common ancestor of birds and lizards has lost nearly 20% of its DNA content up until the present. Expansion of transposable elements can counteract the effect of deletions in an equilibrium mutation model; however, since the activity of transposable elements has been low in the avian lineage, the deletion bias is likely to have had a significant effect on genome size evolution in dinosaurs and birds, contributing to the maintenance of a small genome. We also demonstrate that most of the observed correlations between recombination rate and genome contraction parameters are seen in the human genome, including for segregating indel polymorphisms. Our data are compatible with a neutral model in which recombination drives vertebrate genome size evolution and gives no direct support for a role of natural selection in this process. PMID:22570634

  1. Negative ion based neutral beam injector for JT-60U

    NASA Astrophysics Data System (ADS)

    Okumura, Y.; Araki, M.; Hanada, M.; Inoue, T.; Kunieda, S.; Kuriyama, M.; Matsuoka, M.; Mizuno, M.; Ohara, Y.; Tanaka, M.; Watanabe, K.

    1992-10-01

    A 500 keV, 10 MW neutral beam injector is to be constructed in JT-60 Upgrade for the experiments of current drive and heating of heat density core plasmas. This is the first neutral beam injector in the world using negative ions as the primary ions. In the design, D- ion beams of 44 A, 500 keV are produced by two ion sources (22 A/each ion source) and neutralized in a long gas neutralizer. The total system efficiency is about 40%. The ion source is a cesium-seeded multicusp volume source having a three stage electrostatic accelerator. To reduce the stripping loss of D- ions in the accelerator, the ion source should be operated at a low pressure of 0.3 Pa with a current density of 13 mA/cm2. The first test of the full-size negative ion source is scheduled from middle of 1993.

  2. Drill drive mechanism

    DOEpatents

    Dressel, Michael O.

    1979-01-01

    A drill drive mechanism is especially adapted to provide both rotational drive and axial feed for a drill of substantial diameter such as may be used for drilling holes for roof bolts in mine shafts. The drill shaft is made with a helical pattern of scroll-like projections on its surface for removal of cuttings. The drill drive mechanism includes a plurality of sprockets carrying two chains of drive links which are arranged to interlock around the drill shaft with each drive link having depressions which mate with the scroll-like projections. As the chain links move upwardly or downwardly the surfaces of the depressions in the links mate with the scroll projections to move the shaft axially. Tangs on the drive links mate with notch surfaces between scroll projections to provide a means for rotating the shaft. Projections on the drive links mate together at the center to hold the drive links tightly around the drill shaft. The entire chain drive mechanism is rotated around the drill shaft axis by means of a hydraulic motor and gear drive to cause rotation of the drill shaft. This gear drive also connects with a differential gearset which is interconnected with a second gear. A second motor is connected to the spider shaft of the differential gearset to produce differential movement (speeds) at the output gears of the differential gearset. This differential in speed is utilized to drive said second gear at a speed different from the speed of said gear drive, this speed differential being utilized to drive said sprockets for axial movement of said drill shaft.

  3. Neutral atom traps.

    SciTech Connect

    Pack, Michael Vern

    2008-12-01

    This report describes progress in designing a neutral atom trap capable of trapping sub millikelvin atom in a magnetic trap and shuttling the atoms across the atom chip from a collection area to an optical cavity. The numerical simulation and atom chip design are discussed. Also, discussed are preliminary calculations of quantum noise sources in Kerr nonlinear optics measurements based on electromagnetically induced transparency. These types of measurements may be important for quantum nondemolition measurements at the few photon limit.

  4. Antihypertensive neutral lipid

    DOEpatents

    Snyder, F.L.; Blank, M.L.

    1984-10-26

    The invention relates to the discovery of a class of neutral acetylated either-linked glycerolipids having the capacity to lower blood presure in warm-blooded animals. This physiological effect is structure sensitive requiring a long chain alkyl group at the sn-1 position and a short carbon chain acyl group (acetyl or propionyl) at the sn-2 position, and a hydroxyl group at the sn-3 position.

  5. Antihypertensive neutral lipid

    DOEpatents

    Snyder, Fred L.; Blank, Merle L.

    1986-01-01

    The invention relates to the discovery of a class of neutral acetylated ether-linked glycerolipids having the capacity to lower blood pressure in warm-blooded animals. This physiological effect is structure sensitive requiring a long chain alkyl group at the sn-1 position and a short carbon chain acyl group (acetyl or propionyl) at the sn-2 position, and a hydroxyl group at the sn-3 position.

  6. Fractionation of the Early Terrestrial Atmospheres: Dynamical Escape

    NASA Technical Reports Server (NTRS)

    Hartle, Richard E.

    2002-01-01

    Hydrodynamic escape may have played a significant role in the early fractionation of the atmospheres of the terrestrial planets. This possibility has been demonstrated in the last two decades by numerous models that show radial, transonic flow of hydrogen can occur in the presence of sufficient solar EUV Hydrodynamic escape may have played a significant role in the early fractionation of the atmospheres of the terrestrial planets. This possibility has been demonstrated in the last two decades by numerous models that show radial, transonic flow of hydrogen can occur in the presence of sufficient solar EUV flux, thought to exist in the first 500 My. The models show that the larger the solar flux the greater the mass of the fractionating species, which are accelerated to escape speeds by the hydrogen wind through drag processes. As the atmospheres evolve and the solar EUV flux wanes, the maximum mass of flowing gas constituents decreases until all gases become static. We show that fractionation can continue beyond this point when non-radial flow and dynamically enhanced Jeans escape are considered. For example, the early terrestrial atmospheres are thought to have had large hydrogen contents, resulting in exobase altitudes of a planetary radius or more. In this case, rotational speeds at the exobases of Earth and Mars would be large enough so that light constituents would "spin" off and fractionate, especially at equatorial latitudes. Also, in the presence of transonic flow of hydrogen only, non-radial expansion throws heavier gases to high altitudes in the exosphere, accompanied by strong bulk speeds at the exobase, which results in enhanced thermal escape fluxes and fractionation. flux, thought to exist in the first 500 My. The models show that the larger the solar flux the greater the mass of the fractionating species, which are accelerated to escape speeds by the hydrogen wind through drag processes. As the atmospheres evolve and the solar EUV flux wanes, the

  7. SOYUZ escape trajectory analysis from Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Heck, Michael L.

    1993-01-01

    It has been proposed to utilize the Russian built SOYUZ as an assured crew return vehicle (ACRV) for Space Station Freedom. Three departure directions (nadir, zenith, minus velocity) are evaluated to determine escape path clearances. In addition, the effects of the following parameters were also evaluated: delta-V magnitude, configuration dependent ballistic coefficients, atmospheric density, Freedom attitude control, and canted docking adaptors. The primary factor influencing the escape trajectory was station contingency attitude rate. The nadir and zenith departures were preferable to minus velocity. The impact of atmospheric density and relative ballistic coefficients was minimal.

  8. Exploring the Escape of Hydrogen Ionizing Photons from Local Galaxies

    NASA Astrophysics Data System (ADS)

    Davis, Jesse A.; Rosenberg, Jessica L.; Venkatesan, Aparna; Cannon, John M.; Salzer, John Joseph

    2016-01-01

    Low-mass galaxies dominate the universe by number and many of these systems have large star formation rates per unit mass. Measurements of the escape fraction of ionizing radiation from dwarf galaxies are an important input to cosmological simulations and theoretical studies but are largely unconstrained by observations. As a result, the role of low-mass galaxies in cosmological reionization and the ionization state of the intergalactic medium (IGM) at high and low redshifts remains poorly understood. Here we study a sample of 18 star-forming galaxies (12 from the Lyman-Alpha Reference Sample, Rivera-Thorsen et al. 2015; 6 from the KISS sample, Salzer et al. 2001), some of which are low-mass systems (10 with M_star < 5 x 10^9 M_sun). All of the sample galaxies were observed in the FUV with the HST/COS spectrograph and these measurements were used to derive limits on their escaping Lyman-alpha radiation (Rivera-Thorsen et al. 2015, Wofford et al. 2013). Using the numerical radiative transfer simulations of Yajima et al. 2014, we relate the escape of Lyman-alpha radiation to limits on the fraction of escaping H-ionizing radiation from these galaxies. This correlation is stronger for low-redshift galaxies (Yajima et al. 2014) and these galaxies are more accessible observationally for these studies. Although the Yajima et al. (2014) study focuses on high-mass galaxies, we derive tentative limits on the escape fraction for H-ionizing radiation for all of the galaxies in this sample. From our analysis, we find escape fractions of less than 5% in all but two extreme cases where the escape fractions are greater than 14%. Our sample averaged escape fraction is insufficient for what reionization requires, although our values are likely to be lower limits and the two outliers are two of the lowest mass systems from the LARS sample. We discuss future directions, including further modeling of the radiative transfer and the galaxy's physical conditions, to better understand the

  9. Rapid endosomal escape of prickly nanodiamonds: implications for gene delivery

    NASA Astrophysics Data System (ADS)

    Chu, Zhiqin; Miu, Kaikei; Lung, Pingsai; Zhang, Silu; Zhao, Saisai; Chang, Huan-Cheng; Lin, Ge; Li, Quan

    2015-06-01

    The prickly nanodiamonds easily entered cells via endocytosis followed by unique intracellular translocation characteristics—quick endosomal escape followed by stable residence in cytoplasm. Endosomal membrane rupturing is identified as the major route of nanodiamonds’ escaping the vesicle confinement and to the cytoplasm. Little cytotoxicity is observed to associate with the nanodiamonds’ cytosolic release. Such features enable its application for gene delivery, which requires both effective cellular uptake and cytosolic release of the gene. Taking green fluorescent protein gene as an example, we demonstrate the successful cytosolic delivery and expression of such a gene using the prickly nanodiamonds as carrier.

  10. Conditional Immune Escape during Chronic Simian Immunodeficiency Virus Infection

    PubMed Central

    Gellerup, Dane D.; Balgeman, Alexis J.; Nelson, Chase W.; Ericsen, Adam J.; Scarlotta, Matthew; Hughes, Austin L.

    2015-01-01

    ABSTRACT Anti-HIV CD8 T cells included in therapeutic treatments will need to target epitopes that do not accumulate escape mutations. Identifying the epitopes that do not accumulate variants but retain immunogenicity depends on both host major histocompatibility complex (MHC) genetics and the likelihood for an epitope to tolerate variation. We previously found that immune escape during acute SIV infection is conditional; the accumulation of mutations in T cell epitopes is limited, and the rate of accumulation depends on the number of epitopes being targeted. We have now tested the hypothesis that conditional immune escape extends into chronic SIV infection and that epitopes with a preserved wild-type sequence have the potential to elicit epitope-specific CD8 T cells. We deep sequenced simian immunodeficiency virus (SIV) from Mauritian cynomolgus macaques (MCMs) that were homozygous and heterozygous for the M3 MHC haplotype and had been infected with SIV for about 1 year. When interrogating variation within individual epitopes restricted by M3 MHC alleles, we found three categories of epitopes, which we called categories A, B, and C. Category B epitopes readily accumulated variants in M3-homozygous MCMs, but this was less common in M3-heterozygous MCMs. We then determined that chronic CD8 T cells specific for these epitopes were more likely preserved in the M3-heterozygous MCMs than M3-homozygous MCMs. We provide evidence that epitopes known to escape from chronic CD8 T cell responses in animals that are homozygous for a set of MHC alleles are preserved and retain immunogenicity in a host that is heterozygous for the same MHC alleles. IMPORTANCE Anti-HIV CD8 T cells that are part of therapeutic treatments will need to target epitopes that do not accumulate escape mutations. Defining these epitope sequences is a necessary precursor to designing approaches that enhance the functionality of CD8 T cells with the potential to control virus replication during chronic

  11. Water-escape velocities in jumping blacktip sharks.

    PubMed

    Brunnschweiler, Juerg M

    2005-09-22

    This paper describes the first determination of water-escape velocities in free-ranging sharks. Two approximations are used to estimate the final swimming speed at the moment of penetrating the water surface. Blacktip sharks were videotaped from below the surface and parameters were estimated by analysing the sequences frame by frame. Water-escape velocities averaged 6.3 ms(-1). These velocities for blacktip sharks seem accurate and are similar to estimates obtained for other shark species of similar size. PMID:16849197

  12. Neutral particle beam intensity controller

    DOEpatents

    Dagenhart, W.K.

    1984-05-29

    The neutral beam intensity controller is based on selected magnetic defocusing of the ion beam prior to neutralization. The defocused portion of the beam is dumped onto a beam dump disposed perpendicular to the beam axis. Selective defocusing is accomplished by means of a magnetic field generator disposed about the neutralizer so that the field is transverse to the beam axis. The magnetic field intensity is varied to provide the selected partial beam defocusing of the ions prior to neutralization. The desired focused neutral beam portion passes along the beam path through a defining aperture in the beam dump, thereby controlling the desired fraction of neutral particles transmitted to a utilization device without altering the kinetic energy level of the desired neutral particle fraction. By proper selection of the magnetic field intensity, virtually zero through 100% intensity control of the neutral beam is achieved.

