548 research outputs found
A modification of the mixed form of Richards equation and its application in vertically inhomogeneous soils
Recently, new soil data maps were developed, which include vertical soil properties like soil type. Implementing those into a multilayer Soil-Vegetation-Atmosphere-Transfer (SVAT) scheme, discontinuities in the water content occur at the interface between dissimilar soils. Therefore, care must be taken in solving the Richards equation for calculating vertical soil water fluxes. We solve a modified form of the mixed (soil water and soil matric potential based) Richards equation by subtracting the equilibrium state of soil matrix potential ÏE from the hydraulic potential Ïh. The sensitivity of the modified equation is tested under idealized conditions. The paper will show that the modified equation can handle with discontinuities in soil water content at the interface of layered soils
Ultrafast IR spectroscopy of photo-induced electron transfer in self-assembled donor-acceptor coordination cages.
Photo-induced processes in self-assembled coordination cages were studied by femtosecond infrared pump-probe spectroscopy. Densely packed, interpenetrated double cages were constructed from eight bis-monodentate redoxactive ligands bound to four Pd(ii) nodes. Two types of ligands consisting of electron rich phenothiazine (PTZ) or electron deficient anthraquinone (ANQ) chromophores were used to assemble either homo-octameric or mixed-ligand cages. Upon photoexcitation the homo-octameric acceptor cage undergoes intersystem crossing to a long-lived triplet state, similar to the free acceptor ligand. Excitation of the free donor ligand leads to a fluorescent state with intramolecular charge transfer character. This fluorescence is completely quenched in the homo-octameric donor double cage due to a ligand-to-metal charge transfer followed by back electron transfer on a ps timescale. Only for the mixed-ligand cage irradiation produces a charge separated state with an oxidized PTZ radical cation and a reduced ANQ radical anion as proven by their vibrational fingerprints in the transient IR spectra. In dichloromethane the lifetime of this charge separated state extends from tens of ps to >1.5 ns which is attributed to the broad distribution of mixed-ligand cages with different stoichiometry and/or stereo configurations
Bestimmung des atmosphĂ€rischen Konvektionspotentials ĂŒber ThĂŒringen
Im Rahmen einer Zusammenarbeit zwischen der ThĂŒringer Landesanstalt fĂŒr Umwelt
und Geologie (TLUG) und der Goethe-UniversitÀt Frankfurt (GUF) fand in
Kooperation mit dem Deutschen Wetterdienst (DWD) eine umfassende Studie zum
konvektiven Unwetterpotential ĂŒber ThĂŒringen statt. Unwetterereignisse, die
durch konvektive Prozesse in der AtmosphÀre verursacht werden, besitzen ein
nicht unerhebliches Schadenspotential, obwohl sie oftmals eine rÀumlich eng
begrenzte Ausdehnung aufweisen. Aufgrund ihrer Charakteristik ist sowohl die
Vorhersage solcher Ereignisse, als auch eine vollstÀndige, systematische
Erfassung fĂŒr eine detaillierte Auswertung lĂ€ngerer Zeitreihen noch immer eine
Herausforderung. ZusÀtzliches Interesse besteht in der AbschÀtzung der durch
den Klimawandel abhĂ€ngigen Entwicklung des zukĂŒnftigen GefĂ€hrdungspotentials
konvektiver Unwetter. FĂŒr eine gezielte Untersuchung des Themenkomplexes ist
eine Vielzahl unterschiedlicher Daten und Methoden verwendet worden. Mit Hilfe
von FernerkundungsdatensÀtzen wird ein rÀumlich differenziertes
GefĂ€hrdungspotential ĂŒber ThĂŒringen nachgewiesen. Bedingt durch das Relief ist
das Auftreten von Konvektion am hĂ€ufigsten und intensivsten ĂŒber dem sĂŒdlichen
ThĂŒringer Wald und dessen Ostrand zu beobachten, wĂ€hrend NordthĂŒringen eine
deutlich geringere AktivitÀt solcher Unwetterereignisse aufweist. Eine
AbschÀtzung mittels globaler Klimamodelle und daraus abgeleiteten Wetterlagen
zeigt unter BerĂŒcksichtigung des RCP8.5 Klimaszenarios fĂŒr die nahe Zukunft
(2016-2045) eine Zunahme des GefÀhrdungspotentials durch konvektive Unwetter.
