Striking Accuracy Research Articles

Born Knowing: Tentacled Snakes Innately Predict Future Prey Behavior

BackgroundAquatic tentacled snakes (Erpeton tentaculatus) can take advantage of their prey's escape response by startling fish with their body before striking. The feint usually startles fish toward the snake's approaching jaws. But when fish are oriented at a right angle to the jaws, the C-start escape response translates fish parallel to the snake's head. To exploit this latter response, snakes must predict the future location of the fish. Adult snakes can make this prediction. Is it learned, or are tentacled snakes born able to predict future fish behavior?Methods and FindingsLaboratory-born, naïve snakes were investigated as they struck at fish. Trials were recorded at 250 or 500 frames per second. To prevent learning, snakes were placed in a water container with a clear transparency sheet or glass bottom. The chamber was placed over a channel in a separate aquarium with fish below. Thus snakes could see and strike at fish, without contact. The snake's body feint elicited C-starts in the fish below the transparency sheet, allowing strike accuracy to be quantified in relationship to the C-starts. When fish were oriented at a right angle to the jaws, naïve snakes biased their strikes to the future location of the escaping fish's head, such that the snake's jaws and the fish's translating head usually converged. Several different types of predictive strikes were observed.ConclusionsThe results show that some predators have adapted their nervous systems to directly compensate for the future behavior of prey in a sensory realm that usually requires learning. Instead of behavior selected during their lifetime, newborn tentacled snakes exhibit behavior that has been selected on a different scale—over many generations. Counter adaptations in fish are not expected, as tentacled snakes are rare predators exploiting fish responses that are usually adaptive.

The Great Hungarian Plain in the sheets of the Habsburg military surveys and some historical maps — A case study of the Körös/Criş Drainage Basin

In this paper old historical maps and the sheets of the Habsburg Military Surveys are analyzed to distinguish different terrace levels in the Great Hungarian Plain (GHP), and particulary in the Körös/Criş river system. The GHP is located in the Pannonian Basin, in the eastern part of Hungary, which is a very flat area. Prior to the river regulations, its meandering rivers (eg. the Tisza and Körös Rivers) flooded the lower areas and created marshlands. The method of the integrated analysis of these different maps was the georeference; to geometric fit the sheets from different sources. While the First Military Survey shows the original extents of these areas the Second Survey displays the situation of the environment at the time of the flood control works in the second half of the 19th century, also with the planned cutoffs. The maps show not only the rivers, but the settlements as well. During this period, these villages and towns became bigger, so they needed more and more agricultural area. They cleared the forests and dried out the marshlands to have more ploughlands. These land types can also be separated easily in the survey sheets. Two study areas were selected to show the effectiveness of environmental reconstruction at some local engineering surveys and the Military Surveys, too. The extents of the different elevation terraces are mapped with striking accuracy.

The star-formation history of the Small Magellanic Cloud star cluster NGC 419

The rich SMC star cluster NGC419 has recently been found to present both a broad main sequence turn-off and a dual red clump of giants, in the sharp colour-magnitude diagrams (CMD) derived from the High Resolution Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope. In this work, we apply to the NGC419 data the classical method of star formation history (SFH) recovery via CMD reconstruction, deriving for the first time this function for a star cluster with multiple turn-offs. The values for the cluster metallicity, reddening, distance and binary fraction, were varied within the limits allowed by present observations. The global best-fitting solution is an excellent fit to the data, reproducing all the CMD features with striking accuracy. The corresponding star formation rate is provided together with estimates of its random and systematic errors. Star formation is found to last for at least 700 Myr, and to have a marked peak at the middle of this interval, for an age of 1.5 Gyr. Our findings argue in favour of multiple star formation episodes (or continued star formation) being at the origin of the multiple main sequence turn-offs in Magellanic Cloud clusters with ages around 1 Gyr. It remains to be tested whether alternative hypotheses, such as a main sequence spread caused by rotation, could produce similarly good fits to the data.

