314 research outputs found
Cluster Persistence for Weighted Graphs.
Persistent homology is a natural tool for probing the topological characteristics of weighted graphs, essentially focusing on their 0-dimensional homology. While this area has been thoroughly studied, we present a new approach to constructing a filtration for cluster analysis via persistent homology. The key advantages of the new filtration is that (a) it provides richer signatures for connected components by introducing non-trivial birth times, and (b) it is robust to outliers. The key idea is that nodes are ignored until they belong to sufficiently large clusters. We demonstrate the computational efficiency of our filtration, its practical effectiveness, and explore into its properties when applied to random graphs
Homological percolation and the Euler characteristic
In this paper we study the connection between the phenomenon of homological
percolation (the formation of "giant" cycles in persistent homology), and the
zeros of the expected Euler characteristic curve. We perform an experimental
study that covers four different models: site-percolation on the cubical and
permutahedral lattices, the Poisson-Boolean model, and Gaussian random fields.
All the models are generated on the flat torus , for . The
simulation results strongly indicate that the zeros of the expected Euler
characteristic curve approximate the critical values for
homological-percolation. Our results also provide some insight about the
approximation error. Further study of this connection could have powerful
implications both in the study of percolation theory, and in the field of
Topological Data Analysis
Ultrastructural localization of extracellular matrix proteins of the lymph node cortex: evidence supporting the reticular network as a pathway for lymphocyte migration
<p>Abstract</p> <p>Background</p> <p>The lymph node (LN) is a crossroads of blood and lymphatic vessels allowing circulating lymphocytes to efficiently recognize foreign molecules displayed on antigen presenting cells. Increasing evidence indicates that after crossing high endothelial venules, lymphocytes migrate within the node along the reticular network (RN), a scaffold of fibers enwrapped by fibroblastic reticular cells (FRC). Light microscopy has shown that the RN contains specific extracellular matrix (ECM) proteins, which are putative molecular "footholds" for migration, and are known ligands for lymphocyte integrin adhesion receptors.</p> <p>Results</p> <p>To investigate whether ECM proteins of the RN are present on the outer surface of the FRC and are thus accessible to migrating lymphocytes, ultrastructural immunohistochemical staining of cynomolgus monkey LN was performed using antibodies to human ECM proteins that were successfully employed at the light microscopic level. The fibrillar collagens I and III were observed primarily within the reticular network fibers themselves. In contrast, the matrix proteins laminin, fibronectin, collagen IV, and tenascin were observed within the reticular fibers and also on the outer membrane surface of the FRC.</p> <p>Conclusions</p> <p>These findings suggest a molecular basis for how the RN functions as a pathway for lymphocyte migration within the lymph node.</p
Reply to comment from Liotta and Rizzo on “Evolution of CO2 , SO2 , HCl and HNO3 in the volcanic plumes from Etna” by Voigt et al. [Geophys. Res. Lett.; 41, doi:10.1002/2013GL058974]
Editor’s Note:
The following comment and reply arise from an article
published in Geophysical Research Letters by Voigt
et al. (2014). The article addresses a volcanology topic,
and the commenters take issue with some conclusions
and offer an analysis of their own. Voigt and co-authors
have responded.
Why is this comment-and-reply being published in
the Bulletin? It is because Geophysical Research
Letters is one of a number of journals that do not offer
any published forum for discussion of the papers they
publish. This is a matter of editorial policy and a
decision for each journal.
The Bulletin of Volcanology does provide a forum for
discussion of articles published. When contacted by
Marcello Liotta with the request that the Bulletin consider
hosting a discussion of the Voigt et al. volcanology article in
GRL, I agreed to do so if the GRL authors were willing to
engage with the comment. Voigt and co-authors were willing
to do so and have been allowed a small amount of additional
space to summarize for Bulletin readers the key points of the
GRL paper under discussion before responding directly to the
comment from Liotta and Rizzo.