Aufgrund des Anstiegs feuchter Wetterlagen (49 % auf 82 %) erhöht sich die
Zunahme der GefĂ€hrdung fĂŒr den Zeitraum 2071-2100 noch deutlicher. Im
Vergleich zu diesem statistischen Ansatz nimmt die projizierte GefÀhrdung
durch extreme Ereignisse erheblich zu (Faktor 6), wenn die Ergebnisse
expliziter Simulationen konvektiver Ereignisse mit einem regionalen
Klimamodell (mit horizontaler Gitterdistanz von 1 km) und eine Zunahme der
Tage mit konvektiven Extremereignissen berĂŒcksichtigt werden. Ein Anstieg der
GefÀhrdung durch konvektive Unwetter in der Zukunft ist wahrscheinlich. Eine
Quantifizierung bleibt jedoch unsicher
Ferkelverluste verringern: Auswirkungen einer verlÀngerten SÀugezeit auf die Konstitution der Aufzuchtferkel
Auf Grund der Vorgaben der EU-Ăko-Verordnung werden Ferkel in der ökologischen Ferkelerzeugung in der Regel mit 6 Wochen abgesetzt. Dies geht in vielen FĂ€llen mit einem verminderten Gesundheits- und Leistungsstatus einher, da sich zu diesem Zeitpunkt Ferkel in einer Ă€uĂerst sensiblen physiologischen Phase befinden. Im vorliegenden Versuch sollte ĂŒberprĂŒft werden, ob die durch einen spĂ€teren Absetzzeitpunkt Ă€lteren Ferkel den Belastungen rund um das Absetzen besser gewachsen sind, und sich durch bessere produktionstechnisch-biologische Leistungen (Modul 1) sowie einen besseren Immunstatus (Modul 2) auszeichnen. Dazu wurden auf dem Versuchsbetrieb Wulmenau des Instituts fĂŒr ökologischen Landbau 36 Sauen auf 2 Verfahren (Kontrolle: 42 Tage SĂ€ugezeit; Versuch: 63 Tage SĂ€ugezeit) mit je 18 Tieren aufgeteilt. Der dritte und letzte Durchgang endete im Sommer 2007. Im Modul 1 wurden insgesamt 3 Wurfnummern mit 108 WĂŒrfen von 36 Sauen mit zusammen mehr als 1400 Ferkeln ausgewertet. Es zeigte sich, dass die lĂ€nger gesĂ€ugten Ferkel signifikant bessere produktionstechnische Leistungsdaten und signifikant verringerte Behandlungsinzidenzen aufwiesen, die Abgangsraten sich aber nicht statistisch gesichert unterschieden. Auf die Kondition der Sauen und den Zustand der GesĂ€ugeleiste hatte die verlĂ€ngerte SĂ€ugezeit keinerlei negative Auswirkungen. Das Modul 2 umfasste die Wurfnum-mern 2 und 3 mit 72 WĂŒrfen von 36 Sauen mit einer Stichprobe von 576 Ferkeln (8 Ferkel/Wurf). Es wurden die Ferkel zu unterschiedlichen Zeitpunkten mit einem ihnen âbekanntenâ Antigen (durch Muttertier-Vakzinierung und passiven Transfer ĂŒber die Sauenmilch) und mit einem ihnen âunbekanntenâ Antigen vakziniert. Im Plasma wurden mittels ELISA die Konzentration von Immunglobulin G (IgG) sowie die antigenspezifischen IgG-Antikörper gemessen. Die Untersuchungen des Moduls 2 ergaben keinen besseren Immunstatus fĂŒr die spĂ€ter abgesetzten Ferkel. Trotzdem erscheint eine VerlĂ€ngerung der SĂ€ugezeit ĂŒber die Mindestvorgabe von 40 Tagen hinaus empfehlenswert
Identification of Pesticide Transformation Products in Surface Water Using Suspect Screening Combined with National Monitoring Data
Pesticides are widespread anthropogenic chemicals and well-known environmental contaminants of concern. Much less is known about transformation products (TPs) of pesticides and their presence in the environment. We developed a novel suspect screening approach for not well-explored pesticides (n = 16) and pesticide TPs (n = 242) by integrating knowledge from national monitoring with high-resolution mass spectrometry data. Weekly time-integrated samples were collected in two Swedish agricultural streams using the novel Time-Integrating, MicroFlow, In-line Extraction (TIMFIE) sampler. The integration of national monitoring data in the screening approach increased the number of prioritized compounds approximately twofold (from 23 to 42). Ultimately, 11 pesticide TPs were confirmed by reference standards and 12 TPs were considered tentatively identified with varying levels of confidence. Semiquantification of the newly confirmed TPs indicated higher concentrations than their corresponding parent pesticides in some cases, which highlights concerns related to (unknown) pesticide TPs in the environment. Some TPs were present in the environment without co-occurrence of their corresponding parent compounds, indicating higher persistency or mobility of the identified TPs. This study showcased the benefits of integrating monitoring knowledge in this type of studies, with advantages for suspect screening performance and the possibility to increase relevance of future monitoring programs
Relativistic nuclear structure effects in quasielastic neutrino scattering
Charged-current cross sections are calculated for quasielastic neutrino and
antineutrino scattering using a relativistic meson-nucleon model. We examine
