1,161 research outputs found
Hydrodynamic Trapping of Swimming Bacteria by Convex Walls
Swimming bacteria display a remarkable tendency to move along flat surfaces for prolonged times. This behavior may have a biological importance but can also be exploited by using microfabricated structures to manipulate bacteria. The main physical mechanism behind the surface entrapment of swimming bacteria is, however, still an open question. By studying the swimming motion of Escherichia coli cells near microfabricated pillars of variable size, we show that cell entrapment is also present for convex walls of sufficiently low curvature. Entrapment is, however, markedly reduced below a characteristic radius. Using a simple hydrodynamic model, we predict that trapped cells swim at a finite angle with the wall and a precise relation exists between the swimming angle at a flat wall and the critical radius of curvature for entrapment. Both predictions are quantitatively verified by experimental data. Our results demonstrate that the main mechanism for wall entrapment is hydrodynamic in nature and show the possibility of inhibiting cell adhesion, and thus biofilm formation, using convex features of appropriate curvature
Developing E-learning Courses for Mobile Devices
The recent and rapid development of mobile devices and the increasing popularity of e learning have created a demand for mobile learning packages and environments. We have analyzed the possibilities of adapting the existing content for mobile devices, and have implemented two fundamentally different systems to satisfy the demand that has arisen. One of the systems creates e learning courses from existing materials and adapts them to the specified platform (this system realizes the functionalities of the Content Management System). The other system is a modified version of the Moodle Learning Management System, which can adapt existing courses right before displaying them. This paper discuses the fundamentals of e learning, the design considerations and investigates various methods of scalable video coding. Finally the realization details of the two systems are presented.
Use of juvenile grape berry as antioxidant rich food ingredient
Both grape and wine production have several useful by-products what have been discovered more and more due their important positive health effects in the last decades. The grape seed is one of them because its high antioxidant power. On the other hand, the marc is also more and more widely evaluated because of its high amount and useful chemical components. However, the grape berries what arise during cluster or grape thinning are rarely evaluated. Their positive properties and high antioxidant activity has been well known for a long time but their utilization is very rare. It is known as verjus, that is known from its sour taste as souring agent, but in Hungary it is not known. In our research we have evaluated six grape varieties in the Tokaj region during grape maturing in three stages of veraison. Clusters were collected and berries were removed from the pedicles manually and the chemical composition of whole berries, separated seeds and peel and flesh were analysed. Furthermore, dried berry parts were grinded and added to wheat flour and biscuits made from them were also analysed both chemically and sensory. We found that their use can result antioxidant rich and tasty bakery products
Use ofJuvenile Grape Berry as Antioxidant Rich Food Ingredient
Both grape and wine production have several useful by-products what have been discovered more and more due their important positive health effects in the last decades. The grape seed is one of them because its high antioxidant power. On the other hand, the marc is also more and more widely evaluated because of its high amount and useful chemical components. However, the grape berries what arise during cluster or grape thinning are rarely evaluated. Their positive properties and high antioxidant activity has been well known for a long time but their utilization is very rare. It is known as verjus, that is known from its sour taste as souring agent, but in Hungary it is not known. In our research we have evaluated six grape varieties in the Tokaj region during grape maturing in three stages of veraison. Clusters were collected and berries were removed from the pedicles manually and the chemical composition of whole berries, separated seeds and peel and flesh were analysed. Furthermore, dried berry parts were grinded and added to wheat flour and biscuits made from them were also analysed both chemically and sensory. We found that their use can result antioxidant rich and tasty bakery products
Morphological evidence for enhanced kisspeptin and neurokinin B signaling in the infundibular nucleus of the aging man.
Peptidergic neurons synthesizing kisspeptin (KP) and neurokinin B (NKB) in the hypothalamic infundibular nucleus have been implicated in negative sex steroid feedback to GnRH neurons. In laboratory rodents, testosterone decreases KP and NKB expression in this region. In the present study, we addressed the hypothesis that the weakening of this inhibitory testosterone feedback in elderly men coincides with enhanced KP and NKB signaling in the infundibular nucleus. This central hypothesis was tested in a series of immunohistochemical studies on hypothalamic sections of male human individuals that were divided into arbitrary "young" (21-49 yr, n = 11) and "aged" (50-67 yr, n = 9) groups. Quantitative immunohistochemical experiments established that the regional densities of NKB-immunoreactive (IR) perikarya and fibers, and the incidence of afferent contacts they formed onto GnRH neurons, exceeded several times those of the KP-IR elements. Robust aging-dependent enhancements were identified in the regional densities of KP-IR perikarya and fibers and the incidence of afferent contacts they established onto GnRH neurons. The abundance of NKB-IR perikarya, fibers, and axonal appositions to GnRH neurons also increased with age, albeit to lower extents. In dual-immunofluorescent studies, the incidence of KP-IR NKB perikarya increased from 36% in young to 68% in aged men. Collectively, these immunohistochemical data suggest an aging-related robust enhancement in central KP signaling and a moderate enhancement in central NKB signaling. These changes are compatible with a reduced testosterone negative feedback to KP and NKB neurons. The heavier KP and NKB inputs to GnRH neurons in aged, compared with young, men may play a role in the enhanced central stimulation of the reproductive axis. It requires clarification to what extent the enhanced KP and NKB signaling upstream from GnRH neurons is an adaptive response to hypogonadism or, alternatively, a consequence of a decline in the androgen sensitivity of KP and NKB neurons
