845 research outputs found
The phosphate balance : current developments and future outlook
Phosphate is essential for agricultural production and therefore plays a key role in the global production of food and biofuels. There are no agricultural alternatives for phosphate, and a substantial fraction of our annual phosphate consumption is dispersed into the environment where it is largely lost to agriculture. Phosphate is an irreplaceable, and to a considerable extent non-renewable, resource that is being exploited at an ever increasing rate. The ongoing depletion of phosphate resources combined with recently increased phosphate prices urge us to reconsider our phosphate consumption patterns. In addition to economic and geo-political reasons, further reducing phosphate consumption would moreover be beneficial to the quality of our environment. Even if we increase the reserve base, for which there are plenty of opportunities, it is clear that the phosphate industry will sooner or later have to make a switch from a reserve-based industry to a recycling industry
Parallelization of chip-based fluorescence immuno-assays with quantum-dot labelled beads
This paper presents an optical concept for the read-out of a parallel, bead-based fluorescence immunoassay conducted on a lab-on-a-disk platform. The reusable part of the modular setup comprises a detection unit featuring a single LED as light source, two emission-filters, and a color CCD-camera as standard components together with a spinning drive as actuation unit. The miniaturized lab-on-a-disk is devised as a disposable. In the read-out process of the parallel assay, beads are first identified by the color of incorporated quantum dots (QDs). Next, the reaction-specific fluorescence signal is quantified with FluoSpheres-labeled detection anti-bodies. To enable a fast and automated read-out, suitable algorithms have been implemented in this work. Based on this concept, we successfully demonstrated a Hepatitis-A assay on our disk-based lab-on-a-chip
X-ray Bright Active Galactic Nuclei in Massive Galaxy Clusters II: The Fraction of Galaxies Hosting Active Nuclei
We present a measurement of the fraction of cluster galaxies hosting X-ray
bright Active Galactic Nuclei (AGN) as a function of clustercentric distance
scaled in units of . Our analysis employs high quality Chandra X-ray
and Subaru optical imaging for 42 massive X-ray selected galaxy cluster fields
spanning the redshift range of . In total, our study involves
176 AGN with bright () optical counterparts above a keV flux
limit of . When excluding
central dominant galaxies from the calculation, we measure a cluster-galaxy AGN
fraction in the central regions of the clusters that is times lower
that the field value. This fraction increases with clustercentric distance
before becoming consistent with the field at . Our data
exhibit similar radial trends to those observed for star formation and
optically selected AGN in cluster member galaxies, both of which are also
suppressed near cluster centers to a comparable extent. These results strongly
support the idea that X-ray AGN activity and strong star formation are linked
through their common dependence on available reservoirs of cold gas.Comment: 9 Pages, 4 Figures, accepted for publication in MNRAS, please contact
Steven Ehlert ([email protected]) with any querie
X-ray bright active galactic nuclei in massive galaxy clusters III: New insights into the triggering mechanisms of cluster AGN
We present the results of a new analysis of the X-ray selected Active
Galactic Nuclei (AGN) population in the vicinity of 135 of the most massive
galaxy clusters in the redshift range of 0.2 < z < 0.9 observed with Chandra.
With a sample of more than 11,000 X-ray point sources, we are able to measure,
for the first time, evidence for evolution in the cluster AGN population beyond
the expected evolution of field AGN. Our analysis shows that overall number
density of cluster AGN scales with the cluster mass as .
