Intermittency, quasiperiodicity and chaos in probe-induced ferroelectric domain switching

Memristive materials and devices, which enable information storage and processing on one and the same physical platform, offer an alternative to conventional von Neumann computation architectures. Their continuous spectra of states with intricate field-history dependence give rise to complex dynamics, the spatial aspect of which has not been studied in detail yet. Here, we demonstrate that ferroelectric domain switching induced by a scanning probe microscopy tip exhibits rich pattern dynamics, including intermittency, quasiperiodicity and chaos. These effects are due to the interplay between tip-induced polarization switching and screening charge dynamics, and can be mapped onto the logistic map. Our findings may have implications for ferroelectric storage, nanostructure fabrication and transistor-less logic.

Risk-Taking Differences Across the Adult Life Span:A Question of Age and Domain

Older adults face important risky decisions about their health, their financial future, and their social environment. We examine age differences in risk-taking behaviors in multiple risk domains across the adult life span.

Switching ferroelectric domain configurations using both electric and magnetic fields in Pb(Zr,Ti)O3–Pb(Fe,Ta)O3 single-crystal lamellae

Thin single-crystal lamellae cut from Pb(Zr,Ti)O3–Pb(Fe,Ta)O3 ceramic samples have been integrated into simple coplanar capacitor devices. The influence of applied electric and magnetic fields on ferroelectric domain configurations has been mapped, using piezoresponse force microscopy. The extent to which magnetic fields alter the ferroelectric domains was found to be strongly history dependent: after switching had been induced by applying electric fields, the susceptibility of the domains to change under a magnetic field (the effective magnetoelectric coupling parameter) was large. Such large, magnetic field-induced changes resulted in a remanent domain state very similar to the remanent state induced by an electric field. Subsequent magnetic field reversal induced more modest ferroelectric switching.

Influence of a Single Grain Boundary on Domain Wall Motion in Ferroelectrics

Epitaxial tetragonal 425 and 611 nm thick Pb(ZrTi)O (PZT) films are deposited by pulsed laser deposition on SrRuO-coated (100) SrTiO 24° tilt angle bicrystal substrates to create a single PZT grain boundary with a well-defined orientation. On either side of the bicrystal boundary, the films show square hysteresis loops and have dielectric permittivities of 456 and 576, with loss tangents of 0.010 and 0.015, respectively. Using piezoresponse force microscopy (PFM), a decrease in the nonlinear piezoelectric response is observed in the vicinity (720-820 nm) of the grain boundary. This region represents the width over which the extrinsic contributions to the piezoelectric response (e.g., those associated with the domain density/configuration and/or the domain wall mobility) are influenced by the presence of the grain boundary. Transmission electron microscope (TEM) images collected near and far from the grain boundary indicate a strong preference for (101)/(1-01) type domain walls at the grain boundary, whereas (011)/(01-1) and (101)/(1-01) are observed away from this region. It is proposed that the elastic strain field at the grain boundary interacts with the ferro-electric/elastic domain structure, stabilizing (101)/(1-01) rather than (011)/(01-1) type domain walls, which inhibits domain wall motion under applied field and decreases non-linearity. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Clamping-induced changes of domain morphology in 88%Pb(Zn1/3Nb2/3)O3-12%PbTiO3 (invited)

Domain microstructures in single crystal lamellae of 88%Pb(Zn1/3Nb2/3)O3-12%PbTiO3 (cut from bulk using focused ion beam milling) have been mapped using both piezoresponse force microscopy and transmission electron microscopy. Dramatic changes from mottled microstructures typical of relaxors to larger scale domains typical of ferroelectrics have been noted. Stresses associated with substrate clamping are suspected as the cause for the transition from short- to long-range polar order, akin to effects induced by cation ordering achieved by thermal quenching.

