Escape Event Research Articles

The August 27, 1886 earthquake in Messenia (Peloponnesus) and reported flames over the Ionian Sea—a Mediterranean Ridge gas escape event?

The 1960 bathymetric map of Pfannenstiel showed a submarine volcano west of the Peloponnesus which could not be confirmed by modern bathymetric surveys. Pfannenstiel's interpretation was supported by a report of flames on the sea in 1886. It is most likely that the strong earthquake on August 27, 1886, triggered a submarine mud volcano eruption and gas escapes on the Mediterranean Ridge (MR), and burning gas was observed from several places on land and on sea.

On the escape process during phase inversion of an emulsion

This paper deals with a phenomenon which plays an important role in the phase inversion process of emulsions. This process is governed by the interplay of coalescence of droplets, often leading to double emulsions, and the escape of those internal droplets. The latter process retards the inversion process. Coalescence has been the subject of many studies, contrary to the escape event. This paper addresses the escape process both theoretically and experimentally. The model developed analyses the rate of the escape of internal droplets from the mother droplet via a coalescence process, where the internal flow, as generated by the external flow, generates the viscous force for coalescence. Incomplete mixing in the droplet has been assumed. Experimental data on the escape rate of oil droplets from O/W/O emulsions have been analysed using a Computational Fluid Dynamics approach, where the model as indicated above has been incorporated. Experimental data and simulations compare very well. Data have been compared on varying the size of the inner droplets and the rotational speed of the vessel where the double emulsion has been formed and where the escape took place.

Resonances while surmounting a fluctuating barrier

Electronic analog experiments on escape over a fluctuating potential barrier are performed for the case when the fluctuations are caused by Ornstein-Uhlenbeck noise (OUN). In its dependence on the relation between the two OUN parameters (the correlation time tau and noise strength Q) the nonmonotonic variation of the mean escape time T as a function of tau can exhibit either a minimum (resonant activation), or a maximum (inhibition of activation), or both these effects. The possible resonant nature of these features is discussed. We claim that T is not a good quantity to describe the resonancelike character of the problem. Independently of the specific relation between the OUN parameters, the resonance manifests itself as a maximal lowering of the potential barrier during the escape event, and it appears for tau of the order of the relaxation time toward the metastable state.

Physiological Response of Scup, Stenotomus chrysops, to a Simulated Trawl Capture and Escape Event

Scup (Stenotomus chrysops) were severely exercised by manual chasing for 6 min, and the clearance of lactate over a 12 hr period was evaluated. Lactate peaked from 0.5 to 1.0 hr following exercise with concentrations ranging from 61.0 to 126.0 mg/dL and returned to rested concentrations within 4 hr post-exercise. Concentrations of lactate in rested fish ranged from 5.2 to approximately 23.0 mg/dL. Fish were observed for 10 days following exercise for delayed mortality. A 100% survival of scup was observed with no significant difference between control and experimental populations.Swimming performance was evaluated for 14.0 to 15.0 cm fork length scup, with a towed stimulus through a still-water circular swimming channel, at prolonged and burst speeds. A maximum sustainable swimming speed of 2.2 BL/sec was observed. Between the speeds of 3.0 and 3.3 BL/sec and 4.4 BL/sec, endurance time significantly decreased with the increase in swimming speed. Blood lactate concentrations were measured at 0.5 and 4.0 hr post exercise, and were used as an indicator of white muscle recruitment. A significant difference was not found between rested and experimental mean lactate concentrations at the maximum sustainable swimming speed of 2.2 BL/sec. White muscle recruitment indicated by increases in lactic acid, was recorded at speeds above the maximum sustained swimming speed, and mean blood lactate concentrations were significantly different within blood sampling times and between swimming speeds.Based on the results of our investigations of lactate recovery in scup following a simulated trawl capture and escape event, we believe that scup interacting with a bottom trawl and subsequently escaping, are physiologically stressed by the event, but recover in less than 6 hr. AU experimentally treated fish survived both exhaustive exercise and prolonged swimming, suggesting encounter mortality is minimal. The results of this study do not address the effects of possible physical damage on escape or the effect of multiple encounters.

Rejecting escape events in large volume Ge detectors by a pulse shape selection procedure

The dependence of the response to γ-rays of a large volume Ge detector on the interval width of a selected initial rise pulse slope is investigated. The number of escape events associated with a small pulse slope is found to be greater than the corresponding number of full energy events. An escape event rejection procedure based on the observed correlation between energy deposition and pulse shape is discussed. Such a procedure seems particularly suited for the design of highly granular large volume Ge detector arrays.

Dynamic Mechanical Properties of Extensor Muscle Cells of the ShrimpPandalus Danae:Cell Design for Escape Locomotion

ABSTRACTWe measured the dynamic stiffness of passive single extensor cells from the abdomen of the shrimp Pandalus danae. These stiffness measurements, consisting of both elastic and viscous moduli, were carried out by imposing sinusoidal length changes on single cells and recording, simultaneously, the resultant force. Our measurements were made over a broad range of loading frequencies (1–120 Hz) and sarcomere lengths (1·9–3·2μm), encompassing the physiological range of these parameters.We found that: (1) there is an exponential increase in both elastic and viscous moduli with increases in sarcomere length; (2) there is a weak increase in these moduli with increasing frequency; (3) the relative energy dissipated by the viscous behavior of cells is largest in the relevant physiological range of loading frequencies and sarcomere lengths, with the magnitude of the viscous modulus nearly equal to the elastic modulus; and (4) the energy dissipated by the viscous behavior of these cells alone constitutes about 10 % of the total energy required to accelerate the animal in its aquatic environment. We propose that such large values for viscous energy dissipation in passive cells may be necessary to prevent unstable responses of muscle to the rapid dynamic loads imposed by the escape event.

