Science.gov

Sample records for escape systems

  1. 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…

  2. 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…

  3. 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

  4. Escape rate scaling in infinite measure preserving systems

    NASA Astrophysics Data System (ADS)

    Munday, Sara; Knight, Georgie

    2016-02-01

    We investigate the scaling of the escape rate from piecewise linear dynamical systems displaying intermittency due to the presence of an indifferent fixed point. Strong intermittent behaviour in the dynamics can result in the system preserving an infinite measure. We define a neighbourhood of the indifferent fixed point to be a hole through which points escape and investigate the scaling of the rate of this escape as the length of the hole decreases, both in the finite measure preserving case and infinite measure preserving case. In the infinite measure preserving systems we observe logarithmic corrections to and polynomial scaling of the escape rate with hole length. Finally we conjecture a relationship between the wandering rate and the observed scaling of the escape rate.

  5. Emergency escape system protects personnel from explosion and fire

    NASA Technical Reports Server (NTRS)

    Offik, W. G.

    1966-01-01

    Elevator-type emergency escape system evacuates personnel from tall structures, especially when the possibility of explosion or fire exists. The system consists of a spike shaped rescue cabin which descends along a vertical guide cable, penetrates the dome shaped roof of an underground blast shelter and stops in a deceleration bed of granular material.

  6. 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.

  7. Mean escape time in a system with stochastic volatility

    NASA Astrophysics Data System (ADS)

    Bonanno, Giovanni; Valenti, Davide; Spagnolo, Bernardo

    2007-01-01

    We study the mean escape time in a market model with stochastic volatility. The process followed by the volatility is the Cox, Ingersoll, and Ross process which is widely used to model stock price fluctuations. The market model can be considered as a generalization of the Heston model, where the geometric Brownian motion is replaced by a random walk in the presence of a cubic nonlinearity. We investigate the statistical properties of the escape time of the returns, from a given interval, as a function of the three parameters of the model. We find that the noise can have a stabilizing effect on the system, as long as the global noise is not too high with respect to the effective potential barrier experienced by a fictitious Brownian particle. We compare the probability density function of the return escape times of the model with those obtained from real market data. We find that they fit very well.

  8. Facilities and capabilities catalog for landing and escape systems

    NASA Technical Reports Server (NTRS)

    Meyerson, Robert E. (Editor)

    1992-01-01

    This catalog serves as a single source reference for designers of landing and escape systems for spacecraft, aircraft, weapons, and airdrop system. It includes those facilities which may be required by a system designer in planning a development test program for many applications. The primary objective of this catalog is to provide a means for identifying critical facilities with the U.S. which can be used for the development of landing and escape systems. A secondary objective is to provide a useful tool to the system designer for picking and choosing facilities and capabilities. The six chapters in this volume include wind tunnels, drop zones, test aircraft, fabrication facilities, design tools, and other miscellaneous facilities. A different data sheet format is used for each of the chapters which provides information on performance, location, special capabilities, and a local point of contact. All inputs were solicited from the individual facilities and have not been independently verified for accuracy.

  9. Mean field escapers in non-equilibrium systems

    NASA Astrophysics Data System (ADS)

    Theuns, T.; David, M.

    1990-08-01

    Results are reported from a study on nonequilibrium N-body systems that undergo initial collapse. This collapse is followed by global pulsations of the system. During these pulsations, the mean gravitational field fluctuates violently. Some particles pick up enough energy to be ejected from the system into the halo or even fly off to infinity. Also discussed are the region in phase space from which these mean-field escapers originate and their erergy frequency distribution, for the illustrative case of a uniform spherical initial state. The pulsations lead to the production of shells in the halo.

  10. Lightning tests of the orbiter pyrotechnic escape system

    NASA Technical Reports Server (NTRS)

    Cohen, R.; Schulte, E. H.

    1977-01-01

    An experimental test program was undertaken to demonstrate that the Space Shuttle Orbiter Vehicle pyrotechnics actuated Crew Escape System was not subject to failure resulting from a lightning strike in the vicinity of the cockpit. A test sample representing a full-scale portion of the Orbiter Outer Panel was preheated to 325 F and struck with three different current waveforms to simulate the various effects of lightning: (1) 2 micro sec risetime, to 180 kA pulse to evaluate fast current rise shock effects; (2) a 205 kA, 100 micro sec wide pulse to evaluate full energy shock effects; and (3) a 490 ampere, 370 msec continuing current to evaluate the thermal effects of a lightning strike. These tests show that the Orbiter outer panel pyrotechnics are adequately protected against damage resulting from a lightning strike.

  11. The Solar system's post-main-sequence escape boundary

    NASA Astrophysics Data System (ADS)

    Veras, Dimitri; Wyatt, Mark C.

    2012-04-01

    The Sun will eventually lose about half of its current mass non-linearly over several phases of post-main-sequence evolution. This mass loss will cause any surviving orbiting body to increase its semimajor axis and perhaps vary its eccentricity. Here, we use a range of solar models spanning plausible evolutionary sequences and assume isotropic mass loss to assess the possibility of escape from the Solar system. We find that the critical semimajor axis in the Solar system within which an orbiting body is guaranteed to remain bound to the dying Sun due to perturbations from stellar mass loss alone is ≈103-104 au. The fate of objects near or beyond this critical semimajor axis, such as the Oort Cloud, outer scattered disc and specific bodies such as Sedna, will significantly depend on their locations along their orbits when the Sun turns off the main sequence. These results are applicable to any exoplanetary system containing a single star with a mass, metallicity and age which are approximately equal to the Sun's, and suggest that few extrasolar Oort Clouds could survive post-main-sequence evolution intact.

  12. Threshold law for escaping from the Hénon-Heiles system.

    PubMed

    Zhao, H J; Du, M L

    2007-08-01

    We report a theoretical study of the escape rates of the Hénon-Heiles system above threshold. An analytic formula for the escape rate as a function of energy is presented. We also simulated the escaping process by following the motions of a large number of particles. Two algorithms are employed to solve the equations of motion. One is the Runge-Kutta-Fehlberg method, and another is a recently proposed fourth order symplectic method. Our simulations show the escape of Hénon-Heiles system follows exponential laws. We extracted the escape rates from the time dependence of particle numbers in the Hénon-Heiles potential. The extracted escape rates agree with the analytic result. Close to threshold we find the rate alpha(DeltaE) can be written as a series expansion, the first term of this expansion is 4/3DeltaE.

  13. Development of the Rocket Extraction Escape System for the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Langsmith, Owen; Nagel, Steven R.

    1989-01-01

    Six tests have been successfully conducted for a Space Shuttle Rocket Extraction Escape System (REES) for astronauts, using a modified Convair 240 aircraft with a simulated Shuttle Orbiter hatch. All escape trajectories are judged to have been able to clear the Orbiter by an acceptable margin, and the crew-extraction loads were found to be within accepted physiological tolerances. The REES concept can be applied to numerous other aircraft configurations for crew escape.

  14. Escape dynamics and fractal basin boundaries in the planar Earth-Moon system

    NASA Astrophysics Data System (ADS)

    de Assis, Sheila C.; Terra, Maisa O.

    2014-10-01

    The escape of trajectories of a spacecraft, or comet or asteroid in the presence of the Earth-Moon system is investigated in detail in the context of the planar circular restricted three-body problem, in a scattering region around the Moon. The escape through the necks around the collinear points and as well as the leaking produced by considering collisions with the Moon surface, taking the lunar mean radius into account, were considered. Given that different transport channels are available as a function of the Jacobi constant, four distinct escape regimes are analyzed. Besides the calculation of exit basins and of the spatial distribution of escape time, the qualitative dynamical investigation through Poincaré sections is performed in order to elucidate the escape process. Our analyses reveal the dependence of the properties of the considered escape basins with the energy, with a remarkable presence of fractal basin boundaries along all the escape regimes. Finally, we observe the plentiful presence of stickiness motion near stability islands which plays a remarkable role in the longest escape time behavior. The application of this analysis is important both in space mission design and study of natural systems, given that fractal boundaries are related with high sensitivity to initial conditions, implying in uncertainty between safe and unsafe solutions, as well as between escaping solutions that evolve to different phase space regions.

  15. Time-dependent Kramers escape rate in overdamped system with power-law distribution

    NASA Astrophysics Data System (ADS)

    Zhou, Yanjun; Yin, Cangtao

    2016-05-01

    The probability distribution of Brownian particles moving in an overdamped complex system follows the generalized Smoluchowski equation, which can be rigorously proven that the exact time-dependent solution for this equation follows Tsallis form. Time-dependent escape rate in overdamped system with power-law distributions is then established based on the flux over population theory. The stationary state escape rate in overdamped system with power-law distribution which has been obtained before based on mean first passage time theory is recovered from time-dependent escape rate as time toward infinity.

  16. How a system moves in noise-induced escape from a metastable state

    NASA Astrophysics Data System (ADS)

    Zhukov, A.; Dykman, M. I.

    2000-03-01

    We provide a theory and results of numerical simulations of noise-induced escape from a metastable state, a phenomenon which underlies numerous processes in physics and biology. Of particular interest is a system's dynamics during escape. Understanding this dynamics is necessary for controlling the escape rate. The escape dynamics can be characterized by the distribution of trajectories along which the escaped system has been moving. This distribution peaks at a certain path, which is the most probable escape path (MPEP). The MPEP displays several characteristic features, including slowing down near the unstable stationary state over which the system goes in escape (e.g., top of the potential barrier). The width of the paths distribution is strongly nonmonotonic as a function of time counted off backward from the time when the system reaches an observation point behind the potential barrier. We investigate the shape of the paths distribution as a function of time and dynamical variables of the system, for a broad range of noise intensities. The data are obtained for a Brownian particle in a potential with a metastable minimum. The results are used to discuss experimental observations on dropout events in semiconductor lasers.

  17. Lévy noise-induced escape in an excitable system

    NASA Astrophysics Data System (ADS)

    Cai, Rui; Chen, Xiaoli; Duan, Jinqiao; Kurths, Jürgen; Li, Xiaofan

    2017-06-01

    This paper considers the dynamics of escape in the stochastic FitzHugh-Nagumo (FHN) neuronal model driven by symmetric α-stable Lévy noise. External or internal stimulation may make the excitable system produce a pulse or not, which can be interpreted as an escape problem. A new method to analyse the state transition from the rest state to the excitatory state is presented. This approach consists of two deterministic indices: the first escape probability (FEP) and the mean first exit time (MFET). We find that higher FEP in the rest state (equilibrium) promotes such a transition and MFET reflects the stability of the rest state directly with the selected escape region. The developed two dimensional numerical simulation method to calculate FEP and MFET can not only avoid a dimension reduction, but is also applicable for the cases with large noise. In addition, FEP provides us with a new perspective to understand the seperatrix of the stochastic FHN model. It can be seen that smaller jumps of the Lévy motion and relatively small noise intensity are conducive to the production of spikes. In order to characterize the effect of noise on the selected escape region in which the equilibrium lies, the area of higher FEP and MFET in the escape region are calculated. Meanwhile, Brownian motion as a special case is also taken into account for comparison. This work was partly supported by the NSF grant 1620449, and NSFC grants 11531006, 11371367 and 11271290.

  18. Influence of the breeding system on the escape response of red-legged partridges (Alectoris rufa).

    PubMed

    Pérez, J A; Alonso, M E; Prieto, R; Bartolomé, D; Gaudioso, D V R

    2010-01-01

    This study aimed to determine the influence of the breeding system on the escape response of red-legged partridges comparing 147 free-born partridges captured in the wild (W) and 164 partridges from a commercial hunting farm with an intensive production system (F). All birds were individually released to the natural environment using wooden cages; the escape response was recorded with a high resolution video camera and 4 behavior parameters were analyzed: reaction time or latency, escape type, angle at the moment of flight start, and distance flown. There were significant differences on the mean reaction time depending on the origin of the partridges: 0.43 s, with a maximum of 9 s, for the W and 52.90 s, with a maximum of 120 s, in 32.3% of the F birds. Only one of the W partridges (0.68%) escaped by walking, whereas all the other W birds, and 69.5% of the F partridges, flew; the differences in the type of escape reaction between origins were significant. Considering the angle of flight start, the differences were also significant because 98.6% of W partridges showed less than 45 degrees angles, whereas 37.7% of F birds showed angles of more than 45 degrees. Thus, we can conclude that the breeding system has a great influence on the escape response of the red-legged partridges. The intensive management production systems used on the commercial game farms produced obvious changes in the escape reaction of the red-legged partridges, and this could explain the low ability of these birds to integrate and to survive in the wild due to the high predation pressure they undergo when they are used in repopulation processes.

  19. Status report of a new recovery parachute system for the F111 aircraft crew escape module

    SciTech Connect

    Johnson, D.W.

    1986-01-01

    A new recovery parachute system for the F111 aircraft crew escape module has been designed. Six proof-of-design tests were conducted to determine if it is feasible to meet the requirements for a replacement recovery parachute system. The design of the proposed system is presented and the results of the tests discussed.

  20. Shuttle crew escape systems (CES) rocket test at Hurricane Mesa, Utah

    NASA Image and Video Library

    1987-11-12

    Shuttle crew escape systems (CES) tractor rocket tests conducted at Hurricane Mesa, Utah. This preliminary ground test of the tractor rocket will lead up to in-air evaluations. View shows tractor rocket as it is fired from side hatch mockup. The tractor rocket concept is one of two escape methods being studied to provide crew egress capability during Space Shuttle controlled gliding flight. In-air tests of the system, utilizing a Convair-240 aircraft, will begin 11-19-87 at the Naval Weapons Center in China Lake, California.

  1. 23. "GAFFTC 20 APR 60, H65A F106A; ESCAPE SYSTEM RUN ...

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

    23. "G-AFFTC 20 APR 60, H-6-5A F-106A; ESCAPE SYSTEM RUN 5A." Testing the ejection system on a Convair sled. - Edwards Air Force Base, South Base Sled Track, Edwards Air Force Base, North of Avenue B, between 100th & 140th Streets East, Lancaster, Los Angeles County, CA

  2. Role of the lateral line mechanosensory system in directionality of goldfish auditory evoked escape response

    PubMed Central

    Mirjany, Mana; Preuss, Thomas; Faber, Donald S.

    2011-01-01

    SUMMARY Goldfish (Carassius auratus) escape responses to sudden auditory stimuli are mediated by a pair of reticulospinal neurons, the Mauthner (M-) cells, which integrate mechanosensory inputs from the inner ear and the lateral line (LL) to initiate a fast directional response away from the aversive stimulus. This behavior is context dependent; when near an obstruction the fish may rather turn towards the sound to avoid hitting the object. Mechanisms underlying this directionality remain unknown. Here we investigate the contribution of the LL system to auditory evoked escapes and provide behavioral evidence that it transmits stimulus – and environmental-dependent information that determines the initial response direction of the escape. We quantified escape latency, probability and directionality following abrupt sound stimuli before and after removal of the entire LL with 0.03 mmol l–1 cobalt chloride (CoCl2), 0.002% gentamicin or selective posterior LL nerve (pLLn) transection. CoCl2 significantly increased escape onset latency without affecting probability and reduced open field directionality from 77% to chance, 52%. This effect on directionality was also observed with gentamicin. Transection of the pLLn had no effect on directionality, indicating the anterior LL nerve (aLLn) afferents are more likely to transmit directional information to the M-cell. When the fish were near a wall, the error rate was quadrupled by both CoCl2 and pLLn transection. Visual elimination had no influence on directionality unless combined with LL elimination. PMID:21957099

  3. Role of the lateral line mechanosensory system in directionality of goldfish auditory evoked escape response.

    PubMed

    Mirjany, Mana; Preuss, Thomas; Faber, Donald S

    2011-10-15

    Goldfish (Carassius auratus) escape responses to sudden auditory stimuli are mediated by a pair of reticulospinal neurons, the Mauthner (M-) cells, which integrate mechanosensory inputs from the inner ear and the lateral line (LL) to initiate a fast directional response away from the aversive stimulus. This behavior is context dependent; when near an obstruction the fish may rather turn towards the sound to avoid hitting the object. Mechanisms underlying this directionality remain unknown. Here we investigate the contribution of the LL system to auditory evoked escapes and provide behavioral evidence that it transmits stimulus - and environmental-dependent information that determines the initial response direction of the escape. We quantified escape latency, probability and directionality following abrupt sound stimuli before and after removal of the entire LL with 0.03 mmol l(-1) cobalt chloride (CoCl(2)), 0.002% gentamicin or selective posterior LL nerve (pLLn) transection. CoCl(2) significantly increased escape onset latency without affecting probability and reduced open field directionality from 77% to chance, 52%. This effect on directionality was also observed with gentamicin. Transection of the pLLn had no effect on directionality, indicating the anterior LL nerve (aLLn) afferents are more likely to transmit directional information to the M-cell. When the fish were near a wall, the error rate was quadrupled by both CoCl(2) and pLLn transection. Visual elimination had no influence on directionality unless combined with LL elimination.

  4. Low dose systemic morphine attenuates operant escape but facilitates innate reflex responses to thermal stimulation.

    PubMed

    Vierck, Charles J; Acosta-Rua, Antonio; Nelligan, Russell; Tester, Nicole; Mauderli, Andre

    2002-08-01

    Effects of systemic morphine on operant escape responses of rats to thermal stimulation were compared directly with effects on innate licking and guarding responses. For these independent tests, thermal stimulation was delivered via the floor of testing chambers with or without platforms that provided an escape option. The principal findings were (1) administration of 0.5 to 1.5 mg/kg morphine attenuated escape from nociceptive heat and (2) in distinct contrast, licking and guarding responses to heat were enhanced by these doses. When escape responding was calculated as time on the heated plate without licking or guarding, sensitivity to morphine was greater for 44 degrees C than for 47 degrees C or 50 degrees C. Also, escape responses to cold (0 degrees C or 10 degrees C) were unaffected by 1.5 mg/kg morphine. The preferential reduction of heat nociception by morphine was demonstrated also by an operant preference task that gave the animals the option of standing on a cold (10 degrees C) or a hot (45 degrees C) surface. Administration of 0.5 mg/kg morphine increased occupancy of the hot surface. Platform time during operant tests was low and variable for warm stimulation (36 degrees C) and was significantly increased by each level of heat, showing that platform occupancy represented escape from nociception rather than avoidance responses. A lack of significant effects of 1.5 mg/kg morphine on operant performance during cold or warm stimulation controls for effects of systemic morphine other than antinociception.

  5. ESCAPE: Eco-Behavioral System for Complex Assessments of Preschool Environments. Research Draft.

    ERIC Educational Resources Information Center

    Carta, Judith J.; And Others

    The manual details an observational code designed to track a child during an entire day in a preschool setting. The Eco-Behavioral System for Complex Assessments of Preschool Environments (ESCAPE) encompasses assessment of the following three major categories of variables with their respective subcategories: (1) ecological variables (designated…

  6. Hypervelocity Technology Escape System Concepts. Volume 1. Development and Evaluation

    DTIC Science & Technology

    1988-07-01

    the areas of virtual instrument technology, helmet-mounted display technology, voice interface technology and tactile data input technology, and...Instrumentation. The voice interface technology allows the pilot to simply talk to the flight director system and avionics system and the craft can respond to

  7. Pluto-Charon system - the escape of Charon's primordial atmosphere

    SciTech Connect

    Trafton, L.; Stern, S.A.; Gladstone, G.R.

    1988-04-01

    Although Charon seems to have lost its atmosphere and surface volatiles, a lack of heating that would be sufficient to generate melting and consequent separation of the lighter and heavier nonvolatiles has probably resulted in the outer layers' retention of the primordial mix of nonvolatiles. Spectroscopically-determined relative abundances for the Charon surface should accordingly be representative of its entire mass, and thereby constitutes the basis of an understanding of Charon's origin. The study of Charon's exposed nonvolatile ices may ascertain whether the Pluto-Charon system condensed out of the solar nebula directly or from a protoplanetary nebula. 46 references.

  8. Modeling cancer evolution: evolutionary escape under immune system control

    NASA Astrophysics Data System (ADS)

    Korobeinikov, Andrei; Starkov, Konstantin E.; Valle, Paul A.

    2017-02-01

    It can be expected that adequate immune response should be able to annihilate cancer at a very early stage of its appearance. However, in some cases cancer is able to persist avoiding immune response. One can conject that cancer is able to avoid immune response control due to a succession of mutations leading to the development of immune-resistant cells. In order to illustrate this possibility, in this paper we present a 2n-dimensional mathematical model that describes interaction of n subtypes of tumor cells with corresponding genotype-specific immune response. The model postulates that there is a probability for tumor cells of each of n subtype to produce offsprings of other types. Each of the subtypes activates the genotype-specific immune response with a possibility of suppressing cancer cells of other genotypes (the cross-immunity). Numerical simulations show that if cancer cells are able to mutate comparatively fast and if immune response is not strong enough, then, despite immune system pressure, cancer is able to persist.

  9. Tests for the joint evolution of mating system and drought escape in Mimulus.

    PubMed

    Ivey, Christopher T; Carr, David E

    2012-02-01

    Self-fertilizing taxa are often found at the range margins of their progenitors, where sub-optimal habitats may select for alternative physiological strategies. The extent to which self-fertilization is favoured directly vs. arising indirectly through correlations with other adaptive life history traits is unclear. Trait responses to selection depend on genetic variation and covariation, as well as phenotypic and genetic responses to altered environmental conditions. We tested predictions of the hypothesis that self-fertilization in Mimulus arises through direct selection on physiological and developmental traits that allow seasonal drought escape. Phenotypic selection on mating system and drought escape traits was estimated in field populations of M. guttatus. In addition, trait phenotype and phenotypic selection were compared between experimental wet and dry soil in two greenhouse populations each of M. guttatus and M. nasutus. Finally, genetic variation and covariation for traits were compared between wet and dry soil treatments in a greenhouse population of M. guttatus. Consistent with predictions, selection for early flowering was generally stronger than for mating system traits, and selection for early flowering was stronger in dry soil. Inconsistent with predictions, selection for water-use efficiency was largely absent; selection for large flowers was stronger than for drought escape in the field; and most drought escape and mating system traits were not genetically correlated. A positive genetic correlation between flowering time and flower size, which opposed the adaptive contour, emerged only in wet soil, suggesting that variation in water availability may maintain variation in these traits. Plastic responses to soil moisture treatments supported the idea that taxonomic divergence could have been facilitated by plasticity in flowering time and selfing. The hypothesis that plant mating systems may evolve indirectly via selection on correlated life history

  10. Crew escape system test at Naval Weapons Center, China Lake, California

    NASA Technical Reports Server (NTRS)

    1988-01-01

    As part of a crew escape system (CES) test program, a lifelike dummy is pulled by a tractor rocket from an airborne Convair-240 (C-240) aircraft at Naval Weapons Center, China Lake, California. A P-3 chase plane accompanies the C-240. The C-240 was modified with a space shuttle side hatch mockup for the tests which will evaluate candidate concepts developed to provide crew egress capability during Space Shuttle controlled gliding flight.

  11. Tests for the joint evolution of mating system and drought escape in Mimulus

    PubMed Central

    Ivey, Christopher T.; Carr, David E.

    2012-01-01

    Background and Aims Self-fertilizing taxa are often found at the range margins of their progenitors, where sub-optimal habitats may select for alternative physiological strategies. The extent to which self-fertilization is favoured directly vs. arising indirectly through correlations with other adaptive life history traits is unclear. Trait responses to selection depend on genetic variation and covariation, as well as phenotypic and genetic responses to altered environmental conditions. We tested predictions of the hypothesis that self-fertilization in Mimulus arises through direct selection on physiological and developmental traits that allow seasonal drought escape. Methods Phenotypic selection on mating system and drought escape traits was estimated in field populations of M. guttatus. In addition, trait phenotype and phenotypic selection were compared between experimental wet and dry soil in two greenhouse populations each of M. guttatus and M. nasutus. Finally, genetic variation and covariation for traits were compared between wet and dry soil treatments in a greenhouse population of M. guttatus. Key Results Consistent with predictions, selection for early flowering was generally stronger than for mating system traits, and selection for early flowering was stronger in dry soil. Inconsistent with predictions, selection for water-use efficiency was largely absent; selection for large flowers was stronger than for drought escape in the field; and most drought escape and mating system traits were not genetically correlated. A positive genetic correlation between flowering time and flower size, which opposed the adaptive contour, emerged only in wet soil, suggesting that variation in water availability may maintain variation in these traits. Plastic responses to soil moisture treatments supported the idea that taxonomic divergence could have been facilitated by plasticity in flowering time and selfing. Conclusions The hypothesis that plant mating systems may evolve

  12. Approach for Service Life Extension of Explosive Devices for Aircraft Escape Systems

    NASA Technical Reports Server (NTRS)

    Bement, L. J.; Schimmel, M. L.

    1985-01-01

    The service life evaluation of explosive devices used in a wide variety of aircraft escape systems is described. The purpose was to develop a service extension approach, supported by tests on candidate devices, to evaluate the effects of service, age, and degradation, and allow responsible, conservative, service life determinations. An overview is given on the recommended approach and experimental procedures for accurate service evaluations with test results on rigid and flexible explosive transfer lines, one-way transfers, and flexible linear shaped charges.

  13. Crew escape system test at Naval Weapons Center, China Lake, California

    NASA Technical Reports Server (NTRS)

    1988-01-01

    As part of a crew escape system (CES) test program, a lifelike dummy is pulled by a tractor rocket from an airborne Convair-240 (C-240) aircraft at Naval Weapons Center, China Lake, California. A P-3 chase plane accompanies the C-240. The C-240 was modified with a space shuttle side hatch mockup for the tests which will evaluate candidate concepts developed to provide crew egress capability during Space Shuttle controlled gliding flight.

  14. STS-45 payload specialists with crew escape system (CES) mockup at JSC's MAIL

    NASA Technical Reports Server (NTRS)

    1991-01-01

    STS-45 Atlantis, Orbiter Vehicle (OV) 104, payload specialists Byron K. Lichtenberg (left) and Dirk D. Frimout (European Space Agency (ESA) Belgian crewmember) practice crew escape system (CES) pole opeation using a side hatch mockup. Lichtenberg is engaging the handle which extends the CES pole out the side hatch. The payload specialists along with the other STS-45 crewmembers are participating in side hatch emergency egress exercises in JSC's Mockup and Integration Laboratory (MAIL) Bldg 9A.

  15. Using the Two-Burn Escape Maneuver for Fast Transfers in the Solar System and Beyond

    NASA Technical Reports Server (NTRS)

    Adams, Robert B.; Richardson, Georgia A.

    2010-01-01

    The two-burn maneuver to escape the gravitational pull of a central body is described. The maneuver, originally suggested by Hermann Oberth, improves efficiency considerably for a wide range of missions of interest in space exploration and scientific investigation. A clear delineation of when the maneuver is more effective is given, as are methods to extract the most advantage when using the maneuver. Some examples are given of how this maneuver can enable exploration of the outer solar system, near interstellar space, and crewed missions to Mars and beyond. The maneuver has the potential to halve the required infrastructure associated with a crewed mission to Mars and achieve increased solar escape velocities with existing spacecraft technologies.

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

    NASA Astrophysics Data System (ADS)

    Srokowski, Tomasz

    2016-06-01

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

  17. Expected value analysis for an unmanned expendable launch vehicle payload escape system

    NASA Astrophysics Data System (ADS)

    Wagner, Fred E.

    1987-12-01

    Since the beginning of the U.S. Space Program, there have been numerous schemes for humans to escape from spacecraft in distress. This has not been the case for payloads of unmanned, expendable launch vehicles (ELV). The literature review revealed no concepts or design in the U.S. Space Program for saving or salvaging unmanned payloads if an ELV failed during the boost phase. The purpose of this thesis was to develop a methodology to define a mathematical cost relation for a payload escape system (PES). That relation demonstrates when it is economically feasible to use a payload escape system. This methodology draws heavily upon Decision Analysis Techniques, although a classical decision analysis involving a decision maker was not performed. A mathematical relation was developed for two launch cases: the first assumed 100 percent insurance coverage for losses and the other assumed no insurance coverage for losses. The study found that the mathematical relations could be used to develop graphs defining when it is economically feasible to use a PES. The model is flexible and could be modified for use with a particular payload program.

  18. THE HYADES CLUSTER: IDENTIFICATION OF A PLANETARY SYSTEM AND ESCAPING WHITE DWARFS

    SciTech Connect

    Zuckerman, B.; Xu, S.; Klein, B.; Jura, M. E-mail: sxu@astro.ucla.edu E-mail: jura@astro.ucla.edu

    2013-06-20

    Recently, some hot DA-type white dwarfs have been proposed to plausibly be escaping members of the Hyades. We used hydrogen Balmer lines to measure the radial velocities of seven such stars and confirm that three, and perhaps two others, are/were indeed cluster members and one is not. The other candidate Hyad is strongly magnetic and its membership status remains uncertain. The photospheres of at least one quarter of field white dwarf stars are ''polluted'' by elements heavier than helium that have been accreted. These stars are orbited by extended planetary systems that contain both debris belts and major planets. We surveyed the seven classical single Hyades white dwarfs and the newly identified (escaping) Hyades white dwarfs and found calcium in the photosphere of LP 475-242 of type DBA (now DBAZ), thus implying the presence of an orbiting planetary system. The spectrum of white dwarf GD 31, which may be, but probably is not, an escaping member of the Hyades, displays calcium absorption lines; these originate either from the interstellar medium or, less likely, from a gaseous circumstellar disk. If GD 31 was once a Hyades member, then it would be the first identified white dwarf Hyad with a cooling age >340 Myr.

  19. Crossover of the Thermal Escape Problem in Annular Spatially Distributed Systems

    SciTech Connect

    Fedorov, Kirill G.; Pankratov, Andrey L.

    2009-12-31

    The computer simulations of fluctuational dynamics of an annular system governed by the sine-Gordon model with a white noise source are performed. It is demonstrated that the mean escape time (MET) of a phase string for an annular structure can be much larger than for a linear one and has a strongly pronounced maximum as a function of system's length. The location of the MET maximum roughly equals the size of the kink-antikink pair, which leads to evidence of a spatial crossover between two dynamical regimes: when the phase string escapes over the potential barrier as a whole and when the creation of kink-antikink pairs is the main mechanism of the escape process. For large lengths and in the limit of small noise intensity gamma, for both MET and inverse concentration of kinks, we observe the same dependence versus the kink energy E{sub k}: approxexp(2E{sub k}/gamma) for the annular structure and approxexp(E{sub k}/gamma) for the linear one.

  20. Crossover of the thermal escape problem in annular spatially distributed systems.

    PubMed

    Fedorov, Kirill G; Pankratov, Andrey L

    2009-12-31

    The computer simulations of fluctuational dynamics of an annular system governed by the sine-Gordon model with a white noise source are performed. It is demonstrated that the mean escape time (MET) of a phase string for an annular structure can be much larger than for a linear one and has a strongly pronounced maximum as a function of system's length. The location of the MET maximum roughly equals the size of the kink-antikink pair, which leads to evidence of a spatial crossover between two dynamical regimes: when the phase string escapes over the potential barrier as a whole and when the creation of kink-antikink pairs is the main mechanism of the escape process. For large lengths and in the limit of small noise intensity gamma, for both MET and inverse concentration of kinks, we observe the same dependence versus the kink energy E(k): approximately exp(2E(k)/gamma) for the annular structure and approximately exp(E(k)/gamma) for the linear one.

  1. Physical Theory of the Competition that Allows HIV to Escape from the Immune System

    NASA Astrophysics Data System (ADS)

    Wang, Guanyu; Deem, Michael W.

    2006-11-01

    Competition within the immune system may degrade immune control of viral infections. We formalize the evolution that occurs in both HIV-1 and the immune system quasispecies. Inclusion of competition in the immune system leads to a novel balance between the immune response and HIV-1, in which the eventual outcome is HIV-1 escape rather than control. The analytical model reproduces the three stages of HIV-1 infection. We propose a vaccine regimen that may be able to reduce competition between T cells, potentially eliminating the third stage of HIV-1.

  2. A Physical Theory of the Competition that Allows HIV to Escape from the Immune System

    NASA Astrophysics Data System (ADS)

    Deem, Michael

    2007-03-01

    Competition within the immune system may degrade immune control of viral infections. We formalize the evolution that occurs in both HIV-1 and the immune system quasispecies [1]. Inclusion of competition in the immune system leads to a novel balance between the immune response and HIV-1, in which the eventual outcome is HIV-1 escape rather than control. The analytical model reproduces the three stages of HIV-1 infection. We propose a vaccine regimen that may be able to reduce competition between T cells, potentially eliminating the third stage of HIV-1. 1) G. Wang and M. W. Deem, Phys. Rev. Lett. 97 (2006) 188106.

  3. A three body dynamic simulation of a seated tractor rocket escape system for the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Ondler, R. M.

    1989-01-01

    In the tractor-rocket seated-extraction candidate system for Space Shuttle Orbiter crew escape, the crewmember is pulled from his seat and away from the Orbiter via an elastic pendant, using a system of rails to guide the extraction trajectory through an opening on the window frame for flight deck crew and through the side hatch for the middeck crew. A three-body simulation has been developed to model the flight-mechanics aspects of the concept, where the three bodies are the astronaut (six DOF), the tractor rocket (six DOF), and the Shuttle Orbiter (three DOF); attention is given to crewmembers' clearance of the Orbiter structure and engine plumes.

  4. Rarefied gas dynamic simulation of transfer and escape in the Pluto-Charon system

    NASA Astrophysics Data System (ADS)

    Hoey, William A.; Yeoh, Seng Keat; Trafton, Laurence M.; Goldstein, David B.; Varghese, Philip L.

    2017-05-01

    NH encounter. Results computed from a fit to the NH encounter exobase (Gladstone et al., 2016) predict a system escape rate of 7 × 1025 CH4 s-1 in close agreement with those reported by NH (Bagenal et al., 2016; Gladstone et al., 2016), and a net depositional flux to Charon of 2 × 1024 s-1, of which ∼98% is methane.

  5. STS-45 payload specialists with crew escape system (CES) mockup at JSC's MAIL

    NASA Technical Reports Server (NTRS)

    1991-01-01

    STS-45 Atlantis, Orbiter Vehicle (OV) 104, Payload Specialist Dirk D. Frimout (European Space Agency (ESA) Belgian crewmember) (left), backup Payload Specialist Charles R. Chappell (center), and Payload Specialist Byron K. Lichtenberg (right) listen to technician explain the operation of the crew escape system (CES) pole. Frimout is engaging the handle which extends the CES pole out the side hatch. The payload specialists along with the other STS-45 crewmembers are participating in side hatch emergency egress exercises in JSC's Mockup and Integration Laboratory (MAIL) Bldg 9A.

  6. Dust escape from Io

    NASA Astrophysics Data System (ADS)

    Flandes, Alberto

    2004-08-01

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

  7. Age Life Evaluation of Space Shuttle Crew Escape System Pyrotechnic Components Loaded with Hexanitrostilbene (HNS)

    NASA Technical Reports Server (NTRS)

    Hoffman, William C., III

    1996-01-01

    Determining deterioration characteristics of the Space Shuttle crew escape system pyrotechnic components loaded with hexanitrostilbene would enable us to establish a hardware life-limit for these items, so we could better plan our equipment use and, possibly, extend the useful life of the hardware. We subjected components to accelerated-age environments to determine degradation characteristics and established a hardware life-limit based upon observed and calculated trends. We extracted samples using manufacturing lots currently installed in the Space Shuttle crew escape system and from other NASA programs. Hardware included in the study consisted of various forms and ages of mild detonating fuse, linear shaped charge, and flexible confined detonating cord. The hardware types were segregated into 5 groups. One was subjected to detonation velocity testing for a baseline. Two were first subjected to prolonged 155 F heat exposure, and the other two were first subjected to 255 F, before undergoing detonation velocity testing and/or chromatography analysis. Test results showed no measurable changes in performance to allow a prediction of an end of life given the storage and elevated temperature environments the hardware experiences. Given the lack of a definitive performance trend, coupled with previous tests on post-flight Space Shuttle hardware showing no significant changes in chemical purity or detonation velocity, we recommend a safe increase in the useful life of the hardware to 20 years, from the current maximum limits of 10 and 15 years, depending on the hardware.

  8. Preliminary Study for Manned Spacecraft with Escape System and H-IIB Rocket

    NASA Astrophysics Data System (ADS)

    Imada, Takane; Ito, Michio; Takata, Shinichi

    HTV (H-II Transfer Vehicle) is the first Japanese un-manned service vehicle that will transport several pieces of equipments to ISS (International Space Station) and support human activities on orbit. HTV will be launched by the first H-IIB rocket in September 2009 and JAXA will have the capability to access LEO (Low Earth Orbit) bases with enough volume/weight as the human transport system. This paper is the preliminary study for developing a manned spacecraft from the HTV design and includes clarification of necessary development items. In addition, missing parts in the current HTV design are identified with some analysis, such as LES (Launch Escape System), which is mandatory for all human transport systems.

  9. Approach for service life extension of explosive devices for aircraft escape systems

    NASA Technical Reports Server (NTRS)

    Bement, L. J.; Schimmel, M. L.

    1985-01-01

    Service life extension of explosive devices used in aircraft escape systems can achieve considerable savings. An overall approach is needed to challenge the logic of explosive component service extension from design to removal from service for evaluation. The purpose of the effort described in this paper was to develop a service-extension approach on explosive devices used in aircraft systems, supported by actual testing of representative candidate devices, to evaluate quantitatively the effects of service, age, and degradation, and allow responsible, conservative service life determinations. Evaluated were five explosive components: rigid and flexible explosive transfer lines, one-way transfers, flexible linear shaped charges, and initiation handles. The service extension approach generated in this effort is summarized by eight recommendations.

  10. PHYSIOLOGICAL EVALUATION OF THE ACED SUBMARINE ESCAPE SUIT-RAFT SYSTEM.

    DTIC Science & Technology

    SUBMARINE ESCAPE, *SEA RESCUE EQUIPMENT), LIFE RAFTS, PROTECTIVE CLOTHING, EXPOSURE(PHYSIOLOGY), WATER, TEMPERATURE, PHYSIOLOGY, TISSUES(BIOLOGY), DAMAGE, MORTALITY RATES , STRESS(PHYSIOLOGY), TOLERANCES(PHYSIOLOGY)

  11. Sensory-Motor Systems of Copepods involved in their Escape from Suction Feeding.

    PubMed

    Yen, Jeannette; Murphy, David W; Fan, Lin; Webster, Donald R

    2015-07-01

    Copepods escape well by detecting minute gradients in the flow field; they react quickly, and swim away strongly. As a key link in the aquatic food web, these small planktonic organisms often encounter suction-feeding fish. Studies have identified certain hydrodynamic features that are created by the approach of this visual predator and the generation of its suction flow for capturing food. Similarly, studies have identified certain hydrodynamic features that evoke the evasive response of copepods. This is a review of the copepod sensory motor system as pertains to understanding their response to suction-feeding fish. Analyses of the reaction time, threshold sensitivity, structure of sensors, and evasive behavior by this key prey of fish can be useful for evaluating the effectiveness of feeding tactics in response to suction flow. To illustrate, we present results comparing a copepod from a fishless lake (Hesperodiaptomus shoshone) to a copepod from a rich fishing ground (Calanus finmarchicus). We designed a flow mimic that produces a realistic mushroom-cap-shaped flow field and realistic accelerations of flow; the copepods treated the mimic as a threat and performed jumps directed up and away from the siphon. Calanus finmarchicus responded at an average threshold strain rate of 18.7/s, escaped at 0.46 m/s, and traveled 5.99 mm, most frequently as a single jump. Hesperodiaptomus shoshone responded at a strain rate of 15.1/s that is not significantly different, escaped more slowly at 0.22 m/s and traveled a shorter distance of 3.01 mm using a series of hops. The high variability noted in the initial angle of the body and the maximum change in body angle suggests that unpredictability in the escape maneuver is another aspect of the tactic of copepods. The speed of the escape by small copepods 2-3 mm long is overwhelmed by the speed of the attack by the much larger, faster fish; if the copepod reacts when it is within the fish's arena of capture (<1.5 mm from mouth

  12. Extension of service life of rigid transfer lines /SMDC/. [explosive components for aircraft escape systems

    NASA Technical Reports Server (NTRS)

    Bement, L. J.; Kayser, E. G.; Schimmel, M. L.

