1,364 research outputs found
Method and Apparatus for a Miniature Bioreactor System for Long-Term Cell Culture
A bioreactor and method that permits continuous and simultaneous short, moderate, or long term cell culturing of one or more cell types or tissue in a laminar flow configuration is disclosed, where the bioreactor supports at least two laminar flow zones, which are isolated by laminar flow without the need for physical barriers between the zones. The bioreactors of this invention are ideally suited for studying short, moderate and long term studies of cell cultures and the response of cell cultures to one or more stressors such as pharmaceuticals, hypoxia, pathogens, or any other stressor. The bioreactors of this invention are also ideally suited for short, moderate or long term cell culturing with periodic cell harvesting and/or medium processing for secreted cellular components
Miniature Bioreactor System for Long-Term Cell Culture
A prototype miniature bioreactor system is designed to serve as a laboratory benchtop cell-culturing system that minimizes the need for relatively expensive equipment and reagents and can be operated under computer control, thereby reducing the time and effort required of human investigators and reducing uncertainty in results. The system includes a bioreactor, a fluid-handling subsystem, a chamber wherein the bioreactor is maintained in a controlled atmosphere at a controlled temperature, and associated control subsystems. The system can be used to culture both anchorage-dependent and suspension cells, which can be either prokaryotic or eukaryotic. Cells can be cultured for extended periods of time in this system, and samples of cells can be extracted and analyzed at specified intervals. By integrating this system with one or more microanalytical instrument(s), one can construct a complete automated analytical system that can be tailored to perform one or more of a large variety of assays
A proper motion study of the globular cluster M10
We present the first proper motion study of M10 (NGC6254). Absolute proper
motions of about 532 stars in the field of the globular cluster M10 were
determined with respect to Hipparcos and ACT reference stars. In addition to
photographic plates of Bonn and Shanghai also wide field CCD observations as
second epoch plates were used. The wide field CCD observations show an accuracy
comparable to that of the photographic plates. A good coincidence of the
solutions based on reference stars from Hipparcos and from ACT was found. Our
final proper motions allow a sufficient separation of cluster and field stars.
Two population II Cepheids were confirmed to be members of M10. The absolute
proper motion of M10 was determined and combined with its distance from the Sun
and its radial velocity. The space motion and metallicity of M10 indicates the
characteristics of a halo object with an orbit reaching to a maximal z-distance
of less than 3kpc.Comment: 5 pages, LaTeX, incl. 2 PostScript figures. Accepted for publication
by Astronomy & Astrophysics (main journal
The Magic Number Problem for Subregular Language Families
We investigate the magic number problem, that is, the question whether there
exists a minimal n-state nondeterministic finite automaton (NFA) whose
equivalent minimal deterministic finite automaton (DFA) has alpha states, for
all n and alpha satisfying n less or equal to alpha less or equal to exp(2,n).
A number alpha not satisfying this condition is called a magic number (for n).
It was shown in [11] that no magic numbers exist for general regular languages,
while in [5] trivial and non-trivial magic numbers for unary regular languages
were identified. We obtain similar results for automata accepting subregular
languages like, for example, combinational languages, star-free, prefix-,
suffix-, and infix-closed languages, and prefix-, suffix-, and infix-free
languages, showing that there are only trivial magic numbers, when they exist.
For finite languages we obtain some partial results showing that certain
numbers are non-magic.Comment: In Proceedings DCFS 2010, arXiv:1008.127
Algorithms for Colourful Simplicial Depth and Medians in the Plane
The colourful simplicial depth of a point x in the plane relative to a
configuration of n points in k colour classes is exactly the number of closed
simplices (triangles) with vertices from 3 different colour classes that
contain x in their convex hull. We consider the problems of efficiently
computing the colourful simplicial depth of a point x, and of finding a point,
called a median, that maximizes colourful simplicial depth.
