2,418 research outputs found
Constraints on the broad line region from regularized linear inversion: Velocity-delay maps for five nearby active galactic nuclei
Reverberation mapping probes the structure of the broad emission-line region
(BLR) in active galactic nuclei (AGN). The kinematics of the BLR gas can be
used to measure the mass of the central supermassive black hole. The main
uncertainty affecting black hole mass determinations is the structure of the
BLR. We present a new method for reverberation mapping based on regularized
linear inversion (RLI) that includes modelling of the AGN continuum light
curves. This enables fast calculation of velocity-resolved response maps to
constrain BLR structure. RLI allows for negative response, such as when some
areas of the BLR respond in inverse proportion to a change in ionizing
continuum luminosity. We present time delays, integrated response functions,
and velocity-delay maps for the broad emission line in five
nearby AGN, as well as for and in Arp 151,
using data from the Lick AGN Monitoring Project 2008. We find indications of
prompt response in three of the objects (Arp 151, NGC 5548 and SBS 1116+583A)
with additional prompt response in the red wing of . In SBS
1116+583A we find evidence for a multimodal broad prompt response followed by a
second narrow response at 10 days. We find no clear indications of negative
response. The results are complementary to, and consistent with, other methods
such as cross correlation, maximum entropy and dynamical modelling. Regularized
linear inversion with continuum light curve modelling provides a fast,
complementary method for velocity-resolved reverberation mapping and is
suitable for use on large datasets.Comment: 20 pages, 13 figures, accepted to MNRA
Modeling reverberation mapping data II: dynamical modeling of the Lick AGN Monitoring Project 2008 dataset
We present dynamical modeling of the broad line region (BLR) for a sample of
five Seyfert 1 galaxies using reverberation mapping data taken by the Lick AGN
Monitoring Project in 2008. By modeling the AGN continuum light curve and
H line profiles directly we are able to constrain the geometry and
kinematics of the BLR and make a measurement of the black hole mass that does
not depend upon the virial factor, , needed in traditional reverberation
mapping analysis. We find that the geometry of the BLR is generally a thick
disk viewed close to face-on. While the H emission is found to come
preferentially from the far side of the BLR, the mean size of the BLR is
consistent with the lags measured with cross-correlation analysis. The BLR
kinematics are found to be consistent with either inflowing motions or
elliptical orbits, often with some combination of the two. We measure black
hole masses of for Arp
151, for Mrk 1310, for NGC 5548,
for NGC 6814, and for SBS
1116+583A. The factors measured individually for each AGN are found to
correlate with inclination angle, although not with , ,
or FWHM/ of the emission line profile.Comment: 21 pages, 24 figures, 3 tables, Accepted for publication in MNRAS,
corrected masses for NGC 5548 and NGC 6814 in the abstrac
Etablierung DNA-basierender Nanostrukturen aus DNA-Tetraedern über Kissing-Loop-Annealing
In dieser Arbeit konnten auf DNA basierende Nanotetraeder durch bis zu vier DNA-Hairpin-Strukturen an den Tetraederecken funktionalisiert werden. Durch geschicktes Design der Loop-Sequenzen konnte gezeigt werden, dass die funktionalisierten DNA-Tetraeder mittels dieser Sequenzen, über sogenanntes Kissing-Loop-Annealing, miteinander interagieren können. Dieses Kissing-Loop-Annealing wurde in dieser Arbeit im Hinblick auf verschiedene Einflussfaktoren detailliert charakterisiert
Prospects for measuring supermassive black hole masses with future extremely large telescopes
The next generation of giant-segmented mirror telescopes ( 20 m) will
enable us to observe galactic nuclei at much higher angular resolution and
sensitivity than ever before. These capabilities will introduce a revolutionary
shift in our understanding of the origin and evolution of supermassive black
holes by enabling more precise black hole mass measurements in a mass range
that is unreachable today. We present simulations and predictions of the
observations of nuclei that will be made with the Thirty Meter Telescope (TMT)
and the adaptive optics assisted integral-field spectrograph IRIS, which is
capable of diffraction-limited spectroscopy from band (0.9 m) to
band (2.2 m). These simulations, for the first time, use realistic values
for the sky, telescope, adaptive optics system, and instrument, to determine
the expected signal-to-noise ratio of a range of possible targets spanning
intermediate mass black holes of \msun to the most massive black
holes known today of . We find that IRIS will be able to
observe Milky Way-mass black holes out the distance of the Virgo cluster, and
will allow us to observe many more brightest cluster galaxies where the most
massive black holes are thought to reside. We also evaluate how well the
kinematic moments of the velocity distributions can be constrained at the
different spectral resolutions and plate scales designed for IRIS. We find that
a spectral resolution of will be necessary to measure the masses of
intermediate mass black holes. By simulating the observations of galaxies found
in SDSS DR7, we find that over massive black holes will be observable at
distances between with the estimated sensitivity and angular
resolution provided by access to -band (0.9 m) spectroscopy from IRIS
and the TMT adaptive optics system. (Abridged)Comment: 19 pages, 20 figures, accepted to A
Framework for Construction of Multi-scale Models for Biological Wastewater Treatment Processes - Case Study: Autotrophic Nitrogen Conversion
High-yield production of a super-soluble miniature spidroin for biomimetic high-performance materials
The mechanical properties of artificial spider silks are approaching a stage where commercial applications become realistic. However, the yields of recombinant silk proteins that can be used to produce fibers with good mechanical properties are typically very low and many purification and spinning protocols still require the use of urea, hexafluoroisopropanol, and/or methanol. Thus, improved production and spinning methods with a minimal environmental impact are needed. We have previously developed a miniature spider silk protein that is characterized by high solubility in aqueous buffers and spinnability in biomimetic set-ups. In this study, we developed a production protocol that resulted in an expression level of >20 g target protein per liter in an Escherichia coli fedbatch culture, and subsequent purification under native conditions yielded 14.5 g/l. This corresponds to a nearly six-fold increase in expression levels, and a 10-fold increase in yield after purification compared to reports for recombinant spider silk proteins. Biomimetic spinning using only aqueous buffers resulted in fibers with a toughness modulus of 74 MJ/m(3), which is the highest reported for biomimetically as-spun artificial silk fibers. Thus, the process described herein represents a milestone for the economic production of biomimetic silk fibers for industrial applications
DNA-DNA kissing complexes as a new tool for the assembly of DNA nanostructures
Kissing-loop annealing of nucleic acids occurs in nature in several viruses and in prokaryotic replication, among other circumstances. Nucleobases of two nucleic acid strands (loops) interact with each other, although the two strands cannot wrap around each other completely because of the adjacent doublestranded regions (stems). In this study, we exploited DNA kissing-loop interaction for nanotechnological application. We functionalized the vertices of DNA tetrahedrons with DNA stem-loop sequences. The complementary loop sequence design allowed the hybridization of different tetrahedrons via kissingloop interaction, which might be further exploited for nanotechnology applications like cargo transport and logical elements. Importantly, we were able to manipulate the stability of those kissing-loop complexes based on the choice and concentration of cations, the temperature and the number of complementary loops per tetrahedron either at the same or at different vertices. Moreover, variations in loop sequences allowed the characterization of necessary sequences within the loop as well as additional stability control of the kissing complexes. Therefore, the properties of the presented nanostructures make them an important tool for DNA nanotechnology
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