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  • American Institute of Physics (AIP)  (65)
  • Nature Publishing Group (NPG)  (16)
  • 11
    Publikationsdatum: 2014-10-28
    Beschreibung: Solid state dewetting and the subsequent morphological changes for platinum thin films grown on zinc oxide (ZnO) buffered (001) silicon substrates (Pt/ZnO/SiO 2 /(001)Si system) is investigated under vacuum conditions via a custom-designed confocal laser microscope coupled with a laser heating system. Live imaging of thin film dewetting under a range of heating and quenching vacuum ambients reveals events including hillock formation, hole formation, and hole growth that lead to formation of a network of Pt ligaments, break up of Pt ligaments to individual islands and subsequent Pt islands shape reformation, in chronological fashion. These findings are corroborated by ex-situ materials characterization and quantitative electron microscopy analysis. A secondary hole formation via blistering before film rupture is revealed to be the critical stage, after which a rapid dewetting catastrophe occurs. This process is instantaneous and cannot be captured by ex-situ methods. Finally, an intermetallic phase forms at 900 °C and alters the morphology of Pt islands, suggesting a practical limit to the thermal environments that may be used for these platinized silicon wafers in vacuum conditions.
    Print ISSN: 0021-8979
    Digitale ISSN: 1089-7550
    Thema: Physik
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  • 12
    Publikationsdatum: 2014-09-06
    Beschreibung: The electronic transport properties in individual niobium disulphide (NbS 2 ) nanoflakes mechanically exfoliated from the bulk crystal with three rhombohedral (3R) structure grown by chemical vapor transport were investigated. It is found that the conductivity values of the single-crystalline nanoflakes are approximately two orders of magnitude lower than that of their bulk counterparts. Temperature-dependent conductivity measurements show that the 3R-NbS 2 nanoflakes exhibit semiconducting transport behavior, which is also different from the metallic character in the bulk crystals. In addition, the noncontinuous conductivity variations were observed at the temperature below 180 K for both the nanoflakes and the bulks, which is attributed to the probable charge density wave transition. The photoconductivities in the semiconducting nanoflakes were also observed under the excitation at 532 nm wavelength. The probable mechanisms resulting in the different transport behaviors between the NbS 2 nanostructure and bulk were discussed.
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
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  • 13
    Publikationsdatum: 2014-09-12
    Beschreibung: We investigate the magnetic and magnetocaloric properties of the new Mn 4−x Fe x Ga 2 Sn compounds (x = 0, 0.1, 0.4, 0.6, and 0.8) from DC magnetization measurements. These phases crystallize in a lacunar form of the η-Fe 2−x Ge type of structure (P6 3 /mmc). They present a second-order paramagnetic to ferromagnetic transition whose temperature increases upon increasing the Fe content from T C  = 317 K for x = 0 up to T C  = 411 K for x = 0.8. The alloys with x ≤ 0.4 further exhibit another transition at lower temperature associated with a spin reorientation. The maximal magnetization and magnetic entropy change are found almost constant throughout the series close to ∼7.4 μ B /f.u. and ∼12 mJ cm −3 K −1 (for μ 0 ΔH = 2.4 T), respectively. The magnetocaloric properties of Mn 4−x Fe x Ga 2 Sn are compared with those of previously investigated materials with high-temperature magnetic transition and their potential interest for high-temperature magnetocaloric applications is briefly discussed.
    Print ISSN: 0021-8979
    Digitale ISSN: 1089-7550
    Thema: Physik
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  • 14
    Publikationsdatum: 2015-03-20
    Beschreibung: The spontaneous surface luminescence properties of InGaN/GaN quantum structure lattice (QSL) are reported. The QSL consists of a two-dimensional array of InGaN/GaN quantum boxes (QBs) arranged in a rectangular pattern of 200 nm periodicity. The measured angular dependent photoluminescence (PL) spectra show a strong dependence on the in-plane Bragg diffractions between QBs. The maximum PL intensity of the InGaN/GaN QSL array that fulfill the Bragg condition points in the normal direction of the sample surface with a narrow radiation angle of ∼ ±12°. In addition, a small side lobe is also shown at ±40°. For the QSL sample that does not fulfill the Bragg diffraction condition, the radiation pattern shows a conventional cosine distribution. The finite-difference time-domain numerical analysis confirms that the lowest order and higher order Bragg diffractions between QBs determine the main and the small side lobe of the radiation pattern measured in QSLs, respectively.
