301 research outputs found

    Nanoantenna-enhanced ultrafast nonlinear spectroscopy of a single gold nanoparticle

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    Optical nanoantennas are a novel tool to investigate previously unattainable dimensions in the nanocosmos. Just like their radio-frequency equivalents, nanoantennas enhance the light-matter interaction in their feed gap. Antenna enhancement of small signals promises to open a new regime in linear and nonlinear spectroscopy on the nanoscale. Without antennas especially the nonlinear spectroscopy of single nanoobjects is very demanding. Here, we present for the first time antenna-enhanced ultrafast nonlinear optical spectroscopy. In particular, we utilize the antenna to determine the nonlinear transient absorption signal of a single gold nanoparticle caused by mechanical breathing oscillations. We increase the signal amplitude by an order of magnitude which is in good agreement with our analytical and numerical models. Our method will find applications in linear and nonlinear spectroscopy of nanoobjects, ranging from single protein binding events via nonlinear tensor elements to the limits of continuum mechanics

    Direct Observation of Martensitic Phase-Transformation Dynamics in Iron by 4D Single-Pulse Electron Microscopy

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    The in situ martensitic phase transformation of iron, a complex solid-state transition involving collective atomic displacement and interface movement, is studied in real time by means of four-dimensional (4D) electron microscopy. The iron nanofilm specimen is heated at a maximum rate of ∼10^(11) K/s by a single heating pulse, and the evolution of the phase transformation from body-centered cubic to face-centered cubic crystal structure is followed by means of single-pulse, selected-area diffraction and real-space imaging. Two distinct components are revealed in the evolution of the crystal structure. The first, on the nanosecond time scale, is a direct martensitic transformation, which proceeds in regions heated into the temperature range of stability of the fcc phase, 1185−1667 K. The second, on the microsecond time scale, represents an indirect process for the hottest central zone of laser heating, where the temperature is initially above 1667 K and cooling is the rate-determining step. The mechanism of the direct transformation involves two steps, that of (barrier-crossing) nucleation on the reported nanosecond time scale, followed by a rapid grain growth typically in ∼100 ps for 10 nm crystallites

    Differential Ly-6C expression identifies the recruited macrophage phenotype, which orchestrates the regression of murine liver fibrosis

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    Although macrophages are widely recognized to have a profibrotic role in inflammation, we have used a highly tractable CCl(4)-induced model of reversible hepatic fibrosis to identify and characterize the macrophage phenotype responsible for tissue remodeling: the hitherto elusive restorative macrophage. This CD11B(hi) F4/80(int) Ly-6C(lo) macrophage subset was most abundant in livers during maximal fibrosis resolution and represented the principle matrix metalloproteinase (MMP) -expressing subset. Depletion of this population in CD11B promoter–diphtheria toxin receptor (CD11B-DTR) transgenic mice caused a failure of scar remodeling. Adoptive transfer and in situ labeling experiments showed that these restorative macrophages derive from recruited Ly-6C(hi) monocytes, a common origin with profibrotic Ly-6C(hi) macrophages, indicative of a phenotypic switch in vivo conferring proresolution properties. Microarray profiling of the Ly-6C(lo) subset, compared with Ly-6C(hi) macrophages, showed a phenotype outside the M1/M2 classification, with increased expression of MMPs, growth factors, and phagocytosis-related genes, including Mmp9, Mmp12, insulin-like growth factor 1 (Igf1), and Glycoprotein (transmembrane) nmb (Gpnmb). Confocal microscopy confirmed the postphagocytic nature of restorative macrophages. Furthermore, the restorative macrophage phenotype was recapitulated in vitro by the phagocytosis of cellular debris with associated activation of the ERK signaling cascade. Critically, induced phagocytic behavior in vivo, through administration of liposomes, increased restorative macrophage number and accelerated fibrosis resolution, offering a therapeutic strategy to this orphan pathological process

    Parton distribution benchmarking with LHC data

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    We present a detailed comparison of the most recent sets of NNLO PDFs from the ABM, CT, HERAPDF, MSTW and NNPDF collaborations. We compare parton distributions at low and high scales and parton luminosities relevant for LHC phenomenology. We study the PDF dependence of LHC benchmark inclusive cross sections and differential distributions for electroweak boson and jet production in the cases in which the experimental covariance matrix is available. We quantify the agreement between data and theory by computing the χ 2 for each data set with all the various PDFs. PDF comparisons are performed consistently for common values of the strong coupling. We also present a benchmark comparison of jet production at the LHC, comparing the results from various available codes and scale settings. Finally, we discuss the implications of the updated NNLO PDF sets for the combined PDF+α s uncertainty in the gluon fusion Higgs production cross section

    The Type III Effectors NleE and NleB from Enteropathogenic E. coli and OspZ from Shigella Block Nuclear Translocation of NF-κB p65

