9,058 research outputs found
Longitudinal variations, the opposition effect and monochromatic albedos for Mars
Magnitude at zero phase, phase coefficient, and monochromatic albedo computed for Mars as function of wavelengt
Habitat conversion and global avian biodiversity loss
The magnitude of the impacts of human activities on global biodiversity has been documented at several organizational levels. However, although there have been numerous studies of the effects of local-scale changes in land use (e.g. logging) on the abundance of groups of organisms, broader continental or global-scale analyses addressing the same basic issues remain largely wanting. None the less, changing patterns of land use, associated with the appropriation of increasing proportions of net primary productivity by the human population, seem likely not simply to have reduced the diversity of life, but also to have reduced the carrying capacity of the environment in terms of the numbers of other organisms that it can sustain.
Here, we estimate the size of the existing global breeding bird population, and then make a first approximation as to how much this has been modified as a consequence of land-use changes wrought by human activities. Summing numbers across different land-use classes gives a best current estimate of a global population of less than 100 billion breeding bird individuals. Applying the same methodology to estimates of original land-use distributions suggests that conservatively this may represent a loss of between a fifth and a quarter of pre-agricultural bird numbers. This loss is shared across a range of temperate and tropical land-use types
Tethered balloon measurements during Arctic autumn conditions in the framework of HALO-(AC)3
The BalloonbornE moduLar Utility for profilinG the lower Atmosphere
(BELUGA) was deployed in autumn 2021 in the Arctic at the AWIPEV research station
in Ny-Ålesund (Svalbard). In-situ profiles of thermodynamic parameters, broadband
radiation, turbulence, aerosol particle concentrations, and cloud microphysical structure,
were performed. Additionally, samples of ice nucleating particles were collected.
Thermal infrared radiation profiles are presented for different cloud conditions. The
data provides the base for studying the vertical distribution of cloud radiative effects,
and extends the common view of the bi-modal distribution of the Arctic surface energy
budget.Das Fesselballonsystem BalloonbornE moduLar Utility for profilinG
the lower Atmosphere (BELUGA) wurde im Herbst 2021 an der Forschungsstation
Ny-Ålesund in der Arktis eingesetzt. Es wurden In-situ Profile von thermodynamischen
Parametern, breitbandiger Strahlung, Turbulenz, Aerosolpartikelkonzentrationen
und der mikrophysikalischer Wolkenstruktur erstellt. Zusätzlich wurden Proben von
eiskeimbildenden Partikeln gesammelt. Strahlungsprofile wurden unter verschiedenen
Wolkenbedeckungen gemessen und quantifizieren die vertikale Verteilung der Wolkenstrahlungseffekte.
Die Profilmessungen erweitern damit die für bodennahe Messungen
bekannte modale Verteilung des Energiehaushalts der Arktis
On the and as Bound States and Approximate Nambu-Goldstone Bosons
We reconsider the two different facets of and mesons as
bound states and approximate Nambu-Goldstone bosons. We address several topics,
including masses, mass splittings between and and between and
, meson wavefunctions, charge radii, and the wavefunction overlap.Comment: 15 pages, late
Bunge’s Mathematical Structuralism Is Not a Fiction
In this paper, I explore Bunge’s fictionism in philosophy of mathematics. After an overview of Bunge’s views, in particular his mathematical structuralism, I argue that the comparison between mathematical objects and fictions ultimately fails. I then sketch a different ontology for mathematics, based on Thomasson’s metaphysical work. I conclude that mathematics deserves its own ontology, and that, in the end, much work remains to be done to clarify the various forms of dependence that are involved in mathematical knowledge, in particular its dependence on mental/brain states and material objects
Growth of Patterned Surfaces
During epitaxial crystal growth a pattern that has initially been imprinted
on a surface approximately reproduces itself after the deposition of an integer
number of monolayers. Computer simulations of the one-dimensional case show
that the quality of reproduction decays exponentially with a characteristic
time which is linear in the activation energy of surface diffusion. We argue
that this life time of a pattern is optimized, if the characteristic feature
size of the pattern is larger than , where is the surface
diffusion constant, the deposition rate and the surface dimension.Comment: 4 pages, 4 figures, uses psfig; to appear in Phys. Rev. Let
Forest albedo in the context of different cloud situations derived from irradiance measurements at the Leipzig floodplain crane: A pilot study
The surface albedo significantly modulates the atmospheric energy budget
and, thus, vertical radiation, energy, and mass fluxes. Therefore, it regulates the local
and regional effects of climate warming. Over a forest canopy, the surface albedo mainly
depends on the seasonal leaf state. Furthermore, for certain surface types, such as snow,
it has been shown that the surface albedo changes as a function of cloudiness. A similar
effect is expected over forest surfaces, leading to complex feedback loops between forest
surfaces and climate. To investigate these processes, a pilot study was performed at the
Leipzig floodplain crane to observe the forest canopy albedo under different atmospheric
conditions in 2021. First analyses revealed a dependency of the forest albedo from the
cloud state, which is slightly stronger in the near-infrared wavelength range compared to
the visible wavelength range.Der atmosphärische Strahlungshaushalt und damit auch die vertikale
Strahlungsverteilung, Energie- und Massenflüsse werden signifikant durch die
Bodenalbedo gesteuert. Diese regulieren somit lokale und regionale Effekte der Klimaerwärmung.
