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Träfflista för sökning "WFRF:(Pfeifer Thomas) srt2:(2015-2019)"

Sökning: WFRF:(Pfeifer Thomas) > (2015-2019)

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  • Hermann, Markus, et al. (författare)
  • An optical particle size spectrometer for aircraft-borne measurements in IAGOS-CARIBIC
  • 2016
  • Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 9:5, s. 2179-2194
  • Tidskriftsartikel (refereegranskat)abstract
    • The particle number size distribution is an important parameter to characterize the atmospheric aerosol and its influence on the Earth's climate. Here we describe a new optical particle size spectrometer (OPSS) for measurements of the accumulation mode particle number size distribution in the tropopause region on board a passenger aircraft (IAGOS-CARIBIC observatory: In-service Aircraft for a Global Observing System - Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container). A modified KS93 particle sensor from RION Co., Ltd., together with a new airflow system and a dedicated data acquisition system, is the key component of the CARIBIC OPSS. The instrument records individual particle pulse signal curves in the particle size range 130-1110 nm diameter (for a particle refractive index of 1.47-i0.006) together with a time stamp and thus allows the post-flight choice of the time resolution and the size distribution bin width. The CARIBIC OPSS has a 50 % particle detection diameter of 152 nm and a maximum asymptotic counting efficiency of 98 %. The instrument's measurement performance shows no pressure dependency and no particle coincidence for free tropospheric conditions. The size response function of the CARIBIC OPSS was obtained by a polystyrene latex calibration in combination with model calculations. Particle number size distributions measured with the new OPSS in the lowermost stratosphere agreed within a factor of 2 in concentration with balloon-borne measurements over western North America. Since June 2010 the CARIBIC OPSS is deployed once per month in the IAGOS-CARIBIC observatory.
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  • Ueda, Kiyoshi, et al. (författare)
  • Roadmap on photonic, electronic and atomic collision physics : I. Light-matter interaction
  • 2019
  • Ingår i: Journal of Physics B. - : IOP PUBLISHING LTD. - 0953-4075 .- 1361-6455. ; 52:17
  • Tidskriftsartikel (refereegranskat)abstract
    • We publish three Roadmaps on photonic, electronic and atomic collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap I, we focus on the light-matter interaction. In this area, studies of ultrafast electronic and molecular dynamics have been rapidly growing, with the advent of new light sources such as attosecond lasers and x-ray free electron lasers. In parallel, experiments with established synchrotron radiation sources and femtosecond lasers using cutting-edge detection schemes are revealing new scientific insights that have never been exploited. Relevant theories are also being rapidly developed. Target samples for photon-impact experiments are expanding from atoms and small molecules to complex systems such as biomolecules, fullerene, clusters and solids. This Roadmap aims to look back along the road, explaining the development of these fields, and look forward, collecting contributions from twenty leading groups from the field.
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  • Madueño, Leizel, et al. (författare)
  • A new method to measure real-world respiratory tract deposition of inhaled ambient black carbon
  • 2019
  • Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491. ; 248, s. 295-303
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, we present the development of a mobile system to measure real-world total respiratory tract deposition of inhaled ambient black carbon (BC). Such information can be used to supplement the existing knowledge on air pollution-related health effects, especially in the regions where the use of standard methods and intricate instrumentation is limited. The study is divided in two parts. Firstly, we present the design of portable system and methodology to evaluate the exhaled air BC content. We demonstrate that under real-world conditions, the proposed system exhibit negligible particle losses, and can additionally be used to determine the minute ventilation. Secondly, exemplary experimental data from the system is presented. A feasibility study was conducted in the city of La Paz, Bolivia. In a pilot experiment, we found that the cumulative total respiratory tract deposition dose over 1-h commuting trip would result in approximately 2.6 μg of BC. This is up to 5 times lower than the values obtained from conjectural approach (e.g. using physical parameters from previously reported worksheets). Measured total respiratory tract deposited BC fraction varied from 39% to 48% during walking and commuting inside a micro-bus, respectively. To the best of our knowledge, no studies focusing on experimental determination of real-world deposition dose of BC have been performed in developing regions. This can be especially important because the BC mass concentration is significant and determines a large fraction of particle mass concentration. In this work, we propose a potential method, recommendations, as well as the limitations in establishing an easy and relatively cheap way to estimate the respiratory tract deposition of BC. In this study we present a novel method to measure real-world respiratory tract deposition dose of Black Carbon. Results from a pilot study in La Paz, Bolivia, are presented.
