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Direct nanoscopic observation of plasma waves in the channel of a graphene field-effect transistor

Light(Science & Applications) 2020年第1期9卷 1079-1085页

作者： Amin Soltani Frederik Kuschewski Marlene Bonmann Andrey Generalov Andrei Vorobiev Florian Ludwig Matthias M.Wiecha Dovile cibiraite Frederik Walla Stephan Winnerl susanne c.kehr Lukas M.Eng Jan Stake Hartmut G.Roskos Physikalisches Institut Johann Wolfgang Goethe-UniversitatMax-von-Laue-Str.1D-60438 Frankfurt am MainGermany Institut für Angewandte Physik Technische Universitat DresdenNöthnitzer Str.61D-01187 DresdenGermany Department of Microtechnology and Nanoscience Chalmers University of TechnologySE-41296 GothenburgSweden Institute of Ion Beam Physics and Materials Research Helmholtz-Zentrum Dresden-RossendorfBautzner Landstraße 400D-01328 DresdenGermany complexity and Topology in Quantum Matter(cT.QMAT) Cluster of Excellence EXC 2147Dresden/WurzburgGermany Department of Electronics and Nanoengineering Aalto UniversityTietotie 302150EspooFinland

Plasma waves play an important role in many solid-state phenomena and *** also become significant in electronic device structures as the operation frequencies of these devices increase.A prominent example is field-effect transistors(FETs),that witness increased attention for application as rectifying detectors and mixers of electromagnetic waves at gigahertz and terahertz frequencies,where they exhibit very good sensitivity even high above the cut-off frequency defined by the carrier transit *** theory predicts that the coupling of radiation at THz frequencies into the channel of an antenna-coupled FET leads to the development of a gated plasma wave,collectively involving the charge carriers of both the two-dimensional electron gas and the gate *** this paper,we present the first direct visualization of these *** graphene FETs containing a buried gate electrode,we utilize near-field THz nanoscopy at room temperature to directly probe the envelope function of the electric field amplitude on the exposed graphene sheet and the neighboring antenna *** of the field distribution documents that wave injection is unidirectional from the source side since the oscillating electrical potentials on the gate and drain are equalized by capacitive *** plasma waves,excited at 2 THz,are overdamped,and their decay time lies in the range of 25-70 *** this short decay time,the decay length is rather long,i.e.,0.3-0.5μm,because of the rather large propagation speed of the plasma waves,which is found to lie in the range of 3.5-7×10^(6)m/s,in good agreement with *** propagation speed depends only weakly on the gate voltage swing and is consistent with the theoretically predicted 1/4 power law.

关键词： antenna channel transistor

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Additive effects of functionally dissimilar above- and belowground organisms on a grassland plant community

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Journal of Plant Ecology 2011年第4期4卷 221-227页

作者： susanne Wurst Matthias c.Rillig Plant Ecology/Functional Biodiversity Dahlem Centre of Plant SciencesInstitut für BiologieFreie Universität BerlinAltensteinstr.614195 BerlinGermany

In nature,plant communities are affected simultaneously by a variety of functionally dissimilar organisms both above and below the ***,there is a gap of knowledge on interactive effects of functionally dissimilar organisms on plant communities that is needed to be filled to better understand and predict the general impact of biotic factors on plant *** We conducted a full-factorial mesocosm study to investigate the individual and combined impacts of above-and belowground functionally dissimilar organisms on a grassland plant *** studied the effects of aboveground herbivores(Helix aspersa,Gastropoda),arbuscular mycorrhizal fungi(AMF;Glomus spp.,Glomeromycota)and endogeic earthworms(Aporrectodea spp.,Lumbricidae)on the diversity,structure and productivity of an experimental grassland plant community and each *** Findings Aboveground herbivory by snails decreased,AMF increased and earthworms had no effects on the diversity of the grassland plant community,while their combined effects were *** biomass of the plant community was negatively affected by snails and AMF,while no effects of earthworms or interaction effects were *** plant species were differently affected by snails and *** effects of the above-and belowground organisms on each other’s performance were *** the effects of the functionally dissimilar organisms on the grassland plant community were mainly independent,the results indicate that their combined effects may be predicted by knowing the individual effects,at least under the conditions used in the present mesocosm study.