    1982-01-01

    The results of a life evaluation program on rigid explosive transfer lines, which are used to initiate aircraft emergency crew escape functions, are presented in order to provide quantitative information on rigid explosive transfer lines which can contribute to responsible, conservative, service life determinations. The program involved the development of a test methodology, testing of the three types of transfer lines in use in the U.S., testing of these lines following a repeat of the thermal test conducted in the original qualification, and conducting a degradation investigation. Results from the testing of more than 800 components showed that rigid explosive transfer lines were not affected by age, service, or a repeat of the thermal qualification tests on full-service lines. The explosive degradation limits were approximated and the mechanisms examined. It is concluded that the service lives of rigid explosive transfer lines should be considered for extension in order to provide cost savings and increased system reliability.

  13. Extension of service life of rigid transfer lines /SMDC/. [explosive components for aircraft escape systems

    NASA Technical Reports Server (NTRS)

    Bement, L. J.; Kayser, E. G.; Schimmel, M. L.

    1982-01-01

    The results of a life evaluation program on rigid explosive transfer lines, which are used to initiate aircraft emergency crew escape functions, are presented in order to provide quantitative information on rigid explosive transfer lines which can contribute to responsible, conservative, service life determinations. The program involved the development of a test methodology, testing of the three types of transfer lines in use in the U.S., testing of these lines following a repeat of the thermal test conducted in the original qualification, and conducting a degradation investigation. Results from the testing of more than 800 components showed that rigid explosive transfer lines were not affected by age, service, or a repeat of the thermal qualification tests on full-service lines. The explosive degradation limits were approximated and the mechanisms examined. It is concluded that the service lives of rigid explosive transfer lines should be considered for extension in order to provide cost savings and increased system reliability.

  14. Atmospheric escape from unmagnetized bodies

    NASA Astrophysics Data System (ADS)

    Brain, D. A.; Bagenal, F.; Ma, Y.-J.; Nilsson, H.; Stenberg Wieser, G.

    2016-12-01

    The upper atmospheres of unmagnetized solar system bodies interact more directly with their local plasma environment than their counterparts on magnetized bodies such as Earth. One consequence of this interaction is that atmospheric particles can gain energy from the flowing plasma, as well as solar photons, and escape to space. Escape proceeds through a number of different mechanisms that can remove neutral particles (Jeans escape, photochemical escape, and sputtering) and mechanisms that can remove ions (ion pickup, magnetic shear and tension-related escape, and pressure gradients). Here we discuss the plasma interactions and escape processes and rates from five solar system objects spanning 3 orders of magnitude in size: comets, Pluto, Titan, Mars, and Venus. We describe similarities and differences in escape for the different objects and provide four open questions that should be addressed in the coming years.

  15. The escape problem and stochastic resonance in a bistable system driven by fractional Gaussian noise

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Yan, Zhi; Liu, Xianbin

    2017-08-01

    In the present paper, for a symmetrical bistable system that is excited by a fractional Gaussian noise, via the examination upon the qualitative changes of the stationary probability densities, the phenomena of the noise induced transition and escape and the stochastic resonance, which is in the sense of that the particles oscillate between the double-well potential, are investigated. For a high noise intensity, the probability density function obtained by Monte Carlo method changes from bimodal to unimodal by decreasing the values of Hurst index H. However, in the low noise intensity regime the transition could not occur for all H. Based on numerical results we demonstrate the fact that the mean first passage time (MFPT) is dependent on the Hurst index H and the noise intensity D, and possesses an exponential form as T (D , H) =k1 (H) exp ⁡ (k2 (H) / D). In particular, with a higher noise intensity, T (D , H) represents itself as a monotonous increasing function of the MFPT with the increasing H, whereas it exhibits as a non-monotonic function of H in the low noise intensity regime. Finally, nonlinear response theory is applied to investigate the stochastic resonance induced by Hurst index H and noise intensity D, for which we find that only for low noise intensities the stochastic resonance exists via increasing Hurst index which means the effect of noise reduction. This phenomenon is quite different from the one of the classical case.

  16. Mechanisms of tumor escape from immune system: role of mesenchymal stromal cells.

    PubMed

    Poggi, Alessandro; Musso, Alessandra; Dapino, Irene; Zocchi, Maria Raffaella

    2014-01-01

    Tumor microenvironment represents the site where the tumor tries to survive and escape from immune system-mediated recognition. Indeed, to proliferate tumor cells can divert the immune response inducing the generation of myeloid derived suppressor cells and regulatory T cells which can limit the efficiency of effector antitumor lymphocytes in eliminating neoplastic cells. Many components of the tumor microenvironment can serve as a double sword for the tumor and the host. Several types of fibroblast-like cells, which herein we define mesenchymal stromal cells (MSC), secrete extracellular matrix components and surrounding the tumor mass can limit the expansion of the tumor. On the other hand, MSC can interfere with the immune recognition of tumor cells producing immunoregulatory cytokines as transforming growth factor (TGF)ß, releasing soluble ligands of the activating receptors expressed on cytolytic effector cells as decoy molecules, affecting the correct interaction among lymphocytes and tumor cells. MSC can also serve as target for the same anti-tumor effector lymphocytes or simply impede the interaction between these lymphocytes and neoplastic cells. Thus, several evidences point out the role of MSC, both in epithelial solid tumors and hematological malignancies, in regulating tumor cell growth and immune response. Herein, we review these evidences and suggest that MSC can be a suitable target for a more efficient anti-tumor therapy.

  17. Longitudinal and lateral-directional static aerodynamic characteristics of an unpowered escape system extraction rocket model with attached launch tubes

    NASA Technical Reports Server (NTRS)

    Huffman, J. K.; Fox, C. H., Jr.; Satterthwaite, R. E.

    1977-01-01

    An escape system extraction rocket proposed for use on the Rotor Systems Research Aircraft was tested at Mach numbers of 0.1 and 0.3 through an angle of attack range from -2 deg to 102 deg and an angle of sideslip range from 0 deg to 15 deg in the Langley 7- by 10-foot high speed tunnel. The data are presented without analysis.

  18. Hypervelocity Technology (HVT) crew escape

    NASA Technical Reports Server (NTRS)

    Jines, Lanny A.

    1987-01-01

    Conceptual designs are being investigated for escape systems applicable to hypervelocity technology class aerospace vehicles. The concepts selected for further development will provide survivable escape and recovery throughout all phases of flight. Sixteen conceptual escape systems were identified, of which two were viable. The study vehicles included a horizontally launched vehicle (HLV) and a vertically launched vehicle (VLV). Computer-aided design models of the candidate escape systems were developed. State-of-the-art or near-term enabling technologies were identified in such areas as propulsion, life support, thermal protection, and deceleration.

  19. Assessing Scientific and Technological Enquiry Skills at Age 11 Using the E-Scape System

    ERIC Educational Resources Information Center

    Davies, Dan; Collier, Chris; Howe, Alan

    2012-01-01

    This article reports on the outcomes from the "e-scape Primary Scientific and Technological Understanding Assessment Project" (2009-2010), which aimed to support primary teachers in developing valid portfolio-based tasks to assess pupils' scientific and technological enquiry skills at age 11. This was part of the wider…

  20. Assessing Scientific and Technological Enquiry Skills at Age 11 Using the E-Scape System

    ERIC Educational Resources Information Center

    Davies, Dan; Collier, Chris; Howe, Alan

    2012-01-01

    This article reports on the outcomes from the "e-scape Primary Scientific and Technological Understanding Assessment Project" (2009-2010), which aimed to support primary teachers in developing valid portfolio-based tasks to assess pupils' scientific and technological enquiry skills at age 11. This was part of the wider…

  1. Type III CRISPR-Cas systems can provide redundancy to counteract viral escape from type I systems

    PubMed Central

    Silas, Sukrit; Lucas-Elio, Patricia; Jackson, Simon A; Aroca-Crevillén, Alejandra; Hansen, Loren L; Fineran, Peter C

    2017-01-01

    CRISPR-Cas-mediated defense utilizes information stored as spacers in CRISPR arrays to defend against genetic invaders. We define the mode of target interference and role in antiviral defense for two CRISPR-Cas systems in Marinomonas mediterranea. One system (type I-F) targets DNA. A second system (type III-B) is broadly capable of acquiring spacers in either orientation from RNA and DNA, and exhibits transcription-dependent DNA interference. Examining resistance to phages isolated from Mediterranean seagrass meadows, we found that the type III-B machinery co-opts type I-F CRISPR-RNAs. Sequencing and infectivity assessments of related bacterial and phage strains suggests an ‘arms race’ in which phage escape from the type I-F system can be overcome through use of type I-F spacers by a horizontally-acquired type III-B system. We propose that the phage-host arms race can drive selection for horizontal uptake and maintenance of promiscuous type III interference modules that supplement existing host type I CRISPR-Cas systems. PMID:28826484

  2. Type III CRISPR-Cas systems can provide redundancy to counteract viral escape from type I systems.

    PubMed

    Silas, Sukrit; Lucas-Elio, Patricia; Jackson, Simon A; Aroca-Crevillén, Alejandra; Hansen, Loren L; Fineran, Peter C; Fire, Andrew Z; Sánchez-Amat, Antonio

    2017-08-17

    CRISPR-Cas-mediated defense utilizes information stored as spacers in CRISPR arrays to defend against genetic invaders. We define the mode of target interference and role in antiviral defense for two CRISPR-Cas systems in Marinomonas mediterranea. One system (type I-F) targets DNA. A second system (type III-B) is broadly capable of acquiring spacers in either orientation from RNA and DNA, and exhibits transcription-dependent DNA interference. Examining resistance to phages isolated from Mediterranean seagrass meadows, we found that the type III-B machinery co-opts type I-F CRISPR-RNAs. Sequencing and infectivity assessments of related bacterial and phage strains suggests an 'arms race' in which phage escape from the type I-F system can be overcome through use of type I-F spacers by a horizontally-acquired type III-B system. We propose that the phage-host arms race can drive selection for horizontal uptake and maintenance of promiscuous type III interference modules that supplement existing host type I CRISPR-Cas systems.

  3. [The Research for Trace Ammonia Escape Monitoring System Based on Tunable Diode Laser Absorption Spectroscopy].

    PubMed

    Zhang, Li-fang; Wang, Fei; Yu, Li-bin; Yan, Jian-hua; Cen, Ke-fa

    2015-06-01

    In order to on-line measure the trace ammonia slip of the commercial power plant in the future, this research seeks to measure the trace ammonia by using tunable diode laser absorption spectroscopy under ambient temperature and pressure, and at different temperatures, and the measuring temperature is about 650 K in the power plant. In recent years lasers have become commercially available in the near-infrared where the transitions are much stronger, and ammonia's spectroscopy is pretty complicated and the overlapping lines are difficult to resolve. A group of ammonia transitions near 4 433.5 cm(-1) in the v2 +v3 combination band have been thoroughly selected for detecting lower concentration by analyzing its absorption characteristic and considering other absorption interference in combustion gases where H2O and CO2 mole fraction are very large. To illustrate the potential for NH3 concentration measurements, predictions for NH3, H2O and CO2 are simultaneously simulated, NH3 absorption lines near 4 433.5 cm(-1) wavelength meet weaker H2O absorption than the commercial NH3 lines, and there is almost no CO2 absorption, all the parameters are based on the HITRAN database, and an improved detection limit was obtained for interference-free NH3 monitoring, this 2.25 μm band has line strengths several times larger than absorption lines in the 1.53 μm band which was often used by NH3 sensors for emission monitoring and analyzing. The measurement system was developed with a new Herriott cell and a heated gas cell realizing fast absorption measurements of high resolution, and combined with direct absorption and wavelenguh modulation based on tunable diode laser absorption spectroscopy at different temperatures. The lorentzian line shape is dominant at ambient temperature and pressure, and the estimated detectivity is approximately 0.225 x 10(-6) (SNR = 1) for the directed absorption spectroscopy, assuming a noise-equivalent absorbance of 1 x 10(-4). The heated cell

  4. Ion Escape Rates from Mars

    NASA Astrophysics Data System (ADS)

    Brain, Dave; McFadden, Jim; Halekas, Jasper; Connerney, Jack; Eparvier, Frank; Mitchell, Dave; Andersson, Laila; Jakosky, Bruce; Dong, Yaxue; Egan, Hilary; Weber, Tristan; Ma, Yingjuan; Dong, Chuanfei; Modolo, Ronan; Bougher, Steve; Luhmann, Janet

    2017-04-01

    The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been making science measurements of the Martian upper atmosphere and its escape to space since November 2014. A key part of this effort is the measurement of the escape rates of charged particles (ions) at present and over solar system history. The lack of a global dynamo magnetic field at Mars leaves its upper atmosphere more directly exposed to the impinging solar wind than magnetized planets such as Earth. For this reason it is thought that ion escape at Mars may have played a significant role in long term climate change. MAVEN measures escaping planetary ions directly, with high energy, mass, and time resolution. With more than two years of observations in hand, we will report the average ion escape rate and the spatial distribution of escaping ions as measured by MAVEN, including escape as a function of mass and energy. We will then report on the measured variability in ion escape rates with different drivers (e.g. solar EUV, solar wind pressure, etc.). We will use these results to provide an estimate of the total ion escape from Mars over billions of years, and discuss the implications for Mars and unmagnetized planets in general.

  5. A Biomedical Review of the U.S. Navy Submarine Escape System: 1996.

    DTIC Science & Technology

    2007-11-02

    navies conducting ascent training in preparation for actual escape STTe- \\a fdy °f thC JapanCSe MaritÜne Self-Defense Force traming, Ikeda and Oiwa...a. Each man hold his nose shut through the hood fabric. b. On the leader’s signal take a deep breath and hold it. c. Inflate the hoods instantly...d. Open the trunk BLOW rapidly and fully. e. Start continuous deep breaths while the trunk is being pressurized. f. Attempt to equalize at each

  6. Testing of a new recovery parachute system for the F111 aircraft crew escape module: An update

    SciTech Connect

    Johnson, D.W.

    1989-01-01

    A new recovery parachute system has been designed for the F111 crew escape module (CEM). The system includes a cluster of three 49-ft-dia ringslot-solid parachutes, a Kevlar deployment bag, and an explosively fired drogue gun to deploy the pilot parachute. Tests have been conducted that indicate the parachute system will meet the rate of descent requirement of 25 ft/sec at 5000 ft pressure altitude. To control the drag load developed by the parachutes, a new central reefing/disreefing system has been developed. Since the recovery parachute system is normally deployed crosswind from the CEM, line sail of the suspension lines during early tests was a problem but has been minimized by a dual pilot parachute system. 6 refs., 7 figs.

  7. 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.

  8. Francisella requires dynamic type VI secretion system and ClpB to deliver effectors for phagosomal escape

    PubMed Central

    Brodmann, Maj; Dreier, Roland F.; Broz, Petr; Basler, Marek

    2017-01-01

    Francisella tularensis is an intracellular pathogen that causes the fatal zoonotic disease tularaemia. Critical for its pathogenesis is the ability of the phagocytosed bacteria to escape into the cell cytosol. For this, the bacteria use a non-canonical type VI secretion system (T6SS) encoded on the Francisella pathogenicity island (FPI). Here we show that in F. novicida T6SS assembly initiates at the bacterial poles both in vitro and within infected macrophages. T6SS dynamics and function depends on the general purpose ClpB unfoldase, which specifically colocalizes with contracted sheaths and is required for their disassembly. T6SS assembly depends on iglF, iglG, iglI and iglJ, whereas pdpC, pdpD, pdpE and anmK are dispensable. Importantly, strains lacking pdpC and pdpD are unable to escape from phagosome, activate AIM2 inflammasome or cause disease in mice. This suggests that PdpC and PdpD are T6SS effectors involved in phagosome rupture. PMID:28621333

  9. Quantifying model uncertainty in dynamical systems driven by non-Gaussian Lévy stable noise with observations on mean exit time or escape probability

    NASA Astrophysics Data System (ADS)

    Gao, Ting; Duan, Jinqiao

    2016-10-01

    Complex systems are sometimes subject to non-Gaussian α-stable Lévy fluctuations. A new method is devised to estimate the uncertain parameter α and other system parameters, using observations on mean exit time or escape probability for the system evolution. It is based on solving an inverse problem for a deterministic, nonlocal partial differential equation via numerical optimization. The existing methods for estimating parameters require observations on system state sample paths for long time periods or probability densities at large spatial ranges. The method proposed here, instead, requires observations on mean exit time or escape probability only for an arbitrarily small spatial domain. This new method is beneficial to systems for which mean exit time or escape probability is feasible to observe.

  10. The great escape: An intra-Messinian gas system in the eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Lazar, Michael; Schattner, Uri; Reshef, Moshe

    2012-10-01

    This study explores, for the first time, the response of the Mediterranean seafloor to desiccation and its affect on climate during the Messinian lowstand. New high-resolution 3-D pre-stack depth migrated seismic reflection data show evidence for gas outflow stemming from pre-Messinian sources. Our results indicate that giant pockmarks formed during this lowstand. Emission continued throughout the Messinian and persisted after it ended as evident by pockmark arrays on the then-seafloor. High reflectivity between the top-Messinian and overlying Pliocene sediments indicates significant gas accumulation immediately below the latter. Attribute analysis show minor chaotic paths through the Plio-Pleistocene, which do not reach the present-day seafloor. Our data indicate that as long as sea level was low there was massive gas escape to the shallow sea and atmosphere. We suggest that this probably resulted in the mid-Messinian climatic shift. Major emissions identified here indicate an indirect cause to negative climatic feedback during this period.

  11. De-submergence responses of antioxidative defense systems in two wetland plants having escape and quiescence strategies.

    PubMed

    Luo, Fang-Li; Thiele, Björn; Janzik, Ingar; Zeng, Bo; Schurr, Ulrich; Matsubara, Shizue

    2012-11-15

    Fast recovery after de-submergence requires efficient protection against oxidative injuries. We investigated whether de-submergence responses of antioxidant systems differ in two wetland plants, Alternanthera philoxeroides and Hemarthria altissima, characterized by 'escape' and 'quiescence' strategies of flood tolerance, respectively. The antioxidant capacity was assessed in the two species during 10d of recovery following 20d of complete submergence (low light+low O(2)) or severe shading (low light+ambient O(2)). The activities of superoxide dismutase and catalase were measured in leaf and root tissues, along with the concentrations of reduced ascorbate, malondialdehyde, and acetaldehyde. In addition, formation of superoxide (O(2)(-)) and hydrogen peroxide (H(2)O(2)) was detected in leaves by chemical staining. Following de-submergence, plants of A. philoxeroides showed a transient burst of acetaldehyde, while the concentration of acetaldehyde increased slowly and stayed high in leaves of H. altissima. In leaves of A. philoxeroides, the variations in O(2)(-) and H(2)O(2) correlated with the levels of light and O(2), respectively, whereas neither of the two reactive oxygen species was detected in H. altissima. For A. philoxeroides, the antioxidant capacities changed mainly in leaves during the recovery. For H. altissima, changes in reduced ascorbate were found in leaves and those of antioxidant enzyme activities in roots. De-submergence caused some lipid peroxidation in leaves of both species. We conclude that de-submergence responses of the detoxification systems differ between A. philoxeroides and H. altissima, especially in leaves. Dynamic changes were found in A. philoxeroides (having the escape strategy), as opposed to little or slow changes in H. altissima (having the quiescence strategy). Whereas the antioxidant capacities are often strongly influenced by light environments, the toxic compounds and lipid peroxidation indicate harmful effects of changing O(2

  12. Enhanced endosomal/lysosomal escape by distearoyl phosphoethanolamine-polycarboxybetaine lipid for systemic delivery of siRNA.

    PubMed

    Li, Yan; Cheng, Qiang; Jiang, Qian; Huang, Yuanyu; Liu, Hongmei; Zhao, Yuliang; Cao, Weipeng; Ma, Guanghui; Dai, Fengying; Liang, Xingjie; Liang, Zicai; Zhang, Xin

    2014-02-28

    Cationic liposome based siRNA delivery system has improved the efficiencies of siRNA. However, cationic liposomes are prone to be rapidly cleared by the reticuloendothelial system (RES). Although modification of cationic liposomes with polyethylene glycol (PEG) could prolong circulation lifetime, PEG significantly inhibits siRNA entrapment efficiency, cellular uptake and endosomal/lysosomal escape process, resulting in low gene silencing efficiency of siRNA. In this study, we report the synthesis of zwitterionic polycarboxybetaine (PCB) based distearoyl phosphoethanolamine-polycarboxybetaine (DSPE-PCB) lipid for cationic liposome modification. The DSPE-PCB20 cationic liposome/siRNA complexes (lipoplexes) show an excellent stability in serum medium. The siRNA encapsulation efficiency of DSPE-PCB20 lipoplexes could reach 92% at N/P ratio of 20/1, but only 73% for DSPE-PEG lipoplexes. The zeta potential of DSPE-PCB20 lipoplexes is 8.19±0.53mV at pH 7.4, and increases to 24.6±0.87mV when the pH value is decreased to 4.5, which promotes the endosomal/lysosomal escape of siRNA. The DSPE-PCB20 modification could enhance the silencing efficiency of siRNA by approximately 20% over the DSPE-PEG 2000 lipoplexes at the same N/P ratio in vitro. Furthermore, DSPE-PCB20 lipoplexes could efficiently mediate the down-regulation of Apolipoprotein B (ApoB) mRNA in the liver and consequently decrease the total cholesterol in the serum in vivo, suggesting therapeutic potentials for siRNA delivery in hypercholesterolemia-related diseases. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. In-Flight Operation of the Dawn Ion Propulsion System Through the Preparations for Escape From Vesta

    NASA Technical Reports Server (NTRS)

    Garner, Charles E.; Rayman, Marc D.; Brophy, John R.; Mikes, Steven C.

    2012-01-01

    The Dawn mission, part of NASA's Discovery Program, has as its goal the scientific exploration of the two most massive main-belt asteroids, 4 Vesta, and the dwarf planet 1 Ceres. The Dawn spacecraft was launched from the Cape Canaveral Air Force Station on September 27, 2007 on a Delta-II 7925H-9.5 rocket that placed the 1218-kg spacecraft into an Earth-escape trajectory. On-board the spacecraft is an ion propulsion system (IPS) developed at the Jet Propulsion Laboratory which will provide a total delta-V of approximately 11 km/s for the heliocentric transfer to Vesta, orbit capture at Vesta, transfer between Vesta science orbits, departure and escape from Vesta, heliocentric transfer to Ceres, orbit capture at Ceres, transfer between Ceres science orbits, and orbit maintenance maneuvers for all Vesta and Ceres science orbits. Full-power thrusting from December 2007 through October 2008 was used to successfully target a Mars gravity assist flyby in February 2009 that provided an additional delta-V of 2.6 km/s. Deterministic thrusting for the heliocentric transfer to Vesta resumed in June 2009 and concluded with orbit capture at Vesta on July 16, 2011. An additional 231 hours of IPS thrusting was used to enter the first Vesta science orbit, called Survey orbit, on August 3, 2011 at an altitude of about 2,735 km. The IPS was then used over the next year to transfer the spacecraft to the other science orbits: a high altitude mapping orbit (HAMO-1) in September 2011 at an altitude of approximately 673 km, a low altitude mapping orbit (LAMO) at approximately 210 km altitude, and a second high altitude mapping orbit (HAMO-2) at approximately 673 km altitude. To date the IPS has been operated for approximately 24,327 hours, consumed approximately 260 kg of xenon, and provided a delta-V of approximately 7 km/s. IPS performance characteristics are very close to the expected performance based on analysis and testing performed pre-launch. Thrusting for escape from Vesta and

  14. In-Flight Operation of the Dawn Ion Propulsion System Through the Preparations for Escape From Vesta

    NASA Technical Reports Server (NTRS)

    Garner, Charles E.; Rayman, Marc D.; Brophy, John R.; Mikes, Steven C.

    2012-01-01

    The Dawn mission, part of NASA's Discovery Program, has as its goal the scientific exploration of the two most massive main-belt asteroids, 4 Vesta, and the dwarf planet 1 Ceres. The Dawn spacecraft was launched from the Cape Canaveral Air Force Station on September 27, 2007 on a Delta-II 7925H-9.5 rocket that placed the 1218-kg spacecraft into an Earth-escape trajectory. On-board the spacecraft is an ion propulsion system (IPS) developed at the Jet Propulsion Laboratory which will provide a total delta-V of approximately 11 km/s for the heliocentric transfer to Vesta, orbit capture at Vesta, transfer between Vesta science orbits, departure and escape from Vesta, heliocentric transfer to Ceres, orbit capture at Ceres, transfer between Ceres science orbits, and orbit maintenance maneuvers for all Vesta and Ceres science orbits. Full-power thrusting from December 2007 through October 2008 was used to successfully target a Mars gravity assist flyby in February 2009 that provided an additional delta-V of 2.6 km/s. Deterministic thrusting for the heliocentric transfer to Vesta resumed in June 2009 and concluded with orbit capture at Vesta on July 16, 2011. An additional 231 hours of IPS thrusting was used to enter the first Vesta science orbit, called Survey orbit, on August 3, 2011 at an altitude of about 2,735 km. The IPS was then used over the next year to transfer the spacecraft to the other science orbits: a high altitude mapping orbit (HAMO-1) in September 2011 at an altitude of approximately 673 km, a low altitude mapping orbit (LAMO) at approximately 210 km altitude, and a second high altitude mapping orbit (HAMO-2) at approximately 673 km altitude. To date the IPS has been operated for approximately 24,327 hours, consumed approximately 260 kg of xenon, and provided a delta-V of approximately 7 km/s. IPS performance characteristics are very close to the expected performance based on analysis and testing performed pre-launch. Thrusting for escape from Vesta and

  15. Expected Value Analysis for an Unmanned Expendable Launch Vehicle Payload Escape System

    DTIC Science & Technology

    1987-12-01

    68 i V List of Figures Figure Page 2.1 Apollo Spacecraft . . . . . . . . . . . . . . . . 10 2.2 Paraglider Recovery...few cm/s at the moment of contact" (17t5). Paraglider System. Crawford and MoNerney discuss Space-General Corporation’s study of three applications of... paragliders as recovery systems (4:293). The first, was a paraglider assembly designed to recover the Saturn SI-C 10 I booster. The second, a system

  16. 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.

  17. Emergency escape system uses self-braking mechanism on fixed cable

    NASA Technical Reports Server (NTRS)

    Billings, C. R.; Mc Daris, R. A.; Mc Gough, J. T.; Neal, P. F.

    1966-01-01

    Slide-wire system with a twist level slide device incorporates automatic descent and braking for the safe and rapid evacuation of personnel from tall structures. This device is used on any tall structure that might require emergency evacuation. It is also used to transfer materials and equipment.

  18. Robust HCV Genotype 3a Infectious Cell Culture System Permits Identification of Escape Variants With Resistance to Sofosbuvir.

    PubMed

    Ramirez, Santseharay; Mikkelsen, Lotte S; Gottwein, Judith M; Bukh, Jens

    2016-11-01

    developed a system for highly efficient culture of HCV genotype 3a. Genotype 1a has a high genetic barrier to resistance for sofosbuvir, whereas resistance to this DAA can be induced in genotype 3a. We therefore isolated HCV genotype 3a variants with reduced sensitivity to sofosbuvir, with increased fitness and with cross-resistance to other NS5B inhibitors. These findings indicate that sofosbuvir escape variants could compromise the effectiveness of nucleotide analogs against HCV. GenBank accession numbers: KX280712-KX280716. Copyright © 2016 AGA Institute. Published by Elsevier Inc. All rights reserved.

  19. A Generalized Escape System Simulation Computer Program: A User’s Manual.

    DTIC Science & Technology

    1981-08-01

    PAII/Ls Flo.4 ft (met) length of rails XMeR *To Be Aded Later XPOSLRE FI . 4 ft (met) X - position of left rail attadirrt point in ACS XPOSRRE Fi0.4...burn tine for rocket 5 06 FI .4 secs bun tine for rocket 6 13 N.A. roket 1 ignition flag 0, 1 0 =>rocket ignition is a tine I = > rocket ignition is...0.14-0.15 D-20 * -- - - - - -- - - - - NADC-81224-60 ( 1. Control Data Cyber 70 Series Modes 72/73/74 6000 Series Corputer Systems KRONOS 2.1

  20. Bacteriophage ΦM1 of Pectobacterium evolves to escape two bifunctional Type III toxin-antitoxin and abortive infection systems through mutations in a single viral gene.

    PubMed

    Blower, Tim R; Chai, Ray; Przybilski, Rita; Chindhy, Shahzad; Fang, Xinzhe; Kidman, Samuel E; Tan, Hui; Luisi, Ben F; Fineran, Peter C; Salmond, George P C

    2017-02-03

    Some bacteria, when infected by their viral parasites (bacteriophages), undergo a suicidal response that also terminates productive viral replication (abortive infection; Abi). This response can be viewed as an altruistic act protecting the uninfected bacterial clonal population. Abortive infection can occur through the action of Type III protein-RNA toxin-antitoxin (TA) systems, such as ToxINPa from the phytopathogen, Pectobacterium atrosepticum Rare spontaneous mutants evolved in the generalized transducing phage, ΦM1, which escaped ToxINPa-mediated abortive infection in P. atrosepticum ΦM1 is a member of the Podoviridae and member of the "KMV-like viruses", a subset of the T7 supergroup. Genomic sequencing of ΦM1 escape mutants revealed single-base changes which clustered in a single open reading frame. The "escape" gene product, M1-23, was highly toxic to the host bacterium when over-expressed, but mutations in M1-23 that enabled an escape phenotype caused M1-23 to be less toxic. M1-23 is encoded within the DNA metabolism modular section of the phage genome, and when it was over-expressed, it co-purified with the host nucleotide excision repair protein, UvrA. While the M1-23 protein interacted with UvrA in co-immunoprecipitation assays, a UvrA mutant strain still aborted ΦM1, suggesting that the interaction is not critical for the Type III TA Abi activity. Additionally, ΦM1 escaped a heterologous Type III TA system (TenpINPl) from Photorhabdus luminescens (reconstituted in P. atrosepticum) through mutations in the same protein, M1-23. The mechanistic action of M1-23 is currently unknown but further analysis of this protein could provide insights into the mode of activation of both systems.

  1. Air Pollution from Road Traffic and Systemic Inflammation in Adults: A Cross-Sectional Analysis in the European ESCAPE Project.

    PubMed

    Lanki, Timo; Hampel, Regina; Tiittanen, Pekka; Andrich, Silke; Beelen, Rob; Brunekreef, Bert; Dratva, Julia; De Faire, Ulf; Fuks, Kateryna B; Hoffmann, Barbara; Imboden, Medea; Jousilahti, Pekka; Koenig, Wolfgang; Mahabadi, Amir A; Künzli, Nino; Pedersen, Nancy L; Penell, Johanna; Pershagen, Göran; Probst-Hensch, Nicole M; Schaffner, Emmanuel; Schindler, Christian; Sugiri, Dorothea; Swart, Wim J R; Tsai, Ming-Yi; Turunen, Anu W; Weinmayr, Gudrun; Wolf, Kathrin; Yli-Tuomi, Tarja; Peters, Annette

    2015-08-01

    Exposure to particulate matter air pollution (PM) has been associated with cardiovascular diseases. In this study we evaluated whether annual exposure to ambient air pollution is associated with systemic inflammation, which is hypothesized to be an intermediate step to cardiovascular disease. Six cohorts of adults from Central and Northern Europe were used in this cross-sectional study as part of the larger ESCAPE project (European Study of Cohorts for Air Pollution Effects). Data on levels of blood markers for systemic inflammation-high-sensitivity C-reactive protein (CRP) and fibrinogen-were available for 22,561 and 17,428 persons, respectively. Land use regression models were used to estimate cohort participants' long-term exposure to various size fractions of PM, soot, and nitrogen oxides (NOx). In addition, traffic intensity on the closest street and traffic load within 100 m from home were used as indicators of traffic air pollution exposure. Particulate air pollution was not associated with systemic inflammation. However, cohort participants living on a busy (> 10,000 vehicles/day) road had elevated CRP values (10.2%; 95% CI: 2.4, 18.8%, compared with persons living on a quiet residential street with < 1,000 vehicles/day). Annual NOx concentration was also positively associated with levels of CRP (3.2%; 95% CI: 0.3, 6.1 per 20 μg/m3), but the effect estimate was more sensitive to model adjustments. For fibrinogen, no consistent associations were observed. Living close to busy traffic was associated with increased CRP concentrations, a known risk factor for cardiovascular diseases. However, it remains unclear which specific air pollutants are responsible for the association.

  2. Escape from Tumor Cell Dormancy

    DTIC Science & Technology

    2012-10-01

    3 ESCAPE FROM TUMOR CELL DORMANCY An Organotypic Liver System to Study Tumor Cell Dormancy Alan Wells and Donna Stolz (UPitt), Linda Griffith (MIT...insights into dormancy and the transition that heralds metastatic emergenceis due mainly to the lack of tractable experimental systems with which to... systems are being optimized in others. The main efforts during the first year of this two-year project have been focused on the establishing the

  3. Atmospheric escape, redox evolution, and planetary habitability

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  4. Escape from Vela X

    SciTech Connect

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

    2012-02-15

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

  5. ESCAPE FROM VELA X

    SciTech Connect

    Hinton, J. A.; Ohm, S.; Funk, S.; Parsons, R. D.

    2011-12-10

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

  6. THERMALLY DRIVEN ATMOSPHERIC ESCAPE

    SciTech Connect

    Johnson, Robert E.

    2010-06-20

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

  7. 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.

  8. Exposure to Melan-A/MART-126-35 tumor epitope specific CD8(+)T cells reveals immune escape by affecting the ubiquitin-proteasome system (UPS).

    PubMed

    Ebstein, Frédéric; Keller, Martin; Paschen, Annette; Walden, Peter; Seeger, Michael; Bürger, Elke; Krüger, Elke; Schadendorf, Dirk; Kloetzel, Peter-M; Seifert, Ulrike

    2016-05-04

    Efficient processing of target antigens by the ubiquitin-proteasome-system (UPS) is essential for treatment of cancers by T cell therapies. However, immune escape due to altered expression of IFN-γ-inducible components of the antigen presentation machinery and consequent inefficient processing of HLA-dependent tumor epitopes can be one important reason for failure of such therapies. Here, we show that short-term co-culture of Melan-A/MART-1 tumor antigen-expressing melanoma cells with Melan-A/MART-126-35-specific cytotoxic T lymphocytes (CTL) led to resistance against CTL-induced lysis because of impaired Melan-A/MART-126-35 epitope processing. Interestingly, deregulation of p97/VCP expression, which is an IFN-γ-independent component of the UPS and part of the ER-dependent protein degradation pathway (ERAD), was found to be essentially involved in the observed immune escape. In support, our data demonstrate that re-expression of p97/VCP in Melan-A/MART-126-35 CTL-resistant melanoma cells completely restored immune recognition by Melan-A/MART-126-35 CTL. In conclusion, our experiments show that impaired expression of IFN-γ-independent components of the UPS can exert rapid immune evasion of tumor cells and suggest that tumor antigens processed by distinct UPS degradation pathways should be simultaneously targeted in T cell therapies to restrict the likelihood of immune evasion due to impaired antigen processing.

  9. Exposure to Melan-A/MART-126-35 tumor epitope specific CD8+T cells reveals immune escape by affecting the ubiquitin-proteasome system (UPS)

    PubMed Central

    Ebstein, Frédéric; Keller, Martin; Paschen, Annette; Walden, Peter; Seeger, Michael; Bürger, Elke; Krüger, Elke; Schadendorf, Dirk; Kloetzel, Peter-M.; Seifert, Ulrike

    2016-01-01

    Efficient processing of target antigens by the ubiquitin-proteasome-system (UPS) is essential for treatment of cancers by T cell therapies. However, immune escape due to altered expression of IFN-γ-inducible components of the antigen presentation machinery and consequent inefficient processing of HLA-dependent tumor epitopes can be one important reason for failure of such therapies. Here, we show that short-term co-culture of Melan-A/MART-1 tumor antigen-expressing melanoma cells with Melan-A/MART-126-35-specific cytotoxic T lymphocytes (CTL) led to resistance against CTL-induced lysis because of impaired Melan-A/MART-126-35 epitope processing. Interestingly, deregulation of p97/VCP expression, which is an IFN-γ-independent component of the UPS and part of the ER-dependent protein degradation pathway (ERAD), was found to be essentially involved in the observed immune escape. In support, our data demonstrate that re-expression of p97/VCP in Melan-A/MART-126-35 CTL-resistant melanoma cells completely restored immune recognition by Melan-A/MART-126-35 CTL. In conclusion, our experiments show that impaired expression of IFN-γ-independent components of the UPS can exert rapid immune evasion of tumor cells and suggest that tumor antigens processed by distinct UPS degradation pathways should be simultaneously targeted in T cell therapies to restrict the likelihood of immune evasion due to impaired antigen processing. PMID:27143649

  10. Retrograde air escape via the nasolacrimal system: a previously unrecognized complication of continuous positive airway pressure in the management of obstructive sleep apnea.

    PubMed

    Singh, Narinder Pal; Walker, Robbie James Eades; Cowan, Fiona; Davidson, Arthur Craig; Roberts, David Newton

    2014-05-01

    Continuous positive airway pressure (CPAP) is the gold standard treatment for moderate to severe obstructive sleep apnoea (OSA). Eye-related side effects of CPAP are commonly attributed to a poorly sealed mask, allowing leaked air to blow over the eye. We present 3 cases where attended polysomnography (A-PSG) demonstrated CPAP-associated retrograde air escape via the nasolacrimal system (CRANS) in the absence of any mask leaks. Symptoms included dry eye, epiphora, air escape from the medial canthus, and eyelid flutter. Symptoms were controlled with a variety of surgical and nonsurgical techniques. CRANS represents a previously undescribed clinical entity. CRANS may be responsible for some CPAP-related eye side effects and possibly for rarer secondary eye complications, including conjunctivitis and corneal ulceration. CRANS should be suspected in any patient on CPAP complaining of eye symptoms. CRANS may be diagnosed through careful observation during A-PSG and confirmed by performing a "saline bubble test." Management options include nonsurgical (mask alternatives, humidification, nasopharyngeal airway) and surgical techniques (nasal airway surgery, inferior turbinate out-fracture and adhesion, injection of bulking agent around Hasner's valve).

  11. Geometry of escaping dynamics in nonlinear ship motion

    NASA Astrophysics Data System (ADS)

    Naik, Shibabrat; Ross, Shane D.

    2017-06-01

    Escape from a potential well is a paradigm to understand critical events in chemical physics, celestial mechanics, structural mechanics, and ship dynamics, to name but a few. The consequences of escape could be desirable or undesirable depending on the specific problem at hand, however, the general question is how escape occurs and the effects of environmental noise on the escape. In this article, we answer the first question by discovering the phase space structures that lead to escape and the second question by investigating the effects of random forcing on these structures in the context of ship dynamics and capsize. The phase space structures that lead to escape are the tube manifolds associated to the rank-1 saddles in the conservative system. They are also robust in the sense of predicting high probability regions of escape even in the presence of random forcing.

