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.

Construction of a hepatitis B virus neutralizing chimeric monoclonal antibody recognizing escape mutants of the viral surface antigen (HBsAg).

PubMed

Golsaz-Shirazi, Forough; Amiri, Mohammad Mehdi; Farid, Samira; Bahadori, Motahareh; Bohne, Felix; Altstetter, Sebastian; Wolff, Lisa; Kazemi, Tohid; Khoshnoodi, Jalal; Hojjat-Farsangi, Mohammad; Chudy, Michael; Jeddi-Tehrani, Mahmood; Protzer, Ulrike; Shokri, Fazel

2017-08-01

Hepatitis B virus (HBV) infection is a global burden on the health-care system and is considered as the tenth leading cause of death in the world. Over 248 million patients are currently suffering from chronic HBV infection worldwide and annual mortality rate of this infection is 686000. The "a" determinant is a hydrophilic region present in all antigenic subtypes of hepatitis B surface antigen (HBsAg), and antibodies against this region can neutralize the virus and are protective against all subtypes. We have recently generated a murine anti-HBs monoclonal antibody (4G4), which can neutralize HBV infection in HepaRG cells and recognize most of the escape mutant forms of HBsAg. Here, we describe the production and characterization of the chimeric human-murine antibody 4G4 (c-4G4). Variable region genes of heavy and light chains of the m-4G4 were cloned and fused to constant regions of human kappa and IgG1 by splice overlap extension (SOE) PCR. The chimeric antibody was expressed in Chinese Hamster Ovary (CHO)-K1 cells and purified from culture supernatant. Competition ELISA proved that both antibodies bind the same epitope within HBsAg. Antigen-binding studies using ELISA and Western blot showed that c-4G4 has retained the affinity and specificity of the parental murine antibody, and displayed a similar pattern of reactivity to 13 escape mutant forms of HBsAg. Both, the parental and c-4G4 showed a comparably high HBV neutralization capacity in cell culture even at the lowest concentration (0.6μg/ml). Due to the ability of c-4G4 to recognize most of the sub-genotypes and escape mutants of HBsAg, this antibody either alone or in combination with other anti-HBs antibodies could be considered as a potent alternative for Hepatitis B immune globulin (HBIG) as an HBV infection prophylactic or for passive immunotherapy against HBV infection. Copyright © 2017 Elsevier B.V. All rights reserved.

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

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.

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.

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.

Dependence of Photochemical Escape of Oxygen at Mars on Solar Radiation and Solar Wind Interaction

NASA Astrophysics Data System (ADS)

Cravens, T.; Rahmati, A.; Lillis, R. J.; Fox, J. L.; Bougher, S. W.; Jakosky, B. M.

2016-12-01

The evolution of the atmosphere of Mars and the loss of volatiles over the life of the solar system is a key topic in planetary science. An important loss process in the ionosphere is photochemical escape. In particular, dissociative recombination of O2+ ions (the major ion species) produces fast oxygen atoms, some of which can escape from the planet. Several theoretical models have been constructed over the years to study hot oxygen and its escape from Mars. These model have a number of uncertainties, particularly for the elastic cross sections of O collisions with target neutral species. Recently, the Mars Atmosphere and Volatile Evolution Mission (MAVEN) mission has been rapidly improving our understanding of the upper atmosphere and ionosphere of Mars and its interaction with the external environment (e.g., the solar wind). The purpose of the current paper is to take a simple analytical approach to the oxygen escape problem in order to: (1) study the role that solar flux and solar wind variations have on escape and (2) isolate the effects of uncertainties in oxygen cross sections on the derived oxygen escape rates. Not surprisingly, we find, in agreement with more elaborate numerical models, that the escape flux is directly proportional to the incident solar extreme ultraviolet irradiance and is inversely proportional to the backscatter elastic cross section. The role for atmospheric loss that ion transport plays in the topside ionosphere and how the solar wind interaction drives this will also be discussed.

Substitution at aspartic acid 1128 in the SARS coronavirus spike glycoprotein mediates escape from a S2 domain-targeting neutralizing monoclonal antibody.

PubMed

Ng, Oi-Wing; Keng, Choong-Tat; Leung, Cynthia Sau-Wai; Peiris, J S Malik; Poon, Leo Lit Man; Tan, Yee-Joo

2014-01-01

The Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) is the etiological agent for the infectious disease, SARS, which first emerged 10 years ago. SARS-CoV is a zoonotic virus that has crossed the species barriers to infect humans. Bats, which harbour a diverse pool of SARS-like CoVs (SL-CoVs), are believed to be the natural reservoir. The SARS-CoV surface Spike (S) protein is a major antigenic determinant in eliciting neutralizing antibody production during SARS-CoV infection. In our previous work, we showed that a panel of murine monoclonal antibodies (mAbs) that target the S2 subunit of the S protein are capable of neutralizing SARS-CoV infection in vitro (Lip KM et al, J Virol. 2006 Jan; 80(2): 941-50). In this study, we report our findings on the characterization of one of these mAbs, known as 1A9, which binds to the S protein at a novel epitope within the S2 subunit at amino acids 1111-1130. MAb 1A9 is a broadly neutralizing mAb that prevents viral entry mediated by the S proteins of human and civet SARS-CoVs as well as bat SL-CoVs. By generating mutant SARS-CoV that escapes the neutralization by mAb 1A9, the residue D1128 in S was found to be crucial for its interaction with mAb 1A9. S protein containing the substitution of D1128 with alanine (D1128A) exhibited a significant decrease in binding capability to mAb 1A9 compared to wild-type S protein. By using a pseudotyped viral entry assay, it was shown that the D1128A substitution in the escape virus allows it to overcome the viral entry blockage by mAb 1A9. In addition, the D1128A mutation was found to exert no effects on the S protein cell surface expression and incorporation into virion particles, suggesting that the escape virus retains the same viral entry property as the wild-type virus.

Longitudinal Analysis of Early HIV-1-Specific Neutralizing Activity in an Elite Neutralizer and in Five Patients Who Developed Cross-Reactive Neutralizing Activity

PubMed Central

Euler, Zelda; van den Kerkhof, Tom L. G. M.; van Gils, Marit J.; Burger, Judith A.; Edo-Matas, Diana; Phung, Pham; Wrin, Terri

2012-01-01

We previously established that at 3 years postseroconversion, ∼30% of HIV-infected individuals have cross-reactive neutralizing activity (CrNA) in their sera. Here we studied the kinetics with which CrNA develops and how these relate to the development of autologous neutralizing activity as well as viral escape and diversification. For this purpose, sera from five individuals with CrNA and one elite neutralizer that were obtained at three monthly intervals in the first year after seroconversion and at multiple intervals over the disease course were tested for neutralizing activity against an established multiclade panel of six viruses. The same serum samples, as well as sera from three individuals who lacked CrNA, were tested for their neutralizing activities against autologous clonal HIV-1 variants from multiple time points covering the disease course from seroconversion onward. The elite neutralizer already had CrNA at 9.8 months postseroconversion, in contrast with the findings for the other five patients, in whom CrNA was first detected at 20 to 35 months postseroconversion and peaked around 35 months postseroconversion. In all patients, CrNA coincided with neutralizing activity against autologous viruses that were isolated <12 months postseroconversion, while viruses from later time points had already escaped autologous neutralizing activity. Also, the peak in gp160 sequence diversity coincided with the peak of CrNA titers. Individuals who lacked CrNA had lower peak autologous neutralizing titers, viral escape, and sequence diversity than individuals with CrNA. A better understanding of the underlying factors that determine the presence of CrNA or even an elite neutralizer phenotype may aid in the design of an HIV-1 vaccine. PMID:22156522

Increased Antibody Affinity Confers Broad In Vitro Protection against Escape Mutants of Severe Acute Respiratory Syndrome Coronavirus

PubMed Central

Rani, Mridula; Bolles, Meagan; Donaldson, Eric F.; Van Blarcom, Thomas; Baric, Ralph; Iverson, Brent

2012-01-01

Even though the effect of antibody affinity on neutralization potency is well documented, surprisingly, its impact on neutralization breadth and escape has not been systematically determined. Here, random mutagenesis and DNA shuffling of the single-chain variable fragment of the neutralizing antibody 80R followed by bacterial display screening using anchored periplasmic expression (APEx) were used to generate a number of higher-affinity variants of the severe acute respiratory syndrome coronavirus (SARS-CoV)-neutralizing antibody 80R with equilibrium dissociation constants (KD) as low as 37 pM, a >270-fold improvement relative to that of the parental 80R single-chain variable fragment (scFv). As expected, antigen affinity was shown to correlate directly with neutralization potency toward the icUrbani strain of SARS-CoV. Additionally, the highest-affinity antibody fragment displayed 10-fold-increased broad neutralization in vitro and completely protected against several SARS-CoV strains containing substitutions associated with antibody escape. Importantly, higher affinity also led to the suppression of viral escape mutants in vitro. Escape from the highest-affinity variant required reduced selective pressure and multiple substitutions in the binding epitope. Collectively, these results support the hypothesis that engineered antibodies with picomolar dissociation constants for a neutralizing epitope can confer escape-resistant protection. PMID:22696652

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.

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

Emergent neutrality drives phytoplankton species coexistence

PubMed Central

Segura, Angel M.; Calliari, Danilo; Kruk, Carla; Conde, Daniel; Bonilla, Sylvia; Fort, Hugo

2011-01-01

The mechanisms that drive species coexistence and community dynamics have long puzzled ecologists. Here, we explain species coexistence, size structure and diversity patterns in a phytoplankton community using a combination of four fundamental factors: organism traits, size-based constraints, hydrology and species competition. Using a ‘microscopic’ Lotka–Volterra competition (MLVC) model (i.e. with explicit recipes to compute its parameters), we provide a mechanistic explanation of species coexistence along a niche axis (i.e. organismic volume). We based our model on empirically measured quantities, minimal ecological assumptions and stochastic processes. In nature, we found aggregated patterns of species biovolume (i.e. clumps) along the volume axis and a peak in species richness. Both patterns were reproduced by the MLVC model. Observed clumps corresponded to niche zones (volumes) where species fitness was highest, or where fitness was equal among competing species. The latter implies the action of equalizing processes, which would suggest emergent neutrality as a plausible mechanism to explain community patterns. PMID:21177680

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].

Structural Basis for Escape of Human Astrovirus from Antibody Neutralization: Broad Implications for Rational Vaccine Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogdanoff, Walter A.; Perez, Edmundo I.; López, Tomás

induces a structural change in a loop that is responsible for antibody binding. Our findings reveal how viruses can escape antibody neutralization and provide insight for the rational design of vaccines to elicit diverse antibodies that provide broader protection from infection.« less

Neutral escape at Mars induced by the precipitation of high-energy protons and hydrogen atoms of the solar wind origin

NASA Astrophysics Data System (ADS)

Shematovich, Valery I.

2017-04-01

One of the first surprises of the NASA MAVEN mission was the observation by the SWIA instrument of a tenuous population of protons with solar wind energies travelling anti-sunward near periapsis, at altitudes of 150-250 km (Halekas et al., 2015). While the penetration of solar wind protons to low altitude is not completely unexpected given previous Mars Express results, this population maintains exactly the same velocity as the solar wind observed. From previous studies it was known that some fraction of the solar wind can interact with the extended corona of Mars. By charge exchange with the neutral particles in this corona, some fraction of the incoming solar wind protons can gain an electron and become an energetic neutral hydrogen atom. Once neutral, these particles penetrate through the Martian induced magnetosphere with ease, with free access to the collisional atmosphere/ionosphere. The origin, kinetics and transport of the suprathermal O atoms in the transition region (from thermosphere to exosphere) of the Martian upper atmosphere due to the precipitation of the high-energy protons and hydrogen atoms are discussed. Kinetic energy distribution functions of suprathermal and superthermal (ENA) oxygen atoms formed in the Martian upper atmosphere were calculated using the kinetic Monte Carlo model (Shematovich et al., 2011, Shematovich, 2013) of the high-energy proton and hydrogen atom precipitation into the atmosphere. These functions allowed us: (a) to estimate the non-thermal escape rates of neutral oxygen from the Martian upper atmosphere, and (b) to compare with available MAVEN measurements of oxygen corona. Induced by precipitation the escape of hot oxygen atoms may become dominant under conditions of extreme solar events - solar flares and coronal mass ejections, - as it was shown by recent observations of the NASA MAVEN spacecraft (Jakosky et al., 2015). This work is supported by the RFBR project and by the Basic Research Program of the Praesidium of

Modulation of terrestrial ion escape flux composition /by low-altitude acceleration and charge exchange chemistry/

NASA Technical Reports Server (NTRS)

Moore, T. E.

1980-01-01

Motivated by recent observations of highly variable hot plasma composition in the magnetosphere, control of the ionospheric escape flux composition by low-altitude particle dynamics and ion chemistry has been investigated for an e(-), H(+), O(+) ionosphere. It is found that the fraction of the steady state escape flux which is O(+) can be controlled very sensitively by the occurrence of parallel or transverse ion acceleration at altitudes below the altitude where the neutral oxygen density falls rapidly below the neutral hydrogen density and the ionospheric source of O(+) tends to be rapidly converted by charge exchange to H(+). The acceleration is required both to overcome the gravitational confinement of O(+) and to violate charge exchange equilibrium so that the neutral hydrogen atmosphere appears 'optically' thin to escaping O(+). Constraints are placed on the acceleration processes, and it is shown that O(+) escape is facilitated by observed ionospheric responses to magnetic activity.

Near-horizon Structure of Escape Zones of Electrically Charged Particles around Weakly Magnetized Rotating Black Hole

NASA Astrophysics Data System (ADS)

Kopáček, Ondřej; Karas, Vladimír

2018-01-01

An interplay of magnetic fields and gravitation drives accretion and outflows near black holes. However, a specific mechanism is still a matter of debate; it is very likely that different processes dominate under various conditions. In particular, for the acceleration of particles and their collimation in jets, an ordered component of the magnetic field seems to be essential. Here we discuss the role of large-scale magnetic fields in transporting the charged particles and dust grains from the bound orbits in the equatorial plane of a rotating (Kerr) black hole and the resulting acceleration along trajectories escaping the system in a direction parallel to the symmetry axis (perpendicular to the accretion disk). We consider a specific scenario of destabilization of circular geodesics of initially neutral matter by charging (e.g., due to photoionization). Some particles may be set on escaping trajectories and attain relativistic velocity. The case of charged particles differs from charged dust grains by their charge-to-mass ratio, but the acceleration mechanism operates in a similar manner. It appears that the chaotic dynamics controls the outflow and supports the formation of near-horizon escape zones. We employ the technique of recurrence plots to characterize the onset of chaos in the outflowing medium. We investigate the system numerically and construct the basin-boundary plots, which show the location and the extent of the escape zones. The effects of black hole spin and magnetic field strength on the formation and location of escape zones are discussed, and the maximal escape velocity is computed.

Probing the Martian Exosphere and Neutral Escape Using Pickup Ions Measured by MAVEN

NASA Astrophysics Data System (ADS)

Rahmati, A.; Larson, D. E.; Cravens, T.; Halekas, J. S.; Lillis, R. J.; McFadden, J. P.; Mitchell, D. L.; Thiemann, E.; Connerney, J. E. P.; Dunn, P.; DiBraccio, G. A.; Espley, J. R.; Eparvier, F. G.; Jakosky, B. M.

2016-12-01

Soon after the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft started orbiting Mars in September 2014, the SEP (Solar Energetic Particle), SWIA (Solar Wind Ion Analyzer), and STATIC (Supra-Thermal and Thermal Ion Composition) instruments onboard the spacecraft started detecting planetary pickup ions. SEP can measure energetic (>50 keV) oxygen pickup ions, the source of which is the extended hot oxygen exosphere of Mars. Model results show that these pickup ions originate from tens of Martian radii upstream of Mars and are energized by the solar wind motional electric field as they gyrate back towards Mars. SEP is blind to pickup hydrogen, as the low energy threshold for detection of hydrogen in SEP is 20 keV; well above the maximum pickup hydrogen energy, which is four times the solar wind proton energy. SWIA and STATIC, on the other hand, can detect both pickup oxygen and pickup hydrogen with energies below 30 keV and created closer to Mars. During the times when MAVEN is outside the Martian bow shock and in the upstream undisturbed solar wind, the solar wind velocity measured by SWIA and the solar wind (or interplanetary) magnetic field measured by the MAG (magnetometer) instrument can be used to model pickup oxygen and hydrogen fluxes near Mars. Solar wind flux measurements of the SWIA instrument are used in calculating charge-exchange frequencies, and data from the EUVM (Extreme Ultraviolet Monitor) and SWEA (Solar Wind Electron Analyzer) instruments are also used in calculating photo-ionization and electron impact frequencies of neutral species in the Martian exosphere. By comparing SEP, SWIA, and STATIC measured pickup ion fluxes with model results, the Martian thermal hydrogen and hot oxygen neutral densities can be probed outside the bow shock, which would place constraints on estimates of oxygen and hydrogen neutral escape rates. We will present model-data comparisons of pickup ions measured outside the Martian bow shock. Our analysis reveals an

Photochemical escape of oxygen from Mars: constraints from MAVEN in situ measurements

NASA Astrophysics Data System (ADS)

Lillis, R. J.; Deighan, J.; Fox, J. L.; Bougher, S. W.; Lee, Y.; Cravens, T.; Rahmati, A.; Mahaffy, P. R.; Andersson, L.; Combi, M. R.; Benna, M.; Jakosky, B. M.; Gröller, H.

2016-12-01

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. Photochemical escape of oxygen is expected to be a significant channel for atmospheric loss, particularly in the early solar system when extreme ultraviolet (EUV) fluxes were much higher. We use near-periapsis (<400 km altitude) data from three 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 a series of calculations, each as a function of altitude. The first uses electron and ion temperatures to calculate the probability distribution for initial energies of hot O atoms. The second calculates the probability that a hot atom born at that altitude will escape. The third takes calculates the production rate of the 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. We integrate with respect to altitude to give us the escape flux of hot oxygen atoms for that periapsis pass. We will present escape fluxes and derived escape rates from the first Mars year of data collected. Total photochemical loss over time is not very useful to calculate from such escape fluxes derived from current conditions because a thicker atmosphere and much higher solar EUV in the past may change the dynamics of escape dramatically. In the future, we intend to use 3-D Monte Carlo models of global atmospheric escape, in concert with our in situ and remote measurements, to fully characterize photochemical escape under current conditions and carefully extrapolate back in time using further simulations with new boundary conditions.

Effects of MHD instabilities on neutral beam current drive

NASA Astrophysics Data System (ADS)

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

2015-05-01

Neutral beam injection (NBI) is 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. 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. A 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. Implications for fast ion transport modeling in integrated tokamak simulations are briefly discussed.

Triton: topside ionosphere and nitrogen escape.

PubMed

Yung, Y L; Lyons, J R

1990-09-01

The principal ion in the ionosphere of Triton is N+. Energetic electrons of magnetospheric origin are the primary source of ionization, with a smaller contribution due to photoionization. To explain the topside plasma scale height, we postulate that N+ ions escape from Triton. The loss rate is 3.4 x 10(7) cm-2 s-1 or 7.9 x 10(24) ions s-1. Dissociative recombination of N2+ produces neutral exothermic fragments that can escape from Triton. The rate is estimated to be 8.6 x 10(6) N cm-2 s-1 or 2.0 x 10(24) atoms s-1. Implications for the magnetosphere of Neptune and Triton's evolution are discussed.

Applying antibody-sensitive hypervariable region 1-deleted hepatitis C virus to the study of escape pathways of neutralizing human monoclonal antibody AR5A

PubMed Central

Velázquez-Moctezuma, Rodrigo; Bukh, Jens

2017-01-01

Hepatitis C virus (HCV) is a major cause of end-stage liver diseases. With 3–4 million new HCV infections yearly, a vaccine is urgently needed. A better understanding of virus escape from neutralizing antibodies and their corresponding epitopes are important for this effort. However, for viral isolates with high antibody resistance, or antibodies with moderate potency, it remains challenging to induce escape mutations in vitro. Here, as proof-of-concept, we used antibody-sensitive HVR1-deleted (ΔHVR1) viruses to generate escape mutants for a human monoclonal antibody, AR5A, targeting a rare cross-genotype conserved epitope. By analyzing the genotype 1a envelope proteins (E1/E2) of recovered Core-NS2 recombinant H77/JFH1ΔHVR1 and performing reverse genetic studies we found that resistance to AR5A was caused by substitution L665W, also conferring resistance to the parental H77/JFH1. The mutation did not induce viral fitness loss, but abrogated AR5A binding to HCV particles and intracellular E1/E2 complexes. Culturing J6/JFH1ΔHVR1 (genotype 2a), for which fitness was decreased by L665W, with AR5A generated AR5A-resistant viruses with the substitutions I345V, L665S, and S680T, which we introduced into J6/JFH1 and J6/JFH1ΔHVR1. I345V increased fitness but had no effect on AR5A resistance. L665S impaired fitness and decreased AR5A sensitivity, while S680T combined with L665S compensated for fitness loss and decreased AR5A sensitivity even further. Interestingly, S680T alone had no fitness effect but sensitized the virus to AR5A. Of note, H77/JFH1L665S was non-viable. The resistance mutations did not affect cell-to-cell spread or E1/E2 interactions. Finally, introducing L665W, identified in genotype 1, into genotypes 2–6 parental and HVR1-deleted variants (not available for genotype 4a) we observed diverse effects on viral fitness and a universally pronounced reduction in AR5A sensitivity. Thus, we were able to take advantage of the neutralization-sensitive HVR1

Effects of MHD instabilities on neutral beam current drive

DOE PAGES

Podestà, M.; Gorelenkova, M.; Darrow, D. S.; ...

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

European SpaceCraft for the study of Atmospheric Particle Escape (ESCAPE): a planetary mission to Earth, proposed in response to the ESA M5-call

NASA Astrophysics Data System (ADS)

Dandouras, I.; Yamauchi, M.; Rème, H.; De Keyser, J.; Marghitu, O.; Fazakerley, A.; Grison, B.; Kistler, L.; Milillo, A.; Nakamura, R.; Paschalidis, N.; Paschalis, A.; Pinçon, J.-L.; Sakanoi, T.; Wieser, M.; Wurz, P.; Yoshikawa, I.; Häggström, I.; Liemohn, M.; Tian, F.

2017-09-01

ESCAPE is a mission proposed in response to the ESA-M5 call that will quantitatively estimate the amount of escaping particles of the major atmospheric components (nitrogen and oxygen), as neutral and ionised species, escaping from the Earth as a magnetised planet. The goal is to understand the importance of each escape mechanism, its dependence on solar and geomagnetic activity, and to infer the history of the Earth's atmospheric composition over a long (geological scale) time period. 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. The result will be used as a reference to understand the atmospheric/ionospheric evolution of magnetised planets, which is essential for habitability.

Enhanced Endosomal Escape by Light-Fueled Liquid-Metal Transformer.

PubMed

Lu, Yue; Lin, Yiliang; Chen, Zhaowei; Hu, Quanyin; Liu, Yang; Yu, Shuangjiang; Gao, Wei; Dickey, Michael D; Gu, Zhen

2017-04-12

Effective endosomal escape remains as the "holy grail" for endocytosis-based intracellular drug delivery. To date, most of the endosomal escape strategies rely on small molecules, cationic polymers, or pore-forming proteins, which are often limited by the systemic toxicity and lack of specificity. We describe here a light-fueled liquid-metal transformer for effective endosomal escape-facilitated cargo delivery via a chemical-mechanical process. The nanoscale transformer can be prepared by a simple approach of sonicating a low-toxicity liquid-metal. When coated with graphene quantum dots (GQDs), the resulting nanospheres demonstrate the ability to absorb and convert photoenergy to drive the simultaneous phase separation and morphological transformation of the inner liquid-metal core. The morphological transformation from nanospheres to hollow nanorods with a remarkable change of aspect ratio can physically disrupt the endosomal membrane to promote endosomal escape of payloads. This metal-based nanotransformer equipped with GQDs provides a new strategy for facilitating effective endosomal escape to achieve spatiotemporally controlled drug delivery with enhanced efficacy.

Antibody neutralization of retargeted measles viruses

PubMed Central

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

2014-01-01

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

Stabilizing effect of driving and dissipation on quantum metastable states

NASA Astrophysics Data System (ADS)

Valenti, Davide; Carollo, Angelo; Spagnolo, Bernardo

2018-04-01

We investigate how the combined effects of strong Ohmic dissipation and monochromatic driving affect the stability of a quantum system with a metastable state. We find that, by increasing the coupling with the environment, the escape time makes a transition from a regime in which it is substantially controlled by the driving, displaying resonant peaks and dips, to a regime of frequency-independent escape time with a peak followed by a steep falloff. The escape time from the metastable state has a nonmonotonic behavior as a function of the thermal-bath coupling, the temperature, and the frequency of the driving. The quantum noise-enhanced stability phenomenon is observed in the investigated system.

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. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Fitness-Balanced Escape Determines Resolution of Dynamic Founder Virus Escape Processes in HIV-1 Infection

PubMed Central

Sunshine, Justine E.; Larsen, Brendan B.; Maust, Brandon; Casey, Ellie; Deng, Wenje; Chen, Lennie; Westfall, Dylan H.; Kim, Moon; Zhao, Hong; Ghorai, Suvankar; Lanxon-Cookson, Erinn; Rolland, Morgane; Collier, Ann C.; Maenza, Janine; Mullins, James I.

2015-01-01

ABSTRACT To understand the interplay between host cytotoxic T-lymphocyte (CTL) responses and the mechanisms by which HIV-1 evades them, we studied viral evolutionary patterns associated with host CTL responses in six linked transmission pairs. HIV-1 sequences corresponding to full-length p17 and p24 gag were generated by 454 pyrosequencing for all pairs near the time of transmission, and seroconverting partners were followed for a median of 847 days postinfection. T-cell responses were screened by gamma interferon/interleukin-2 (IFN-γ/IL-2) FluoroSpot using autologous peptide sets reflecting any Gag variant present in at least 5% of sequence reads in the individual's viral population. While we found little evidence for the occurrence of CTL reversions, CTL escape processes were found to be highly dynamic, with multiple epitope variants emerging simultaneously. We found a correlation between epitope entropy and the number of epitope variants per response (r = 0.43; P = 0.05). In cases in which multiple escape mutations developed within a targeted epitope, a variant with no fitness cost became fixed in the viral population. When multiple mutations within an epitope achieved fitness-balanced escape, these escape mutants were each maintained in the viral population. Additional mutations found to confer escape but undetected in viral populations incurred high fitness costs, suggesting that functional constraints limit the available sites tolerable to escape mutations. These results further our understanding of the impact of CTL escape and reversion from the founder virus in HIV infection and contribute to the identification of immunogenic Gag regions most vulnerable to a targeted T-cell attack. IMPORTANCE Rapid diversification of the viral population is a hallmark of HIV-1 infection, and understanding the selective forces driving the emergence of viral variants can provide critical insight into the interplay between host immune responses and viral evolution. We used

European SpaceCraft for the study of Atmospheric Particle Escape (ESCAPE): a mission proposed in response to the ESA M5-call

NASA Astrophysics Data System (ADS)

Dandouras, Iannis; Yamauchi, Masatoshi; Rème, Henri; De Keyser, Johan; Marghitu, Octav; Fazakerley, Andrew; Grison, Benjamin; Kistler, Lynn; Milillo, Anna; Nakamura, Rumi; Paschalidis, Nikolaos; Paschalis, Antonis; Pinçon, Jean-Louis; Sakanoi, Takeshi; Wieser, Martin; Wurz, Peter; Yoshikawa, Ichiro; Häggström, Ingemar; Liemohn, Mike; Tian, Feng

2017-04-01

ESCAPE is a mission proposed in response to the ESA-M5 call that will quantitatively estimate the amount of escaping particles of the major atmospheric components (nitrogen and oxygen), as neutral and ionised species, escaping from the Earth as a magnetised planet. The spatial distribution and temporal variability of the flux of these species and their isotopic composition will be for the first time systematically investigated in an extended altitude range, from the exobase/upper ionosphere (500 km altitude) up to the magnetosphere. The goal is to understand the importance of each escape mechanism, its dependence on solar and geomagnetic activity, and to infer the history of the Earth's atmosphere over a long (geological scale) time period. 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. The result will be used as a reference to understand the atmospheric/ionospheric evolution of magnetised planets. To achieve this goal, a slowly spinning spacecraft is proposed equipped with a suite of instruments developed and supplied by an international consortium. These instruments will detect the upper atmosphere and magnetosphere escaping populations by a combination of in-situ measurements and of remote-sensing observations.

Non-thermal escape rates of atmospheric H and D from Mars using MAVEN data

NASA Astrophysics Data System (ADS)

Gacesa, M.; Zahnle, K. J.

2017-12-01

Geological evidence suggests that an ocean of liquid water existed on Mars until at least middle to late Noachian era (4.1 to 3.8 Ga) and possibly, at least episodically, as late as Hesperian. Between 67% and 87% of the total primordial amount of water, equal to about 70 to 110 meters equivalent (spread over the entire Mars' surface), is believed to have escape to space, while about 35 meters remains on or beneath the surface as water ice. Establishing better constraints on these numbers and identifying the responsible atmospheric loss processes remains the major objective of NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. The ratio of atmospheric Deuterium and Hydrogen (D/H) on Mars is one of the best indicators of water loss to space. While majority of H and D escape through thermal Jeans escape, up to 10% of D can escape to space via non-thermal mechanisms, such as collisions with superthermal neutral atoms. In this study, we present new estimates of non-thermal escape rates of light molecules of interest to the water evolution, including H2, HD, OH, and OD, based on recent measurements of atmospheric density and temperature profiles by MAVEN. The escape mechanisms considered include photochemical sources of hot O, as well as collisions with energetic neutral atoms produced in charge-exchange of solar wind ions with atmospheric gases1,2. Energy transport and escape rates are modeled using quantum reactive scattering formalism3 and seasonal variations are illustrated. Finally, a simple estimate of the role of the non-thermal escape mechanisms in previous eras is given. We conclude that D escape rates can be affected by the non-thermal processes with consequences on the estimates of primordial water inventory based on the D/H ratio. [1] N. Lewkow and V. Kharchenko, Astroph. J., 790, 98 (2014) [2] M. Gacesa, N. Lewkow, V. Kharchenko, Icarus 284, 90 (2017) [3] M. Gacesa and V. Kharchenko, Geophys. Res. Lett., 39, L10203 (2012)

In vivo emergence of HIV-1 highly sensitive to neutralizing antibodies.

PubMed

Aasa-Chapman, Marlén M I; Cheney, Kelly M; Hué, Stéphane; Forsman, Anna; O'Farrell, Stephen; Pellegrino, Pierre; Williams, Ian; McKnight, Áine

2011-01-01

The rapid and continual viral escape from neutralizing antibodies is well documented in HIV-1 infection. Here we report in vivo emergence of viruses with heightened sensitivity to neutralizing antibodies, sometimes paralleling the development of neutralization escape. Sequential viral envs were amplified from seven HIV-1 infected men monitored from seroconversion up to 5 years after infection. Env-recombinant infectious molecular clones were generated and tested for coreceptor use, macrophage tropism and neutralization sensitivity to homologous and heterologous serum, soluble CD4 and monoclonal antibodies IgG1b12, 2G12 and 17b. We found that HIV-1 evolves sensitivity to contemporaneous neutralizing antibodies during infection. Neutralization sensitive viruses grow out even when potent autologous neutralizing antibodies are present in patient serum. Increased sensitivity to neutralization was associated with susceptibility of the CD4 binding site or epitopes induced after CD4 binding, and mediated by complex envelope determinants including V3 and V4 residues. The development of neutralization sensitive viruses occurred without clinical progression, coreceptor switch or change in tropism for primary macrophages. We propose that an interplay of selective forces for greater virus replication efficiency without the need to resist neutralizing antibodies in a compartment protected from immune surveillance may explain the temporal course described here for the in vivo emergence of HIV-1 isolates with high sensitivity to neutralizing antibodies.

Mars H Escape is potentially dominated by a high-altitude water source

NASA Astrophysics Data System (ADS)

Chaffin, Michael; Deighan, Justin; Schneider, Nick; Stewart, Ian

2017-04-01

H escape from the Mars atmosphere has removed a large part of Mars' initial water inventory. Until recently, this escape was thought to be slow and steady, sourced from long-lived molecular hydrogen whose lightness and volatility in comparison with water allow it to penetrate the upper atmosphere. Contradicting this thinking, observations from the Hubble Space Telescope and Mars Express, as well as more recent MAVEN measurements, indicate that H escape varies by at least a factor of ten over the Mars year and is largest in Southern Summer near perihelion. At the largest rates, H escape exceeds the ability of molecular hydrogen to supply the escape fluxes observed. At the same time in Southern Summer, Mars Express solar occultations have shown unexpectedly large concentrations of water at high altitude, potentially providing a source of escaping H unaccounted for in standard models. Here we show via photochemical modeling that the presence of this high altitude water can partially explain the large escape rates observed in Southern Summer. We further show that this escaping H is not in immediate balance with O escape, and therefore that short-term atmospheric dynamics can drive long-term variations in the oxidation balance and volatile content of planetary atmospheres. Future simultaneous observations by MAVEN, Mars Express, and the Trace Gas Orbiter may provide a direct test of this mechanism.

The Escaping Upper Atmospheres of Hot Jupiters

NASA Astrophysics Data System (ADS)

Davidson, Eric; Jones, Gabrielle; Uribe, Ana; Carson, Joseph

2017-01-01

Hot Jupiters are massive gaseous planets which orbit closely to their parent star. The strong stellar irradiation at these small orbital separations causes the temperature of the upper atmosphere of the planet to rise. This can cause the planet's atmosphere to escape into space, creating an exoplanet outflow. We ascertained which factors determine the presence and structure of these outflows by creating one dimensional simulations of the density, pressure, velocity, optical depth, and neutral fraction of hot Jupiter atmospheres. This was done for planets of masses and radii ranging from 0.5-1.5 Mj and 0.5-1.5 Rj. We found the outflow rate to be highest for a planet of 0.5 Mj and 1.5 Rj at 5.3×10-14 Mj/Yr. We also found that the higher the escape velocity, the lower the chance of the planet having an outflow.

Neutral ISM, Ly α , and Lyman-continuum in the Nearby Starburst Haro 11

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivera-Thorsen, T. Emil; Östlin, Göran; Hayes, Matthew

2017-03-01

Star-forming galaxies are believed to be a major source of Lyman continuum (LyC) radiation responsible for reionizing the early universe. Direct observations of escaping ionizing radiation have however been sparse and with low escape fractions. In the local universe, only 10 emitters have been observed, with typical escape fractions of a few percent. The mechanisms regulating this escape need to be strongly evolving with redshift in order to account for the epoch of reionization. Gas content and star formation feedback are among the main suspects, known to both regulate neutral gas coverage and evolve with cosmic time. In this paper,more » we reanalyze Hubble Space Telescope ( HST )-Cosmic Origins Spectrograph (COS) spectrocopy of the first detected local LyC leaker, Haro 11. We examine the connection between LyC leakage and Ly α line shape, and feedback-influenced neutral interstellar medium (ISM) properties like kinematics and gas distribution. We discuss the two extremes of an optically thin, density bounded ISM and a riddled, optically thick, ionization bounded ISM, and how Haro 11 fits into theoretical predictions. We find that the most likely ISM model is a clumpy neutral medium embedded in a highly ionized medium with a combined covering fraction of unity and a residual neutral gas column density in the ionized medium high enough to be optically thick to Ly α , but low enough to be at least partly transparent to LyC and undetected in Si ii. This suggests that star formation feedback and galaxy-scale interaction events play a major role in opening passageways for ionizing radiation through the neutral medium.« less

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.

How single mutations affect viral escape from broad and narrow antibodies to H1 influenza hemagglutinin.

PubMed

Doud, Michael B; Lee, Juhye M; Bloom, Jesse D

2018-04-11

Influenza virus can escape most antibodies with single mutations. However, rare antibodies broadly neutralize many viral strains. It is unclear how easily influenza virus might escape such antibodies if there was strong pressure to do so. Here, we map all single amino-acid mutations that increase resistance to broad antibodies to H1 hemagglutinin. Our approach not only identifies antigenic mutations but also quantifies their effect sizes. All antibodies select mutations, but the effect sizes vary widely. The virus can escape a broad antibody to hemagglutinin's receptor-binding site the same way it escapes narrow strain-specific antibodies: via single mutations with huge effects. In contrast, broad antibodies to hemagglutinin's stalk only select mutations with small effects. Therefore, among the antibodies we examine, breadth is an imperfect indicator of the potential for viral escape via single mutations. Antibodies targeting the H1 hemagglutinin stalk are quantifiably harder to escape than the other antibodies tested here.

How does ionizing radiation escape from galaxies?

NASA Astrophysics Data System (ADS)

Orlitova, Ivana

2016-10-01

Search for sources that reionized the Universe from z 15 to z 6 is one of the main drivers of present-day astronomy. Low-mass star-forming galaxies are the most favoured sources of ionizing photons, but the searches of escaping Lyman continuum (LyC) have not been extremely successful. Our team has recently detected prominent LyC escape from five Green Pea galaxies at redshift 0.3, using the HST/COS spectrograph, which represents a significant breakthrough. We propose here to study the LyC escape of the strongest among these leakers, J1152, with spatial resolution. From the comparison of the ionizing and non-ionizing radiation maps, and surface brightness profiles, we will infer the major mode in which LyC is escaping: from the strongest starburst, from the galaxy edge, through a hole along our line-of-sight, through clumpy medium, or directly from all the production sites due to highly ionized medium in the entire galaxy. In parallel, we will test the predictive power of two highly debated indirect indicators of LyC leakage: the [OIII]5007/[OII]3727 ratio, and Lyman-alpha. We predict that their spatial distribution should closely follow that of the ionizing continuum if column densities of the neutral gas are low. This combined study, which relies on the HST unique capabilities, will bring crucial information on the structure of the leaking galaxies, provide constraints for hydrodynamic simulations, and will lead to efficient future searches for LyC leakers across a large range of redshifts.

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.

The Receptor-Binding Site of the Measles Virus Hemagglutinin Protein Itself Constitutes a Conserved Neutralizing Epitope

PubMed Central

Ohno, Shinji; Sakai, Kouji; Ito, Yuri; Fukuhara, Hideo; Komase, Katsuhiro; Brindley, Melinda A.; Rota, Paul A.; Plemper, Richard K.; Maenaka, Katsumi; Takeda, Makoto

2013-01-01

Here, we provide direct evidence that the receptor-binding site of measles virus (MV) hemagglutinin protein itself forms an effective conserved neutralizing epitope (CNE). Several receptor-interacting residues constitute the CNE. Thus, viral escape from neutralization has to be associated with loss of receptor-binding activity. Since interactions with both the signaling lymphocyte activation molecule (SLAM) and nectin4 are critical for MV pathogenesis, its escape, which results from loss of receptor-binding activity, should not occur in nature. PMID:23283964

Human Monoclonal Antibodies to a Novel Cluster of Conformational Epitopes on HCV E2 with Resistance to Neutralization Escape in a Genotype 2a Isolate

PubMed Central

Keck, Zhen-yong; Xia, Jinming; Wang, Yong; Wang, Wenyan; Krey, Thomas; Prentoe, Jannick; Carlsen, Thomas; Li, Angela Ying-Jian; Patel, Arvind H.; Lemon, Stanley M.; Bukh, Jens; Rey, Felix A.; Foung, Steven K. H.

2012-01-01

The majority of broadly neutralizing antibodies to hepatitis C virus (HCV) are against conformational epitopes on the E2 glycoprotein. Many of them recognize overlapping epitopes in a cluster, designated as antigenic domain B, that contains residues G530 and D535. To gain information on other regions that will be relevant for vaccine design, we employed yeast surface display of antibodies that bound to genotype 1a H77C E2 mutant proteins containing a substitution either at Y632A (to avoid selecting non-neutralizing antibodies) or D535A. A panel of nine human monoclonal antibodies (HMAbs) was isolated and designated as HC-84-related antibodies. Each HMAb neutralized cell culture infectious HCV (HCVcc) with genotypes 1–6 envelope proteins with varying profiles, and each inhibited E2 binding to the viral receptor CD81. Five of these antibodies neutralized representative genotypes 1–6 HCVcc. Epitope mapping identified a cluster of overlapping epitopes that included nine contact residues in two E2 regions encompassing aa418–446 and aa611–616. Effect on virus entry was measured using H77C HCV retroviral pseudoparticles, HCVpp, bearing an alanine substitution at each of the contact residues. Seven of ten mutant HCVpp showed over 90% reduction compared to wild-type HCVpp and two others showed approximately 80% reduction. Interestingly, four of these antibodies bound to a linear E2 synthetic peptide encompassing aa434–446. This region on E2 has been proposed to elicit non-neutralizing antibodies in humans that interfere with neutralizing antibodies directed at an adjacent E2 region from aa410–425. The isolation of four HC-84 HMAbs binding to the peptide, aa434–446, proves that some antibodies to this region are to highly conserved epitopes mediating broad virus neutralization. Indeed, when HCVcc were passaged in the presence of each of these antibodies, virus escape was not observed. Thus, the cluster of HC-84 epitopes, designated as antigenic domain D, is

Energetic neutral particles from Jupiter and Saturn

NASA Astrophysics Data System (ADS)

Cheng, A. F.

1986-04-01

The Voyager 1 spacecraft has detected energetic neutral particles escaping from the magnetospheres of Jupiter and Saturn. These energetic neutrals are created in charge exchange reactions between radiation belt ions and ambient atoms or molecules in the magnetosphere. If the Io torus is assumed to be the dominant Jovian source region for energetic neutrals, the Voyager observations can be used to infer upper limits to the average ion intensities there below about 200 keV. No readily interpretable in-situ measurements are available in the Io torus at these energies. The middle and outer Jovian magnetospheres may also be a significant source of energetic neutrals. At Saturn, the observed neutral particle count rates are too high to be explained by charge exchange between fast protons and H atoms of the Titan torus. Most of the energetic neutrals may be produced by charge exchanges between heavy ions and a neutral cloud containing H2O in Saturn's inner magnetosphere. If so, the Voyager measurements of energetic neutral fluxes would be the first detected emissions from this region of Saturn's magnetosphere.

Neutralization Escape Variants of Human Immunodeficiency Virus Type 1 Are Transmitted from Mother to Infant

PubMed Central

Wu, Xueling; Parast, Adam B.; Richardson, Barbra A.; Nduati, Ruth; John-Stewart, Grace; Mbori-Ngacha, Dorothy; Rainwater, Stephanie M. J.; Overbaugh, Julie

2006-01-01

Maternal passive immunity typically plays a critical role in protecting infants from new infections; however, the specific contribution of neutralizing antibodies in limiting mother-to-child transmission of human immunodeficiency virus type 1 is unclear. By examining cloned envelope variants from 12 transmission pairs, we found that vertically transmitted variants were more resistant to neutralization by maternal plasma than were maternal viral variants near the time of transmission. The vertically transmitted envelope variants were poorly neutralized by monoclonal antibodies biz, 2G12, 2F5, and 4E10 individually or in combination. Despite the fact that the infant viruses were among the most neutralization resistant in the mother, they had relatively few glycosylation sites. Moreover, the transmitted variants elicited de novo neutralizing antibodies in the infants, indicating that they were not inherently difficult to neutralize. The neutralization resistance of vertically transmitted viruses is in contrast to the relative neutralization sensitivity of viruses sexually transmitted within discordant couples, suggesting that the antigenic properties of viruses that are favored for transmission may differ depending upon mode of transmission. PMID:16378985

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

DOE PAGES

Moody, M.  Anthony; Gao, Feng; Gurley, Thaddeus  C.; ...

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

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

PubMed

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 HIV-1 envelope are frequently targeted by neutralizing antibodies (nAbs) in infected individuals. In chronic infection, HIV-1 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 V3 and 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. Copyright © 2015 Elsevier Inc. All rights reserved.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moody, M.  Anthony; Gao, Feng; Gurley, Thaddeus  C.

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

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).

THERMALLY DRIVEN ATMOSPHERIC ESCAPE: TRANSITION FROM HYDRODYNAMIC TO JEANS ESCAPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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}.more » 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.« less

Neutral ISM, Lyα, and Lyman-continuum in the Nearby Starburst Haro11

NASA Astrophysics Data System (ADS)

Rivera-Thorsen, T. Emil; Östlin, Göran; Hayes, Matthew; Puschnig, Johannes

2017-03-01

Star-forming galaxies are believed to be a major source of Lyman continuum (LyC) radiation responsible for reionizing the early universe. Direct observations of escaping ionizing radiation have however been sparse and with low escape fractions. In the local universe, only 10 emitters have been observed, with typical escape fractions of a few percent. The mechanisms regulating this escape need to be strongly evolving with redshift in order to account for the epoch of reionization. Gas content and star formation feedback are among the main suspects, known to both regulate neutral gas coverage and evolve with cosmic time. In this paper, we reanalyze Hubble Space Telescope (HST)-Cosmic Origins Spectrograph (COS) spectrocopy of the first detected local LyC leaker, Haro 11. We examine the connection between LyC leakage and Lyα line shape, and feedback-influenced neutral interstellar medium (ISM) properties like kinematics and gas distribution. We discuss the two extremes of an optically thin, density bounded ISM and a riddled, optically thick, ionization bounded ISM, and how Haro 11 fits into theoretical predictions. We find that the most likely ISM model is a clumpy neutral medium embedded in a highly ionized medium with a combined covering fraction of unity and a residual neutral gas column density in the ionized medium high enough to be optically thick to Lyα, but low enough to be at least partly transparent to LyC and undetected in Si II. This suggests that star formation feedback and galaxy-scale interaction events play a major role in opening passageways for ionizing radiation through the neutral medium. Based on observations with HST-COS, program GO 13017, obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and

Characterization of human monoclonal antibodies that neutralize multiple poliovirus serotypes.

