464 research outputs found
Universal scaling of distances in complex networks
Universal scaling of distances between vertices of Erdos-Renyi random graphs,
scale-free Barabasi-Albert models, science collaboration networks, biological
networks, Internet Autonomous Systems and public transport networks are
observed. A mean distance between two nodes of degrees k_i and k_j equals to
=A-B log(k_i k_j). The scaling is valid over several decades. A simple
theory for the appearance of this scaling is presented. Parameters A and B
depend on the mean value of a node degree _nn calculated for the nearest
neighbors and on network clustering coefficients.Comment: 4 pages, 3 figures, 1 tabl
A Mixed Solar Core, Solar Neutrinos and Helioseismology
We consider a wide class of solar models with mixed core.
Most of these models can be excluded as the predicted sound speed profile is
in sharp disagreement with helioseismic constraints. All the remaining models
predict Be and/or B neutrino fluxes at least as large as those of SSMs.
In conclusion, helioseismology shows that a mixed solar core cannot account for
the neutrino deficit implied by the current solar neutrino experiments.Comment: 6 pages, RevTeX, plus 5 postscript figure
Log-periodic oscillations due to discrete effects in complex networks
We show that discretization of internode distribution in complex networks
affects internode distances l_ij calculated as a function of degrees (k_i k_j)
and an average path length as function of network size N. For dense
networks there are log-periodic oscillations of above quantities. We present
real-world examples of such a behavior as well as we derive analytical
expressions and compare them to numerical simulations. We consider a simple
case of network optimization problem, arguing that discrete effects can lead to
a nontrivial solution.Comment: 5 pages, 5 figures, REVTE
Multitraits evaluation of Pakistani ecotypes of berseem clover (Trifolium alexandrinum L.) under full-irrigation and water restriction conditions
Berseem clover (Trifolium alexandrinum L.) is an important forage crop in Pakistan and many ecotypes are grown across the country. Its yield is however frequently affected by insufficient irrigation due to unavailability of water. In the present study, twenty Pakistani ecotypes of berseem clover have been evaluated in lysimeters under full irrigation and water restriction conditions. In the full irrigation treatment soil humidity was maintained at field capacity, while in the water restriction treatment water was only supplied after severe wilting and to maintain humidity in the deep profile of the soil. Assessed traits included forage yield, calculated as the sum of the biomass harvested at 70 and 110 DA days after emergence, and morpho-physiological traits. Significant effects of water restriction were noted on yield, leaf gas exchange parameters, canopy temperature and osmotic adjustment. Most morpho-physiological traits had higher broad sense heritability than forage yield, both under full irrigation and water restriction conditions. Water restriction increased genetic and phenotypic variability and heritability of most traits under study. Under these conditions forage yield was positively associated to leaf temperature and recovery rate index and, under full irrigation, to net photosynthetic rate, canopy depression temperature and leaf area. The possible use of these traits as indirect selection criteria in berseem clover breeding programs is discussed. Some ecotypes with favorable traits such as high forage yield potential, good adaptation to water restriction and aptitude to multiple harvesting have also been identified
Statistical Analysis of the Road Network of India
In this paper we study the Indian Highway Network as a complex network where
the junction points are considered as nodes, and the links are formed by an
existing connection. We explore the topological properties and community
structure of the network. We observe that the Indian Highway Network displays
small world properties and is assortative in nature. We also identify the most
important road-junctions (or cities) in the highway network based on the
betweenness centrality of the node. This could help in identifying the
potential congestion points in the network. Our study is of practical
importance and could provide a novel approach to reduce congestion and improve
the performance of the highway networ
Urban traffic from the perspective of dual graph
In this paper, urban traffic is modeled using dual graph representation of
urban transportation network where roads are mapped to nodes and intersections
