Ballistic transport pdf

At t 5 0, animals and close-up images of the bill, throat, x 5 0, the distance x t corresponded to the and tongue movements during each feeding horizontal distance from time of release.

Only truly lateral sequences for each The distance covered by the projected food of the species 15 sequences per animal were used was approximately similar to the distance J. Feeding behaviour in toucans. Gape is the angle between tip of the upper jaw and jaw corner and tip of the lower jaw.

The gape cycle used for food catching is not presented because the bird turned the head in all of the recorded sequences. The dashed lines separate the three successive cycles into the positioning phase.

For each step, the images of the bird show three selected times during one cycle see text for explanations. The birds of both species always use one transport cycle in each feeding sequence. The position of these times are indicated by the blue lines. The vertical line corresponds to the time of release of the food. We focus primarily on the test of the effect The method of calculation is described in of species. Our data adhere to the assumptions of Appendix A.

Kinematic Kinematic variables were calculated on 30 variables were compared using a two-way ANOVA transport cycles 8—12 per individual in R. A same model was also conducted R.

The transport cycles are independent for initial velocity V0, the angle a, the kinetic because they were digitized from feeding energy, the maximal height of the food at the J. The effect of individuals and interac- between the upper and lower beaks.

During the tions were then tested over the residual. The food followed a trajectory divided into two successive steps Figs. For food items beak by using various number of successive gape of mean weight 5. When the food was positioned, the head of the food at the time of release was 0. Table 1 presents the kinematic variables Table 2.

This velocity was 0. The birds took Fig. The angle a Time and Maximal gape was for R. The food followed a closing cycle without slow and fast stages.

The throat Table 2. Kinematics of the ballistic trajectories generated during food transport Kinematics Maximal gape 1 2. These para- Kinetic energy J 0. Representative trajectory of the food in R. The colors indicate the observed trajectory of the food green before time of release, to along ballistic curve observed: red; calculated: blue. V0: initial velocity, a: angle at time of release, x—y: axes of the 2D plane where the trajectory of the food was followed, W: weight.

The axes are indicated at the time of release for R. Colors as in c. The labels of the vertical axis in a are degrees for a and cm for distances. With large food items Our study reveals a highly specialized feeding individually ingested, the food also is moved by mechanism in neognathous birds: the ballistic inertial transport. When mouth is closed, depres- transport mechanism. In such tongue never participates in food catching, posi- cranioinertial feeding, the head of the bird is tioning, or transporting.

Our kinematic data can either angled toward the substratum in prepara- be compared with previous studies in neognathous tion for the next pecking or oriented almost and paleognathous birds. In paleognathous birds horizontally Tomlinson, ; Gussekloo and i.

In the pigeon Zeigler used to move food near or into the entrance of the et al. Never is the to the esophagus in three steps for small food J. Each step involves a combined move- therefore in a almost vertical movement. In neognathous based food transport. Parrots use a complex birds, Tomlinson states that kinetic energy movement of the tongue for manipulating and is imparted to large food items by rapid lifting of transporting the food Homberger, Our data to move the food from the tip of the beak to show that both species of toucans use a transport the pharynx, suggesting a similar mechanism mechanism showing some similarities to the Figs.

The direction of the movement of the food mostly only effect of food weight was in the number of vertical in other birds and oblique to the hori- positioning cycles, which tends to increase for zontal plane in toucans are completely different. Time to maximal tongue elevation coin- called inertial feeding. The head is never moved cides with time to maximal throat depression, forward to the food after its rotation.

Compared with other neognathous birds, the This jaw—hyolingual coordination seems to be features of the ballistic transport mechanism similar to that recorded for cranioinertial feeding recorded in toucans and also in hornbills, in Paleognatha, and is rather different compared Baussart and Bels, ; Baussart et al. However, tongue action food items available in the canopy of tropical in ballistic transport is different from the cranio- forests e.

The described motor inertial mechanism. The tongue is not employed to response can presumably allow the beak to enlarge the buccal cavity because it is elevated maintain morphological specializations that can within the space between the upper and lower bills be used in other functions i. This mechanism is also associated with with kinetic energy provided during backward head a major change in lingual size and shape.

The rotation without any contact with the tongue. The food is moving the food from tip of the beak to the clearly thrown between the upper and lower jaws pharynx.

Functionally, this highly specialized with low kinetic energy. The shape of the beak is not a accelerated upward and slightly backward in constraint for ballistical movement of the food inertial transport in birds. The jaws then open with the trajectory between the open lower and and the head moves slightly forward. The acceler- upper jaws. The possible role of the tongue ated food continues its upward movement while in other functions remains to be discovered.

The food The difference in beak length and therefore the is therefore transported toward the pharynx by distance that must be covered by the food, in the opposing movement of the food and the head.

The longer beak in R. Both species and therefore swallow whole fruits or large show a similar mean of initial velocity, and the pieces of fruits. Currently, only hornbills are food covers the required distance between known to use a similar mechanism, although head position at the time of release and the entrance movements and postures seem to be different of the esophagus with a different angle a at the from those recorded in both species of toucans time of release.

