3,710 research outputs found
Unified force law for granular impact cratering
Experiments on the low-speed impact of solid objects into granular media have
been used both to mimic geophysical events and to probe the unusual nature of
the granular state of matter. Observations have been interpreted in terms of
conflicting stopping forces: product of powers of projectile depth and speed;
linear in speed; constant, proportional to the initial impact speed; and
proportional to depth. This is reminiscent of high-speed ballistics impact in
the 19th and 20th centuries, when a plethora of empirical rules were proposed.
To make progress, we developed a means to measure projectile dynamics with 100
nm and 20 us precision. For a 1-inch diameter steel sphere dropped from a wide
range of heights into non-cohesive glass beads, we reproduce prior observations
either as reasonable approximations or as limiting behaviours. Furthermore, we
demonstrate that the interaction between projectile and medium can be
decomposed into the sum of velocity-dependent inertial drag plus
depth-dependent friction. Thus we achieve a unified description of low-speed
impact phenomena and show that the complex response of granular materials to
impact, while fundamentally different from that of liquids and solids, can be
simply understood
Investigating non-classical correlations between decision fused multi-modal documents
Correlation has been widely used to facilitate various information retrieval methods such as query expansion, relevance feedback, document clustering, and multi-modal fusion. Especially, correlation and independence are important issues when fusing different modalities that influence a multi-modal information retrieval process. The basic idea of correlation is that an observable can help predict or enhance another observable. In quantum mechanics, quantum correlation, called entanglement, is a sort of correlation between the observables measured in atomic-size particles when these particles are not necessarily collected in ensembles. In this paper, we examine a multimodal fusion scenario that might be similar to that encountered in physics by firstly measuring two observables (i.e., text-based relevance and image-based relevance) of a multi-modal document without counting on an ensemble of multi-modal documents already labeled in terms of these two variables. Then, we investigate the existence of non-classical correlations between pairs of multi-modal documents. Despite there are some basic differences between entanglement and classical correlation encountered in the macroscopic world, we investigate the existence of this kind of non-classical correlation through the Bell inequality violation. Here, we experimentally test several novel association methods in a small-scale experiment. However, in the current experiment we did not find any violation of the Bell inequality. Finally, we present a series of interesting discussions, which may provide theoretical and empirical insights and inspirations for future development of this direction
Evidence for dark matter in the inner Milky Way
The ubiquitous presence of dark matter in the universe is today a central
tenet in modern cosmology and astrophysics. Ranging from the smallest galaxies
to the observable universe, the evidence for dark matter is compelling in
dwarfs, spiral galaxies, galaxy clusters as well as at cosmological scales.
However, it has been historically difficult to pin down the dark matter
contribution to the total mass density in the Milky Way, particularly in the
innermost regions of the Galaxy and in the solar neighbourhood. Here we present
an up-to-date compilation of Milky Way rotation curve measurements, and compare
it with state-of-the-art baryonic mass distribution models. We show that
current data strongly disfavour baryons as the sole contribution to the
galactic mass budget, even inside the solar circle. Our findings demonstrate
the existence of dark matter in the inner Galaxy while making no assumptions on
its distribution. We anticipate that this result will compel new
model-independent constraints on the dark matter local density and profile,
thus reducing uncertainties on direct and indirect dark matter searches, and
will shed new light on the structure and evolution of the Galaxy.Comment: First submitted version of letter published in Nature Physics on
Febuary 9, 2015:
http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys3237.htm
Four Generations: SUSY and SUSY Breaking
We revisit four generations within the context of supersymmetry. We compute
the perturbativity limits for the fourth generation Yukawa couplings and show
that if the masses of the fourth generation lie within reasonable limits of
their present experimental lower bounds, it is possible to have perturbativity
only up to scales around 1000 TeV. Such low scales are ideally suited to
incorporate gauge mediated supersymmetry breaking, where the mediation scale
can be as low as 10-20 TeV. The minimal messenger model, however, is highly
constrained. While lack of electroweak symmetry breaking rules out a large part
of the parameter space, a small region exists, where the fourth generation stau
is tachyonic. General gauge mediation with its broader set of boundary
conditions is better suited to accommodate the fourth generation.Comment: 27 pages, 5 figure
Forward-backward Asymmetry and Branching Ratio of B \rar K_1 \ell^+ \ell^- Transition in Supersymmetric Models
The mass eigen states and are mixture of the strange
members of two axial-vector SU(3) octet, and .
