18O/16O isotope exchange for yttria stabilised zirconia in dry and humid oxygen

The oxygen surface kinetics and mechanism of oxygen interaction between oxygen from the gas phase and yttria-stabilised zirconia nano-sized powder have been studied by pulse ¹⁸O/¹⁶O isotope exchange (PIE) in dry (O₂) and humid (mixture O₂ + H₂O with pH₂O = 2.6 kPa at T = 22 °C) oxygen atmospheres in comparison with micro-sized powder. Dependences of the heterogeneous oxygen exchange rate (r_H) in the temperature range from 550 to 900 °C, and oxygen partial pressure range in the carrier gas and pulses of 5–19% have been obtained. It has been established that the presence of water causes a decrease in the heterogeneous oxygen exchange rate due to the presence of strongly bound hydroxyl groups in the nanopores of the sample. Differences between the mechanisms of isotopic exchange for dry and humid atmospheres have been found in this temperature range (550–700 °C). The observed differences are associated with the interaction of the gas phase and hydroxyls in the adsorbed layer of the oxide. An original method for the separation of the contributions of three types of oxygen exchange for dry and humid atmospheres has been proposed.     

An Efficient Approach to Fabricate Air-Stable Perovskite Solar Cells via Addition of a Self-Polymerizing Ionic Liquid

Despite the excellent photovoltaic properties achieved by perovskite solar cells at the laboratory scale, hybrid perovskites decompose in the presence of air, especially at high temperatures and in humid environments. Consequently, high-efficiency perovskites are usually prepared in dry/inert environments, which are expensive and less convenient for scale-up purposes. Here, a new approach based on the inclusion of an in situ polymerizable ionic liquid, 1,3-bis(4-vinylbenzyl)imidazolium chloride ([bvbim]Cl), is presented, which allows perovskite films to be manufactured under humid environments, additionally leading to a material with improved quality and long-term stability. The approach, which is transferrable to several perovskite formulations, allows efficiencies as high as 17% for MAPbI₃ processed in air % relative humidity (RH) ≥30 (from an initial 15%), and 19.92% for FAMAPbI₃ fabricated in %RH ≥50 (from an initial 17%), providing one of the best performances to date under similar conditions.     

Colchicine activates actin polymerization by microtubule depolymerization

Dog exposure to doses from 39 to 124 Gy results in an increase of heart rate and tension in control of the cardiac rhythm, the extent being dose dependent. An additional physical load on the cardiovascular animals system reveals a high functional control reserves of the cardiovascular system which provides stable functioning even after exposure to the above doses.     

Prognostic factors in patients with carcinoma of the uterine cervix treated with external beam irradiation and IR-192 high-dose-rate brachytherapy

The spectral properties of the protochlorophyllide forms in the epicotyls of dark-grown pea seedlings have been studied in a temperature range, from 10 to 293 K with conventional fluorescence emission and excitation spectroscopy as well as by fluorescence line narrowing (FLN) at cryogenic temperatures. The conventional fluorescence techniques at lower temperatures revealed separate bands at 628, 634-636, 644 and 655 nm. At room temperature (293 K) the 628 and 634-636 nm emission bands strongly overlapped and the band shape was almost independent of the excitation wavelength. Under FLN conditions, vibronically resolved fluorescence spectra could be measured for the 628 and 634-636 nm bands. The high resolution of this technique excluded the excitonic nature of respective excited states and made it possible to determine the pure electronic (0,0) range of the spectra of the two components. Thus it was concluded that the 628 and 634-636 nm (0,0) emission bands originate from two monomeric forms of protochlorophyllide and the spectral difference is interpreted as a consequence of environmental effects of the surrounding matrix. On the basis of earlier results and the data presented here, a model is discussed in which the 636 nm form is considered as an enzyme-bound protochlorophyllide and the 628 nm form as a protochlorophyllide pool from which the substrate is replaced when the epicotyl is illuminated with continuous light.     

Conopressin affects excitability, firing, and action potential shape through stimulation of transient and persistent inward currents in mulluscan neurons

