Circadian variations in biologically closed electrochemical circuits in Aloe vera and Mimosa pudica

The circadian clock regulates a wide range of electrophysiological and developmental processes in plants. This paper presents, for the first time, the direct influence of a circadian clock on biologically closed electrochemical circuits in vivo. Here we show circadian variation of the plant responses to electrical stimulation. The biologically closed electrochemical circuits in the leaves of Aloe vera and Mimosa pudica, which regulate their physiology, were analyzed using the charge stimulation method. The electrostimulation was provided with different timing and different voltages. Resistance between Ag/AgCl electrodes in the leaf of Aloe vera was higher during the day than at night. Discharge of the capacitor in Aloe vera at night was faster than during the day. Discharge of the capacitor in a pulvinus of Mimosa pudica was faster during the day. The biologically closed electrical circuits with voltage gated ion channels in Mimosa pudica are also activated the next day, even in the darkness. These results show that the circadian clock can be maintained endogenously and has electrochemical oscillators, which can activate ion channels in biologically closed electrochemical circuits. We present the equivalent electrical circuits in both plants and their circadian variation to explain the experimental data.     

A 3D Shape Measurement Technique that Makes Use of a Printed Line Pattern

The in-house validation of finite element models for bird strike events is currently carried out by means of experimental tests on flat plates. High displacement speeds in these experiments require a low exposure time of the high-speed camera (up to 1/50,000 s). In order to acquire images of sufficient quality, a special, high-intensity light source has to be used, which does not always turn out to be possible. Therefore, the regions with high displacement speeds often result in blurry images. In such cases, a printed line pattern to estimate the shape of the plate during the test, offers major advantages over a speckle pattern in terms of the reconstruction and optimization of the blurry regions. In this article, a stereo vision technique is presented that was developed to reconstructs 3D shape maps using images of impacted plates with printed line patterns. It is shown that two cameras are necessary to calculate accurate shape maps in case of large deflections. The resulting shapes can be used for the validation of numerical simulations.     

Synthesis and Characterization of Oxazaborinin Phosphonate for Blue OLED Emitter Applications

A blue-light emitting material based on a boron complex containing heteroaromatic phosphonate ligand is synthesized and characterized. The Phospho-Fries rearrangement is used in the synthesis route of the ligand as a convenient method of introducing phosphonate groups into phenols. Structural, thermal and photophysical properties of the resulting oxazaborinin phosphonate compound have been characterized. DFT geometry optimizations were studied as well as the spatial position and symmetry of the HOMO and LUMO. Good thermal stability up to 250 °C enables vacuum deposition methods next to solution processing. Combining the work function with the optical band gap from UV-Vis measurements shows that band alignment is possible with standard contact materials. Photoluminescence reveals an emission peak at 428 nm, which is suitable for a blue light-emitter.     

Phenol-Catalyzed Discharge in the Aprotic Lithium-Oxygen Battery

Discharge in the lithium-O₂ battery is known to occur either by a solution mechanism, which enables high capacity and rates, or a surface mechanism, which passivates the electrode surface and limits performance. The development of strategies to promote solution-phase discharge in stable electrolyte solutions is a central challenge for development of the lithium-O₂ battery. Here we show that the introduction of the protic additive phenol to ethers can promote a solution-phase discharge mechanism. Phenol acts as a phase-transfer catalyst, dissolving the product Li₂O₂, avoiding electrode passivation and forming large particles of Li₂O₂ product—vital requirements for high performance. As a result, we demonstrate capacities of over 9 mAh cm⁻²_areal, which is a 35-fold increase in capacity compared to without phenol. We show that the critical requirement is the strength of the conjugate base such that an equilibrium exists between protonation of the base and protonation of Li₂O₂.     

Variational inequalities with cone constraints

The present paper considers variational inequalities with cone and operator constraints. The characterization of solutions is given. An algorithm for numerical solution of the problem is proposed, and the convergence of the generated sequence of points is proved.This research was supported in part by the Science Foundation of the Republic of Serbia.The author thanks two anonymous referees for their helpful remarks.     

