64 research outputs found
Electromagnetic Polarizabilities of Nucleons bound in Ca, O and He
Differential cross sections for elastic scattering of photons have been
measured for Ca at energies of 58 and 74 MeV and for O and He
at 61 MeV, in the angular range from 45 to 150. Evidence is obtained
that there are no significant in-medium modifications of the electromagnetic
polarizabilities except for those originating from meson exchange currents.Comment: 20 pages including 5 Figure
Meson-induced correlations of nucleons in nuclear Compton scattering
The non-resonant (seagull) contribution to the nuclear Compton amplitude at
low energies is strongly influenced by nucleon correlations arising from meson
exchange. We study this problem in a modified Fermi gas model, where nuclear
correlation functions are obtained with the help of perturbation theory. The
dependence of the mesonic seagull amplitude on the nuclear radius is
investigated and the influence of a realistic nuclear density on this amplitude
is dicussed. We found that different form factors appear for the static part
(proportional to the enhancement constant ) of the mesonic seagull
amplitude and for the parts, which contain the contribution from
electromagnetic polarizabilities.Comment: 15 pages, Latex, epsf.sty, 9 eps figures
Reconstruction of cellular variability from spatiotemporal patterns of Dictyostelium discoideum
Variability in cell properties can be an important driving mechanism behind spatiotemporal patterns in biological systems, as the degree of cell-to-cell differences determines the capacity of cells to locally synchronize and, consequently, form patterns on a larger spatial scale. In principle, certain features of spatial patterns emerging with time may be regulated by variability or, more specifically, by certain constellations of cell-to-cell differences. Similarly, measuring variability in a system (i.e. the spatial distribution of cell-cell differences) may help predict properties of later-stage patterns
Phase Synchronization in Railway Timetables
Timetable construction belongs to the most important optimization problems in
public transport. Finding optimal or near-optimal timetables under the
subsidiary conditions of minimizing travel times and other criteria is a
targeted contribution to the functioning of public transport. In addition to
efficiency (given, e.g., by minimal average travel times), a significant
feature of a timetable is its robustness against delay propagation. Here we
study the balance of efficiency and robustness in long-distance railway
timetables (in particular the current long-distance railway timetable in
Germany) from the perspective of synchronization, exploiting the fact that a
major part of the trains run nearly periodically. We find that synchronization
is highest at intermediate-sized stations. We argue that this synchronization
perspective opens a new avenue towards an understanding of railway timetables
by representing them as spatio-temporal phase patterns. Robustness and
efficiency can then be viewed as properties of this phase pattern
Patterns of subnet usage reveal distinct scales of regulation in the transcriptional regulatory network of Escherichia coli
The set of regulatory interactions between genes, mediated by transcription
factors, forms a species' transcriptional regulatory network (TRN). By
comparing this network with measured gene expression data one can identify
functional properties of the TRN and gain general insight into transcriptional
control. We define the subnet of a node as the subgraph consisting of all nodes
topologically downstream of the node, including itself. Using a large set of
microarray expression data of the bacterium Escherichia coli, we find that the
gene expression in different subnets exhibits a structured pattern in response
to environmental changes and genotypic mutation. Subnets with less changes in
their expression pattern have a higher fraction of feed-forward loop motifs and
a lower fraction of small RNA targets within them. Our study implies that the
TRN consists of several scales of regulatory organization: 1) subnets with more
varying gene expression controlled by both transcription factors and
post-transcriptional RNA regulation, and 2) subnets with less varying gene
expression having more feed-forward loops and less post-transcriptional RNA
regulation.Comment: 14 pages, 8 figures, to be published in PLoS Computational Biolog
Polarization degrees of freedom in photoinduced two-nucleon knockout from finite nuclei
The polarization degrees of freedom in photoinduced two-nucleon knockout from
finite nuclei are studied. It is pointed out that they open good perspectives
to study the dynamics of dinucleons in the medium in detail. The ()
and () angular cross sections, photon asymmetries and outgoing
nucleon polarizations are calculated for the target nuclei O and
C and photonenergies ranging from 100 up to 500 MeV. It is investigated
to which degree the two-nucleon emission reaction is dominated by
photoabsorption on proton-neutron and proton-proton
pairs in the nuclear medium. The calculations demonstrate that dominance of
wave photoabsorption in the () channel does not necessarily imply
that the reaction mechanism is similar to what is observed in deuteron
photodisintegration.Comment: 27 pages, REVTeX 3.0 with epsf.sty, 11 figures in EPS forma
Coherent Compton scattering on light nuclei in the delta resonance region
Coherent Compton scattering on light nuclei in the delta resonance region is
studied in the impulse approximation and is shown to be a sensitive probe of
the in-medium properties of the delta resonance. The elementary amplitude on a
single nucleon is calculated from the unitary K-matrix approach developed
previously. Modifications of the properties of the delta resonance due to the
nuclear medium are accounted for through the self-energy operator of the delta,
calculated from the one-pion loop. The dominant medium effects such as the
Pauli blocking, mean-field modification of the nucleon and delta masses, and
particle-hole excitations in the pion propagator are consistently included in
nuclear matter.Comment: 30 pages, 11 figures, accepted for publication in Phys. Rev.
