1,10‐Phenanthroline–H2O2–KSCN–CuSO4–NaOH oscillating chemiluminescence system

In this paper, oscillating chemiluminescence (CL), 1,10‐phenanthroline H₂O₂–KSCN–CuSO₄–NaOH system, was studied in a batch reactor. The system described is a novel, slowly damped oscillating CL system, generated by coupling the well‐known Epstein–Orban, H₂O₂–KSCN–CuSO₄–NaOH chemical oscillator reaction with the CL reaction involving the oxidation of 1,10‐phenanthroline by hydrogen peroxide, catalyzed by copper(II) in alkaline medium. In this system, the CL reaction acts as a detector or indicator system of the far‐from‐equilibrium dynamic system. Narrow and slightly asymmetric light pulses of 1.2 s half‐width are emitted at 440 nm with an emitted light time of 200–1000 s, induction period of 3.5–357 s and oscillation period of 28–304 s depending on the reagent concentrations. In this report the effect of the concentration variation of components involved in the oscillating CL system on the induction period, the oscillation period and amplitude was investigated and the parameters were plotted with respect to reagent concentrations. Copper concentration showed a significant effect on the oscillation period. The possible mechanism for the oscillating CL reaction was also discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

From central–peripheral to adaxial–abaxial

Higher plants are constructed of three organs – the stem, the root and the leaf. The stem and the root have two axes, apical–basal and central–peripheral, which cross orthogonally. Leaves develop from the shoot apical meristem as lateral organs that have three different axes, apical–basal, adaxial–abaxial and right–left. Recent data point to the possibility that the adaxial–abaxial axis in the leaf is formed from the central–peripheral axis in the stem.     

Predator–rodent–plant interactions along a coast–inland gradient in Fennoscandian tundra

Spatial variation in the strength of trophic cascades in arctic tundra has been related to flows of subsidies across ecosystem boundaries. Here, we ask whether the input of marine subsidies in tundra systems would cause spatial variation in the strength of rodent–plant interactions between coastal areas, where predators have access to marine‐derived resources, and non‐subsidized inland areas of northern Fennoscandia. We present a detailed evaluation of predator–rodent–vegetation interactions along a coast‐inland gradient, during the 2011 rodent outbreak and the two following decline years, by using direct assessments of rodent impacts and tracing of marine‐derived nutrients in the food web. Our results revealed that the main rodent predator during summer, the long‐tailed jaeger Stercorarius longicaudus, did not benefit from marine resources while breeding (relative dietary proportion in chicks’ diet = 0–3%). Contrary to this pattern, parasitic jaegers S. parasiticus, bred exclusively near the coast and preyed effectively on both marine resources (41% of chicks’ diet) and rodents (12%). Mammalian predators also showed a higher activity during winter near the coast. Despite overall higher predator numbers, no evidence was found for lower rodent population growth rates during the three monitoring summers and for weaker rodent grazing impacts in the coastal area. Instead, we documented pronounced damages caused by lemmings and voles on bryophytes and vascular plants, especially dwarf shrubs (e.g. Vaccinum myrtillus) all along the coast–inland gradient. Taken together, our results did not support the hypothesis that marine subsidies would trigger a trophic cascade in coastal tundra areas of northern Fennoscandia during a major rodent outbreak, probably due to a relatively low diversity of marine‐subsidized predators in the region. Comparative observational and experimental studies at large spatial scales in various arctic regions are absolutely necessary for a better understanding of factors causing regional variations in the functioning of arctic food webs.     

Metal–Air Batteries with High Energy Density: Li–Air versus Zn–Air

In the past decade, there have been exciting developments in the field of lithium ion batteries as energy storage devices, resulting in the application of lithium ion batteries in areas ranging from small portable electric devices to large power systems such as hybrid electric vehicles. However, the maximum energy density of current lithium ion batteries having topatactic chemistry is not sufficient to meet the demands of new markets in such areas as electric vehicles. Therefore, new electrochemical systems with higher energy densities are being sought, and metal‐air batteries with conversion chemistry are considered a promising candidate. More recently, promising electrochemical performance has driven much research interest in Li‐air and Zn‐air batteries. This review provides an overview of the fundamentals and recent progress in the area of Li‐air and Zn‐air batteries, with the aim of providing a better understanding of the new electrochemical systems.     

