Proton Flow Research Articles

Kinetic simulation of electron, proton and helium acceleration in a non-relativistic quasi-parallel shock

ABSTRACT In addition to accelerating electrons and protons, non-relativistic quasi-parallel shocks are expected to possess the ability to accelerate heavy ions. The shocks in supernova remnants are generally supposed to be accelerators of Galactic cosmic rays, which consist of many species of particles. We investigate the diffusive shock acceleration of electrons, protons and helium ions in a non-relativistic quasi-parallel shock through a 1D particle-in-cell simulation with a helium-to-proton number density ratio of 0.1, which is relevant for Galactic cosmic rays. The simulation indicates that waves can be excited by the flow of energetic protons and helium ions upstream of a non-relativistic quasi-parallel shock with a sonic Mach number of 14 and an Alfvén Mach number of 19.5 in the shock rest frame, and that the charged particles are scattered by the self-generated waves and accelerated gradually. Moreover, the spectra of the charged particles downstream of the shock are thermal with a non-thermal tail, and the acceleration is efficient, with about $7{{\ \rm per\ cent}}$ and $5.4{{\ \rm per\ cent}}$ of the bulk kinetic energy transferred into the non-thermal protons and helium ions, respectively, in the near downstream region by the end of the simulation.

Estimating Non-Flow Effects in Measurements of Anisotropic Flow of Protons with the HADES Experiment at GSI

Estimating Non-Flow Effects in Measurements of Anisotropic Flow of Protons with the HADES Experiment at GSI

Electrochemical hydrogen storage in porous carbons with acidic electrolytes: Uncovering the potential

Electrochemical hydrogen storage in porous carbon materials is emerging as a cost-effective hydrogen storage and transport technology with competitive power and energy densities. The merits of electrochemical hydrogen storage using porous conductive carbon-based electrodes are reviewed. The employment of acidic electrolytes in such storage systems is compared with alkaline electrolytes. The recent innovations of a proton battery for smaller-scale electricity storage, and a proton flow reactor system for larger (grid)-scale storage and bulk export of hydrogen produced from renewable energy, are briefly described. It is argued that such systems, along with variants proposed by others, all of which rely on electrochemical hydrogen storage in porous carbons, can contribute to the search for energy storage technologies essential for the transition to a zero-emission global economy.

Time dependent hydrogen ENAs fluxes and structure of the heliosphere in the solar magneto-gravitational field

Energetic neutral atoms (ENAs) consisting mainly of hydrogen with energies of several keV and coming from the outer heliosphere have been detected by various spacecraft missions. The characteristics of the energy spectrum of ENAs include a dependence on the proton distribution at the heliospheric boundaries where the solar wind interaction with the local interstellar medium (LISM) occurs. We determine here the time-dependent differential flux for the neutral hydrogen atoms resulting from the kinetic exchange of energy in the outer heliosphere under the solar magnetic field. With the proton flow along the magnetic field lines, the mean kinetic energy of the particles is shown to increases due to the magnetic field line compression at the outer heliosphere, causing the acceleration of the solar wind protons to the observed range of speeds. Also, the toroidal field driven compression and expansion of the magnetic field lines corresponds to the temperature variations observed in the INCA line-of-sight observations of the ENAs in the inner heliosheath, where as the pickup ions retain their accelerated speed inside the heliosphere in the subsequent motion up to ∼1au.

Pioneering the Equation of State of Dense Nuclear Matter with Strange Particles Emitted in Heavy-Ion Collisions: The KaoS Experiment at GSI

High-energy heavy-ion collisions offer the unique possibility to study fundamental properties of nuclear matter in the laboratory, which are relevant for our understanding of the structure of compact stellar objects and the dynamics of neutron star mergers. Of particular interest are the nuclear matter equation of state (EOS), the in-medium modifications of hadrons and the degrees of freedom of matter at high densities and temperatures. Pioneering experiments exploring the EOS for symmetric matter were performed at the SIS18 accelerator of GSI, measuring, as function of beam energy, the collective flow of protons and of light fragments and subthreshold strangeness production. These data were reproduced by various microscopic transport model calculations, providing, up to date, the best constraint for the EOS of symmetric matter with an incompressibility of about 200 MeV for densities up to twice the saturation density. This article reviews the experimental results on subthreshold kaon production together with the theoretical interpretation and gives a brief outlook towards future experiments at higher densities.