PubMed

Puligedda, Rama Devudu; Kouiavskaia, Diana; Al-Saleem, Fetweh H; Kattala, Chandana Devi; Nabi, Usman; Yaqoob, Hamid; Bhagavathula, V Sandeep; Sharma, Rashmi; Chumakov, Konstantin; Dessain, Scott K

2017-10-04

Following the eradication of wild poliovirus (PV), achieving and maintaining a polio-free status will require eliminating potentially pathogenic PV strains derived from the oral attenuated vaccine. For this purpose, a combination of non-cross-resistant drugs, such as small molecules and neutralizing monoclonal antibodies (mAbs), may be ideal. We previously isolated chimpanzee and human mAbs capable of neutralizing multiple PV types (cross-neutralization). Here, we describe three additional human mAbs that neutralize types 1 and 2 PV and one mAb that neutralizes all three types. Most bind conformational epitopes and have unusually long heavy chain complementarity determining 3 domains (HC CDR3). We assessed the ability of the mAbs to neutralize A12 escape mutant PV strains, and found that the neutralizing activities of the mAbs were disrupted by different amino acid substitutions. Competitive binding studies further suggested that the specific mAb:PV interactions that enable cross-neutralization differ among mAbs and serotypes. All of the cloned mAbs bind PV in the vicinity of the "canyon", a circular depression around the 5-fold axis of symmetry through which PV recognizes its cellular receptor. We were unable to generate escape mutants to two of the mAbs, suggesting that their epitopes are important for the PV life cycle. These data indicate that PV cross-neutralization involves binding to highly conserved structures within the canyon that binds to the cellular receptor. These may be facilitated by the long HC CDR3 domains, which may adopt alternative binding configurations. We propose that the human and chimpanzee mAbs described here could have potential as anti-PV therapeutics. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis of Titan's neutral upper atmosphere from Cassini Ion Neutral Mass Spectrometer measurements in the Closed Source Neutral mode

NASA Astrophysics Data System (ADS)

Cui, Jun

-1 , referred to Titan's surface. The H 2 escape flux is about a factor of ~3 higher than the Jeans value, which is interpreted as enhanced thermal escape driven primarily by an upward conductive heat flux. Such a conclusion is based on kinetic model calculations in the 13-moment approximation that require energy continuity at the upper boundary. On the other hand, a proper interpretation of the observed CH 4 escape has to rely on the detailed nonthermal processes, which are still unknown at the present time. The INMS observations of the nitrogen isotope ratio implies 14 N/ 15 N=131.6 near Titan's surface. The profile of carbon isotope ratio combining INMS and GCMS results implies that both CH 4 and its isotope escape from Titan's exobase with roughly the same drift velocity, in contrast to the Jeans case which requires that CH 4 escapes with a much larger velocity due to its smaller mass. The INMS data also suggest horizontal/diurnal variations of temperature and neutral gas distribution in Titan's thermosphere. The equatorial regions, the ramside, as well as the nightside hemisphere of Titan appear to be warmer and present some evidences for the depletion of light species such as CH 4 . Meridional variations of most heavy species are also observed, with a trend of depletion toward the north pole. Though some of the above variations might be interpreted by either the solar-driven models or plasma-driven models, a physical scenario that reconciles all the observed horizontal/diurnal variations in a consistent way is still missing, With a careful evaluation of the effect of restricted sampling, some of the features shown in the INMS data are more likely to be observational biases.

Influenza A virus hemagglutinin glycosylation compensates for antibody escape fitness costs.

PubMed

Kosik, Ivan; Ince, William L; Gentles, Lauren E; Oler, Andrew J; Kosikova, Martina; Angel, Matthew; Magadán, Javier G; Xie, Hang; Brooke, Christopher B; Yewdell, Jonathan W

2018-01-01

Rapid antigenic evolution enables the persistence of seasonal influenza A and B viruses in human populations despite widespread herd immunity. Understanding viral mechanisms that enable antigenic evolution is critical for designing durable vaccines and therapeutics. Here, we utilize the primerID method of error-correcting viral population sequencing to reveal an unexpected role for hemagglutinin (HA) glycosylation in compensating for fitness defects resulting from escape from anti-HA neutralizing antibodies. Antibody-free propagation following antigenic escape rapidly selected viruses with mutations that modulated receptor binding avidity through the addition of N-linked glycans to the HA globular domain. These findings expand our understanding of the viral mechanisms that maintain fitness during antigenic evolution to include glycan addition, and highlight the immense power of high-definition virus population sequencing to reveal novel viral adaptive mechanisms.

Inhibition of chaotic escape from a potential well by incommensurate escape-suppressing excitations.

PubMed

Chacón, R; Martínez, J A

2002-03-01

Theoretical results are presented concerning the reduction of chaotic escape from a potential well by means of a harmonic parametric excitation that satisfies an ultrasubharmonic resonance condition with the escape-inducing excitation. The possibility of incommensurate escape-suppressing excitations is demonstrated by studying rational approximations to the irrational escape-suppressing frequency. The analytical predictions for the suitable amplitudes and initial phases of the escape-suppressing excitation are tested against numerical simulations based on a high-resolution grid of initial conditions. These numerical results indicate that the reduction of escape is reliably achieved for small amplitudes and at, and only at, the predicted initial phases. For the case of irrational escape-suppressing frequencies, the effective escape-reducing initial phases are found to lie close to the accumulation points of the set of suitable initial phases that are associated with the complete series of convergents up to the convergent giving the chosen rational approximation.

Photochemical escape of oxygen from Mars: First results from MAVEN in situ data

NASA Astrophysics Data System (ADS)

Lillis, Robert J.; Deighan, Justin; Fox, Jane L.; Bougher, Stephen W.; Lee, Yuni; Combi, Michael R.; Cravens, Thomas E.; Rahmati, Ali; Mahaffy, Paul R.; Benna, Mehdi; Elrod, Meredith K.; McFadden, James P.; Ergun, Robert. E.; Andersson, Laila; Fowler, Christopher M.; Jakosky, Bruce M.; Thiemann, Ed; Eparvier, Frank; Halekas, Jasper S.; Leblanc, François; Chaufray, Jean-Yves

2017-03-01

Photochemical escape of atomic oxygen is thought to be one of the dominant channels for Martian atmospheric loss today and played a potentially major role in climate evolution. Mars Atmosphere and Volatile Evolution Mission (MAVEN) is the first mission capable of measuring, in situ, the relevant quantities necessary to calculate photochemical escape fluxes. We utilize 18 months of data from three MAVEN instruments: Langmuir Probe and Waves, Neutral Gas and Ion Mass Spectrometer, and SupraThermal And Thermal Ion Composition. From these data, we calculate altitude profiles of the production rate of hot oxygen atoms from the dissociative recombination of O2+ and the probability that such atoms will escape the Mars atmosphere. From this, we determine escape fluxes for 815 periapsis passes. Derived average dayside hot O escape rates range from 1.2 to 5.5 × 1025 s-1, depending on season and EUV flux, consistent with several pre-MAVEN predictions and in broad agreement with estimates made with other MAVEN measurements. Hot O escape fluxes do not vary significantly with dayside solar zenith angle or crustal magnetic field strength but depend on CO2 photoionization frequency with a power law whose exponent is 2.6 ± 0.6, an unexpectedly high value which may be partially due to seasonal and geographic sampling. From this dependence and historical EUV measurements over 70 years, we estimate a modern-era average escape rate of 4.3 × 1025 s-1. Extrapolating this dependence to early solar system, EUV conditions gives total losses of 13, 49, 189, and 483 mbar of oxygen over 1-3 and 3.5 Gyr, respectively, with uncertainties significantly increasing with time in the past.

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.

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…

Anomalous barrier escape: The roles of noise distribution and correlation.

PubMed

Hu, Meng; Zhang, Jia-Ming; Bao, Jing-Dong

2017-05-28

We study numerically and analytically the barrier escape dynamics of a particle driven by an underlying correlated Lévy noise for a smooth metastable potential. A "quasi-monochrome-color" Lévy noise, i.e., the first-order derivative variable of a linear second-order differential equation subjected to a symmetric α-stable white Lévy noise, also called the harmonic velocity Lévy noise, is proposed. Note that the time-integral of the noise Green function of this kind is equal to zero. This leads to the existence of underlying negative time correlation and implies that a step in one direction is likely followed by a step in the other direction. By using the noise of this kind as a driving source, we discuss the competition between long flights and underlying negative correlations in the metastable dynamics. The quite rich behaviors in the parameter space including an optimum α for the stationary escape rate have been found. Remarkably, slow diffusion does not decrease the stationary rate while a negative correlation increases net escape. An approximate expression for the Lévy-Kramers rate is obtained to support the numerically observed dependencies.

Anomalous barrier escape: The roles of noise distribution and correlation

NASA Astrophysics Data System (ADS)

Hu, Meng; Zhang, Jia-Ming; Bao, Jing-Dong

2017-05-01

We study numerically and analytically the barrier escape dynamics of a particle driven by an underlying correlated Lévy noise for a smooth metastable potential. A "quasi-monochrome-color" Lévy noise, i.e., the first-order derivative variable of a linear second-order differential equation subjected to a symmetric α-stable white Lévy noise, also called the harmonic velocity Lévy noise, is proposed. Note that the time-integral of the noise Green function of this kind is equal to zero. This leads to the existence of underlying negative time correlation and implies that a step in one direction is likely followed by a step in the other direction. By using the noise of this kind as a driving source, we discuss the competition between long flights and underlying negative correlations in the metastable dynamics. The quite rich behaviors in the parameter space including an optimum α for the stationary escape rate have been found. Remarkably, slow diffusion does not decrease the stationary rate while a negative correlation increases net escape. An approximate expression for the Lévy-Kramers rate is obtained to support the numerically observed dependencies.

Extinction Correction Significantly Influences the Estimate of the Lyα Escape Fraction

NASA Astrophysics Data System (ADS)

An, Fang Xia; Zheng, Xian Zhong; Hao, Cai-Na; Huang, Jia-Sheng; Xia, Xiao-Yang

2017-02-01

The Lyα escape fraction is a key measure to constrain the neutral state of the intergalactic medium and then to understand how the universe was fully reionized. We combine deep narrowband imaging data from the custom-made filter NB393 and the {{{H}}}2S1 filter centered at 2.14 μm to examine the Lyα emitters and Hα emitters at the same redshift z = 2.24. The combination of these two populations allows us to determine the Lyα escape fraction at z = 2.24. Over an area of 383 arcmin2 in the Extended Chandra Deep Field South (ECDFS), 124 Lyα emitters are detected down to NB393 = 26.4 mag at the 5σ level, and 56 Hα emitters come from An et al. Of these, four have both Lyα and Hα emissions (LAHAEs). We also collect the Lyα emitters and Hα emitters at z = 2.24 in the COSMOS field from the literature, and increase the number of LAHAEs to 15 in total. About one-third of them are AGNs. We measure the individual/volumetric Lyα escape fraction by comparing the observed Lyα luminosity/luminosity density to the extinction-corrected Hα luminosity/luminosity density. We revisit the extinction correction for Hα emitters using the Galactic extinction law with color excess for nebular emission. We also adopt the Calzetti extinction law together with an identical color excess for stellar and nebular regions to explore how the uncertainties in extinction correction affect the estimate of individual and global Lyα escape fractions. In both cases, an anti-correlation between the Lyα escape fraction and dust attenuation is found among the LAHAEs, suggesting that dust absorption is responsible for the suppression of the escaping Lyα photons. However, the estimated Lyα escape fraction of individual LAHAEs varies by up to ˜3 percentage points between the two methods of extinction correction. We find the global Lyα escape fraction at z = 2.24 to be (3.7 ± 1.4)% in the ECDFS. The variation in the color excess of the extinction causes a discrepancy of ˜1 percentage point

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

Detection of Escaping Lyman Continuum Radiation in Two Local Starbursts Using FUSE

NASA Astrophysics Data System (ADS)

Leitet, E.; Bergvall, N.; Andersson, B.-G.; Zackrisson, E.

2007-05-01

Dwarf galaxies may play a significant role in the reionization history of the universe, and as such also for the history of structure formation. These galaxies are however too faint to be observed at high redshifts, and it is therefore important to establish the amount of Lyman continuum (LyC) radiation that escape local starbursting dwarf galaxies. The amount of leakage is important to know also in order to improve models of star formation and spectral evolution of galaxies, which if neglected, might lead to false conclusions about the properties of the galaxies themself. Previous attempts to directly observe the leakage of hydrogen-ionizing radiation from local galaxies has before this resulted only in one successful case. In Bergvall et al. (2006 A&A 448, 513) an escape fraction of 4-10 % for the blue compact galaxy Haro 11, was found. In this work the detection and quantification of the LyC escape fractions for two additional local starburst galaxies using the Far Ultraviolet Spectroscopic Explorer, FUSE, is presented. The detections were made using FUSE archival data reduced with the latest, and much improved, pipeline. The LyC continuum can be seen as a faint structure between the Lyman limit of the target galaxies and the Milky Way. From line profile fitting it was found that both galaxies have high column densities of neutral gas, indicating that the LyC radiation is escaping through holes in the ISM. The escape fractions are calculated using spectral evolutionary models, based on the f(900Å), f(960Å) and f(Ha) fluxes. The fact that LyC leakage now is detected in three local starbursting dwarf galaxies is going to have a deep impact on future research on structure formation and galaxy evolution. The next challenge would be to statistically determine the escape fraction in extended surveys of starbursting dwarf galaxies.

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

PubMed

Marchese, Andrew D; Onal, Cagdas D; Rus, Daniela

2014-03-01

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.

Progress Toward an Neutral Yb Frequency Standard

NASA Astrophysics Data System (ADS)

Cramer, Claire; Hong, Tao; Nagourney, Warren; Fortson, Norval

2004-05-01

We report recent progress toward a direct observation of the ^1S_0^ -- ^3P0 clock transition at 578 nm in atomic Yb and review the experimental path to an optical frequency standard based on neutral Yb confined in a Stark-free optical lattice. Lamb-Dicke confinement in an optical lattice at the ``magic wavelength'' (λ _M) at which ground and excited state light shifts cancel will free the spectrum from Doppler and recoil shifts, providing an optimal environment for a clock consisting of an ensemble of cold, trapped atoms. In^171Yb the ^3P0 level has a hfs induced lifetime of 21 s. With this isotope in a Stark-free lattice at λ M ng 750 nm, perturbations to the clock energy levels can be held below the mHz level, providing an accuracy of a few parts in 10^18[1]. To observe the clock transition we use a shelving scheme that creates a leak in a MOT on the ^1S_0^ -- ^1P1 transition. A laser resonant with the clock transition drives atoms into the ^3P0 state, in which they can escape the MOT, leading to an observable decrease in MOT fluorescence. [1] S. Porsev and A. Derevianko, to be published in PRA

Survivors Remorse: antibody-mediated protection against HIV-1.

PubMed

Lewis, George K; Pazgier, Marzena; DeVico, Anthony L

2017-01-01

It is clear that antibodies can play a pivotal role in preventing the transmission of HIV-1 and large efforts to identify an effective antibody-based vaccine to quell the epidemic. Shortly after HIV-1 was discovered as the cause of AIDS, the search for epitopes recognized by neutralizing antibodies became the driving strategy for an antibody-based vaccine. Neutralization escape variants were discovered shortly thereafter, and, after almost three decades of investigation, it is now known that autologous neutralizing antibody responses and their selection of neutralization resistant HIV-1 variants can lead to broadly neutralizing antibodies in some infected individuals. This observation drives an intensive effort to identify a vaccine to elicit broadly neutralizing antibodies. In contrast, there has been less systematic study of antibody specificities that must rely mainly or exclusively on other protective mechanisms, although non-human primate (NHP) studies as well as the RV144 vaccine trial indicate that non-neutralizing antibodies can contribute to protection. Here we propose a novel strategy to identify new epitope targets recognized by these antibodies for which viral escape is unlikely or impossible. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Monte Carlo simulation of neutral-beam injection for mirror fusion reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Ronald Lee

1979-01-01

Computer simulation techniques using the Monte Carlo method have been developed for application to the modeling of neutral-beam intection into mirror-confined plasmas of interest to controlled thermonuclear research. The energetic (10 to 300 keV) neutral-beam particles interact with the target plasma (T i ~ 10 to 100 keV) through electron-atom and ion-atom collisional ionization as well as ion-atom charge-transfer (charge-exchange) collisions to give a fractional trapping of the neutral beam and a loss of charge-transfer-produced neutrals which escape to bombard the reactor first wall. Appropriate interaction cross sections for these processes are calculated for the assumed anisotropic, non-Maxwellian plasma ionmore » phase-space distributions.« less

ESCAPE AS REINFORCEMENT AND ESCAPE EXTINCTION IN THE TREATMENT OF FEEDING PROBLEMS

PubMed Central

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 swallowing), escape as reinforcement for mouth clean plus escape extinction (EE), and EE alone as treatment for the food refusal of 5 children. Results were similar to those of previous studies, in that reinforcement alone did not result in increases in mouth clean or decreases in inappropriate behavior (e.g., Piazza, Patel, Gulotta, Sevin, & Layer, 2003). Increases in mouth clean and decreases in inappropriate behavior occurred when the therapist implemented EE independent of the presence or absence of reinforcement. Results are discussed in terms of the role of negative reinforcement in the etiology and treatment of feeding problems. PMID:22219525

Analysis of variola and vaccinia virus neutralization assays for smallpox vaccines.

PubMed

Hughes, Christine M; Newman, Frances K; Davidson, Whitni B; Olson, Victoria A; Smith, Scott K; Holman, Robert C; Yan, Lihan; Frey, Sharon E; Belshe, Robert B; Karem, Kevin L; Damon, Inger K

2012-07-01

Possible smallpox reemergence drives research for third-generation vaccines that effectively neutralize variola virus. A comparison of neutralization assays using different substrates, variola and vaccinia (Dryvax and modified vaccinia Ankara [MVA]), showed significantly different 90% neutralization titers; Dryvax underestimated while MVA overestimated variola neutralization. Third-generation vaccines may rely upon neutralization as a correlate of protection.

Energy transfer in O collisions with He isotopes and helium escape from Mars

NASA Astrophysics Data System (ADS)

Bovino, S.; Zhang, P.; Kharchenko, V.; Dalgarno, A.

2010-12-01

Helium is one of the dominant constituents in the upper atmosphere of Mars [1]. Thermal (Jeans’) escape of He is negligible on Mars [2] and major mechanism of escape is related to the collisional ejection of He atoms by energetic oxygen. Collisional ejection dominates over ion-related mechanisms [3] and evaluation of the escape flux of neutral He becomes an important issue. The dissociative recombination of O2+ is considered to be the major source of energetic oxygen atoms [4]. We report accurate data on energy-transfer collisions between hot oxygen atoms and the atmospheric helium gas. Angular dependent scattering cross sections for elastic collisions of O(3P) and O(1D) atoms with helium gas have been calculated quantum mechanically and found to be surprisingly similar. Cross sections, computed for collisions with both helium isotopes, 3He and 4He, have been used to construct the kernel of the Boltzmann equation, describing the energy relaxation of hot oxygen atoms. Computed rates of energy transfer in O + He collisions have been used to evaluate the flux of He atoms escaping from the Mars atmosphere at different solar conditions. We have identified atmospheric layers mostly responsible for production of the He escape flux. Our results are consistent with recent data from Monte Carlo simulations of the escape of O atoms: strong angular anisotropy of atomic cross sections leads to an increased transparency of the upper atmosphere for escaping O flux [5] and stimulate the collisional ejection of He atoms. References [1] Krasnopolsky, V. A., and G. R. Gladstone (2005), Helium on Mars and Venus: EUVE observations and modeling, Icarus, 176, 395. [2] Chassefiere E. and F. Leblanc (2004), Mars atmospheric escape and evolution; interaction with the solar wind, Planetary and Space Science, 52, 1039 [3] Krasnopolsky, V. (2010), Solar activity variations of thermospheric temperatures on Mars and a problem of CO in the lower atmoshpere, Icarus, 207, 638. [4] Fox, J. L

Specific features of measuring the isotopic composition of hydrogen ions in ITER plasma by using neutral particle diagnostics under neutral beam injection conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afanasyev, V. I.; Goncharov, P. R., E-mail: p.goncharov@spbstu.ru; Mironov, M. I.

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 energymore » range. The injection of a diagnostic hydrogen (H{sup 0}) beam does not affect measurements owing to the high mass resolution of the analyzers.« less

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

Code of Federal Regulations, 2013 CFR

2013-10-01

... 42 Public Health 1 2013-10-01 2013-10-01 false Entry and escape, or escape only; classification. 84.51 Section 84.51 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF RESPIRATORY PROTECTIVE DEVICES...

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

Code of Federal Regulations, 2010 CFR

2010-10-01

... 42 Public Health 1 2010-10-01 2010-10-01 false Entry and escape, or escape only; classification. 84.51 Section 84.51 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF RESPIRATORY PROTECTIVE DEVICES...

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

Code of Federal Regulations, 2011 CFR

2011-10-01

... 42 Public Health 1 2011-10-01 2011-10-01 false Entry and escape, or escape only; classification. 84.51 Section 84.51 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF RESPIRATORY PROTECTIVE DEVICES...

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

Code of Federal Regulations, 2014 CFR

2014-10-01

... 42 Public Health 1 2014-10-01 2014-10-01 false Entry and escape, or escape only; classification. 84.51 Section 84.51 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF RESPIRATORY PROTECTIVE DEVICES...

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

Code of Federal Regulations, 2012 CFR

2012-10-01

... 42 Public Health 1 2012-10-01 2012-10-01 false Entry and escape, or escape only; classification. 84.51 Section 84.51 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF RESPIRATORY PROTECTIVE DEVICES...

A Quantitative Quasispecies Theory-Based Model of Virus Escape Mutation Under Immune Selection

DTIC Science & Technology

2012-01-01

immune pressure, and their capacity for rapid escape mutation underlies many of the difficulties in combating pathogens, including HIV -1. In a typical...interpreted as the total number of virions within a finite sys- tem. The HIV -1 viral load during the acute infection phase can reach up to 104 ∼ 106...therefore models both the de- crease of the mean fitness away from WT and the distribution of neutral, deleterious, and beneficial mutants for a

INDIRECT EVIDENCE FOR ESCAPING IONIZING PHOTONS IN LOCAL LYMAN BREAK GALAXY ANALOGS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexandroff, Rachael M.; Heckman, Timothy M.; Borthakur, Sanchayeeta

2015-09-10

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):more » (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

Escape of Hydrogen from the Exosphere of Mars

NASA Astrophysics Data System (ADS)

Bhattacharyya, Dolon; Clarke, John T.; Bertaux, Jean-Loup; Chaufray, Jean-Yves; Mayyasi-Matta, Majd A.

2016-10-01

After decades of exploration, the martian neutral hydrogen exosphere has remained largely uncharacterized even today. In my dissertation I have attempted to constrain the characteristics of the martian hydrogen exosphere using Hubble Space Telescope observations obtained during October-November 2007 and 2014. These observations reveal short-term seasonal changes exhibited by the martian hydrogen exosphere that are inconsistent with the diffusion-limited escape scenario. This seasonal behavior adds a new element towards backtracking the history of water loss from Mars. Modeling of the data also indicates the likely presence of a superthermal population of hydrogen created by non-thermal processes at Mars, another key element to understand the present-day escape. Exploration of the latitudinal symmetry of the martian exosphere indicates that it is symmetric above 2.5 martian radii and asymmetric below this altitude, which could be due to temperature differences between the day and night sides. Finally, the large uncertainties in determining the characteristics of the martian exosphere after decades of exploration is due to various assumptions about the intrinsic characteristics of the martian exosphere in the modeling process, degeneracy in the two modeling parameters temperature and density of the hydrogen atoms, unaccounted seasonal effects, and uncertainties introduced from spacecraft instrumentation as well as their viewing geometry.

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

DOE PAGES

Chrystal, Colin; Burrell, Keith H.; Grierson, Brian A.; ...

2015-10-20

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 diagnostic (CER) 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 informationmore » 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. Lastly, the methods developed to perform the integrated spatial calibration could be useful for tokamaks with limited physical access.« less

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.

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.

An empirical investigation of time-out with and without escape extinction to treat escape-maintained noncompliance.

PubMed

Everett, Gregory E; Joe Olmi, D; Edwards, Ron P; Tingstrom, Daniel H; Sterling-Turner, Heather E; Christ, Theodore J

2007-07-01

The present study evaluates the effectiveness of two time-out (TO) procedures in reducing escape-maintained noncompliance of 4 children. Noncompliant behavioral function was established via a functional assessment (FA), including indirect and direct descriptive procedures and brief confirmatory experimental analyses. Following FA, parents were taught to consequate noncompliance with two different TO procedures, one without and one with escape extinction following TO release. Although results indicate TO without escape extinction is effective in increasing compliance above baseline levels, more optimal levels of compliance were obtained for all 4 children when escape extinction was added to the TO procedures already in place. Results indicate efficacy of TO with escape extinction when applied to escape-maintained noncompliance and are discussed as an initial example of the successful application of TO to behaviors maintained by negative reinforcement.

Relationship of scores on the Escapism Scale of the MMPI to escape from minimum security federal custody.

PubMed

White, R B

1979-04-01

Investigated the ability of the Escapism (Ec) scale of the MMPI to differentiate between escape and non-escape minimum security federal prisoners. At the .05 level there was no difference between the scores of the two groups on the Ec scale or on comparisons of other correctional data, age, and ethnic composition. It appears that the Ec scale alone or in combination with other data will be a poor predictor of escape. Also, the rate of escape was so low as to make accurate prediction from any criteria extremely unlikely.

HIV therapy by a combination of broadly neutralizing antibodies in humanized mice.

PubMed

Klein, Florian; Halper-Stromberg, Ariel; Horwitz, Joshua A; Gruell, Henning; Scheid, Johannes F; Bournazos, Stylianos; Mouquet, Hugo; Spatz, Linda A; Diskin, Ron; Abadir, Alexander; Zang, Trinity; Dorner, Marcus; Billerbeck, Eva; Labitt, Rachael N; Gaebler, Christian; Marcovecchio, Paola; Incesu, Reha-Baris; Eisenreich, Thomas R; Bieniasz, Paul D; Seaman, Michael S; Bjorkman, Pamela J; Ravetch, Jeffrey V; Ploss, Alexander; Nussenzweig, Michel C

2012-12-06

Human antibodies to human immunodeficiency virus-1 (HIV-1) can neutralize a broad range of viral isolates in vitro and protect non-human primates against infection. Previous work showed that antibodies exert selective pressure on the virus but escape variants emerge within a short period of time. However, these experiments were performed before the recent discovery of more potent anti-HIV-1 antibodies and their improvement by structure-based design. Here we re-examine passive antibody transfer as a therapeutic modality in HIV-1-infected humanized mice. Although HIV-1 can escape from antibody monotherapy, combinations of broadly neutralizing antibodies can effectively control HIV-1 infection and suppress viral load to levels below detection. Moreover, in contrast to antiretroviral therapy, the longer half-life of antibodies led to control of viraemia for an average of 60 days after cessation of therapy. Thus, combinations of potent monoclonal antibodies can effectively control HIV-1 replication in humanized mice, and should be re-examined as a therapeutic modality in HIV-1-infected individuals.

Rational Engineering and Characterization of an mAb that Neutralizes Zika Virus by Targeting a Mutationally Constrained Quaternary Epitope.

PubMed

Tharakaraman, Kannan; Watanabe, Satoru; Chan, Kuan Rong; Huan, Jia; Subramanian, Vidya; Chionh, Yok Hian; Raguram, Aditya; Quinlan, Devin; McBee, Megan; Ong, Eugenia Z; Gan, Esther S; Tan, Hwee Cheng; Tyagi, Anu; Bhushan, Shashi; Lescar, Julien; Vasudevan, Subhash G; Ooi, Eng Eong; Sasisekharan, Ram

2018-05-09

Following the recent emergence of Zika virus (ZIKV), many murine and human neutralizing anti-ZIKV antibodies have been reported. Given the risk of virus escape mutants, engineering antibodies that target mutationally constrained epitopes with therapeutically relevant potencies can be valuable for combating future outbreaks. Here, we applied computational methods to engineer an antibody, ZAb_FLEP, that targets a highly networked and therefore mutationally constrained surface formed by the envelope protein dimer. ZAb_FLEP neutralized a breadth of ZIKV strains and protected mice in distinct in vivo models, including resolving vertical transmission and fetal mortality in infected pregnant mice. Serial passaging of ZIKV in the presence of ZAb_FLEP failed to generate viral escape mutants, suggesting that its epitope is indeed mutationally constrained. A single-particle cryo-EM reconstruction of the Fab-ZIKV complex validated the structural model and revealed insights into ZAb_FLEP's neutralization mechanism. ZAb_FLEP has potential as a therapeutic in future outbreaks. Copyright © 2018. Published by Elsevier Inc.

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.

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.

Wabble gear drive mechanism. [for aerospace environments

NASA Technical Reports Server (NTRS)

Winiarski, F. J. (Inventor)

1967-01-01

The wabble gear principle was applied in the design of a driving mechanism for controlling spacecraft solar panels. The moving elements, other than the output gear, are contained within a hermetically sealed package to prevent escape of lubricants and ingestion of contaminant particles. The driving gear contains one more tooth than the output gear on a concave, conical pitch surface of slightly larger apex angle. The two gears mesh face to face such that engagement takes place at one point along the circumference. The driving gear is not permitted to rotate by virtue of its attachment through the bellows which permits flexure in the pitch and yaw position, but not in roll. As the bearing carrier rotates, the inclined mounting of the bearing causes the driving gear to perform a wabbling, irrotational motion. This wabbling motion causes the contact point between the output gear and the driving gear to traverse around the circumference of the gears once per revolution of the bearing carrier.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aoki, Scott T.; Settembre, Ethan C.; Trask, Shane D.

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 ismore » 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.« less

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.

Ion current in a magnetic neutral region - Generation of an incipient magnetopause

NASA Technical Reports Server (NTRS)

Whipple, E. C.; Silevitch, M. B.

1982-01-01

The current contributed by ions trapped in the vicinity of a magnetic X line is calculated. The three dimensional configuration of the neutral region is found to be critical in determining the current in that the escape mechanism and trapping times depend on the three-dimensional aspects. A trapping criterion is defined. In the neutral region the ions can gain substantial kinetic energy, and the current will change the X line configuration in such a way that there will be a positive feedback effect, rapidly forming an extended magnetopauselike structure for even very small incident plasma densities.

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

Spatial Distribution of Io's Neutral Oxygen Cloud Observed by Hisaki

NASA Astrophysics Data System (ADS)

Koga, Ryoichi; Tsuchiya, Fuminori; Kagitani, Masato; Sakanoi, Takeshi; Yoneda, Mizuki; Yoshioka, Kazuo; Yoshikawa, Ichiro; Kimura, Tomoki; Murakami, Go; Yamazaki, Atsushi; Smith, H. Todd; Bagenal, Fran

2018-05-01

We report on the spatial distribution of a neutral oxygen cloud surrounding Jupiter's moon Io and along Io's orbit observed by the Hisaki satellite. Atomic oxygen and sulfur in Io's atmosphere escape from the exosphere mainly through atmospheric sputtering. Some of the neutral atoms escape from Io's gravitational sphere and form neutral clouds around Jupiter. The extreme ultraviolet spectrograph called EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) installed on the Japan Aerospace Exploration Agency's Hisaki satellite observed the Io plasma torus continuously in 2014-2015, and we derived the spatial distribution of atomic oxygen emissions at 130.4 nm. The results show that Io's oxygen cloud is composed of two regions, namely, a dense region near Io and a diffuse region with a longitudinally homogeneous distribution along Io's orbit. The dense region mainly extends on the leading side of Io and inside of Io's orbit. The emissions spread out to 7.6 Jupiter radii (RJ). Based on Hisaki observations, we estimated the radial distribution of the atomic oxygen number density and oxygen ion source rate. The peak atomic oxygen number density is 80 cm-3, which is spread 1.2 RJ in the north-south direction. We found more oxygen atoms inside Io's orbit than a previous study. We estimated the total oxygen ion source rate to be 410 kg/s, which is consistent with the value derived from a previous study that used a physical chemistry model based on Hisaki observations of ultraviolet emission ions in the Io plasma torus.

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.

Heating and current drive on NSTX

NASA Astrophysics Data System (ADS)

Wilson, J. R.; Batchelor, D.; Carter, M.; Hosea, J.; Ignat, D.; LeBlanc, B.; Majeski, R.; Ono, M.; Phillips, C. K.; Rogers, J. H.; Schilling, G.

1997-04-01

Low aspect ratio tokamaks pose interesting new challenges for heating and current drive. The NSTX (National Spherical Tokamak Experiment) device to be built at Princeton is a low aspect ratio toroidal device that has the achievement of high toroidal beta (˜45%) and non-inductive operation as two of its main research goals. To achieve these goals significant auxiliary heating and current drive systems are required. Present plans include ECH (Electron cyclotron heating) for pre-ionization and start-up assist, HHFW (high harmonic fast wave) for heating and current drive and eventually NBI (neutral beam injection) for heating, current drive and plasma rotation.

Creating Engaging Escape Rooms for the Classroom

ERIC Educational Resources Information Center

Nicholson, Scott

2018-01-01

Escape rooms are "live-action team-based games where players discover clues, solve puzzles, and accomplish tasks in one or more rooms in order to accomplish a specific goal (usually escaping from the room) in a limited amount of time." Escape Rooms are one type of Escape Game, which are narrative-based challenges that use puzzles, tasks,…

Two Regimes of Interaction of a Hot Jupiter’s Escaping Atmosphere with the Stellar Wind and Generation of Energized Atomic Hydrogen Corona

NASA Astrophysics Data System (ADS)

Shaikhislamov, I. F.; Khodachenko, M. L.; Lammer, H.; Kislyakova, K. G.; Fossati, L.; Johnstone, C. P.; Prokopov, P. A.; Berezutsky, A. G.; Zakharov, Yu. P.; Posukh, V. G.

2016-12-01

The interaction of escaping the upper atmosphere of a hydrogen-rich non-magnetized analog of HD 209458b with a stellar wind (SW) of its host G-type star at different orbital distances is simulated with a 2D axisymmetric multi-fluid hydrodynamic (HD) model. A realistic Sun-like spectrum of X-ray and ultraviolet radiation, which ionizes and heats the planetary atmosphere, together with hydrogen photochemistry, as well as stellar-planetary tidal interaction are taken into account to generate self-consistently an atmospheric HD outflow. Two different regimes of the planetary and SW interaction have been modeled. These are: (1) the “captured by the star” regime, when the tidal force and pressure gradient drive the planetary material beyond the Roche lobe toward the star, and (2) the “blown by the wind” regime, when sufficiently strong SW confines the escaping planetary atmosphere and channels it into the tail. The model simulates in detail the HD interaction between the planetary atoms, protons and the SW, as well as the production of energetic neutral atoms (ENAs) around the planet due to charge exchange between planetary atoms and stellar protons. The revealed location and shape of the ENA cloud, either as a paraboloid shell between the ionopause and bowshock (for the “blown by the wind” regime), or a turbulent layer at the contact boundary between the planetary stream and SW (for the “captured by the star” regime) are of importance for the interpretation of Lyα absorption features in exoplanetary transit spectra and characterization of the plasma environments.

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.

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.; Ji, Qing; Persaud, Arun; Seidl, Peter A.; Schenkel, Thomas

2016-10-01

Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams. Here we present experimental results on charge neutralization of a high-perveance 38 keV Ar+ beam by a FEPS plasma. 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. 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. 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 suggest that plasma can be generated for tens of μs after the high voltage pulse is applied. This is confirmed by fast photography of the plasma in the 1-meter long FEPS on NDCX-II, where effective charge neutralization of the beam was achieved with the optimized FEPS timing. This work was supported by the Office of Science of the US Department of Energy under contracts DE-AC0209CH11466 (PPPL) and DE-AC0205CH11231 (LBNL).

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

Dynamics of ion beam charge neutralization by ferroelectric plasma sources

DOE PAGES

Stepanov, Anton D.; Gilson, Erik P.; Grisham, Larry R.; ...

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 0.3more » 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 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

Neutralizing antibody fails to impact the course of Ebola virus infection in monkeys.

PubMed

Oswald, Wendelien B; Geisbert, Thomas W; Davis, Kelly J; Geisbert, Joan B; Sullivan, Nancy J; Jahrling, Peter B; Parren, Paul W H I; Burton, Dennis R

2007-01-01

Prophylaxis with high doses of neutralizing antibody typically offers protection against challenge with viruses producing acute infections. In this study, we have investigated the ability of the neutralizing human monoclonal antibody, KZ52, to protect against Ebola virus in rhesus macaques. This antibody was previously shown to fully protect guinea pigs from infection. Four rhesus macaques were given 50 mg/kg of neutralizing human monoclonal antibody KZ52 intravenously 1 d before challenge with 1,000 plaque-forming units of Ebola virus, followed by a second dose of 50 mg/kg antibody 4 d after challenge. A control animal was exposed to virus in the absence of antibody treatment. Passive transfer of the neutralizing human monoclonal antibody not only failed to protect macaques against challenge with Ebola virus but also had a minimal effect on the explosive viral replication following infection. We show that the inability of antibody to impact infection was not due to neutralization escape. It appears that Ebola virus has a mechanism of infection propagation in vivo in macaques that is uniquely insensitive even to high concentrations of neutralizing antibody.

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

Physics escape room as an educational tool

NASA Astrophysics Data System (ADS)

Vörös, Alpár István Vita; Sárközi, Zsuzsa

2017-12-01

Escape rooms have flourished in the last decade. These are adventure games in which players work together to solve puzzles using hints, clues and a strategy to escape from a locked room. In many cases they use different phenomena related to physics. Hence the idea of using escape rooms in science centers or even in classroom activities. Escape rooms are designed for one single team of players, the method is more suitable for activities in a science centre. In our paper, we show that escape rooms' puzzle solving methods could be used in physics classroom activities as well, taking into account that several teams have to work together in the same room/place. We have developed an educational escape game for physics of fluids, as this topic is left out from the Romanian high-school curriculum. We have tried out our game during the project week called "Şcoala altfel" ("school in a different way") and in a physics camp for gifted students. We present the designed physics escape game and the results.

Immune Escape Mutations Detected within HIV-1 Epitopes Associated with Viral Control During Treatment Interruption

PubMed Central

Schweighardt, Becky; Wrin, Terri; Meiklejohn, Duncan A.; Spotts, Gerald; Petropoulos, Christos J.; Nixon, Douglas F.; Hecht, Frederick M.

2010-01-01

We analyzed immune responses in chronically HIV-infected individuals who took part in a treatment interruption (TI) trial designed for patients who initiated anti-retroviral therapy within 6 months of seroconversion. In the two subjects that exhibited the best viral control, we detected CD8+ T cell responses against 1-2 Gag epitopes during the early weeks of TI and a subsequent increase in the number of epitopes recognized by the later time points. Each of these subjects developed mutations within the epitopes targeted by the highest magnitude responses. In the subject with the worst viral control, we detected responses against two Gag epitopes throughout the entire TI and no Gag mutations. The magnitude of these responses increased dramatically with time, greatly exceeding those detected in the virologic controllers. The highest levels of contemporaneous autologous neutralizing antibody activity were detected in the virologic controllers, and a subsequent escape mutation developed within the envelope gene of one controller that abrogated the response. These data suggest that immune escape mutations are a sign of viral control during TI, and that the absence of immune escape mutations in the presence of high-levels of viral replication indicates the lack of an effective host immune response. PMID:19910798

Radiative lifetimes for 29 N2+ and implications for planetary escape and isotope enrichment

NASA Astrophysics Data System (ADS)

Guberman, Steven L.

2017-07-01

The Viking missions to Mars found that 15N/14N is enhanced by a factor of 1.62 compared to Earth and it was suggested that the cause was dissociative recombination (DR) of N2+. The high kinetic energy imparted to N in DR drives atmospheric escape. More recent models of the Martian ionosphere show that much of the N2+ is vibrationally excited. If DR of vibrationally excited 29N2+ is important, the energetics are such that the isotope enhancement would be greatly reduced. Here I show that at the Mars exobase electron temperature and density, the excited vibrational levels of 29N2+ radiate before they can recombine. The isotope enhancement arising from DR is due entirely to DR of 28N2+ with a small contribution to 14N escape arising from DR of the ground vibrational level of 29N2+.

Energy Deposition and Escape Fluxes Induced by Energetic Solar Wind Ions and ENAs Precipitating into Mars Atmosphere: Accurate Consideration of Energy Transfer Collisions

NASA Astrophysics Data System (ADS)

Kharchenko, V. A.; Lewkow, N.; Gacesa, M.

2014-12-01

Formation and evolution of neutral fluxes of atoms and molecules escaping from the Mars atmosphere have been investigated for the sputtering and photo-chemical mechanisms. Energy and momentum transfer in collisions between the atmospheric gas and fast atoms and molecules have been considered using our recently obtained angular and energy dependent cross sections[1]. We have showed that accurate angular dependent collision cross sections are critical for the description of the energy relaxation of precipitating keV energetic ions/ENAs and for computations of altitude profiles of the fast atom and molecule production rates in recoil collisions. Upward and escape fluxes of the secondary energetic He and O atoms and H2, N2, CO and CO2 molecules, induced by precipitating ENAs, have been determined and their non-thermal energy distribution functions have been computed at different altitudes for different solar conditions. Precipitation and energy deposition of the energetic H2O molecules and products of their dissociations into the Mars atmosphere in the Comet C/2013 A1 (Siding Spring) - Mars interaction have been modeled using accurate cross sections. Reflection of precipitating ENAs by the Mars atmosphere has been analyzed in detail. [1] N. Lewkow and V. Kharchenko, "Precipitation of Energetic Neutral Atoms and Escape Fluxes induced from the Mars Atmosphere, ApJ, v.790, p.98 (2014).

Autoresonant Control of Elliptical Non-neutral Plasmas

NASA Astrophysics Data System (ADS)

Friedland, Lazar

1999-11-01

It is shown that placing a magnetized non-neutral plasma column in a weak oscillating transverse quadrupolar potential with chirped oscillation frequency allows excitation and control of the ellipticity and rotation phase of the plasma cross section. For a given chirp rate of the driving frequency, the phenomenon has a sharp threshold on the amplitude of the perturbing potential. The effect is analogous to that reported in controlling Kirchhoff vortices in fluid dynamics [1]. The ellipticity of the plasma cross section is manipulated by using autoresonance (nonlinear phase locking) in the system between the ExB drifting plasma particles and adiabatically varying driving potential. A similar idea was used recently in controlling the l=1 diocotron mode in a non-neutral plasma [2]. [1] L. Friedland, Phys. Rev. E59, 4106 (1999). [2] J. Fajans, E. Gilson, and L. Friedland, Phys. Rev. Lett. 82, 4444 (1999).

30 CFR 75.382 - Mechanical escape facilities.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Mechanical escape facilities. 75.382 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.382 Mechanical escape facilities. (a) Mechanical escape facilities shall be provided with overspeed, overwind, and automatic stop...

Escape of magnetic toroids from the Sun

NASA Technical Reports Server (NTRS)

Bieber, John W.; Rust, David M.

1995-01-01

Analysis of heliospheric magnetic fields at 1 AU shows that 10(exp 24) Mx of net azimuthal flux escapes from the Sun per solar cycle. This rate is consistent with rates derived from other indicators of flux escape, including coronal mass ejections and filament eruptions. The toroidal flux escape rate is compared with the apparent rate of flux emergence at the solar surface, and it is concluded that escaping toroids will remove at least 20% of the emerging flux, and may remove as much as 100% of emerging flux if multiple eruptions occur on the toroids. The data imply that flux escapes the Sun with an efficiency far exceeding Parker's upper limit estimate of 3%. Toroidal flux escape is almost certainly the source of the observed overwinding of the interplanetary magnetic field spiral. Two mechanisms to facilitate net flux escape are discussed: helicity charging to push open the fields and flux transport with reconnection to close them off. We estimate the Sun will shed approximately 2 x 10(exp 45) of magnetic helicity per solar cycle, leading to a mean helicity density of 100 Mx(exp 2)cm(exp -3) at 1 AU, which agrees well with observations.

MAVEN Observations of Atmospheric Loss at Mars

NASA Astrophysics Data System (ADS)

Curry, Shannon; Luhmann, Janet; Jakosky, Bruce M.; Brain, David; LeBlanc, Francis; Modolo, Ronan; Halekas, Jasper S.; Schneider, Nicholas M.; Deighan, Justin; McFadden, James; Espley, Jared R.; Mitchell, David L.; Connerney, J. E. P.; Dong, Yaxue; Dong, Chuanfei; Ma, Yingjuan; Cohen, Ofer; Fränz, Markus; Holmström, Mats; Ramstad, Robin; Hara, Takuya; Lillis, Robert J.

2016-06-01

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been making observations of the Martian upper atmosphere and its escape to space since November 2014. The subject of atmospheric loss at terrestrial planets is a subject of intense interest not only because of the implications for past and present water reservoirs, but also for its impacts on the habitability of a planet. Atmospheric escape may have been especially effective at Mars, relative to Earth or Venus, due to its smaller size as well as the lack of a global dynamo magnetic field. Not only is the atmosphere less gravitationally bound, but also the lack of global magnetic field allows the impinging solar wind to interact directly with the Martian atmosphere. When the upper atmosphere is exposed to the solar wind, planetary neutrals can be ionized and 'picked up' by the solar wind and swept away.Both neutral and ion escape have played significant roles the long term climate change of Mars, and the MAVEN mission was designed to directly measure both escaping planetary neutrals and ions with high energy, mass, and time resolution. We will present 1.5 years of observations of atmospheric loss at Mars over a variety of solar and solar wind conditions, including extreme space weather events. We will report the average ion escape rate and the spatial distribution of escaping ions as measured by MAVEN and place them in context both with previous measurements of ion loss by other spacecraft (e.g. Phobos 2 and Mars Express) and with estimates of neutral escape rates by MAVEN. We will then report on the measured variability in ion escape rates with different drivers (e.g. solar EUV, solar wind pressure, etc.) and the implications for the total ion escape from Mars over time. Additionally, we will also discuss the implications for atmospheric escape at exoplanets, particularly weakly magnetized planetary bodies orbiting M-dwarfs, and the dominant escape mechanisms that may drive atmospheric erosion in other

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+.

Hostility, driving anger, and dangerous driving: the emerging role of hemispheric preference.

