8,730 research outputs found
AMOC Recovery in a Multicentennial Scenario Using a Coupled AtmosphereâOceanâIce Sheet Model
We simulate the two Coupled Model Intercomparison Project scenarios RCP4.5 and RCP8.5, to assess the effects of meltâinduced fresh water on the Atlantic meridional overturning circulation (AMOC). We use a newly developed climate model with high resolution at the coasts, resolving the complex ocean dynamics. Our results show an AMOC recovery in simulations run with and without an included ice sheet model. We find that the ice sheet adds a strong decadal variability on the freshwater release, resulting in intervals in which it reduces the surface runoff by high accumulation rates. This compensating effect is missing in climate models without dynamic ice sheets. Therefore, we argue to assess those freshwater hosing experiments critically, which aim to parameterize Greenland's freshwater release. We assume the increasing net evaporation over the Atlantic and the resulting increase in ocean salinity, to be the main driver of the AMOC recovery
Tiny Publics and Social WorldsâToward a Sociology of the Local. Gary Alan Fine in Conversation With Reiner Keller
Gary Alan FINE gehört weltweit zu den prominentesten Persönlichkeiten der zeitgenössischen soziologischen Ethnografie. In diesem GesprĂ€ch spricht er ĂŒber EinflĂŒsse in seiner akademischen Laufbahn und prĂ€gende intellektuelle Entscheidungen. Er gilt als "serieller Ethnograf", der in zahlreichen Feldkontexten gearbeitet hat und dabei einerseits Kleingruppen und eine von Menschen bevölkerte Ethnografie favorisiert, sich andererseits mit GerĂŒchten, Klatsch und moralischen Geschichten beschĂ€ftigt, die in kleinen und gröĂeren Publiken erzĂ€hlt werden. FINE beschreibt sein theoretisches Kerninteresse als die Untersuchung des Wechselspiels von Struktur, Interaktion und Kultur. In seinem Werk analysiert er die vielfĂ€ltigen ortsgebundenen Arten und Weisen, in denen Gesellschaft von Menschen in formellen und informellen sozialen Settings verwirklicht wird, angefangen bei Baseballteams ĂŒber RestaurantkĂŒchen oder die Wetterberichterstattung bis hin zum Schachspielen âum nur einige wenige GegenstĂ€nde seiner Forschungen zu nennen. Wesentlich beeinflusst durch symbolisch-interaktionistisches Denken und im Rekurs auf weitere wichtige Perspektiven auf soziale Welten plĂ€diert er fĂŒr eine selbstbewusste Haltung der ethnografischen Forschung und des ethnografischen Schreibens sowie fĂŒr die Bedeutung der Konzeptarbeit in einer theorie-informierten empirischen Soziologie dessen, was Menschen zusammen tun.Gary Alan FINE is among the most prominent figures in contemporary sociological ethnography worldwide. In this conversation, he talks about influences in his academic career and key intellectual choices. Considered to be a "serial ethnographer" who has worked in multiple settings, his work focuses on small groups and peopled ethnography, as well as on rumors, gossip, and moral story telling in tiny and larger publics. FINE describes his core theoretical interest as residing in the interplay of structure, interaction, and culture and discusses the multiple local ways society is realized by people in formal and informal social settings: ranging from baseball teams, restaurant kitchens, weather reporting to chess playersâto name but a few research sites. Influenced by symbolic interactionist thinking and other important approaches to social worlds, he argues for a confident voice of ethnographic research and writing as well as the importance of conceptual work in a theory-informed empirical sociology of what people do together
September Arctic sea ice minimum prediction â a skillful new statistical approach
Sea ice in both polar regions is an important indicator of the
expression of global climate change and its polar amplification.
Consequently, broad interest exists on sea ice coverage, variability and
long-term change. However, its predictability is complex and it depends
strongly on different atmospheric and oceanic parameters. In order to
provide insights into the potential development of a monthly/seasonal signal
of sea ice evolution, we applied a robust statistical model based on
different oceanic and atmospheric parameters to calculate an estimate of the
September sea ice extent (SSIE) on a monthly timescale. Although previous
statistical attempts of monthly/seasonal SSIE forecasts show a relatively
reduced skill, when the trend is removed, we show here that the September
sea ice extent has a high predictive skill, up to 4Â months ahead, based on
previous months' oceanic and atmospheric conditions. Our statistical model
skillfully captures the interannual variability of the SSIE and could
provide a valuable tool for identifying relevant regions and oceanic and
atmospheric parameters that are important for the sea ice development in the
Arctic and for detecting sensitive/critical regions in global coupled
climate models with a focus on sea ice formation.</p
Antimatter and Matter Production in Heavy Ion Collisions at CERN (The NEWMASS Experiment NA52)
Besides the dedicated search for strangelets NA52 measures light
(anti)particle and (anti)nuclei production over a wide range of rapidity.