  12. Submarine tower escape decompression sickness risk estimation.

    PubMed

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

    2014-01-01

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

  13. Polymer escape from a confining potential

    SciTech Connect

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

    2014-02-07

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

  14. PROPERTIES OF QSO METAL-LINE ABSORPTION SYSTEMS AT HIGH REDSHIFTS: NATURE AND EVOLUTION OF THE ABSORBERS AND NEW EVIDENCE ON ESCAPE OF IONIZING RADIATION FROM GALAXIES

    SciTech Connect

    Boksenberg, Alec; Sargent, Wallace L. W.

    2015-05-15

    Using Voigt-profile-fitting procedures on Keck High Resolution Spectrograph spectra of nine QSOs, we identify 1099 C IV absorber components clumped in 201 systems outside the Lyman forest over 1.6 ≲ z ≲ 4.4. With associated Si IV, C II, Si II  and N V where available, we investigate the bulk statistical and ionization properties of the components and systems and find no significant change in redshift for C IV and Si IV while C II, Si II  and N V change substantially. The C IV components exhibit strong clustering, but no clustering is detected for systems on scales from 150 km s{sup –1} out to 50,000 km s{sup –1}. We conclude that the clustering is due entirely to the peculiar velocities of gas present in the circumgalactic media of galaxies. Using specific combinations of ionic ratios, we compare our observations with model ionization predictions for absorbers exposed to the metagalactic ionizing radiation background augmented by proximity radiation from their associated galaxies and find that the generally accepted means of radiative escape by transparent channels from the internal star-forming sites is spectrally not viable for our stronger absorbers. We develop an active scenario based on runaway stars with resulting changes in the efflux of radiation that naturally enable the needed spectral convergence, and in turn provide empirical indicators of morphological evolution in the associated galaxies. Together with a coexisting population of relatively compact galaxies indicated by the weaker absorbers in our sample, the collective escape of radiation is sufficient to maintain the intergalactic medium ionized over the full range 1.9 < z ≲ 4.4.

  15. Properties of QSO Metal-line Absorption Systems at High Redshifts: Nature and Evolution of the Absorbers and New Evidence on Escape of Ionizing Radiation from Galaxies

    NASA Astrophysics Data System (ADS)

    Boksenberg, Alec; Sargent, Wallace L. W.

    2015-05-01

    Using Voigt-profile-fitting procedures on Keck High Resolution Spectrograph spectra of nine QSOs, we identify 1099 C IV absorber components clumped in 201 systems outside the Lyman forest over 1.6 <~ z <~ 4.4. With associated Si IV, C II, Si II and N V where available, we investigate the bulk statistical and ionization properties of the components and systems and find no significant change in redshift for C IV and Si IV while C II, Si II and N V change substantially. The C IV components exhibit strong clustering, but no clustering is detected for systems on scales from 150 km s-1 out to 50,000 km s-1. We conclude that the clustering is due entirely to the peculiar velocities of gas present in the circumgalactic media of galaxies. Using specific combinations of ionic ratios, we compare our observations with model ionization predictions for absorbers exposed to the metagalactic ionizing radiation background augmented by proximity radiation from their associated galaxies and find that the generally accepted means of radiative escape by transparent channels from the internal star-forming sites is spectrally not viable for our stronger absorbers. We develop an active scenario based on runaway stars with resulting changes in the efflux of radiation that naturally enable the needed spectral convergence, and in turn provide empirical indicators of morphological evolution in the associated galaxies. Together with a coexisting population of relatively compact galaxies indicated by the weaker absorbers in our sample, the collective escape of radiation is sufficient to maintain the intergalactic medium ionized over the full range 1.9 < z <~ 4.4. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck

  16. 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

  17. 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

  18. 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

  19. 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.

  20. Black holes escaping from domain walls

    SciTech Connect

    Flachi, Antonino; Sasaki, Misao; Pujolas, Oriol; Tanaka, Takahiro

    2006-06-15

    Previous studies concerning the interaction of branes and black holes suggested that a small black hole intersecting a brane may escape via a mechanism of reconnection. Here we consider this problem by studying the interaction of a small black hole and a domain wall composed of a scalar field and simulate the evolution of this system when the black hole acquires an initial recoil velocity. We test and confirm previous results, however, unlike the cases previously studied, in the more general set-up considered here, we are able to follow the evolution of the system also during the separation, and completely illustrate how the escape of the black hole takes place.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  2. A Generalized Escape System Simulation (GESS) Computer Program. Volume 2. GESS Programmer’s Manual. Version II.

    DTIC Science & Technology

    1984-04-01

    FIGURES FIGURE TITLE PAGE 2-I Coordinate Systems .................................... 2-2 4-I GESS Execution Job Stream for CDC KRONOS /OS ........... 4-3... KRONOS operating system. This job stream provides for: the loading of the prepared input file (GESSI) * the loading of the ACT program-generated...as a direct access file, or as several indirect files. Refer to Reference 4 for details on direct file creation on the KRONOS system. 4-2 NADC-84068-60

  3. A Generalized Escape System Simulation (GESS) Computer Program: GESS User’s Guide. Version II. Volume 1.

    DTIC Science & Technology

    1983-09-01

    Dynamic CG Z-Axis Spring Constants ..................... 4-37 4-19 GESS Execution Job Stream for CDC KRONOS /OS ........... 4-39 5-1 Plotting File...Corporation computers located at the Naval Air Development Center with the KRONOS operating system, and was programmed using the ASCII FORTRAN IV language (1...computer which will control the program execution and assem- ble the output report data. The job stream is detailed for the KRONOS operating system in

  4. Electronic Escape Trails for Firefighters

    NASA Technical Reports Server (NTRS)

    Jorgensen, Charles; Schipper, John; Betts, Bradley

    2008-01-01

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

  5. Reconstructing the Alcatraz escape

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  6. Escape from viscosity: the kinematics and hydrodynamics of copepod foraging and escape swimming.

    PubMed

    van Duren, Luca A; Videler, John J

    2003-01-01

    Feeding and escape swimming in adult females of the calanoid copepod Temora longicornis Müller were investigated and compared. Swimming velocities were calculated using a 3-D filming setup. Foraging velocities ranged between 2 and 6 mm s(-1), while maximum velocities of up to 80 mm s(-1) were reached during escape responses. Foraging took place at Reynolds numbers between 2 and 6, indicating that viscous forces are considerable during this swimming mode. Inertial forces are much more important during escape responses, when Reynolds numbers of more than 100 are reached. High-speed film recordings at 500 frames s(-1) of the motion pattern of the feeding appendages and the escape movement of the swimming legs revealed that the two swimming modes are essentially very different. While foraging, the first three mouth appendages (antennae, mandibular palps and maxillules) create a backwards motion of water with a metachronal beating pattern. During escape movements the mouth appendages stop moving and the swimming legs beat in a very fast metachronal rhythm, accelerating a jet of water backwards. The large antennules are folded backwards, resulting in a streamlined body shape. Particle image velocimetry analysis of the flow around foraging and escaping copepods revealed that during foraging an asymmetrical vortex system is created on the ventral side of the animal. The feeding motion is steady over a long period of time. The rate of energy dissipation due to viscous friction relates directly to the energetic cost of the feeding current. During escape responses a vortex ring appears behind the animal, which dissipates over time. Several seconds after cessation of swimming leg movements, energy dissipation can still be measured. During escape responses the rate of energy dissipation due to viscous friction increases by up to two orders of magnitude compared to the rate when foraging.

  7. The role of immune system exhaustion on cancer cell escape and anti-tumor immune induction after irradiation.

    PubMed

    Mendes, Fernando; Domingues, Cátia; Rodrigues-Santos, Paulo; Abrantes, Ana Margarida; Gonçalves, Ana Cristina; Estrela, Jéssica; Encarnação, João; Pires, Ana Salomé; Laranjo, Mafalda; Alves, Vera; Teixo, Ricardo; Sarmento, Ana Bela; Botelho, Maria Filomena; Rosa, Manuel Santos

    2016-04-01

    Immune surveillance seems to represent an effective tumor suppressor mechanism. However, some cancer cells survive and become variants, being poorly immunogenic and able to enter a steady-state phase. These cells become functionally dormant or remain hidden clinically throughout. Neoplastic cells seem to be able to instruct immune cells to undergo changes promoting malignancy. Radiotherapy may act as a trigger of the immune response. After radiotherapy a sequence of reactions occurs, starting in the damage of oncogenic cells by multiple mechanisms, leading to the immune system positive feedback against the tumor. The link between radiotherapy and the immune system is evident. T cells, macrophages, Natural Killer cells and other immune cells seem to have a key role in controlling the tumor. T cells may be dysfunctional and remain in a state of T cell exhaustion, nonetheless, they often retain a high potential for successful defense against cancer, being able to be mobilized to become highly functional. The lack of clinical trials on a large scale makes data a little robust, in spite of promising information, there are still many variables in the studies relating to radiation and immune system. The clarification of the mechanisms underlying immune response to radiation exposure may contribute to treatment improvement, gain of life quality and span of patients. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. How to escape from Haller's rule: Olfactory system complexity in small and large Trichogramma evanescens parasitic wasps.

    PubMed

    van der Woude, Emma; Smid, Hans M

    2016-06-15

    While Haller's rule states that small animals have relatively larger brains, minute Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) parasitic wasps scale brain size linearly with body size. This linear brain scaling allows them to decrease brain size beyond the predictions of Haller's rule, and is facilitated by phenotypic plasticity in brain size. In the present study we addressed whether this plasticity resulted in adaptations to the complexity of the morphology of the olfactory system of small and large T. evanescens. We used confocal laser scanning microscopy to compare size and number of glomeruli in the antennal lobe in the brain, and scanning electron microscopy to compare length and number of olfactory sensilla on the antennae. The results show a similar level of complexity of the olfactory system morphology of small and large wasps. Wasps with a similar genotype but very different brain and body size have similarly sized olfactory sensilla and most of them occur in equal numbers on the antennae. Small and large wasps also have a similar number of glomeruli in the antennal lobe. Glomeruli in small brains are, however, smaller in both absolute and relative volume. These similarities between small and large wasps may indicate that plasticity in brain size does not require plasticity in the gross morphology of the olfactory system. It may be vital for wasps of all sizes to have a large number of olfactory receptor types, to maintain olfactory precision in their search for suitable hosts, and consequently maintain their reproductive success and Darwinian fitness. © 2015 Wiley Periodicals, Inc.

  9. Cockroaches keep predators guessing by using preferred escape trajectories

    PubMed Central

    Domenici, P.; Booth, D.; Blagburn, J.M.; Bacon, J. P.

    2009-01-01

    Summary Anti-predator behaviour is vital for most animals, and calls for accurate timing and swift motion. While fast reaction times [1] and predictable, context-dependent, escape initiation distances [2] are common features of most escape systems, previous work has highlighted the need for unpredictability in escape directions, in order to prevent predators from learning a repeated, fixed pattern [3–5]. Ultimate unpredictability would result from random escape trajectories. Although this strategy would deny any predictive power to the predator, it would also result in some escape trajectories towards the threat. Previous work has shown that escape trajectories are in fact generally directed away from the threat, although with a high variability [5–8]. However, the rules governing this variability are largely unknown. Here, we demonstrate tha t individual cockroaches (Periplaneta americana, a much studied model prey species [9–14]) keep each escape unpredictable by running along one of a set of preferred trajectories at fixed angles from the direction of the threatening stimulus. These results provide a new paradigm for understanding the behavio ural strategies for escape responses, underscoring the need to revisit the neural mechanisms controlling escape directions in the cockroach and similar animal models, and the evolutionary forces driving unpredictable, or “protean” [3], anti-predator behaviour. PMID:19013065

  10. 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

    % of populations. Escapement estimation type (quality of the data resulting from survey methods) was rated as excellent for <1%, good for 30%, fair for 3%, poor for 22%, and nonexistent for 45%. Numerous recommendations for improvements in escapement mangement are made in this chapter. In general, improvements are needed on theoretical escapement management techniques, escapement goal setting methods, and escapement and run size data quality. There is also a need to change managers' and harvesters' expectations to coincide with the natural variation and uncertainty in the abundance of salmon populations. All the recommendations are aimed at optimizing the number of spawners-healthy escapements ensure salmon sustainability by providing eggs for future production, nutrients to the system, and genetic diversity.

  11. Inconsistent genetic structure among members of a multitrophic system: did bruchid parasitoids (Horismenus spp.) escape the effects of bean domestication?

    PubMed

    Laurin-Lemay, S; Angers, B; Benrey, B; Brodeur, J

    2013-04-01

    Anthropogenic range expansion and cultural practices have modified the distribution, abundance and genetic diversity of domesticated organisms, thereby altering multitrophic assemblages through space and time. The putative Mesoamerican domestication centre of the common bean, Phaseolus vulgaris L., in Mexico allows investigating the effects of plant domestication on the genetic structure of members of a multitrophic system. The aim of this study was to compare the evolutionary history of Horismenus parasitoids (Hymenoptera: Eulophidae) to those of their bruchid beetle hosts (Coleoptera: Bruchidae) and their domesticated host plant (P. vulgaris), in the context of traditional agriculture in Mexico. We analyzed the population genetic structure of four Horismenus species in Mexico using mitochondrial COI haplotype data. The two most abundant parasitoid species were Horismenus depressus and Horismenus missouriensis. Horismenus missouriensis were infected by Wolbachia endosymbionts and had little to no population differentiation (F(ST) = 0.06). We suspect the mitochondrial history of H. missouriensis to be blurred by Wolbachia, because differentiation among infected vs. non-infected individuals exists (F(ST) = 0.11). Populations of H. depressus were found to be highly differentiated (F(ST) = 0.34), but the genetic structuring could not be explained by tested spatial components. We then compared the genetic structure observed in this parasitoid species to previously published studies on bruchid beetles and their host plants. Despite extensive human-mediated migration and likely population homogenization of its two Acanthoscelides bruchid beetle hosts, H. depressus populations are structured like its host plant, by a recent dispersal from a diverse ancestral gene pool. Distinct evolutionary dynamics may explain inconsistent patterns among trophic levels. Parasitoids likely migrate from wild bean populations and are poorly adapted to bean storage conditions similar to

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

    SciTech Connect

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

    2011-03-10

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

  13. Bursty Escape on Mars

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Woch, J.; Lundin, R.; Wei, J.; Barabash, S.

    2011-10-01

    Bursty or filamentary structuring of plasma flows is a typical feature of the Martian space. This phenomenon is revealed during time periods when MEX-ASPERA- 3 is operating in the high temporal resolution mode. Frequency of oscillations is about 10-50 mHz. Amplitude of flux variations reaches a factor of 10-30. Bursty origin of fluxes of oxygen ions can be the important process for solar wind induced escape on Mars. There are several mechanisms which can be responsible for the observed periodic bursts. Large-amplitude coherent pressure pulses generated by ion beams upstream the bow shock impact the magnetosphere and produce periodic pulses in forces pushing planetary plasma. Pressure pulses can arise downstream the bow shock - in the magnetosheath, which becomes to be decomposed into a sequence of periodic compressive waves. A wavy dynamics can also appear due to a multi-ion origin of the interacting plasmas since such a medium behaves as a specific rotator. At last, not at least, K-H or other types of large-scale MHD instabilities probably excited in the interface region can generate surface waves which will also modulate the tension forces. We present the different observations which can be interpreted in a favor of all the above mechanisms implying a complex and diverse plasma wave environment at Mars.

  14. Escape behavior and escape circuit activation in juvenile crayfish during prey-predator interactions.

    PubMed

    Herberholz, Jens; Sen, Marjorie M; Edwards, Donald H

    2004-05-01

    The neural systems that control escape behavior have been studied intensively in several animals, including mollusks, fish and crayfish. Surprisingly little is known, however, about the activation and the utilization of escape circuits during prey-predator interactions. To complement the physiological and anatomical studies with a necessary behavioral equivalent, we investigated encounters between juvenile crayfish and large dragonfly nymphs in freely behaving animals using a combination of high-speed video-recordings and measurements of electric field potentials. During attacks, dragonfly nymphs rapidly extended their labium, equipped with short, sharp palps, to capture small crayfish. Crayfish responded to the tactile stimulus by activating neural escape circuits to generate tail-flips directed away from the predator. Tail-flips were the sole defense mechanism in response to an attack and every single strike was answered by tail-flip escape behavior. Crayfish used all three known types of escape tail-flips during the interactions with the dragonfly nymphs. Tail-flips generated by activity in the giant neurons were predominantly observed to trigger the initial escape responses to an attack, but non-giant mediated tail-flips were often generated to attempt escape after capture. Attacks to the front of the crayfish triggered tail-flips mediated either by the medial giant neuron or by non-giant circuitry, whereas attacks to the rear always elicited tail-flips mediated by the lateral giant neuron. Overall, tail flipping was found to be a successful behavior in preventing predation, and only a small percentage of crayfish were killed and consumed.

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

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

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

  16. How many ions have escaped the Martian atmosphere?

    NASA Astrophysics Data System (ADS)

    Brain, David; McFadden, James; Halekas, Jasper; Connerney, J. E. P.; Eparvier, Frank; Mitchell, David; Bougher, Stephen W.; Bowers, Charlie; Curry, Shannon; Dong, Chuanfei; Dong, Yaxue; Egan, Hilary; Fang, Xiaohua; Harada, Yuki; Jakosky, Bruce; Lillis, Robert; Luhmann, Janet; Ma, Yingjuan; Modolo, Ronan; Weber, Tristan

    2016-10-01

    The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been making science measurements of the Martian upper atmosphere and its escape to space since November 2014. A key part of this effort is the measurement of the escape rates of charged particles (ions) at present and over solar system history. The lack of a global dynamo magnetic field at Mars leaves its upper atmosphere more directly exposed to the impinging solar wind than magnetized planets such as Earth. For this reason it is thought that ion escape at Mars may have played a significant role in long term climate change. MAVEN measures escaping planetary ions directly, with high energy, mass, and time resolution.With nearly two years of observations in hand, we will report the average ion escape rate and the spatial distribution of escaping ions as measured by MAVEN and place them in context with previous measurements of ion loss by other spacecraft (e.g. Phobos 2 and Mars Express). We will then report on the measured variability in ion escape rates with different drivers (e.g. solar EUV, solar wind pressure, etc.). Finally, we will use these results to provide an initial estimate of the total ion escape from Mars over billions of years.

  17. Cross Sections for Planetary Escape

    NASA Astrophysics Data System (ADS)

    Tully, C.

    2001-05-01

    Energetic charged-particle bombardment, dissociative recombination and photodissociation processes produce energetic recoil atoms which heat the thermosphere and can lead to escape from a planet affecting the evolution of the atmosphere. In describing these processes by Monte Carlo methods, many of the critical cross sections are not available in the energy range of interest, a few eV to 1 keV. Here we present our recent results for elastic collision and collisional dissociation cross sections relevant to Titan, Triton, Europa and the terrestrial planets [1,2]. Elastic and diffusion cross sections were calculated using both quantum mechanical techniques and the semiclassical JWKB approximation for the collision of ground state oxygen atoms in the energy range 1-10eV [2]. This involved calculation of phase shifts for each of the 18 molecular energy states of O2 which separate to two ground state O atoms. For an O thermosphere the total elastic cross section is close to that typically assumed but the escape depths are shown to be larger than those typically used. Dissociation cross sections of N + N2 were calculated using a semiclassical method, in the energy range 0-30eV. This required treating the vibrational motion quantum mechanically while the rotational and the relative translational motion were treated classically. The evolution of the system was calculated by simultaneous propagation of the classical as well as the quantal degrees of freedom. The solution to the classical part was carried out by solving Hamilton equations of motion using an effective London-Eyring-Polanyi-Sato potential energy surface, calculated by Laganá et al [3]. Propagation of the quantal wavefunction was carried out by solving the time dependent Schrödinger equation using the split operator technique with the help of the fast fourier transform which was used to calculate the second derivatives arising from the kinetic energy operator. This work was supported by NASA's Planetary

  18. Dissociated neural effects of cortisol depending on threat escapability.

    PubMed

    Montoya, Estrella R; van Honk, Jack; Bos, Peter A; Terburg, David

    2015-11-01

    Evolution has provided us with a highly flexible neuroendocrine threat system which, depending on threat imminence, switches between active escape and passive freezing. Cortisol, the "stress-hormone", is thought to play an important role in both fear behaviors, but the exact mechanisms are not understood. Using pharmacological functional magnetic resonance imaging we investigated how cortisol modulates the brain's fear systems when humans are under virtual-predator attack. We show dissociated neural effects of cortisol depending on whether escape from threat is possible. During inescapable threat cortisol reduces fear-related midbrain activity, whereas in anticipation of active escape cortisol boosts activity in the frontal salience network (insula and anterior cingulate cortex), which is involved in autonomic control, visceral perception and motivated action. Our findings suggest that cortisol adjusts the human neural threat system from passive fear to active escape, which illuminates the hormone's crucial role in the adaptive flexibility of fear behaviors.

  19. F111 Crew Escape Module pilot parachute

    SciTech Connect

    Tadios, E.L.

    1991-01-01

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

  20. Lyman-Werner UV escape fractions from primordial haloes

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  1. Predictions for the escape of CH4 from Pluto

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Observations of Pluto’s extended atmosphere by the New Horizons/ALICE instrument have the potential to constrain models of energy-limited escape from planetary atmospheres. Such models have wide applicability, ranging from dwarf planets in the solar system to giant extrasolar planets, but the opportunities to test them in actual atmospheres are limited. We adapted a multi-species escape model from close-in extrasolar planets to calculate the escape rates of CH4 and N2 from Pluto. In the absence of escape, CH4 should overtake N2 as the dominant species below the exobase. Theory suggests, however, that Pluto’s atmosphere undergoes rapid escape that leads to a nearly constant CH4 mixing ratio of about 1 % below the exobase, with CH4 escaping at a rate that is only 5-10 % of the N2 escape rate. Simultaneous observations of the N2 and CH4 profiles in the upper atmosphere, together with our model, can be used to test if this is the case and infer an estimate of the mass loss rate.

  2. 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.

  3. 42 CFR 84.51 - Entry and escape, or escape only; classification.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  4. 42 CFR 84.51 - Entry and escape, or escape only; classification.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

  5. 42 CFR 84.51 - Entry and escape, or escape only; classification.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

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

  6. 42 CFR 84.51 - Entry and escape, or escape only; classification.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

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

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  9. 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.

  10. DYNAMICS OF THE ESCAPE RESPONSE.

    DTIC Science & Technology

    requirements. It has been shown that force is a lawful response measure under positive reinforcement (Notterman and Mintz, 1965). Subjects will adjust...concluded that response force in an escape situation is a lawful response measure, and that it operates in a manner similar to force under positive reinforcement .

  11. Mechanisms of Ionospheric Mass Escape

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  12. Generation of Escape Variants of Neutralizing Influenza Virus Monoclonal Antibodies.

    PubMed

    Leon, Paul E; Wohlbold, Teddy John; He, Wenqian; Bailey, Mark J; Henry, Carole J; Wilson, Patrick C; Krammer, Florian; Tan, Gene S

    2017-08-29

    Influenza viruses exhibit a remarkable ability to adapt and evade the host immune response. One way is through antigenic changes that occur on the surface glycoproteins of the virus. The generation of escape variants is a powerful method in elucidating how viruses escape immune detection and in identifying critical residues required for antibody binding. Here, we describe a protocol on how to generate influenza A virus escape variants by utilizing human or murine monoclonal antibodies (mAbs) directed against the viral hemagglutinin (HA). With the use of our technique, we previously characterized critical residues required for the binding of antibodies targeting either the head or stalk of the novel avian H7N9 HA. The protocol can be easily adapted for other virus systems. Analyses of escape variants are important for modeling antigenic drift, determining single nucleotide polymorphisms (SNPs) conferring resistance and virus fitness, and in the designing of vaccines and/or therapeutics.

  13. Escaping from Rejection

    PubMed Central

    Lynch, Raymond J.; Platt, Jeffrey L.

    2009-01-01

    Summary Those engaged in clinical transplantation and transplantation immunology have always taken as a central objective the elucidation of means to prevent graft rejection by the recipient immune system. Conceptually, such mechanisms stem from the concept of Paul Ehrlich that all organisms can selectively avoid autotoxicity; i.e. they exhibit horror autotoxicus. Some mechanisms of horror autotoxicus now understood. T lymphocytes and B lymphocytes recognize foreign antigens but not some auto-antigens. Clonal deletion generates lacunae in what is otherwise a virtually limitless potential to recognize antigens. We call this mechanism structural tolerance. Where imperfections in structural tolerance allow self-recognition, the full activation of lymphocytes and generation of effector activity depends on delivery of accessory signals generated by infection and/or injury. The absence of accessory signals prevents or even suppresses immunological responses. We call this dichotomy of responsiveness conditional tolerance. When, despite structural and conditional tolerance, effector activity perturbs autologous cells, metabolism changes in ways that protect against injury. We use the term accommodation to refer to this acquired protection against injury. Structural and conditional tolerance and accommodation overlap in such a way that potentially toxic products can be generated to control microorganisms and neutralize toxins without overly damaging adjacent cells. The central challenge in transplantation, then, should be the orchestration of structural and conditional tolerance and accommodation in such a way that toxic products can still be generated for defense while preserving graft function and survival. Since the earliest days of transplantation, immunobiologists have sought means by which to prevent recognition and rejection of foreign tissue. The goal of these strategies is the retention of recipient immune function while selectively avoiding graft injury. While

  14. Blue Origin Conducts Pad Escape Test

    NASA Image and Video Library

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

  15. 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.

  16. 46 CFR 108.445 - Alarm and means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Alarm and means of escape. (a) Each CO2 system that has a supply of more than 136 kilograms (300 pounds) of CO2, except a system that protects a tank, must have an alarm that sounds for at least 20 seconds before the CO2 is released into the space. (b) Each audible alarm for a CO2 system must have the...

  17. 46 CFR 108.445 - Alarm and means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Alarm and means of escape. (a) Each CO2 system that has a supply of more than 136 kilograms (300 pounds) of CO2, except a system that protects a tank, must have an alarm that sounds for at least 20 seconds before the CO2 is released into the space. (b) Each audible alarm for a CO2 system must have the...

  18. Belt fires and mine escape problems

    SciTech Connect

    Kovac, J.G.; Lazzara, C.P.; Kravitz, J.H.

    1996-12-31

    A conveyor belt fire in an underground coal mine is a serious threat to life and property. About 30% of the reportable underground coal mine fires from 1988 through 1992 occurred in belt entries. In one instance, a fire started in the drive area of a belt line, spread rapidly, and resulted in seating of the entire mine. Large-scale studies conducted by the U.S. Bureau of Mines in an aboveground fire gallery at Lake Lynn Laboratory clearly show the hazards of conveyor belt fires. Mine conveyor belt formulations which passed the current Federal acceptance test for fire-resistant betting were completely consumed by propagating fires or propagated flame, with flame spread rates ranging from 0.3 to 9 m/min. High downstream temperatures and large quantities of smoke and toxic gases, such as carbon monoxide, were generated as the belting burned. The smoke and gases can be spread by the mine`s ventilation system and can create significant problems for miners in the process of evacuation, such as reduction in visibility and incapacitation. In the aftermath of a belt fire, the atmosphere inside of the mine can become smoke filled or unbreathable, forcing miners to evacuate while wearing Self-Contained Self-Rescuers (SCSR`s), Sometimes there is confusion about how to regard the rated duration of an MSHA/NIOSH-approved 60-min. SCSR, especially when an SCSR is used in a way which takes it outside of the test conditions under which it was approved. As examples, for a mine escape that takes a miner from the deepest point of penetration in the mine to the surface: How long will a 60-min. SCSR actually last? and How many SCSR`s will a miner need? To answer these kinds of questions, in-mine data being gathered on escape times, distance and heart rates using miners escaping on foot and under oxygen. A model will be developed and validated which predicts how much oxygen is actually needed for a mine escape, and compares oxygen consumption bare faced versus wearing an SCSR.

  19. Malaria Parasites: The Great Escape

    PubMed Central

    Rénia, Laurent; Goh, Yun Shan

    2016-01-01

    Parasites of the genus Plasmodium have a complex life cycle. They alternate between their final mosquito host and their intermediate hosts. The parasite can be either extra- or intracellular, depending on the stage of development. By modifying their shape, motility, and metabolic requirements, the parasite adapts to the different environments in their different hosts. The parasite has evolved to escape the multiple immune mechanisms in the host that try to block parasite development at the different stages of their development. In this article, we describe the mechanisms reported thus far that allow the Plasmodium parasite to evade innate and adaptive immune responses. PMID:27872623

  20. Oxygen or carbogen breathing before simulated submarine escape.

    PubMed

    Gennser, M; Blogg, S L

    2008-01-01

    Raised internal pressure in a distressed submarine increases the risk of bubble formation and decompression illness after submarine escape. The hypothesis that short periods of oxygen breathing before submarine escape would reduce decompression stress was tested, using Doppler-detectable venous gas emboli as a measure. Twelve goats breathed oxygen for 15 min at 0.1 MPa before exposure to a simulated submarine escape profile to and from 2.5 MPa (240 m/seawater), whereas 28 control animals underwent the same dive without oxygen prebreathe. No decompression sickness (DCS) occurred in either of these two groups. Time with high bubble scores (Kisman-Masurel >or=3) was significantly (P < 0.001) shorter in the prebreathe group. In a second series, 30 goats breathed air at 0.2 MPa for 6 h. Fifteen minutes before escape from 2.5 MPa, animals were provided with either air (n = 10), oxygen (n = 12), or carbogen (97.5% O(2) and 2.5% CO(2)) gas (n = 8) as breathing gas. Animals breathed a hyperoxic gas (60% O(2)-40% N(2)) during the escape. Two animals (carbogen group) suffered oxygen convulsions during the escape but recovered on surfacing. Only one case of DCS occurred (carbogen group). The initial bubble score was reduced in the oxygen group (P < 0.001). The period with bubble score of Kisman-Masurel >or=3 was also significantly reduced in the oxygen group (P < 0.001). Oxygen breathing before submarine escape reduces initial bubble scores, although its significance in reducing central nervous system DCS needs to be investigated further.

  1. 46 CFR 108.445 - Alarm and means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  2. 46 CFR 108.445 - Alarm and means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Alarm and means of escape. 108.445 Section 108.445 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Fire Extinguishing Systems Fixed Carbon Dioxide Fire Extinguishing Systems § 108.445...

  3. 46 CFR 108.445 - Alarm and means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Alarm and means of escape. 108.445 Section 108.445 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Fire Extinguishing Systems Fixed Carbon Dioxide Fire Extinguishing Systems § 108.445...

  4. Escape of coupled Brownian particles across a fluctuating barrier

    NASA Astrophysics Data System (ADS)

    Singh, R. K.

    2017-09-01

    The escape of two harmonically coupled Brownian particles across the fluctuating barrier of a bistable potential is investigated with correlated additive and multiplicative fluctuations. Positive correlations enhance the rate of escape across the barrier when the coupling is effective, whereas for weakly coupled particles, escape becomes difficult. It is found that the system exhibits the phenomenon of resonant activation when the rate of barrier fluctuations is comparable to the relaxation time in the bistable potential. Using a decoupling ansatz, we derive the Markovian limit of the problem in the steady state, under the constraint that the barriers fluctuate on a time scale faster than the relative oscillation of the two particles. Adiabatic elimination of the fast variable of the dynamical system is discussed in appropriate limits.

  5. Escape of water molecular from Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Li, Jiaxi; Li, Wenfeng; Zhang, Jianwei

    2014-03-01

    Understanding and controlling the transport of water molecules through nanopores have attracted great interest due to potential applications for designing novel nanofluidic devices, machines and sensors. In this work, we theoretically investigate the effects of an external nonuniform electric field on the escape of water molecules through single-walled carbon nanotubes (SWNTs) by using of molecular dynamics (MD) simulations. When polar water molecules are placed in the gradient electric field, the electric force is experienced that can drive the water molecules. Molecular dynamics simulations show that the escape probability of water obeys the Boltzmann distribution. Our results show that energy barrier delta E is independent of temperature which indicates that it is a single-barrier system. From the MD results statistics, the key parameters could be determined such that the relationship between energy barrier delta E and diameter of SWNTs and nozzle distance of the charge r would be revealed that could deepen our current theoretical understanding on transport of water molecular inside SWNTs with the nonuniform electric field.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  8. 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.

  9. THE ESCAPE FRACTION OF IONIZING RADIATION FROM GALAXIES

    SciTech Connect

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

    2013-06-10

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

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

    PubMed

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

    2016-07-15

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

  11. 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.

  12. Escape dynamics through a continuously growing leak

    NASA Astrophysics Data System (ADS)

    Kovács, Tamás; Vanyó, József

    2017-06-01

    We formulate a model that describes the escape dynamics in a leaky chaotic system in which the size of the leak depends on the number of the in-falling particles. The basic motivation of this work is the astrophysical process, which describes the planetary accretion. In order to study the dynamics generally, the standard map is investigated in two cases when the dynamics is fully hyperbolic and in the presence of Kolmogorov-Arnold-Moser islands. In addition to the numerical calculations, an analytic solution to the temporal behavior of the model is also derived. We show that in the early phase of the leak expansion, as long as there are enough particles in the system, the number of survivors deviates from the well-known exponential decay. Furthermore, the analytic solution returns the classical result in the limiting case when the number of particles does not affect the leak size.

  13. Norethandrolone produces temporary loss of the ability to escape from salt-retaining steroids.

    PubMed

    Zumoff, B

    1989-01-01

    Patients with diseases characterized by salt retention manifest a loss of the normal ability of healthy persons to escape from repeat injections of aldosterone or other salt-retaining steroids. This phenomenon may be a clue to the pathophysiological mechanisms of salt retention. Administration of norethandrolone to a subject who had demonstrated the ability to escape from the salt-retaining effect of corticosteroid administration temporarily and reversibly deleted his ability to escape. Thus norethandrolone administration provides the basis for a model system for exploring the mechanisms of escape (and therefore of salt retention).

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  17. Evolving Project E-Scape for National Assessment

    ERIC Educational Resources Information Center

    Kimbell, Richard

    2012-01-01

    In the opening paper in this Special Edition I outlined the major issues that led to the establishment of "project e-scape". The project was intended to develop systems and approaches that enabled learners to build real-time web-based portfolios of their performance (initially) in design & technology and additionally to build systems…

  18. Escape of Black Holes from the Brane

    NASA Astrophysics Data System (ADS)

    Flachi, Antonino; Tanaka, Takahiro

    2005-10-01

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

  19. 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.

  20. 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.

  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…

  2. Escaping hydrogen from HD209458b

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    Recent modeling of the atmosphere of HD209458b has been used to interpret the Lyman-α line and other observations during transits. In this presentation, we model the hydrogen exosphere of the short period, Hot Jupiter planet to investigate the dynamics of the extended hydrogen cloud and to determine the observability of the solar ionization and acceleration on the escaping hydrogen.Koskinen et al (2010) used a hydrostatic density profile in the thermosphere combined with the Voigt profile to estimate the Lyman-α transit depths for an array of model parameters. A detailed photochemical-dynamical model of the thermosphere was developed by Koskinen et al (2013a) and used to again estimate model parameters to fit not only the Lyman-α transits, but also the transits in the O I, C II and Si III lines (Koskinen et al, 2013b).Recently, Bourrier et al (2013) modeled the escape of hydrogen from the extended atmospheres of HD209458b and HD189733b and used the results to interpret Lyman-α observations. They included acceleration of hydrogen by stellar radiation pressure to obtain the high velocity tails in the escaping velocity distribution, arguing that the observations are explained by high velocity gas in the system, while Voigt broadening is negligible.In this work we connect a free molecular flow (FMF) model, similar to Bourrier et al (2013), to the results of Koskinen et al (2013b) to simulate the extended atmosphere of HD209458b. We include ionization and radiation pressure in the extended atmosphere along with self-shielding due to the extended atmosphere and thermosphere. The extended atmosphere and absorption rates are iteratively computed to obtain a consistent solution. In this manner, we can interpret the importance of the various physical processes by comparing the simulated line profiles, consisting of velocity and natural broadening, to observations (Koskinen et al, 2010). Furthermore, the transit depths of this model can be used to re-evaluate the

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

    PubMed

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

    2014-01-01

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

  4. Escaping in Literature. Teaching in the Library.

    ERIC Educational Resources Information Center

    Hurst, Carol Otis

    1993-01-01

    Explores the "escape" genre of children's literature, and recommends and describes several books that deal with such topics as escape from prison camps, from slavery, from the Holocaust, from war, and from Utopian societies. These books should provoke meaningful classroom discussions and allow children to view their own world from different…

  5. 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...

  6. 30 CFR 57.11051 - Escape routes.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Escape routes. 57.11051 Section 57.11051 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... read direction signs that clearly indicate the ways of escape....

  7. 30 CFR 57.11051 - Escape routes.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Escape routes. 57.11051 Section 57.11051 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE... read direction signs that clearly indicate the ways of escape....

  8. Tumor escape from immune response: mechanisms and targets of activity.

    PubMed

    Gabrilovich, Dmitry; Pisarev, Vladimir

    2003-10-01

    Immune system plays an important role in control of tumor progression. Effective antitumor immune response depends on close interaction of several elements of immune system. They include antigen-presenting cells, different subsets of T cells, B cells and NK cells. However, tumor cells developed a number of mechanisms to escape recognition and elimination by immune system. In this review we will discuss these mechanisms and address possible approaches to correct them.

  9. Formulation of a Cooperative-Confinement-Escape problem of multiple cooperative defenders against an evader escaping from a circular region

    NASA Astrophysics Data System (ADS)

    Li, Wei

    2016-10-01

    In this paper, we propose and formulate the Cooperative-Confinement-Escape (CCE) problem of multiple cooperative defenders against an evader escaping from a circular region, in which the defenders are moving on the circle with attempt to prevent possible escape of a single evader who is initially located inside the circle. The main contributions are summarized as follows: (1) we first provide an effective formulation of the CCE problem, which is an emphasis of this paper, with design of two nonlinear control strategies for the cooperative defenders and the adversarial evader, respectively. Particularly, we consider to include a proper interaction between each pair of the nearest-neighbor defenders, and an adaptive trajectory prediction mechanism in the strategies of the defenders to increase the chance of successful confinement. (2) For the first attempt on analyzing the CCE dynamics which is unavoidably strongly nonlinear, we analyze the minimum energy of the evader for possible escape. (3) For understanding of the behaviors of the system under different parameters, (i) we illustrate the effectiveness of the confinement strategy using the adaptive trajectory prediction mechanism, and (ii) the physical roles of the system parameters with respect to the system dynamics, some of which may be unexpected or not straightforward. A separate paper will be presented for systematic analysis of the agents' behaviors with respect to the large intervals of the parameter settings.

  10. Exploitation of an ancient escape circuit by an avian predator: relationships between taxon-specific prey escape circuits and the sensitivity to visual cues from the predator.

