Electrical Conductivity and In Situ SAXS Probing of Block Copolymer Nanocomposites Under Mechanical Stretching.

Elastomers based on block copolymers can self-organize into ordered nanoscale structures, making them attractive for use as flexible conductive nanocomposites. Understanding how ordered structures impact electrical properties is essential for practical applications. This study investigated the morphological evolution of flexible conductive elastomers based on polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) block copolymers with aligned single- or multi-wall carbon nanotubes (SWCNTs or MWCNTs) and their electrical conductivity under large deformations. Oriented nanocomposites were obtained through injection molding and characterized using two different setups: tensile testing monitored by in situ small-angle X-ray scattering (SAXS) and tensile testing with simultaneous electrical conductivity measurements. Our findings demonstrate that structural orientation significantly influences electrical conductivity, with higher conductivity in the longitudinal direction due to the preferred orientation of carbon nanotubes. Tensile testing demonstrated that carbon nanotubes accelerate the process of realignment of the ordered structure. As a consequence, higher deformations reduced the conductivity of samples with longitudinal alignment due to the disruption of percolation contacts between nanotubes, while in samples with a transverse alignment the process promoted the formation of a new conductive network, increasing electrical conductivity.

Thermal skyrmion diffusion used in a reshuffler device.

Magnetic skyrmions in thin films can be efficiently displaced with high speed by using spin-transfer torques1,2 and spin-orbit torques3-5 at low current densities. Although this favourable combination of properties has raised expectations for using skyrmions in devices6,7, only a few publications have studied the thermal effects on the skyrmion dynamics8-10. However, thermally induced skyrmion dynamics can be used for applications11 such as unconventional computing approaches12, as they have been predicted to be useful for probabilistic computing devices13. In our work, we uncover thermal diffusive skyrmion dynamics by a combined experimental and numerical study. We probed the dynamics of magnetic skyrmions in a specially tailored low-pinning multilayer material. The observed thermally excited skyrmion motion dominates the dynamics. Analysing the diffusion as a function of temperature, we found an exponential dependence, which we confirmed by means of numerical simulations. The diffusion of skyrmions was further used in a signal reshuffling device as part of a skyrmion-based probabilistic computing architecture. Owing to its inherent two-dimensional texture, the observation of a diffusive motion of skyrmions in thin-film systems may also yield insights in soft-matter-like characteristics (for example, studies of fluctuation theorems, thermally induced roughening and so on), which thus makes it highly desirable to realize and study thermal effects in experimentally accessible skyrmion systems.

Current-Induced Skyrmion Generation through Morphological Thermal Transitions in Chiral Ferromagnetic Heterostructures.

Magnetic skyrmions promise breakthroughs in future memory and computing devices due to their inherent stability and small size. Their creation and current driven motion have been recently observed at room temperature, but the key mechanisms of their formation are not yet well-understood. Here it is shown that in heavy metal/ferromagnet heterostructures, pulsed currents can drive morphological transitions between labyrinth-like, stripe-like, and skyrmionic states. Using high-resolution X-ray microscopy, the spin texture evolution with temperature and magnetic field is imaged and it is demonstrated that with transient Joule heating, topological charges can be injected into the system, driving it across the stripe-skyrmion boundary. The observations are explained through atomistic spin dynamic and micromagnetic simulations that reveal a crossover to a global skyrmionic ground state above a threshold magnetic field, which is found to decrease with increasing temperature. It is demonstrated how by tuning the phase stability, one can reliably generate skyrmions by short current pulses and stabilize them at zero field, providing new means to create and manipulate spin textures in engineered chiral ferromagnets.

Medical i2b2 NLP smoking challenge: the A-Life system architecture and methodology.

We describe the architecture of LifeCode (A-Life Medical, Inc.), a natural language processing system for free-text clinical information extraction, our methodology in applying LifeCode to the i2b2 smoking challenge, and statistical measures for performance evaluation. Due to the limited test size and the coefficient of variation in the test standard, it is difficult to draw conclusions regarding the relative efficacy of approaches that were applied to this challenge.

Automated extraction and normalization of findings from cancer-related free-text radiology reports.

UNLABELLED: We describe the performance of a particular natural language processing system that uses knowledge vectors to extract findings from radiology reports. LifeCode (A-Life Medical, Inc.) has been successfully coding reports for billing purposes for several years. In this study, we describe the use of LifeCode to code all findings within a set of 500 cancer-related radiology reports against a test set in which all findings were manually tagged. The system was trained with 1400 reports prior to running the test set. RESULTS: LifeCode had a recall of 84.5% and precision of 95.7% in the coding of cancer-related radiology report findings. CONCLUSION: Despite the use of a modest sized training set and minimal training iterations, when applied to cancer-related reports the system achieved recall and precision measures comparable to other reputable natural language processors in this domain.