PubMed

Gidron, Yori; Gaygısız, Esma; Lajunen, Timo

2014-12-01

Various studies have implicated psychosocial variables (e.g., hostility) in risk of dangerous driving and traffic accidents. However, whether these variables are related to more basic neurobiological factors, and whether such associations have implications for the modification of psychosocial risk factors in the context of driving, have not been examined in depth. This study examined the relationship between hemispheric preference (HP), hostility and self-reported dangerous driving, and the ability to affect driving anger via hemisphere activating cognitive exercises (HACE). In Study 1, 254 Turkish students completed questionnaires of hostility, HP and driving behavior. In Study 2, we conducted a "proof of concept" experimental study, and tested effects of left, right and neutral HACE on driving anger, by exposing N=650 Turkish students to written scenarios including either logical (left hemisphere), visuo-spatial (right hemisphere) or "mild doses" of both types of contents (control). In Study 1, left-HP was associated with higher hostility and with more dangerous driving, and hostility mediated the relationship between L-HP and reported driving behavior. In Study 2, only right-HACE led to immediate significant reductions in self-reported driving anger. Left-HP is related to hostility and to dangerous driving, and it may be possible to partly reduce driving anger by right-HACE. Future studies must replicate these findings with objective measures, more enduring interventions and longer follow-ups. Copyright © 2014. Published by Elsevier Ltd.

Measurements of Lyman-Alpha Escape From HST Far-UV Spectral SNAP Survey of 33 Starforming Galaxies: Initial Results

NASA Astrophysics Data System (ADS)

Redwine, Keith

2018-01-01

This thesis will describe and analyze far-UV spectra from nearby starforming galaxies to investigate how line features like the hydrogen Lyman-alpha (Lyα) line at 1216 Å are related to the local properties of the host galaxy. It has been suggested that Lyα can be used as a proxy for the escape of Lyman continuum (LyC) radiation, the escape of of which from bright regions of galaxies is of particular interest. Most notably, the reionization epoch of neutral atomic hydrogen in the universe over a redshift range from z∼6 to z∼12, was highly dependent on the flux of ionizing LyC photons in the interstellar and intergalactic media. Expanding our understanding of the dynamics of the Lyα escape fraction (fLyα) from the local environment of its emission could be key to determining a total LyC escape fraction (fLyC) across all morphologies of galaxies. The wide range of Lyα emitters and absorbors (occasionally both) of this Cycle 22 SNAP survey observed by the Cosmic Origins Spectrograph (COS) onboard Hubble Space Telescope (HST) provides a unique look at far-UV spectra in candidate LyC emitters. Lyα profiles are easily observable in short exposures, and line features discernable in the low-resolution G140L mode can inform and guide future observations by COS or other FUV spectroscopy.

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.

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.

Morphology of the Saturn Magnetospheric Neutral gas

NASA Astrophysics Data System (ADS)

Shemansky, D. E.

2009-05-01

Although it has been known that Saturn's magnetospheric volume is filled with neutral gas, from the time of the Voyager encounters and subsequent HST observations, the Cassini Mission was essential for revealing the depth of complexity in the source processes and structure of this system. The state of the magnetosphere is unique, containing a plasma environment quenched by neutral gas from the top of the atmosphere to beyond the bow shock with neutral/plasma mixing ratios in the range 100 to ˜ 3000. The dominant neutral species identified in the magnetosphere by remote sensing are atomic hydrogen and oxygen, OH and H2O . Atomic hydrogen was mapped using the Voyager UVS and found to have an asymmetric distribution in local time, filling the entire magnetosphere, with a broad latitudinal distribution. These observations were followed by the measurement of the OH spectrum using the HST FOS. The definition of the HST distribution was limited to a few points in the system, showing a peak near 3. Saturn radii (RS ) from system center. Atomic oxygen was detected and mapped using the Cassini UVIS system, showing orbital asymmetry and temporal variation, with a substantially broader distribution than OH. All of the observed species emissions from the magnetosphere are produced by solar photon fluorescence, the ambient plasma volume being too low in density and temperature to generate measurable particle excited emission. H2O has been measured in Cassini UVIS stellar occultations at the south polar plumes at Enceladus, with a total mass injection rate that is the same order needed to maintain the oxygen population. The oxygen distribution, however, indicates that sources other than Enceladus may be contributing. Virtually all of the atomic hydrogen in the system is attributed to escape from the top of the Saturn atmosphere. The complexity of this process was graphically revealed in the Cassini UVIS system higher resolution images showing a plume of atoms in ballistic and

Hepatitis C Virus Evasion Mechanisms from Neutralizing Antibodies

PubMed Central

Di Lorenzo, Caterina; Angus, Allan G. N.; Patel, Arvind H.

2011-01-01

Hepatitis C virus (HCV) represents a major public health problem, affecting 3% of the world’s population. The majority of infected individuals develop chronic hepatitis, which can progress to cirrhosis and hepatocellular carcinoma. To date, a vaccine is not available and current therapy is limited by resistance, adverse effects and high costs. Although it is very well established that cell-mediated immunity is necessary for viral clearance, the importance of host antibodies in clearing HCV infection is being increasingly recognized. Indeed, recent studies indicate that neutralizing antibodies are induced in the early phase of infection by patients who subsequently clear viral infection. Conversely, patients who do not clear the virus develop high titers of neutralizing antibodies during the chronic stage. Surprisingly, these antibodies are not able to control HCV infection. HCV has therefore developed mechanisms to evade immune elimination, allowing it to persist in the majority of infected individuals. A detailed understanding of the mechanisms by which the virus escapes immune surveillance is therefore necessary if novel preventive and therapeutic treatments have to be designed. This review summarizes the current knowledge of the mechanisms used by HCV to evade host neutralizing antibodies. PMID:22163345

The Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution Mission

NASA Technical Reports Server (NTRS)

Mahaffy, Paul R.; Benna, Mehdi; King, Todd; Harpold, Daniel N.; Arvey, Robert; Barciniak, Michael; Bendt, Mirl; Carrigan, Daniel; Errigo, Therese; Holmes, Vincent;

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

Neutral Beam Development for the Lockheed Martin Compact Fusion Reactor

NASA Astrophysics Data System (ADS)

Ebersohn, Frans; Sullivan, Regina

2017-10-01

The Compact Fusion Reactor project at Lockheed Martin Skunk Works is developing a neutral beam injection system for plasma heating. The neutral beam plasma source consists of a high current lanthanum hexaboride (LaB6) hollow cathode which drives an azimuthal cusp discharge similar to gridded ion thrusters. The beam is extracted with a set of focusing grids and is then neutralized in a chamber pumped with Titanium gettering. The design, testing, and analyses of individual components are presented along with the most current full system results. The goal of this project is to advance in-house neutral beam expertise at Lockheed Martin to aid in operation, procurement, and development of neutral beam technology. ©2017 Lockheed Martin Corporation. All Rights Reserved.

Interspecific evaluation of octopus escape behavior.

PubMed

Wood, James B; Anderson, Roland C

2004-01-01

The well-known ability of octopuses to escape enclosures is a behavior that can be fatal and, therefore, is an animal welfare issue. This study obtained survey data from 38 participants-primarily scientists and public aquarists who work with octopuses-on 25 described species of octopus. The study demonstrates that the likeliness to escape is species specific (p =.001). The study gives husbandry techniques to keep captive octopuses contained. This first interspecific study of octopus escape behavior allows readers to make informed species-specific husbandry choices.

Project Mercury Escape Tower Rockets Tests

NASA Image and Video Library

1960-04-21

A Mercury capsule is mounted inside the Altitude Wind Tunnel for a test of its escape tower rockets at the National Aeronautics and Space Administration (NASA) Lewis Research Center. In October 1959 NASA’s Space Task Group allocated several Project Mercury assignments to Lewis. The Altitude Wind Tunnel was quickly modified so that its 51-foot diameter western leg could be used as a test chamber. The final round of tests in the Altitude Wind Tunnel sought to determine if the smoke plume from the capsule’s escape tower rockets would shroud or compromise the spacecraft. The escape tower, a 10-foot steel rig with three small rockets, was attached to the nose of the Mercury capsule. It could be used to jettison the astronaut and capsule to safety in the event of a launch vehicle malfunction on the pad or at any point prior to separation from the booster. Once actuated, the escape rockets would fire, and the capsule would be ejected away from the booster. After the capsule reached its apex of about 2,500 feet, the tower, heatshield, retropackage, and antenna would be ejected and a drogue parachute would be released. Flight tests of the escape system were performed at Wallops Island as part of the series of Little Joe launches. Although the escape rockets fired prematurely on Little Joe’s first attempt in August 1959, the January 1960 follow-up was successful.

Non-thermal escape of molecular hydrogen from Mars

NASA Astrophysics Data System (ADS)

Gacesa, M.; Zhang, P.; Kharchenko, V.

2012-05-01

We present a detailed theoretical analysis of non-thermal escape of molecular hydrogen from Mars induced by collisions with hot atomic oxygen from the Martian corona. To accurately describe the energy transfer in O + H2(v, j) collisions, we performed extensive quantum-mechanical calculations of state-to-state elastic, inelastic, and reactive cross sections. The escape flux of H2 molecules was evaluated using a simplified 1D column model of the Martian atmosphere with realistic densities of atmospheric gases and hot oxygen production rates for low solar activity conditions. An average intensity of the non-thermal escape flux of H2 of 1.9 × 105 cm-2s-1 was obtained considering energetic O atoms produced in dissociative recombinations of O2+ ions. Predicted ro-vibrational distribution of the escaping H2 was found to contain a significant fraction of higher rotational states. While the non-thermal escape rate was found to be lower than Jeans rate for H2 molecules, the non-thermal escape rates of HD and D2 are significantly higher than their respective Jeans rates. The accurate evaluation of the collisional escape flux of H2 and its isotopes is important for understanding non-thermal escape of molecules from Mars, as well as for the formation of hot H2 Martian corona. The described molecular ejection mechanism is general and expected to contribute to atmospheric escape of H2 and other light molecules from planets, satellites, and exoplanetary bodies.

Survival in Emergency Escape from Passenger Aircraft,

DTIC Science & Technology

ESCAPE SYSTEMS, *TRANSPORT AIRCRAFT, ESCAPE SYSTEMS, CIVIL AVIATION, STATISTICAL DATA, AIRCRAFT DOORS, EVACUATION, MORTALITY RATE, ADULTS , CHILDREN, SEX, AIRCRAFT FIRES, AIRCRAFT CABINS, FEMALES, BEHAVIOR.

XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of Terrestrial Planets. Part II: Hydrogen Coronae and Ion Escape

PubMed Central

Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V.; Leitzinger, Martin; Khodachenko, Maxim L.; Kulikov, Yuri N.; Güdel, Manuel; Hanslmeier, Arnold

2013-01-01

Abstract We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a “super-Earth” with a radius of 2 REarth and a mass of 10 MEarth, located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×1025 s−1 to ∼5.3×1030 s−1, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EOH) to <3 EOH and usually is several times smaller in comparison to the thermal atmospheric escape rates. Key Words: Stellar activity—Low-mass stars—Early atmospheres—Earth-like exoplanets—Energetic neutral

Titan impacts and escape

NASA Astrophysics Data System (ADS)

Korycansky, D. G.; Zahnle, Kevin J.

2011-01-01

We report on hydrodynamic calculations of impacts of large (multi-kilometer) objects on Saturn's moon Titan. We assess escape from Titan, and evaluate the hypothesis that escaping ejecta blackened the leading hemisphere of Iapetus and peppered the surface of Hyperion. We carried out two- and three-dimensional simulations of impactors ranging in size from 4 to 100 km diameter, impact velocities between 7 and 15 km s -1, and impact angles from 0° to 75° from the vertical. We used the ZEUSMP2 hydrocode for the calculations. Simulations were made using three different geometries: three-dimensional Cartesian, two-dimensional axisymmetric spherical polar, and two-dimensional plane polar. Three-dimensional Cartesian geometry calculations were carried out over a limited domain (e.g. 240 km on a side for an impactor of size di = 10 km), and the results compared to ones with the same parameters done by Artemieva and Lunine (2005); in general the comparison was good. Being computationally less demanding, two-dimensional calculations were possible for much larger domains, covering global regions of the satellite (from 800 km below Titan's surface to the exobase altitude 1700 km above the surface). Axisymmetric spherical polar calculations were carried out for vertical impacts. Two-dimensional plane-polar geometry calculations were made for both vertical and oblique impacts. In general, calculations among all three geometries gave consistent results. Our basic result is that the amount of escaping material is less than or approximately equal to the impactor mass even for the most favorable cases. Amounts of escaping material scaled most strongly as a function of velocity, with high-velocity impacts generating the largest amount, as expected. Dependence of the relative amount of escaping mass fesc = mesc/ Mi on impactor diameter di was weak. Oblique impacts (impact angle θi > 45°) were more effective than vertical or near-vertical impacts; ratios of mesc/ Mi ˜ 1-2 were

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.

46 CFR 185.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Escape hatches and emergency exits. 185.606 Section 185... 100 GROSS TONS) OPERATIONS Markings Required § 185.606 Escape hatches and emergency exits. All escape hatches and other emergency exits used as means of escape must be marked on both sides in clearly legible...

46 CFR 185.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Escape hatches and emergency exits. 185.606 Section 185... 100 GROSS TONS) OPERATIONS Markings Required § 185.606 Escape hatches and emergency exits. All escape hatches and other emergency exits used as means of escape must be marked on both sides in clearly legible...

46 CFR 185.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Escape hatches and emergency exits. 185.606 Section 185... 100 GROSS TONS) OPERATIONS Markings Required § 185.606 Escape hatches and emergency exits. All escape hatches and other emergency exits used as means of escape must be marked on both sides in clearly legible...

46 CFR 185.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Escape hatches and emergency exits. 185.606 Section 185... 100 GROSS TONS) OPERATIONS Markings Required § 185.606 Escape hatches and emergency exits. All escape hatches and other emergency exits used as means of escape must be marked on both sides in clearly legible...

46 CFR 185.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Escape hatches and emergency exits. 185.606 Section 185... 100 GROSS TONS) OPERATIONS Markings Required § 185.606 Escape hatches and emergency exits. All escape hatches and other emergency exits used as means of escape must be marked on both sides in clearly legible...

Prosthetic Mitral Valve Leaflet Escape

PubMed Central

Kim, Darae; Hun, Sin Sang; Cho, In-Jeong; Shim, Chi-Young; Ha, Jong-Won; Chung, Namsik; Ju, Hyun Chul; Sohn, Jang Won

2013-01-01

Leaflet escape of prosthetic valve is rare but potentially life threatening. It is essential to make timely diagnosis in order to avoid mortality. Transesophageal echocardiography and cinefluoroscopy is usually diagnostic and the location of the missing leaflet can be identified by computed tomography (CT). Emergent surgical correction is mandatory. We report a case of fractured escape of Edward-Duromedics mitral valve 27 years after the surgery. The patient presented with symptoms of acute decompensated heart failure and cardiogenic shock. She was instantly intubated and mechanically ventilated. After prompt evaluation including transthoracic echocardiography and CT, the escape of the leaflet was confirmed. The patient underwent emergent surgery for replacement of the damaged prosthetic valves immediately. Eleven days after the surgery, the dislodged leaflet in iliac artery was removed safely and the patient recovered well. PMID:23837121

Risks incurred by hydrogen escaping from containers and conduits

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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.

Emergence of Ebola Virus Escape Variants in Infected Nonhuman Primates Treated with the MB-003 Antibody Cocktail.

PubMed

Kugelman, Jeffrey R; Kugelman-Tonos, Johanny; Ladner, Jason T; Pettit, James; Keeton, Carolyn M; Nagle, Elyse R; Garcia, Karla Y; Froude, Jeffrey W; Kuehne, Ana I; Kuhn, Jens H; Bavari, Sina; Zeitlin, Larry; Dye, John M; Olinger, Gene G; Sanchez-Lockhart, Mariano; Palacios, Gustavo F

2015-09-29

MB-003, a plant-derived monoclonal antibody cocktail used effectively in treatment of Ebola virus infection in non-human primates, was unable to protect two of six animals when initiated 1 or 2 days post-infection. We characterized a mechanism of viral escape in one of the animals, after observation of two clusters of genomic mutations that resulted in five nonsynonymous mutations in the monoclonal antibody target sites. These mutations were linked to a reduction in antibody binding and later confirmed to be present in a viral isolate that was not neutralized in vitro. Retrospective evaluation of a second independent study allowed the identification of a similar case. Four SNPs in previously identified positions were found in this second fatality, suggesting that genetic drift could be a potential cause for treatment failure. These findings highlight the importance selecting different target domains for each component of the cocktail to minimize the potential for viral escape. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

30 CFR 77.1101 - Escape and evacuation; plan.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 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 and...

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 and...

30 CFR 77.1101 - Escape and evacuation; plan.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 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 and...

30 CFR 77.1101 - Escape and evacuation; plan.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 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 and...

Crystal engineering of a zwitterionic drug to neutral cocrystals: a general solution for floxacins.

PubMed

Gunnam, Anilkumar; Suresh, Kuthuru; Ganduri, Ramesh; Nangia, Ashwini

2016-10-18

The transformation of zwitterionic Sparfloxacin (SPX) to the neutral form is achieved by cocrystallization. Neutral forms of drugs are important for higher membrane permeability, while zwitterions are more soluble in water. The twin advantages of higher solubility/dissolution rate and good stability of neutral SPX are achieved in a molecular cocrystal compared to its zwitterionic SPX hydrate. The amine-phenol supramolecular synthon drives cocrystal formation, with the paraben ester acting as a "proton migrator" for the ionic to neutral transformation.

Phenotypic Mismatches Reveal Escape from Arms-Race Coevolution

PubMed Central

Hanifin, Charles T; Brodie, Edmund D; Brodie, Edmund D

2008-01-01

Because coevolution takes place across a broad scale of time and space, it is virtually impossible to understand its dynamics and trajectories by studying a single pair of interacting populations at one time. Comparing populations across a range of an interaction, especially for long-lived species, can provide insight into these features of coevolution by sampling across a diverse set of conditions and histories. We used measures of prey traits (tetrodotoxin toxicity in newts) and predator traits (tetrodotoxin resistance of snakes) to assess the degree of phenotypic mismatch across the range of their coevolutionary interaction. Geographic patterns of phenotypic exaggeration were similar in prey and predators, with most phenotypically elevated localities occurring along the central Oregon coast and central California. Contrary to expectations, however, these areas of elevated traits did not coincide with the most intense coevolutionary selection. Measures of functional trait mismatch revealed that over one-third of sampled localities were so mismatched that reciprocal selection could not occur given current trait distributions. Estimates of current locality-specific interaction selection gradients confirmed this interpretation. In every case of mismatch, predators were “ahead” of prey in the arms race; the converse escape of prey was never observed. The emergent pattern suggests a dynamic in which interacting species experience reciprocal selection that drives arms-race escalation of both prey and predator phenotypes at a subset of localities across the interaction. This coadaptation proceeds until the evolution of extreme phenotypes by predators, through genes of large effect, allows snakes to, at least temporarily, escape the arms race. PMID:18336073

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

Narrow Escape of Interacting Diffusing Particles

NASA Astrophysics Data System (ADS)

Agranov, Tal; Meerson, Baruch

2018-03-01

The narrow escape problem deals with the calculation of the mean escape time (MET) of a Brownian particle from a bounded domain through a small hole on the domain's boundary. Here we develop a formalism which allows us to evaluate the nonescape probability of a gas of diffusing particles that may interact with each other. In some cases the nonescape probability allows us to evaluate the MET of the first particle. The formalism is based on the fluctuating hydrodynamics and the recently developed macroscopic fluctuation theory. We also uncover an unexpected connection between the narrow escape of interacting particles and thermal runaway in chemical reactors.

Mars atmospheric escape and evolution; interaction with the solar wind

NASA Astrophysics Data System (ADS)

Chassefière, Eric; Leblanc, François

2004-09-01

This tutorial deals with the question of atmospheric escape on Mars. After a brief introduction describing the general context of Mars escape studies, we will present in Section 2 a simplified theory of thermal escape, of both Jeans and hydrodynamic types. The phenomenon of hydrodynamic escape, still hypothetical and not proved to have ever existed on terrestrial planets, will be treated with the help of two well known examples: (i) the isotopic fractionation of xenon in Mars and Earth atmospheres, (ii) the paradox of missing oxygen in Venus atmosphere. In Section 3, a simplified approach of non-thermal escape will be developed, treating in a specific way the different kinds of escape (photochemical escape, ion sputtering, ion escape and ionospheric outflow). As a matter of illustration, some calculations of the relative contributions of these mechanisms, and of their time evolutions, will be given, and the magnitude of the total amount of atmosphere lost by non-thermal escape will be estimated. Section 4 will present the state of knowledge concerning the constraints derived from Mars isotopic geochemistry in terms of past escape and evolution. Finally, a few conclusions, which are more interrogations, will be proposed.

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.

Residential smoke alarms and fire escape plans.

PubMed

Harvey, P A; Sacks, J J; Ryan, G W; Bender, P F

1998-01-01

To estimate the proportion of U.S. homes with installed smoke alarms, smoke alarms on the same floor as occupants' bedrooms, and fire escape plans. The authors analyzed data on smoke alarm use and fire escape planning from a 1994 stratified random telephone survey of 5238 U.S. households. Respondents from 91% of surveyed households reported the presence of at least one installed smoke alarm, and 94% of respondents reported having an alarm on the same level of the home as their sleeping area. The prevalence of installed smoke alarms varied by highest education level in the household and income level. Sixty percent of all households had designed or discussed a fire escape plan at least once; only 17% of these households had actually practiced one. Although overall use of smoke alarms was high, certain population subgroups were less likely to have smoke alarms or to have them installed on the same floor as bedrooms. Fire escape planning, another important safety measure, was somewhat less common, and very few respondents reported having practiced a fire escape plan with the members of their household.

Potent Autologous and Heterologous Neutralizing Antibody Responses Occur in HIV-2 Infection across a Broad Range of Infection Outcomes

PubMed Central

Aasa-Chapman, Marlén; Cotten, Matthew; Hué, Stéphane; Robinson, James; Bibollet-Ruche, Frederic; Sarge-Njie, Ramu; Berry, Neil; Jaye, Assan; Aaby, Peter; Whittle, Hilton; Rowland-Jones, Sarah; Weiss, Robin

2012-01-01

Few studies have explored the role of neutralizing antibody (NAb) responses in controlling HIV-2 viremia and disease progression. Using a TZM-bl neutralization assay, we assessed heterologous and autologous NAb responses from a community cohort of HIV-2-infected individuals with a broad range of disease outcomes in rural Guinea-Bissau. All subjects (n = 40) displayed exceptionally high heterologous NAb titers (50% inhibitory plasma dilution or 50% inhibitory concentration [IC50], 1:7,000 to 1:1,000,000) against 5 novel primary HIV-2 envelopes and HIV-2 7312A, whereas ROD A and 3 primary envelopes were relatively resistant to neutralization. Most individuals also showed high autologous NAb against contemporaneous envelopes (78% of plasma-envelope combinations in 69 envelopes from 21 subjects), with IC50s above 1:10,000. No association between heterologous or autologous NAb titer and greater control of HIV-2 was found. A subset of envelopes was found to be more resistant to neutralization (by plasma and HIV-2 monoclonal antibodies). These envelopes were isolated from individuals with greater intrapatient sequence diversity and were associated with changes in potential N-linked glycosylation sites but not CD4 independence or CXCR4 use. Plasma collected from up to 15 years previously was able to potently neutralize recent autologous envelopes, suggesting a lack of escape from NAb and the persistence of neutralization-sensitive variants over time, despite significant NAb pressure. We conclude that despite the presence of broad and potent NAb responses in HIV-2-infected individuals, these are not the primary forces behind the dichotomous outcomes observed but reveal a limited capacity for adaptive selection and escape from host immunity in HIV-2 infection. PMID:22072758

Decompression illness in goats following simulated submarine escape: 1993-2006.

PubMed

Seddon, F M; Thacker, J C; Fisher, A S; Jurd, K M; White, M G; Loveman, G A M

2014-01-01

The United Kingdom Ministry of Defence commissioned work to define the relationship between the internal pressure of a distressed submarine (DISSUB), the depth from which escape is made and the risk of decompression illness (DCI). The program of work used an animal model (goat) to define these risks and this paper reports the incidence and type of DCI observed. A total of 748 pressure exposures comprising saturation only, escape only or saturation followed by escape were conducted in the submarine escape simulator between 1993 and 2006. The DCI following saturation exposures was predominantly limb pain, whereas following escape exposures the DCI predominantly involved the central nervous system and was fast in onset. There was no strong relationship between the risk of DCI and the range of escape depths investigated. The risk of DCI incurred from escape following saturation was greater than that obtained by combining the risks for the independent saturation only, and escape only, exposures. The output from this program of work has led to improved advice on the safety of submarine escape.

Room Escape at Class: Escape Games Activities to Facilitate the Motivation and Learning in Computer Science

ERIC Educational Resources Information Center

Borrego, Carlos; Fernández, Cristina; Blanes, Ian; Robles, Sergi

2017-01-01

Real-life room-escape games are ludic activities in which participants enter a room in order to get out of it only after solving some riddles. In this paper, we explain a Room Escape teaching experience developed in the Engineering School at Universitat Autònoma de Barcelona. The goal of this activity is to increase student's motivation and to…

Memory B cells, but not long-lived plasma cells, possess antigen specificities for viral escape mutants

PubMed Central

Purtha, Whitney E.; Tedder, Thomas F.; Johnson, Syd

2011-01-01

Memory B cells (MBCs) and long-lived plasma cells (LLPCs) persist after clearance of infection, yet the specific and nonredundant role MBCs play in subsequent protection is unclear. After resolution of West Nile virus infection in mice, we demonstrate that LLPCs were specific for a single dominant neutralizing epitope, such that immune serum poorly inhibited a variant virus that encoded a mutation at this critical epitope. In contrast, a large fraction of MBC produced antibody that recognized both wild-type (WT) and mutant viral epitopes. Accordingly, antibody produced by the polyclonal pool of MBC neutralized WT and variant viruses equivalently. Remarkably, we also identified MBC clones that recognized the mutant epitope better than the WT protein, despite never having been exposed to the variant virus. The ability of MBCs to respond to variant viruses in vivo was confirmed by experiments in which MBCs were adoptively transferred or depleted before secondary challenge. Our data demonstrate that class-switched MBC can respond to variants of the original pathogen that escape neutralization of antibody produced by LLPC without a requirement for accumulating additional somatic mutations. PMID:22162833

Orbital and escape dynamics in barred galaxies - III. The 3D system: correlations between the basins of escape and the NHIMs

NASA Astrophysics Data System (ADS)

Zotos, Euaggelos E.; Jung, Christof

2018-01-01

The escape dynamics of the stars in a barred galaxy composed of a spherically symmetric central nucleus, a bar, a flat thin disc and a dark matter halo component is investigated by using a realistic three degrees of freedom (3-d.o.f.) dynamical model. Modern colour-coded diagrams are used for distinguishing between bounded and escaping motion. In addition, the smaller alignment index method is deployed for determining the regular, sticky or chaotic nature of bounded orbits. We reveal the basins of escape corresponding to the escape through the two symmetrical escape channels around the Lagrange points L2 and L3 and also we relate them with the corresponding distribution of the escape times of the orbits. Furthermore, we demonstrate how the stable manifolds, around the index-1 saddle points, accurately define the fractal basin boundaries observed in the colour-coded diagrams. The development scenario of the fundamental vertical Lyapunov periodic orbit is thoroughly explored for obtaining a more complete view of the unfolding of the singular behaviour of the dynamics at the cusp values of the parameters. Finally, we examine how the combination of the most important parameters of the bar (such as the semimajor axis and the angular velocity) influences the observed stellar structures (rings and spirals), which are formed by escaping stars guided by the invariant manifolds near the saddle points.

Residential smoke alarms and fire escape plans.

PubMed Central

Harvey, P A; Sacks, J J; Ryan, G W; Bender, P F

1998-01-01

OBJECTIVE: To estimate the proportion of U.S. homes with installed smoke alarms, smoke alarms on the same floor as occupants' bedrooms, and fire escape plans. METHODS: The authors analyzed data on smoke alarm use and fire escape planning from a 1994 stratified random telephone survey of 5238 U.S. households. RESULTS: Respondents from 91% of surveyed households reported the presence of at least one installed smoke alarm, and 94% of respondents reported having an alarm on the same level of the home as their sleeping area. The prevalence of installed smoke alarms varied by highest education level in the household and income level. Sixty percent of all households had designed or discussed a fire escape plan at least once; only 17% of these households had actually practiced one. CONCLUSIONS: Although overall use of smoke alarms was high, certain population subgroups were less likely to have smoke alarms or to have them installed on the same floor as bedrooms. Fire escape planning, another important safety measure, was somewhat less common, and very few respondents reported having practiced a fire escape plan with the members of their household. PMID:9769771

A New Paradigm for Evaluating Avoidance/Escape Motivation.

PubMed

Tsutsui-Kimura, Iku; Bouchekioua, Youcef; Mimura, Masaru; Tanaka, Kenji F

2017-07-01

Organisms have evolved to approach pleasurable opportunities and to avoid or escape from aversive experiences. These 2 distinct motivations are referred to as approach and avoidance/escape motivations and are both considered vital for survival. Despite several recent advances in understanding the neurobiology of motivation, most studies addressed approach but not avoidance/escape motivation. Here we develop a new experimental paradigm to quantify avoidance/escape motivation and examine the pharmacological validity. We set up an avoidance variable ratio 5 task in which mice were required to press a lever for variable times to avoid an upcoming aversive stimulus (foot shock) or to escape the ongoing aversive event if they failed to avoid it. We i.p. injected ketamine (0, 1, or 5 mg/kg) or buspirone (0, 5, or 10 mg/kg) 20 or 30 minutes before the behavioral task to see if ketamine enhanced avoidance/escape behavior and buspirone diminished it as previously reported. We found that the performance on the avoidance variable ratio 5 task was sensitive to the intensity of the aversive stimulus. Treatment with ketamine increased while that with buspirone decreased the probability of avoidance from an aversive stimulus in the variable ratio 5 task, being consistent with previous reports. Our new paradigm will prove useful for quantifying avoidance/escape motivation and will contribute to a more comprehensive understanding of motivation. © The Author 2017. Published by Oxford University Press on behalf of CINP.

On the escape of oxygen and hydrogen from Mars

NASA Technical Reports Server (NTRS)

Fox, J. L.

1993-01-01

Escape rates of oxygen atoms from dissociative recombination of O2(+) above the Martian exobase are computed in light of new information from ab initio calculations of the dissociative recombination process and our recently revised understanding of the Martian dayside ionosphere. Only about 60 percent of the dissociative recombinations occur in channels in which the O atoms are released with energies in excess of the escape velocity. Futhermore, we find that the computed escape fluxes for O depend greatly on the nature of the ion loss process that has been found necessary to reproduce the topside ion density profiles measured by Viking. If it is assumed that the ions are not lost from the gravitational field of the planet, as required by an analysis of nitrogen escape, the computed average O escape rate is 3 x 10 exp 6/sq cm/s, much less than half the H escape rates inferred from measurements of the Lyman-alpha dayglow, which are in the range (1-2) x 10 exp 8/sq cm/s. Suggestions for restoring the relative escape rates of H and O to the stoichiometric ratio of water are explored.

Interactive Ion-Neutral Dynamics in the Low Latitude Evening Ionosphere

NASA Astrophysics Data System (ADS)

Evonosky, W. R.; Richmond, A. D.; Fang, T. W.; Maute, A. I.

2015-12-01

Neutral winds in the ionosphere drive global electrodynamic phenomena which alter theupper-atmosphere so significantly that they can affect the orbit of satellites andground-to-spacecraft communications. Understanding these winds and what drives them is centralto prediction and risk management associated with such a dynamic upper atmosphere. This studyexamined the relationship between accelerations acting on neutral winds in the ionosphere and theformation of a vertical shear of those winds in low latitudes (between ±30 magnetic) and earlyevening local times (16-22 LT). Accelerations were calculated using variables output by thethermosphere ionosphere electrodynamics general circulation model (TIEGCM) under differentsolar activity and night-time ionization conditions and visualized both spatially and temporally. Ingeneral, with acceleration values averaged along magnetic latitudes between ±30 degrees(inclusive) and only considering medium solar activity conditions, we found that the ionosphereexhibits distinct layering defined by the dominant accelerations in each layer. We also found hintsthat during different night-time ionization levels, ion drag acceleration tends to remain constantwhile ion and neutral velocities change to conserve the difference between them. When consideringspecific latitudes and solar conditions, previously unreported structures appear which involveinteractions between the ion drag and viscous forces.

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)

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.

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.

Managing Pacific salmon escapements: The gaps between theory and reality

USGS Publications Warehouse

Knudsen, E. Eric; Knudsen, E. Eric; Steward, Cleveland R.; MacDonald, Donald D.; Williams, Jack E.; Reiser, Dudley W.

1999-01-01

There are myriad challenges to estimating intrinsic production capacity for Pacific salmon populations that are heavily exploited and/or suffering from habitat alteration. Likewise, it is difficult to determine whether perceived decreases in production are due to harvest, habitat, or hatchery influences, natural variation, or some combination of all four. There are dramatic gaps between the true nature of the salmon spawner/recruit relationship and the theoretical basis for describing and understanding the relationship. Importantly, there are also extensive practical difficulties associated with gathering and interpreting accurate escapement and run-size information and applying it to population management. Paradoxically, certain aspects of salmon management may well be contributing to losses in abundance and biodiversity, including harvesting salmon in mixed population fisheries, grouping populations into management units subject to a common harvest rate, and fully exploiting all available hatchery fish at the expense of wild fish escapements. Information on U.S. Pacific salmon escapement goal-setting methods, escapement data collection methods and estimation types, and the degree to which stocks are subjected to mixed stock fisheries was summarized and categorized for 1,025 known management units consisting of 9,430 known populations. Using criteria developed in this study, only 1% of U.S. escapement goals are by methods rated as excellent. Escapement goals for 16% of management units were rated as good. Over 60% of escapement goals have been set by methods rated as either fair or poor and 22% of management units have no escapement goals at all. Of the 9,430 populations for which any information was available, 6,614 (70%) had sufficient information to categorize the method by which escapement data are collected. Of those, data collection methods were rated as excellent for 1%, good for 1%, fair for 2%, and poor for 52%. Escapement estimates are not made for 44

46 CFR 122.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Escape hatches and emergency exits. 122.606 Section 122.606 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING... Markings Required § 122.606 Escape hatches and emergency exits. All escape hatches and other emergency...

46 CFR 122.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Escape hatches and emergency exits. 122.606 Section 122.606 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING... Markings Required § 122.606 Escape hatches and emergency exits. All escape hatches and other emergency...

46 CFR 122.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Escape hatches and emergency exits. 122.606 Section 122.606 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING... Markings Required § 122.606 Escape hatches and emergency exits. All escape hatches and other emergency...

46 CFR 122.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Escape hatches and emergency exits. 122.606 Section 122.606 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING... Markings Required § 122.606 Escape hatches and emergency exits. All escape hatches and other emergency...

46 CFR 122.606 - Escape hatches and emergency exits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Escape hatches and emergency exits. 122.606 Section 122.606 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING... Markings Required § 122.606 Escape hatches and emergency exits. All escape hatches and other emergency...

Escape from Mars

NASA Image and Video Library

2017-07-10

This image from NASA's Mars Reconnaissance Orbiter shows one of millions of small (10s of meters in diameter) craters and their ejecta material that dot the Elysium Planitia region of Mars. The small craters were likely formed when high-speed blocks of rock were thrown out by a much larger impact (about 10-kilometers in diameter) and fell back to the ground. Some of these blocks may actually escape Mars, which is how we get samples in the form of meteorites that fall to Earth. Other ejected blocks have insufficient velocity, or the wrong trajectory, to escape the Red Planet. As such, when one of these high-speed blocks impacts the surface, it makes what is called a "secondary" crater. These secondaries can form dense "chains" or "rays," which are radial to the crater that formed them. https://photojournal.jpl.nasa.gov/catalog/PIA21769

On geometric factors for neutral particle analyzers

DOE Office of Scientific and Technical Information (OSTI.GOV)

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)]more » 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.« less

Affinity maturation in an HIV broadly neutralizing B-cell lineage through reorientation of variable domains.

PubMed

Fera, Daniela; Schmidt, Aaron G; Haynes, Barton F; Gao, Feng; Liao, Hua-Xin; Kepler, Thomas B; Harrison, Stephen C

2014-07-15

Rapidly evolving pathogens, such as human immunodeficiency and influenza viruses, escape immune defenses provided by most vaccine-induced antibodies. Proposed strategies to elicit broadly neutralizing antibodies require a deeper understanding of antibody affinity maturation and evolution of the immune response to vaccination or infection. In HIV-infected individuals, viruses and B cells evolve together, creating a virus-antibody "arms race." Analysis of samples from an individual designated CH505 has illustrated the interplay between an antibody lineage, CH103, and autologous viruses at various time points. The CH103 antibodies, relatively broad in their neutralization spectrum, interact with the CD4 binding site of gp120, with a contact dominated by CDRH3. We show by analyzing structures of progenitor and intermediate antibodies and by correlating them with measurements of binding to various gp120s that there was a shift in the relative orientation of the light- and heavy-chain variable domains during evolution of the CH103 lineage. We further show that mutations leading to this conformational shift probably occurred in response to insertions in variable loop 5 (V5) of the HIV envelope. The shift displaced the tips of the light chain away from contact with V5, making room for the inserted residues, which had allowed escape from neutralization by the progenitor antibody. These results, which document the selective mechanism underlying this example of a virus-antibody arms race, illustrate the functional significance of affinity maturation by mutation outside the complementarity determining region surface of the antibody molecule.

Trapped as a Group, Escape as a Team: Applying Gamification to Incorporate Team-building Skills Through an 'Escape Room' Experience.

PubMed

Zhang, Xiao Chi; Lee, Hyunjoo; Rodriguez, Carlos; Rudner, Joshua; Chan, Teresa M; Papanagnou, Dimitrios

2018-03-02

Teamwork, a skill critical for quality patient care, is recognized as a core competency by the Accreditation Council for Graduate Medical Education (ACGME). To date, there is no consensus on how to effectively teach these skills in a forum that engages learners, immerses members in life-like activities, and builds both trust and rapport. Recreational 'Escape Rooms' have gained popularity in creating a life-like environment that rewards players for working together, solving puzzles, and completing successions of mind-bending tasks in order to effectively 'escape the room' in the time allotted. In this regard, escape rooms share many parallels with the multitasking and teamwork that is essential for a successful emergency department (ED) shift. A pilot group of nine emergency medicine (EM) residents and one senior EM faculty member underwent a commercial escape room as part of a team-building exercise in January 2018. The escape room required participants to practice teamwork, communication, task delegation, and critical thinking to tackle waves of increasingly complex puzzles, ranging from hidden objects, physical object assembly (i.e., jigsaw puzzles), and symbol matching. Activities required members to recognize and utilize the collective experiences, skills, knowledge base, and physical abilities of the group. After the game, players underwent a structured 'game-master' debriefing facilitated by an employee of the commercial escape room; this was followed by a post-event survey facilitated by a faculty member, which focused on participants' feelings, experiences, and problem-solving techniques. Escape rooms afford learners the opportunity to engage in an activity that rewards teamwork and effective leadership through experiences that directly link to specific ACGME milestones and educational learning theories. EM participants were engaged in the activity and felt that the escape room reproduced an environment analogous to the ED. The debriefing that followed

Limits of neutral drift: lessons from the in vitro evolution of two ribozymes.

PubMed

Petrie, Katherine L; Joyce, Gerald F

2014-10-01

The relative contributions of adaptive selection and neutral drift to genetic change are unknown but likely depend on the inherent abundance of functional genotypes in sequence space and how accessible those genotypes are to one another. To better understand the relative roles of selection and drift in evolution, local fitness landscapes for two different RNA ligase ribozymes were examined using a continuous in vitro evolution system under conditions that foster the capacity for neutral drift to mediate genetic change. The exploration of sequence space was accelerated by increasing the mutation rate using mutagenic nucleotide analogs. Drift was encouraged by carrying out evolution within millions of separate compartments to exploit the founder effect. Deep sequencing of individuals from the evolved populations revealed that the distribution of genotypes did not escape the starting local fitness peak, remaining clustered around the sequence used to initiate evolution. This is consistent with a fitness landscape where high-fitness genotypes are sparse and well isolated, and suggests, at least in this context, that neutral drift alone is not a primary driver of genetic change. Neutral drift does, however, provide a repository of genetic variation upon which adaptive selection can act.

GREEN PEA GALAXIES REVEAL SECRETS OF Lyα ESCAPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Huan; Wang, Junxian; Malhotra, Sangeeta

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 fractionmore » 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.« less

Escape strategies for turboprop aircraft in microburst windshear

NASA Technical Reports Server (NTRS)

Bobbitt, Richard B.; Howard, Richard M.

1991-01-01

The dynamic reponse of a P-3 aircraft and a light twin-engine turboprop to a low-level microburst encounter is modeled. The response to the microburst is depicted for various escape maneuvers. Plots of altitude, velocity, and specific energy are shown for all cases. Takeoff escape strategies are discussed. The optimal escape procedure is found to be flying a constant value of pitch angle. Constant angle of attack maneuvers sometimes result in superior performance.

Extreme Doppler Shifting of Io's Neutral Jets

NASA Astrophysics Data System (ADS)

Schmidt, Carl

2017-08-01

The dynamics and the extension of Jupiter's magnetosphere are determined by the massive internal plasma sources combined with the fast rotation. The vast majority of the plasma originates from the atmosphere of the moon Io, the most volcanically active body in our solar system. Here we propose to characterize the density and velocity of energetic neutral atoms escaping from Io's atmosphere. Exploiting the high resolution and sensitivity of the COS G130M spectral mode, we will measure the Doppler velocities of atomic O, S and Cl streams, which are energized through charge exchange and dissociative recombination of molecular ions. Prior COS observations of Io revealed a large number of emission lines from several ion and neutral species with excellent S/N, obtained over a single HST orbit. Those spectra were obtained surrounding eclipse geometry, where Doppler shifts are minimized and were restricted to Io itself rather than the stream region. Here we will target the extended clouds with only two orbits total when the moon is at eastern and western elongation for maximum Doppler shifts. The observations will provide new constraints on the diffuse large-scale cloud structures in the Jovian system and significantly improve our understanding of the transport of mass and energy within the Io-torus interaction. The absolute brightness, in combination with plasma parameters from line ratios/collision strengths, will allow us to quantify the outflow of energetic neutral atoms from Io's main sulfur-oxygen atmosphere for the first time.

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.

Photochemical Escape of Atomic Carbon from Mars

NASA Astrophysics Data System (ADS)

Fox, J. L.; Hac, A. B.

2009-12-01

Determining the escape rate of C over time is necessary to reconstructing the time-dependent history of volatiles on Mars. We report initial results from a one-dimensional spherical Monte Carlo calculation of photochemical escape fluxes and rates of atomic carbon from the Martian atmosphere. This model has recently been used to estimate the photochemical escape flux of O from Mars. We include as sources photodissociation of CO, dissociative recombination of CO+, photoelectron-impact dissociation of CO, photodissociative ionization and photoelectron impact dissociative ionization. Dissociative recombination of CO2+ has been suggested as a source of C (in the channel that produces C + O2) but later studies have found that the yield of this channel is negligible. We test the potential importance of this reaction by comparing the final results produced by including it and excluding it. Finally we compare the range of the escape rate to that of C in ions that have been modeled or measured by ASPERA instruments on MEX and Phobos.

46 CFR 169.745 - Escape hatches and emergency exits.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Escape hatches and emergency exits. 169.745 Section 169... VESSELS Vessel Control, Miscellaneous Systems, and Equipment Markings § 169.745 Escape hatches and emergency exits. Each escape hatch and other emergency exit must be marked on both sides using at least 1...

46 CFR 169.745 - Escape hatches and emergency exits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Escape hatches and emergency exits. 169.745 Section 169... VESSELS Vessel Control, Miscellaneous Systems, and Equipment Markings § 169.745 Escape hatches and emergency exits. Each escape hatch and other emergency exit must be marked on both sides using at least 1...

46 CFR 169.745 - Escape hatches and emergency exits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Escape hatches and emergency exits. 169.745 Section 169... VESSELS Vessel Control, Miscellaneous Systems, and Equipment Markings § 169.745 Escape hatches and emergency exits. Each escape hatch and other emergency exit must be marked on both sides using at least 1...

46 CFR 169.745 - Escape hatches and emergency exits.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Escape hatches and emergency exits. 169.745 Section 169... VESSELS Vessel Control, Miscellaneous Systems, and Equipment Markings § 169.745 Escape hatches and emergency exits. Each escape hatch and other emergency exit must be marked on both sides using at least 1...

46 CFR 169.745 - Escape hatches and emergency exits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Escape hatches and emergency exits. 169.745 Section 169... VESSELS Vessel Control, Miscellaneous Systems, and Equipment Markings § 169.745 Escape hatches and emergency exits. Each escape hatch and other emergency exit must be marked on both sides using at least 1...

DR-induced escape of O and C from early Mars

NASA Astrophysics Data System (ADS)

Zhao, Jinjin; Tian, Feng; Ni, Yufang; Huang, Xiaomeng

2017-03-01

Energetic particles produced in Dissociative recombination (DR) reactions could escape planets with low gravity, such as Mars, if they could overcome collisions with the surrounding background gases. In this work, a 3-D Monte Carlo model is developed to study these photochemical escape processes on early Mars. Although the DR reaction rates of O2+, CO2+, and CO+ increase monotonically with solar soft X-ray and extreme ultraviolet (XUV) flux, the peak of the calculated DR-induced escape rates of O is near 3 × XUV, and the DR-induced escape rates of C increase with XUV until 10 × XUV. The non-monotonic behavior can be explained by the increased column densities of background species in high XUV conditions, which can deflect energetic particles through collisions more efficiently. At 20 × XUV, CO+ DR is the main source of escaping O and C, and the escape of secondary particles could contribute to 30∼40% and 10% of the total escape of O and C respectively. The time-integrated DR-induced escape of O and C is equivalent to 1 m of H2O and 20 mbar of CO2 escaping early Mars since 4.5 billion years ago. The accumulated CO2 loss is much lower than what's needed to explain the carbon isotopic ratios on Mars and much lower than the total CO2 needed to warm up early Mars. If more vigorous escape mechanisms were absent on early Mars, substantial inventories of volatiles have not been detected yet.