    PubMed

    Jabłoński, P G; Strausfeld, N J

    2001-01-01

    The painted redstart Myioborus pictus uses visual displays to flush, pursue, and then capture an abundance of brachyceran Diptera that are equipped with giant fiber escape circuits. This paper investigates the relationships between features of the giant fiber system, the structure of visual stimuli produced by redstarts and their effectiveness in eliciting escape reactions by flies. The results show that dipterous taxa having large-diameter giant fibers extending short distances from the brain to motor neurons involved in escape are flushed at greater distances than taxa with longer and small-diameter giant fibers. The results of behavioral tests show the importance of angular acceleration of expanding image edges on the compound eye in eliciting escape responses. Lateral motion of stimulus profile edges as well as structured visual profiles additionally contribute to the sensitivity of one or more neural systems that trigger escape. Retinal subtense and angular velocity are known to trigger physiological responses in fly giant fiber circuits, but the contributions of edge length and lateral motion in a looming stimulus suggest that escape pathways might also receive inputs from circuits that are tuned to different types of motion. The present results suggest that these several properties of escape pathways have contributed to the evolution of foraging displays and plumage patterns in flush-pursuing birds.

  11. ESCAP migration study gathers momentum.

    PubMed

    1980-01-01

    A comparative study is being conducted in the ESCAP (Economic and Social Commission for Asia and the Pacific) region on the relationships of migration and urbanization to development. The 1st stage of the study will entail the preparation of country reports on the census analysis of migration, urbanization and development. The 2nd stage will involve preparation of a series of national migration surveys. The 3rd phase will involve assisting member governments to formulate a comprehensive population redistribution policy as part of their national development planning. 1st-phase country reports have been completed in Sri Lanka, South Korea, the Philippines, and Indonesia. Migration in Sri Lanka has largely been rural-to-rural with little urbanization so far. The picture in South Korea has been the opposite, with rapid urbanization in the 1960s and 1970s; the government is hoping to divert some population to smaller cities away from Seoul. The pattern in the Philippines is 1 of urban primacy with the metropolis of Manila accounting for over 1/3 of the country's total population. Indonesia is characterized by a dense heartland in the Java-Bali regions. However, the rate of urbanization here has been slower. Migrants in all the countries studied are preponderantly young. The sex differential varies from country to country. The influence of migration on subsequent fertility is unknown.

  12. 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

  13. 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.

  14. Statin escape phenomenon: Fact or fiction?

    PubMed Central

    Barkas, Fotios; Elisaf, Moses; Klouras, Eleftherios; Dimitriou, Theodora; Tentolouris, Nikolaos; Liberopoulos, Evangelos

    2017-01-01

    AIM To evaluate the presence of the so called “statin escape” phenomenon among hyperlipidemic subjects attending a lipid clinic. METHODS This was a retrospective analysis of 1240 hyperlipidemic individuals followed-up for ≥ 3 years. We excluded those individuals meeting one of the following criteria: Use of statin therapy at baseline visit, discontinuation of statin treatment at most recent visit, change in statin treatment during follow-up and poor compliance to treatment. Statin escape phenomenon was defined as an increase in low-density lipoprotein cholesterol (LDL-C) levels at the most recent visit by > 10% compared with the value at 6 mo following initiation of statin treatment. RESULTS Of 181 eligible subjects, 31% exhibited the statin escape phenomenon. No major differences regarding baseline characteristics were found between statin escapers and non-statin escapers. Both escapers and non-escapers had similar baseline LDL-C levels [174 (152-189) and 177 (152-205) mg/dL, respectively]. In comparison with non-escapers, statin escapers demonstrated lower LDL-C levels at 6 mo after treatment initiation [88 (78-97) mg/dL vs 109 (91-129) mg/dL, P < 0.05], but higher levels at the most recent visit [103 (96-118) mg/dL vs 94 (79-114) mg/dL, P < 0.05]. CONCLUSION These data confirm the existence of an escape phenomenon among statin-treated individuals. The clinical significance of this phenomenon remains uncertain. PMID:28261552

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  16. The fast escaping set for quasiregular mappings

    NASA Astrophysics Data System (ADS)

    Bergweiler, Walter; Drasin, David; Fletcher, Alastair

    2014-06-01

    The fast escaping set of a transcendental entire function is the set of all points which tend to infinity under iteration as fast as possible compatible with the growth of the function. We study the analogous set for quasiregular mappings in higher dimensions and show, among other things, that various equivalent definitions of the fast escaping set for transcendental entire functions in the plane also coincide for quasiregular mappings. We also exhibit a class of quasiregular mappings for which the fast escaping set has the structure of a spider's web.

  17. 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.

  18. The Neuroethology of C. elegans Escape

    PubMed Central

    Pirri, Jennifer K.; Alkema, Mark J.

    2012-01-01

    Escape behaviors are crucial to survive predator encounters. Touch to the head of C. elegans induces an escape response where the animal rapidly backs away from the stimulus and suppresses foraging head movements. The coordination of head and body movements facilitates escape from predacious fungi that cohabitate with nematodes in organic debris. An appreciation of the natural habitat of laboratory organisms, like C. elegans, enables a comprehensive neuroethological analysis of behavior. In this review we discuss the neuronal mechanisms and the ecological significance of the C. elegans touch response. PMID:22226513

  19. Plasma-induced Escape and Alterations of Planetary Atmospheres

    NASA Astrophysics Data System (ADS)

    Johnson, R. E.; Tucker, O. J.; Ewrin, J.; Cassidy, T. A.; Leblanc, F.

    2009-12-01

    The atmospheres of planets and planetary satellites are typically imbedded in space plasmas. Depending on the interaction with the induced or intrinsic fields energetic ions can have access to the thermosphere and the corona affecting their composition and thermal structure and causing loss to space. These processes are often lumped together as ‘atmospheric sputtering’ (Johnson 1994). In this talk I will review the results of simulations of the plasma bombardment at a number of solar system bodies and use those data to describe the effect on the upper atmosphere and on escape. Of considerable recent interest is the modeling of escape from Titan. Prior to Cassini’s tour of the Saturnian system, plasma-induced escape was suggested to be the dominant loss process, but recent models of enhanced thermal escape, often referred to as ‘slow hydrodynamic’ escape, have been suggested to lead to much larger Titan atmospheric loss rates (Strobel 2008; Cui et al. 2008). Such a process has been suggested to be active at some point in time on a number of solar system bodies. I will present hybrid fluid/ kinetic models of the upper atmosphere of certain bodies in order to test both the plasma-induced and thermal escape processes. Preliminary results suggest that the loss rates estimated using the ‘slow hydrodynamic’ escape process can be orders of magnitude too large. The implications for Mars, Titan and Pluto will be discussed. Background for this talk is contained in the following papers (Johnson 2004; 2009; Chaufray et al. 2007; Johnson et al. 2008; 2009; Tucker and Johnson 2009). References: Chaufray, J.Y., R. Modolo, F. Leblanc, G. Chanteur, R.E. Johnson, and J.G. Luhmann, Mars Solar Wind interaction: formation of the Martian corona and atmosphric loss to space, JGR 112, E09009, doi:10.1029/2007JE002915 (2007) Cui, J., Yelle, R. V., Volk, K. Distribution and escape of molecular hydrogen in Titan's thermosphere and exosphere. J. Geophys. Res. 113, doi:10

  20. Technical evaluation of the Aerospace Medical Panel Specialists Meeting on Escape Problems and Manoeuvres in Combat Aircraft

    NASA Technical Reports Server (NTRS)

    Jones, W. L.

    1974-01-01

    A technical evaluation of the papers presented at a conference on escape systems for helicopters and V/STOL aircraft was made. The subjects discussed include the following: (1) bioengineering aspects of spinal injury during ejection, (2) aerodynamic forces acting on crewman during escape, (3) operational practicality of fly away ejection seats, (4) helicopter survivability requirements, (5) ejection experience from V/STOL aircraft, and (6) research projects involving escape and retrieval systems.

  1. Technical evaluation of the Aerospace Medical Panel Specialists Meeting on Escape Problems and Manoeuvres in Combat Aircraft

    NASA Technical Reports Server (NTRS)

    Jones, W. L.

    1974-01-01

    A technical evaluation of the papers presented at a conference on escape systems for helicopters and V/STOL aircraft was made. The subjects discussed include the following: (1) bioengineering aspects of spinal injury during ejection, (2) aerodynamic forces acting on crewman during escape, (3) operational practicality of fly away ejection seats, (4) helicopter survivability requirements, (5) ejection experience from V/STOL aircraft, and (6) research projects involving escape and retrieval systems.

  2. Escape for the Slow Solar Wind

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-05-01

    Plasma from the Sun known as the slow solar wind has been observed far away from where scientists thought it was produced. Now new simulations may have resolved the puzzle of where the slow solar wind comes from and how it escapes the Sun to travel through our solar system.An Origin PuzzleA full view of a coronal hole (dark portion) from SDO. The edges of the coronal hole mark the boundary between open and closed magnetic field lines. [SDO; adapted from Higginson et al. 2017]The Suns atmosphere, known as the corona, is divided into two types of regions based on the behavior of magnetic field lines. In closed-field regions, the magnetic field is firmly anchored in the photosphere at both ends of field lines, so traveling plasma is confined to coronal loops and must return to the Suns surface. In open-field regions, only one end of each magnetic field line is anchored in the photosphere, so plasma is able to stream from the Suns surface out into the solar system.This second type of region known as a coronal hole is thought to be the origin of fast-moving plasma measured in our solar system and known as the fast solar wind. But we also observe a slow solar wind: plasma that moves at speeds of less than 500 km/s.The slow solar wind presents a conundrum. Its observational properties strongly suggest it originates in the hot, closed corona rather than the cooler, open regions. But if the slow solar wind plasma originates in closed-field regions of the Suns atmosphere, then how does it escape from the Sun?Slow Wind from Closed FieldsA team of scientists led by Aleida Higginson (University of Michigan) has now used high-resolution, three-dimensional magnetohydrodynamic simulations to show how the slow solar wind can be generated from plasma that starts outin closed-field parts of the Sun.A simulated heliospheric arc, composed of open magnetic field lines. [Higginson et al. 2017]Motions on the Suns surface near the boundary between open and closed-field regions the boundary

  3. Outcrossing and photosynthetic rates vary independently within two Clarkia species: implications for the joint evolution of drought escape physiology and mating system.

    PubMed

    Ivey, Christopher T; Dudley, Leah S; Hove, Alisa A; Emms, Simon K; Mazer, Susan J

    2016-07-21

    Mating systems of plants are diverse and evolutionarily labile. Abiotic environmental factors, such as seasonal drought, may impose selection on physiological traits that could lead to transitions in mating system if physiological traits are genetically correlated with traits that influence mating system. Within Clarkia, self-fertilizing taxa have higher photosynthetic rates, earlier flowering phenology, faster individual floral development and more compressed flowering periods than their outcrossing sister taxa, potentially reducing the selfing taxa's exposure to drought. In theory, this contrast in trait combinations between sister taxa could have arisen via correlated evolution due to pleiotropy or genetic linkage. Alternatively, each trait may evolve independently as part of a life history that is adaptive in seasonally dry environments. To evaluate these hypotheses, we examined relationships between photosynthetic rates (adjusted for plant height and leaf node position) and outcrossing rates (estimated by allozyme variation in progeny arrays) during two consecutive years in multiple wild populations of two mixed-mating Clarkia taxa, each of which is sister to a derived selfing taxon. If the negative association between photosynthetic rate and outcrossing previously observed between sister taxa reflects correlated evolution due to a strong negative genetic correlation between these traits, then a similarly negative relationship would be observed within populations of each taxon. By contrast, if the combination of elevated photosynthetic rates and reduced outcrossing evolved independently within taxa, we predicted no consistent relationship between photosynthetic rate and outcrossing rate. We found no significant difference in outcrossing rates within populations between groups of plants with high versus low photosynthetic rates. Overall, these results provide support for the hypothesis that the joint divergence in photosynthetic rate and mating system observed

  4. Wind enhanced planetary escape: Collisional modifications

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  5. Biogeochemistry: Nocturnal escape route for marsh gas

    NASA Astrophysics Data System (ADS)

    Anthony, Katey Walter; MacIntyre, Sally

    2016-07-01

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

  6. Evolutionary dynamics of escape from biomedical intervention.

    PubMed Central

    Iwasa, Yoh; Michor, Franziska; Nowak, Martin A

    2003-01-01

    Viruses, bacteria, eukaryotic parasites, cancer cells, agricultural pests and other inconvenient animates have an unfortunate tendency to escape from selection pressures that are meant to control them. Chemotherapy, anti-viral drugs or antibiotics fail because their targets do not hold still, but evolve resistance. A major problem in developing vaccines is that microbes evolve and escape from immune responses. The fundamental question is the following: if a genetically diverse population of replicating organisms is challenged with a selection pressure that has the potential to eradicate it, what is the probability that this population will produce escape mutants? Here, we use multi-type branching processes to describe the accumulation of mutants in independent lineages. We calculate escape dynamics for arbitrary mutation networks and fitness landscapes. Our theory shows how to estimate the probability of success or failure of biomedical intervention, such as drug treatment and vaccination, against rapidly evolving organisms. PMID:14728779

  7. 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

  8. Promoter clearance and escape in prokaryotes.

    PubMed

    Hsu, Lilian M

    2002-09-13

    Promoter escape is the last stage of transcription initiation when RNA polymerase, having initiated de novo phosphodiester bond synthesis, must begin to relinquish its hold on promoter DNA and advance to downstream regions (DSRs) of the template. In vitro, this process is marked by the release of high levels of abortive transcripts at most promoters, reflecting the high instability of initial transcribing complexes (ITCs) and indicative of the existence of barriers to the escape process. The high abortive initiation level is the result of the existence of unproductive ITCs that carry out repeated initiation and abortive release without escaping the promoter. The formation of unproductive ITCs is a widespread phenomenon, but it occurs to different extent on different promoters. Quantitative analysis of promoter mutations suggests that the extent and pattern of abortive initiation and promoter escape is determined by the sequence of promoter elements, both in the promoter recognition region (PRR) and the initial transcribed sequence (ITS). A general correlation has been found that the stronger the promoter DNA-polymerase interaction, the poorer the ability of RNA polymerase to escape the promoter. In gene regulation, promoter escape can be the rate-limiting step for transcription initiation. An increasing number of regulatory proteins are known to exert their control at this step. Examples are discussed with an emphasis on the diverse mechanisms involved. At the molecular level, the X-ray crystal structures of RNA polymerase and its various transcription complexes provide the framework for understanding the functional data on abortive initiation and promoter escape. Based on structural and biochemical evidence, a mechanism for abortive initiation and promoter escape is described.

  9. Dynamics of the Pin Pallet Runaway Escapement

    DTIC Science & Technology

    1978-06-01

    pin pallet simulation to a spring- driven timing mechanism. 3. Modification of the present model to accommcdate the simulation of a plate pallet ...NUMULER( Technical Report ARLCD-TFR-77062 4. TITLE (and Sublttle) 5. TYPE OF REPORT & PERIOD COVERED DYNAMICS OF THE PIN PALLET RUNAWAY ESCAPEMENT 6...instantaneous positions of the pallet pin and the escape-wheel form the basis of the controls in the computer program. DO I FJAN 1473AVr1t’I o INOV 6IS

  10. Immune Escape Strategies of Malaria Parasites

    PubMed Central

    Gomes, Pollyanna S.; Bhardwaj, Jyoti; Rivera-Correa, Juan; Freire-De-Lima, Celio G.; Morrot, Alexandre

    2016-01-01

    Malaria is one of the most life-threatening infectious diseases worldwide. Immunity to malaria is slow and short-lived despite the repeated parasite exposure in endemic areas. Malaria parasites have evolved refined machinery to evade the immune system based on a range of genetic changes that include allelic variation, biomolecular exposure of proteins, and intracellular replication. All of these features increase the probability of survival in both mosquitoes and the vertebrate host. Plasmodium species escape from the first immunological trap in its invertebrate vector host, the Anopheles mosquitoes. The parasites have to pass through various immunological barriers within the mosquito such as anti-microbial molecules and the mosquito microbiota in order to achieve successful transmission to the vertebrate host. Within these hosts, Plasmodium species employ various immune evasion strategies during different life cycle stages. Parasite persistence against the vertebrate immune response depends on the balance among virulence factors, pathology, metabolic cost of the host immune response, and the parasites ability to evade the immune response. In this review we discuss the strategies that Plasmodium parasites use to avoid the vertebrate host immune system and how they promote successful infection and transmission. PMID:27799922

  11. Immune Escape Strategies of Malaria Parasites.

    PubMed

    Gomes, Pollyanna S; Bhardwaj, Jyoti; Rivera-Correa, Juan; Freire-De-Lima, Celio G; Morrot, Alexandre

    2016-01-01

    Malaria is one of the most life-threatening infectious diseases worldwide. Immunity to malaria is slow and short-lived despite the repeated parasite exposure in endemic areas. Malaria parasites have evolved refined machinery to evade the immune system based on a range of genetic changes that include allelic variation, biomolecular exposure of proteins, and intracellular replication. All of these features increase the probability of survival in both mosquitoes and the vertebrate host. Plasmodium species escape from the first immunological trap in its invertebrate vector host, the Anopheles mosquitoes. The parasites have to pass through various immunological barriers within the mosquito such as anti-microbial molecules and the mosquito microbiota in order to achieve successful transmission to the vertebrate host. Within these hosts, Plasmodium species employ various immune evasion strategies during different life cycle stages. Parasite persistence against the vertebrate immune response depends on the balance among virulence factors, pathology, metabolic cost of the host immune response, and the parasites ability to evade the immune response. In this review we discuss the strategies that Plasmodium parasites use to avoid the vertebrate host immune system and how they promote successful infection and transmission.

  12. [Escape of transgenes and its ecological risks].

    PubMed

    Lu, Baorong; Zhang, Wenju; Li, Bo

    2003-06-01

    The rapid development of biotechnology, particularly the transgenic technology, has brought us with tremendous opportunities to solve the world's starvation problems that have been caused by the continued expanding of the global population. However, the application of transgenic biotechnology and the environmental release of transgenic organisms have evoked a series of extraordinary debates on biosafety issues related to the prosperity and the future of transgenic technology. The public and scientific communities are desperately interested in knowing whether the transgenic products would pose negative influences on plants and animals, human life and health, as well as on genetic resources and environment. These concerns have become universal hot topics over the last decade. Among the most debated biosafety issues caused potentially by transgenic products, transgene escape to the environment and its consequent ecological risks become one of the appealing focal points. In this review, a series of biosafety issues concerned by public, including the possibility of transgene escape and its various paths, as well as the potential ecological risks caused by such escape were discussed, and various approaches for controlling for transgene escape and the factors to consider when designing safety isolation distance between transgenic varieties and other concerned plants were also examined. The objective of this review is to allow readers to understand the potential biosafety problems caused by environmental release of transgenic crops and by the escape of foreign transgenes in particular, and to use the effective tools to control and avoid transgene escape.

  13. Gated escaping of ligand out of protein

    NASA Astrophysics Data System (ADS)

    Sheu, Sheh-Yi; Yang, Dah-Yen

    2000-01-01

    We construct a new gating model and develop a new theory to study the escaping process of a ligand out of a spherical cavity with a puncture (or gate) on the surface. The gate undulation can be regulated by any time-dependent function and the motion of the ligand inside the spherical cavity is mapped into a two-dimensional entropy potential surface. Hence the driving force of our model is entropy only. For a static gate, the escaping process corresponds to climbing a two-dimensional entropy barrier. When the gate open angle is small, the escaping rate is proportional to the square of the opening angle. The prefactor of the escaping rate constant depends on the curvature of the entropy potential surface. For coherent gating, the survival time depends not only on the gate undulation frequency but also on how the initial state is defined. On the escaping from protein, our escaping rate shows it is qualitatively consistent with the experimental result of ligand recombination in myoglobin.

  14. Rabies viral mechanisms to escape the IFN system: the viral protein P interferes with IRF-3, Stat1, and PML nuclear bodies.

    PubMed

    Chelbi-Alix, Mounira K; Vidy, Aurore; El Bougrini, Jamila; Blondel, Danielle

    2006-05-01

    Interferons (IFNs) are a family of secreted proteins with antiviral, antiproliferative, and immunomodulatory activities. The different biologic actions of IFN are believed to be mediated by the products of specifically IFN-stimulated genes (ISG) in the target cells. The IFN response is the first line of defense against viral infections. Viruses, which require the cellular machinery for their replication, have evolved different ways to counteract the action of IFN by inhibiting IFN production or Jak-Stat signaling or by altering ISG products. This review focuses on the role of viral proteins from the RNA virus family, particularly rabies P protein. P protein mediates inhibition of the IFN system by different pathways: it inhibits IFN production by impairing IFN regulatory factor-3 (IRF-3) phosphorylation and IFN signaling by blocking nuclear transport of Stat1 and alters promyelocytic leukemia (PML) nuclear bodies by retaining PML in the cytoplasm.

  15. Orbital and escape dynamics in barred galaxies - II. The 3D system: exploring the role of the normally hyperbolic invariant manifolds

    NASA Astrophysics Data System (ADS)

    Jung, Christof; Zotos, Euaggelos E.

    2016-12-01

    A three degrees of freedom (3-dof) barred galaxy model composed of a spherically symmetric nucleus, a bar, a flat disc and a spherically symmetric dark matter halo is used for investigating the dynamics of the system. We use colour-coded plots to demonstrate how the value of the semimajor axis of the bar influences the regular or chaotic dynamics of the 3-dof system. For distinguishing between ordered and chaotic motion, we use the Smaller ALingment Index (SALI) method, a fast yet very accurate tool. Undoubtedly, the most important elements of the dynamics are the normally hyperbolic invariant manifolds (NHIMs) located in the vicinity of the index 1 Lagrange points L2 and L3. These manifolds direct the flow of stars over the saddle points, while they also trigger the formation of rings and spirals. The dynamics in the neighbourhood of the saddle points is visualized by bifurcation diagrams of the Lyapunov orbits as well as by the restriction of the Poincaré map to the NHIMs. In addition, we reveal how the semimajor axis of the bar influences the structure of these manifolds which determine the final stellar structure (rings or spirals). Our numerical simulations suggest that in galaxies with weak bars the formation of R1 rings or R_1^' } pseudo-rings is favoured. In the case of galaxies with intermediate and strong bars, the invariant manifolds seem to give rise to R1R2 rings and twin spiral formations, respectively. We also compare our numerical outcomes with earlier related work and with observational data.

  16. Maturation of escape circuit function during the early adulthood of cockroaches Periplaneta americana.

    PubMed

    Libersat, Frederic; Leung, Vicky; Mizrahi, Adi; Mathenia, Nick; Comer, Christopher

    2005-01-01

    During postembryonic development of insects, sensorimotor pathways, which generate specific behaviors, undergo maturational changes. It is less clear whether such pathways are typically stable, or undergo further maturation, during the adult stage. In the present study, we have examined this issue by multilevel analysis of a simple model system, the escape behavior of the cockroach, from identified synapses to behavior. We show that the escape system is highly responsive immediately after the molt to adulthood, but that the latency of escape responses was not at its typical value immediately after the molt to adult. The latency of escape behavior increased over the first 30 days of adult life, perhaps indicating maturational adjustments of the escape sensorimotor pathway. The first station in the escape circuitry is the synaptic connections between the cercal wind receptors and the giant interneurons. We measured unitary excitatory synaptic potentials between single sensory neurons and an identified giant interneuron (GI(2)). We found a decrease in the synaptic strength between identified cercal hairs from a single column and GI(2) over the first month after the adult molt. Consequently, the latency and the number of action potentials of GI(2) in response to natural stimuli increased and decreased respectively during this time. Thus, we show that both behavioral performance and the wind sensitivity of GI(2) decreased over the first month after molt. We conclude that the cockroach escape system undergoes further sensorimotor maturation over a period of 1 month, and that cellular changes correlate with, or predict, some changes in behavioral performance.

  17. Simple control laws for continuous-thrust escape or capture and their use in optimisation

    NASA Technical Reports Server (NTRS)

    Petropoulos, A. E.; Whiffen, G. J.; Sims, J. A.

    2002-01-01

    Interplanetary missions which use low-thrust, high specific impulse propulsion can further capitalise on the capabilities of the propulsion system by using it to effect escape from the launch body or capture at a target body.

  18. Implications of Advanced Technologies for Air and Spacecraft Escape

    DTIC Science & Technology

    1990-02-01

    when joint strength is exceeded or when the long bones are fractured by contact with the seat structure. Injury of the cervical spine is caused by...accelerations with the operational injury rates asPaciated with the specific escape systems (12.13). After operational verification and use of the model in...York,309-342, 1974. 4. Ewing C.L. : Injury criteriaand human tolerance for the neck . Aircraft crashworthiness, University press of Virginia

  19. WANDERING STARS: AN ORIGIN OF ESCAPED POPULATIONS

    SciTech Connect

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

    2009-12-10

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

  20. Heterochrony and the development of the escape response: prehatching movements in the rainbow trout Oncorhynchus mykiss.

    PubMed

    Gibb, Alice C; Liu, Corina; Swanson, Brook O

    2007-10-01

    Teleost fishes produce coordinated escape responses (C-starts) at hatching. This implies that essential swimming morphologies and motor behaviors develop during the incubation interval while the embryo is in the chorion. We examined prehatching motor behaviors in rainbow trout Oncorhycus mykiss (considered morphologically mature at hatching) and compared this species with zebrafish Danio rerio (considered morphologically immature) and assessed two hypotheses concerning the development of escape behavior. (1) Escape behavior is associated with the formation of key elements of the musculoskeletal and nervous systems; thus, the escape response appears early in ontogeny, when these elements form. (2) Escape behavior is not directly associated with the formation of underlying morphological elements; instead, it appears at hatching (i.e. when needed). We find that rainbow trout, like zebrafish, respond to touch early in the incubation interval, but do not demonstrate a complete C-start (including the second, propulsive stage) until shortly before hatching. At hatching, rainbow trout and zebrafish are similar in the degree of development of the chondocranium, paired fins and visceral arches (which comprise the larval jaw and gill support); however, rainbow trout have incipient rays in their unpaired fins (dorsal, anal and caudal), whereas zebrafish retain the embryonic fin fold. Although rainbow trout are more mature in axial swimming morphology at hatching, the essential neural and musculoskeletal systems that produce a coordinated escape response are functional at hatching in both species. This finding supports the evolutionary hypothesis that an effective escape response is critical for the survival of newly hatched teleost fishes.

  1. The double-H maze test, a novel, simple, water-escape memory task: acquisition, recall of recent and remote memory, and effects of systemic muscarinic or NMDA receptor blockade during training.

    PubMed

    Pol-Bodetto, Sarah; Jeltsch-David, Hélène; Lecourtier, Lucas; Rusnac, Nathalia; Mam-Lam-Fook, Célia; Cosquer, Brigitte; Geiger, Karin; Cassel, Jean-Christophe

    2011-03-17

    To explore spatial cognition in rodents, research uses maze tasks, which differ in complexity, number of goals and pathways, behavioural flexibility, memory duration, but also in the experimenter's control over the strategy developed to reach a goal (e.g., allocentric vs. egocentric). This study aimed at validating a novel spatial memory test: the double-H maze test. The transparent device made of an alley with two opposite arms at each extremity and two in its centre is flooded. An escape platform is submerged in one arm. For experiments 1-3, rats were released in unpredictable sequences from one of both central arms to favour an allocentric approach of the task. Experiment 1 (3 trials/day over 6 days) demonstrated classical learning curves and evidence for recent and nondegraded remote memory performance. Experiment 2 (2 days, 3 trials/day) showed a dose-dependent alteration of task acquisition/consolidation by muscarinic or NMDA receptor blockade; these drug effects vanished with sustained training (experiment 3; 4 days, 3 trials/day). Experiment 4 oriented rats towards a procedural (egocentric) approach of the task. Memory was tested in a misleading probe trial. Most rats immediately switched from response learning-based to place learning-based behaviour, but only when their initial view on environmental cues markedly differed between training and probe trials. Because this simple task enables the formation of a relatively stable memory trace, it could be particularly adapted to study consolidation processes at a system level or/and the interplay between procedural and declarative-like memory systems.

  2. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  3. Hydrogen Escape from early Earth and Mars

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  4. MEMO: Mars Escape and Magnetic Orbiter

    NASA Astrophysics Data System (ADS)

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

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

  5. 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…

  6. Jet-propelled escape in the squid Loligo opalescens: concerted control by giant and non-giant motor axon pathways.

    PubMed Central

    Otis, T S; Gilly, W F

    1990-01-01

    Recordings of stellar nerve activity were made during escape responses in living squid. Short-latency activation of the giant axons is triggered by light-flash stimulation that elicits a stereotyped startle-escape response and powerful jet. Many other types of stimuli produce a highly variable, delayed-escape response with strong jetting primarily controlled by a small axon motor pathway. In such cases, activation of the giant axons is not necessary for a vigorous escape jet. When they are utilized, the giant axons are not activated until well after the non-giant system initiates the escape response, and excitation is critically timed to boost the rise in intramantle pressure. Squid thus show at least two escape modes in which the giant axons can contribute in different ways to the control of a highly flexible behavior. PMID:2326255

  7. 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

  8. Genes that escape from X inactivation.

    PubMed

    Berletch, Joel B; Yang, Fan; Xu, Jun; Carrel, Laura; Disteche, Christine M

    2011-08-01

    To achieve a balanced gene expression dosage between males (XY) and females (XX), mammals have evolved a compensatory mechanism to randomly inactivate one of the female X chromosomes. Despite this chromosome-wide silencing, a number of genes escape X inactivation: in women about 15% of X-linked genes are bi-allelically expressed and in mice, about 3%. Expression from the inactive X allele varies from a few percent of that from the active allele to near equal expression. While most genes have a stable inactivation pattern, a subset of genes exhibit tissue-specific differences in escape from X inactivation. Escape genes appear to be protected from the repressive chromatin modifications associated with X inactivation. Differences in the identity and distribution of escape genes between species and tissues suggest a role for these genes in the evolution of sex differences in specific phenotypes. The higher expression of escape genes in females than in males implies that they may have female-specific roles and may be responsible for some of the phenotypes observed in X aneuploidy.

  9. 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

  10. 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

  11. Escape as reinforcement and escape extinction in the treatment of feeding problems.

    PubMed

    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.

  12. Effects of predator and prey hunting and escape strategies on ecosystem dynamics

    NASA Astrophysics Data System (ADS)

    Cho, Jung-Hee; Lee, Sang-Hee

    2014-03-01

    Understanding of an ecosystem's resilience and stability requires an understanding of predatorprey dynamics because ecosystems consist of dynamical interacting subsystems that include predator-prey relationships. These relationships are closely related to the hunting-escaping strategies employed by the predator and prey. Therefore, understanding the effects of hunting and escaping strategies on ecosystems will lead to a better understanding of those systems. To this end, we constructed a spatially explicit lattice model to simulate integrative predator-prey-plant relationships. When an individual simultaneously encounters its predator and prey, either hunting or escaping should take priority. Hunting priority is referred to as a hunting preferred strategy ( HPS), while escape priority is referred to as an escape preferred strategy ( EPS). These strategies are associated with some degree of willingness to either hunt ( H) or escape ( E). In our model, the willingness of an individual to hunt or escape increased with increasing value of H or E, respectively we investigated changes in the predicted population densities for predator, prey, and plant species with changes in the values of H and E. Simulation results indicated that HPS positively contributed to ecosystem stability because those individuals that employed HPS had a greater chance of reproduction than those that employed EPS. In addition, we briefly discuss the development of our model as a tool for understanding behavioral strategies in specific predator-prey interactions.

  13. Thermal escape from extrasolar giant planets

    PubMed Central

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

    2014-01-01

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

  14. 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.

  15. Bacillus anthracis factors for phagosomal escape.

    PubMed

    Tonello, Fiorella; Zornetta, Irene

    2012-07-01

    The mechanism of phagosome escape by intracellular pathogens is an important step in the infectious cycle. During the establishment of anthrax, Bacillus anthracis undergoes a transient intracellular phase in which spores are engulfed by local phagocytes. Spores germinate inside phagosomes and grow to vegetative bacilli, which emerge from their resident intracellular compartments, replicate and eventually exit from the plasma membrane. During germination, B. anthracis secretes multiple factors that can help its resistance to the phagocytes. Here the possible role of B. anthracis toxins, phospholipases, antioxidant enzymes and capsules in the phagosomal escape and survival, is analyzed and compared with that of factors of other microbial pathogens involved in the same type of process.

  16. Statistical theory of asteroid escape rates.

    PubMed

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

    2002-07-01

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

  17. 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

  18. Escape factors in zero-dimensional radiation-transfer codes

    NASA Astrophysics Data System (ADS)

    Phillips, G. J.; Wark, J. S.; Kerr, F. M.; Rose, S. J.; Lee, R. W.

    2008-04-01

    Several zero-dimensional non-LTE radiation-transfer codes are in common use within the laser-plasma community (for example, RATION, FLY, FLYCHK and GALAXY). These codes are capable of generating calculated emission spectra for a plasma of given density and temperature in the presence of a radiation field. Although dimensionless in nature, these codes can take into account the coupling of radiation and populations by use of the escape factor method, and in this sense the codes incorporate the finite size of the plasma of interest in two ways - firstly in the calculation of the effect of the radiation on the populations and secondly when using these populations to generate a spectrum. Different lengths can be used within these two distinct operations, though it has not been made clear what these lengths should be. We submit that the appropriate length to use for the calculation of populations in such zero-dimensional codes is the mean chord of the system, whilst when calculating the spectrum the appropriate length is the size of the plasma along the line of sight. Indeed, for specific plasma shapes using the appropriate escape factors it can be shown that this interpretation agrees with analytic results. However, this is only the case if the correct escape factor is employed: use of the Holstein escape factor (which is in widely distributed versions of the codes mentioned above) is found to be significantly in error under most conditions. We also note that for the case where a plasma is close to coronal equilibrium, some limited information concerning the shape of the plasma can be extracted merely from the ratio of optically thick to optically thin lines, without the need for any explicit spatial resolution.

  19. On the escape of CH4 from Pluto's atmosphere

    NASA Astrophysics Data System (ADS)

    Koskinen, T. T.; Erwin, J. T.; Yelle, R. V.

    2015-09-01

    We adapted a multispecies escape model, developed for close-in extrasolar planets, to calculate the escape rates of CH4 and N2 from Pluto. In the absence of escape, CH4 should overtake N2 as the dominant species below the exobase. The CH4 profile depends strongly on the escape rate, however, and the typical escape rates predicted for Pluto lead to a nearly constant mixing ratio of less than 1% below the exobase. In this case the CH4 escape rate is only 5-10% of the N2 escape rate. Observations of the CH4 profile by the New Horizons/ALICE spectrograph can constrain the CH4 escape rate and provide a unique test for escape models.

  20. Escape of Hydrogen from HD209458b

    NASA Astrophysics Data System (ADS)

    Erwin, Justin; Yelle, Roger; Koskinen, Tommi

    2017-04-01

    Recent modeling of the atmosphere of HD209458b has been used to interpret the Lyman-α line and other observations during transits. Koskinen et al. (2010) used a hydrostatic density profile in the thermosphere combined with the Voigt profile to estimate the Lyman-alpha transit depths for an array of model parameters. A detailed photochemical-dynamical model of the thermosphere was developed by Koskinen et al. (2013a) and used to again estimate model parameters to fit not only the Lyman-alpha transits, but also the transits in the O I, C II and Si III lines (Koskinen et al., 2013b). Recently, Bourrier and Lecavelier (2013) modeled the escape of hydrogen from the extended atmospheres of HD209458b and HD189733b and used the results to interpret Lyman-alpha observations. They included acceleration of hydrogen by radiation pressure and stellar wind protons to simulate the high velocity tails of the velocity distribution, arguing that the observations are explained by high velocity gas in the system while Voigt broadening is negligible. In this work we connect a free molecular flow (FMF) model similar to Bourrier and Lecavelier (2013) to the results of Koskinen et al. (2013b) and properly include absorption by the extended thermosphere in the transit model. In this manner, we can interpret the necessity of the various physical processes in matching the observed line profiles. Furthermore, the transit depths of this model can be used to re-evaluate the atmospheric model parameters to determine if they need to be adjusted due

  1. 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

  2. Centrifugally Stimulated Exospheric Ion Escape at Mercury

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  3. Unconventional Interrogation Yields HIV's Escape Plan.

    PubMed

    Kepler, Thomas B

    2017-06-14

    Chasing HIV-1 across the genotype landscape, unequipped to anticipate its maneuvers, the antibody variable-region genes pursue the virus in futility. In this issue of Cell Host & Microbe, Dingens et al. (2017) exhibit a powerful technology that reveals the escape pathways of HIV-1 and may enable its capture. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. 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)

  5. 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.

  6. 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...

  7. Escape of photons from two fixed extreme Reissner-Nordstroem black holes

    SciTech Connect

    Alonso, Daniel; Ruiz, Antonia; Sanchez-Hernandez, Manuel

    2008-11-15

    We study the scattering of light (null geodesics) by two fixed extreme Reissner-Nordstroem black holes, in which the gravitational attraction of their masses is exactly balanced with the electrostatic repulsion of their charges, allowing a static spacetime. We identify the set of unstable periodic orbits that form part of the fractal repeller that completely describes the chaotic escape dynamics of photons. In the framework of periodic orbit theory, the analysis of the linear stability of the unstable periodic orbits is used to obtain the main quantities of chaos that characterize the escape dynamics of the photons scattered by the black holes. In particular, the escape rate that is compared with the result obtained from numerical simulations that consider statistical ensembles of photons. We also analyze the dynamics of photons in the proximity of a perturbed black hole and give an analytic estimate of the escape rate in this system.

  8. Service-Life Extension of Explosive Escape Devices

    NASA Technical Reports Server (NTRS)

    Bement, L. J.; Schimmel, M. L.

    1987-01-01

    Chemical and functional tests yield conservative service-life estimates. Approach to extension of service lives of explosive devices in aircraft escape system developed, supported by testing of representative candidate devices to evaluate quantitatively effects of service, age, and degradation, and to enable responsible, conservative service-life determinations. Five types of explosive components evaluated: rigid and flexible explosive transfer lines; one-way transfers; flexible, linear-shaped charges; and initiation-handles. Extension of service in realistic manner provides both cost savings and increased system reliability.

  9. 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.

  10. 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.

  11. 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.

  12. Escape driven by α -stable white noises

    NASA Astrophysics Data System (ADS)

    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 β of the Lévy noise, the escape can either become enhanced or suppressed: a negative asymmetry parameter β typically yields a decrease for the escape rate while the rate itself depicts a non-monotonic behavior as a function of the stability index α that characterizes the jump length distribution of Lévy noise, exhibiting a marked discontinuity at α=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.

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  1. 46 CFR 127.240 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... any interior door giving access to either of the two required means of escape, except that a crash... escape that could cause injury, ensnare clothing, or damage lifejackets. (i) No interior stairway, other...

  2. An approximate analytic model of a star cluster with potential escapers

    NASA Astrophysics Data System (ADS)

    Daniel, Kathryne J.; Heggie, Douglas C.; Varri, Anna Lisa

    2017-06-01

    In the context of a star cluster moving on a circular galactic orbit, a 'potential escaper' is a cluster star that has orbital energy greater than the escape energy, and yet is confined within the Jacobi radius of the stellar system. On the other hand, analytic models of stellar clusters typically have a truncation energy equal to the cluster escape energy, and therefore explicitly exclude these energetically unbound stars. Starting from the landmark analysis performed by Hénon of periodic orbits of the circular Hill equations, we present a numerical exploration of the population of 'non-escapers', defined here as those stars that remain within two Jacobi radii for several galactic periods, with energy above the escape energy. We show that they can be characterized by the Jacobi integral and two further approximate integrals, which are based on perturbation theory and ideas drawn from Lidov-Kozai theory. Finally, we use these results to construct an approximate analytic model that includes a phase-space description of a population resembling that of potential escapers, in addition to the usual bound population.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Escape of atmospheres and loss of water

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  9. Escape of atmospheres and loss of water

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  10. Fixed-ratio escape reinforcement1

    PubMed Central

    Azrin, N. H.; Holz, W. C.; Hake, D. F.; Ayllon, T.