Unimolecular Helix-Based Transmembrane Nanochannel with a Smallest Luminal Cavity of 1 Å Expressing High Proton Selectivity and Transport Activity.

Natural protein channels have evolved with exquisite structures to transport ions selectively and rapidly. Learning from nature to construct biomimetic artificial channels is always challenging. Herein we present a unimolecular transmembrane proton channel by quinoline-derived helix, which exhibited highly selective and ultrafast proton transport behaviors. This helix-based channel possesses a small luminal cavity of 1 Å in diameter, which could efficiently reject the permeation of cations, anions or water molecules but only permits the translocation of protons owing to the size effect. The proton flow rate exceeded 107 H+ s-1 channel-1 and reached the same magnitude with gramicidin A. Mechanism investigation revealed that the directionally arrayed NH-chain inside the synthetic channel played a pivotal role during the proton flux. This work not only presented a helix-based channel with the smallest observable nanopore, but also unveiled an unexplored pathway for realizing efficient transport of protons via the consecutive NH-chain.

Electrochemical storage reactions of hydrogen in activated carbon from phenolic resin

Electrochemical storage of neutralised protons in porous carbon materials such as activated carbons and multi-layer graphene is becoming possible using novel technologies such as the proton battery and proton flow reactor. This set-up is a promising option for electrical energy storage at various scales, and possibly for exporting a zero-emission hydrogen-based fuel. This paper focusses on understanding and identifying the contributions to hydrogen storage in activated carbon from phenolic resin (aC PR) from processes such as electric double layer capacitance, electrosorption, cationic concentration by intercalation in ultramicropores, and reversible faradaic (redox) reactions between hydronium, and negatively-charged carbon surfaces inside pores with and without intermediary oxygen groups. A combination of XPS, Raman, and infrared spectroscopy is employed to identify the forms of C⋯H reactions involved, together with temperature programmed desorption, cyclic voltammetry and galvanostatic charging and discharging. Experimental evidence for the formation of C⋯H bonding in aC PR is presented, which promises to be sufficient for use of this and similar carbon materials as a solid-state hydrogen storage material with competitive energy density.

Ion Selective Membranes

Ion Selective Membranes

Vacuolar-type proton ATPase is required for maintenance of apicobasal polarity of embryonic visceral endoderm

The endocytic compartments keep their interior acidic through the inward flow of protons and anions from the cytosol. Acidification is mediated by a proton pump known as vacuolar-type ATPase (V-ATPase) and transporters conferring anion conductance to the organellar membrane. In this study, we analysed the phenotype of mouse embryos lacking the V-ATPase c-subunit. The mutant embryos differentiated embryonic epithelial tissues, primitive endoderm, epiblast, and extraembryonic ectoderm; however, the organisation of these epithelia was severely affected. The apical-basal polarity in the visceral endoderm layer was not properly established in the mutant embryos, resulting in abnormal epithelial morphology. Thus, the function of V-ATPase is imperative for the establishment and/or maintenance of epithelial cell polarity, which is required for early embryogenesis.

Ambiplasma separation into matter and antimatter by a train of baryon-acoustic solitons in the problem of the baryon asymmetry of the Universe

Longitudinal electrostatic baryon-acoustic waves have been studied systematically which can propagate in the uniform thermodynamically-nonequilibrium unmagnetized ambiplasma. The research was carried out in the frames of the linear theory and nonlinear theory according to the method of Sagdeev's pseudopotential. Two types of the periodic waves with in-phase (slow wave) and antiphase oscillations (fast wave) of protons and antiprotons were specified. The unknown before possibility of the existence of super-nonlinear waves in ambiplasma was shown for the first time. Fast and slow solitons were specified also. Wave profiles were calculated for all types of waves, they include flux profiles in the laboratory frame.Average proton and antiproton fluxes were calculated for the period of oscillations in the waves. It was shown that periodic trains of fast solitons could direct flows of protons and antiprotons in the opposite directions. This fact can be provided as a possible explanation of the baryon asymmetry of the modern Universe.