Size Limits in Escape Locomotion of Carridean Shrimp

ABSTRACT Escape locomotion of the common dock shrimp, Pandalus danae Stimpson, is the result of a rapid flexion of the abdomen that lasts approximately 30 ms. The hydrodynamic forces that result from this motion lead to body accelerations in excess of 100 ms−2 and body rotations of about 75°. We examined the mechanics and kinematics of this mode of locomotion with both experimental and theoretical approaches. Using a system of differential equations that rely on conservation of both linear and angular momenta, we develop predictions for body movements, thrust forces and muscle stresses associated with escape locomotion. The predicted movements of the body agree to within 10 % with data from high-speed ciné-photography for body translations and rotations. The thrust from rapid tail flexion is dominated by accelerational forces and by the force required to squeeze fluid out of the gap created by the cephalothorax and the abdomen at the end of tail flexion. This squeeze force overwhelms any propulsive drag forces that arise from the tail-flip. Using the theoretical analysis, we identify two additional features about unsteady, rotational aquatic locomotion. First, as either the relative length of the propulsive appendage increases or the absolute body size increases, rotational motions become disproportionately greater than translational motions, and escape performance decays. Second, if muscle stresses developed during escape cannot exceed the maximum isometric stress, there is a unique body length (6 cm) that maximizes the distance travelled during the escape event.

Mass fractionation during transonic escape and implications for loss of water from Mars and Venus

Hydrodynamic escape of hydrogen from a planetary atmosphere can remove heavier gases as well as hydrogen, provided that the escape rate is sufficiently large. Here, analytic approximations for the degree of mass fractionation of a trace species during hydrodynamic escape are compared with accurate numerical solutions for the case of transonic outflow. Even the simplest analytic approximation is found to be surprisingly good, despite numerous assumptions made in the course of its derivation. The analytic approximations are most accurate when the ratio of molecular weights of the heavier and lighter constituents is large so that nonlinear terms in the momentum equation for the heavy constituent become small. The simplest analytic formula is readily generalized to the case where a heavy constituent is also a major species. Application of the generalized formula to hypothetical episodes of hydrodynamic escape from Venus and Mars suggests that both hydrogen and oxygen could have escaped; thus, substantial quantities of water may have been lost without the need to oxidize large amounts of the crust. Mars could have lost large amounts of rare gases in this manner, but if so it may also have lost significant quantities of carbon dioxide and nitrogen. Venusian argon and neon isotope ratios indicate that Venus lost little or no argon and 50% or less of its original complement of neon. Terrestrial noble gas patterns resemble those that would have resulted had an initially Venus-like Earth undergone a short-lived but locally very energetic escape event.

THE INSTABILITY OF NEUROSPORA DUPLICATION Dp(IL⇒IR)H4250, AND ITS GENETIC CONTROL

Previous work (Newmeyer and Taylor 1967) showed that a nontandem duplication, Dp(IL-->IR)H4250, is regularly produced by recombination in crosses heterozygous for the effectively terminal pericentric inversion In(IL-->IR)H4250. The duplications initially have strongly inhibited growth because they are heterozygous for mating type, which behaves like a vegetative-incompatibility (het) locus. Such cultures "escape" from the inhibition as a result of events that eliminate the mating-type heterozygosity. The product of a given escape event may be barren or fertile. (Neurospora duplications are characteristically barren; that is, when crossed, they make many perithecia but few ascospores.)-The present paper reports on a genetic analysis of the instability of Dp(IL-->IR)H4250 . Most of the barren escape products behave as if due either to mitotic crossovers, which make mating type and distal markers homozygous, or to very long deletions which uncover mating type and all distal markers; presumably the latter would retain enough duplicated material to render them barren. It is difficult to distinguish between these two possibilities, but homozygosis seems more probable and has been clearly demonstrated in one case. Only a few barren escapes could be due to short deletions or to changes at the mating-type locus.-The fertile escape products appear to be euploid. Most of these behave as if they arose by precise deletion of one or the other duplicated segment, thus restoring one of the parental sequences. A large majority of the precise deletions restore normal sequence; only a few restore inversion sequence. Preferential restoration of the normal sequence has also been found by other workers for Neurospora duplications from several other rearrangements. A hypothesis is presented to explain these findings; it is posulated that the precise deletions result from mitotic crossing over in homologous material located at chromosome tips and tip-break-points.-There is a smaller group of fertile escapes that are unlike either parental sequence; at least one of these involves a chromosome break outside the duplicated region.-Duplications in which the vegetative incompatibility is suppressed by the unlinked modifier tol are extremely barren; they only rarely lose a duplicated segment so as to become fertile.-The instability of Dp(IL-->IR)H4250 , with and without tol, is markedly altered by factors in the genetic background. The two factors studied in detail have qualitatively different effects.