| 1. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 2. |
- Wang, Tiegang, et al.
(författare)
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Study on nanocrystalline Cr2O3 films deposited by arc ion plating: I. composition, morphology, and microstructure analysis
- 2012
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972. ; 206:10, s. 2629-2637
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Tidskriftsartikel (refereegranskat)abstract
- Nanocrystalline Cr2O3 thin films were deposited on silicon wafers with (100) orientation by arc ion plating (AIP) technique at various negative bias voltages. By virtue of X-ray diffraction analysis, scanning electron microscope, and high-resolution transmission electron microscope, the influence of substrate bias voltage on the film growth process, microstructure, and characteristics was investigated systematically, including the phase constituents, grain size, lattice constant, chemical compositions, as well as surface and cross-section morphologies. With increasing the bias voltage, the grain size and lattice constant of AIP Cr2O3 films first decreased slightly, and then increased gradually again. Both reached the minimum (35 nm and 13.57 angstrom) when the bias voltage was - 100 V. However, the bias voltage had little effect on the phase constituents and chemical compositions of AIP Cr2O3 films. During the film growth process, the surfaces of Cr2O3 films were getting smoother with the negative bias voltage increase, in the meantime, their microstructures evolved from coarse columnar grains to fine columnar grains, short columnar recrystallized grains, and fine columnar grains again. (C) 2011 Elsevier B.V. All rights reserved.
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| 3. |
- Lebegue, Sebastien, et al.
(författare)
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Semimetallic dense hydrogen above 260 GPa
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:25, s. 9766-9769
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Tidskriftsartikel (refereegranskat)abstract
- Being the lightest and the most abundant element in the universe, hydrogen is fascinating to physicists. In particular, the conditions of its metallization associated with a possible superconducting state at high temperature have been a matter of much debate in the scientific community, and progress in this field is strongly correlated with the advancements in theoretical methods and experimental techniques. Recently, the existence of hydrogen in a metallic state was reported experimentally at room temperature under a pressure of 260-270 GPa, but was shortly after that disputed in the light of more experiments, finding either a semimetal or a transition to an other phase. With the aim to reconcile the different interpretations proposed, we propose by combining several computational techniques, such as density functional theory and the GW approximation, that phase III at ambient temperature of hydrogen is the Cmca-12 phase, which becomes a semimetal at 260 GPa. From phonon calculations, we demonstrate it to be dynamically stable; calculated electron-phonon coupling is rather weak and therefore this phase is not expected to be a high-temperature superconductor.
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| 4. |
- Li, Bing, et al.
(författare)
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Rhodium dihydride (RhH(2)) with high volumetric hydrogen density
- 2011
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 108:46, s. 18618-18621
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Tidskriftsartikel (refereegranskat)abstract
- Materials with very high hydrogen density have attracted considerable interest due to a range of motivations, including the search for chemically precompressed metallic hydrogen and hydrogen storage applications. Using high-pressure synchrotron X-ray diffraction technique and theoretical calculations, we have discovered a new rhodium dihydride (RhH(2)) with high volumetric hydrogen density (163.7 g/L). Compressing rhodium in fluid hydrogen at ambient temperature, the fcc rhodium metal absorbs hydrogen and expands unit-cell volume by two discrete steps to form NaCl-typed fcc rhodium monohydride at 4 GPa and fluorite-typed fcc RhH(2) at 8 GPa. RhH(2) is the first dihydride discovered in the platinum group metals under high pressure. Our low-temperature experiments show that RhH(2) is recoverable after releasing pressure cryogenically to 1 bar and is capable of retaining hydrogen up to 150 K for minutes and 77 K for an indefinite length of time.
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| 5. |
- Mao, Wendy L., et al.