I hope that Bulletin readers find the discussion and reply of
interest
A Search for leptophilic Z_(l) boson at future linear colliders
We study the possible dynamics associated with leptonic charge in future
linear colliders. Leptophilic massive vector boson, Z_(l), have been
investigated through the process e^(+)e^(-) -> mu^(+)mu^(-). We have shown that
ILC and CLIC will give opportunity to observe Z_(l) with masses up to the
center of mass energy if the corresponding coupling constant g_(l) exceeds
10^(-3).Comment: 12 pages, 10 figure
An improved observable for the forward-backward asymmetry in B -> K* l+ l- and Bs -> phi l+ l-
We study the decay B -> K* l+ l- in the QCD factorization approach and
propose a new integrated observable whose dependence on the form factors is
almost negligible, consequently the non--perturbative error is significantly
reduced and indeed its overall theoretical error is dominated by perturbative
scale uncertainties. The new observable we propose is the ratio between the
integrated forward--backward asymmetry in the [4,6] GeV^2 and [1,4] GeV^2
dilepton invariant mass bins. This new observable is particularly interesting
because, when compared to the location of the zero of the FBA spectrum, it is
experimentally easier to measure and its theoretical uncertainties are almost
as small; moreover it displays a very strong dependence on the phase of the
Wilson coefficient C_10 that is otherwise only accessible through complicated
CP violating asymmetries. We illustrate the new physics sensitivity of this
observable within the context of few extensions of the Standard Model, namely
the SM with four generations, an MSSM with non--vanishing source of flavor
changing neutral currents in the down squark sector and a Z' model with tree
level flavor changing couplings.Comment: 19 pages, 7 figure
Holocene resource exploitation along the Nile:diet and subsistence strategies of Mesolithic and Neolithic societies at Khor Shambat 1, Sudan
The subsistence practices of Holocene communities living in the Nile Valley of Central Sudan are comparatively little known. Recent excavations at Khor Shambat, Sudan, have yielded well-defined Mesolithic and Neolithic stratigraphy. Here, for the first time, archaeozoological, palaeobotanical, phytolith and dental calculus studies are combined with lipid residue analysis of around 100 pottery fragments and comparative analysis of faunal remains and organic residues. This holistic approach provides valuable information on changes in adaptation strategies, from Mesolithic hunter-gatherers to Neolithic herders exploiting domesticates. A unique picture is revealed of the natural environment and human subsistence, demonstrating the potential wider value of combining multiple methods
Precision Gauge Unification from Extra Yukawa Couplings
We investigate the impact of extra vector-like GUT multiplets on the
predicted value of the strong coupling. We find in particular that Yukawa
couplings between such extra multiplets and the MSSM Higgs doublets can resolve
the familiar two-loop discrepancy between the SUSY GUT prediction and the
measured value of alpha_3. Our analysis highlights the advantages of the
holomorphic scheme, where the perturbative running of gauge couplings is
saturated at one loop and further corrections are conveniently described in
terms of wavefunction renormalization factors. If the gauge couplings as well
as the extra Yukawas are of O(1) at the unification scale, the relevant
two-loop correction can be obtained analytically. However, the effect persists
also in the weakly-coupled domain, where possible non-perturbative corrections
at the GUT scale are under better control.Comment: 26 pages, LaTeX. v6: Important early reference adde
High Resolution Millimeter Imaging of the Proto-Planetary Nebula He 3-1475
We report high resolution (1-2 arcsec) imaging of the CO 2-1 line and the
millimeter continuum in the proto-planetary nebula He 3-1475. The observations
reveal the presence of a massive (~0.6 M_sun} envelope of molecular gas around
the origin of the remarkable bipolar jet system seen in optical images with the
HST. The CO kinematics are well modeled by an expanding, bi-conical envelope:
the prominent, high-velocity (~50 km/s) wings seen in single-dish CO spectra
arise where the sides of the bi-cones are projected along the line of sight.
The continuum is detected at 1.3 mm and 2.6 mm and is due to thermal emission
from warm (~80 K) circumstellar dust. The structure, kinematics, and expansion
time of the envelope provide strong evidence for entrainment of the molecular
gas by the high velocity jets. The observations support an evolutionary
scenario in which a period of enhanced mass loss by the central star is
followed by the development of the bipolar jets which burst through the
molecular envelope. The jet-envelope interactions play a crucial role in
shaping the subsequent ionized nebula.Comment: Astronomy & Astrophysics in pres
On CP Asymmetries in Two-, Three- and Four-Body D Decays
Indirect and direct CP violations have been established in K_L and B_d
decays. They have been found in two-body decay channels -- with the exception
of K_L to pi^+ pi^- e^+ e^- transitions. Evidence for direct CP asymmetry has
just appeared in LHCb data on A_{CP}(D^0 to K^+ K^-) - A_{CP}(D^0 to pi^+ pi^-)
with 3.5 sigma significance. Manifestations of New Dynamics (ND) can appear in
CP asymmetries just below experimental bounds. We discuss D^{\pm}_{(s)},
D^0/\bar D^0 and D_L/D_S transitions to 2-, 3- and 4-body final states with a
comment on predictions for inclusive vs. exclusive CP asymmetries. In
particular we discuss T asymmetries in D to h_1 h_2 l^+ l^- in analogy with K_L
to pi^+ pi^- e^+ e^- transitions due to interference between M1, internal
bremsstrahlung and possible E1 amplitudes. Such an effect depends on the
strength of CP violation originating from the ND -- as discussed here for
Little Higgs Models with T parity and non-minimal Higgs sectors -- but also in
the interferences between these amplitudes even in the Standard Model (SM).
More general lessons can be learnt for T asymmetries in non-leptonic D decays
like D to h_1h_2 h_3 h_4. Such manifestations of ND can be tested at LHCb and
other Super-Flavour Factories like the projects at KEK near Tokyo and at Tor
Vergata/Frascati near Rome.Comment: 27 pages, 6 figures. Revised with current results from LHCb and HFAG
and further interpretation
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