1,154 research outputs found
Biogenic 2âmethylâ3âbutenâ2âol increases regional ozone and HO x sources
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95042/1/grl23505.pd
Persistent Intersection Homology for the Analysis of Discrete Data
Topological data analysis is becoming increasingly relevant to support the
analysis of unstructured data sets. A common assumption in data analysis is
that the data set is a sample---not necessarily a uniform one---of some
high-dimensional manifold. In such cases, persistent homology can be
successfully employed to extract features, remove noise, and compare data sets.
The underlying problems in some application domains, however, turn out to
represent multiple manifolds with different dimensions. Algebraic topology
typically analyzes such problems using intersection homology, an extension of
homology that is capable of handling configurations with singularities. In this
paper, we describe how the persistent variant of intersection homology can be
used to assist data analysis in visualization. We point out potential pitfalls
in approximating data sets with singularities and give strategies for resolving
them.Comment: Topology-based Methods in Visualization 201
Experimental Test of Relativistic Quantum State Collapse with Moving Reference Frames
An experimental test of relativistic wave-packet collapse is presented. The
tested model assumes that the collapse takes place in the reference frame
determined by the massive measuring detectors. Entangled photons are measured
at 10 km distance within a time interval of less than 5 ps. The two apparatuses
are in relative motion so that both detectors, each in its own inertial
reference frame, are first to perform the measurement. The data always
reproduces the quantum correlations and thus rule out a class of collapse
models. The results also set a lower bound on the "speed of quantum
information" to 0.66 x 10^7 and 1.5 x 10^4 times the speed of light in the
Geneva and the background radiation reference frames, respectively. The very
difficult and deep question of where the collapse takes place - if it takes
place at all - is considered in a concrete experimental context.Comment: 4 pages + 2 ps figure
Hierarchies and Ranks for Persistence Pairs
We develop a novel hierarchy for zero-dimensional persistence pairs, i.e.,
connected components, which is capable of capturing more fine-grained spatial
relations between persistence pairs. Our work is motivated by a lack of spatial
relationships between features in persistence diagrams, leading to a limited
expressive power. We build upon a recently-introduced hierarchy of pairs in
persistence diagrams that augments the pairing stored in persistence diagrams
with information about which components merge. Our proposed hierarchy captures
differences in branching structure. Moreover, we show how to use our hierarchy
to measure the spatial stability of a pairing and we define a rank function for
persistence pairs and demonstrate different applications.Comment: Topology-based Methods in Visualization 201
Random geometric complexes
We study the expected topological properties of Cech and Vietoris-Rips
complexes built on i.i.d. random points in R^d. We find higher dimensional
analogues of known results for connectivity and component counts for random
geometric graphs. However, higher homology H_k is not monotone when k > 0. In
particular for every k > 0 we exhibit two thresholds, one where homology passes
from vanishing to nonvanishing, and another where it passes back to vanishing.
We give asymptotic formulas for the expectation of the Betti numbers in the
sparser regimes, and bounds in the denser regimes. The main technical
contribution of the article is in the application of discrete Morse theory in
geometric probability.Comment: 26 pages, 3 figures, final revisions, to appear in Discrete &
Computational Geometr
The K^*_0(800) scalar resonance from Roy-Steiner representations of pi K scattering
We discuss the existence of the light scalar meson K^*_0(800) (also called
kappa) in a rigorous way, by showing the presence of a pole in the pi K --> pi
K amplitude on the second Riemann sheet. For this purpose, we study the domain
of validity of two classes of Roy-Steiner representations in the complex energy
plane. We prove that one of them is valid in a region sufficiently broad in the
imaginary direction. From this representation, we compute the l=0 partial wave
in the complex plane with neither additional approximation nor model
dependence, relying only on experimental data. A scalar resonance with
strangeness S=1 is found with the following mass and width: E_kappa = 658 \pm
13 MeV and Gamma_kappa = 557 \pm 24 MeV.Comment: 16 pages, 8 figures. Domain of validity of a Roy-Steiner
representation corrected and enlarged, and features of the K^*_0(800) pole
discussed in more details. Conclusions unchange
VOC reactivity in central California: comparing an air quality model to ground-based measurements