Über einem Wald hängt die Bodenalbedo hauptsächlich vom saisonalen
Blattstatus ab. Zudem wurde für bestimmte Bodentypen wie Schneeoberflächen gezeigt,
dass die Bodenalbedo eine Funktion der Bewölkung ist. Ähnlicher Effekte werden für
Waldoberflächen erwartet, welche zu komplexen Rückkopplungseffekten zwischenWaldoberflächen
und dem Klima führen. Um diese Prozesse zu untersuchen wurde im Jahr
2021 eine Vorstudie am Leipziger Auwaldkran durchgeführt, um die Waldalbedo unter
verschiedenen atmosphärischen Bedingungen zu beobachten. Erste Analysen zeigen,
dass auch die Albedo des Waldes von den Bewölkungsbedingungen abhängt. Der Effekt
ist dabei etwas stärker im nah-infrarotem als im sichtbaren Wellenlängenbereich zu
beobachten
Lattice Effects in Crystal Evaporation
We study the dynamics of a stepped crystal surface during evaporation, using
the classical model of Burton, Cabrera and Frank, in which the dynamics of the
surface is represented as a motion of parallel, monoatomic steps. The validity
of the continuum approximation treated by Frank is checked against numerical
calculations and simple, qualitative arguments. The continuum approximation is
found to suffer from limitations related, in particular, to the existence of
angular points. These limitations are often related to an adatom detachment
rate of adatoms which is higher on the lower side of each step than on the
upper side ("Schwoebel effect").Comment: DRFMC/SPSMS/MDN, Centre d'Etudes Nucleaires de Grenoble, 25 pages,
LaTex, revtex style. 8 Figures, available upon request, report# UBFF30119
CIRRUS-HL: Overview of LIM contributions
From June to July 2021, the Leipzig Institute for Meteorology (LIM)
participated in the Cirrus in High Latitudes (CIRRUS-HL) campaign. Utilizing the
German High Altitude Long Range Research Aircraft (HALO), 24 research flights were
conducted out of Oberpfaffenhofen, Germany. The initial goal of the campaign was
to sample high-latitude cirrus clouds with a combination of in-situ and remote sensing
instrumentation. However, due to the global coronavirus pandemic, the flights had to
be carried out from southern Germany instead of northern Sweden. Thus, the flight
time in Arctic latitudes was limited. Therefore, more objectives concerning midlatitude
cirrus were included in the campaign goals. LIM contributed to CIRRUS-HL with
measurements by the Broadband AirCrAft RaDiometer Instrumentation (BACARDI)
and the Spectral Modular Airborne Radiation measurement sysTem (SMART). While
BACARDI measured broadband solar and terrestrial upward and downward irradiance,
SMART measured spectrally resolved solar upward radiance as well as upward and
downward irradiance.Von Juni bis Juli 2021 nahmen einige Mitarbeitende des LIM
an der CIRRUS-HL Kampagne teil. Mit dem deutschen Forschungsflugzeug HALO
(High Altitude Long Range Research Aircraft) wurden 24 Forschungsflüge von Oberpfaffenhofen,
Deutschland, aus durchgeführt. Ursprüngliches Ziel der Kampagne war es,
Zirruswolken in hohen Breitengraden mit einer Kombination aus In-situ- und Fernerkundungsinstrumenten
zu untersuchen. Aufgrund der weltweiten Corona-Pandemie mussten
die Flüge jedoch von Süddeutschland statt von Nordschweden aus durchgeführt werden.
Daher wurden weitere Ziele in Bezug auf Zirruswolken in mittleren Breiten in die Ziele
der Kampagne aufgenommen. Das LIM-Team betrieb die breitbandigen und spektralen
Strahlungssensoren BACARDI (Broadband AirCrAft RaDiometer Instrumentation) und
SMART (Spectral Modular Airborne Radiation measurement sysTem), wobeiBACARDI
die breitbandige solare und terrestrische Auf- und Abwärtsstrahlung und SMART die
spektral aufgelöste solareAuf- undAbwärtsstrahlung sowie dieAufwärtsstrahlungsdichte
maß
Laparoscopic Wide Mesocolic Excision and Central Vascular Ligation for Carcinoma of the Colon
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