Summary The role of Dicer's helicase domain is enigmatic, but in vivo it is required for processing certain endogenous siRNA, but not miRNA. Using C. elegans extracts, or purified Drosophila Dicer-2, we compared activities of wildtype enzymes and those containing mutations in the helicase domain. We found the helicase domain was essential for cleaving dsRNA with blunt or 5' overhanging termini, but not those with 3' overhangs, as found on miRNA precursors. Further, blunt termini, but not 3' overhangs, led to increased siRNAs from internal regions of dsRNA; this activity required ATP and a functional helicase domain. Our data suggest that blunt or 5' overhanging termini engage Dicer's helicase domain to facilitate accumulation of siRNAs from internal regions of a dsRNA, an activity suited for processing long siRNA precursors of low abundance, but not necessary for the single cleavage required for miRNA processing.

Single-phase multiferroic materials are of considerable interest for future memory and sensing applications. Thin films of Aurivillius phase Bi7Ti3Fe3O21 and Bi6Ti2.8Fe1.52Mn0.68O18 (possessing six and five perovskite units per half-cell, respectively) have been prepared by chemical solution deposition on c-plane sapphire. Superconducting quantum interference device magnetometry reveal Bi7Ti3Fe3O21 to be antiferromagnetic (TN = 190 K) and weakly ferromagnetic below 35 K, however, Bi6Ti2.8Fe1.52Mn0.68O18 gives a distinct room-temperature in-plane ferromagnetic signature (Ms = 0.74 emu/g, μ0Hc =7 mT). Microstructural analysis, coupled with the use of a statistical analysis of the data, allows us to conclude that ferromagnetism does not originate from second phase inclusions, with a confidence level of 99.5%. Piezoresponse force microscopy (PFM) demonstrates room-temperature ferroelectricity in both films, whereas PFM observations on Bi6Ti2.8Fe1.52Mn0.68O18 show Aurivillius grains undergo ferroelectric domain polarization switching induced by an applied magnetic field. Here, we show for the first time that Bi6Ti2.8Fe1.52Mn0.68O18 thin films are both ferroelectric and ferromagnetic and, demonstrate magnetic field-induced switching of ferroelectric polarization in individual Aurivillius phase grains at room temperature

Highly dense hexagonal ordered arrays of superparamagnetic iron oxides nanodots are fabricated by a simple and cost-effective route. Spectroscopic, microscopic and magnetic measurements show that the nanodots have uniform size, shape and their placement mimics the original self-assembled block copolymer pattern. The nanodots show good thermal stability and strong adherence to the substrate surface, making them useful for practical device applications.

We observe an enormous spontaneous exchange bias (~300-600 Oe)--measured in an unmagnetized state following zero-field cooling--in a nanocomposite of BiFeO(3) (~94%)-Bi(2)Fe(4)O(9) (~6%) over a temperature range 5-300 K. Depending on the path followed in tracing the hysteresis loop--positive (p) or negative (n)--as well as the maximum field applied, the exchange bias (H(E)) varies significantly with | - H(Ep) | > | H(En) |. The temperature dependence of H(E) is nonmonotonic. It increases, initially, till ~150 K and then decreases as the blocking temperature T(B) is approached. All these rich features appear to be originating from the spontaneous symmetry breaking and consequent onset of unidirectional anisotropy driven by "superinteraction bias coupling" between the ferromagnetic core of Bi(2)Fe(4)O(9) (of average size ~19 nm) and the canted antiferromagnetic structure of BiFeO(3) (of average size ~112 nm) via superspin glass moments at the shell.

The rare earth orthochromites are extremely interesting due to the richness of their optical, dielectric, and magnetic properties as well as due to their multiferroic properties which make them suitable materials to study in the nanoregime. However, the wet-chemical synthesis of these materials in nanosize is nontrivial. Here, we report for the first time, the detailed Raman spectra as well as magnetic and dielectric properties of chemically synthesized GdCrO3 nanoparticles of size ranging from 40 to 60 nm. The magnetic properties are dictated by competing Cr3+–Cr3+, Gd3+–Cr3+, and Gd3+–Gd3+ superexchange interactions in different temperature regions, resulting into an antiferromagnetic ordering at 167 K due to the Cr3+–Cr3+ followed by weak ferromagnetic ordering due to the onset of Cr3+–Gd3+ interactions. At lower temperature, it shows weak antiferromagnetic ordering due to Gd3+–Gd3+ interaction. Below 95 K, GdCrO3 nanoparticles showed the presence of negative magnetization due to Gd3+ and Cr3+ interactions resulting into weak ferromagnetic coupling. The Raman spectroscopy shows the characteristic Raman shifts indicating that below 450 cm−1, Gd3+ ions play a dominant role in determining the phonon frequencies of GdCrO3, and above 450 cm−1, the Cr+3 ions dominate. We also present for the first time the low temperature dielectric constant and loss tangent data for GdCrO3 in a broad temperature and frequency range. The dielectric constant shows a decrease in comparison to the bulk values due to the size dependent effects. It also shows a peak centered at around 320 K above which it shows a sharp decrease. The dielectric loss value in GdCrO3 nanoparticles is quite small and shows an interesting frequency dependent anomaly at lower temperature which might be due to the coupling between magnetic and dielectric order parameters.