Ho3+‐doped strontium–aluminium–bismuth–borate glasses for green light emission

Strontium–aluminium–bismuth–borate glasses (SAlBiB) doped with different concentrations of Ho³⁺ were prepared using conventional melt quenching technique and their structural and optical properties investigated. X‐ray diffraction and scanning electron microscopy analysis were used to study the structural properties. Optical properties were studied by measuring the optical absorption and visible luminescence spectra. The Judd–Ofelt (J‐O) theory was applied to evaluate J‐O intensity parameters, Ω_λ (λ = 2, 4 and 6). Using J‐O intensity parameters, radiative properties such as spontaneous transition probabilities (A_R), branching ratios (β_R) and radiative lifetimes (τ_R) were determined. From the emission spectra, a strong green emission nearly at 549 nm corresponding to the transition, ⁵S₂(⁵F₄)→⁵I₈ was observed. Emission peak positions (λ_P), effective bandwidths (Δλ_eff) and stimulated emission cross‐sections (σ_p) were calculated for the observed emission transitions, ⁵F₃→⁵I₈, ⁵S₂(⁵F₄)→⁵I₈ and ⁵F₅→⁵I₈ of Ho³⁺ in all the glass matrices. Chromaticity color coordinates were calculated using the emission spectra. The experimental results suggest that SAlBiB glass matrix with 1.5 mol% of Ho³⁺ has better emission properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Optimal design of the Wilcoxon–Mann–Whitney‐test

In scientific research, many hypotheses relate to the comparison of two independent groups. Usually, it is of interest to use a design (i.e., the allocation of sample sizes m and n for fixed ) that maximizes the power of the applied statistical test. It is known that the two‐sample t‐tests for homogeneous and heterogeneous variances may lose substantial power when variances are unequal but equally large samples are used. We demonstrate that this is not the case for the nonparametric Wilcoxon–Mann–Whitney‐test, whose application in biometrical research fields is motivated by two examples from cancer research. We prove the optimality of the design in case of symmetric and identically shaped distributions using normal approximations and show that this design generally offers power only negligibly lower than the optimal design for a wide range of distributions.     

An ionic–chemical–mechanical model for muscle contraction

The dynamic process underlying muscle contraction is the parallel sliding of thin actin filaments along an immobile thick myosin fiber powered by oar‐like movements of protruding myosin cross bridges (myosin heads). The free energy for functioning of the myosin nanomotor comes from the hydrolysis of ATP bound to the myosin heads. The unit step of translational movement is based on a mechanical‐chemical cycle involving ATP binding to myosin, hydrolysis of the bound ATP with ultimate release of the hydrolysis products, stress‐generating conformational changes in the myosin cross bridge, and relief of built‐up stress in the myosin power stroke. The cycle is regulated by a transition between weak and strong actin–myosin binding affinities. The dissociation of the weakly bound complex by addition of salt indicates the electrostatic basis for the weak affinity, while structural studies demonstrate that electrostatic interactions among negatively charged amino acid residues of actin and positively charged residues of myosin are involved in the strong binding interface. We therefore conjecture that intermediate states of increasing actin–myosin engagement during the weak‐to‐strong binding transition also involve electrostatic interactions. Methods of polymer solution physics have shown that the thin actin filament can be regarded in some of its aspects as a net negatively charged polyelectrolyte. Here we employ polyelectrolyte theory to suggest how actin–myosin electrostatic interactions might be of significance in the intermediate stages of binding, ensuring an engaged power stroke of the myosin motor that transmits force to the actin filament, and preventing the motor from getting stuck in a metastable pre‐power stroke state. We provide electrostatic force estimates that are in the pN range known to operate in the cycle.     

A constraint–relaxation–recovery mechanism for stomatal dynamics

Models of guard cell dynamics, built on the OnGuard platform, have provided quantitative insights into stomatal function, demonstrating substantial predictive power. However, the kinetics of stomatal opening predicted by OnGuard models were threefold to fivefold slower than observed in vivo. No manipulations of parameters within physiological ranges yielded model kinetics substantially closer to these data, thus highlighting a missing component in model construction. One well‐documented process influencing stomata is the constraining effect of the surrounding epidermal cells on guard cell volume and stomatal aperture. Here, we introduce a mechanism to describe this effect in OnGuard2 constructed around solute release and a decline in turgor of the surrounding cells and its subsequent recovery during stomatal opening. The results show that this constraint–relaxation–recovery mechanism in OnGuard2 yields dynamics that are consistent with experimental observations in wild‐type Arabidopsis, and it predicts the altered opening kinetics of ost2 H⁺‐ATPase and slac1 Cl^? channel mutants. Thus, incorporating solute flux of the surrounding cells implicitly through their constraint on guard cell expansion provides a satisfactory representation of stomatal kinetics, and it predicts a substantial and dynamic role for solute flux across the apoplastic space between the guard cells and surrounding cells in accelerating stomatal kinetics.     

Tetrodotoxin–cholesterol interactions at the air–water interface

A claimed, specific interaction of tetrodotoxin with cholesterol monolayers could not be repeated. An observed expansion of cholesterol monolayers on a subphase of the toxin in citrate and phosphate buffer was shown to be time dependent and probably due to a surfactant impurity of the phosphate salts.