  13. Martian oxygen escape rate as a function of upstream solar wind density: results from a hybrid model

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Dong; Holmstroem, Mats

    2015-04-01

    We investigate the dependence of oxygen escape rate at Mars on the proton density of the upstream solar wind using a parallel hybrid model. The model handles ions as particles and electrons as a massless, neutralizing fluid. The model currently contains three ion species: protons and alpha particles from the solar wind, and a heavy ion species from Martian ionosphere, which is atomic oxygen ion in this study. The interplanetary magnetic field is set to follow the typical Parker spiral at Mars with an intensity of 3 nT. The upstream solar wind velocity is 400 km/s, along the -x axis. We vary the upstream proton density from np =0.2 cm-3 to np =25 cm-3 while keeping all other parameters fixed. The oxygen escape rate Q shows a negative correlation with np within the range 0.5 < np < 3.5 cm-3. The ratio between the maximum and the minimum escape rates is ~3. Outside this density range the correlation is positive. This anticorrelation between Q and np within the most probable range of the upstream proton density, and the relative variation of Q are consistent with the latest experimental investigations on the same topic using the ion data from MEX/ASPERA-3 [Ramstad et al., 2014]. We also investigated cases under 500 km/s upstream velocity and CO2+ ions, the results are qualitatively consistent. The modeled magnetospheric morphology reveals two competing escape channels that depend differently on the upstream density. The channel including the pickup ions and the plasma sheet intensifies with increasing upstream density. The channel including the lobe region and the boundary layer intensifies with decreasing upstream density due to a more expanded induced magnetosphere. The latter dominates the ion escape when the density is lower than ~2.5 cm-3. We also investigate the momentum transfer from the shocked solar wind to the induced magnetosphere. References: R. Ramstad, S. Barabash, Y. Futaana, H. Nilsson, M. Holmstroem [2014]: The Martian escape rate as a function of

  14. Selectionism and Neutralism in Molecular Evolution

    PubMed Central

    Nei, Masatoshi

    2006-01-01

    Charles Darwin proposed that evolution occurs primarily by natural selection, but this view has been controversial from the beginning. Two of the major opposing views have been mutationism and neutralism. Early molecular studies suggested that most amino acid substitutions in proteins are neutral or nearly neutral and the functional change of proteins occurs by a few key amino acid substitutions. This suggestion generated an intense controversy over selectionism and neutralism. This controversy is partially caused by Kimura's definition of neutrality, which was too strict (|2Ns| ≤ 1). If we define neutral mutations as the mutations that do not change the function of gene products appreciably, many controversies disappear because slightly deleterious and slightly advantageous mutations are engulfed by neutral mutations. The ratio of the rate of nonsynonymous nucleotide substitution to that of synonymous substitution is a useful quantity to study positive Darwinian selection operating at highly variable genetic loci, but it does not necessarily detect adaptively important codons. Previously, multigene families were thought to evolve following the model of concerted evolution, but new evidence indicates that most of them evolve by a birth-and-death process of duplicate genes. It is now clear that most phenotypic characters or genetic systems such as the adaptive immune system in vertebrates are controlled by the interaction of a number of multigene families, which are often evolutionarily related and are subject to birth-and-death evolution. Therefore, it is important to study the mechanisms of gene family interaction for understanding phenotypic evolution. Because gene duplication occurs more or less at random, phenotypic evolution contains some fortuitous elements, though the environmental factors also play an important role. The randomness of phenotypic evolution is qualitatively different from allele frequency changes by random genetic drift. However, there is

  15. Magnetostrictive roller drive motor

    NASA Astrophysics Data System (ADS)

    Vranish, John M.

    1992-01-01

    A magnetostrictive drive motor is disclosed which has a rotary drive shaft in the form of a drum which is encircled by a plurality of substantially equally spaced roller members in the form of two sets of cones which are in contact with the respective cam surfaces on the inside surface of an outer drive ring. The drive ring is attached to sets of opposing pairs of magnetostrictive rods. Each rod in a pair is mutually positioned end to end within respective energizing coils. When one of the coils in an opposing pair is energized, the energized rod expands while the other rod is caused to contract, causing the drive ring to rock, i.e., rotate slightly in either the clockwise or counterclockwise direction, depending upon which rod in a pair is energized. As the drive ring is activated in repetitive cycles in either direction, one set of drive cones attempts to roll up their respective cam surface but are pinned between the drive shaft drum and the drive ring. As the frictional force preventing sliding builds up, the cones become locked, setting up reaction forces including a tangential component which is imparted to the drive shaft drum to provide a source of motor torque. Simultaneously the other set of cones are disengaged from the drive shaft drum. Upon deactivation of the magnetostrictive rod coils, the force on the drive cones is released, causing the system to return to an initial rest position. By repetitively cycling the energization of the magnetostrictive rods, the drive shaft drum indexes in microradian rotational steps.

  16. Neutrality between Government and Religion.

    ERIC Educational Resources Information Center

    Mawdsley, Ralph D.

    1996-01-01

    The overall guiding principle of neutrality between government and religion masks a tension that exists between free exercise of religion and establishment of religion. Reviews the development and current status of "Lemon" as a test for neutrality; proposes a new test for neutrality, evenhandedness, that is common to both the Free Exercise and…

  17. Brain size as a driver of avian escape strategy

    PubMed Central

    Samia, Diogo S. M.; Pape Møller, Anders; Blumstein, Daniel T.

    2015-01-01

    After detecting an approaching predator, animals make a decision when to flee. Prey will initiate flight soon after detecting a predator so as to minimize attentional costs related to on-going monitoring of the whereabouts of the predator. Such costs may compete with foraging and other maintenance activities and hence be larger than the costs of immediate flight. The drivers of interspecific variation in escape strategy are poorly known. Here we investigated the morphological, life history and natural history traits that correlate with variation in avian escape strategy across a sample of 96 species of birds. Brain mass, body size, habitat structure and group size were the main predictors of escape strategy. The direction of the effect of these traits was consistent with selection for a reduction of monitoring costs. Therefore, attentional costs depend on relative brain size, which determines the ability to monitor the whereabouts of potential predators and the difficulty of this task as reflected by habitat and social complexity. Thus brain size, and the cognitive functions associated with it, constitute a general framework for explaining the effects of body size, habitat structure and sociality identified as determinants of avian escape strategy. PMID:26139474

  18. Speed kills: ineffective avian escape responses to oncoming vehicles

    PubMed Central

    DeVault, Travis L.; Blackwell, Bradley F.; Seamans, Thomas W.; Lima, Steven L.; Fernández-Juricic, Esteban

    2015-01-01

    Animal–vehicle collisions cause high levels of vertebrate mortality worldwide, and what goes wrong when animals fail to escape and ultimately collide with vehicles is not well understood. We investigated alert and escape behaviours of captive brown-headed cowbirds (Molothrus ater) in response to virtual vehicle approaches of different sizes and at speeds ranging from 60 to 360 km h−1. Alert and flight initiation distances remained similar across vehicle speeds, and accordingly, alert and flight initiation times decreased at higher vehicle speeds. Thus, avoidance behaviours in cowbirds appeared to be based on distance rather than time available for escape, particularly at 60–150 km h−1; however, at higher speeds (more than or equal to 180 km h−1) no trend in response behaviour was discernible. As vehicle speed increased, cowbirds did not have enough time to assess the approaching vehicle, and cowbirds generally did not initiate flight with enough time to avoid collision when vehicle speed exceeded 120 km h−1. Although potentially effective for evading predators, the decision-making process used by cowbirds in our study appears maladaptive in the context of avoiding fast-moving vehicles. Our methodological approach and findings provide a framework to assess how novel management strategies could affect escape rules, and the sensory and cognitive abilities animals use to avoid vehicle collisions. PMID:25567648

  19. 6. UNDERGROUND FIRING CONTROL ROOM, INTERIOR. Looking southeast to escape ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. UNDERGROUND FIRING CONTROL ROOM, INTERIOR. Looking southeast to escape tunnel. - Edwards Air Force Base, Air Force Rocket Propulsion Laboratory, Firing Control Building, Test Area 1-100, northeast end of Test Area 1-100 Road, Boron, Kern County, CA

  20. 12. CLOSEUP VIEW FROM NORTHWEST, SHOWING DETAILS OF FIRE ESCAPE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. CLOSE-UP VIEW FROM NORTHWEST, SHOWING DETAILS OF FIRE ESCAPE NEAR CORNER OF MILLS HALL MAIN WING NORTH WALL, AND MILLS HALL NORTH WING WEST WALL. - Mills Hall, Mills College, 5000 MacArthur Boulevard, Oakland, Alameda County, CA

  1. Entrapment and Escape: Inventional Metaphors in Ronald Reagan's Economic Rhetoric.

    ERIC Educational Resources Information Center

    Aden, Roger C.

    1989-01-01

    Examines Ronald Reagan's use of inventional metaphors of entrapment and escape, language meshing with the American public's perception of the economy in the early 1980s. Notes that Reagan's reliance on inventional metaphors produced a rigidity in his approach to new situations, ultimately damaging his ability to lead the nation. (MM)

  2. Enuresis Control through Fading, Escape, and Avoidance Training.

    ERIC Educational Resources Information Center

    Hansen, Gordon D.

    1979-01-01

    A twin signal device that provides both escape and avoidance conditioning in enuresis control was documented with case studies of two enuretic children (eight and nine years old). In addition, a technique of fading as an adjunct to the process was utilized with one subject. (Author/SBH)

  3. Action of cocaine and chronic sympathetic denervation on vagal escape

    PubMed Central

    Campos, H. A.; Urquilla, P. R.

    1969-01-01

    1. The effect of cocaine has been studied on vagal escape and on the tachycardia due to vagal stimulation in the atropinized dog. All the dogs were submitted to acute cervical section of the spinal cord and acute or chronic sympathetic denervation. 2. Cocaine, 5 mg/kg or 40 μg/kg/min, I.V., induces a significant enhancement of the ventricular escape. The effects of a continuous infusion of cocaine are more reproducible than those of a single injection of the drug. 3. Cocaine, 40 μg/kg/min, I.V., potentiates the tachycardia due to vagal stimulation in the atropinized dog. 4. Chronic thoracic sympathectomy markedly retards the recovery of the ventricular rate from the inhibitory action of the vagus. Under this condition, the infusion of cocaine does not significantly enhance the ventricular escape. 5. These findings suggest that an adrenergic mechanism located at the sympathetic nerves supplying the heart is substantially involved in the phenomenon of vagal escape. PMID:5249864

  4. Speed kills: ineffective avian escape responses to oncoming vehicles.

    PubMed

    DeVault, Travis L; Blackwell, Bradley F; Seamans, Thomas W; Lima, Steven L; Fernández-Juricic, Esteban

    2015-02-22

    Animal-vehicle collisions cause high levels of vertebrate mortality worldwide, and what goes wrong when animals fail to escape and ultimately collide with vehicles is not well understood. We investigated alert and escape behaviours of captive brown-headed cowbirds (Molothrus ater) in response to virtual vehicle approaches of different sizes and at speeds ranging from 60 to 360 km h(-1). Alert and flight initiation distances remained similar across vehicle speeds, and accordingly, alert and flight initiation times decreased at higher vehicle speeds. Thus, avoidance behaviours in cowbirds appeared to be based on distance rather than time available for escape, particularly at 60-150 km h(-1); however, at higher speeds (more than or equal to 180 km h(-1)) no trend in response behaviour was discernible. As vehicle speed increased, cowbirds did not have enough time to assess the approaching vehicle, and cowbirds generally did not initiate flight with enough time to avoid collision when vehicle speed exceeded 120 km h(-1). Although potentially effective for evading predators, the decision-making process used by cowbirds in our study appears maladaptive in the context of avoiding fast-moving vehicles. Our methodological approach and findings provide a framework to assess how novel management strategies could affect escape rules, and the sensory and cognitive abilities animals use to avoid vehicle collisions. PMID:25567648

  5. Hepatitis B escape mutants in Scottish blood donors.

    PubMed

    Larralde, Osmany; Dow, Brian; Jarvis, Lisa; Davidson, Fiona; Petrik, Juraj

    2013-06-01

    Hepatitis B virus (HBV) remains as the viral infection with the highest risk of transmission by transfusion. This risk is associated with window period donations, occult HBV infection (OBI) and the emergence of escape mutants, which render blood donations false negative for hepatitis B surface antigen (HBsAg) serological testing. A retrospective study was conducted to gain insights into the molecular epidemiology of HBV escape mutants in Scottish blood donors. The criterion for selection was HBV positivity either by serology or nucleic acid testing (NAT). HBsAg detection was compared across several commercial immunoassays. The full length S gene from plasma samples was PCR amplified, cloned and expressed in HepG2 cells. Eight samples showed HBsAg discordant results, while 5 OBI samples were found. Four escape mutants, containing missense mutations in the S gene, are described here. These mutations impaired HBsAg detection both from HBV infected plasma samples and from recombinant proteins derived from its infected donors. Phylogenetic analysis showed that most of the mutants were clustered in the genotype D and were closely related to strains from Asia and the Middle East. We report here a proline substitution, outside the major hydrophilic region, that impaired HBsAg detection in vivo and in vitro, warning about the risk for the emergence of vaccine escape mutants with mutations outside the major neutralisation site. PMID:23274404

  6. The magnetic anomalies significantrly reduce the Martian ionospheric escape rate

    NASA Astrophysics Data System (ADS)

    Fedorov, A.; Barabash, S.; Sauvaud, J.-A.