Antibody-Dependent Cell-Mediated Viral Inhibition Emerges after Simian Immunodeficiency Virus SIVmac251 Infection of Rhesus Monkeys Coincident with gp140-Binding Antibodies and Is Effective against Neutralization-Resistant Viruses▿

PubMed Central

Asmal, Mohammed; Sun, Yue; Lane, Sophie; Yeh, Wendy; Schmidt, Stephen D.; Mascola, John R.; Letvin, Norman L.

2011-01-01

Antibody-dependent cell-mediated viral inhibition (ADCVI) is an attractive target for vaccination because it takes advantage of both the anamnestic properties of an adaptive immune response and the rapid early response characteristics of an innate immune response. Effective utilization of ADCVI in vaccine strategies will depend on an understanding of the natural history of ADCVI during acute and chronic human immunodeficiency virus type 1 (HIV-1) infection. We used the simian immunodeficiency virus (SIV)-infected rhesus monkey as a model to study the kinetics of ADCVI in early infection, the durability of ADCVI through the course of infection, and the effectiveness of ADCVI against viruses with envelope mutations that are known to confer escape from antibody neutralization. We demonstrate the development of ADCVI, capable of inhibiting viral replication 100-fold, within 3 weeks of infection, preceding the development of a comparable-titer neutralizing antibody response by weeks to months. The emergence of ADCVI was temporally associated with the emergence of gp140-binding antibodies, and in most animals, ADCVI persisted through the course of infection. Highly evolved viral envelopes from viruses isolated at late time points following infection that were resistant to plasma neutralization remained susceptible to ADCVI, suggesting that the epitope determinants of neutralization escape are not shared by antibodies that mediate ADCVI. These findings suggest that despite the ability of SIV to mutate and adapt to multiple immunologic pressures during the course of infection, SIV envelope may not escape the binding of autologous antibodies that mediate ADCVI. PMID:21450829

Clustering and Phase Transitions on a Neutral Landscape

NASA Astrophysics Data System (ADS)

Scott, Adam; King, Dawn; Maric, Nevena; Bahar, Sonya

2012-02-01

The problem of speciation and species aggregation on a neutral landscape, subject to random mutational fluctuations rather than selective drive, has been a focus of research since the seminal work of Kimura on genetic drift. These ideas have received increased attention due to the more recent development of a neutral ecological theory by Hubbell. De Aguiar et al. recently demonstrated, in a computational model, that speciation can occur under neutral conditions; this study bears some comparison with more mathematical studies of clustering on neutral landscapes in the context of branching and annihilating random walks. Here, we show that clustering can occur on a neutral landscape where the dimensions specify the simulated organisms' phenotypes. Unlike the De Aguiar et al. model, we simulate sympatric speciation: the organisms cluster phenotypically, but are not spatially separated. Moreover, we find that clustering occurs not only in the case of assortative mating, but also in the case of asexual fission. Clustering is not observed in a control case where organisms can mate randomly. We find that the population size and the number of clusters undergo phase-transition-like behavior as the maximum mutation size is varied.

Lunar mission safety and rescue: Escape/rescue analysis and plan

NASA Technical Reports Server (NTRS)

1971-01-01

The results are presented of the technical analysis of escape/rescue/survival situations, crew survival techniques, alternate escape/rescue approaches and vehicles, and the advantages and disadvantages of each for advanced lunar exploration. Candidate escape/rescue guidelines are proposed and elements of a rescue plan developed. The areas of discussions include the following: lunar arrival/departure operations, lunar orbiter operations, lunar surface operations, lunar surface base escape/rescue analysis, lander tug location operations, portable airlock, emergency pressure suit, and the effects of no orbiting lunar station, no lunar surface base, and no foreign lunar orbit/surface operations on the escape/rescue plan.

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…

The influence of panic on the efficiency of escape

NASA Astrophysics Data System (ADS)

Shen, Jia-Quan; Wang, Xu-Wen; Jiang, Luo-Luo

2018-02-01

Whenever we (such as pedestrians) perceive a high density or imminent danger in a confined space, we tend to be panic, which can lead to severe injuries even in the absence of real dangers. Although it is difficult to measure panics in real conditions, we introduced a simple model to study the collective behaviors in condition of fire with dense smoke. Owing to blocking the sight with dense smoke, pedestrians in this condition have two strategies to escape: random-walking or walking along the wall. When the pedestrians are in moderate panic that mean the two types of behaviors are mixed(random-walking and walking along the wall). Our simulation results show that moderate panic, meaning that two escape strategies are mixed, reduces the escape time. In addition, the results indicate that moderate panic can improve the efficiency of escape, this theory also can be useful in a real escape situation. We hope that our research provides the theoretical understanding of underlying mechanisms of panic escape in the condition of poor sight.

Effects of convincing power and neutrality on minority opinion spreading

NASA Astrophysics Data System (ADS)

Wu, Yue; Xiong, Xi; Zhang, Yi

2017-02-01

The dynamics evolution of the minority opinion in public debates is studied using a convincing power (CP) model with neutrality. In a given group, an agent with a definite standpoint (yes or no) can be persuaded to be a neutral agent, if its capacity of persuasion is lower than the average CP of its opponents. Besides that a neutral agent will change its state and follow a more persuasive opinion. Starting from two opposite opinions with different rates, repeated local discussions are found to drive the minority reversal. It reveals that in addition to the initial minority, the number of neutral agents is also an important factor to the eventual winners. During the process of consensus, there exists a threshold of initial fraction to guarantee one side win. The results have a guiding significance for designing strategies to win a public debate.

Beyond ITER: neutral beams for a demonstration fusion reactor (DEMO) (invited).

PubMed

McAdams, R

2014-02-01

In the development of magnetically confined fusion as an economically sustainable power source, International Tokamak Experimental Reactor (ITER) is currently under construction. Beyond ITER is the demonstration fusion reactor (DEMO) programme in which the physics and engineering aspects of a future fusion power plant will be demonstrated. DEMO will produce net electrical power. The DEMO programme will be outlined and the role of neutral beams for heating and current drive will be described. In particular, the importance of the efficiency of neutral beam systems in terms of injected neutral beam power compared to wallplug power will be discussed. Options for improving this efficiency including advanced neutralisers and energy recovery are discussed.

Modulation of Endosomal Escape of IRQ-PEGylated Nano-carrier

NASA Astrophysics Data System (ADS)

Mudhakir, Diky; Akita, Hidetaka; Harashima, Hideyoshi

2011-12-01

The novel IRQ peptide is one of cell penetrating peptides (CPPs) that has ability to induce endosomal escape. It has been demonstrated that IRQ ligand had ability to facilitate an escape of liposomes encapsulating siRNA from the endosomes presumably by fusion-independent mechanism [1,2]. In the present study, we attempted to modulate the intracellular trafficking of IRQ-modified nano-carrier in term of escaping process by changing the lipid composition. The peptide was attached to the terminal end of maleimide group of polyethylene glycol-modified liposomes (IRQ-PEG-Lip). The liposomes were composed of DOTAP, DOPE and cholesterol and it was labeled by water soluble sulpho-rhodamine B (Sr-B). The escape of PEG-coated liposomes was then observed by confocal laser scanning microscope after the endosomes were stained with Lysosensor. The results exhibited that IRQ-PEG-Lip was escaped from endosomal compartment after 1 h transfection when 40% of DOPE was incorporated into the nanostructure comparing to that of PEG-Lip. These results are consistent with the previous results that the IRQ facilitates endosomal escape via independent-mechanism. However, IRQ-PEG-Lip were then completely co-localized in the acidic compartment when density of DOPE was reduced approximately 20%. These results indicated that the utilizing of DOPE is important for the escape process even in the presence of hydrophilic PEG polymer. In conclusion, the regulation of endosomal escape ability of the PEGylated-IRQ nano-carrier was induced by fusion-independent manner as well as fusogenic lipid.

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.

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 GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Construction and Arrangement Hull Structure § 169.313 Means of escape. (a) Except as provided by paragraph (f) of...

XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of Terrestrial Planets. Part I: Atmospheric Expansion and Thermal Escape

PubMed Central

Lammer, Helmut; Odert, Petra; Kulikov, Yuri N.; Kislyakova, Kristina G.; Khodachenko, Maxim L.; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

2013-01-01

Abstract The recently discovered low-density “super-Earths” Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H2O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 REarth and a mass of 10 MEarth. We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general. Key Words: Stellar activity—Low-mass stars—Early atmospheres—Earth-like exoplanets—Energetic neutral atoms—Ion escape—Habitability. Astrobiology 13, 1011–1029. PMID:24251443

Virtual driving and risk taking: do racing games increase risk-taking cognitions, affect, and behaviors?

PubMed

Fischer, Peter; Kubitzki, Jörg; Guter, Stephanie; Frey, Dieter

2007-03-01

Research has consistently shown that aggressive video console and PC games elicit aggressive cognitions, affect, and behaviors. Despite the increasing popularity of racing (driving) games, nothing is known about the psychological impact of this genre. This study investigated whether playing racing games affects cognitions, affect, and behaviors that can promote risk taking in actual road traffic situations. In Study 1, the authors found that the frequency of playing racing games was positively associated with competitive driving, obtrusive driving, and car accidents; a negative association with cautious driving was observed. To determine cause and effect, in Study 2, the authors manipulated whether participants played 1 of 3 racing games or 1 of 3 neutral games. Participants who played a racing game subsequently reported a higher accessibility of cognitions and affect positively associated with risk taking than did participants who played a neutral game. Finally, on a more behavioral level, in Study 3, the authors found that men who played a racing game subsequently took higher risks in computer-simulated critical road traffic situations than did men who played a neutral game. Theoretical and practical implications are discussed. ((c) 2007 APA, all rights reserved).

Influenza virus resistance to human neutralizing antibodies.

PubMed

Crowe, James E

2012-01-01

The human antibody repertoire has an exceptionally large capacity to recognize new or changing antigens through combinatorial and junctional diversity established at the time of V(D)J recombination and through somatic hypermutation. Influenza viruses exhibit a relentless capacity to escape the human antibody response by altering the amino acids of their surface proteins in hypervariable domains that exhibit a high level of structural plasticity. Both parties in this high-stakes game of shape shifting drive structural evolution of their functional proteins (the B cell receptor/antibody on one side and the viral hemagglutinin and neuraminidase proteins on the other) using error-prone polymerase systems. It is likely that most of the genetic mutations that occur in these systems are deleterious, resulting in the failure of the B cell or virus with mutations to propagate in the immune repertoire or viral quasispecies. A subset of mutations is tolerated in functional surface proteins that enter the B cell or virus progeny pool. In both cases, selection occurs in the population of mutated and unmutated species. In cases where the functional avidity of the B cell receptor is increased significantly, that clone may be selected for preferential expansion. In contrast, an influenza virus that "escapes" the inhibitory effect of secreted antibodies may represent a high proportion of the progeny virus in that host. The recent paper by O'Donnell et al. [C. D. O'Donnell et al., mBio 3(3):e00120-12, 2012] identifies a mechanism for antibody resistance that does not require escape from binding but rather achieves a greater efficiency in replication.

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.

Trapped as a Group, Escape as a Team: Applying Gamification to Incorporate Team-building Skills Through an ‘Escape Room’ Experience

PubMed Central

Lee, Hyunjoo; Rodriguez, Carlos; Rudner, Joshua; Chan, Teresa M; Papanagnou, Dimitrios

2018-01-01

Teamwork, a skill critical for quality patient care, is recognized as a core competency by the Accreditation Council for Graduate Medical Education (ACGME). To date, there is no consensus on how to effectively teach these skills in a forum that engages learners, immerses members in life-like activities, and builds both trust and rapport. Recreational ‘Escape Rooms’ have gained popularity in creating a life-like environment that rewards players for working together, solving puzzles, and completing successions of mind-bending tasks in order to effectively ‘escape the room’ in the time allotted. In this regard, escape rooms share many parallels with the multitasking and teamwork that is essential for a successful emergency department (ED) shift. A pilot group of nine emergency medicine (EM) residents and one senior EM faculty member underwent a commercial escape room as part of a team-building exercise in January 2018. The escape room required participants to practice teamwork, communication, task delegation, and critical thinking to tackle waves of increasingly complex puzzles, ranging from hidden objects, physical object assembly (i.e., jigsaw puzzles), and symbol matching. Activities required members to recognize and utilize the collective experiences, skills, knowledge base, and physical abilities of the group. After the game, players underwent a structured ‘game-master’ debriefing facilitated by an employee of the commercial escape room; this was followed by a post-event survey facilitated by a faculty member, which focused on participants’ feelings, experiences, and problem-solving techniques. Escape rooms afford learners the opportunity to engage in an activity that rewards teamwork and effective leadership through experiences that directly link to specific ACGME milestones and educational learning theories. EM participants were engaged in the activity and felt that the escape room reproduced an environment analogous to the ED. The debriefing

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.

How moths escape bats: predicting outcomes of predator-prey interactions.

PubMed

Corcoran, Aaron J; Conner, William E

2016-09-01

What determines whether fleeing prey escape from attacking predators? To answer this question, biologists have developed mathematical models that incorporate attack geometries, pursuit and escape trajectories, and kinematics of predator and prey. These models have rarely been tested using data from actual predator-prey encounters. To address this problem, we recorded multi-camera infrared videography of bat-insect interactions in a large outdoor enclosure. We documented 235 attacks by four Myotis volans bats on a variety of moths. Bat and moth flight trajectories from 50 high-quality attacks were reconstructed in 3-D. Despite having higher maximum velocity, deceleration and overall turning ability, bats only captured evasive prey in 69 of 184 attacks (37.5%); bats captured nearly all moths not evading attack (50 of 51; 98%). Logistic regression indicated that prey radial acceleration and escape angle were the most important predictors of escape success (44 of 50 attacks correctly classified; 88%). We found partial support for the turning gambit mathematical model; however, it underestimated the escape threshold by 25% of prey velocity and did not account for prey escape angle. Whereas most prey escaping strikes flee away from predators, moths typically escaped chasing bats by turning with high radial acceleration toward 'safety zones' that flank the predator. This strategy may be widespread in prey engaged in chases. Based on these findings, we developed a novel geometrical model of predation. We discuss implications of this model for the co-evolution of predator and prey kinematics and pursuit and escape strategies. © 2016. Published by The Company of Biologists Ltd.

Learning from escaped prescribed fire reviews [Abstract

Treesearch

Anne Black; Dave Thomas; James Saveland

2011-01-01

Over the past decade, the wildland fire community has developed a number of innovative methods for conducting a review following escape of a prescribed fire. The stated purpose been to identify methods that not only meet policy requirements, but to reduce future escapes. Implicit is the assumption that a review leads to learning. Yet, as organizational learning expert...

46 CFR 177.500 - Means of escape.

Code of Federal Regulations, 2012 CFR

2012-10-01

... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the... windows. (d) The number and dimensions of the means of escape from each space must be sufficient for rapid...

46 CFR 177.500 - Means of escape.

Code of Federal Regulations, 2013 CFR

2013-10-01

... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the... windows. (d) The number and dimensions of the means of escape from each space must be sufficient for rapid...

46 CFR 177.500 - Means of escape.

Code of Federal Regulations, 2014 CFR

2014-10-01

... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the... windows. (d) The number and dimensions of the means of escape from each space must be sufficient for rapid...

46 CFR 177.500 - Means of escape.

Code of Federal Regulations, 2011 CFR

2011-10-01

... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the... windows. (d) The number and dimensions of the means of escape from each space must be sufficient for rapid...

46 CFR 116.500 - Means of escape.

Code of Federal Regulations, 2010 CFR

2010-10-01

... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the... windows. (d) The number and dimensions of the means of escape from each space must be sufficient for rapid...

46 CFR 116.500 - Means of escape.

Code of Federal Regulations, 2014 CFR

2014-10-01

... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the... windows. (d) The number and dimensions of the means of escape from each space must be sufficient for rapid...

46 CFR 116.500 - Means of escape.

Code of Federal Regulations, 2011 CFR

2011-10-01

... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the... windows. (d) The number and dimensions of the means of escape from each space must be sufficient for rapid...

46 CFR 116.500 - Means of escape.

Code of Federal Regulations, 2012 CFR

2012-10-01

... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the... windows. (d) The number and dimensions of the means of escape from each space must be sufficient for rapid...

46 CFR 116.500 - Means of escape.

Code of Federal Regulations, 2013 CFR

2013-10-01

... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the... windows. (d) The number and dimensions of the means of escape from each space must be sufficient for rapid...

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.

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.

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

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.

Split-second escape decisions in blue tits (Parus caeruleus)

NASA Astrophysics Data System (ADS)

Lind, Johan; Kaby, Ulrika; Jakobsson, Sven

2002-07-01

Bird mortality is heavily affected by birds of prey. Under attack, take-off is crucial for survival and even minor mistakes in initial escape response can have devastating consequences. Birds may respond differently depending on the character of the predator's attack and these split-second decisions were studied using a model merlin (Falco columbarius) that attacked feeding blue tits (Parus caeruleus) from two different attack angles in two different speeds. When attacked from a low attack angle they took off more steeply than when attacked from a high angle. This is the first study to show that escape behaviour also depends on predator attack speed. The blue tits responded to a high-speed attack by dodging sideways more often than when attacked at a low speed. Escape speed was not significantly affected by the different treatments. Although they have only a split-second before escaping an attack, blue tits do adjust their escape strategy to the prevailing attack conditions.

Structure-Based Design of Hepatitis C Virus Vaccines That Elicit Neutralizing Antibody Responses to a Conserved Epitope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, Brian G.; Boucher, Elisabeth N.; Piepenbrink, Kurt H.

Despite recent advances in therapeutic options, hepatitis C virus (HCV) remains a severe global disease burden, and a vaccine can substantially reduce its incidence. Due to its extremely high sequence variability, HCV can readily escape the immune response; thus, an effective vaccine must target conserved, functionally important epitopes. Using the structure of a broadly neutralizing antibody in complex with a conserved linear epitope from the HCV E2 envelope glycoprotein (residues 412 to 423; epitope I), we performed structure-based design of immunogens to induce antibody responses to this epitope. This resulted in epitope-based immunogens based on a cyclic defensin protein, asmore » well as a bivalent immunogen with two copies of the epitope on the E2 surface. We solved the X-ray structure of a cyclic immunogen in complex with the HCV1 antibody and confirmed preservation of the epitope conformation and the HCV1 interface. Mice vaccinated with our designed immunogens produced robust antibody responses to epitope I, and their serum could neutralize HCV. Notably, the cyclic designs induced greater epitope-specific responses and neutralization than the native peptide epitope. Beyond successfully designing several novel HCV immunogens, this study demonstrates the principle that neutralizing anti-HCV antibodies can be induced by epitope-based, engineered vaccines and provides the basis for further efforts in structure-based design of HCV vaccines. IMPORTANCEHepatitis C virus is a leading cause of liver disease and liver cancer, with approximately 3% of the world's population infected. To combat this virus, an effective vaccine would have distinct advantages over current therapeutic options, yet experimental vaccines have not been successful to date, due in part to the virus's high sequence variability leading to immune escape. In this study, we rationally designed several vaccine immunogens based on the structure of a conserved epitope that is the target of broadly

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

Lyman-Werner escape fractions from the first galaxies

NASA Astrophysics Data System (ADS)

Schauer, Anna T. P.; Agarwal, Bhaskar; Glover, Simon C. O.; Klessen, Ralf S.; Latif, Muhammad A.; Mas-Ribas, Lluís; Rydberg, Claes-Erik; Whalen, Daniel J.; Zackrisson, Erik

2017-05-01

Direct collapse black holes forming in pristine, atomically cooling haloes at z ≈ 10-20 may act as the seeds of supermassive black holes (BHs) at high redshifts. In order to create a massive BH seed, the host halo needs to be prevented from forming stars. H2 therefore needs to be irradiated by a large flux of Lyman-Werner (LW) UV photons in order to suppress H2 cooling. A key uncertainty in this scenario is the escape fraction of LW radiation from first galaxies, which is the dominant source of UV photons at this epoch. To better constrain this escape fraction, we have performed radiation-hydrodynamical simulations of the growth of H II regions and their associated photodissociation regions in the first galaxies using the zeus-mp code. We find that the LW escape fraction crucially depends on the propagation of the ionization front (I-front). For an R-type I-front overrunning the halo, the LW escape fraction is always larger than 95 per cent. If the halo recombines later from the outside-in, due to a softened and weakened spectrum, the LW escape fraction in the rest frame of the halo (the near-field) drops to zero. A detailed and careful analysis is required to analyse slowly moving, D-type I-fronts, where the escape fraction depends on the microphysics and can be as small as 3 per cent in the near-field and 61 per cent in the far-field or as large as 100 per cent in both the near-field and the far-field.

The effects of taboo-related distraction on driving performance.

PubMed

Chan, Michelle; Madan, Christopher R; Singhal, Anthony

2016-07-01

Roadside billboards containing negative and positive emotional content have been shown to influence driving performance, however, the impact of highly arousing taboo information is unknown. Taboo information more reliably evokes emotional arousal and can lead to greater attentional capture due to its inherent 'shock value.' The objective of the present study was to examine driver distraction associated with four types of information presented on roadside billboards: highly arousing taboo words, moderately arousing positive and negative words, and non-arousing neutral words. Participants viewed blocks of taboo, positive, negative and neutral words presented on roadside billboards while operating a driving simulator. They also responded to target (household-related) words by pressing a button on the steering wheel. At the end of the session, a surprise recall task was completed for all the words they saw while driving. Results showed that taboo words captured the most attention as revealed by better memory recall compared to all the other word types. Interestingly, taboo words were associated with better lane control compared to the other word types. We suggest that taboo-related arousal can enhance attentional focus during a complex task like simulated driving. That is, in a highly arousing situation, attention is selectively narrowed to the road ahead, resulting in better lane control. Copyright © 2016 Elsevier B.V. All rights reserved.

75 FR 61386 - Emergency Escape Breathing Apparatus Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-05

...-0044, Notice No. 1] RIN 2130-AC14 Emergency Escape Breathing Apparatus Standards AGENCY: Federal... breathing apparatus (EEBA) to the members of the train crew and certain other employees while they are... EEBA--emergency escape breathing apparatus FRA--Federal Railroad Administration FRSA--the former...

High Resolution Observations of Escaping Ions in the Martian Magnetotail

NASA Astrophysics Data System (ADS)

Halekas, J. S.; Raman, C.; Brain, D.; DiBraccio, G. A.; Harada, Y.; McFadden, J. P.; Mitchell, D. L.; Connerney, J. E. P.; Jakosky, B. M.

2016-12-01

Ions escape from the Martian upper atmosphere via a number of channels, including the central plasmasheet of the magnetotail. Mars Express observations show that the heavy ions O+ and O2+ escaping through the central tail often have approximately the same energy, suggesting acceleration in a quasi-static electric field, which has been interpreted as a Hall electric field. The Solar Wind Ion Analyzer (SWIA) on MAVEN was designed to measure the upstream solar wind. However, during orbit segments with appropriate spacecraft attitude, SWIA can also make high resolution measurements of escaping ions in the tail. During the prime mission, these observations were only returned sporadically, during periods of intense escaping fluxes that fortuitously triggered a mode switch. Now, in the extended mission, we return high resolution observations from SWIA routinely. Some of these high resolution measurements reveal slight differences in both the direction and energy of escaping O+ and O2+ ions, which may help determine the acceleration process(es). We investigate the location and solar wind conditions for which the escaping ions separate in energy and angle and the systematics of their energies and flow vectors, and discuss the implications for ion acceleration and the overall picture of Martian atmospheric escape.

Reduced Potency and Incomplete Neutralization of Broadly Neutralizing Antibodies against Cell-to-Cell Transmission of HIV-1 with Transmitted Founder Envs.

PubMed

Li, Hongru; Zony, Chati; Chen, Ping; Chen, Benjamin K

2017-05-01

Broadly neutralizing antibodies (bNAbs) have been isolated from HIV-1 patients and can potently block infection of a wide spectrum of HIV-1 subtypes. These antibodies define common epitopes shared by many viral isolates. While bNAbs potently antagonize infection with cell-free virus, inhibition of HIV-1 transmission from infected to uninfected CD4 + T cells through virological synapses (VS) has been found to require greater amounts of antibody. In this study, we examined two well-studied molecular clones and two transmitted/founder (T/F) clones for their sensitivities to a panel of bNAbs in cell-free and cell-to-cell infection assays. We observed resistance of cell-to-cell transmission to antibody neutralization that was reflected not only by reductions of antibody potency but also by decreases in maximum neutralization capacity relative to the levels seen with cell-free infections. BNAbs targeting different epitopes exhibited incomplete neutralization against cell-associated virus with T/F Envs, which was not observed with the cell-free form of the same virus. We further identified the membrane-proximal internal tyrosine-based sorting motif as a determinant that can affect the incomplete neutralization of these T/F clones in cell-to-cell infection. These findings indicate that the signal that affects surface expression and/or internalization of Env from the plasma membrane can modulate the presentation of neutralizing epitopes on infected cells. These results highlight that a fraction of virus can escape from high concentrations of antibody through cell-to-cell infection while remaining sensitive to neutralization in cell-free infection. The ability to fully inhibit cell-to-cell transmission may represent an important consideration in the development of antibodies for treatment or prophylaxis. IMPORTANCE In recent years, isolation of new-generation HIV-1 bNAbs has invigorated HIV vaccine research. These bNAbs display remarkable potency and breadth of coverage

The DYNAMO Orbiter Project: High Resolution Mapping of Gravity/Magnetic Fields and In Situ Investigation of Mars Atmospheric Escape

NASA Technical Reports Server (NTRS)

Smrekar, S.; Chassefiere, E.; Forget, F.; Reme, H.; Mazelle, C.; Blelly, P. -L.; Acuna, M.; Connerney, J.; Purucker, M.; Lin, R.

2000-01-01

Dynamo is a small Mars orbiter planned to be launched in 2005 or 2007, in the frame of the NASA/CNES Mars exploration program. It is aimed at improving gravity and magnetic field resolution, in order to better understand the magnetic, geologic and thermal history of Mars, and at characterizing current atmospheric escape, which is still poorly constrained. These objectives are achieved by using a low periapsis orbit, similar to the one used by the Mars Global Surveyor spacecraft during its aerobraking phases. The proposed periapsis altitude for Dynamo of 120-130 km, coupled with the global distribution of periapses to be obtained during one Martian year of operation, through about 5000 low passes, will produce a magnetic/gravity field data set with approximately five times the spatial resolution of MGS. Low periapsis provides a unique opportunity to investigate the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, therefore atmospheric escape, which may have played a crucial role in removing atmosphere, and water, from the planet. There is much room for debate on the importance of current atmosphere escape processes in the evolution of the Martian atmosphere, as early "exotic" processes including hydrodynamic escape and impact erosion are traditionally invoked to explain the apparent sparse inventory of present-day volatiles. Yet, the combination of low surface gravity and the absence of a substantial internally generated magnetic field have undeniable effects on what we observe today. In addition to the current losses in the forms of Jeans and photochemical escape of neutrals, there are solar wind interaction-related erosion mechanisms because the upper atmosphere is directly exposed to the solar wind. The solar wind related loss rates, while now comparable to those of a modest comet, nonetheless occur continuously, with the intriguing possibility of important cumulative and

Modeling the Extended Neutral Atmosphere and Plasma Environment near Saturn

NASA Technical Reports Server (NTRS)

Richardson, John D.

2003-01-01

In the three years of this study we have published five papers in refereed journals. We have first examined satellite sources and their contribution to the observed neutral cloud. Based on the total calculated satellite sources and the spatial distribution of sputtered H20, we concluded that they cannot produce observed OH cloud. The E-ring contribution has been also studied in detail.In order to produce observed OH cloud we suggested that the E-ring might be the dominant source in inner Saturnian magnetosphere. We proposed a possible resupply mechanism which is needed to keep both E-ring and OH cloud in the present state: collisions between E-ring grains and remains of a disrupted satellite near Enceladus Lagrangian points. In this scenario a large amount of material, ranging from a few micrometers to hundred of meters, which is optically invisible at present, is likely to exist there. The fourth paper compares the magnetosheaths of the outer planets. A surprising result is that the hot proton component comprises about 40% of the total density, much larger than predicted by shock theory. Gas dynamic models of the boundaries show that the magnetospheres of Jupiter and Saturn are flattened at the poles. The last paper was published in GRL and is the first based of the model of neutrals developed as a main goal of this grant and which is now operational.This Monte Carlo collision code self- consistently determines the neutral distribution. from the rings and satellites until they are lost by ionization, by collisions with rings, moons, or Saturn, or by escape from Saturn. Our model is unique in that it includes the effects of plasma chemistry and both plasma-neutral and neutral neutral collisions to determine the dynamical evolution of the water group neutrals in Saturn's magnetosphere. The lifetimes of the neutrals against loss to photoionization, charge exchange, electron dissociation and electron impact dissociation are based on the model given by (Richardson et

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

Charge Exchange Contribution to the Decay of the Ring Current, Measured by Energetic Neutral Atoms (ENAs)

NASA Technical Reports Server (NTRS)

Jorgensen, A. M.; Henderson, M. G.; Roelof, E. C.; Reeves, G. D.; Spence, H. E.

2001-01-01

In this paper we calculate the contribution of charge exchange to the decay of the ring current. Past works have suggested that charge exchange of ring current protons is primarily responsible for the decay of the ring current during the late recovery phase, but there is still much debate about the fast decay of the early recovery phase. We use energetic neutral atom (ENA) measurements from Polar to calculate the total ENA energy escape. To get the total ENA escape we apply a forward modeling technique, and to estimate the total ring current energy escape we use the Dessler-Parker-Sckopke relationship. We find that during the late recovery phase of the March 10, 1998 storm ENAs with energies greater than 17.5 keV can account for 75% of the estimated energy loss from the ring current. During the fast recovery the measured ENAs can only account for a small portion of the total energy loss. We also find that the lifetime of the trapped ions is significantly shorter during the fast recovery phase than during the late recovery phase, suggesting that different processes are operating during the two phases.

Current profile redistribution driven by neutral beam injection in a reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parke, E.; Department of Physics, University of Wisconsin-Madison 1150 University Ave., Madison, Wisconsin 53706; Anderson, J. K.

2016-05-15

Neutral beam injection in reversed-field pinch (RFP) plasmas on the Madison Symmetric Torus [Dexter et al., Fusion Sci. Technol. 19, 131 (1991)] drives current redistribution with increased on-axis current density but negligible net current drive. Internal fluctuations correlated with tearing modes are observed on multiple diagnostics; the behavior of tearing mode correlated structures is consistent with flattening of the safety factor profile. The first application of a parametrized model for island flattening to temperature fluctuations in an RFP allows inferrence of rational surface locations for multiple tearing modes. The m = 1, n = 6 mode is observed to shift inward by 1.1 ± 0.6 cm withmore » neutral beam injection. Tearing mode rational surface measurements provide a strong constraint for equilibrium reconstruction, with an estimated reduction of q{sub 0} by 5% and an increase in on-axis current density of 8% ± 5%. The inferred on-axis current drive is consistent with estimates of fast ion density using TRANSP [Goldston et al., J. Comput. Phys. 43, 61 (1981)].« less

Current profile redistribution driven by neutral beam injection in a reversed-field pinch

NASA Astrophysics Data System (ADS)

Parke, E.; Anderson, J. K.; Brower, D. L.; Den Hartog, D. J.; Ding, W. X.; Johnson, C. A.; Lin, L.

2016-05-01

Neutral beam injection in reversed-field pinch (RFP) plasmas on the Madison Symmetric Torus [Dexter et al., Fusion Sci. Technol. 19, 131 (1991)] drives current redistribution with increased on-axis current density but negligible net current drive. Internal fluctuations correlated with tearing modes are observed on multiple diagnostics; the behavior of tearing mode correlated structures is consistent with flattening of the safety factor profile. The first application of a parametrized model for island flattening to temperature fluctuations in an RFP allows inferrence of rational surface locations for multiple tearing modes. The m = 1, n = 6 mode is observed to shift inward by 1.1 ± 0.6 cm with neutral beam injection. Tearing mode rational surface measurements provide a strong constraint for equilibrium reconstruction, with an estimated reduction of q0 by 5% and an increase in on-axis current density of 8% ± 5%. The inferred on-axis current drive is consistent with estimates of fast ion density using TRANSP [Goldston et al., J. Comput. Phys. 43, 61 (1981)].

Random perturbations of a periodically driven nonlinear oscillator: escape from a resonance zone

NASA Astrophysics Data System (ADS)

Lingala, Nishanth; Sri Namachchivaya, N.; Pavlyukevich, Ilya

2017-04-01

For nonlinear oscillators, frequency of oscillations depends on the oscillation amplitude. When a nonlinear oscillator is periodically driven, the phase space consists of many resonance zones where the oscillator frequency and the driving frequency are commensurable. It is well known that, a small subset of initial conditions can lead to capture in one of the resonance zones. In this paper we study the effect of weak noise on the escape from a resonance zone. Using averaging techniques we obtain the mean exit time from a resonance zone and study the dependence of the exit rate on the parameters of the oscillator. Paper dedicated to Professor Peter W Sauer of University of Illinois on the occasion of his 70th birthday.

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.

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.

Inferring HIV Escape Rates from Multi-Locus Genotype Data

DOE PAGES

Kessinger, Taylor A.; Perelson, Alan S.; Neher, Richard A.

2013-09-03

Cytotoxic T-lymphocytes (CTLs) recognize viral protein fragments displayed by major histocompatibility complex molecules on the surface of virally infected cells and generate an anti-viral response that can kill the infected cells. Virus variants whose protein fragments are not efficiently presented on infected cells or whose fragments are presented but not recognized by CTLs therefore have a competitive advantage and spread rapidly through the population. We present a method that allows a more robust estimation of these escape rates from serially sampled sequence data. The proposed method accounts for competition between multiple escapes by explicitly modeling the accumulation of escape mutationsmore » and the stochastic effects of rare multiple mutants. Applying our method to serially sampled HIV sequence data, we estimate rates of HIV escape that are substantially larger than those previously reported. The method can be extended to complex escapes that require compensatory mutations. We expect our method to be applicable in other contexts such as cancer evolution where time series data is also available.« less

Behavioral analyses of wind-evoked escape of the cricket, Gryllodes sigillatus.

PubMed

Kanou, Masamichi; Konishi, Atsuko; Suenaga, Rie

2006-04-01

The wind-evoked escape behavior of the cricket Gryllodes sigillatus was investigated using an air puff stimulus. A high velocity air puff elicited the escape behavior in many crickets. The crickets tended to escape away from the stimulus source, but the direction was not accurately oriented 180 degrees from the stimulus. After bilateral cercal ablation, only a few crickets showed wind-evoked escape behavior, and their response rates did not increase even 19 days after ablation. Therefore, information on air motion detected by cercal filiform hairs is essential for triggering wind-evoked behavior. After unilateral cercal ablation, the 81.3% response rate of intact crickets decreased to 16.5%, that is, it decreased to almost 20% that of intact crickets. One week after unilateral cercal ablation, the response rate recovered to more than 60% that of intact crickets. However, the accuracy rate of the escape direction of G. sigillatus showed no change even immediately after the unilateral cercal ablation. Therefore, both cerci are not necessarily required to determine the escape direction. The behavioral characteristics of wind-evoked escape of G. sigillatus are compared with those of another species of cricket, Gryllus bimaculatus. The two species of cricket employ different strategies for wind-evoked escape.

Centering Single Cells in Microgels via Delayed Crosslinking Supports Long-Term 3D Culture by Preventing Cell Escape.

PubMed

Kamperman, Tom; Henke, Sieger; Visser, Claas Willem; Karperien, Marcel; Leijten, Jeroen

2017-06-01

Single-cell-laden microgels support physiological 3D culture conditions while enabling straightforward handling and high-resolution readouts of individual cells. However, their widespread adoption for long-term cultures is limited by cell escape. In this work, it is demonstrated that cell escape is predisposed to off-center encapsulated cells. High-speed microscopy reveals that cells are positioned at the microgel precursor droplets' oil/water interface within milliseconds after droplet formation. In conventional microencapsulation strategies, the droplets are typically gelled immediately after emulsification, which traps cells in this off-center position. By delaying crosslinking, driving cells toward the centers of microgels is succeeded. The centering of cells in enzymatically crosslinked microgels prevents their escape during at least 28 d. It thereby uniquely enables the long-term culture of individual cells within <5-µm-thick 3D uniform hydrogel coatings. Single cell analysis of mesenchymal stem cells in enzymatically crosslinked microgels reveals unprecedented high cell viability (>90%), maintained metabolic activity (>70%), and multilineage differentiation capacity (>60%) over a period of 28 d. The facile nature of this microfluidic cell-centering method enables its straightforward integration into many microencapsulation strategies and significantly enhances control, reproducibility, and reliability of 3D single cell cultures. © 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Modelling the Evolution and Spread of HIV Immune Escape Mutants

PubMed Central

Fryer, Helen R.; Frater, John; Duda, Anna; Roberts, Mick G.; Phillips, Rodney E.; McLean, Angela R.

2010-01-01

During infection with human immunodeficiency virus (HIV), immune pressure from cytotoxic T-lymphocytes (CTLs) selects for viral mutants that confer escape from CTL recognition. These escape variants can be transmitted between individuals where, depending upon their cost to viral fitness and the CTL responses made by the recipient, they may revert. The rates of within-host evolution and their concordant impact upon the rate of spread of escape mutants at the population level are uncertain. Here we present a mathematical model of within-host evolution of escape mutants, transmission of these variants between hosts and subsequent reversion in new hosts. The model is an extension of the well-known SI model of disease transmission and includes three further parameters that describe host immunogenetic heterogeneity and rates of within host viral evolution. We use the model to explain why some escape mutants appear to have stable prevalence whilst others are spreading through the population. Further, we use it to compare diverse datasets on CTL escape, highlighting where different sources agree or disagree on within-host evolutionary rates. The several dozen CTL epitopes we survey from HIV-1 gag, RT and nef reveal a relatively sedate rate of evolution with average rates of escape measured in years and reversion in decades. For many epitopes in HIV, occasional rapid within-host evolution is not reflected in fast evolution at the population level. PMID:21124991

Reporter Assay for Endo/Lysosomal Escape of Toxin-Based Therapeutics

PubMed Central

Gilabert-Oriol, Roger; Thakur, Mayank; von Mallinckrodt, Benedicta; Bhargava, Cheenu; Wiesner, Burkhard; Eichhorst, Jenny; Melzig, Matthias F.; Fuchs, Hendrik; Weng, Alexander

2014-01-01

Protein-based therapeutics with cytosolic targets are capable of exhibiting their therapeutic effect once they have escaped from the endosomes or lysosomes. In this study, the reporters—horseradish peroxidase (HRP), Alexa Fluor 488 (Alexa) and ricin A-chain (RTA)—were investigated for their capacity to monitor the endo/lysosomal escape of the ribosome-inactivating protein, saporin. The conjugates—saporin-HRP, Alexasaporin and saporin-KQ-RTA—were constructed, and the endo/lysosomal escape of these conjugates alone (lack of endo/lysosomal release) or in combination with certain structurally-specific triterpenoidal saponins (efficient endo/lysosomal escape) was characterized. HRP failed in reporting the endo/lysosomal escape of saporin. Contrastingly, Alexa Fluor 488 successfully allowed the report of the process at a toxin concentration of 1000 nM. In addition, single endo/lysosome analysis facilitated the determination of the amount of Alexasaporin released from each vesicle. RTA was also successful in reporting the endo/lysosomal escape of the enzymatically inactive mutant, saporin-KQ, but in this case, the sensitivity of the method reached a toxin concentration of 10 nM. In conclusion, the simultaneous usage of Alexa Fluor 488 and RTA as reporters may provide the possibility of monitoring the endo/lysosomal escape of protein-based therapeutics in the concentration range of 10–1000 nM. PMID:24859158

Prediction of Protection against Asian Enterovirus 71 Outbreak Strains by Cross-neutralizing Capacity of Serum from Dutch Donors, The Netherlands

PubMed Central

Koen, Gerrit; van Eijk, Hetty; Koekkoek, Sylvie M.; de Jong, Menno D.; Wolthers, Katja C.

2016-01-01

Outbreaks of human enterovirus 71 (EV-71) in Asia are related to high illness and death rates among children. To gain insight into the potential threat for the population of Europe, we determined the neutralizing activity in intravenous immunoglobulin (IVIg) batches and individual serum samples from donors in the Netherlands against EV-71 strains isolated in Europe and in Asia. All IVIg batches and 41%, 79%, and 65% of serum samples from children ≤5 years of age, women of childbearing age, and HIV-positive men, respectively, showed high neutralizing activity against a Dutch C1 strain, confirming widespread circulation of EV-71 in the Netherlands. Asian B3–4 and C4 strains were efficiently cross-neutralized, predicting possible protection against extensive circulation and associated outbreaks of those types in Europe. However, C2 and C5 strains that had few mutations in the capsid region consistently escaped neutralization, emphasizing the importance of monitoring antigenic diversity among circulating EV-71 strains. PMID:27533024

Cold Ion Escape from the Martian Ionosphere

NASA Astrophysics Data System (ADS)

Fränz, M.; Dubinin, E.; Wei, Y.; Woch, J.; Morgan, D.; Barabash, S.; Fedorov, A.

2012-09-01

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 O+ 2 ions with a super-sonic velocity of around 5km/s and fluxes of 0.8 · 109/cm2s. If we assume a symmetric flux around the terminator this corresponds to an ion flow of 3.1 ± 0.5 × 1025/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 Alfvénic regime.

Cold Ion Escape from the Martian Ionosphere

NASA Astrophysics Data System (ADS)

Fränz, Markus; Dubinin, Eduard; Wei, Yong; Morgan, David; Barabash, Stas; Lundin, Rickard; Fedorov, Andrei

2013-04-01

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 0.8 ? 109/cm2s. If we assume a symmetric flux around the terminator this corresponds to an ion flow of 3.1 ± 0.5 × 1025-s half of which is expected to escape from Mars (Fraenz et al, Plan.Space Sci., 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 measurements which often coincide with ASPERA-3 measurements. In a new 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 half a Martian radius 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.

Escape driven by alpha-stable white noises.

PubMed

Dybiec, B; Gudowska-Nowak, E; Hänggi, P

2007-02-01

We explore the archetype problem of an escape dynamics occurring in a symmetric double well potential when the Brownian particle is driven by white Lévy noise in a dynamical regime where inertial effects can safely be neglected. The behavior of escaping trajectories from one well to another is investigated by pointing to the special character that underpins the noise-induced discontinuity which is caused by the generalized Brownian paths that jump beyond the barrier location without actually hitting it. This fact implies that the boundary conditions for the mean first passage time (MFPT) are no longer determined by the well-known local boundary conditions that characterize the case with normal diffusion. By numerically implementing properly the set up boundary conditions, we investigate the survival probability and the average escape time as a function of the corresponding Lévy white noise parameters. Depending on the value of the skewness beta of the Lévy noise, the escape can either become enhanced or suppressed: a negative asymmetry parameter beta typically yields a decrease for the escape rate while the rate itself depicts a non-monotonic behavior as a function of the stability index alpha that characterizes the jump length distribution of Lévy noise, exhibiting a marked discontinuity at alpha=1. We find that the typical factor of 2 that characterizes for normal diffusion the ratio between the MFPT for well-bottom-to-well-bottom and well-bottom-to-barrier-top no longer holds true. For sufficiently high barriers the survival probabilities assume an exponential behavior versus time. Distinct non-exponential deviations occur, however, for low barrier heights.

Life events and escape in conversion disorder.

PubMed

Nicholson, T R; Aybek, S; Craig, T; Harris, T; Wojcik, W; David, A S; Kanaan, R A

2016-09-01

Psychological models of conversion disorder (CD) traditionally assume that psychosocial stressors are identifiable around symptom onset. In the face of limited supportive evidence such models are being challenged. Forty-three motor CD patients, 28 depression patients and 28 healthy controls were assessed using the Life Events and Difficulties Schedule in the year before symptom onset. A novel 'escape' rating for events was developed to test the Freudian theory that physical symptoms of CD could provide escape from stressors, a form of 'secondary gain'. CD patients had significantly more severe life events and 'escape' events than controls. In the month before symptom onset at least one severe event was identified in 56% of CD patients - significantly more than 21% of depression patients [odds ratio (OR) 4.63, 95% confidence interval (CI) 1.56-13.70] and healthy controls (OR 5.81, 95% CI 1.86-18.2). In the same time period 53% of CD patients had at least one 'high escape' event - again significantly higher than 14% in depression patients (OR 6.90, 95% CI 2.05-23.6) and 0% in healthy controls. Previous sexual abuse was more commonly reported in CD than controls, and in one third of female patients was contextually relevant to life events at symptom onset. The majority (88%) of life events of potential aetiological relevance were not identified by routine clinical assessments. Nine per cent of CD patients had no identifiable severe life events. Evidence was found supporting the psychological model of CD, the Freudian notion of escape and the potential aetiological relevance of childhood traumas in some patients. Uncovering stressors of potential aetiological relevance requires thorough psychosocial evaluation.

Escape from rich-to-lean transitions: Stimulus change and timeout.

PubMed

Retzlaff, Billie J; Parthum, Elizabeth T P; Pitts, Raymond C; Hughes, Christine E

2017-01-01

Extended pausing during discriminable transitions from rich-to-lean conditions can be viewed as escape (i.e., rich-to-lean transitions function aversively). In the current experiments, pigeons' key pecking was maintained by a multiple fixed-ratio fixed-ratio schedule of rich or lean reinforcers. Pigeons then were provided with another, explicit, mechanism of escape by changing the stimulus from the transition-specific stimulus used in the multiple schedule to a mixed-schedule stimulus (Experiment 1) or by producing a period of timeout in which the stimulus was turned off and the schedule was suspended (Experiment 2). Overall, escape was under joint control of past and upcoming reinforcer magnitudes, such that responses on the escape key were most likely during rich-to-lean transitions, and second-most likely during lean-to-lean transitions. Even though pigeons pecked the escape key, they paused before doing so, and the latency to begin the fixed ratio (i.e., the pause) remained extended during rich-to-lean transitions. These findings suggest that although the stimulus associated with rich-to-lean transitions functioned aversively, pausing is more than simply escape responding from the stimulus. © 2017 Society for the Experimental Analysis of Behavior.

