157 research outputs found
Cosmogenic Neutrinos Through the GRAND Lens Unveil the Nature of Cosmic Accelerators
The sources of cosmic rays with energies above 55 EeV are still mysterious. A
guaranteed associated flux of ultra high energy neutrinos known as the
cosmogenic neutrino flux will be measured by next generation radio facilities,
such as the proposed Giant Radio Array for Neutrino Detection (GRAND). By using
the orthogonal information provided by the cosmogenic neutrino flux, we here
determine the prospects of GRAND to constrain the source redshift evolution and
the chemical composition of the cosmic ray sources. If the redshift evolution
is known, independently on GRAND's energy resolution, GRAND with 200,000
antennas will constrain the proton/iron fraction to the level
after one year of data taking; on the other hand, if hints on the average
source composition are given, GRAND will measure the redshift evolution of the
sources to a uncertainty. However, the foreseen configuration of
GRAND alone will not be able to break the degeneracy between redshift evolution
of the sources and their composition. Our findings underline the discriminating
potential of next generation radio array detectors and motivate further efforts
in this direction.Comment: 18 pages, 6 figures, 1 table, comments welcome; clarifying comments
added, matches published versio
Measuring the supernova unknowns at the next-generation neutrino telescopes through the diffuse neutrino background
The detection of the diffuse supernova neutrino background (DSNB) will
preciously contribute to gauge the properties of the core-collapse supernova
population. We estimate the DSNB event rate in the next-generation neutrino
detectors, Hyper-Kamiokande enriched with Gadolinium, JUNO, and DUNE. The
determination of the supernova unknowns through the DSNB will be heavily driven
by Hyper-Kamiokande, given its higher expected event rate, and complemented by
DUNE that will help in reducing the parameters uncertainties. Meanwhile, JUNO
will be sensitive to the DSNB signal over the largest energy range. A joint
statistical analysis of the expected rates in 20 years of data taking from the
above detectors suggests that we will be sensitive to the local supernova rate
at most at a 20-33% level. A non-zero fraction of supernovae forming black
holes will be confirmed at a 90% CL, if the true value of that fraction is
larger than 20%. On the other hand, the DSNB events show extremely poor
statistical sensitivity to the nuclear equation of state and mass accretion
rate of the progenitors forming black holes.Comment: 29 pages, including 15 figures. Minor changes in the text, matches
version accepted for publication in JCA
The Effects of Acute Thermoneutral and Hot Water Immersion on Cerebrovascular Reactivity
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Waldbodenverdichtung durch schwere Erntemaschinen und natürliches Regenerationspotenzial - untersucht auf der Basis echter Zeitreihen
Um unter Weltmarktbedingungen wettbewerbsfähig zu sein, erfolgt seit vielen Jahren eine zunehmende Technisierung in der Forstwirtschaft mittels Einsatz immer leistungsfähigerer, aber auch schwererer Maschinen, besonders in der Holzernte. Zunehmend höhere mechanische Belastungen der Waldböden mit teilweise extremer Überschreitungen der mechanischen Tragfähigkeit sind die Folge. Dies führt zu Bodenschadverdichtungen. Flächenhaft negative, nachhaltig wirksame Effekte auf ökologisch und ökonomisch wichtige Bodenfunktionen wie Wasseraufnahme- und –speicherfähigkeit, Durchwurzelungsfähigkeit, Wuchsleistung der Bäume sind zu erwarten. Das Regenerationspotenzial für derartige Schadverdichtungen von Waldböden wird kontrovers diskutiert.
Um die mittel- und langfristigen Auswirkungen des Einsatzes schwerer Holzerntemaschinen und das natürliche Regenerationspotenzial der Waldböden anhand echter Zeitreihen zu untersuchen, wurden drei Dauerbeobachtungsflächen mit Befahrungsversuchen (unbefahrene Kontrolle, 1-fach Befahrung, 5-fach Befahrung) in Rheinland-Pfalz auf unterschiedlichen Ausgangssubstraten und Feuchtebedingungen angelegt, wobei die älteste Fläche bei den aktuellen Untersuchungen schon ein Alter von 28 Jahren erreicht hat.