    1963-01-01

    Escape responses of squirrel monkeys were reinforced according to a fixed-ratio schedule. The reinforcement was a period of safety from a stimulus that signalled the delivery of intermittent pain-shocks. When the frequency of shock was gradually reduced, the performance remained at a high level until the shocks were quite infrequent. Similarly, the duration of the period of safety could be reduced to a few seconds with little loss of behavior. Thus, the responses appeared to be reinforced by even a brief period of safety, the actual degree of shock reduction being fairly slight. The changes in responding during this fixed-ratio escape procedure were comparable to the response changes typically obtained during fixed-ratio food procedures. PMID:13965780

  11. [Escape mutants of hepatitis B virus].

    PubMed

    Jaramillo, Carlos Mario; Navas, María-Cristina

    2015-04-01

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

  12. Dynamic Escape Routes for Naval Ships

    DTIC Science & Technology

    2005-09-01

    3 o Increase the likelihood of successfully salvaging the ship, and o Increase the likelihood that the crew is rescued safely. It will be possible...spans the period before the event that triggers ship abandonment. Escape routes can be configured based on two factors: 6 o “Crew distribution...crewmembers but the guards are resting in cabins and berthing rooms. This is a plausible scenario at night when the ship is in a non-home port. o

  13. Mars Planetary Ion Escape: Assessing Transitional Trajectories

    NASA Astrophysics Data System (ADS)

    Johnson, B. C.

    2016-12-01

    The availability of in situ observations of ions escaping from Mars' atmosphere is vital to descriptions of atmospheric loss, but such point measurements taken by orbiting spacecraft cannot easily differentiate between spatial changes along the spacecraft trajectory and temporal changes, nor can they directly provide information about atmospheric loss rates during Mars' long history. Numerical models are therefore crucial to crystalizing understanding of ion escape processes. One such category are test particle models that release non-interacting ions into background electric and magnetic fields and then calculate ion trajectories and loss rates. To date, such models have focused on the collisionless regime. Another approach is to include collisions between the particles, the Direct Simulation Monte Carlo (DSMC) approach. We present the results of the first fully three dimensional collisional Mars ion DSMC model capable of peering deep into the collionsional atmosphere, beneath the ionospheric peak, i.e., the ion version of the Adaptive Mesh Particle Simulator (AMPS) configured for Mars. Multiple model runs are performed, each with a different cutoff altitude below which collisions are included. Escape rates of O+ are calculated for each run, providing both the asymptotic escape rate as the cutoff altitude extends into the exosphere and also an idea of the altitude range for which collisions must be included for the results to reasonably converge to this value. In other words, how low can a collisionless model go? Furthermore, these results can be used to interpret satellite data of planetary ions, helping to determine if the spacecraft is in the upflow or outflow regime. In other words, how low can observations be used for measuring the loss of planetary ions to deep space? This entire process is repeated a second time, with the first set of runs corresponding to solar minimum input parameters, and the second set of runs corresponding to solar maximum parameters.

  14. Lithium clearance in mineralocorticoid escape in humans

    SciTech Connect

    Boer, W.H.; Koomans, H.A.; Mees, E.J.D.

    1987-03-01

    Lithium clearance (C/sub Li/) has been advanced as an indicator of Na delivery from the proximal tubules. The authors studied C/sub Li/ in eight healthy males before and after mineralocorticoid escape, a maneuver that may induce suppression of fractional proximal Na reabsorption (FPR/sub Na/). FPR/sub Na/ was also estimated from changes in maximal free water clearance (C/sub H/sub 2/O/). Plasma volume was measured as the /sup 131/I-labeled albumin distribution space. Extracellular fluid volume was estimated as the /sup 82/Br vector distribution volume. According to the latter method, FPR/sub Na/ dropped whereas inulin clearance rose. The changes in C/sub Li/ were surprisingly large. If lithium is a valid marker of Na handling in the proximal tubule in humans, this change would imply a fall in FPR/sub Na/, suggesting a much larger shift in tubular Na reabsorption in escape than hitherto suspected. In addition, it would suggest that the inevitable back diffusion of a part of the solute-free water in the distal nephron, and thus overestimation of FPR/sub Na/ by the C/sub H/sub 2/O/ method, increases importantly during escape. Alternately, lithium may not be a good marker of proximal tubular Na handling. For instance, both lithium reabsorption and escape may take place beyond the proximal tubule, or lithium may be excreted in the distal nephron in certain conditions. Present methods do not permit further analysis of these options in the human model.

  15. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... a means of escape must be such as to allow easy movement of persons when wearing life jackets. There must be no protrusions in means of escape that could cause injury, ensnare clothing, or damage life jackets. (f) The minimum clear opening of a door or passageway used as a means of escape must not be less...

  16. 30 CFR 77.1101 - Escape and evacuation; plan.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 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... Fire Protection § 77.1101 Escape and evacuation; plan. (a) Before September 30, 1971, each operator of...

  17. 30 CFR 77.1101 - Escape and evacuation; plan.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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... Fire Protection § 77.1101 Escape and evacuation; plan. (a) Before September 30, 1971, each operator of...

  18. 30 CFR 77.1101 - Escape and evacuation; plan.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 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... Fire Protection § 77.1101 Escape and evacuation; plan. (a) Before September 30, 1971, each operator of...

  19. 30 CFR 77.1101 - Escape and evacuation; plan.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 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... Fire Protection § 77.1101 Escape and evacuation; plan. (a) Before September 30, 1971, each operator of...

  20. 30 CFR 77.1101 - Escape and evacuation; plan.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 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... Fire Protection § 77.1101 Escape and evacuation; plan. (a) Before September 30, 1971, each operator of...

  1. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 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...

  2. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 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...

  3. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 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...

  4. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 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...

  5. 46 CFR 108.153 - Location of means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Location of means of escape. 108.153 Section 108.153 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Construction and Arrangement Means of Escape § 108.153 Location of means of escape....

  6. 46 CFR 108.153 - Location of means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Location of means of escape. 108.153 Section 108.153 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE DRILLING UNITS DESIGN AND EQUIPMENT Construction and Arrangement Means of Escape § 108.153 Location of means of escape....

  7. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 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... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Mechanical escape facilities. 75.382 Section...

  8. Scrunching: a novel escape gait in planarians.

    PubMed

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

    2015-09-10

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

  9. Scrunching: a novel escape gait in planarians

    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.

  10. Transfer to near-Earth asteroids from a lunar orbit via Earth flyby and direct escaping trajectories

    NASA Astrophysics Data System (ADS)

    Wang, Yamin; Zhang, Yonghe; Qiao, Dong; Mao, Qingyun; Jiang, Jun

    2017-04-01

    In this paper, transfer trajectories from the Moon to near-Earth asteroids with different escaping trajectory options, Earth flyby and direct escaping, are investigated. The former executes an Earth flyby maneuver to increase the orbital energy during the transfer. The latter realizes the transfer by a single impulse at perilune. In this work, these two kinds of escaping orbits in the Earth-Moon planar circular-restricted three-body (PCRTB) system are analyzed firstly. The abilities to achieve the same Earth hyperbolic excess velocity for both orbits with minimum velocity impulse expenditure are calculated and analyzed. Then, the asteroid flyby trajectory in ephemeris model via two types of escaping orbits is designed. Asteroids 4179 Toutatis from Apollo and 3908 Nyx from Amor, represent the small and large transfer energy, respectively, are chosen as targets. The selection strategy of escaping trajectories for small and large-energy transfers is discussed.

  11. 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

  12. 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.

  13. Risks incurred by hydrogen escaping from containers and conduits

    SciTech Connect

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

    1998-08-01

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

  14. Effects of temperature on escape jetting in the squid Loligo opalescens.

    PubMed

    Neumeister, H; Ripley, B; Preuss, T; Gilly, W F

    2000-02-01

    In Loligo opalescens, a sudden visual stimulus (flash) elicits a stereotyped, short-latency escape response that is controlled primarily by the giant axon system at 15 C. We used this startle response as an assay to examine the effects of acute temperature changes down to 6 C on behavioral and physiological aspects of escape jetting. In free-swimming squid, latency, distance traveled and peak velocity for single escape jets all increased as temperature decreased. In restrained squid, intra-mantle pressure transients during escape jets increased in latency, duration and amplitude at low temperature. Recordings of stellar nerve activity revealed repetitive firing of the giant motor axon accompanied by increased activity in the non-giant motor axons that run in parallel. Selective stimulation of giant and non-giant motor axons in isolated nerve-muscle preparations failed to show the effects seen in vivo, i.e. increased peak force and increased neural activity at low temperature. Taken together, these results suggest that L. opalescens is able to compensate escape jetting performance for the effects of acute temperature reduction. A major portion of this compensation appears to occur in the central nervous system and involves alterations in the recruitment pattern of both the giant and non-giant axon systems.

  15. Slow and Fast Escape for Open Intermittent Maps

    NASA Astrophysics Data System (ADS)

    Demers, Mark F.; Todd, Mike

    2017-04-01

    If a system mixes too slowly, putting a hole in it can completely destroy the richness of the dynamics. Here we study this instability for a class of intermittent maps with a family of slowly mixing measures. We show that there are three regimes: (1) standard hyperbolic-like behavior where the rate of mixing is faster than the rate of escape through the hole, there is a unique limiting absolutely continuous conditionally invariant measure (accim) and there is a complete thermodynamic description of the dynamics on the survivor set; (2) an intermediate regime, where the rate of mixing and escape through the hole coincide, limiting accims exist, but much of the thermodynamic picture breaks down; (3) a subexponentially mixing regime where the slow mixing means that mass simply accumulates on the parabolic fixed point. We give a complete picture of the transitions and stability properties (in the size of the hole and as we move through the family) in this class of open systems. In particular, we are able to recover a form of stability in the third regime above via the dynamics on the survivor set, even when no limiting accim exists.

  16. Cold Ion Escape from the Martian Ionosphere

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  17. Heating and acceleration of escaping planetary ions

    NASA Astrophysics Data System (ADS)

    Nilsson, Hans

    2010-05-01

    The magnetic field of the Earth acts like a shield against the solar wind, leading to a magnetopause position many planetary radii away from the planet, in contrast to the situation at non- or weakly magnetized planets such as Mars and Venus. Despite this there is significant ion outflow due to solar wind interaction from the cusp and polar cap regions of the Earth's ionosphere. Effective interaction regions form, in particular in the ionospheric projection of the cusp, where ionospheric plasma flows up along the field-lines in response to magnetospheric energy input. Strong wave-particle interaction at altitudes above the ionosphere further accelerates the particles so that gravity is overcome. For the particles to enter a direct escape path they must be accelerated along open magnetic field lines so that they cross the magnetopause or reach a distance beyond the region of return flow in the tail. This return flow may also be either lost to space or returned to the atmosphere. Throughout this transport chain the heating and acceleration experienced by the particles will have an influence on the final fate of the particles. We will present quantitative estimates of centrifugal acceleration and perpendicular heating along the escape path from the cusp, through the high altitude polar cap/mantle, based on Cluster spacecraft data. We will open up for a discussion on the benefits of a ponderomotive force description of the acceleration affecting the ion circulation and escape. Finally we will compare with the situation at the unmagnetized planets Mars and Venus and discuss to what extent a magnetic field protects an atmosphere from loss through solar wind interaction.

  18. X-chromosome inactivation and escape

    PubMed Central

    DISTECHE, CHRISTINE M.; BERLETCH, JOEL B.

    2016-01-01

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

  19. Suicide as escape from psychotic panic.

    PubMed

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

    2016-01-01

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

  20. Evolutionary escape from the prisoner's dilemma.

    PubMed

    Worden, Lee; Levin, Simon A

    2007-04-07

    The classic prisoner's dilemma model of game theory is modified by introducing occasional variations on the options available to players. Mutation and selection of game options reliably change the game matrix, gradually, from a prisoner's dilemma game into a byproduct mutualism one, in which cooperation is stable, and "temptation to defect" is replaced by temptation to cooperate. This result suggests that when there are many different potential ways of interacting, exploring those possibilities may make escape from prisoner's dilemmas a common outcome in the world. A consequence is that persistent prisoner's dilemma structures may be less common than one might otherwise expect.

  1. Modeling Fluorescence Escape from Tissue Phantoms

    NASA Astrophysics Data System (ADS)

    Gardner, Craig Morris

    1995-01-01

    This dissertation represents a contribution to the field of quantitative fluorescence spectroscopy of biological tissue. The absorption and scattering properties of a turbid medium affect the propagation of fluorescence to the medium surface. Optical properties also affect the amount of light reaching a detector placed to monitor fluorescence non-invasively. These facts have in part limited fluorescence spectroscopy of turbid media to a qualitative science. To study the general characteristics of turbid medium fluorescence, a Monte Carlo algorithm of fluorescence light propagation was developed. Modifications to the general algorithm were made to study several specific light distribution quantities associated with optical fiber fluorescent measurement devices. The Monte Carlo-based studies were also used to develop simple, accurate expressions describing the one -dimensional distribution of excitation light within a turbid medium and the escape of fluorescence from the medium. The expressions have accuracy comparable to solutions of the radiative transport equation. The two expressions were combined to derive a simple expression relating the fluorescence power escaping a turbid medium due to surface excitation, to the medium intrinsic fluorescence coefficient, as a function of the medium optical properties. Based on this expression and a description of the fluorescence escape power intercepted by a distant detector, a method was developed to recover the intrinsic fluorescence coefficient from surface measurements of fluorescence and optical properties. Experiments with water-based, turbid media verified the recovery method. The method used to recover the intrinsic fluorescence coefficient was modified for use with a clinical measurement geometry, specifically a small diameter optical fiber probe. Modification required a calibration method to estimate two optical property variables from two unique surface measurements of diffuse reflectance made with the optical

  2. 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.

  3. 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

  4. MAVEN Imaging UV Spectrograph Results on the Mars Atmosphere and Atmospheric Escape

    NASA Astrophysics Data System (ADS)

    Chaffin, Michael; Schneider, Nick; McClintock, Bill; Stewart, Ian; Deighan, Justin; Jain, Sonal; Clarke, John; Holsclaw, Greg; Montmessin, Franck; Lefevre, Franck; Chaufray, Jean-Yves; Stiepen, Arnaud; Crismani, Matteo; Mayyasi, Majd; Evans, Scott; Stevens, Mike; Yelle, Roger; Jakosky, Bruce

    2016-04-01

    The Imaging Ultraviolet Spectrograph (IUVS) is one of nine science instruments aboard the Mars Atmosphere and Volatile and EvolutioN (MAVEN) spacecraft, whose payload is dedicated to exploring the upper atmosphere of Mars and understanding the magnitude and drivers of Mars' atmospheric escape rate. IUVS uses ultraviolet light to investigate the lower and upper atmosphere and ionosphere of Mars. The instrument is among the most powerful spectrographs sent to another planet, with several key capabilities: (1) separate Far-UV & Mid-UV channels for stray light control, (2) a high resolution echelle mode to resolve deuterium and hydrogen emission, (3) internal instrument pointing and scanning capabilities to allow complete mapping and nearly continuous operation, and (4) optimization for airglow studies. IUVS, along with other MAVEN instruments, obtains a comprehensive picture of the current state of the Mars upper atmosphere and ionosphere and the processes that control atmospheric escape. We present an overview of selected IUVS results, including (1) the discovery of diffuse aurora at Mars, and its contrast with previously detected discrete aurora localized near crustal magnetic fields; (2) widespread detection of mesospheric clouds; (3) Significant seasonal and short-timescale variability in thermospheric composition; (4) Global ozone maps spanning six months of seasonal evolution; and (5) mapping of the Mars H and O coronas, deriving the escape rates of H and O and their variability. This last is of particular importance for understanding the long term evolution of Mars and its atmosphere, with the observed preset escape of H potentially capable of removing a large fraction of Mars' initial water inventory, and the differential escape of O relative to H potentially providing a net source of oxidizing power to the atmosphere and planet at present, in contrast with a photochemical theory that predicts stoichiometrically balanced escape. The atmospheric and escape

  5. Influence of Sae-regulated and Agr-regulated factors on the escape of Staphylococcus aureus from human macrophages.

    PubMed

    Münzenmayer, Lisa; Geiger, Tobias; Daiber, Ellen; Schulte, Berit; Autenrieth, Stella E; Fraunholz, Martin; Wolz, Christiane

    2016-08-01

    Although Staphylococcus aureus is not a classical intracellular pathogen, it can survive within phagocytes and many other cell types. However, the pathogen is also able to escape from cells by mechanisms that are only partially understood. We analysed a series of isogenic S. aureus mutants of the USA300 derivative JE2 for their capacity to destroy human macrophages from within. Intracellular S. aureus JE2 caused severe cell damage in human macrophages and could efficiently escape from within the cells. To obtain this full escape phenotype including an intermittent residency in the cytoplasm, the combined action of the regulatory systems Sae and Agr is required. Mutants in Sae or mutants deficient in the Sae target genes lukAB and pvl remained in high numbers within the macrophages causing reduced cell damage. Mutants in the regulatory system Agr or in the Agr target gene psmα were largely similar to wild-type bacteria concerning cell damage and escape efficiency. However, these strains were rarely detectable in the cytoplasm, emphasizing the role of phenol-soluble modulins (PSMs) for phagosomal escape. Thus, Sae-regulated toxins largely determine damage and escape from within macrophages, whereas PSMs are mainly responsible for the escape from the phagosome into the cytoplasm. Damage of macrophages induced by intracellular bacteria was linked neither to activation of apoptosis-related caspase 3, 7 or 8 nor to NLRP3-dependent inflammasome activation.

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

    PubMed

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

    2016-06-01

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

  7. Structured Observations Reveal Slow HIV-1 CTL Escape

    PubMed Central

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

    2015-01-01

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

  8. Tectonic escape in the evolution of the continental crust

    NASA Technical Reports Server (NTRS)

    Burke, K.; Sengor, C.

    1986-01-01

    The continental crust originated by processes similar to those operating today and continents consist of material most of which originated long ago in arc-systems that have later been modified, especially at Andean margins and in continental collisions where crustal thickening is common. Collision-related strike-slip motion is a general process in continental evolution. Because buoyant continental (or arc) material generally moves during collision toward a nearby oceanic margin where less buoyant lithosphere crops out, the process of major strike-slip dominated motion toward a 'free-face' is called 'tectonic escape'. Tectonic escape is and has been an element in continental evolution throughout recorded earth-history. It promotes: (1) rifting and the formation of rift-basins with thinning of thickened crust; (2) pervasive strike-slip faulting late in orogenic history which breaks up mountain belts across strike and may juxtapose unrelated sectors in cross-section; (3) localized compressional mountains and related foreland-trough basins.

  9. Autoimmunity as a result of escape from RNA surveillance.

    PubMed

    Bachmann, Michael P; Bartsch, Holger; Gross, Joanne K; Maier, Shannon M; Gross, Timothy F; Workman, Jennifer L; James, Judith A; Farris, A Darise; Jung, Bettina; Franke, Claudia; Conrad, Karsten; Schmitz, Marc; Büttner, Cordula; Buyon, Jill P; Semsei, Imre; Harley, John B; Rieber, E Peter

    2006-08-01

    In previous studies, we detected a frame shift mutation in the gene encoding the autoantigen La of a patient with systemic lupus erythematosus. The mutant La mRNA contains a premature termination codon. mRNAs that prematurely terminate translation should be eliminated by RNA quality control mechanisms. As we find Abs specific for the mutant La form in approximately 30% of sera from anti-La-positive patients, we expected that mutant La mRNAs circumvent RNA control and the expression of mutant La protein could become harmful. Indeed, real-time PCR, immunostaining, and immunoblotting data of mice transgenic for the mutant La form show that mutant La mRNAs are not repressed in these animals and are translated to mutant La protein. In addition to the mutant La protein, we detected a minor portion of native human La in the mutant La-transgenic mice. Therefore, ribosomal frame shifting may allow the mutant La mRNA to escape from RNA control. Interestingly, expression of the mutant La mRNA results in a lupus-like disease in the experimental mice. Consequently, escape of mutant La mRNA from RNA control can have two effects: it 1) results in the expression of an immunogenic (neo)epitope, and 2) predisposes to autoimmunity.

  10. Autoimmunity as a Result of Escape from RNA Surveillance

    PubMed Central

    Bachmann, Michael P.; Bartsch, Holger; Gross, Joanne K.; Maier, Shannon M.; Gross, Timothy F.; Workman, Jennifer L.; James, Judith A.; Farris, A. Darise; Jung, Bettina; Franke, Claudia; Conrad, Karsten; Schmitz, Marc; Büttner, Cordula; Buyon, Jill P.; Semsei, Imre; Harley, John B.; Rieber, E. Peter

    2006-01-01

    In previous studies we detected a frame shift mutation in the gene encoding the autoantigen La of a patient with systemic lupus erythematosus. The mutant La mRNA contains a premature termination codon. mRNAs that prematurely terminate translation should be eliminated by RNA quality control mechanisms. As we find Abs specific for the mutant La form in about 30% of sera from anti-La positive patients we expected that mutant La mRNAs circumvent RNA control and the expression of mutant La protein could become harmful. Indeed, realtime PCR, immunostaining, and immunoblotting data of mice transgenic for the mutant La form show that mutant La mRNAs are not repressed in these animals and are translated to mutant La protein. In addition to the mutant La protein, we detected a minor portion of native human La in the mutant La transgenic mice. Therefore, ribosomal frame shifting may allow the mutant La mRNA to escape from RNA control. Interestingly, expression of the mutant La mRNA results in a lupus like disease in the experimental mice. Consequently, escape of mutant La mRNA from RNA control can have two effects: It (i) results in the expression of an immunogenic (neo)epitope, and (ii) predisposes to autoimmunity. PMID:16849479

  11. Tectonic escape in the evolution of the continental crust

    NASA Technical Reports Server (NTRS)

    Burke, K.; Sengor, C.

    1986-01-01

    The continental crust originated by processes similar to those operating today and continents consist of material most of which originated long ago in arc-systems that have later been modified, especially at Andean margins and in continental collisions where crustal thickening is common. Collision-related strike-slip motion is a general process in continental evolution. Because buoyant continental (or arc) material generally moves during collision toward a nearby oceanic margin where less buoyant lithosphere crops out, the process of major strike-slip dominated motion toward a 'free-face' is called 'tectonic escape'. Tectonic escape is and has been an element in continental evolution throughout recorded earth-history. It promotes: (1) rifting and the formation of rift-basins with thinning of thickened crust; (2) pervasive strike-slip faulting late in orogenic history which breaks up mountain belts across strike and may juxtapose unrelated sectors in cross-section; (3) localized compressional mountains and related foreland-trough basins.

  12. Formation and Internal Structure of Terrestrial Planets, and Atmospheric Escape

    NASA Astrophysics Data System (ADS)

    Jin, S.

    2014-11-01

    As of 2014 April 21, over 1490 confirmed exoplanets and 3705 Kepler candidates have been detected. This implies that exoplanets may be ubiquitous in the universe. In this paper, we focus on the formation, evolution, and internal structure of terrestrial planets, and the atmospheric escape of close-in planets. In chapter 2, we investigate the dynamical evolution of planetary system after the protoplanetary disk has dissipated. We find that in the final assembly stage, the occurrence of terrestrial planets is quite common and in 40% of our simulations finally at least one planet is formed in the habitable zone. We also find that if there is a highly-inclined giant planet in the system, a great many bodies will be either driven out of the system, or collide with the giant planet or the central star. This will lead to the difficulty in planetary accretion. Moreover, our results show that planetary migration can lead to the formation of close-in planets. Besides migration, close-in terrestrial planets can also be formed by a collision-merger mechanism, which means that planetary embryos can kick terrestrial planets directly into orbits that are extremely close to their parent stars. In chapter 3, we construct numerically an internal structure model for terrestrial planets, and provide three kinds of possible internal structures of Europa (Jupiter's moon) based on this model. Then, we calculate the radii of low-mass exoplanets for various mass combinations of core and mantle, and find that some of them are inconsistent with the observed radius of rocky planets. This phenomenon can be explained only if there exists a large amount of water in the core, or they own gaseous envelopes. In chapter 4, we improve our planetary evolution codes using the semi-gray model of Guillot (2010), which includes the incident flux from the host star as a heating source in planetary atmosphere. The updated codes can solve the structure of the top radiative zone of intensely irradiated

  13. A New Maneuver for Escape Trajectories

    NASA Technical Reports Server (NTRS)

    Adams, Robert B.

    2008-01-01

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

  14. Escape mechanisms of dust in Io

    NASA Astrophysics Data System (ADS)

    Flandes, A.

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

  15. 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.

  16. 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.

  17. 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.

  18. Effects of escape to alone versus escape to enriched environments on adaptive and aberrant behavior.

    PubMed Central

    Golonka, Z; Wacker, D; Berg, W; Derby, K M; Harding, J; Peck, S

    2000-01-01

    Escape-maintained aberrant behavior may be influenced by two outcomes: (a) a break from the activity and (b) subsequent access to preferred activities. To assess this hypothesis, a treatment was developed that analyzed response allocation across two break options: break alone and break with access to preferred social activities. The break with preferred activities decreased aberrant behavior and increased appropriate behavior. PMID:10885532

  19. 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.

  20. Sputtering at Mars: MAVEN observations of precipitating and escaping oxygen during nominal and extreme conditions

    NASA Astrophysics Data System (ADS)

    Curry, Shannon; Luhmann, Janet; Dong, Chuanfei; Ma, Yingjuan; Leblanc, Francois; Modolo, Ronan; Brain, David; Gruesbeck, Jacob; Hara, Takuya; Halekas, Jasper; Dong, Yaxue; Williamson, Hayley N.; Johnson, Robert E.; McFadden, James; Espley, Jared R.; Mitchell, David; Connerney, Jack; Eparvier, Frank; Lillis, Robert J.; Jakosky, Bruce

    2016-10-01

    Sputtering is believed to be one of the dominant escape mechanisms during the early epochs of our solar system when the solar activity and EUV intensities were much higher than the present day. Mars lacks a global dynamo magnetic field, which creates a scenario where the solar wind directly interacts with the upper atmosphere and newly created ions can be picked up and swept away by the background convection electric field. These pick-up ions can directly escape or precipitate back into the atmosphere and induce atmospheric sputtering of neutrals.The MAVEN spacecraft has observed the Mars upper atmosphere, ionosphere, magnetic topology and interactions with the Sun and solar wind during numerous Interplanetary Coronal Mass Ejection (ICME) impacts spanning from March 2015 to June 2016. ICMEs are associated with enhanced solar wind velocities, densities and magnetic field strength, and often drive heavy ion precipitation at much higher rates than during nominal conditions. Thus, ICMEs provide a unique environment for observing sputtering. We will compare MAVEN observations of heavy ion precipitation during nominal conditions as well as during ICMEs. Additionally, we will present global MHD and test particle simulations of the ICMEs in order to calculate sputtering escape rates for oxygen. Finally, we will use the observed and modeled sputtering escape rates to provide an initial estimate of the total sputtered atmospheric escape from Mars over billions of years.

  1. 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.

  2. Bacillus cereus immune escape: a journey within macrophages.

    PubMed

    Tran, Seav-Ly; Ramarao, Nalini

    2013-10-01

    During bacterial infection, professional phagocytes are attracted to the site of infection, where they constitute a first line of host cell defense. Their function is to engulf and destroy the pathogens. Thus, bacteria must withstand the bactericidal activity of professional phagocytes, including macrophages to counteract the host immune system. Bacillus cereus infections are characterized by bacteremia despite the accumulation of inflammatory cells at the site of infection. This implies that the bacteria have developed means of resisting the host immune system. Bacillus cereus spores survive, germinate, and multiply in contact with macrophages, eventually producing toxins that kill these cells. However, the exact mechanism by which B. cereus evades immune attack remains unclear. This review addresses the interaction between B. cereus and macrophages, highlighting, in particular, the ways in which the bacteria escape the microbicidal activities of professional phagocytes.

  3. 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.

  4. Strong purifying selection at genes escaping X chromosome inactivation.

    PubMed

    Park, Chungoo; Carrel, Laura; Makova, Kateryna D

    2010-11-01

    To achieve dosage balance of X-linked genes between mammalian males and females, one female X chromosome becomes inactivated. However, approximately 15% of genes on this inactivated chromosome escape X chromosome inactivation (XCI). Here, using a chromosome-wide analysis of primate X-linked orthologs, we test a hypothesis that such genes evolve under a unique selective pressure. We find that escape genes are subject to stronger purifying selection than inactivated genes and that positive selection does not significantly affect the evolution of these genes. The strength of selection does not differ between escape genes with similar versus different expression levels in males versus females. Intriguingly, escape genes possessing Y homologs evolve under the strongest purifying selection. We also found evidence of stronger conservation in gene expression levels in escape than inactivated genes. We hypothesize that divergence in function and expression between X and Y gametologs is driving such strong purifying selection for escape genes.

  5. 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+.

  6. Feedback regulated escape of ionising radiation from high redshift galaxies

    NASA Astrophysics Data System (ADS)

    Trebitsch, M.; Blaizot, J.

    2016-12-01

    Small galaxies are thought to provide the bulk of the radiation necessary to reionise the Universe by z ˜ 6. Their ionising efficiency is usually quantified by their escape fraction f_{esc}, but it is extremely hard to constrain from observations. With the goal of studying the physical processes that determine the values of the escape fraction, we have run a series of high resolution, cosmological, radiative hydrodynamics simulations centred on three galaxies. We find that the variability of the escape fraction follows that of the star formation rate, and that local feedback is necessary for radiation to escape.

  7. Experimental self-punishment and superstitious escape behavior.

    PubMed

    MIGLER, B

    1963-07-01

    Rats were trained to escape from shock by pressing a bar. Bar holding was subsequently punished with very brief shocks. This treatment failed to depress bar-holding behavior. In some cases, although the escape shocks were delivered very infrequently, bar holding was maintained and resulted in the delivery of several thousand punishments per session. These and other effects of the punishment treatment were investigated. Finally, some of the possibilities of superstitious escape responding were explored by presenting inescapable shocks to rats that had been trained to escape shock by lever pressing. Although responding during these shocks had no programmed consequences, responding was sustained.

  8. Experimental self-punishment and superstitious escape behavior

    PubMed Central

    Migler, Bernard

    1963-01-01

    Rats were trained to escape from shock by pressing a bar. Bar holding was subsequently punished with very brief shocks. This treatment failed to depress bar-holding behavior. In some cases, although the escape shocks were delivered very infrequently, bar holding was maintained and resulted in the delivery of several thousand punishments per session. These and other effects of the punishment treatment were investigated. Finally, some of the possibilities of superstitious escape responding were explored by presenting inescapable shocks to rats that had been trained to escape shock by lever pressing. Although responding during these shocks had no programmed consequences, responding was sustained. PMID:13935675

  9. Gated Narrow Escape Time for Molecular Signaling

    NASA Astrophysics Data System (ADS)

    Reingruber, Jürgen; Holcman, David

    2009-10-01

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

  10. Simulating dynamical features of escape panic

    NASA Astrophysics Data System (ADS)

    Helbing, Dirk; Farkas, Illés; Vicsek, Tamás

    2000-09-01

    One of the most disastrous forms of collective human behaviour is the kind of crowd stampede induced by panic, often leading to fatalities as people are crushed or trampled. Sometimes this behaviour is triggered in life-threatening situations such as fires in crowded buildings; at other times, stampedes can arise during the rush for seats or seemingly without cause. Although engineers are finding ways to alleviate the scale of such disasters, their frequency seems to be increasing with the number and size of mass events. But systematic studies of panic behaviour and quantitative theories capable of predicting such crowd dynamics are rare. Here we use a model of pedestrian behaviour to investigate the mechanisms of (and preconditions for) panic and jamming by uncoordinated motion in crowds. Our simulations suggest practical ways to prevent dangerous crowd pressures. Moreover, we find an optimal strategy for escape from a smoke-filled room, involving a mixture of individualistic behaviour and collective `herding' instinct.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  12. STS-100 crew members practice emergency escape from the pad

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - As part of emergency escape training at Launch Pad 39A, the STS-100 crew climb into slidewire baskets that, during a real emergency, would propel them off the Fixed Service Structure to a landing area away from the pad. The crew is taking part in Terminal Countdown Demonstration Test activities that also include a simulated launch countdown. The mission is carrying the Multi-Purpose Logistics Module Raffaello and the SSRMS, to the International Space Station. Raffaello carries six system racks and two storage racks for the U.S. Lab. The SSRMS is crucial to the continued assembly of the orbiting complex. Launch of mission STS-100 is scheduled for April 19 at 2:41 p.m. EDT from Launch Pad 39A.

  13. STS-100 crew members practice emergency escape from the pad

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - During emergency escape training at Launch Pad 39A, STS-100 Pilot Jeffrey S. Ashby (left) and Commander Kent V. Rominger are in their slidewire basket that, during a real emergency, would propel them off the Fixed Service Structure to a landing area away from the pad. The crew is taking part in Terminal Countdown Demonstration Test activities that also include a simulated launch countdown. The mission is carrying the Multi-Purpose Logistics Module Raffaello and the SSRMS, to the International Space Station. Raffaello carries six system racks and two storage racks for the U.S. Lab. The SSRMS is crucial to the continued assembly of the orbiting complex. Launch of mission STS-100 is scheduled for April 19 at 2:41 p.m. EDT from Launch Pad 39A.

  14. Escape behaviour in the stomatopod crustacean Squilla mantis, and the evolution of the caridoid escape reaction.

    PubMed

    Heitler, W J; Fraser, K; Ferrero, E A

    2000-01-01

    The mantis shrimp Squilla mantis shows a graded series of avoidance/escape responses to visual and mechanical (vibration and touch) rostral stimuli. A low-threshold response is mediated by the simultaneous protraction of the thoracic walking legs and abdominal swimmerets and telson, producing a backwards 'lurch' or jump that can displace the animal by up to one-third of its body length, but leaves it facing in the same direction. A stronger response starts with similar limb protraction, but is followed by partial abdominal flexion. The maximal response also consists of limb protraction followed by abdominal flexion, but in this case the abdominal flexion is sufficiently vigorous to pull the animal into a tight vertical loop, which leaves it inverted and facing away from the stimulus. The animal then swims forward (away from the stimulus) and rights itself by executing a half-roll. A bilaterally paired, large-diameter, rapidly conducting axon in the dorsal region of the ventral nerve excites swimmeret protractor motoneurons in several ganglia and is likely to be the driver neuron for the limb-protraction response. The same neuron also excites unidentified abdominal trunk motoneurons, but less reliably. The escape response is a key feature of the malacostracan caridoid facies, and we provide the first detailed description of this response in a group that diverged early in malacostracan evolution. We show that the components of the escape response contrast strongly with those of the full caridoid reaction, and we provide physiological and behavioural evidence for the biological plausibility of a limb-before-tail thesis for the evolution of the escape response.

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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...

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. 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...

  8. 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…

  9. 33 CFR 143.101 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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

  10. 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…

  11. Green Pea Galaxies Reveal Secrets of Lyα Escape

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  12. 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…

  13. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... a hold-back to hold the scuttle in an open position. (e) The required means of escape must not have... escape is acceptable provided that— (1) There is no source of fire in the space, such as a galley stove... back of the ladder; and (4) Except when unavoidable obstructions are encountered, there must be...

  14. Complete mapping of viral escape from neutralizing antibodies

    PubMed Central

    Hensley, Scott E.

    2017-01-01

    Identifying viral mutations that confer escape from antibodies is crucial for understanding the interplay between immunity and viral evolution. We describe a high-throughput approach to quantify the selection that monoclonal antibodies exert on all single amino-acid mutations to a viral protein. This approach, mutational antigenic profiling, involves creating all replication-competent protein variants of a virus, selecting with antibody, and using deep sequencing to identify enriched mutations. We use mutational antigenic profiling to comprehensively identify mutations that enable influenza virus to escape four monoclonal antibodies targeting hemagglutinin, and validate key findings with neutralization assays. We find remarkable mutation-level idiosyncrasy in antibody escape: for instance, at a single residue targeted by two antibodies, some mutations escape both antibodies while other mutations escape only one or the other. Because mutational antigenic profiling rapidly maps all mutations selected by an antibody, it is useful for elucidating immune specificities and interpreting the antigenic consequences of viral genetic variation. PMID:28288189

  15. 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.

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

    PubMed

    Lind, Johan; Kaby, Ulrika; Jakobsson, Sven

    2002-09-01

    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.

  17. Evaluating Melanoma Drug Response and Therapeutic Escape with Quantitative Proteomics*

    PubMed Central

    Rebecca, Vito W.; Wood, Elizabeth; Fedorenko, Inna V.; Paraiso, Kim H. T.; Haarberg, H. Eirik; Chen, Yi; Xiang, Yun; Sarnaik, Amod; Gibney, Geoffrey T.; Sondak, Vernon K.; Koomen, John M.; Smalley, Keiran S. M.

    2014-01-01

    The evolution of cancer therapy into complex regimens with multiple drugs requires novel approaches for the development and evaluation of companion biomarkers. Liquid chromatography-multiple reaction monitoring mass spectrometry (LC-MRM) is a versatile platform for biomarker measurement. In this study, we describe the development and use of the LC-MRM platform to study the adaptive signaling responses of melanoma cells to inhibitors of HSP90 (XL888) and MEK (AZD6244). XL888 had good anti-tumor activity against NRAS mutant melanoma cell lines as well as BRAF mutant cells with acquired resistance to BRAF inhibitors both in vitro and in vivo. LC-MRM analysis showed HSP90 inhibition to be associated with decreased expression of multiple receptor tyrosine kinases, modules in the PI3K/AKT/mammalian target of rapamycin pathway, and the MAPK/CDK4 signaling axis in NRAS mutant melanoma cell lines and the inhibition of PI3K/AKT signaling in BRAF mutant melanoma xenografts with acquired vemurafenib resistance. The LC-MRM approach targeting more than 80 cancer signaling proteins was highly sensitive and could be applied to fine needle aspirates from xenografts and clinical melanoma specimens (using 50 μg of total protein). We further showed MEK inhibition to be associated with signaling through the NFκB and WNT signaling pathways, as well as increased receptor tyrosine kinase expression and activation. Validation studies identified PDGF receptor β signaling as a potential escape mechanism from MEK inhibition, which could be overcome through combined use of AZD6244 and the PDGF receptor inhibitor, crenolanib. Together, our studies show LC-MRM to have unique value as a platform for the systems level understanding of the molecular mechanisms of drug response and therapeutic escape. This work provides the proof-of-principle for the future development of LC-MRM assays for monitoring drug responses in the clinic. PMID:24760959

  18. Sensitization of the Tritonia escape swim.

    PubMed

    Frost, W N; Brandon, C L; Mongeluzi, D L

    1998-03-01

    When repeatedly elicited, the oscillatory escape swim of the marine mollusc Tritonia diomedea undergoes habituation of the number of cycles per swim. Previous work has shown that this habituation is accompanied by sensitization of another feature of the behavior: latency to swim onset. Here we focused on the behavioral features of sensitization itself. Test swims elicited 5 min after a strong sensitizing head stimulus differed in several ways from control swims: sensitized animals had shorter latencies for gill and rhinophore withdrawal, a shorter latency for swim onset, a lower threshold for swim initiation, and an increased number of cycles per swim. Sensitized animals did not, however, swim any faster (no change in cycle period). A separate experiment found that swim onset latency also sensitized when Tritonia came into contact with one of their natural predators, the seastar Pycnopodia helianthoides, demonstrating the ecological relevance of this form of nonassociative learning. These results define the set of behavioral changes to be explained by cellular studies of sensitization in Tritonia.