关键词： aboveground–belowground interactions AMF earthworms snails

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Between fighting and tolerance： reproductive biology of wingless males in the ant cardiocondyla venustula

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Insect Science 2017年第5期24卷 818-828页

作者： susanne Jacobs Jurgen Heinze LS ZoologielEvolutionsbiologie Universitat Regensburg Regensburg Germany

Male reproductive tactics vary widely across the species of the ant genus cardiocondyla, from obligatory lethal combat among co-occurring males to complete mutual tolerance. The African species c. venustula Wheeler, 1908 has an intermediate phylogenetic position between taxa with fighting males and taxa with tolerant males and also shows an intermediate male behavior. Males from 2 native populations in South Africa and a population introduced to Puerto Rico attacked and killed freshly eclosing rivals but rarely engaged in deadly fights with adult competitors, Instead, several males per colony established small ＂territories＂ in their natal nests and defended them against other males. Males with a stable territory had more contact with female sexuals than nonterritorial males and more frequently engaged in mating attempts. In controlled choice experiments, female sexuals did not show any preference for particular males. We suggest that male territoriality in c. venustula is an adaptation to the seasonal production of large numbers of female sexuals by multiple mothers.

关键词： cardiocondyla ergatoid males Formicidae male competition sexual selection territoriality

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Uptake of citrate-coated iron oxide nanoparticles into atherosclerotic lesions in mice occurs via accelerated transcytosis through plaque endothelial cells

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Nano Research 2016年第11期9卷 3437-3452页

作者： Wolfram c. Poller Evelyn Ramberger Philipp Boehm-Sturm susanne Mueller Konstantin Moller Norbert Lowa Frank Wiekhorst susanne Wagner Matthias Taupitz Eyk Schellenberger Gert Baumann Karl Stangl Verena Stangl Antje Ludwig Medizinische Klinik mit Schwerpunkt Kardiologie und Angiologie Charite-Universitatsmedizin Berlin Campus Mitte Chariteplatz 1 10117 Berlin Germany Abteilung fur Experimentelle Neurologie Center for Stroke Research Charite-Universitatsmedizin Berlin Chariteplatz 1 10117 Berlin Germany charite core Facility '7 T experimental MRIs' Charite-Universitatsmedizin Berlin Chariteplatz 1 10117 Berlin Germany Physikalisch-Technische Bundesanstalt Abbestr. 2-12 10587Berlin Germany Institut fur Radiologie Charite-Universitatsmedizin Berlin Campus Mitte Charit@platz 1 10117 Berlin Germany DZHK (German centre for cardiovascular Research) partner site Berlin 10115 Berlin Germany Berlin Institute of Health (BIH) 10117 Berlin Germany

Very small superparamagnetic iron oxide nanoparticles （VSOPs） rapidly accumulate in atherosclerotic lesions, thereby enabling plaque visualization by magnetic resonance imaging （MRI）. This study was performed to identify the uptake mechanisms of VSOPs into atherosclerotic plaques. Low-density lipoprotein receptor-deficient （LDLR^-/-） mice with advanced atherosclerosis were analyzed using MRI and transmission electron microscopy （TEM） at various time points after intravenous administration of VSOPs. Post-mortem MRI detected VSOP labeling of atherosclerotic plaques 10 min after injection, and the signal increased over the first 3 h. TEM revealed that the intensive plaque labeling was mediated by accelerated transcytosis of VSOPs through endothelial cells overlaying atherosclerotic lesions. Experiments with endocytosis inhibitors and small interfering RNA （siRNA） revealed a dynamin-dependent mechanism involving both clathrin- and caveolin-mediated processes. In cell culture experiments, endothelial VSOP uptake was enhanced under proatherogenic flow and TNFα stimulation, conditions that are both present in plaque areas. Our study demonstrates that VSOPs enable non-invasive MRI assessment of accelerated endothelial transcytosis, an important pathomechanism in atherosclerotic plaque formation.

关键词： atherosclerosis,unstable plaques,magnetic resonanceimaging decreased endothelial barrier function,superparamagnetic ironoxide nanoparticles

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Magnetic resonance spectroscopy to study hepatic metabolism in diffuse liver diseases, diabetes and cancer

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World Journal of Gastroenterology 2010年第13期16卷 1577-1586页

作者： Pieter c Dagnelie susanne Leij-Halfwerk Department of Epidemiology Maastricht University

This review provides an overview of the current state of the art of magnetic resonance spectroscopy (MRS) in in vivo investigations of diffuse liver disease. So far, MRS of the human liver in vivo has mainly been used as a research tool rather than a clinical tool. The liver is particularly suitable for static and dynamic metabolic studies due to its high metabolic activity. Furthermore, its relatively superfi cial position allows excellent MRS localization, while its large volume allows detection of signals with relatively low intensity. This review describes the application of MRS to study the metabolic consequences of different conditions including diffuse and chronic liver diseases, congenital diseases, diabetes, and the presence of a distant malignancy on hepatic metabolism. In addition, future prospects of MRS are discussed. It is anticipated that future technical developments such as clinical MRS magnets with higher fi eld strength (3 T) and improved delineation of multicomponent signals such as phosphomonoester and phosphodiester using proton decoupling, especially if combined with price reductions for stable isotope tracers, will lead to intensifi ed research into metabolic syndrome, cardiovascular disease, hepato-biliary diseases, as well as non-metastatic liver metabolism in patients with a distant malignant tumor.

