Science.gov

Sample records for escape systems

  1. Lunar escape systems feasibility study

    NASA Technical Reports Server (NTRS)

    Matzenauer, J. O.

    1976-01-01

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

  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. Serial Escape System For Aircraft Crews

    NASA Technical Reports Server (NTRS)

    Wood, Kenneth E.

    1990-01-01

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

  5. 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.

  6. 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.

  7. RS-88 Rocket Engine Tested for Pad Abort Escape System

    NASA Technical Reports Server (NTRS)

    2003-01-01

    In this photo, an RS-88 development rocket engine is being test fired at NASA's Marshall Space Flight Center in Huntsville, Alabama, in support of the Pad Abort Demonstration (PAD) test flights for NASA's Orbital Space Plane (OSP). The tests could be instrumental in developing the first crew launch escape system in almost 30 years. Paving the way for a series of integrated PAD test flights, the engine tests support development of a system that could pull a crew safely away from danger during liftoff. A series of 16 hot fire tests of a 50,000-pound thrust RS-88 rocket engine were conducted, resulting in a total of 55 seconds of successful engine operation. The engine is being developed by the Rocketdyne Propulsion and Power unit of the Boeing Company. Integrated launch abort demonstration tests in 2005 will use four RS-88 engines to separate a test vehicle from a test platform, simulating pulling a crewed vehicle away from an aborted launch. Four 156-foot parachutes will deploy and carry the vehicle to landing. Lockheed Martin is building the vehicles for the PAD tests. Seven integrated tests are plarned for 2005 and 2006.

  8. RS-88 Rocket Engine Tested for Pad Abort Escape System

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This photo gives an overhead look at an RS-88 development rocket engine being test fired at NASA's Marshall Space Flight Center in Huntsville, Alabama, in support of the Pad Abort Demonstration (PAD) test flights for NASA's Orbital Space Plane (OSP). The tests could be instrumental in developing the first crew launch escape system in almost 30 years. Paving the way for a series of integrated PAD test flights, the engine tests support development of a system that could pull a crew safely away from danger during liftoff. A series of 16 hot fire tests of a 50,000-pound thrust RS-88 rocket engine were conducted, resulting in a total of 55 seconds of successful engine operation. The engine is being developed by the Rocketdyne Propulsion and Power unit of the Boeing Company. Integrated launch abort demonstration tests in 2005 will use four RS-88 engines to separate a test vehicle from a test platform, simulating pulling a crewed vehicle away from an aborted launch. Four 156-foot parachutes will deploy and carry the vehicle to landing. Lockheed Martin is building the vehicles for the PAD tests. Seven integrated tests are plarned for 2005 and 2006.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Denny, Mark

    2010-09-01

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

  11. 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.

  12. Camouflage and sabotage: tumor escape from the immune system.

    PubMed

    Poschke, Isabel; Mougiakakos, Dimitrios; Kiessling, Rolf

    2011-08-01

    The field of tumor immunology has made great progress in understanding tumor immune interactions. As a consequence a number of immuno-therapeutic approaches have been successfully introduced into the clinic and a large number of promising therapeutic strategies are investigated in ongoing clinical trials. Evaluation of anti-tumor immunity in such trials as well as in animal models has shown that tumor escape from immune recognition and tumor-mediated suppression of anti-tumor immunity can pose a significant obstacle to successful cancer therapy. Here, we review mechanisms of tumor immune escape and immune-subversion with a focus on the research interests in our laboratory: loss of MHC class I on tumor cells, increased oxidative stress, recruitment of myeloid-derived suppressor cells, and regulatory T cells. PMID:21626032

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

    NASA Technical Reports Server (NTRS)

    1987-01-01

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

  14. 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.

  15. 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

  16. 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

  17. STS-26 MS Lounge during crew escape system (CES) testing in JSC WETF Bldg 29

    NASA Technical Reports Server (NTRS)

    1988-01-01

    STS-26 Discovery, Orbiter Vehicle (OV) 103, Mission Specialist (MS) John M. Lounge participates in crew escape system (CES) testing in JSC Weightless Environment Training Facility (WETF) Bldg 29. Lounge, wearing the newly designed (navy blue) launch and entry suit (LES), floats in WETF pool with the aid of an underarm flotation device (modern version of Mae West floats). Four SCUBA-equipped divers assist Lounge during the simulation of escape and rescue operations utilizing a new CES pole for emergency exit from the Space Shuttle. Lounge is wearing gear like that each STS-26 crewmember and subsequent crews will carry onboard during launch.

  18. STS-26 MS Nelson during Crew escape system (CES) testing in JSC WETF Bldg 29

    NASA Technical Reports Server (NTRS)

    1988-01-01

    STS-26 Discovery, Orbiter Vehicle (OV) 103, Mission Specialist (MS) George D. Nelson participates in crew escape system (CES) testing in JSC Weightless Environment Training Facility (WETF) Bldg 29. Nelson, wearing the newly designed (navy blue) launch and entry suit (LES), floats in WETF pool with the aid of an underarm flotation device (modern version of Mas West floats). He awaits the assistance of SCUBA-equipped divers during a simulation of escape and rescue operations utilizing a new CES pole for emergency exit from the Space Shuttle.

  19. STS-26 MS Nelson during Crew Escape System (CES) testing in JSC WETF Bldg 29

    NASA Technical Reports Server (NTRS)

    1988-01-01

    STS-26 Discovery, Orbiter Vehicle (OV) 103, Mission Specialist (MS) George D. Nelson participates in crew escape system (CES) testing in JSC Weightless Environment Training Facility (WETF) Bldg 29. With helmet visor down, Nelson, wearing the newly designed (navy blue) launch and entry suit (LES), floats in WETF pool with the aid of an underarm flotation device (modern version of Mae West floats). He awaits the assistance of SCUBA-equipped divers during a simulation of escape and rescue operations utilizing a new CES pole for emergency exit from the Space Shuttle.

  20. STS-26 Pilot Covey during crew escape system (CES) testing in JSC WETF

    NASA Technical Reports Server (NTRS)

    1988-01-01

    STS-26 Discovery, Orbiter Vehicle (OV) 103, Pilot Richard O. Covey participates in crew escape system (CES) testing in JSC Weightless Environment Training Facility (WETF) Bldg 29. Covey, wearing the newly designed (navy blue) launch and entry suit (LES), floats in WETF pool with the aid of an underarm flotation device (modern version of Mae West floats). He awaits the assistance of SCUBA-equipped divers during a simulation of escape and rescue operations utilizing a new CES pole for emergency exit from the Space Shuttle.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. Pupillary escape quantification with an image-processing system in clinical perimetry

    NASA Astrophysics Data System (ADS)

    Suaste-Gomez, Ernesto; Rivera-Arzola, Palmira; Salazar-Rodarte, Victor

    1996-05-01

    We present a new technique to quantify the pupillary escape with an image-processing system during visual field examination in routine ophthalmological practice. Visual field evaluation is important in the detection, diagnosis and assessment of ophthalmologic and neurologic dysfunction. With the conditions during the perimetric study: an initially large pupil and a small step light stimuli, it presents the pupillary escape where the pupil responds with a very fast constriction and then redilates almost back to its original level. In order to measure this response, we obtain automatic and objective determinations for each spot of light in peripheric and central zones. The automatic perimeter is based on the physical dimensions of Goldmann perimeter and the index projector is based on fiber optics target. The pupillary escape and the pupillary response are captured by means of an infrared-sensitive camera and recorded in a VCR to analyze off line with an image processing system. This system consists of a computer equipped with a frame grabber DT2853 and eye movements detector for monitoring the initial position of the eye, during the examination. The algorithms to detect and analyze are: mensuration (area, perimeter, latencies) and matching template based on the stochastic sign change criterion.

  6. Escape dynamics and fractal basins boundaries in the three-dimensional Earth-Moon system

    NASA Astrophysics Data System (ADS)

    Zotos, Euaggelos E.

    2016-03-01

    The orbital dynamics of a spacecraft, or a comet, or an asteroid in the Earth-Moon system in a scattering region around the Moon using the three dimensional version of the circular restricted three-body problem is numerically investigated. The test particle can move in bounded orbits around the Moon or escape through the openings around the Lagrange points L1 and L2 or even collide with the surface of the Moon. We explore in detail the first four of the five possible Hill's regions configurations depending on the value of the Jacobi constant which is of course related with the total orbital energy. We conduct a thorough numerical analysis on the phase space mixing by classifying initial conditions of orbits in several two-dimensional types of planes and distinguishing between four types of motion: (i) ordered bounded, (ii) trapped chaotic, (iii) escaping and (iv) collisional. In particular, we locate the different basins and we relate them with the corresponding spatial distributions of the escape and collision times. Our outcomes reveal the high complexity of this planetary system. Furthermore, the numerical analysis suggests a strong dependence of the properties of the considered basins with both the total orbital energy and the initial value of the z coordinate, with a remarkable presence of fractal basin boundaries along all the regimes. Our results are compared with earlier ones regarding the planar version of the Earth-Moon system.

  7. 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.

  8. 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.

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

    PubMed

    Srokowski, Tomasz

    2016-06-01

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

  10. 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.

  11. The Hyades Cluster: Identification of a Planetary System and Escaping White Dwarfs

    NASA Astrophysics Data System (ADS)

    Zuckerman, B.; Xu, S.; Klein, B.; Jura, M.

    2013-06-01

    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.

  12. 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.

  13. 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.

  14. Examples of the nonlinear dynamics of ballistic capture and escape in the earth-moon system

    NASA Technical Reports Server (NTRS)

    Belbruno, Edward A.

    1990-01-01

    An example of a trajectory is given which is initially captured in an elliptic resonant orbit about the earth and then ballistically escapes the earth-moon system. This is demonstrated by a numerical example in three-dimensions using a planetary ephemeris. Another example shows a mechanism of how an elliptic orbit about the earth can increase its energy by performing a complex nonlinear transition to an elliptic orbit of a larger semi-major axis. Capture is also considered. An application of ballistic capture at the moon via an unstable periodic orbit using the four-body sun-earth-moon-S/C interaction is described.

  15. Crew Escape Certification Test

    NASA Technical Reports Server (NTRS)

    1988-01-01

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

  16. 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.

  17. 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.

  18. Macroscopic quantum tunneling and quantum - classical phase transitions of the escape rate in large spin systems

    NASA Astrophysics Data System (ADS)

    Owerre, S. A.; Paranjape, M. B.

    2015-01-01

    This article presents a review on the theoretical and the experimental developments on macroscopic quantum tunneling and quantum-classical phase transitions of the escape rate in large spin systems. A substantial amount of research work has been done in this area of research over the years, so this article does not cover all the research areas that have been studied, for instance the effect of dissipation is not discussed and can be found in other review articles. We present the basic ideas with simplified calculations so that it is readable to both specialists and nonspecialists in this area of research. A brief derivation of the path integral formulation of quantum mechanics in its original form using the orthonormal position and momentum basis is reviewed. For tunneling of a particle into the classically forbidden region, the imaginary time (Euclidean) formulation of path integral is useful, we review this formulation and apply it to the problem of tunneling in a double well potential. For spin systems such as single molecule magnets, the formulation of path integral requires the use of non-orthonormal spin coherent states in (2 s + 1) dimensional Hilbert space, the coordinate independent and the coordinate dependent form of the spin coherent state path integral are derived. These two (equivalent) forms of spin coherent state path integral are applied to the tunneling of single molecule magnets through a magnetic anisotropy barrier. Most experimental and numerical results are presented. The suppression of tunneling for half-odd integer spin (spin-parity effect) at zero magnetic field is derived using both forms of spin coherent state path integral, which shows that this result (spin-parity effect) is independent of the choice of coordinate. At nonzero magnetic field we present both the experimental and the theoretical results of the oscillation of tunneling splitting as a function of the applied magnetic field applied along the spin hard anisotropy axis

  19. Atmospheric Escape from the Pluto/Charon System: Monte Carlo Simulations

    NASA Astrophysics Data System (ADS)

    Johnson, Robert E.; Tucker, O. J.; Young, L. A.

    2013-10-01

    Recent hybrid fluid/molecular kinetic models for Pluto’s atmosphere (Erwin et al., 2013; Tucker et al. 2012) demonstrate that Pluto’s upper atmosphere is warmer and more extended than previously thought. For such an extended atmosphere we examine the effect of Charon on the molecular escape rate for approximate solar minimum, medium and maximum conditions at ~33AU. In addition we consider Pluto’s primary constituent N2 as a source of molecules for Charon that can be re-emitted and form a tenuous atmosphere. Including Charon’s gravity and orbital motion in the simulations, the atmosphere on the Pluto’s Charon facing hemisphere is more strongly bound to the system and becomes more extended than the atmosphere on Pluto’s the anti-Charon hemisphere. Accounting for Charon’s gravity the net escape from the system is reduced by ~10-15%. Most of the loss is direct from Pluto’s exobase region with ~1-2% due to scattering by Charon. Less than 1%, of the flux from Pluto’s exobase impinges on Charon resulting in a source rate of ~10^25 - 10^26 N2/s. This produces thick layers of nitrogen on ice in the cold regions, which when exposed to particle radiation might account for the observed ammonia hydrides. The flux of N2 also produces a tenuous surface-boundary layer atmosphere on Charon. If such an atmosphere is detectable during the solar occultation that will occur during the New Horizon encounter, it would provide a measure of the transfer of gas between bodies in binary systems. Finally, we consider possible cryovolcanism and surface sputtering on Charon as a source of water molecules for this system.

  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 "e-scape" project…

  1. 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. PMID:24657523

  2. 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.

  3. Escape behaviors in insects.

    PubMed

    Card, Gwyneth M

    2012-04-01

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

  4. Burkholderia pseudomallei type III secretion system mutants exhibit delayed vacuolar escape phenotypes in RAW 264.7 murine macrophages.

    PubMed

    Burtnick, Mary N; Brett, Paul J; Nair, Vinod; Warawa, Jonathan M; Woods, Donald E; Gherardini, Frank C

    2008-07-01

    Burkholderia pseudomallei is a facultative intracellular pathogen capable of surviving and replicating within eukaryotic cells. Recent studies have shown that B. pseudomallei Bsa type III secretion system 3 (T3SS-3) mutants exhibit vacuolar escape and replication defects in J774.2 murine macrophages. In the present study, we characterized the interactions of a B. pseudomallei bsaZ mutant with RAW 264.7 murine macrophages. Following uptake, the mutant was found to survive and replicate within infected RAW 264.7 cells over an 18-h period. In addition, high levels of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), granulocyte-macrophage colony-stimulating factor (GM-CSF), and RANTES, but not IL-1alpha and IL-1beta, were detected in culture supernatants harvested from infected monolayers. The subcellular location of B. pseudomallei within infected RAW 264.7 cells was determined, and as expected, the bsaZ mutant demonstrated early-vacuolar-escape defects. Interestingly, however, experiments also indicated that this mutant was capable of delayed vacuolar escape. Consistent with this finding, evidence of actin-based motility and multinucleated giant cell formation were observed between 12 and 18 h postinfection. Further studies demonstrated that a triple mutant defective in all three B. pseudomallei T3SSs exhibited the same phenotype as the bsaZ mutant, indicating that functional T3SS-1 and T3SS-2 did not appear to be responsible for the delayed escape phenotype in RAW 264.7 cells. Based upon these findings, it appears that B. pseudomallei may not require T3SS-1, -2, and -3 to facilitate survival, delayed vacuolar escape, and actin-based motility in activated RAW 264.7 macrophages. PMID:18443088

  5. [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

  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. The Francisella tularensis Pathogenicity Island Encodes a Secretion System that is required for Phagosome Escape and Virulence

    PubMed Central

    Barker, Jeffrey R.; Chong, Audrey; Wehrly, Tara D.; Yu, Jieh-Juen; Rodriguez, Stephen A.; Liu, Jirong; Celli, Jean; Arulanandam, Bernard P.; Klose, Karl E.

    2009-01-01

    Summary Francisella tularensis causes the human disease tularemia. F. tularensis is able to survive and replicate within macrophages, a trait that has been correlated with its high virulence, but it is unclear the exact mechanism(s) this organism uses to escape killing within this hostile environment. F. tularensis virulence is dependent upon the Francisella Pathogenicity Island (FPI), a cluster of genes that we show here shares homology with Type VI secretion gene clusters in Vibrio cholerae and Pseudomonas aeruginosa. We demonstrate that two FPI proteins, VgrG and IglI, are secreted into the cytosol of infected macrophages. VgrG and IglI are required for F. tularensis phagosomal escape, intramacrophage growth, inflammasome activation, and virulence in mice. Interestingly, VgrG secretion does not require the other FPI genes. However, VgrG and other FPI genes, including PdpB (an IcmF homologue), are required for the secretion of IglI into the macrophage cytosol, suggesting VgrG and other FPI factors are components of a secretion system. This is the first report of F. tularensis FPI virulence proteins required for intramacrophage growth that are translocated into the macrophage. PMID:20054881

  9. Advanced Crew Escape Suit.

    PubMed

    1995-09-01

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

  10. 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.

  11. 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.

  12. The Pluto-Charon system - The escape of Charon's primordial atmosphere

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  13. Anomalous barrier escaping in an externally modulated environment of system-reservoir coupling

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Yang

    2015-10-01

    The time-dependent barrier passage of an activated rate process is studied where the heat bath in the system-reservoir coupling environment is modulated by an external fluctuation. For a thorough inspection on the barrier recrossing dynamics, the Kramers rate and effective transmission coefficient are calculated of the reactive flux method. In the particular case of a δ-correlated noise activated Ornstein-Uhlenbeck process, it is found that, the external modulation can in some cases result in an maximum effective transmission coefficient. This reveals a maximum net flux and can be obtained from the minimum barrier recrossing resulted from appropriate external modulation.

  14. The great escape

    PubMed Central

    Sin, Ho-Su; Namekawa, Satoshi H

    2013-01-01

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

  15. Viral escape from antisense RNA.

    PubMed

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

    1998-05-01

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

  16. Mars atmosphere evolution: Escape to space

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.

    1992-01-01

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

  17. Automated Escape Guidance Algorithms for An Escape Vehicle

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  18. Central nervous system-specific consequences of simian immunodeficiency virus Gag escape from major histocompatibility complex class I-mediated control.

    PubMed

    Beck, Sarah E; Queen, Suzanne E; Viscidi, Raphael; Johnson, Darius; Kent, Stephen J; Adams, Robert J; Tarwater, Patrick M; Mankowski, Joseph L

    2016-08-01

    In the fourth decade of the HIV epidemic, the relationship between host immunity and HIV central nervous system (CNS) disease remains incompletely understood. Using a simian immunodeficiency virus (SIV)/macaque model, we examined CNS outcomes in pigtailed macaques expressing the MHC class I allele Mane-A1*084:01 which confers resistance to SIV-induced CNS disease and induces the prototypic viral escape mutation Gag K165R. Insertion of gag K165R into the neurovirulent clone SIV/17E-Fr reduced viral replication in vitro compared to SIV/17E-Fr. We also found lower cerebrospinal fluid (CSF), but not plasma, viral loads in macaques inoculated with SIV/17E-Fr K165R versus those inoculated with wildtype. Although escape mutation K165R was genotypically stable in plasma, it rapidly reverted to wildtype Gag KP9 in both CSF and in microglia cultures. We induced robust Gag KP9-specific CTL tetramer responses by vaccinating Mane-A*084:01-positive pigtailed macaques with a Gag KP9 virus-like particle (VLP) vaccine. Upon SIV/17E-Fr challenge, vaccinated animals had lower SIV RNA in CSF compared to unvaccinated controls, but showed no difference in plasma viral loads. These data clearly demonstrate that viral fitness in the CNS is distinct from the periphery and underscores the necessity of understanding the consequences of viral escape in CNS disease with the advent of new therapeutic vaccination strategies. PMID:26727909

  19. 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

  20. 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.

  1. 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.

  2. The Shigella flexneri Type 3 Secretion System Is Required for Tyrosine Kinase-Dependent Protrusion Resolution, and Vacuole Escape during Bacterial Dissemination

    PubMed Central

    Kuehl, Carole J.; Dragoi, Ana-Maria; Agaisse, Hervé

    2014-01-01

    Shigella flexneri is a human pathogen that triggers its own entry into intestinal cells and escapes primary vacuoles to gain access to the cytosolic compartment. As cytosolic and motile bacteria encounter the cell cortex, they spread from cell to cell through formation of membrane protrusions that resolve into secondary vacuoles in adjacent cells. Here, we examined the roles of the Type 3 Secretion System (T3SS) in S. flexneri dissemination in HT-29 intestinal cells infected with the serotype 2a strain 2457T. We generated a 2457T strain defective in the expression of MxiG, a central component of the T3SS needle apparatus. As expected, the ΔmxiG strain was severely affected in its ability to invade HT-29 cells, and expression of mxiG under the control of an arabinose inducible expression system (ΔmxiG/pmxiG) restored full infectivity. In this experimental system, removal of the inducer after the invasion steps (ΔmxiG/pmxiG (Ara withdrawal)) led to normal actin-based motility in the cytosol of HT-29 cells. However, the time spent in protrusions until vacuole formation was significantly increased. Moreover, the number of formed protrusions that failed to resolve into vacuoles was also increased. Accordingly, the ΔmxiG/pmxiG (Ara withdrawal) strain failed to trigger tyrosine phosphorylation in membrane protrusions, a signaling event that is required for the resolution of protrusions into vacuoles. Finally, the ΔmxiG/pmxiG (Ara withdrawal) strain failed to escape from the formed secondary vacuoles, as previously reported in non-intestinal cells. Thus, the T3SS system displays multiple roles in S. flexneri dissemination in intestinal cells, including the tyrosine kinase signaling-dependent resolution of membrane protrusions into secondary vacuoles, and the escape from the formed secondary vacuoles. PMID:25405985

  3. 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.

  4. Escape and rescue model

    NASA Astrophysics Data System (ADS)

    Alvord, D.; Nelson, H. E.

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

  5. Apollo experience report: Launch escape propulsion subsystem

    NASA Technical Reports Server (NTRS)

    Townsend, N. A.

    1973-01-01

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

  6. 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

    2016-01-01

    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

  7. 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

  8. Type three secretion system-mediated escape of Burkholderia pseudomallei into the host cytosol is critical for the activation of NFκB

    PubMed Central

    2014-01-01

    Background Burkholderia pseudomallei is the causative agent of melioidosis, a potentially fatal disease endemic in Southeast Asia and Northern Australia. This Gram-negative pathogen possesses numerous virulence factors including three “injection type” type three secretion systems (T3SSs). B. pseudomallei has been shown to activate NFκB in HEK293T cells in a Toll-like receptor and MyD88 independent manner that requires T3SS gene cluster 3 (T3SS3 or T3SSBsa). However, the mechanism of how T3SS3 contributes to NFκB activation is unknown. Results Known T3SS3 effectors are not responsible for NFκB activation. Furthermore, T3SS3-null mutants are able to activate NFκB almost to the same extent as wildtype bacteria at late time points of infection, corresponding to delayed escape into the cytosol. NFκB activation also occurs when bacteria are delivered directly into the cytosol by photothermal nanoblade injection. Conclusions T3SS3 does not directly activate NFκB but facilitates bacterial escape into the cytosol where the host is able to sense the presence of the pathogen through cytosolic sensors leading to NFκB activation. PMID:24884837

  9. 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.

  10. Polymer escape from a confining potential

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  11. Submarine tower escape decompression sickness risk estimation.

    PubMed

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

    2014-01-01

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

  12. 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

  13. 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

  14. 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

  15. Cerebrospinal Fluid HIV Escape from Antiretroviral Therapy.

    PubMed

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

    2015-06-01

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

  16. Escape from X Inactivation Varies in Mouse Tissues

    PubMed Central

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

    2015-01-01

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

  17. 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.

  18. 46 CFR 108.445 - Alarm and means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  19. 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.

  20. 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.

  1. 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. PMID:26868867

  2. 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. PMID:26560192

  3. 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.

  4. 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

  5. An escape from crowding.

    PubMed

    Freeman, Jeremy; Pelli, Denis G

    2007-01-01

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

  6. Suicide as Escape from Self.

    ERIC Educational Resources Information Center

    Baumeister, Roy F.

    1990-01-01

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

  7. 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.

  8. Plasma Escape from Unmagnetized Bodies

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  9. 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.

  10. Endosomal escape: a bottleneck in intracellular delivery.

    PubMed

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

    2014-01-01

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

  11. 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.

  12. Collective Predation and Escape Strategies

    NASA Astrophysics Data System (ADS)

    Angelani, Luca

    2012-09-01

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

  13. 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.

  14. CRV Escape Trajectories from the ISS

    NASA Technical Reports Server (NTRS)

    Foti, Tony M.

    1999-01-01

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

  15. Preparing a discreet escape

    PubMed Central

    Szumowski, Suzannah C.; Estes, Kathleen A.; Troemel, Emily R.

    2012-01-01

    Intracellular pathogens commonly invade and replicate inside of intestinal cells and exit from these cells is a crucial step in pathogen transmission. For convenience, studies of intracellular pathogens are often conducted using in vitro cell culture systems, which unfortunately lack important features of polarized, intact intestinal epithelial cells. The nematode C. elegans provides a tractable system to study intracellular pathogens in vivo, where features of differentiated epithelial cells are easily visualized. In a recent paper, we used C. elegans as a host organism to study the exit strategy of Nematocida parisii, a naturally occurring intracellular pathogen in the microsporidia phylum. We showed that N. parisii remodels the C. elegans host cytoskeleton, and then exits host cells in an actin-dependent, non-lytic fashion. These findings illuminate key details about the transmission of microsporidia, which are poorly understood but ubiquitous pathogens. More generally, these findings have implications for exit strategies used by other intracellular pathogens that also infect epithelial cells. PMID:24058850

  16. 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....

  17. 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....

  18. 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....

  19. 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....

  20. 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....

  1. 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.

  2. 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.

  3. 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

  4. Blue Origin Conducts Pad Escape Test

    NASA Video Gallery

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

  5. Genetic Algorithms with Local Minimum Escaping Technique

    NASA Astrophysics Data System (ADS)

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

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

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

    PubMed

    Oda, Yoichi

    2015-10-01

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

  7. Escape dynamics of many hard disks.

    PubMed

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

    2014-11-01

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

  8. Escape Dynamics in Quasihomogeneous Fields

    NASA Astrophysics Data System (ADS)

    Mioc, Vasile; Stavinschi, Magda

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

  9. 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 §...