Effects of nuclear deformation in U$+$U collisions at the intermediate energy

Nuclear deformation is an important topic in the study of nuclear structure. The influence of nuclear structure on nuclear reactions and heavy-ion collisions has attracted considerable attention recently. Based on the ultra-relativistic quantum molecular dynamics (UrQMD) model, the effect of nuclear deformation in $^{238}$U$+$$^{238}$U at the beam energy of łinebreak 0.4 GeV/nucleon is investigated and several observables, such as the stopping power, collective flow, and $\pi^{-}/\pi^{+}$ yield ratio, are calculated. It is found that the stopping power obtained with tip-tip (the two nuclei with their long axes head-on) collisions is the largest among collisions with different deformations. For belly-belly (the two nuclei with their short axes head-on and long axes parallel in the reaction plane) collisions, the elliptic flow exists even for the most central collision ($b$=0 fm). $\pi^{-}/\pi^{+}$yield ratio obtained with tip-tip collision is larger than that obtained with belly-belly collision. In addition, the influence of nuclear deformation on the elliptic flow of free protons is stronger than that of nuclear symmetry energy in $^{238}$U$+$$^{238}$U collisions at 0.4 GeV/nucleon, while the elliptic flow ratio between neutrons and protons shows hardly any sensitivity to different deformations of uranium.

Clarification of Arachidonic Acid Metabolic Pathway Intricacies.

Surrounding inflammation activates phospholipase A2, which cleaves and releases arachidonic acid (ARA) from cell membranes. The four cis double bonds are instrumental in ARA susceptibility to oxidation, resulting in the generation of numerous bioactive metabolites of critical importance for the immune system, namely inflammation in response to pathogens, resolution of inflammation, wound healing, and mood and energy balance. The ARA metabolism steps are replete with intricacies, deterring researchers from identifying targets, which could be useful in modulating the synthesis of ARA metabolites toward exclusive protection of the host from pathogens, endogenous excessive danger signals, pain, inflammation, stress, and anxiety disorders. While ARA metabolic pathways are reasonably defined, it was deemed mandatory to fully clarify the flow and direction of protons, electrons, and oxygen atoms and the intricacies behind formation and breakage of double bonds and cyclic structures. This in-depth novel information will perfect the development of strategies and drugs aimed at counteracting inflammation and promoting healing.

$$\alpha$$-clustering effect on flows of direct photons in heavy-ion collisions

In this work, we reconstruct the $\gamma$-photon energy spectrum which is in good agreement with the experimental data of $^{86}$Kr + $^{12}$C at $E/A$ = 44 MeV in the framework of our modified EQMD model. The directed flow and elliptic flow of free protons and direct photons have been investigated by taking $\alpha$-clustering structure of $^{12}$C into account. Comparing with the free proton, the direct photon flows give a clearer information about early stage of nuclear reaction. Difference of collective flows between different configurations of $^{12}$C is observed in this work. This indicates that collective flows of direct photons are sensitive to the initial configuration, therefore the $\gamma$ bremsstrahlung process might be taken as an alternative probe to investigate $\alpha$-clustering structure in light nucleus from heavy ion collisions at Fermi-energy region.