Progesterone After Estradiol Modulates Shuttle-Cage Escape by Facilitating Volition

PubMed Central

Mayeaux, Darryl J.; Tandle, Sarah M.; Cilano, Sean M.; Fitzharris, Matthew J.

2015-01-01

In animal models of depression, depression is defined as performance on a learning task. That task is typically escaping a mild electric shock in a shuttle cage by moving from one side of the cage to the other. Ovarian hormones influence learning in other kinds of tasks, and these hormones are associated with depressive symptoms in humans. The role of these hormones in shuttle-cage escape learning, however, is less clear. This study manipulated estradiol and progesterone in ovariectomized female rats to examine their performance in shuttle-cage escape learning without intentionally inducing a depressive-like state. Progesterone, not estradiol, within four hours of testing affected latencies to escape. The improvement produced by progesterone was in the decision to act, not in the speed of learning or speed of escaping. This parallels depression in humans in that depressed people are slower in volition, in their decisions to take action. PMID:26823653

Escape probability of the super-Penrose process

NASA Astrophysics Data System (ADS)

Ogasawara, Kota; Harada, Tomohiro; Miyamoto, Umpei; Igata, Takahisa

2017-06-01

We consider a head-on collision of two massive particles that move in the equatorial plane of an extremal Kerr black hole, which results in the production of two massless particles. Focusing on a typical case, where both of the colliding particles have zero angular momenta, we show that a massless particle produced in such a collision can escape to infinity with arbitrarily large energy in the near-horizon limit of the collision point. Furthermore, if we assume that the emission of the produced massless particles is isotropic in the center-of-mass frame but confined to the equatorial plane, the escape probability of the produced massless particle approaches 5 /12 , and almost all escaping massless particles have arbitrarily large energy at infinity and an impact parameter approaching 2 G M /c2, where M is the mass of the black hole.

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…

Concerning neutral flux shielding in the U-3M torsatron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dreval, N. B., E-mail: mdreval@kipt.kharkov.ua

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.more » 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.« less

Quantification of simian immunodeficiency virus cytotoxic T lymphocyte escape mutant viruses.

PubMed

Loh, Liyen; Kent, Stephen J

2008-08-01

Escape from cytotoxic T-lymphocyte (CTL) pressure is common in HIV-1 infection of humans and simian immunodeficiency virus (SIV) infections of macaques. CTL escape typically incurs a fitness cost as reversion back to wild-type can occur upon transmission. We utilized sequence-specific primers and DNA probes with real-time polymerase chain reaction (PCR) to sensitively and specifically track wild-type and escape mutant viremia at the Mane-A*17-restricted SIV Gag(371379) epitope AF9 in pigtail macaques. The generation of minor escape mutant populations is detected by the real-time PCR 2 weeks earlier than observed using standard sequencing techniques. We passaged the AF9 CTL escape mutant virus into two naïve Mane-A*17-negative pigtail macaques and showed that reversion to wild-type was rapid during acute infection and then slowed considerably at later stages of the infection. These data help refine our understanding of how CTL escape mutant viruses evolve.

Staphylococcus aureus synthesizes adenosine to escape host immune responses

PubMed Central

Thammavongsa, Vilasack; Kern, Justin W.; Missiakas, Dominique M.

2009-01-01

Staphylococcus aureus infects hospitalized or healthy individuals and represents the most frequent cause of bacteremia, treatment of which is complicated by the emergence of methicillin-resistant S. aureus. We examined the ability of S. aureus to escape phagocytic clearance in blood and identified adenosine synthase A (AdsA), a cell wall–anchored enzyme that converts adenosine monophosphate to adenosine, as a critical virulence factor. Staphylococcal synthesis of adenosine in blood, escape from phagocytic clearance, and subsequent formation of organ abscesses were all dependent on adsA and could be rescued by an exogenous supply of adenosine. An AdsA homologue was identified in the anthrax pathogen, and adenosine synthesis also enabled escape of Bacillus anthracis from phagocytic clearance. Collectively, these results suggest that staphylococci and other bacterial pathogens exploit the immunomodulatory attributes of adenosine to escape host immune responses. PMID:19808256

Measurements of Ion-Neutral Coupling in the Auroral F Region in Response to Increases in Particle Precipitation

NASA Astrophysics Data System (ADS)

Kiene, A.; Bristow, W. A.; Conde, M. G.; Hampton, D. L.

2018-05-01

Neutral winds are a key factor in the dynamics of the ionosphere-thermosphere system. Previous observations have shown that neutral and ion flows are strongly coupled during periods of auroral activity when ion drag forcing can become the dominant force driving neutral wind flow. This is primarily due to increases in ion density due to enhanced particle precipitation as well as associated increases the strength of the electric fields that drive ion motions. Due to this strong coupling, numerical simulations of neutral dynamics have difficulty reproducing neutral wind observations when they are driven by modeled precipitation and modeled convection. It is therefore desirable whenever possible to have concurrent coincident measurements of auroral precipitation and ion convection. Recent advancements in high-resolution fitting of Super Dual Auroral Radar Network ion convection data have enabled the generation of steady maps of ion drifts over Alaska, coinciding with several optics sites. The Super Dual Auroral Radar Network measurements are compared with scanning Doppler imager neutral wind measurements at similar altitude, providing direct comparisons of ion and neutral velocities over a wide field and for long periods throughout the night. Also present are a digital all-sky imager and a meridian spectrograph, both of which provide measurements of auroral intensity on several wavelengths. In this study, we combine these data sets to present three case studies that show significant correlation between increases in F region precipitation and enhancements in ion-neutral coupling in the evening sector. We investigate the time scales over which the coupling takes place and compare our findings to previous measurements.

Danger detection and escape behaviour in wood crickets.

PubMed

Dupuy, Fabienne; Casas, Jérôme; Body, Mélanie; Lazzari, Claudio R

2011-07-01

The wind-sensitive cercal system of Orthopteroid insects that mediates the detection of the approach of a predator is a very sensitive sensory system. It has been intensively analysed from a behavioural and neurobiological point of view, and constitutes a classical model system in neuroethology. The escape behaviour is triggered in orthopteroids by the detection of air-currents produced by approaching objects, allowing these insects to keep away from potential dangers. Nevertheless, escape behaviour has not been studied in terms of success. Moreover, an attacking predator is more than "air movement", it is also a visible moving entity. The sensory basis of predator detection is thus probably more complex than the perception of air movement by the cerci. We have used a piston mimicking an attacking running predator for a quantitative evaluation of the escape behaviour of wood crickets Nemobius sylvestris. The movement of the piston not only generates air movement, but it can be seen by the insect and can touch it as a natural predator. This procedure allowed us to study the escape behaviour in terms of detection and also in terms of success. Our results showed that 5-52% of crickets that detected the piston thrust were indeed touched. Crickets escaped to stimulation from behind better than to a stimulation from the front, even though they detected the approaching object similarly in both cases. After cerci ablation, 48% crickets were still able to detect a piston approaching from behind (compared with 79% of detection in intact insects) and 24% crickets escaped successfully (compared with 62% in the case of intact insects). So, cerci play a major role in the detection of an approaching object but other mechanoreceptors or sensory modalities are implicated in this detection. It is not possible to assure that other sensory modalities participate (in the case of intact animals) in the behaviour; rather, than in the absence of cerci other sensory modalities can

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

Escape of asteroids from the main belt

NASA Astrophysics Data System (ADS)

Granvik, Mikael; Morbidelli, Alessandro; Vokrouhlický, David; Bottke, William F.; Nesvorný, David; Jedicke, Robert

2017-02-01

Aims: We locate escape routes from the main asteroid belt, particularly into the near-Earth-object (NEO) region, and estimate the relative fluxes for different escape routes as a function of object size under the influence of the Yarkovsky semimajor-axis drift. Methods: We integrated the orbits of 78 355 known and 14 094 cloned main-belt objects and Cybele and Hilda asteroids (hereafter collectively called MBOs) for 100 Myr and recorded the characteristics of the escaping objects. The selected sample of MBOs with perihelion distance q > 1.3 au and semimajor axis a < 4.1 au is essentially complete, with an absolute magnitude limit ranging from HV < 15.9 in the inner belt (a < 2.5 au) to HV < 14.4 in the outer belt (2.5 au < a < 4.1 au). We modeled the semimajor-axis drift caused by the Yarkovsky force and assigned four different sizes (diameters of 0.1, 0.3, 1.0, and 3.0 km) and random spin obliquities (either 0 deg or 180 deg) for each test asteroid. Results: We find more than ten obvious escape routes from the asteroid belt to the NEO region, and they typically coincide with low-order mean-motion resonances with Jupiter and secular resonances. The locations of the escape routes are independent of the semimajor-axis drift rate and thus are also independent of the asteroid diameter. The locations of the escape routes are likewise unaffected when we added a model for Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) cycles coupled with secular evolution of the rotation pole as a result of the solar gravitational torque. A Yarkovsky-only model predicts a flux of asteroids entering the NEO region that is too high compared to the observationally constrained flux, and the discrepancy grows larger for smaller asteroids. A combined Yarkovsky and YORP model predicts a flux of small NEOs that is approximately a factor of 5 too low compared to an observationally constrained estimate. This suggests that the characteristic timescale of the YORP cycle is longer than our canonical

Cold Ion Escape from Mars

NASA Astrophysics Data System (ADS)

Fränz, M.; Dubinin, E.; Wei, Y.; Morgan, D.; Andrews, D.; Barabash, S.; Lundin, R.; Fedorov, A.

2013-09-01

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 in combination with the MARSIS radar experiment. We first compare calculations of the mean ion flux observed by ASPERA-3 alone with previously published results. We then combine observations of the cold ion velocity by ASPERA-3 with observations of the cold plasma density by MARSIS since ASPERA-3 misses the cold core of the ion distribution. We show that the mean density of the nightside plasma observed by MARSIS is about two orders higher than observed by ASPERA-3 (Fig.1). Combining both datasets we show that the main escape channel is along the shadow boundary on the tailside of Mars (Fig. 2). At a distance of about 0.5 R_M the flux settles at a constant value (Fig. 3) 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.

Control of power, torque, and instability drive using in-shot variable neutral beam energy in tokamaks

DOE PAGES

Pace, D. C.; Collins, C. S.; Crowley, B.; ...

2016-09-28

A first-ever demonstration of controlling power and torque injection through time evolution of neutral beam energy has been achieved in recent experiments at the DIII-D tokamak. Pre-programmed waveforms for the neutral beam energy produce power and torque inputs that can be separately and continuously controlled. Previously, these inputs were tailored using on/off modulation of neutral beams resulting in large perturbations (e.g. power swings of over 1 MW). The new method includes, importantly for experiments, the ability to maintain a fixed injected power while varying the torque. In another case, different beam energy waveforms (in the same plasma conditions) produce significantmore » changes in the observed spectrum of beam ion-driven instabilities. Measurements of beam ion loss show that one energy waveform results in the complete avoidance of coherent losses due to Alfvénic instabilities. This new method of neutral beam operation is intended for further application in a variety of DIII-D experiments including those concerned with high-performance steady state scenarios, fast particle effects, and transport in the low torque regime. As a result, developing this capability would provide similar benefits and improved plasma control for other magnetic confinement fusion facilities.« less

Control of power, torque, and instability drive using in-shot variable neutral beam energy in tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pace, D. C.; Collins, C. S.; Crowley, B.

A first-ever demonstration of controlling power and torque injection through time evolution of neutral beam energy has been achieved in recent experiments at the DIII-D tokamak. Pre-programmed waveforms for the neutral beam energy produce power and torque inputs that can be separately and continuously controlled. Previously, these inputs were tailored using on/off modulation of neutral beams resulting in large perturbations (e.g. power swings of over 1 MW). The new method includes, importantly for experiments, the ability to maintain a fixed injected power while varying the torque. In another case, different beam energy waveforms (in the same plasma conditions) produce significantmore » changes in the observed spectrum of beam ion-driven instabilities. Measurements of beam ion loss show that one energy waveform results in the complete avoidance of coherent losses due to Alfvénic instabilities. This new method of neutral beam operation is intended for further application in a variety of DIII-D experiments including those concerned with high-performance steady state scenarios, fast particle effects, and transport in the low torque regime. As a result, developing this capability would provide similar benefits and improved plasma control for other magnetic confinement fusion facilities.« less

Control of power, torque, and instability drive using in-shot variable neutral beam energy in tokamaks

NASA Astrophysics Data System (ADS)

Pace, D. C.; Collins, C. S.; Crowley, B.; Grierson, B. A.; Heidbrink, W. W.; Pawley, C.; Rauch, J.; Scoville, J. T.; Van Zeeland, M. A.; Zhu, Y. B.; The DIII-D Team

2017-01-01

A first-ever demonstration of controlling power and torque injection through time evolution of neutral beam energy has been achieved in recent experiments at the DIII-D tokamak (Luxon 2002 Nucl. Fusion 42 614). Pre-programmed waveforms for the neutral beam energy produce power and torque inputs that can be separately and continuously controlled. Previously, these inputs were tailored using on/off modulation of neutral beams resulting in large perturbations (e.g. power swings of over 1 MW). The new method includes, importantly for experiments, the ability to maintain a fixed injected power while varying the torque. In another case, different beam energy waveforms (in the same plasma conditions) produce significant changes in the observed spectrum of beam ion-driven instabilities. Measurements of beam ion loss show that one energy waveform results in the complete avoidance of coherent losses due to Alfvénic instabilities. This new method of neutral beam operation is intended for further application in a variety of DIII-D experiments including those concerned with high-performance steady state scenarios, fast particle effects, and transport in the low torque regime. Developing this capability would provide similar benefits and improved plasma control for other magnetic confinement fusion facilities.

Ferroelectric Plasma Sources for Ion Beam Neutralization

NASA Astrophysics Data System (ADS)

Stepanov, A.; Gilson, E. P.; Grisham, L. R.; Davidson, R. C.

2014-10-01

A 40 keV Ar+ beam with a dimensionless perveance of 4 ×10-4 is propagated through a Ferroelectric Plasma Source (FEPS) to determine the effects of charge neutralization on the transverse beam profile. Neutralization is established 5 μs after the FEPS is triggered, and lasts between 10 and 35 μs. When the beam is fully neutralized, the profile has a Gaussian shape with a half-angle divergence of 0.87°, which is attributed to ion optics. The effects of the resistance and capacitance in the pulser circuit on the FEPS discharge are studied. The electron current emitted by the FEPS is calculated from measurements of the forward and return currents in the circuit. Electron emission typically begins 0.5 μs after the driving pulse, lasting for tens of μs, which is similar to the duration of ion beam neutralization. The total emitted charge does not depend significantly on the resistance, but depends strongly on the storage capacitance. Lowering the capacitance from 141 nF to 47 nF results in a near-complete shut-off of charge emission, although the amplitude of the applied voltage pulse is as high as when high-density plasma is produced. Overall, the data suggest that ferroelectric effects are significant in the physics of the FEPS discharge.

High-Latitude Neutral Mass Density Maxima

NASA Astrophysics Data System (ADS)

Huang, C. Y.; Huang, Y.; Su, Y.-J.; Huang, T.; Sutton, E. K.

2017-10-01

Recent studies have reported that thermospheric effects due to solar wind driving can be observed poleward of auroral latitudes. In these papers, the measured neutral mass density perturbations appear as narrow, localized maxima in the cusp and polar cap. They conclude that Joule heating below the spacecraft is the cause of the mass density increases, which are sometimes associated with local field-aligned current structures, but not always. In this paper we investigate neutral mass densities measured by accelerometers on the CHAllenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) spacecraft from launch until years 2010 (CHAMP) and 2012 (GRACE), approximately 10 years of observations from each satellite. We extract local maxima in neutral mass densities over the background using a smoothing window with size of one quarter of the orbit. The maxima have been analyzed for each year and also for the duration of each set of satellite observations. We show where they occur, under what solar wind conditions, and their relation to magnetic activity. The region with the highest frequency of occurrence coincides approximately with the cusp and mantle, with little direct evidence of an auroral zone source. Our conclusions agree with the "hot polar cap" observations that have been reported and studied in the past.

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.

Water-escape velocities in jumping blacktip sharks

PubMed Central

Brunnschweiler, Juerg M

2005-01-01

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 m s−1. These velocities for blacktip sharks seem accurate and are similar to estimates obtained for other shark species of similar size. PMID:16849197

Driving under the influence--a level-I trauma center's experience.

PubMed

Fantus, R J; Zautcke, J L; Hickey, P A; Fantus, P P; Nagorka, F W

1991-11-01

Alcohol-impaired driving is a major issue confronting today's society. New legislation is emerging to help curtail this ongoing problem. To evaluate the legislative effects in terms of outcome pertaining to injured drivers, we analyzed the records of 116 consecutive motor vehicle drivers who were admitted to our trauma center over a 16-month period. Medical reports, police reports, and drivers' abstracts were reviewed. Of the 116 drives, 61 (53%) had blood alcohol concentrations that exceeded the legal limit (blood alcohol level greater than or equal to 100 mg/dL) on arrival at the emergency department. Only four of these patients were ticketed for driving under the influence and received the mandatory suspension of their driver's license. None was convicted of this offense, which carries criminal charges and a revocation of the driver's license. Mechanisms for efficient collection of blood specimens and mandatory occurrence reporting are two recommendations that merit investigation to obviate further escape of injured, intoxicated drivers from the legal net. In addition, alcohol rehabilitation and education cannot be overlooked and should warrant strong societal support.

Identification of conformational neutralization sites on the fusion protein of mumps virus.

PubMed

Šantak, Maja; Örvell, Claes; Gulija, Tanja Košutić

2015-05-01

In spite of the success of the mumps vaccination, recent mumps outbreaks have been reported even among individuals with a history of mumps vaccination. For a better understanding of why the vaccination failed in cases of vaccinees who fell ill during recent mumps outbreaks, the immunological events during infection and/or vaccination should be better defined. In the work presented here we sought to identify new neutralization sites on the mumps virus surface glycoproteins. By using anti-mumps mAbs, three amino acid positions at residues 221, 323 and 373 in the F protein of mumps virus were shown to be located in at least two conformational neutralization epitopes. mAbs that specifically target these sites effectively neutralized mumps virus in vitro. The newly acquired glycosylation site at position 373 or loss of the existing one at position 323 was identified as the mechanism behind the escape from the specific mAbs. Based on the findings of this study, we suggest that the influence of the antigenic structure of the F protein should not be ignored in a thorough investigation of the underlying mechanism of the mumps vaccine failure or when making a strategy for development of a new vaccine. © 2015 The Authors.

Ventilation and oxygen uptake during escape from a civil aircraft.

PubMed

Ross, J A; Watt, S J; Henderson, G D; Vant, J H

1990-01-01

To help develop a specification for equipment providing personal respiratory protection in the event of aircraft fire a study was carried out to quantify ventilation and oxygen consumption during escape from a Trident aircraft. Data were gathered using the P.K. Morgan 'Oxylog' apparatus after its response time to rapid changes in inspired to expired oxygen concentration difference was assessed using a bench test. The 'Oxylog' had a lag time of 30-32 s and a 5-95% response typified by a half time of 20 s. The data gathered were corrected in the light of these findings. Fourteen male subjects aged 17-38 years were studied under two conditions. Four mass evacuations each involving 40 people; a total of nine subjects escaping from the front rank over eight seats being monitored. Six evacuations each involving only two people escaping from the rear of the cabin; a total of 11 subjects escaping over 14 seats being monitored. Escape was made over the seat backs, down an escape chute to a position 12 m from the base of the chute. Resting minute ventilation (mean 16.7 1 STPD) and oxygen consumption (mean 0.41 min-1 STPD) were similar before both evacuations. There were no significant differences between the two conditions either during, or up to 180 s after escape. Ventilation and oxygen consumption were greatest in the recovery period. The highest oxygen consumption seen was 2.08 l min-1 and maximum minute ventilation was 641. Mean total oxygen consumption for the escape and a 150 s recovery period was 2.41 l (s.d. 0.64, max. 3.11) for the mass evacuation and 2.97 l (s.d. 0.68, max. 4.09) for the two person evacuation. The mean total amount of gas inhaled during the same time period was 89.3 l (s.d. 25.6, max. 121.3) for the mass evacuation and 99.01 (s.d. 26.2, max. 137.3) for the other. These was no correlation between ventilation or oxygen consumption and either escape time, body weight, height or age.

Noise-induced escape in an excitable system

NASA Astrophysics Data System (ADS)

Khovanov, I. A.; Polovinkin, A. V.; Luchinsky, D. G.; McClintock, P. V. E.

2013-03-01

We consider the stochastic dynamics of escape in an excitable system, the FitzHugh-Nagumo (FHN) neuronal model, for different classes of excitability. We discuss, first, the threshold structure of the FHN model as an example of a system without a saddle state. We then develop a nonlinear (nonlocal) stability approach based on the theory of large fluctuations, including a finite-noise correction, to describe noise-induced escape in the excitable regime. We show that the threshold structure is revealed via patterns of most probable (optimal) fluctuational paths. The approach allows us to estimate the escape rate and the exit location distribution. We compare the responses of a monostable resonator and monostable integrator to stochastic input signals and to a mixture of periodic and stochastic stimuli. Unlike the commonly used local analysis of the stable state, our nonlocal approach based on optimal paths yields results that are in good agreement with direct numerical simulations of the Langevin equation.

Virtual Genomes in Flux: An Interplay of Neutrality and Adaptability Explains Genome Expansion and Streamlining

PubMed Central

Cuypers, Thomas D.; Hogeweg, Paulien

2012-01-01

The picture that emerges from phylogenetic gene content reconstructions is that genomes evolve in a dynamic pattern of rapid expansion and gradual streamlining. Ancestral organisms have been estimated to possess remarkably rich gene complements, although gene loss is a driving force in subsequent lineage adaptation and diversification. Here, we study genome dynamics in a model of virtual cells evolving to maintain homeostasis. We observe a pattern of an initial rapid expansion of the genome and a prolonged phase of mutational load reduction. Generally, load reduction is achieved by the deletion of redundant genes, generating a streamlining pattern. Load reduction can also occur as a result of the generation of highly neutral genomic regions. These regions can expand and contract in a neutral fashion. Our study suggests that genome expansion and streamlining are generic patterns of evolving systems. We propose that the complex genotype to phenotype mapping in virtual cells as well as in their biological counterparts drives genome size dynamics, due to an emerging interplay between adaptation, neutrality, and evolvability. PMID:22234601

Almost certain escape from black holes in final state projection models.

PubMed

Lloyd, Seth

2006-02-17

Recent models of the black-hole final state suggest that quantum information can escape from a black hole by a process akin to teleportation. These models rely on a controversial process called final-state projection. This Letter discusses the self-consistency of the final-state projection hypothesis and investigates escape from black holes for arbitrary final states and for generic interactions between matter and Hawking radiation. Quantum information escapes with fidelity approximately = (8/3pi)2: only half a bit of quantum information is lost on average, independent of the number of bits that escape from the hole.

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

DOUBLE code simulations of emissivities of fast neutrals for different plasma observation view-lines of neutral particle analyzers on the COMPASS tokamak

NASA Astrophysics Data System (ADS)

Mitosinkova, K.; Tomes, M.; Stockel, J.; Varju, J.; Stano, M.

2018-03-01

Neutral particle analyzers (NPA) measure line-integrated energy spectra of fast neutral atoms escaping the tokamak plasma, which are a product of charge-exchange (CX) collisions of plasma ions with background neutrals. They can observe variations in the ion temperature T i of non-thermal fast ions created by additional plasma heating. However, the plasma column which a fast atom has to pass through must be sufficiently short in comparison with the fast atom’s mean-free-path. Tokamak COMPASS is currently equipped with one NPA installed at a tangential mid-plane port. This orientation is optimal for observing non-thermal fast ions. However, in this configuration the signal at energies useful for T i derivation is lost in noise due to the too long fast atoms’ trajectories. Thus, a second NPA is planned to be connected for the purpose of measuring T i. We analyzed different possible view-lines (perpendicular mid-plane, tangential mid-plane, and top view) for the second NPA using the DOUBLE Monte-Carlo code and compared the results with the performance of the present NPA with tangential orientation. The DOUBLE code provides fast-atoms’ emissivity functions along the NPA view-line. The position of the median of these emissivity functions is related to the location from where the measured signal originates. Further, we compared the difference between the real central T i used as a DOUBLE code input and the T iCX derived from the exponential decay of simulated energy spectra. The advantages and disadvantages of each NPA location are discussed.

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

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…

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

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

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

Seasonal variability of Martian ion escape through the plume and tail from MAVEN observations

NASA Astrophysics Data System (ADS)

Dong, Y.; Fang, X.; Brain, D. A.; McFadden, J. P.; Halekas, J. S.; Connerney, J. E. P.; Eparvier, F.; Andersson, L.; Mitchell, D.; Jakosky, B. M.

2017-04-01

We study the Mars Atmosphere and Volatile Evolution spacecraft observations of Martian planetary ion escape during two time periods: 11 November 2014 to 19 March 2015 and 4 June 2015 to 24 October 2015, with the focus on understanding the seasonal variability of Martian ion escape in response to the solar extreme ultraviolet (EUV) flux. We organize the >6 eV O+ ion data by the upstream electric field direction to estimate the escape rates through the plume and tail. To investigate the ion escape dependence on the solar EUV flux, we constrain the solar wind dynamic pressure and interplanetary magnetic filed strength and compare the ion escape rates through the plume and tail in different energy ranges under high and low EUV conditions. We found that the total >6 eV O+ escape rate increases from 2 to 3 × 1024 s-1 as the EUV irradiance increases by almost the same factor, mostly on the <1 keV tailward escape. The plume escape rate does not vary significantly with EUV. The relative contribution from the plume to the total escape varies between 30% and 20% from low to high EUV. Our results suggest that the Martian ion escape is sensitive to the seasonal EUV variation, and the contribution from plume escape becomes more important under low EUV conditions.

Diversity of the Lyman continuum escape fractions of high-z galaxies and its origins

NASA Astrophysics Data System (ADS)

Sumida, Takumi; Kashino, Daichi; Hasegawa, Kenji

2018-04-01

The Lyman continuum (LyC) escape fraction is a key quantity to determine the contribution of galaxies to cosmic reionization. It has been known that the escape fractions estimated by observations and numerical simulations show a large diversity. However, the origins of the diversity are still uncertain. In this work, to understand what quantities of galaxies are responsible for controlling the escape fraction, we numerically evaluate the escape fraction by performing ray-tracing calculation with simplified disc galaxy models. With a smooth disc model, we explore the dependence of the escape fraction on the disposition of ionizing sources and find that the escape fraction varies up to ˜3 orders of magnitude. It is also found that the halo mass dependence of disc scale height determines whether the escape fraction increases or decreases with halo mass. With a clumpy disc model, it turns out that the escape fraction increases as the clump mass fraction increases because the density in the inter-clump region decreases. In addition, we find that clumpiness regulates the escape fraction via two ways when the total clump mass dominates the total gas mass; the escape fraction is controlled by the covering factor of clumps if the clumps are dense sufficient to block LyC photons, otherwise the clumpiness works to reduce the escape fraction by increasing the total number of recombination events in a galaxy.

Danger Comes from All Fronts: Predator-Dependent Escape Tactics of Túngara Frogs

PubMed Central

Bulbert, Matthew W.; Page, Rachel A.; Bernal, Ximena E.

2015-01-01

The escape response of an organism is generally its last line of defense against a predator. Because the effectiveness of an escape varies with the approach behaviour of the predator, it should be advantageous for prey to alter their escape trajectories depending on the mode of predator attack. To test this hypothesis we examined the escape responses of a single prey species, the ground-dwelling túngara frog (Engystomops pustulosus), to disparate predators approaching from different spatial planes: a terrestrial predator (snake) and an aerial predator (bat). Túngara frogs showed consistently distinct escape responses when attacked by terrestrial versus aerial predators. The frogs fled away from the snake models (Median: 131°). In stark contrast, the frogs moved toward the bat models (Median: 27°); effectively undercutting the bat’s flight path. Our results reveal that prey escape trajectories reflect the specificity of their predators’ attacks. This study emphasizes the flexibility of strategies performed by prey to outcompete predators with diverse modes of attack. PMID:25874798

Simulation of field-induced molecular dissociation in atom-probe tomography: Identification of a neutral emission channel

NASA Astrophysics Data System (ADS)

Zanuttini, David; Blum, Ivan; Rigutti, Lorenzo; Vurpillot, François; Douady, Julie; Jacquet, Emmanuelle; Anglade, Pierre-Matthieu; Gervais, Benoit

2017-06-01

We investigate the dynamics of dicationic metal-oxide molecules under large electric-field conditions, on the basis of ab initio calculations coupled to molecular dynamics. Applied to the case of ZnO2 + in the field of atom probe tomography (APT), our simulation reveals the dissociation into three distinct exit channels. The proportions of these channels depend critically on the field strength and on the initial molecular orientation with respect to the field. For typical field strength used in APT experiments, an efficient dissociation channel leads to emission of neutral oxygen atoms, which escape detection. The calculated composition biases and their dependence on the field strength show remarkable consistency with recent APT experiments on ZnO crystals. Our work shows that bond breaking in strong static fields may lead to significant neutral atom production, and therefore to severe elemental composition biases in measurements.

XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part II: hydrogen coronae and ion escape.

PubMed

Kislyakova, Kristina G; Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V; Leitzinger, Martin; Khodachenko, Maxim L; Kulikov, Yuri N; Güdel, Manuel; Hanslmeier, Arnold

2013-11-01

We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a "super-Earth" with a radius of 2 R(Earth) and a mass of 10 M(Earth), located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×10²⁵ s⁻¹ to ∼5.3×10³⁰ s⁻¹, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EO(H)) to <3 EO(H) and usually is several times smaller in comparison to the thermal atmospheric escape rates.

The BepiColombo SERENA/ELENA unit development: a new technique to detect sputtered neutral atoms escaping from Mercury surface.

NASA Astrophysics Data System (ADS)

di Lellis, Andrea Maria; Selci, Stefano; de Angelis, Elisabetta; Leoni, Roberto; Milillo, Anna; Orsini, Stefano; Dandouras, Iannis

2010-05-01

ELENA (Emitted Low-Energy Neutral Atoms) is one of the four units of the SERENA experiment for the ESA cornerstone BepiColombo mission to Mercury. It is primarily devoted to understanding of Ion Sputtering processes and emission from planetary surfaces, particle back-scattering and Charge Exchange via neutral atoms detections in the energy range ~20 eV - 5 keV ELENA instrument is the first attempt of a new design techniques approached for the neutral particles identification in the low energy range. It is a Time-of-Flight system based on a peculiar Start section: an oscillating shutter (operated at frequencies up to a 100 kHz) and mechanical grating (two self-standing silicon nitride (Si3N4) membranes, patterned with arrays of long and narrow openings) that allows to identify the start time of the particles entering in the Time-of-Flight chamber. The Stop section at the end of the pattern is a 1-dimensional array composed by MCPs detector with discrete anodes corresponding to a Field of View of 4,5°x76°. This system allows having the determination of velocity and direction of the incoming particles. The instrument has a good capability to reject UV photons with the start section and to reject charged particle with a deflector system. In this paper the crucial parts of the instrument and test results will be described: the nano-structure membranes manufacturing, the shuttering system, the position encoder, the optical propriety of the membranes, the photon and particle test, the electronic box.

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.

Heat-induced symmetry breaking in ant (Hymenoptera: Formicidae) escape behavior

PubMed Central

Chung, Yuan-Kai

2017-01-01

The collective egress of social insects is important in dangerous situations such as natural disasters or enemy attacks. Some studies have described the phenomenon of symmetry breaking in ants, with two exits induced by a repellent. However, whether symmetry breaking occurs under high temperature conditions, which are a common abiotic stress, remains unknown. In our study, we deposited a group of Polyrhachis dives ants on a heated platform and counted the number of escaping ants with two identical exits. We discovered that ants asymmetrically escaped through two exits when the temperature of the heated platform was >32.75°C. The degree of asymmetry increased linearly with the temperature of the platform. Furthermore, the higher the temperature of heated platform was, the more ants escaped from the heated platform. However, the number of escaping ants decreased for 3 min when the temperature was higher than the critical thermal limit (39.46°C), which is the threshold for ants to endure high temperature without a loss of performance. Moreover, the ants tended to form small groups to escape from the thermal stress. A preparatory formation of ant grouping was observed before they reached the exit, indicating that the ants actively clustered rather than accidentally gathered at the exits to escape. We suggest that a combination of individual and grouping ants may help to optimize the likelihood of survival during evacuation. PMID:28355235

Elevated atmospheric escape of atomic hydrogen from Mars induced by high-altitude water

NASA Astrophysics Data System (ADS)

Chaffin, M. S.; Deighan, J.; Schneider, N. M.; Stewart, A. I. F.

2017-01-01

Atmospheric loss has controlled the history of Martian habitability, removing most of the planet’s initial water through atomic hydrogen and oxygen escape from the upper atmosphere to space. In standard models, H and O escape in a stoichiometric 2:1 ratio because H reaches the upper atmosphere via long-lived molecular hydrogen, whose abundance is regulated by a photochemical feedback sensitive to atmospheric oxygen content. The relatively constant escape rates these models predict are inconsistent with known H escape variations of more than an order of magnitude on seasonal timescales, variation that requires escaping H to have a source other than H2. The best candidate source is high-altitude water, detected by the Mars Express spacecraft in seasonally variable concentrations. Here we use a one-dimensional time-dependent photochemical model to show that the introduction of high-altitude water can produce a large increase in the H escape rate on a timescale of weeks, quantitatively linking these observations. This H escape pathway produces prompt H loss that is not immediately balanced by O escape, influencing the oxidation state of the atmosphere for millions of years. Martian atmospheric water loss may be dominated by escape via this pathway, which may therefore potentially control the planet’s atmospheric chemistry. Our findings highlight the influence that seasonal atmospheric variability can have on planetary evolution.

Biomechanics of Tetrahymena escaping from a dead end

PubMed Central

Kikuchi, Kenji

2018-01-01

Understanding the behaviours of swimming microorganisms in various environments is important for understanding cell distribution and growth in nature and industry. However, cell behaviour in complex geometries is largely unknown. In this study, we used Tetrahymena thermophila as a model microorganism and experimentally investigated cell behaviour between two flat plates with a small angle. In this configuration, the geometry provided a ‘dead end' line where the two flat plates made contact. The results showed that cells tended to escape from the dead end line more by hydrodynamics than by a biological reaction. In the case of hydrodynamic escape, the cell trajectories were symmetric as they swam to and from the dead end line. Near the dead end line, T. thermophila cells were compressed between the two flat plates while cilia kept beating with reduced frequency; those cells again showed symmetric trajectories, although the swimming velocity decreased. These behaviours were well reproduced by our computational model based on biomechanics. The mechanism of hydrodynamic escape can be understood in terms of the torque balance induced by lubrication flow. We therefore conclude that a cell's escape from the dead end was assisted by hydrodynamics. These findings pave the way for understanding cell behaviour and distribution in complex geometries. PMID:29491169

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

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

A Mechanistic Understanding of Allosteric Immune Escape Pathways in the HIV-1 Envelope Glycoprotein

PubMed Central

Sethi, Anurag; Tian, Jianhui; Derdeyn, Cynthia A.; Korber, Bette; Gnanakaran, S.

2013-01-01

The HIV-1 envelope (Env) spike, which consists of a compact, heterodimeric trimer of the glycoproteins gp120 and gp41, is the target of neutralizing antibodies. However, the high mutation rate of HIV-1 and plasticity of Env facilitates viral evasion from neutralizing antibodies through various mechanisms. Mutations that are distant from the antibody binding site can lead to escape, probably by changing the conformation or dynamics of Env; however, these changes are difficult to identify and define mechanistically. Here we describe a network analysis-based approach to identify potential allosteric immune evasion mechanisms using three known HIV-1 Env gp120 protein structures from two different clades, B and C. First, correlation and principal component analyses of molecular dynamics (MD) simulations identified a high degree of long-distance coupled motions that exist between functionally distant regions within the intrinsic dynamics of the gp120 core, supporting the presence of long-distance communication in the protein. Then, by integrating MD simulations with network theory, we identified the optimal and suboptimal communication pathways and modules within the gp120 core. The results unveil both strain-dependent and -independent characteristics of the communication pathways in gp120. We show that within the context of three structurally homologous gp120 cores, the optimal pathway for communication is sequence sensitive, i.e. a suboptimal pathway in one strain becomes the optimal pathway in another strain. Yet the identification of conserved elements within these communication pathways, termed inter-modular hotspots, could present a new opportunity for immunogen design, as this could be an additional mechanism that HIV-1 uses to shield vulnerable antibody targets in Env that induce neutralizing antibody breadth. PMID:23696718

Behavioral regulation of gravity - Schedule effects under escape-avoidance procedures

NASA Technical Reports Server (NTRS)

Clark, F. C.; Lange, K. O.; Belleville, R. E.

1973-01-01

Squirrel monkeys were restrained in a centrifuge capsule and trained to escape and avoid increases in artificial gravity. During escape-avoidance, lever responses reduced centrifugally simulated gravity or postponed scheduled increases. The effect of variation in the interval of postponement (equal to the duration of decrease produced by escape responses) was studied under a multiple schedule of four components. Three components were gravity escape-avoidance with postponement times of 20, 40, and 60 sec. The fourth component was extinction. Each component was associated with a different auditory stimulus. Rate of responding decreased with increasing postponement time and higher mean g-levels occurred at shorter intervals of postponement. Effects of the schedule parameter on response rate and mean g-level were similar to effects of the schedule on free-operant avoidance and on titration behavior maintained by shock.

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…

Neutral Buoyancy Simulator - SADE NBS Test

NASA Technical Reports Server (NTRS)

1983-01-01

One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured is an astronaut practicing climbing a space platform that was necessary in making repairs on the HST.

An anticipative escape system for vehicles in water crashes

NASA Astrophysics Data System (ADS)

Shen, Chuanliang; Wang, Jiawei; Yin, Qi; Zhu, Yantao; Yang, Jiawei; Liao, Mengdi; Yang, Liming

2017-07-01

In this article, it designs an escape system for vehicles in water crashes. The structure mainly contains sensors, control organs and actuating mechanism for both doors and windows. Sensors judge whether the vehicle falls into water or is in the falling process. The actuating mechanism accepts the signal delivered by the control organs, then open the electronic central lock on doors and meanwhile lower the window. The water escape system is able to anticipate drowning situations for vehicles and controls both doors and windows in such an emergency. Under the premise of doors staying in an undamaged state, it is for sure that people in the vehicle can open the door while drowning in the water and safely escape.

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

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

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.

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

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)

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

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

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

Perceived risk of home fire and escape plans in rural households.

PubMed

Yang, Jingzhen; Peek-Asa, Corinne; Allareddy, Veerasathpurush; Zwerling, Craig; Lundell, John

2006-01-01

Homes in rural areas have a higher fire death rate. Although successful exit from a home fire could greatly reduce fire-related deaths and injuries, little is known about factors associated with behaviors of developing and practicing an escape plan. Between July 2003 and June 2004, a baseline survey was administered, in person, to 691 rural households. Information collected included a history of previous home fire, perceived risk of home fire, existing smoke alarms and their working status, and home fire safety practices, as well as home and occupant characteristics. The association of residents' perceived risk of home fire and fire escape plans was assessed. Forty-two percent of rural households reported having a fire escape plan. Of the households with a plan, less than two thirds (56.9%) discussed or practiced the plan. Households with children were more likely to develop and practice a fire escape plan. Households with an elderly or disabled person were less likely to develop or practice the plan. Compared to respondents who perceived low or very low risk of home fire, those who perceived a high or very high risk had 3.5 times greater odds of having a fire escape plan and 5.5 times greater odds of discussion or practicing their plan. Increasing awareness of the potential risk of home fires may help occupants develop and practice home fire escape plans. In order to reduce fire deaths and injuries, different strategies need to be developed for those households in which the occupants lack the ability to escape.

Unsteady motion: escape jumps in planktonic copepods, their kinematics and energetics

PubMed Central

Kiørboe, Thomas; Andersen, Anders; Langlois, Vincent J.; Jakobsen, Hans H.

2010-01-01

We describe the kinematics of escape jumps in three species of 0.3–3.0 mm-sized planktonic copepods. We find similar kinematics between species with periodically alternating power strokes and passive coasting and a resulting highly fluctuating escape velocity. By direct numerical simulations, we estimate the force and power output needed to accelerate and overcome drag. Both are very high compared with those of other organisms, as are the escape velocities in comparison to startle velocities of other aquatic animals. Thus, the maximum weight-specific force, which for muscle motors of other animals has been found to be near constant at 57 N (kg muscle)−1, is more than an order of magnitude higher for the escaping copepods. We argue that this is feasible because most copepods have different systems for steady propulsion (feeding appendages) and intensive escapes (swimming legs), with the muscular arrangement of the latter probably adapted for high force production during short-lasting bursts. The resulting escape velocities scale with body length to power 0.65, different from the size-scaling of both similar sized and larger animals moving at constant velocity, but similar to that found for startle velocities in other aquatic organisms. The relative duration of the pauses between power strokes was observed to increase with organism size. We demonstrate that this is an inherent property of swimming by alternating power strokes and pauses. We finally show that the Strouhal number is in the range of peak propulsion efficiency, again suggesting that copepods are optimally designed for rapid escape jumps. PMID:20462876

Venus, Earth, Mars: Comparative ion escape caused by the interaction with the solar wind

NASA Astrophysics Data System (ADS)

Barabash, Stas

For the solar system planets the non-thermal atmospheric escape exceeds by far the Jean escape for particles heavier than helium. In this talk we consider only ion escape and compare the total ion escape rates for Venus, Earth, and Mars caused by the interaction with the solar wind. We review the most recent data on the escape rates based on measurements from Mars Express, Venus Express, and Cluster. The comparison of the available numbers show that despite large differences in the atmospheric masses between these three planets (a factor of 100 -200), different types of the interactions with the solar wind (magnetized and non-magnetized obstacles), the escape rates for Mars, Venus, and the Earth are within the range 1024 - 1025 s-1 . Surprisingly, the expected shielding of the Earth atmosphere by the intrinsic magnetic field is not as efficient as one may think. The reason for this is the non-thermal escape caused by the solar wind interaction is a energy -limited process. Indeed, normalizing the escape rates to the planet-dependent escape energy and power available in the solar wind results in the normalized escape rates deferring only on a factor between three planets. The larger Earth's magnetosphere intercepts and tunnels down to the ionosphere more energy from the solar wind than more compact interaction regions of non-magnetized planets.

Why an intrinsic magnetic field does not protect a planet against atmospheric escape

NASA Astrophysics Data System (ADS)

Gunell, Herbert; Maggiolo, Romain; Nilsson, Hans; Stenberg Wieser, Gabriella; Slapak, Rikard; Lindkvist, Jesper; Hamrin, Maria; De Keyser, Johan

2018-06-01

The presence or absence of a magnetic field determines the nature of how a planet interacts with the solar wind and what paths are available for atmospheric escape. Magnetospheres form both around magnetised planets, such as Earth, and unmagnetised planets, like Mars and Venus, but it has been suggested that magnetised planets are better protected against atmospheric loss. However, the observed mass escape rates from these three planets are similar (in the approximate (0.5-2) kg s-1 range), putting this latter hypothesis into question. Modelling the effects of a planetary magnetic field on the major atmospheric escape processes, we show that the escape rate can be higher for magnetised planets over a wide range of magnetisations due to escape of ions through the polar caps and cusps. Therefore, contrary to what has previously been believed, magnetisation is not a sufficient condition for protecting a planet from atmospheric loss. Estimates of the atmospheric escape rates from exoplanets must therefore address all escape processes and their dependence on the planet's magnetisation.

Evolution of the human immunodeficiency virus type 2 envelope in the first years of infection is associated with the dynamics of the neutralizing antibody response

DOE PAGES

Rocha, Cheila; Calado, Rita; Borrego, Pedro; ...