St. Valentine—patron saint of epilepsy: Illustrating the semiology of seizures over the course of six centuries

From the 15th century to the present day, Christian art has portrayed people who suffer from epilepsy as attributes in illustrations of Saint Valentine (SV). The objective of our study was to interpret the works of art from a modern epileptological perspective on the basis of a collection of portrayals of SV in Europe that was as comprehensive as possible. The people depicted as attributes were analyzed with respect to their age, gender, social status, and possible seizure semiology. Three hundred forty-one illustrations of SV from Austria, Belgium, Croatia, Czech Republic, France, Germany, Hungary, Ireland, Italy, Luxembourg, Poland, Scotland, Slovakia, and Switzerland were systematically analyzed. Irrespective of the age of the work of art, among the 143 pictures of people with possible epilepsy characteristics, there were more males than females from various levels of society. As far as could be interpreted, there were 17 infants, 35 children, 7 adolescents, and 84 adults. With respect to possible seizure semiology, infantile spasms (n=10), atonic seizures (n=13), tonic seizures (n=53), absences (n=2), psychogenic seizures (n=4), and postictal or undefinable states (n=61) were differentiated in a subjective assessment. Despite the fact that from a modern perspective, the 15th to 20th centuries in Europe seemed to be dominated by a rather superstitious attitude toward epilepsy, there is striking accuracy in the detail of the semiology in many of the historic portrayals, and a well-founded knowledge of epilepsy is apparent.

Investigating Self-Similarity and Heavy-Tailed Distributions on a Large-Scale Experimental Facility

After the seminal work by Taqqu et al. relating self-similarity to heavy-tailed distributions, a number of research articles verified that aggregated Internet traffic time series show self-similarity and that Internet attributes, like Web file sizes and flow lengths, were heavy-tailed. However, the validation of the theoretical prediction relating self-similarity and heavy tails remains unsatisfactorily addressed, being investigated using either numerical or network simulations, or from uncontrolled Web traffic data. Notably, this prediction has never been conclusively verified on real networks using controlled and stationary scenarios, prescribing specific heavy-tailed distributions, and estimating confidence intervals. With this goal in mind, we use the potential and facilities offered by the large-scale, deeply reconfigurable and fully controllable experimental Grid5000 instrument, combined with state-of-the-art estimators, to investigate the prediction's observability on real networks. To this end, we organize a large number of controlled traffic circulation sessions on a nationwide real network involving 200 independent hosts. We use a FPGA-based measurement system to collect the corresponding traffic at packet level. We then estimate both the self-similarity exponent of the aggregated time series and the heavy-tail index of flow-size distributions, independently. Not only do our results complement and validate, with a striking accuracy, some conclusions drawn from a series of pioneering studies, but they also bring in new insights on the controversial role of certain components of real networks.

The uncertainty of "accuracy". On the reliability of a variably employed concept

A diagnostic "striking accuracy" causes more inaccuracy than accuracy. Undefined terms like this are nearly worthless because they are used differently in the literature and cannot be compared. To compare the results of diagnostic studies scientifically it is necessary to use defined terms.

Timing is everything: coordination of strike kinematics affects the force exerted by suction feeding fish on attached prey

During aquatic suction feeding, the predator opens its mouth and rapidly expands its buccal cavity, generating a flow field external to the mouth. The rapid expansion of the buccal cavity produces high fluid velocities and accelerations that extend only a short distance from the mouth (about half of one mouth diameter), and only persist for several milliseconds. Therefore, the predator must precisely time its strike to locate the prey within the narrow region of high flow, during the brief period when flow is at its peak. With flow being the agent for transferring force to the prey, the predator may enhance these forces by producing higher water velocities and faster acceleration at the mouth, but also through increasing the strike's accuracy, i.e. locating the prey closer to the mouth at the instant of peak flow speed. The objectives of this study were to directly measure forces exerted by bluegill Lepomis macrochirus on their prey and to determine how bluegill modify force output. Bluegill were offered ghost shrimp tethered to a load cell that recorded force at 5000 Hz, and feeding sequences were synchronously recorded using 500 Hz video. Peak forces exerted on attached 20 mm shrimp ranged from 0.005 N to 0.506 N. In accordance with the short duration of the strikes (average time to peak gape of approximately 13 ms), the forces recorded were brief (approximately 12 ms from initiation to peak force), and force magnitude declined rapidly after peak force. Statistical analysis indicated that rate of buccal expansion, and prey size, but not strike initiation distance, significantly affected peak force. These observed variables were used with results from flow visualization studies to estimate the flow at the prey's location, which allowed the calculation of drag, pressure gradient force and acceleration reaction force. The relationship between these calculated forces and the measured forces was strong, indicating that the model can be used to estimate forces from strike kinematics. This model was then used to study the effects of strike initiation distance on peak force and on the rate of increasing force. Comparisons of model output to empirical results indicated that bluegill time their strike so as to exert an average of approximately 70% of the peak possible force on the prey, and that the observed strike initiation distance corresponded to the distance that maximized modeled force on an attached prey. Our results highlight the ability of bluegill to produce high forces on their prey, and indicate that precision and visual acuity play important roles in prey acquisition, beyond their recognized role in prey detection.

