Striking Accuracy Research Articles

The defensive strike of the Eastern Brownsnake, Pseudonaja textilis (Elapidae)

Abstract1. The Eastern Brownsnake, Pseudonaja textilis, is a large (to 2 m), slender‐bodied, highly venomous elapid that causes most snakebite human fatalities in Australia. The response of recently captured snakes to human harassment was quantified. Using high‐speed film, the type of neck display, time taken to strike, strike accuracy, strike speed and effectiveness of bite were recorded.2. The snakes were surprisingly tolerant of harassment, especially at body temperatures similar to those that they exhibit in the field during the activity season. Smaller snakes spent more time trying to escape than did larger snakes. Most snakes gave warning prior to the strike, 58% by full (high) display and 19% by partial (low) display. Some 25% of strikes were bluff.3. Body temperature (over the range 18–36 °C) had little effect on most of the variables measured, including: the frequency of display and bluff, the duration of the strike (mean 0·28 s), the strike distance (mean 0·34 m), the mean overall strike speed (1·1 m s−1, range 0·25–1·80), the mean fastest strike speed (during 1/25 s, = 1·7 m s−1, range 0·3–3·4), or the accuracy of the strike.4. Instead, the type of prestrike display was related to strike speed and accuracy: strikes preceded by a full neck display were slower but more accurate (and more likely to involve venom transfer) than those preceded by minimal display.5. Contrary to popular opinion, Eastern Brownsnakes are reluctant to deliver firm bites in response to human harassment even when continuously provoked. It is estimated that only 15% of the strikes recorded had the potential to cause significant envenomation.

Constant-step Lagrange meshes for central potentials

The existence conditions of Lagrange meshes, i.e. meshes leading to very accurate results without analytical calculation of potential matrix elements, are studied in relation with sine and cosine bases on a finite interval. For each one of three different types of boundary conditions, three Lagrange meshes are found. A numerical example shows that (i) the Lagrange-mesh calculations nearly reach the same accuracy as a variational calculation involving the same basis in spite of the approximation on the potential matrix elements and (ii) they are much more accurate than mesh calculations which do not satisfy the existence conditions. The striking accuracy of the Gauss quadrature employed in the mesh approximation for the significant eigenvalues remains unexplained in view of the limited accuracy of the same quadrature for individual potential matrix elements.

Visuomotor adaptation to displacing prisms by adult and baby barn owls

The capacity of barn owls to adapt visuomotor behavior in response to prism-induced displacement of the visual field was tested in babies and adults. Matched, binocular Fresnel prisms, which displaced the visual field 11 degrees, 23 degrees, or 34 degrees to the right, were placed on owls for periods of up to 99 d. Seven baby owls wore the prisms from the day the eyelids first opened; 2 owls wore them as adults. Prism adaptation was measured by the accuracy with which a target was approached and struck with the talons, a behavior similar to pointing behavior used commonly to assess prism adaptation in primates. Baby and adult owls exhibited a limited capacity to adapt this visuomotor behavior. Acquisition of adapted behavior was slow, taking place over a period of weeks, and was never complete even for owls that were raised viewing the world through relatively weak (11 degrees) displacing prisms. When the prisms were removed from adapted owls, they struck to the opposite side of the target. The recovery of strike accuracy following prism removal was rapid; 7 of 9 owls recovered normal accuracy within 30 min of prism removal, despite having worn the prisms for months. This limited capacity for adaptation contrasts dramatically with the extensive and rapid adaptation exhibited by adult primates exposed to comparable prismatic displacements. The mechanism of adaptation used by the owls was to alter the movements employed for approaching targets. Instead of moving straight ahead, the head and body moved diagonally relative to the orientation of the head. Thus, in contrast to prism adaptation by humans that can involve reinterpretation of eye, head, and limb position, prism adaptation by owls is based on changes in the motor commands that underlie approach behavior.

Bypass and termination at apurinic sites during replication of single-stranded DNA in vitro: a model for apurinic site mutagenesis.