  10. 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.

  11. 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.

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

    PubMed

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

    2016-07-15

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

  13. 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.

  14. Escape Rates in a Stochastic Environment with Multiple Scales

    NASA Astrophysics Data System (ADS)

    Forgoston, Eric; Schwartz, Ira B.

    2009-01-01

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

  15. Mars atmospheric escape constrained using MAVEN IUVS coronal observations

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  18. 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.

  19. Escape nightmares and postescape stressful events.

    PubMed

    Cernovsky, Z Z

    1988-04-01

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

  20. Model of a mechanical clock escapement

    NASA Astrophysics Data System (ADS)

    Moline, David; Wagner, John; Volk, Eugene

    2012-07-01

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

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

    PubMed

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

    2016-02-01

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

  2. 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

  3. Escape of Black Holes from the Brane

    SciTech Connect

    Flachi, Antonino; Tanaka, Takahiro

    2005-10-14

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

  4. 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…

  5. 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. PMID:25041843

  6. MEMO: Mars Escape and Magnetic Orbiter

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

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

  7. Escaping Homelessness: Anticipated and Perceived Facilitators

    ERIC Educational Resources Information Center

    Patterson, Allisha; Tweed, Roger

    2009-01-01

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

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

    PubMed

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

    2014-01-01

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

  9. 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. PMID:11964498

  10. The Addition of Recombinant Vaccinia HER2/neu to Oncolytic Vaccinia-GMCSF Given into the Tumor Microenvironment Overcomes MDSC-Mediated Immune Escape and Systemic Anergy

    PubMed Central

    de Vries, Christiaan R.; Monken, Claude E.; Lattime, Edmund C.

    2015-01-01

    Effective immunotherapeutic strategies require the ability to generate a systemic antigen-specific response capable of impacting both primary and metastatic disease. We have built on our oncolytic vaccinia GM-CSF strategy by adding recombinant tumor antigen to increase the response in the tumor microenvironment and systemically. In the present study, orthotopic growth of a syngeneic HER2/neu-overexpressing mammary carcinoma in FVB/N mice (NBT1) was associated with increased Gr1+CD11b+ myeloid derived suppressor cells (MDSCs) both systemically and in the tumor microenvironment. This MDSC population had inhibitory effects on the HER2/neu specific Th1 immune response. VVneu and VVGMCSF are recombinant oncolytic vaccinia viruses that encode HER2/neu and GM-CSF, respectively. Naïve FVB mice vaccinated with combined VVneu and VVGMCSF given systemically developed systemic HER2/neu-specific immunity. NBT1 bearing mice became anergic to systemic immunization with combined VVneu and VVGMCSF. Intratumoral VVGMCSF failed to result in systemic antitumor immunity until combined with intratumoral VVneu. Infection/transfection of the tumor microenvironment with combined VVGMCSF and VVneu resulted in development of systemic tumor-specific immunity, reduction in splenic and tumor MDSC, and therapeutic efficacy against tumor. These studies demonstrate the enhanced efficacy of oncolytic vaccinia virus recombinants encoding combined tumor antigen and GM-CSF in modulating the microenvironment of MDSC-rich tumors. PMID:25633483

  11. 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

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 46 CFR 28.390 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  19. 46 CFR 28.390 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

  20. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

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

  1. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

  2. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

  3. 46 CFR 177.500 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

  4. 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...

  5. 46 CFR 28.390 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

  6. Hydrogen Escape from early Earth and Mars

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  7. 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

  8. 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

  9. Self-assembling dual component nanoparticles with endosomal escape capability.

    PubMed

    Wong, Adelene S M; Mann, Sarah K; Czuba, Ewa; Sahut, Audrey; Liu, Haiyin; Suekama, Tiffany C; Bickerton, Tayla; Johnston, Angus P R; Such, Georgina K

    2015-04-21

    This study reports a novel nanoparticle system with simple and modular one-step assembly, which can respond intelligently to biologically relevant variations in pH. Importantly, these particles also show the ability to induce escape from the endosomal/lysosomal compartments of the cell, which is integral to the design of efficient polymeric delivery systems. The nanoparticles were formed by the nanoprecipitation of pH-responsive poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) and poly(2-(diethylamino)ethyl methacrylate)-b-poly(ethylene glycol) (PDEAEMA-b-PEG). Rhodamine B octadecyl ester perchlorate was successfully encapsulated within the hydrophobic core of the nanoparticle upon nanoprecipitation into PBS at pH 8. These particles disassembled when the pH was reduced below 6.8 at 37 °C. Cellular experiments showed the successful uptake of the nanoparticles into the endosomal/lysosomal compartments of 3T3 fibroblast cells. The ability to induce escape from the endosomes was demonstrated by the use of calcein, a membrane-impermeable fluorophore. The modular nature of these particles combined with promising endosomal escape capabilities make these dual component PDEAEMA nanoparticles useful for drug and gene delivery applications. PMID:25731820

  10. Radiative equilibrium and escape of Pluto's atmosphere

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  11. Thermal escape from extrasolar giant planets.

    PubMed

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

    2014-04-28

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

  12. 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

  13. Statistical theory of asteroid escape rates.

    PubMed

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

    2002-07-01

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

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

    PubMed Central

    Höper, Dirk; Kalthoff, Donata; Hoffmann, Bernd

    2012-01-01

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

  15. 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

  16. Changes in escape fire occurrence rate under climate change

    NASA Astrophysics Data System (ADS)

    Wotton, B. M.; Gowman, L.

    2009-04-01

    There has been considerable study of the general impacts of climate change on the circumpolar boreal forest, and in particular on potential changes in the level of forest fire activity. Recent studies have shown that overall fire occurrence (from both human and lightning causes) is expected to increase across the boreal forest in Canada (and in many other regions of the world) under the changed fire weather expected to accompany climate change over the 21st Century. In terms of fire on a managed forest landscape, it is not so much the total number of fires occurring but that very small number of fires that escape initial attack that have the greatest impact in terms of area burned or loss of values. We developed models of the probability of fire occurrences escaping initial attack based on weather-based outputs of the Canadian FWI System and general fire cause type. Using these with outputs from recent GCM scenarios from the Hadley and Canadian Climate Centre we find an overall increase in expected fire escapes as well across the forested region of Canada. Increases in some areas can be higher that the increases expected in total number of fires. Assumptions going into this analysis are that fire management agency effort in terms of response time and suppression resource levels remains constant over time.

  17. 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.

  18. 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.

  19. 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

  20. Evolution: Escaping the Inevitability of Ageing.

    PubMed

    Archer, C Ruth; Hosken, David J

    2016-03-01

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

  1. 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.

  2. 33 CFR 143.101 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

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

  3. 33 CFR 143.101 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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

  4. 33 CFR 143.101 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. [Escape mutants of hepatitis B virus].

    PubMed

    Jaramillo, Carlos Mario; Navas, María-Cristina

    2015-04-01

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

  13. 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.

  14. 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.

  15. 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.

  16. Cold ion escape from the Martian ionosphere

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  17. Cold Ion Escape from the Martian Ionosphere

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  18. 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.

  19. Scrunching: a novel escape gait in planarians.

    PubMed

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

    2015-10-01

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

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

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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

  1. 30 CFR 77.1101 - Escape and evacuation; plan.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

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

  2. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

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

  3. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

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

  4. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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

  5. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

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

  6. 30 CFR 75.382 - Mechanical escape facilities.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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

  7. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  8. 46 CFR 127.240 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

  9. 46 CFR 127.240 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

  10. 46 CFR 127.240 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

  11. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

  12. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

  13. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

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

  14. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

  15. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

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

  16. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

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

  17. 46 CFR 169.313 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

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

  18. 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

  19. 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.

  20. 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.

  1. Cold Ion Escape from the Martian Ionosphere

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  2. X-chromosome inactivation and escape

    PubMed Central

    DISTECHE, CHRISTINE M.; BERLETCH, JOEL B.

    2016-01-01

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

  3. Suicide as escape from psychotic panic.

    PubMed

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

    2016-01-01

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

  4. Escape Artists of the X Chromosome.

    PubMed

    Balaton, Bradley P; Brown, Carolyn J

    2016-06-01

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

  5. 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

  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. PMID:27161016

  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. The escape model for Galactic cosmic rays

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  9. 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.

  10. 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.

  11. 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.

  12. How some T cells escape tolerance induction.

    PubMed

    Gammon, G; Sercarz, E

    1989-11-01

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

  13. Viral resistance evolution fully escapes a rationally designed lethal inhibitor.

    PubMed

    Keller, Thomas E; Molineux, Ian J; Bull, James J

    2009-09-01

    Viruses are notoriously capable of evolving resistance to drugs. However, if the endpoint of resistance evolution is only partial escape, a feasible strategy should be to stack drugs, so the combined effect of partial inhibition by several drugs results in net inhibition. Assessing the feasibility of this approach requires quantitative data on viral fitness before and after evolution of resistance to a drug, as done here with bacteriophage T7. An inhibitory gene expressed from a phage promoter aborts wild-type T7 infections. The effect is so severe that the phage population declines when exposed to the inhibitor but expands a billion-fold per hour in its absence. In prior work, T7 evolved modest resistance to this inhibitor, an expected result. Given the nature of the inhibitor, that it used the phage's own promoter to target the phage's destruction, we anticipated that resistance evolution would be limited as the phage may need to evolve a new regulatory system, with simultaneous changes in its RNA polymerase (RNAP) and many of its promoters to fully escape inhibition. We show here that further adaptation of the partially resistant phage led to complete resistance. Resistance evolution was due to three mutations in the RNAP gene and two other genes; unexpectedly, no changes were observed in promoters. Consideration of other mechanisms of T7 inhibition leaves hope that permanent inhibition of viral growth with drugs can in principle be achieved. PMID:19494036

  14. 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.

  15. 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. PMID:16849479

  16. 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

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

    NASA Astrophysics Data System (ADS)

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

    2003-03-01

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

  18. 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. PMID:26895738

  19. 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

  20. Energetic particle recurrence and escape during solar cycle 20

    NASA Astrophysics Data System (ADS)

    Gold, R. E.; Roelof, E. C.

    1980-10-01

    Low-energy solar particle data have been combined from a multi-spacecraft near-earth data set covering most of solar cycle 20 (1966-1976). Particle intensity profiles have been ordered in the natural heliographic coordinate system of the estimated high coronal connection longitude of the foot point of the interplanetary field line. The recurrence trends of approximately 1-MeV solar particles become more apparent in this coordinate system than when plotted versus time, and thereby extend the evidence for regions of continual injection and escape from the corona. Intercomparison of solar particles and solar wind streams in heliographic longitude suggests that the origin of stream-associated spatial particle events seen at 1 AU is solar rather than interplanetary.

  1. Novel Anti-Melanoma Immunotherapies: Disarming Tumor Escape Mechanisms

    PubMed Central

    Sapoznik, Sivan; Hammer, Ohad; Ortenberg, Rona; Besser, Michal J.; Ben-Moshe, Tehila; Schachter, Jacob; Markel, Gal

    2012-01-01

    The immune system fights cancer and sometimes temporarily eliminates it or reaches an equilibrium stage of tumor growth. However, continuous immunological pressure also selects poorly immunogenic tumor variants that eventually escape the immune control system. Here, we focus on metastatic melanoma, a highly immunogenic tumor, and on anti-melanoma immunotherapies, which recently, especially following the FDA approval of Ipilimumab, gained interest from drug development companies. We describe new immunomodulatory approaches currently in the development pipeline, focus on the novel CEACAM1 immune checkpoint, and compare its potential to the extensively described targets, CTLA4 and PD1. This paper combines multi-disciplinary approaches and describes anti-melanoma immunotherapies from molecular, medical, and business angles. PMID:22778766

  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. PMID:23827020

  3. New Analysis of Hydrogen and Deuterium Escape from Venus

    NASA Astrophysics Data System (ADS)

    Donahue, Thomas M.

    1999-10-01

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

  4. 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+.

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

    NASA Astrophysics Data System (ADS)

    Hartle, R. E.

    2001-05-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    PubMed Central

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

    2005-01-01

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

  8. The polarization of escaping terrestrial continuum radiation

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  9. Gated narrow escape time for molecular signaling.

    PubMed

    Reingruber, Jürgen; Holcman, David

    2009-10-01

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

  10. Micellar Effects on Photoinduced Electron Transfer in Aqueous Solutions Revisited: Dramatic Enhancement of Cage Escape Yields in Surfactant Ru(II) Diimine Complex/[Ru(NH3)6](2+) Systems.

    PubMed

    Adams, Rebecca E; Schmehl, Russell H

    2016-08-30

    The effect of cationic micelle incorporation on light induced electron transfer, charge separation and back electron transfer between an aqueous electron donor, [Ru(NH3)6](2+), and a series of Ru(II) diimine complex chromophores/acceptors, is presented. The chromophores have the general formula [(bpy)2Ru(LL)](2+) (LL = bpy; 4-R-4'-methyl-2,2'-bpy, R = pentyl (MC5), terdecyl (MC13), heptadecyl (MC17); 4,4'-di(heptadecyl)-2,2'-bpy (DC17)). Of the five chromophores, the MC13, MC17, and DC17 complexes associate with the added micelle forming surfactant, cetyltrimethylammonium bromide (CTAB). Quenching of the luminescence of the bpy and MC5 complexes by [Ru(NH3)6](2+) is unaffected by addition of surfactant, while rate constants for quenching of the MC13 and MC17 complexes are decreased. Cage escape yields following photoinduced electron transfer to generate [(bpy)2Ru(LL)](+) and [Ru(NH3)6](3+) are approximately 0.1 for all the water-soluble chromophores (excluding DC17) in the absence of added CTAB. In the presence of surfactant, the cage escape yields dramatically increase for the MC13 (0.4) and MC17 (0.6) complexes, while remaining unchanged for [Ru(bpy)3](2+) and the MC5 complex. Back electron transfer of the solvent separated ions is also strongly influenced by the presence of surfactant. For the MC13 and MC17 complexes, back electron transfer rate constants decrease by factors of 270 and 190, respectively. The MC5 complex exhibits two component back electron transfer, with the fast component having a rate constant close to that in the absence of surfactant and a slow component nearly 200 times smaller. Results are interpreted in terms of the partitioning of the 2+ and 1+ forms of the chromophores between aqueous and micellar phases. The extended lifetimes of the radical ions may prove useful in coupling the strong reductants formed to kinetically facile catalysts for reduction of water to hydrogen. PMID:27486891

  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. Angiogenesis in cancer: Anti-VEGF escape mechanisms

    PubMed Central

    Poettler, Marina; Unseld, Matthias; Zielinski, Christoph C.

    2012-01-01

    It is now widely accepted that tumor-angiogenesis plays a crucial role in tumor growth, tumor propagation and metastasis formation. Among several angiogenic activators, the vascular endothelial growth factor (VEGF) and its receptors represent one of the major inducers of tumor angiogenesis. Thus, this system has become the focus of therapeutic interventions, which led to the approval of the anti-VEGF blocking antibody bevacizumab and the VEGFR-2 pathway inhibitors pazopanib, sorafenib and sunitinib. However, not every cancer patient benefits from such treatment or finally becomes resistant to anti-VEGF approaches; others are suffering from adverse effects. Thus, there is an urgent need for a better understanding of VEGF-independent mechanisms leading to angiogenesis in cancer. This review focuses on anti-VEGF escape mechanisms of tumor cells and its microenvironment. PMID:25806151

  13. 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.

  14. 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.

  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. MAVEN Observations of Escaping Planetary Ions from the Martian Atmosphere: Mass, Velocity, and Spatial Distributions

    NASA Astrophysics Data System (ADS)

    Dong, Yaxue; Fang, Xiaohua; Brain, D. A.; McFadden, James P.; Halekas, Jasper; Connerney, Jack

    2015-04-01

    The Mars-solar wind interaction accelerates and transports planetary ions away from the Martian atmosphere through a number of processes, including ‘pick-up’ by electromagnetic fields. The MAVEN spacecraft has made routine observations of escaping planetary ions since its arrival at Mars in September 2014. The SupraThermal And Thermal Ion Composition (STATIC) instrument measures the ion energy, mass, and angular spectra. It has detected energetic planetary ions during most of the spacecraft orbits, which are attributed to the pick-up process. We found significant variations in the escaping ion mass and velocity distributions from the STATIC data, which can be explained by factors such as varying solar wind conditions, contributions of particles from different source locations and different phases during the pick-up process. We also study the spatial distributions of different planetary ion species, which can provide insight into the physics of ion escaping process and enhance our understanding of atmospheric erosion by the solar wind. Our results will be further interpreted within the context of the upstream solar wind conditions measured by the MAVEN Solar Wind Ion Analyzer (SWIA) instrument and the magnetic field environment measured by the Magnetometer (MAG) instrument. Our study shows that the ion spatial distribution in the Mars-Sun-Electric-Field (MSE) coordinate system and the velocity space distribution with respect to the local magnetic field line can be used to distinguish the ions escaping through the polar plume and those through the tail region. The contribution of the polar plume ion escape to the total escape rate will also be discussed.

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

    ERIC Educational Resources Information Center

    PTA Today, 1994

    1994-01-01

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

  18. 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...

  19. 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.

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

    PubMed

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

    2005-03-01

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

  1. 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…

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

    ERIC Educational Resources Information Center

    PTA Today, 1991

    1991-01-01

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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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…

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  11. Prediction of anti-angiogenesis escape.

    PubMed

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

    2016-04-01

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

  12. Escaping the resource curse in China.

    PubMed

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

    2015-02-01

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

  13. 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

  14. Evolutionary escape on complex genotype-phenotype networks.

    PubMed

    Ibáñez-Marcelo, Esther; Alarcón, Tomás

    2016-04-01

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

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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.

  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. 46 CFR 116.500 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  2. 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...

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

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

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

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

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

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

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

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

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

  6. 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

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

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

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

  8. 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

  9. STS-26 Preflight Press Briefing: Crew Escape/Crew Equipment. Part 4 of 9

    NASA Technical Reports Server (NTRS)

    1988-01-01

    This NASA KSC video release presents part of a press conference held prior to Discovery flight STS-26, the first shuttle mission flown following the 51-L Challenger accident. The five member panel present individual viewgraph discussions followed by a question and answer period for the benefit of scientific journalists. William A. Chandler (Asst. to the Dir. of Engineering and the NSTS program) gives a brief overview of the crew escape system followed by Steven Nagel's (Astronaut) presentation on crew equipment. Robert Rice (Crew Escape System Manager) describes the flight test program and the innovative pyrotechnics system test program. Tim Pelischek (Pole Design Team) gives an assessment of the critical design review and Ricardo Machin reviews aerodynamic flight tests performed at Texas A&M and California. The second part of the video includes Robert Crippen's (Deputy Dir. of Operations, Kennedy Space Center) overview of NASA Management, the organizational changes and actions taken to meet the Roger's Commission recommendations.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  12. Initiation and spread of escape waves within animal groups

    PubMed Central

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

    2015-01-01

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

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

    PubMed

    Pinheiro, C E G; Freitas, A V L

    2014-10-01

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

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

    PubMed

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

    2013-11-01

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

  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. PMID:26362229

  16. Escaping ion measurement with high time resolution on CHS

    SciTech Connect

    Shinohara, K.; Isobe, M.; Darrow, D. S.

    2006-10-15

    A scintillator-based lost ion probe can measure the temporal evolution of both the gyroradius and the pitch angle of energetic ions escaping a magnetically confined plasma. For the probe on the Compact Helical System, the time resolution of this detailed two-dimensional measurement is determined by a framing rate of the video camera that records the luminous images produced by the ions striking the scintillator plate. The framing rate of the old camera was 30 Hz, thus the time resolution was about 33 ms. Our interest is to understand the energetic ion transport in fast events such as a bursting energetic ion driven mode. The typical time scale of these events is less than 1 ms, meaning that the old camera was too slow. By replacing it with an image-intensified high-speed video camera system, the temporal resolution was improved from 33 to 0.07 ms. We have successfully installed the fast camera and captured some fast events caused by magnetohydrodynamics, which were unobservable using the original camera.

  17. The Escaping Spectroscopic Binary θ^1 Ori E

    NASA Astrophysics Data System (ADS)

    Costero, R.; Allen, C.; Echevarría, J.; Georgiev, L.; Poveda, A.; Richer, M. G.

    2008-12-01

    θ^1 Ori E was found to be a double-lined spectroscopic binary by Costero et al. (2006). From the analysis of 86 Echelle spectra obtained during three years, in which the systems of both components are separable, we found that the nearly identical spectra are consistent with both stars being early- to mid-G subgiant stars, with strong Li I λ 6708Å absorption and moderate emission Ca II K lines. The latter features are indicative of the pre-main-sequence evolutionary stage of the binary and, hence, of its membership to the Orion Nebula Cluster (ONC). The radial velocitiy curves of both components yield a circular orbit (e < 10^{-3}) for the binary, with a period of 9.8952+/-0.0007 d. The semi-amplitudes of the curves are almost identical (84.4+/-1.0 km s^{-1}) and the systemic velocity is 34.3+/-0.7 km s^{-1}. The latter value is 8.3 km s^{-1} larger, by at least 3σ, than the average radial velocity of the ONC members, and very similar to the transverse velocity (relative to component A in the Trapezium) derived for the star by Allen et al. (2004) and Sánchez et al. (2008). We conclude that the binary is escaping from the cluster in which it was formed.

  18. 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

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

    PubMed

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

    2015-01-01

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

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

    PubMed

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

    2016-02-01

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

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

    PubMed Central

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

    2016-01-01

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

  2. Stars on the run: escaping from stellar clusters

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  3. 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.

  4. MAVEN Measurements of the Ion Escape Rate from Mars

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Bui, Phuong Thuy; Hoang, Trinh Xuan

    2016-03-01

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

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

    PubMed

    Bui, Phuong Thuy; Hoang, Trinh Xuan

    2016-03-01

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

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

    PubMed

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

    2016-01-01

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

  9. 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

  10. 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.

  11. Immunosuppressive cells in tumor immune escape and metastasis.

    PubMed

    Liu, Yang; Cao, Xuetao

    2016-05-01

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

  12. Deterministic escape dynamics of two-dimensional coupled nonlinear oscillator chains.

    PubMed

    Fugmann, S; Hennig, D; Schimansky-Geier, L; Hänggi, P

    2008-06-01

    We consider the deterministic escape dynamics of a chain of coupled oscillators under microcanonical conditions from a metastable state over a cubic potential barrier. The underlying dynamics is conservative and noise free. We introduce a two-dimensional chain model and assume that neighboring units are coupled by Morse springs. It is found that, starting from a homogeneous lattice state, due to the nonlinearity of the external potential the system self-promotes an instability of its initial preparation and initiates complex lattice dynamics leading to the formation of localized large amplitude breathers, evolving in the direction of barrier crossing, accompanied by global oscillations of the chain transverse to the barrier. A few chain units accumulate locally sufficient energy to cross the barrier. Eventually the metastable state is left and either these particles dissociate or pull the remaining chain over the barrier. We show this escape for both linear rodlike and coil-like configurations of the chain in two dimensions. PMID:18643245

  13. 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

  14. 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

  15. Multiplexing of motor information in the discharge of a collision detecting neuron during escape behaviors.

    PubMed

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

    2011-01-13

    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. Cocontraction 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-probably control three distinct motor aspects of escape behaviors. PMID:21220105

  16. 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. PMID:11111136

  17. 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.

  18. Coexisting chaotic and periodic dynamics in clock escapements.

    PubMed

    Moon, Francis C; Stiefel, Preston D

    2006-09-15

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

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

    SciTech Connect

    Mitchell, Kevin A.; Steck, Daniel A.

    2007-09-15

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

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

    PubMed

    Mert, Murat; Ozkara, Ahmet; Hatemi, AliCan

    2003-07-01

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

  1. Group nightmares about escape from ex-homeland.

    PubMed

    Cernovsky, Z

    1990-09-01

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

  2. 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

  3. 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.

  4. 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. PMID:24640534

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

  6. 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.

  7. Fractionation of the Early Terrestrial Atmospheres: Dynamical Escape

    NASA Technical Reports Server (NTRS)

    Hartle, Richard E.

    2002-01-01

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

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  10. Conditional Immune Escape during Chronic Simian Immunodeficiency Virus Infection

    PubMed Central

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

    2015-01-01

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

  11. Water-escape velocities in jumping blacktip sharks.

    PubMed

    Brunnschweiler, Juerg M

    2005-09-22

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

  12. Changes in escape fire occurrence rate in Canada's boreal forest under climate change

    NASA Astrophysics Data System (ADS)

    Wotton, Mike

    2010-05-01

    Recent studies have shown that fire occurrence (from both human and lightning causes) is expected to increase across the boreal forest in Canada (and in many other regions of the world) with the fire weather expected to accompany climatic change in the 21st Century. Knowing total number of fires on the landscape is important for fire managers as part of their determination of load on the suppression organization's resources; however in terms of impact on the landscape (e.g., area burned or loss of values) it is that very small number of fires that escape initial attack that have the greatest impact. In this study, which covers the forest area of Canada, models of the probability of a fire escaping initial attack are developed based on the outputs of the Canadian FWI System, general fire cause and fire load. Using these models with outputs from recent General Circulation Model scenarios from the Hadley and Canadian Climate Centre were used and indicated an overall increase in expected fire escapes across the forested region of Canada. These increases are spatially quite variable however, due to the interaction between increased temperature and increased precipitation. Results between these two GCM scenarios do show some variation in parts of the country however, leading to some uncertainty in the absolute level of predicted change. The basic assumption of this analysis is that Canadian fire management agency efforts, in terms of response time and suppression resource levels, remain constant over time.

  13. 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.