2013-10-24

Background: therapy and the majority of HIV-2 infected individuals survive as elite controllers with normal CD4 + T cell counts and low or undetectable plasma viral load. Neutralizing antibodies (Nabs) are thought to play a central role in HIV-2 evolution and pathogenesis. However, the dynamic of the Nab response and resulting HIV-2 escape during acute infection and their impact in HIV-2 evolution and disease progression remain largely unknown. Our objective was to characterize the Nab response and the molecular and phenotypic evolution of HIV-2 in association with Nab escape in the first years of infection in two children infected atmore » birth. As a result, CD4 + T cells decreased from about 50% to below 30% in both children in the first five years of infection and the infecting R5 viruses were replaced by X4 viruses within the same period. With antiretroviral therapy, viral load in child 1 decreased to undetectable levels and CD4 + T cells recovered to normal levels, which have been sustained at least until the age of 12. In contrast, viral load increased in child 2 and she progressed to AIDS and death at age 9. Beginning in the first year of life, child 1 raised high titers of antibodies that neutralized primary R5 isolates more effectively than X4 isolates, both autologous and heterologous. Child 2 raised a weak X4-specific Nab response that decreased sharply as disease progressed. Rate of evolution, nucleotide and amino acid diversity, and positive selection, were significantly higher in the envelope of child 1 compared to child 2. Rates of R5-to-X4 tropism switch, of V1 and V3 sequence diversification, and of convergence of V3 to a β-hairpin structure were related with rate of escape from the neutralizing antibodies. Finally, our data suggests that the molecular and phenotypic evolution of the human immunodeficiency virus type 2 envelope are related with the dynamics of the neutralizing antibody response providing further support for a model in which

Evolution of the human immunodeficiency virus type 2 envelope in the first years of infection is associated with the dynamics of the neutralizing antibody response

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rocha, Cheila; Calado, Rita; Borrego, Pedro

Background: therapy and the majority of HIV-2 infected individuals survive as elite controllers with normal CD4 + T cell counts and low or undetectable plasma viral load. Neutralizing antibodies (Nabs) are thought to play a central role in HIV-2 evolution and pathogenesis. However, the dynamic of the Nab response and resulting HIV-2 escape during acute infection and their impact in HIV-2 evolution and disease progression remain largely unknown. Our objective was to characterize the Nab response and the molecular and phenotypic evolution of HIV-2 in association with Nab escape in the first years of infection in two children infected atmore » birth. As a result, CD4 + T cells decreased from about 50% to below 30% in both children in the first five years of infection and the infecting R5 viruses were replaced by X4 viruses within the same period. With antiretroviral therapy, viral load in child 1 decreased to undetectable levels and CD4 + T cells recovered to normal levels, which have been sustained at least until the age of 12. In contrast, viral load increased in child 2 and she progressed to AIDS and death at age 9. Beginning in the first year of life, child 1 raised high titers of antibodies that neutralized primary R5 isolates more effectively than X4 isolates, both autologous and heterologous. Child 2 raised a weak X4-specific Nab response that decreased sharply as disease progressed. Rate of evolution, nucleotide and amino acid diversity, and positive selection, were significantly higher in the envelope of child 1 compared to child 2. Rates of R5-to-X4 tropism switch, of V1 and V3 sequence diversification, and of convergence of V3 to a β-hairpin structure were related with rate of escape from the neutralizing antibodies. Finally, our data suggests that the molecular and phenotypic evolution of the human immunodeficiency virus type 2 envelope are related with the dynamics of the neutralizing antibody response providing further support for a model in which

Design and Comparison of Cascaded H-Bridge, Modular Multilevel Converter, and 5-L Active Neutral Point Clamped Topologies for Motor Drive Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marzoughi, Alinaghi; Burgos, Rolando; Boroyevich, Dushan

This paper presents the design procedure and comparison of converters currently used in medium-voltage high-power motor drive applications. For this purpose, the cascaded H-bridge (CHB), modular multilevel converter (MMC), and five-level active neutral point clamped (5-L ANPC) topologies are targeted. The design is performed using 1.7-kV insulated gate bipolar transistors (IGBTs) for CHB and MMC converters, and utilizing 3.3- and 4.5-kV IGBTs for 5-L ANPC topology as normally done in industry. The comparison is done between the designed converter topologies at three different voltage levels (4.16, 6.9, and 13.8 kV, with only the first two voltage levels in case ofmore » the 5-L ANPC) and two different power levels (3 and 5 MVA), in order to elucidate the dependence of different parameters on voltage and power rating. Finally, the comparison is done from several points of view such as efficiency, capacitive energy storage, semiconductor utilization, parts count (for measure of reliability), and power density.« less

Capacitive Neutralization Dialysis for Direct Energy Generation.

PubMed

Liu, Yue; Zhang, Yi; Ou-Yang, Wei; Bastos Sales, Bruno; Sun, Zhuo; Liu, Fei; Zhao, Ran

2017-08-15

Capacitive neutralization dialysis energy (CNDE) is proposed as a novel energy-harvesting technique that is able to utilize waste acid and alkaline solutions to produce electrical energy. CNDE is a modification based on neutralization dialysis. It was found that a higher NaCl concentration led to a higher open-circuit potential when the concentrations of acid and alkaline solutions were fixed. Upon closing of the circuit, the membrane potential was used as a driving force to move counter ions into the electrical double layers at the electrode-liquid interface, thereby creating an ionic current. Correspondingly, in the external circuit, electrons flow through an external resistor from one electrode to the other, thereby generating electrical energy directly. The influence of external resistances was studied to achieve greater energy extraction, with the maximum output of 110 mW/m 2 obtained by employing an external resistance of 5 Ω together with the AC-coated electrode.

Dynamic neutral beam current and voltage control to improve beam efficacy in tokamaks

NASA Astrophysics Data System (ADS)

Pace, D. C.; Austin, M. E.; Bardoczi, L.; Collins, C. S.; Crowley, B.; Davis, E.; Du, X.; Ferron, J.; Grierson, B. A.; Heidbrink, W. W.; Holcomb, C. T.; McKee, G. R.; Pawley, C.; Petty, C. C.; Podestà, M.; Rauch, J.; Scoville, J. T.; Spong, D. A.; Thome, K. E.; Van Zeeland, M. A.; Varela, J.; Victor, B.

2018-05-01

An engineering upgrade to the neutral beam system at the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] enables time-dependent programming of the beam voltage and current. Initial application of this capability involves pre-programmed beam voltage and current injected into plasmas that are known to be susceptible to instabilities that are driven by energetic ( E ≥ 40 keV) beam ions. These instabilities, here all Alfvén eigenmodes (AEs), increase the transport of the beam ions beyond a classical expectation based on particle drifts and collisions. Injecting neutral beam power, P beam ≥ 2 MW, at reduced voltage with increased current reduces the drive for Alfvénic instabilities and results in improved ion confinement. In lower-confinement plasmas, this technique is applied to eliminate the presence of AEs across the mid-radius of the plasmas. Simulations of those plasmas indicate that the mode drive is decreased and the radial extent of the remaining modes is reduced compared to a higher beam voltage case. In higher-confinement plasmas, this technique reduces AE activity in the far edge and results in an interesting scenario of beam current drive improving as the beam voltage reduces from 80 kV to 65 kV.

Dynamic neutral beam current and voltage control to improve beam efficacy in tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Austin, Max E.; Bardoczi, Laszlo; Collins, Cami S.

Here, an engineering upgrade to the neutral beam system at the DIII-D tokamak enables time-dependent programming of the beam voltage and current. Initial application of this capability involves pre-programmed beam voltage and current injected into plasmas that are known to be susceptible to instabilities that are driven by energetic (E ≥ 40 keV) beam ions. These instabilities, here all Alfvén eigenmodes (AEs), increase the transport of the beam ions beyond a classical expectation based on particle drifts and collisions. Injecting neutral beam power, P beam ≥ 2MW, at reduced voltage with increased current reduces the drive for Alfvénic instabilities andmore » results in improved ion confinement. In lower-confinement plasmas, this technique is applied to eliminate the presence of AEs across the mid-radius of the plasmas. Simulations of those plasmas indicate that the mode drive is decreased and the radial extent of the remaining modes is reduced compared to a higher beam voltage case. In higher-confinement plasmas, this technique reduces AE activity in the far edge and results in an interesting scenario of beam current drive improving as the beam voltage reduces from 80 kV to 65 kV.« less

Dynamic neutral beam current and voltage control to improve beam efficacy in tokamaks

DOE PAGES

Austin, Max E.; Bardoczi, Laszlo; Collins, Cami S.; ...

2018-04-20

Here, an engineering upgrade to the neutral beam system at the DIII-D tokamak enables time-dependent programming of the beam voltage and current. Initial application of this capability involves pre-programmed beam voltage and current injected into plasmas that are known to be susceptible to instabilities that are driven by energetic (E ≥ 40 keV) beam ions. These instabilities, here all Alfvén eigenmodes (AEs), increase the transport of the beam ions beyond a classical expectation based on particle drifts and collisions. Injecting neutral beam power, P beam ≥ 2MW, at reduced voltage with increased current reduces the drive for Alfvénic instabilities andmore » results in improved ion confinement. In lower-confinement plasmas, this technique is applied to eliminate the presence of AEs across the mid-radius of the plasmas. Simulations of those plasmas indicate that the mode drive is decreased and the radial extent of the remaining modes is reduced compared to a higher beam voltage case. In higher-confinement plasmas, this technique reduces AE activity in the far edge and results in an interesting scenario of beam current drive improving as the beam voltage reduces from 80 kV to 65 kV.« less

Driving Force of Plasma Bullet in Atmospheric-Pressure Plasma

NASA Astrophysics Data System (ADS)

Yambe, Kiyoyuki; Masuda, Seiya; Kondo, Shoma

2018-06-01

When plasma is generated by applying high-voltage alternating current (AC), the driving force of the temporally and spatially varying electric field is applied to the plasma. The strength of the driving force of the plasma at each spatial position is different because the electrons constituting the atmospheric-pressure nonequilibrium (cold) plasma move at a high speed in space. If the force applied to the plasma is accelerated only by the driving force, the plasma will be accelerated infinitely. The equilibrium between the driving force and the restricting force due to the collision between the plasma and neutral particles determines the inertial force and the drift velocity of the plasma. Consequently, the drift velocity depends on the strength of the time-averaged AC electric field. The pressure applied by the AC electric field equilibrates with the plasma pressure. From the law of conservation of energy, the pressure equilibrium is maintained by varying the drift velocity of the plasma.

Effects of Visual Information on Wind-Evoked Escape Behavior of the Cricket, Gryllus bimaculatus.

PubMed

Kanou, Masamichi; Matsuyama, Akane; Takuwa, Hiroyuki

2014-09-01

We investigated the effects of visual information on wind-evoked escape behavior in the cricket, Gryllus bimaculatus. Most agitated crickets were found to retreat into a shelter made of cardboard installed in the test arena within a short time. As this behavior was thought to be a type of escape, we confirmed how a visual image of a shelter affected wind-evoked escape behavior. Irrespective of the brightness of the visual background (black or white) or the absence or presence of a shelter, escape jumps were oriented almost 180° opposite to the source of the air puff stimulus. Therefore, the direction of wind-evoked escape depends solely depended on the direction of the stimulus air puff. In contrast, the turning direction of the crickets during the escape was affected by the position of the visual image of the shelter. During the wind-evoked escape jump, most crickets turned in the direction in which a shelter was presented. This behavioral nature is presumably necessary for crickets to retreat into a shelter within a short time after their escape jump.

Combination Antimicrobial Nanocomposite Materials for Neutralization of Biological Threat Agents (PREPRINT)

DTIC Science & Technology

2008-09-01

AFRL-RX-TY-TP-2008-4601 PREPRINT COMBINATION ANTIMICROBIAL NANOCOMPOSITE MATERIALS FOR NEUTRALIZATION OF BIOLOGICAL THREAT AGENTS...AIRBASE TECHNOLOGIES DIVISION MATERIALS AND MANUFACTURING DIRECTORATE AIR FORCE RESEARCH LABORATORY AIR FORCE MATERIEL COMMAND 139 BARNES DRIVE, SUITE 2...a composite material that combines the protein and inorganic components. The process can be mimicked in vitro to some degree, providing methods for

What You May Not See Might Slow You Down Anyway: Masked Images and Driving

PubMed Central

Lewis-Evans, Ben; de Waard, Dick; Jolij, Jacob; Brookhuis, Karel A.

2012-01-01

Many theories of driver behaviour suggest that unconscious or implicit emotions play a functional role in the shaping and control of behaviour. This has not been experimentally tested however. Therefore, in this study the effects of emotive masked images on driver behaviour were examined. While driving a simulator, participants were repeatedly exposed to negative or neutral emotionally laden target images that were sandwich masked by emotionally neutral images. These images were encountered across two different trials each of which consisted of 3–4 minutes of driving on a rural road. The results indicate an effect of the negative target images primarily in reducing the extent of familiarisation occurring between the first and second experimental drives. This is evident in a reduced decrease in heart rate and a reduced increase in high band heart rate variability and actual travelling speed from the first to second drives if the negative target image was presented in the second drive. In addition to these findings there was no clear effect of the target image on subjective ratings of effort or feelings of risk. There was however an effect of gender, with the majority of the effects found in the study being limited to the larger female dataset. These findings suggest that unconscious or implicit emotional stimuli may well influence driver behaviour without explicit awareness. PMID:22279549

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

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.

Correlates of Protective Cellular Immunity Revealed by Analysis of Population-Level Immune Escape Pathways in HIV-1

PubMed Central

Brumme, Chanson J.; Martin, Eric; Listgarten, Jennifer; Brockman, Mark A.; Le, Anh Q.; Chui, Celia K. S.; Cotton, Laura A.; Knapp, David J. H. F.; Riddler, Sharon A.; Haubrich, Richard; Nelson, George; Pfeifer, Nico; DeZiel, Charles E.; Heckerman, David; Apps, Richard; Carrington, Mary; Mallal, Simon; Harrigan, P. Richard; John, Mina

2012-01-01

HLA class I-associated polymorphisms identified at the population level mark viral sites under immune pressure by individual HLA alleles. As such, analysis of their distribution, frequency, location, statistical strength, sequence conservation, and other properties offers a unique perspective from which to identify correlates of protective cellular immunity. We analyzed HLA-associated HIV-1 subtype B polymorphisms in 1,888 treatment-naïve, chronically infected individuals using phylogenetically informed methods and identified characteristics of HLA-associated immune pressures that differentiate protective and nonprotective alleles. Over 2,100 HLA-associated HIV-1 polymorphisms were identified, approximately one-third of which occurred inside or within 3 residues of an optimally defined cytotoxic T-lymphocyte (CTL) epitope. Differential CTL escape patterns between closely related HLA alleles were common and increased with greater evolutionary distance between allele group members. Among 9-mer epitopes, mutations at HLA-specific anchor residues represented the most frequently detected escape type: these occurred nearly 2-fold more frequently than expected by chance and were computationally predicted to reduce peptide-HLA binding nearly 10-fold on average. Characteristics associated with protective HLA alleles (defined using hazard ratios for progression to AIDS from natural history cohorts) included the potential to mount broad immune selection pressures across all HIV-1 proteins except Nef, the tendency to drive multisite and/or anchor residue escape mutations within known CTL epitopes, and the ability to strongly select mutations in conserved regions within HIV's structural and functional proteins. Thus, the factors defining protective cellular immune responses may be more complex than simply targeting conserved viral regions. The results provide new information to guide vaccine design and immunogenicity studies. PMID:23055555

Effects of the crustal magnetic fields on the Martian atmospheric ion escape rate

NASA Astrophysics Data System (ADS)

Ramstad, Robin; Barabash, Stas; Futaana, Yoshifumi; Nilsson, Hans; Holmström, Mats

2016-10-01

Eight years (2007-2015) of ion flux measurements from Mars Express are used to statistically investigate the influence of the Martian magnetic crustal fields on the atmospheric ion escape rate. We combine all Analyzer of Space Plasmas and Energetic Atoms/Ion Mass Analyzer (ASPERA-3/IMA) measurements taken during nominal upstream solar wind and solar extreme ultraviolet conditions to compute global average ion distribution functions, individually for the north/south hemispheres and for varying solar zenith angles (SZAs) of the strongest crustal magnetic field. Escape rates are subsequently calculated from each of the average distribution functions. The maximum escape rate (4.2 ± 1.2) × 1024s-1 is found for SZA = 60°-80°, while the minimum escape rate (1.7 ± 0.6) × 1024s-1 is found for SZA = 28°-60°, showing that the dayside orientation of the crustal fields significantly affects the global escape rate (p = 97%). However, averaged over time, independent of SZA, we find no statistically significant difference in the escape rates from the two hemispheres (escape from southern hemisphere 46% ± 18% of global rate).

Escaping and Falling into Poverty in India Today.

PubMed

Thorat, Amit; Vanneman, Reeve; Desai, Sonalde; Dubey, Amaresh

2017-05-01

The study examines the dynamic nature of movements into and out of poverty over a period when poverty has fallen substantially in India. The analysis identifies people who escaped poverty and those who fell into it over the period 2005 to 2012. The analysis identifies people who escaped poverty and those who fell into it over the period 2005 to 2012. Using panel data from the India Human Development Survey for 2005 and 2012, we find that the risks of marginalized communities such as Dalits and Adivasis of falling into or remaining in poverty were higher than those for more privileged groups. Some, but not all of these higher risks are explained by educational, financial, and social disadvantages of these groups in 2005. Results from a logistic regression show that some factors that help people escape poverty differ from those that push people into it and that the strength of their effects varies.

Escaping and Falling into Poverty in India Today

PubMed Central

Thorat, Amit; Vanneman, Reeve; Desai, Sonalde; Dubey, Amaresh

2017-01-01

The study examines the dynamic nature of movements into and out of poverty over a period when poverty has fallen substantially in India. The analysis identifies people who escaped poverty and those who fell into it over the period 2005 to 2012. The analysis identifies people who escaped poverty and those who fell into it over the period 2005 to 2012. Using panel data from the India Human Development Survey for 2005 and 2012, we find that the risks of marginalized communities such as Dalits and Adivasis of falling into or remaining in poverty were higher than those for more privileged groups. Some, but not all of these higher risks are explained by educational, financial, and social disadvantages of these groups in 2005. Results from a logistic regression show that some factors that help people escape poverty differ from those that push people into it and that the strength of their effects varies. PMID:28966435

The influence of Mars' magnetic topology on atmospheric escape

NASA Astrophysics Data System (ADS)

Curry, S.; Luhmann, J. G.; DiBraccio, G. A.; Dong, C.; Xu, S.; Mitchell, D.; Gruesbeck, J.; Espley, J. R.; Connerney, J. E. P.; McFadden, J. P.; Ma, Y. J.; Brain, D.

2017-12-01

At weakly magnetized planets such as Mars and Venus, the solar wind directly interacts with the upper atmosphere where ions can be picked up and swept away by the background convection electric field. These pick-up ions have a gyroradius on the planetary scale that is largely dominated by the interplanetary magnetic field (IMF). But at Mars, their trajectory is also influenced by the existence of remanent crustal magnetic fields, which are thought to create a shielding effect for escaping planetary ions when they are on the dayside. Consequently, the magnetic topology changes at Mars as magnetic reconnection occurs between the draped (IMF) and the crustal magnetic fields (closed). The resulting topology includes open field lines in the solar wind with one footprint attached to the planet. Using magnetohydrodynamic (MHD) and test particle simulations, we will explore the influence of the magnetic topology on ion escape. We will present escape rates for planetary ions for different crustal field positions during different IMF configurations, with +/-BY and +/-BZ components in the Mars Sun Orbit (MSO) coordinate system. We will also compare global maps of ion outflow and escape with open / closed magnetic field line maps and compare our results with ion fluxes and magnetic field data from the Mars Atmospheric and Volatile EvolutioN (MAVEN) mission. Our results relating the dynamic magnetic field topology at Mars and planetary ion escape are an important aspect of magnetospheric physics and planetary evolution, both of which have applications to our own solar system and the increasing number of exoplanets discovered every year.

Ancient village fire escape path planning based on improved ant colony algorithm

NASA Astrophysics Data System (ADS)

Xia, Wei; Cao, Kang; Hu, QianChuan

2017-06-01

The roadways are narrow and perplexing in ancient villages, it brings challenges and difficulties for people to choose route to escape when a fire occurs. In this paper, a fire escape path planning method based on ant colony algorithm is presented according to the problem. The factors in the fire environment which influence the escape speed is introduced to improve the heuristic function of the algorithm, optimal transfer strategy, and adjustment pheromone volatile factor to improve pheromone update strategy adaptively, improve its dynamic search ability and search speed. Through simulation, the dynamic adjustment of the optimal escape path is obtained, and the method is proved to be feasible.

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

Survey of heating and current drive for K-DEMO

NASA Astrophysics Data System (ADS)

Mikkelsen, D. R.; Kessel, C. E.; Poli, F. M.; Bertelli, N.; Kim, K.

2018-03-01

We present calculations of heating and current drive by neutral injection and by electromagnetic waves in the ion cyclotron, helicon, lower hybrid, and electron cyclotron frequency ranges for the steady state burn conditions in a K-DEMO configuration with I_p=12.3 MA, a  =  2.1 m, R_o=6.8 m, B_o=7.4 T, \

Escape for the Slow Solar Wind

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-05-01

that marks the edges of coronal holes and extends outward as the heliospheric current sheet are caused by supergranule-like convective flows. These motions drive magnetic reconnection that funnel plasma from the closed-field region onto enormous arcs that extend far away from the heliospheric current sheet, spanning tens of degrees in latitude and longitude.The simulations by Higginson and collaborators demonstrate that closed-field plasma from coronal-hole boundaries can be successfully channeled into the solar system. Due to the geometry and dynamics of the coronal holes, the plasma can travel far from the heliospheric current sheet, resulting in a slow solar wind of closed-field plasma consistent with our observations. These simulations therefore suggest aprocessthat resolves the long-standing puzzle of the slow solar wind.BonusCheck out the animation below, made from the results of the teams simulations. This video shows the location of a forming heliospheric arc at a distance of 12 solar radii. The arc forms as magnetic field lines at the boundary of a coronal hole change from closed to open, allowing closed-field flux to escape along them.http://aasnova.org/wp-content/uploads/2017/05/apjlaa6d72f4_video.mp4CitationA. K. Higginson et al 2017 ApJL 840 L10. doi:10.3847/2041-8213/aa6d72

Sharks modulate their escape behavior in response to predator size, speed and approach orientation.

PubMed

Seamone, Scott; Blaine, Tristan; Higham, Timothy E

2014-12-01

Escape responses are often critical for surviving predator-prey interactions. Nevertheless, little is known about how predator size, speed and approach orientation impact escape performance, especially in larger prey that are primarily viewed as predators. We used realistic shark models to examine how altering predatory behavior and morphology (size, speed and approach orientation) influences escape behavior and performance in Squalus acanthias, a shark that is preyed upon by apex marine predators. Predator models induced C-start escape responses, and increasing the size and speed of the models triggered a more intense response (increased escape turning rate and acceleration). In addition, increased predator size resulted in greater responsiveness from the sharks. Among the responses, predator approach orientation had the most significant impact on escapes, such that the head-on approach, as compared to the tail-on approach, induced greater reaction distances and increased escape turning rate, speed and acceleration. Thus, the anterior binocular vision in sharks renders them less effective at detecting predators approaching from behind. However, it appears that sharks compensate by performing high-intensity escapes, likely induced by the lateral line system, or by a sudden visual flash of the predator entering their field of view. Our study reveals key aspects of escape behavior in sharks, highlighting the modulation of performance in response to predator approach. Copyright © 2014 Elsevier GmbH. All rights reserved.

Active avoidance: escape and dodging behaviors for reactive control

NASA Astrophysics Data System (ADS)

Arkin, Ronald C.; Carter, William M.

1992-03-01

New methods for producing avoidance behavior among moving obstacles within the context of reactive robotic control are described. These specifically include escape and dodging behaviors. Dodging is concerned with the avoidance of a ballistic projectile while escape is more useful within the context of chase. The motivation and formulation of these new reactive behaviors are presented. Simulation results of a robot in a cluttered and moving world are also provided.

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

Plasma Clouds and Snowplows: Bulk Plasma Escape from Mars Observed by MAVEN

NASA Technical Reports Server (NTRS)

Halekas, J. S.; Brain, D. A.; Ruhunusiri, S.; McFadden, J. P.; Mitchell, D. L.; Mazelle, C.; Connerney, J. E. P.; Harada, Y.; Hara, T.; Espley, J. R.;

Lyman continuum escape fraction of faint galaxies at z 3.3 in the CANDELS/GOODS-North, EGS, and COSMOS fields with LBC

NASA Astrophysics Data System (ADS)

Grazian, A.; Giallongo, E.; Paris, D.; Boutsia, K.; Dickinson, M.; Santini, P.; Windhorst, R. A.; Jansen, R. A.; Cohen, S. H.; Ashcraft, T. A.; Scarlata, C.; Rutkowski, M. J.; Vanzella, E.; Cusano, F.; Cristiani, S.; Giavalisco, M.; Ferguson, H. C.; Koekemoer, A.; Grogin, N. A.; Castellano, M.; Fiore, F.; Fontana, A.; Marchi, F.; Pedichini, F.; Pentericci, L.; Amorín, R.; Barro, G.; Bonchi, A.; Bongiorno, A.; Faber, S. M.; Fumana, M.; Galametz, A.; Guaita, L.; Kocevski, D. D.; Merlin, E.; Nonino, M.; O'Connell, R. W.; Pilo, S.; Ryan, R. E.; Sani, E.; Speziali, R.; Testa, V.; Weiner, B.; Yan, H.

2017-06-01

Context. The reionization of the Universe is one of the most important topics of present-day astrophysical research. The most plausible candidates for the reionization process are star-forming galaxies, which according to the predictions of the majority of the theoretical and semi-analytical models should dominate the H I ionizing background at z ≳ 3. Aims: We measure the Lyman continuum escape fraction, which is one of the key parameters used to compute the contribution of star-forming galaxies to the UV background. It provides the ratio between the photons produced at λ ≤ 912 Å rest-frame and those that are able to reach the inter-galactic medium, I.e. that are not absorbed by the neutral hydrogen or by the dust of the galaxy's inter-stellar medium. Methods: We used ultra-deep U-band imaging (U = 30.2 mag at 1σ) from Large Binocular Camera at the Large Binocular Telescope (LBC/LBT) in the CANDELS/GOODS-North field and deep imaging in the COSMOS and EGS fields in order to estimate the Lyman continuum escape fraction of 69 star-forming galaxies with secure spectroscopic redshifts at 3.27 ≤ z ≤ 3.40 to faint magnitude limits (L = 0.2L∗, or equivalently M1500 - 19). The narrow redshift range implies that the LBC U-band filter exclusively samples the λ ≤ 912 Å rest-frame wavelengths. Results: We measured through stacks a stringent upper limit (<1.7% at 1σ) for the relative escape fraction of H I ionizing photons from bright galaxies (L>L∗), while for the faint population (L = 0.2L∗) the limit to the escape fraction is ≲ 10%. We computed the contribution of star-forming galaxies to the observed UV background at z 3 and find that it is not sufficient to keep the Universe ionized at these redshifts unless their escape fraction increases significantly (≥ 10%) at low luminosities (M1500 ≥ - 19). Conclusions: We compare our results on the Lyman continuum escape fraction of high-z galaxies with recent estimates in the literature, and discuss

Behavioral regulation of gravity: schedule effects under escape-avoidance procedures1

PubMed Central

Clark, Fogle C.; Lange, Karl O.; Belleville, Richard E.

1973-01-01

Squirrel monkeys were restrained in a centrifuge capsule and trained to escape and avoid increases in artificial gravity. During escape-avoidance, lever responses reduced centrifugally simulated gravity or postponed scheduled increases. The effect of variation in the interval of postponement (equal to the duration of decrease produced by escape responses) was studied under a multiple schedule of four components. Three components were gravity escape-avoidance with postponement times of 20, 40, and 60 sec. The fourth component was extinction. Each component was associated with a different auditory stimulus. Rate of responding decreased with increasing postponement time and higher mean g-levels occurred at shorter intervals of postponement. Effects of the schedule parameter on response rate and mean g-level were similar to effects of the schedule on free-operant avoidance and on titration behavior maintained by shock. ImagesFig. 1. PMID:4202386

Foundational errors in the Neutral and Nearly-Neutral theories of evolution in relation to the Synthetic Theory: is a new evolutionary paradigm necessary?

PubMed

Valenzuela, Carlos Y

2013-01-01

The Neutral Theory of Evolution (NTE) proposes mutation and random genetic drift as the most important evolutionary factors. The most conspicuous feature of evolution is the genomic stability during paleontological eras and lack of variation among taxa; 98% or more of nucleotide sites are monomorphic within a species. NTE explains this homology by random fixation of neutral bases and negative selection (purifying selection) that does not contribute either to evolution or polymorphisms. Purifying selection is insufficient to account for this evolutionary feature and the Nearly-Neutral Theory of Evolution (N-NTE) included negative selection with coefficients as low as mutation rate. These NTE and N-NTE propositions are thermodynamically (tendency to random distributions, second law), biotically (recurrent mutation), logically and mathematically (resilient equilibria instead of fixation by drift) untenable. Recurrent forward and backward mutation and random fluctuations of base frequencies alone in a site make life organization and fixations impossible. Drift is not a directional evolutionary factor, but a directional tendency of matter-energy processes (second law) which threatens the biotic organization. Drift cannot drive evolution. In a site, the mutation rates among bases and selection coefficients determine the resilient equilibrium frequency of bases that genetic drift cannot change. The expected neutral random interaction among nucleotides is zero; however, huge interactions and periodicities were found between bases of dinucleotides separated by 1, 2... and more than 1,000 sites. Every base is co-adapted with the whole genome. Neutralists found that neutral evolution is independent of population size (N); thus neutral evolution should be independent of drift, because drift effect is dependent upon N. Also, chromosome size and shape as well as protein size are far from random.

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

Dynamical Effects on the Escape of H and D: Martian Water Reservoirs

NASA Technical Reports Server (NTRS)

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

2002-01-01

The evolution of water on Mars is dependent on the loss rates of H and D from its atmosphere, where the dominant loss mechanism for these constituents is Jeans escape. Throughout time, preferential escape of H over D has produced a deuterium rich atmosphere with a D/H ratio 5.2 times that of terrestrial water. Motion in the atmosphere of Mars is shown to change the Jeans escape rates of H and D in two important ways: (1) Atmospheric wind and rotation at the exobase increase the escape fluxes of H and D above the corresponding Jeans fluxes. (2) The percentage increase in escape flux due to motion is greatest for D. Recently, several models have been used to estimate the magnitudes of current and ancient crustal water reservoirs on Mars that freely exchange with its atmosphere. Differences in the reservoir sizes are influenced by differences in the composition at the exobase, thermal history of the atmosphere and the D/H ratio of earlier epochs as inferred from meteorites. When motion enhanced Jeans escape is applied to each of these models, it is shown in every case that factors (1) and (2) above lead to current and ancient crustal water reservoirs that are larger than those obtained without motion.

8. VIEW OF ESCAPE TRAINING TANK, LOOKING NORTHEAST FROM 50FOOT ...

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

8. VIEW OF ESCAPE TRAINING TANK, LOOKING NORTHEAST FROM 50-FOOT PASSAGEWAY, SHOWING PORTION OF SPIRAL STAIR AND REPRESENTATIVE FLOOD LIGHT BLISTER - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

About Climate Neutral Research Campuses | Climate Neutral Research Campuses

Science.gov Websites

| NREL About Climate Neutral Research Campuses About Climate Neutral Research Campuses Research an example of climate neutrality. To better understand the concept of climate neutral research

Escape Excel: A tool for preventing gene symbol and accession conversion errors.

PubMed

Welsh, Eric A; Stewart, Paul A; Kuenzi, Brent M; Eschrich, James A

2017-01-01

Microsoft Excel automatically converts certain gene symbols, database accessions, and other alphanumeric text into dates, scientific notation, and other numerical representations. These conversions lead to subsequent, irreversible, corruption of the imported text. A recent survey of popular genomic literature estimates that one-fifth of all papers with supplementary gene lists suffer from this issue. Here, we present an open-source tool, Escape Excel, which prevents these erroneous conversions by generating an escaped text file that can be safely imported into Excel. Escape Excel is implemented in a variety of formats (http://www.github.com/pstew/escape_excel), including a command line based Perl script, a Windows-only Excel Add-In, an OS X drag-and-drop application, a simple web-server, and as a Galaxy web environment interface. Test server implementations are accessible as a Galaxy interface (http://apostl.moffitt.org) and simple non-Galaxy web server (http://apostl.moffitt.org:8000/). Escape Excel detects and escapes a wide variety of problematic text strings so that they are not erroneously converted into other representations upon importation into Excel. Examples of problematic strings include date-like strings, time-like strings, leading zeroes in front of numbers, and long numeric and alphanumeric identifiers that should not be automatically converted into scientific notation. It is hoped that greater awareness of these potential data corruption issues, together with diligent escaping of text files prior to importation into Excel, will help to reduce the amount of Excel-corrupted data in scientific analyses and publications.

Escape Excel: A tool for preventing gene symbol and accession conversion errors

PubMed Central

Stewart, Paul A.; Kuenzi, Brent M.; Eschrich, James A.

2017-01-01

Background Microsoft Excel automatically converts certain gene symbols, database accessions, and other alphanumeric text into dates, scientific notation, and other numerical representations. These conversions lead to subsequent, irreversible, corruption of the imported text. A recent survey of popular genomic literature estimates that one-fifth of all papers with supplementary gene lists suffer from this issue. Results Here, we present an open-source tool, Escape Excel, which prevents these erroneous conversions by generating an escaped text file that can be safely imported into Excel. Escape Excel is implemented in a variety of formats (http://www.github.com/pstew/escape_excel), including a command line based Perl script, a Windows-only Excel Add-In, an OS X drag-and-drop application, a simple web-server, and as a Galaxy web environment interface. Test server implementations are accessible as a Galaxy interface (http://apostl.moffitt.org) and simple non-Galaxy web server (http://apostl.moffitt.org:8000/). Conclusions Escape Excel detects and escapes a wide variety of problematic text strings so that they are not erroneously converted into other representations upon importation into Excel. Examples of problematic strings include date-like strings, time-like strings, leading zeroes in front of numbers, and long numeric and alphanumeric identifiers that should not be automatically converted into scientific notation. It is hoped that greater awareness of these potential data corruption issues, together with diligent escaping of text files prior to importation into Excel, will help to reduce the amount of Excel-corrupted data in scientific analyses and publications. PMID:28953918

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.

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.

Survey of heating and current drive for K-DEMO

DOE PAGES

Mikkelsen, D. R.; Kessel, C. E.; Poli, F. M.; ...

2018-01-22

Here, we present calculations of heating and current drive by neutral injection and by electromagnetic waves in the ion cyclotron, helicon, lower hybrid, and electron cyclotron frequency ranges for the steady state burn conditions in a K-DEMO configuration withmore » $$I_{\\rm p}=12.3$$ MA, a = 2.1 m, $$R_{\\rm o}=6.8$$ m, $$B_{\\rm o}=7.4$$ T, $$ \

Survey of heating and current drive for K-DEMO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mikkelsen, D. R.; Kessel, C. E.; Poli, F. M.

Here, we present calculations of heating and current drive by neutral injection and by electromagnetic waves in the ion cyclotron, helicon, lower hybrid, and electron cyclotron frequency ranges for the steady state burn conditions in a K-DEMO configuration withmore » $$I_{\\rm p}=12.3$$ MA, a = 2.1 m, $$R_{\\rm o}=6.8$$ m, $$B_{\\rm o}=7.4$$ T, $$ \

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.

Escape problem under stochastic volatility: The Heston model

NASA Astrophysics Data System (ADS)

Masoliver, Jaume; Perelló, Josep

2008-11-01

We solve the escape problem for the Heston random diffusion model from a finite interval of span L . We obtain exact expressions for the survival probability (which amounts to solving the complete escape problem) as well as for the mean exit time. We also average the volatility in order to work out the problem for the return alone regardless of volatility. We consider these results in terms of the dimensionless normal level of volatility—a ratio of the three parameters that appear in the Heston model—and analyze their form in several asymptotic limits. Thus, for instance, we show that the mean exit time grows quadratically with large spans while for small spans the growth is systematically slower, depending on the value of the normal level. We compare our results with those of the Wiener process and show that the assumption of stochastic volatility, in an apparently paradoxical way, increases survival and prolongs the escape time. We finally observe that the model is able to describe the main exit-time statistics of the Dow-Jones daily index.

The neutral wind 'flywheel' as a source of quiet-time, polar-cap currents

NASA Technical Reports Server (NTRS)

Lyons, L. R.; Walterscheid, R. L.; Killeen, T. L.

1985-01-01

The neutral wind pattern over the summer polar cap can be driven by plasma convection to resemble the convection pattern. For a north-south component of the interplanetary magnetic field Bz directed southward, the wind speeds in the conducting E-region can become approximately 25 percent of the electric field drift speeds. If convection ceases, this neutral wind distribution can drive a significant polar cap current system for approximately 6 hours. The currents are reversed from those driven by the electric fields for southward Bz, and the Hall and field-aligned components of the current system resemble those observed during periods of northward Bz. The current magnitudes are similar to those observed during periods of small, northward Bz; however, observations indicate that electric fields often contribute to the currents as much as, or more than, the neutral winds.

Animal escapology I: theoretical issues and emerging trends in escape trajectories

PubMed Central

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

2011-01-01

Summary Escape responses are used by many animal species as their main defence against predator attacks. Escape success is determined by a number of variables; important are the directionality (the percentage of responses directed away from the threat) and the escape trajectories (ETs) measured relative to the threat. Although logic would suggest that animals should always turn away from a predator, work on various species shows that these away responses occur only approximately 50–90% of the time. A small proportion of towards responses may introduce some unpredictability and may be an adaptive feature of the escape system. Similar issues apply to ETs. Theoretically, an optimal ET can be modelled on the geometry of predator–prey encounters. However, unpredictability (and hence high variability) in trajectories may be necessary for preventing predators from learning a simple escape pattern. This review discusses the emerging trends in escape trajectories, as well as the modulating key factors, such as the surroundings and body design. The main ET patterns identified are: (1) high ET variability within a limited angular sector (mainly 90–180 deg away from the threat; this variability is in some cases based on multiple peaks of ETs), (2) ETs that allow sensory tracking of the threat and (3) ETs towards a shelter. These characteristic features are observed across various taxa and, therefore, their expression may be mainly related to taxon-independent animal design features and to the environmental context in which prey live – for example whether the immediate surroundings of the prey provide potential refuges. PMID:21753039

Hot oxygen escape from Mars: Simple scaling with solar EUV irradiance

NASA Astrophysics Data System (ADS)

Cravens, T. E.; Rahmati, A.; Fox, Jane L.; Lillis, R.; Bougher, S.; Luhmann, J.; Sakai, S.; Deighan, J.; Lee, Yuni; Combi, M.; Jakosky, B.

2017-01-01

The evolution of the atmosphere of Mars and the loss of volatiles over the lifetime of the solar system is a key topic in planetary science. An important loss process for atomic species, such as oxygen, is ionospheric photochemical escape. Dissociative recombination of O2+ ions (the major ion species) produces fast oxygen atoms, some of which can escape from the planet. Many theoretical hot O models have been constructed over the years, although a number of uncertainties are present in these models, particularly concerning the elastic cross sections of O atoms with CO2. Recently, the Mars Atmosphere and Volatile Evolution mission has been rapidly improving our understanding of the upper atmosphere and ionosphere of Mars and its interaction with the external environment (e.g., solar wind), allowing a new assessment of this important loss process. The purpose of the current paper is to take a simple analytical approach to the oxygen escape problem in order to (1) study the role that variations in solar radiation or solar wind fluxes could have on escape in a transparent fashion and (2) isolate the effects of uncertainties in oxygen cross sections on the derived oxygen escape rates. In agreement with several more elaborate numerical models, we find that the escape flux is directly proportional to the incident solar extreme ultraviolet irradiance and is inversely proportional to the backscatter elastic cross section. The amount of O lost due to ion transport in the topside ionosphere is found to be about 5-10% of the total.

Space weathering on near-Earth objects investigated by neutral-particle detection

NASA Astrophysics Data System (ADS)

Plainaki, C.; Milillo, A.; Orsini, S.; Mura, A.; De Angelis, E.; Di Lellis, A. M.; Dotto, E.; Livi, S.; Mangano, V.; Massetti, S.; Palumbo, M. E.

2009-03-01

The ion-sputtering (IS) process is active in many planetary environments in the solar system where plasma precipitates directly on the surface (for instance, Mercury, Moon and Europa). In particular, solar wind sputtering is one of the most important agents for the surface erosion of a near-Earth object (NEO), acting together with other surface release processes, such as photon stimulated desorption (PSD), thermal desorption (TD) and micrometeoroid impact vaporization (MIV). The energy distribution of the IS-released neutrals peaks at a few eVs and extends up to hundreds of eVs. Since all other release processes produce particles of lower energies, the presence of neutral atoms in the energy range above 10 eV and below a few keVs (sputtered high-energy atoms (SHEA)) identifies the IS process. SHEA easily escape from the NEO, due to NEO's extremely weak gravity. Detection and analysis of SHEA will give important information on surface-loss processes as well as on surface elemental composition. The investigation of the active release processes, as a function of the external conditions and the NEO surface properties, is crucial for obtaining a clear view of the body's present loss rate as well as for getting clues on its evolution, which depends significantly on space weather. In this work, an attempt to analyze processes that take place on the surface of these small airless bodies, as a result of their exposure to the space environment, has been realized. For this reason, a new space weathering model (space weathering on NEO-SPAWN) is presented. Moreover, an instrument concept of a neutral-particle analyzer specifically designed for the measurement of neutral density and the detection of SHEA from a NEO is proposed.

Space weathering on near-Earth objects investigated by neutral-particle detection

NASA Astrophysics Data System (ADS)

Plainaki, C.; Milillo, A.; Orsini, S.; Mura, A.; de Angelis, E.; di Lellis, A. M.; Dotto, E.; Livi, S.; Mangano, V.; Palumbo, M. E.

2009-04-01

The ion-sputtering (IS) process is active in many planetary environments in the solar system where plasma precipitates directly on the surface (for instance, Mercury, Moon and Europa). In particular, solar wind sputtering is one of the most important agents for the surface erosion of a near-Earth object (NEO), acting together with other surface release processes, such as photon stimulated desorption (PSD), thermal desorption (TD) and micrometeoroid impact vaporization (MIV). The energy distribution of the IS-released neutrals peaks at a few eVs and extends up to hundreds of eVs. Since all other release processes produce particles of lower energies, the presence of neutral atoms in the energy range above 10 eV and below a few keVs (sputtered high-energy atoms (SHEA)) identifies the IS process. SHEA easily escape from the NEO, due to NEO's extremely weak gravity. Detection and analysis of SHEA will give important information on surface-loss processes as well as on surface elemental composition. The investigation of the active release processes, as a function of the external conditions and the NEO surface properties, is crucial for obtaining a clear view of the body's present loss rate as well as for getting clues on its evolution, which depends significantly on space weather. In this work, an attempt to analyze processes that take place on the surface of these small airless bodies, as a result of their exposure to the space environment, has been realized. For this reason, a new space weathering model (space weathering on NEO-SPAWN) is presented. Moreover, an instrument concept of a neutral-particle analyzer specifically designed for the measurement of neutral density and the detection of SHEA from a NEO is proposed.

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

The role of plasma/neutral source and loss processes in shaping the giant planet magnetospheres

NASA Astrophysics Data System (ADS)

Delamere, P. A.

2014-12-01

The giant planet magnetospheres are filled with neutral and ionized gases originating from satellites orbiting deep within the magnetosphere. The complex chemical and physical pathways for the flow of mass and energy in this partially ionized plasma environment is critical for understanding magnetospheric dynamics. The flow of mass at Jupiter and Saturn begins, primarily, with neutral gases emanating from Io (~1000 kg/s) and Enceladus (~200 kg/s). In addition to ionization losses, the neutral gases are absorbed by the planet, its rings, or escape at high speeds from the magnetosphere via charge exchange reactions. The net result is a centrifugally confined torus of plasma that is transported radially outward, distorting the magnetic field into a magnetodisc configuration. Ultimately the plasma is lost to the solar wind. A critical parameter for shaping the magnetodisc and determining its dynamics is the radial plasma mass transport rate (~500 kg/s and ~50 kg/s for Jupiter and Saturn respectively). Given the plasma transport rates, several simple properties of the giant magnetodiscs can be estimated including the physical scale of the magnetosphere, the magnetic flux transport, and the magnitude of azimuthal magnetic field bendback. We will discuss transport-related magnetic flux conservation and the mystery of plasma heating—two critical issues for shaping the giant planet magnetospheres.

A New Glycan-Dependent CD4-Binding Site Neutralizing Antibody Exerts Pressure on HIV-1 In Vivo

PubMed Central

Freund, Natalia T.; Horwitz, Joshua A.; Nogueira, Lilian; Sievers, Stuart A.; Scharf, Louise; Scheid, Johannes F.; Gazumyan, Anna; Liu, Cassie; Velinzon, Klara; Goldenthal, Ariel; Sanders, Rogier W.; Moore, John P.; Bjorkman, Pamela J.; Seaman, Michael S.; Walker, Bruce D.; Klein, Florian; Nussenzweig, Michel C.

2015-01-01

The CD4 binding site (CD4bs) on the envelope glycoprotein is a major site of vulnerability that is conserved among different HIV-1 isolates. Many broadly neutralizing antibodies (bNAbs) to the CD4bs belong to the VRC01 class, sharing highly restricted origins, recognition mechanisms and viral escape pathways. We sought to isolate new anti-CD4bs bNAbs with different origins and mechanisms of action. Using a gp120 2CC core as bait, we isolated antibodies encoded by IGVH3-21 and IGVL3-1 genes with long CDRH3s that depend on the presence of the N-linked glycan at position-276 for activity. This binding mode is similar to the previously identified antibody HJ16, however the new antibodies identified herein are more potent and broad. The most potent variant, 179NC75, had a geometric mean IC80 value of 0.42 μg/ml against 120 Tier-2 HIV-1 pseudoviruses in the TZM.bl assay. Although this group of CD4bs glycan-dependent antibodies can be broadly and potently neutralizing in vitro, their in vivo activity has not been tested to date. Here, we report that 179NC75 is highly active when administered to HIV-1-infected humanized mice, where it selects for escape variants that lack a glycan site at position-276. The same glycan was absent from the virus isolated from the 179NC75 donor, implying that the antibody also exerts selection pressure in humans. PMID:26516768

An objective assessment of safety to drive in an upper limb cast.

PubMed

Stevenson, H L; Peterson, N; Talbot, C; Dalal, S; Watts, A C; Trail, I A

2013-03-01

Patients managed with upper limb cast immobilization often seek advice about driving. There is very little published data to assist in decision making, and advice given varies between healthcare professionals. There are no specific guidelines available from the UK Drivers and Vehicles Licensing Agency, police, or insurance companies. Evidence-based guidelines would enable clinicians to standardize the advice given to patients. Six individuals (three male, three female; mean age 36 years, range 27-43 years) were assessed by a mobility occupational therapist and driving standards agency examiner while completing a formal driving test in six different types of upper limb casts (above-elbow, below-elbow neutral, and below-elbow cast incorporating the thumb [Bennett's cast]) on both left and right sides. Of the 36 tests, participants passed 31 tests, suggesting that most people were able to safely drive with upper limb cast immobilization. However, driving in a left above-elbow cast was considered unsafe.

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

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

On becoming neutral: effects of experimental neutralizing reconsidered.

PubMed

van den Hout, M; van Pol, M; Peters, M

2001-12-01

Behaviour Research and Therapy 34 (1996) 889-898 found that writing out a negative thought produced anxiety and an urge to neutralize the thought, that instructing participants to neutralize the thought reduced anxiety/neutralization urge in the short run (i.e. within 2 min), but that in the control group 20 min without instruction was attended by the same reduction in anxiety/urge to neutralize ("natural decay"). The observations were made with pariticipants who scored high on "thought action fusion" and the experiment was set up as exerimental model of obsessions. We repeated the study with participants that were not selected on thought action fusion. All the findings reported by Behaviour Research and Therapy 34 (1996) 889-898 were replicated. Correlational analysis indicated that the strength of the effect was not related to scores on scales measuring "thought action fusion". Behaviour Research and Therapy 34 (1996) 889-898 did not assess whether non-neutralizing was followed by immediate reductions in distress. We did assess this and found that the larger part of the immediate reduction of distress after neutralization also occurs when no neutralization instruction is given. The effects of neutralization instructions in the present type of experiment are considerably less powerful than suggested earlier.