关键词： cancer cirrhosis Diabetes Diffuse liver disease Hepatitis Magnetic resonance spectroscopy

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TWO-LEVEL ADDITIVE ScHWARZ PREcONDITIONERS FOR PLATE ELEMENTS

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Wuhan University Journal of Natural Sciences 1996年第Z1期1卷 658-667页

作者： susanne c. BRENNER Department of Mathematics University of South Carolina Columbia USA

Abstract We present a theory of two-level additive Schwas preconditions for plate elements. It is applicable to the cases where the finite element spaces on the two levels are(I) conforming and nested,(II)conforming and nonsked, and (III) nonconforming and nonnested. The condition number of the preconditioned system is independent of the mesh sizes and the number of subdomains in the case of generous overlap.

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Long-term effects of environmentally relevant concentrations of silver nanoparticles on microbial biomass, enzyme activity,and functional genes involved in the nitrogen cycle of loamy soil

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Journal of Environmental Sciences 2018年第7期30卷 12-22页

作者： Anna-Lena Grün susanne Straskraba Stefanie Schulz Michael Schloter christoph Emmerling Faculty of Regional and Environmental Sciences Department of Soil Science University of Trier J.W.Goethe University Institute of Molecular Biosciences Research for comparative Microbiome Analysis Helmholtz Zentrum München chair for Soil Science Technische Universit?t München

The increasing production and use of engineered silver nanoparticles（AgNP） in industry and private households are leading to increased concentrations of AgNP in the environment. An ecological risk assessment of AgNP is needed, but it requires understanding the long term effects of environmentally relevant concentrations of AgNP on the soil microbiome. Hence, the aim of this study was to reveal the long-term effects of AgNP on soil microorganisms. The study was conducted as a laboratory incubation experiment over a period of one year using a loamy soil and AgNP concentrations ranging from 0.01 to 1 mg AgNP/kg soil. The short term effects of AgNP were, in general, ***, after one year of exposure to 0.01 mg AgNP/kg, there were significant negative effects on soil microbial biomass（quantified by extractable DNA; p = 0.000） and bacterial ammonia oxidizers（quantified by amo A gene copy numbers; p = 0.009）. Furthermore, the tested AgNP concentrations significantly decreased the soil microbial biomass, the leucine aminopeptidase activity（quantified by substrate turnover; p = 0.014）, and the abundance of nitrogen fixing microorganisms（quantified by nif H gene copy numbers; p = 0.001）. The results of the positive control with Ag NO3 revealed predominantly stronger effects due to Ag＋ion release. Thus, the increasing toxicity of AgNP during the test period may reflect the long-term release of Ag^＋ions. Nevertheless, even very low concentrations of AgNP caused disadvantages for the microbial soil community, especially for nitrogen cycling, and our results confirmed the risks of releasing AgNP into the environment.

关键词： Silver nanoparticles Soil Microbiome amoA nifH Leucine aminopeptidase activity AgPure

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Seasonal movements of American horseshoe crabs Limulus polyphemus in the Great Bay Estuary,New Hampshire (USA)

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current Zoology 2010年第5期56卷 587-598页

作者： susanne Y ScHALLER christopher c.cHABOT Winsor H.WATSON Ⅲ Department of Biological Sciences University of New Hampshire Department of Biology Plymouth State University

The goal of this study was to determine the year round movement patterns of American horseshoe crabs, Limulus polyphemus, in the Great Bay Estuary, New Hampshire （USA） by using acoustic telemetry to track the movements of 37 adult Limulus, for periods ranging from 2 to 31 months. During the winter （December-March） horseshoe crabs moved very little. In the spring, when water temperatures exceeded II^c, horseshoe crabs moved at least 1 km further up into the estuary to shallower subtidal areas about a month prior to spawning. The mean distance traveled during spring migrations was 2.6 ＋ 0.5 （n=20） km up the estuary. Mating occurred in May and June and during these months animals spent most of their time in shallow subtidal areas adjacent to mating beaches. In the summer （July-Augnst）, animals moved 1.5 ± 0.5 （n=26） km down the estuary, towards the ocean, and ranged widely, using extensive portions of the estuary. In the fall （September-November） movement was more limited （0.5 ± 0.5 km; n = 24） while animals settled into wintering locations, where they remained until spring. The mean annual linear range for all animals was 4.5 ± 0.3 km （n =35） and the maximum distance traveled by an individual horseshoe crab within one year was 9.2 km. There was no evidence that any of the horseshoe crabs tracked during this study left the estuary

