37 research outputs found
Bioaerosols in the Amazon rain forest: temporal variations and vertical profiles of Eukarya, Bacteria, and Archaea
The Amazon rain forest plays a major role in global hydrological cycling, and biogenic aerosols are likely to influence the formation of clouds and precipitation. Information about the sources and altitude profiles of primary biological aerosol particles, however, is sparse. We used fluorescence in situ hybridization (FISH), a molecular biological staining technique largely unexplored in aerosol research, to investigate the sources and spatiotemporal distribution of Amazonian bioaerosols on the domain level. We found wet season bioaerosol number concentrations in the range of 1â5âĂâ105âmâ3 accounting for >â70â% of the coarse mode aerosol. Eukaryotic and bacterial particles predominated, with fractions of âŒâ56â% and âŒâ26â% of the intact airborne cells. Archaea occurred at very low concentrations. Vertical profiles exhibit a steep decrease in bioaerosol numbers from the understory to 325âm height on the Amazon Tall Tower Observatory (ATTO), with a stronger decrease in Eukarya compared to Bacteria. Considering earlier investigations, our results can be regarded as representative for near-pristine Amazonian wet season conditions. The observed concentrations and profiles provide new insights into the sources and dispersion of different types of Amazonian bioaerosols as a solid basis for model studies on biosphereâatmosphere interactions such as bioprecipitation cycling.</p
On Star Formation Rates and Star Formation Histories of Galaxies out to z ~ 3
We compare multi-wavelength SFR indicators out to z~3 in GOODS-South. Our
analysis uniquely combines U-to-8um photometry from FIREWORKS, MIPS 24um and
PACS 70, 100, and 160um photometry from the PEP survey, and Ha spectroscopy
from the SINS survey. We describe a set of conversions that lead to a
continuity across SFR indicators. A luminosity-independent conversion from 24um
to total infrared luminosity yields estimates of LIR that are in the median
consistent with the LIR derived from PACS photometry, albeit with significant
scatter. Dust correction methods perform well at low to intermediate levels of
star formation. They fail to recover the total amount of star formation in
systems with large SFR_IR/SFR_UV ratios, typically occuring at the highest SFRs
(SFR_UV+IR \gtrsim 100 Msun/yr) and redshifts (z \gtrsim 2.5) probed. Finally,
we confirm that Ha-based SFRs at 1.5<z<2.6 are consistent with SFR_SED and
SFR_UV+IR provided extra attenuation towards HII regions is taken into account
(Av,neb = Av,continuum / 0.44). With the cross-calibrated SFR indicators in
hand, we perform a consistency check on the star formation histories inferred
from SED modeling. We compare the observed SFR-M relations and mass functions
at a range of redshifts to equivalents that are computed by evolving lower
redshift galaxies backwards in time. We find evidence for underestimated
stellar ages when no stringent constraints on formation epoch are applied. We
demonstrate how resolved SED modeling, or alternatively deep UV data, may help
to overcome this bias. The age bias is most severe for galaxies with young
stellar populations, and reduces towards older systems. Finally, our analysis
suggests that SFHs typically vary on timescales that are long (at least several
100 Myr) compared to the galaxies' dynamical time.Comment: Accepted for publication in The Astrophysical Journal, 19 pages, 15
figure
ERIS: revitalising an adaptive optics instrument for the VLT
ERIS is an instrument that will both extend and enhance the fundamental
diffraction limited imaging and spectroscopy capability for the VLT. It will
replace two instruments that are now being maintained beyond their operational
lifetimes, combine their functionality on a single focus, provide a new
wavefront sensing module that makes use of the facility Adaptive Optics System,
and considerably improve their performance. The instrument will be competitive
with respect to JWST in several regimes, and has outstanding potential for
studies of the Galactic Center, exoplanets, and high redshift galaxies. ERIS
had its final design review in 2017, and is expected to be on sky in 2020. This
contribution describes the instrument concept, outlines its expected
performance, and highlights where it will most excel.Comment: 12 pages, Proc SPIE 10702 "Ground-Based and Airborne Instrumentation
for Astronomy VII
Superconductivity in Weyl Semimetal Candidate MoTe2
In recent years, layered transition-metal dichalcogenides (TMDs) have
attracted considerable attention because of their rich physics; for example,
these materials exhibit superconductivity, charge density waves, and the valley
Hall effect. As a result, TMDs have promising potential applications in
electronics, catalysis, and spintronics. Despite the fact that the majority of
related research focuses on semiconducting TMDs (e.g., MoS2), the
characteristics of WTe2 are provoking strong interest in semimetallic TMDs with
extremely large magnetoresistance, pressure-driven superconductivity, and the
predicted Weyl semimetal (WSM) state. In this work, we investigate the sister
compound of WTe2, MoTe2, which is also predicted to be a WSM and a quantum spin
Hall insulator in bulk and monolayer form, respectively. We find that MoTe2
exhibits superconductivity with a resistive transition temperature Tc of 0.1 K.