Dependence of Solar Wind Proton Temperature on the Polarization Properties of Alfvénic Fluctuations at Ion-kinetic Scales

Abstract We use fluctuating magnetic helicity to investigate the polarization properties of Alfvénic fluctuations at ion-kinetic scales in the solar wind as a function of β p , the ratio of proton thermal pressure to magnetic pressure, and θ vB , the angle between the proton flow and local mean magnetic field, B 0. Using almost 15 yr of Wind observations, we separate the contributions to helicity from fluctuations with wavevectors, k , quasi-parallel and oblique to B 0, finding that the helicity of Alfvénic fluctuations is consistent with predictions from linear Vlasov theory. This result suggests that the nonlinear turbulent fluctuations at these scales share at least some polarization properties with Alfvén waves. We also investigate the dependence of proton temperature in the β p –θ vB plane to probe for possible signatures of turbulent dissipation, finding that it correlates with θ vB . The proton temperature parallel to B 0 is higher in the parameter space where we measure the helicity of right-handed Alfvénic fluctuations, and the temperature perpendicular to B 0 is higher where we measure left-handed fluctuations. This finding is inconsistent with the general assumption that by sampling different θ vB in the solar wind we can analyze the dependence of the turbulence distribution on θ kB , the angle between k and B 0. After ruling out both instrumental and expansion effects, we conclude that our results provide new evidence for the importance of local kinetic processes that depend on θ vB in determining proton temperature in the solar wind.

Three dimensional multi-physics modeling and simulation for assessment of mass transport impact on the performance of a high temperature polymer electrolyte membrane fuel cell

The impact of multi-species transports on the performance of a high temperature polymer electrolyte membrane fuel cell (HTPEMFC) is studied by incorporating multi-physics electro-kinetics in a 3D model at 180 °C. A base-case 3D model simulation was carried-out and the validation results showed a very good agreement with the experimental results. The results showed overall performance improvements in HTPEMFC at various parametric conditions. Higher membrane thickness has reduced the cell performance significantly due to increased membrane resistance to the proton flow whereas higher membrane conductivity produced the largest performance improvements among all operating conditions considered. The results showed that the electrolyte ionic current transport is higher close to the channel and lower in the center regions. The hydrogen concentrations went down significantly at the outlet due to uniform consumption of hydrogen throughout the porous electrode. A non-uniform oxygen concentration pattern was observed within the HTPEMFC due to non-homogeneous transport and consumption of oxygen from inlet to the outlet. The water vapor concentration is higher at the outlet, since more water vapor production through increased electro-chemical reactions, as the reactants transported from inlet to the outlet. The 3D model simulation results will be advantageous for further diagnostic analysis of the HTPEMFC systems.

Hydrous Proton Transfer through Graphene Interlayer: An Extraordinary Mechanism under Magnifier

AbstractBalancing ionic selectivity against permeability in filters made from graphene remains a challenge today. Interlayer distance, as the most important factor, dominates nearly all aspects of the flow inside the channel, from the formation of water molecules to the hydration shell of the ions. Unraveling the effects of the interlayer distance on the proton diffusion process helps lay a foundation for the cutting‐edge proton conduction technology. Here, the reactive molecular dynamics simulations are used to probe the proton flow through a series of hydrated graphene channels with different interlayer distance values. The results show that the proton‐selectivity experiences a sharp increase when the channel height is reduced to values under 8 Å, which is near the end of the hydration radii range of the monovalent and divalent cations. Reducing the interlayer distance also decreases the number of confined water molecules, consequently reducing the proton diffusion rate as the hopping platform fades. This way, spatial hindrance combined with the proton‐selective Grotthuss mechanism provide a proton‐exclusive membrane. The outputs of this work can be used for the optimization of proton‐exclusive nanochannels and to serve affordable proton‐exchange membranes (PEMs) for technological advancement in diverse fields from PEM fuel cells to storing liquid hydrogen.