Baussart and Bels, For example, several birds i. This model is suggested to show features The specialization of the feeding mechanism in of the plesiomorphic transport gape cycle in these two lineages of birds toucans and hornbills Amniotes.

Slow opening I SO-I is determined has evidently profound ecological implications by a low gape angle and tongue sliding beneath the because eating whole fruits permits these animals food item. In the model pro- Park Paradisio Mr.

Both models assume that our study. We thank Dr. The key toucans. We are McBrayer and Reilly, Ballistic cycle re- very grateful to K. Kardong for constructive corded in toucans can be viewed as a deriving comments. First, the gape cycle is simply divided into comments. The tongue movement only equal to the product of the mass of a solid occurs at the end of the ballistic movement of the by acceleration due to the acceleration of its food in association with the opening of the centre of inertia, in a Gallilean reference.

In this pharyngeal cavity. The food follows a! Ballistic characteristics can be associated with the As we are working in a 2D plane, we ignored the length of the beak of these birds. This kind of acceleration along the z-axis. The coordinates of transport could be one specialized solution to the acceleration are calculated as following: J.

We thus obtain coordinates X and Y in obtained by integration of the above equation: meters according to time. Baussart S, Bels VL. Evolutionary analysis of feeding Coordinates of the position of the food are then mechanism in hornbills. Comp Biochem Physiol A Biomechanics in animal behaviour.

Bels V, Baussart S. In: Bels V, editor. Feeding in domestic condition of the food by two constants k3 and k4 vertebrates from structure to behaviour.

Bock WJ. Functional vertebrate morphology. To compare all of the trajectories, we need to Cambridge: Harvard University Press. De Vree F, Gans C. Feeding in tetrapods. Therefore, the constants k3 and k4 in vertebrates. Berlin: Springer Verlag. The use of distal rhynchokin- are null. At time t 5 0, h height of the food 5 0, esis by birds feeding in water.

J Exp Biol — J Exp Mar Biol Ecol — Non-neotenous origin of the palaeognathous Aves pterygoid-palate complex. Cranial kinesis in palaeog- The form of the trajectory of the food item is nathous birds.

Funct the equation of the trajectory to characterize food Ecol — The avian tongue and larynx: multiple gx functions in nutrition and vocalization. Durban: University of Natal. Solid dashed lines indicate Eq. Approaching the Dirac point in transport S. Figure 10 Temperature-dependent conductivity of SG corresponding to the experimental data of ab Bolotin et al. We theoretically consider, comparing with the existing experimental literature, the electrical conductivity of gated monolayer graphene as a function of carrier density, temperature, and disorder in order to assess the prospects of accessing the Dirac point using transport i in high-quality suspended graphene.

Das Sarma 1 and E. Here we show that the fluctuations are significantly reduced in suspended graphene samples and we report low-temperature mobility approachingcm2 V-1 s-1 for carrier densities below 5 x cm Figure 2 Temperature-dependent electron density n T [Eq.

Das Sarma and E. We show that the temperature dependence of graphene conductivity around the charge neutrality point provides information about how closely the system can approach the Dirac point, although competition between long-range and ballistjc disorder as well as between diffusive and ballistic transport may considerably complicate the picture.

Unlike two-dimensional electron layers in semiconductors, where the charge carriers become immobile at low densities, the carrier mobility in graphene can remain high, even when their density vanishes at the Dirac point.

Solid dashed lines indicate the results with without phonon scattering. The same parameters used in Figs. However, when the graphene sample is supported on an insulating substrate, potential fluctuations induce charge puddles that obscure the Dirac point physics. Figure 5 Conductivity corresponding to the experimental data of Mayorov et al.

The discovery of graphene raises approching prospect of a new class of nanoelectronic devices based on the extraordinary physical properties of this one-atom-thick layer of carbon. Figure 4 Conductivity corresponding to the experimental data of Du et al. Figure 6 Calculated conductivity as a function of density for different temperatures: At higher temperatures, above K, we observe the onset of thermally induced trnasport scattering.

The dashed line indicates the conductivity due to the Coulomb disorder and the short-range disorder. Sign up to receive regular email alerts from Physical Review B. Abstract We theoretically consider, comparing with the existing experimental literature, the electrical conductivity of gated monolayer graphene as a function of carrier density, temperature, and disorder in order to assess the prospects of accessing the Dirac point using transport studies in high-quality suspended graphene.

Such values cannot be attained in semiconductors or non-suspended graphene. Weyl fermions are observed in a solid. Moreover, unlike graphene samples supported by a substrate, the conductivity of suspended graphene at the Dirac point is strongly dependent on temperature and approaches ballistic values at liquid helium temperatures. In d the nonmonotonic behavior at high densities does not appear due to the strong short-range potential scattering, but in high-mobility samples b the nonmonotonic behavior shows up due to the grapgene weaker neutral impurity scatterings.