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  • Naderi, Ali, et al. (författare)
  • Sulfoethylated nanofibrillated cellulose : Production and properties
  • 2017
  • Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 169, s. 515-523
  • Tidskriftsartikel (refereegranskat)abstract
    • Sulfoethylated nanofibrillated cellulose (NFCsulf) was produced by an industrially relevant process. The properties of the NFCsulf were compared with those of carboxymethylated nanofibrillated cellulose (NFCcarb), which has been identified as an attractive NFC for several industrial applications. The investigations revealed that NFCsulf is characterized by a higher degree of fibrillation and has superior redispersion properties. Furthermore, NFCsulf displays higher stability in varying pH values as compared to NFCcarb. Hence, NFCsulf may be a more attractive alternative than NFCcarb in applications such as rheological modifiers or adsorbing components in personal care products, in which the performance of NFC must remain unaffected in varying ambient conditions. The superior properties of NFCsulf compared to NFCcarb were proposed to be due to the combination of the unique chemical characteristics of the sulfoethylated reagent, and the larger size of the sulfonate group compared to the carboxymethyl group.
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  • Neumann, Hartmut P., et al. (författare)
  • 65 YEARS OF THE DOUBLE HELIX Genetics informs precision practice in the diagnosis and management of pheochromocytoma
  • 2018
  • Ingår i: Endocrine-Related Cancer. - : BIOSCIENTIFICA LTD. - 1351-0088 .- 1479-6821. ; 25:8, s. T201-T219
  • Forskningsöversikt (refereegranskat)abstract
    • Although the authors of the present review have contributed to genetic discoveries in the field of pheochromocytoma research, we can legitimately ask whether these advances have led to improvements in the diagnosis and management of patients with pheochromocytoma. The answer to this question is an emphatic Yes! In the field of molecular genetics, the well-established axiom that familial (genetic) pheochromocytoma represents 10% of all cases has been overturned, with amp;gt;35% of cases now attributable to germline disease-causing mutations. Furthermore, genetic pheochromocytoma can now be grouped into five different clinical presentation types in the context of the ten known susceptibility genes for pheochromocytoma-associated syndromes. We now have the tools to diagnose patients with genetic pheochromocytoma, identify germline mutation carriers and to offer gene-informed medical management including enhanced surveillance and prevention. Clinically, we now treat an entire family of tumors of the paraganglia, with the exact phenotype varying by specific gene. In terms of detection and classification, simultaneous advances in biochemical detection and imaging localization have taken place, and the histopathology of the paraganglioma tumor family has been revised by immunohistochemical-genetic classification by gene-specific antibody immunohistochemistry. Treatment options have also been substantially enriched by the application of minimally invasive and adrenal-sparing surgery. Finally and most importantly, it is now widely recognized that patients with genetic pheochromocytoma/paraganglioma syndromes should be treated in specialized centers dedicated to the diagnosis, treatment and surveillance of this rare neoplasm.
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  • Pfeifer, Marion, et al. (författare)
  • Tropical forest canopies and their relationships with climate and disturbance : results from a global dataset of consistent field-based measurements
  • 2018
  • Ingår i: Forest Ecosystems. - : Elsevier BV. - 2095-6355 .- 2197-5620. ; 5:7
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundCanopy structure, defined by leaf area index (LAI), fractional vegetation cover (FCover) and fraction of absorbed photosynthetically active radiation (fAPAR), regulates a wide range of forest functions and ecosystem services. Spatially consistent field-measurements of canopy structure are however lacking, particularly for the tropics.MethodsHere, we introduce the Global LAI database: a global dataset of field-based canopy structure measurements spanning tropical forests in four continents (Africa, Asia, Australia and the Americas). We use these measurements to test for climate dependencies within and across continents, and to test for the potential of anthropogenic disturbance and forest protection to modulate those dependences.ResultsUsing data collected from 887 tropical forest plots, we show that maximum water deficit, defined across the most arid months of the year, is an important predictor of canopy structure, with all three canopy attributes declining significantly with increasing water deficit. Canopy attributes also increase with minimum temperature, and with the protection of forests according to both active (within protected areas) and passive measures (through topography). Once protection and continent effects are accounted for, other anthropogenic measures (e.g. human population) do not improve the model.ConclusionsWe conclude that canopy structure in the tropics is primarily a consequence of forest adaptation to the maximum water deficits historically experienced within a given region. Climate change, and in particular changes in drought regimes may thus affect forest structure and function, but forest protection may offer some resilience against this effect.
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10.
  • Schmid, Georg, et al. (författare)
  • Tracing charge transfer in argon dimers by XUV-pump IR-probe experiments at FLASH
  • 2019
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 151:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Charge transfer (CT) at avoided crossings of excited ionized states of argon dimers is observed using a two-color pump-probe experiment at the free-electron laser in Hamburg (FLASH). The process is initiated by the absorption of three 27-eV-photons from the pump pulse, which leads to the population of Ar2+*-Ar states. Due to nonadiabatic coupling between these one-site doubly ionized states and two-site doubly ionized states of the type Ar+*-Ar+, CT can take place leading to the population of the latter states. The onset of this process is probed by a delayed infrared (800 nm) laser pulse. The latter ionizes the dimers populating repulsive Ar2+ -Ar+ states, which then undergo a Coulomb explosion. From the delay-dependent yields of the obtained Ar2+ and Ar+ ions, the lifetime of the charge-transfer process is extracted. The obtained experimental value of (531 ± 136) fs agrees well with the theoretical value computed from Landau-Zener probabilities.
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