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    Many bacterial pathogens utilize a type III secretion system to deliver multiple effector proteins into host cells. Here we found that the type III effectors, NleE from enteropathogenic E. coli (EPEC) and OspZ from Shigella, blocked translocation of the p65 subunit of the transcription factor, NF-κB, to the host cell nucleus. NF-κB inhibition by NleE was associated with decreased IL-8 expression in EPEC-infected intestinal epithelial cells. Ectopically expressed NleE also blocked nuclear translocation of p65 and c-Rel, but not p50 or STAT1/2. NleE homologues from other attaching and effacing pathogens as well OspZ from Shigella flexneri 6 and Shigella boydii, also inhibited NF-κB activation and p65 nuclear import; however, a truncated form of OspZ from S. flexneri 2a that carries a 36 amino acid deletion at the C-terminus had no inhibitory activity. We determined that the C-termini of NleE and full length OspZ were functionally interchangeable and identified a six amino acid motif, IDSY(M/I)K, that was important for both NleE- and OspZ-mediated inhibition of NF-κB activity. We also established that NleB, encoded directly upstream from NleE, suppressed NF-κB activation. Whereas NleE inhibited both TNFα and IL-1β stimulated p65 nuclear translocation and IκB degradation, NleB inhibited the TNFα pathway only. Neither NleE nor NleB inhibited AP-1 activation, suggesting that the modulatory activity of the effectors was specific for NF-κB signaling. Overall our data show that EPEC and Shigella have evolved similar T3SS-dependent means to manipulate host inflammatory pathways by interfering with the activation of selected host transcriptional regulators

    Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers

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    "This is the peer reviewed version of the following article: Gottselig, N., W. Amelung, J. W. Kirchner, R. Bol, W. Eugster, S. J. Granger, C. Hernández-Crespo, et al. 2017. Elemental Composition of Natural Nanoparticles and Fine Colloids in European Forest Stream Waters and Their Role as Phosphorus Carriers. Global Biogeochemical Cycles 31 (10). American Geophysical Union (AGU): 1592 1607. doi:10.1002/2017gb005657, which has been published in final form at https://doi.org/10.1002/2017GB005657. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] Biogeochemical cycling of elements largely occurs in dissolved state, but many elements may also be bound to natural nanoparticles (NNP, 1-100 nm) and fine colloids (100-450 nm). We examined the hypothesis that the size and composition of stream water NNP and colloids vary systematically across Europe. To test this hypothesis, 96 stream water samples were simultaneously collected in 26 forested headwater catchments along two transects across Europe. Three size fractions (similar to 1-20 nm, >20-60 nm, and >60 nm) of NNP and fine colloids were identified with Field Flow Fractionation coupled to inductively coupled plasma mass spectrometry and an organic carbon detector. The results showed that NNP and fine colloids constituted between 2 +/- 5% (Si) and 53 +/- 21% (Fe; mean +/- SD) of total element concentrations, indicating a substantial contribution of particles to element transport in these European streams, especially for P and Fe. The particulate contents of Fe, Al, and organic C were correlated to their total element concentrations, but those of particulate Si, Mn, P, and Ca were not. The fine colloidal fractions >60 nm were dominated by clay minerals across all sites. The resulting element patterns of NNP <60 nm changed from North to South Europe from Fe-to Ca-dominated particles, along with associated changes in acidity, forest type, and dominant lithology.The authors gratefully acknowledge the assistance of the following people in locating suitable sampling sites, contacting site operators, performing the sampling, and providing data: A. Avila Castells (Autonomous University of Barcelona), R. Batalla (University of Lleida), P. Blomkvist (Swedish University of Agricultural Sciences), H. Bogena (Julich Research Center), A.K. Boulet (University of Aveiro), D. Estany (University of Lleida), F. Garnier (French National Institute of Agricultural Research), H.J. Hendricks-Franssen (Research Center Julich), L. JacksonBlake (James Hutton Institute, NIVA), T. Laurila (Finnish Meteorological Institute), A. Lindroth (Lund University), M.M. Monerris (Universitat Politecnica de Valencia), M. Ottosson Lofvenius (Swedish University of Agricultural Sciences), I. Taberman (Swedish University of Agricultural Sciences), F. Wendland (Research Center Julich), T. Zetterberg (Swedish University of Agricultural Sciences and The Swedish Environmental Research Institute, IVL) and further unnamed contributors. The Swedish Infrastructure for Ecosystem Science (SITES) and the Swedish Integrated Monitoring, the latter financed by the Swedish Environmental Protection Agency, and ICOS Sweden have supported sampling and provided data for the Swedish sites. J.J.K. gratefully acknowledges the support from CESAM (UID/AMB/50017/2013), funded by the FCT/MCTES (PIDDAC) with cofunding by FEDER through COMPETE. N.G. gratefully acknowledges all those who contributed to organizing and implementing the continental sampling. The raw data can be found at http://hdl.handle.net/2128/14937. This project was partly funded by the German Research Foundation (DFG KL2495/1-1).Gottselig, N.; Amelung, W.; Kirchner, J.; Bol, R.; Eugster, W.; Granger, S.; Hernández Crespo, C.... 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