107 research outputs found
Real-time image-based investigation of spheronization and drying phenomena using different pellet formulations
Shell-like structures in our cosmic neighbourhood
Signatures of the processes in the early Universe are imprinted in the cosmic
web. Some of them may define shell-like structures characterised by typical
scales. We search for shell-like structures in the distribution of nearby rich
clusters of galaxies drawn from the SDSS DR8. We calculate the distance
distributions between rich clusters of galaxies, and groups and clusters of
various richness, look for the maxima in the distance distributions, and select
candidates of shell-like structures. We analyse the space distribution of
groups and clusters forming shell walls. We find six possible candidates of
shell-like structures, in which galaxy clusters have maxima in the distance
distribution to other galaxy groups and clusters at the distance of about 120
Mpc/h. The rich galaxy cluster A1795, the central cluster of the Bootes
supercluster, has the highest maximum in the distance distribution of other
groups and clusters around them at the distance of about 120 Mpc/h among our
rich cluster sample, and another maximum at the distance of about 240 Mpc/h.
The structures of galaxy systems causing the maxima at 120 Mpc/h form an almost
complete shell of galaxy groups, clusters and superclusters. The richest
systems in the nearby universe, the Sloan Great Wall, the Corona Borealis
supercluster and the Ursa Major supercluster are among them. The probability
that we obtain maxima like this from random distributions is lower than 0.001.
Our results confirm that shell-like structures can be found in the distribution
of nearby galaxies and their systems. The radii of the possible shells are
larger than expected for a BAO shell (approximately 109 Mpc/h versus
approximately 120 Mpc/h), and they are determined by very rich galaxy clusters
and superclusters with high density contrast while BAO shells are barely seen
in the galaxy distribution. We discuss possible consequences of these
differences.Comment: Comments: 9 pages, 10 figures, Astronomy and Astrophysics, in pres
Mapping the three-body system - decay time and reversibility
In this paper we carry out a quantitative analysis of the three-body systems
and map them as a function of decaying time and intial conguration, look at
this problem as an example of a simple deterministic system, and ask to what
extent the orbits are really predictable. We have investigated the behavior of
about 200 000 general Newtonian three body systems using the simplest initial
conditions. Within our resolution these cover all the possible states where the
objects are initially at rest and have no angular momentum. We have determined
the decay time-scales of the triple systems and show that the distribution of
this parameter is fractal in appearance. Some areas that appear stable on large
scales exhibit very narrow strips of instability and the overall pattern,
dominated by resonances, reminds us of a traditional Maasai warrior shield.
Also an attempt is made to recover the original starting conguration of the
three bodies by backward integration. We find there are instances where the
evolution to the future and to the past lead to different orbits, in spite of
time symmetric initial conditions. This implies that even in simple
deterministic systems there exists an Arrow of Time.Comment: 8 pages, 9 figures. Accepted for publication in MNRAS. Includes
low-resolution figures. High-resolution figures are available as PNG
Clusters and Superclusters in the Las Campanas Redshift Survey
Two-dimensional high-resolution density field of galaxies of the Las Campanas
Redshift Survey (LCRS) with a smoothing length 0.8 Mpc/h is used to extract
clusters and groups of galaxies, and a low-resolution field with a smoothing
length 10 Mpc/h to find superclusters of galaxies. Properties of these density
field (DF) clusters and superclusters are studied and compared with the
properties of Abell clusters and superclusters, and LCRS loose groups. We
calculate the DF-cluster luminosity function, and show that most luminous
clusters in high-density environments are about ten times brighter than most
luminous clusters in low-density environments. We present a catalogue of
DF-superclusters and show that superclusters that contain Abell clusters are
richer and more luminous than superclusters without Abell clusters. A pdf file
of the paper with high-resolution figures is available in Tartu Observatory
web-site (http://www.aai.ee/~maret/cosmoweb.html)Comment: 19 pages LaTeX text, 15 PostScript Figures, submitted to Astronomy
and Astrophysic
Environmental Enhancement of Loose Groups around Rich Clusters of Galaxies
We have studied the properties of Las Campanas Loose Groups in the neighbourhood of rich (Abell, APM and X-ray) clusters of galaxies. These loose groups show strong evidence of segregation measured in terms of the group richness and the group velocity dispersion: loose groups in the neighbourhood of a rich cluster are typically 2.5 times more massive and 1.6 times more luminous than groups on average, and these loose groups havevelocity dispersions 1.3 times larger than groups on average. This is evidence that the large-scale gravitational field causing the formation of rich clusters enhances the evolution of neighbouring poor systems, a phenomenon recently established in numerical simulations of group and cluster formation
Environmental Enhancement of DM Haloes
We study the properties of dark matter haloes of a LCDM model in different
environments. Using the distance of the 5th nearest neighbour as an
environmental density indicator, we show that haloes in a high density
environment are more massive, richer, have larger radii and larger velocity
dispersions than haloes in a low density environment. Haloes in high density
regions move with larger velocities, and are more spherical than haloes in low
density regions. In addition, low mass haloes in the vicinity of the most
massive haloes are themselves more massive, larger, and have larger rms
velocities and larger 3D velocities than low mass haloes far from massive
haloes. The velocities of low mass haloes near massive haloes increase with the
parent halo mass. Our results are in agreement with recent findings about
environmental effects for groups and clusters of galaxies from deep (SDSS and
LCRS) surveys.Comment: 9 pages, 7 figures, submitted for Astronomy and Astrophysic
Fast imaging-based single particle analysis method for solubility determination
The solubility and dissolution rates of chemical compounds are crucial properties in several fields of industry and research. However, accurate, rapid and green methods for their measurement, which only consume micrograms of compound, are lacking. Here, the unique approach of non-specific, image-based single particle analysis (SPA) for solubility testing is directly compared to and thus validated on the mid-solubility range with the current gold standard shake-flask method with UV-Vis spectroscopy employed for determining sample concentrations. Five biologically active compounds representing a range of physicochemical properties including pK(a) and logP were analyzed with both methods. The comparison of SPA and the shake-flask (SF) analysis shows excellent linear correlation (R-2 = 0.99). Higher variability of the SPA method is attributed to variability between the properties of individual particles, which cannot be detected with traditional methods. Due to the similar average solubility values compared to those produced with SF, it is concluded that the SPA method has great potential as an analytical tool for small-scale solubility studies. It also has several practical advantages over the current gold standard shake-flask method, such as speed, low consumables consumption, and no requirement for prior knowledge of compound chemistry.Peer reviewe
Ultrasound-enhanced electrospinning
Electrospinning is commonly used to produce polymeric nanofibers. Potential applications for such fibers include novel drug delivery systems, tissue engineering scaffolds, and filters. Electrospinning, however, has shortcomings such as needle clogging and limited ability to control the fiber-properties in a non-chemical manner. This study reports on an orifice-less technique that employs high-intensity focused ultrasound, i.e. ultrasound-enhanced electrospinning. Ultrasound bursts were used to generate a liquid protrusion with a Taylor cone from the surface of a polymer solution of polyethylene oxide. When the polymer was charged with a high negative voltage, nanofibers jetted off from the tip of the protrusion landed on an electrically grounded target held at a constant distance from the tip. Controlling the ultrasound characteristics permitted physical modification of the nanofiber topography at will without using supplemental chemical intervention. Possible applications of tailor-made fibers generated by ultrasound-enhanced electrospinning include pharmaceutical controlled-release applications and biomedical scaffolds with spatial gradients in fiber thickness and mechanical properties.Peer reviewe
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