Sequential injection of domain walls into ferroelectrics at different bias voltages: Paving the way for “domain wall memristors”

Simple meso-scale capacitor structures have been made by incorporating thin (300 nm) single crystal lamellae of KTiOPO4 (KTP) between two coplanar Pt electrodes. The influence that either patterned protrusions in the electrodes or focused ion beam milled holes in the KTP have on the nucleation of reverse domains during switching was mapped using piezoresponse force microscopy imaging. The objective was to assess whether or not variations in the magnitude of field enhancement at localised “hot-spots,” caused by such patterning, could be used to both control the exact locations and bias voltages at which nucleation events occurred. It was found that both the patterning of electrodes and the milling of various hole geometries into the KTP could allow controlled sequential injection of domain wall pairs at different bias voltages; this capability could have implications for the design and operation of domain wall electronic devices, such as memristors, in the future.

A Spherical Array Approach for Simulation of Binaural Impulse Responses using the Finite Difference Time Domain Method

The finite difference time domain (FDTD) method has direct applications in musical instrument modeling, simulation of environmental acoustics, room acoustics and sound reproduction paradigms, all of which benefit from auralization. However, rendering binaural impulse responses from simulated
data is not straightforward to accomplish as the calculated pressure at FDTD grid nodes does not contain any directional information. This paper addresses this issue by introducing a spherical array to capture sound pressure on a finite difference grid, and decomposing it into a plane-wave density
function. Binaural impulse responses are then constructed in the spherical harmonics domain by combining the decomposed grid data with free field head-related transfer functions. The effects of designing a spherical array in a Cartesian grid are studied, and emphasis is given to the relationships
between array sampling and the spatial and spectral design parameters of several finite-difference
schemes.

Shared decision making in patients at risk of cancer: The role of domain and numeracy

Background
Shared decision making has become an integral part of medical consultation. Research has, however, reported wide differences in individuals' desires to be involved in the decision-making process, and these differences in preferences are likely to be the result of a number of factors including age, education and numeracy.

Objective
To investigate whether patients at genetic risk for cancer had preferences for shared decision making that differed depending on medical domain (general health vs. cancer) and whether decision preferences are linked to numeracy abilities.

Methods
Four hundred and seventy-six women who consented to participate in response to an email sent by a local branch of the U.S.-based Cancer Genetics Network (CGN) to its members. Participants completed the Control Preference Scale, as well as an objective and subjective numeracy scales.

Results
Decision domain (cancer vs. general health) was not associated with women's preferences for involvement in decision making. Objective and subjective numeracy predicted a preference for decision involvement in general, and only objective numeracy was predictive with regard to cancer.

Conclusion
Participants were equally likely to state they wanted to play an active, collaborative or passive role in both medical domains (general and cancer). High-numeracy participants were more likely to express a desire for an active role in general and in case they were diagnosed with cancer.

Practice implications
Health authorities' recommendations to clinicians to include patients in their medical decisions are supported by patients' desires, and clinicians should be cognizant of their patients' preferences as well as their numeracy skills.

Impact of vitamin D3 on cutaneous immunity and antimicrobial peptide expression

Antimicrobial peptides (AMPs) are effectors of cutaneous innate immunity and protect primarily against microbial infections. An array of AMPs can be found in and on the skin. Those include peptides that were first discovered for their antimicrobial properties but also proteins with antimicrobial activity first characterized for their activity as chemokines, enzymes, enzyme inhibitors and neuropeptides. Cathelicidins were among the first families of AMPs discovered in skin. They are now known to exert a dual role in innate immune defense: they have direct antimicrobial activity and will also initiate a host cellular response resulting in cytokine release, inflammation and angiogenesis. Altered cathelicidin expression and function was observed in several common inflammatory skin diseases such as atopic dermatitis, rosacea and psoriasis. Until recently the molecular mechanisms underlying cathelicidin regulation were not known. Lately, vitamin D3 was identified as the major regulator of cathelicidin expression and entered the spotlight as an immune modulator with impact on both, innate and adaptive immunity. Therapies targeting vitamin D3 signalling may provide novel approaches for the treatment of infectious and inflammatory skin diseases by affecting both innate and adaptive immune functions through AMP regulation.

