Breakdown of the lattice polaron picture in La0.7Ca0.3MnO3 single crystals

When heated through the magnetic transition at Tc, La0.7Ca0.3MnO3 changes from a band metal to a polaronic insulator. The Hall constant R_H, through its activated behavior and sign anomaly, provides key evidence for polaronic behavior. We use R_H and the Hall mobility to demonstrate the breakdown of the polaron phase. Above 1.4Tc, the polaron picture holds in detail, while below, the activation energies of both R_H and the mobility deviate strongly from their polaronic values. These changes reflect the presence of metallic, ferromagnetic fluctuations, in the volume of which the Hall effect develops additional contributions tied to quantal phases.Comment: 11 pages, 3 figures, final version to appear in Phys. Rev. B Rapi

Anti-fibrotic effects of Rhus javanica Linn (Anacardiaceae) extract against Activated hepatic stellate cells via regulation of TGF-beta and smad signaling

Purpose: To evaluate the anti-fibrotic effects of ethanol extract of Rhus javanica Linn. (Anacardiaceae) (RJE) in activated hepatic stellate cells (HSCs) as well as explore the underlying mechanisms.Methods: The cytotoxic effect of RJE (100, 300 and 500 μg/mL) was analyzed using 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyl tetrazolium bromide (MTT) assay in Chang liver cells. The mRNA expression of collagen type I, alpha 2 (COL1A2), transforming growth factor-beta (TGF-β), α-smooth muscle actin (α-SMA) and platelet-derived growth factor (PDGF) were determined using reverse transcription-polymerase chain reaction (RT-PCR) in HSCs. Protein expression of collagen and Smad were measured by Western blot analysis.Results: Treatment with RJE extract at 100, 300 and 500 μg/mL did not show any signs of cytotoxicity to Chang liver cells. RJE at 500 μg/mL concentration influenced the morphology, reduced the stretched fiber and  decreased the number of viable cells in activated HSCs. The increased expressional levels of fibrosis mediators such as COL1A2, TGF-β, α-SMA were decreased by RJE (500 μg/mL) pre-treatment. Quantification data showed that the increased band intensity of COL1A2 (1.41 ± 0.08), TGF-β (1.23 ± 0.13), α-SMA (1.71 ± 0.14) were significantly (p < 0.05) reduced to 0.39 ± 0.12, 0.35 ± 0.11 and 0.04 ± 0.08, respectively upon RJE treatment. However, RJE did not suppress the expression of PDGF gene. Mechanistic study revealed that RJE prevented fibrosis in HSCs via regulation of TGF-β and Smad signaling pathways.Conclusion: The findings show that RJE inhibits fibrosis production in HSCs and can be developed as a novel therapy for hepatic fibrosis. This is the first report showing the beneficial effects of R. javanica as an anti-fibrotic agent

Augmenting x-ray single particle imaging reconstruction with self-supervised machine learning

The development of X-ray Free Electron Lasers (XFELs) has opened numerous opportunities to probe atomic structure and ultrafast dynamics of various materials. Single Particle Imaging (SPI) with XFELs enables the investigation of biological particles in their natural physiological states with unparalleled temporal resolution, while circumventing the need for cryogenic conditions or crystallization. However, reconstructing real-space structures from reciprocal-space x-ray diffraction data is highly challenging due to the absence of phase and orientation information, which is further complicated by weak scattering signals and considerable fluctuations in the number of photons per pulse. In this work, we present an end-to-end, self-supervised machine learning approach to recover particle orientations and estimate reciprocal space intensities from diffraction images only. Our method demonstrates great robustness under demanding experimental conditions with significantly enhanced reconstruction capabilities compared with conventional algorithms, and signifies a paradigm shift in SPI as currently practiced at XFELs

Machine learning enabled experimental design and parameter estimation for ultrafast spin dynamics

Advanced experimental measurements are crucial for driving theoretical developments and unveiling novel phenomena in condensed matter and material physics, which often suffer from the scarcity of facility resources and increasing complexities. To address the limitations, we introduce a methodology that combines machine learning with Bayesian optimal experimental design (BOED), exemplified with x-ray photon fluctuation spectroscopy (XPFS) measurements for spin fluctuations. Our method employs a neural network model for large-scale spin dynamics simulations for precise distribution and utility calculations in BOED. The capability of automatic differentiation from the neural network model is further leveraged for more robust and accurate parameter estimation. Our numerical benchmarks demonstrate the superior performance of our method in guiding XPFS experiments, predicting model parameters, and yielding more informative measurements within limited experimental time. Although focusing on XPFS and spin fluctuations, our method can be adapted to other experiments, facilitating more efficient data collection and accelerating scientific discoveries

Colossal Magnetoresistance is a Griffiths Singularity

It is now widely accepted that the magnetic transition in doped manganites that show large magnetoresistance is a type of percolation effect. This paper demonstrates that the transition should be viewed in the context of the Griffiths phase that arises when disorder suppresses a magnetic transition. This approach explains unusual aspects of susceptibility and heat capacity data from a single crystal of La$_{0.7}$Ca$_{0.3}$MnO$_{3}.$Comment: 4 page