For computing the colourful simplicial depth of x, our algorithm runs in time
O(n log(n) + k n) in general, and O(kn) if the points are sorted around x. For
finding the colourful median, we get a time of O(n^4). For comparison, the
running times of the best known algorithm for the monochrome version of these
problems are O(n log(n)) in general, improving to O(n) if the points are sorted
around x for monochrome depth, and O(n^4) for finding a monochrome median.Comment: 17 pages, 8 figure
A Far-Ultraviolet Survey of 47 Tucanae.II The Long-Period Cataclysmic Variable AKO 9
We present time-resolved, far-ultraviolet (FUV) spectroscopy and photometry
of the 1.1 day eclipsing binary system AKO 9 in the globular cluster 47
Tucanae. The FUV spectrum of AKO 9 is blue and exhibits prominent C IV and He
II emission lines. The spectrum broadly resembles that of long-period,
cataclysmic variables in the galactic field.
Combining our time-resolved FUV data with archival optical photometry of 47
Tuc, we refine the orbital period of AKO 9 and define an accurate ephemeris for
the system. We also place constraints on several other system parameters, using
a variety of observational constraints. We find that all of the empirical
evidence is consistent with AKO 9 being a long-period dwarf nova in which mass
transfer is driven by the nuclear expansion of a sub-giant donor star. We
therefore conclude that AKO 9 is the first spectroscopically confirmed
cataclysmic variable in 47 Tuc.
We also briefly consider AKO 9's likely formation and ultimate evolution.
Regarding the former, we find that the system was almost certainly formed
dynamically, either via tidal capture or in a 3-body encounter. Regarding the
latter, we show that AKO 9 will probably end its CV phase by becoming a
detached, double WD system or by exploding in a Type Ia supernova.Comment: 40 pages, 11 figures, to appear in the Dec 20 issue of ApJ; minor
changes to match final published versio
Studying the populations of our Galaxy using the kinematics of sdB stars
We have analysed the kinematics of a sample of 114 hot subdwarf stars, for
2/3 of which we present new proper motions, spectroscopic and photometric data.
The vast majority of the stars show a kinematic behaviour that is similar to
that of Thick Disk stars. Some stars have velocities rather fitting to solar,
i.e. Thin Disk, kinematics. 16 objects have orbital velocities which differ
considerably from those of Disk stars. These are members of the Galactic Halo.
We analysed the velocity dispersions and calculated orbits. Most stars feature
orbits with disk character (eccentricity <= 0.5), a few reach far above the
Galactic plane and have very eccentric orbits (ecc >= 0.7). The intermediate
eccentricity range is poorly populated. This indicates that the (Thick) Disk
and the Halo are kinematically disjunct. Plotting a histogram of the orbit data
points along z leads to the z-distance probability distribution of the star;
doing this for all stars leads to the z-distance probability distribution of
the sample. The logarithmic histogram shows two slopes, each representing the
scale height of a population. The disk component has a scale height of 0.9
(0.1) kpc, which is consistent with earlier results and is similar to that of
the Thick Disk. The other slope represents a component with a scale height ~7
kpc, a much flatter gradient than for the disk component. This shows that the
vast majority of the sdBs are Disk stars, but a Halo minority is present, too.
The kinematic history and population membership of the sdB stars on the whole
is different from that of the cooler HBA stars, which are predominantly or even
exclusively Halo objects. This leads to the question, whether the Halo sdB
stars are of similar origin as the HBAs, or whether their kinematical behaviour
possibly represents another origin, such as infalling stellar aggregates.Comment: accepted for publication in Astronomy and Astrophysics (A&A), 20
pages, 9 figures, 4 table
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Search for anomalous t t-bar production in the highly-boosted all-hadronic final state
A search is presented for a massive particle, generically referred to as a
Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are
sufficiently massive to produce highly Lorentz-boosted top quarks, which yield
collimated decay products that are partially or fully merged into single jets.
The analysis uses new methods to analyze jet substructure, providing
suppression of the non-top multijet backgrounds. The analysis is based on a
data sample of proton-proton collisions at a center-of-mass energy of 7 TeV,
corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits
in the range of 1 pb are set on the product of the production cross section and
branching fraction for a topcolor Z' modeled for several widths, as well as for
a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any
enhancement in t t-bar production beyond expectations of the standard model for
t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version
includes a minor typo correction that will be submitted as an erratu
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