  14. 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. PMID:25804818

  15. Semi-automatic inspecting instrument for watch escape wheel based on machine vision

    NASA Astrophysics Data System (ADS)

    Wang, Zhong; Wang, Zhen-wei; Zhang, Jin; Cai, Zhen-xing; Liu, Xin-bo

    2011-12-01

    Escape wheel as a typical precision micro-machinery part is one of the most precision parts in one mechanical watch. A new inspecting instrument based on machine vision technology used to achieve semi-automatic inspection of watch escape wheel is introduced in this paper. This instrument makes use of high resolution CCD sensor and independent designed lens as the imaging system. It can not only achieve to image an area with 7mm diameter once, but also has the resolving power in micrometer and cooperates with two-dimensional moving station to achieve a continuous and automatic measurement of the work pieces placed in array type. In which, the following aspects are highlighted: measuring princeple and process, the basic components of array type measuring workbench, positioning process and verticality, parallelism and other precision adjusting mechanism. Cooperating with novelty escape wheel preparation tool this instrument forms an array type semi-automatic measuring mode. At present, the instrument has been successfully running in the industry field.

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

    PubMed

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

    2005-03-21

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

  17. 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.

  18. Immune Escape Mechanisms of Intraocular Tumors

    PubMed Central

    Niederkorn, Jerry Y.

    2009-01-01

    The notion that the immune system might control the growth of tumors was suggested over 100 years ago by the eminent microbiologist Paul Ehrlich. This concept was refined and expanded by Burnet and Thomas fifty years later with their articulation of the “immune surveillance” hypothesis. In its simplest form, the immune surveillance hypothesis suggests that neoplasms arise spontaneously and express novel antigens that are recognized by the immune system, which either eliminates the tumors or restrains their growth. Within the eye, immune responses are controlled and sometimes profoundly inhibited - a condition known as immune privilege. Immune privilege in the eye is the result of a complex array of anatomical, physiological, and immunoregulatory mechanisms that prevent the induction and expression of many immune responses. Tumors arising in the eye would seem to have an advantage in evading immune surveillance due to ocular immune privilege. Uveal melanoma, the most common and malignant intraocular tumor in adults not only benefits from the immune privilege of the eye, but has adopted many of the mechanisms that contribute to ocular immune privilege as a strategy for protecting uveal melanoma cells once they leave the sanctuary of the eye and are disseminated systemically in the form of metastases. Although the immune system possesses a battery of effector mechanisms designed to rid the body of neoplasms, tumors are capable of rapidly evolving and countering even the most sophisticated immunological effector mechanisms. To date, tumors seem to be winning this arms race, but an increased understanding of these mechanisms should provide insights for designing immunotherapy that was envisioned over half a century ago, but has failed to materialize to date. PMID:19563908

  19. Brain size as a driver of avian escape strategy

    PubMed Central

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

    2015-01-01

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

  20. 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

  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. 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

  3. Entrapment and Escape: Inventional Metaphors in Ronald Reagan's Economic Rhetoric.

    ERIC Educational Resources Information Center

    Aden, Roger C.

    1989-01-01

    Examines Ronald Reagan's use of inventional metaphors of entrapment and escape, language meshing with the American public's perception of the economy in the early 1980s. Notes that Reagan's reliance on inventional metaphors produced a rigidity in his approach to new situations, ultimately damaging his ability to lead the nation. (MM)

  4. 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)

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

    PubMed

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

    2015-02-22

    Animal-vehicle collisions cause high levels of vertebrate mortality worldwide, and what goes wrong when animals fail to escape and ultimately collide with vehicles is not well understood. We investigated alert and escape behaviours of captive brown-headed cowbirds (Molothrus ater) in response to virtual vehicle approaches of different sizes and at speeds ranging from 60 to 360 km h(-1). Alert and flight initiation distances remained similar across vehicle speeds, and accordingly, alert and flight initiation times decreased at higher vehicle speeds. Thus, avoidance behaviours in cowbirds appeared to be based on distance rather than time available for escape, particularly at 60-150 km h(-1); however, at higher speeds (more than or equal to 180 km h(-1)) no trend in response behaviour was discernible. As vehicle speed increased, cowbirds did not have enough time to assess the approaching vehicle, and cowbirds generally did not initiate flight with enough time to avoid collision when vehicle speed exceeded 120 km h(-1). Although potentially effective for evading predators, the decision-making process used by cowbirds in our study appears maladaptive in the context of avoiding fast-moving vehicles. Our methodological approach and findings provide a framework to assess how novel management strategies could affect escape rules, and the sensory and cognitive abilities animals use to avoid vehicle collisions. PMID:25567648

  7. Hepatitis B escape mutants in Scottish blood donors.

    PubMed

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

    2013-06-01

    Hepatitis B virus (HBV) remains as the viral infection with the highest risk of transmission by transfusion. This risk is associated with window period donations, occult HBV infection (OBI) and the emergence of escape mutants, which render blood donations false negative for hepatitis B surface antigen (HBsAg) serological testing. A retrospective study was conducted to gain insights into the molecular epidemiology of HBV escape mutants in Scottish blood donors. The criterion for selection was HBV positivity either by serology or nucleic acid testing (NAT). HBsAg detection was compared across several commercial immunoassays. The full length S gene from plasma samples was PCR amplified, cloned and expressed in HepG2 cells. Eight samples showed HBsAg discordant results, while 5 OBI samples were found. Four escape mutants, containing missense mutations in the S gene, are described here. These mutations impaired HBsAg detection both from HBV infected plasma samples and from recombinant proteins derived from its infected donors. Phylogenetic analysis showed that most of the mutants were clustered in the genotype D and were closely related to strains from Asia and the Middle East. We report here a proline substitution, outside the major hydrophilic region, that impaired HBsAg detection in vivo and in vitro, warning about the risk for the emergence of vaccine escape mutants with mutations outside the major neutralisation site. PMID:23274404

  8. The magnetic anomalies significantrly reduce the Martian ionospheric escape rate

    NASA Astrophysics Data System (ADS)

    Fedorov, A.; Barabash, S.; Sauvaud, J.-A.

    2012-09-01

    Looking forward to the MAVEN mission, it seems very useful to return to Mars Express data to refresh an important problem of Martian atmosphere escape: what role the crustal magnetic field may play in this process? There are several publications on this topic with completely opposite conclusions. The last hybrid simulations show that the magnetic anomalies significantly reduce the ion loss rate during solar minimum. We are trying to use a new approach to Mars Express IMA data analysis to check how it is possible. On the base of a statistical study of the ion distributions in the Martian magnetotail we show that the characteristic accelerated ions are not associated with the magnetic anomalies but only with interplanetary magnetic field clock angle. Moreover the magnetic anomalies screen and deviate the escaping flow leading to reducing of the total loss rate. We have calculated a "quasiexperimental" escaping rate in an assumption of the total absence of the magnetic anomalies. We are comparing this value with a real measured escape rate.

  9. Overcoming Antigen Escape with CAR T-cell Therapy.

    PubMed

    Jackson, Hollie J; Brentjens, Renier J

    2015-12-01

    Sotillo and colleagues describe the molecular events associated with apparent loss of target antigen expression following CAR T-cell therapy. We propose that broader immune activation is required to prevent outgrowth of tumor antigen escape variants following targeted therapies. PMID:26637657

  10. 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,…

  11. 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…

  12. 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.

  13. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  14. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  15. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  16. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  17. 46 CFR 167.20-10 - Means of escape.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Means of escape. 167.20-10 Section 167.20-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) NAUTICAL SCHOOLS PUBLIC NAUTICAL SCHOOL SHIPS Hull Requirements, Construction and Arrangement of Nautical School Ships § 167.20-10 Means of...

  18. 30 CFR 57.11053 - Escape and evacuation plans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Escape and evacuation plans. 57.11053 Section 57.11053 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Travelways and Escapeways Escapeways-Underground Only §...

  19. 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

  20. [Effectiveness of methotrexate for the escape by salazosulfapyridine].

    PubMed

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

    2005-07-01

    Although disease modifying anti-rheumatic drugs (DMARDs) are used in the treatment of rheumatoid arthritis (RA), the selection of agents in the case of relapse (escape phenomenon) lacks clear-cut standards. We compared the effectiveness in a salazosulfapyridine and then methotrexate (SASP-->MTX) group with that in the mothotrexate (SASP+MTX) group after escape phenomenon expression in C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) data. Outpatients of the Matsubara Mayflower Hospital with a history of DMARD administration during the 4 years prior to May 2003 were studied. The CRP level in the SASP-->MTX group (n=8) after the escape phenomenon expression showed a decline after 3 months, but no decline was seen even after 3 months the two in the CRP level in the SASP+MTX group (n=10). However, the difference between groups was not significant. The fluctuation in ESR was similar to that in CRP. However, ESR was significantly lower in the SASP-->MTX group 20 weeks after escape phenomenon expression. In evaluating treatment effectiveness after escape phenomenon expression in each group, SASP-->MTX was effective in 10 and SASP+MTX in 7 patients. Side effects necessitated cessation of treatment in 1 patient in the SASP-->MTX group. Treatment continued in 4 patients in the SASP-->MTX group and 2 in the SASP+MTX group, even though side effects occurred. It should be borne in mind that combination therapy often has greater clinical benefit than single agent therapy but not always. PMID:15997214

  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. Hydrodynamic Vs. Evaporative Escape: Exoplanets And The Ex-planet

    NASA Astrophysics Data System (ADS)

    Johnson, Robert E.; Volkov, A.; Erwin, J.; Tucker, O.

    2012-10-01

    In studies of exoplanets, early terrestrial atmospheres, and even Pluto’s atmosphere it has been convenient to use the equations of fluid dynamics, rather than a more detailed molecular kinetic model, to describe the loss of atmosphere over long time periods. However, the boundary conditions in the far field are always problematic. Therefore, it is assumed that the upward flow either goes through a sonic point or that the loss is Jeans-like at the exobase. The so-called energy limited loss rate, an approximation obtained from the fluid equations, is also often used. Therefore, in a series of molecular kinetic studies of Pluto’s atmosphere, we confirmed that the energy limited loss rate gives a reasonable estimate over a broad range of solar heating conditions, but the flow did not go sonic although the Jeans parameter was relatively small and the escape rates large (Tucker et al. 2012; Erwin et al. 2012). Because the nature of the flow, and not just escape rate, determines the structure of the upper atmosphere, and because the simulation results scale (Volkov et al. 2011), we developed a criterion for determining when the flow associated with atmospheric escape goes sonic or remains Jeans-like. This criterion is verified in a series of kinetic simulations performed using a range of heating rates. In this talk we will discuss the validity of the energy limited escape rate and the nature of the criterion with applications to escape from a variety of exoplanet atmospheres. Erwin, J. et al. Icarus submitted (2012); Tucker, O.J.et al. Icarus 217, 408 (2012); Volkov et al. ApJLetts 729,L24 (2012)

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

    PubMed

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

    2006-01-01

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

  4. 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).

  5. 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

  6. Escape manoeuvres in the spiny dogfish (Squalus acanthias).

    PubMed

    Domenici, Paolo; Standen, Emily M; Levine, Robert P

    2004-06-01

    The locomotor performance of dogfish during escape responses was observed by means of high-speed video. Dogfish show C-type escape responses that are comparable with those shown previously in teleosts. Dogfish show high variability of turning rates of the anterior part of the body (head to centre of mass), i.e. with peak values from 434 to 1023 deg. s(-1). We suggest that this variability may be due to the presence of two types of escape manoeuvres, i.e. responses with high and low turning rates, as previously found in a teleost species. Fast responses (i.e. with high maximum turning rates, ranging between 766 and 1023 deg. s(-1)) showed significantly higher locomotor performance than slow responses (i.e. with low maximum turning rates, ranging between 434 and 593 deg. s(-1)) in terms of distance covered, speed and acceleration, although no differences were found in the turning radius of the centre of mass during the escape manoeuvres. The existence of two types of escape responses would have implications in terms of both neural control and muscular activation patterns. When compared with literature data for the locomotor performance of bony fishes, dogfish showed relatively low speed and acceleration, comparable turning rates and a turning radius that is in the low part of the range when compared with teleosts, indicating relatively high manoeuvrability. The locomotor performance observed in dogfish is consistent with their morphological characteristics: (1) low locomotor performance associated with low thrust developed by their relatively small posterior depth of section and (2) relatively high manoeuvrability associated with their high flexibility. PMID:15159438

  7. 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.

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

    PubMed

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

    2013-09-12

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

  9. 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…

  10. Evidence for local regulatory control of escape from imprinted X chromosome inactivation.

    PubMed

    Mugford, Joshua W; Starmer, Joshua; Williams, Rex L; Calabrese, J Mauro; Mieczkowski, Piotr; Yee, Della; Magnuson, Terry

    2014-06-01

    X chromosome inactivation (XCI) is an epigenetic process that almost completely inactivates one of two X chromosomes in somatic cells of mammalian females. A few genes are known to escape XCI and the mechanism for this escape remains unclear. Here, using mouse trophoblast stem (TS) cells, we address whether particular chromosomal interactions facilitate escape from imprinted XCI. We demonstrate that promoters of genes escaping XCI do not congregate to any particular region of the genome in TS cells. Further, the escape status of a gene was uncorrelated with the types of genomic features and gene activity located in contacted regions. Our results suggest that genes escaping imprinted XCI do so by using the same regulatory sequences as their expressed alleles on the active X chromosome. We suggest a model where regulatory control of escape from imprinted XCI is mediated by genomic elements located in close linear proximity to escaping genes. PMID:24653000

  11. Evidence for Local Regulatory Control of Escape from Imprinted X Chromosome Inactivation

    PubMed Central

    Mugford, Joshua W.; Starmer, Joshua; Williams, Rex L.; Calabrese, J. Mauro; Mieczkowski, Piotr; Yee, Della; Magnuson, Terry

    2014-01-01

    X chromosome inactivation (XCI) is an epigenetic process that almost completely inactivates one of two X chromosomes in somatic cells of mammalian females. A few genes are known to escape XCI and the mechanism for this escape remains unclear. Here, using mouse trophoblast stem (TS) cells, we address whether particular chromosomal interactions facilitate escape from imprinted XCI. We demonstrate that promoters of genes escaping XCI do not congregate to any particular region of the genome in TS cells. Further, the escape status of a gene was uncorrelated with the types of genomic features and gene activity located in contacted regions. Our results suggest that genes escaping imprinted XCI do so by using the same regulatory sequences as their expressed alleles on the active X chromosome. We suggest a model where regulatory control of escape from imprinted XCI is mediated by genomic elements located in close linear proximity to escaping genes. PMID:24653000

  12. 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

  13. Escape of heated ions upstream of quasi-parallel shocks

    NASA Technical Reports Server (NTRS)

    Edmiston, J. P.; Kennel, C. F.; Eichler, D.

    1982-01-01

    A simple theoretical criterion by which quasi-parallel and quasi-perpendicular collisionless shocks may be distinguished is proposed on the basis of an investigation of the free escape of ions from the post-shock plasma into the region upstream of a fast collisionless shock. It was determined that the accessibility of downstream ions to the upstream region depends on upstream magnetic field shock normal angle, in addition to the upstream plasma parameters, with post-shock ions escaping upstream for shock normal angles of less than 45 deg, in agreement with the observed transition between quasi-parallel and quasi-perpendicular shock structure. Upstream ion distribution functions resembling those of observed intermediate ions and beams are also calculated.

  14. Self-organized escape of oscillator chains in nonlinear potentials.

    PubMed

    Hennig, D; Fugmann, S; Schimansky-Geier, L; Hänggi, P

    2007-10-01

    We present the noise-free escape of a chain of linearly interacting units from a metastable state over a cubic on-site potential barrier. The underlying dynamics is conservative and purely deterministic. The mutual interplay between nonlinearity and harmonic interactions causes an initially uniform lattice state to become unstable, leading to an energy redistribution with strong localization. As a result, a spontaneously emerging localized mode grows into a critical nucleus. By surpassing this transition state, the nonlinear chain manages a self-organized, deterministic barrier crossing. Most strikingly, these noise-free, collective nonlinear escape events proceed generally by far faster than transitions assisted by thermal noise when the ratio between the average energy supplied per unit in the chain and the potential barrier energy assumes small values. PMID:17994939

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Escape of Mars atmospheric carbon through time by photochemical means

    NASA Technical Reports Server (NTRS)

    Luhmann, J. G.; Kim, J.; Nagy, A. F.

    1993-01-01

    Luhmann et al. recently suggested that sputtering of the Martian atmosphere by re-entering O(+) pickup ions could have provided a significant route of escape for CO2 and its products throughout Mars' history. They estimated that the equivalent of C in an approximately 140-mbar CO2 atmosphere should have been lost this way if the Sun and solar wind evolved according to available models. Another source of escaping C (and O) that is potentially important is the dissociative recombination of ionospheric CO(+) near the exobase. We have evaluated the loss rates due to this process for 'ancient' solar EUV radiation fluxes of 1, 3, and 6 times the present flux in order to calculate the possible cumulative loss over the last 3.5 Gyr.

  20. Planetary loss from light ion escape on Venus

    NASA Technical Reports Server (NTRS)

    Hartle, R. E.; Grebowsky, J. M.

    1995-01-01

    Using Pioneer Venus data, hydrogen and deuterium ions are shown to escape from the hydrogen bulge region in the nightside ionosphere. The polarization electric field propels these light ions upward through the ionosphere and into the ion-exosphere, where H(+) and D(+) continue to be accelerated away from Venus and move into the ionotail and beyond. The vertical flow speeds of H(+) and D(+) are found to be about the same; therefore, selective escape between H(+) and D(+) is negligible for this mechanism. Present day planetary loss rates of about 8.6 x 10(exp 25)/s and 3.2 X 10(exp 23)/s were obtained for H(+) and D(+), respectively. Such rates, persisting over a few billion years, should have significantly affected the planetary water budget.

  1. Escape of Mars atmospheric carbon through time by photochemical means

    NASA Astrophysics Data System (ADS)

    Luhmann, J. G.; Kim, J.; Nagy, A. F.

    Luhmann et al. recently suggested that sputtering of the Martian atmosphere by re-entering O(+) pickup ions could have provided a significant route of escape for CO2 and its products throughout Mars' history. They estimated that the equivalent of C in an approximately 140-mbar CO2 atmosphere should have been lost this way if the Sun and solar wind evolved according to available models. Another source of escaping C (and O) that is potentially important is the dissociative recombination of ionospheric CO(+) near the exobase. We have evaluated the loss rates due to this process for 'ancient' solar EUV radiation fluxes of 1, 3, and 6 times the present flux in order to calculate the possible cumulative loss over the last 3.5 Gyr.

  2. 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.

  3. Lens Design: An Attempt to Use `Escape Function' as a Tool in Global Optimization

    NASA Astrophysics Data System (ADS)

    Isshiki, Masaki; Ono, Hiroki; Nakadate, Suezou

    1995-01-01

    In designing lenses with the damped least squares method, the solution obtained by optimization routine is a local minimum of the merit function. To get out of this and seek a different solution, we propose to use an ‘escape function’ as an additional operand of the lens system, to be controlled. Experiments were made on simple models of merit function and the advantage of this technique was ascertained. We also planted this algorithm into OSLO SIX (lens design software by Sinclair Optics) by means of CCL (C-compatible language) and applied it to actual lens design. Experiments convinced us that the method would be an effective tool for global optimization.

  4. Fleeing to refuge: Escape decisions in the race for life.

    PubMed

    Cooper, William E

    2016-10-01

    Economic escape theory that predicts that flight initiation distance (FID=predator-prey distance when a prey begins to flee from an approaching predator) increases as predation risk increases has been overwhelmingly supported. However, the vast majority of empirical tests have focused on effects of single predation risk factors. Even studies that have included multiple risk factors have not predicted how they jointly affect FID. I present a model that predicts joint effects of several predation risk factors that affect the outcome of a race between predator and prey to the prey's refuge. As a prey's distance to refuge and predator attack speed increase, and as the prey's location forces it to flee more toward a predator to reach refuge, FID increases. A published model proposed and experiment showed that FID is longer when prey flee directly toward than directly away from a predator to a refuge. We present a new geometric model that predicts FID for all angles between the prey's and predator's paths to refuge, distance of the prey from refuge when escape begins, predator and prey speeds, and a margin of safety allowing the prey to reach refuge before the predator. The model provides many new, testable predictions about relationships among its variables and FID. Most notably, it predicts that FID increases sigmoidally as the angle between predator and prey paths to refuge increases. Although the model is not economic (cost-benefit), we discuss its relationship to economic escape theory. PMID:27343624

  5. A Treatment Package without Escape Extinction to Address Food Selectivity.

    PubMed

    Weber, Jessica; Gutierrez, Anibal

    2015-01-01

    Feeding difficulties and feeding disorders are a commonly occurring problem for young children, particularly children with developmental delays including autism. Behavior analytic interventions for the treatment of feeding difficulties oftentimes include escape extinction as a primary component of treatment. The use of escape extinction, while effective, may be problematic as it is also associated with the emergence of challenging behavior (e.g., extinction burst). Such challenging behavior may be an acceptable side effect in treatment cases where feeding problems are severe and chronic (e.g., failure to thrive). However, in more acute cases (e.g., selective eating), the negative side effect may be unwarranted and undesired. More recent research on the behavioral treatment of food selectivity has begun to evaluate treatments for feeding difficulties that do not include escape extinction (e.g., demand fading, behavioral momentum), with some success. However, research to date reveals individual differences in responsiveness to such treatments and no clear preferable treatment has emerged. This manuscript describes a multi-component treatment package that includes shaping, sequential presentation and simultaneous presentation, for the treatment of food selectivity in four young children with developmental delays. This treatment package extends the literature on the behavioral treatment for food selectivity and offers a multi-component treatment protocol that may be clinically applicable across a range of treatment scenarios and settings. PMID:26325108

  6. Transitions between three swimming gaits in Paramecium escape.

    PubMed

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

    2011-05-01

    Paramecium and other protists are able to swim at velocities reaching several times their body size per second by beating their cilia in an organized fashion. The cilia beat in an asymmetric stroke, which breaks the time reversal symmetry of small scale flows. Here we show that Paramecium uses three different swimming gaits to escape from an aggression, applied in the form of a focused laser heating. For a weak aggression, normal swimming is sufficient and produces a steady swimming velocity. As the heating amplitude is increased, a higher acceleration and faster swimming are achieved through synchronized beating of the cilia, which begin by producing oscillating swimming velocities and later give way to the usual gait. Finally, escape from a life-threatening aggression is achieved by a "jumping" gait, which does not rely on the cilia but is achieved through the explosive release of a group of trichocysts in the direction of the hot spot. Measurements through high-speed video explain the role of trichocysts in defending against aggressions while showing unexpected transitions in the swimming of microorganisms. These measurements also demonstrate that Paramecium optimizes its escape pattern by taking advantage of its inertia. PMID:21464291

  7. 46 CFR 108.155 - Restrictions on means of escape utilized.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Restrictions on means of escape utilized. 108.155 Section 108.155 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) A-MOBILE OFFSHORE... means of escape utilized. A required means of escape may not be a vertical ladder or deck...

  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. 78 FR 13811 - Safety Zone; Underwater Escape Event, Seaport, East River, NY

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-01

    ... Federal Register on November 9, 2011 (76 FR 69614). ] Table 1 1. Merlini Underwater Escape Launch site... SECURITY Coast Guard 33 CFR Part 165 Safety Zone; Underwater Escape Event, Seaport, East River, NY AGENCY... escape artist event and associated pyrotechnics display. During the enforcement period, no person...

  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. 78 FR 54585 - Safety Zone; Escape to Miami Triathlon, Biscayne Bay, Miami, FL

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-05

    .... SUPPLEMENTARY INFORMATION: Table of Acronyms DHS Department of Homeland Security FR Federal Register NPRM Notice... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Escape to Miami Triathlon, Biscayne Bay... during the Publix Escape to Miami Triathlon. The Publix Escape to Miami Triathlon is scheduled to...

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

    NASA Technical Reports Server (NTRS)

    1971-01-01

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

  14. Mechanical properties of the cuticles of three cockroach species that differ in their wind-evoked escape behavior

    PubMed Central

    Clark, Andrew J.