Mutations produced in Escherichia coli by apurinic sites are believed to arise via SOS-assisted translesion replication. Analysis of replication products synthesized on depurinated single-stranded DNA by DNA polymerase III holoenzyme revealed that apurinic sites frequently blocked in vitro replication. Bypass frequency of an apurinic site was estimated to be 10-15%. Direct evidence for replicative bypass was obtained in a complete single-stranded----replicative form replication system containing DNA polymerase III holoenzyme, single-stranded DNA binding protein, DNA polymerase I, and DNa ligase, by demonstrating the sensitivity of fully replicated products to the apurinic endonuclease activity of E. coli exonuclease III. Termination at apurinic sites, like termination at pyrimidine photodimers, involved dissociation of the polymerase from the blocked termini, followed by initiations at available primer templates. When no regular primer templates were available, the polymerase underwent repeated cycles of dissociation and rebinding at the blocked termini and, while bound, carried out multiple polymerization-excision reactions opposite the apurinic sites, leading to turnover of dNTPs into dNMPs. From the in vitro turnover rates, we could predict with striking accuracy the specificity of apurinic site mutagenesis, as determined in vivo in depurinated single-stranded DNA from an M13-lac hybrid phage. This finding is consistent with the view that DNA polymerase III holoenzyme carries out the mutagenic "misinsertion" step during apurinic site mutagenesis in vivo and that the specificity of the process is determined primarily by the polymerase. SOS-induced proteins such as UmuD/C might act as processivity-like factors to stabilize the polymerase-DNA complex, thus increasing the efficiency of the next stage of past-lesion polymerization required to complete the bypass reaction.

Hyperosmotic Saline Environment Alters Feeding Behavior in the Western Toad, Bufo boreas

Exposure of western toads, Bufo boreas, to 344, 372 or 400 mOs solutions of NaCl is accompanied by a decrease in the accuracy of the tongue strike during feeding behavior. After two to four days in such solutions, average strike accuracy of toads which attempt to feed falls to a low of 45%, 35% and 16%, respectively, compared with average levels of 75% to 93% in freshwater-acclimated toads. With continued exposure to the saline solutions, strike accuracy returns toward normal levels; the rate of reversion toward normal is inversely related to the degree of salinity. Toads kept in NaCl solutions at concentrations of 288 and 316 mOs do not differ in their strike accuracy from freshwater controls.

A new method for summation of divergent power series

A new method for summation of divergent power series is developed. It only requires the knowledge of the form of both the small and large λ-power expansion (λ being the perturbation parameter) and few coefficients of one of them to yield excellent results. Convergence is proved for a simple two-level model, and reasonable arguments are given for more complex and interesting models. The method is quite general and contains some resummation techniques reported previously as particular cases. The anharmonic, mean square, displacement function, the ground-state eigenvalue of the quantum-mechanical anharmonic oscillator, and the ground-state energy of the hydrogen atom in a magnetic field calculated in this way are shown to be of striking accuracy in the whole range of the perturbation parameter.

Moment‐magnitude relations in theory and practice

The observation that motivates this study is the difference in c values in moment‐magnitude relations of the form log MO = cML + d between central and southern California. This difference is not at all related to geographical area; rather, it results from positive curvature in the log MO ‐ ML plane and the relatively large number of ML<5 earthquakes in the central California data set. With the prescription that the far‐field shear waves from which ML is taken be finite‐duration, band‐limited, white Gaussian noise in acceleration, we can estimate ML as a function of MO alone, by fixing the arms stress drop at 100 bars and ƒmax at 15 Hz. These model calculations fit available California moment‐magnitude data for 0≲ML≲7,1017≲MO≲1028 dyne cm with striking accuracy. This range in source strength is entire: earthquakes with MO≥1028 dyne cm are unlikely to occur in California, and earthquakes with ML<0 cannot be recorded in California, at least under ordinary conditions of recording earthquakes at ordinary hypocentral depths. More fundamentally, the remarkably good fit of model to data implies that the arms stress drop of 100 bars (to a factor of 2 or so) is a stable and pervasive feature of all (ML≳2 1/2) California earthquakes whose spectral corner frequency lies in the “visible” bandwidth, ƒ0≤ƒmax.

Probability of alarm detection in a search and rescue system

Diagnostic systems are often based on the detection of weak periodic signals buried in noise. As an illustrative example, a maritime search and rescue system is described. Here, alarms consist of frequency-modulated signals where the carrier frequency may vary in a certain range due to Doppler shifts. The signals are strongly corrupted by additive noise and by fading. For a given averaging time, the probability of missed alarms is computed and minimised, comparing different receiver structures and detection schemes. The theoretical investigations were verified in practical tests with striking accuracy.