Strong plume fluxes at Mars observed by MAVEN: An important planetary ion escape channel

NASA Astrophysics Data System (ADS)

Dong, Y.; Fang, X.; Brain, D. A.; McFadden, J. P.; Halekas, J. S.; Connerney, J. E.; Curry, S. M.; Harada, Y.; Luhmann, J. G.; Jakosky, B. M.

2015-11-01

We present observations by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission of a substantial plume-like distribution of escaping ions from the Martian atmosphere, organized by the upstream solar wind convection electric field. From a case study of MAVEN particle-and-field data during one spacecraft orbit, we identified three escaping planetary ion populations: plume fluxes mainly along the upstream electric field over the north pole region of the Mars-Sun-Electric field (MSE) coordinate system, antisunward ion fluxes in the tail region, and much weaker upstream pickup ion fluxes. A statistical study of O+ fluxes using 3 month MAVEN data shows that the plume is a constant structure with strong fluxes widely distributed in the MSE northern hemisphere, which constitutes an important planetary ion escape channel. The escape rate through the plume is estimated to be ~30% of the tailward escape and ~23% of the total escape for > 25 eV O+ ions.

Optimized AAV rh.10 Vectors That Partially Evade Neutralizing Antibodies during Hepatic Gene Transfer

PubMed Central

Selot, Ruchita; Arumugam, Sathyathithan; Mary, Bertin; Cheemadan, Sabna; Jayandharan, Giridhara R.

2017-01-01

Of the 12 common serotypes used for gene delivery applications, Adeno-associated virus (AAV)rh.10 serotype has shown sustained hepatic transduction and has the lowest seropositivity in humans. We have evaluated if further modifications to AAVrh.10 at its phosphodegron like regions or predicted immunogenic epitopes could improve its hepatic gene transfer and immune evasion potential. Mutant AAVrh.10 vectors were generated by site directed mutagenesis of the predicted targets. These mutant vectors were first tested for their transduction efficiency in HeLa and HEK293T cells. The optimal vector was further evaluated for their cellular uptake, entry, and intracellular trafficking by quantitative PCR and time-lapse confocal microscopy. To evaluate their potential during hepatic gene therapy, C57BL/6 mice were administered with wild-type or optimal mutant AAVrh.10 and the luciferase transgene expression was documented by serial bioluminescence imaging at 14, 30, 45, and 72 days post-gene transfer. Their hepatic transduction was further verified by a quantitative PCR analysis of AAV copy number in the liver tissue. The optimal AAVrh.10 vector was further evaluated for their immune escape potential, in animals pre-immunized with human intravenous immunoglobulin. Our results demonstrate that a modified AAVrh.10 S671A vector had enhanced cellular entry (3.6 fold), migrate rapidly to the perinuclear region (1 vs. >2 h for wild type vectors) in vitro, which further translates to modest increase in hepatic gene transfer efficiency in vivo. More importantly, the mutant AAVrh.10 vector was able to partially evade neutralizing antibodies (~27–64 fold) in pre-immunized animals. The development of an AAV vector system that can escape the circulating neutralizing antibodies in the host will substantially widen the scope of gene therapy applications in humans. PMID:28769791

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

A comparison of positive and negative reinforcement for compliance to treat problem behavior maintained by escape.

PubMed

Slocum, Sarah K; Vollmer, Timothy R

2015-09-01

Previous research has shown that problem behavior maintained by escape can be treated using positive reinforcement. In the current study, we directly compared functional (escape) and nonfunctional (edible) reinforcers in the treatment of escape-maintained problem behavior for 5 subjects. In the first treatment, compliance produced a break from instructions. In the second treatment, compliance produced a small edible item. Neither treatment included escape extinction. Results suggested that the delivery of a positive reinforcer for compliance was effective for treating escape-maintained problem behavior for all 5 subjects, and the delivery of escape for compliance was ineffective for 3 of the 5 subjects. Implications and future directions related to the use of positive reinforcers in the treatment of escape behavior are discussed. © Society for the Experimental Analysis of Behavior.

Hepatitis A Virus Vaccine Escape Variants and Potential New Serotype Emergence

PubMed Central

Pérez-Sautu, Unai; Costafreda, M. Isabel; Caylà, Joan; Tortajada, Cecilia; Lite, Josep; Bosch, Albert

2011-01-01

Six hepatitis A virus antigenic variants that likely escaped the protective effect of available vaccines were isolated, mostly from men who have sex with men. The need to complete the proper vaccination schedules is critical, particularly in the immunocompromised population, to prevent the emergence of vaccine-escaping variants.

Structure and Recognition of a Novel HIV-1 gp120-gp41 Interface Antibody that Caused MPER Exposure through Viral Escape

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wibmer, Constantinos Kurt; Gorman, Jason; Ozorowski, Gabriel

A comprehensive understanding of the regions on HIV-1 envelope trimers targeted by broadly neutralizing antibodies may contribute to rational design of an HIV-1 vaccine. We previously identified a participant in the CAPRISA cohort, CAP248, who developed trimer-specific antibodies capable of neutralizing 60% of heterologous viruses at three years post-infection. Here, we report the isolation by B cell culture of monoclonal antibody CAP248-2B, which targets a novel membrane proximal epitope including elements of gp120 and gp41. Despite low maximum inhibition plateaus, often below 50% inhibitory concentrations, the breadth of CAP248-2B significantly correlated with donor plasma. Site-directed mutagenesis, X-ray crystallography, and negative-stainmore » electron microscopy 3D reconstructions revealed how CAP248-2B recognizes a cleavage-dependent epitope that includes the gp120 C terminus. While this epitope is distinct, it overlapped in parts of gp41 with the epitopes of broadly neutralizing antibodies PGT151, VRC34, 35O22, 3BC315, and 10E8. CAP248-2B has a conformationally variable paratope with an unusually long 19 amino acid light chain third complementarity determining region. Two phenylalanines at the loop apex were predicted by docking and mutagenesis data to interact with the viral membrane. Neutralization by CAP248-2B is not dependent on any single glycan proximal to its epitope, and low neutralization plateaus could not be completely explained by N- or O-linked glycosylation pathway inhibitors, furin co-transfection, or pre-incubation with soluble CD4. Viral escape from CAP248-2B involved a cluster of rare mutations in the gp120-gp41 cleavage sites. Simultaneous introduction of these mutations into heterologous viruses abrogated neutralization by CAP248-2B, but enhanced neutralization sensitivity to 35O22, 4E10, and 10E8 by 10-100-fold. Altogether, this study expands the region of the HIV-1 gp120-gp41 quaternary interface that is a target for broadly

Structure and Recognition of a Novel HIV-1 gp120-gp41 Interface Antibody that Caused MPER Exposure through Viral Escape

PubMed Central

Elliott, Debra H.; Rouelle, Julie; Smira, Ashley; Ndabambi, Nonkululeko; Druz, Aliaksandr; Williamson, Carolyn

2017-01-01

A comprehensive understanding of the regions on HIV-1 envelope trimers targeted by broadly neutralizing antibodies may contribute to rational design of an HIV-1 vaccine. We previously identified a participant in the CAPRISA cohort, CAP248, who developed trimer-specific antibodies capable of neutralizing 60% of heterologous viruses at three years post-infection. Here, we report the isolation by B cell culture of monoclonal antibody CAP248-2B, which targets a novel membrane proximal epitope including elements of gp120 and gp41. Despite low maximum inhibition plateaus, often below 50% inhibitory concentrations, the breadth of CAP248-2B significantly correlated with donor plasma. Site-directed mutagenesis, X-ray crystallography, and negative-stain electron microscopy 3D reconstructions revealed how CAP248-2B recognizes a cleavage-dependent epitope that includes the gp120 C terminus. While this epitope is distinct, it overlapped in parts of gp41 with the epitopes of broadly neutralizing antibodies PGT151, VRC34, 35O22, 3BC315, and 10E8. CAP248-2B has a conformationally variable paratope with an unusually long 19 amino acid light chain third complementarity determining region. Two phenylalanines at the loop apex were predicted by docking and mutagenesis data to interact with the viral membrane. Neutralization by CAP248-2B is not dependent on any single glycan proximal to its epitope, and low neutralization plateaus could not be completely explained by N- or O-linked glycosylation pathway inhibitors, furin co-transfection, or pre-incubation with soluble CD4. Viral escape from CAP248-2B involved a cluster of rare mutations in the gp120-gp41 cleavage sites. Simultaneous introduction of these mutations into heterologous viruses abrogated neutralization by CAP248-2B, but enhanced neutralization sensitivity to 35O22, 4E10, and 10E8 by 10-100-fold. Altogether, this study expands the region of the HIV-1 gp120-gp41 quaternary interface that is a target for broadly neutralizing

Time Intervals in Sequence Sampling, Not Data Modifications, Have a Major Impact on Estimates of HIV Escape Rates

PubMed Central

2018-01-01

The ability of human immunodeficiency virus (HIV) to avoid recognition by humoral and cellular immunity (viral escape) is well-documented, but the strength of the immune response needed to cause such a viral escape remains poorly quantified. Several previous studies observed a more rapid escape of HIV from CD8 T cell responses in the acute phase of infection compared to chronic infection. The rate of HIV escape was estimated with the help of simple mathematical models, and results were interpreted to suggest that CD8 T cell responses causing escape in acute HIV infection may be more efficient at killing virus-infected cells than responses that cause escape in chronic infection, or alternatively, that early escapes occur in epitopes mutations in which there is minimal fitness cost to the virus. However, these conclusions were challenged on several grounds, including linkage and interference of multiple escape mutations due to a low population size and because of potential issues associated with modifying the data to estimate escape rates. Here we use a sampling method which does not require data modification to show that previous results on the decline of the viral escape rate with time since infection remain unchanged. However, using this method we also show that estimates of the escape rate are highly sensitive to the time interval between measurements, with longer intervals biasing estimates of the escape rate downwards. Our results thus suggest that data modifications for early and late escapes were not the primary reason for the observed decline in the escape rate with time since infection. However, longer sampling periods for escapes in chronic infection strongly influence estimates of the escape rate. More frequent sampling of viral sequences in chronic infection may improve our understanding of factors influencing the rate of HIV escape from CD8 T cell responses. PMID:29495443

Time Intervals in Sequence Sampling, Not Data Modifications, Have a Major Impact on Estimates of HIV Escape Rates.

PubMed

Ganusov, Vitaly V

2018-02-27

The ability of human immunodeficiency virus (HIV) to avoid recognition by humoral and cellular immunity (viral escape) is well-documented, but the strength of the immune response needed to cause such a viral escape remains poorly quantified. Several previous studies observed a more rapid escape of HIV from CD8 T cell responses in the acute phase of infection compared to chronic infection. The rate of HIV escape was estimated with the help of simple mathematical models, and results were interpreted to suggest that CD8 T cell responses causing escape in acute HIV infection may be more efficient at killing virus-infected cells than responses that cause escape in chronic infection, or alternatively, that early escapes occur in epitopes mutations in which there is minimal fitness cost to the virus. However, these conclusions were challenged on several grounds, including linkage and interference of multiple escape mutations due to a low population size and because of potential issues associated with modifying the data to estimate escape rates. Here we use a sampling method which does not require data modification to show that previous results on the decline of the viral escape rate with time since infection remain unchanged. However, using this method we also show that estimates of the escape rate are highly sensitive to the time interval between measurements, with longer intervals biasing estimates of the escape rate downwards. Our results thus suggest that data modifications for early and late escapes were not the primary reason for the observed decline in the escape rate with time since infection. However, longer sampling periods for escapes in chronic infection strongly influence estimates of the escape rate. More frequent sampling of viral sequences in chronic infection may improve our understanding of factors influencing the rate of HIV escape from CD8 T cell responses.

Escape from R-peptide deletion in a {gamma}-retrovirus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, Irene C.; Eckhardt, Manon; Brynza, Julia

2011-09-30

The R peptide in the cytoplasmic tail (C-tail) of {gamma}-retroviral envelope proteins (Env) prevents membrane fusion before budding. To analyse its role in the formation of replication competent, infectious particles, we developed chimeric murine leukaemia viruses (MLV) with unmodified or R-peptide deleted Env proteins of the gibbon ape leukaemia virus (GaLV). While titres of these viruses were unaffected, R-peptide deficiency led to strongly impaired spreading. Most remarkably, we isolated an escape mutant which had restored an open reading frame for a C-terminal extension of the truncated C-tail. A reconstituted virus encoding this escape C-tail replicated in cell culture. In contrastmore » to R-peptide deficient Env, particle incorporation of the escape Env was effective due to an enhanced protein expression and restored intracellular co-localisation with Gag proteins. Our data demonstrate that the R peptide not only regulates membrane fusion but also mediates efficient Env protein particle incorporation in {gamma}-retrovirus infected cells.« less

Neural circuits underlying visually evoked escapes in larval zebrafish

PubMed Central

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

2015-01-01

SUMMARY 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. Together, we establish a circuit for the processing of aversive stimuli in the context of an innate visual behavior. PMID:26804997

Assessment of a New Procedure to Prevent Timeout Escape in Preschoolers.

ERIC Educational Resources Information Center

McNeil, Cheryl Bodiford; And Others

1994-01-01

Many agencies provide parent training to groups for whom spanking as a response to timeout escape is not an option. An alternative was developed, the "two-chair hold" technique, which showed some success in decreasing timeout escape and improving overall behavior. Discusses clinical issues regarding use of this technique. (LKS)

Effects of metamorphosis on the aquatic escape response of the two-lined salamander (Eurycea bislineata).

PubMed

Azizi, Emanuel; Landberg, Tobias

2002-03-01

Although numerous studies have described the escape kinematics of fishes, little is known about the aquatic escape responses of salamanders. We compare the escape kinematics of larval and adult Eurycea bislineata, the two-lined salamander, to examine the effects of metamorphosis on aquatic escape performance. We hypothesize that shape changes associated with resorption of the larval tail fin at metamorphosis will affect aquatic locomotor performance. Escape responses were recorded using high-speed video, and the effects of life stage and total length on escape kinematics were analyzed statistically using analysis of covariance. Our results show that both larval and adult E. bislineata use a two-stage escape response (similar to the C-starts of fishes) that consists of a preparatory (stage 1) and a propulsive (stage 2) stroke. The duration of both kinematic stages and the distance traveled during stage 2 increased with total length. Both larval and adult E. bislineata had final escape trajectories that were directed away from the stimulus. The main kinematic difference between larvae and adults is that adults exhibit significantly greater maximum curvature during stage 1. Total escape duration and the distance traveled during stage 2 did not differ significantly between larvae and adults. Despite the significantly lower tail aspect ratio of adults, we found no significant decrease in the overall escape performance of adult E. bislineata. Our results suggest that adults may compensate for the decrease in tail aspect ratio by increasing their maximum curvature. These findings do not support the hypothesis that larvae exhibit better locomotor performance than adults as a result of stronger selective pressures on early life stages.

iDriving (Intelligent Driving)

DOE Office of Scientific and Technical Information (OSTI.GOV)

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.

Hydrogen escape from Mars enhanced by deep convection in dust storms

NASA Astrophysics Data System (ADS)

Heavens, Nicholas G.; Kleinböhl, Armin; Chaffin, Michael S.; Halekas, Jasper S.; Kass, David M.; Hayne, Paul O.; McCleese, Daniel J.; Piqueux, Sylvain; Shirley, James H.; Schofield, John T.

2018-02-01

Present-day water loss from Mars provides insight into Mars's past habitability1-3. Its main mechanism is thought to be Jeans escape of a steady hydrogen reservoir sourced from odd-oxygen reactions with near-surface water vapour2, 4,5. The observed escape rate, however, is strongly variable and correlates poorly with solar extreme-ultraviolet radiation flux6-8, which was predicted to modulate escape9. This variability has recently been attributed to hydrogen sourced from photolysed middle atmospheric water vapour10, whose vertical and seasonal distribution is only partly characterized and understood11-13. Here, we report multi-annual observational estimates of water content and dust and water transport to the middle atmosphere from Mars Climate Sounder data. We provide strong evidence that the transport of water vapour and ice to the middle atmosphere by deep convection in Martian dust storms can enhance hydrogen escape. Planet-encircling dust storms can raise the effective hygropause (where water content rapidly decreases to effectively zero) from 50 to 80 km above the areoid (the reference equipotential surface). Smaller dust storms contribute to an annual mode in water content at 40-50 km that may explain seasonal variability in escape. Our results imply that Martian atmospheric chemistry and evolution can be strongly affected by the meteorology of the lower and middle atmosphere of Mars.

Crew Escape Technologies (CREST) Mission Area Requirements Study Current and Future Crew Escape Requirements

DTIC Science & Technology

1992-02-01

purchased from: National Tecnical Information Service 5285 Port Royal Road Springfield VA 22161 Federal Governmet agencies and their contractors registered...Engineering Incpora:ted (IME) to organize and executi a tecnical approach to the QP= 14. SUIUECT TERMS Mission Area Requiremts, REST Escape SystM IS...the aerodynamic stabilization subsystems to become effective (drogue parachutes, or fins for the S4S), and the time required for the recovery parachute

Several immune escape patterns in non-Hodgkin's lymphomas

PubMed Central

Laurent, Camille; Charmpi, Konstantina; Gravelle, Pauline; Tosolini, Marie; Franchet, Camille; Ysebaert, Loïc; Brousset, Pierre; Bidaut, Alexandre; Ycart, Bernard; Fournié, Jean-Jacques

2015-01-01

Follicular Lymphomas (FL) and diffuse large B cell lymphomas (DLBCL) must evolve some immune escape strategy to develop from lymphoid organs, but their immune evasion pathways remain poorly characterized. We investigated this issue by transcriptome data mining and immunohistochemistry (IHC) of FL and DLBCL lymphoma biopsies. A set of genes involved in cancer immune-evasion pathways (Immune Escape Gene Set, IEGS) was defined and the distribution of the expression levels of these genes was compared in FL, DLBCL and normal B cell transcriptomes downloaded from the GEO database. The whole IEGS was significantly upregulated in all the lymphoma samples but not in B cells or other control tissues, as shown by the overexpression of the PD-1, PD-L1, PD-L2 and LAG3 genes. Tissue microarray immunostainings for PD-1, PD-L1, PD-L2 and LAG3 proteins on additional biopsies from 27 FL and 27 DLBCL patients confirmed the expression of these proteins. The immune infiltrates were more abundant in FL than DLBCL samples, and the microenvironment of FL comprised higher rates of PD-1+ lymphocytes. Further, DLBCL tumor cells comprised a higher proportion of PD-1+, PD-L1+, PD-L2+ and LAG3+ lymphoma cells than the FL tumor cells, confirming that DLBCL mount immune escape strategies distinct from FL. In addition, some cases of DLBCL had tumor cells co-expressing both PD-1, PD-L1 and PD-L2. Among the DLBCLs, the activated B cell (ABC) subtype comprised more PD-L1+ and PD-L2+ lymphoma cells than the GC subtype. Thus, we infer that FL and DLBCL evolved several pathways of immune escape. PMID:26405585

Measles Virus Hemagglutinin epitopes immunogenic in natural infection and vaccination are targeted by broad or genotype-specific neutralizing monoclonal antibodies.

PubMed

Muñoz-Alía, Miguel Angel; Casasnovas, José M; Celma, María Luisa; Carabaña, Juan; Liton, Paloma B; Fernandez-Muñoz, Rafael

2017-05-15

Measles virus (MV) remains a leading cause of vaccine-preventable deaths in children. Protection against MV is associated with neutralizing antibodies that preferentially recognize the viral hemagglutinin (MV-H), and to a lesser extent, the fusion protein (MV-F). Although MV is serologically monotypic, 24 genotypes have been identified. Here we report three neutralization epitopes conserved in the more prevalent circulating MV genotypes, two located in the MV-H receptor binding site (RBS) (antigenic site III) and a third in MV-H/MV-F interphase (antigenic site Ia) which are essential for MV multiplication. In contrast, two MV-H neutralization epitopes, showed a genotype-specific neutralization escape due to a single amino acid change, that we mapped in the "noose" antigenic site, or an enhanced neutralization epitope (antigenic site IIa). The monoclonal antibody (mAb) neutralization potency correlated with its binding affinity and was mainly driven by kinetic dissociation rate (k off ). We developed an immunoassay for mAb binding to MV-H in its native hetero-oligomeric structure with MV-F on the surface of a MV productive steady-state persistently infected (p.i.) human cell lines, and a competitive-binding assay with serum from individuals with past infection by different MV genotypes. Binding assays revealed that a broad neutralization epitope, in RBS antigenic site, a genotype specific neutralization epitopes, in noose and IIa sites, were immunogenic in natural infection and vaccination and may elicit long-lasting humoral immunity that might contribute to explain MV immunogenic stability. These results support the design of improved measles vaccines, broad-spectrum prophylactic or therapeutic antibodies and MV-used in oncolytic therapies. Copyright © 2017 Elsevier B.V. All rights reserved.

Injury rate in a helicopter underwater escape trainer (HUET) from 2005-2012.

PubMed

Brooks, Christopher J; MacDonald, Conor V; Gibbs, Peter N A

2014-08-01

Helicopter underwater escape training (HUET) carries a potential for injury and this paper identifies the injury rate. A marine survival training school registry of all students trained between 2005-2012 in HUET and the coinciding accident records were examined. There were 8902 students trained in a helicopter underwater escape simulator for a total of 59,245 underwater escapes. There were 40 cases where only first-aid was required and 3 serious injuries (a laceration requiring 5 sutures, 1 dislocated shoulder, and 1 water aspiration requiring hospitalization). There were no deaths and no problems reported with using the Emergency Breathing System (EBS) or Air Pocket. Of the injuries, 11 were due to the student using a poor escape technique. The overall probability of injury was 0.74 per 1000 ascents. In HUET training, there is a very low injury rate with almost no significant severity. Although not scientifically proven, this would suggest that the low incident rate is due to good medical screening and the attention given by instructors to anxious students. Compared to other training such as diving, parachute jumping, and submarine escape training, the rate of injury was considerably lower.

Escape Distance in Ground-Nesting Birds Differs with Individual Level of Camouflage.

PubMed

Wilson-Aggarwal, Jared K; Troscianko, Jolyon T; Stevens, Martin; Spottiswoode, Claire N

2016-08-01

Camouflage is one of the most widespread antipredator strategies in the animal kingdom, yet no animal can match its background perfectly in a complex environment. Therefore, selection should favor individuals that use information on how effective their camouflage is in their immediate habitat when responding to an approaching threat. In a field study of African ground-nesting birds (plovers, coursers, and nightjars), we tested the hypothesis that individuals adaptively modulate their escape behavior in relation to their degree of background matching. We used digital imaging and models of predator vision to quantify differences in color, luminance, and pattern between eggs and their background, as well as the plumage of incubating adult nightjars. We found that plovers and coursers showed greater escape distances when their eggs were a poorer pattern match to the background. Nightjars sit on their eggs until a potential threat is nearby, and, correspondingly, they showed greater escape distances when the pattern and color match of the incubating adult's plumage-rather than its eggs-was a poorer match to the background. Finally, escape distances were shorter in the middle of the day, suggesting that escape behavior is mediated by both camouflage and thermoregulation.

Escape rate for nonequilibrium processes dominated by strong non-detailed balance force

NASA Astrophysics Data System (ADS)

Tang, Ying; Xu, Song; Ao, Ping

2018-02-01

Quantifying the escape rate from a meta-stable state is essential to understand a wide range of dynamical processes. Kramers' classical rate formula is the product of an exponential function of the potential barrier height and a pre-factor related to the friction coefficient. Although many applications of the rate formula focused on the exponential term, the prefactor can have a significant effect on the escape rate in certain parameter regions, such as the overdamped limit and the underdamped limit. There have been continuous interests to understand the effect of non-detailed balance on the escape rate; however, how the prefactor behaves under strong non-detailed balance force remains elusive. In this work, we find that the escape rate formula has a vanishing prefactor with decreasing friction strength under the strong non-detailed balance limit. We both obtain analytical solutions in specific examples and provide a derivation for more general cases. We further verify the result by simulations and propose a testable experimental system of a charged Brownian particle in electromagnetic field. Our study demonstrates that a special care is required to estimate the effect of prefactor on the escape rate when non-detailed balance force dominates.

Transitions between three swimming gaits in Paramecium escape.

PubMed

Hamel, Amandine; Fisch, Cathy; Combettes, Laurent; Dupuis-Williams, Pascale; Baroud, Charles N

2011-05-03

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.

Transitions between three swimming gaits in Paramecium escape

PubMed Central

Hamel, Amandine; Fisch, Cathy; Combettes, Laurent; Dupuis-Williams, Pascale; Baroud, Charles N.

2011-01-01

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

Effects of photon escape on diagnostic diagrams for H II regions

NASA Astrophysics Data System (ADS)

Giammanco, C.; Beckman, J. E.; Cedrés, B.

2005-08-01

In this article we first outline the mounting evidence that a significant fraction of the ionizing photons emitted by OB stars within H ii regions escape from their immediate surroundings, i.e from what is normally defined as the H ii region, and explain how an H ii region structure containing high density contrast inhomogeneities facilitates this escape. Next we describe sets of models containing inhomogeneities which are used to predict tracks in the commonly used diagnostic diagrams (based on ratios of emission lines) whose only independent variable is the photon escape fraction, ξ. We show that the tracks produced by the models in two of the most cited of these diagrams conform well to the distribution of observed data points, with the models containing optically thick inhomogeneities (“CLUMPY” models) yielding somewhat better agreement than those with optically thin inhomogeneities (“FF” models). We show how variations in the ionization parameter U, derived from emission line ratios, could be due to photon escape, such that for a given region from which 50% of its ionizing photons leak out we would derive the same value of U as for a region with no photon escape but with an input ionizing flux almost an order of magnitude higher. This effect will occur whether the individual inhomogeneities are optically thick or thin. Photon escape will also lead to a change in the derived value of the radiation hardness parameter, and this change differs significantly between models with optically thin and optically thick clumps. Using a rather wide range of assumptions about the filling factor of dense clumps we find, for a selected set of regions observed in M 51 by Díaz et al. (1991) an extreme limiting range of computed photon escape fractions between near zero and 90%, but with the most plausible values ranging between 30% and 50%. We show, using oxygen as the test element, that models with different assumptions about the gas inhomogeneity will tend to give

Shuttle crew escape systems test conducted in JSC Bldg 9A CCT

NASA Image and Video Library

1987-03-20

Shuttle crew escape systems test is conducted by astronauts Steven R. Nagel (left) and Manley L. (Sonny) Carter in JSC One Gravity Mockup and Training Facilities Bldg 9A crew compartment trainer (CCT). Nagel and Carter are evaluating methods for crew escape during Space Shuttle controlled gliding flight. JSC test was done in advance of tests scheduled for facilities in California and Utah. Here, Carter serves as test subject evaluating egress positioning for the tractor rocket escape method - one of the two systems currently being closely studied by NASA.

Incomplete Neutralization and Deviation from Sigmoidal Neutralization Curves for HIV Broadly Neutralizing Monoclonal Antibodies

PubMed Central

McCoy, Laura E.; Falkowska, Emilia; Doores, Katie J.; Le, Khoa; Sok, Devin; van Gils, Marit J.; Euler, Zelda; Burger, Judith A.; Seaman, Michael S.; Sanders, Rogier W.; Schuitemaker, Hanneke; Poignard, Pascal; Wrin, Terri; Burton, Dennis R.

2015-01-01

The broadly neutralizing HIV monoclonal antibodies (bnMAbs) PG9, PG16, PGT151, and PGT152 have been shown earlier to occasionally display an unusual virus neutralization profile with a non-sigmoidal slope and a plateau at <100% neutralization. In the current study, we were interested in determining the extent of non-sigmoidal slopes and plateaus at <100% for HIV bnMAbs more generally. Using both a 278 panel of pseudoviruses in a CD4 T-cell (U87.CCR5.CXCR4) assay and a panel of 117 viruses in the TZM-bl assay, we found that bnMAbs targeting many neutralizing epitopes of the spike had neutralization profiles for at least one virus that plateaued at <90%. Across both panels the bnMAbs targeting the V2 apex of Env and gp41 were most likely to show neutralization curves that plateaued <100%. Conversely, bnMAbs targeting the high-mannose patch epitopes were less likely to show such behavior. Two CD4 binding site (CD4bs) Abs also showed this behavior relatively infrequently. The phenomenon of incomplete neutralization was also observed in a large peripheral blood mononuclear cells (PBMC)-grown molecular virus clone panel derived from patient viral swarms. In addition, five bnMAbs were compared against an 18-virus panel of molecular clones produced in 293T cells and PBMCs and assayed in TZM-bl cells. Examples of plateaus <90% were seen with both types of virus production with no consistent patterns observed. In conclusion, incomplete neutralization and non-sigmoidal neutralization curves are possible for all HIV bnMAbs against a wide range of viruses produced and assayed in both cell lines and primary cells with implications for the use of antibodies in therapy and as tools for vaccine design. PMID:26267277

Incomplete Neutralization and Deviation from Sigmoidal Neutralization Curves for HIV Broadly Neutralizing Monoclonal Antibodies.

PubMed

McCoy, Laura E; Falkowska, Emilia; Doores, Katie J; Le, Khoa; Sok, Devin; van Gils, Marit J; Euler, Zelda; Burger, Judith A; Seaman, Michael S; Sanders, Rogier W; Schuitemaker, Hanneke; Poignard, Pascal; Wrin, Terri; Burton, Dennis R

2015-08-01

The broadly neutralizing HIV monoclonal antibodies (bnMAbs) PG9, PG16, PGT151, and PGT152 have been shown earlier to occasionally display an unusual virus neutralization profile with a non-sigmoidal slope and a plateau at <100% neutralization. In the current study, we were interested in determining the extent of non-sigmoidal slopes and plateaus at <100% for HIV bnMAbs more generally. Using both a 278 panel of pseudoviruses in a CD4 T-cell (U87.CCR5.CXCR4) assay and a panel of 117 viruses in the TZM-bl assay, we found that bnMAbs targeting many neutralizing epitopes of the spike had neutralization profiles for at least one virus that plateaued at <90%. Across both panels the bnMAbs targeting the V2 apex of Env and gp41 were most likely to show neutralization curves that plateaued <100%. Conversely, bnMAbs targeting the high-mannose patch epitopes were less likely to show such behavior. Two CD4 binding site (CD4bs) Abs also showed this behavior relatively infrequently. The phenomenon of incomplete neutralization was also observed in a large peripheral blood mononuclear cells (PBMC)-grown molecular virus clone panel derived from patient viral swarms. In addition, five bnMAbs were compared against an 18-virus panel of molecular clones produced in 293T cells and PBMCs and assayed in TZM-bl cells. Examples of plateaus <90% were seen with both types of virus production with no consistent patterns observed. In conclusion, incomplete neutralization and non-sigmoidal neutralization curves are possible for all HIV bnMAbs against a wide range of viruses produced and assayed in both cell lines and primary cells with implications for the use of antibodies in therapy and as tools for vaccine design.

Optimal combinations of broadly neutralizing antibodies for prevention and treatments of HIV-1 clade C infection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagh, Kshitij; Bhattacharya, Tanmoy; Williamson, Carolyn

In this study, the identification of a new generation of potent broadly neutralizing HIV-1 antibodies (bnAbs) has generated substantial interest in their potential use for the prevention and/or treatment of HIV-1 infection. While combinations of bnAbs targeting distinct epitopes on the viral envelope (Env) will likely be required to overcome the extraordinary diversity of HIV-1, a key outstanding question is which bnAbs, and how many, will be needed to achieve optimal clinical benefit. We assessed the neutralizing activity of 15 bnAbs targeting four distinct epitopes of Env, including the CD4-binding site (CD4bs), the V1/V2-glycan region, the V3-glycan region, and themore » gp41 membrane proximal external region (MPER), against a panel of 200 acute/early clade C HIV-1 Env pseudoviruses. A mathematical model was developed that predicted neutralization by a subset of experimentally evaluated bnAb combinations with high accuracy. Using this model, we performed a comprehensive and systematic comparison of the predicted neutralizing activity of over 1,600 possible double, triple, and quadruple bnAb combinations. The most promising bnAb combinations were identified based not only on breadth and potency of neutralization, but also other relevant measures, such as the extent of complete neutralization and instantaneous inhibitory potential (IIP). By this set of criteria, triple and quadruple combinations of bnAbs were identified that were significantly more effective than the best double combinations, and further improved the probability of having multiple bnAbs simultaneously active against a given virus, a requirement that may be critical for countering escape in vivo. These results provide a rationale for advancing bnAb combinations with the best in vitro predictors of success into clinical trials for both the prevention and treatment of HIV-1 infection.« less

Optimal combinations of broadly neutralizing antibodies for prevention and treatments of HIV-1 clade C infection

DOE PAGES

Wagh, Kshitij; Bhattacharya, Tanmoy; Williamson, Carolyn; ...

2016-03-30

In this study, the identification of a new generation of potent broadly neutralizing HIV-1 antibodies (bnAbs) has generated substantial interest in their potential use for the prevention and/or treatment of HIV-1 infection. While combinations of bnAbs targeting distinct epitopes on the viral envelope (Env) will likely be required to overcome the extraordinary diversity of HIV-1, a key outstanding question is which bnAbs, and how many, will be needed to achieve optimal clinical benefit. We assessed the neutralizing activity of 15 bnAbs targeting four distinct epitopes of Env, including the CD4-binding site (CD4bs), the V1/V2-glycan region, the V3-glycan region, and themore » gp41 membrane proximal external region (MPER), against a panel of 200 acute/early clade C HIV-1 Env pseudoviruses. A mathematical model was developed that predicted neutralization by a subset of experimentally evaluated bnAb combinations with high accuracy. Using this model, we performed a comprehensive and systematic comparison of the predicted neutralizing activity of over 1,600 possible double, triple, and quadruple bnAb combinations. The most promising bnAb combinations were identified based not only on breadth and potency of neutralization, but also other relevant measures, such as the extent of complete neutralization and instantaneous inhibitory potential (IIP). By this set of criteria, triple and quadruple combinations of bnAbs were identified that were significantly more effective than the best double combinations, and further improved the probability of having multiple bnAbs simultaneously active against a given virus, a requirement that may be critical for countering escape in vivo. These results provide a rationale for advancing bnAb combinations with the best in vitro predictors of success into clinical trials for both the prevention and treatment of HIV-1 infection.« less

Development of three-layered rumen escapable capsules for cattle

PubMed Central

SEYAMA, Tomohiro; HIRAYASU, Hirofumi; YAMAWAKI, Kenji; ADACHI, Takuhiko; SUGIMOTO, Takayuki; KASAI, Koji

2016-01-01

A new rumen escapable tool is presented for cattle in prospect of developing medical treatment or supplementing trace elements for disease prevention. This tool consists of a three-layered capsule that dissolves in the lower digestive tract, but not in the rumen. The capsule was manufactured by capsule-forming techniques through the use of liquid surface tension. This method does not involve high-temperature treatment, so the capsule can contain not only lipophilic substances but also hydrophilic or heat-sensitive substances. Furthermore, the capsule has a specific gravity of 1.3 and diameter of 6.0 mm, which were previously shown to be appropriate to avoid rumination. The objective of this study was to confirm the effectiveness of the capsule pertinent to rumen escaping. In order to validate rumen escape, capsules containing 30 g of water-soluble vitamin (thiamine hydrochloride) per head were administered to four lactating cows assigned in a crossover trial. In the group administered encapsulated thiamine hydrochloride, blood thiamine levels increased from 12.4 ± 1.03 ng/ml before administration to 54.8 ± 2.21 ng/ml at 6 hr following administration, whereas the level remained at 13.3 ± 2.05 ng/ml in the control group administered via aqueous solution. This indicates that the three-layered capsules passed through the rumen and dissolved in the lower digestive tract, thus functioning as a rumen escapable tool. PMID:27546371

Neutral Buoyancy Simulator-NB50B-SADE Training Exercises

NASA Technical Reports Server (NTRS)

1983-01-01

One of the main components of the Hubble Space Telescope (HST) is the Solar Array Drive Electronics (SADE) system. This system interfaces with the Support System Module (SSM) for exchange of operational commands and telemetry data. SADE operates and controls the Solar Array Drive Mechanisms (SADM) for the orientation of the Solar Array Drive (SAD). It also monitors the position of the arrays and the temperature of the SADM. During the first HST servicing mission, the astronauts replaced the SADE component because of some malfunctions. This turned out to be a very challenging extravehicular activity (EVA). Two transistors and two diodes had been thermally stressed with the conformal coating discolored and charred. Soldered cornections became molten and reflowed between the two diodes. The failed transistors gave no indication of defective construction. All repairs were made and the HST was redeposited into orbit. Prior to undertaking this challenging mission, the orbiter's crew trained at Marshall Space Flight Center's (MSFC) Neutral Buoyancy Simulator (NBS) to prepare themselves for working in a low gravity environment. They also practiced replacing HST parts and exercised maneuverability and equipment handling. Pictured are crew members practicing on a space platform.

Staged induction of HIV-1 glycan–dependent broadly neutralizing antibodies

DOE PAGES

Bonsignori, Mattia; Kreider, Edward F.; Fera, Daniela; ...

2017-03-15

A preventive HIV-1 vaccine should induce HIV-1–specific broadly neutralizing antibodies (bnAbs). However, bnAbs generally require high levels of somatic hypermutation (SHM) to acquire breadth, and current vaccine strategies have not been successful in inducing bnAbs. Because bnAbs directed against a glycosylated site adjacent to the third variable loop (V3) of the HIV-1 envelope protein require limited SHM, the V3-glycan epitope is an attractive vaccine target. By studying the cooperation among multiple V3-glycan B cell lineages and their coevolution with autologous virus throughout 5 years of infection, we identify key events in the ontogeny of a V3- glycan bnAb. Two autologousmore » neutralizing antibody lineages selected for virus escape mutations and consequently allowed initiation and affinity maturation of a V3-glycan bnAb lineage. The nucleotide substitution required to initiate the bnAb lineage occurred at a low-probability site for activation-induced cytidine deaminase activity. Cooperation of B cell lineages and an improbable mutation critical for bnAb activity defined the necessary events leading to breadth in this V3- glycan bnAb lineage. These findings may, in part, explain why initiation of V3-glycan bnAbs is rare, and suggest an immunization strategy for inducing similar V3-glycan bnAbs.« less

Staged induction of HIV-1 glycan–dependent broadly neutralizing antibodies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonsignori, Mattia; Kreider, Edward F.; Fera, Daniela

A preventive HIV-1 vaccine should induce HIV-1–specific broadly neutralizing antibodies (bnAbs). However, bnAbs generally require high levels of somatic hypermutation (SHM) to acquire breadth, and current vaccine strategies have not been successful in inducing bnAbs. Because bnAbs directed against a glycosylated site adjacent to the third variable loop (V3) of the HIV-1 envelope protein require limited SHM, the V3-glycan epitope is an attractive vaccine target. By studying the cooperation among multiple V3-glycan B cell lineages and their coevolution with autologous virus throughout 5 years of infection, we identify key events in the ontogeny of a V3- glycan bnAb. Two autologousmore » neutralizing antibody lineages selected for virus escape mutations and consequently allowed initiation and affinity maturation of a V3-glycan bnAb lineage. The nucleotide substitution required to initiate the bnAb lineage occurred at a low-probability site for activation-induced cytidine deaminase activity. Cooperation of B cell lineages and an improbable mutation critical for bnAb activity defined the necessary events leading to breadth in this V3- glycan bnAb lineage. These findings may, in part, explain why initiation of V3-glycan bnAbs is rare, and suggest an immunization strategy for inducing similar V3-glycan bnAbs.« less

Noise induced escape from a nonhyperbolic chaotic attractor of a periodically driven nonlinear oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zhen, E-mail: czkillua@icloud.com, E-mail: xbliu@nuaa.edu.cn; Li, Yang; Liu, Xianbin, E-mail: czkillua@icloud.com, E-mail: xbliu@nuaa.edu.cn

2016-06-15

Noise induced escape from the domain of attraction of a nonhyperbolic chaotic attractor in a periodically excited nonlinear oscillator is investigated. The general mechanism of the escape in the weak noise limit is studied in the continuous case, and the fluctuational path is obtained by statistical analysis. Selecting the primary homoclinic tangency as the initial condition, the action plot is presented by parametrizing the set of escape trajectories and the global minimum gives rise to the optimal path. Results of both methods show good agreements. The entire process of escape is discussed in detail step by step using the fluctuationalmore » force. A structure of hierarchical heteroclinic crossings of stable and unstable manifolds of saddle cycles is found, and the escape is observed to take place through successive jumps through this deterministic hierarchical structure.« less

Complexation-induced supramolecular assembly drives metal-ion extraction.

PubMed

Ellis, Ross J; Meridiano, Yannick; Muller, Julie; Berthon, Laurence; Guilbaud, Philippe; Zorz, Nicole; Antonio, Mark R; Demars, Thomas; Zemb, Thomas

2014-09-26

Combining experiment with theory reveals the role of self-assembly and complexation in metal-ion transfer through the water-oil interface. The coordinating metal salt Eu(NO3)3 was extracted from water into oil by a lipophilic neutral amphiphile. Molecular dynamics simulations were coupled to experimental spectroscopic and X-ray scattering techniques to investigate how local coordination interactions between the metal ion and ligands in the organic phase combine with long-range interactions to produce spontaneous changes in the solvent microstructure. Extraction of the Eu(3+)-3(NO3(-)) ion pairs involves incorporation of the "hard" metal complex into the core of "soft" aggregates. This seeds the formation of reverse micelles that draw the water and "free" amphiphile into nanoscale hydrophilic domains. The reverse micelles interact through attractive van der Waals interactions and coalesce into rod-shaped polynuclear Eu(III) -containing aggregates with metal centers bridged by nitrate. These preorganized hydrophilic domains, containing high densities of O-donor ligands and anions, provide improved Eu(III) solvation environments that help drive interfacial transfer, as is reflected by the increasing Eu(III) partitioning ratios (oil/aqueous) despite the organic phase approaching saturation. For the first time, this multiscale approach links metal-ion coordination with nanoscale structure to reveal the free-energy balance that drives the phase transfer of neutral metal salts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Substantial Plume of Escaping Planetary Ions in the MSE Northern Hemisphere Observed by MAVEN

NASA Astrophysics Data System (ADS)

Dong, Y.; Fang, X.; Brain, D. A.; McFadden, J. P.; Halekas, J. S.; Connerney, J. E. P.; Curry, S.; Harada, Y.; Luhmann, J. G.; Jakosky, B. M.

2015-12-01

The Mars-solar wind interaction accelerates and transports planetary ions away from Mars through a number of processes, including pick-up by the electromagnetic fields. The Mars Atmospheric and Volatile EvolutioN (MAVEN) spacecraft has frequently detected strong escaping planetary ion fluxes in both tailward and upstream solar wind motional electric field directions since the beginning of its science phase in November 2014. Our statistical study using three-month MAVEN data from November 2014 through February 2015 illustrates a substantial plume-like escaping planetary ion population organized by the upstream electric field with strong fluxes widely distributed in the northern hemisphere of the Mars-Sun-Electric-field (MSE) coordinate system, which is generally consistent with model predictions. The plume constitutes an important planetary ion escape channel from the Martian atmosphere in addition to the tailward escape. The >25eV O+ escape rate through the plume is estimated to be ~35% of the tailward escape and ~25% of the total escape. We will compare the dynamics of the plume and tailward escaping ions based on their velocity-space distributions with respect to the electromagnetic fields. We will also discuss the variations of the plume characteristics between different ion species (O+, O2+, and CO2+) and from the effect of different solar wind and interplanetary magnetic field (IMF) conditions.

Escape from Albuquerque: An Apache Memorate.

ERIC Educational Resources Information Center

Greenfeld, Philip J.

2001-01-01

Clarence Hawkins, a White Mountain Apache, escaped from the Albuquerque Indian School around 1920. His 300-mile trip home, made with two other boys, exemplifies the reaction of many Indian youths to the American government's plans for cultural assimilation. The tale is told in the form of traditional Apache narrative. (TD)

Particle and momentum confinement in tokamak plasmas with unbalanced neutral beam injection and strong rotation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malik, M.A.

1988-01-01

There is a self-consistent theory of the effects of neutral beam injection on impurity transport in tokamak plasmas. The theory predicts that co-injection drives impurities outward and that counter-injection enhances the normally inward flow of impurities. The theory was applied to carry out a detailed analysis of the large experimental database from the PLT and the ISX-B tokamaks. The theory was found to generally model the experimental data quite well. It is, therefore, concluded that neutral beam co-injection can drive impurities outward to achieve clean central plasmas and a cool radiating edge. Theoretical predictions for future thermonuclear reactors such asmore » INTOR, TIBER II, and ITER indicated that neutral beam driven flow reversal might be an effective impurity control method if the rate of beam momentum deposited per plasma ion is adequate. The external momentum drag, which is a pivotal concept in impurity flow reversal theory, is correctly predicted by the gyroviscous theory of momentum confinement. The theory was applied to analyze experimental data from the PLT and the PDX tokamaks with exact experimental conditions. The theory was found to be in excellent agreement with experiment over a wide range of parameters. It is, therefore, possible to formulate the impurity transport theory from first principles, without resort to empiricism.« less

Fluctuating bottleneck model studies on kinetics of DNA escape from α-hemolysin nanopores

NASA Astrophysics Data System (ADS)

Bian, Yukun; Wang, Zilin; Chen, Anpu; Zhao, Nanrong

2015-11-01

We have proposed a fluctuation bottleneck (FB) model to investigate the non-exponential kinetics of DNA escape from nanometer-scale pores. The basic idea is that the escape rate is proportional to the fluctuating cross-sectional area of DNA escape channel, the radius r of which undergoes a subdiffusion dynamics subjected to fractional Gaussian noise with power-law memory kernel. Such a FB model facilitates us to obtain the analytical result of the averaged survival probability as a function of time, which can be directly compared to experimental results. Particularly, we have applied our theory to address the escape kinetics of DNA through α-hemolysin nanopores. We find that our theoretical framework can reproduce the experimental results very well in the whole time range with quite reasonable estimation for the intrinsic parameters of the kinetics processes. We believe that FB model has caught some key features regarding the long time kinetics of DNA escape through a nanopore and it might provide a sound starting point to study much wider problems involving anomalous dynamics in confined fluctuating channels.