The application of a small pressure (such as 0.4 GPa) is shown to dramatically
enhance the Tc, with a maximum value of 8.2 K being obtained at 11.7 GPa (a
more than 80-fold increase in Tc). This yields a dome-shaped superconducting
phase diagram. Further explorations into the nature of the superconductivity in
this system may provide insights into the interplay between strong correlations
and topological physics.Comment: 20 pages, 5 figure
The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI
The GRAVITY instrument has been revolutionary for near-infrared
interferometry by pushing sensitivity and precision to previously unknown
limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer
(VLTI) in GRAVITY+, these limits will be pushed even further, with vastly
improved sky coverage, as well as faint-science and high-contrast capabilities.
This upgrade includes the implementation of wide-field off-axis
fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser
guide stars in an upgraded facility. GRAVITY+ will open up the sky to the
measurement of black hole masses across cosmic time in hundreds of active
galactic nuclei, use the faint stars in the Galactic centre to probe General
Relativity, and enable the characterisation of dozens of young exoplanets to
study their formation, bearing the promise of another scientific revolution to
come at the VLTI.Comment: Published in the ESO Messenge
Search for dark matter produced in association with bottom or top quarks in âs = 13 TeV pp collisions with the ATLAS detector
A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fbâ1 of protonâproton collision data recorded by the ATLAS experiment at âs = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements
Spatially resolved twin domain distribution and lattice parameter variations in the near-surface region of SrTiO_3 single crystals
The second "Safety in the transportation of dangerous goods" research programme
Im Auftrag des Bundesministeriums fĂŒr Verkehr, Bau- und Wohnungswesen (BMVBW) hat die Projektgruppe "Gefahrguttransport" Forschungsbedarf zur Sicherheit in der Gefahrgutbeförderung ermittelt. Experten der drei LandverkehrstrĂ€ger Bahn, Binnenschiffahrt und StraĂe sowie von Sicherheitsinstitutionen waren Mitglieder in der Projektgruppe. Durch eine enge Zusammenarbeit mit Sicherheitsbehörden, SachverstĂ€ndigenorganisationen, den stĂ€ndigen ArbeitsausschĂŒssen des Gefahrgut-Verkehrs-Beirats des BMVBW, ASV und ATT und FachverbĂ€nden der chemischen Industrie, der Mineralölwirtschaft und des Transportgewerbes konnte der Forschungsbedarf fĂŒr den Landverkehr sehr umfassend erhoben werden. Leitideen bei der Auswahl des Forschungsbedarfs waren die Umsetzung der Forderungen nach Vernetzung der VerkehrstrĂ€ger, der Harmonisierung der Beförderungsbedingungen und -vorschriften im liberalisierten europĂ€ischen Verkehrsmarkt und Aspekte des globalisierten Wirtschaftens. Die vorliegenden Forschungsergebnisse zur Risikoanalyse des Gefahrguttransports sollen um weitere Forschungsvorhaben zum Aufbau eines Risiko-Analyse-Systems ergĂ€nzt werden. Ausgehend von den Ergebnissen eines Forschungs- und Entwicklungs (F&E)-Vorhabens zur Entwicklung einer Strategie fĂŒr ein integriertes Forschungskonzept zum Einfluss menschlicher Faktoren auf die Sicherheit des Gefahrguttransports werden ProjektvorschlĂ€ge entwickelt, in denen zu untersuchen sein wird, inwieweit verkehrspĂ€dagogische Konzepte und Interventionen BeitrĂ€ge zur Unfallvorsorge leisten können und wie Anreizsysteme und technische Systeme der Vermeidung von UnfĂ€llen förderlich sind. In der zukĂŒnftigen Forschungsarbeit zum Regelwerk soll Fragen zur Harmonisierung der Regelwerke, der Anwenderfreundlichkeit der Vorschriften einschlieĂlich vermittelnder Institutionen wie der des Gefahrgutbeauftragten nachgegangen werden. Ein verkehrstrĂ€gerĂŒbergreifendes Sicherheitskonzept mit Bezug auf EuropĂ€isierung und Liberalisierung in der Gefahrgutklassifizierung wird mit zahlreichen VorschlĂ€gen zu Stoff- und UmschlieĂungsvorhaben angestrebt. Einen anderen Schwerpunkt bilden ProjektvorschlĂ€ge, mit denen risikoanalytische Grundlagen zur Tankkonstruktion und -zulassung erarbeitet werden sollen. In einem Kapitel zur Verkehrs- und Fahrzeugtechnik werden fĂŒr die Sicherheit auf BinnenwasserstraĂen Forschungsvorhaben empfohlen, die dem Schutz der Schiffsbesatzungen und der Umwelt dienen. Die Sicherheit im Eisenbahnverkehr soll mit Forschungsvorhaben zur aktiven und passiven Sicherheit, insbesondere durch eine informationstechnologisch gestĂŒtzte ZugĂŒberwachung verbessert werden. FĂŒr den Bereich StraĂe wurden Themen konzipiert, die zum Ziel haben, Unfallvorsorge durch Kfz-Technik zu verbessern. Mit Forschungsvorhaben zur Ladungssicherung und zur Schnittstellenproblematik soll vorhandenes Wissen systematisiert und Grundlagenwissen erarbeitet werden. Unter dem Stichwort "Sicherheit durch vernetzte Informationen" werden Konzepte vorgeschlagen, die verkehrstrĂ€gerĂŒbergreifend