Potential of South African medicinal plants targeting the reduction of Aβ42 protein as a treatment of Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE : Twenty South African medicinal plant species were selected by conducting a literature review based on the relevant information of their reported traditional medicinal uses and scientific reports against Alzheimer's disease, dementia, anxiety, mental illness, depression, acetylcholinesterase inhibition, headache, epilepsy, convulsion, hysteria, and sedative effects. AIM OF STUDY : The goal of this study was to investigate the biological activity of the traditionally used medicinal plant extracts against Alzheimer's disease by in vitro screening of the extracts to determine their potential to decrease levels of Aβ42 protein. MATERIAL AND METHODS: Different plant parts (leaves, stem, bark, and stalks) of twenty selected plants were collected from the Manie van der Schijff Botanical Garden, University of Pretoria. Plant parts were dried, ground and then extracted using DCM:MeOH (1:1). We measured the levels of β-amyloid precursor protein proteolytic products in HeLa cells stably transfected with APP carrying the Swedish mutation using ELISA. RESULTS : Of 33 plant extract 10 (30.3%) were found active based on the potential to significantly reduce the production of Aβ42. Amongst them extracts of leaves of Xysmalobium undulatum (Apocynaceae), leaves of Cussonia paniculata (Araliaceae) and leaves of Schotia brachypetala (Fabaceae) potently decreased the production of Aβ42 by 77.3 ± 0.5%, 57.5 ± 1.3%, and 44.8 ± 0.1%, respectively. X. undulatum and S. brachypetala enhanced non-amyloidogenic processing of β-amyloid precursor protein, thereby decreasing Aβ42 level. We also showed that C. paniculata induced the decrease of Aβ42 level through inhibiting APP processing. In addition, we isolated two cardenolides, compound [A] and [B], from X. undulatum and found that they potently decreased the Aβ42 production. CONCLUSION : These data suggest that the extract of X. undulatum, C. paniculata, and S. brachypetala have potential to be developed for Alzheimer's disease treatment. These active extracts and compounds are considered for further studies which examine their efficacy towards the reduction of Aβ42 through inhibiting APP process.The University of Pretoria Post Graduate Research Support Bursay, South Africa and by the Bio-Synergy Research Project (NRF-2012M3A9C4048793) and the Bio & Medical Technology Development Program (NRF-2015M3A9A5030735) of the Ministry of Science, ICT, and Future Planning through the National Research Foundation, Republic of Korea.http://www.elsevier.com/locate/jethpharm2020-03-01hj2019Chemistr

UKIRT Widefield Infrared Survey for Fe+

The United Kingdom Infrared Telescope (UKIRT)Widefield Infrared Survey for Fe+ (UWIFE) is a 180 deg2 imaging survey of the first Galactic quadrant (7° < l < 62° |b| <1°.5) that uses a narrow-band filter centred on the [Fe II] 1.644-μm emission line. The [Fe II] 1.644-μm emission is a good tracer of dense, shock-excited gas, and the survey will probe violent environments around stars: star-forming regions, evolved stars, and supernova remnants, among others. The UWIFE survey is designed to complement the existing UKIRTW idefield Infrared Survey for H2 (UWISH2). The survey will also complement existing broad-band surveys. The observed images have a nominal 5Ï? detection limit of 18.7 mag for point sources, with a median seeing of 0.83 arcsec. For extended sources, we estimate a surface brightness limit of 8.1 Ã? 10-20 W m-2 arcsec-2. In this paper, we present an overview and some preliminary results of this survey. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Charge Transport in Manganites: Hopping Conduction, the Anomalous Hall Effect and Universal Scaling

The low-temperature Hall resistivity \rho_{xy} of La_{2/3}A_{1/3}MnO_3 single crystals (where A stands for Ca, Pb and Ca, or Sr) can be separated into Ordinary and Anomalous contributions, giving rise to Ordinary and Anomalous Hall effects, respectively. However, no such decomposition is possible near the Curie temperature which, in these systems, is close to metal-to-insulator transition. Rather, for all of these compounds and to a good approximation, the \rho_{xy} data at various temperatures and magnetic fields collapse (up to an overall scale), on to a single function of the reduced magnetization m=M/M_{sat}, the extremum of this function lying at m~0.4. A new mechanism for the Anomalous Hall Effect in the inelastic hopping regime, which reproduces these scaling curves, is identified. This mechanism, which is an extension of Holstein's model for the Ordinary Hall effect in the hopping regime, arises from the combined effects of the double-exchange-induced quantal phase in triads of Mn ions and spin-orbit interactions. We identify processes that lead to the Anomalous Hall Effect for localized carriers and, along the way, analyze issues of quantum interference in the presence of phonon-assisted hopping. Our results suggest that, near the ferromagnet-to-paramagnet transition, it is appropriate to describe transport in manganites in terms of carrier hopping between states that are localized due to combined effect of magnetic and non-magnetic disorder. We attribute the qualitative variations in resistivity characteristics across manganite compounds to the differing strengths of their carrier self-trapping, and conclude that both disorder-induced localization and self-trapping effects are important for transport.Comment: 29 pages, 20 figure

X-ray holography with a customizable reference

In X-ray Fourier-transform holography, images are formed by exploiting the interference pattern between the X-rays scattered from the sample and a known reference wave. To date, this technique has only been possible with a limited set of special reference waves. We demonstrate X-ray Fourier-transform holography with an almost unrestricted choice for the reference wave, permitting experimental geometries to be designed according to the needs of each experiment and opening up new avenues to optimize signal-to-noise and resolution. The optimization of holographic references can aid the development of holographic techniques to meet the demands of resolution and fidelity required for single-shot imaging applications with X-ray lasers