    2014-01-01

    The structural and material properties of insect cuticle remain largely unexplored, even though they comprise the majority (approximately 80%) of animals. Insect cuticle serves many functions, including protection against predatory attacks, which is especially beneficial to species failing to employ effective running escape responses. Despite recent advances in our understanding of insect escape behaviors and the biomechanics of insect cuticle, there are limited studies on the protective qualities of cuticle to extreme mechanical stresses and strains imposed by predatory attacks, and how these qualities vary between species employing different escape responses. Blattarians (cockroaches) provide an appropriate model system for such studies. Wind-evoked running escape responses are strong in Periplaneta americana, weak in Blaberus craniifer and absent in Gromphodorhina portentosa, putting the latter two species at greater risk of being struck by a predator. We hypothesized that the exoskeletons in these two larger species could provide more protection from predatory strikes relative to the exoskeleton of P. americana. We quantified the protective qualities of the exoskeletons by measuring the puncture resistance, tensile strength, strain energy storage, and peak strain in fresh samples of thoracic and abdominal cuticles from these three species. We found a continuum in puncture resistance, tensile strength, and strain energy storage between the three species, which were greatest in G. portentosa, moderate in B. craniifer, and smallest in P. americana. Histological measurements of total cuticle thickness followed this same pattern. However, peak strain followed a different trend between species. The comparisons in the material properties drawn between the cuticles of G. portentosa, B. craniifer, and P. americana demonstrate parallels between cuticular biomechanics and predator running escape responses. PMID:25101230

  15. Cytoplasmic replication of Staphylococcus aureus upon phagosomal escape triggered by phenol-soluble modulin α.

    PubMed

    Grosz, Magdalena; Kolter, Julia; Paprotka, Kerstin; Winkler, Ann-Cathrin; Schäfer, Daniel; Chatterjee, Som Subra; Geiger, Tobias; Wolz, Christiane; Ohlsen, Knut; Otto, Michael; Rudel, Thomas; Sinha, Bhanu; Fraunholz, Martin

    2014-04-01

    Staphylococcus aureus is a Gram-positive human pathogen that is readily internalized by professional phagocytes such as macrophages and neutrophils but also by non-professional phagocytes such as epithelial or endothelial cells. Intracellular bacteria have been proposed to play a role in evasion of the innate immune system and may also lead to dissemination within migrating phagocytes. Further, S. aureus efficiently lyses host cells with a battery of cytolytic toxins. Recently, phenol-soluble modulins (PSM) have been identified to comprise a genus-specific family of cytolytic peptides. Of these the PSMα peptides have been implicated in killing polymorphonuclear leucocytes after phagocytosis. We questioned if the peptides were active in destroying endosomal membranes to avoid lysosomal killing of the pathogen and monitored integrity of infected host cell endosomes by measuring the acidity of the intracellular bacterial microenvironment via flow cytometry and by a reporter recruitment technique. Isogenic mutants of the methicillin-resistant S. aureus (MRSA) strains USA300 LAC, USA400 MW2 as well as the strongly cytolytic methicillin-sensitive strain 6850 were compared with their respective wild type strains. In all three genetic backgrounds, PSMα mutants were unable to escape from phagosomes in non-professional (293, HeLa, EAhy.926) and professional phagocytes (THP-1), whereas mutants in PSMβ and δ-toxin as well as β-toxin, phosphatidyl inositol-dependent phospholipase C and Panton Valentine leucotoxin escaped with efficiencies of the parental strains. S. aureus replicated intracellularly only in presence of a functional PSMα operon thereby illustrating that bacteria grow in the host cell cytoplasm upon phagosomal escape. PMID:24164701

  16. Cytoplasmic replication of Staphylococcus aureus upon phagosomal escape triggered by phenol-soluble modulin α

    PubMed Central

    Grosz, Magdalena; Kolter, Julia; Paprotka, Kerstin; Winkler, Ann-Cathrin; Schäfer, Daniel; Chatterjee, Som Subra; Geiger, Tobias; Wolz, Christiane; Ohlsen, Knut; Otto, Michael; Rudel, Thomas; Sinha, Bhanu; Fraunholz, Martin

    2013-01-01

    Staphylococcus aureus is a Gram-positive human pathogen that is readily internalized by professional phagocytes such as macrophages and neutrophils but also by non-professional phagocytes such as epithelial or endothelial cells. Intracellular bacteria have been proposed to play a role in evasion of the innate immune system and may also lead to dissemination within migrating phagocytes. Further, S. aureus efficiently lyses host cells with a battery of cytolytic toxins. Recently, phenol-soluble modulins (PSM) have been identified to comprise a genus-specific family of cytolytic peptides. Of these the PSMα peptides have been implicated in killing polymorphonuclear leukocytes after phagocytosis. We questioned if the peptides were active in destroying endosomal membranes to avoid lysosomal killing of the pathogen and monitored integrity of infected host cell endosomes by measuring the acidity of the intracellular bacterial microenvironment via flow cytometry and by a reporter recruitment technique. Isogenic mutants of the methicillin-resistant S. aureus (MRSA) strains USA300 LAC, USA400 MW2 as well as the strongly cytolytic methicillin-sensitive strain 6850 were compared to their respective wild type strains. In all three genetic backgrounds, PSMα mutants were unable to escape from phagosomes in non-professional (293, HeLa, EAhy.926) and professional phagocytes (THP-1), whereas mutants in PSMβ and δ-toxin as well as β-toxin, phosphatidyl inositol-dependent phospholipase C and Panton Valentine leukotoxin escaped with efficiencies of the parental strains. S. aureus replicated intracellularly only in presence of a functional PSMα operon thereby illustrating that bacteria grow in the host cell cytoplasm upon phagosomal escape. PMID:24164701

  17. Hematological Malignancies Escape from NK Cell Innate Immune Surveillance: Mechanisms and Therapeutic Implications

    PubMed Central

    Farnault, Laure; Sanchez, Carole; Baier, Céline; Le Treut, Thérèse; Costello, Régis T.

    2012-01-01

    Hematological malignancies treatment improved over the last years resulting in increased achievement of complete or partial remission, but unfortunately high relapse rates are still observed. Therefore, sustainment of long-term remission is crucial. Immune system has a key role in tumor surveillance. Natural killer (NK) cells, at the frontier of innate and adaptive immune system, have a central role in tumor cells surveillance as demonstrated in the setting of allogenic stem cell transplantation. Nevertheless, tumor cells develop various mechanisms to escape from NK cells innate immune pressure. Abnormal NK cytolytic functions have been described in nearly all hematological malignancies. We present here various mechanisms involved in the escape of hematological malignancies from NK cells surveillance: NK cells quantitative deficiency and NK cell qualitative deficiency by increased inhibition signaling or decreased activating stimuli. A challenge of immunotherapy is to restore an efficient antitumor response. A combination of classical therapy plus immune modulation strategies will soon become a standard of care for hematological malignancies. PMID:22899948

  18. Photodynamic therapy with simultaneous suppression of multiple treatment escape pathways (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Spring, Bryan Q.; Sears, R. Bryan; Zheng, Lei Z.; Mai, Zhiming; Watanabe, Reika; Sherwood, Margaret E.; Schoenfeld, David A.; Pogue, Brian W.; Pereira, Stephen P.; Villa, Elizabeth; Hasan, Tayyaba

    2016-03-01

    We introduce photoactivatable multi-inhibitor nanoliposomes (PMILs) for photodynamic tumor cell and microvessel damage in synchrony with photo-initiation of tumor-confined, multikinase inhibitor release. The PMIL is a biodegradable delivery system comprised of a nanoliposome carrying a photoactivable chromophore (benzoporphyrin derivative monoacid A, BPD) in its bilayer. A multikinase inhibitor-loaded PEG-PLGA nanoparticle is encapsulated within the liposome, which acts a barrier to nanoparticle erosion and drug release. Following intravenous PMIL administration, near infrared irradiation of tumors triggers photodynamic therapy and initiates tumor-confined drug release from the nanoparticle. This talk presents promising preclinical data in mouse models of pancreatic cancer utilizing this concept to suppress the VEGF and MET signaling pathways—both critical to cancer progression, metastasis and treatment escape. A single PMIL treatment using low doses of a multikanse inhibitor (cabozantinib, XL184) achieves sustained tumor reduction and suppresses metastatic escape, whereas combination therapy by co-administration of the individual agents has significantly reduced efficacy. The PMIL concept is amenable to a number of molecular inhibitors and offers new prospects for spatiotemporal synchronization of combination therapies whilst reducing systemic drug exposure and associated toxicities.

  19. Atrial natriuretic peptide increases microvascular blood flow and macromolecular escape during renin infusion in the hamster

    SciTech Connect

    Boric, M.P.; Albertini, R. )

    1990-02-01

    The effects of Atrial Natriuretic Peptide (ANP) on microvascular hemodynamics and macromolecular permselectivity were studied in the hamster cheek pouch under resting conditions and during intravenous renin infusion. Fluorescent intravital microscopy was used to observe arteriolar diameters and to detect escape of fluorescent dextran of 150 K-Daltons (FITC-Dx-150). Microvascular plasma flow was estimated by clearance of 51Cr-EDTA and net macromolecular transport by clearance of FITC-Dx-150. At rest, topical ANP (2-250 ng/ml) had no effect on arteriolar diameter, 51Cr-EDTA clearance, relative vascular conductance (RVC) or FITC-Dx-150 clearance. Infusion of renin (10 mU/Kg/Hr, iv) elevated systemic arterial pressure by 30% and reduced cheek pouch RVC by 26%. During renin infusion, topical ANP (50 ng/ml) produced transient arteriolar vasodilation, and increased 51Cr-EDTA clearance (+35%), RVC (+58%) and FITC-Dx-150 clearance (+54%), without affecting systemic pressure. ANP did not induce venular leakage sites under any condition, but changes in FITC-Dx-150 clearance were highly correlated with changes in 51Cr-EDTA clearance, suggesting that the larger macromolecular escape was due to increases in microvascular blood flow and capillary/post-capillary hydrostatic pressure.

  20. Escape erosion and relaxation of craters on Pluto

    NASA Astrophysics Data System (ADS)

    Porter, S.; Zangari, A.; Stern, A.

    2014-07-01

    Pluto and its major satellite Charon will be the most distant objects ever visited when NASA's New Horizons spacecraft flies past them in mid-2015. Both bodies should have suffered impacts from other transneptunian objects, though those impacts are of much lower velocity than typical on giant-planet satellites. New Horizons will image the illuminated hemispheres of Pluto and Charon seen at closest approach at better than 0.5 km/pix and 1.0 km/pix, respectively. We compare new different predictions of the impactor population on Pluto and Charon, including the effects of escape erosion from Pluto, and examine the crater size distributions those impactors would produce over the range observable to the imagers on New Horizons. The impact distribution models diverge the most for craters smaller than 10 km. We expect the crater size distribution on Charon to be determined by the impactor distribution and the rheology of the surface. Inverting the Charon size distribution seen by New Horizons will then constrain the overall size frequency distribution in the Kuiper belt, and the location of any break in that size frequency distribution. However, owing to escape erosion, craters on Pluto may be much more modified than on Charon. To constrain this modification, we present a range of possible Pluto crater distributions, as a function of impactor distribution, atmospheric escape rate, and surface ice viscosity. Pluto's atmosphere is primarily made of molecular nitrogen and is currently escaping at between 10^{27} and 10^{28} N_2/s according to model estimates. To sustain these escape rates for 3.5 billion years, a global layer of N_2 ice 0.3 to 3 km thick would need to have sublimated from the surface. We show that this gradual mass loss could have erased many of the smaller craters on Pluto, especially craters with diameters smaller than 10 km. This sublimation erosion process does not occur on Charon, which has a water ice surface and no observed atmosphere. We also show

  1. Containing the accidental laboratory escape of potential pandemic influenza viruses

    PubMed Central

    2013-01-01

    Background The recent work on the modified H5N1 has stirred an intense debate on the risk associated with the accidental release from biosafety laboratory of potential pandemic pathogens. Here, we assess the risk that the accidental escape of a novel transmissible influenza strain would not be contained in the local community. Methods We develop here a detailed agent-based model that specifically considers laboratory workers and their contacts in microsimulations of the epidemic onset. We consider the following non-pharmaceutical interventions: isolation of the laboratory, laboratory workers’ household quarantine, contact tracing of cases and subsequent household quarantine of identified secondary cases, and school and workplace closure both preventive and reactive. Results Model simulations suggest that there is a non-negligible probability (5% to 15%), strongly dependent on reproduction number and probability of developing clinical symptoms, that the escape event is not detected at all. We find that the containment depends on the timely implementation of non-pharmaceutical interventions and contact tracing and it may be effective (>90% probability per event) only for pathogens with moderate transmissibility (reproductive number no larger than R0 = 1.5). Containment depends on population density and structure as well, with a probability of giving rise to a global event that is three to five times lower in rural areas. Conclusions Results suggest that controllability of escape events is not guaranteed and, given the rapid increase of biosafety laboratories worldwide, this poses a serious threat to human health. Our findings may be relevant to policy makers when designing adequate preparedness plans and may have important implications for determining the location of new biosafety laboratories worldwide. PMID:24283203

  2. The production and escape of nitrogen atoms on Mars

    NASA Technical Reports Server (NTRS)

    Fox, J. L.

    1992-01-01

    The lack of agreement between our previously computed values and those measured by Viking of the N-15:N-14 isotope enhancement ratio has led us to reevaluate our model of the Martian ionosphere. In previous models, we were unable to reproduce the ion profiles measured by the RPA on Viking using electron temperatures that were higher that the ion temperatures. When we increased the electron temperatures to 2500-3000 K and with a zero flux upper boundary condition, the ion densities at high altitudes exceeded the measured values by a large factor. We found that we can better fit the observed profiles if we impose a loss process at the upper boundary of our model. If the horizontal fluxes of ions do not constitute a net loss of ions, then the escape of N due to dissociative recombination is also inhibited and better agreement with the measured isotope ratio is found. The production of escaping nitrogen atoms is closely related to the production of thermospheric odd nitrogen; therefore, the densities of NO measured by Viking provide a convenient check on our nitrogen escape model. Our standard model NO densities are less that the measured values by a factor of 2-3, as are those of previous models. We find that reasonable agreement can be obtained by assuming that the rate coefficient for loss of odd nitrogen in the reaction of N with NO is smaller at temperatures that prevail in the lower Martian thermosphere than the standard value, which applies to temperatures of 200-400 K. Other aspects of this investigation are presented.

  3. Cold Ion Escape from the Martian Ionosphere - 2005-2014

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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. 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 RM the flux settles at a constant value which indicates that about half of the transterminator ionospheric flow escapes from the planet. To derive the mean escape flux we include all combined observations of ASPERA-3 and MARSIS from 2005 to 2014. 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.

  4. The Zonal Satellite Problem. I. Near-Escape Flow

    NASA Astrophysics Data System (ADS)

    Mioc, V.; Stavinschi, M.

    The study of the zonal satellite problem is continued by tackling the situation r-> infty. New equations of motion (for which the infinite distance is a singularity) and the corresponding first integrals of energy and angular momentum are set up. The infinity singularity is blown up via McGehee-type transformations, and the infinity manifold is pasted on the phase space. The fictitious flow on this manifold is described. Then, resorting to the rotational symmetry of the problem and to the angular momentum integral, the near-escape local flow is depicted. The corresponding phase curves are interpreted as physical motions.

  5. Approximate formula for the escape function for nearly conservative scattering

    NASA Astrophysics Data System (ADS)

    Yanovitskij, E. G.

    2002-02-01

    The escape function u(μ) (i.e., the boundary solution of the Milne problem for a semi-infinite atmosphere) is considered. It is presented in the form u(μ) = u0 (μ ) + √ {1 - λ}u1(μ) + (1-λ)u2(μ) + ldots, where λ is the single-scattering albedo. A rather accurate approximate formula for a the function u0 (μ) is obtained for not highly elongated phase function. An approximate expression for the function u2 (μ) is also derived, it is exact in the case of the most simple anisotropic scattering.

  6. Development of a canine nociceptive thermal escape model.

    PubMed

    Wegner, Kirsten; Horais, Kjersti A; Tozier, Nicolle A; Rathbun, Michael L; Shtaerman, Yuri; Yaksh, Tony L

    2008-02-15

    Acute nociceptive models which have been validated for large animal species are limited, yet nociceptive assessment in non-rodent species is important in analgesic drug development where larger animals may be necessary because of the technical requirements of the study. Here we report development and validation of a canine hind paw thermal escape model and the effect of analgesics on withdrawal latencies. Individual focused projection bulbs were used as left and right voltage-adjusted thermal stimuli placed below a glass plate in a specifically designed canine holding apparatus. After acclimation, dogs were lightly restrained in a fabric sling while standing on the glass plate. The anterior center of the metatarsal pad of the left and right hind paw was positioned on the glass over each light, and duration of stimulation tolerance timed. For every trial, the escape latency from lamp actuation to paw withdrawal was recorded twice for each hind paw. The mean population baseline withdrawal latency of 9.3+/-1.7s (mean+/-S.D., n=12 dogs) was shown to be repeatable between paws, within and between individual animals, and between test days. This latency corresponded to a glass surface temperature of 49.5 degrees C. A cut-off time of 20s (corresponding to a glass surface temperature of 56.5 degrees C) was set to prevent tissue damage. Intravenous administration (mg/kg) of morphine (1.0), hydromorphone (0.2), butorphanol (0.4), fentanyl (0.01), and dexmedetomidine (0.01) significantly (p<0.05) increased withdrawal latency from baseline within 15-30 min of administration while buprenorphine (0.03) produced a delayed, modest but significant latency increase. Rank order of opioid analgesic duration was morphine=hydromorphone>butorphanol>bupenorphine>fentanyl=saline. A dose-effect curve for hydromorphone was generated and corresponded to previously described dose-effect relationships in other species. The non-analgesic tranquilizer acepromazine (0.1mg/kg) produced mild sedation

  7. 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. PMID:26342537

  8. Numerical simulation of a self-propelled copepod during escape

    NASA Astrophysics Data System (ADS)

    Sotiropoulos, Fotis; Borazjani, Iman; Malkiel, Edwin; Katz, Josef

    2008-11-01

    Obtaining the 3D flow field, forces, and power is essential for understanding the high accelerations of a copepod during the escap. We carry out numerical simulations to study a free swimming copepod using the sharp-interface immersed boundary, fluid-structure interaction (FSI) approach of Borazjani et al. (J Compu Phys, 2008, 227, p 7587-7620). We use our previous tethered copepod model with a realistic copepod-like body, including all the appendages with the appendages motion prescribed from high-resolution, cinematic dual digital holography. The simulations are performed in a frame of reference attached to the copepod whose velocity is calculated by considering the forces acting on the copepod. The self-propelled simulations are challenging due to the destabilizing effects of the large added mass resulting from the low copepod mass and fast acceleration during the escape. Strongly-coupled FSI with under-relaxation and the Aitken acceleration technique is used to obtain stable and robust FSI iterations. The computed results for the self-propelled model are analyzed and compared with our earlier results for the tethered model.

  9. Pair interaction of catalytically active colloids: from assembly to escape

    NASA Astrophysics Data System (ADS)

    Sharifi-Mood, Nima; Mozaffari, Ali; Córdova-Figueroa, Ubaldo M.

    2016-07-01

    The dynamics and pair trajectory of two self-propelled colloids are reported. The autonomous motions of the colloids are due to a catalytic chemical reaction taking place asymmetrically on their surfaces that generates a concentration gradient of interactive solutes around the particles and actuate particle propulsion. We consider two spherical particles with symmetric catalytic caps extending over the local polar angles $\\theta^1_{cap}$ and $\\theta^2_{cap}$ from the centers of active sectors in an otherwise quiescent fluid. A combined analytical-numerical technique was developed to solve the coupled mass transfer equation and the hydrodynamics in the Stokes flow regime. The ensuing pair trajectory of the colloids is controlled by the reacting coverages $\\theta^j_{cap}$ and their initial relative orientation with respect to each other. Our analysis indicates two possible scenarios for pair trajectories of catalytic self-propelled particles: either the particles approach, come into contact and assemble or they interact and move away from each other (escape). For arbitrary motions of the colloids, it is found that the direction of particle rotations is the key factor in determining the escape or assembly scenario. Based on the analysis, a phase diagram is sketched for the pair trajectory of the catalytically active particles as a function of active coverages and their initial relative orientations. We believe this study has important implications in elucidation of collective behaviors of auotophoretically self-propelled colloids.

  10. FEM analysis of escape capsule suffered to gas explosion

    NASA Astrophysics Data System (ADS)

    Li, Chang-lu; Mei, Rui-bin; Li, Chang-sheng; Cai, Ban; Liu, Xiang-hua

    2013-05-01

    Escape capsules are new devices for underground coal mines that provide air, water, food and supplies in the event of an emergency in where miners are unable to escape. It is difficult to carry out the experiments of explosion and safety because the danger and nonrepeatability of explosion. The structure deformation and distribution of equivalent stress has been investigated under different impact pressure conditions including unimodal and bimodal loads based on the FEM and software LS-DYNA. The results show that the distribution of deformation and equivalent stress has the same trend on the same surface with the increment of explosion pressure. The deformation and stress are larger with side impact pressure compared with that of the same front impact pressure. Furthermore, the maximum equivalent stress is 246MPa and 260MPa on the front and sides of capsule with five times for national standard impact pressure 1.5MPa. Under these conditions, the deformation is less than about 9.97mm and 10.47mm, respectively. When the front impact pressure is 2.0MPa, the deformation of capsule still belongs to elasticity but the less plastic deformation occurs on the Ushape stiffening channels with the same side impact pressure. However, it is safe for capsule structure because the equivalent stress 283MPa is much less than the tensile strength. It is noted that bimodal load accelerates the capsule deformation so that it is more dangerous compared with unimodal load.

  11. Trapped subsurface oil plumes and critical escape phenomena

    NASA Astrophysics Data System (ADS)

    Tzou, Chung-Nan; Camassa, Roberto; Lin, Zhi; McLaughlin, Rich; Mertens, Keith; White, Brian

    2012-11-01

    A critical phenomenon concerning the escape/trap of buoyant miscible plumes rising through strongly stratified fluids is presented experimentally and theoretically. The criticality is determined by the distance between plume release height and depth of ambient density transition. For fluid released closer to the background density transition than this critical distance, the buoyant fluid escapes and rises indefinitely. For fluid released further than this critical distance, the buoyant fluid is forever trapped within the fluid. Two new mathematically exact formulas will be presented for the cases of linear and sharp ambient stratification and they show quantitative agreement with experiments. The new solution for linear stratification is analyzed in the limit of vanishing transition layer thickness. The analytic solution for sharp stratification is shown to accurately estimate the depth at which subsurface plumes trapped during the Deepwater Horizon oil disaster. Also, a dimensional analysis argument is presented which captures the essential physics to provide a simple understanding of this phenomenon. We gratefully acknowledge support from NSF CMG ARC-1025523, NSF RAPID CBET-1045653, NSF DMS-1009750 and NSF RTG DMS-0943851.

  12. Quantification of Nociceptive Escape Response in C.elegans

    NASA Astrophysics Data System (ADS)

    Leung, Kawai; Mohammadi, Aylia; Ryu, William; Nemenman, Ilya

    2013-03-01

    Animals cannot rank and communicate their pain consciously. Thus in pain studies on animal models, one must infer the pain level from high precision experimental characterization of behavior. This is not trivial since behaviors are very complex and multidimensional. Here we explore the feasibility of C.elegans as a model for pain transduction. The nematode has a robust neurally mediated noxious escape response, which we show to be partially decoupled from other sensory behaviors. We develop a nociceptive behavioral response assay that allows us to apply controlled levels of pain by locally heating worms with an IR laser. The worms' motions are captured by machine vision programming with high spatiotemporal resolution. The resulting behavioral quantification allows us to build a statistical model for inference of the experienced pain level from the behavioral response. Based on the measured nociceptive escape of over 400 worms, we conclude that none of the simple characteristics of the response are reliable indicators of the laser pulse strength. Nonetheless, a more reliable statistical inference of the pain stimulus level from the measured behavior is possible based on a complexity-controlled regression model that takes into account the entire worm behavioral output. This work was partially supported by NSF grant No. IOS/1208126 and HFSP grant No. RGY0084/2011.

  13. Group chase and escape model with chasers' interaction

    NASA Astrophysics Data System (ADS)

    Saito, Takuya; Nakamura, Tomomichi; Ohira, Toru

    2016-04-01

    Group chase and escape is a new direction of studying collective behaviors merged with the traditional mathematical problems of chases and escapes proposed by Kamimura and Ohira in 2010. In their model, the chasers recognize only the escapees and pursue the nearest neighbor escapee, and the escapees recognize only the chasers and flee from the nearest neighbor chaser. We call the basic moving rule the nearest opponent interaction (NOI) strategy. In this paper we introduce a new strategy in the model. It is a local interaction that the chasers do not get too close each other, where we call the chasers' local interaction (CLI) strategy. The result of comparisons of the two strategies shows that when the number of the chasers is relatively small compared to the number of the escapees, the trapping time by the CLI strategy is much shorter than that by the NOI strategy. On the other hand, when the number of the chasers is larger than that of the escapees, this advantage of the CLI strategy does not appear. Also, we find that although chasers form clusters (spatial aggregates of chasers) when we apply the NOI strategy, the clusters appear less when we apply the CLI strategy.

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

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1984-01-01

    A loss of magnetic flux through the free surface of a star into the surrounding space has important implications for the generation of the field within the star. The present investigation is concerned with the physics of the escape of net azimuthal flux from a star. The obtained results are used as a basis for the interpretation of some recent observations of the detailed behavior of magnetic fields emerging through the surface of the sun. The buoyancy of an isolated horizontal magnetic flux tube beneath the surface of a star causes the tube to rise at a rate comparable to the Alfven speed. The necessary conditions for escape of the flux are considered along with aspects of magnetic buoyancy, and the conditions on the sun. It appears that the observed retraction of bipolar magnetic fields at the end of their life at the surface is the one phenomenon which requires dynamical intervention. Attention is given to known dynamical effects which suppress the buoyant rise of an azimuthal magnetic field.

  15. The C. elegans touch response facilitates escape from predacious fungi.

    PubMed

    Maguire, Sean M; Clark, Christopher M; Nunnari, John; Pirri, Jennifer K; Alkema, Mark J

    2011-08-01

    Predator-prey interactions are vital determinants in the natural selection of behavioral traits. Gentle touch to the anterior half of the body of Caenorhabditis elegans elicits an escape response in which the animal quickly reverses and suppresses exploratory head movements [1, 2]. Here, we investigate the ecological significance of the touch response in predator-prey interactions between C. elegans and predacious fungi that catch nematodes using constricting hyphal rings. We show that the constricting rings of Drechslerella doedycoides catch early larval stages with a diameter similar to the trap opening. There is a delay between the ring entry and ring closure, which allows the animal to withdraw from the trap before being caught. Mutants that fail to suppress head movements in response to touch are caught more efficiently than the wild-type. This demonstrates that the coordination of motor programs allows C. elegans to smoothly retract from a fungal noose and evade capture. Our results suggest that selective pressures imposed by predacious fungi have shaped the evolution of C. elegans escape behavior. PMID:21802299

  16. Ultra-fast Escape of a Octopus-inspired Rocket

    NASA Astrophysics Data System (ADS)

    Weymouth, Gabriel; Triantafyllou, Michael

    2013-11-01

    The octopus, squid, and other cephalopods inflate with water and then release a jet to accelerate in the opposite direction. This escape mechanism is particularly interesting in the octopus because they become initially quite bluff, yet this does not hinder them in achieving impressive bursts of speed. We examine this somewhat paradoxical maneuver using a simple deflating spheroid model in both potential and viscous flow. We demonstrate that the dynamic reduction of the width of the body completely changes the flow and forces acting on the escaping rocket in three ways. First, a body which reduces in size can generate an added mass thrust which counteracts the added mass inertia. Second, the motion of the shrinking wall acts similar to suction on a static wall, reducing separation and drag forces in a viscous fluid, but that this effects depends on the rate of size change. Third, using a combination of these two features it is possible to initially load the fluid with kinetic energy when heavy and bluff and then recover that energy when streamlined and light, enabling ultra-fast accelerations. As a notable example, these mechanisms allow a shrinking spheroid rocket in a heavy inviscid fluid to achieve speeds greater than an identical rocket in the vacuum of space. Southampton Marine and Maritime Institute.