    2012-09-01

    Looking forward to the MAVEN mission, it seems very useful to return to Mars Express data to refresh an important problem of Martian atmosphere escape: what role the crustal magnetic field may play in this process? There are several publications on this topic with completely opposite conclusions. The last hybrid simulations show that the magnetic anomalies significantly reduce the ion loss rate during solar minimum. We are trying to use a new approach to Mars Express IMA data analysis to check how it is possible. On the base of a statistical study of the ion distributions in the Martian magnetotail we show that the characteristic accelerated ions are not associated with the magnetic anomalies but only with interplanetary magnetic field clock angle. Moreover the magnetic anomalies screen and deviate the escaping flow leading to reducing of the total loss rate. We have calculated a "quasiexperimental" escaping rate in an assumption of the total absence of the magnetic anomalies. We are comparing this value with a real measured escape rate.

  7. Overcoming Antigen Escape with CAR T-cell Therapy.

    PubMed

    Jackson, Hollie J; Brentjens, Renier J

    2015-12-01

    Sotillo and colleagues describe the molecular events associated with apparent loss of target antigen expression following CAR T-cell therapy. We propose that broader immune activation is required to prevent outgrowth of tumor antigen escape variants following targeted therapies. PMID:26637657

  8. Escaping Embarrassment: Face-Work in the Rap Cipher

    ERIC Educational Resources Information Center

    Lee, Jooyoung

    2009-01-01

    How do individuals escape embarrassing moments in interaction? Drawing from ethnographic fieldwork, in-depth interviews, and video recordings of weekly street corner ciphers (impromptu rap sessions), this paper expands Goffman's theory of defensive and protective face-work. The findings reveal formulaic and indirect dimensions of face-work. First,…

  9. Spatial and Nonspatial Escape Strategies in the Barnes Maze

    ERIC Educational Resources Information Center

    Harrison, Fiona E.; Reiserer, Randall S.; Tomarken, Andrew J.; McDonald, Michael P.

    2006-01-01

    The Barnes maze is a spatial memory task that requires subjects to learn the position of a hole that can be used to escape the brightly lit, open surface of the maze. Two experiments assessed the relative importance of spatial (extra-maze) versus proximal visible cues in solving the maze. In Experiment 1, four groups of mice were trained either…

  10. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  11. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  12. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  13. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  14. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  15. 46 CFR 108.445 - Alarm and means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Alarm and means of escape. 108.445 Section 108.445 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Fire Extinguishing Systems Fixed Carbon Dioxide Fire Extinguishing Systems §...

  16. 30 CFR 57.11053 - Escape and evacuation plans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Escape and evacuation plans. 57.11053 Section 57.11053 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Travelways and Escapeways Escapeways-Underground Only §...

  17. 2. WEST REAR, WITH PORTHOLE ESCAPE HATCH ABOVE ENTRY DOOR. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. WEST REAR, WITH PORTHOLE ESCAPE HATCH ABOVE ENTRY DOOR. - Edwards Air Force Base, South Base Sled Track, Firing & Control Blockhouse for 10,000-foot Track, South of Sled Track at midpoint of 20,000-foot track, Lancaster, Los Angeles County, CA

  18. Superluminal warp drive

    NASA Astrophysics Data System (ADS)

    González-Díaz, Pedro F.

    2007-09-01

    In this Letter we consider a warp drive spacetime resulting from that suggested by Alcubierre when the spaceship can only travel faster than light. Restricting to the two dimensions that retains most of the physics, we derive the thermodynamic properties of the warp drive and show that the temperature of the spaceship rises up as its apparent velocity increases. We also find that the warp drive spacetime can be exhibited in a manifestly cosmological form.

  19. Plasma-induced Escape and Alterations of Planetary Atmospheres

    NASA Astrophysics Data System (ADS)

    Johnson, R. E.; Tucker, O. J.; Ewrin, J.; Cassidy, T. A.; Leblanc, F.

    2009-12-01

    The atmospheres of planets and planetary satellites are typically imbedded in space plasmas. Depending on the interaction with the induced or intrinsic fields energetic ions can have access to the thermosphere and the corona affecting their composition and thermal structure and causing loss to space. These processes are often lumped together as ‘atmospheric sputtering’ (Johnson 1994). In this talk I will review the results of simulations of the plasma bombardment at a number of solar system bodies and use those data to describe the effect on the upper atmosphere and on escape. Of considerable recent interest is the modeling of escape from Titan. Prior to Cassini’s tour of the Saturnian system, plasma-induced escape was suggested to be the dominant loss process, but recent models of enhanced thermal escape, often referred to as ‘slow hydrodynamic’ escape, have been suggested to lead to much larger Titan atmospheric loss rates (Strobel 2008; Cui et al. 2008). Such a process has been suggested to be active at some point in time on a number of solar system bodies. I will present hybrid fluid/ kinetic models of the upper atmosphere of certain bodies in order to test both the plasma-induced and thermal escape processes. Preliminary results suggest that the loss rates estimated using the ‘slow hydrodynamic’ escape process can be orders of magnitude too large. The implications for Mars, Titan and Pluto will be discussed. Background for this talk is contained in the following papers (Johnson 2004; 2009; Chaufray et al. 2007; Johnson et al. 2008; 2009; Tucker and Johnson 2009). References: Chaufray, J.Y., R. Modolo, F. Leblanc, G. Chanteur, R.E. Johnson, and J.G. Luhmann, Mars Solar Wind interaction: formation of the Martian corona and atmosphric loss to space, JGR 112, E09009, doi:10.1029/2007JE002915 (2007) Cui, J., Yelle, R. V., Volk, K. Distribution and escape of molecular hydrogen in Titan's thermosphere and exosphere. J. Geophys. Res. 113, doi:10

  20. Diabetes and driving.

    PubMed

    Inkster, B; Frier, B M

    2013-09-01

    The principal safety concern for driving for people treated with insulin or insulin secretagogues is hypoglycaemia, which impairs driving performance. Other complications, such as those causing visual impairment and peripheral neuropathy, are also relevant to medical fitness to drive. Case control studies have suggested that drivers with diabetes pose a modestly increased but acceptable and measurable risk of motor vehicle accidents compared to non-diabetic drivers, but many studies are limited and of poor quality. Factors which have been shown to increase driving risk include previous episodes of severe hypoglycaemia, previous hypoglycaemia while driving, strict glycaemic control (lower HbA1c) and absence of blood glucose monitoring before driving. Impaired awareness of hypoglycaemia may be counteracted by frequent blood glucose testing. The European Union Third directive on driving (2006) has necessitated changes in statutory regulations for driving licences for people with diabetes in all European States, including the UK. Stricter criteria have been introduced for Group 1 vehicle licences while those for Group 2 licences have been relaxed. Insulin-treated drivers can now apply to drive Group 2 vehicles, but in the UK must meet very strict criteria and be assessed by an independent specialist to be issued with a 1-year licence. PMID:23350766

  1. SOURCES AND SINKS OF NEUTRALS AND PLASMA IN THE SATURNIAN MAGNETOSPHERE (Invited)

    NASA Astrophysics Data System (ADS)

    Richardson, J. D.

    2009-12-01

    This talk will review current knowledge on the source and sinks of plasm and energy in Saturn's magnetosphere. Enceladus dominates the water group source, with most of the material escaping from the plume near the southern pole. The relatively low corotation energy in this region results in less energy being available to heat electrons. The electrons are too cold to ionize the neutrals and the inner magnetosphere is dominated by neutrals. In addition, Saturn's atmosphere is a large source of neutral H, the rings contribute O2, and Titan is a source whose magnitude is controversial. In the inner magnetosphere most particles and energy are removed as fast neutrals; transport is more important further out and may be dominated by fingers of inflow and outflow as at Jupiter.

  2. Neutralization distances of Ar^Z+ Rydberg ions interacting with solid surfaces

    NASA Astrophysics Data System (ADS)

    Majkic, M. D.; Nedeljkovic, N. N.; Galijas, S. M. D.

    2008-07-01

    We apply the recently developed time-symmetrized, two-state vector model to investigate the intermediate stages of the electron capture into the Rydberg states of multiply charged Ar^Z+ ions (core charge Z >> 1, principal quantum number n_A >> 1) escaping Al-solid surface at low velocity. The simple analytical formulae derived for the corresponding neutralization rates enable us to analyze the neutralization distances for the low-l Rydberg states (n_A,l_A,m_A), for different charge states Z of the ion. It is found that the inclusion of core polarization significantly reduces the neutralization distances. The neutralization distances for the highest Rydberg levels that can be populated in the vicinity of solid surface are in agreement with the data deduced from experiments in which the kinetic energy gain due to the image acceleration of the ions is measured.

  3. Pulsed field sample neutralization

    DOEpatents

    Appelhans, Anthony D.; Dahl, David A.; Delmore, James E.

    1990-01-01

    An apparatus and method for alternating voltage and for varying the rate of extraction during the extraction of secondary particles, resulting in periods when either positive ions, or negative ions and electrons are extracted at varying rates. Using voltage with alternating charge during successive periods to extract particles from materials which accumulate charge opposite that being extracted causes accumulation of surface charge of opposite sign. Charge accumulation can then be adjusted to a ratio which maintains a balance of positive and negative charge emission, thus maintaining the charge neutrality of the sample.

  4. [Effectiveness of methotrexate for the escape by salazosulfapyridine].

    PubMed

    Kawasaki, Yoichi; Moriyama, Masahiro; Shibata, Kazuhiko; Gomita, Yutaka

    2005-07-01

    Although disease modifying anti-rheumatic drugs (DMARDs) are used in the treatment of rheumatoid arthritis (RA), the selection of agents in the case of relapse (escape phenomenon) lacks clear-cut standards. We compared the effectiveness in a salazosulfapyridine and then methotrexate (SASP-->MTX) group with that in the mothotrexate (SASP+MTX) group after escape phenomenon expression in C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) data. Outpatients of the Matsubara Mayflower Hospital with a history of DMARD administration during the 4 years prior to May 2003 were studied. The CRP level in the SASP-->MTX group (n=8) after the escape phenomenon expression showed a decline after 3 months, but no decline was seen even after 3 months the two in the CRP level in the SASP+MTX group (n=10). However, the difference between groups was not significant. The fluctuation in ESR was similar to that in CRP. However, ESR was significantly lower in the SASP-->MTX group 20 weeks after escape phenomenon expression. In evaluating treatment effectiveness after escape phenomenon expression in each group, SASP-->MTX was effective in 10 and SASP+MTX in 7 patients. Side effects necessitated cessation of treatment in 1 patient in the SASP-->MTX group. Treatment continued in 4 patients in the SASP-->MTX group and 2 in the SASP+MTX group, even though side effects occurred. It should be borne in mind that combination therapy often has greater clinical benefit than single agent therapy but not always. PMID:15997214

  5. Hydrodynamic Vs. Evaporative Escape: Exoplanets And The Ex-planet

    NASA Astrophysics Data System (ADS)

    Johnson, Robert E.; Volkov, A.; Erwin, J.; Tucker, O.

    2012-10-01

    In studies of exoplanets, early terrestrial atmospheres, and even Pluto’s atmosphere it has been convenient to use the equations of fluid dynamics, rather than a more detailed molecular kinetic model, to describe the loss of atmosphere over long time periods. However, the boundary conditions in the far field are always problematic. Therefore, it is assumed that the upward flow either goes through a sonic point or that the loss is Jeans-like at the exobase. The so-called energy limited loss rate, an approximation obtained from the fluid equations, is also often used. Therefore, in a series of molecular kinetic studies of Pluto’s atmosphere, we confirmed that the energy limited loss rate gives a reasonable estimate over a broad range of solar heating conditions, but the flow did not go sonic although the Jeans parameter was relatively small and the escape rates large (Tucker et al. 2012; Erwin et al. 2012). Because the nature of the flow, and not just escape rate, determines the structure of the upper atmosphere, and because the simulation results scale (Volkov et al. 2011), we developed a criterion for determining when the flow associated with atmospheric escape goes sonic or remains Jeans-like. This criterion is verified in a series of kinetic simulations performed using a range of heating rates. In this talk we will discuss the validity of the energy limited escape rate and the nature of the criterion with applications to escape from a variety of exoplanet atmospheres. Erwin, J. et al. Icarus submitted (2012); Tucker, O.J.et al. Icarus 217, 408 (2012); Volkov et al. ApJLetts 729,L24 (2012)

  6. Spatial and nonspatial escape strategies in the Barnes maze.

    PubMed

    Harrison, Fiona E; Reiserer, Randall S; Tomarken, Andrew J; McDonald, Michael P

    2006-01-01

    The Barnes maze is a spatial memory task that requires subjects to learn the position of a hole that can be used to escape the brightly lit, open surface of the maze. Two experiments assessed the relative importance of spatial (extra-maze) versus proximal visible cues in solving the maze. In Experiment 1, four groups of mice were trained either with or without a discrete visible cue marking the location of the escape hole, which was either in a fixed or variable location across trials. In Experiment 2, all mice were trained with the discrete visible cue marking the target hole location. Two groups were identical to the cued-target groups from Experiment 1, with either fixed or variable escape locations. For these mice, the discrete cue either was the sole predictor of the target location or was perfectly confounded with the spatial extra-maze cues. The third group also used a cued variable target, but a curtain was drawn around the maze to prevent the use of spatial cues to guide navigation. Probe trials with all escape holes blocked were conducted to dissociate the use of spatial and discrete proximal cues. We conclude that the Barnes maze can be solved efficiently using spatial, visual cue, or serial-search strategies. However, mice showed a strong preference for using the distal room cues, even when a discrete visible cue clearly marked the escape location. Importantly, these data show that the cued-target control version of the Barnes maze as typically conducted does not dissociate spatial from nonspatial abilities. PMID:17101874

  7. Erratum: The Escape of Ionizing Photons from the Galaxy

    NASA Astrophysics Data System (ADS)

    Bland-Hawthorn, J.; Maloney, P. R.