Mid-infrared interferometric variability of DG Tau: implications for the inner-disk structure
Context. DG Tau is a low-mass pre-main sequence star, whose strongly
accreting protoplanetary disk exhibits a so-far enigmatic behavior: its
mid-infrared thermal emission is strongly time-variable, even turning the 10
m silicate feature from emission to absorption temporarily. Aims. We look
for the reason for the spectral variability at high spatial resolution and at
multiple epochs. Methods. We study the temporal variability of the mid-infrared
interferometric signal, observed with the VLTI/MIDI instrument at six epochs
between 2011 and 2014. We fit a geometric disk model to the observed
interferometric signal to obtain spatial information about the disk. We also
model the mid-infrared spectra by template fitting to characterize the profile
and time dependence of the silicate emission. We use physically motivated
radiative transfer modeling to interpret the mid-infrared interferometric
spectra. Results. The inner disk (r<1-3 au) spectra exhibit a 10 m
absorption feature related to amorphous silicate grains. The outer disk (r>1-3
au) spectra show a crystalline silicate feature in emission, similar to the
spectra of comet Hale-Bopp. The striking difference between the inner and outer
disk spectral feature is highly unusual among T Tauri stars. The mid-infrared
variability is dominated by the outer disk. The strength of the silicate
feature changed by more than a factor of two. Between 2011 and 2014 the
half-light radius of the mid-infrared-emitting region decreased from 1.15 to
0.7 au. Conclusions. For the origin of the absorption we discuss four possible
explanations: a cold obscuring envelope, an accretion heated inner disk, a
temperature inversion on the disk surface and a misaligned inner geometry. The
silicate emission in the outer disk can be explained by dusty material high
above the disk plane, whose mass can change with time, possibly due to
turbulence in the disk.Comment: 16 pages, 13 figure
A topological classification of convex bodies
The shape of homogeneous, generic, smooth convex bodies as described by the
Euclidean distance with nondegenerate critical points, measured from the center
of mass represents a rather restricted class M_C of Morse-Smale functions on
S^2. Here we show that even M_C exhibits the complexity known for general
Morse-Smale functions on S^2 by exhausting all combinatorial possibilities:
every 2-colored quadrangulation of the sphere is isomorphic to a suitably
represented Morse-Smale complex associated with a function in M_C (and vice
versa). We prove our claim by an inductive algorithm, starting from the path
graph P_2 and generating convex bodies corresponding to quadrangulations with
increasing number of vertices by performing each combinatorially possible
vertex splitting by a convexity-preserving local manipulation of the surface.
Since convex bodies carrying Morse-Smale complexes isomorphic to P_2 exist,
this algorithm not only proves our claim but also generalizes the known
classification scheme in [36]. Our expansion algorithm is essentially the dual
procedure to the algorithm presented by Edelsbrunner et al. in [21], producing
a hierarchy of increasingly coarse Morse-Smale complexes. We point out
applications to pebble shapes.Comment: 25 pages, 10 figure
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Systematic evaluation of spliced alignment programs for RNA-seq data
High-throughput RNA sequencing is an increasingly accessible method for studying gene structure and activity on a genome-wide scale. A critical step in RNA-seq data analysis is the alignment of partial transcript reads to a reference genome sequence. To assess the performance of current mapping software, we invited developers of RNA-seq aligners to process four large human and mouse RNA-seq data sets. In total, we compared 26 mapping protocols based on 11 programs and pipelines and found major performance differences between methods on numerous benchmarks, including alignment yield, basewise accuracy, mismatch and gap placement, exon junction discovery and suitability of alignments for transcript reconstruction. We observed concordant results on real and simulated RNA-seq data, confirming the relevance of the metrics employed. Future developments in RNA-seq alignment methods would benefit from improved placement of multimapped reads, balanced utilization of existing gene annotation and a reduced false discovery rate for splice junctions
The 2008 outburst of EX Lup - silicate crystals in motion
EX Lup is the prototype of the EXor class of eruptive young stars. These
objects show optical outbursts which are thought to be related to runaway
accretion onto the star. In a previous study we observed in-situ crystal
formation in the disk of EX Lup during its latest outburst in 2008, making the
object an ideal laboratory to investigate circumstellar crystal formation and
transport. This outburst was monitored by a campaign of ground-based and
Spitzer Space Telescope observations. Here we modeled the spectral energy
distribution of EX Lup in the outburst from optical to millimeter wavelengths
with a 2D radiative transfer code. Our results showed that the shape of the SED
at optical wavelengths was more consistent with a single temperature blackbody
than a temperature distribution. We also found that this single temperature
component emitted 80-100 % of the total accretion luminosity. We concluded that
a thermal instability, the most widely accepted model of EXor outbursts, was
likely not the triggering mechanism of the 2008 outburst of EX Lup. Our
mid-infrared Spitzer spectra revealed that the strength of all crystalline
bands between 8 and 30 um increased right after the end of the outburst. Six
months later, however, the crystallinity in the 10 um silicate feature complex
decreased. Our modeling of the mid-infrared spectral evolution of EXLup showed
that, although vertical mixing should be stronger during the outburst than in
the quiescent phase, fast radial transport of crystals (e.g., by stellar/disk
wind) was required to reproduce the observed mid-infrared spectra.Comment: Accepted for publication in ApJ, 37 pages, 11 figures, 2 table
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