Evaluation of Interfacial Structure of Self-Assembled Nanoparticle Layers: Use of Standard Deviation between Calculated and Experimental Drop Profiles as a Novel Method.

The self-assembly of nanoparticles (NPs) at interfaces is currently a topic of increasing interest due to numerous applications in food technology, pharmaceuticals, cosmetology, and oil recovery. It is possible to create tunable interfacial structures with desired characteristics using tailored nanoparticles that can be precisely controlled with respect to shape, size, and surface chemistry. To address these functionalities, it is essential to develop techniques to study the properties of the underlying structure. In this work, we propose an experimental approach utilizing the standard deviation of drop profiles calculated by the Laplace equation from experimental drop profiles (STD), as an alternative to the Langmuir trough or precise microscopic methods, to detect the initiation of closely packed conditions and the collapse of the adsorbed layers of CTAB-nanosilica complexes. The experiments consist of dynamic surface/interfacial tension measurements using drop profile analysis tensiometry (PAT) and large-amplitude drop surface area compression/expansion cycles. The results demonstrate significant changes in STD values at the onset of the closely packed state of nanoparticle-surfactant complexes and the monolayer collapse. The STD trend was explained in detail and shown to be a powerful tool for analyzing the adsorption and interfacial structuring of nanoparticles. Different collapse mechanisms were reported for NP monolayers at the liquid/liquid and air/liquid interfaces. We show that the interfacial tension (IFT) is solely dependent on the extent of interfacial coverage by nanoparticles, while the surfactants regulate only the hydrophobicity of the self-assembled complexes. Also, the irreversible adsorption of nanoparticles and the increasing number of adsorbed complexes after the collapse were observed by performing consecutive drop surface compression/expansion cycles. In addition to a qualitative characterization of adsorption layers, the potential of a quantitative calculation of the parameter STD such as the number of adsorbed nanoparticles at the interface and the distance between them at different states of the interfacial layer was discussed.

Environmental influences on mare reproductive loss syndrome: Do they fit with a toxin as the causative agent?

Mare Reproductive Loss Syndrome (MRLS) is the term given to abortions in mares associated with Eastern Tent caterpillars (ETC; Malacosoma americanum). This paper aims to examine if the hypothesis for a toxin as the cause of MRLS holds up to testing using Westerman's Correlates of Causal Strength of Evidence (WCCSE) and fits with known environmental factors that influence the occurrence of MRLS. Using WCCSE all correlates fit with a toxin as a potential causative agent. Environmental factors also fitted with this hypothesis. MRLS events were associated with higher than normal ambient temperatures and lower than normal precipitation. Higher temperatures facilitated a rapid tightly grouped hatching interval which produced a higher population density of ETCs during a specific time period and encouraged more active ingestion of Black Cherry tree leaves. These leaves contain prunasin, the precursor of a toxin produced by the ETCs, which protects the caterpillars from predation. ETCs serve as the vector for the toxin which contaminated pasture and water during off-tree feeding bouts. The toxin accumulated on the pasture forage in the absence of rainfall, thus increasing exposure and clinical responses. Precipitation diluted the contaminate which reduced the toxin dose and clinical affects following ingestion of the contaminated grass or water. The pathogenesis of MRLS remains unconfirmed. However, the potential role of a toxin in this syndrome should be considered.

The Experimentalist's Guide to the Cycloid, or Noncollinear Antiferromagnetism in Epitaxial BiFeO3.

Bismuth ferrite (BiFeO3 ) is one of the most widely studied multiferroics. The coexistence of ferroelectricity and antiferromagnetism in this compound has driven an intense search for electric-field control of the magnetic order. Such efforts require a complete understanding of the various exchange interactions that underpin the magnetic behavior. An important characteristic of BiFeO3 is its noncollinear magnetic order; namely, a long-period incommensurate spin cycloid. Here, the progress in understanding this fascinating aspect of BiFeO3 is reviewed, with a focus on epitaxial films. The advances made in developing the theory used to capture the complexities of the cycloid are first chronicled, followed by a description of the various experimental techniques employed to probe the magnetic order. To help the reader fully grasp the nuances associated with thin films, a detailed description of the spin cycloid in the bulk is provided. The effects of various perturbations on the cycloid are then described: magnetic and electric fields, doping, epitaxial strain, finite size effects, and temperature. To conclude, an outlook on possible device applications exploiting noncollinear magnetism in BiFeO3 films is presented. It is hoped that this work will act as a comprehensive experimentalist's guide to the spin cycloid in BiFeO3 thin films.

Deterministic Switching in Bismuth Ferrite Nanoislands.

We report deterministic selection of polarization variant in bismuth BiFeO3 nanoislands via a two-step scanning probe microscopy procedure. The polarization orientation in a nanoisland is toggled to the desired variant after a reset operation by scanning a conductive atomic force probe in contact over the surface while a bias is applied. The final polarization variant is determined by the direction of the inhomogeneous in-plane trailing field associated with the moving probe tip. This work provides the framework for better control of switching in rhombohedral ferroelectrics and for a deeper understanding of exchange coupling in multiferroic nanoscale heterostructures toward the realization of magnetoelectric devices.