The molluscan vasopressin/oxytocin-related neuropeptide conopressin activates two persistent inward currents in neurons from the anterior lobe of the right cerebral ganglion of Lymnaea stagnalis that are involved in the control of male copulatory behavior. The low-voltage-activated (LVA) current is activated at a wide range of membrane potentials, its amplitude being only weakly voltage dependent. The high-voltage-activated (HVA) current is activated at potentials positive to -40 mV only and shows a steep voltage dependence. Occurrence of both currents varies from cell to cell, some expressing both and others only the HVA current. In most neurons that have the LVA current, a conopressin-independent persistent inward current (INSR) is found that resembles the HVA current in its voltage dependence. The functional importance of the LVA and HVA currents was studied under current-clamp conditions in isolated anterior lobe neurons. In cells exhibiting both current types, the effect of activation of the LVA current alone was investigated as follows: previously recorded LVA current profiles were injected into the neurons, and the effects were compared with responses induced by conopressin. Both treatments resulted in a strong depolarization and firing activity. No differences in firing frequency and burst duration were observed, indicating that activation of the LVA current is sufficient to evoke bursts. In cells exhibiting only the HVA current, the effect of conopressin on the response to a depolarizing stimulus was tested. Conopressin reversibly increased the number of action potentials generated by the stimulus, suggesting that the HVA current enhances excitability and counteracts accommodation. Conopressin enhanced action potential broadening during depolarizing stimuli in many neurons. Voltage-clamp experiments performed under ion-selective conditions revealed the presence of transient sodium and calcium currents. Using the action potential clamp technique, it was shown that both currents contribute to the action potential. The calcium current, which is activated mainly during the repolarizing phase of the action potential, is augmented by conopressin. Thus conopressin may directly modulate the shape of the action potential. In summary, conopressin may act simultaneously on multiple inward currents in anterior lobe neurons of Lymnaea to affect firing activity, excitability, and action potential shape.     

Effect of flow on first-pass metabolism of drugs: single pass studies on 4-methylumbelliferone conjugation in the serially perfused rat intestine and liver preparations

Intracellular in vivo recordings of physiologically identified inferior colliculus central nucleus (ICc) auditory neurons (n = 71) were carried out in anesthetized guinea pigs. The neuronal membrane characteristics are described showing mainly quantitative differences with a previous report [Nelson, P.G. and Erulkar, S.D., J. Neurophysiol., 26 (1963) 908-923]. The spontaneous spike activity was consistent with the discharge pattern of most extracellularly recorded units. The action potentials showed different spike durations, short and long, and some of them exhibited hyperpolarizing post-potentials. There were also differences in firing rate. The ICc neurons exhibited irregular activity producing spike trains as well as long silent periods (without spikes). Intracellular current injection revealed membrane potential adaptation and shifts that outlasted the electrical stimuli by 20-30 ms. Both evoked synaptic potentials and the spike activity in response to click and tone-burst stimulation were analyzed. Depolarizing-hyperpolarizing synaptic potentials were found in response to contralateral and binaural sound stimulation that far outlasted the stimulus (up to 90 ms). When ipsilaterally stimulated, inhibitory responses and no-responses were also recorded. Although few cells were studied, a similar phenomenon was observed using tone-burst stimulation; moreover, a good correlation was obtained between membrane potential shifts and the triggered spikes (input-output relationship). These in vivo results demonstrate the synaptic activity underlying many of the extracellularly recorded discharge patterns. The data are consistent with the known multi-synaptic ascending pathway by which signals arrive at the ICc as well as the descending corticofugal input that may contribute to the generation of long duration post-synaptic potentials.     

Cross-validation of two liquid water path retrieval algorithms applied to ground-based microwave radiation measurements by the RPG-HATPRO instrument

A built-in operational regression algorithm (REA) of liquid water path (LWP) retrieval supplied by the manufacturer of the RPG-HATPRO microwave (MW) radiometer has been compared to a so-called physical algorithm (PHA) based on the inversion of the radiative transfer equation. The comparison has been performed for different scenarios of MW observations by the RPG-HATPRO instrument that has been operating at St. Petersburg University since June 2012. The data for the scenarios have been collected within the time period December 2012–December 2014. The estimations of bias and random error for both REA and PHA have been obtained. Special attention has been paid to the analysis of the quality of the LWP retrievals before and after rain events that have been detected by the built-in rain sensor. The estimation has been done of the time period after a rain event when the retrieval quality should be considered as insufficient.     

Tailoring Surface Properties via Functionalized Hydrofluorinated Graphene Compounds

A new compound material of 2D hydrofluorinated graphene (HFG) is demonstrated whose relative hydrogen/fluorine concentrations can be tailored between the extremes of either hydrogenated graphene (HG) and fluorinated graphene (FG). The material is fabricated through subsequent exposures to indirect hydrogen plasma and xenon difluoride (XeF₂). Controlling the relative concentration in the HFG compound enables tailoring of material properties between the extremes offered by the constituent materials and in‐plane patterning produces micrometer‐scale regions with different surface properties. The utility of the technique to tailor the surface wettability, surface friction, and electrical conductivity is demonstrated. HFG compounds display wettability between the extremes of pure FG with contact angle of 95° ± 5° and pure HG with contact angle of 42° ± 2°. Similarly, the HFG surface friction may be tailored between the two extremes. Finally, the HFG electrical conductivity tunes through five orders of magnitude when transitioning from FG to HG. When combined with simulation, the electrical measurements reveal the mechanism producing the compound to be a dynamic process of adatom desorption and replacement. This study opens a new class of 2D compound materials and innovative chemical patterning with applications for atomically thin 2D circuits consisting of chemically/electrically modulated regions.