  19. Escaping the resource curse in China.

    PubMed

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

    2015-02-01

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

  20. 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

  1. 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

  2. Dependence of device performance on carrier escape sequence in multi-quantum-well p-i-n solar cells

    NASA Astrophysics Data System (ADS)

    Alemu, A.; Coaquira, J. A. H.; Freundlich, A.

    2006-04-01

    This work is a study relating device performance and carrier escape sequence in a large set of InAsP/InP p-i-n multi-quantum-well solar cells. The devices encompass nearly identical i-region thickness and built-in electric field and present similar absorption threshold energies. The escape sequence of the first confined electron-to-conduction band continuum and heavy/light holes-to-valence band continuum is extracted from the photoluminescence versus temperature analysis and by comparing the measured activation energies to calculated hole/electron well depths and thermionic escape times. Light holes, as expected for most III-V nanostructure systems, are found to be the fastest escaping carriers in all samples. The escape of electrons prior to heavy holes is shown to be a prerequisite to prevent severe open circuit voltage degradation. A possible explanation of the origin of this effect is offered. InP/InAsP multi-quantum-well solar cells with high built-in electric field and fast electronic escape time display better open circuit voltage and performance.

  3. Modelling the evolution and spread of HIV immune escape mutants.

    PubMed

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

    2010-11-18

    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.

  4. The Impacts of Orbital Distance on Exoplanetary Atmospheric Escape

    NASA Astrophysics Data System (ADS)

    Yang, M.; Guo, J. H.

    2016-11-01

    Driven by the high energy radiation of host stars, atmospheric escape is very important for planet evolution. While the flux drops dramatically with the increase of orbital distance, it is essential to study the impacts of orbital distance on atmospheric escape. We consider the hydrodynamic escape of exoplanets driven by the XUV (X-ray and extreme-ultraviolet) radiation of their host stars. We aim to study the mass-loss rate, the transition of escape mechanism, the structures of temperature and velocity, based on a one-dimensional hydrodynamic model which includes radiative transfer processes and photochemical reactions. As the stellar XUV emission varies with the stellar evolution, we use XSPEC (X-Ray Spectral Fitting Package) to construct the XUV spectra of solar-type stars at different ages. We find that with the increase of orbital distance, the mass-loss rates drop significantly, and when the stellar XUV flux is too small to preserve the hydrodynamic escape, it will turn to Jeans escape. This transition occurs in larger distance for younger and smaller planets. For young planets, hydrodynamic escape can occur in 1-2 au. For very young and close-in planets, the relation between mass-loss rate and stellar flux is not as significant as planets that are not close to their host stars, and the energy-limited equation can lead to large overestimate.

  5. A new paradigm for evaluating avoidance/escape motivation.

    PubMed

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

    2017-05-06

    Organisms have evolved to approach pleasurable opportunities and to avoid or escape from aversive experiences. These two 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 (VR-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 mice failed to avoid it. We intraperitoneally injected ketamine (0, 1, or 5 mg/kg) or buspirone (0, 5, or 10 mg/kg) 20 or 30 minutes before the behavioral task in order to see if ketamine enhanced avoidance/escape behavior and buspirone diminished it as previously reported. We found that the performance on the avoidance VR-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 VR-5 task, being consistent with previous reports. Our new paradigm will prove usefulness for quantifying avoidance/escape motivation and will contribute to a more comprehensive understanding of motivation.

  6. Evolutionary escape on complex genotype-phenotype networks.

    PubMed

    Ibáñez-Marcelo, Esther; Alarcón, Tomás

    2016-04-07

    We study the problem of evolutionary escape that is the process whereby a population under sudden changes in the selective pressures acting upon it try to evade extinction by evolving from previously well-adapted phenotypes to those that are favoured by the new selective pressure. We perform a comparative analysis between results obtained by modelling genotype space as a regular hypercube (H-graphs), which is the scenario considered in previous work on the subject, to those corresponding to a complex genotype-phenotype network (B-graphs). In order to analyse the properties of the escape process on both these graphs, we apply a general theory based on multi-type branching processes to compute the evolutionary dynamics and probability of escape. We show that the distribution of distances between phenotypes in B-graphs exhibits a much larger degree of heterogeneity than in H-graphs. This property, one of the main structural differences between both types of graphs, causes heterogeneous behaviour in all results associated to the escape problem. We further show that, due to the heterogeneity characterising escape on B-graphs, escape probability can be underestimated by assuming a regular hypercube genotype network, even if we compare phenotypes at the same distance in H-graphs. Similarly, it appears that the complex structure of B-graphs slows down the rate of escape. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. 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.

  8. 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.

  9. 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

  10. Oxygen ion escape from Venus: The acceleration mechanisms and the escape rate under different IMF configurations

    NASA Astrophysics Data System (ADS)

    Masunaga, K.; Futaana, Y.; Yamauchi, M.; Barabash, S.; Zhang, T.; Fedorov, A.; Okano, S.; Terada, N.

    2012-12-01

    Using data obtained from ASPERA-4 (Analyser of Space Plasma and Energetic Atoms) and MAG (magnetometer) experiments onboard Venus Express, we investigate the acceleration mechanisms, the escape rate of the oxygen ions from the Venus upper atmosphere, and the contribution of the upstream condition to them. We first produce spatial distribution maps of O+ fluxes (>100 eV) around Venus for two different convection electric fields, namely the solar wind electric field (SWEF; Esw = -Vsw x Bsw) and the local convection electric field (LCEF; EL = -VL x BL where VL and BL are the local proton velocity and the local magnetic field that obtained over one-scan (192 s)). Comparison between the two distributions, we find that the O+ fluxes are frequently observed in the hemisphere where LCEF orients. Moreover, such structure can be identified regardless of the upstream interplanetary magnetic field (IMF) direction. Thus we conclude that the O+ ions are accelerated more effectively by LCEF rather than SWEF in the Venusian upper atmosphere. In the induced magnetosphere, O+ fluxes are frequently associated with Bx reversals where the IMF curvature is strong. It indicates that a magnetic tension force also contributes to O+ acceleration. We also investigate the dependency of the O+ escape rates on the upstream IMF directions. Here, the IMF condition is classified into two cases: the perpendicular IMF case and the parallel IMF case, where IMF directs nearly perpendicular to the Venus-Sun line (60° < θ < 120°) and nearly parallel to it (0° < θ < 30° or 150° < θ < 180°). During the data period between 20 Jun 2006 and 20 Dec 2009 we have obtained 141 perpendicular IMF cases and 71 parallel IMF cases. Using these data, total O+ escape rates are estimated by integrating the anti-sunward fluxes in the nightside region. We find that the total escape rates between the two IMF cases are of the same order, and thus we conclude that the upstream IMF direction does not significantly

  11. 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

  12. Nonlinear enhancement of the fractal structure in the escape dynamics of Bose-Einstein condensates

    SciTech Connect

    Mitchell, Kevin A.; Ilan, Boaz

    2009-10-15

    We consider the escape dynamics of an ensemble of Bose-Einstein-condensed atoms from an optical-dipole trap consisting of two overlapping Gaussian wells. Earlier theoretical studies (based on a model of quantum evolution using ensembles of classical trajectories) predicted that self-similar fractal features could be visible in this system by measuring the escaping flux as a function of time for varying initial conditions. Here, direct numerical quantum simulations show the clear influence of quantum interference on the escape data. Fractal features are still evident in the data, albeit with interference fringes superposed. Furthermore, the nonlinear influence of atom-atom interactions is also considered, in the context of the (2+1)-dimensional Gross-Pitaevskii equation. Of particular note is that an attractive nonlinear interaction enhances the resolution of fractal structures in the escape data. Thus, the interplay between nonlinear focusing and dispersion results in dynamics that resolve the underlying classical fractal more faithfully than the noninteracting quantum (or classical) dynamics.

  13. 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.

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

    PubMed Central

    Onal, Cagdas D.; Rus, Daniela

    2014-01-01

    Abstract In this work we describe an autonomous soft-bodied robot that is both self-contained and capable of rapid, continuum-body motion. We detail the design, modeling, fabrication, and control of the soft fish, focusing on enabling the robot to perform rapid escape responses. The robot employs a compliant body with embedded actuators emulating the slender anatomical form of a fish. In addition, the robot has a novel fluidic actuation system that drives body motion and has all the subsystems of a traditional robot onboard: power, actuation, processing, and control. At the core of the fish's soft body is an array of fluidic elastomer actuators. We design the fish to emulate escape responses in addition to forward swimming because such maneuvers require rapid body accelerations and continuum-body motion. These maneuvers showcase the performance capabilities of this self-contained robot. The kinematics and controllability of the robot during simulated escape response maneuvers are analyzed and compared with studies on biological fish. We show that during escape responses, the soft-bodied robot has similar input–output relationships to those observed in biological fish. The major implication of this work is that we show soft robots can be both self-contained and capable of rapid body motion. PMID:27625912

  15. Distribution and escape of the major neutral species from Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Tenishev, Valeriy; Tucker, Orenthal; Borovikov, Dmitry; Combi, Michael R.

    2016-10-01

    Titan possesses the most significant atmosphere among all satellites in the Solar system, and is an important source of material for the Saturn's magnetosphere. Understanding of the neutral species distribution and escape is important for further understanding of the Titan's atmosphere evolution and loss.The first in situ observations of the Titan's atmosphere were performed by Voyager and continued by Cassini, which measured the atmospheric composition, velocity and temperature, as well as the energy spectra of neutral species, ions and electrons. Analysis and interpretation of the acquired data involves coupled modeling of the Saturn magnetosphere and Titan's atmosphere.Having that in mind we have undertaken numerical modeling of the major neutral species (N2 and CH4) in Titan's upper atmosphere to investigate the effect of the solar EUV and magnetospheric ion energy deposition on the neutral species atmospheric distribution and escape. This modeling combines MHD simulation of the Saturn's magnetosphere plasma interacting with Titan's atmosphere, fluid type simulation of the neutral species in Titan's lower atmosphere, and kinetic modeling of the upper atmosphere and exosphere. Here we present estimations of the neutral species escape rate, and discuss the effect of the magnetospheric ion energy deposition on the atmospheric escape concluded from the results of our modeling.This work was supported by NASA Outer Planet Research grant NNX13AL04G.

  16. Mass fractionation in hydrodynamic escape. [of gases from planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Hunten, Donald M.; Pepin, Robert O.; Walker, James C. G.

    1987-01-01

    In mass fractionation during the hydrodynamic escape of gases from an inner planet's atmosphere, the readier escape of light gases generates a linear or concave downward line in a plotting of the log of remaining inventory against atomic mass. Just as such an episode of hydrodynamic escape during Mars' early history could have led to the mass-dependent depletion of the noble gases that has been noted in the Martian atmosphere, in the event that the Martian atmosphere was initially hydrogen-rich, an early earth-history episode may have resulted in a mass-dependent fractionation of the xenon isotopes.

  17. Delayed escape from light by the albino rat1

    PubMed Central

    Keller, John V.

    1966-01-01

    Two albino rats were trained to terminate an aversive light for 1 min by pressing a bar. After 19 hr of conditioning they were exposed to successive delays of 1, 2, 5, and 10 sec imposed between occurrence of the escape response and light termination. No stimulus change accompanied the delay interval, and any additional responses made at this time reset the delay timer. For both rats the relative frequency of escape responses with very long latencies increased as the delay interval increased. The modal escape latency, however, remained essentially unchanged for all delay values of greater than 1 sec. “Superstitious” responding was observed during the delay interval. PMID:5970387

  18. Oxygen Escape from Venus During High Dynamic Pressure ICMEs

    NASA Astrophysics Data System (ADS)

    McEnulty, Tess; Luhmann, J. G.; Brain, D. A.; Fedorov, A.; Jian, L. K.; Russell, C. T.; Zhang, T.; Möstl, C.; Futaana, Y.; de Pater, I.

    2013-10-01

    Previous studies using data from Pioneer Venus suggested that oxygen ion escape flux may be enhanced by orders of magnitude during Interplanetary Coronal Mass Ejections. However, this large enhancement has been ambiguous in Venus Express ion data - with some analyses showing no flux enhancement or a small enhancement (within 2 times undisturbed cases). One possible explanation is that high escape flux may be due to high dynamic pressure in the solar wind, and the dynamic pressure has been lower during the VEX time period. So, we focus on ICMEs with the largest dynamic pressure and with VEX sampling of the escaping ions during the sheath of the ICMEs (during which the highest dynamic pressures in the solar wind occur). We will show the characteristics of these large events measured by VEX, and compare them to the largest ICMEs measured by PVO. We will then discuss estimates of the oxygen ion escape flux during these events.

  19. Pilot Fullerton dons ejection escape suit (EES) on middeck

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Pilot Fullerton dons ejection escape suit (EES) (high altitude pressure garment) life preserver unit (LPU) on forward port side of middeck above potable water tank. Fullerton also adjusts lapbelt fitting and helmet holddown strap.

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

    USGS Publications Warehouse

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

    1993-01-01

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

  1. Experimental Analysis and Extinction of Self-Injurious Escape Behavior.

    ERIC Educational Resources Information Center

    Iwata, Brian A.; And Others

    1990-01-01

    Three studies investigated environmental correlates of self-injurious behavior in seven developmentally disabled children and adolescents which were then later used for treatment. Correlates investigated included positive reinforcement, negative reinforcement, automatic reinforcement, and control. "Escape extinction" was successfully…

  2. 39. VIEW OF HORSE AND ESCAPE STEPS ON ARIZONA CANAL, ...

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

    39. VIEW OF HORSE AND ESCAPE STEPS ON ARIZONA CANAL, LOOKING NORTH ON THE SALT RIVER INDIAN RESERVATION Photographer: James Eastwood, June 1990 - Arizona Canal, North of Salt River, Phoenix, Maricopa County, AZ

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

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

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

  4. Electron yields and escape depths from spacecraft materials

    SciTech Connect

    Yang, K.Y.

    1986-01-01

    Secondary electron emission (SEE) characteristics and photoelectron yields were determined for several insulating materials used onboard a space shuttle. These materials are: kapton, teflon, spaceshuttle tiles, and space suit cloth. Secondary electron escape depth and photoelectron escape depth from kapton were calculated from the experimental data. Sternglass' theory and Dionne's method were used in the calculation. Some semi-empirical theories of SEE and three-step theory of photoemission were reviewed. Pulsed beam techniques were used to reduce surface charging problems. Three ..mu..sec pulses of electrons were used in SEE experiments, and 100 msec to 1 sec pulses were used in photoemission experiments. The maximum SEE yields of the materials studied range from 1.75 ro 2.70. The secondary electron escape depth in kapton was calculated to be 55 +/- 5 A. All samples have photoyields lower than 1.0%. The photoelectrons excited by 21-eV photons have 87 +/- 30 A escape depth in kapton.

  5. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

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

  6. Critical escape velocity of black holes from branes

    SciTech Connect

    Flachi, Antonino; Sasaki, Misao; Pujolas, Oriol; Tanaka, Takahiro

    2006-08-15

    In recent work we have shown that a black hole stacked on a brane escapes once it acquires a recoil velocity. This result was obtained in the probe-brane approximation, i.e., when the tension of the brane is negligibly small. Therefore, it is not clear whether the effect of the brane tension may prevent the black hole from escaping for small recoil velocities. The question is whether a critical escape velocity exists. Here, we analyze this problem by studying the interaction between a Dirac-Nambu-Goto brane and a black hole assuming adiabatic (quasistatic) evolution. By describing the brane in a fixed black hole spacetime, which restricts our conclusions to lowest order effects in the tension, we find that the critical escape velocity does not exist for codimension one branes, while it does for higher codimension branes.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  8. Space Weathering of Super-Earths: Model Simulations of Exospheric Sodium Escape from 61 Virgo b

    NASA Astrophysics Data System (ADS)

    Yoneda, M.; Berdyugina, S.; Kuhn, J.

    2017-10-01

    Rocky exoplanets are expected to be eroded by space weather in a similar way as in the solar system. In particular, Mercury is one of the dramatically eroded planets whose material continuously escapes into its exosphere and further into space. This escape is well traced by sodium atoms scattering sunlight. Due to solar wind impact, micrometeorite impacts, photo-stimulated desorption and thermal desorption, sodium atoms are released from surface regolith. Some of these released sodium atoms are escaping from Mercury’s gravitational-sphere. They are dragged anti-Sun-ward and form a tail structure. We expect similar phenomena on exoplanets. The hot super-Earth 61 Vir b orbiting a G3V star at only 0.05 au may show a similar structure. Because of its small separation from the star, the sodium release mechanisms may be working more efficiently on hot super-Earths than on Mercury, although the strong gravitational force of Earth-sized or even more massive planets may be keeping sodium atoms from escaping from the planet. Here, we performed model simulations for Mercury (to verify our model) and 61 Vir b as a representative super-Earth. We have found that sodium atoms can escape from this exoplanet due to stellar wind sputtering and micrometeorite impacts, to form a sodium tail. However, in contrast to Mercury, the tail on this hot super-Earth is strongly aligned with the anti-starward direction because of higher light pressure. Our model suggests that 61 Vir b seems to have an exo-base atmosphere like that of Mercury.

  9. Ion heating, acceleration and escape at Mars and Venus, similarities and differences

    NASA Astrophysics Data System (ADS)

    Nilsson, H.; Stenberg, G.; Diéval, C.; Yamauchi, M.; Barabash, S.; Lundin, R.

    2012-09-01

    Using data from the ASPERA-3 (Mars) and ASPERA- 4 (Venus) instruments we have investigated the heating, acceleration and escape of ionospheric origin ions from Mars and Venus. We have first determined the average flow properties and average ion distributions in the vicinity of the planets, from which a net escape flux as well as spatial asymmetries in the escape fluxes can be determined. One of the main uncertainties concerning the net escape is the possible presence of plasma of too low energy to be observed by the ion spectrometers, but still of sufficient energy to escape. Observations show that there is a clear and efficient heating of outflowing ionospheric ions. The large temporal and spatial variability of both plasma distribution and ion heating still allows for part of this plasma to remain cold. At Earth hot and cold plasma follow different outflow trajectories and are typically found in different regions, with hot outflowing plasma in the cusp / mantle and cold outflowing plasma in the lobes. We discuss whether a similar situation may exist in the more compact induced magnetospheres of Mars and Venus. Finally we show how different the induced magnetosphere boundaries of Mars and Venus are. At Mars there is much more transport across the boundary, with ionospheric origin heavy ions flowing into the magnetosheath. Solar wind plasma consistently, though only sporadically, penetrate the induced magnetosphere boundary of Mars and precipitate. At Venus we find essentially no ionospheric origin heavy ions in the magnetosheath, and solar wind penetration cases are very rare as compared to Mars. Previous studies have shown clear differences between the bow shock regions of the two planets. It appears as if the relatively smaller size of the Mars system in terms of gyro radii of typical solar wind ions lead to a more dynamic magnetosheath and induced magnetosphere boundary, allowing for a different coupling between the solar wind and planetary plasmas as compared

  10. 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.

  11. GREEN PEA GALAXIES REVEAL SECRETS OF Lyα ESCAPE

    SciTech Connect

    Yang, Huan; Wang, Junxian; Malhotra, Sangeeta; Rhoads, James E.; Gronke, Max; Dijkstra, Mark; Jaskot, Anne; Zheng, Zhenya E-mail: huan.y@asu.edu E-mail: James.Rhoads@asu.edu

    2016-04-01

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

  12. Ion escape from Venus using statistical distribution functions

    NASA Astrophysics Data System (ADS)

    Nordstrom, T.; Stenberg, G.; Nilsson, H.; Barabash, S.; Futaana, Y.

    2012-04-01

    We use more than three years of data from the ASPERA-4 instrument onboard Venus Express to compile statistical distribution functions of ion flux in and around induced magnetosphere of Venus. We present samples of statistical distribution functions, as well average flux patterns in the near Venus space based on the statistical distribution functions. The statistical distribution functions allows for a compensation of biased sampling regarding both position and angular coverage of the instrument. Protons and heavy ions (mass/charge > 16) are the major ion species escaping from Venus. The escape is due to acceleration of planetary ions by energy transfer from the solar wind. The ion escape appears to exclusively take place in the induced magnetotail region and no heavy ions are present in the magnetosheath. Protons of solar wind origin are travelling around the planet and penetrating the tail, resulting in a mix of planetary and solar wind protons inside the induced magnetosphere boundary. The escape rates of ions inside the tail agree with results from recent published studies, where other analysis methods have been used. We also compare our results for Venus with a recent study of ion escape from Mars, where the same analysis method has been applied to data from the ASPERA-3 instrument on Mars Express. Both Mars and Venus are unmagnetized planets and are expected to interact similarly with the solar wind. On Mars the heavy ions are seen escaping in both the magnetosheath and tail regions as opposed to Venus where escape only takes place inside the tail. A possible explanation is that the magnetosphere of Mars is smaller compared to the ion gyroradius, making it easier for the ions to pass through the induced magnetosphere boundary. On both planets the escape rates of heavy ions in the tail are constant with increasing tail distance, verifying that the ions are leaving the planet in this region.

  13. Constraints on bounded motion and mutual escape for the full 3-body problem

    NASA Astrophysics Data System (ADS)

    Scheeres, D. J.

    2017-06-01

    When gravitational aggregates are spun to fission they can undergo complex dynamical evolution, including escape and reconfiguration. Previous work has shown that a simple analysis of the full 2-body problem provides physically relevant insights for whether a fissioned system can lead to escape of the components and the creation of asteroid pairs. In this paper we extend the analysis to the full 3-body problem, utilizing recent advances in the understanding of fission mechanics of these systems. Specifically, we find that the full 3-body problem can eject a body with as much as 0.31 of the total system mass, significantly larger than the 0.17 mass limit previously calculated for the full 2-body problem. This paper derives rigorous limits on a fissioned 3-body system with regards to whether fissioned system components can physically escape from each other and what other stable relative equilibria they could settle in. We explore this question with a narrow focus on the Spherical Full Three Body Problem studied in detail earlier.

  14. Link between intraphagosomal biotin and rapid phagosomal escape in Francisella

    PubMed Central

    Napier, Brooke A.; Meyer, Lena; Bina, James E.; Miller, Mark A.; Sjöstedt, Anders; Weiss, David S.

    2012-01-01

    Cytosolic bacterial pathogens require extensive metabolic adaptations within the host to replicate intracellularly and cause disease. In phagocytic cells such as macrophages, these pathogens must respond rapidly to nutrient limitation within the harsh environment of the phagosome. Many cytosolic pathogens escape the phagosome quickly (15–60 min) and thereby subvert this host defense, reaching the cytosol where they can replicate. Although a great deal of research has focused on strategies used by bacteria to resist antimicrobial phagosomal defenses and transiently pass through this compartment, the metabolic requirements of bacteria in the phagosome are largely uncharacterized. We previously identified a Francisella protein, FTN_0818, as being essential for intracellular replication and involved in virulence in vivo. We now show that FTN_0818 is involved in biotin biosynthesis and required for rapid escape from the Francisella-containing phagosome (FCP). Addition of biotin complemented the phagosomal escape defect of the FTN_0818 mutant, demonstrating that biotin is critical for promoting rapid escape during the short time that the bacteria are in the phagosome. Biotin also rescued the attenuation of the FTN_0818 mutant during infection in vitro and in vivo, highlighting the importance of this process. The key role of biotin in phagosomal escape implies biotin may be a limiting factor during infection. We demonstrate that a bacterial metabolite is required for phagosomal escape of an intracellular pathogen, providing insight into the link between bacterial metabolism and virulence, likely serving as a paradigm for other cytosolic pathogens. PMID:23071317

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

    PubMed

    Holden, Matthew H; Conrad, Jon M

    2015-11-01

    Stage-structured population models are commonly used to understand fish population dynamics and additionally for stock assessment. Unfortunately, there is little theory on the optimal harvest of stage-structured populations, especially in the presence of stochastic fluctuations. In this paper, we find closed form optimal equilibrium escapement policies for a three-dimensional, discrete-time, stage-structured population model with linear growth, post-harvest nonlinear recruitment, and stage-specific pricing and extend the analytic results to structured populations with environmental stochasticity. When only fishing reproductive adults, stochasticity does not affect optimal escapement policies. However, when harvesting immature fish, the addition of stochasticity can increase or decrease optimal escapement depending on the second and third derivative of the recruitment function. For logistic recruitment, stochasticity reduces optimal immature escapement by a multiplicative factor of one over one plus the variance of the environmental noise. Using hard clam, Mercenaria mercenaria, as an example and assuming Beverton-Holt recruitment, we show that optimal fishing of hard clam targets the immature stage class exclusively and that environmental stochasticity increases optimal escapement for low discount rates and decreases optimal escapement for high discount rates. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Extreme hydrodynamic atmospheric loss near the critical thermal escape regime

    NASA Astrophysics Data System (ADS)

    Erkaev, N. V.; Lammer, H.; Odert, P.; Kulikov, Yu. N.; Kislyakova, K. G.

    2015-04-01

    By considering martian-like planetary embryos inside the habitable zone of solar-like stars we study the behaviour of the hydrodynamic atmospheric escape of hydrogen for small values of the Jeans escape parameter β < 3, near the base of the thermosphere, that is defined as a ratio of the gravitational and thermal energy. Our study is based on a 1D hydrodynamic upper atmosphere model that calculates the volume heating rate in a hydrogen-dominated thermosphere due to the absorption of the stellar soft X-ray and extreme ultraviolet (XUV) flux. In case of a monatomic gas, we find that when the β value near the mesopause/homopause level exceeds a critical value of ˜2.5, there exists a steady hydrodynamic solution with a smooth transition from subsonic to supersonic flow. For a fixed XUV flux, the escape rate of the upper atmosphere is an increasing function of the temperature at the lower boundary. Our model results indicate a crucial enhancement of the atmospheric escape rate, when the Jeans escape parameter β decreases to this critical value. When β becomes ≤2.5, there is no stationary hydrodynamic transition from subsonic to supersonic flow. This is the case of a fast non-stationary atmospheric expansion that results in extreme thermal atmospheric escape rates.

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

    PubMed

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

    2013-11-01

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

  18. Group chase and escape with sight-limited chasers

    NASA Astrophysics Data System (ADS)

    Wang, Huodong; Han, Wenchen; Yang, Junzhong

    2017-01-01

    We study group chase and escape with sight-limited chasers. Two search strategies, random-walk-strategy and relocation-strategy, are introduced for chasers when escapers are out of their fields of vision. There exist two regimes for the group lifetime of escapers. In the narrow sight regime, the group lifetime is a decreasing function of chasers' sight range. In the wide sight regime, the group lifetime stays at a constant when chasers adopting random-walk-strategy while increases with the sight range when chasers adopting relocation-strategy. The impacts of the two search strategies on group chase and escape are studied by investigating the lifetime distribution of all escapers and the dependence of the minimum lifetime on the number of chasers. We also find that, to reach the most efficient and the lowest energy cost chase for chasers, the ratio between the number of chasers and escapers stays at around 6 under random-walk-strategy. However, the optimal number of chasers vanishes and the energy cost monotonically increases with increasing the number of chasers under relocation-strategy.

  19. 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

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

    PubMed Central

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

    2015-01-01

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

  1. Elliptic Anisotropy ν2 May Be Dominated by Particle Escape instead of Hydrodynamic Flow

    NASA Astrophysics Data System (ADS)

    Lin, Zi-Wei; He, Liang; Edmonds, Terrence; Liu, Feng; Molnar, Denes; Wang, Fuqiang

    2016-12-01

    It is commonly believed that azimuthal anisotropies in relativistic heavy ion collisions are generated by hydrodynamic evolution of the strongly interacting quark-gluon plasma. Here we use transport models to study how azimuthal anisotropies depend on the number of collisions that each parton suffers. We find that the majority of ν2 comes from the anisotropic escape of partons, not from the parton collective flow, for semi-central Au+Au collisions at 200A GeV. As expected, the fraction of ν2 from the anisotropic particle escape is even higher for smaller systems such as d+Au. Our transport model results also confirm that azimuthal anisotropies would be dominated by hydrodynamic flow at unrealistically-high parton cross sections. Our finding thus naturally explains the similarity of azimuthal anisotropies in small and large systems; however, it presents a challenge to the paradigm of anisotropic flow.

  2. Complex Economies Have a Lateral Escape from the Poverty Trap

    PubMed Central

    Pugliese, Emanuele; Chiarotti, Guido L.; Zaccaria, Andrea; Pietronero, Luciano

    2017-01-01

    We analyze the decisive role played by the complexity of economic systems at the onset of the industrialization process of countries over the past 50 years. Our analysis of the input growth dynamics, considering a further dimension through a recently introduced measure of economic complexity, reveals that more differentiated and more complex economies face a lower barrier (in terms of GDP per capita) when starting the transition towards industrialization. As a consequence, we can extend the classical concept of a one-dimensional poverty trap, by introducing a two-dimensional poverty trap: a country will start the industrialization process if it is rich enough (as in neo-classical economic theories), complex enough (using this new dimension and laterally escaping from the poverty trap), or a linear combination of the two. This naturally leads to the proposal of a Complex Index of Relative Development (CIRD) which shows, when analyzed as a function of the growth due to input, a shape of an upside down parabola similar to that expected from the standard economic theories when considering only the GDP per capita dimension. PMID:28072867

  3. Complex Economies Have a Lateral Escape from the Poverty Trap.

    PubMed

    Pugliese, Emanuele; Chiarotti, Guido L; Zaccaria, Andrea; Pietronero, Luciano

    2017-01-01

    We analyze the decisive role played by the complexity of economic systems at the onset of the industrialization process of countries over the past 50 years. Our analysis of the input growth dynamics, considering a further dimension through a recently introduced measure of economic complexity, reveals that more differentiated and more complex economies face a lower barrier (in terms of GDP per capita) when starting the transition towards industrialization. As a consequence, we can extend the classical concept of a one-dimensional poverty trap, by introducing a two-dimensional poverty trap: a country will start the industrialization process if it is rich enough (as in neo-classical economic theories), complex enough (using this new dimension and laterally escaping from the poverty trap), or a linear combination of the two. This naturally leads to the proposal of a Complex Index of Relative Development (CIRD) which shows, when analyzed as a function of the growth due to input, a shape of an upside down parabola similar to that expected from the standard economic theories when considering only the GDP per capita dimension.

  4. Green Pea Galaxies Reveal Secrets of Lyα Escape

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  5. Broad Targeting Specificity during Bacterial Type III CRISPR-Cas Immunity Constrains Viral Escape.

    PubMed

    Pyenson, Nora C; Gayvert, Kaitlyn; Varble, Andrew; Elemento, Olivier; Marraffini, Luciano A

    2017-09-13

    CRISPR loci are a cluster of repeats separated by short "spacer" sequences derived from prokaryotic viruses and plasmids that determine the targets of the host's CRISPR-Cas immune response against its invaders. For type I and II CRISPR-Cas systems, single-nucleotide mutations in the seed or protospacer adjacent motif (PAM) of the target sequence cause immune failure and allow viral escape. This is overcome by the acquisition of multiple spacers that target the same invader. Here we show that targeting by the Staphylococcus epidermidis type III-A CRISPR-Cas system does not require PAM or seed sequences, and thus prevents viral escape via single-nucleotide substitutions. Instead, viral escapers can only arise through complete target deletion. Our work shows that, as opposed to type I and II systems, the relaxed specificity of type III CRISPR-Cas targeting provides robust immune responses that can lead to viral extinction with a single spacer targeting an essential phage sequence. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. 42 CFR 84.300 - Closed-circuit escape respirator; description.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Closed-circuit escape respirator; description. 84... Closed-Circuit Escape Respirators § 84.300 Closed-circuit escape respirator; description. The closed-circuit escape respirator (CCER), technically a subset of self-contained breathing apparatus (SCBAs) which...

  7. 42 CFR 84.300 - Closed-circuit escape respirator; description.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Closed-circuit escape respirator; description. 84... Closed-Circuit Escape Respirators § 84.300 Closed-circuit escape respirator; description. The closed-circuit escape respirator (CCER), technically a subset of self-contained breathing apparatus (SCBAs) which...

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  9. Structural controls on fluid escape from the subduction interface

    NASA Astrophysics Data System (ADS)

    Reynard, Bruno; Tauzin, Benoit; Bodin, Thomas; Perrillat, Jean-Philippe; Debayle, Eric

    2017-04-01

    Seismic activity and non-volcanic tremors are often associated with fluid circulation resulting from the dehydration of subducting plates. Tremors in the overriding continental crust of several subduction zones suggest fluid circulation at shallower depths, but potential fluid pathways are still poorly documented. Fluids are also released at different depths in hot and cold subduction zones, which may result in different schemes of fluid escape. We document potential fluid pathways in Cascadia, one of the hottest subduction zone, using receiver function analysis. We provide evidence for a seismic discontinuity near 15 km depth in the crust of the overriding North American plate. This interface is segmented, and its interruptions are spatially correlated with conductive regions of the forearc and shallow swarms of seismicity and non-volcanic tremors. The comparison of seismological and electrical conductivity profiles suggests that fluid escape is controlled by fault zones between blocks of accreted terranes in the overriding plate. These zones constitute fluid escape routes that may influence the seismic cycle by releasing fluid pressure from the megathrust. Results on Cascadia are compared to fluid escape routes suggested by former geophysical observations in NE Japan, one of the coldest subduction zones. Links between fluid escape, permeability and fluid-rock reactions at or above the plate interface are discussed.

  10. Inferring HIV Escape Rates from Multi-Locus Genotype Data

    SciTech Connect

    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 mutations 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.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-09-08

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

  13. 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

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  15. Improving the Endosomal Escape of Cell-Penetrating Peptides and Their Cargos: Strategies and Challenges

    PubMed Central

    Erazo-Oliveras, Alfredo; Muthukrishnan, Nandhini; Baker, Ryan; Wang, Ting-Yi; Pellois, Jean-Philippe

    2012-01-01

    Cell penetrating peptides (CPPs) can deliver cell-impermeable therapeutic cargos into cells. In particular, CPP-cargo conjugates tend to accumulate inside cells by endocytosis. However, they often remain trapped inside endocytic organelles and fail to reach the cytosolic space of cells efficiently. In this review, the evidence for CPP-mediated endosomal escape is discussed. In addition, several strategies that have been utilized to enhance the endosomal escape of CPP-cargos are described. The recent development of branched systems that display multiple copies of a CPP is presented. The use of viral or synthetic peptides that can disrupt the endosomal membrane upon activation by the low pH of endosomes is also discussed. Finally, we survey how CPPs labeled with chromophores can be used in combination with light to stimulate endosomal lysis. The mechanisms and challenges associated with these intracellular delivery methodologies are discussed. PMID:24223492

  16. Tunneling lifetimes of electrons escaping from atoms under a static electric field.

    PubMed

    Zhao, Rundong; Sarwono, Yanoar Pribadi; Zhang, Rui-Qin

    2017-08-14

    The tunneling lifetime of an electron escaping from an atom is calculated using a projected Green's function method, combining with the radial potential of the atom which is obtained from density functional theory. Results of the calculated electron tunneling lifetimes in model systems such as a quantum dot are shown to be comparable with other theoretical studies. For the first time, we have obtained the tunneling lifetimes of electrons escaping from a series of atoms (He, Ne, Ar, Kr, H, Li, Na, K) under a static electric field. Dependent on both the barrier width/height and the bound strength of the ground state electron, the calculated tunneling lifetime under a static electric field spans from femtosecond level to picosecond level, consistent with the attosecond-level results in experiments using a time-dependent external field.

  17. Tunneling lifetimes of electrons escaping from atoms under a static electric field

    NASA Astrophysics Data System (ADS)

    Zhao, Rundong; Sarwono, Yanoar Pribadi; Zhang, Rui-Qin

    2017-08-01

    The tunneling lifetime of an electron escaping from an atom is calculated using a projected Green's function method, combining with the radial potential of the atom which is obtained from density functional theory. Results of the calculated electron tunneling lifetimes in model systems such as a quantum dot are shown to be comparable with other theoretical studies. For the first time, we have obtained the tunneling lifetimes of electrons escaping from a series of atoms (He, Ne, Ar, Kr, H, Li, Na, K) under a static electric field. Dependent on both the barrier width/height and the bound strength of the ground state electron, the calculated tunneling lifetime under a static electric field spans from femtosecond level to picosecond level, consistent with the attosecond-level results in experiments using a time-dependent external field.

  18. Multiplexing of Motor Information in the Discharge of a Collision Detecting Neuron during Escape Behaviors

    PubMed Central

    Fotowat, Haleh; Harrison, Reid R; Gabbiani, Fabrizio

    2010-01-01

    Locusts possess an identified neuron, the descending contralateral movement detector (DCMD), conveying visual information about impending collision from the brain to thoracic motor centers. We built a telemetry system to simultaneously record, in freely behaving animals, the activity of the DCMD and of motoneurons involved in jump execution. Co-contraction of antagonistic leg muscles, a required preparatory phase, was triggered after the DCMD firing rate crossed a threshold. Thereafter, the number of DCMD spikes predicted precisely motoneuron activity and jump occurrence. Additionally, the time of DCMD peak firing rate predicted that of jump. Ablation experiments suggest that the DCMD, together with a nearly identical ipsilateral descending neuron, is responsible for the timely execution of the escape. Thus, three distinct features that are multiplexed in a single neuron’s sensory response to impending collision – firing rate threshold, peak firing time, and spike count – likely control three distinct motor aspects of escape behaviors. PMID:21220105

  19. Exploitation of an ancient escape circuit by an avian predator: prey sensitivity to model predator display in the field.

    PubMed

    Jabloński, P G; Strausfeld, N J

    2000-08-01

    Certain insectivorous birds, such as the painted redstart (Myioborus pictus), undertake flush pursuit--a characteristic display that elicits an escape reaction by an insect, which the bird then chases in the air and eats. This account describes experiments showing that flush pursuit uses visual displays, which are likely to exploit an ancient neural circuit in dipteran insects, the visual systems of which are well documented as detecting looming stimuli and triggering an escape responses. Using models that decompose components of the redstart display, specific elements of the display were analyzed for their contribution in triggering visually induced escape behavior by dipterous insects. Elements tested were pivoting body movements, patterning on the spread tail and wings, and visual contrast of model redstarts against pale and dark backgrounds. We show that contrasting patterns within the plumage are crucial to foraging success, as is contrast of the bird against a background. Visual motion also significantly contributes to the successful flushing. In contrast, unpatterned models and patterned models that do not contrast with the background are less successful in eliciting escape responses of flies. Natural visual stimuli provided by Myioborus pictus are similar to those known to trigger looming and time-to-collision neurons in the escape circuits of flies and other insects, such as orthopterans. We propose that the tuning properties of these neural pathways might have contributed to the evolution of foraging displays in flush-pursuing birds.

  20. Computational method for phase space transport with applications to lobe dynamics and rate of escape

    NASA Astrophysics Data System (ADS)

    Naik, Shibabrat; Lekien, Francois; Ross, Shane D.

    2017-05-01

    Lobe dynamics and escape from a potential well are general frameworks introduced to study phase space transport in chaotic dynamical systems.While the former approach studies how regions of phase space get transported by reducing the flow to a two-dimensional map, the latter approach studies the phase space structures that lead to critical events by crossing certain barriers. Lobe dynamics describes global transport in terms of lobes, parcels of phase space bounded by stable and unstable invariant manifolds associated to hyperbolic fixed points of the system. Escape from a potential well describes how the critical events occur and quantifies the rate of escape using the flux across the barriers. Both of these frameworks require computation of curves, intersection points, and the area bounded by the curves. We present a theory for classification of intersection points to compute the area bounded between the segments of the curves. This involves the partition of the intersection points into equivalence classes to apply the discrete form of Green's theorem. We present numerical implementation of the theory, and an alternate method for curves with nontransverse intersections is also presented along with a method to insert points in the curve for densification.