Auf allen Standorten wurden unmittelbar nach der Versuchsanlage erhebliche negative, initiale Auswirkungen auf relevante Bodenfunktionen ermittelt, bis hin zur völligen Bodenzerstörung an einem Standort. Die aktuellen bodenphysikalischen, -chemischen und mikrobiologischen Analysen sowie Wurzeluntersuchungen belegen standorts- und variantenspezifische Unterschiede. Einerseits haben sich an einem Standort die initialen, negativen Effekte nahezu unverändert über einen Zeitraum von mehr als 10 Jahren erhalten, andererseits finden sich aber auch Anzeichen für natürliche Regenerationsprozesse
KiDS-i-800: Comparing weak gravitational lensing measurements in same-sky surveys
We present a weak gravitational lensing analysis of 815 square degree of
-band imaging from the Kilo-Degree Survey (KiDS--800). In contrast to the
deep -band observations, which take priority during excellent seeing
conditions and form the primary KiDS dataset (KiDS--450), the complementary
yet shallower KiDS--800 spans a wide range of observing conditions. The
overlapping KiDS--800 and KiDS--450 imaging therefore provides a unique
opportunity to assess the robustness of weak lensing measurements. In our
analysis, we introduce two new `null' tests. The `nulled' two-point shear
correlation function uses a matched catalogue to show that the calibrated
KiDS--800 and KiDS--450 shear measurements agree at the level of \%. We use five galaxy lens samples to determine a `nulled' galaxy-galaxy
lensing signal from the full KiDS--800 and KiDS--450 surveys and find
that the measurements agree to \% when the KiDS--800 source
redshift distribution is calibrated using either spectroscopic redshifts, or
the 30-band photometric redshifts from the COSMOS survey.Comment: 24 pages, 20 figures. Submitted to MNRAS. Comments welcom
Climate change and equestrian empires in the Eastern Steppes: new insights from a high-resolution Lake Core in Central Mongolia
The repeated expansion of East Asian steppe cultures was a key driver of Eurasian history, forging new social, economic, and biological links across the continent. Climate has been suggested as important driver of these poorly understood cultural expansions, but paleo-climate records from the Mongolian Plateau often suffer from poor age control or ambiguous proxy interpretation. Here, we use a combination of geochemical analyses and comprehensive radiocarbon dating to establish the first robust and detailed record of paleo-hydrological conditions for Lake Telmen, Mongolia, covering the past ~4000 years. Our record shows that humid conditions coincided with solar minima, and hydrological modelling confirms the high sensitivity of the lake to paleo-climate changes. Careful comparisons with archaeological and historical records suggest that in the vast semi-arid grasslands of eastern Eurasia, solar minima led to reduced temperatures, less evaporation, and high biomass production, expanding the power base for pastoral economies and horse cavalry. Our findings suggest a crucial link between temperature dynamics in the Eastern Steppe and key social developments, such as the emergence of pastoral empires, and fuel concerns that global warming enhances water scarcity in the semi-arid regions of interior Eurasia.1. Introduction 2. Results 2.1 Sediment core chronology 2.2 Sedimentological and geochemical analyses 2.3 Isotope analyses, evaporation index (EI), and paleohydrology 3. Discussion 3.1 External forcing on the regional climate 3.2 Hydrological modelling 3.3 Climate impact on human history in Mongolia Method
The rare ERBB2 variant Ile654Val is associated with an increased familial breast cancer risk
739 observed NEAs and new 2-4m survey statistics within the EURONEAR network
We report follow-up observations of 477 program Near-Earth Asteroids (NEAs)
using nine telescopes of the EURONEAR network having apertures between 0.3 and
4.2 m. Adding these NEAs to our previous results we now count 739 program NEAs
followed-up by the EURONEAR network since 2006. The targets were selected using
EURONEAR planning tools focusing on high priority objects. Analyzing the
resulting orbital improvements suggests astrometric follow-up is most important
days to weeks after discovery, with recovery at a new opposition also valuable.
Additionally we observed 40 survey fields spanning three nights covering 11 sq.
degrees near opposition, using the Wide Field Camera on the 2.5m Isaac Newton
Telescope (INT), resulting in 104 discovered main belt asteroids (MBAs) and
another 626 unknown one-night objects. These fields, plus program NEA fields
from the INT and from the wide field MOSAIC II camera on the Blanco 4m
telescope, generated around 12,000 observations of 2,000 minor planets (mostly
MBAs) observed in 34 square degrees. We identify Near Earth Object (NEO)
candidates among the unknown (single night) objects using three selection
criteria. Testing these criteria on the (known) program NEAs shows the best
selection methods are our epsilon-miu model which checks solar elongation and
sky motion and the MPC's NEO rating tool. Our new data show that on average 0.5
NEO candidates per square degree should be observable in a 2m-class survey (in
agreement with past results), while an average of 2.7 NEO candidates per square
degree should be observable in a 4m-class survey (although our Blanco
statistics were affected by clouds). At opposition just over 100 MBAs (1.6
unknown to every 1 known) per square degree are detectable to R=22 in a 2m
survey based on the INT data, while our two best ecliptic Blanco fields away
from opposition lead to 135 MBAs (2 unknown to every 1 known) to R=23.Comment: Published in Planetary and Space Sciences (Sep 2013
2dFLenS and KiDS: determining source redshift distributions with cross-correlations
We develop a statistical estimator to infer the redshift probability distribution of a photometric sample of galaxies from its angular cross-correlation in redshift bins with an overlapping spectroscopic sample. This estimator is a minimum-variance weighted quadratic function of the data: a quadratic estimator. This extends and modifies the methodology presented by McQuinn & White. The derived source redshift distribution is degenerate with the source galaxy bias, which must be constrained via additional assumptions. We apply this estimator to constrain source galaxy redshift distributions in the Kilo-Degree imaging survey through cross-correlation with the spectroscopic 2-degree Field Lensing Survey, presenting results first as a binned step-wise distribution in the range z < 0.8, and then building a continuous distribution using a Gaussian process model. We demonstrate the robustness of our methodology using mock catalogues constructed from N-body simulations, and comparisons with other techniques for inferring the redshift distribution
KiDS-i-800: Comparing weak gravitational lensing measurements from same-sky surveys
We present a weak gravitational lensing analysis of 815 deg2 of i-band imaging from the Kilo-Degree Survey (KiDS-i-800). In contrast to the deep r-band observations, which take priority during excellent seeing conditions and form the primary KiDS data set (KiDS-r-450), the complementary yet shallower KiDS-i-800 spans a wide range of observing conditions. The overlapping KiDS-i-800 and KiDS-r-450 imaging therefore provides a unique opportunity to assess the robustness of weak lensing measurements. In our analysis we introduce two new 'null' tests. The 'nulled' two-point shear correlation function uses a matched catalogue to show that the calibrated KiDS-i-800 and KiDS-r-450 shear measurements agree at the level of 1 ± 4 per cent.We use five galaxy lens samples to determine a 'nulled' galaxy-galaxy lensing signal from the full KiDS-i-800 and KiDS-r-450 surveys and find that the measurements agree to 7 ± 5 per cent when the KiDS-i-800 source redshift distribution is calibrated using either spectroscopic redshifts, or the 30-band photometric redshifts from the COSMOS survey
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