Enhanced hydrogen production of Rhodobacter sphaeroides promoted by extracellular H+ of Halobacterium salinarum

PurposeThis study utilized the principle that the bacteriorhodopsin (BR) produced by Halobacterium salinarum could increase the hydrogen production of Rhodobacter sphaeroides. H. salinarum are co-cultured with R. sphaeroides to determine the impact of purple membrane fragments (PM) on R. sphaeroides and improve its hydrogen production capacity.MethodsIn this study, low-salinity in 14 % NaCl domesticates H salinarum. Then, 0–160 nmol of different concentration gradient groups of bacteriorhodopsin (BR) and R. sphaeroides was co-cultivated, and the hydrogen production and pH are measured; then, R. sphaeroides and immobilized BR of different concentrations are used to produce hydrogen to detect the amount of hydrogen. Two-chamber microbial hydrogen production system with proton exchange membrane-assisted proton flow was established, and the system was operated. As additional electricity added under 0.3 V, the hydrogen production rate increased with voltages in the coupled system.ResultsH salinarum can still grow well after low salt in 14% NaCl domestication. When the BR concentration is 80 nmol, the highest hydrogen production reached 217 mL per hour. Both immobilized PC (packed cells) and immobilized PM (purple membrane) of H. salinarum could promote hydrogen production of R. sphaeroides to some extent. The highest production of hydrogen was obtained by the coupled system with 40 nmol BR of immobilized PC, which increased from 127 to 232 mL, and the maximum H2 production rate was 18.2 mL−1 h−1 L culture. In the 192 h experiment time, when the potential is 0.3 V, the hydrogen production amount can reach 920 mL, which is 50.3% higher than the control group.ConclusionsThe stability of the system greatly improved after PC was immobilized, and the time for hydrogen production of R. sphaeroides significantly extended on same condition. As additional electricity added under 0.3 V, the hydrogen production rate increased with voltages in the coupled system. These results are helpful to build a hydrogen production-coupled system by nitrogenase of R. sphaeroides and proton pump of H. salinarum.Graphical abstract

Probing the boundary of phase transition of nuclear matter using proton flows in heavy-ion collisions at 2-8 GeV/nucleon

Based on the relativistic transport model ART with the hadronic equation of state extended to have a phase transition via the use of the MIT bag model, properties of phase transition of dense nuclear matter formed in relativistic heavy-ion collisions are investigated. Proton sideward and directed flows are calculated with different equation of states in Au + Au collisions at beam energies of 2, 4, 6 and 8 GeV/nucleon. Compared with AGS experimental data in existence, the boundary of first-order phase transition is roughly confined, i.e., in the range of 2.5-4 times saturation density with temperature about 64-94 MeV. Such constraints are useful for ongoing RHIC Beam Energy Scan-II program to study the QCD matter phase diagram.

Structure and mechanism of the proton-driven motor that powers type 9 secretion and gliding motility.

Three classes of ion-driven protein motors have been identified to date: ATP synthase, the bacterial flagellar motor, and a proton-driven motor that powers gliding motility and the Type 9 protein secretion system (T9SS) in Bacteroidetes bacteria. Here, we present cryo-EM structures of the gliding motility/T9SS motors GldLM from Flavobacterium johnsoniae and PorLM from Porphyromonas gingivalis. The motor is an asymmetric inner membrane protein complex in which the single transmembrane helices of two periplasm-spanning GldM/PorM proteins are positioned inside a ring of five GldL/PorL proteins. Mutagenesis and single-molecule tracking identifies protonatable amino acid residues in the transmembrane domain of the complex that are important for motor function. Our data provide evidence for a mechanism in which proton flow results in rotation of the periplasm-spanning GldM/PorM dimer inside the intra-membrane GldL/PorL ring to drive processes at the bacterial outer membrane.

Random pore-network model for polymer electrolyte membranes.

A random pore-network model for polymer electrolyte membranes (PEM) is presented that couples the flow of protons and water through cylindrical channels to the swelling of the membrane. While the flows are determined by closed-form solutions of the Poisson-Nernst-Planck-Stokes equations, the fluid-structure interaction is described by a pressure balance at the channel walls. Macroscopic membrane properties, such as the conductivity, permeability and electro-osmotic coefficient, are computed and compared to experimental data in the literature. In light of the model simplifications, the results compare favourably to data but they also point to the importance of describing proton diffusion in PEM nanopores accurately.