  1. Extreme solar coronagraphy in Antarctica (ESCAPE) to support ASPIICS/PROBA-3 ESA program

    NASA Astrophysics Data System (ADS)

    Damé, Luc

    approach of critical sub-systems of future space coronagraphy missions (e.g. the 587 nm filters of ASPIICS), bring ground simultaneous/complementary observations, and will open the way to future and more ambitious projects in Antarctica (e.g. AFSIIC) and in Space (e.g. HiRISE, NEOCE). ESCAPE is part of the SCAR/AAA research working group international effort.

  2. Accounting for escape mortality in fisheries: implications for stock productivity and optimal management.

    PubMed

    Baker, Matthew R; Schindler, Daniel E; Essington, Timothy E; Hilborn, Ray

    2014-01-01

    Few studies have considered the management implications of mortality to target fish stocks caused by non-retention in commercial harvest gear (escape mortality). We demonstrate the magnitude of this previously unquantified source of mortality and its implications for the population dynamics of exploited stocks, biological metrics, stock productivity, and optimal management. Non-retention in commercial gillnet fisheries for Pacific salmon (Oncorhynchus spp.) is common and often leads to delayed mortality in spawning populations. This represents losses, not only to fishery harvest, but also in future recruitment to exploited stocks. We estimated incidence of non-retention in Alaskan gillnet fisheries for sockeye salmon (O. nerka) and found disentanglement injuries to be extensive and highly variable between years. Injuries related to non-retention were noted in all spawning populations, and incidence of injury ranged from 6% to 44% of escaped salmon across nine river systems over five years. We also demonstrate that non-retention rates strongly correlate with fishing effort. We applied maximum likelihood and Bayesian approaches to stock-recruitment analyses, discounting estimates of spawning salmon to account for fishery-related mortality in escaped fish. Discounting spawning stock estimates as a function of annual fishing effort improved model fits to historical stock-recruitment data in most modeled systems. This suggests the productivity of exploited stocks has been systematically underestimated. It also suggests that indices of fishing effort may be used to predict escape mortality and correct for losses. Our results illustrate how explicitly accounting for collateral effects of fishery extraction may improve estimates of productivity and better inform management metrics derived from estimates of stock-recruitment analyses.

  3. Coexisting chaotic and periodic dynamics in clock escapements.

    PubMed

    Moon, Francis C; Stiefel, Preston D

    2006-09-15

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

  4. Social escape behaviors in children with fragile X syndrome.

    PubMed

    Hall, Scott; DeBernardis, Marie; Reiss, Allan

    2006-10-01

    Social escape behavior is a common behavioral feature of individuals with fragile X syndrome (fraX). In this observational study, we examined the effect of antecedent social and performance demands on problem behaviors in four conditions: face-to-face interview, silent reading, oral reading and a singing task. Results showed that problem behaviors were significantly more likely to occur during the interview and singing conditions. Higher levels of salivary cortisol were predictive of higher levels of fidgeting behavior and lower levels of eye contact in male participants. There were no associations between level of FMRP expression and social escape behaviors. These data suggest that specific antecedent biological and environmental factors evoke social escape behaviors in fragile X syndrome.

  5. Kramers escape of a self-propelled particle

    NASA Astrophysics Data System (ADS)

    Geiseler, Alexander; Hänggi, Peter; Schmid, Gerhard

    2016-08-01

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

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

    PubMed Central

    Wang, Shujie; Lv, Wei; Song, Weiguo

    2015-01-01

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

  7. 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.

  8. Escape rate and diffusion of a Stochastically Driven particle

    PubMed Central

    Piscitelli, Antonio; Pica Ciamarra, Massimo

    2017-01-01

    The dynamical properties of a tracer repeatedly colliding with heat bath particles can be described within a Langevin framework provided that the tracer is more massive than the bath particles, and that the collisions are frequent. Here we consider the escape of a particle from a potential well, and the diffusion coefficient in a periodic potential, without making these assumptions. We have thus investigated the dynamical properties of a Stochastically Driven particle that moves under the influence of the confining potential in between successive collisions with the heat bath. In the overdamped limit, both the escape rate and the diffusion coefficient coincide with those of a Langevin particle. Conversely, in the underdamped limit the two dynamics have a different temperature dependence. In particular, at low temperature the Stochastically Driven particle has a smaller escape rate, but a larger diffusion coefficient. PMID:28120904

  9. MOLECULAR-KINETIC SIMULATIONS OF ESCAPE FROM THE EX-PLANET AND EXOPLANETS: CRITERION FOR TRANSONIC FLOW

    SciTech Connect

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

    2013-05-01

    The equations of gas dynamics are extensively used to describe atmospheric loss from solar system bodies and exoplanets even though the boundary conditions at infinity are not uniquely defined. Using molecular-kinetic simulations that correctly treat the transition from the continuum to the rarefied region, we confirm that the energy-limited escape approximation is valid when adiabatic expansion is the dominant cooling process. However, this does not imply that the outflow goes sonic. Rather large escape rates and concomitant adiabatic cooling can produce atmospheres with subsonic flow that are highly extended. Since this affects the heating rate of the upper atmosphere and the interaction with external fields and plasmas, we give a criterion for estimating when the outflow goes transonic in the continuum region. This is applied to early terrestrial atmospheres, exoplanet atmospheres, and the atmosphere of the ex-planet, Pluto, all of which have large escape rates.

  10. Aircrew Automated Escape Systems (AAES) In-Service Usage Data Analyses. Volume 2. Papers Presented at the Annual SAFE Symposium (21st), San Antonio, Texas, 5,6,7,8 November 1983.

    DTIC Science & Technology

    1983-11-05

    Commander, Naval Air Systems Command (AIR-5111C & 531E) the man years and associated cost , cost of materials, travel and cost of contracts awarded for...Contracts to perform all or por of this WUA are hereby authorized within the funding indicated by the cost t Aate. 7. Source and Disposition of Equipment...and ALSS in- service experience. d. Detailed Requirements/ Cost Estimates: (1) The primary effort shall be fo’. establishment of baseline data to aid in

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  13. SOYUZ escape trajectory analysis from Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Heck, Michael L.

    1993-01-01

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

  14. Case of escape in cassava, Manihot esculenta Crantz.

    PubMed

    Nassar, N M A; Mendonza, M

    2017-02-08

    Two cassava escapes where collected from cultivated fields near natural habitat in Bolivia. They are described morphologically and analyzed cytogenetically in this study. It is suggested that they are the product of backcrosses of cassava interspecific hybrids with the cultigen itself, and that selective conditions have developed in which certain forms of cassava segregates have adapted to grow wildly in natural habitats near cassava fields. These segregates may hybridize with cultivated cassava upon coming in contact with such varieties. Because these escapes have incorporated useful genes from the wild into their genetic structure, they could be used for cassava improvement since their genetic barriers with other forms of cassava are very weak.

  15. Escape routes, weak links, and desynchronization in fluctuation-driven networks

    NASA Astrophysics Data System (ADS)

    Schäfer, Benjamin; Matthiae, Moritz; Zhang, Xiaozhu; Rohden, Martin; Timme, Marc; Witthaut, Dirk

    2017-06-01

    Shifting our electricity generation from fossil fuel to renewable energy sources introduces large fluctuations to the power system. Here, we demonstrate how increased fluctuations, reduced damping, and reduced intertia may undermine the dynamical robustness of power grid networks. Focusing on fundamental noise models, we derive analytic insights into which factors limit the dynamic robustness and how fluctuations may induce a system escape from an operating state. Moreover, we identify weak links in the grid that make it particularly vulnerable to fluctuations. These results thereby not only contribute to a theoretical understanding of how fluctuations act on distributed network dynamics, they may also help designing future renewable energy systems to be more robust.

  16. Initial Concepts for a Mars Upper Atmosphere Orbiter Mission to Study Atmospheric Escape

    NASA Astrophysics Data System (ADS)

    Retherford, K. D.; Gladstone, G. R.; Stern, S. A.; Miller, G. P.; Slater, D. C.; Young, D. T.; Waite, J. H.; Bougher, S. W.; Nagy, A. F.

    2003-05-01

    According to the recent decadal survey "New Frontiers in the Solar System: An Integrated Exploration Strategy" report by the National Academy of Sciences, a Mars Upper Atmosphere Orbiter (MUAO) mission is required to "provide quantitative information on the various atmospheric escape fluxes, thus quantifying current escape rates and providing a basis for backwards extrapolation in our attempt to understand the evolution of Mars' atmosphere." Mars' atmosphere may once have been thick, warm, and wet, but how did it evolve into the thin, dry atmosphere of today? Specifically, how much water was lost by escape to space versus sequestration in the surface? We are investigating several candidate MUAO missions and instrument suites that address these questions of Martian climate change. SwRI held a workshop last spring (and a general Mars Aeronomy Workshop is planned for this meeting) to discuss the science goals and measurement needs for this mission with members of the Mars upper atmosphere community. We report a preliminary list of science goals and needed measurements for a MUAO mission. Initial results from a design study of neutral mass spectrometer, plasma analyzer, and far-ultraviolet spectrometer instruments conducted by SwRI will be discussed, along with future prospects for a NASA Mars Scout size MUAO mission. We gratefully acknowledge internal support from SwRI, through Southwest Initiative for Mars (SwIM) grant 15-R9366.

  17. Mechanism of escape, extrasystolic, and parasystolic arrhythmias. Study on an electrical analogue.

    PubMed

    Sideris, D A

    1976-01-01

    A simple analogue of the heart consisting of a system of neon relaxation oscillators is presented. The analogue may display rhythm patterns similar to sinus rhythm, escape rhythm, isorrhythmic dissociation with synchronization, atrial extrasystoles, ventricular extrasystoles, and parasystole. The strict rules followed by these arrhythmias, as well as the deviations from the rules commonly followed by the equivalent heart arrhythmias, may be easily reproduced on the analogue. Such features are the Treppe phenomenon and captured beats in escape rhythm, fixed coupling intervals in extrasystoles, partial or complete atrioventricular block in very premature atrial extrasystoles, prolongation of the period following an atrial extrasystole, interpolated premature beats, complete compensatory pause and the rule of bigeminy in ventricular extrasystoles, slight instability of the parasystolic period, multiple length parasystolic periods slightly different from the exact multiples of the parasystolic idioperiod, preference of the parasystoles for certain phase in the sinus cycle, synchronization at a phase difference and fluctuation repeatedly and without interruption from a parasystolic to an extrasystolic rhythm and synchronization in escape rhythm with isorrhythmic dissociation. The mechanisms involved in these phenomena are discussed in detail. The striking similarity between the properties of the cardiac pacemakers and those of the relaxation oscillators on the one hand and betwen the rhythm patterns of the heart and those of the analogue on the other may permit the hypothesis that the mechanisms operating in the analogue may be used in analyzing and understanding heart arrhythmias.

  18. The evolution of drought escape and avoidance in natural herbaceous populations.

    PubMed

    Kooyers, Nicholas J

    2015-05-01

    While the functional genetics and physiological mechanisms controlling drought resistance in crop plants have been intensely studied, less research has examined the genetic basis of adaptation to drought stress in natural populations. Drought resistance adaptations in nature reflect natural rather than human-mediated selection and may identify novel mechanisms for stress tolerance. Adaptations conferring drought resistance have historically been divided into alternative strategies including drought escape (rapid development to complete a life cycle before drought) and drought avoidance (reducing water loss to prevent dehydration). Recent studies in genetic model systems such as Arabidopsis, Mimulus, and Panicum have begun to elucidate the genes, expression profiles, and physiological changes responsible for ecologically important variation in drought resistance. Similar to most crop plants, variation in drought escape and avoidance is complex, underlain by many QTL of small effect, and pervasive gene by environment interactions. Recently identified major-effect alleles point to a significant role for genetic constraints in limiting the concurrent evolution of both drought escape and avoidance strategies, although these constraints are not universally found. This progress suggests that understanding the mechanistic basic and fitness consequences of gene by environment interactions will be critical for crop improvement and forecasting population persistence in unpredictable environments. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  19. Plasticity and evolution in drought avoidance and escape in the annual plant Brassica rapa.

    PubMed

    Franks, Steven J

    2011-04-01

    A key question in ecological genetics is to what extent do plants adapt to changes in climatic conditions, such as drought, through plasticity or evolution. To address this question, seeds of 140 maternal families of Brassica rapa were generated from collections made before (1997) and after (2004) a natural drought. These seeds were planted in the glasshouse and grown under low-water and high-water conditions. Post-drought lines flowered earlier than pre-drought lines, showing an evolutionary shift to earlier flowering. There was significant genetic variation and genotype by environment (G × E) interactions in flowering time, indicating genetic variation in plasticity in this trait. Plants that flowered earlier had fewer leaf nodes and lower instantaneous (A/g) and integrated (δ(13)C) water use efficiency than late-flowering plants. These results suggest that B. rapa plants escape drought through early flowering rather than avoid drought through increased water use efficiency. The mechanism of this response appears to be high transpiration and inefficient water use, leading to rapid development. These findings demonstrate a trade-off between drought avoidance and escape, and indicate that, in this system, where drought acts to shorten the growing season, selection for drought escape through earlier flowering is more important than phenotypic plasticity. © 2011 The Author. New Phytologist © 2011 New Phytologist Trust.

  20. Suppressing escape events in maps of the unit interval with demographic noise

    NASA Astrophysics Data System (ADS)

    Parra-Rojas, César; Challenger, Joseph D.; Fanelli, Duccio; McKane, Alan J.

    2016-11-01

    We explore the properties of discrete-time stochastic processes with a bounded state space, whose deterministic limit is given by a map of the unit interval. We find that, in the mesoscopic description of the system, the large jumps between successive iterates of the process can result in probability leaking out of the unit interval, despite the fact that the noise is multiplicative and vanishes at the boundaries. By including higher-order terms in the mesoscopic expansion, we are able to capture the non-Gaussian nature of the noise distribution near the boundaries, but this does not preclude the possibility of a trajectory leaving the interval. We propose a number of prescriptions for treating these escape events, and we compare the results with those obtained for the metastable behavior of the microscopic model, where escape events are not possible. We find that, rather than truncating the noise distribution, censoring this distribution to prevent escape events leads to results which are more consistent with the microscopic model. The addition of higher moments to the noise distribution does not increase the accuracy of the final results, and it can be replaced by the simpler Gaussian noise.

  1. Hubble space telescope emission line galaxies at z ∼ 2: the Lyα escape fraction

    SciTech Connect

    Ciardullo, Robin; Zeimann, Gregory R.; Gronwall, Caryl; Gebhardt, Henry; Schneider, Donald P.; Hagen, Alex; Malz, A. I. E-mail: grzeimann@psu.edu E-mail: gebhardt@psu.edu E-mail: hagen@psu.edu; and others

    2014-11-20

    We compare the Hβ line strengths of 1.90 < z < 2.35 star-forming galaxies observed with the near-IR grism of the Hubble Space Telescope with ground-based measurements of Lyα from the HETDEX Pilot Survey and narrow-band imaging. By examining the line ratios of 73 galaxies, we show that most star-forming systems at this epoch have a Lyα escape fraction below ∼6%. We confirm this result by using stellar reddening to estimate the effective logarithmic extinction of the Hβ emission line (c {sub Hβ} = 0.5) and measuring both the Hβ and Lyα luminosity functions in a ∼100, 000 Mpc{sup 3} volume of space. We show that in our redshift window, the volumetric Lyα escape fraction is at most 4.4{sub −1.2}{sup +2.1}%, with an additional systematic ∼25% uncertainty associated with our estimate of extinction. Finally, we demonstrate that the bulk of the epoch's star-forming galaxies have Lyα emission line optical depths that are significantly greater than that for the underlying UV continuum. In our predominantly [O III] λ5007-selected sample of galaxies, resonant scattering must be important for the escape of Lyα photons.

  2. Suppressing escape events in maps of the unit interval with demographic noise.

    PubMed

    Parra-Rojas, César; Challenger, Joseph D; Fanelli, Duccio; McKane, Alan J

    2016-11-01

    We explore the properties of discrete-time stochastic processes with a bounded state space, whose deterministic limit is given by a map of the unit interval. We find that, in the mesoscopic description of the system, the large jumps between successive iterates of the process can result in probability leaking out of the unit interval, despite the fact that the noise is multiplicative and vanishes at the boundaries. By including higher-order terms in the mesoscopic expansion, we are able to capture the non-Gaussian nature of the noise distribution near the boundaries, but this does not preclude the possibility of a trajectory leaving the interval. We propose a number of prescriptions for treating these escape events, and we compare the results with those obtained for the metastable behavior of the microscopic model, where escape events are not possible. We find that, rather than truncating the noise distribution, censoring this distribution to prevent escape events leads to results which are more consistent with the microscopic model. The addition of higher moments to the noise distribution does not increase the accuracy of the final results, and it can be replaced by the simpler Gaussian noise.

  3. Immune Escape Mechanisms are Plasmodium's Secret Weapons Foiling the Success of Potent and Persistently Efficacious Malaria Vaccines.

    PubMed

    Farooq, Fouzia; Bergmann-Leitner, Elke S

    2015-12-01

    Despite decades of active research, an efficacious vaccine mediating long-term protection is still not available. This review highlights various mechanisms and the different facets by which the parasites outsmart the immune system. An understanding of how the parasites escape immune recognition and interfere with the induction of a protective immune response that provides sterilizing immunity will be crucial to vaccine design.

  4. Sensory activation and receptive field organization of the lateral giant escape neurons in crayfish.

    PubMed

    Liu, Yen-Chyi; Herberholz, Jens

    2010-08-01

    Crayfish (Procambarus clarkii) have bilateral pairs of giant interneurons that control rapid escape movements in response to predatory threats. The medial giant neurons (MGs) can be made to fire an action potential by visual or tactile stimuli directed to the front of the animal and this leads to an escape tail-flip that thrusts the animal directly backward. The lateral giant neurons (LGs) can be made to fire an action potential by strong tactile stimuli directed to the rear of the animal, and this produces flexions of the abdomen that propel the crayfish upward and forward. These observations have led to the notion that the receptive fields of the giant neurons are locally restricted and do not overlap with each other. Using extra- and intracellular electrophysiology in whole animal preparations of juvenile crayfish, we found that the receptive fields of the LGs are far more extensive than previously assumed. The LGs receive excitatory inputs from descending interneurons originating in the brain; these interneurons can be activated by stimulation of the antenna II nerve or the protocerebral tract. In our experiments, descending inputs alone could not cause action potentials in the LGs, but when paired with excitatory postsynaptic potentials elicited by stimulation of tail afferents, the inputs summed to yield firing. Thus the LG escape neurons integrate sensory information received through both rostral and caudal receptive fields, and excitatory inputs that are activated rostrally can bring the LGs' membrane potential closer to threshold. This enhances the animal's sensitivity to an approaching predator, a finding that may generalize to other species with similarly organized escape systems.

  5. Low LET radiolysis escape yields for reducing radicals and H2 in pressurized high temperature water

    NASA Astrophysics Data System (ADS)

    Sterniczuk, Marcin; Yakabuskie, Pamela A.; Wren, J. Clara; Jacob, Jasmine A.; Bartels, David M.

    2016-04-01

    Low Linear Energy Transfer (LET) radiolysis escape yields (G values) are reported for the sum (G(radH)+G(e-)aq) and for G(H2) in subcritical water up to 350 °C. The scavenger system 1-10 mM acetate/0.001 M hydroxide/0.00048 M N2O was used with simultaneous mass spectroscopic detection of H2 and N2 product. Temperature-dependent measurements were carried out with 2.5 MeV electrons from a van de Graaff accelerator, while room temperature calibration measurements were done with a 60Co gamma source. The concentrations and dose range were carefully chosen so that initial spur chemistry is not perturbed and the N2 product yield corresponds to those reducing radicals that escape recombination in pure water. In comparison with a recent review recommendation of Elliot and Bartels (AECL report 153-127160-450-001, 2009), the measured reducing radical yield is seven percent smaller at room temperature but in fairly good agreement above 150 °C. The H2 escape yield is in good agreement throughout the temperature range with several previous studies that used much larger radical scavenging rates. Previous analysis of earlier high temperature measurements of Gesc(radOH) is shown to be flawed, although the actual G values may be nearly correct. The methodology used in the present report greatly reduces the range of possible error and puts the high temperature escape yields for low-LET radiation on a much firmer quantitative foundation than was previously available.

  6. Alanine mutagenesis of the primary antigenic escape residue cluster, c1, of apical membrane antigen 1.

    PubMed

    Dutta, Sheetij; Dlugosz, Lisa S; Clayton, Joshua W; Pool, Christopher D; Haynes, J David; Gasser, Robert A; Batchelor, Adrian H

    2010-02-01

    Antibodies against apical membrane antigen 1 (AMA1) inhibit invasion of Plasmodium merozoites into red cells, and a large number of single nucleotide polymorphisms on AMA1 allow the parasite to escape inhibitory antibodies. The availability of a crystal structure makes it possible to test protein engineering strategies to develop a monovalent broadly reactive vaccine. Previously, we showed that a linear stretch of polymorphic residues (amino acids 187 to 207), localized within the C1 cluster on domain 1, conferred the highest level of escape from inhibitory antibodies, and these were termed antigenic escape residues (AER). Here we test the hypothesis that immunodampening the C1 AER will divert the immune system toward more conserved regions. We substituted seven C1 AER of the FVO strain Plasmodium falciparum AMA1 with alanine residues (ALA). The resulting ALA protein was less immunogenic than the native protein in rabbits. Anti-ALA antibodies contained a higher proportion of cross-reactive domain 2 and domain 3 antibodies and had higher avidity than anti-FVO. No overall enhancement of cross-reactive inhibitory activity was observed when anti-FVO and anti-ALA sera were compared for their ability to inhibit invasion. Alanine mutations at the C1 AER had shifted the immune response toward cross-strain-reactive epitopes that were noninhibitory, refuting the hypothesis but confirming the importance of the C1 cluster as an inhibitory epitope. We further demonstrate that naturally occurring polymorphisms that fall within the C1 cluster can predict escape from cross-strain invasion inhibition, reinforcing the importance of the C1 cluster genotype for antigenic categorization and allelic shift analyses in future phase 2b trials.

  7. Involvement of HLA class I molecules in the immune escape of urologic tumors.

    PubMed

    Carretero, R; Gil-Julio, H; Vázquez-Alonso, F; Garrido, F; Castiñeiras, J; Cózar, J M

    2014-04-01

    To analyze the influence of different alterations in human leukocyte antigen class I molecules (HLA I) in renal cell carcinoma, as well as in bladder and prostate cancer. We also study the correlation between HLA I expression and the progression of the disease and the response after immunotherapy protocols. It has been shown, experimentally, that the immune system can recognize and kill neoplastic cells. By analyzing the expression of HLA I molecules on the surface of cancer cells, we were able to study the tumor escape mechanisms against the immune system. Alteration or irreversible damage in HLA I molecules is used by the neoplastic cells to escape the immune system. The function of these molecules is to recognize endogenous peptides and present them to T cells of the immune system. There is a clear relationship between HLA I reversible alterations and success of therapy. Irreversible lesions also imply a lack of response to treatment. The immune system activation can reverse HLA I molecules expression in tumors with reversible lesions, whereas tumors with irreversible ones do not respond to such activation. Determine the type of altered HLA I molecules in tumors is of paramount importance when choosing the type of treatment to keep looking for therapeutic success. Those tumors with reversible lesions can be treated with traditional immunotherapy; however, tumour with irreversible alterations should follow alternative protocols, such as the use of viral vectors carrying the HLA genes to achieve damaged re-expression of the protein. From studies in urologic tumors, we can conclude that the HLA I molecules play a key role in these tumors escape to the immune system. Copyright © 2013 AEU. Published by Elsevier Espana. All rights reserved.

  8. An antibody tag-team: driving neutralization through escape.

    PubMed

    Alter, Galit; Ackerman, Margaret E

    2014-09-01

    HIV rapidly mutates to escape antibody detection, and B cells counter this mutation by continual evolution to restore recognition, serendipitously resulting in the evolution of neutralizing activity in a fraction of infected individuals. A recent Cell paper describes how antibody repertoires stochastically collaborated, shaping the viral swarm and utilizing viral immune evasion to their advantage. Copyright © 2014. Published by Elsevier Ltd.

  9. Purinergic Inhibition of ENaC Produces Aldosterone Escape

    PubMed Central

    Mironova, Elena; Bugaj, Vladislav; Rieg, Timo; Insel, Paul A.; Vallon, Volker; Peti-Peterdi, Janos

    2010-01-01

    The mechanisms underlying “aldosterone escape,” which refers to the excretion of sodium (Na+) during high Na+ intake despite inappropriately increased levels of mineralocorticoids, are incompletely understood. Because local purinergic tone in the aldosterone-sensitive distal nephron downregulates epithelial Na+ channel (ENaC) activity, we tested whether this mechanism mediates aldosterone escape. Here, urinary ATP concentration increased with dietary Na+ intake in mice. Physiologic concentrations of ATP decreased ENaC activity in a dosage-dependent manner. P2Y2−/− mice, which lack the purinergic receptor, had significantly less increased Na+ excretion than wild-type mice in response to high-Na+ intake. Exogenous deoxycorticosterone acetate and deletion of the P2Y2 receptor each modestly increased the resistance of ENaC to changes in Na+ intake; together, they markedly increased resistance. Under the latter condition, ENaC could not respond to changes in Na+ intake. In contrast, as a result of aldosterone escape, wild-type mice had increased Na+ excretion in response to high-Na+ intake regardless of the presence of high deoxycorticosterone acetate. These data suggest that control of ENaC by purinergic signaling is necessary for aldosterone escape. PMID:20813869

  10. 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

  11. Escaping Embarrassment: Face-Work in the Rap Cipher

    ERIC Educational Resources Information Center

    Lee, Jooyoung

    2009-01-01

    How do individuals escape embarrassing moments in interaction? Drawing from ethnographic fieldwork, in-depth interviews, and video recordings of weekly street corner ciphers (impromptu rap sessions), this paper expands Goffman's theory of defensive and protective face-work. The findings reveal formulaic and indirect dimensions of face-work. First,…

  12. Plasma amino acid response to graded levels of escape protein.

    PubMed

    Gibb, D J; Klopfenstein, T J; Britton, R A; Lewis, A J

    1992-09-01

    A trial was conducted to examine the potential of using plasma amino acid responses to graded levels of escape protein to determine limiting amino acids in cattle. Growing calves (n = 120; mean BW = 220 +/- 21 kg) were fed a basal diet of corncob:sorghum silage (61:39) and were individually supplemented with distillers' dried grains (DDG), heat-damaged DDG (H-DDG), feather meal (FTH), or urea. The urea supplement was mixed with DDG and H-DDG to allow 0, 20, 35, 50, 65, or 80% of the supplemental CP to come from distillers' protein and maintain an 11.5% CP diet. Urea supplement was mixed with FTH to allow 0, 22, 39, 56, 73, or 90% of the supplemental CP to come from FTH. Dietary CP ranged from 11.5% at the 0% level to 17.3% at the 90% level. Plasma concentration of most essential plasma amino acids responded (P less than .10) linearly and(or) quadratically to increased escape protein. The broken-line response of plasma methionine at low DDG intake suggested that methionine was limiting at low levels of escape protein. An initial decrease followed by a plateau fit by a broken line indicated that histidine became limiting in FTH diets, and lysine eventually became limiting for DDG, H-DDG, and FTH diets before maximum BW gain was reached. Results indicate that plasma amino acid responses may identify amino acids that become limiting with increasing escape protein.

  13. Hepatitis B escape mutants in Scottish blood donors.

    PubMed

    Larralde, Osmany; Dow, Brian; Jarvis, Lisa; Davidson, Fiona; Petrik, Juraj

    2013-06-01

    Hepatitis B virus (HBV) remains as the viral infection with the highest risk of transmission by transfusion. This risk is associated with window period donations, occult HBV infection (OBI) and the emergence of escape mutants, which render blood donations false negative for hepatitis B surface antigen (HBsAg) serological testing. A retrospective study was conducted to gain insights into the molecular epidemiology of HBV escape mutants in Scottish blood donors. The criterion for selection was HBV positivity either by serology or nucleic acid testing (NAT). HBsAg detection was compared across several commercial immunoassays. The full length S gene from plasma samples was PCR amplified, cloned and expressed in HepG2 cells. Eight samples showed HBsAg discordant results, while 5 OBI samples were found. Four escape mutants, containing missense mutations in the S gene, are described here. These mutations impaired HBsAg detection both from HBV infected plasma samples and from recombinant proteins derived from its infected donors. Phylogenetic analysis showed that most of the mutants were clustered in the genotype D and were closely related to strains from Asia and the Middle East. We report here a proline substitution, outside the major hydrophilic region, that impaired HBsAg detection in vivo and in vitro, warning about the risk for the emergence of vaccine escape mutants with mutations outside the major neutralisation site.

  14. Escaping Embarrassment: Face-Work in the Rap Cipher

    ERIC Educational Resources Information Center

    Lee, Jooyoung

    2009-01-01

    How do individuals escape embarrassing moments in interaction? Drawing from ethnographic fieldwork, in-depth interviews, and video recordings of weekly street corner ciphers (impromptu rap sessions), this paper expands Goffman's theory of defensive and protective face-work. The findings reveal formulaic and indirect dimensions of face-work. First,…

  15. Social Escape Behaviors in Children with Fragile X Syndrome

    ERIC Educational Resources Information Center

    Hall, Scott; DeBernardis, Marie; Reiss, Allan

    2006-01-01

    Social escape behavior is a common behavioral feature of individuals with fragile X syndrome (fraX). In this observational study, we examined the effect of antecedent social and performance demands on problem behaviors in four conditions: face-to-face interview, silent reading, oral reading and a singing task. Results showed that problem behaviors…

  16. Purinergic inhibition of ENaC produces aldosterone escape.

    PubMed

    Stockand, James D; Mironova, Elena; Bugaj, Vladislav; Rieg, Timo; Insel, Paul A; Vallon, Volker; Peti-Peterdi, Janos; Pochynyuk, Oleh

    2010-11-01

    The mechanisms underlying "aldosterone escape," which refers to the excretion of sodium (Na(+)) during high Na(+) intake despite inappropriately increased levels of mineralocorticoids, are incompletely understood. Because local purinergic tone in the aldosterone-sensitive distal nephron downregulates epithelial Na(+) channel (ENaC) activity, we tested whether this mechanism mediates aldosterone escape. Here, urinary ATP concentration increased with dietary Na(+) intake in mice. Physiologic concentrations of ATP decreased ENaC activity in a dosage-dependent manner. P2Y(2)(-/-) mice, which lack the purinergic receptor, had significantly less increased Na(+) excretion than wild-type mice in response to high-Na(+) intake. Exogenous deoxycorticosterone acetate and deletion of the P2Y(2) receptor each modestly increased the resistance of ENaC to changes in Na(+) intake; together, they markedly increased resistance. Under the latter condition, ENaC could not respond to changes in Na(+) intake. In contrast, as a result of aldosterone escape, wild-type mice had increased Na(+) excretion in response to high-Na(+) intake regardless of the presence of high deoxycorticosterone acetate. These data suggest that control of ENaC by purinergic signaling is necessary for aldosterone escape.

  17. 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

  18. Seasonal Dependence of the Escape of Martian Water

    NASA Astrophysics Data System (ADS)

    Clarke, John

    2013-10-01

    This proposal is to obtain ACS/SBC images and STIS spectra of the extended H Ly alpha and O 1304 emissions from H and O atoms in the atmosphere of Mars to study seasonal changes in the escape rate of H and O atoms, and thereby water. Prior HST observations have revealed a surprising rapid change in the H escape rate in late martian summer following a global dust storm, and have shown that STIS spectra can easily detect superthermal O atoms. The relative degree of influence of seasons and dust storms on the H density and escape flux are not known, and little is known about variations in the hot O density and escape rate. The timing of these observations is key to these scientific goals. Mars is now approaching the Sun, HST can observe Mars over a wide range of seasons from April - Nov 2014, and HST will not be able to observe Mars again until after the prime mission of MAVEN. These observations will provide strong support for the NASA MAVEN mission, scheduled to arrive at Mars in Sept. 2014. This proposal is for a single visit of 3 HST orbits in late sprign 2014 to establish the baseline conditions when Mars is far from the Sun.

  19. Learning from escaped prescribed fires - lessons for high reliability

    Treesearch

    Deirdre Dether; Anne Black

    2006-01-01

    Meeting national goals for hazardous fuels reduction and ecosystem restoration would be difficult - if not impossible - without utilizing prescribed fire. Suspension of prescribed fire programs, as often happens following an escape, limits Federal capacity to meet programmatic, social, and ecological goals.

  20. The Effect of Laziness in Group Chase and Escape

    NASA Astrophysics Data System (ADS)

    Masuko, Makoto; Hiraoka, Takayuki; Ito, Nobuyasu; Shimada, Takashi

    2017-08-01

    The effect of laziness in the group chase and escape problem is studied using a simple model. Laziness is introduced as random walks in two ways: uniformly and in a "division of labor" way. It is shown that while the former is always ineffective, the latter can improve the efficiency of catching, through the formation of pincer attack configuration by diligent and lazy chasers.

  1. 6. UNDERGROUND FIRING CONTROL ROOM, INTERIOR. Looking southeast to escape ...

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

    6. UNDERGROUND FIRING CONTROL ROOM, INTERIOR. Looking southeast to escape tunnel. - Edwards Air Force Base, Air Force Rocket Propulsion Laboratory, Firing Control Building, Test Area 1-100, northeast end of Test Area 1-100 Road, Boron, Kern County, CA

  2. Spatial and Nonspatial Escape Strategies in the Barnes Maze

    ERIC Educational Resources Information Center

    Harrison, Fiona E.; Reiserer, Randall S.; Tomarken, Andrew J.; McDonald, Michael P.

    2006-01-01

    The Barnes maze is a spatial memory task that requires subjects to learn the position of a hole that can be used to escape the brightly lit, open surface of the maze. Two experiments assessed the relative importance of spatial (extra-maze) versus proximal visible cues in solving the maze. In Experiment 1, four groups of mice were trained either…

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

    NASA Astrophysics Data System (ADS)

    Parker, E. N.

    1984-06-01

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

  4. Solar forcing and planetary ion escape from Mars

    NASA Astrophysics Data System (ADS)

    Lundin, R.; Barabash, S.; Fedorov, A.; Holmström, M.; Nilsson, H.; Sauvaud, J.-A.; Yamauchi, M.

    2008-05-01

    The variability of planetary ion escape from Mars is studied using data from the Ion Mass Analyzer, IMA, on Mars Express (MEX). 42 orbits were selected during 17 months for different solar wind conditions, focusing on the low energy (~30 - 800 eV) heavy ion (e.g. O+, O2 + and CO2 +) outflow. A strong correlation is found between solar wind forcing of the obstacle, the cross-sectional area enclosing the ion outflow from Mars and the total heavy ion escape flux. The at least one order of magnitude changes of the ion outflow on the short term (hours, days), is directly connected with the variability of solar wind, solar soft x-ray and solar EUV (XEUV). The latter was first inferred from an analysis of how the obstacle size changes with changing solar wind and solar XEUV forcing. The 17-month trend of decreasing ion outflow with EUV during a declining phase of solar cycle 23, the EUV determined from the Neutral Particle Imager (NPI) on MEX, illustrates the influence of solar EUV forcing. On the basis of this we conclude that changes in solar wind- and solar XEUV forcing governs the variable ion escape from Mars. Both forcing terms appear to be equally important for the escape rate. Considering the difference in travel time for XEUV and the solar wind to Mars, the XEUV effect will precede the solar wind effect by several (3-9) days.

  5. Action of cocaine and chronic sympathetic denervation on vagal escape

    PubMed Central

    Campos, H. A.; Urquilla, P. R.

    1969-01-01

    1. The effect of cocaine has been studied on vagal escape and on the tachycardia due to vagal stimulation in the atropinized dog. All the dogs were submitted to acute cervical section of the spinal cord and acute or chronic sympathetic denervation. 2. Cocaine, 5 mg/kg or 40 μg/kg/min, I.V., induces a significant enhancement of the ventricular escape. The effects of a continuous infusion of cocaine are more reproducible than those of a single injection of the drug. 3. Cocaine, 40 μg/kg/min, I.V., potentiates the tachycardia due to vagal stimulation in the atropinized dog. 4. Chronic thoracic sympathectomy markedly retards the recovery of the ventricular rate from the inhibitory action of the vagus. Under this condition, the infusion of cocaine does not significantly enhance the ventricular escape. 5. These findings suggest that an adrenergic mechanism located at the sympathetic nerves supplying the heart is substantially involved in the phenomenon of vagal escape. PMID:5249864

  6. Spatial and Nonspatial Escape Strategies in the Barnes Maze

    ERIC Educational Resources Information Center

    Harrison, Fiona E.; Reiserer, Randall S.; Tomarken, Andrew J.; McDonald, Michael P.

    2006-01-01

    The Barnes maze is a spatial memory task that requires subjects to learn the position of a hole that can be used to escape the brightly lit, open surface of the maze. Two experiments assessed the relative importance of spatial (extra-maze) versus proximal visible cues in solving the maze. In Experiment 1, four groups of mice were trained either…

  7. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Means of escape. 169.313 Section 169.313 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Construction... apart, uniform for the length of the ladder; (3) At least 3 inches from the nearest permanent object...

  8. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Means of escape. 169.313 Section 169.313 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS SAILING SCHOOL VESSELS Construction... apart, uniform for the length of the ladder; (3) At least 3 inches from the nearest permanent object...

  9. Social Escape Behaviors in Children with Fragile X Syndrome

    ERIC Educational Resources Information Center

    Hall, Scott; DeBernardis, Marie; Reiss, Allan

    2006-01-01

    Social escape behavior is a common behavioral feature of individuals with fragile X syndrome (fraX). In this observational study, we examined the effect of antecedent social and performance demands on problem behaviors in four conditions: face-to-face interview, silent reading, oral reading and a singing task. Results showed that problem behaviors…

  10. Pilot Fullerton dons ejection escape suit (EES) on middeck

    NASA Image and Video Library

    1982-03-30

    STS003-23-165 (22-30 March 1982) --- Astronaut Gordon Fullerton, STS-3 pilot, dons ejection escape suit (EES) (high altitude pressure garment) life preserver unit (LPU) on forward port side of middeck above potable water tank. Fullerton also adjusts lapbelt fitting and helmet holddown strap. Photo credit: NASA

  11. Enuresis Control through Fading, Escape, and Avoidance Training.

    ERIC Educational Resources Information Center

    Hansen, Gordon D.

    1979-01-01

    A twin signal device that provides both escape and avoidance conditioning in enuresis control was documented with case studies of two enuretic children (eight and nine years old). In addition, a technique of fading as an adjunct to the process was utilized with one subject. (Author/SBH)

  12. Thermally activated escape from a Lennard-Jones potential well

    NASA Astrophysics Data System (ADS)

    Larson, Richard S.; Lightfoot, Edwin J.