International audienceVolatile organic compound (VOC) reactivity in central California is examined using a photochemical air quality model (the Community Multiscale Air Quality model; CMAQ) and ground-based measurements to evaluate the contribution of VOC to photochemical activity. We classify VOC into four categories: anthropogenic, biogenic, aldehyde, and other oxygenated VOC. Anthropogenic and biogenic VOC consist of primary emissions, while aldehydes and other oxygenated VOC include both primary anthropogenic emissions and secondary products from primary VOC oxidation. To evaluate the model treatment of VOC chemistry, we compare calculated and modeled OH and VOC reactivities using the following metrics: 1) cumulative distribution functions of NO<sub>x</sub> concentration and VOC reactivity (R<sub>OH,VOC</sub>), 2) the relationship between R<sub>OH,VOC</sub> and NO<sub>x</sub>, 3) total OH reactivity (R<sub>OH,total</sub>) and speciated contributions, and 4) the relationship between speciated R<sub>OH,VOC</sub> and NO<sub>x</sub>. We find that the model predicts R<sub>OH,total</sub> to within 25?40% at three sites representing urban (Sacramento), suburban (Granite Bay) and rural (Blodgett Forest) chemistry. However in the urban area of Fresno, the model under predicts NO<sub>x</sub> and VOC emissions by a factor of 2?3. At all locations the model is consistent with observations of the relative contributions of total VOC. In urban areas, anthropogenic and biogenic R<sub>OH,VOC</sub> are predicted fairly well over a range of NO<sub>x</sub> conditions. In suburban and rural locations, anthropogenic and other oxygenated R<sub>OH,VOC</sub> relationships are reproduced, but calculated biogenic and aldehyde R<sub>OH,VOC</sub> are often poorly characterized by measurements, making evaluation of the model with available data unreliable. In central California, 30?50% of the modeled urban VOC reactivity is due to aldehydes and other oxygenated species, and the total oxygenated R<sub>OH,VOC</sub> is nearly equivalent to anthropogenic VOC reactivity. In rural vegetated regions, biogenic and aldehyde reactivity dominates. This indicates that more attention needs to be paid to the accuracy of models and measurements of both primary emissions of oxygenated VOC and secondary production of oxygenates, especially formaldehyde and other aldehydes, and that a more comprehensive set of oxygenated VOC measurements is required to include all of the important contributions to atmospheric reactivity
From Loom to Machine: Tibetan Aprons and the Configuration of Place
In this paper I examine how objects become connected to place in complex and contradictory ways. Over the past ten to fi fteen years, rapid transformations in Chinese manufacturing and transportation networks have signifi cantly altered the production, marketing, and consumption of commodities made in the Tibet Autonomous Region and traded in Kalimpong, India, and Kathmandu, Nepal. In an attempt to connect the ethnographic study of material culture with more macrolevel processes of geoeconomic change, I begin the piece with an examination of the changing production, materials, and styles of a very specifi c commodity, the Tibetan womenâs apron. I then explore tradersâ narratives about the values of handmade, machine-made, wool, and synthetic commodities, arguing that we ought to look beyond dichotomies of âoldâ versus ânewâ or âauthenticâ versus âinauthenticâ objects to show in detail how the attachment of commodities to representations of place fi gures importantly in the contemporary study both of globalization and uneven development. Finally, I suggest that Karl Marxâs notion of dead labor is useful in analyzing the recent move towards the revitalization of Tibetan wool for both the domestic Chinese industry and the global tourist industry
Time to revise classification of phyllodes tumors of breast? Results of a French multicentric study
OBJECTIVE: To assess prognostic factors of recurrence of phyllodes tumors (PT) of the breast.
METHODS: We performed a retrospective, multicentric cohort study, including all patients who underwent breast surgery for grade 1 (benign), 2 (borderline) or 3 (malignant) PT between 2000 and 2016 in five tertiary University hospitals, diagnosed according to World Health Organisation classification.
RESULTS: 230 patients were included: 144 (63%), 60 (26%) and 26 (11%) with grade 1, 2 and 3 PT, respectively. Recurrence occurred in 10 (7%), 7 (12%) and 5 (19%) patients with grade 1, 2 and 3 PT, respectively. In univariate analysis, moderate to severe nuclear stromal pleomorphism (HR 8.00 [95% CI: 1.65-38.73], p < 0.009) was correlated with recurrence in all groups including grade 1 (HR 14.3 [95% CI: 1.29-160], p = 0.031). In multivariate analysis, surgical margin >5 mm, (HR 0.20 [95% CI: 0.06-0.63], p = 0.013) were significantly correlated with less recurrence in all PT grades. For grade 1 PT, there was also significantly less recurrence with surgical margin >5 mm, (HR 0.09 [95% CI: 0.01-0.85], p = 0.047) in multivariate analysis.
CONCLUSION: The surgical margin should be at least 5Â mm whatever the grade of PT. Moderate to severe nuclear stromal pleomorphism identified a subgroup of grade 1Â PT with a higher rate of recurrence. This suggests that the WHO classification could be revised with the introduction of nuclear stromal pleomorphism to tailor PT management
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