Cutoff solitons and bistability of the discrete inductance-capacitance electrical line: Theory and experiments

A discrete nonlinear system driven at one end by a periodic excitation of frequency above the upper band edge (the discreteness induced cutoff) is shown to be a means to (1) generate propagating breather excitations in a long chain and (2) reveal the bistable property of a short chain. After detailed numerical verifications, the bistability prediction is demonstrated experimentally on an electrical transmission line made of 18 inductance-capacitance (LC) cells. The numerical simulations of the LC -line model allow us also to verify the breather generation prediction with a striking accuracy.

Simulation of Conventional and Inverted Braced Excavations Using Subloading tij Model

ABSTRACT Different construction sequences may be used in braced excavations. In the conventional or “ordinary method”, temporary retaining walls are initially placed and struts are used to brace them as the excavation proceeds downwards. In an “alternative method”, sometimes called “inverted excavation”, the tunnel walls are used to retain the surrounding earth, while the roof slab helps to brace the excavation. Laboratory model tests were devised to simulate these construction procedures. The tests were carried out under two-dimensional conditions, using aluminum rods to represent the soil mass. The walls were constructed with aluminum plates fully instrumented with strain gauges in both sides to measure the bending strains of the wall. Cylindrical bars with and without springs were used to brace the excavation in the ordinary method; while an instrumented aluminum block was used as the top slab in the alternative method. As excavation proceeded, all data relative to surface settlements, wall deflections and bending moments, as well as axial strut loads was carefully recorded. Later the laboratory tests were simulated with finite element analyses using the recently proposed subloading tij model (Nakai and Hinokio, 2004). The numerical results were compared with the experimental data obtained during the models tests for both construction methods. The overall recorded behavior in terms of displacements, deflection, bending moment and axial load could be reproduced with striking accuracy both qualitatively and quantitatively. This shows the capability of the model to represent the complex behavior of granular materials even under the low stress range used in the model tests. The results of model tests and numerical analyses show that the alternative method is viable and effective in controlling induced surface settlements, provided that the tunnel walls are constructed with an appropriate thickness.

The defensive strike of five species of lanceheads of the genus Bothrops (Viperidae)

We studied the defensive strike of one species of each of five recognized lineages within the genus Bothrops, namely, B. alternatus, B. jararaca, B. jararacussu, B. moojeni and B. pauloensis. The defensive strike of the studied species was in general similar to that of Crotalus viridis and C. atrox, but some important differences were observed. Bothrops alternatus and B. pauloensis struck preferentially from a tight body posture, whereas B. jararaca and B. moojeni from a loose body posture. Defensive strikes were either true or false (during the latter, the mouth remains closed or partially open). Almost all strikes were successful; only on a few occasions snakes missed their target (flawed strikes). Strike variables were very conservative among the five species, especially strike distance and height, and one possible explanation may be related to constraints imposed on strike variables as a way of increasing strike accuracy.