  17. A tale of two tumours: comparison of the immune escape strategies of contagious cancers.

    PubMed

    Siddle, Hannah V; Kaufman, Jim

    2013-09-01

    The adaptive immune system should prevent cancer cells passing from one individual to another, in much the same way that it protects against pathogens. However, in rare cases cancer cells do not die within a single individual, but successfully pass between individuals, escaping the adaptive immune response and becoming a contagious cancer. There are two naturally occurring contagious cancers, Devil Facial Tumour Disease (DFTD), found in Tasmanian devils, and Canine Transmissible Venereal Tumour (CTVT), found in dogs. Despite sharing an ability to pass as allografts, these cancers have a very different impact on their hosts. While DFTD causes 100% mortality among infected devils and has had a devastating impact on the devil population, CTVT co-exists with its host in a manner that does not usually cause death of the dog. Although immune evasion strategies for CTVT have been defined, why DFTD is not rejected as an allograft is not understood. We have made progress in revealing mechanisms of immune evasion for DFTD both in vitro and in vivo, and here we compare how DFTD and CTVT interact with their respective hosts and avoid rejection. Our findings highlight factors that may be important for the evolution of contagious cancers and cancer more generally. Perhaps most importantly, this work has opened up important areas for future research, including the effect of epigenetic factors on immune escape mechanisms and the basis of a vaccine strategy that may protect Tasmanian devils against DFTD. PMID:23200636

  18. A photoactivable multi-inhibitor nanoliposome for tumour control and simultaneous inhibition of treatment escape pathways

    PubMed Central

    Spring, Bryan Q.; Sears, R. Bryan; Zheng, Lei Zak; Mai, Zhiming; Watanabe, Reika; Sherwood, Margaret E.; Schoenfeld, David A.; Pogue, Brian W.; Pereira, Stephen P.; Villa, Elizabeth; Hasan, Tayyaba

    2015-01-01

    Nanoscale drug delivery vehicles can facilitate multimodal therapies of cancer by promoting tumour-selective drug release. However, few are effective because cancer cells develop ways to resist and evade treatment. Here, we introduce a photoactivatable multi-inhibitor nanoliposome (PMIL) that imparts light-induced cytotoxicity in synchrony with photo-initiated and sustained release of inhibitors that suppress tumour regrowth and treatment escape signalling pathways. The PMIL consists of a nanoliposome doped with a photoactivatable chromophore (benzoporphyrin derivative, BPD) in the lipid bilayer, and a nanoparticle containing cabozantinib (XL184)—a multikinase inhibitor—encapsulated inside. Near infrared tumour irradiation, following intravenous PMIL administration, triggers photodynamic damage of tumour cells and microvessels, and simultaneously initiates release of XL184 inside the tumour. A single PMIL treatment achieves prolonged tumour reduction in two mouse models and suppresses metastatic escape in an orthotopic pancreatic tumour model. The PMIL offers new prospects for cancer therapy by enabling spatiotemporal control of drug release whilst reducing systemic drug exposure and associated toxicities. PMID:26780659

  19. Early endosomal escape of a cyclic cell-penetrating peptide allows effective cytosolic cargo delivery.

    PubMed

    Qian, Ziqing; LaRochelle, Jonathan R; Jiang, Bisheng; Lian, Wenlong; Hard, Ryan L; Selner, Nicholas G; Luechapanichkul, Rinrada; Barrios, Amy M; Pei, Dehua

    2014-06-24

    Cyclic heptapeptide cyclo(FΦRRRRQ) (cFΦR4, where Φ is l-2-naphthylalanine) was recently found to be efficiently internalized by mammalian cells. In this study, its mechanism of internalization was investigated by perturbing various endocytic events through the introduction of pharmacologic agents and genetic mutations. The results show that cFΦR4 binds directly to membrane phospholipids, is internalized into human cancer cells through endocytosis, and escapes from early endosomes into the cytoplasm. Its cargo capacity was examined with a wide variety of molecules, including small-molecule dyes, linear and cyclic peptides of various charged states, and proteins. Depending on the nature of the cargos, they may be delivered by endocyclic (insertion of cargo into the cFΦR4 ring), exocyclic (attachment of cargo to the Gln side chain), or bicyclic approaches (fusion of cFΦR4 and cyclic cargo rings). The overall delivery efficiency (i.e., delivery of cargo into the cytoplasm and nucleus) of cFΦR4 was 4-12-fold higher than those of nonaarginine, HIV Tat-derived peptide, or penetratin. The higher delivery efficiency, coupled with superior serum stability, minimal toxicity, and synthetic accessibility, renders cFΦR4 a useful transporter for intracellular cargo delivery and a suitable system for investigating the mechanism of endosomal escape. PMID:24896852

  20. Local trichocyst exocytosis provides an efficient escape mechanism for Paramecium cells.

    PubMed

    Knoll, G; Haacke-Bell, B; Plattner, H

    1991-11-29

    More than 1000 secretory organelles (trichocysts) are docked at the plasma membrane of Paramecium cells. After stimulation, the trichocyst contents are expelled as needle-like structures in an exocytotic response. Neither the function nor the natural stimulus of trichocyst exocytosis are known in this well established system. Several hypotheses have been put forward during the last 100 years, but as yet, none has withstood critical experimental testing. Using video-aided light microscopic evaluation of the explosive trichocyst exocytosis we have obtained conclusive evidence for a defensive mechanism. When stimulated locally by a non-cytotoxic chemical secretagogue, cells were rapidly propelled in the opposite direction by vigorous local trichocyst discharge. The same phenomenon was observed during encounter with a predatory ciliate, Dileptus. Whereas exocytosis-competent paramecia escaped by rapid propulsion away from the attacking predator, cells non-competent for exocytosis were paralysed and engulfed. Thus, oriented locomotion by locally stimulated trichocyst exocytosis serves as a rapid escape mechanism of Paramecium. PMID:23194850

  1. Marine mollusc predator-escape behaviour altered by near-future carbon dioxide levels

    PubMed Central

    Watson, Sue-Ann; Lefevre, Sjannie; McCormick, Mark I.; Domenici, Paolo; Nilsson, Göran E.; Munday, Philip L.

    2014-01-01

    Ocean acidification poses a range of threats to marine invertebrates; however, the potential effects of rising carbon dioxide (CO2) on marine invertebrate behaviour are largely unknown. Marine gastropod conch snails have a modified foot and operculum allowing them to leap backwards rapidly when faced with a predator, such as a venomous cone shell. Here, we show that projected near-future seawater CO2 levels (961 µatm) impair this escape behaviour during a predator–prey interaction. Elevated-CO2 halved the number of snails that jumped from the predator, increased their latency to jump and altered their escape trajectory. Physical ability to jump was not affected by elevated-CO2 indicating instead that decision-making was impaired. Antipredator behaviour was fully restored by treatment with gabazine, a GABA antagonist of some invertebrate nervous systems, indicating potential interference of neurotransmitter receptor function by elevated-CO2, as previously observed in marine fishes. Altered behaviour of marine invertebrates at projected future CO2 levels could have potentially far-reaching implications for marine ecosystems. PMID:24225456

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

    NASA Astrophysics Data System (ADS)

    Parkinson, Christopher; Liemohn; Fang, Xiaohua

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

  3. Marine mollusc predator-escape behaviour altered by near-future carbon dioxide levels.

    PubMed

    Watson, Sue-Ann; Lefevre, Sjannie; McCormick, Mark I; Domenici, Paolo; Nilsson, Göran E; Munday, Philip L

    2014-01-01

    Ocean acidification poses a range of threats to marine invertebrates; however, the potential effects of rising carbon dioxide (CO2) on marine invertebrate behaviour are largely unknown. Marine gastropod conch snails have a modified foot and operculum allowing them to leap backwards rapidly when faced with a predator, such as a venomous cone shell. Here, we show that projected near-future seawater CO2 levels (961 µatm) impair this escape behaviour during a predator-prey interaction. Elevated-CO2 halved the number of snails that jumped from the predator, increased their latency to jump and altered their escape trajectory. Physical ability to jump was not affected by elevated-CO2 indicating instead that decision-making was impaired. Antipredator behaviour was fully restored by treatment with gabazine, a GABA antagonist of some invertebrate nervous systems, indicating potential interference of neurotransmitter receptor function by elevated-CO2, as previously observed in marine fishes. Altered behaviour of marine invertebrates at projected future CO2 levels could have potentially far-reaching implications for marine ecosystems. PMID:24225456

  4. A photoactivable multi-inhibitor nanoliposome for tumour control and simultaneous inhibition of treatment escape pathways

    NASA Astrophysics Data System (ADS)

    Spring, Bryan Q.; Bryan Sears, R.; Zheng, Lei Zak; Mai, Zhiming; Watanabe, Reika; Sherwood, Margaret E.; Schoenfeld, David A.; Pogue, Brian W.; Pereira, Stephen P.; Villa, Elizabeth; Hasan, Tayyaba

    2016-04-01

    Nanoscale drug delivery vehicles can facilitate multimodal therapies of cancer by promoting tumour-selective drug release. However, few are effective because cancer cells develop ways to resist and evade treatment. Here, we introduce a photoactivable multi-inhibitor nanoliposome (PMIL) that imparts light-induced cytotoxicity in synchrony with a photoinitiated and sustained release of inhibitors that suppress tumour regrowth and treatment escape signalling pathways. The PMIL consists of a nanoliposome doped with a photoactivable chromophore (benzoporphyrin derivative, BPD) in the lipid bilayer, and a nanoparticle containing cabozantinib (XL184)—a multikinase inhibitor—encapsulated inside. Near-infrared tumour irradiation, following intravenous PMIL administration, triggers photodynamic damage of tumour cells and microvessels, and simultaneously initiates release of XL184 inside the tumour. A single PMIL treatment achieves prolonged tumour reduction in two mouse models and suppresses metastatic escape in an orthotopic pancreatic tumour model. The PMIL offers new prospects for cancer therapy by enabling spatiotemporal control of drug release while reducing systemic drug exposure and associated toxicities.

  5. A two-component volatile atmosphere for Pluto. I. The bulk hydrodynamic escape regime

    SciTech Connect

    Trafton, L. )

    1990-08-01

    The seasonal effects on Pluto's atmosphere of a simplified system of CH{sub 4} and N{sub 2} saturated over a solid solution are investigated, and the results are compared with previous CH{sub 4} models. It is found that bulk escape occurs for CH{sub 4} mole fractions less than 0.7 of Pluto's volatile reservoir. Greater CH{sub 4} abundance leads to diffusive separation during the escape of both species and an atmospheric mixing ratio of about Xc(0). If Xc(0) is in the range 0.02-0.10, Pluto's atmosphere remains largely intact at aphelion rather than virtually freezing out as it does for Xc(0) greater than 0.3 or less than 0.001, or form an atmosphere with only a single volatile gas. An upper limit for the CH{sub 4} mixing ratio is about 0.07 if N{sub 2} is the second gas. On the other hand, CH{sub 4} is the dominant surface constituent of the volatile deposit if Xc(0) is greater than 0.0001. 29 refs.

  6. Prey fish escape by sensing the bow wave of a predator.

    PubMed

    Stewart, William J; Nair, Arjun; Jiang, Houshuo; McHenry, Matthew J

    2014-12-15

    Prey fish possess a remarkable ability to sense and evade an attack from a larger fish. Despite the importance of these events to the biology of fishes, it remains unclear how sensory cues stimulate an effective evasive maneuver. Here, we show that larval zebrafish (Danio rerio) evade predators using an escape response that is stimulated by the water flow generated by an approaching predator. Measurements of the high-speed responses of larvae in the dark to a robotic predator suggest that larvae respond to the subtle flows in front of the predator using the lateral line system. This flow, known as the bow wave, was visualized and modeled with computational fluid dynamics. According to the predictions of the model, larvae direct their escape away from the side of their body exposed to more rapid flow. This suggests that prey fish use a flow reflex that enables predator evasion by generating a directed maneuver at high speed. These findings demonstrate a sensory-motor mechanism that underlies a behavior that is crucial to the ecology and evolution of fishes. PMID:25520384

  7. Deformation-driven fluid escape in the Levant Basin, offshore southern Israel

    NASA Astrophysics Data System (ADS)

    Eruteya, Ovie Emmanuel; Waldmann, Nicolas; Reshef, Moshe; Ben-Avraham, Zvi

    2016-04-01

    Submarine fluid emissions are global phenomena, which can be inferred from the presence of seafloor morphologies (e.g. pockmarks, mud volcanoes) occurring in various geological settings. However, despite the Levant Basin been a prolific hydrocarbon province, only a paucity of fluid escape morphologies have been identified on the present-day seafloor. In this study, we present a detailed analysis of a newly available high-resolution 3D seismic reflection dataset from offshore southern Israel. Evidences of subsurface fluid plumbing and escape are manifested here as present-day seafloor pockmarks, paleo-pockmarks, pipe structures and enhanced reflectivity patterns. Interestingly, these pockmarks are situated on and around bathymetric highs, which are ridges related to the Palmachim Disturbance. Our initial results show the fluid flow structures are spatially localized above a region of complex evaporites evacuation at depth, and likewise proximal to a shallower region characterized by high amplitude reflectors. The latter may be evidences for a shallow gas system. Our initial hypothesis proposes a dual shallow-source driven focused fluid flow system. Yet, we favour a deeper Messinian plumbing system driving fluid flow across the overburden in the study area. Corroborating this are fault systems characterized near the pipes feeding the seafloor pockmarks and paleo-pockmark, detaching in the upper Messinian evaporite. We further suggest that a combined supra-salt deformation system arising from the evacuation of the Messinian evaporites coupled with gravitational tectonics are in charge of modulating focused fluid flow. Under this scenario the emplaced mass transport complex acts as a transient reservoir for fluid flow, dewatering under deformation and channelling fluids towards the seafloor for expulsion. However, the contributions from microbially-generated methane in the shallow Quaternary overburden associated with the channel-levee complex cannot be neglected.

  8. A simulation study of emergency lunar escape to orbit using several simplified manual guidance and control techniques

    NASA Technical Reports Server (NTRS)

    Middleton, D. B.; Hurt, G. J., Jr.

    1971-01-01

    A fixed-base piloted simulator investigation has been made of the feasibility of using any of several manual guidance and control techniques for emergency lunar escape to orbit with very simplified, lightweight vehicle systems. The escape-to-orbit vehicles accommodate two men, but one man performs all of the guidance and control functions. Three basic attitude-control modes and four manually executed trajectory-guidance schemes were used successfully during approximately 125 simulated flights under a variety of conditions. These conditions included thrust misalinement, uneven propellant drain, and a vehicle moment-of-inertia range of 250 to 12,000 slugs per square foot. Two types of results are presented - orbit characteristics and pilot ratings of vehicle handling qualities.

  9. Near-infrared-light-based nano-platform boosts endosomal escape and controls gene knockdown in vivo.

    PubMed

    Jayakumar, Muthu Kumara Gnanasammandhan; Bansal, Akshaya; Huang, Kai; Yao, Risheng; Li, Bing Nan; Zhang, Yong

    2014-05-27

    Current nanoparticle-based gene delivery techniques face two major limitations, namely, endosomal degradation and poor cytosolic release of the nanoparticles and nonspecificity of treatment. These limitations can be overcome with certain light-based techniques, such as photochemical internalization to enable endosomal escape of the delivered nanoparticles and light-controlled gene expression to overcome the nonspecific effects. However, these techniques require UV/visible light, which is either phototoxic and/or has low tissue penetration capabilities, thus preventing their use in deep tissues in a clinical setting. In an effort to overcome these barriers, we have successfully demonstrated a light-based gene delivery system that significantly boosts cytosolic gene delivery, with precise control over gene expression and the potential for use in nonsuperficial tissues. Core-shell fluorescent upconversion nanoparticles excited by highly penetrating near-infrared radiation and emitting simultaneously in the ultraviolet and visible ranges were synthesized and used as remote nanotransducers to simultaneously activate endosomal escape and gene knockdown. Gene knockdown using photomorpholinos was enhanced as much as 30% in vitro compared to the control without endosomal escape facilitation. A similar trend was seen in vivo in a murine melanoma model, demonstrating the enormous clinical potential of this system. PMID:24730360

  10. Escape through a time-dependent hole in the doubling map

    NASA Astrophysics Data System (ADS)

    Livorati, André L. P.; Georgiou, Orestis; Dettmann, Carl P.; Leonel, Edson D.

    2014-05-01

    We investigate the escape dynamics of the doubling map with a time-periodic hole. Ulam's method was used to calculate the escape rate as a function of the control parameters. We consider two cases, oscillating or breathing holes, where the sides of the hole are moving in or out of phase respectively. We find out that the escape rate is well described by the overlap of the hole with its images, for holes centered at periodic orbits.

  11. The Martian escape rate as a function of upstream solar conditions

    NASA Astrophysics Data System (ADS)

    Ramstad, R.; Barabash, S.; Futaana, Y.; Nilsson, H.; Holmstrom, M.

    2014-12-01

    We investigate potential factors for influence on the Martian heavy ion escape rate (Q) by integrating Mars Express ASPERA-3/IMA heavy ion flux measurements in the Martian tail, taken at similar (binned) solar wind density (n), velocity (v) and EUV radiation flux (FEUV) upstream conditions. In the best sampled cases, with v and FEUV constrained, we find a statistically significant decrease in heavy ion escape rate with increased solar wind density. An empirical-analytical model for atmospheric escape is developed by fitting calculated escape rates to all sufficiently sampled solar conditions, indicating an overall negative dependence on solar wind density.

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

    NASA Astrophysics Data System (ADS)

    Volkov, A. N.

    2016-06-01

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

  13. Sources of polar plume ion escape on Mars

    NASA Astrophysics Data System (ADS)

    Curry, S.; Liemohn, M.; Ma, Y.; Fang, X.

    2011-10-01

    The Mars pick-up ion transport model has been developed to study the relative role of kinetic processes on ion transport through near-Mars space. Mars does not have a strong, intrinsic dipole magnetic field and consequently the solar wind directly interacts with the dayside upper atmosphere causing particles to be stripped away from the atmosphere. The Mars Pickup Ion Model calculates the detailed ion velocity space distribution (VSD) through a background magnetic and electric field model at specific locations. The main objective of this work is to robustly probe the sources of polar plume ion escape relative to loss down the central tail. Because the VSDs are non-Maxwellian and reveal asymmetric, non-gyrotropic features, our simulation can investigate the role of kinetics in polar plume loss without using the Maxwellian assumptions of current MHD models.

  14. Test of time: what if little Albert had escaped?

    PubMed

    Field, Andy P; Nightingale, Zoë C

    2009-04-01

    Watson and Rayner's (1920) ;Little Albert' experiment has become one of the most famous studies in psychology. It is a staple of many general psychology textbooks and is part of the very fabric of the discipline's folklore. Despite this fame, the study has been widely criticized in the nearly 90 years since it was published for its lack of methodological rigour. This article attempts to evaluate the contribution of the ;little Albert' study to modern clinical psychology by speculating on what theories and treatments of child anxiety would look like in a parallel universe in which the study never took place because ;little Albert' escaped from the hospital in which Watson tested him. PMID:19293325

  15. Extended narrow escape problem: Boundary homogenization-based analysis

    PubMed Central

    Berezhkovskii, A. M.; Barzykin, A. V.

    2016-01-01

    Diffusion of particles in confined domains with absorbing spots on the otherwise reflecting boundaries is ubiquitous in nature and technology. Because of nonuniform boundary conditions, the problem of finding the mean first passage time (MFPT) of the particle to one of the spots is extremely complicated. We show how the difficulties can be overcome by means of boundary homogenization when the domain is a circular disk whose boundary contains n nonoverlapping identical absorbing arcs, which may occupy an arbitrary fraction of the boundary. We find the MFPT as a function of the fraction of the boundary occupied by the arcs (i) for n evenly spaced arcs and (ii) for two arcs arbitrarily located on the boundary. As the arc length tends to zero, our approximate solution reduces to the known asymptotic formula for the MFPT rigorously derived in studies devoted of the narrow escape problem. PMID:20866572

  16. Fatal leaflet escape in an Edwards TEKNA aortic prosthesis.

    PubMed

    Pfeiffer, Heidi; Bertolini, Julia; Scheld, Hans Heinrich; Brinkmann, Bernd

    2006-01-01

    The case is reported of a 26-year-old male patient who died eight years after the replacement of an aortic valve with a bileaflet mechanical valve (TEKNA; Edwards, USA). Following prosthesis implantation, the patient had been in a good state of health, and his death occurred unexpectedly. Forensic autopsy revealed a leaflet escape, with two fragments of the leaflet being found bilaterally in the common iliac arteries. Death occurred due to an acute cardiac insufficiency. Immunohistochemical investigations revealed fresh myocardial fiber necroses. Stereomicroscopic and scanning electron microscopic investigations demonstrated surface erosions of the leaflet. Although the valve was withdrawn from the market in June 2000, it had previously been implanted in over 18,000 patients. Thus, from a clinical viewpoint, the question of using a prophylactic replacement in affected patients must be discussed. PMID:16480019

  17. Aggregation increases prey survival time in group chase and escape

    NASA Astrophysics Data System (ADS)

    Yang, Sicong; Jiang, Shijie; Jiang, Li; Li, Geng; Han, Zhangang

    2014-08-01

    Recently developed chase-and-escape models have addressed a fascinating pursuit-and-evasion problem that may have both theoretical significance and potential applications. We introduce three aggregation strategies for the prey in a group chase model on a lattice. Simulation results show that aggregation dramatically increases the group survival time, even allowing immortal prey. The average survival time τ and the aggregation probability P have a power-law dependence of \\tau \\sim {{(1-P)}^{-1}} for P\\in [0.9,0.997]. With increasing numbers of predators, there is still a phase transition. When the number of predators is less than the critical point value, the prey group survival time increases significantly.

  18. Escaping Antiangiogenic Therapy: Strategies Employed by Cancer Cells.

    PubMed

    Pinto, Mauricio P; Sotomayor, Paula; Carrasco-Avino, Gonzalo; Corvalan, Alejandro H; Owen, Gareth I

    2016-01-01

    Tumor angiogenesis is widely recognized as one of the "hallmarks of cancer". Consequently, during the last decades the development and testing of commercial angiogenic inhibitors has been a central focus for both basic and clinical cancer research. While antiangiogenic drugs are now incorporated into standard clinical practice, as with all cancer therapies, tumors can eventually become resistant by employing a variety of strategies to receive nutrients and oxygen in the event of therapeutic assault. Herein, we concentrate and review in detail three of the principal mechanisms of antiangiogenic therapy escape: (1) upregulation of compensatory/alternative pathways for angiogenesis; (2) vasculogenic mimicry; and (3) vessel co-option. We suggest that an understanding of how a cancer cell adapts to antiangiogenic therapy may also parallel the mechanisms employed in the bourgeoning tumor and isolated metastatic cells delivering responsible for residual disease. Finally, we speculate on strategies to adapt antiangiogenic therapy for future clinical uses. PMID:27608016

  19. Molecular motor with a built-in escapement device

    NASA Astrophysics Data System (ADS)

    Oshanin, G.; Klafter, J.; Urbakh, M.

    2004-10-01

    We study the dynamics of a classical particle in a one-dimensional potential composed of two identical spatially periodic components, one of which is externally driven by a random force. We demonstrate that, under certain conditions, the particle may move unidirectionally with a constant velocity, despite the fact that the average external force is zero. We show that the physical mechanism underlying such a phenomenon resembles the work of an escapement-type device in watches; upon reaching a certain level, random fluctuations exercise a locking function creating points of irreversibility which the particle cannot overpass. Repeated (randomly) in each cycle, this results in a saltatory ballistic-type motion. In the overdamped limit, we work out simple analytical estimates for the particle's terminal velocity. Our analytical results are in a very good agreement with Monte Carlo results.

  20. ESCAP holds expert group meeting on population issues facing adolescents.

    PubMed

    1997-01-01

    This article summarizes the activities at the ESCAP Population Division Expert Group Meeting on Adolescents that was held during September-October 1997 in Bangkok, Thailand. The meeting was a follow-up to the 1994 International Conference on Population and Development (ICPD). The meeting considered 1) the ICPD recommendations; 2) the recommendations contained in the Jakarta Plan of Action on Human Resource Development; and 3) the Proposals for Action on Human Resources Development for Youth in Asia and the Pacific. Participants included about 25 people from Australia, Bangladesh, China, India, Indonesia, Philippines, Sri Lanka, and Thailand. The conference relied on 8 invited experts, two resource persons, advisors from the UNFPA Country Support Team for East and Southeast Asia, and representatives of UNFPA, the Population Council, and the East-West Center. A concern was the declining age of menarche of girls in the ESCAP region and the increasing age of marriage. During the time of menarche and marriage, girls are migrating and moving away from their family and community in rural areas. Family structure and relationships are changing. Increases are observed in adolescent premarital sexual activity, the incidence of sexually transmitted diseases, substance abuse, teenage pregnancy, and abortion. The mass media and information technologies have both a positive and a negative influence on adolescents. Parent-child communication exchanges and teacher-student exchanges are "less than ideal." Old traditions and practices change slower than people change. Boys and girls are affected differently by the sociocultural and economic environment. The societal norms set expectations for behavior that may conflict with individual beliefs and practices. Changes brought by globalization and rapid economic growth provide greater opportunity for young girls and women to obtain employment and autonomy. PMID:12293003

  1. Flare Particle Escape in 3D Solar Eruptive Events

    NASA Astrophysics Data System (ADS)

    Antiochos, Spiro K.; Masson, Sophie; DeVore, C. R.

    2015-04-01

    Among the most important, but least understood forms of space weather are the so-called Impulsive Solar Energetic Particle (SEP) events, which can be especially hazardous to deep-space astronauts. These energetic particles are generally believed to be produced by the flare reconnection that is the primary driver of solar eruptive events (SEE). A key point is that in the standard model of SEEs, the particles should remain trapped in the coronal flare loops and in the ejected plasmoid, the CME. However, flare-accelerated particles frequently reach the Earth long before the CME does. In previous 2.5D calculations we showed how the external reconnection that is an essential element of the breakout model for CME initiation could lead to the escape of flare-accelerated particles. The problem, however, is that in 2.5D this reconnection also tends to destroy the plasmoid, which disagrees with the observation that SEP events are often associated with well-defined plasmoids at 1 AU known as “magnetic clouds”. Consequently, we have extended our model to a fully 3D topology that includes a multi-polar coronal field suitable for a breakout SEE near a coronal hole region. We performed high-resolution 3D MHD numerical simulations with the Adaptively Refined MHD Solver (ARMS). Our results demonstrate that the model allows for the effective escape of energetic particles from deep within an ejecting well-defined plasmoid. We show how the complex interactions between the flare and breakout reconnection reproduce all the main observational features of SEEs and SEPs. We discuss the implications of our calculations for the upcoming Solar Orbiter and Solar Probe Plus missions, which will measure SEEs and SEPs near the Sun, thereby, mitigating propagation effects.This research was supported, in part, by the NASA SR&T and TR&T Programs.

