9,600 research outputs found
Euclidean N=2 Supergravity
Euclidean special geometry has recently been investigated in the context of
Euclidean supersymmetric theories with vector multiplets. In the rigid case,
the scalar manifold is described by affine special para-Kahler geometry while
the target geometries of Euclidean vector multiplets coupled to supergravity
are given by projective special para-Kahler manifolds. In this letter, we
derive the Killing spinor equations of Euclidean N=2 supergravity theories
coupled to vector multiplets. These equations provide the starting point for
finding general supersymmetric instanton solutions.Comment: 12 pages, latex. Minor sign corrections in section
Enhancement of preasymptotic effects in inclusive beauty decays
We extend Voloshin's recent analysis of charmed and beauty hyperon decays
based on SU(3) symmetry and heavy quark effective theory, by introducing a
rather moderate model-dependence, in order to obtain more predictive power,
e.g. the values of lifetimes of the (\Lambda_{b},\Xi_{b}) hyperon triplet and
the lifetime of \Omega_{b}. In this way we obtain an improvement of the ratio
\tau(\Lambda_{b})/\tau(B_{d}^{0}) \sim 0.9 and the hierarchy of lifetimes
\tau(\Lambda_{b}) \simeq \tau(\Xi_{b}^{0}) < \tau(\Xi_{b}^{-}) <
\tau(\Omega_{b}) with lifetimes of \Xi_{b}^{-} and \Omega_{b} exceeding the
lifetime of \Lambda_{b} by 22% and 35%, respectively.Comment: Latex2e, 12 pages, 3 eps figures include
A novel chromosome segregation mechanism during female meiosis.
In a wide range of eukaryotes, chromosome segregation occurs through anaphase A, in which chromosomes move toward stationary spindle poles, anaphase B, in which chromosomes move at the same velocity as outwardly moving spindle poles, or both. In contrast, Caenorhabditis elegans female meiotic spindles initially shorten in the pole-to-pole axis such that spindle poles contact the outer kinetochore before the start of anaphase chromosome separation. Once the spindle pole-to-kinetochore contact has been made, the homologues of a 4-μm-long bivalent begin to separate. The spindle shortens an additional 0.5 μm until the chromosomes are embedded in the spindle poles. Chromosomes then separate at the same velocity as the spindle poles in an anaphase B-like movement. We conclude that the majority of meiotic chromosome movement is caused by shortening of the spindle to bring poles in contact with the chromosomes, followed by separation of chromosome-bound poles by outward sliding
On Security and Sparsity of Linear Classifiers for Adversarial Settings
Machine-learning techniques are widely used in security-related applications,
like spam and malware detection. However, in such settings, they have been
shown to be vulnerable to adversarial attacks, including the deliberate
manipulation of data at test time to evade detection. In this work, we focus on
the vulnerability of linear classifiers to evasion attacks. This can be
considered a relevant problem, as linear classifiers have been increasingly
used in embedded systems and mobile devices for their low processing time and
memory requirements. We exploit recent findings in robust optimization to
investigate the link between regularization and security of linear classifiers,
depending on the type of attack. We also analyze the relationship between the
sparsity of feature weights, which is desirable for reducing processing cost,
and the security of linear classifiers. We further propose a novel octagonal
regularizer that allows us to achieve a proper trade-off between them. Finally,
we empirically show how this regularizer can improve classifier security and
sparsity in real-world application examples including spam and malware
detection
Probing Transversity GPDs in Photo and Electroproduction of Two Vector Mesons
Electroproduction of two mesons well separated in rapidity allows the first
feasible selective access to chiral-odd transversity GPDs provided one of these
mesons is a transversely polarized vector meson rho_T.Comment: 3 pages, 5 figures, to be published in the proceedings of the
International Conference on the Structure and Interactions of the Photon
(Photon 2007) Paris, july 200
Scientific visualization in mineral and material processing
Journal ArticleScientific visualization is an ideal methodology for investigating complex phenomena that are characterized by large amounts of data. Furthermore, it is invaluable in the study of processes that evolve in time. Scientific visualization relies heavily on computer graphics, image processing and video technologies. Specific applications of scientific visualization in the minerals and materials processing fields that are considered in this paper include: 1) applied CT technology for multiphase materials and minerals, 2) time averaged density profiles in airsparged hydrocyclone (ASH) flotation and 3) dynamic motion analysis of ball mill grinding
Enhancing Sensitivity Classification with Semantic Features using Word Embeddings
Government documents must be reviewed to identify any sensitive information
they may contain, before they can be released to the public. However,
traditional paper-based sensitivity review processes are not practical for reviewing
born-digital documents. Therefore, there is a timely need for automatic sensitivity
classification techniques, to assist the digital sensitivity review process.
However, sensitivity is typically a product of the relations between combinations
of terms, such as who said what about whom, therefore, automatic sensitivity
classification is a difficult task. Vector representations of terms, such as word
embeddings, have been shown to be effective at encoding latent term features
that preserve semantic relations between terms, which can also be beneficial to
sensitivity classification. In this work, we present a thorough evaluation of the
effectiveness of semantic word embedding features, along with term and grammatical
features, for sensitivity classification. On a test collection of government
documents containing real sensitivities, we show that extending text classification
with semantic features and additional term n-grams results in significant improvements
in classification effectiveness, correctly classifying 9.99% more sensitive
documents compared to the text classification baseline
ATRA mechanically reprograms pancreatic stellate cells to suppress matrix remodelling and inhibit cancer cell invasion
Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a dismal survival rate. Persistent activation of pancreatic stellate cells (PSCs) can perturb the biomechanical homoeostasis of the tumour microenvironment to favour cancer cell invasion. Here we report that ATRA, an active metabolite of vitamin A, restores mechanical quiescence in PSCs via a mechanism involving a retinoic acid receptor beta (RAR-β)-dependent downregulation of actomyosin (MLC-2) contractility. We show that ATRA reduces the ability of PSCs to generate high traction forces and adapt to extracellular mechanical cues (mechanosensing), as well as suppresses force-mediated extracellular matrix remodelling to inhibit local cancer cell invasion in 3D organotypic models. Our findings implicate a RAR-β/MLC-2 pathway in peritumoural stromal remodelling and mechanosensory-driven activation of PSCs, and further suggest that mechanical reprogramming of PSCs with retinoic acid derivatives might be a viable alternative to stromal ablation strategies for the treatment of PDAC
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