und international anwendbar sein sollen. Einzelprobleme rettungsdienstlicher AusrĂŒstung zur Bergung von Gefahrgut sowie systematische Schwachstellenanalysen ausgewĂ€hlter Teilsysteme stehen im Mittelpunkt der Auswahl von Forschungsvorhaben fĂŒr das Rettungswesen. In einem abschlieĂenden Kapitel werden Empfehlungen zum Forschungsmanagement vorgelegt und eine zeitliche Dringlichkeitsreihung der vorgeschlagenen Forschungsvorhaben aufgestellt.The "Dangerous Goods Transportation" project group, under commission to the Federal Ministry of Transport, Building and Housing (BMVBW), ascertained the requirements for research into safety in dangerous goods transportation. The project group was made up of specialists in the three modes of transport: rail, inland waterway and road; and experts from safety institutions. lt was possible to attain highly detailed data regarding the requirements for research into the modes of transport on account of dose collaboration with safety authorities, specialist organisations, the standing working committees of the BMVBW's Dangerous Goods Transport Advisory Board and specialist associations from the chemical, mineral oil and transport industries. The central ideas guiding the selection of the research requirements were the implementation of the demands for networking the different modes of transport, the harmonisation of transport conditions and regulations in the liberalised European transport market and aspects relating to global economic activity. lt is intended that the present research results on risk analysis of dangerous goods transportation should be supplemented by further research projects aimed at constructing a risk-analysis system. Proposals for research projects will be developed based on the results of a research and development project aimed at developing a strategy for integrated research into the influence of human factors on the safety of dangerous goods transportation; the objective of these proposed projects will be to investigate the extent to which it is possible for traffic education-related concepts and interventions to contribute to accident prevention and how incentive systems and technical systems are conducive to the avoidance of accidents. lt is intended that future research into standards and regulations will look at questions relating to harmonisation of regulations and to their userfriendliness, including intermediary institutions such as that of the officer for the prevention of risk. Numerous proposals for projects dealing with substances and containers are given in an attempt to elaborate an inter-modal safety concept which takes into consideration European harmonisation and liberalisation in the classification of dangerous goods. Proposals for projects aimed at drawing up risk analytical principles for tank construction and tank homologation form another focal point. Research projects for safety on inland waterways are recommended in a chapter on traffic and automobile engineering; these projects would serve to protect boat crews and the environment. lt is aimed to improve rail safety through research projects on active and passive safety and in particular through an IT-assisted train monitoring system. Projects were developed for the road which aim to improve accident prevention through vehicle technology. Research projects on cargo safety and on Interface problems aim to systemise existent knowledge and elaborate fundamental principles. Concepts are proposed under the heading "Safety through Networked Information"; the objective of these is to be inter-modal and internationally applicable. The research projects relating to the rescue services focus on individual problems regarding rescue service equipment used for recovering dangerous goods and on analyses of weak areas of selected sub-systems. The final chapter contains recommendations for research management and a list of the suggested proposals in order of priority
CCR7 Coordinates the Primary Immune Response by Establishing Functional Microenvironments in Secondary Lymphoid Organs.
The proper function of immune surveillance requires well-coordinated mechanisms in order to guide the patrolling immune cells through peripheral tissues and into secondary lymphoid organs. Analyzing gene-targeted mice, we identified the chemokine receptor CCR7 as an important organizer of the primary immune response. CCR7-deficient mice show severely delayed kinetics regarding the antibody response and lack contact sensitivity and delayed type hypersensitivity reactions. Due to the impaired migration of lymphocytes, these animals reveal profound morphological alterations in all secondary lymphoid organs. Upon activation, mature skin dendritic cells fail to migrate into the draining lymph nodes. Thus, in order to bring together lymphocytes and dendritic cells to form the characteristic microarchitecture of secondary lymphoid organs, CCR7 is required to rapidly initiate an adoptive immune response