关键词： Limuluspolyphemus Acoustic telemetry Horseshoe crab Tracking Estuary Home range

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Multiscale morphological analysis of bone microarchitecture around Mg-10Gd implants

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Bioactive Materials 2023年第12期30卷 154-168页

作者： Sandra Sefa Jonathan Espiritu Hanna cwieka Imke Greving Silja Flenner Olga Will susanne Beuer D.c Florian Wieland Regine Willumeit-Romer Berit Zeller-Plumhoff Institute of Metallic Biomaterials Helmholtz Zentrum HereonGeesthachtGermany Syntellix AG HannoverGermany Institute of Materials Physics Helmholtz Zentrum HereonGeesthachtGermany Molecular Imaging North competence center Kiel UniversityKielGermany Fraunhofer Institut für Integrierte Systeme und Bauelementetechnologie(IISB) ErlangenGermany

The utilization of biodegradable magnesium(Mg)-based implants for restoration of bone function following trauma represents a transformative approach in orthopaedic *** such alloy,magnesium-10 weight percent gadolinium(Mg-10Gd),has been specifically developed to address the rapid degradation of Mg while enhancing its mechanical properties to promote bone *** studies have demonstrated that Mg-10Gd exhibits favorable osseointegration;however,it exhibits distinct ultrastructural adaptation in comparison to conventional implants like titanium(Ti).A crucial aspect that remains unexplored is the impact of Mg-10Gd degradation on the bone *** address this,we employed hierarchical three-dimensional imaging using synchrotron radiation in conjunction with image-based finite element *** using the methods outlined,the vascular porosity,lacunar porosity and the lacunar-canaliculi network(LcN)morphology of bone around Mg-10Gd in comparison to Ti in a rat model from 4 weeks to 20 weeks post-implantation was *** investigation revealed that within our observation period,the degradation of Mg-10Gd implants was associated with significantly lower(pcunar density in the surrounding bone,compared to ***,the LcN morphology and the fluid flow analysis did not significantly differ for both implant *** summary,a more pronounced lower lacunae distribution rather than their morphological changes was detected in the surrounding bone upon the degradation of Mg-10Gd *** implies potential disparities in bone remodelling rates when compared to Ti *** findings shed light on the intricate relationship between Mg-10Gd degradation and bone microarchitecture,contributing to a deeper understanding of the implications for successful osseointegration.

关键词： Biodegradable magnesium implants Lacunar-canalicular network(LcN) Vascular porosity Synchrotron radiation micro computed tomography(SRμcT) Transmission x-ray microscopy(TXM)

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Solid phase microextraction(SPME) sampling under turbulent conditions and for the simultaneous collecting of tracer gases

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International Journal of Mining Science and Technology 2015年第4期25卷 559-563页

作者： Underwood susanne W. Jong Edmund c. Luxbacher Kray D. Sarver Emily A. Ripepi Nino S. Mc Nair Harold M. Department of Mining and Minerals Engineering Virginia Tech Department of chemistry Virginia Tech

Solid phase microextraction （SPME） is a solvent-flee method of sample collection. SPME is an appealing method for sample collection because it is designed for the sampling of trace level analytes with short sampling times in a variety of environments. Additionally, SPME can be used to directly deliver a sample to a gas chromatograph （Gc） for analysis by means of thermal desorption. In this paper, the performance of SPME under dynamic conditions was investigated. Additionally, the competence of SPME sampling for the simultaneous analysis of multiple trace analytes was also evaluated. This work is discussed in the context of underground mine ventilation surveys but is applicable to any industry in which ventilation circuits must be evaluated. The results of this paper showed that the performance of the 100 ~m PDMS SPME fiber was both precise and rapid under dynamic conditions. This SPME fiber was also able to simultaneously collect sulfur hexafluoride （SF6） and perfluoromethylcyclohexane （PMcH） with adequate sensitivity.

关键词： Solid phase microextraction Sulfur hexafluoride Perfluoromethylcyclohexane Tracer gas Mine ventilation Air sampling

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