(författare)
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Distortions and stabilization of simple-cubic calcium at high pressure and low temperature
- 2010
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 107:22, s. 9965-9968
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Tidskriftsartikel (refereegranskat)abstract
- Ca-III, the first superconducting calcium phase under pressure, was identified as simple-cubic (sc) by previous X-ray diffraction (XRD) experiments. In contrast, all previous theoretical calculations showed that sc had a higher enthalpy than many proposed structures and had an imaginary (unstable) phonon branch. By using our newly developed submicrometer high-pressure single-crystal XRD, cryogenic high-pressure XRD, and theoretical calculations, we demonstrate that Ca-III is neither exactly sc nor any of the lower-enthalpy phases, but sustains the sc-like, primitive unit by a rhombohedral distortion at 300 K and a monoclinic distortion below 30 K. This surprising discovery reveals a scenario that the high-pressure structure of calcium does not go to the zero-temperature global enthalpy minimum but is dictated by high-temperature anharmonicity and low-temperature metastability fine-tuned with phonon stability at the local minimum.
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| 6. |
- Wang, Tiegang, et al.
(författare)
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High-temperature thermal stability of nanocrystalline Cr2O3 films deposited on silicon wafers by arc ion plating
- 2013
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972. ; 228, s. 140-147
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the high-temperature thermal stability of nanocrystalline Cr2O3 films on Si wafers deposited at various bias voltages was systematically investigated by means of a symmetrical high-resolution thermogravimetric system. In the meantime, the effects of substrate bias voltage on the morphology, microstructure, crack area percentage, phase constituents, and grain size of the heat-treated Cr2O3 films were also studied in detail. The results showed that the Cr2O3 films presented the higher thermal stability in pure nitrogen than in air up to 1200 degrees C because the brittle oxidation product was more prone to cracking and chipping. As the bias voltage was -100 V, the Cr2O3 film showed the highest thermal stability which was attributed to its most compact structure and the lowest defect density. After the heat treatments, all the films cracked due to the big difference in thermal expansion coefficient between the Cr2O3 film and Si wafer, which caused large thermal stresses. And some obvious micro-cavities were left in the film cross section after oxidation owing to the vaporization of Cr2O3 in oxygen containing atmosphere. In addition, the heat treatment also had a strong influence on the grain size of the Cr2O3 films. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.
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| 7. |
- Wang, Tiegang, et al.
(författare)
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Influence of residual stress on the adhesive behavior of detonation gun sprayed WC-Co coatings
- 2012
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Ingår i: Current Applied Physics. - : Elsevier BV. - 1567-1739. ; 12, s. 59-62
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Tidskriftsartikel (refereegranskat)abstract
- The residual stresses generated during D-Gun spraying process act as pre-existing stresses and seriously affect the various types of coating performance. To produce a reliable coating, it is necessary to know the influence of residual stress on the adhesive behavior of coating/substrate system. Based on the residual stress formula for thick coatings and accurate curvature measurements, the residual stresses of D-Gun sprayed WC-Co coatings were obtained. And a strong link was built between the residual stress and the adhesive strength of the coating, namely, the compressive stress in the coating could significantly improve the adhesion, whereas the tensile stress weakened the adhesion. The larger compressive residual stress is in the coating, the stronger adhesion between the coating and substrate. (C) 2012 Elsevier B.V. All rights reserved.
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| 8. |
- Wang, Tiegang, et al.
(författare)
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Study on nanocrystalline Cr2O3 films deposited by arc ion plating: II. Mechanical and tribological properties
- 2012
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972. ; 206:10, s. 2638-2644
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the influence of substrate bias voltage on the microhardness, adhesive strength, friction coefficient, and wear rate of AIP Cr2O3 films deposited on AISI 304 stainless steel substrates was investigated systematically. In the meantime, the wear failure mechanism of AIP Cr2O3 films in dry sliding contact was also analyzed and discussed. The results showed that the mechanical properties, adhesive behaviors, and tribological performance of AIP Cr2O3 films were greatly altered by applying a negative bias voltage. With increasing the bias voltage, the hardness, critical load, and tribological performance of AIP Cr2O3 films first were improved gradually, and then were impaired slightly again. When the bias voltage is - 100 V. the Cr2O3 film possessed the highest hardness, the strongest adhesion, and the best wear resistance. The essence of above phenomena was attributed to the variations of microstructure and defect density in the films induced by the substrate bias voltage increase. The main wear failure mechanism of AIP Cr2O3 films is crack initiation and propagation under the high contact stresses, inducing the local film with small area to flake off gradually, and eventually leading to the formation of a wear scar. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.
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