Reinterpretation of Velocity-Dependent Atomic Friction: Influence of the Inherent Instrumental Noise in Friction Force Microscopes

We have applied both the master equation method and harmonic transition state theory to interpret the velocity-dependent friction behavior observed in atomic friction experiments. To understand the discrepancy between attempt frequencies measured in atomic force microscopy experiments and those estimated by theoretical models, both thermal noise and instrumental noise are introduced into the model. It is found that the experimentally observed low attempt frequency and the transition point at low velocity regimes can be interpreted in terms of the instrumental noise inherent in atomic force microscopy. In contrast to previous models, this model also predicts (1) the existence of a two-slope curve of velocity dependence and (2) the decrease of critical velocity with temperature, which provides clues for further experimental verification of the influence of instrumental noise in friction measurements

Atomic Friction Studied by Modeling the Buried Inteface

Molecular dynamics simulation is carried out to model the single-asperity friction in atomic force microscope experiments. Superlubricity is achieved through misalignment between the AFM tip and substrate. Direct observation of the buried interface reveals that incommensurability-induced inhomogeneous shear stress can cause ultra-low atomic scale friction

Speed Dependence of Atomic Stick-Slip Friction in Optimally Matched Experiments and Molecular Dynamics Simulations

The atomic stick-slip behavior of a Pt tip sliding on a Au(111) surface is studied with atomic force microscopy (AFM) experiments and accelerated (i.e., reduced sliding speed) molecular dynamics (MD) simulations. The MD and AFM conditions are controlled to match, as closely as possible, the geometry and orientation, load, temperature, and compliance. We observe clear stick-slip without any damage. Comparison of bothMDand AFM results with the thermally activated Prandtl-Tomlinson model shows that MD results at the highest speeds are not in the thermally activated regime. At lower speeds, within the thermally activated regime, AFM and MD provide consistent energetics, but attempt frequencies differ by orders of magnitude. Because this discrepancy lies in attempt frequencies and not energetics, atomistic details in MD simulations can be reliably used in interpreting AFM data if the MD speeds are slow enough

SFCNeXt: a simple fully convolutional network for effective brain age estimation with small sample size

Deep neural networks (DNN) have been designed to predict the chronological age of a healthy brain from T1-weighted magnetic resonance images (T1 MRIs), and the predicted brain age could serve as a valuable biomarker for the early detection of development-related or aging-related disorders. Recent DNN models for brain age estimations usually rely too much on large sample sizes and complex network structures for multi-stage feature refinement. However, in clinical application scenarios, researchers usually cannot obtain thousands or tens of thousands of MRIs in each data center for thorough training of these complex models. This paper proposes a simple fully convolutional network (SFCNeXt) for brain age estimation in small-sized cohorts with biased age distributions. The SFCNeXt consists of Single Pathway Encoded ConvNeXt (SPEC) and Hybrid Ranking Loss (HRL), aiming to estimate brain ages in a lightweight way with a sufficient exploration of MRI, age, and ranking features of each batch of subjects. Experimental results demonstrate the superiority and efficiency of our approach.Comment: This paper has been accepted by IEEE ISBI 202

Antifungal agents for invasive candidiasis in non-neutropenic critically ill adults: What do the guidelines recommend?

Objectives: Recommendations in clinical practice guidelines (CPG) may differ and cause confusion. Our objective was to appraise CPGs for antifungal treatment of invasive candidiasis (IC) in non-neutropenic critically-ill adult patients. Methods: We systematically searched the literature for CPGs published between 2008 and 2018. We assessed the quality of each guideline using six domains of the AGREE II instrument. We extracted and compared recommendations for different treatment strategies and assessed content quality.Results: Of 19 guidelines, the mean overall AGREE II score was 58%. The domain 'clarity of presentation' received the highest scores (88%) and 'applicability' the lowest (18%). CPGs provided detailed recommendations on antifungal prophylaxis (n = 10), with fluconazole recommended as initial prophylaxis in all seven CPGs citing a specific drug. Echinocandin was recommended as the initial drug in all 16 CPGs supporting empirical/pre-emptive treatment; and in 18 of 19 for targeted invasive candidiasis treatment. However, it remains unclear when to initiate prophylaxis, empirical or pre-emptive therapy or when to step down. Conclusions: The methodological quality of CPGs for antifungal treatment of IC in non-neutropenic critically-ill patients is suboptimal. Some treatment recommendations were inconsistent across indications and require local guidance to help clinicians make better informed decisions

Measurement of the Intertablet Coating Uniformity of a Pharmaceutical Pan Coating Process With Combined Terahertz and Optical Coherence Tomography In-Line Sensing.