Integrating geographical information and augmented reality techniques for mobile escape guidelines on nuclear accident sites.

PubMed

Tsai, Ming-Kuan; Lee, Yung-Ching; Lu, Chung-Hsin; Chen, Mei-Hsin; Chou, Tien-Yin; Yau, Nie-Jia

2012-07-01

During nuclear accidents, when radioactive materials spread into the environment, the people in the affected areas should evacuate immediately. However, few information systems are available regarding escape guidelines for nuclear accidents. Therefore, this study constructs escape guidelines on mobile phones. This application is called Mobile Escape Guidelines (MEG) and adopts two techniques. One technique is the geographical information that offers multiple representations; the other is the augmented reality that provides semi-realistic information services. When this study tested the mobile escape guidelines, the results showed that this application was capable of identifying the correct locations of users, showing the escape routes, filtering geographical layers, and rapidly generating the relief reports. Users could evacuate from nuclear accident sites easily, even without relief personnel, since using slim devices to access the mobile escape guidelines is convenient. Overall, this study is a useful reference for a nuclear accident emergency response. Copyright © 2012 Elsevier Ltd. All rights reserved.

Subauroral Ion-neutral Coupling During the March 2015 Superstorm

NASA Astrophysics Data System (ADS)

Zhang, S.; Erickson, P. J.; Foster, J. C.; Holt, J. M.; Coster, A. J.; Makela, J. J.; Noto, J.; Meriwether, J. W.; Otsuka, Y.; Nicolls, M. J.; McCready, M. A.

2015-12-01

The arrival of solar Coronal Mass Ejection materials overlapping a high-speed solar wind stream originated from a nearby coronal hole caused huge magnetic disturbances during March 17-18, 2015. We have coordinated an international campaign to monitor their geospace effects using ground-based facilities, including incoherent scatter radars and Fabry-Perot Interferometers in the America sectors and other instruments in East Asia sectors, forming an observational network along approximately the 60W/120E meridional circle. The presentation will provide highlights of these observations, with a focus on the ion-neutral coupling processes at subauroral and mid-latitudes. One of the most stiking findings is the northward neutral wind surge, observed in multiple sites, accompanying strong westward winds developed at earlier times. We ascribe this unexpected wind disturbances to Subauroal Polarization Stream (SAPS) asscoated strong plasma flows driving ion-neutral coupling. SAPS and strong ion flow were observed by Millstone Hill ISR and DMSP in situ measurements. We will also report the Millstone Hill ISR observations of a significant enhancement in the storm-time molecular ion composition in the F1-region height. This enhancement appears to be caused by strong vertical ion drift due to penetration electric fields.

Dodging silver bullets: good CRISPR gene-drive design is critical for eradicating exotic vertebrates.

PubMed

Prowse, Thomas A A; Cassey, Phillip; Ross, Joshua V; Pfitzner, Chandran; Wittmann, Talia A; Thomas, Paul

2017-08-16

Self-replicating gene drives that can spread deleterious alleles through animal populations have been promoted as a much needed but controversial 'silver bullet' for controlling invasive alien species. Homing-based drives comprise an endonuclease and a guide RNA (gRNA) that are replicated during meiosis via homologous recombination. However, their efficacy for controlling wild populations is threatened by inherent polymorphic resistance and the creation of resistance alleles via non-homologous end-joining (NHEJ)-mediated DNA repair. We used stochastic individual-based models to identify realistic gene-drive strategies capable of eradicating vertebrate pest populations (mice, rats and rabbits) on islands. One popular strategy, a sex-reversing drive that converts heterozygous females into sterile males, failed to spread and required the ongoing deployment of gene-drive carriers to achieve eradication. Under alternative strategies, multiplexed gRNAs could overcome inherent polymorphic resistance and were required for eradication success even when the probability of NHEJ was low. Strategies causing homozygotic embryonic non-viability or homozygotic female sterility produced high probabilities of eradication and were robust to NHEJ-mediated deletion of the DNA sequence between multiplexed endonuclease recognition sites. The latter two strategies also purged the gene drive when eradication failed, therefore posing lower long-term risk should animals escape beyond target islands. Multiplexing gRNAs will be necessary if this technology is to be useful for insular extirpation attempts; however, precise knowledge of homing rates will be required to design low-risk gene drives with high probabilities of eradication success. © 2017 The Author(s).

In-situ observation of Martian neutral exosphere: Results from MENCA aboard Indian Mars Orbiter Mission (MOM)

NASA Astrophysics Data System (ADS)

Bhardwaj, Anil; Pratim Das, Tirtha; Dhanya, M. B.; Thampi, Smitha V.

2016-07-01

Till very recently, the only in situ measurements of the Martian upper atmospheric composition was from the mass spectrometer experiments aboard the two Viking landers, which covered the altitude region from 120 to 200 km. Hence, the exploration by the Mars Exospheric Neutral Composition Analyser (MENCA) aboard the Mars Orbiter Mission (MOM) spacecraft of ISRO and the Neutral Gas and Ion Mass Spectrometer (NGIMS) experiment aboard the Mars Atmosphere and Volatile ENvironment (MAVEN) mission of NASA are significant steps to further understand the Martian neutral exosphere and its variability. MENCA is a quadrupole based neutral mass spectrometer which observes the radial distribution of the Martian neutral exosphere. The analysis of the data from MENCA has revealed unambiguous detection of the three major constituents, which are amu 44 (CO2), amu 28 (contributions from CO and N2) and amu 16 (atomic O), as well as a few minor species. Since MOM is in a highly elliptical orbit, the MENCA observations pertain to different local times, in the low-latitude region. Examples of such observations would be presented, and compared with NGIMS results. Emphasis would be given to the observations pertaining to high solar zenith angles and close to perihelion period. During the evening hours, the transition from CO2 to O dominated region is observed near 270 km, which is significantly different from the previous observations corresponding to sub-solar point and SZA of ~45°. The mean evening time exospheric temperature derived using these observations is 271±5 K. These are the first observations corresponding to the Martian evening hours, which would help to provide constraints to the thermal escape models.

The impact of escaped farmed Atlantic salmon (Salmo salar L.) on catch statistics in Scotland.

PubMed

Green, Darren M; Penman, David J; Migaud, Herve; Bron, James E; Taggart, John B; McAndrew, Brendan J

2012-01-01

In Scotland and elsewhere, there are concerns that escaped farmed Atlantic salmon (Salmo salar L.) may impact on wild salmon stocks. Potential detrimental effects could arise through disease spread, competition, or inter-breeding. We investigated whether there is evidence of a direct effect of recorded salmon escape events on wild stocks in Scotland using anglers' counts of caught salmon (classified as wild or farmed) and sea trout (Salmo trutta L.). This tests specifically whether documented escape events can be associated with reduced or elevated escapes detected in the catch over a five-year time window, after accounting for overall variation between areas and years. Alternate model frameworks were somewhat inconsistent, however no robust association was found between documented escape events and higher proportion of farm-origin salmon in anglers' catch, nor with overall catch size. A weak positive correlation was found between local escapes and subsequent sea trout catch. This is in the opposite direction to what would be expected if salmon escapes negatively affected wild fish numbers. Our approach specifically investigated documented escape events, contrasting with earlier studies examining potentially wider effects of salmon farming on wild catch size. This approach is more conservative, but alleviates some potential sources of confounding, which are always of concern in observational studies. Successful analysis of anglers' reports of escaped farmed salmon requires high data quality, particularly since reports of farmed salmon are a relatively rare event in the Scottish data. Therefore, as part of our analysis, we reviewed studies of potential sensitivity and specificity of determination of farmed origin. Specificity estimates are generally high in the literature, making an analysis of the form we have performed feasible.

The Impact of Escaped Farmed Atlantic Salmon (Salmo salar L.) on Catch Statistics in Scotland

PubMed Central

Green, Darren M.; Penman, David J.; Migaud, Herve; Bron, James E.; Taggart, John B.; McAndrew, Brendan J.

2012-01-01

In Scotland and elsewhere, there are concerns that escaped farmed Atlantic salmon (Salmo salar L.) may impact on wild salmon stocks. Potential detrimental effects could arise through disease spread, competition, or inter-breeding. We investigated whether there is evidence of a direct effect of recorded salmon escape events on wild stocks in Scotland using anglers' counts of caught salmon (classified as wild or farmed) and sea trout (Salmo trutta L.). This tests specifically whether documented escape events can be associated with reduced or elevated escapes detected in the catch over a five-year time window, after accounting for overall variation between areas and years. Alternate model frameworks were somewhat inconsistent, however no robust association was found between documented escape events and higher proportion of farm-origin salmon in anglers' catch, nor with overall catch size. A weak positive correlation was found between local escapes and subsequent sea trout catch. This is in the opposite direction to what would be expected if salmon escapes negatively affected wild fish numbers. Our approach specifically investigated documented escape events, contrasting with earlier studies examining potentially wider effects of salmon farming on wild catch size. This approach is more conservative, but alleviates some potential sources of confounding, which are always of concern in observational studies. Successful analysis of anglers' reports of escaped farmed salmon requires high data quality, particularly since reports of farmed salmon are a relatively rare event in the Scottish data. Therefore, as part of our analysis, we reviewed studies of potential sensitivity and specificity of determination of farmed origin. Specificity estimates are generally high in the literature, making an analysis of the form we have performed feasible. PMID:22970132

Constraining Lyman continuum escape using Machine Learning

NASA Astrophysics Data System (ADS)

Giri, Sambit K.; Zackrisson, Erik; Binggeli, Christian; Pelckmans, Kristiaan; Cubo, Rubén; Mellema, Garrelt

2018-05-01

The James Webb Space Telescope (JWST) will observe the rest-frame ultraviolet/optical spectra of galaxies from the epoch of reionization (EoR) in unprecedented detail. While escaping into the intergalactic medium, hydrogen-ionizing (Lyman continuum; LyC) photons from the galaxies will contribute to the bluer end of the UV slope and make nebular emission lines less prominent. We present a method to constrain leakage of the LyC photons using the spectra of high redshift (z >~ 6) galaxies. We simulate JWST/NIRSpec observations of galaxies at z =6-9 by matching the fluxes of galaxies observed in the Frontier Fields observations of galaxy cluster MACS-J0416. Our method predicts the escape fraction fesc with a mean absolute error Δfesc ~ 0.14. The method also predicts the redshifts of the galaxies with an error .

Competing Contingencies for Escape Behavior: Effects of Negative Reinforcement Magnitude and Quality

ERIC Educational Resources Information Center

Hammond, Jennifer L.

2009-01-01

Previous research has shown that problem behavior maintained by social-negative reinforcement can be treated without escape extinction by enhancing the quality of positive reinforcement for an appropriate alternative response such as compliance. By contrast, negative reinforcement (escape) for compliance generally has been ineffective in the…

Studying Lyman-alpha escape and reionization in Green Pea galaxies

NASA Astrophysics Data System (ADS)

Yang, Huan; Malhotra, Sangeeta; Rhoads, James E.; Gronke, Max; Leitherer, Claus; Wofford, Aida; Dijkstra, Mark

2017-01-01

Green Pea galaxies are low-redshift galaxies with extreme [OIII]5007 emission line. We built the first statistical sample of Green Peas observed by HST/COS and used them as analogs of high-z Lyman-alpha emitters to study Ly-alpha escape and Ly-alpha sizes. Using the HST/COS 2D spectra, we found that Ly-alpha sizes of Green Peas are larger than the UV continuum sizes. We found many correlations between Ly-alpha escape fraction and galactic properties -- dust extinction, Ly-alpha kinematic features, [OIII]/[OII] ratio, and gas outflow velocities. We fit an empirical relation to predict Ly-alpha escape fraction from dust extinction and Ly-alpha red-peak velocity. In the JWST era, we can use this relation to derive the IGM HI column density along the line of sight of each high-z Ly-alpha emitter and probe the reionization process.

Means of escape provisions and evacuation simulation of public building in Malaysia and Singapore

NASA Astrophysics Data System (ADS)

Samad, Muna Hanim Abdul; Taib, Nooriati; Ying, Choo Siew

2017-10-01

The Uniform Building By-law 1984 of Malaysia is the legal document governing fire safety requirements in buildings. Its prescriptive nature has made the requirements out dated from the viewpoint of current performance based approach in most developed countries. The means of escape provisions is a critical requirement to safeguard occupants' safety in fire especially in public buildings. As stipulated in the UBBL 1984, the means of escape provisions includes sufficient escape routes, travel distance, protection of escape routes, etc. designated as means to allow occupants to escape within a safe period of time. This research aims at investigating the effectiveness of those provisions in public buildings during evacuation process involving massive crowd during emergencies. This research includes a scenario-based study on evacuation processes using two software i.e. PyroSim, a crowd modelling software to conduct smoke study and Pathfinder to stimulate evacuation model of building in Malaysia and Singapore as comparative study. The results show that the buildings used as case study were designed according to Malaysian UBBL 1984 and Singapore Firecode, 2013 respectively provide relative safe means of escape. The simulations of fire and smoke and coupled with simulation of evacuation have demonstrated that although there are adequate exits designated according to fire requirements, the impact of the geometry of atriums on the behavior of fire and smoke have significant effect on escape time especially for unfamiliar user of the premises.

Simulations of Atmospheric Neutral Wave Coupling to the Ionosphere

NASA Astrophysics Data System (ADS)

Siefring, C. L.; Bernhardt, P. A.

2005-12-01

atmospheric model for periodic structures with Kelvin-Helmholtz (KH) wavelengths is used to show the development of quasi-periodic structures in the E-layer. For the model, a background atmosphere near 100 km altitude with a scale height of 12.2 km is subjected to a wind shear profile varying by 100 m/s over a distance of 1.7 km. This neutral speed shear drives the KH instability with a growth time of about 100 seconds. The neutral KH wave is a source of plasma turbulence. The E-layer responds to the KH-Wave structure in the neutral atmosphere as an electrodynamic tracer. The plasma flow leads to small scale plasma field aligned irregularities from a gradient drift, plasma interchange instability (GDI) or a Farley-Buneman, two-stream instability (FBI). These irregularities are detected by radar scatter as quasi-periodic structures. All of these plasma phenomena would not occur without the initiation by neutral atmospheric waves.

Examing the Effects of Different IMF, F10.7, and Auroral Inputs on the Thermospheric Neutral Winds

NASA Astrophysics Data System (ADS)

Deng, Y.; Ridley, A. J.

2003-12-01

To obtain a better understanding of how the magnetosphere effects the global thermospheric and ionospheric structure, we conduct some numerical experiments using the University of Michigan's Global Ionosphere-Thermosphere Model (GITM). We have run GITM to roughly steady-state using different strengths of the high-latitude electric potential pattern, F10.7, and auroral inputs to determine how these effect the temporal history and stead-state of the thermospheric neutral winds. Our model reproduces the well known fact that the neutral winds are strongly driven by the ion convection above approximately 300 km, and that the ramp-up time is very dependent upon the altitude. We show quantitative results of the ramp-up times and maximum neutral wind speeds for the different driving conditions.

Survival in emergency escape from passenger aircraft.

DOT National Transportation Integrated Search

1970-10-01

The human factors data from three aircraft accidents involving emergency evacuations are reviewed. Of the 261 passengers aboard, 105 died in attempts to escape during the 1- to 3-minutes prior to the build-up of a lethal thermotoxic environment withi...

Learning from escaped prescribed fire reviews

Treesearch

Anne E. Black; Dave Thomas; James Saveland; Jennifer D. Ziegler

2011-01-01

The U.S. wildland fire community has developed a number of innovative methods for conducting a review following escape of a prescribed fire (expanding on the typical regional or local reviews, to include more of a learning focus - expanded After Action Reviews, reviews that incorporate High Reliability Organizing, Facilitated Learning Analyses, etc). The stated purpose...

Design of a toroidal device with a high temperature superconductor coil for non-neutral plasma trap

NASA Astrophysics Data System (ADS)

Ogawa, Yuichi; Morikawa, Junji; Nihei, Hitoshi; Ozawa, Daisaku; Yoshida, Zensho; Mito, Toshiyuki; Yanagi, Nagato; Iwakuma, Masataka

2002-01-01

The non-neutral plasma confinement device with a floating internal coil is under construction, where the high temperature superconductor (HTS) Ag-sheathed BSCCO-2223 is employed as the floating coil. We have two topics with this device: one is a trap of a non-neutral plasma consisting of one species, and another is an exploration of a high beta plasma based on two-fluid MHD relaxation theory. In the latter case the plasma should be non-neutralized in order to drive the plasma flow in the toroidal direction. The expected plasma parameters are discussed. Key elements of engineering issues have already developed. In addition, we have fabricated a small HTS coil and succeeded in levitating it within an accuracy of 25˜30 μm for 4 min or more.

Never ever? Characteristics, outcomes and motivations of patients who abscond or escape: A 5-year review of escapes and absconds from two medium and low secure forensic units.

PubMed

Mezey, Gillian; Durkin, Catherine; Dodge, Liam; White, Sarah

2015-12-01

Absconds and escapes by psychiatric patients from secure forensic psychiatric settings create public anxiety and are poorly understood. To describe secure hospital patients who escape from within the secure perimeter or abscond, and test for differences between these groups. Escapes and absconds between 2008 and 2012 from the medium and low secure forensic psychiatric inpatient units of two London National Health Service Trusts were identified through the Trusts' databases. Demographic, offending, mental health and incident data were extracted from records for each. Seventy-seven incidents, involving 54 patients, were identified over the five years. These were 13 escapes involving 12 patients, representing a rate of 0.04 per 1000 bed days, and 64 absconds involving 42 patients, a rate of 0.26 per 1000 bed days; 15 (28%) patients were absent without leave more than once. Over half of the patients came back voluntarily within 24 hours of leaving. Over 50% of them had drunk alcohol or taken drugs while away from the unit. Escapees were more likely to be transferred prisoners and to have planned their escape, less likely to return to the unit voluntarily and away longer than patients who absconded. Offending was rare during unauthorised leave--just three offences among the 77 incidents; self-harm was more likely. Motives for absconding included: wanting freedom or drink or drugs, family worries and/or dissatisfaction with aspects of treatment. Escapes or absconding from secure healthcare units have different characteristics, but may best be prevented by convergent strategies. Relational security is likely to be as important for foiling plans for the former as it is for reducing boredom, building strong family support and managing substance misuse in the latter. Copyright © 2015 John Wiley & Sons, Ltd.

The escape problem for mortal walkers

NASA Astrophysics Data System (ADS)

Grebenkov, D. S.; Rupprecht, J.-F.

2017-02-01

We introduce and investigate the escape problem for random walkers that may eventually die, decay, bleach, or lose activity during their diffusion towards an escape or reactive region on the boundary of a confining domain. In the case of a first-order kinetics (i.e., exponentially distributed lifetimes), we study the effect of the associated death rate onto the survival probability, the exit probability, and the mean first passage time. We derive the upper and lower bounds and some approximations for these quantities. We reveal three asymptotic regimes of small, intermediate, and large death rates. General estimates and asymptotics are compared to several explicit solutions for simple domains and to numerical simulations. These results allow one to account for stochastic photobleaching of fluorescent tracers in bio-imaging, degradation of mRNA molecules in genetic translation mechanisms, or high mortality rates of spermatozoa in the fertilization process. Our findings provide a mathematical ground for optimizing storage containers and materials to reduce the risk of leakage of dangerous chemicals or nuclear wastes.

The effects of positive emotion priming on self-reported reckless driving.

PubMed

Taubman-Ben-Ari, Orit

2012-03-01

Five studies examined the effects of positive emotion priming on the willingness to drive recklessly. In all five, young drivers were exposed to one of the following primes of positive affect: a positive mood story; happy memories; an exciting film; a relaxing film; or thoughts on the meaning in life. Following the prime, the participants were asked to report on their willingness to drive recklessly. The responses were compared to those of groups exposed either to neutral affect, another kind of positive affect, or negative affect priming. In two of the studies, participants were also asked to report on their driving styles (risky, anxious, angry, or careful) as a second dependent variable. Positive affect, especially in the form of arousal, was found to be related to higher willingness to drive recklessly. Although men tended to report higher intentions to drive recklessly, men and women did not react differently to the emotional induction. Most interestingly, positive emotions of a relaxing nature, as well as thinking about the meaning in life, lowered the willingness to engage in risky driving. The discussion emphasizes the importance of looking for new ways to use positive emotions effectively in road safety interventions, and considers the practical implications of the studies. Copyright © 2011 Elsevier Ltd. All rights reserved.

Effects of Serotonergic and Opioidergic Drugs on Escape Behaviors and Social Status of Male Crickets

NASA Astrophysics Data System (ADS)

Dyakonova, V. E.; Schürmann, F.-W.; Sakharov, D. A.

We examined the effects of selective serotonin depletion and opioid ligands on social rank and related escape behavior of the cricket Gryllus bimaculatus. Establishment of social rank in a pair of males affected their escape reactions. Losers showed a lower and dominants a higher percentage of jumps in response to tactile cercal stimulation than before a fight. The serotonin-depleting drug α-methyltryptophan (AMTP) caused an activation of the escape reactivity in socially naive crickets. AMTP-treated animals also showed a lower ability to become dominants. With an initial 51.6+/-3.6% of wins in the AMTP group, the percentage decreased to 26+/-1.6% on day 5 after injection. The opiate receptor antagonist naloxone affected fight and escape similarly as AMTP. In contrast to naloxone, the opioid agonist [d-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin decreased escape responsiveness to cercal stimulation in naive and subordinate crickets. We suggest that serotonergic and opioid systems are involved in the dominance induced depression of escape behavior.

Globally fixed-time synchronization of coupled neutral-type neural network with mixed time-varying delays.

PubMed

Zheng, Mingwen; Li, Lixiang; Peng, Haipeng; Xiao, Jinghua; Yang, Yixian; Zhang, Yanping; Zhao, Hui

2018-01-01

This paper mainly studies the globally fixed-time synchronization of a class of coupled neutral-type neural networks with mixed time-varying delays via discontinuous feedback controllers. Compared with the traditional neutral-type neural network model, the model in this paper is more general. A class of general discontinuous feedback controllers are designed. With the help of the definition of fixed-time synchronization, the upper right-hand derivative and a defined simple Lyapunov function, some easily verifiable and extensible synchronization criteria are derived to guarantee the fixed-time synchronization between the drive and response systems. Finally, two numerical simulations are given to verify the correctness of the results.

Globally fixed-time synchronization of coupled neutral-type neural network with mixed time-varying delays

PubMed Central

2018-01-01

This paper mainly studies the globally fixed-time synchronization of a class of coupled neutral-type neural networks with mixed time-varying delays via discontinuous feedback controllers. Compared with the traditional neutral-type neural network model, the model in this paper is more general. A class of general discontinuous feedback controllers are designed. With the help of the definition of fixed-time synchronization, the upper right-hand derivative and a defined simple Lyapunov function, some easily verifiable and extensible synchronization criteria are derived to guarantee the fixed-time synchronization between the drive and response systems. Finally, two numerical simulations are given to verify the correctness of the results. PMID:29370248

How Hospitable Are Space Weather Affected Habitable Zones? The Role of Ion Escape

NASA Astrophysics Data System (ADS)

Airapetian, Vladimir S.; Glocer, Alex; Khazanov, George V.; Loyd, R. O. P.; France, Kevin; Sojka, Jan; Danchi, William C.; Liemohn, Michael W.

2017-02-01

Atmospheres of exoplanets in the habitable zones around active young G-K-M stars are subject to extreme X-ray and EUV (XUV) fluxes from their host stars that can initiate atmospheric erosion. Atmospheric loss affects exoplanetary habitability in terms of surface water inventory, atmospheric pressure, the efficiency of greenhouse warming, and the dosage of the UV surface irradiation. Thermal escape models suggest that exoplanetary atmospheres around active K-M stars should undergo massive hydrogen escape, while heavier species including oxygen will accumulate forming an oxidizing atmosphere. Here, we show that non-thermal oxygen ion escape could be as important as thermal, hydrodynamic H escape in removing the constituents of water from exoplanetary atmospheres under supersolar XUV irradiation. Our models suggest that the atmospheres of a significant fraction of Earth-like exoplanets around M dwarfs and active K stars exposed to high XUV fluxes will incur a significant atmospheric loss rate of oxygen and nitrogen, which will make them uninhabitable within a few tens to hundreds of Myr, given a low replenishment rate from volcanism or cometary bombardment. Our non-thermal escape models have important implications for the habitability of the Proxima Centauri’s terrestrial planet.

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…

Automated guidance algorithms for a space station-based crew escape vehicle.

PubMed

Flanary, R; Hammen, D G; Ito, D; Rabalais, B W; Rishikof, B H; Siebold, K H

2003-04-01

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 first 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 first 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 requires

The cold driver: Cold stress while driving results in dangerous behavior.

PubMed

Morris, Drew M; Pilcher, June J

2016-10-01

Cool vehicle cabin temperatures can induce short-term non-hypothermic cold stress. The current study created a cold condition to examine the impact of cold stress on driving behavior. Forty-four participants drove a high-fidelity driving simulator during a thermal neutral or local torso cooled condition. Participants performed additional tasks to assess attention, psychomotor vigilance, and manual dexterity. Skin temperature was significantly lower in the cold condition while internal temperature was unaffected. Participants who had higher subjective ratings of cold followed lead vehicles closer and started to brake later. Participants in the cold condition followed the lead car 22% (0.82s) closer and started braking 20% (2.35s) later when approaching a stop sign during the car-following task. No change in attention, psychomotor vigilance, or dexterity was observed. The current results suggest that cold environmental conditions can contribute to dangerous driving behaviors. Measures of cold perception were also shown to predict changes in driving behavior. Copyright © 2016 Elsevier B.V. All rights reserved.

Improved Temperature Diagnostic for Non-Neutral Plasmas with Single-Electron Resolution

NASA Astrophysics Data System (ADS)

Shanman, Sabrina; Evans, Lenny; Fajans, Joel; Hunter, Eric; Nelson, Cheyenne; Sierra, Carlos; Wurtele, Jonathan

2016-10-01

Plasma temperature diagnostics in a Penning-Malmberg trap are essential for reliably obtaining cold, non-neutral plasmas. We have developed a setup for detecting the initial electrons that escape from a trapped pure electron plasma as the confining electrode potential is slowly reduced. The setup minimizes external noise by using a silicon photomultiplier to capture light emitted from an MCP-amplified phosphor screen. To take advantage of this enhanced resolution, we have developed a new plasma temperature diagnostic analysis procedure which takes discrete electron arrival times as input. We have run extensive simulations comparing this new discrete algorithm to our existing exponential fitting algorithm. These simulations are used to explore the behavior of these two temperature diagnostic procedures at low N and at high electronic noise. This work was supported by the DOE DE-FG02-06ER54904, and the NSF 1500538-PHY.

On the temperature prediction in a fire escape passage

NASA Astrophysics Data System (ADS)

Casano, G.; Piva, S.

2017-11-01

Fire safety engineering requires a detailed understanding of fire behaviour and of its effects on structures and people. Many factors may condition the fire scenario, as for example, heat transfer between the flame and the boundary structures. Currently advanced numerical codes for the prediction of the fire behaviour are available. However, these solutions often require heavy calculations and long times. In this context analytical solutions can be useful for a fast analysis of simplified schematizations. After that, it is more effective the final utilization of the advanced fire codes. In this contribution, the temperature in a fire escape passage, separated with a thermally resistant wall from a fire room, is analysed. The escape space is included in a building where the neighbouring rooms are at a constant undisturbed temperature. The presence of the neighbouring rooms is considered with an equivalent heat transfer coefficient, in a boundary condition of the third type. An analytical solution is used to predict the temperature distribution during the fire. It allows to obtain useful information on the temperature reached in the escape area in contact with a burning room; it is useful also for a fast choice of the thermal characteristics of a firewall.

European policymaking on the tobacco advertising ban: the importance of escape routes.

PubMed

Adamini, Sandra; Versluis, Esther; Maarse, Hans

2011-01-01

This article analyses the European Union policymaking process regarding tobacco advertising. While others already highlighted the importance of intergovernmental bargaining between member states to explain the outcome of the tobacco advertising case, the main aim of this article is to identify the use of escape routes by the Commission, the European Parliament, the Council and interest groups that played an important role in overcoming the deadlock. When looking at the different institutions that structure policymaking, we argue that indeed focusing on escape routes provides a clear insight in the process and in what strategies were necessary to 'make Europe work'. In the end, it appears to be a combination of escape routes that resulted in the final decision.

An Imposed Dynamo Current Drive Experiment: Demonstration of Confinement

NASA Astrophysics Data System (ADS)

Jarboe, Thomas; Hansen, Chris; Hossack, Aaron; Marklin, George; Morgan, Kyle; Nelson, Brian; Sutherland, Derek; Victor, Brian

2014-10-01

An experiment for studying and developing the efficient sustainment of a spheromak with sufficient confinement (current-drive power heats the plasma to its stability β-limit) and in the keV temperature range is discussed. A high- β spheromak sustained by imposed dynamo current drive (IDCD) is justified because: previous transient experiments showed sufficient confinement in the keV range with no external toroidal field coil; recent results on HIT-SI show sustainment with sufficient confinement at low temperature; the potential of IDCD of solving other fusion issues; a very attractive reactor concept; and the general need for efficient current drive in magnetic fusion. The design of a 0.55 m minor radius machine with the required density control, wall loading, and neutral shielding for a 2 s pulse is presented. Peak temperatures of 1 keV and toroidal currents of 1.35 MA and 16% wall-normalized plasma beta are envisioned. The experiment is large enough to address the key issues yet small enough for rapid modification and for extended MHD modeling of startup and code validation.

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.

A convergent and essential interneuron pathway for Mauthner-cell-mediated escapes.

PubMed

Lacoste, Alix M B; Schoppik, David; Robson, Drew N; Haesemeyer, Martin; Portugues, Ruben; Li, Jennifer M; Randlett, Owen; Wee, Caroline L; Engert, Florian; Schier, Alexander F

2015-06-01

The Mauthner cell (M-cell) is a command-like neuron in teleost fish whose firing in response to aversive stimuli is correlated with short-latency escapes [1-3]. M-cells have been proposed as evolutionary ancestors of startle response neurons of the mammalian reticular formation [4], and studies of this circuit have uncovered important principles in neurobiology that generalize to more complex vertebrate models [3]. The main excitatory input was thought to originate from multisensory afferents synapsing directly onto the M-cell dendrites [3]. Here, we describe an additional, convergent pathway that is essential for the M-cell-mediated startle behavior in larval zebrafish. It is composed of excitatory interneurons called spiral fiber neurons, which project to the M-cell axon hillock. By in vivo calcium imaging, we found that spiral fiber neurons are active in response to aversive stimuli capable of eliciting escapes. Like M-cell ablations, bilateral ablations of spiral fiber neurons largely eliminate short-latency escapes. Unilateral spiral fiber neuron ablations shift the directionality of escapes and indicate that spiral fiber neurons excite the M-cell in a lateralized manner. Their optogenetic activation increases the probability of short-latency escapes, supporting the notion that spiral fiber neurons help activate M-cell-mediated startle behavior. These results reveal that spiral fiber neurons are essential for the function of the M-cell in response to sensory cues and suggest that convergent excitatory inputs that differ in their input location and timing ensure reliable activation of the M-cell, a feedforward excitatory motif that may extend to other neural circuits. Copyright © 2015 Elsevier Ltd. All rights reserved.

Leaflet escape in a new bileaflet mechanical valve: TRI technologies.

PubMed

Bottio, Tomaso; Casarotto, Dino; Thiene, Gaetano; Caprili, Luca; Angelini, Annalisa; Gerosa, Gino

2003-05-13

Leaflet escape is a mode of structural valve failure for mechanical prostheses. This complication previously has been reported for both monoleaflet and bileaflet valve models. We report 2 leaflet escape occurrences observed in 2 patients who underwent valve replacement with a TRI Technologies valve prosthesis. At the University of Padua, between November 2000 and February 2002, 36 TRI Technologies valve prostheses (26 aortic and 10 mitral) were implanted in 34 patients (12 women and 22 men) with a mean age of 59.9+/-10.3 years (range, 30 to 75 years). There were 5 deaths: 3 in hospital, 1 early after discharge, and 1 late. Two patients experienced a catastrophic prosthetic leaflet escape; the first patient was a 52-year-old man who died 10 days after aortic valve and ascending aorta replacement, and the second was a 58-year-old man who underwent a successful emergency reoperation 20 months after mitral valve replacement. Examination of the explanted prostheses showed in both cases a leaflet escape caused by a leaflet's pivoting system fracture. Prophylactic replacement was then successfully accomplished so far in 12 patients, without evidence of structural valve failure in any of them. Among other significant postoperative complications, we observed 3 major thromboembolisms, 1 hemorrhage, and 1 paravalvular leak. These catastrophes prompted us to interrupt the implantation program, and they cast a shadow on the durability of the TRI Technologies valve prosthesis because of its high risk of structural failure.

Flowing water affects fish fast-starts: escape performance of the Hawaiian stream goby, Sicyopterus stimpsoni.

PubMed

Diamond, Kelly M; Schoenfuss, Heiko L; Walker, Jeffrey A; Blob, Richard W

2016-10-01

Experimental measurements of escape performance in fishes have typically been conducted in still water; however, many fishes inhabit environments with flow that could impact escape behavior. We examined the influences of flow and predator attack direction on the escape behavior of fish, using juveniles of the amphidromous Hawaiian goby Sicyopterus stimpsoni In nature, these fish must escape ambush predation while moving through streams with high-velocity flow. We measured the escape performance of juvenile gobies while exposing them to a range of water velocities encountered in natural streams and stimulating fish from three different directions. Frequency of response across treatments indicated strong effects of flow conditions and attack direction. Juvenile S. stimpsoni had uniformly high response rates for attacks from a caudal direction (opposite flow); however, response rates for attacks from a cranial direction (matching flow) decreased dramatically as flow speed increased. Mechanical stimuli produced by predators attacking in the same direction as flow might be masked by the flow environment, impairing the ability of prey to detect attacks. Thus, the likelihood of successful escape performance in fishes can depend critically on environmental context. © 2016. Published by The Company of Biologists Ltd.

30 CFR 75.382 - Mechanical escape facilities.

Code of Federal Regulations, 2011 CFR

2011-07-01

....382 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.382 Mechanical escape... shall be run through one complete cycle of operation to determine that it is operating properly. (d) A...

Radial and azimuthal distribution of Io's oxygen neutral cloud observed by Hisaki/EXCEED

NASA Astrophysics Data System (ADS)

Koga, R.; Tsuchiya, F.; Kagitani, M.; Sakanoi, T.; Yoneda, M.; Yoshikawa, I.; Yoshioka, K.; Murakami, G.; Yamazaki, A.; Kimura, T.; Smith, H. T.

2017-12-01

We report the spatial distributions of oxygen neural cloud surrounding Jupiter's moon Io and along Io's orbit observed by the HISAKI satellite. Atomic oxygen and sulfur in Io's atmosphere escape from the exobase and move to corona (< 5.8 Io radii, the boundary where Jupiter's gravity begins to dominate) and neutral clouds (> 5.8 Io radii) mainly due to atmospheric sputtering. Io plasma torus is formed by ionization of these atoms by electron impact and charge exchange processes. It is essential to examine the dominant source of Io plasma torus, particularly in the vicinity of Io (<5.8 Io radii; atmosphere and corona) or the region away from Io (>5.8 Io radii; extended neutral clouds). The spatial distribution of oxygen and sulfur neutral clouds is important to understand the source. The extreme ultraviolet spectrometer called EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) installed on the Hisaki satellite observed Io plasma torus continuously in 2014-2015, and we carried out the monitoring of the distribution of atomic oxygen emission at 130.4 nm. The emission averaged over the distance range of 4.5-6.5 Jovian radii on the dawn and dusk sides strongly depends on the Io phase angle (IPA), and has a emission peak between IPA of 60-90 degrees on the dawn side, and between 240-270 degrees on the dusk side, respectively. It also shows the asymmetry with respect to Io's position: the intensity averaged for IPA 60-90 degrees (13.3 Rayleighs (R)) is 1.2 times greater than that for IPA 90-120 degrees (11.1 R) on the dawn side. The similar tendency is found on the dusk side. Weak atomic oxygen emission (4 R) uniformly distributes in every IPA. We also examined the radial distribution of the oxygen neutral cloud during the same period and found the emission peak near Io's orbit with decreasing the intensity toward 8.0 Jupiter radii. The results show the high density component of the oxygen neutral cloud is concentrated around Io and extends mainly toward

On the run: mapping the escape speed across the Galaxy with SDSS

NASA Astrophysics Data System (ADS)

Williams, Angus A.; Belokurov, Vasily; Casey, Andrew R.; Evans, N. Wyn

2017-06-01

We measure the variation of the escape speed of the Milky Way across a range of ˜40 kpc in Galactocentric radius. The local escape speed is found to be 521^{+46}_{-30}{ km s^{-1}}, in good agreement with other studies. We find that this has already fallen to 379^{+34}_{-28}{ km s^{-1}} at a radius of 50 kpc. Through measuring the escape speed and its variation, we obtain constraints on the Galactic mass profile and rotation curve. The gradient in the escape speed suggests that the total mass contained within 50 kpc is 30^{+7}_{-5}× 10^{10} M_{⊙}, implying a relatively light dark halo for the Milky Way. The local circular speed is found to be v_c(R_0) = 223^{+40}_{-34}{ km s^{-1}} and falls with radius as a power law with index -0.19 ± 0.05. Our method represents a novel way of estimating the mass of the Galaxy, and has very different systematics to more commonly used models of tracers, which are more sensitive to the central parts of the halo velocity distributions. Using our inference on the escape speed, we then investigate the orbits of high-speed Milky Way dwarf galaxies. For each considered dwarf, we predict small pericentre radii and large orbital eccentricities. This naturally explains the large observed ellipticities of two of the dwarfs, which are likely to have been heavily disrupted at pericentre.

Fractionation of terrestrial neon by hydrodynamic hydrogen escape from ancient steam atmospheres

NASA Technical Reports Server (NTRS)

Zahnle, K.

1991-01-01

Atmospheric neon is isotopically heavier than mantle neon. By contrast, nonradiogenic mantle Ar, Kr, and Xe are not known to differ from the atmosphere. These observations are most easily explained by selective neon loss to space; however, neon is much too massive to escape from the modern atmosphere. Steam atmospheres are a likely, if intermittent, feature of the accreting Earth. They occur because, on average, the energy liberated during accretion places Earth above the runaway greenhouse threshold, so that liquid water is not stable at the surface. It is found that steam atmospheres should have lasted some ten to fifty million years. Hydrogen escape would have been vigorous, but abundant heavy constituents would have been retained. There is no lack of plausible candidates; CO2, N2, or CO could all suffice. Neon can escape because it is less massive than any of the likely pollutants. Neon fractionation would have been a natural byproduct. Assuming that the initial Ne-20/Ne-22 ratio was solar, it was found that it would have taken some ten million years to effect the observed neon fractionation in a 30 bar steam atmosphere fouled with 10 bars of CO. Thicker atmospheres would have taken longer; less CO, shorter. This mechanism for fractionating neon has about the right level of efficiency. Because the lighter isotope escapes much more readily, total neon loss is pretty minimal; less than half of the initial neon endowment escapes.

Biomechanics of Tetrahymena escaping from dead ends

NASA Astrophysics Data System (ADS)

Ishikawa, Takuji; Kikuchi, Kenji

2017-11-01

Behaviors of swimming microorganisms in complex environments are important in understanding cells' distribution in nature and in industries. Although cell's swimming and spreading in an infinite fluid has been intensively investigated, that in a narrow region bounded by walls is still unclear. Thus, in this study, we used Tetrahymena thermophila as a model microorganism, and experimentally investigated its behavior between flat plates with an angle. The results showed that the cells tended to escape from the narrow region, and the swimming velocity and the radius of curvature of the trajectories decreased as they swam narrower region. We then developed a computational model of swimming Tetrahymena. The results showed that the escaping behavior could be well explained by fluid mechanics. The obtained knowledge is useful in understanding cells' behaviors in complex environments, such as in porous media and in a granular matter. This research was supported by JSPS KAKENHI Grants, numbers 25000008 and 17H00853.

Widespread Impact of HLA Restriction on Immune Control and Escape Pathways of HIV-1

PubMed Central

Listgarten, Jennifer; Pfeifer, Nico; Tan, Vincent; Kadie, Carl; Walker, Bruce D.; Ndung'u, Thumbi; Shapiro, Roger; Frater, John; Brumme, Zabrina L.; Goulder, Philip J. R.; Heckerman, David

2012-01-01

The promiscuous presentation of epitopes by similar HLA class I alleles holds promise for a universal T-cell-based HIV-1 vaccine. However, in some instances, cytotoxic T lymphocytes (CTL) restricted by HLA alleles with similar or identical binding motifs are known to target epitopes at different frequencies, with different functional avidities and with different apparent clinical outcomes. Such differences may be illuminated by the association of similar HLA alleles with distinctive escape pathways. Using a novel computational method featuring phylogenetically corrected odds ratios, we systematically analyzed differential patterns of immune escape across all optimally defined epitopes in Gag, Pol, and Nef in 2,126 HIV-1 clade C-infected adults. Overall, we identified 301 polymorphisms in 90 epitopes associated with HLA alleles belonging to shared supertypes. We detected differential escape in 37 of 38 epitopes restricted by more than one allele, which included 278 instances of differential escape at the polymorphism level. The majority (66 to 97%) of these resulted from the selection of unique HLA-specific polymorphisms rather than differential epitope targeting rates, as confirmed by gamma interferon (IFN-γ) enzyme-linked immunosorbent spot assay (ELISPOT) data. Discordant associations between HLA alleles and viral load were frequently observed between allele pairs that selected for differential escape. Furthermore, the total number of associated polymorphisms strongly correlated with average viral load. These studies confirm that differential escape is a widespread phenomenon and may be the norm when two alleles present the same epitope. Given the clinical correlates of immune escape, such heterogeneity suggests that certain epitopes will lead to discordant outcomes if applied universally in a vaccine. PMID:22379086

Driving with a short arm cast in a simulator.

PubMed

Mansour, Damian; Mansour, Kristin Gotaas; Kenny, Benjamin William; Attia, John; Meads, Bryce

2015-12-01

To test the ability to steer in a driving simulator in subjects with a short arm cast. 17 men and 13 women aged 23 to 67 (mean, 37) years who had a valid driver's licence were randomised to the cast-first group (n=16; 7 had the cast on the dominant arm) or the cast-second group (n=14; 8 had the cast on the dominant arm) and drove in a simulator. A short arm plaster-of-Paris cast was applied in a neutral position, allowing free movement of the metacarpophalangeal joints, thumb, and elbow joint. Outcome measures included the number of driving off track instances, the number of crashes, the lap time, and the effect of hand dominance on these parameters. Subjects were asked whether the cast had impeded their steering ability. Subjects with or without a cast were comparable in terms of the number of driving off track instances, number of crashes, and lap time. Compared with no cast, the odds ratio (OR) of a subject in a cast driving off the track was 1.02 (p=0.921) and having a crash was 0.79 (p=0.047). All subjects were 1.23 times more likely to drive off the track in their first lap (OR=2.66, p=0.019). The mean lap time decreased for each consecutive lap from the 2nd to 5th laps. Subjects driving with a cast on the dominant or non-dominant arm were comparable. 26 out of the 30 participants considered that the plaster cast impeded their steering ability. Compared with no cast, driving with a short arm cast did not significantly decrease steering ability in a driving simulator.

On the relative contributions of noncontingent reinforcement and escape extinction in the treatment of food refusal.

PubMed

Reed, Gregory K; Piazza, Cathleen C; Patel, Meeta R; Layer, Stacy A; Bachmeyer, Melanie H; Bethke, Stephanie D; Gutshall, Katharine A

2004-01-01

In the current investigation, we evaluated the relative effects of noncontingent reinforcement (NCR), escape extinction, and a combination of NCR and escape extinction as treatment for the feeding problems exhibited by 4 children. For each participant, consumption increased only when escape extinction was implemented, independent of whether NCR was present or absent. These results were consistent with prior research suggesting that positive reinforcement alone is insufficient for increasing consumption, and that escape extinction often is necessary to increase and maintain food acceptance. However, NCR appeared to decrease inappropriate behavior for some participants.

Basic Properties of Plasma-Neutral Coupling in the Solar Atmosphere

NASA Astrophysics Data System (ADS)

Goodman, Michael

2015-04-01

Plasma-neutral coupling (PNC) in the solar atmosphere concerns the effects of collisions between charged and neutral species’. It is most important in the chromosphere, which is the weakly ionized, strongly magnetized region between the weakly ionized, weakly magnetized photosphere and the strongly ionized, strongly magnetized corona. The charged species’ are mainly electrons, protons, and singly charged heavy ions. The neutral species’ are mainly hydrogen and helium. The resistivity due to PNC can be several orders of magnitude larger than the Spitzer resistivity. This enhanced resistivity is confined to the chromosphere, and provides a highly efficient dissipation mechanism unique to the chromosphere. PNC may play an important role in many processes such as heating and acceleration of plasma; wave generation, propagation, and dissipation; magnetic reconnection; maintaining the near force-free state of the corona; and limiting mass flux into the corona. It might play a major role in chromospheric heating, and be responsible for the existence of the chromosphere as a relatively thin layer of plasma that emits a net radiative flux 10-100 times greater than that of the overlying corona. The required heating rate might be generated by Pedersen current dissipation triggered by the rapid increase of magnetization with height in the lower chromosphere, where most of the net radiative flux is emitted. Relatively cool regions of the chromosphere might be regions of minimal Pedersen current dissipation due to smaller magnetic field strength or perpendicular current density. This talk will discuss PNC from an MHD point of view, and focus on the basic parameters that determine its effectiveness. These parameters are ionization fraction, magnetization, and the electric field that drives current perpendicular to the magnetic field. By influencing this current and the electric field that drives it, PNC directly influences the rate at which energy is exchanged between the

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.

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.

Approaches to the induction of HIV broadly neutralizing antibodies.