Multidimensional analysis of suction feeding performance in fishes: fluid speed, acceleration, strike accuracy and the ingested volume of water

Suction feeding fish draw prey into the mouth using a flow field that they generate external to the head. In this paper we present a multidimensional perspective on suction feeding performance that we illustrate in a comparative analysis of suction feeding ability in two members of Centrarchidae, the largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus). We present the first direct measurements of maximum fluid speed capacity, and we use this to calculate local fluid acceleration and volumetric flow rate. We also calculated the ingested volume and a novel metric of strike accuracy. In addition, we quantified for each species the effects of gape magnitude, time to peak gape, and swimming speed on features of the ingested volume of water. Digital particle image velocimetry (DPIV) and high-speed video were used to measure the flow in front of the mouths of three fish from each species in conjunction with a vertical laser sheet positioned on the mid-sagittal plane of the fish. From this we quantified the maximum fluid speed (in the earthbound and fish's frame of reference), acceleration and ingested volume. Our method for determining strike accuracy involved quantifying the location of the prey relative to the center of the parcel of ingested water. Bluegill sunfish generated higher fluid speeds in the earthbound frame of reference, accelerated the fluid faster, and were more accurate than largemouth bass. However, largemouth bass ingested a larger volume of water and generated a higher volumetric flow rate than bluegill sunfish. In addition, because largemouth bass swam faster during prey capture, they generated higher fluid speeds in the fish's frame of reference. Thus, while bluegill can exert higher drag forces on stationary prey items, largemouth bass more quickly close the distance between themselves and prey. The ingested volume and volumetric flow rate significantly increased as gape increased for both species, while time to peak gape had little effect on the volume. However, peak gape distance did not affect the maximum fluid speed entering the mouth for either species. We suggest that species that generate high fluid speeds in the earthbound frame of reference will commonly exhibit small mouths and a high capacity to deliver force to buccal expansion, while species that ingest a large volume of water and generate high volumetric flow rates will have larger buccal cavities and cranial expansion linkage systems that favor displacement over force delivery.

On the fine structure of sunspot penumbrae

In this paper we study the fine structure of the penumbra as inferred from the uncombed model (flux tube embedded in a magnetic surrounding) when applied to penumbral spectropolarimetric data from the neutral iron lines at 6300 Å. The inversion infers very similar radial dependences in the physical quantities (LOS velocity, magnetic field strength etc.) as those obtained from the inversion of the Fe I 1.56 μm lines. In addition, the large Stokes V area asymmetry exhibited by the visible lines helps to constrain the size of the penumbral flux tubes. As we demonstrate here, the uncombed model is able to reproduce the area asymmetry with striking accuracy, returning flux tubes as thick as 100-300 kilometers in the vertical direction, in good agreement with previous investigations.

Model of molecular bonding based on the Bohr–Sommerfeld picture of atoms

We develop a model of molecular binding based on the Bohr–Sommerfeld description of atoms together with a constraint taken from conventional quantum mechanics. The model can describe the binding energy curves of H 2, H 3 and other molecules with striking accuracy. Our approach treats electrons as point particles with positions determined by extrema of an algebraic energy function. Our constrained model provides a physically appealing, accurate description of multi-electron chemical bonds.

Binary Liquid Mixtures. The Relation between Surface Tension and Surface Composition as Studied by MIES (Metastable Induced Electron Spectroscopy)

For a binary liquid mixture, we define the surface fraction of a component as the fraction of the surface which is covered by this species. The perfectly surface-sensitive electron spectroscopy MIES (metastable induced electron spectroscopy) allows to derive this quantity in a very direct manner from experiment with no model assumption needed. We find for several binary mixtures that the surface tension depends linearly on the surface fraction with striking accuracy. Even more surprising is the fact that for a system which deviates from this simple linear behavior the surface tension turns out to be a piecewise linear function of the surface fraction. Tentatively, we introduce as possible explanation the concept of phase separation within the surface layer. Further, we show that the surface molar fraction, i.e., the molar fraction within the top surface layer, deviates significantly from a linear or a piecewise linear relation to the surface tension.

The study of a new designed table tennis racket for training strike accuracy

This chapter reviews the use of natural and synthetic fibres in composite nonwovens. It begins by reviewing the use of natural fibres including the most widely used: cotton, jute, kenaf and flax. Most nonwoven fibres are still, however, synthetic. The rest of the chapter discusses the use of polypropylene, polyester, polyethylene and nylon. The chapter concludes by reviewing the use of bicomponent fibres to combine the properties of different fibre types in maximising the functionality of nonwovens.