Eigenvalues of anharmonic oscillators from a variational functional method

Analytic expressions for the eigenvalues of anharmonic oscillators are obtained from a simple variational method. Numerical results show striking accuracy in the whole range of the characteristic anharmonic oscillator parameters. The procedure also allows one to classify the set of states in three classes and yields a way of defining clearly the anharmonic and harmonic regime

Predatory success in the water stick insect: The role of visual and mechanical stimulations after moulting

The more foreleg femur and claw movements that a water stick insect, Ranatra linearis, performs during the 4-h period following a moult, the higher will be its subsequent strike efficiency. The amount of movement is influenced by external factors such as the presence of prey or light. The experiments reported here show that the absence of visual cues during the post-moult periods impairs subsequent performance, but not as much as the absence of both visual and mechanical cues. Perception of mechanical stimuli only during that period subsequently influences the accuracy of simple type strikes elicited when prey is near the forelegs; whereas perception of visual stimuli subsequently improves the accuracy of more complex predatory movements.

Anion-ligand interactions: ab initio study of the binding of H 2O, CO 2 and SO 2 to the nitrite ion

Binding enthalpies of single attachment of H 2O, CO 2 and SO 2 to NO − 2 in the gas phase are reproduced with striking accuracy by SCF ab initio computations using a minimal basis set with counterpoise correction. The positions of binding to NO − 2 are predicted. The charge-transfer character of the binding, small for water, is slightly increased for CO 2 and appreciable for SO 2.

Numerical solution of Fisher's equation

The accurate space derivative (ASD) method for the numerical treatment of nonlinear partial differential equations has been applied to the solution of Fisher's equation, a nonlinear diffusion equation describing the rate of advance of a new advantageous gene, and which is also related to certain water waves and plasma shock waves described by the Korteweg-de-Vries-Burgers equation. The numerical experiments performed indicate how from a variety of initial conditions, (including a step function, and a wave with local perturbation) the concentration of advantageous gene evolves into the travelling wave of minimal speed. For an initial superspeed wave this evolution depends on the cutting off of the right-hand tail of the wave, which is physically plausible; this condition is necessary for the convergence of the ASD method. Detailed comparisons with an analytic solution for the travelling waves illustrate the striking accuracy of the ASD method for other than very small values of the concentration.

Numerical solution of Fisher's equation

The accurate space derivative (ASD) method for the numerical treatment of nonlinear partial differential equations has been applied to the solution of Fisher's equation, a nonlinear diffusion equation describing the rate of advance of a new advantageous gene, and which is also related to certain water waves and plasma shock waves described by the Korteweg-de-Vries-Burgers equation. The numerical experiments performed indicate how from a variety of initial conditions, (including a step function, and a wave with local perturbation) the concentration of advantageous gene evolves into the travelling wave of minimal speed. For an initial superspeed wave this evolution depends on the cutting off of the right-hand tail of the wave, which is physically plausible; this condition is necessary for the convergence of the ASD method. Detailed comparisons with an analytic solution for the travelling waves illustrate the striking accuracy of the ASD method for other than very small values of the concentration.

The Early History of Glacial Theory in British Geology

AbstractMuch of the history of British geological thought in the second quarter of the nineteenth century centered on problems which are now explained by reference to the events of the Ice Age. This paper reviews the data and theories then current among British geologists as the background of the British response to Louis Agassiz’s “modern” theory of a glacial epoch. Today, as we read Agassiz’s amazing speculation, our own sympathy for the striking accuracy of his ideas masks from us the difficulty they faced in gaining acceptance. By first examining the context into which the glacial theory was introduced, we can then appreciate the novelty of Agassiz's efforts and understand the long delay in their achieving prominence. The present examination suggests that this delay was due to the unfortunate merger of Agassiz’s new ideas with the older drift theory of Charles Lyell.

The Early History of Glacial Theory in British Geology

AbstractMuch of the history of British geological thought in the second quarter of the nineteenth century centered on problems which are now explained by reference to the events of the Ice Age. This paper reviews the data and theories then current among British geologists as the background of the British response to Louis Agassiz’s “modern” theory of a glacial epoch. Today, as we read Agassiz’s amazing speculation, our own sympathy for the striking accuracy of his ideas masks from us the difficulty they faced in gaining acceptance. By first examining the context into which the glacial theory was introduced, we can then appreciate the novelty of Agassiz's efforts and understand the long delay in their achieving prominence. The present examination suggests that this delay was due to the unfortunate merger of Agassiz’s new ideas with the older drift theory of Charles Lyell.