    1988-03-01

    The Kramers theory of chemical kinetics is modified in order to describe the escape of particles from a potential well of the Lennard-Jones type, for which there is no well-defined barrier position or curvature. Approximate analytical methods are used to derive from the Fokker-Planck equation two distinct formulas for the escape rate, each valid in a different regime of the friction constant β. The large-β result is seen to be consistent with that obtained from the Smoluchoeski equation, and it shows that the resistance to escape is dominated by a purely diffusive component that causes nonequilibrium effects to be felt well down into the reactant region. On the other hand, the small-β result describes a situation in which diffusional resistance is of minor importance, and the escape rate is determined largely by the characteristics of the well itself. The approximate formulas give a reasonably good picture of the transition between the two kinds of limiting behavior.

  13. Brain size as a driver of avian escape strategy.

    PubMed

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

    2015-07-03

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

  14. 12. CLOSEUP VIEW FROM NORTHWEST, SHOWING DETAILS OF FIRE ESCAPE ...

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

    12. CLOSE-UP VIEW FROM NORTHWEST, SHOWING DETAILS OF FIRE ESCAPE NEAR CORNER OF MILLS HALL MAIN WING NORTH WALL, AND MILLS HALL NORTH WING WEST WALL. - Mills Hall, Mills College, 5000 MacArthur Boulevard, Oakland, Alameda County, CA

  15. 2. WEST REAR, WITH PORTHOLE ESCAPE HATCH ABOVE ENTRY DOOR. ...

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

    2. WEST REAR, WITH PORTHOLE ESCAPE HATCH ABOVE ENTRY DOOR. - Edwards Air Force Base, South Base Sled Track, Firing & Control Blockhouse for 10,000-foot Track, South of Sled Track at midpoint of 20,000-foot track, Lancaster, Los Angeles County, CA

  16. Unravelling the escape dynamics and the nature of the normally hyperbolic invariant manifolds in tidally limited star clusters

    NASA Astrophysics Data System (ADS)

    Zotos, Euaggelos E.; Jung, Christof

    2017-02-01

    The escape mechanism of orbits in a star cluster rotating around its parent galaxy in a circular orbit is investigated. A three degrees of freedom model is used for describing the dynamical properties of the Hamiltonian system. The gravitational field of the star cluster is represented by a smooth and spherically symmetric Plummer potential. We distinguish between ordered and chaotic orbits as well as between trapped and escaping orbits, considering only unbounded motion for several energy levels. The Smaller ALignment Index (SALI) method is used for determining the regular or chaotic nature of the orbits. The basins of escape are located and they are also correlated with the corresponding escape time of the orbits. Areas of bounded regular or chaotic motion and basins of escape were found to coexist in the (x, z) plane. The properties of the normally hyperbolic invariant manifolds (NHIMs), located in the vicinity of the index-1 Lagrange points L1 and L2, are also explored. These manifolds are of paramount importance as they control the flow of stars over the saddle points, while they also trigger the formation of tidal tails observed in star clusters. Bifurcation diagrams of the Lyapunov periodic orbits as well as restrictions of the Poincaré map to the NHIMs are deployed for elucidating the dynamics in the neighbourhood of the saddle points. The extended tidal tails, or tidal arms, formed by stars with low velocity which escape through the Lagrange points are monitored. The numerical results of this work are also compared with previous related work.

  17. HLA-B27 Selects for Rare Escape Mutations that Significantly Impair Hepatitis C Virus Replication and Require Compensatory Mutations

    PubMed Central

    Neumann-Haefelin, Christoph; Oniangue-Ndza, Cesar; Kuntzen, Thomas; Schmidt, Julia; Nitschke, Katja; Sidney, John; Caillet-Saguy, Célia; Binder, Marco; Kersting, Nadine; Kemper, Michael W.; Power, Karen A.; Ingber, Susan; Reyor, Laura L.; Hills-Evans, Kelsey; Kim, Arthur Y.; Lauer, Georg M.; Lohmann, Volker; Sette, Alessandro; Henn, Matthew R.; Bressanelli, Stéphane; Thimme, Robert; Allen, Todd M.

    2011-01-01

    HLA-B27 is associated with spontaneous viral clearance in hepatitis C virus (HCV) infection. Viral escape within the immunodominant HLA-B27 restricted HCV-specific CD8+ T cell epitope NS5B2841-2849 (ARMILMTHF) has been shown to be limited by viral fitness costs as well as broad T cell cross-recognition, suggesting a potential mechanism of protection by HLA-B27. Here, we studied the subdominant HLA-B27 restricted epitope NS5B2936-2944 (GRAAICGKY) in order to further define the mechanisms of protection by HLA-B27. We identified a unique pattern of escape mutations within this epitope in a large cohort of HCV genotype 1a infected patients. The predominant escape mutations represented conservative substitutions at the main HLA-B27 anchor residue or a T cell receptor contact site, neither of which impaired viral replication capacity as assessed in a subgenomic HCV replicon system. In contrast, however, in a subset of HLA-B27+ subjects rare escape mutations arose at the HLA-B27 anchor residue R2937, which nearly abolished viral replication. Notably, these rare mutations only occurred in conjunction with the selection of two equally rare, and structurally proximal, upstream mutations. Co-expression of these upstream mutations with the rare escape mutations dramatically restored viral replication capacity from <5% to ≥70% of wild-type levels. Conclusion The selection of rare CTL escape mutations in this HLA-B27 restricted epitope dramatically impairs viral replicative fitness unless properly compensated. These data support a role for the targeting of highly-constrained regions by HLA-B27 in its ability to assert immune control of HCV and other highly variable pathogens. PMID:22006856

  18. 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.

  19. Spatial and nonspatial escape strategies in the Barnes maze.

    PubMed

    Harrison, Fiona E; Reiserer, Randall S; Tomarken, Andrew J; McDonald, Michael P

    2006-01-01

    The Barnes maze is a spatial memory task that requires subjects to learn the position of a hole that can be used to escape the brightly lit, open surface of the maze. Two experiments assessed the relative importance of spatial (extra-maze) versus proximal visible cues in solving the maze. In Experiment 1, four groups of mice were trained either with or without a discrete visible cue marking the location of the escape hole, which was either in a fixed or variable location across trials. In Experiment 2, all mice were trained with the discrete visible cue marking the target hole location. Two groups were identical to the cued-target groups from Experiment 1, with either fixed or variable escape locations. For these mice, the discrete cue either was the sole predictor of the target location or was perfectly confounded with the spatial extra-maze cues. The third group also used a cued variable target, but a curtain was drawn around the maze to prevent the use of spatial cues to guide navigation. Probe trials with all escape holes blocked were conducted to dissociate the use of spatial and discrete proximal cues. We conclude that the Barnes maze can be solved efficiently using spatial, visual cue, or serial-search strategies. However, mice showed a strong preference for using the distal room cues, even when a discrete visible cue clearly marked the escape location. Importantly, these data show that the cued-target control version of the Barnes maze as typically conducted does not dissociate spatial from nonspatial abilities.

  20. Spatial and nonspatial escape strategies in the Barnes maze

    PubMed Central

    Harrison, Fiona E.; Reiserer, Randall S.; Tomarken, Andrew J.; McDonald, Michael P.

    2006-01-01

    The Barnes maze is a spatial memory task that requires subjects to learn the position of a hole that can be used to escape the brightly lit, open surface of the maze. Two experiments assessed the relative importance of spatial (extra-maze) versus proximal visible cues in solving the maze. In Experiment 1, four groups of mice were trained either with or without a discrete visible cue marking the location of the escape hole, which was either in a fixed or variable location across trials. In Experiment 2, all mice were trained with the discrete visible cue marking the target hole location. Two groups were identical to the cued-target groups from Experiment 1, with either fixed or variable escape locations. For these mice, the discrete cue either was the sole predictor of the target location or was perfectly confounded with the spatial extra-maze cues. The third group also used a cued variable target, but a curtain was drawn around the maze to prevent the use of spatial cues to guide navigation. Probe trials with all escape holes blocked were conducted to dissociate the use of spatial and discrete proximal cues. We conclude that the Barnes maze can be solved efficiently using spatial, visual cue, or serial-search strategies. However, mice showed a strong preference for using the distal room cues, even when a discrete visible cue clearly marked the escape location. Importantly, these data show that the cued-target control version of the Barnes maze as typically conducted does not dissociate spatial from nonspatial abilities. PMID:17101874

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

    NASA Astrophysics Data System (ADS)

    Kollmann, P.; Brandt, P. C.

    2013-12-01

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

  2. Erratum: The Escape of Ionizing Photons from the Galaxy

    NASA Astrophysics Data System (ADS)

    Bland-Hawthorn, J.; Maloney, P. R.

    2001-04-01

    In the Letter ``The Escape of Ionizing Photons from the Galaxy'' by J. Bland-Hawthorn & P. R. Maloney (ApJ, 510, L33 [1999]), there is an error in Figure 4 that bears on the derived escape fraction of ionizing photons from star-forming regions in the Galaxy's disk. For the quoted distance (55 kpc) of the Magellanic Stream, the predicted emission measures should be reduced by a factor of (20/55)2. Our derived value of fesc~6%, the escape fraction normal to the disk, must be raised by the inverse of this factor, which makes it unlikely that the Stream Hα arises from UV produced by the Galaxy's young stellar disk. This is exacerbated by new Hα observations that show that the Stream is even brighter than originally thought (Weiner, Vogel, & Williams 2001). Bland-Hawthorn & Putman (2001) discuss possible sources of ionization for the Magellanic Stream. We note with interest that high-velocity clouds have now been detected in Hα (e.g., Tufte, Reynolds, & Haffner 1998). Some of these have well-established distance bounds. Bland-Hawthorn & Putman (2001) and Weiner et al. (2001) find that the observed Hα is roughly consistent with fesc~5%, although the present uncertainties are about a factor of 2. It should be noted that fesc refers to the escape fraction normal to the disk. The escape fraction averaged over 4π sr, fesc, is about a factor of 3 smaller and depends on the details of the opacity model (Bland-Hawthorn 1998, Appendix 1). The present uncertainties on fesc for the Galaxy mean that we cannot determine whether star-forming regions dominate the extragalactic UV background (cf. Shull et al. 1999).

  3. 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

  4. Challenging zebrafish escape responses by increasing water viscosity.

    PubMed

    Danos, Nicole; Lauder, George V

    2012-06-01

    Escape responses of fishes have long been studied as a model locomotor behavior in which hypothesized maximal or near-maximal muscle power output is used to generate rapid body bending. In this paper we present the results of experiments that challenged zebrafish (Danio rerio) to perform escape responses in water of altered viscosity, to better understand the effects that the fluid mechanical environment exerts on kinematics. We quantified escape kinematics using 1000 frames s(-1) high-speed video, and compared escape response kinematics of fish in three media that differed in viscosity: 1 mPa s (normal water), 10 mPa s and 20 mPa s (20 times normal water viscosity). We hypothesized that because viscosity is increased but not density there will be a different effect on kinematic variables resulting from unsteady (acceleration-dependent) hydrodynamic forces and steady (velocity-dependent) ones. Similarly, we hypothesized that the kinematics of stage 1 will be less affected by viscosity than those of stage 2, as higher angular velocities are reached during stage 1 resulting in higher Reynolds numbers. Our results showed a significant overall effect of viscosity on escape response kinematics but the effect was not in accordance with our predictions. Statistical tests showed that increasing viscosity significantly decreased displacement of the center of mass during stage 1 and after 30 ms, and decreased maximum velocity of the center of mass, maximum angular velocity and acceleration during stage 1, but increased time to maximum angular acceleration and time to maximum linear velocity of the center of mass. Remarkably, increasing water viscosity 20 times did not significantly affect the duration of stage 1 or stage 2.

  5. An Empirical Investigation of Time-Out with and without Escape Extinction to Treat Escape-Maintained Noncompliance

    ERIC Educational Resources Information Center

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

    2007-01-01

    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…

  6. Rapid vascular escape of arterially injected 16alpha-radioiodo, 17beta-estradiol

    SciTech Connect

    Scharl, A.; Holt, J.A. )

    1993-03-20

    The authors undertook this study because confirmation of a rapid vascular escape and slow release back into the circulatory system suggests that arterial injection of radiohalogenated steroid receptor ligands might provide an efficacious route of administration for imaging or treatment of receptor-rich malignant tumors in peripheral tissues. The authors injected radiolabeled 16alpha-iodo, 17beta-estradiol ([I]-E) into the femoral artery of swine in a solution that contained [[sup 125]I]-E in a known ratio to [[sup 99]Tc]-labeled red blood cells. Fractions of femoral venous blood were collected at short intervals during 10 min. They looked for changes in the ratio of the radiolabeles. [[sup 99m]Tc]-labeled red blood cells are known to remain in the vascular system for an hour or more. After passage of the injectate through the capillary bed of the swine leg, a dramatic decrease of the initial [sup 125]I:[sup 99m]Tc ratio to only 10% was observed in the femoral venous blood. This ratio increased gradually during the next 10 min to approximately 30% of that in the injectate, indicating that a significant portion (approximately 90%) of the [[sup 125]I]-E was initially trapped in the limb and then slowly re-entered the vascular system. To obtain visual confirmation of the rapid vascular escape of iodo-estrogen, they injected either an imageable form of [I]-E ([[sup 123]I]-E) or [[sup 99m]Tc]-labeled red blood cells into the dorsal aorta of superovulated rabbits, whose smaller size allowed whole-body imaging. The biodistributions of these radiopharmaceuticals were surveyed continuously by real-time planar gamma imaging. A large fraction of [I]-E escapes from the vascular system during the first pass through an organ or limb, without regard to the estrogen receptor content of the tissue. 28 refs., 3 figs., 1 tab.

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

    ERIC Educational Resources Information Center

    Denny, Mark

    2010-01-01

    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…

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

    ERIC Educational Resources Information Center

    Denny, Mark

    2010-01-01

    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…

  9. Anatomy of an escape tectonic zone: Western Irian Jaya (Indonesia)

    NASA Astrophysics Data System (ADS)

    Pubellier, Manuel; Ego, Frédéric

    2002-07-01

    The western fold-and-thrust belt of New Guinea in Irian Jaya is presently a complex boundary, dominated by the Bird's Head block escape from the collision between the Australian plate and the remnants of volcanic belts carried by the Pacific plate. The escape rate given by geodetic measurements is of the order of 7 cm/yr, and movement is accommodated by a broad shear zone. We analyze this shear pattern using fault slip analyses performed in the field from 1992 to 1996, combined with focal mechanism inversions, moment tensors summations, and surface trace of structures inferred from radar and multispectral satellite images. Time control of the deformation is attained by isotope dating of the recent syntectonic intrusives. The geometry of the macro and microstructures occurred in two stages from the early Pliocene to the Present. The first stage (5 to 2 Ma) is marked by flat-and-ramps structures guided by N60°E lateral ramps associated with a N60°E cleavage, affecting the whole of western Irian Jaya. The second stage (2 Ma to Present) shows the collapse of the western fold-and-thrust belt and the escape of the Bird's Head and the Lengguru belts along N60°E transtensile faults. In the latter stage, the strike-slip offset is distributed on the N60°E schistosity zone along which some fracture planes are reactivated as left-lateral transtensile faults. Shallow earthquakes moment tensors have been inverted for stress and summed to get strain rates to define contrasting structural provinces. The spatial variations in both stress and strain fields from earthquakes and microtectonics show that (1) they are consistent and are assumed to be coeval, (2) they reveal that oblique convergence is partitioned, and (3) they are influenced by the existence of a free boundary. We see no significant rotation of stress axes laterally along the escape zone. Instead, stresses change according to the different orientations of basement structures and thus undergo rapid spatial variations

  10. 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

  11. Ion Escape Processes of Mars with a Weak Intrinsic Magnetic Field

    NASA Astrophysics Data System (ADS)

    Sakai, S.; Seki, K.; Terada, N.; Shinagawa, H.; Tanaka, T.; Ebihara, Y.

    2017-10-01

    The ion tailward flux increases by the magnetization of Mars. Ions escape through four channels in the magnetotail, which are related to the cusp region and the reconnection. This could result in the escape rate from the upper atmosphere enhanced.

  12. Escape from the competence state in Streptococcus mutans is governed by the bacterial population density.

    PubMed

    Dufour, D; Villemin, C; Perry, J A; Lévesque, C M

    2016-12-01

    Horizontal gene transfer through natural DNA transformation is an important evolutionary mechanism among bacteria. Transformation requires that the bacteria are physiologically competent to take and incorporate free DNA directly from the environment. Although natural genetic transformation is a remarkable feature of many naturally competent bacteria, the process is energetically expensive for the cells. Consequently, a tight control of the competence state is necessary. The objective of the present work was to help decipher the molecular mechanisms regulating the escape from the competence state in Streptococcus mutans, the principal etiological agent responsible for tooth decay in humans. Our results showed that the cessation of competence in S. mutans was abrupt, and did not involve the accumulation of a competence inhibitor nor the depletion of a competence activator in the extracellular environment. The competence state was repressed at high cell population density via concomitant repression of sigX gene encoding the master regulator of the competence regulon. Co-culture experiments performed with oral and non-oral bacteria showed that S. mutans assesses its own population density and also the microbial density of its surroundings to regulate its competence escape. Interestingly, neither the intra-species and extra-species quorum-sensing systems nor the other 13 two-component regulatory systems identified in S. mutans were involved in the cell-density-dependent escape of the competence state. Altogether, our results suggest a complex mechanism regulating the competence shut-off involving cell-density-dependent repression of sigX through an as yet undefined system, and possibly SigX protein stability. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Antibody Escape Kinetics of Equine Infectious Anemia Virus Infection of Horses

    PubMed Central

    Mealey, Robert H.

    2015-01-01

    Lentivirus escape from neutralizing antibodies (NAbs) is not well understood. In this work, we quantified antibody escape of a lentivirus, using antibody escape data from horses infected with equine infectious anemia virus. We calculated antibody blocking rates of wild-type virus, fitness costs of mutant virus, and growth rates of both viruses. These quantitative kinetic estimates of antibody escape are important for understanding lentiviral control by antibody neutralization and in developing NAb-eliciting vaccine strategies. PMID:25878104

  14. Chasing and escaping by three groups of species.

    PubMed

    Sato, Masahide

    2012-06-01

    We study group chasing and escaping between three species. In our model, one species acts as a group of chasers for another species and acts as a group of targets for the third species. When a particle is caught by a target, the particle becomes a new chaser. Although the ratio of three species is changed, the total number of particles is conserved. When particles move randomly, the numbers of the three species change periodically but no species seems to become extinct. If particles escape from the nearest chaser and chase the nearest target, the extinction of a species occurs. The extinction induces that of the second species and finally only one species survives.

  15. The production and escape of nitrogen atoms on Mars

    NASA Technical Reports Server (NTRS)

    Fox, J. L.

    1993-01-01

    Updated rate coefficients and a revised ionosphere-thermosphere model are used to compute the production rates and densities of odd nitrogen species in the Martian atmosphere. Computed density profiles for N(4S), N(2D), N(2P), and NO are presented. The model NO densities are found to be about a factor of 2-3 less than those measured by the Viking 1 mass spectrometer. Revised values for the escape rates of N atoms from dissociative recombination and ionospheric reactions are also computed. Dissociative recombination is found to be comparable in importance to photodissociation at low solar activity, but it is still the most important escape mechanism for N-14 at high solar activity.

  16. Escape rate of active particles in the effective equilibrium approach

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Wittmann, R.; Brader, J. M.

    2017-01-01

    The escape rate of a Brownian particle over a potential barrier is accurately described by the Kramers theory. A quantitative theory explicitly taking the activity of Brownian particles into account has been lacking due to the inherently out-of-equilibrium nature of these particles. Using an effective equilibrium approach [Farage et al., Phys. Rev. E 91, 042310 (2015), 10.1103/PhysRevE.91.042310] we study the escape rate of active particles over a potential barrier and compare our analytical results with data from direct numerical simulation of the colored noise Langevin equation. The effective equilibrium approach generates an effective potential that, when used as input to Kramers rate theory, provides results in excellent agreement with the simulation data.

  17. Fractionation of noble gases by thermal escape from accreting planetesimals

    NASA Technical Reports Server (NTRS)

    Donahue, T. M.

    1986-01-01

    Assuming solar initial elemental and isotopic ratios and a determination of the degree of fractionation occurring by competition between gravitational binding and escape, a model is developed for selective noble gas loss through escape during the growth of planetesimals to form the terrestrial planets. Of the two classes of planetesimals that can form on a time scale that is consistent with modern accretion models, one is depleted in neon while the other is neon-rich. The mechanism is noted to be capable of accounting for all known properties of the noble gas volatiles on the terrestrial planets, with only one exception, namely the Ar-36/Ar-38 ratios for Mars and the earth, which are much lower than observed.

  18. Ionospheric Flow and Escape of Ions from Titan and Venus

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Intriligator, D. S.; Grebowsky, Joseph M.; Vondrak, Richard R. (Technical Monitor)

    2001-01-01

    Knowledge gained from measurements and models is used to study the high-speed plasmas interacting with the atmospheres and ionospheres of Titan and Venus. Considering the similarities of the interactions, comparative analysis is used to support the interpretations of observations made at each body. Ionospheric flow inferred to exist by analysis of measurements made from the Pioneer Venus Orbiter supports the interpretation of similar flow in the ionosphere of Titan. The concept that cold ions escape from the ionosphere of Venus is supported by the Voyager I observation that cold ions escape down the magnetic tail of Titan. Pickup O+ ion energy distributions observed at their source in the ionosheath of Venus are shown to be influenced by finite gyroradius effects. The signatures of such effects are expected to be retained as the ions move into the wakes of Titan and Venus.

  19. The production and escape of nitrogen atoms on Mars

    NASA Astrophysics Data System (ADS)

    Fox, J. L.

    1993-02-01

    Updated rate coefficients and a revised ionosphere-thermosphere model are used to compute the production rates and densities of odd nitrogen species in the Martian atmosphere. Computed density profiles for N(4S), N(2D), N(2P), and NO are presented. The model NO densities are found to be about a factor of 2-3 less than those measured by the Viking 1 mass spectrometer. Revised values for the escape rates of N atoms from dissociative recombination and ionospheric reactions are also computed. Dissociative recombination is found to be comparable in importance to photodissociation at low solar activity, but it is still the most important escape mechanism for N-14 at high solar activity.

  20. Behavioral analysis of the escape response in larval zebrafish

    NASA Astrophysics Data System (ADS)

    Feng, Ruopei; Girdhar, Kiran; Chemla, Yann; Gruebele, Martin

    The behavior of larval zebrafish is of great interest because the limited number of locomotor neurons in larval zebrafish couples with its rich repertoire of movements as a vertebrate animal. Current research uses a priori-selected parameters to describe their swimming behavior while our lab has built a parameter-free model based on singular value decomposition analysis to characterize it. Our previous work has analyzed the free swimming of larval zebrafish and presented a different picture from the current classification of larval zebrafish locomotion. Now we are extending this work to the studies of their escape response to acoustic stimulus. Analysis has shown intrinsic difference in the locomotion between escape response and free swimming.

  1. Virus Escape and Manipulation of Cellular Nonsense-Mediated mRNA Decay

    PubMed Central

    Balistreri, Giuseppe; Bognanni, Claudia; Mühlemann, Oliver

    2017-01-01

    Nonsense-mediated mRNA decay (NMD), a cellular RNA turnover pathway targeting RNAs with features resulting in aberrant translation termination, has recently been found to restrict the replication of positive-stranded RNA ((+)RNA) viruses. As for every other antiviral immune system, there is also evidence of viruses interfering with and modulating NMD to their own advantage. This review will discuss our current understanding of why and how NMD targets viral RNAs, and elaborate counter-defense strategies viruses utilize to escape NMD. PMID:28124995

  2. [Selection of digital filtering in the escaping ammonia monitoring with TDLAS].

    PubMed

    Zou, De-Bao; Chen, Wen-Liang; Du, Zhen-Hui; Jia, Hao; Qi, Ru-Bin; Li, Hong-Lian; Zhen, Yang; Hou, Yan-Xia; Xu, Ke-Xin

    2012-09-01

    Tunable diode laser absorption spectroscopy technology (TDLAS), with its advantages of high selectivity and accuracy, provides a reliable approach to the on-line detection of escaping ammonia. Firstly, the present paper introduces the TDLAS principle, experimental system and the analyses of system noise. Then with the concentration of 90 x 10(-6) and 30 x 10(-6) NH3 for example, we used TDLAS system to collect their second harmonic original spectrum with all kinds of noise interference. To improve the signal spectrum, five types of digital filtering methods were respectively used to filter the original spectrum. Finally we did the NH3 experiments of concentration gradient and the long time monitoring: NH3 experiment of 20 x 10(-6). The analysis indicated that the averaging-wavelet filtering is validated to be more accurate than the other filtering methods in the noise reduction, which can improve the precision of the monitoring system from 10 x 10(-6) to 1.25 x 10(-6) and the SNR also increases by 14 times. It provides an effective pretreatment during the monitoring of escaping ammonia of extremely low concentration.

  3. Escape Strategies for Turboprop Aircraft in a Microburst Windshear

    DTIC Science & Technology

    1991-03-01

    embodied theser echarcerisics ofthemicobursencountered by Delta Flight 191 during an q~oc olnin tDla /t Worth, 2 August, 1985. Different escape strategies...miles) or less. In spite of its small horizontal scale, an intense microburst could induce damaging winds as high as 75 m/sec (168 mph). Conclusions...resulted in a loss of airspeed accompanied by a sharp nose down pitch. A very high sink rate resulted. The aircraft exited the bottom of the thunderstorm

  4. Escaping radio emission from pulsars: Possible role of velocity shear

    SciTech Connect

    Mahajan, S.M. |; Machabeli, G.Z.; Rogava, A.D. |

    1997-01-01

    It is demonstrated that the velocity shear, intrinsic to the e{sup +}e{sup {minus}} plasma present in the pulsar magnetosphere, can efficiently convert the nonescaping longitudinal Langmuir waves (produced by some kind of a beam or stream instability) into propagating (escaping) electromagnetic waves. It is suggested that this shear induced transformation may be the basic mechanism needed for the eventual generation of the observed pulsar radio emission.

  5. Helicopter crash in water: effects of simulator escape training.

    PubMed

    Hytten, K

    1989-01-01

    Findings are presented from an interview study of five crew members who survived a helicopter crash. Four of the five surviving men had received simulated helicopter accident training prior to the crash. One untrained crew member died. The four previously trained survivors claimed that the training was of decisive moment in their escape and survival. Contributions from training appeared to be provision of confidence and thought control. The author discusses these as the development of a positive response-outcome expectancy.

  6. Self-Organizing Reactive Fluid Escape from Dehydrating Rocks

    NASA Astrophysics Data System (ADS)

    John, T.; Pluemper, O.; Podladchikov, Y.; Vrijmoed, J. C.; Scambelluri, M.

    2014-12-01

    Water escape from dehydrating rocks within the Earth's interior is a key process for long-term global water and element cycles, eg. at subduction zones a fluid escape mechanism must exist that prevents ocean water to be drained into the mantle. Existing fluid flow models require a priori physical assumptions (eg. preexisting porosity) and cannot resolve the evolution from initial fluid production to flow channelization. In order to develop a model of this evolution, we need to unravel natural laboratories that display the incipient dehydration stages and the micro- to macro-scale fluid escape route evolution. The Erro-Tobbio meta-serpentinites (Italy) provide a unique snapshot into these early dehydration stages, recording the breakdown of hydrous antigorite to anhydrous olivine plus fluid and the formation of an olivine-vein network. We find that dehydration, fluid pooling, and flow initiation are controlled by micro-scale compositional rock differences. Our model starts with a rock in which all water is stored in solid and any preexisting porosity is negligible (zero-porosity case). As the rock descents into the mantle increasing T will initiate dehydration reactions, dividing the rock continuously into a dry solid and a fluid-filled porosity. Spatially variable reaction progress results in dynamically evolving porosity/permeability and heterogeneous fluid-pore pressure distributions. Fluid-pressure gradient relaxation causes fluid flow and its thermodynamic feedback triggers reactions to progress, resulting in a self-amplifying process. Our new thermodynamic-mechanical model for reaction-porosity waves shows that fluid flow occurs solely in the reaction products and self-organizes into channelized fluid escape networks. This holds the key to formulating future quantitative models that address spatiotemporal processes such as the coupling between fluid release at depth and volcanic eruptions and the amounts of structurally bound water transferred into deep Earth.

  7. 46 CFR 56.50-25 - Safety and relief valve escape piping.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Safety and relief valve escape piping. 56.50-25 Section 56.50-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING... valve escape piping. (a) Escape piping from unfired steam generator, boiler, and superheater safety...

  8. 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…

  9. On the Relative Contributions of Noncontingent Reinforcement and Escape Extinction in the Treatment of Food Refusal

    ERIC Educational Resources Information Center

    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…

  10. 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…

  11. 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…

  12. Theoretical UV absorption spectra of hydrodynamically escaping O{sub 2}/CO{sub 2}-rich exoplanetary atmospheres

    SciTech Connect

    Gronoff, G.; Mertens, C. J.; Norman, R. B.; Maggiolo, R.; Wedlund, C. Simon; Bell, J.; Bernard, D.; Parkinson, C. J.; Vidal-Madjar, A.

    2014-06-20

    Characterizing Earth- and Venus-like exoplanets' atmospheres to determine if they are habitable and how they are evolving (e.g., equilibrium or strong erosion) is a challenge. For that endeavor, a key element is the retrieval of the exospheric temperature, which is a marker of some of the processes occurring in the lower layers and controls a large part of the atmospheric escape. We describe a method to determine the exospheric temperature of an O{sub 2}- and/or CO{sub 2}-rich transiting exoplanet, and we simulate the respective spectra of such a planet in hydrostatic equilibrium and hydrodynamic escape. The observation of hydrodynamically escaping atmospheres in young planets may help constrain and improve our understanding of the evolution of the solar system's terrestrial planets' atmospheres. We use the dependency of the absorption spectra of the O{sub 2} and CO{sub 2} molecules on the temperature to estimate the temperature independently of the total absorption of the planet. Combining two observables (two parts of the UV spectra that have a different temperature dependency) with the model, we are able to determine the thermospheric density profile and temperature. If the slope of the density profile is inconsistent with the temperature, then we infer the hydrodynamic escape. We address the question of the possible biases in the application of the method to future observations, and we show that the flare activity should be cautiously monitored to avoid large biases.

  13. Multifunctional ZnPc-loaded mesoporous silica nanoparticles for enhancement of photodynamic therapy efficacy by endolysosomal escape.

    PubMed

    Tu, Jing; Wang, Tianxiao; Shi, Wei; Wu, Guisen; Tian, Xinhua; Wang, Yuhua; Ge, Dongtao; Ren, Lei

    2012-11-01

    The cellular uptake and localization of photosensitizer-loaded nanoparticles have significant impact on photodynamic therapy (PDT) efficacy due to short lifetime and limited action radius of singlet oxygen. Herein, we develop poly(ethylene glycol) (PEG)- and polyethylenimine (PEI)-functionalized zinc(II) phthalocyanine (ZnPc)-loaded mesoporous silica nanoparticles (MSNs), which are able to distribute in the cytosol by endolysosomal escape. In this photosensitizer-carrier system (PEG-PEI-MSNs/ZnPc), ZnPc is a PDT agent; MSNs are the nanocarrier for encapsulating ZnPc; PEI facilitates endosomal escape; and PEG enhances biocompatibility. The as-synthesized PEG-PEI-MSNs/ZnPc have a high escape efficiency from the lysosome to the cytosol due to the "proton sponge" effect of PEI. Compared with the ZnPc-loaded MSNs, the phototoxicity of the PEG-PEI-MSNs/ZnPc is greatly enhanced in vitro. By measuring the mitochondrial membrane potential, a significant loss of >80% Δψm after treatment with PEG-PEI-MSNs/ZnPc-PDT is observed. It is further demonstrated that the ultra-efficient passive tumor targeting and excellent PDT efficacy are achieved in tumor-bearing mice upon intravenous injection of PEG-PEI-MSNs/ZnPc and the followed light exposure. We present here a strategy for enhancement of PDT efficacy by endolysosomal escape and highlight the promise of using multifunctional MSNs for cancer therapy.

  14. Atmospheric Escape and Climate Evolution of Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Tian, F.; Chassefière, E.; Leblanc, F.; Brain, D.

    The climate of a planet is primarily determined by its orbital distance from its star, the luminosity of the star, the existence of oceans, the pressure of its atmosphere, and the composition of its atmosphere. The last two components are what could be impacted by atmosphere escape. The Sun, as the dominant energy source driving the climate of terrestrial planets, was not always as bright as it is today. Stellar evolution theory predicts that the luminosity of the young Sun was 75% of its present luminosity, at approximately 4 b.y. ago (4 Ga) (Gough, 1981). Although the Sun could have lost some of its mass, thus making the very young Sun somewhat more massive than it is now and therefore could have emitted more energy, most of this mass loss was completed prior to 4 Ga (Wood et al., 2005). Thus the Sun has provided increasingly more energy to solar system planets during the past 4 b.y. Contrary to the evolutionary trend of the total luminosity increasing with time, the young Sun should have emitted much stronger EUV, soft X-ray, and far-UV photons than at present. These photons are from the upper atmosphere of the Sun and are linked to solar magnetic activity. Generally speaking, a young star rotates much faster and thus has stronger magnetic activity. Observations of solar-type stars with different ages show that the EUV energy flux from a 0.5-b.y.-old solar-type star could be as much as 20 times that of the present Sun (Ribas et al., 2005). Accompanying this much-enhanced solar extreme ultraviolet (XUV) radiation is a much stronger solar wind, with mass flux up to 1000 times more intense than the present solar wind flux (Wood et al., 2005). It can be expected that many more energetic-particle events were caused by the young Sun. The fate of the atmospheres of terrestrial planets in such an environment and the consequences for their climates are the focus of this chapter.

  15. Effect of Co-60 single escape peak on detection of Cs-137 in analysis of radionuclide from research reactor

    SciTech Connect

    Kim, M. S.; Park, S. J.

    2006-07-01

    The effect of the single escape peak of 1173 keV gamma-rays from Co-60 on the detection of Cs-137 activity is analyzed. The single escape peak of 1173 keV gamma-rays from Co-60 is located at the 662 keV, which is very close to the energy of gamma-rays from Cs-137. This single escape peak may be mistaken for the gamma-ray peak from Cs-137 activity in the case of large area of 1173 keV peak. The detection of Cs-137 is very important to the judgment of the contamination or the leakage of the material containing the fission product like reactor pool water and in the several experiments for reactor physics such as burn-up estimation. In this work, the areas of the single escape peak of the 1173 keV gamma-rays from Co-60 are measured with several full energy peak areas by using the HPGe detector. The critical limit by which we can decide whether the net count of 662 keV peak due to Co-60 would be significant or not is deduced. For this detection system, when the area of full energy peak is larger than 4.5 million, the single escape peak of 1173 keV gamma-rays from Co-60 can be regarded as the single significant peak. Therefore, it is confirmed that the detection of the Cs-137 activity is affected by the Co-60 in this case. Conservatively, for this detection system, it is recommended that the area of 1173 keV peak of Co-60 would be less than 2 million for neglecting the effect of Co-60. (authors)

  16. Oxygen and carbogen breathing following simulated submarine escape.

    PubMed

    Gennser, Mikael; Loveman, Geoff; Seddon, Fiona; Thacker, Julian; Blogg, S Lesley

    2014-01-01

    Escape from a disabled submarine exposes escapers to a high risk of decompression sickness (DCS). The initial bubble load is thought to emanate from the fast tissues; it is this load that should be lowered to reduce risk of serious neurological DCS. The breathing of oxygen or carbogen (5% CO2, 95% O2) post-surfacing was investigated with regard to its ability to reduce the initial bubble load in comparison to air breathing. Thirty-two goats were subject to a dry simulated submarine escape profile to and from 240 meters (2.5 MPa). On surfacing, they breathed air (control), oxygen or carbogen for 30 minutes. Regular Doppler audio bubble grading was carried out, using the Kisman Masurel (KM) scale. One suspected case of DCS was noted. No oxygen toxicity or arterial gas embolism occurred. No significant difference was found between the groups in terms of the median peak KM grade or the period before the KM grade dropped below III. Time to disappearance of bubbles was significantly different between groups; oxygen showed faster bubble resolution than carbogen and air. This reduction in time to bubble resolution may be beneficial in reducing decompression stress, but probably does not affect the risk of fast-tissue DCS.

  17. Fleeing to refuge: Escape decisions in the race for life.

    PubMed

    Cooper, William E

    2016-10-07

    Economic escape theory that predicts that flight initiation distance (FID=predator-prey distance when a prey begins to flee from an approaching predator) increases as predation risk increases has been overwhelmingly supported. However, the vast majority of empirical tests have focused on effects of single predation risk factors. Even studies that have included multiple risk factors have not predicted how they jointly affect FID. I present a model that predicts joint effects of several predation risk factors that affect the outcome of a race between predator and prey to the prey's refuge. As a prey's distance to refuge and predator attack speed increase, and as the prey's location forces it to flee more toward a predator to reach refuge, FID increases. A published model proposed and experiment showed that FID is longer when prey flee directly toward than directly away from a predator to a refuge. We present a new geometric model that predicts FID for all angles between the prey's and predator's paths to refuge, distance of the prey from refuge when escape begins, predator and prey speeds, and a margin of safety allowing the prey to reach refuge before the predator. The model provides many new, testable predictions about relationships among its variables and FID. Most notably, it predicts that FID increases sigmoidally as the angle between predator and prey paths to refuge increases. Although the model is not economic (cost-benefit), we discuss its relationship to economic escape theory.

  18. A Treatment Package without Escape Extinction to Address Food Selectivity.

    PubMed

    Weber, Jessica; Gutierrez, Anibal

    2015-08-21

    Feeding difficulties and feeding disorders are a commonly occurring problem for young children, particularly children with developmental delays including autism. Behavior analytic interventions for the treatment of feeding difficulties oftentimes include escape extinction as a primary component of treatment. The use of escape extinction, while effective, may be problematic as it is also associated with the emergence of challenging behavior (e.g., extinction burst). Such challenging behavior may be an acceptable side effect in treatment cases where feeding problems are severe and chronic (e.g., failure to thrive). However, in more acute cases (e.g., selective eating), the negative side effect may be unwarranted and undesired. More recent research on the behavioral treatment of food selectivity has begun to evaluate treatments for feeding difficulties that do not include escape extinction (e.g., demand fading, behavioral momentum), with some success. However, research to date reveals individual differences in responsiveness to such treatments and no clear preferable treatment has emerged. This manuscript describes a multi-component treatment package that includes shaping, sequential presentation and simultaneous presentation, for the treatment of food selectivity in four young children with developmental delays. This treatment package extends the literature on the behavioral treatment for food selectivity and offers a multi-component treatment protocol that may be clinically applicable across a range of treatment scenarios and settings.

  19. Comparison of operant escape and reflex tests of nociceptive sensitivity.

    PubMed

    Vierck, Charles J; Yezierski, Robert P

    2015-04-01

    Testing of reflexes such as flexion/withdrawal or licking/guarding is well established as the standard for evaluating nociceptive sensitivity and its modulation in preclinical investigations of laboratory animals. Concerns about this approach have been dismissed for practical reasons - reflex testing requires no training of the animals; it is simple to instrument; and responses are characterized by observers as latencies or thresholds for evocation. In order to evaluate this method, the present review summarizes a series of experiments in which reflex and operant escape responding are compared in normal animals and following surgical models of neuropathic pain or pharmacological intervention for pain. Particular attention is paid to relationships between reflex and escape responding and information on the pain sensitivity of normal human subjects or patients with pain. Numerous disparities between results for reflex and operant escape measures are described, but the results of operant testing are consistent with evidence from humans. Objective reasons are given for experimenters to choose between these and other methods of evaluating the nociceptive sensitivity of laboratory animals. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. 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.