    Print ISSN: 0003-6951
    Digitale ISSN: 1077-3118
    Thema: Physik
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  • 15
    Publikationsdatum: 2015-01-15
    Print ISSN: 0021-8979
    Digitale ISSN: 1089-7550
    Thema: Physik
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  • 16
    Publikationsdatum: 2007
    Beschreibung: Biodegradation of crude oil in subsurface petroleum reservoirs has adversely affected the majority of the world's oil, making recovery and refining of that oil more costly. The prevalent occurrence of biodegradation in shallow subsurface petroleum reservoirs has been attributed to aerobic bacterial hydrocarbon degradation stimulated by surface recharge of oxygen-bearing meteoric waters. This hypothesis is empirically supported by the likelihood of encountering biodegraded oils at higher levels of degradation in reservoirs near the surface. More recent findings, however, suggest that anaerobic degradation processes dominate subsurface sedimentary environments, despite slow reaction kinetics and uncertainty as to the actual degradation pathways occurring in oil reservoirs. Here we use laboratory experiments in microcosms monitoring the hydrocarbon composition of degraded oils and generated gases, together with the carbon isotopic compositions of gas and oil samples taken at wellheads and a Rayleigh isotope fractionation box model, to elucidate the probable mechanisms of hydrocarbon degradation in reservoirs. We find that crude-oil hydrocarbon degradation under methanogenic conditions in the laboratory mimics the characteristic sequential removal of compound classes seen in reservoir-degraded petroleum. The initial preferential removal of n-alkanes generates close to stoichiometric amounts of methane, principally by hydrogenotrophic methanogenesis. Our data imply a common methanogenic biodegradation mechanism in subsurface degraded oil reservoirs, resulting in consistent patterns of hydrocarbon alteration, and the common association of dry gas with severely degraded oils observed worldwide. Energy recovery from oilfields in the form of methane, based on accelerating natural methanogenic biodegradation, may offer a route to economic production of difficult-to-recover energy from oilfields.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jones, D M -- Head, I M -- Gray, N D -- Adams, J J -- Rowan, A K -- Aitken, C M -- Bennett, B -- Huang, H -- Brown, A -- Bowler, B F J -- Oldenburg, T -- Erdmann, M -- Larter, S R -- England -- Nature. 2008 Jan 10;451(7175):176-80. Epub 2007 Dec 12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Civil Engineering and Geosciences, University of Newcastle, Newcastle upon Tyne, NE1 7RU, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18075503" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Alkanes/chemistry/metabolism ; Anaerobiosis ; Archaea/genetics/metabolism ; Bacteria/genetics/metabolism ; Biodegradation, Environmental ; Canada ; Carbon Dioxide/chemistry/metabolism ; Carbon Isotopes/analysis ; Gases/analysis/chemistry/metabolism ; Methane/*biosynthesis/chemistry ; Petroleum/*metabolism
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 17
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    Nature Publishing Group (NPG)
    Publikationsdatum: 2009-05-22
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huang, Paul H -- Marais, Richard -- 10433/Cancer Research UK/United Kingdom -- 10437/Cancer Research UK/United Kingdom -- England -- Nature. 2009 May 21;459(7245):336-7. doi: 10.1038/459336a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19458705" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Humans ; MAP Kinase Signaling System/drug effects ; Melanoma/genetics/*metabolism/*pathology ; Phosphoproteins/metabolism ; Phosphorylation/drug effects ; Proto-Oncogene Proteins B-raf/genetics/*metabolism
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 18
    Publikationsdatum: 2015-09-17