how nuclear-structure effects, such as relativistic random-phase-approximation
(RPA) corrections and momentum-dependent nucleon self-energies, influence the
extraction of the axial form factor of the nucleon. RPA corrections are
important only at low-momentum transfers. In contrast, the momentum dependence
of the relativistic self-energies changes appreciably the value of the
axial-mass parameter, , extracted from dipole fits to the axial form
factor. Using Brookhaven's experimental neutrino spectrum we estimate the
sensitivity of M to various relativistic nuclear-structure effects.Comment: 26 pages, revtex, 6 postscript figures (available upon request
Enhancing spectral quality in complex environmental matrices: Supporting suspect and non-target screening in zebra mussels with ion mobility
Identification of bioaccumulating contaminants of emerging concern (CECs) via suspect and non-target screening remains a challenging task. In this study, ion mobility separation with high-resolution mass spectrometry (IM-HRMS) was used to investigate the effects of drift time (DT) alignment on spectrum quality and peak annotation for screening of CECs in complex sample matrices using data independent acquisition (DIA). Data treatment approaches (Binary Sample Comparison) and prioritisation strategies (Halogen Match, co-occurrence of features in biota and the water phase) were explored in a case study on zebra mussel (Dreissena polymorpha) in Lake Ma center dot laren, Sweden's largest drinking water reservoir. DT alignment evidently improved the fragment spectrum quality by increasing the similarity score to reference spectra from on average (+/- standard deviation) 0.33 +/- 0.31 to 0.64 +/- 0.30 points, thus positively influencing structure elucidation efforts. Thirty-two features were tenta-tively identified at confidence level 3 or higher using MetFrag coupled with the new PubChemLite database, which included predicted collision cross-section values from CCSbase. The implementation of predicted mobility data was found to support compound annotation. This study illustrates a quantitative assessment of the benefits of IM-HRMS on spectral quality, which will enhance the performance of future screening studies of CECs in complex environmental matrices
Novel technique for supernova detection with IceCube
The current supernova detection technique used in IceCube relies on the
sudden deviation of the summed photomultiplier noise rate from its nominal
value during the neutrino burst, making IceCube a Megaton effective
detection volume - class supernova detector. While galactic supernovae can be
resolved with this technique, the supernova neutrino emission spectrum remains
unconstrained and thus presents a limited potential for the topics related to
supernova core collapse models.
The paper elaborates analytically on the capabilities of IceCube to detect
supernovae through the analysis of hits in the detector correlated in space and
time. These arise from supernova neutrinos interacting in the instrumented
detector volume along single strings. Although the effective detection volume
for such coincidental hits is much smaller (kton, about the scale
of SuperK), a wealth of information is obtained due to the comparatively low
coincidental noise rate. We demonstrate that a neutrino flux from a core
collapse supernova will produce a signature enabling the resolution of rough
spectral features and, in the case of a strong signal, providing indication on
its location.
We further discuss the enhanced potential of a rather modest detector
extension, a denser array in the center of IceCube, within our one dimensional
analytic calculation framework. Such an extension would enable the exploration
of the neutrino sky above a few GeV and the detection of supernovae up to a few
100's of kilo parsec. However, a Mpc detection distance, necessary for
routine supernova detection, demands a significant increase of the effective
detection volume and can be obtained only with a more ambitious instrument,
particularly the boosting of sensor parameters such as the quantum efficiency
and light collection area.Comment: 12 p., 10 fi
Flavor content of nucleon form factors in the space- and time-like region
I discuss a two-component model of nucleon form factors in which the external
photon couples both to an intrinsic three-quark structure and to a meson cloud
via vector-meson dominance, and present a simultaneous analysis of the
electromagnetic form factors of the nucleon in the space- and time-like regions
as well as their strangeness content.Comment: 7 pages, 3 figures, invited talk at FB18, Santos, Brazil, August
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