    2001-04-01

    In the Letter ``The Escape of Ionizing Photons from the Galaxy'' by J. Bland-Hawthorn & P. R. Maloney (ApJ, 510, L33 [1999]), there is an error in Figure 4 that bears on the derived escape fraction of ionizing photons from star-forming regions in the Galaxy's disk. For the quoted distance (55 kpc) of the Magellanic Stream, the predicted emission measures should be reduced by a factor of (20/55)2. Our derived value of fesc~6%, the escape fraction normal to the disk, must be raised by the inverse of this factor, which makes it unlikely that the Stream Hα arises from UV produced by the Galaxy's young stellar disk. This is exacerbated by new Hα observations that show that the Stream is even brighter than originally thought (Weiner, Vogel, & Williams 2001). Bland-Hawthorn & Putman (2001) discuss possible sources of ionization for the Magellanic Stream. We note with interest that high-velocity clouds have now been detected in Hα (e.g., Tufte, Reynolds, & Haffner 1998). Some of these have well-established distance bounds. Bland-Hawthorn & Putman (2001) and Weiner et al. (2001) find that the observed Hα is roughly consistent with fesc~5%, although the present uncertainties are about a factor of 2. It should be noted that fesc refers to the escape fraction normal to the disk. The escape fraction averaged over 4π sr, fesc, is about a factor of 3 smaller and depends on the details of the opacity model (Bland-Hawthorn 1998, Appendix 1). The present uncertainties on fesc for the Galaxy mean that we cannot determine whether star-forming regions dominate the extragalactic UV background (cf. Shull et al. 1999).

  8. Recording Field Potentials From Zebrafish Larvae During Escape Responses

    PubMed Central

    Monesson-Olson, Bryan D.; Troconis, Eileen L.; Trapani, Josef G.

    2014-01-01

    Among vertebrates, startle responses are a ubiquitous method for alerting, and avoiding or escaping from alarming or dangerous stimuli. In zebrafish larvae, fast escape behavior is easily evoked through either acoustic or tactile stimuli. For example, a light touch to the head will excite trigeminal neurons that in turn excite a large reticulospinal neuron in the hindbrain called the Mauthner cell (M-cell). The M-cell action potential then travels down the contralateral trunk of the larva exciting motoneurons, which subsequently excite the entire axial musculature, producing a large amplitude body bend away from the source of the stimulus. This body conformation is known as the “C-bend” due to the shape of the larva during the behavior. As a result of the semi-synchronized activation of the M-cell, the population of motor neurons, and the axial trunk muscles, a large field potential is generated and can be recorded from free-swimming or fixed-position larvae. Undergraduate laboratories that record field potentials during escape responses in larval zebrafish are relatively simple to setup and allow students to observe and study the escape reflex circuit. Furthermore, by testing hypotheses, analyzing data and writing journal-style laboratory reports, students have multiple opportunities to learn about many neuroscience topics including vertebrate reflexes; sensory transduction; synaptic-, neuro-, and muscle-physiology; the M-cell mediated escape response; and the zebrafish as a model organism. Here, we detail the equipment, software, and recording setup necessary to observe field potentials in an undergraduate teaching lab. Additionally, we discuss potential advanced laboratory exercises and pedagogical outcomes. Finally, we note possible low-cost alternatives for recording field potentials. PMID:25565920

  9. Escape manoeuvres in the spiny dogfish (Squalus acanthias).

    PubMed

    Domenici, Paolo; Standen, Emily M; Levine, Robert P

    2004-06-01

    The locomotor performance of dogfish during escape responses was observed by means of high-speed video. Dogfish show C-type escape responses that are comparable with those shown previously in teleosts. Dogfish show high variability of turning rates of the anterior part of the body (head to centre of mass), i.e. with peak values from 434 to 1023 deg. s(-1). We suggest that this variability may be due to the presence of two types of escape manoeuvres, i.e. responses with high and low turning rates, as previously found in a teleost species. Fast responses (i.e. with high maximum turning rates, ranging between 766 and 1023 deg. s(-1)) showed significantly higher locomotor performance than slow responses (i.e. with low maximum turning rates, ranging between 434 and 593 deg. s(-1)) in terms of distance covered, speed and acceleration, although no differences were found in the turning radius of the centre of mass during the escape manoeuvres. The existence of two types of escape responses would have implications in terms of both neural control and muscular activation patterns. When compared with literature data for the locomotor performance of bony fishes, dogfish showed relatively low speed and acceleration, comparable turning rates and a turning radius that is in the low part of the range when compared with teleosts, indicating relatively high manoeuvrability. The locomotor performance observed in dogfish is consistent with their morphological characteristics: (1) low locomotor performance associated with low thrust developed by their relatively small posterior depth of section and (2) relatively high manoeuvrability associated with their high flexibility. PMID:15159438

  10. RAMI Analyses of Heating Neutral Beam and Diagnostic Neutral Beam Systems for ITER

    NASA Astrophysics Data System (ADS)

    Chang, D. H.; Lee, S.; Hemsworth, R.; van Houtte, D.; Okayama, K.; Sagot, F.; Schunke, B.; Svensson, L.

    2011-09-01

    A RAMI (Reliability, Availability, Maintainability, Inspectability) analysis has been performed for the heating (& current drive) neutral beam (HNB) and diagnostic neutral beam (DNB) systems of the ITER device [1-3]. The objective of these analyses is to implement RAMI engineering requirements for design and testing to prepare a reliability-centred plan for commissioning, operation, and maintenance of the system in the framework of technical risk control to support the overall ITER Project. These RAMI requirements will correspond to the RAMI targets for the ITER project and the compensating provisions to reach them as deduced from the necessary actions to decrease the risk level of the function failure modes. The RAMI analyses results have to match with the procurement plan of the systems.

  11. Both Neutralizing and Non-Neutralizing Human H7N9 Influenza Vaccine-Induced Monoclonal Antibodies Confer Protection.

    PubMed

    Henry Dunand, Carole J; Leon, Paul E; Huang, Min; Choi, Angela; Chromikova, Veronika; Ho, Irvin Y; Tan, Gene S; Cruz, John; Hirsh, Ariana; Zheng, Nai-Ying; Mullarkey, Caitlin E; Ennis, Francis A; Terajima, Masanori; Treanor, John J; Topham, David J; Subbarao, Kanta; Palese, Peter; Krammer, Florian; Wilson, Patrick C

    2016-06-01

    Pathogenic H7N9 avian influenza viruses continue to represent a public health concern, and several candidate vaccines are currently being developed. It is vital to assess if protective antibodies are induced following vaccination and to characterize the diversity of epitopes targeted. Here we characterized the binding and functional properties of twelve H7-reactive human antibodies induced by a candidate A/Anhui/1/2013 (H7N9) vaccine. Both neutralizing and non-neutralizing antibodies protected mice in vivo during passive transfer challenge experiments. Mapping the H7 hemagglutinin antigenic sites by generating escape mutant variants against the neutralizing antibodies identified unique epitopes on the head and stalk domains. Further, the broadly cross-reactive non-neutralizing antibodies generated in this study were protective through Fc-mediated effector cell recruitment. These findings reveal important properties of vaccine-induced antibodies and provide a better understanding of the human monoclonal antibody response to influenza in the context of vaccines. PMID:27281570

  12. Vortex Formation in a Plasma Interacting with Neutral Flow

    SciTech Connect

    Tanaka, M. Y.; Ogiwara, K.; Etoh, S.; Aramaki, M.; Yoshimura, S.; Varanjes, J.

    2008-10-15

    Recently, it has been observed that there exists a class of vortices which rotates in the opposite direction to ExB drift (referred to as anti-ExB vortex). This result suggests that a predominant force other than electric field is acting on ions. It is found that momentum transport and resultant force generation through the interaction between ions and neutral flow play an essential role on anti-ExB vortex formation. The existence of inward neutral flow, which drives the ions in the anti-ExB direction, has been confirmed using a newly-developed high-resolution laser induced fluorescence (LIF) spectroscopy system.

  13. Reading Text While Driving

    PubMed Central

    Horrey, William J.; Hoffman, Joshua D.

    2015-01-01

    Objective In this study, we investigated how drivers adapt secondary-task initiation and time-sharing behavior when faced with fluctuating driving demands. Background Reading text while driving is particularly detrimental; however, in real-world driving, drivers actively decide when to perform the task. Method In a test track experiment, participants were free to decide when to read messages while driving along a straight road consisting of an area with increased driving demands (demand zone) followed by an area with low demands. A message was made available shortly before the vehicle entered the demand zone. We manipulated the type of driving demands (baseline, narrow lane, pace clock, combined), message format (no message, paragraph, parsed), and the distance from the demand zone when the message was available (near, far). Results In all conditions, drivers started reading messages (drivers’ first glance to the display) before entering or before leaving the demand zone but tended to wait longer when faced with increased driving demands. While reading messages, drivers looked more or less off road, depending on types of driving demands. Conclusions For task initiation, drivers avoid transitions from low to high demands; however, they are not discouraged when driving demands are already elevated. Drivers adjust time-sharing behavior according to driving demands while performing secondary tasks. Nonetheless, such adjustment may be less effective when total demands are high. Application This study helps us to understand a driver’s role as an active controller in the context of distracted driving and provides insights for developing distraction interventions. PMID:25850162

  14. Modified Advanced Crew Escape Suit Intravehicular Activity Suit for Extravehicular Activity Mobility Evaluations

    NASA Technical Reports Server (NTRS)

    Watson, Richard D.

    2014-01-01

    The use of an intravehicular activity (IVA) suit for a spacewalk or extravehicular activity (EVA) was evaluated for mobility and usability in the Neutral Buoyancy Laboratory (NBL) environment at the Sonny Carter Training Facility near NASA Johnson Space Center in Houston, Texas. The Space Shuttle Advanced Crew Escape Suit was modified to integrate with the Orion spacecraft. The first several missions of the Orion Multi-Purpose Crew Vehicle will not have mass available to carry an EVA-specific suit; therefore, any EVA required will have to be performed by the Modified Advanced Crew Escape Suit (MACES). Since the MACES was not designed with EVA in mind, it was unknown what mobility the suit would be able to provide for an EVA or whether a person could perform useful tasks for an extended time inside the pressurized suit. The suit was evaluated in multiple NBL runs by a variety of subjects, including crewmembers with significant EVA experience. Various functional mobility tasks performed included: translation, body positioning, tool carrying, body stabilization, equipment handling, and tool usage. Hardware configurations included with and without Thermal Micrometeoroid Garment, suit with IVA gloves and suit with EVA gloves. Most tasks were completed on International Space Station mock-ups with existing EVA tools. Some limited tasks were completed with prototype tools on a simulated rocky surface. Major findings include: demonstrating the ability to weigh-out the suit, understanding the need to have subjects perform multiple runs prior to getting feedback, determining critical sizing factors, and need for adjusting suit work envelope. Early testing demonstrated the feasibility of EVA's limited duration and limited scope. Further testing is required with more flight-like tasking and constraints to validate these early results. If the suit is used for EVA, it will require mission-specific modifications for umbilical management or Primary Life Support System integration

  15. Piezoelectric drive circuit

    DOEpatents

    Treu, C.A. Jr.

    1999-08-31

    A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes. 7 figs.

  16. Piezoelectric drive circuit

    DOEpatents

    Treu, Jr., Charles A.

    1999-08-31

    A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes.

  17. Dual drive actuators

    NASA Technical Reports Server (NTRS)

    Packard, D. T.

    1982-01-01

    A new class of electromechanical actuators is described. These dual drive actuators were developed for the NASA-JPL Galileo Spacecraft. The dual drive actuators are fully redundant and therefore have high inherent reliability. They can be used for a variety of tasks, and they can be fabricated quickly and economically.

  18. Design of traction drives

    NASA Technical Reports Server (NTRS)

    Loewenthal, S. H.; Zaretsky, E. V.