Taking into account this mixture, the forward-backward asymmetry and branching
ratio of B \rar K_1(1270,1400) \ell^+ \ell^- transitions are studied in the
framework of different supersymmetric models. It is found that the results have
considerable deviation from the standard model predictions. Any measurement of
these physical observables and their comparison with the results obtained in
this paper can give useful information about the nature of interactions beyond
the standard model.Comment: 14 pages, 4 figure
A comparison of isolated circulating tumor cells and tissue biopsies using whole-genome sequencing in prostate cancer
Previous studies have demonstrated focal but limited molecular similarities between circulating tumor cells (CTCs) and biopsies using isolated genetic assays. We hypothesized that molecular similarity between CTCs and tissue exists at the single cell level when characterized by whole genome sequencing (WGS). By combining the NanoVelcro CTC Chip with laser capture microdissection (LCM), we developed a platform for single-CTC WGS. We performed this procedure on CTCs and tissue samples from a patient with advanced prostate cancer who had serial biopsies over the course of his clinical history. We achieved 30X depth and ≥ 95% coverage. Twenty-nine percent of the somatic single nucleotide variations (SSNVs) identified were founder mutations that were also identified in CTCs. In addition, 86% of the clonal mutations identified in CTCs could be traced back to either the primary or metastatic tumors. In this patient, we identified structural variations (SVs) including an intrachromosomal rearrangement in chr3 and an interchromosomal rearrangement between chr13 and chr15. These rearrangements were shared between tumor tissues and CTCs. At the same time, highly heterogeneous short structural variants were discovered in PTEN, RB1, and BRCA2 in all tumor and CTC samples. Using high-quality WGS on single-CTCs, we identified the shared genomic alterations between CTCs and tumor tissues. This approach yielded insight into the heterogeneity of the mutational landscape of SSNVs and SVs. It may be possible to use this approach to study heterogeneity and characterize the biological evolution of a cancer during the course of its natural history
Probing the charged Higgs boson at the LHC in the CP-violating type-II 2HDM
We present a phenomenological study of a CP-violating two-Higgs-doublet Model
with type-II Yukawa couplings at the Large Hadron Collider (LHC). In the light
of recent LHC data, we focus on the parameter space that survives the current
and past experimental constraints as well as theoretical bounds on the model.
Once the phenomenological scenario is set, we analyse the scope of the LHC in
exploring this model through the discovery of a charged Higgs boson produced in
association with a W boson, with the former decaying into the lightest neutral
Higgs and a second W state, altogether yielding a b\bar b W^+W^- signature, of
which we exploit the W^+W^- semileptonic decays.Comment: 37 pages, 16 figures; v2 updated treatment of LHC constraint
Cracking in asphalt materials
This chapter provides a comprehensive review of both laboratory characterization and modelling of bulk material fracture in asphalt mixtures. For the purpose of organization, this chapter is divided into a section on laboratory tests and a section on models. The laboratory characterization section is further subdivided on the basis of predominant loading conditions (monotonic vs. cyclic). The section on constitutive models is subdivided into two sections, the first one containing fracture mechanics based models for crack initiation and propagation that do not include material degradation due to cyclic loading conditions. The second section discusses phenomenological models that have been developed for crack growth through the use of dissipated energy and damage accumulation concepts. These latter models have the capability to simulate degradation of material capacity upon exceeding a threshold number of loading cycles.Peer ReviewedPostprint (author's final draft
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