897 research outputs found
Reciprocal bias compensation and ensuing uncertainties in model-based climate projections: pelagic biogeochemistry versus ocean mixing
Anthropogenic emissions of greenhouse gases such as CO2
and N2O impinge on the Earth system, which in turn modulates
atmospheric greenhouse gas concentrations. The underlying feedback mechanisms
are complex and, at times, counterintuitive. So-called Earth system models
have recently matured to standard tools tailored to assess these feedback
mechanisms in a warming world. Applications for these models range from being
targeted at basic process understanding to the assessment of geo-engineering
options. A problem endemic to all these applications is the need to estimate
poorly known model parameters, specifically for the biogeochemical component,
based on observational data (e.g., nutrient fields). In the present study, we
illustrate with an Earth
system model that through such an approach biases and other model deficiencies in the physical ocean circulation model component can
reciprocally compensate for biases in the pelagic biogeochemical model
component (and vice versa). We present two model configurations that share a
remarkably similar steady state (based on ad hoc measures) when driven by
historical boundary conditions, even though they feature substantially
different configurations (parameter sets) of ocean mixing and biogeochemical
cycling. When projected into the future the similarity between the model
responses breaks. Metrics such as changes in total oceanic carbon content and
suboxic volume diverge between the model configurations as the Earth warms.
Our results reiterate that advancing the understanding of oceanic mixing
processes will reduce the uncertainty of future projections of oceanic
biogeochemical cycles. Related to the latter, we suggest that an advanced
understanding of oceanic biogeochemical cycles can be used for advancements
in ocean circulation modules.</p
Discrimination of different volcanic rock units by magnetic properties — geothermal field at Reykjanes peninsula (SW-Iceland)
The geothermal field at Reykjanes
peninsula is located at the boundary
where the submarine Reykjanes Ridge
passes over into the rift zone of southwestern
Iceland. The geothermal field
coincides with a magnetic low in the
aeromagnetic anomaly map and is situated
within a dense NE–SW fissure and
fault zone. Surface geology is characterized
by different historic fissure eruptions
(youngest from 1226AD), shield
lava (12.5–14.5 ka) and intercalated pillow
basalt–hyaloclastite ridges probably
formed during the last glacial episode
(14.5–20 ka). During a field magnetic
study in the vicinity of the geothermal
field in summer 2005 different
volcanic rock units have been sampled
to correlate rock magnetic and
magneto-mineralogical properties with
magnetic field intensity. Additionally,
measurements on a dense dolerite intrusion,
recovered from the RN–19 borehole
(2245–2248m depth) in May 2005
within the frame of IDDP, should shed
light on the influence of crustal rocks on
the total magnetic field intensity.
Generally, the natural remanent magnetization
and magnetic susceptibility,
measured on rock specimen, is high,
ranging between 2.5 and 33.6Am−1
and 2–37 ×10−3 SI, respectively...conferenc
Bloch- und Néel-Wände in dünnen ferromagnetischen Schichten
In dünnen ferromagnetischen Schichten erzeugen Domänenwände ein Streufeld. Dies führt dazu, daß die Struktur und Energie solcher Wände gegenüber Wänden im unendlich ausgedehnten Material erheblich beeinflußt werden. NÉEL hat bereits gefunden, daß in dünnen Schichten zwei verschiedene Wandtypen existieren müssen. Das Néelsche Verfahren zur Abschätzung der Streufeldenergie wird in dieser Arbeit durch ein konsequentes Variationsverfahren ersetzt und daraus die Energie und Struktur einer 180°-Wand in einer dünnen Schicht mit einachsiger magnetischer Anisotropie berechnet
Theoretical Investigation of the Size Effect on the Oxygen Adsorption Energy of Coinage Metal Nanoparticles
This study evaluates the finite size effect on the oxygen adsorption energy of coinage metal (Cu, Ag and Au) cuboctahedral nanoparticles in the size range of 13 to 1415 atoms (0.7–3.5\ua0nm in diameter). Trends in particle size effects are well described with single point calculations, in which the metal atoms are frozen in their bulk position and the oxygen atom is added in a location determined from periodic surface calculations. This is shown explicitly for Cu nanoparticles, for which full geometry optimization only leads to a constant offset between relaxed and unrelaxed adsorption energies that is independent of particle size. With increasing cluster size, the adsorption energy converges systematically to the limit of the (211) extended surface. The 55-atomic cluster is an outlier for all of the coinage metals and all three materials show similar behavior with respect to particle size
Biochemistry and functional aspects of human glandular kallikreins
Human urinary kallikrein was purified by gel filtration on Sephacryl S-200 and affinity chromatography on aprotinin-Sepharose, followed by ion exchange chromatography on DEAE-Sepharose. In dodecylsulfate gel electrophoresis two protein bands with molecular weights of 41,000 and 34,000 were separated. The amino acid composition and the carbohydrate content of the kallikrein preparation were determined; isoleucine was identified as the only aminoterminal amino acid. The bimolecular velocity constant for the inhibition by diisopropyl fluorophosphate was determined as 9±2 l mol–1 min–1. The hydrolysis of a number of substrates was investigated and AcPheArgOEt was found to be the most sensitive substrate for human urinary kallikrein. Using this substrate an assay method for kallikrein in human urine was developed.
It was shown by radioimmunoassay that pig pancreatic kallikrein can be absorbed in the rat intestinal tract. Furthermore, in dogs the renal excretion of glandular kallikrein from blood was demonstrated by radioimmunological methods
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