Comparison of empirical bond-valence and first-principles energy calculations for a complex structural instability

A simple bond-strain parameter, the so-called global-instability index, defined within the bond-valence model reproduces with striking accuracy the basic features of the ab initio total-energy surface around the energy minimum of $\mathrm{Sr}{\mathrm{Bi}}_{2}{\mathrm{Ta}}_{2}{\mathrm{O}}_{9}$, but only for the degrees of freedom within the subspace of energetically unstable modes. These results imply that ab initio total-energy calculations and bond-valence criteria could be combined in the study and prediction of structural instabilities. The quantitative agreement between total-energy and bond-valence maps might be related to the irrelevance of cation-cation and anion-anion interactions within this subspace.

The Effects of Differing Overhead Heights on Shoulder Fatigue during a Repetitive Intermittent Task

The purpose of this study was to determine the effect of different overhead work heights on shoulder fatigue. Ten participants (6 males, 4 females) with manual work experience were recruited to perform a dynamic intermittent overhead task simulating automotive assembly work. Participants performed a keyboard tapping task using a hand tool at three different heights, relatively to individual anthropometry, for up to one hour. Throughout the trials, electromyography (EMG) was recorded from three shoulder muscles (anterior deltoid, middle deltoid, and trapezius), and subjective ratings of perceived discomfort (RPD) were obtained. Key striking accuracy was used as a measure of task performance. Though results were not always statistically significant, the EMG, RPD, and performance measures all indicated that higher working heights generally lead to more rapid onset of fatigue.

The use of ground-borne vibrations for prey localization in the Saharan sand vipers (Cerastes).

Sand vipers of the genus Cerastes are specialized semi-fossorial snakes that launch predatory strikes at rodents and lizards while partially buried in the soft sand of the Saharan desert. This study attempted to document which environmental stimuli are used by these snakes as a trigger for the ambush behavior. Denervating the olfactory and vomeronasal organs produced no changes in prey capture behavior in Cerastes cerastes. Occluding the eyes of the denervated specimens resulted in significant decreases in strike distance, diversity of strike angle and strike accuracy, demonstrating the importance of visual stimuli for target acquisition in this species. Nevertheless, every olfactory-denervated, temporarily blinded specimen succeeded in capturing free-ranging mice in every trial. Presentation of chemosensory-neutral targets to the olfactory-denervated, temporarily blinded specimens resulted in similar predatory behaviors, whether the target was isothermic to the environment or heated to mammalian body temperature. Collectively, these results provide evidence for the importance of visual stimuli during foraging in C. cerastes, the first experimental evidence for foraging by vibration detection in snakes and the strongest evidence to date that snakes are capable of 'hearing' vibrational stimuli.

The unexplained accuracy of the Lagrange-mesh method.

The Lagrange-mesh method is an approximate variational calculation which resembles a mesh calculation because of the use of a Gauss quadrature. In order to analyze its accuracy, four different Lagrange-mesh calculations based on the zeros of Laguerre polynomials are compared with exact variational calculations based on the corresponding Laguerre basis. The comparison is performed for three solvable radial potentials: the Morse, harmonic-oscillator, and Coulomb potentials. The results show that the accuracies of the energies obtained for different partial waves with the different mesh approximations are very close to the variational accuracy, even in the presence of the centrifugal singularity. The same property holds for the approximate wave functions. This striking accuracy remains unexplained.

A chaotic attractor in ecology: theory and experimental data

Chaos has now been documented in a laboratory population. In controlled laboratory experiments, cultures of flour beetles ( Tribolium castaneum) undergo bifurcations in their dynamics as demographic parameters are manipulated. These bifurcations, including a specific route to chaos, are predicted by a well-validated deterministic model called the “LPA model”. The LPA model is based on the nonlinear interactions among the life cycle stages of the beetle (larva, pupa and adult). A stochastic version of the model accounts for the deviations of data from the deterministic model and provides the means for parameterization and rigorous statistical validation. The chaotic attractor of the deterministic LPA model and the stationary distribution of the stochastic LPA model describe the experimental data in phase space with striking accuracy. In addition, model-predicted temporal patterns on the attractor are observed in the data. This paper gives a brief account of the interdisciplinary effort that obtained these results.