Compared to previous runs the statistics has been increased in the 1998 run by
more than one order of magnitude for negatively charged objects at different
spectrometer rigidities. Together with previous data taking at a rigidity of
-20 GeV/c we obtained 10^6 antiprotons 10^3 antideuterons and two antihelium3
without centrality requirements. We measured nuclei and antinuclei
(p,d,antiprotons, antideuterons) near midrapidity covering an impact parameter
range of b=2-12 fm. Our results strongly indicate that nuclei and antinuclei
are mainly produced via the coalescence mechanism. However the centrality
dependence of the antibaryon to baryon ratios show that antibaryons are
diminished due to annihilation and breakup reactions in the hadron dense
environment. The volume of the particle source extracted from coalescence
models agrees with results from pion interferometry for an expanding source.
The chemical and thermal freeze-out of nuclei and antinuclei appear to coincide
with each other and with the thermal freeze-out of hadrons.Comment: 12 pages, 8 figures, to appear in the proceedings of the conference
on 'Fundamental Issues in Elementary Matter' Bad Honnef, Germany, Sept.
25-29, 200
Brief communication: An ice surface melt scheme including the diurnal cycle of solar radiation
We propose a surface melt scheme for glaciated
land surfaces, which only requires monthly mean short-wave radiation and
temperature as inputs, yet implicitly accounts for the diurnal cycle of
short-wave radiation. The scheme is deduced from the energy balance of a
daily melt period, which is defined by a minimum solar elevation angle. The
scheme yields a better spatial representation of melting than common
empirical schemes when applied to the Greenland Ice Sheet, using a 1948â2016
regional climate and snowpack simulation as a reference. The scheme is
physically constrained and can be adapted to other regions or time periods.</p
Tunable nano Peltier cooling device from geometric effects using a single graphene nanoribbon
Based on the phenomenon of curvature-induced doping in graphene we propose a
class of Peltier cooling devices, produced by geometrical effects, without
gating. We show how a graphene nanorib- bon laid on an array of curved nano
cylinders can be used to create a targeted and tunable cooling device. Using
two different approaches, the Nonequlibrium Green's Function (NEGF) method and
experimental inputs, we predict that the cooling power of such a device can
approach the order of kW/cm2, on par with the best known techniques using
standard superlattice structures. The struc- ture proposed here helps pave the
way toward designing graphene electronics which use geometry rather than gating
to control devices.Comment: 12 pages, 5 figure
Analysis of Optical Pulse Propagation with ABCD Matrices
We review and extend the analogies between Gaussian pulse propagation and
Gaussian beam diffraction. In addition to the well-known parallels between
pulse dispersion in optical fiber and CW beam diffraction in free space, we
review temporal lenses as a way to describe nonlinearities in the propagation
equations, and then introduce further concepts that permit the description of
pulse evolution in more complicated systems. These include the temporal
equivalent of a spherical dielectric interface, which is used by way of example
to derive design parameters used in a recent dispersion-mapped soliton
transmission experiment. Our formalism offers a quick, concise and powerful
approach to analyzing a variety of linear and nonlinear pulse propagation
phenomena in optical fibers.Comment: 10 pages, 2 figures, submitted to PRE (01/01
A short note on marine reservoir age simulations used in IntCal20
Beyond ~13.9 cal kBP, the IntCal20 radiocarbon (14C) calibration curve is based upon combining data across a range of different archives including corals and planktic foraminifera. In order to reliably incorporate such marine data into an atmospheric curve, we need to resolve these records into their constituent atmospheric signal and marine reservoir age. We present results of marine reservoir age simulations enabling this resolution, applying the LSG ocean general circulation model forced with various climatic background conditions and with atmospheric radiocarbon changes according to the Hulu Cave speleothem record. Simulating the spatiotemporal evolution of reservoir ages between 54,000 and 10,700 cal BP, we find reservoir ages between 500 and 1400 yr in the low- and mid-latitudes, but also more than 3000 yr in the polar seas. Our results are broadly in agreement with available marine radiocarbon reconstructions, with the caveat that continental margins, marginal seas, or tropical lagoons are not properly resolved in our coarse-resolution model
Nearby low-mass triple system GJ795
We report the results of our optical speckle-interferometric observations of
the nearby triple system GJ795 performed with the 6-m BTA telescope with
diffraction-limited angular resolution. The three components of the system were
optically resolved for the first time. Position measurements allowed us to
determine the elements of the inner orbit of the triple system. We use the
measured magnitude differences to estimate the absolute magnitudes and spectral
types of the components of the triple: =7.310.08,
=8.660.10, =8.420.10, K5,
K9, K8. The total mass of the system is
equal to =1.69. We show
GJ795 to be a hierarchical triple system which satisfies the empirical
stability criteria.Comment: 6 pages, 2 figures, published in Astrophysical Bulleti
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