Control of cutaneous antimicrobial peptides by vitamin D3

Constant exposure to a wide variety of microbial pathogens represents a major challenge for our skin. Antimicrobial peptides (AMPs) are mediators of cutaneous innate immunity and protect primarily against microbial infections. Cathelicidins were among the first AMPs identified in human skin and recent evidence suggests that they exert a dual role in innate immune defense: At first, due to their antimicrobial activity they kill pathogens directly. In addition, these peptides initiate a potent host response to infection resulting in cytokine release, inflammation and a cellular response. Disturbed cathelicidin expression and function was observed in several common inflammatory skin diseases, such as psoriasis where cathelicidin peptide converts inert self-DNA and self-RNA into an autoimmune stimulus. In atopic dermatitis decreased levels of cathelicidin facilitating microbial superinfections have been discussed. Furthermore, abnormally processed cathelicidin peptides induce inflammation and a vascular response in rosacea. Until recently, the molecular mechanisms underlying cathelicidin regulation were unknown. Recently, the vitamin D3 pathway was identified as the major regulator of cathelicidin expression. Consequently, vitamin D3 entered the spotlight as an immune modulator with impact on both innate and adaptive immunity. Therapies targeting vitamin D3 signaling may provide new approaches for infectious and inflammatory skin diseases by affecting both innate and adaptive immune functions.

A conserved spider silk domain acts as a molecular switch that controls fibre assembly

A huge variety of proteins are able to form fibrillar structures(1), especially at high protein concentrations. Hence, it is surprising that spider silk proteins can be stored in a soluble form at high concentrations and transformed into extremely stable fibres on demand(2,3). Silk proteins are reminiscent of amphiphilic block copolymers containing stretches of polyalanine and glycine-rich polar elements forming a repetitive core flanked by highly conserved non-repetitive amino-terminal(4,5) and carboxy-terminal(6) domains. The N-terminal domain comprises a secretion signal, but further functions remain unassigned. The C-terminal domain was implicated in the control of solubility and fibre formation(7) initiated by changes in ionic composition(8,9) and mechanical stimuli known to align the repetitive sequence elements and promote beta-sheet formation(10-14). However, despite recent structural data(15), little is known about this remarkable behaviour in molecular detail. Here we present the solution structure of the C-terminal domain of a spider dragline silk protein and provide evidence that the structural state of this domain is essential for controlled switching between the storage and assembly forms of silk proteins. In addition, the C-terminal domain also has a role in the alignment of secondary structural features formed by the repetitive elements in the backbone of spider silk proteins, which is known to be important for the mechanical properties of the fibre.

Patient safety and communication: A new assessment for doctors trained in countries where language differs from that of the host country: Results of a pilot using a domain-based assessment

Objective

Global migration of healthcare workers places responsibility on employers to comply with legal employment rights whilst ensuring patient safety remains the central goal. We describe the pilot of a communication assessment designed for doctors who trained and communicated with patients and colleagues in a different language from that of the host country. It is unique in assessing clinical communication without assessing knowledge.

A 14-station OSCE was developed using a domain-based marking scheme, covering professional communication and English language skills (speaking, listening, reading and writing) in routine, acute and emotionally challenging contexts, with patients, carers and healthcare teams. Candidates (n = 43), non-UK trained volunteers applying to the UK Foundation Programme, were provided with relevant station information prior to the exam.

The criteria for passing the test included achieving the pass score and passing 10 or more of the 14 stations. Of the 43 candidates, nine failed on the station criteria. Two failed the pass score and also the station criteria. The Cronbach's alpha coefficient was 0.866.

This pilot tested ‘proof of concept’ of a new domain-based communication assessment for non-UK trained doctors.

The test would enable employers and regulators to verify communication competence and safety in clinical contexts, independent of clinical knowledge, for doctors who trained in a language different from that of the host country.