    1985-01-01

    Traction drives are among the simplest of all speed-changing mechanisms. Because of their simplicity and their ability to smoothly and continuously adjust speed, they are excellent choices for many drive system applications. They have been used in industrial service for more than 100 years. Today's traction drives have power capacities which rival the best gear and belt drives due to modern traction fluids and highly fatigue-resistant bearing steels. This report summarizes methods to analyze and size traction drives. Lubrication principles, contact kinematics, stress, fatigue life, and performance prediction methods are presented. The effects of the lubricant's traction characteristics on life and power loss are discussed. An example problem is given which illustrates the effects of spin on power loss. Loading mechanism design and the design of nonlubricated friction wheels and rings are also treated.

  19. Specific features of measuring the isotopic composition of hydrogen ions in ITER plasma by using neutral particle diagnostics under neutral beam injection conditions

    SciTech Connect

    Afanasyev, V. I.; Goncharov, P. R.; Mironov, M. I.; Nesenevich, V. G. Petrov, M. P.; Petrov, S. Ya.; Sergeev, V. Yu.

    2015-12-15

    Results of numerical simulation of signals from neutral particle analyzers under injection of the heating and diagnostic neutral beams in different operating modes of the ITER tokamak are presented. The distribution functions of fast ions in plasma are simulated, and the corresponding neutral particle fluxes escaping from the plasma along the line of sight of the analyzers are calculated. It is shown that the injection of heating deuterium (D{sup 0}) beams results in the appearance of an intense background signal hampering measurements of the ratio between the densities of deuterium and tritium fuel ions in plasma in the thermal energy range. The injection of a diagnostic hydrogen (H{sup 0}) beam does not affect measurements owing to the high mass resolution of the analyzers.

  20. Specific features of measuring the isotopic composition of hydrogen ions in ITER plasma by using neutral particle diagnostics under neutral beam injection conditions

    NASA Astrophysics Data System (ADS)

    Afanasyev, V. I.; Goncharov, P. R.; Mironov, M. I.; Nesenevich, V. G.; Petrov, M. P.; Petrov, S. Ya.; Sergeev, V. Yu.

    2015-12-01

    Results of numerical simulation of signals from neutral particle analyzers under injection of the heating and diagnostic neutral beams in different operating modes of the ITER tokamak are presented. The distribution functions of fast ions in plasma are simulated, and the corresponding neutral particle fluxes escaping from the plasma along the line of sight of the analyzers are calculated. It is shown that the injection of heating deuterium (D0) beams results in the appearance of an intense background signal hampering measurements of the ratio between the densities of deuterium and tritium fuel ions in plasma in the thermal energy range. The injection of a diagnostic hydrogen (H0) beam does not affect measurements owing to the high mass resolution of the analyzers.

  1. Evidence for local regulatory control of escape from imprinted X chromosome inactivation.

    PubMed

    Mugford, Joshua W; Starmer, Joshua; Williams, Rex L; Calabrese, J Mauro; Mieczkowski, Piotr; Yee, Della; Magnuson, Terry

    2014-06-01

    X chromosome inactivation (XCI) is an epigenetic process that almost completely inactivates one of two X chromosomes in somatic cells of mammalian females. A few genes are known to escape XCI and the mechanism for this escape remains unclear. Here, using mouse trophoblast stem (TS) cells, we address whether particular chromosomal interactions facilitate escape from imprinted XCI. We demonstrate that promoters of genes escaping XCI do not congregate to any particular region of the genome in TS cells. Further, the escape status of a gene was uncorrelated with the types of genomic features and gene activity located in contacted regions. Our results suggest that genes escaping imprinted XCI do so by using the same regulatory sequences as their expressed alleles on the active X chromosome. We suggest a model where regulatory control of escape from imprinted XCI is mediated by genomic elements located in close linear proximity to escaping genes. PMID:24653000

  2. Evidence for Local Regulatory Control of Escape from Imprinted X Chromosome Inactivation

    PubMed Central

    Mugford, Joshua W.; Starmer, Joshua; Williams, Rex L.; Calabrese, J. Mauro; Mieczkowski, Piotr; Yee, Della; Magnuson, Terry

    2014-01-01

    X chromosome inactivation (XCI) is an epigenetic process that almost completely inactivates one of two X chromosomes in somatic cells of mammalian females. A few genes are known to escape XCI and the mechanism for this escape remains unclear. Here, using mouse trophoblast stem (TS) cells, we address whether particular chromosomal interactions facilitate escape from imprinted XCI. We demonstrate that promoters of genes escaping XCI do not congregate to any particular region of the genome in TS cells. Further, the escape status of a gene was uncorrelated with the types of genomic features and gene activity located in contacted regions. Our results suggest that genes escaping imprinted XCI do so by using the same regulatory sequences as their expressed alleles on the active X chromosome. We suggest a model where regulatory control of escape from imprinted XCI is mediated by genomic elements located in close linear proximity to escaping genes. PMID:24653000

  3. 20. DETAIL VIEW IN 18FOOT LOCK, ESCAPE TRAINING TANK, SHOWING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. DETAIL VIEW IN 18-FOOT LOCK, ESCAPE TRAINING TANK, SHOWING DOOR INTO TANK AT RIGHT - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

  4. Cryoprotectant toxicity neutralization.

    PubMed

    Fahy, Gregory M

    2010-07-01

    Cryoprotectant toxicity is a fundamental limiting factor for the successful cryopreservation of living systems by both freezing and vitrification, and the ability to negate it would be attractive. Past attempts to demonstrate "cryoprotectant toxicity neutralization" (CTN) have had many ups and downs. First convincingly introduced by Baxter and Lathe in 1971, the concept that certain amides can block toxic effects of dimethyl sulfoxide (Me(2)SO) was contradicted by direct experiments in 1990. But in 1995, the opposite mode of CTN, in which Me(2)SO blocked the damaging effects of formamide, was robustly demonstrated. Recent experiments have verified the original 1995 results and extended them to urea and acetamide, but no CTN was detected for N-methylamides (N-methylformamide, N,N-dimethylformamide, and N-methylacetamide). On the theory that the latter amides and acetamide might serve as low-toxicity structural analogs of formamide, urea, or Me(2)SO, competition experiments were carried out between them and formamide or urea, but CTN was not observed for these amide-amide systems. The idea that the N-methylamides might have non-specific rather than specific toxicity was supported by the fact that the concentrations of these amides that cause toxicity are similar to the concentrations that denature model proteins. Clear examples of neutralization of the toxicity of glycerol, propylene glycol, ethylene glycol, or Me(2)SO are presently lacking, but effects of the latter that depend on sulfhydryl oxidation have been reversed with reducing agents. In summary, CTN is a useful phenomenon with significant theoretical and practical implications. PMID:19501081

  5. Transient ion neutralization by electrons.

    NASA Technical Reports Server (NTRS)

    Wilhelm, H. E.

    1973-01-01

    The nonlinear initial-boundary-value problems describing the lateral neutralization of ion beams for the cases that (1) an auxiliary electric field accelerates the electrons into the ion space, and (2) the electrons are injected into the ion space at a prescribed current density are treated. Analytical solutions are derived which give the position and speed of the neutralization front as a function of time, and the temporal development of the electron density, velocity, and electric fields during the neutralization process.

  6. Antigenic Determinants of Possible Vaccine Escape by Porcine Circovirus Subtype 2b Viruses

    PubMed Central

    Constans, Megan; Ssemadaali, Marvin; Kolyvushko, Oleksandr; Ramamoorthy, Sheela

    2015-01-01

    Currently available commercial vaccines against porcine circovirus strain 2 (PCV2) solely target the PCV2a genotype. While PCV2 vaccines are highly effective in preventing clinical signs, PCV2b has dominated over the PCV2a genotype in prevalence, corresponding with the introduction of PCV2a vaccines. A recently emerged PCV2b recombinant with an additional amino acid in the capsid protein, designated the mutant PCV2b (mPCV2b), is cause for concern due to its increased virulence and rapid spread. The accumulation of recent evidence for the increased genetic diversity in PCV2 suggests that current vaccines against PCV2a may be inducing selection pressure and driving viral evolution. In this study, the hypothesis that differences in key immune epitopes between the PCV2a vaccine strains, a classical PCV2b strain called PCV2b 41513 obtained from a vaccine-failure case, and mPCV2b strains could promote vaccine escape was tested using immuno-informatic tools. In the major viral proteins, 9 of the 18 predicted swine leukocyte antigens (SLA) class-I epitopes, 8 of the 22 predicted SLA class-II epitopes, and 7 of the 25 predicted B cell epitopes varied between the vaccine and field strains. A majority of the substitutions in both the T- and B-cell epitopes were located in the capsid protein. Some B- and T-cell epitopes that were identified as immunogenic in the vaccine strain were not identified as epitopes in the field strains, indicating a subtle shift in the antigenic profile of the field strains. Several nonconserved epitopes had both predicted B- and T-cell functions. Therefore, substitutions in the dual epitopes could affect both arms of the immune response simultaneously, causing immune escape. Our findings support further rational design of PCV2 vaccines to increase the current threshold of protection. PMID:26339187

  7. Deformation-driven fluid escape in the Levant Basin, offshore southern Israel

    NASA Astrophysics Data System (ADS)

    Eruteya, Ovie Emmanuel; Waldmann, Nicolas; Reshef, Moshe; Ben-Avraham, Zvi

    2016-04-01

    Submarine fluid emissions are global phenomena, which can be inferred from the presence of seafloor morphologies (e.g. pockmarks, mud volcanoes) occurring in various geological settings. However, despite the Levant Basin been a prolific hydrocarbon province, only a paucity of fluid escape morphologies have been identified on the present-day seafloor. In this study, we present a detailed analysis of a newly available high-resolution 3D seismic reflection dataset from offshore southern Israel. Evidences of subsurface fluid plumbing and escape are manifested here as present-day seafloor pockmarks, paleo-pockmarks, pipe structures and enhanced reflectivity patterns. Interestingly, these pockmarks are situated on and around bathymetric highs, which are ridges related to the Palmachim Disturbance. Our initial results show the fluid flow structures are spatially localized above a region of complex evaporites evacuation at depth, and likewise proximal to a shallower region characterized by high amplitude reflectors. The latter may be evidences for a shallow gas system. Our initial hypothesis proposes a dual shallow-source driven focused fluid flow system. Yet, we favour a deeper Messinian plumbing system driving fluid flow across the overburden in the study area. Corroborating this are fault systems characterized near the pipes feeding the seafloor pockmarks and paleo-pockmark, detaching in the upper Messinian evaporite. We further suggest that a combined supra-salt deformation system arising from the evacuation of the Messinian evaporites coupled with gravitational tectonics are in charge of modulating focused fluid flow. Under this scenario the emplaced mass transport complex acts as a transient reservoir for fluid flow, dewatering under deformation and channelling fluids towards the seafloor for expulsion. However, the contributions from microbially-generated methane in the shallow Quaternary overburden associated with the channel-levee complex cannot be neglected.

  8. Escape of heated ions upstream of quasi-parallel shocks

    NASA Technical Reports Server (NTRS)

    Edmiston, J. P.; Kennel, C. F.; Eichler, D.

    1982-01-01

    A simple theoretical criterion by which quasi-parallel and quasi-perpendicular collisionless shocks may be distinguished is proposed on the basis of an investigation of the free escape of ions from the post-shock plasma into the region upstream of a fast collisionless shock. It was determined that the accessibility of downstream ions to the upstream region depends on upstream magnetic field shock normal angle, in addition to the upstream plasma parameters, with post-shock ions escaping upstream for shock normal angles of less than 45 deg, in agreement with the observed transition between quasi-parallel and quasi-perpendicular shock structure. Upstream ion distribution functions resembling those of observed intermediate ions and beams are also calculated.

  9. Facilities and capabilities catalog for landing and escape systems

    NASA Technical Reports Server (NTRS)

    Meyerson, Robert E. (Editor)

    1992-01-01

    This catalog serves as a single source reference for designers of landing and escape systems for spacecraft, aircraft, weapons, and airdrop system. It includes those facilities which may be required by a system designer in planning a development test program for many applications. The primary objective of this catalog is to provide a means for identifying critical facilities with the U.S. which can be used for the development of landing and escape systems. A secondary objective is to provide a useful tool to the system designer for picking and choosing facilities and capabilities. The six chapters in this volume include wind tunnels, drop zones, test aircraft, fabrication facilities, design tools, and other miscellaneous facilities. A different data sheet format is used for each of the chapters which provides information on performance, location, special capabilities, and a local point of contact. All inputs were solicited from the individual facilities and have not been independently verified for accuracy.

  10. Self-organized escape of oscillator chains in nonlinear potentials.

    PubMed

    Hennig, D; Fugmann, S; Schimansky-Geier, L; Hänggi, P

    2007-10-01

    We present the noise-free escape of a chain of linearly interacting units from a metastable state over a cubic on-site potential barrier. The underlying dynamics is conservative and purely deterministic. The mutual interplay between nonlinearity and harmonic interactions causes an initially uniform lattice state to become unstable, leading to an energy redistribution with strong localization. As a result, a spontaneously emerging localized mode grows into a critical nucleus. By surpassing this transition state, the nonlinear chain manages a self-organized, deterministic barrier crossing. Most strikingly, these noise-free, collective nonlinear escape events proceed generally by far faster than transitions assisted by thermal noise when the ratio between the average energy supplied per unit in the chain and the potential barrier energy assumes small values. PMID:17994939

  11. The production and escape of nitrogen atoms on Mars

    NASA Astrophysics Data System (ADS)

    Fox, J. L.