  2. Initiating a watch list for Ebola virus antibody escape mutations.

    PubMed

    Miller, Craig R; Johnson, Erin L; Burke, Aran Z; Martin, Kyle P; Miura, Tanya A; Wichman, Holly A; Brown, Celeste J; Ytreberg, F Marty

    2016-01-01

    The 2014 Ebola virus (EBOV) outbreak in West Africa is the largest in recorded history and resulted in over 11,000 deaths. It is essential that strategies for treatment and containment be developed to avoid future epidemics of this magnitude. With the development of vaccines and antibody-based therapies using the envelope glycoprotein (GP) of the 1976 Mayinga strain, one important strategy is to anticipate how the evolution of EBOV might compromise these efforts. In this study we have initiated a watch list of potential antibody escape mutations of EBOV by modeling interactions between GP and the antibody KZ52. The watch list was generated using molecular modeling to estimate stability changes due to mutation. Every possible mutation of GP was considered and the list was generated from those that are predicted to disrupt GP-KZ52 binding but not to disrupt the ability of GP to fold and to form trimers. The resulting watch list contains 34 mutations (one of which has already been seen in humans) at six sites in the GP2 subunit. Should mutations from the watch list appear and spread during an epidemic, it warrants attention as these mutations may reflect an evolutionary response from the virus that could reduce the effectiveness of interventions such as vaccination. However, this watch list is incomplete and emphasizes the need for more experimental structures of EBOV interacting with antibodies in order to expand the watch list to other epitopes. We hope that this work provokes experimental research on evolutionary escape in both Ebola and other viral pathogens. PMID:26925318

  3. Initiating a watch list for Ebola virus antibody escape mutations

    PubMed Central

    Johnson, Erin L.; Burke, Aran Z.; Martin, Kyle P.; Miura, Tanya A.; Wichman, Holly A.; Brown, Celeste J.

    2016-01-01

    The 2014 Ebola virus (EBOV) outbreak in West Africa is the largest in recorded history and resulted in over 11,000 deaths. It is essential that strategies for treatment and containment be developed to avoid future epidemics of this magnitude. With the development of vaccines and antibody-based therapies using the envelope glycoprotein (GP) of the 1976 Mayinga strain, one important strategy is to anticipate how the evolution of EBOV might compromise these efforts. In this study we have initiated a watch list of potential antibody escape mutations of EBOV by modeling interactions between GP and the antibody KZ52. The watch list was generated using molecular modeling to estimate stability changes due to mutation. Every possible mutation of GP was considered and the list was generated from those that are predicted to disrupt GP-KZ52 binding but not to disrupt the ability of GP to fold and to form trimers. The resulting watch list contains 34 mutations (one of which has already been seen in humans) at six sites in the GP2 subunit. Should mutations from the watch list appear and spread during an epidemic, it warrants attention as these mutations may reflect an evolutionary response from the virus that could reduce the effectiveness of interventions such as vaccination. However, this watch list is incomplete and emphasizes the need for more experimental structures of EBOV interacting with antibodies in order to expand the watch list to other epitopes. We hope that this work provokes experimental research on evolutionary escape in both Ebola and other viral pathogens. PMID:26925318

  4. New ESCAP-type resist with enhanced etch resistance and its application to future DRAM and logic devices

    NASA Astrophysics Data System (ADS)

    Conley, Will; Brunsvold, William R.; Buehrer, Fred; DellaGuardia, Ronald; Dobuzinsky, David; Farrell, Timothy R.; Ho, Hok; Katnani, Ahmad D.; Keller, Robin; Marsh, James T.; Muller, Paul; Nunes, Ronald; Ng, Hung Y.; Oberschmidt, James M.; Pike, Michael; Ryan, Deborah; Cotler-Wagner, Tina; Schulz, Ron; Ito, Hiroshi; Hofer, Donald C.; Breyta, Gregory; Fenzel-Alexander, Debra; Wallraff, Gregory M.; Opitz, Juliann; Thackeray, James W.; Barclay, George G.; Cameron, James F.; Lindsay, Tracy K.; Cronin, Michael F.; Moynihan, Matthew L.; Nour, Sassan; Georger, Jacque H., Jr.; Mori, Mike; Hagerty, Peter; Sinta, Roger F.; Zydowsky, Thomas M.

    1997-07-01

    This new photoresist system extends the capability of the ESCAP platform previously discussed. (1) This resist material features a modified ESCAP type 4-hydroxystyrene-t-butyl acrylate polymer system which is capable of annealing due to the increased stability of the t-butyl ester blocking group. The resist based on this polymer system exhibits excellent delay stability and enhanced etch resistance versus previous DUV resists, APEX and UV2HS. Improved stabilization of chemically amplified photoresist images can be achieved through reduction of film volume by film densification. When the host polymer provides good thermal stability the soft bake conditions can be above or near the Tg (glass transition) temperature of the polymer. The concept of annealing (film densification) can significantly improve the environmental stability of the photoresist system. Improvements in the photoacid generator, processing conditions and overall formulation coupled with high NA (numerical aperture) exposure systems, affords linear lithography down to 0.15 micrometer for isolated lines with excellent post exposure delay stability. In this paper, we discuss the UV4 and UV5 photoresist systems based on the ESCAP materials platform. The resist based on this polymer system exhibits excellent delay stability and enhanced etch resistance versus APEX-E and UV2HS. Due to lower acrylate content, the Rmax for this system can be tuned for feature-type optimization. We demonstrate sub-0.25 micrometer process window for isolated lines using these resists on a conventional exposure tool with chrome on glass masks. We also discuss current use for various device levels including gate structures for advanced microprocessor designs. Additional data will be provided on advanced DRAM applications for 0.25 micrometer and sub-0.25 micrometer programs.

  5. The density and thermal structure of Pluto's atmosphere and associated escape processes and rates

    NASA Astrophysics Data System (ADS)

    Zhu, Xun; Strobel, Darrell F.; Erwin, Justin T.

    2014-01-01

    The original Strobel et al. (Strobel, D.F., Zhu, X., Summers, M.E., Stevens, M.E. [1996]. Icarus 120, 266-289) model for Pluto's stratospheric density and thermal structure is augmented to include a radial momentum equation with radial velocity associated with atmospheric escape of N2 and in the energy equation to also include the solar far ultraviolet and extreme ultraviolet (FUV-EUV) heating in the upper atmosphere and adiabatic cooling due to hydrodynamic expansion. The inclusion of radial velocity introduces important negative feedback processes such as increased solar heating leading to enhanced escape rate and higher radial velocity with stronger adiabatic cooling in the upper atmosphere accompanied by reduced temperature. The coupled set of equations for mass, momentum, and energy are solved subject to two types of upper boundary conditions that represent two different descriptions of atmospheric escape: Jeans escape and hydrodynamic escape. For the former which is physically correct, an enhanced Jeans escape rate is prescribed at the exobase and parameterized according to the direct simulation Monte Carlo kinetic model results. For the latter, the atmosphere is assumed to remain a fluid to infinity with the escape rate determined by the temperature and density at the transonic point subject to vanishing temperature and pressure at infinity. For Pluto, the two escape descriptions approach the same limit when the exobase coincides with the transonic level and merge to a common escape rate ˜1028 N2 s-1 under elevated energy input. For Pluto's current atmosphere, the hydrodynamic approach underestimates the escape rate by about 13%. In all cases, the escape rate is limited by the solar FUV-EUV power input.

  6. Escape tectonics and the extrusion of Alaska: Past, present, and future

    USGS Publications Warehouse

    Redfield, T.F.; Scholl, D. W.; Fitzgerald, P.G.; Beck, M.E., Jr.

    2007-01-01

    The North Pacific Rim is a tectonically active plate boundary zone parts of which may be characterized as a laterally moving orogenic stream. Crustal blocks are transported along large-magnitude strike-slip faults in western Canada and central Alaska toward the Aleutian-Bering Sea subduction zones. Throughout much of the Cenozoic, at and west of its Alaskan nexus, the North Pacific Rim orogenic Stream (NPRS) has undergone tectonic escape. During transport, relatively rigid blocks acquired paleomagnetic rotations and fault-juxtaposed boundaries while flowing differentially through the system, from their original point of accretion and entrainment toward the free face defined by the Aleutian-Bering Sea subduction zones. Built upon classical terrane tectonics, the NPRS model provides a new framework with which to view the mobilistic nature of the western North American plate boundary zone. ?? 2007 The Geological Society of America.

  7. Use of escape and reward in the management of young children during dental treatment.

    PubMed Central

    Allen, K D; Stokes, T F

    1987-01-01

    A reinforced practice procedure was used to facilitate cooperative behavior in five children, aged 3 to 6 years, during dental treatment. In a multiple baseline design across subjects, the children were rewarded with escape, inexpensive stickers, and praise for cooperative behavior in the presence of the sights, sounds, and some sensations of the dental instruments prior to actual dental treatment. Direct observations of disruptive behavior via a 15-s interval recording system indicated baseline levels as high as 90% were reduced to less than 15% by the final treatment visit. In addition, the procedure was effective in reducing overall heart rate and blood pressure reactivity to dental treatment. All children were rated by the involved dental professionals as more cooperative and relaxed following exposure to reinforced practice. PMID:3429360

  8. On the roles of escape erosion and the viscous relaxation of craters on Pluto

    NASA Astrophysics Data System (ADS)

    Stern, S. Alan; Porter, Simon; Zangari, Amanda

    2015-04-01

    Pluto and its satellites will be the most distant objects ever reconnoitered when NASA's New Horizons spacecraft conducts its intensive flyby of this system in 2015. The size-frequency distribution (SFD) of craters on the surfaces in the Pluto system have long been expected to provide a useful measure of the size distribution of Kuiper Belt Objects (KBOs) down to much smaller size scales than presently observed. However, currently predicted escape rates of Pluto's atmosphere suggest that of order one-half to several kilometers of nitrogen ice has been removed from Pluto's surface over geologic time. Because this range of depths is comparable to or greater than most expected crater depths on Pluto, one might expect that many craters on Pluto's surface may have been removed or degraded by this process, biasing the observed crater SFD relative to the production-function crater SFD. Further, if Pluto's surface volatile layer is comparable to or deeper than crater depths, and if the viscosity of this layer surface ice is low like the viscosity of pure N2 ice at Pluto's measured 35 K surface temperature (or as low as the viscosity of CH4 ice at warmer but plausible temperatures on isolated pure-CH4 surfaces on Pluto), then craters on Pluto may also have significantly viscously relaxed, also potentially biasing the observed crater SFD and surface crater retention age. Here we make a first exploration of how these processes can affect the displayed cratering record on Pluto. We find that Pluto's surface may appear to be younger owing to these effects than it actually is. We also find that by comparing Pluto's cratering record to Charon's, it may be possible to estimate the total loss depth of material from Pluto's surface over geologic time, and therefore to estimate Pluto's time-averaged escape rate.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  10. 50 CFR Figure 12 to Part 223 - Escape Opening & Cover Dimensions for 71-inch TED

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 50 Wildlife and Fisheries 9 2011-10-01 2011-10-01 false Escape Opening & Cover Dimensions for 71-inch TED 12 Figure 12 to Part 223 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL... ANADROMOUS SPECIES Pt. 223, Fig. 12 Figure 12 to Part 223—Escape Opening & Cover Dimensions for 71-inch...

  11. 50 CFR Figure 12 to Part 223 - Escape Opening & Cover Dimensions for 71-inch TED

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false Escape Opening & Cover Dimensions for 71-inch TED 12 Figure 12 to Part 223 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL... ANADROMOUS SPECIES Pt. 223, Fig. 12 Figure 12 to Part 223—Escape Opening & Cover Dimensions for 71-inch...

  12. Computer Self-Efficacy, Competitive Anxiety and Flow State: Escaping from Firing Online Game

    ERIC Educational Resources Information Center

    Hong, Jon-Chao; Pei-Yu, Chiu; Shih, Hsiao-Feng; Lin, Pei-Shin; Hong, Jon-Chao

    2012-01-01

    Flow state in game playing affected by computer self-efficacy and game competitive anxiety was studied. In order to examine the effect of those constructs with high competition, this study select "Escaping from firing online game" which require college students to escape from fire and rescue people and eliminate the fire damage along the way of…

  13. Pilot Escape from Spinning Airplanes as Determined from Free-spinning-tunnel Tests

    NASA Technical Reports Server (NTRS)

    Scher, Stanley H

    1951-01-01

    Procedure for pilot escape from spinning airplanes has been determined by means of tests in which pilot escape was simulated from 21 airplane models spinning in the Langley 20-foot free-spinning tunnel. The results in general indicated that the pilot should bail out of the outboard side. Calculated centripetal accelerations acting on the pilot during a spin are presented.

  14. Reducing Escape Behavior and Increasing Task Completion with Functional Communication Training, Extinction, and Response Chaining.

    ERIC Educational Resources Information Center

    Lalli, Joseph S.; And Others

    1995-01-01

    Functional communication training, extinction, and response chaining decreased escape-maintained aberrant behavior and increased task participation of 3 youth, ages 10 through 15, with moderate mental retardation, 2 of whom also had autism. Task escape was contingent on verbally responding and completing task steps. Behavior chaining also…

  15. Identification of genes escaping X inactivation by allelic expression analysis in a novel hybrid mouse model

    PubMed Central

    Berletch, Joel B.; Ma, Wenxiu; Yang, Fan; Shendure, Jay; Noble, William S.; Disteche, Christine M.; Deng, Xinxian

    2015-01-01

    X chromosome inactivation (XCI) is a female-specific mechanism that serves to balance gene dosage between the sexes whereby one X chromosome in females is inactivated during early development. Despite this silencing, a small portion of genes escape inactivation and remain expressed from the inactive X (Xi). Little is known about the distribution of escape from XCI in different tissues in vivo and about the mechanisms that control tissue-specific differences. Using a new binomial model in conjunction with a mouse model with identifiable alleles and skewed X inactivation we are able to survey genes that escape XCI in vivo. We show that escape from X inactivation can be a common feature of some genes, whereas others escape in a tissue specific manner. Furthermore, we characterize the chromatin environment of escape genes and show that expression from the Xi correlates with factors associated with open chromatin and that CTCF co-localizes with escape genes. Here, we provide a detailed description of the experimental design and data analysis pipeline we used to assay allele-specific expression and epigenetic characteristics of genes escaping X inactivation. The data is publicly available through the GEO database under ascension numbers GSM1014171, GSE44255, and GSE59779. Interpretation and discussion of these data are included in a previously published study (Berletch et al., 2015) [1]. PMID:26693509

  16. The Effects of Fixed-Time Escape on Inappropriate and Appropriate Classroom Behavior

    ERIC Educational Resources Information Center

    Waller, Rachael D.; Higbee, Thomas S.

    2010-01-01

    Few studies have explored the effects of fixed-time (FT) reinforcement on escape-maintained behavior of students in a classroom setting. We measured the effects of an FT schedule on the disruptive and appropriate academic behaviors of 2 junior high students in a public school setting. Results demonstrated that FT escape from tasks resulted in a…

  17. 33 CFR 149.691 - What means of escape are required?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... and secondary means of escape. Each of these means must either: (1) Comply with 46 CFR 108.151; or (2... in 29 CFR 1910.2, for use in evacuating the port. (b) A primary means of escape consists of a fixed... (CONTINUED) DEEPWATER PORTS DEEPWATER PORTS: DESIGN, CONSTRUCTION, AND EQUIPMENT Design and Equipment...

  18. 14 CFR 25.810 - Emergency egress assist means and escape routes.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... exits located over the wing and, if the place on the airplane structure at which the escape route... Provisions § 25.810 Emergency egress assist means and escape routes. (a) Each non over-wing Type A, Type B or Type C exit, and any other non over-wing landplane emergency exit more than 6 feet from the ground...

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

    ERIC Educational Resources Information Center

    McNeil, Cheryl Bodiford; And Others

    1994-01-01

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

  20. The Efficacy of Noncontingent Escape for Decreasing Children's Disruptive Behavior during Restorative Dental Treatment

    ERIC Educational Resources Information Center

    O'Callaghan, Patrick M.; Allen, Keith D.; Powell, Shawn; Salama, Fouad

    2006-01-01

    We evaluated the effectiveness of a dentist-implemented behavioral intervention in which brief escape from dental treatment was provided on a regular basis, independent of the child's behavior. Within a multiple baseline design across subjects, 5 children, ages 4 to 7 years, were provided with temporary escape from dental treatment on a fixed-time…

  1. Vertical T cell immunodominance and epitope entropy determine HIV-1 escape

    PubMed Central

    Liu, Michael K.P.; Hawkins, Natalie; Ritchie, Adam J.; Ganusov, Vitaly V.; Whale, Victoria; Brackenridge, Simon; Li, Hui; Pavlicek, Jeffrey W.; Cai, Fangping; Rose-Abrahams, Melissa; Treurnicht, Florette; Hraber, Peter; Riou, Catherine; Gray, Clive; Ferrari, Guido; Tanner, Rachel; Ping, Li-Hua; Anderson, Jeffrey A.; Swanstrom, Ronald; B, CHAVI Core; Cohen, Myron; Karim, Salim S. Abdool; Haynes, Barton; Borrow, Persephone; Perelson, Alan S.; Shaw, George M.; Hahn, Beatrice H.; Williamson, Carolyn; Korber, Bette T.; Gao, Feng; Self, Steve; McMichael, Andrew; Goonetilleke, Nilu

    2012-01-01

    HIV-1 accumulates mutations in and around reactive epitopes to escape recognition and killing by CD8+ T cells. Measurements of HIV-1 time to escape should therefore provide information on which parameters are most important for T cell–mediated in vivo control of HIV-1. Primary HIV-1–specific T cell responses were fully mapped in 17 individuals, and the time to virus escape, which ranged from days to years, was measured for each epitope. While higher magnitude of an individual T cell response was associated with more rapid escape, the most significant T cell measure was its relative immunodominance measured in acute infection. This identified subject-level or “vertical” immunodominance as the primary determinant of in vivo CD8+ T cell pressure in HIV-1 infection. Conversely, escape was slowed significantly by lower population variability, or entropy, of the epitope targeted. Immunodominance and epitope entropy combined to explain half of all the variability in time to escape. These data explain how CD8+ T cells can exert significant and sustained HIV-1 pressure even when escape is very slow and that within an individual, the impacts of other T cell factors on HIV-1 escape should be considered in the context of immunodominance. PMID:23221345

  2. Treatment of Escape-Maintained Behavior with Positive Reinforcement: The Role of Reinforcement Contingency and Density

    ERIC Educational Resources Information Center

    Ingvarsson, Einar T.; Hanley, Gregory P.; Welter, Katherine M.

    2009-01-01

    Functional analyses suggested that the disruptive behavior of three preschool children was maintained by escape from demands. While keeping the escape contingency intact, we conducted (a) a density analysis in which the children earned preferred items for task completion according to two schedules that varied in reinforcement density, and (b) a…

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

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

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

  4. 33 CFR 149.691 - What means of escape are required?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false What means of escape are required? 149.691 Section 149.691 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DEEPWATER PORTS DEEPWATER PORTS: DESIGN, CONSTRUCTION, AND EQUIPMENT Design and Equipment Means of Escape § 149.691 What means...

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

    ERIC Educational Resources Information Center

    Hammond, Jennifer L.

    2009-01-01

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

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

    PubMed

    Kanou, Masamichi; Matsuyama, Akane; Takuwa, Hiroyuki

    2014-09-01

    We investigated the effects of visual information on wind-evoked escape behavior in the cricket, Gryllus bimaculatus. Most agitated crickets were found to retreat into a shelter made of cardboard installed in the test arena within a short time. As this behavior was thought to be a type of escape, we confirmed how a visual image of a shelter affected wind-evoked escape behavior. Irrespective of the brightness of the visual background (black or white) or the absence or presence of a shelter, escape jumps were oriented almost 180° opposite to the source of the air puff stimulus. Therefore, the direction of wind-evoked escape depends solely depended on the direction of the stimulus air puff. In contrast, the turning direction of the crickets during the escape was affected by the position of the visual image of the shelter. During the wind-evoked escape jump, most crickets turned in the direction in which a shelter was presented. This behavioral nature is presumably necessary for crickets to retreat into a shelter within a short time after their escape jump. PMID:25186926

  7. Evaluating the potential ecological effects of transgene escape and persistence in constructed plant communities

    EPA Science Inventory

    To date, published studies with herbicide tolerant transgenic crops have failed to demonstrate that transgene escape to wild relatives results in more competitive hybrids. However, it is important to consider transgene escape in the context of the types of traits, which will lik...

  8. Plasma clouds and snowplows: Bulk plasma escape from Mars observed by MAVEN

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    We present initial Mars Atmosphere and Volatile EvolutioN (MAVEN) observations and preliminary interpretation of bulk plasma loss from Mars. MAVEN particle and field measurements show that planetary heavy ions derived from the Martian atmosphere can escape in the form of discrete coherent structures or "clouds." The ions in these clouds are unmagnetized or weakly magnetized, have velocities well above the escape speed, and lie directly downstream from magnetic field amplifications, suggesting a "snowplow" effect. This postulated escape process, similar to that successfully used to explain the dynamics of active gas releases in the solar wind and terrestrial magnetosheath, relies on momentum transfer from the shocked solar wind protons to the planetary heavy ions, with the electrons and magnetic field acting as intermediaries. Fluxes of planetary ions on the order of 107 cm-2 s-1 can escape by this process, and if it operates regularly, it could contribute 10-20% of the current ion escape from Mars.

  9. Hydrogen and deuterium loss from the terrestrial atmosphere - A quantitative assessment of nonthermal escape fluxes

    NASA Technical Reports Server (NTRS)

    Yung, Yuk L.; Wen, Jun-Shan; Moses, Julianne I.; Landry, Bridget M.; Allen, Mark; Hsu, Kuang-Jung

    1989-01-01

    A comprehensive one-dimensional photochemical model extending from the middle atmosphere (50 km) to the exobase (432 km) has been used to study the escape of hydrogen and deuterium from the earth's atmosphere. The model incorporates recent advances in chemical kinetics as well as atmospheric observations by satellites, especially the Atmosphere Explorer C satellite. The results suggest that the escape fluxes of both H and D are limited by the upward transport of total hydrogen and total deuterium at the homopause. About one fourth of total hydrogen escape is thermal, the rest being nonthermal. It is shown that escape of D is nonthermal and that charge exchange and polar wind are important mechanisms for the nonthermal escape of H and D.

  10. Modeling magnetospheric energetic particle escape across Earth's magnetopause as observed by the MMS mission

    NASA Astrophysics Data System (ADS)

    Mauk, Barry H.; Cohen, Ian J.; Westlake, Joseph H.; Anderson, Brian J.

    2016-05-01

    A longstanding puzzle is that the escape of magnetospheric energetic particles (greater than tens of keV) across Earth's magnetopause into the magnetosheath is common irrespective of conditions thought to engender magnetic reconnection and boundary normal magnetic fields. Multiple causes for escape have been invoked, including interactions with strong gradients, wave scattering, boundary dynamics, and boundary normal fields. Here we tackle only part of the problem by developing a relatively simple kinetic model including critical features not utilized in previous models. We find that particles can often completely escape without invoking waves or unmodeled magnetosheath structures for both northwardly and southwardly magnetosheath fields. Because multiple means of escape are found to be available, the particles are hard to completely contain, consistent with observations. The model also predicts specific pitch angle evolution signatures that uniquely identify boundary normal field-enabled escape, now reported in a companion paper as observed by the Magnetospheric Multiscale (MMS) mission.

  11. Dentist-implemented contingent escape for management of disruptive child behavior.

    PubMed

    Allen, K D; Loiben, T; Allen, S J; Stanley, R T

    1992-01-01

    We evaluated the effectiveness of a dentist-implemented intervention in which brief escape from dental treatment was provided to manage disruptive child behavior during restorative dental treatment. Within a multiple baseline design across subjects, 4 children, aged 3 to 7 years, were provided temporary escape from dental treatment contingent upon brief periods of cooperative behavior. Disruptive behavior decreased when the appropriate escape contingency was used at least 80% of the time. The escape contingency required no more time than traditional management procedures (e.g., tell-show-do, reprimands and loud commands, restraint) to bring disruptive behavior under control. Independent ratings by two dentists provided social validation of the efficacy of the escape contingency. PMID:1429316

  12. Progesterone After Estradiol Modulates Shuttle-Cage Escape by Facilitating Volition

    PubMed Central

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

    2015-01-01

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

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

    PubMed

    Chen, Zhen; Li, Yang; Liu, Xianbin

    2016-06-01

    Noise induced escape from the domain of attraction of a nonhyperbolic chaotic attractor in a periodically excited nonlinear oscillator is investigated. The general mechanism of the escape in the weak noise limit is studied in the continuous case, and the fluctuational path is obtained by statistical analysis. Selecting the primary homoclinic tangency as the initial condition, the action plot is presented by parametrizing the set of escape trajectories and the global minimum gives rise to the optimal path. Results of both methods show good agreements. The entire process of escape is discussed in detail step by step using the fluctuational force. A structure of hierarchical heteroclinic crossings of stable and unstable manifolds of saddle cycles is found, and the escape is observed to take place through successive jumps through this deterministic hierarchical structure. PMID:27368777

  14. Effects of PAF antagonists on renal vascular escape and tachyphylaxis in perfused rabbit kidney.

    PubMed

    Ferreira, M G; Braquet, P; Fonteles, M C

    1991-12-01

    Renal vascular escape is a physiological phenomenon of adaptation that occurs in vascular smooth muscle. It has been described in many preparations subjected to electrical stimulation or treated with vasoactive agents, such as noreprinephrine, angiotensin and vasopressin. We have recently demonstrated that a naturally occurring ginkgolide (BN 52021), which is a PAF antagonist, was able to block norepinephrine-induced escape in perfused rabbit kidney. In the present work other PAF antagonists, such as the ginkgolides BN 52022 and BN 52024, and the synthetic compounds 48740 RP and WEB 2086, were tested. Their effects on renal vascular escape, perfusion pressure and tachyphylaxis were evaluated. They all were shown to block the escape. Among the ginkgolides, BN 52024 is generally recognized as one of the weaker PAF antagonists. However, in spite of this, BN 52024 was able to significantly and simultaneously block renal vascular escape and tachyphylaxis in perfused rabbit kidney infused with norepinephrine. PMID:1819726

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

    NASA Astrophysics Data System (ADS)

    Chen, Zhen; Li, Yang; Liu, Xianbin

    2016-06-01

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

  16. Historical analysis of sockeye salmon growth among populations affected by the Exxon Valdez oil spill and large spawning escapements. Exxon Valdez oil spill restoration project 86048-BAA: Final report

    SciTech Connect

    Ruggerone, G.T.; Rogers, D.E.

