10,206 research outputs found
Long-tail Relation Extraction via Knowledge Graph Embeddings and Graph Convolution Networks
We propose a distance supervised relation extraction approach for
long-tailed, imbalanced data which is prevalent in real-world settings. Here,
the challenge is to learn accurate "few-shot" models for classes existing at
the tail of the class distribution, for which little data is available.
Inspired by the rich semantic correlations between classes at the long tail and
those at the head, we take advantage of the knowledge from data-rich classes at
the head of the distribution to boost the performance of the data-poor classes
at the tail. First, we propose to leverage implicit relational knowledge among
class labels from knowledge graph embeddings and learn explicit relational
knowledge using graph convolution networks. Second, we integrate that
relational knowledge into relation extraction model by coarse-to-fine
knowledge-aware attention mechanism. We demonstrate our results for a
large-scale benchmark dataset which show that our approach significantly
outperforms other baselines, especially for long-tail relations.Comment: To be published in NAACL 201
How bacterial cells and colonies move on solid substrates
Many bacteria rely on active cell appendages, such as type IV pili, to move
over substrates and interact with neighboring cells. Here, we study the motion
of individual cells and bacterial colonies, mediated by the collective
interactions of multiple pili. It was shown experimentally that the substrate
motility of Neisseria gonorrhoeae cells can be described as a persistent random
walk with a persistence length that exceeds the mean pili length. Moreover, the
persistence length increases for a higher number of pili per cell. With the
help of a simple, tractable stochastic model, we test whether a tug-of-war
without directional memory can explain the persistent motion of single
Neisseria gonorrhoeae cells. While the persistent motion of single cells indeed
emerges naturally in the model, a tug-of-war alone is not capable of explaining
the motility of microcolonies, which becomes weaker with increasing colony
size. We suggest sliding friction between the microcolonies and the substrate
as the missing ingredient. While such friction almost does not affect the
general mechanism of single cell motility, it has a strong effect on colony
motility. We validate the theoretical predictions by using a three-dimensional
computational model that includes explicit details of the pili dynamics, force
generation and geometry of cells.Comment: 25 pages, 17 figure
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Modeling Virus Transport and Removal during Storage and Recovery in Heterogeneous Aquifers
A quantitative understanding of virus removal during aquifer storage and recovery (ASR) in physically and geochemically heterogeneous aquifers is needed to accurately assess human health risks from viral infections. A two-dimensional axisymmetric numerical model incorporating processes of virus attachment, detachment, and inactivation in aqueous and solid phases was developed to systematically evaluate the virus removal performance of ASR schemes. Physical heterogeneity was considered as either layered or randomly distributed hydraulic conductivities (with selected variance and horizontal correlation length). Geochemical heterogeneity in the aquifer was accounted for using Colloid Filtration Theory to predict the spatial distribution of attachment rate coefficient. Simulation results demonstrate that the combined effects of aquifer physical heterogeneity and spatial variability of attachment rate resulted in higher virus concentrations in the recovered water at the ASR well (i.e. reduced virus removal). While the sticking efficiency of viruses to aquifer sediments was found to significantly influence virus concentration in the recovered water, the solid phase inactivation under realistic field conditions combined with the duration of storage phase had a predominant influence on the overall virus removal. The relative importance of physical heterogeneity increased under physicochemical conditions that reduced virus removal (e.g. lower value of sticking efficiency or solid phase inactivation rate). This study provides valuable insight on site selection of ASR projects and an approach to optimize ASR operational parameters (e.g. storage time) for virus removal and to minimize costs associated with post-recovery treatment
HIJING 1.0: A Monte Carlo Program for Parton and Particle Production in High Energy Hadronic and Nuclear Collisions
Based on QCD-inspired models for multiple jets production, we developed a
Monte Carlo program to study jet and the associated particle production in high
energy , and collisions. The physics behind the program which
includes multiple minijet production, soft excitation, nuclear shadowing of
parton distribution functions and jet interaction in dense matter is briefly
discussed. A detailed description of the program and instructions on how to use
it are given.Comment: 38 pages in LaTex, published in Comp. Phys. Comm. 83, 307 (1994)
Dendritic Actin Filament Nucleation Causes Traveling Waves and Patches
The polymerization of actin via branching at a cell membrane containing
nucleation-promoting factors is simulated using a stochastic-growth
methodology. The polymerized-actin distribution displays three types of
behavior: a) traveling waves, b) moving patches, and c) random fluctuations.
Increasing actin concentration causes a transition from patches to waves. The
waves and patches move by a treadmilling mechanism which does not require
myosin II. The effects of downregulation of key proteins on actin wave behavior
are evaluated.Comment: 10 pages, 4 figure
PADS: Practical Attestation for Highly Dynamic Swarm Topologies
Remote attestation protocols are widely used to detect device configuration
(e.g., software and/or data) compromise in Internet of Things (IoT) scenarios.
Unfortunately, the performances of such protocols are unsatisfactory when
dealing with thousands of smart devices. Recently, researchers are focusing on
addressing this limitation. The approach is to run attestation in a collective
way, with the goal of reducing computation and communication. Despite these
advances, current solutions for attestation are still unsatisfactory because of
their complex management and strict assumptions concerning the topology (e.g.,
being time invariant or maintaining a fixed topology). In this paper, we
propose PADS, a secure, efficient, and practical protocol for attesting
potentially large networks of smart devices with unstructured or dynamic
topologies. PADS builds upon the recent concept of non-interactive attestation,
by reducing the collective attestation problem into a minimum consensus one. We
compare PADS with a state-of-the art collective attestation protocol and
validate it by using realistic simulations that show practicality and
efficiency. The results confirm the suitability of PADS for low-end devices,
and highly unstructured networks.Comment: Submitted to ESORICS 201
Sparse Attentive Backtracking: Temporal CreditAssignment Through Reminding
Learning long-term dependencies in extended temporal sequences requires
credit assignment to events far back in the past. The most common method for
training recurrent neural networks, back-propagation through time (BPTT),
requires credit information to be propagated backwards through every single
step of the forward computation, potentially over thousands or millions of time
steps. This becomes computationally expensive or even infeasible when used with
long sequences. Importantly, biological brains are unlikely to perform such
detailed reverse replay over very long sequences of internal states (consider
days, months, or years.) However, humans are often reminded of past memories or
mental states which are associated with the current mental state. We consider
the hypothesis that such memory associations between past and present could be
used for credit assignment through arbitrarily long sequences, propagating the
credit assigned to the current state to the associated past state. Based on
this principle, we study a novel algorithm which only back-propagates through a
few of these temporal skip connections, realized by a learned attention
mechanism that associates current states with relevant past states. We
demonstrate in experiments that our method matches or outperforms regular BPTT
and truncated BPTT in tasks involving particularly long-term dependencies, but
without requiring the biologically implausible backward replay through the
whole history of states. Additionally, we demonstrate that the proposed method
transfers to longer sequences significantly better than LSTMs trained with BPTT
and LSTMs trained with full self-attention.Comment: To appear as a Spotlight presentation at NIPS 201
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