We present in-line coating thickness measurements acquired simultaneously using two independent sensing modalities: terahertz pulsed imaging (TPI) and optical coherence tomography (OCT). Both techniques are sufficiently fast to resolve the coating thickness of individual pharmaceutical tablets in-situ during the film coating operation and both techniques are direct structural imaging techniques that do not require multivariate calibration. The TPI sensor is suitable to measure coatings greater than 50 μm and can penetrate through thick coatings even in the presence of pigments over a wide range of excipients. Due to the long wavelength, terahertz radiation is not affected by scattering from dust within the coater. In contrast, OCT can resolve coating layers as thin as 20 μm and is capable of measuring the intra-tablet coating uniformity as well as the inter-tablet coating thickness distribution within the coating pan. ¬-However, the OCT technique is less robust when it comes to the compatibility with excipients, dust and potentially the maximum coating thickness that can be resolved. Using a custom built laboratory scale coating unit, the coating thickness measurements were acquired independently by the TPI and OCT sensors throughout a film coating operation. Results of the in-line TPI and OCT measurements were compared against one another and validated with off-line TPI and weight gain measurements. Compared to other process analytical technology (PAT) sensors, such as near-infrared and Raman spectroscopy, the TPI/OCT sensors can resolve the inter-tablet thickness distribution based on sampling a significant fraction of the tablet populations in the process. By combining two complementary sensing modalities it was possible to seamlessly monitor the coating process over the range of film thickness from 20 μm to greater than 250 μm.The authors would like to acknowledge the financial support from UK EPSRC Research Grant EP/L019787/1 and EP/L019922/1. The authors acknowledge BASF for providing the materials used in this study, Colorcon Ltd. (Dartford, UK) for coating process recommendations, Hüttlin GmbH (Bosch Packaging Technology, Schopfheim, Germany) for advice on the coating unit design and the staff of the electronics and mechanical workshops in Department of Chemical Engineering and Biotechnology at University of Cambridge. HL also acknowledges travel support from Joy Welch Educational Charitable Trust

Measurement of the Intertablet Coating Uniformity of a Pharmaceutical Pan Coating Process With Combined Terahertz and Optical Coherence Tomography In-Line Sensing.

We present in-line coating thickness measurements acquired simultaneously using 2 independent sensing modalities: terahertz pulsed imaging (TPI) and optical coherence tomography (OCT). Both techniques are sufficiently fast to resolve the coating thickness of individual pharmaceutical tablets in situ during the film coating operation, and both techniques are direct structural imaging techniques that do not require multivariate calibration. The TPI sensor is suitable to measure coatings greater than 50 μm and can penetrate through thick coatings even in the presence of pigments over a wide range of excipients. Due to the long wavelength, terahertz radiation is not affected by scattering from dust within the coater. In contrast, OCT can resolve coating layers as thin as 20 μm and is capable of measuring the intratablet coating uniformity and the intertablet coating thickness distribution within the coating pan. However, the OCT technique is less robust when it comes to the compatibility with excipients, dust, and potentially the maximum coating thickness that can be resolved. Using a custom-built laboratory scale coating unit, the coating thickness measurements were acquired independently by the TPI and OCT sensors throughout a film coating operation. Results of the in-line TPI and OCT measurements were compared against one another and validated with off-line TPI and weight gain measurements. Compared with other process analytical technology sensors, such as near-infrared and Raman spectroscopy, the TPI and OCT sensors can resolve the intertablet thickness distribution based on sampling a significant fraction of the tablet populations in the process. By combining 2 complementary sensing modalities, it was possible to seamlessly monitor the coating process over the range of film thickness from 20 μm to greater than 250 μm.The authors would like to acknowledge the financial support from UK EPSRC Research Grant EP/L019787/1 and EP/L019922/1. The authors acknowledge BASF for providing the materials used in this study, Colorcon Ltd. (Dartford, UK) for coating process recommendations, Hüttlin GmbH (Bosch Packaging Technology, Schopfheim, Germany) for advice on the coating unit design and the staff of the electronics and mechanical workshops in Department of Chemical Engineering and Biotechnology at University of Cambridge. HL also acknowledges travel support from Joy Welch Educational Charitable Trust

Correlation-driven eightfold magnetic anisotropy in a two-dimensional oxide monolayer.

Engineering magnetic anisotropy in two-dimensional systems has enormous scientific and technological implications. The uniaxial anisotropy universally exhibited by two-dimensional magnets has only two stable spin directions, demanding 180° spin switching between states. We demonstrate a previously unobserved eightfold anisotropy in magnetic SrRuO3 monolayers by inducing a spin reorientation in (SrRuO3)1/(SrTiO3) N superlattices, in which the magnetic easy axis of Ru spins is transformed from uniaxial 〈001〉 direction (N < 3) to eightfold 〈111〉 directions (N ≥ 3). This eightfold anisotropy enables 71° and 109° spin switching in SrRuO3 monolayers, analogous to 71° and 109° polarization switching in ferroelectric BiFeO3. First-principle calculations reveal that increasing the SrTiO3 layer thickness induces an emergent correlation-driven orbital ordering, tuning spin-orbit interactions and reorienting the SrRuO3 monolayer easy axis. Our work demonstrates that correlation effects can be exploited to substantially change spin-orbit interactions, stabilizing unprecedented properties in two-dimensional magnets and opening rich opportunities for low-power, multistate device applications

High resolution corneal and single pulse imaging with line field spectral domain optical coherence tomography

We report the development of a Spectral Domain Line Field Optical Coherence Tomography (LF-OCT) system, using a broad bandwidth and spatial coherent Super-Continuum (SC) source. With conventional quasi-Continuous Wave (CW) setup we achieve axial resolutions up to 2.1 μm in air and 3D volume imaging speeds up to 213 kA-Scan/s. Furthermore, we report the use of a single SC pulse, of 2 ns duration, to temporally gate an OCT B-Scan image of 70 A-Scans. This is the equivalent of 35 GA-Scans/s. We apply the CW setup for high resolution imaging of the fine structures of a human cornea sample ex-vivo. The single pulse setup is applied to imaging of a coated pharmaceutical tablet. The fixed pattern noise due to spectral noise is removed by subtracting the median magnitude A-Scan. We also demonstrate that the Fourier phase can be used to remove aberration caused artefacts