    1998-12-01

    Adult sockeye salmon scales, which provide an index of annual salmon growth in fresh and marine waters during 1965--1997, were measured to examine the effects on growth and adult returns of large spawning escapements influenced by the Exxon Valdez oil spill. Scale growth in freshwater was significantly reduced by the large 1989 spawning escapements in the Kenai River system, Red Lake, and Akalura Lake, but not in Chignik Lake. These data suggest that sockeye growth in freshwater may be less stable following the large escapement. Furthermore, the observations of large escapement adversely affecting growth of adjacent brood years of salmon has important implications for stock-recruitment modeling. In Prince William Sound, Coghill Lake sockeye salmon that migrated through oil-contaminated waters did not exhibit noticeably reduced marine growth, but a model was developed that might explain low adult returns in recent years.

  17. The First Billion Years project: the escape fraction of ionizing photons in the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Paardekooper, Jan-Pieter; Khochfar, Sadegh; Dalla Vecchia, Claudio

    2015-08-01

    Protogalaxies forming in low-mass dark matter haloes are thought to provide the majority of ionizing photons needed to reionize the Universe, due to their high escape fractions of ionizing photons. We study how the escape fraction in high-redshift galaxies relates to the physical properties of the halo in which the galaxies form, by computing escape fractions in more than 75 000 haloes between redshifts 27 and 6 that were extracted from the First Billion Years project, high-resolution cosmological hydrodynamical simulations of galaxy formation. We find that the main constraint on the escape fraction is the gas column density in a radius of 10 pc around the stellar populations, causing a strong mass dependence of the escape fraction. The lower potential well in haloes with M200 ≲ 108 M⊙ results in low column densities that can be penetrated by radiation from young stars (age <5 Myr). In haloes with M200 ≳ 108 M⊙ supernova feedback is important, but only ˜30 per cent of the haloes in this mass range have an escape fraction higher than 1 per cent. We find a large range of escape fractions in haloes with similar properties, caused by different distributions of the dense gas in the halo. This makes it very hard to predict the escape fraction on the basis of halo properties and results in a highly anisotropic escape fraction. The strong mass dependence, the large spread and the large anisotropy of the escape fraction may strongly affect the topology of reionization and is something current models of cosmic reionization should strive to take into account.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  19. Upper limits to the fractionation of isotopes due to atmospheric escape: Implications for potential 14N/15N in Pluto's atmosphere

    NASA Astrophysics Data System (ADS)

    Mandt, K.; Mousis, O.

    2014-12-01

    Formation and evolution of the solar system is studied in part using stable isotope ratios that are presumed to be primordial, or representative of conditions in the protosolar Nebula. Comets, meteorites and giant planet atmospheres provide measurements that can reasonably be presumed to represent primordial conditions while the terrestrial planets, Pluto and Saturn's moon Titan have atmospheres that have evolved over the history of the solar system. The stable isotope ratios measured in these atmospheres are, therefore, first a valuable tool for evaluating the history of atmospheric escape and once escape is constrained can provide indications of conditions of formation. D/H ratios in the atmosphere of Venus provide indications of the amount of water lost from Venus over the history of the solar system, while several isotope ratios in the atmosphere of Mars provide evidence for long-term erosion of the atmosphere. We have recently demonstrated that the nitrogen ratios, 14N/15N, in Titan's atmosphere cannot evolve significantly over the history of the solar system and that the primordial ratio for Titan must have been similar to the value recently measured for NH3 in comets. This implies that the building blocks for Titan formed in the protosolar nebula rather than in the warmer subnebula surrounding Saturn at the end of its formation. Our result strongly contrasts with works showing that 14N/15N in the atmosphere of Mars can easily fractionate from the terrestrial value to its current value due to escape processes within the lifetime of the solar system. The difference between how nitrogen fractionates in Mars and Titan's atmospheres presents a puzzle for the fractionation of isotopes in an atmosphere due to atmospheric escape. Here, we present a method aiming at determining an upper limit to the amount of fractionation allowed to occur due to escape, which is a function of the escape flux and the column density of the atmospheric constituent. Through this

  20. Modified Advanced Crew Escape Suit Intravehicular Activity Suit for Extravehicular Activity Mobility Evaluations

    NASA Technical Reports Server (NTRS)

    Watson, Richard D.

    2014-01-01

    The use of an intravehicular activity (IVA) suit for a spacewalk or extravehicular activity (EVA) was evaluated for mobility and usability in the Neutral Buoyancy Laboratory (NBL) environment at the Sonny Carter Training Facility near NASA Johnson Space Center in Houston, Texas. The Space Shuttle Advanced Crew Escape Suit was modified to integrate with the Orion spacecraft. The first several missions of the Orion Multi-Purpose Crew Vehicle will not have mass available to carry an EVA-specific suit; therefore, any EVA required will have to be performed by the Modified Advanced Crew Escape Suit (MACES). Since the MACES was not designed with EVA in mind, it was unknown what mobility the suit would be able to provide for an EVA or whether a person could perform useful tasks for an extended time inside the pressurized suit. The suit was evaluated in multiple NBL runs by a variety of subjects, including crewmembers with significant EVA experience. Various functional mobility tasks performed included: translation, body positioning, tool carrying, body stabilization, equipment handling, and tool usage. Hardware configurations included with and without Thermal Micrometeoroid Garment, suit with IVA gloves and suit with EVA gloves. Most tasks were completed on International Space Station mock-ups with existing EVA tools. Some limited tasks were completed with prototype tools on a simulated rocky surface. Major findings include: demonstrating the ability to weigh-out the suit, understanding the need to have subjects perform multiple runs prior to getting feedback, determining critical sizing factors, and need for adjusting suit work envelope. Early testing demonstrated the feasibility of EVA's limited duration and limited scope. Further testing is required with more flight-like tasking and constraints to validate these early results. If the suit is used for EVA, it will require mission-specific modifications for umbilical management or Primary Life Support System integration

  1. Scorpion Sheds ‘Tail’ to Escape: Consequences and Implications of Autotomy in Scorpions (Buthidae: Ananteris)

    PubMed Central

    Mattoni, Camilo I.; García-Hernández, Solimary; Botero-Trujillo, Ricardo; Ochoa, José A.; Ojanguren-Affilastro, Andrés A.; Pinto-da-Rocha, Ricardo; Prendini, Lorenzo

    2015-01-01

    Autotomy, the voluntary shedding or detachment of a body part at a determined cleavage plane, is a common anti-predation defense mechanism in several animal taxa, including arthropods. Among arachnids, autotomy has been observed in harvestmen, mites, and spiders, always involving the loss of legs. Autotomy of the opisthosoma (abdomen) was recently reported in a single species of the Neotropical buthid scorpion genus Ananteris Thorell, 1891, but few details were revealed. Based on observations in the field and laboratory, examination of material in museum collections, and scanning electron microscopy, we document autotomy of the metasoma (the hind part of the opisthosoma, or ‘tail’) in fourteen species of Ananteris. Autotomy is more common in males than females, and has not been observed in juveniles. When the scorpion is held by the metasoma, it is voluntarily severed at the joints between metasomal segments I and II, II and III, or III and IV, allowing the scorpion to escape. After detachment, the severed metasoma moves (twitches) automatically, much like the severed tail of a lizard or the severed leg of a spider, and reacts to contact, even attempting to sting. The severed surface heals rapidly, scar tissue forming in five days. The lost metasomal segments and telson cannot be regenerated. Autotomy of the metasoma and telson results in permanent loss of the posterior part of the scorpion’s digestive system (the anus is situated posteriorly on metasomal segment V) and the ability to inject venom by stinging. After autotomy, scorpions do not defecate and can only capture small prey items. However, males can survive and mate successfully for up to eight months in the laboratory. In spite of diminished predation ability after autotomy, survival allows males to reproduce. Autotomy in Ananteris therefore appears to be an effective, adaptive, anti-predation escape mechanism. PMID:25629529

  2. Cooling Properties of the Shuttle Advanced Crew Escape Spacesuit: Results of an Environmental Chamber Experiment

    NASA Technical Reports Server (NTRS)

    Hamilton, Douglas; Gillis, David; Bue, Grant; Son, Chan; Norcross, Jason; Kuznetz, Larry; Chapman, Kirt; Chhipwadia, Ketan; McBride, Tim

    2008-01-01

    The shuttle crew wears the Advanced Crew Escape Spacesuit (ACES) to protect themselves from cabin decompression and to support bail out during landing. ACES is cooled by a liquid-cooled garment (LCG) that interfaces to a heat exchanger that dumps heat into the cabin. The ACES outer layer is made of Gore-Tex(Registered TradeMark), permitting water vapor to escape while containing oxygen. The crew can only lose heat via insensible water losses and the LCG. Under nominal landing operations, the average cabin temperature rarely exceeds 75 F, which is adequate for the ACES to function. Problem A rescue shuttle will need to return 11 crew members if the previous mission suffers a thermal protection system failure, preventing it from returning safely to Earth. Initial analysis revealed that 11 crew members in the shuttle will increase cabin temperature at wheel stop above 80 F, which decreases the ACES ability to keep crew members cool. Air flow in the middeck of the shuttle is inhomogeneous and some ACES may experience much higher temperatures that could cause excessive thermal stress to crew members. Methods A ground study was conducted to measure the cooling efficiency of the ACES at 75 F, 85 F, and 95 F at 50% relative humidity. Test subjects representing 5, 50, and 95 percentile body habitus of the astronaut corps performed hand ergometry keeping their metabolic rate at 400, 600, and 800 BTU/hr for one hour. Core temperature was measured by rectal probe and skin, while inside and outside the suit. Environmental chamber wall and cooling unit inlet and outlet temperatures were measured using high-resolution thermistors ( 0.2 C). Conclusions Under these test conditions, the ACES was able to protect the core temperature of all test subjects, however thermal stress due to high insensible losses and skin temperature and skin heat flow may impact crew performance. Further research should be performed to understand the impact on cognitive performance.

  3. mPGES-1 deletion impairs aldosterone escape and enhances sodium appetite

    PubMed Central

    Jia, Zhanjun; Aoyagi, Toshinori; Kohan, Donald E.

    2010-01-01

    Aldosterone (Aldo) is a major sodium-retaining hormone that reduces renal sodium excretion and also stimulates sodium appetite. In the face of excess Aldo, the sodium-retaining action of this steroid is overridden by an adaptive regulatory mechanism, a phenomenon termed Aldo escape. The underlying mechanism of this phenomenon is not well defined but appeared to involve a number of natriuretic factors such prostaglandins (PGs). Here, we investigated the role of microsomal prostaglandin E synthase-1 (mPGES-1) in the response to excess Aldo. A 14-day Aldo infusion at 0.35 mg·kg−1·day−1 via an osmotic minipump in conjunction with normal salt intake did not produce obvious disturbances in fluid metabolism in WT mice as suggested by normal sodium and water balance, plasma sodium concentration, hematocrit, and body weight, despite the evidence of a transient sodium accumulation on days 1 or 2. In a sharp contrast, the 14-day Aldo treatment in mPGES-1 knockoute (KO) mice led to increased sodium and water balance, persistent reduction of hematocrit, hypernatremia, and body weight gain, all evidence of fluid retention. The escaped wild-type (WT) mice displayed a remarkable increase in urinary PGE2 excretion in parallel with coinduction of mPGES-1 in the proximal tubules, accompanied by a remarkable, widespread downregulation of renal sodium and water transporters. The increase in urinary PGE2 excretion together with the downregulation of renal sodium and water transporters were all significantly blocked in the KO mice. Interestingly, compared with WT controls, the KO mice exhibited consistent increases in sodium and water intake during Aldo infusion. Together, these results suggest an important role of mPGES-1 in antagonizing the sodium-retaining action of Aldo at the levels of both the central nervous system and the kidney. PMID:20335314

  4. Salmon subsidize an escape from a size spectrum

    PubMed Central

    Hocking, Morgan D.; Dulvy, Nicholas K.; Reynolds, John D.; Ring, Richard A.; Reimchen, Thomas E.

    2013-01-01

    A general rule in ecology is that the abundance of species or individuals in communities sharing a common energy source decreases with increasing body size. However, external energy inputs in the form of resource subsidies can modify this size spectrum relationship. Here, we provide the first test of how a marine resource subsidy can affect size spectra of terrestrial communities, based on energy derived from Pacific salmon carcasses affecting a forest soil community beside streams in western Canada. Using both species-based and individual approaches, we found size structuring in this forest soil community, and transient community-wide doubling of standing biomass in response to energy pulses from Pacific salmon carcasses. One group of species were clear outliers in the middle of the size spectrum relationship: larval calliphorid and dryomyzid flies, which specialize on salmon carcasses, and which showed a tenfold increase in biomass in their size class when salmon were available. Thus, salmon subsidize their escape from the size spectrum. These results suggest that using a size-based perspective of resource subsidies can provide new insights into the structure and functioning of food webs. PMID:23282994

  5. Habituation of Backward Escape Swimming in the Marbled Crayfish.

    PubMed

    Kasuya, Azusa; Nagayama, Toshiki

    2016-02-01

    In the present study, we performed behavioral analyses of the habituation of backward escape swimming in the marbled crayfish, Procambarus fallax. Application of rapid mechanical stimulation to the rostrum elicited backward swimming following rapid abdominal flexion of crayfish. Response latency was very short-tens of msec-suggesting that backward swimming is mediated by MG neurons. When stimulation was repeated with 10 sec interstimulus intervals the MG-like tailflip did not occur, as the animals showed habituation. Retention of habituation was rather short, with most animals recovering from habituation within 10 min. Previous experience of habituation was remembered and animals habituated faster during a second series of experiments with similar repetitive stimuli. About half the number of stimulus trials was necessary to habituate in the second test compared to the first test. This promotion of habituation was observed in animals with delay periods of rest within 60 min following the first habituation. After 90 min of rest from the first habitation, animals showed a similar time course for the second habituation. With five stimuli at 15 min interval during 90 min of the rest, trained animals showed rapid habituation, indicating reinforcement of the memory of previous experiments. Crayfish also showed dishabituation when mechanical stimulation was applied to the tail following habituation. PMID:26853863

  6. Nosema Tolerant Honeybees (Apis mellifera) Escape Parasitic Manipulation of Apoptosis

    PubMed Central

    Kurze, Christoph; Le Conte, Yves; Dussaubat, Claudia; Erler, Silvio; Kryger, Per; Lewkowski, Oleg; Müller, Thomas; Widder, Miriam; Moritz, Robin F. A.

    2015-01-01

    Apoptosis is not only pivotal for development, but also for pathogen defence in multicellular organisms. Although numerous intracellular pathogens are known to interfere with the host’s apoptotic machinery to overcome this defence, its importance for host-parasite coevolution has been neglected. We conducted three inoculation experiments to investigate in the apoptotic respond during infection with the intracellular gut pathogen Nosema ceranae, which is considered as potential global threat to the honeybee (Apis mellifera) and other bee pollinators, in sensitive and tolerant honeybees. To explore apoptotic processes in the gut epithelium, we visualised apoptotic cells using TUNEL assays and measured the relative expression levels of subset of candidate genes involved in the apoptotic machinery using qPCR. Our results suggest that N. ceranae reduces apoptosis in sensitive honeybees by enhancing inhibitor of apoptosis protein-(iap)-2 gene transcription. Interestingly, this seems not be the case in Nosema tolerant honeybees. We propose that these tolerant honeybees are able to escape the manipulation of apoptosis by N. ceranae, which may have evolved a mechanism to regulate an anti-apoptotic gene as key adaptation for improved host invasion. PMID:26445372

  7. Dynamical correlations in the escape strategy of Influenza A virus

    NASA Astrophysics Data System (ADS)

    Taggi, L.; Colaiori, F.; Loreto, V.; Tria, F.

    2013-03-01

    The evolutionary dynamics of human Influenza A virus presents a challenging theoretical problem. An extremely high mutation rate allows the virus to escape, at each epidemic season, the host immune protection elicited by previous infections. At the same time, at each given epidemic season a single quasi-species, that is a set of closely related strains, is observed. A non-trivial relation between the genetic (i.e., at the sequence level) and the antigenic (i.e., related to the host immune response) distances can shed light into this puzzle. In this paper we introduce a model in which, in accordance with experimental observations, a simple interaction rule based on spatial correlations among point mutations dynamically defines an immunity space in the space of sequences. We investigate the static and dynamic structure of this space and we discuss how it affects the dynamics of the virus-host interaction. Interestingly we observe a staggered time structure in the virus evolution as in the real Influenza evolutionary dynamics.

  8. Escape of a knot from a DNA molecule in flow

    NASA Astrophysics Data System (ADS)

    Renner, Benjamin; Doyle, Patrick

    2014-03-01

    Macroscale knots are an everyday occurrence when trying to unravel an unorganized flexible string (e.g. an iPhone cord taken out of your pocket). In nature, knots are found in proteins and viral capsid DNA, and the properties imbued by their topologies are thought to have biological significance. Unlike their macroscale counterparts, thermal fluctuations greatly influence the dynamics of polymer knots. Here, we use Brownian Dynamics simulations to study knot diffusion along a linear polymer chain. The model is parameterized to dsDNA, a model polymer used in previous simulation and experimental studies of knot dynamics. We have used this model to study the process of knot escape and transport along a dsDNA strand extended by an elongational flow. For a range of knot topologies and flow strengths, we show scalings that result in collapse of the data onto a master curve. We show a topologically mediated mode of transport coincides with observed differences in rates of knot transport, and we provide a simple mechanistic explanation for its effect. We anticipate these results will build on the growing body of fundamental studies of knotted polymers and inform future experimental study. This work is supported by the Singapore-MIT Alliance for Research and Technology (SMART) and National Science Foundation (NSF) grant CBET-0852235.

  9. Narrow escape for a stochastically gated Brownian ligand.

    PubMed

    Reingruber, Jürgen; Holcman, David

    2010-02-17

    Molecular activation in cellular microdomains is usually characterized by a forward binding rate, which is the reciprocal of the arrival time of a ligand to a key target. Upon chemical interactions or conformational changes, a Brownian ligand may randomly switch between different states, and when target activation is possible in a specific state only, switching can significantly alter the activation process. The main goal of this paper is to study the mean time for a switching ligand to activate a small substrate, modelled as the time to exit a microdomain through a small absorbing window on the surface. We present the equations for the mean sojourn times the ligand spends in each state, and study the escape process with switching between two states in dimension one and three. When the ligand can exit in only one of the two states, we find that switching always decreases its sojourn time in the state where it can exit. Moreover, the fastest exit is obtained when the ligand diffuses most of the time in the state with the maximal diffusion coefficient, although this may imply that it spends most of the time 'hidden' in the state where it cannot exit. We discuss the physical mechanisms responsible for this apparent paradox. In dimension three we confirm our results with Brownian simulations. Finally, we suggest possible applications in cellular biology. PMID:21389363

  10. Failure of rats to escape from a potentially lethal microwave field

    SciTech Connect

    Carroll, D.R.; Levinson, D.M.; Justesen, D.R.; Clarke, R.L.

    1980-01-01

    Ocularly pigmented rats, all mature females of the Long-Evans strain, were repeatedly presented an opportunity to escape from an intense 918-MHz field (whole-body dose rate . 60 mW/g) to a field of lower intensity (40, 30, 20, or 2 mW/g) by performing a simple locomotor response. Other rats could escape 800-microamperemeter faradic shock to the feet and tail by performing the same response in the same milieu, a multimode cavity. None of 20 irradiated rats learned to associate entry into a visually well-demarcated area of the cavity with immediate reduction of dose rate, in spite of field-induced elevations of body temperature to levels that exceeded 41 degrees C and would have been lethal but for a limit on durations of irradiation. In contrast, all of ten rats motivated by faradic shock rapidly learned to escape. The failure of escape learning by irradiated animals probably arose from deficiencies of motivation and, especially, sensory feedback. Whole-body hyperthermia induced by a multipath field may lack the painful or directional sensory properties that optimally promote the motive to escape. Moreover, a decline of body temperature after an escape-response-contingent reduction of field strength will be relatively slow because of the large thermal time constants of mammalian tissues. Without timely sensory feedback, which is an essential element of negative reinforcement, stimulus-response associability would be imparied, which could retard or preclude learning of an escape response.

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

    NASA Technical Reports Server (NTRS)

    Hartle, Richard

    1999-01-01

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

  12. Escape response of the crab Neohelice to computer generated looming and translational visual danger stimuli.

    PubMed

    Scarano, Florencia; Tomsic, Daniel

    2014-01-01

    Historically, arthropod behavior has been considered to be a collection of simple, automaton-like routines commanded by domain-specific brain modules working independently. Nowadays, it is evident that the extensive behavioral repertoire of these animals and its flexibility necessarily imply far more complex abilities than originally assumed. For example, even what was thought to be a straightforward behavior of crabs, the escape response to visual danger stimuli, proved to involve a number of sequential stages, each of which implying decisions made on the bases of stimulus and contextual information. Inspired in previous observations on how the stimulus trajectory can affect the escape response of crabs in the field, we investigated the escape response to images of objects approaching directly toward the crab (looming stimuli: LS) or moving parallel to it (translational stimuli: TS) in the laboratory. Computer simulations of moving objects were effective to elicit escapes. LS evoked escapes with higher probability and intensity (speed and distance of escape) than TS, but responses started later. In addition to the escape run, TS also evoked a defensive response of the animal with its claws. Repeated presentations of TS or LS were both capable of inducing habituation. Results are discussed in connection with the possibilities offered by crabs to investigate the neural bases of behaviors occurring in the natural environment. PMID:25220660

  13. Light Primes the Escape Response of the Calanoid Copepod, Calanus finmarchicus

    PubMed Central

    Fields, David M.; Shema, Steven D.; Browman, Howard I.; Browne, Thomas Q.; Skiftesvik, Anne Berit

    2012-01-01

    The timing and magnitude of an escape reaction is often the determining factor governing a copepod’s success at avoiding predation. Copepods initiate rapid and directed escapes in response to fluid signals created by predators; however little is known about how copepods modulate their behavior in response to additional sensory input. This study investigates the effect of light level on the escape behavior of Calanus finmarchicus. A siphon flow was used to generate a consistent fluid signal and the behavioral threshold and magnitude of the escape response was quantified in the dark and in the light. The results show that C. finmarchicus initiated their escape reaction further from the siphon and traveled with greater speed in the light than in the dark. However, no difference was found in the escape distance. These results suggest that copepods use information derived from multiple sensory inputs to modulate the sensitivity and strength of the escape in response to an increase risk of predation. Population and IBM models that predict optimal vertical distributions of copepods in response to visual predators need to consider changes in the copepod's behavioral thresholds when predicting predation risk within the water column. PMID:22761834

  14. Do malaria parasites manipulate the escape behaviour of their avian hosts? An experimental study.

    PubMed

    Garcia-Longoria, Luz; Møller, Anders P; Balbontín, Javier; de Lope, Florentino; Marzal, Alfonso

    2015-12-01

    Escape behaviour is the behaviour that birds and other animals display when already caught by a predator. An individual exhibiting higher intensity of such anti-predator behaviour could have greater probabilities of escape from predators. Parasites are known to affect different aspects of host behaviour to increase their own fitness. Vector-transmitted parasites such as malaria parasites should gain by manipulating their hosts to enhance the probability of transmission. Several studies have shown that malaria parasites can manipulate their vectors leading to increased transmission success. However, little is known about whether malaria parasites can manipulate escape behaviour of their avian hosts thereby increasing the spread of the parasite. Here we used an experimental approach to explore if Plasmodium relictum can manipulate the escape behaviour of one of its most common avian hosts, the house sparrow Passer domesticus. We experimentally tested whether malaria parasites manipulate the escape behaviour of their avian host. We showed a decrease in the intensity of biting and tonic immobility after removal of infection with anti-malaria medication compared to pre-experimental behaviour. These outcomes suggest that infected sparrows performed more intense escape behaviour, which would increase the likelihood of individuals escaping from predators, but also benefit the parasite by increasing its transmission opportunities. PMID:26337268

  15. Manipulation of an Innate Escape Response in Drosophila: Photoexcitation of acj6 Neurons Induces the Escape Response

    PubMed Central

    Manoli, Devanand S.; Zhang, Feng; Deisseroth, Karl; Baker, Bruce S.; Scott, Matthew P.