    1993-02-01

    Updated rate coefficients and a revised ionosphere-thermosphere model are used to compute the production rates and densities of odd nitrogen species in the Martian atmosphere. Computed density profiles for N(4S), N(2D), N(2P), and NO are presented. The model NO densities are found to be about a factor of 2-3 less than those measured by the Viking 1 mass spectrometer. Revised values for the escape rates of N atoms from dissociative recombination and ionospheric reactions are also computed. Dissociative recombination is found to be comparable in importance to photodissociation at low solar activity, but it is still the most important escape mechanism for N-14 at high solar activity.

  12. Ionospheric Flow and Escape of Ions from Titan and Venus

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Intriligator, D. S.; Grebowsky, Joseph M.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    Knowledge gained from measurements and models is used to study the high-speed plasmas interacting with the atmospheres and ionospheres of Titan and Venus. Considering the similarities of the interactions, comparative analysis is used to support the interpretations of observations made at each body. Ionospheric flow inferred to exist by analysis of measurements made from the Pioneer Venus Orbiter supports the interpretation of similar flow in the ionosphere of Titan. The concept that cold ions escape from the ionosphere of Venus is supported by the Voyager I observation that cold ions escape down the magnetic tail of Titan. Pickup O+ ion energy distributions observed at their source in the ionosheath of Venus are shown to be influenced by finite gyroradius effects. The signatures of such effects are expected to be retained as the ions move into the wakes of Titan and Venus.

  13. The production and escape of nitrogen atoms on Mars

    NASA Technical Reports Server (NTRS)

    Fox, J. L.

    1993-01-01

    Updated rate coefficients and a revised ionosphere-thermosphere model are used to compute the production rates and densities of odd nitrogen species in the Martian atmosphere. Computed density profiles for N(4S), N(2D), N(2P), and NO are presented. The model NO densities are found to be about a factor of 2-3 less than those measured by the Viking 1 mass spectrometer. Revised values for the escape rates of N atoms from dissociative recombination and ionospheric reactions are also computed. Dissociative recombination is found to be comparable in importance to photodissociation at low solar activity, but it is still the most important escape mechanism for N-14 at high solar activity.

  14. Behavioral analysis of the escape response in larval zebrafish

    NASA Astrophysics Data System (ADS)

    Feng, Ruopei; Girdhar, Kiran; Chemla, Yann; Gruebele, Martin

    The behavior of larval zebrafish is of great interest because the limited number of locomotor neurons in larval zebrafish couples with its rich repertoire of movements as a vertebrate animal. Current research uses a priori-selected parameters to describe their swimming behavior while our lab has built a parameter-free model based on singular value decomposition analysis to characterize it. Our previous work has analyzed the free swimming of larval zebrafish and presented a different picture from the current classification of larval zebrafish locomotion. Now we are extending this work to the studies of their escape response to acoustic stimulus. Analysis has shown intrinsic difference in the locomotion between escape response and free swimming.

  15. Camouflage and sabotage: tumor escape from the immune system.

    PubMed

    Poschke, Isabel; Mougiakakos, Dimitrios; Kiessling, Rolf

    2011-08-01

    The field of tumor immunology has made great progress in understanding tumor immune interactions. As a consequence a number of immuno-therapeutic approaches have been successfully introduced into the clinic and a large number of promising therapeutic strategies are investigated in ongoing clinical trials. Evaluation of anti-tumor immunity in such trials as well as in animal models has shown that tumor escape from immune recognition and tumor-mediated suppression of anti-tumor immunity can pose a significant obstacle to successful cancer therapy. Here, we review mechanisms of tumor immune escape and immune-subversion with a focus on the research interests in our laboratory: loss of MHC class I on tumor cells, increased oxidative stress, recruitment of myeloid-derived suppressor cells, and regulatory T cells. PMID:21626032

  16. Escape of Mars atmospheric carbon through time by photochemical means

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.; Kim, J.; Nagy, A. F.

    1993-01-01

    Luhmann et al. recently suggested that sputtering of the Martian atmosphere by re-entering O(+) pickup ions could have provided a significant route of escape for CO2 and its products throughout Mars' history. They estimated that the equivalent of C in an approximately 140-mbar CO2 atmosphere should have been lost this way if the Sun and solar wind evolved according to available models. Another source of escaping C (and O) that is potentially important is the dissociative recombination of ionospheric CO(+) near the exobase. We have evaluated the loss rates due to this process for 'ancient' solar EUV radiation fluxes of 1, 3, and 6 times the present flux in order to calculate the possible cumulative loss over the last 3.5 Gyr.

  17. Planetary loss from light ion escape on Venus

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Grebowsky, J. M.

    1995-01-01

    Using Pioneer Venus data, hydrogen and deuterium ions are shown to escape from the hydrogen bulge region in the nightside ionosphere. The polarization electric field propels these light ions upward through the ionosphere and into the ion-exosphere, where H(+) and D(+) continue to be accelerated away from Venus and move into the ionotail and beyond. The vertical flow speeds of H(+) and D(+) are found to be about the same; therefore, selective escape between H(+) and D(+) is negligible for this mechanism. Present day planetary loss rates of about 8.6 x 10(exp 25)/s and 3.2 X 10(exp 23)/s were obtained for H(+) and D(+), respectively. Such rates, persisting over a few billion years, should have significantly affected the planetary water budget.

  18. Escape of Mars atmospheric carbon through time by photochemical means

    NASA Astrophysics Data System (ADS)

    Luhmann, J. G.; Kim, J.; Nagy, A. F.

    Luhmann et al. recently suggested that sputtering of the Martian atmosphere by re-entering O(+) pickup ions could have provided a significant route of escape for CO2 and its products throughout Mars' history. They estimated that the equivalent of C in an approximately 140-mbar CO2 atmosphere should have been lost this way if the Sun and solar wind evolved according to available models. Another source of escaping C (and O) that is potentially important is the dissociative recombination of ionospheric CO(+) near the exobase. We have evaluated the loss rates due to this process for 'ancient' solar EUV radiation fluxes of 1, 3, and 6 times the present flux in order to calculate the possible cumulative loss over the last 3.5 Gyr.

  19. A proposed neutral line signature

    NASA Technical Reports Server (NTRS)

    Doxas, I.; Speiser, T. W.; Dusenbery, P. B.; Horton, W.

    1992-01-01

    An identifying signature is proposed for the existence and location of the neutral line in the magnetotail. The signature, abrupt density, and temperature changes in the Earthtail direction, was first discovered in test particle simulations. Such temperature variations have been observed in ISEE data (Huang et. al. 1992), but their connection to the possible existence of a neutral line in the tail has not yet been established. The proposed signature develops earlier than the ion velocity space ridge of Martin and Speiser (1988), but can only be seen by spacecraft in the vicinity of the neutral line, while the latter can locate a neutral line remotely.

  20. Chemistry of carotenoid neutral radicals.

    PubMed

    Ligia Focsan, A; Magyar, Adam; Kispert, Lowell D

    2015-04-15

    Proton loss from the carotenoid radical cations (Car(+)) to form neutral radicals (#Car) was investigated by numerous electrochemical, EPR, ENDOR and DFT studies described herein. The radical cation and neutral radicals were formed in solution electrochemically and stabilized on solid silica-alumina and MCM-41 matrices. Carotenoid neutral radicals were recently identified in Arabidopsis thaliana plant and photosystem II samples. Deprotonation at the terminal ends of a zeaxanthin radical cation could provide a secondary photoprotection pathway which involves quenching excited state chlorophyll by the long-lived zeaxanthin neutral radicals formed. PMID:25687648

  1. Escaping radio emission from pulsars: Possible role of velocity shear

    SciTech Connect

    Mahajan, S.M. |; Machabeli, G.Z.; Rogava, A.D. |

    1997-01-01

    It is demonstrated that the velocity shear, intrinsic to the e{sup +}e{sup {minus}} plasma present in the pulsar magnetosphere, can efficiently convert the nonescaping longitudinal Langmuir waves (produced by some kind of a beam or stream instability) into propagating (escaping) electromagnetic waves. It is suggested that this shear induced transformation may be the basic mechanism needed for the eventual generation of the observed pulsar radio emission.

  2. Vision and Driving

    PubMed Central

    Owsley, Cynthia; McGwin, Gerald

    2010-01-01

    Driving is the primary means of personal travel in many countries and is relies heavily on vision for its successful execution. Research over the past few decades has addressed the role of vision in driver safety (motor vehicle collision involvement) and in driver performance (both on-road and using interactive simulators in the laboratory). Here we critically review what is currently known about the role of various aspects of visual function in driving. We also discuss translational research issues on vision screening for licensure and re-licensure and rehabilitation of visually impaired persons who want to drive. PMID:20580907

  3. Redundant motor drive system

    NASA Technical Reports Server (NTRS)

    Calvert, J. A. (Inventor)

    1980-01-01

    A drive system characterized by a base supporting a pair of pillars arranged in spaced parallelism, a shaft extended between and supported by the pillars for rotation about the longitudinal axis thereof, a worm gear affixed to the shaft and supported in coaxial relation therewith is described. A bearing housing of a sleeve like configuration is concentrically related to the shaft and is supported thereby for free rotation. A first and a second quiescent drive train, alternatively activatable, is provided for imparting rotation into said bearing housing. Each of the drive trains is characterized by a selectively energizable motor connected to a spur gear.

  4. The Test Drive

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image taken at NASA's Jet Propulsion Laboratory shows engineers rehearsing the sol 133 (June 8, 2004) drive into 'Endurance' crater by NASA's Mars Exploration Rover Opportunity. Engineers and scientists have recreated the martian surface and slope the rover will encounter using a combination of bare and thinly sand-coated rocks, simulated martian 'blueberries' and a platform tilted at a 25-degree angle. The results of this test convinced engineers that the rover was capable of driving up and down a straight slope before it attempted the actual drive on Mars.

  5. Fleeing to refuge: Escape decisions in the race for life.

    PubMed

    Cooper, William E

    2016-10-01

    Economic escape theory that predicts that flight initiation distance (FID=predator-prey distance when a prey begins to flee from an approaching predator) increases as predation risk increases has been overwhelmingly supported. However, the vast majority of empirical tests have focused on effects of single predation risk factors. Even studies that have included multiple risk factors have not predicted how they jointly affect FID. I present a model that predicts joint effects of several predation risk factors that affect the outcome of a race between predator and prey to the prey's refuge. As a prey's distance to refuge and predator attack speed increase, and as the prey's location forces it to flee more toward a predator to reach refuge, FID increases. A published model proposed and experiment showed that FID is longer when prey flee directly toward than directly away from a predator to a refuge. We present a new geometric model that predicts FID for all angles between the prey's and predator's paths to refuge, distance of the prey from refuge when escape begins, predator and prey speeds, and a margin of safety allowing the prey to reach refuge before the predator. The model provides many new, testable predictions about relationships among its variables and FID. Most notably, it predicts that FID increases sigmoidally as the angle between predator and prey paths to refuge increases. Although the model is not economic (cost-benefit), we discuss its relationship to economic escape theory. PMID:27343624

  6. A Treatment Package without Escape Extinction to Address Food Selectivity.

    PubMed

    Weber, Jessica; Gutierrez, Anibal

    2015-01-01

    Feeding difficulties and feeding disorders are a commonly occurring problem for young children, particularly children with developmental delays including autism. Behavior analytic interventions for the treatment of feeding difficulties oftentimes include escape extinction as a primary component of treatment. The use of escape extinction, while effective, may be problematic as it is also associated with the emergence of challenging behavior (e.g., extinction burst). Such challenging behavior may be an acceptable side effect in treatment cases where feeding problems are severe and chronic (e.g., failure to thrive). However, in more acute cases (e.g., selective eating), the negative side effect may be unwarranted and undesired. More recent research on the behavioral treatment of food selectivity has begun to evaluate treatments for feeding difficulties that do not include escape extinction (e.g., demand fading, behavioral momentum), with some success. However, research to date reveals individual differences in responsiveness to such treatments and no clear preferable treatment has emerged. This manuscript describes a multi-component treatment package that includes shaping, sequential presentation and simultaneous presentation, for the treatment of food selectivity in four young children with developmental delays. This treatment package extends the literature on the behavioral treatment for food selectivity and offers a multi-component treatment protocol that may be clinically applicable across a range of treatment scenarios and settings. PMID:26325108

  7. Changes in escape fire occurrence rate under climate change

    NASA Astrophysics Data System (ADS)

    Wotton, B. M.; Gowman, L.

    2009-04-01

    There has been considerable study of the general impacts of climate change on the circumpolar boreal forest, and in particular on potential changes in the level of forest fire activity. Recent studies have shown that overall fire occurrence (from both human and lightning causes) is expected to increase across the boreal forest in Canada (and in many other regions of the world) under the changed fire weather expected to accompany climate change over the 21st Century. In terms of fire on a managed forest landscape, it is not so much the total number of fires occurring but that very small number of fires that escape initial attack that have the greatest impact in terms of area burned or loss of values. We developed models of the probability of fire occurrences escaping initial attack based on weather-based outputs of the Canadian FWI System and general fire cause type. Using these with outputs from recent GCM scenarios from the Hadley and Canadian Climate Centre we find an overall increase in expected fire escapes as well across the forested region of Canada. Increases in some areas can be higher that the increases expected in total number of fires. Assumptions going into this analysis are that fire management agency effort in terms of response time and suppression resource levels remains constant over time.