are mapped to links. The proposed model considers both the navigation of
vehicles on the network and the motion of vehicles along roads. The road's
capacity and the vehicle-turning ability at intersections are naturally
incorporated in the model. The overall capacity of the system can be quantified
by a phase transition from free flow to congestion. Simulation results show
that the system's capacity depends greatly on the topology of transportation
networks. In general, a well-planned grid can hold more vehicles and its
overall capacity is much larger than that of a growing scale-free network.Comment: 7 pages, 10 figure
Recommended from our members
Preface
Preface - The second International Conference on Mathematical Modeling in Physical Sciences (IC-MSQUARE) took place at Prague, Czech Republic, from Sunday 1 September to Thursday 5 September 2013
The rate of X-ray-induced DNA double-strand break repair in the embryonic mouse brain is unaff ected by exposure to 50 Hz magnetic fi elds
Following in utero exposure to low dose radiation
(10 – 200 mGy), we recently observed a linear induction of DNA
double-strand breaks (DSB) and activation of apoptosis in the
embryonic neuronal stem/progenitor cell compartment. No
signifi cant induction of DSB or apoptosis was observed following
exposure to magnetic fi elds (MF). In the present study, we
exploited this in vivo system to examine whether exposure to MF
before and after exposure to 100 mGy X-rays impacts upon DSB
repair rates.
Materials and methods : 53BP1 foci were quantifi ed following
combined exposure to radiation and MF in the embryonic neuronal
stem/progenitor cell compartment. Embryos were exposed
in utero to 50 Hz MF at 300 m T for 3 h before and up to 9 h after
exposure to 100 mGy X-rays. Controls included embryos exposed
to MF or X-rays alone plus sham exposures.
Results : Exposure to MF before and after 100 mGy X-rays did not
impact upon the rate of DSB repair in the embryonic neuronal
stem cell compartment compared to repair rates following radiation
exposure alone.
Conclusions : We conclude that in this sensitive system MF do not
exert any signifi cant level of DNA damage and do not impede
the repair of X-ray induced damage
Microstructure Effects on the Machinability of AM-Produced Superalloys
This paper discusses the microstructure effects on the machinability of Inconel 718 by conducting machining tests on an additively manufactured (AM) workpiece with a strongly textured grain structure and a wrought workpiece incorporating a finer and more equiaxed grain structure. The AM workpiece was produced as a thin tube using Laser Melting Powder Bed Fusion and optimal processing conditions for this alloy. A lathe was used to conduct instrumented orthogonal machining tests on the two workpiece materials under dry cut and coolant conditions using a semisynthetic emulsion coolant. The process parameters studied were feed from 0.05 to 0.15 mm/rev and cutting speed from 60 to 120 m/min with a cut time of 2 sec duration for each process condition. Measures for each process condition included cutting forces in the feed and main cut direction, and images of chip forms were obtained. The grain structures of the workpiece materials were characterized using Electron Back Scattered Diffraction (EBSD). New findings suggest that grain structures can significantly affect the machinability of the superalloy at a higher feed for all cutting speeds studied, and insights into the cause are discussed. Other important findings comment on the effectiveness of the coolant as a lubricant for reducing friction in machining
Helioseismology, solar models and neutrino fluxes
We present our results concerning a systematical analysis of helioseismic
implications on solar structure and neutrino production. We find
Y, and
gr/cm. In the interval , the quantity is
determined with and accuracy of \permille~or better. At the solar center
still one has remarkable accuracy, . We compare the predictions
of recent solar models (standard and non-standard) with the helioseismic
results. By constructing helioseismically constrained solar models, the central
solar temperature is found to be K with a conservatively
estimated accuracy of 1.4%, so that the major unceratainty on neutrino fluxes
is due to nuclear cross section and not to solar inputs.Comment: 14 pages including 9 figures, LaTex file, espcrc2.sty is needed; to
appear in Nucl. Phys. B Proc. Suppl., Proceedings of TAUP97 conference,
Laboratori Nazionali del Gran Sasso, September 199
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