Charge induced closing of Dionaea muscipula Ellis trap

In terms of bioelectrochemistry, Venus flytrap responses can be considered in three stages: stimulus perception, electrical signal transmission, and induction of mechanical and biochemical responses. When an insect touches the trigger hairs, these mechanosensors generate receptor potentials, which induce solitary waves activating the motor cells. We found that the electrical charge injected between a midrib and a lobe closes the Venus flytrap leaf by activating motor cells without mechanical stimulation of trigger hairs. The mean electrical charge required for the closure of the Venus flytrap leaf is 13.6 muC. To close the trap, electrical charge can be submitted as a single charge or applied cumulatively by small portions during a short period of time. Ion channel blocker such as Zn(2+) as well as an uncoupler CCCP, dramatically decreases the speed of the trap closing a few hours after treatment of the soil. This effect is reversible. After soil washing by distilled water, the closing time of Venus flytrap treated by CCCP or ZnCl(2) decreases back from 2-5 s to 0.3 s, but higher electrical charge is needed for trap closure. The mechanism behind closing the upper leaf of Venus flytrap is discussed.     

Anisotropy and nonlinear properties of electrochemical circuits in leaves of Aloe vera L

Plant tissue has biologically closed electrical circuits and electric fields that regulate its physiology. The biologically closed electrochemical circuits in the leaves of Aloe vera were analyzed using the charge stimulation method with Ag/AgCl electrodes inserted along a leaf at 1-2 cm distance. The electrostimulation was provided with different timing and different voltages. Strong electrical anisotropy of the leaves was found. In the direction across the leaf the electrical circuits remained passive and linear, while along the leaf the response remained linear only at small voltages not exceeding 1 V. At higher potentials the circuits became strongly non-linear pointing to the opening of voltage gated ion channels in the plant tissues. Changing the polarity of electrodes located along conductive bundles led to a strong rectification effect and to different kinetics of capacitor discharge. Equivalent electrical circuit models of the leaf were proposed to explain the experimental data.     

Electrocatalytic CO2 Reduction on CuOx Nanocubes: Tracking the Evolution of Chemical State,Geometric Structure,and Catalytic Selectivity using Operando Spectroscopy

The direct electrochemical conversion of carbon dioxide (CO₂) into multi-carbon (C₂₊) products still faces fundamental and technological challenges. While facet-controlled and oxide-derived Cu materials have been touted as promising catalysts, their stability has remained problematic and poorly understood. Herein we uncover changes in the chemical and morphological state of supported and unsupported Cu₂O nanocubes during operation in low-current H-Cells and in high-current gas diffusion electrodes (GDEs) using neutral pH buffer conditions. While unsupported nanocubes achieved a sustained C₂₊ Faradaic efficiency of around 60 % for 40 h, the dispersion on a carbon support sharply shifted the selectivity pattern towards C₁ products. Operando XAS and time-resolved electron microscopy revealed the degradation of the cubic shape and, in the presence of a carbon support, the formation of small Cu-seeds during the surprisingly slow reduction of bulk Cu₂O. The initially (100)-rich facet structure has presumably no controlling role on the catalytic selectivity, whereas the oxide-derived generation of under-coordinated lattice defects, can support the high C₂₊ product yields.     

The importance of surface morphology in controlling the selectivity of polycrystalline copper for CO2 electroreduction

This communication examines the effect of the surface morphology of polycrystalline copper on electroreduction of CO(2). We find that a copper nanoparticle covered electrode shows better selectivity towards hydrocarbons compared with the two other studied surfaces, an electropolished copper electrode and an argon sputtered copper electrode. Density functional theory calculations provide insight into the surface morphology effect.     

Rapid method for determination of protein content in cereals and oilseeds: validation, measurement uncertainty and comparison with the Kjeldahl method

The objective of this research was to test suitability of the Dumas combustion method to completely substitute the Kjeldahl method in routine laboratory determination of crude protein content in cereals and oilseeds. The validation of the method demonstrated that it is able to determine crude protein content in cereals and oilseeds in an efficient and accurate manner, with a detection limit w(N) = 0.006%, quantification limit w(N) = 0.019%, repeatability precision RSD _r = 0.41%, intra-laboratory reproducibility precision RSD _R = 0.74%, trueness, expressed in terms of bias b = 0.43%, and linear response between (2.36–19.2) mg N. Measurement uncertainty, expressed as relative expanded uncertainty (coverage factor k = 2, confidence level 95%), was calculated from validation data (U _rel = 2.24%). In order to examine the relationship between two methods, 15 cereal grain and oilseed samples were analyzed using Dumas and Kjeldahl procedure. The Kjeldahl procedure gave slightly lower w(N) values than the Dumas procedure: w _K(N) = 0.9905 w _D(N) = 0.0376 (R ²  = 0.9996). Relative standard deviations and results of homogeneity test obtained during analysis of complex cereal products (cereal breakfast and muesli bars) show that the Dumas combustion method may be less suitable for analysis of such samples compared to Kjeldahl method.