  8. Transitions between three swimming gaits in Paramecium escape.

    PubMed

    Hamel, Amandine; Fisch, Cathy; Combettes, Laurent; Dupuis-Williams, Pascale; Baroud, Charles N

    2011-05-01

    Paramecium and other protists are able to swim at velocities reaching several times their body size per second by beating their cilia in an organized fashion. The cilia beat in an asymmetric stroke, which breaks the time reversal symmetry of small scale flows. Here we show that Paramecium uses three different swimming gaits to escape from an aggression, applied in the form of a focused laser heating. For a weak aggression, normal swimming is sufficient and produces a steady swimming velocity. As the heating amplitude is increased, a higher acceleration and faster swimming are achieved through synchronized beating of the cilia, which begin by producing oscillating swimming velocities and later give way to the usual gait. Finally, escape from a life-threatening aggression is achieved by a "jumping" gait, which does not rely on the cilia but is achieved through the explosive release of a group of trichocysts in the direction of the hot spot. Measurements through high-speed video explain the role of trichocysts in defending against aggressions while showing unexpected transitions in the swimming of microorganisms. These measurements also demonstrate that Paramecium optimizes its escape pattern by taking advantage of its inertia. PMID:21464291

  9. Self-assembling dual component nanoparticles with endosomal escape capability.

    PubMed

    Wong, Adelene S M; Mann, Sarah K; Czuba, Ewa; Sahut, Audrey; Liu, Haiyin; Suekama, Tiffany C; Bickerton, Tayla; Johnston, Angus P R; Such, Georgina K

    2015-04-21

    This study reports a novel nanoparticle system with simple and modular one-step assembly, which can respond intelligently to biologically relevant variations in pH. Importantly, these particles also show the ability to induce escape from the endosomal/lysosomal compartments of the cell, which is integral to the design of efficient polymeric delivery systems. The nanoparticles were formed by the nanoprecipitation of pH-responsive poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) and poly(2-(diethylamino)ethyl methacrylate)-b-poly(ethylene glycol) (PDEAEMA-b-PEG). Rhodamine B octadecyl ester perchlorate was successfully encapsulated within the hydrophobic core of the nanoparticle upon nanoprecipitation into PBS at pH 8. These particles disassembled when the pH was reduced below 6.8 at 37 °C. Cellular experiments showed the successful uptake of the nanoparticles into the endosomal/lysosomal compartments of 3T3 fibroblast cells. The ability to induce escape from the endosomes was demonstrated by the use of calcein, a membrane-impermeable fluorophore. The modular nature of these particles combined with promising endosomal escape capabilities make these dual component PDEAEMA nanoparticles useful for drug and gene delivery applications. PMID:25731820

  10. 46 CFR 108.155 - Restrictions on means of escape utilized.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Restrictions on means of escape utilized. 108.155 Section 108.155 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE... means of escape utilized. A required means of escape may not be a vertical ladder or deck...

  11. Escape Performance Following Exposure to Inescapable Shock: Deficits in Motor Response Maintenance

    ERIC Educational Resources Information Center

    Anisman, Hymie; And Others

    1978-01-01

    A series of 13 experiments employing mice systematically investigated shock-elicited activity in a circular field and escape performance in a shuttle box following exposure to either escapable or inescapable shock. Results show that escape interference induced by inescapable shock may be comfortably interpreted in terms of a decreased tendency for…

  12. 78 FR 13811 - Safety Zone; Underwater Escape Event, Seaport, East River, NY

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-01

    ... Federal Register on November 9, 2011 (76 FR 69614). ] Table 1 1. Merlini Underwater Escape Launch site... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; Underwater Escape Event, Seaport, East River, NY AGENCY... escape artist event and associated pyrotechnics display. During the enforcement period, no person...

  13. Escape Geography--Developing Middle-School Students' Sense of Place.

    ERIC Educational Resources Information Center

    Allen, Rodney F.; Molina, Laurie E. S.

    1992-01-01

    Suggests a social studies unit on escaping geography. Examines escape from dangerous places including an airliner, hotel fire, or war zone or from a social situation such as a boring speech or party. Describes historic escapes such as the Underground Railroad and the Berlin Wall. Lists learning strategies such as awareness of space and cognitive…

  14. 78 FR 54585 - Safety Zone; Escape to Miami Triathlon, Biscayne Bay, Miami, FL

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-05

    .... SUPPLEMENTARY INFORMATION: Table of Acronyms DHS Department of Homeland Security FR Federal Register NPRM Notice... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Escape to Miami Triathlon, Biscayne Bay... during the Publix Escape to Miami Triathlon. The Publix Escape to Miami Triathlon is scheduled to...

  15. Fast ion profiles during neutral beam and lower hybrid heating

    SciTech Connect

    Heidbrink, W.W.; Strachan, J.D.; Bell, R.E.; Cavallo, A.; Motley, R.; Schilling, G.; Stevens, J.; Wilson, J.R.

    1985-07-01

    Profiles of the d(d,p)t fusion reaction are measured in the PLT tokamak using an array of collimated 3 MeV proton detectors. During deuterium neutral beam injection, the emission profile indicates that the beam deposition is at least as narrow as predicted by a bounce-averaged Fokker-Planck code. The fast ion tail formed by lower hybrid waves (at densities above the critical density for current drive) also peaks strongly near the magnetic axis.

  16. Meiotic drive of chromosomal knobs reshaped the maize genome.

    PubMed Central

    Buckler, E S; Phelps-Durr, T L; Buckler, C S; Dawe, R K; Doebley, J F; Holtsford, T P

    1999-01-01

    Meiotic drive is the subversion of meiosis so that particular genes are preferentially transmitted to the progeny. Meiotic drive generally causes the preferential segregation of small regions of the genome; however, in maize we propose that meiotic drive is responsible for the evolution of large repetitive DNA arrays on all chromosomes. A maize meiotic drive locus found on an uncommon form of chromosome 10 [abnormal 10 (Ab10)] may be largely responsible for the evolution of heterochromatic chromosomal knobs, which can confer meiotic drive potential to every maize chromosome. Simulations were used to illustrate the dynamics of this meiotic drive model and suggest knobs might be deleterious in the absence of Ab10. Chromosomal knob data from maize's wild relatives (Zea mays ssp. parviglumis and mexicana) and phylogenetic comparisons demonstrated that the evolution of knob size, frequency, and chromosomal position agreed with the meiotic drive hypothesis. Knob chromosomal position was incompatible with the hypothesis that knob repetitive DNA is neutral or slightly deleterious to the genome. We also show that environmental factors and transposition may play a role in the evolution of knobs. Because knobs occur at multiple locations on all maize chromosomes, the combined effects of meiotic drive and genetic linkage may have reshaped genetic diversity throughout the maize genome in response to the presence of Ab10. Meiotic drive may be a major force of genome evolution, allowing revolutionary changes in genome structure and diversity over short evolutionary periods. PMID:10471723

  17. Neutral winds above 200 km at high latitudes.

    NASA Technical Reports Server (NTRS)

    Meriwether, J. W.; Heppner, J. P.; Stolarik, J. D.; Wescott, E. M.

    1973-01-01

    Electrically neutral, luminous clouds are a by-product of chemical releases conducted to create barium ion clouds for the measurement of electric fields. Wind measurements provided by the motions of these clouds are particularly valuable in that the motions can be directly compared with convective ion drift motions to test the importance of ion drag forces. Motion from multiple releases between 200 and 300 km from 15 rockets launched from four high-latitude locations is analyzed in this paper. The observations in the evening and midnight hours at magnetic latitudes above 65 deg strongly suggest that in these regions ion drag is the dominant force in driving neutral winds between 200 and 300 km. In the morning sector, it is evident that neutral wind observations cannot be directly interpreted in terms of ion drag; other factors must be considered.

  18. Dementia and driving

    MedlinePlus

    ... getting more dangerous include: Getting lost on familiar roads Reacting more slowly in traffic Driving too slowly ... attention to traffic signs Taking chances on the road Drifting into other lanes Getting more agitated in ...

  19. Control rod drive

    SciTech Connect

    Hawke, Basil C.

    1986-01-01

    A control rod drive uses gravitational forces to insert one or more control rods upwardly into a reactor core from beneath the reactor core under emergency conditions. The preferred control rod drive includes a vertically movable weight and a mechanism operatively associating the weight with the control rod so that downward movement of the weight is translated into upward movement of the control rod. The preferred control rod drive further includes an electric motor for driving the control rods under normal conditions, an electrically actuated clutch which automatically disengages the motor during a power failure and a decelerator for bringing the control rod to a controlled stop when it is inserted under emergency conditions into a reactor core.

  20. Drive program documentation

    NASA Technical Reports Server (NTRS)

    Graham, S.

    1979-01-01

    The program description and user's guide for the Downlist Requirement Integrated Verification and Evaluation (DRIVE) program is provided. The program is used to compare existing telemetry downlist files with updated downlist requirements.

  1. Safe driving for teens

    MedlinePlus

    ... drivers. Do not use cell phones for talking, texting, or email when you are driving. Mobile phones ... pull off of the road before answering or texting. Other tips include: Avoid putting on makeup while ...

  2. CO2-neutral fuels

    NASA Astrophysics Data System (ADS)

    Goede, A. P. H.

    2015-08-01

    The need for storage of renewable energy (RE) generated by photovoltaic, concentrated solar and wind arises from the fact that supply and demand are ill-matched both geographically and temporarily. This already causes problems of overcapacity and grid congestion in countries where the fraction of RE exceeds the 20% level. A system approach is needed, which focusses not only on the energy source, but includes conversion, storage, transport, distribution, use and, last but not least, the recycling of waste. Furthermore, there is a need for more flexibility in the energy system, rather than relying on electrification, integration with other energy systems, for example the gas network, would yield a system less vulnerable to failure and better adapted to requirements. For example, long-term large-scale storage of electrical energy is limited by capacity, yet needed to cover weekly to seasonal demand. This limitation can be overcome by coupling the electricity net to the gas system, considering the fact that the Dutch gas network alone has a storage capacity of 552 TWh, sufficient to cover the entire EU energy demand for over a month. This lecture explores energy storage in chemicals bonds. The focus is on chemicals other than hydrogen, taking advantage of the higher volumetric energy density of hydrocarbons, in this case methane, which has an approximate 3.5 times higher volumetric energy density. More importantly, it allows the ready use of existing gas infrastructure for energy storage, transport and distribution. Intermittent wind electricity generated is converted into synthetic methane, the Power to Gas (P2G) scheme, by splitting feedstock CO2 and H2O into synthesis gas, a mixture of CO and H2. Syngas plays a central role in the synthesis of a range of hydrocarbon products, including methane, diesel and dimethyl ether. The splitting is accomplished by innovative means; plasmolysis and high-temperature solid oxygen electrolysis. A CO2-neutral fuel cycle is

  3. NEUTRAL-BEAM INJECTION

    SciTech Connect

    Kunkel, W.B.

    1980-06-01

    The emphasis in the preceding chapters has been on magnetic confinement of high temperature plasmas. The question of production and heating of such plasmas has been dealt with relatively more briefly. It should not be inferred, however, that these matters must therefore be either trivial or unimportant. A review of the history reveals that in the early days all these aspects of the controlled fusion problem were considered to be on a par, and were tackled simultaneously and with equal vigor. Only the confinement problem turned out to be much more complex than initially anticipated, and richer in challenge to the plasma physicist than the questions of plasma production and heating. On the other hand, the properties of high-temperature plasmas and plasma confinement can only be studied experimentally after the problems of production and of heating to adequate temperatures are solved. It is the purpose of this and the next chapter to supplement the preceding discussions with more detail on two important subjects: neutral-beam injection and radio-frequency heating. These are the major contenders for heating in present and future tokamak and mirror fusion experiments, and even in several proposed reactors. For neutral beams we emphasize here the technology involved, which has undergone a rather remarkable development. The physics of particle and energy deposition in the plasma, and the discussion of the resulting effects on the confined plasma, have been included in previous chapters, and some experimental results are quoted there. Other heating processes of relevance to fusion are mentioned elsewhere in this book, in connection with the experiments where they are used: i.e. ohmic heating, adiabatic compression heating, and alpha-particle heating in Chapter 3 by H.P. Furth; more ohmic heating in Chapter 7, and shock-implosion heating, laser heating, and relativistic-electron beam heating in Chapter 8, both by W. E. Quinn. These methods are relatively straightforward in

  4. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett Lee; Danforth, William; Bevington, Christopher; Stowell, Jesse; Costin, Daniel

    2006-09-19

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  5. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett; Danforth, William; Bevington, Christopher; Jesse, Stowell; Costin, Daniel

    2007-02-27

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  6. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett; Danforth, William; Bevington, Christopher; Stowell, Jesse; Costin, Daniel

    2006-07-11

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  7. Direct drive wind turbine

    DOEpatents

    Bywaters, Garrett; Danforth, William; Bevington, Christopher; Jesse, Stowell; Costin, Daniel

    2006-10-10

    A wind turbine is provided that minimizes the size of the drive train and nacelle while maintaining the power electronics and transformer at the top of the tower. The turbine includes a direct drive generator having an integrated disk brake positioned radially inside the stator while minimizing the potential for contamination. The turbine further includes a means for mounting a transformer below the nacelle within the tower.

