Grain Size Induced Metal-insulator Transition in La0.7Sr0.3MnO3 Compounds

The effect of different synthesis techniques on structural, microstructural and electrical properties of La0.7Sr0.3MnO3 (LSMO) was investigated. Two different techniques viz solid state reaction (SSR) and sol-gel (SG) method were used to prepare the samples. X-ray studies have confirmed the single phase formation of LSMO by both the techniques. The average grain size was 2 m for solid state reaction sample and 22 nm for sol-gel sample. A substantial enhancement in electrical resistivity was observed in the sample with nanosized grains. The micro grain size sample exhibited metallic behaviour whereas nanoparticle sample showed metal-insulator transition around 250 K. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3554

Nanoscale switching characteristics of nearly tetragonal BiFeO3 thin films

We have investigated the nanoscale switching properties of strain-engineered BiFeO3 thin films deposited on LaAlO3 substrates using a combination of scanning probe techniques. Polarized Raman spectral analysis indicate that the nearly-tetragonal films have monoclinic (Cc) rather than P4mm tetragonal symmetry. Through local switching-spectroscopy measurements and piezoresponse force microscopy we provide clear evidence of ferroelectric switching of the tetragonal phase but the polarization direction, and therefore its switching, deviates strongly from the expected (001) tetragonal axis. We also demonstrate a large and reversible, electrically-driven structural phase transition from the tetragonal to the rhombohedral polymorph in this material which is promising for a plethora of applications.Comment: 10 pages, 6 figure

Importance of exosome depletion protocols to eliminate functional and RNA-containing extracellular vesicles from fetal bovine serum

Extracellular vesicles (EVs), including the nano-sized exosomes, have the capacity to transfer multiple functional molecules between cells. In cell culture experiments, fetal bovine serum (FBS) is often used to supplement cell culture medium as a nutrient, but it is important to know that the FBS also contain significant quantities of EVs. The aim of the current study was to determine whether the FBS EVs can influence cultured cell phenotype, and secondly to determine the efficiency of FBS-EV elimination protocols. Firstly, FBS that had not been depleted of EVs induced a migratory phenotype in a lung cancer epithelial cell line (A549 cells), an effect that could be mimicked by isolated FBS EVs alone. FBS-derived EVs also contained RNA, which was protected from consecutive proteinase K and RNase A treatment. Comparison of common isolation protocols suggested that an 18-hour centrifugation period eliminates approximately 95% of RNA-containing FBS EVs, whereas a 1.5-hour protocol is insufficient. In conclusion, this study shows that FBS EVs substantially influence cultured cell behaviour, but also that they can be virtually removed by an 18-hour ultracentrifugation protocol

Nanostructured La0.7Sr0.3MnO3 compounds for effective electromagnetic interference shielding in the X-band frequency range

We report a detailed study on the electromagnetic interference (EMI) shielding effectiveness (SE) properties in La0.7Sr0.3MnO3 (LSMO) nanomaterials. The samples were prepared by a solution chemistry (sol-gel) route at different sintering temperatures. The single-phase samples with grain sizes of 22 and 34 nm showed DC electrical conductivity variation from 0.65 to 13 S cm(-1) at room temperature. The application of a high magnetic field resulted in higher conductivity values. The electrical conductivity variation with temperature could be fitted with a variable range hopping mechanism in a limited temperature range. The variation of frequency dependent electromagnetic parameters measured at room temperature within the X-band region is consistent with the electrical conductivity behavior. The complex permittivity and permeability parameters were determined in line with the Nicolson-Ross-Weir algorithm. The LSMO nanomaterial samples showed EMI shielding effectiveness values of up to 19 dB (96.3% attenuation) over the X-band frequency range, making them suitable for microwave radiation shielding in commercial and defense appliances

Endosomal signalling via exosome surface TGF beta-1

Extracellular vesicles such as exosomes convey biological messages between cells, either by surface-to-surface interaction or by shuttling of bioactive molecules to a recipient cell's cytoplasm. Here we show that exosomes released by mast cells harbour both active and latent transforming growth factor beta-1 (TGF beta-1) on their surfaces. The latent form of TGF beta-1 is associated with the exosomes via heparinase-II and pH-sensitive elements. These vesicles traffic to the endocytic compartment of recipient human mesenchymal stem cells (MSCs) within 60 min of exposure. Further, the exosomes-associated TGF beta-1 is retained within the endosomal compartments at the time of signalling, which results in prolonged cellular signalling compared to free-TGF beta-1. These exosomes induce a migratory phenotype in primary MSCs involving SMAD-dependent pathways. Our results show that mast cell-derived exosomes are decorated with latent TGF beta-1 and are retained in recipient MSC endosomes, influencing recipient cell migratory phenotype. We conclude that exosomes can convey signalling within endosomes by delivering bioactive surface ligands to this intracellular compartment.11Ysciescopu

Minimal information for studies of extracellular vesicles 2018 (MISEV2018):a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points