Tree-level entanglement in quantum electrodynamics

We report on a systematic study on the entanglement between helicity degrees of freedom generated at tree level in quantum electrodynamics two-particle scattering processes. We determine the necessary and sufficient dynamical conditions for outgoing particles to be entangled with one another, and expose the hitherto unknown generation of maximal or nearly maximal entanglement through Bhabha and Compton scattering. Our work is an early step in revisiting quantum field theory and high-energy physics in the light of quantum information theory

Contributions of Intracellular Ions to Kv Channel Voltage Sensor Dynamics

Voltage-sensing domains (VSDs) of Kv channels control ionic conductance through coupling of the movement of charged residues in the S4 segment to conformational changes at the cytoplasmic region of the pore domain, that allow K+ ions to flow. Conformational transitions within the VSD are induced by changes in the applied voltage across the membrane field. However, several other factors not directly linked to the voltage-dependent movement of charged residues within the voltage sensor impact the dynamics of the voltage sensor, such as inactivation, ionic conductance, intracellular ion identity, and block of the channel by intracellular ligands. The effect of intracellular ions on voltage sensor dynamics is of importance in the interpretation of gating current measurements and the physiology of pore/voltage sensor coupling. There is a significant amount of variability in the reported kinetics of voltage sensor deactivation kinetics of Kv channels attributed to different mechanisms such as open state stabilization, immobilization, and relaxation processes of the voltage sensor. Here we separate these factors and focus on the causal role that intracellular ions can play in allosterically modulating the dynamics of Kv voltage sensor deactivation kinetics. These considerations are of critical importance in understanding the molecular determinants of the complete channel gating cycle from activation to deactivation

Uncoupling of Gating Charge Movement and Closure of the Ion Pore During Recovery from Inactivation in the Kv1.5 Channel

Both wild-type (WT) and nonconducting W472F mutant (NCM) Kv1.5 channels are able to conduct Na+ in their inactivated states when K+ is absent. Replacement of K+ with Na+ or NMG+ allows rapid and complete inactivation in both WT and W472F mutant channels upon depolarization, and on return to negative potentials, transition of inactivated channels to closed-inactivated states is the first step in the recovery of the channels from inactivation. The time constant for immobilized gating charge recovery at −100 mV was 11.1 ± 0.4 ms (n = 10) and increased to 19.0 ± 1.6 ms (n = 3) when NMG+o was replaced by Na+o. However, the decay of the Na+ tail currents through inactivated channels at −100 mV had a time constant of 129 ± 26 ms (n = 18), much slower than the time required for gating charge recovery. Further experiments revealed that the voltage-dependence of gating charge recovery and of the decay of Na+ tail currents did not match over a 60 mV range of repolarization potentials. A faster recovery of gating charge than pore closure was also observed in WT Kv1.5 channels. These results provide evidence that the recovery of the gating elements is uncoupled from that of the pore in Na+-conducting inactivated channels. The dissociation of the gating charge movements and the pore closure could also be observed in the presence of symmetrical Na+ but not symmetrical Cs+. This difference probably stems from the difference in the respective abilities of the two ions to limit inactivation to the P-type state or prevent it altogether

NH2-terminal Inactivation Peptide Binding to C-type–inactivated Kv Channels

In many voltage-gated K+ channels, N-type inactivation significantly accelerates the onset of C-type inactivation, but effects on recovery from inactivation are small or absent. We have exploited the Na+ permeability of C-type–inactivated K+ channels to characterize a strong interaction between the inactivation peptide of Kv1.4 and the C-type–inactivated state of Kv1.4 and Kv1.5. The presence of the Kv1.4 inactivation peptide results in a slower decay of the Na+ tail currents normally observed through C-type–inactivated channels, an effective blockade of the peak Na+ tail current, and also a delay of the peak tail current. These effects are mimicked by addition of quaternary ammonium ions to the pipette-filling solution. These observations support a common mechanism of action of the inactivation peptide and intracellular quaternary ammonium ions, and also demonstrate that the Kv channel inner vestibule is cytosolically exposed before and after the onset of C-type inactivation. We have also examined the process of N-type inactivation under conditions where C-type inactivation is removed, to compare the interaction of the inactivation peptide with open and C-type–inactivated channels. In C-type–deficient forms of Kv1.4 or Kv1.5 channels, the Kv1.4 inactivation ball behaves like an open channel blocker, and the resultant slowing of deactivation tail currents is considerably weaker than observed in C-type–inactivated channels. We present a kinetic model that duplicates the effects of the inactivation peptide on the slow Na+ tail of C-type–inactivated channels. Stable binding between the inactivation peptide and the C-type–inactivated state results in slower current decay, and a reduction of the Na+ tail current magnitude, due to slower transition of channels through the Na+-permeable states traversed during recovery from inactivation

Anesthésie locale de la langue des bovidés en vue du titrage du virus aphteux

Fédida Maurice. Anesthésie locale de la langue des bovidés en vue du titrage du virus aphteux. In: Bulletin de l'Académie Vétérinaire de France tome 111 n°8, 1958. pp. 441-447

A dynamic approach for air traffic flow management of arriving aircraft at a congested airport

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1994.Includes bibliographical references (leaves 105-106).by Fabien Fedida.M.S

Entanglement entropy in scalar quantum electrodynamics

We find the entanglement entropy of a subregion of the vacuum state in scalar quantum electrodynamics, working perturbatively to the two-loop level. Doing so leads us to derive the Maxwell-Proca propagator in conical Euclidean space. The area law of entanglement entropy is recovered in both the massive and massless limits of the theory, as is expected. These results yield the renormalization group flow of entanglement entropy, and we find that loop contributions suppress entanglement entropy. We highlight these results in the light of the renormalization group flow of couplings and correlators, which are increased in scalar quantum electrodynamics, so that the potential tension between the increase in correlations between two points of spacetime and the decrease in entanglement entropy between two regions of spacetime with energy is discussed. We indeed show that the vacuum of a subregion of spacetime purifies with energy in scalar quantum electrodynamics, which is related to the concept of screening

N-terminal PDZ-binding domain in Kv1 potassium channels

AbstractWe have investigated the interactions of prototypical PDZ domains with both the C- and N-termini of Kv1.5 and other Kv channels. A combination of in vitro binding and yeast two-hybrid assays unexpectedly showed that PDZ domains derived from PSD95 bind both the C- and N-termini of the channels with comparable avidity. From doubly transfected HEK293 cells, Kv1.5 was found to co-immunoprecipitate with the PDZ protein, irrespective of the presence of the canonical C-terminal PDZ-binding motif in Kv1.5. Imaging analysis of the same HEK cell lines demonstrated that co-localization of Kv1.5 with PSD95 at the cell surface is similarly independent of the canonical PDZ-binding motif. Deletion analysis localized the N-terminal PDZ-binding site in Kv1.5 to the T1 region of the channel. Co-expression of PSD95 with Kv1.5 N- and C-terminal deletions in HEK cells had contrasting effects on the magnitudes of the potassium currents across the membranes of these cells. These findings may have important implications for the regulation of channel expression and function by PDZ proteins like PSD95