Evaluation of the functional efficacy of an antioxidative probiotic in healthy volunteers
BACKGROUND: In persons without clinical symptom it is difficult to assess an impact of probiotics regarding its effect on health. We evaluated the functional efficacy of the probiotic Lactobacillus fermentum ME-3 in healthy volunteers by measuring the influence of two different formulations on intestinal lactoflora, fecal recovery of the probiotic strain and oxidative stress markers of blood and urine after 3 weeks consumption. METHODS: Two 3-week healthy volunteer trials were performed. Open placebo controlled (OPC) study participants (n = 21) consumed either goat milk or by L. fermentum ME-3 fermented goat milk (daily dose 11.8 log CFU (Colony Forming Units). Double blind randomised placebo controlled (DBRP) study participants (n = 24) received either capsules with L. fermentum ME-3 (daily of dose 9.2 CFU) or placebo capsules. The faecal lactoflora composition, faecal ME-3 recovery, effect of the consumption on intestinal lactoflora, and oxidative stress markers of blood (total antioxidative activity; total antioxidative status and glutathione red-ox ratio) was measured. RESULTS: ME-3 was well tolerated and a significant increase in total faecal lactobacilli yet no predominance of ME-3 was detected in all study groups. Faecal recovery of ME-3 was documented by molecular methods only in fermented milk group, however the significant improvement of blood TAA (Total Antioxidative Activity) and TAS (Total Antioxidative Status) indices was seen both in case of fermented goat milk and capsules", yet glutathione re-ox ratio values decreased only in case of fermented by ME-3 goat milk. CONCLUSION: The functional efficacy of both consumed formulations of an antioxidative probiotic L. fermentum ME-3 is proved by the increase of the intestinal lactobacilli counts providing putative defence against enteric infections and by reduction of the oxidative stress indices of blood and urine of healthy volunteers. In non-diseased host the probiotic health claims can be assessed by improvement of some measurable laboratory indices of well-established physiological functions of host, e.g. markers of antioxidative defence system
The diagnostic value of endoscopy and Helicobacter pylori tests for peptic ulcer patients in late post-treatment setting
BACKGROUND: Guidelines for management of peptic ulcer patients after the treatment are largely directed to detection of H. pylori infection using only non-invasive tests. We compared the diagnostic value of non-invasive and endoscopy based H. pylori tests in a late post-treatment setting. METHODS: Altogether 34 patients with dyspeptic complaints were referred for gastroscopy 5 years after the treatment of peptic ulcer using a one-week triple therapy scheme. The endoscopic and histologic findings were evaluated according to the Sydney classification. Bacteriological, PCR and cytological investigations and (13)C-UBT tests were performed. RESULTS: Seventeen patients were defined H. pylori positive by (13)C-UBT test, PCR and histological examination. On endoscopy, peptic ulcer persisted in 4 H. pylori positive cases. Among the 6 cases with erosions of the gastric mucosa, only two patients were H. pylori positive. Mucosal atrophy and intestinal metaplasia were revealed both in the H. pylori positive and H. pylori negative cases. Bacteriological examination revealed three clarithromycin resistant H. pylori strains. Cytology failed to prove validity for diagnosing H. pylori in a post-treatment setting. CONCLUSIONS: In a late post-treatment setting, patients with dyspepsia should not be monitored only by non-invasive investigation methods; it is also justified to use the classical histological evaluation of H. pylori colonisation, PCR and bacteriology as they have shown good concordance with (13)C-UBT. Moreover, endoscopy and histological investigation of a gastric biopsy have proved to be the methods with an additional diagnostic value, providing the physician with information about inflammatory, atrophic and metaplastic lesions of the stomach in dyspeptic H. pylori positive and negative patients. Bacteriological methods are suggested for detecting the putative antimicrobial resistance of H. pylori, aimed at successful eradication of infection in persistent peptic ulcer cases
Critical synchronization dynamics of the Kuramoto model on connectome and small world graphs
The hypothesis, that cortical dynamics operates near criticality also
suggests, that it exhibits universal critical exponents which marks the
Kuramoto equation, a fundamental model for synchronization, as a prime
candidate for an underlying universal model. Here, we determined the
synchronization behavior of this model by solving it numerically on a large,
weighted human connectome network, containing 804092 nodes, in an assumed
homeostatic state. Since this graph has a topological dimension , a real
synchronization phase transition is not possible in the thermodynamic limit,
still we could locate a transition between partially synchronized and
desynchronized states. At this crossover point we observe power-law--tailed
synchronization durations, with , away from experimental
values for the brain. For comparison, on a large two-dimensional lattice,
having additional random, long-range links, we obtain a mean-field value:
. However, below the transition of the connectome we
found global coupling control-parameter dependent exponents ,
overlapping with the range of human brain experiments. We also studied the
effects of random flipping of a small portion of link weights, mimicking a
network with inhibitory interactions, and found similar results. The
control-parameter dependent exponent suggests extended dynamical criticality
below the transition point.Comment: 12 pages, 9 figures + Supplemenraty material pdf 2 pages 4 figs, 1
table, accepted version in Scientific Report
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