  8. CONTROL ROD DRIVE

    DOEpatents

    Chapellier, R.A.

    1960-05-24

    BS>A drive mechanism was invented for the control rod of a nuclear reactor. Power is provided by an electric motor and an outside source of fluid pressure is utilized in conjunction with the fluid pressure within the reactor to balance the loadings on the motor. The force exerted on the drive mechanism in the direction of scramming the rod is derived from the reactor fluid pressure so that failure of the outside pressure source will cause prompt scramming of the rod.

  9. Common drive unit

    NASA Technical Reports Server (NTRS)

    Ellis, R. C.; Fink, R. A.; Moore, E. A.

    1987-01-01

    The Common Drive Unit (CDU) is a high reliability rotary actuator with many versatile applications in mechanism designs. The CDU incorporates a set of redundant motor-brake assemblies driving a single output shaft through differential. Tachometers provide speed information in the AC version. Operation of both motors, as compared to the operation of one motor, will yield the same output torque with twice the output speed.

  10. A Novel Universal Neutralizing Monoclonal Antibody against Enterovirus 71 That Targets the Highly Conserved “Knob” Region of VP3 Protein

    PubMed Central

    Meng, Tao; Chow, Vincent Tak Kwong; Kwang, Jimmy

    2014-01-01

    Hand, foot and mouth disease caused by enterovirus 71(EV71) leads to the majority of neurological complications and death in young children. While putative inactivated vaccines are only now undergoing clinical trials, no specific treatment options exist yet. Ideally, EV71 specific intravenous immunoglobulins could be developed for targeted treatment of severe cases. To date, only a single universally neutralizing monoclonal antibody against a conserved linear epitope of VP1 has been identified. Other enteroviruses have been shown to possess major conformational neutralizing epitopes on both the VP2 and VP3 capsid proteins. Hence, we attempted to isolate such neutralizing antibodies against conformational epitopes for their potential in the treatment of infection as well as differential diagnosis and vaccine optimization. Here we describe a universal neutralizing monoclonal antibody that recognizes a conserved conformational epitope of EV71 which was mapped using escape mutants. Eight escape mutants from different subgenogroups (A, B2, B4, C2, C4) were rescued; they harbored three essential mutations either at amino acid positions 59, 62 or 67 of the VP3 protein which are all situated in the “knob” region. The escape mutant phenotype could be mimicked by incorporating these mutations into reverse genetically engineered viruses showing that P59L, A62D, A62P and E67D abolish both monoclonal antibody binding and neutralization activity. This is the first conformational neutralization epitope mapped on VP3 for EV71. PMID:24875055

  11. Concerning neutral flux shielding in the U-3M torsatron

    SciTech Connect

    Dreval, N. B.

    2015-03-15

    The volume of the torsatron U-3M vacuum chamber is about 70 m{sup 3}, whereas the plasma volume is about 0.3 m{sup 3}. The large buffer volume of the chamber serves as a source of a substantial neutral flux into the U-3M plasma. A fraction of this flux falls onto the torsatron helical coils located in front of the plasma, due to which the dynamics of neutral influx into the plasma modifies. The shielding of the molecular flux from the buffer volume into the plasma is estimated using numerical calculations. Only about 10% of the incident flux reaches the plasma volume. Estimates show that about 20% of atoms escape beyond the helical coils without colliding with them. Under these conditions, the helical coils substantially affect the neutral flux. A discharge regime with a hot low-density plasma produced by a frame antenna is considered. The spatial distribution of the molecular density produced in this regime by the molecular flux from the chamber buffer volume after it has passed between the helical coils is calculated. The contributions of the fluxes emerging from the side and inner surfaces of the helical coils are considered. The calculations show that the shape of the spatial distribution of the molecular density differs substantially from the shape of the magnetic surfaces.

  12. Fast ion behavior during neutral beam injection in ATF

    SciTech Connect

    Wade, M.R.; Thomas, C.E.; Colchin, R.J.; Rome, J.A.; England, A.C.; Fowler, R.H.; Aceto, S.C.

    1993-09-01

    In stellarators, single-particle confinement properties can be more complex than in their tokamak counterparts. Fast-ion behavior in tokamaks has been well characterized through an abundance of measurements on various devices and in general has been shown to be consistent with classical slowing-down theory, although anomalous ion behavior has been observed during intense beam injection in ISX-B, during fishbone instabilities in PDX, and in experiments on TFR. In contrast, fast ion behavior in stellarators is not as wel established experimentally with the primary experiments to date focusing o near-perpendicular or perpendicular neutral beam injection (NBI) on the Wendelstein 7-A stellarator (91 and Heliotron-E. This paper addresses fast-ion confinement properties in a large-aspect-ratio, moderate-shear stellarator, the Advanced Toroidal Facility, during tangential NBI. The primary data used in this study are the experimentally measured energy spectra of charge-exchange neutrals escaping from the plasma, using a two-dimensional scanning neutral particle analyzer. This diagnostic method is well established, having been used on several devices since the early 1970`s. Various aspects of fast-ion behavior are investigated by comparing these data with computed theoretical spectra based on energeticion distributions derived from the fastion Fokker-Planck equation. Ion orbits are studied by computer orbit following, by the computation of J* surfaces, and by Monte Carlo calculations.

  13. Concerning neutral flux shielding in the U-3M torsatron

    NASA Astrophysics Data System (ADS)

    Dreval, N. B.

    2015-03-01

    The volume of the torsatron U-3M vacuum chamber is about 70 m3, whereas the plasma volume is about 0.3 m3. The large buffer volume of the chamber serves as a source of a substantial neutral flux into the U-3M plasma. A fraction of this flux falls onto the torsatron helical coils located in front of the plasma, due to which the dynamics of neutral influx into the plasma modifies. The shielding of the molecular flux from the buffer volume into the plasma is estimated using numerical calculations. Only about 10% of the incident flux reaches the plasma volume. Estimates show that about 20% of atoms escape beyond the helical coils without colliding with them. Under these conditions, the helical coils substantially affect the neutral flux. A discharge regime with a hot low-density plasma produced by a frame antenna is considered. The spatial distribution of the molecular density produced in this regime by the molecular flux from the chamber buffer volume after it has passed between the helical coils is calculated. The contributions of the fluxes emerging from the side and inner surfaces of the helical coils are considered. The calculations show that the shape of the spatial distribution of the molecular density differs substantially from the shape of the magnetic surfaces.

  14. Self-driving carsickness.

    PubMed

    Diels, Cyriel; Bos, Jelte E

    2016-03-01

    This paper discusses the predicted increase in the occurrence and severity of motion sickness in self-driving cars. Self-driving cars have the potential to lead to significant benefits. From the driver's perspective, the direct benefits of this technology are considered increased comfort and productivity. However, we here show that the envisaged scenarios all lead to an increased risk of motion sickness. As such, the benefits this technology is assumed to bring may not be capitalised on, in particular by those already susceptible to motion sickness. This can negatively affect user acceptance and uptake and, in turn, limit the potential socioeconomic benefits that this emerging technology may provide. Following a discussion on the causes of motion sickness in the context of self-driving cars, we present guidelines to steer the design and development of automated vehicle technologies. The aim is to limit or avoid the impact of motion sickness and ultimately promote the uptake of self-driving cars. Attention is also given to less well known consequences of motion sickness, in particular negative aftereffects such as postural instability, and detrimental effects on task performance and how this may impact the use and design of self-driving cars. We conclude that basic perceptual mechanisms need to be considered in the design process whereby self-driving cars cannot simply be thought of as living rooms, offices, or entertainment venues on wheels. PMID:26446454

  15. Parkinson disease and driving

    PubMed Central

    Classen, Sherrilene; Uc, Ergun Y.

    2012-01-01

    ABSTRACT The growing literature on driving in Parkinson disease (PD) has shown that driving is impaired in PD compared to healthy comparison drivers. PD is a complex neurodegenerative disorder leading to motor, cognitive, and visual impairments, all of which can affect fitness to drive. In this review, we examined studies of driving performance (on-road tests and simulators) in PD for outcome measures and their predictors. We searched through various databases and found 25 (of 99) primary studies, all published in English. Using the American Academy of Neurology criteria, a study class of evidence was assigned (I–IV, I indicating the highest level of evidence) and recommendations were made (Level A: predictive or not; B: probably predictive or not; C: possibly predictive or not; U: no recommendations). From available Class II and III studies, we identified various cognitive, visual, and motor measures that met different levels of evidence (usually Level B or C) with respect to predicting on-road and simulated driving performance. Class I studies reporting Level A recommendations for definitive predictors of driving performance in drivers with PD are needed by policy makers and clinicians to develop evidence-based guidelines. PMID:23150533

  16. Hydraulic drive system prevents backlash

    NASA Technical Reports Server (NTRS)

    Acord, J. D.

    1965-01-01

    Hydraulic drive system uses a second drive motor operating at reduced torque. This exerts a relative braking action which eliminates the normal gear train backlash that is intolerable when driving certain heavy loads.

  17. Family Influences and Unconscious Drives.

    ERIC Educational Resources Information Center

    English, Fanita

    2001-01-01

    Drives for survival, expression, and quiescence influence early human development and continue to influence career development throughout life. Turmoil may arise when a drive conflicts with others or is suppressed by other drives. (SK)

  18. Young tectonics of a complex plate boundary zone: Indentation, rotation, and escape in Alaska

    NASA Astrophysics Data System (ADS)

    Wallace, W. K.; Ruppert, N. A.

    2012-12-01

    Convergence of thick crust of the Yakutat block with the southern margin of Alaska is widely recognized as a dominant influence on the tectonics of Alaska since at least late Miocene time. It is less clear how this convergence relates to the distribution, type, and orientation of geologic structures, and to the boundaries between the tectonic provinces that they define. We propose that convergence of Yakutat block includes two distinct components that influence deformation and topography in different ways: 1) The crust of the exposed, southern Yakutat block is too thick to subduct, which has caused the collisional St. Elias orogen. Detachment of the upper part of the mafic basement allows delamination and sinking of the remaining mafic crust and lithospheric mantle. The collisional orogen drives rigid counterclockwise rotation of the southern Alaska block south of the arcuate, right-lateral Denali fault. The western boundary of this block is a zone of distributed contraction in the western Alaska Range and Cook Inlet. 2) The northern part of the Yakutat block is thin enough to subduct but thick and buoyant enough to cause localized flat-slab subduction orthogonal to rotation of the southern Alaska block. Consequences include the gently antiformal Talkeetna Mountains that span the forearc basin, a gap in the magmatic arc, and a basement-involved fold-and-thrust belt in the northern Alaska Range. An arcuate oroclinal hinge from southern Alaska to the northeastern Brooks Range reflects indentation since at least Paleocene time. Traction above the subducted Yakutat block along the southern part of this hinge drives current indentation. North of the subducted Yakutat block, indentation is reflected by left-lateral block rotation that accommodates shortening between the Denali and Tintina faults and by contraction farther north along the northern edge of the arcuate northeastern Brooks Range. Western Alaska accommodates both northward indentation and westward convergence

  19. Review of the experimental papers at the IAEA conference on noninductive current drive, Culham, 1983

    SciTech Connect

    Motley, R.W.

    1983-10-01

    Three types of noninductive current drive experiments have been reported at this conference: (1) neutral beam (2) rf current drive, and (3) relativistic electron beams (REB). If we compare the effort to develop current drive to a horse race, the neutral beam horse was first out of the gates, but it quickly found greener pastures (heating) and has dropped temporarily out of the race. The lower hybrid horse now has a big lead at the first furlong (200 m), but the bulk of the race remains to be run. The fast wave and REB horses have yet to get up speed.

  20. Neutral Buoyancy Simulator (NBS)

    NASA Technical Reports Server (NTRS)

    1972-01-01

    This is a cutaway illustration of the Neutral Buoyancy Simulator (NBS) at the Marshall Space Flight Center (MSFC ). The MSFC NBS provided an excellent environment for testing hardware to examine how it would operate in space and for evaluating techniques for space construction and spacecraft servicing. Here, engineers, designers, and astronauts performed various tests to develop basic concepts, preliminary designs, final designs, and crew procedures. The NBS was constructed of welded steel with polyester-resin coating. The water tank was 75-feet (22.9- meters) in diameter, 40-feet (12.2-meters) deep, and held 1.32 million gallons of water. Since it opened for operation in 1968, the NBS had supported a number of successful space missions, such as the Skylab, Solar Maximum Mission Satellite, Marned Maneuvering Unit, Experimental Assembly of Structures in Extravehicular Activity/Assembly Concept for Construction of Erectable Space Structures (EASE/ACCESS), the Hubble Space Telescope, and the Space Station. The function of the MSFC NBS was moved to the larger simulator at the Johnson Space Center and is no longer operational.