Renormalized Surface Charge Density for a Strongly Charged Plate in Asymmetric Electrolytes: Asymptotic Exact Results in Poisson Boltzmann Theory

The Poisson-Boltzmann equation for a strongly charged plate inside a generic charge-asymmetric electrolyte is solved using the method of asymptotic matching. Both near field and far field asymptotic behaviors of the potential are systematically analyzed. Using these expansions, the renormalized surface charge density is obtained as an asymptotic series in terms of the bare surface charge density.Comment: 11 pages, 4 eps figure

the hidden biodiversity data retained in pre linnaean works a case study with two important xvii century italian entomologists

Before Linnaeus published the Systema Naturae, in which introduced the modern species concept, a huge amount of information on ecology, behaviour and diversity of many animals had been accumulated. This information, often extremely detailed, suffers from the lack of the assignation of the studied organisms to their modern specific names. Here, we examine in detail the works of Antonio Vallisneri (1661–1730), one of the most important figures of early experimental entomology in Italy. We analyse the ecological and ethological contributions of Vallisneri, as well as those that Diacinto Cestoni (1637–1718), another Italian naturalist, sent to Vallisneri, to the knowledge of parasitoid, predatory and gall-making wasps (Hymenoptera), by studying the Saggio de' Dialoghi sopra la curiosa origine di molti Insetti and the Quaderni di Osservazioni I-III, trying to assign current taxonomy to the observed insects based on eco-ethological and morphological descriptions. Valuable data have been found in the analysed works on taxonomically diverse ecological webs involving wasps. Information regarded a variety of hymenopteran parasitoids of other Hymenoptera, dipteran parasitoids of Hymenoptera, coleopteran parasitoids of Hymenoptera, and hymenopteran parasitoids associated with non-hymenopteran hosts. Overall, about 20 wasp genera could have been objects of Vallisneri and Cestoni observations, which include the first detailed ecological and ethological data on many of them. Detailed re-examinations of ancient studies may contribute to our knowledge on biodiversity by providing historical distribution data as well as unveiling trophic interactions that may have been modified due to biodiversity loss in the last century

Segmented and "equivalent" representation of the cable equation.

The linear cable theory has been applied to a modular structure consisting of n repeating units each composed of two subunits with different values of resistance and capacitance. For n going to infinity, i.e., for infinite cables, we have derived analytically the Laplace transform of the solution by making use of a difference method and we have inverted it by means of a numerical procedure. The results have been compared with those obtained by the direct application of the cable equation to a simplified nonmodular model with "equivalent" electrical parameters. The implication of our work in the analysis of the time and space course of the potential of real fibers has been discussed. In particular, we have shown that the simplified ("equivalent") model is a very good representation of the segmented model for the nodal regions of myelinated fibers in a steady situation and in every condition for muscle fibers. An approximate solution for the steady potential of myelinated fibers has been derived for both nodal and internodal regions. The applications of our work to other cases dealing with repeating structures, such as earthworm giant fibers, have been discussed and our results have been compared with other attempts to solve similar problems

Carrying unbalanced weights in hovering flight: effect of prey position on load maximization in wasps

With a simple mathematical model, it was recently shown that wasps which carry their load in flight forward their center of gravity suffer a reduction of the theoretical maximum load that can be carried. Here, we 1) implement the model considering the effect of an additional factor (the presence of induced wind), and 2) apply the model to determine the reduction of maximum load suffered by wasps of the genera Oxybelus and Sceliphron, which carry their resource load posteriorly or anteriorly to the center of gravity along the longitudinal body axis. The induced wind has a negligible effect on maximum load, within the approximation level of the analysis. Assuming that the load is located along the wasp longitudinal body axis, in the unbalanced situation (MmaxU) is strongly reduced (of about 75% in Oxybelus or about 45% in Sceliphron) when compared to balanced situation (Mmax). A way to face this severe reduction could be that to increase the angle x which the straight line connecting the wasp with the load centers of mass makes with the horizontal line; for example, at x=80\uba Oxybelus would suffer a reduction of maximum load of about 40% of Mmax. As a consequence of these results, weight of prey collected by Oxybelus females, on average, resulted lower than the Mmax but heavier than the MmaxU at x=45\uba, and did not differ from MmaxU at x=80\uba. This last situation seems suitable to represent the fact that prey is often maintained below the wasp body axis. As an additional result, we estimated, for Oxybelus, a particular high value of the lift coefficient is necessary. This suggests the presence in Oxybelus (but not in Sceliphron) of non-steady aerodynamical effects

The movement of spermatozoa with helical head: theoretical analysis and experimental results.

The present work is concerned with the study of the swimming of flagellated microscopic organisms with a helical head and a helical pattern of flagellar beating, such as Xenopus sperms. The theoretical approach is similar to that taken by Chang and Wu (1971) in the study of helical flagellar movement. The model used in the present study allows us to determine the velocity of propulsion (U) and the frequency of rotation of the sperm head (fh) as a function of the frequency of the wave of motion (ft) traveling along the tail. The results relative to the case of helical and planar flagellar waves are compared. Our main finding is that the helical shape of the head seems to increase the efficiency of propulsion of the spermatozoon when compared with the more commonly shaped spherical head. Experimentally measured values of fh versus U may be fitted by a linear plot whose slope is much higher than that corresponding to the case of planar flagellar beating. This fact is consistent with an effectively three-dimensional (nonplanar) movement of the flagellar tail. However, the results do not fit those predicted from a circular helix, suggesting that a different shape of the flagellar beating should be considered

Computer reconstruction of the spread of excitation in nerve terminals with inhomogeneous channel distribution.

A direct numerical integration method, as modified by Du Fort and Frankel (1953), has been used to solve the partial differential equation system which describes the spread of action potential in a mammalian nerve terminal. Branching of the terminal as well as inhomogeneous distributions of Na+ and K+ voltage-dependent channels (Brigant and Mallart 1982) have been incorporated in the model. Using the channel densities and the kinetic parameters measured in the node of Ranvier, the depolarization in the terminal branches has an amplitude of only 60% of the action potential in the node. Furthermore, the time courses of the calculated membrane currents differ considerably from the ones measured by Brigant and Mallart (1982) and by Konishi and Sears (1984). Increasing the Na+ and K+ channel densities may considerably increase the terminal depolarization and also reproduce qualitatively the current wave-forms observed experimentally. The model can also reproduce some of the effects of pharmacological channel blocks. The simulation allows a new interpretation of the different components of membrane current along the terminal