There is no evidence for the overall number density of cluster member X-ray AGN
depending on the cluster redshift in a manner different than field AGN, nor
there is any evidence that the spatial distribution of cluster AGN (given in
units of the cluster overdensity radius r_500) strongly depends on the cluster
mass or redshift. The scaling relation we measure is
consistent with theoretical predictions of the galaxy merger rate in clusters,
which is expected to scale with the cluster velocity dispersion, , as or . This consistency suggests that AGN in
clusters may be predominantly triggered by galaxy mergers, a result that is
further corroborated by visual inspection of Hubble images for 23
spectroscopically confirmed cluster member AGN in our sample. A merger-driven
scenario for the triggering of X-ray AGN is not strongly favored by studies of
field galaxies, however, suggesting that different mechanisms may be primarily
responsible for the triggering of cluster and field X-ray AGN.Comment: 21 Pages, 8 figures, 5 tables. Submitted to MNRAS. Comments are
welcome, and please request Steven Ehlert for higher resolution figure
Different cell populations are inducible by BMP-2 covalently covered BioveritÂź II implants in rabbit subcutis and middle ear
To optimize the function of implants the formation of surrounding connective tissue should be adapted in dependence to the mechanical conditions. Therefore, with nanostructured silica coated BioveritÂź II implants were only partly reacted with recombinant BMP-2. The histology was compared 28, 84 and 301 days after implantation in the rabbit middle ear and subcutis, respectively. The whole tissue blocks were embedded in Epon, sequentially grinded, stained with Toluidine Blue O and Eosin G. The granulation tissue covering the implants varies related to cell types, cell amounts, extracellular matrix and vessels. Whereas the high cell density and the angiogenesis predominated in the subcutis, the formation of new bone could only be recognized in the scar around the implants in the middle ear.SFB/599/project D1
Probing the extreme realm of AGN feedback in the massive galaxy cluster, RX J1532.9+3021
We present a detailed Chandra, XMM-Newton, VLA and HST analysis of one of the
strongest cool core clusters known, RX J1532.9+3021 (z=0.3613). Using new, deep
90 ks Chandra observations, we confirm the presence of a western X-ray cavity
or bubble, and report on a newly discovered eastern X-ray cavity. The total
mechanical power associated with these AGN-driven outflows is (22+/-9)*10^44
erg/s, and is sufficient to offset the cooling, indicating that AGN feedback
still provides a viable solution to the cooling flow problem even in the
strongest cool core clusters. Based on the distribution of the optical
filaments, as well as a jet-like structure seen in the 325 MHz VLA radio map,
we suggest that the cluster harbours older outflows along the north to south
direction. The jet of the central AGN is therefore either precessing or
sloshing-induced motions have caused the outflows to change directions. There
are also hints of an X-ray depression to the north aligned with the 325 MHz
jet-like structure, which might represent the highest redshift ghost cavity
discovered to date. We further find evidence of a cold front (r=65kpc) that
coincides with the outermost edge of the western X-ray cavity and the edge of
the radio mini-halo. The common location of the cold front with the edge of the
radio mini-halo supports the idea that the latter originates from electrons
being reaccelerated due to sloshing induced turbulence. Alternatively, its
coexistence with the edge of the X-ray cavity may be due to cool gas being
dragged out by the outburst. We confirm that the central AGN is highly
sub-Eddington and conclude that a >10^10M_Sun or a rapidly spinning black hole
is favoured to explain both the radiative-inefficiency of the AGN and the
powerful X-ray cavities.Comment: Accepted for publication to ApJ (minor corrections), 16 pages, 16
figures, 5 tables. Full resolution at http://www.stanford.edu/~juliehl/M1532
Fosfaatbehoefte van bloembollen; onderbouwing van de fosfaatbemestingsadviezen
De fosfaatbemestingsadviezen voor bloembollen zijn in de periode 1996-2002 onderwerp van onderzoek geweest. De aanleiding daartoe werd gevormd door het feit dat het fosfaatoverschot op bedrijfniveau knelt met het toegelaten overschot volgens MINAS en omdat het advies zwak onderbouwd en gedateerd is. De meststofbehoefte van bolgewassen afhankelijk van de fosfaattoestand van de bodem is vastgesteld. Verder is onderzocht welke fosfaattoestand nagestreefd dient te worden en hoe fosfaatbemesting afgestemd kan worden op de fosfaattoestand zonder in conflict te komen met de milieukwaliteitsdoelstellingen. Een nieuw bemestingsadvies is opgesteld gebaseerd op een combinatie van veld- en procesonderzoek. In het algemeen reageren bolgewassen in vergelijking met andere gewassen weinig of niet op fosfaattoestand en fosfaatbemesting. Strikte evenwichtsbemesting volgens `aanvoer is afvoerÂż volstaat bij de meeste bolgewassen. Reparatiebemesting van een te lage fosfaattoestand van duinzand volgens generieke normen leidt tot verhoogd risico op uitspoeling omdat deze grondsoort zeer zwakke bufferende eigenschappen bezit. Op dergelijke gronden verdient het uit milieuoverwegingen aanbeveling geen reparatiebemesting uit te voeren
Multipartite Entanglement and Frustration
Some features of the global entanglement of a composed quantum system can be
quantified in terms of the purity of a balanced bipartition, made up of half of
its subsystems. For the given bipartition, purity can always be minimized by
taking a suitable (pure) state. When many bipartitions are considered, the
requirement that purity be minimal for all bipartitions can engender conflicts
and frustration arises. This unearths an interesting link between frustration
and multipartite entanglement, defined as the average purity over all
(balanced) bipartitions.Comment: 15 pages, 7 figure
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