    2009-01-01

    Background The genetic analysis of behavior in Drosophila melanogaster has linked genes controlling neuronal connectivity and physiology to specific neuronal circuits underlying a variety of innate behaviors. We investigated the circuitry underlying the adult startle response, using photoexcitation of neurons that produce the abnormal chemosensory jump 6 (acj6) transcription factor. This transcription factor has previously been shown to play a role in neuronal pathfinding and neurotransmitter modality, but the role of acj6 neurons in the adult startle response was largely unknown. Principal Findings We show that the activity of these neurons is necessary for a wild-type startle response and that excitation is sufficient to generate a synthetic escape response. Further, we show that this synthetic response is still sensitive to the dose of acj6 suggesting that that acj6 mutation alters neuronal activity as well as connectivity and neurotransmitter production. Results/Significance These results extend the understanding of the role of acj6 and of the adult startle response in general. They also demonstrate the usefulness of activity-dependent characterization of neuronal circuits underlying innate behaviors in Drosophila, and the utility of integrating genetic analysis into modern circuit analysis techniques. PMID:19340304

  16. Escape of H and D from Mars' Atmosphere and the Evolution of its Crustal Water Reservoirs

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    The evolution of water on Mars involves preferential escape of hydrogen over deuterium, producing its deuterium rich atmosphere with a D/H ratio 5.2 times that of terrestrial water. In the past decade, several estimates have been made of the magnitudes of current and ancient crustal water reservoirs on Mars that freely exchange with its atmosphere. Some of the differences in the magnitudes of the reservoirs are influenced by differences in the following basic parameters: composition of H, D, H2 and HD at the exobase; thermal history of the atmosphere; escape mechanisms; and the D/H ratio of earlier epochs as inferred from meteorites. The dominant escape mechanism used in the estimates is Jeans escape. However, the Jeans escape flux is enhanced considerably when atmospheric winds and rotation are applied at the exobase . This constraint is of particular importance because the enhancement of the D escape flux can be an order of magnitude greater than the enhancement of the H escape flux. This preferential enhancement of the D escape flux over that of H means that a great deal more H must escape (than in the case without winds and rotation) to attain the same D/H ratio in the today's atmosphere. Another new constraint on reservoir magnitudes comes from the recent interpretation of Martian meteorite data, which suggests that the D/H ratio was 2 times that of terrestrial water at the end of the heavy bombardment period (1). These two constraints together lead to larger current and ancient crustal water reservoirs. Applying Rayleigh fractionation, new estimates of the sizes of the water reservoirs are made using the above constraints along with plausible values for hydrogen and deuterium densities, temperatures, wind speeds and rotation rates at the exobase.

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

    PubMed Central

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

    2012-01-01

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

  18. Escape of H and D From Mars' Atmosphere and the Evolution of its Crustal Water Reservoirs

    NASA Astrophysics Data System (ADS)

    Hartle, R. E.

    2001-12-01

    The evolution of water on Mars involves preferential escape of hydrogen over deuterium, producing its deuterium rich atmosphere with a D/H ratio 5.2 times that of terrestrial water. In the past decade, several estimates have been made of the magnitudes of current and ancient crustal water reservoirs on Mars that freely exchange with its atmosphere. Some of the differences in the magnitudes of the reservoirs are influenced by differences in the following basic parameters: composition of H, D, H2 and HD at the exobase; thermal history of the atmosphere; escape mechanisms; and the D/H ratio of earlier epochs as inferred from meteorites. The dominant escape mechanism used in the estimates is Jeans escape. However, the Jeans escape flux is enhanced considerably when atmospheric winds and rotation are applied at the exobase . This constraint is of particular importance because the enhancement of the D escape flux can be an order of magnitude greater than the enhancement of the H escape flux. This preferential enhancement of the D escape flux over that of H means that a great deal more H must escape (than in the case without winds and rotation) to attain the same D/H ratio in the today's atmosphere. Another new constraint on reservoir magnitudes comes from the recent interpretation of Martian meteorite data, which suggests that the D/H ratio was 2 times that of terrestrial water at the end of the heavy bombardment period (1). These two constraints together lead to larger current and ancient crustal water reservoirs. Applying Rayleigh fractionation, new estimates of the sizes of the water reservoirs are made using the above constraints along with plausible values for hydrogen and deuterium densities, temperatures, wind speeds and rotation rates at the exobase. (1) Leshin, L. A., 27, 2017-2020, 2000.

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

    PubMed

    Corcoran, Aaron J; Conner, William E

    2016-09-01

    What determines whether fleeing prey escape from attacking predators? To answer this question, biologists have developed mathematical models that incorporate attack geometries, pursuit and escape trajectories, and kinematics of predator and prey. These models have rarely been tested using data from actual predator-prey encounters. To address this problem, we recorded multi-camera infrared videography of bat-insect interactions in a large outdoor enclosure. We documented 235 attacks by four Myotis volans bats on a variety of moths. Bat and moth flight trajectories from 50 high-quality attacks were reconstructed in 3-D. Despite having higher maximum velocity, deceleration and overall turning ability, bats only captured evasive prey in 69 of 184 attacks (37.5%); bats captured nearly all moths not evading attack (50 of 51; 98%). Logistic regression indicated that prey radial acceleration and escape angle were the most important predictors of escape success (44 of 50 attacks correctly classified; 88%). We found partial support for the turning gambit mathematical model; however, it underestimated the escape threshold by 25% of prey velocity and did not account for prey escape angle. Whereas most prey escaping strikes flee away from predators, moths typically escaped chasing bats by turning with high radial acceleration toward 'safety zones' that flank the predator. This strategy may be widespread in prey engaged in chases. Based on these findings, we developed a novel geometrical model of predation. We discuss implications of this model for the co-evolution of predator and prey kinematics and pursuit and escape strategies. PMID:27340205

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

    PubMed

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

    2012-01-01

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

  1. Escape of the martian protoatmosphere and initial water inventory

    NASA Astrophysics Data System (ADS)

    Erkaev, N. V.; Lammer, H.; Elkins-Tanton, L. T.; Stökl, A.; Odert, P.; Marcq, E.; Dorfi, E. A.; Kislyakova, K. G.; Kulikov, Yu. N.; Leitzinger, M.; Güdel, M.

    2014-08-01

    Latest research in planet formation indicates that Mars formed within a few million years (Myr) and remained as a planetary embryo that never grew to a more massive planet. It can also be expected from dynamical models that most of Mars' building blocks consisted of material that formed in orbital locations just beyond the ice line which could have contained ~ 0.1 - 0.2 wt . % of H2O. By using these constraints, we estimate the nebula-captured and catastrophically outgassed volatile contents during the solidification of Mars' magma ocean and apply a hydrodynamic upper atmosphere model for the study of the soft X-ray and extreme ultraviolet (XUV) driven thermal escape of the martian protoatmosphere during the early active epoch of the young Sun. The amount of gas that has been captured from the protoplanetary disk into the planetary atmosphere is calculated by solving the hydrostatic structure equations in the protoplanetary nebula. Depending on nebular properties such as the dust grain depletion factor, planetesimal accretion rates and luminosities, hydrogen envelopes with masses ≥ 3 ×1019 g to ≤ 6.5 ×1022 g could have been captured from the nebula around early Mars. Depending on the before mentioned parameters, due to the planets low gravity and a solar XUV flux that was ~ 100 times stronger compared to the present value, our results indicate that early Mars would have lost its nebular captured hydrogen envelope after the nebula gas evaporated, during a fast period of ~ 0.1 - 7.5 Myr. After the solidification of early Mars' magma ocean, catastrophically outgassed volatiles with the amount of ~ 50 - 250 bar H2O and ~ 10 - 55 bar CO2 could have been lost during ~ 0.4 - 12 Myr, if the impact related energy flux of large planetesimals and small embryos to the planet's surface lasted long enough, that the steam atmosphere could have been prevented from condensing. If this was not the case, then our results suggest that the timescales for H2O condensation and

  2. Escape of the martian protoatmosphere and initial water inventory

    PubMed Central

    Erkaev, N.V.; Lammer, H.; Elkins-Tanton, L.T.; Stökl, A.; Odert, P.; Marcq, E.; Dorfi, E.A.; Kislyakova, K.G.; Kulikov, Yu.N.; Leitzinger, M.; Güdel, M.

    2014-01-01

    Latest research in planet formation indicates that Mars formed within a few million years (Myr) and remained as a planetary embryo that never grew to a more massive planet. It can also be expected from dynamical models that most of Mars' building blocks consisted of material that formed in orbital locations just beyond the ice line which could have contained ~0.1–0.2wt.% of H2O. By using these constraints, we estimate the nebula-captured and catastrophically outgassed volatile contents during the solidification of Mars' magma ocean and apply a hydrodynamic upper atmosphere model for the study of the soft X-ray and extreme ultraviolet (XUV) driven thermal escape of the martian protoatmosphere during the early active epoch of the young Sun. The amount of gas that has been captured from the protoplanetary disk into the planetary atmosphere is calculated by solving the hydrostatic structure equations in the protoplanetary nebula. Depending on nebular properties such as the dust grain depletion factor, planetesimal accretion rates and luminosities, hydrogen envelopes with masses ≥3×1019g to ≤6.5×1022g could have been captured from the nebula around early Mars. Depending on the before mentioned parameters, due to the planets low gravity and a solar XUV flux that was ~100 times stronger compared to the present value, our results indicate that early Mars would have lost its nebular captured hydrogen envelope after the nebula gas evaporated, during a fast period of ~0.1–7.5Myr. After the solidification of early Mars' magma ocean, catastrophically outgassed volatiles with the amount of ~50–250bar H2O and ~10–55bar CO2 could have been lost during ~0.4–12Myr, if the impact related energy flux of large planetesimals and small embryos to the planet's surface lasted long enough, that the steam atmosphere could have been prevented from condensing. If this was not the case, then our results suggest that the timescales for H2O condensation and ocean formation may

  3. Pickup ions near Mars associated with escaping oxygen atoms

    NASA Astrophysics Data System (ADS)

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

    2002-08-01

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

  4. Water Vapor Permeability of the Advanced Crew Escape Suit

    NASA Technical Reports Server (NTRS)

    Bue, Grant; Kuzneth, Larry; Gillis, David; Jones, Jeffery; Daniel, Brian; Gernhardt, Michael; Hamilton, Douglas

    2009-01-01

    Crew Exploration Vehicle (CEV) crewmembers are expected to return to earth wearing a suit similar to the current Advanced Crew Escape Suit (ACES). To ensure optimum cognitive performance, suited crewmembers must maintain their core body temperature within acceptable limits. There are currently several options for thermal maintenance in the post-landing phase. These include the current baseline, which uses an ammonia boiler, purge flow using oxygen in the suit, accessing sea water for liquid cooling garment (LCG) cooling and/or relying on the evaporative cooling capacity of the suit. These options vary significantly in mass, power, engineering and safety factors, with relying on the evaporative cooling capacity of the suit being the least difficult to implement. Data from previous studies indicates that the evaporative cooling capacity of the ACES was much higher than previously expected, but subsequent tests were performed for longer duration and higher metabolic rates to better define the water vapor permeability of the ACES. In these tests five subjects completed a series of tests performing low to moderate level exercise in order to control for a target metabolic rate while wearing the ACES in an environmentally controlled thermal chamber. Four different metabolic profiles at a constant temperature of 95 F and relative humidity of 50% were evaluated. These tests showed subjects were able to reject about twice as much heat in the permeable ACES as they were in an impermeable suit that had less thermal insulation. All of the heat rejection differential is attributed to the increased evaporation capability through the Gortex bladder of the suit.

  5. Identification of the Energetic Plume Ion Escape Channel at Mars

    NASA Astrophysics Data System (ADS)

    Johnson, B. C.; Liemohn, M. W.; Fraenz, M.; Barabash, S.

    2013-12-01

    Mars lacks a global dipole magnetic field. The resulting induced magnetosphere arising from Mars' atmosphere's direct interaction with the solar wind differs significantly from that of Venus. The weak gravitational field of Mars creates scale heights so large that the exosphere extends out beyond the Induced Magnetosphere Boundary (IMB), where newly ionized exospheric oxygen is exposed to high speed shocked solar wind flow and the associated strong convective electric field (E). The weaker Interplanetary Magnetic Field (IMF) at Mars, combined with this strong electric field, should be expected to result in heavy pickup ions with gyroradii much larger than the radius of Mars. Test particle models and hybrid models have predicted that these pickup ions create an energetic plume of escaping planetary ions that may have a flux on the same order of magnitude as the flow of planetary ions down the central tail loss channel. This study presents an analysis of data from the Ion Mass Analyzer aboard European Space Agency's Mars Express (MEX) to identify the presence of this energetic ion plume. We searched through the time period when Mars Global Surveyor (MGS) was operating simultaneously with MEX, and selected hundreds of time intervals when IMF proxies from MGS show the convective electric field to be aligned with the orbit of MEX. We then examined plots of the MEX orbit during these intervals and selected times when MEX was positioned on the +E side of Mars and outside the nominal IMB. Finally, from these intervals we identified the cases in which oxygen ions were detected with energies above 2 keV. The result is a set of several direct measurements of the energetic plume.

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

    NASA Astrophysics Data System (ADS)

    Ramstad, R.; Barbash, S.; Futaana, Y.; Nilsson, H.; Holmstrom, M.

    2015-12-01

    Eight years (2007-2015) of ion flux measurements from Mars Express are used to empirically investigate the influence of the Martian crustal magnetic fields on the atmospheric ion escape rate. We combine ASPERA-3/IMA (Analyzer of Space Plasmas and Energetic Atoms/Ion Mass Analyzer) measurements taken during nominal upstream solar wind and solar Extreme Ultraviolet (EUV) conditions to compute global average ion distribution functions for varying solar zenith angles (SZA) of the strongest crustal field. Escape rates are subsequently calculated from each of the average distribution functions. A statistically significant increase in escape rate is found for high dayside SZA, compared to low SZA.

  7. The oxygen cost of an escape from an underground coal mine

    SciTech Connect

    Kamon, E.

    1983-07-01

    Six 27 to 63-year-old coal miners performed an 'escape' exercise from an underground mine along a passageway that required walking and running erect or stooped, duckwalking or crawling. The miners travelled at different speeds, for each mode of locomotion. The minute pulmonary ventilation, O/sub 2/ uptake and heart ratio, recorded continuously on magnetic tape, indicated similar average and peak values for all modes of locomotion. Compared to the aerobic capacity obtained during graded treadmill test to exhaustion, the average effort of the 'escape' was performed at 64% and the peak effort at 70% of the miners' aerobic capacity for an 'escape' time of 58 min.

  8. Pseudorabies virus can escape from CRISPR-Cas9-mediated inhibition.

    PubMed

    Peng, Zhiyuan; Ouyang, Ting; Pang, Daxin; Ma, Teng; Chen, Xinrong; Guo, Ning; Chen, Fuwang; Yuan, Lin; Ouyang, Hongsheng; Ren, Linzhu

    2016-09-01

    The CRISPR-Cas9 system is a newly developed genome-engineering tool used to inhibit virus infection by targeting the conserved regions of the viral genomic DNA. In the present study, we constructed a cell line stably expressing Cas9 endonuclease and sgRNA targeting the conserved UL30 gene of pseudorabies virus (PRV). During the PRV infection, the CRISPR-Cas9 system was efficient in cleaving the UL30 gene in each passage. However, deletions and insertions occurred at low passages, while substitutions were frequently observed at high passages. Furthermore, copy numbers and virus titers of PRV were significantly increased in a passage-dependent manner, indicating that viral genomic replication and assembly were more effective at the high passages than at low passages. These results demonstrated that PRV could escape from CRISPR-Cas9-mediated inhibition. Therefore, whether the CRISPR-Cas9 system is suitable for antiviral application should be considered and carefully verified. PMID:27507009

  9. Rapid Endolysosomal Escape and Controlled Intracellular Trafficking of Cell Surface Mimetic Quantum-Dots-Anchored Peptides and Glycopeptides.

    PubMed

    Tan, Roger S; Naruchi, Kentaro; Amano, Maho; Hinou, Hiroshi; Nishimura, Shin-Ichiro

    2015-09-18

    A novel strategy for the development of a high performance nanoparticules platform was established by means of cell surface mimetic quantum-dots (QDs)-anchored peptides/glycopeptides, which was developed as a model system for nanoparticle-based drug delivery (NDD) vehicles with defined functions helping the specific intracellular trafficking after initial endocytosis. In this paper, we proposed a standardized protocol for the preparation of multifunctional QDs that allows for efficient cellular uptake and rapid escaping from the endolysosomal system and subsequent cytoplasmic molecular delivery to the target cellular compartment. Chemoselective ligation of the ketone-functionalized hexahistidine derivative facilitated both efficient endocytic entry and rapid endolysosomal escape of the aminooxy/phosphorylcholine self-assembled monolayer-coated QDs (AO/PCSAM-QDs) to the cytosol in various cell lines such as human normal and cancer cells, while modifications of these QDs with cell-penetrating arginine-rich peptides showed poor cellular uptake and induced self-aggregation of AO/PCSAM-QDs. Combined use of hexahistidylated AO/PCSAM-QDs with serglycine-like glycopeptides, namely synthetic proteoglycan initiators (PGIs), elicited the entry and controlled intracellular trafficking, Golgi localization, and also excretion of these nanoparticles, which suggested that the present approach would provide an ideal platform for the design of high performance NDD systems. PMID:26107406

  10. Effective hydrodynamic hydrogen escape from an early Earth atmosphere inferred from high-accuracy numerical simulation

    NASA Astrophysics Data System (ADS)

    Kuramoto, Kiyoshi; Umemoto, Takafumi; Ishiwatari, Masaki

    2013-08-01

    Hydrodynamic escape of hydrogen driven by solar extreme ultraviolet (EUV) radiation heating is numerically simulated by using the constrained interpolation profile scheme, a high-accuracy scheme for solving the one-dimensional advection equation. For a wide range of hydrogen number densities at the lower boundary and solar EUV fluxes, more than half of EUV heating energy is converted to mechanical energy of the escaping hydrogen. Less energy is lost by downward thermal conduction even giving low temperature for the atmospheric base. This result differs from a previous numerical simulation study that yielded much lower escape rates by employing another scheme in which relatively strong numerical diffusion is implemented. Because the solar EUV heating effectively induces hydrogen escape, the hydrogen mixing ratio was likely to have remained lower than 1 vol% in the anoxic Earth atmosphere during the Archean era.

  11. Microcrustaceans escape behavior as an early bioindicator of copper, chromium and endosulfan toxicity.

    PubMed

    Gutierrez, María Florencia; Paggi, Juan César; Gagneten, Ana María

    2012-03-01

    The purpose of this work was to experimentally analyze the impact of copper, chromium and a commercial pesticide with endosulfan on the escape behavior of two copepods (Notodiaptomus conifer, Argyrodiaptomus falcifer) and three cladocerans (Daphnia magna, Pseudosida variabilis and Ceriodaphnia dubia). The experimental assays were carried out using a novel hydraulic devise designed to mimic three-speed predator capture behavior. Two concentrations, one "high" and one "low", were employed and the exposure time was 15 (±5) minutes. With two exceptions, the species exposed to heavy metals manifested higher ability to escape than controls. Both concentrations of the pesticide reduced the escape ability of cladocerans but copepods responded, in general, in a similar manner as for heavy metals. The immediate apparent advantage of low and early toxic effects is discussed and the high sensitivity of the escape behavior suggests that it could be a complementary endpoint to be used in future ecotoxicological tests. PMID:22038688

  12. Pizza or Pancake? Formation Models of Gas Escape Biosignatures in Terrestrial and Martian Sediments

    NASA Astrophysics Data System (ADS)

    Bonaccorsi, R.; Fairen, A. G.; Baker, L.; McKay, C. P.; Willson, D.

    2016-05-01

    Fine-grained sedimentary hollowed structures were imaged in Gale Crater, but no biomarkers identified to support biology. Our observation-based (gas escape) terrestrial model could inform on possible martian paleoenvironments at time of formation.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  14. Ceramide formation mediated by acid sphingomyelinase facilitates endosomal escape of caliciviruses.

    PubMed

    Shivanna, Vinay; Kim, Yunjeong; Chang, Kyeong-Ok

    2015-09-01

    Our recent results demonstrated that bile acids facilitate virus escape from the endosomes into the cytoplasm for successful replication of porcine enteric calicivirus (PEC). We report a novel finding that bile acids can be substituted by cold treatment for endosomal escape and virus replication. This endosomal escape by cold treatment or bile acids is associated with ceramide formation by acid sphingomyelinase (ASM). ASM catalyzes hydrolysis of sphingomyelin into ceramide, which is known to destabilize lipid bilayer. Treatment of LLC-PK cells with bile acids or cold led to ceramide formation, and small molecule antagonists or siRNA of ASM blocked ceramide formation in the endosomes and significantly reduced PEC replication. Inhibition of ASM resulted in the retention of PEC, feline calicivirus or murine norovirus in the endosomes in correlation with reduced viral replication. These results suggest the importance of viral escape from the endosomes for the replication of various caliciviruses. PMID:25985440

  15. Analysis of establishing operations for self-injury maintained by escape

    PubMed Central

    Smith, Richard G.; Iwata, Brian A.; Goh, Han-Leong; Shore, Bridget A.

    1995-01-01

    Self-injurious behavior (SIB) can be maintained through negative reinforcement when, in the context of training or task requirements, it produces escape as a consequence. Several studies have demonstrated methods for identifying and treating SIB maintained by negative reinforcement; however, few analyses of the establishing operations associated with demand situations have been conducted. The current series of studies illustrates a method for identifying some establishing operations for escape by systematically altering certain dimensions of the demand context while maintaining an escape contingency for SIB. Dimensions assessed in these studies included task novelty, duration of instructional sessions, and rate of task presentation. Data indicate that these variables can have establishing properties for behavior maintained by escape. Implications of the results are discussed, as are potential refinements and extensions of the assessment procedures. PMID:16795880

  16. The relationship between migration and development in the ESCAP region.

    PubMed

    Skeldon, R

    1991-01-01

    The relationship between migration and development in the ESCAP region including southeast and south Asian countries and the Pacific island of Fiji, Papua New Guinea, Vanuatu, Kiribati, Samoa, and the Solomon Islands is discussed in terms of mobility transition and origin and destination factors. The changing patterns of mobility in Asia are further delineated in the discussion of internal movements and international movement. Emigration in the smaller countries of the Pacific are treated separately. Future predictions are that the Asia Pacific region will experience continued fertility decline and stabilization of low rates over the next 20 years. The declines will result in slow labor force growth, and increased demand for labor in traditional core and neocore countries as defined and presented in table form by Friedman will be heightened. International movements are likely to increase in large urban areas within destination countries. Tokyo and Singapore are the principal cities in Asia. Tokyo by restrictive government policy has limited immigration, but future labor shortages of unskilled labor from southeast Asia and China are expected. Singapore is already dependent on foreign labor by 10%. Current labor shortages have led to the creation of a growth triangle between Singapore, Indonesia, and Malaysia. Other cities expected to emerge as primary cities in international regional complexes with spillover into the hinterlands include the Hong Kong, Guangzhou, and Macau triangle in the Pearl River delta, Taipei and Seoul, and possibly Kuala Lumpur. Internal migration is expected to increase in the capital cities of Bangkok, Manila,j and centers such as Shanghai, Beijing, and other large cities of southeast Asia. These cities will be linked through the flows of skilled international migrants, which began in the 1960s and is expected to become a future major flow. Recreational and resource niches will be left in much of the Pacific, the Himalayan Kingdoms, and

  17. Parental use of escape extinctionand differential reinforcement to treat food selectivity.

    PubMed

    Anderson, C M; McMillan, K

    2001-01-01

    Escape extinction combined with differential reinforcement for acceptance has been demonstrated to be an effective treatment for food selectivity when implemented by trained professionals in clinic settings. This study evaluated the efficacy of parent-implemented escape extinction in the child's natural environment using video monitoring to train parents and assess intervention efficacy. Parents were able to use intervention to significantly increase bites accepted and decrease problem behavior. PMID:11800192

  18. Modulation of Endosomal Escape of IRQ-PEGylated Nano-carrier

    NASA Astrophysics Data System (ADS)

    Mudhakir, Diky; Akita, Hidetaka; Harashima, Hideyoshi

    2011-12-01

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

  19. Epidemiology of HBV S-gene mutants in the Liguria Region, Italy: Implications for surveillance and detection of new escape variants.

    PubMed

    Sticchi, Laura; Caligiuri, Patrizia; Cacciani, Roberto; Alicino, Cristiano; Bruzzone, Bianca

    2013-03-01

    HBV surface antigen (HBsAg) variants may impair diagnosis or allow the virus to escape vaccine-induced immunity and their circulation in the population can represent a Public Health threat. Their prevalence, however, is not yet completely established. Evidence indicates that amino acid substitutions within HBsAg can lead to conformational changes which allow mutated HBV to escape the vaccine-induced antibodies used in the screening tests. In such scenario, the aim of this study was to investigate the prevalence of HBV S-Gene escape mutants by sequencing the gene in a cohort of Ligurian patients monitored for viral load, genotype and drug resistance and to evaluate the risk of false negative HBsAg detection by routine screening tests. From 2007 to 2011, in 256 consecutive samples from Ligurian HBV positive patients sequencing assay for detection of RT/S-Gene mutations using Trugene HBV Genotyping kit (Siemens Healthcare Diagnostics Inc., Tarrytown, NY) was performed. Serological HBV tests and viral load were also performed. Analyzed sequences revealed G145R mutation in 8/256 (3.1%) examined sequences, it was alone in 5 patients and accompanied by other HBsAg mutations in 3 samples. HBsAg resulted undetectable by 3 of the 8 samples, derived from patients with multiple mutations: T126I-T131A-C139Y-E/D144G, T126I-M133L, and P120Q-T126I. The emergence of these mutants, at least the G145R, has already been addressed as a public health concern because of its capability of escaping the immune system. In the present study we point out a second aspect connected with their existence and with similar potential negative impact on public health, that is their capability of escape punctual detection. PMID:23296324

  20. Descending influences on escape behavior and motor pattern in the cockroach.

    PubMed

    Schaefer, P L; Ritzmann, R E

    2001-10-01

    The escape behavior of the cockroach is a ballistic behavior with well characterized kinematics. The circuitry known to control the behavior lies in the thoracic ganglia, abdominal ganglia, and abdominal nerve cord. Some evidence suggests inputs may occur from the brain or suboesophageal ganglion. We tested this notion by decapitating cockroaches, removing all descending inputs, and evoking escape responses. The decapitated cockroaches exhibited directionally appropriate escape turns. However, there was a front-to-back gradient of change: the front legs moved little if at all, the middle legs moved in the proper direction but with reduced excursion, and the rear legs moved normally. The same pattern was seen when only inputs from the brain were removed, the suboesophageal ganglion remaining intact and connected to the thoracic ganglia. Electromyogram (EMG) analysis showed that the loss of or reduction in excursion was accompanied by a loss of or reduction in fast motor neuron activity. The loss of fast motor neuron activity was also observed in a reduced preparation in which descending neural signals were reversibly blocked via an isotonic sucrose solution superfusing the neck connectives, indicating that the changes seen were not due to trauma. Our data demonstrate that while the thoracic circuitry is sufficient to produce directional escape, lesion or blockage of the connective affects the excitability of components of the escape circuitry. Because of the rapidity of the escape response, such effects are likely due to the elimination of tonic descending inputs. PMID:11536194