SUMMARYdsRNA binding proteins (dsRBPs) facilitate Dicer functions in RNAi. C. elegans RDE-4 facilitates cleavage of long dsRNA to siRNA, while human TRBP functions downstream to pass siRNA to RISC. We show that these distinct in vivo roles are reflected in in vitro binding properties. RDE-4 preferentially binds long dsRNA, while TRBP binds siRNA with an affinity that is independent of dsRNA length. These properties are mechanistically based in the fact that RDE-4 binds cooperatively, via contributions from multiple domains, while TRBP binds non-cooperatively. Our studies offer a paradigm for how dsRBPs, which are not sequence-specific, discern dsRNA length. Additionally, analyses of the ability of RDE-4 deletion constructs and RDE-4/TRBP chimeras to reconstitute Dicer activity suggest RDE-4 promotes activity using its dsRBM2 to bind dsRNA, its linker region to interact with Dicer, and its C-terminus for Dicer activation.

Highly dense hexagonally arranged iron oxide nanodots array were fabricated using PS-b-PEO self-assembled patterns. The copolymer molecular weight, composition and choice of annealing solvent/s allows dimensional and structural control of the nanopatterns at large scale. A mechanism is proposed to create scaffolds through degradation and/or modification of cylindrical domains. A methodology based on selective metal ion inclusion and subsequent processing was used to create iron oxide nanodots array. The nanodots have uniform size and shape and their placement mimics the original self-assembled nanopatterns. For the first time these precisely defined and size selective systems of ordered nanodots allow careful investigation of magnetic properties in dimensions from 50 nm to 10 nm, which delineate the nanodots are superparamagnetic, well-isolated and size monodispersed. This diameter/spacing controlled iron oxide nanodots systems were demonstrated as a resistant mask over silicon to fabricate densely packed, identical ordered, high aspect ratio silicon nanopillars and nanowire features.

Multiferroic materials displaying coupled ferroelectric and ferromagnetic order parameters could provide a means for data storage whereby bits could be written electrically and read magnetically, or vice versa. Thin films of Aurivillius phase Bi6Ti2.8Fe1.52Mn0.68O18, previously prepared by a chemical solution deposition (CSD) technique, are multiferroics demonstrating magnetoelectric coupling at room temperature. Here we demonstrate the growth of a similar composition, Bi6Ti2.99Fe1.46Mn0.55O18, via the liquid injection chemical vapor deposition technique. High resolution magnetic measurements reveal a considerably higher in-plane ferromagnetic signature than CSD grown films (MS = 24.25 emu/g (215 emu/cm 3 ), MR = 9.916 emu/g (81.5 emu/cm 3 ), HC = 170 Oe). A statistical analysis of the results from a thorough microstructural examination of the samples, allows us to conclude that the ferromagnetic signature can be attributed to the Aurivillius phase, with a confidence level of 99.95 %. In addition, we report the direct piezoresponse force i E-mail: lynette.keeney@tyndall.ieJournal of the American Ceramic Society DOI: 10.1111DOI: 10. /jace.14597 (2016 2 microscopy (PFM) visualization of ferroelectric switching while going through a full in-plane magnetic field cycle, where increased volumes (8.6 to 14 % compared with 4 to 7 % for the CSDgrown films) of the film engage in magnetoelectric coupling and demonstrate both irreversible and reversible magnetoelectric domain switching. IntroductionMultiferroic materials which exhibit more than one mutually-coupled ferroic (e.g. ferroelectric (FE) / ferromagnetic (FM) / ferroelastic) order parameter (OP) in a single phase, provide additional degrees of OP freedom that can be exploited in novel multistate memory and sensing devices.Magnetoelectricity (the generation of a change in magnetization by an applied electric field or vice versa), on the other hand, is a related phenomenon that will arise in any material that is both electrically and magnetically polarizable and possesses an appropriate magnetic symmetry, regardless of whether it is multiferroic or not. For example, the magnetoelectric Cr2O3 is an antiferromagnetic dielectric and is neither FE nor FM 1 . The unique advantage of single phase magnetoelectric multiferroics is that not only could they find application in high storage density, lowpower memory devices that can be electrically written and magnetically read, but also memory technologies with 4-state logic might be achieved by constructing devices that exploit the presence of both ferroelectric and ferromagnetic states 2 -representing a clear improvement over current 2-state logic devices. However, there are relatively few 3-8 materials demonstrating ferroelectric and ferromagnetic properties in a single-phase at room temperature. Due to conflicting electronic structure requirements for ferroelectricity (empty d orbitals) and ferromagnetism (partially filled d orbitals), the two properties tend to be mutually exclusive 9 . Examples of multiferroic material...