Presence Of Open Channels Research Articles

Coupled-channel effects in hadron–hadron correlation functions

Two-particle momentum correlation functions as measured in heavy ion collisions or in high-energetic proton–proton collisions are studied. Special emphasis is put on systems like ΛΛ or K−p where effects from the coupling to other channels could be relevant. In both cases other channels open at relatively low momenta or are already open at the reaction threshold. To have a solid basis, realistic coupled-channel interactions for ΛΛ−ΞN−ΛΣ−ΣΣ and πΛ−πΣ−K¯N are utilized in the actual calculations. It is found that the opening of the ΞN channel leaves a trace in the ΛΛ correlation function that could be detectable in experiments. Should the proposed H-dibaryon be located close to or below the ΞN it will have a very pronounced effect. The presence of open channels in systems like Ξ−p or K−p does influence the correlation functions significantly at low momenta and will certainly complicate any dedicated analysis.

Vanadium Dioxide Reduced Graphene Oxide Composite As Cathode Materials for Rechargeable Li and Na Batteries

In recent years, new cathode materials have been intensively investigated, as the demand for rechargeable batteries are increasing with the rapid growth of technology for electronic devices and electric vehicles. Among them, metastable form of vanadium dioxide, denoted as VO2(B), has gained great interest owing to its electrode potential and its tunnel structure which is ideal for ions intercalation/deintercalation. In this study, VO2(B)]modified with and without reduced graphene oxide (rGO) were synthesized via solvothermal method. The obtained products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). X-ray diffraction study reveals that the electrochemical reaction of VO2(B)/rGO is progressed based on deintercalation and intercalation of alkali ions (Li+ and Na+) into and out of the crystal structure; this is caused by the presence of open channels in the crystal structure of VO2(B). As a result, the resulting electric conductivity of the VO2(B)/rGO composite is improved to ~10-4 cm S-1 (from ~10-7 S cm-1 for the as-received VO2(B)). Electrochemical data of the VO2(B)/rGO composite, tested in both Li and Na cells, shows markedly enhanced electrochemical performance compared to bare VO2(B). The effect of electro-conducting rGO is more evident at high rates. The results show that solvothermally synthesized VO2(B)/rGO composite can be a potential cathode material for rechargeable batteries.

Fracture, failure and compression behaviour of a 3D interconnected carbon aerogel (Aerographite) epoxy composite

Aerographite (AG) is a mechanically robust, lightweight synthetic cellular material, which consists of a 3D interconnected network of tubular carbon [1]. The presence of open channels in AG aids to infiltrate them with polymer matrices, thereby yielding an electrical conducting and lightweight composite. Aerographite produced with densities in the range of 7–15 mg/cm3 was infiltrated with a low viscous epoxy resin by means of vacuum infiltration technique. Detailed morphological and structural investigations on synthesized AG and AG/epoxy composite were performed by scanning electron microscopic techniques. The present study investigates the fracture and failure of AG/epoxy composites and its energy absorption capacity under compression. The composites displayed an extended plateau region when uni-axially compressed, which led to an increase in energy absorption of ∼133% per unit volume for 1.5 wt% of AG, when compared to pure epoxy. Preliminary results on fracture toughness showed an enhancement of ∼19% in KIC for AG/epoxy composites with 0.45 wt% of AG. Observations of fractured surfaces under scanning electron microscope gives evidence of pull-out of arms of AG tetrapod, interface and inter-graphite failure as the dominating mechanism for the toughness improvement in these composites. These observations were consistent with the results obtained from photoelasticity experiments on a thin film AG/epoxy model composite.

Structure–property correlation of nanostructured WO3 thin films produced by electrodeposition

Nanocrystalline tungsten oxide (WO3) films were electrodeposited potentiostatically at room temperature on transparent conducting substrates from an ethanolic solution of acetylated peroxotungstic acid prepared from a wet chemistry process. The changes that occur in the microstructure and the grain size of the as-deposited WO3 films as a function of annealing temperature are simultaneously accompanied by a continually varying electrochromic performance. X-ray diffraction studies revealed the transformation of a nanocrystalline as-deposited WO3 film into a highly crystalline triclinic WO3 as the annealing temperature was raised from room temperature to 500 °C. The microstructural evolution with the increasing annealing temperature of the as-deposited film was further exemplified by transmission electron microscopy (TEM) studies. While the as-deposited film was composed of uniformly distributed ultra fine nanograins, the most noticeable feature seen in these films annealed at 250 °C was the presence of open channels which are believed to promote lithium ion motion. Films annealed at 400 °C exhibited coarse grains with prominent grain boundaries that hinder lithium ion movement, which in turn reduces the film’s ion insertion capacity. In concordance with the TEM results, the 250 °C film had the highest ion storage capacity as it exhibited a charge density of 67.4 mC cm−2 μm−1. The effect of microstructure was also reflected in the high transmission modulation (64%) and coloration efficiency (118 cm2 C−1) of the 250 °C film at 632.8 nm. Contrary to the superior electrochromic performance of the 250 °C film, the optical switching speeds between the colored and bleached states of the as-deposited WO3 film declined considerably as a function of annealing temperature. Also, the diffusion coefficient for lithium ions was greater by at least an order of magnitude for the as-deposited film as compared to the 250 and 500 °C films. In this report, the influence of microstructural changes that are brought about by the annealing of the as-deposited WO3 films on their coloration-bleaching dynamics is evaluated in terms of their structural, electrochromic, and electrochemical properties.

Flexoelectric effects in model and native membranes containing ion channels.

An experimental study of flexoelectricity in model membranes containing ion pores and native membranes containing ion channels has been undertaken with the objective of determining the relationship, if any, between flexoelectricity and ion transport. Model membrane patches containing ion pores induced by a blue-green algal toxin, microcystin-LR, and locust muscle membrane patches containing potassium channels were studied using patch-clamp techniques. A correspondence was established between the presence of open channels and pores and the amplitude of the 1st harmonic of the total membrane current when the membranes or patches were subjected to pressure oscillations. The 2nd harmonic of the membrane current provided a measure of the amplitude of a membrane curvature induced by pressure, thus making it possible to determine the membrane flexoelectric coefficient. This study shows that flexoelectricity could be an effective driving force for ion transport through membrane pores and channels, thus further highlighting the possible biological significance of this mechano-electric phenomenon.

Two-Coulomb-exchange potential in the presence of open channels.

We use the techniques of dispersion theory to study the long-range behavior of the two-Coulomb-exchange potential acting between two atoms, or between an atom and a charged system such as an ion or electron, in the presence of open channels. In contrast to earlier work, we avoid the use of a multipole expansion. We focus on the case of atoms in initial S states. When one of the systems is in an excited state or the relative kinetic energy is large enough to allow excitation, the potential has an imaginary part that falls off exponentially with distance in the absence of degeneracy and as an inverse power in the presence of degeneracy of the initial state. The asymptotic form of the real part is unchanged from that found in the closed-channel case.