    Beschreibung: Inflammatory caspases (caspase-1, -4, -5 and -11) are critical for innate defences. Caspase-1 is activated by ligands of various canonical inflammasomes, and caspase-4, -5 and -11 directly recognize bacterial lipopolysaccharide, both of which trigger pyroptosis. Despite the crucial role in immunity and endotoxic shock, the mechanism for pyroptosis induction by inflammatory caspases is unknown. Here we identify gasdermin D (Gsdmd) by genome-wide clustered regularly interspaced palindromic repeat (CRISPR)-Cas9 nuclease screens of caspase-11- and caspase-1-mediated pyroptosis in mouse bone marrow macrophages. GSDMD-deficient cells resisted the induction of pyroptosis by cytosolic lipopolysaccharide and known canonical inflammasome ligands. Interleukin-1beta release was also diminished in Gsdmd(-/-) cells, despite intact processing by caspase-1. Caspase-1 and caspase-4/5/11 specifically cleaved the linker between the amino-terminal gasdermin-N and carboxy-terminal gasdermin-C domains in GSDMD, which was required and sufficient for pyroptosis. The cleavage released the intramolecular inhibition on the gasdermin-N domain that showed intrinsic pyroptosis-inducing activity. Other gasdermin family members were not cleaved by inflammatory caspases but shared the autoinhibition; gain-of-function mutations in Gsdma3 that cause alopecia and skin defects disrupted the autoinhibition, allowing its gasdermin-N domain to trigger pyroptosis. These findings offer insight into inflammasome-mediated immunity/diseases and also change our understanding of pyroptosis and programmed necrosis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shi, Jianjin -- Zhao, Yue -- Wang, Kun -- Shi, Xuyan -- Wang, Yue -- Huang, Huanwei -- Zhuang, Yinghua -- Cai, Tao -- Wang, Fengchao -- Shao, Feng -- Howard Hughes Medical Institute/ -- England -- Nature. 2015 Oct 29;526(7575):660-5. doi: 10.1038/nature15514. Epub 2015 Sep 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Peking University-Tsinghua University-National Institute of Biological Sciences Joint Graduate Program, School of Life Sciences, Tsinghua University, 100084, China. ; National Institute of Biological Sciences, Beijing 102206, China. ; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China. ; National Institute of Biological Sciences, Beijing, Collaborative Innovation Center for Cancer Medicine, Beijing 102206, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26375003" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
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  • 19
    Publikationsdatum: 2016-04-22
    Beschreibung: The collisionless trapped electron modes in the short wavelength region k ⊥ ρ s 〉 1 (SWTEMs) are studied with the gyrokinetic integral eigenmode equation in tokamak plasmas. Here, we present a systematic study of the correlation between the SWTEMs and short wavelength ion temperature gradient (SWITG) modes. The k θ ρ s spectra of TEM have double humps in the short wavelength and long wavelength regions, respectively. The SWITG modes with trapped electron effects taking into account have broader k θ ρ s spectra. Dependences of growth rate and real frequency of SWTEMs on the various parameters, such as ion temperature gradient (η i ), the temperature gradient of trapped electrons (η e ), toroidicity (ε n ), magnetic shear ( s ̂ ), safety factor (q), and the ratio of temperature (T e /T i ), are investigated in detail. It is found that the SWTEMs propagate in the electron diamagnetic drift direction and require temperature gradient of trapped electrons η e exceeding thresholds. Moreover, the ion temperature gradient has a strong stabilizing effect on the SWTEMs. The SWTEMs become stable in both regimes of toroidicity ε n  〉 0.1 and magnetic shear s ̂ 〉 0.5 regardless of the fraction of trapped electrons. In addition, the properties of short wavelength ITG (SWITG) modes are discussed with different ratio of trapped electrons. It is found that trapped electrons of greater fraction have a stronger destabilizing effect on the SWTEM and SWITG modes. These results are significant for the electrons anomalous transport experiments in the future.
    Print ISSN: 1070-664X
    Digitale ISSN: 1089-7674
    Thema: Physik
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  • 20
    Publikationsdatum: 2016-02-17
    Beschreibung: A novel, compact, TM 01 -TE 10 mode power divider and a novel, compact, four-way TE 10 -TM 01 mode power combiner were theoretically designed and experimentally tested as a proof of principle. The theoretical and experimental S parameters are consistent with each other. High-power experiments show that their power capacities are no less than 1.5 GW and 3 GW, respectively. The devices have the merits of high power capacities and low insertion losses.
    Print ISSN: 0034-6748
    Digitale ISSN: 1089-7623
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
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