8,826 research outputs found
A Hierarchical Recurrent Encoder-Decoder For Generative Context-Aware Query Suggestion
Users may strive to formulate an adequate textual query for their information
need. Search engines assist the users by presenting query suggestions. To
preserve the original search intent, suggestions should be context-aware and
account for the previous queries issued by the user. Achieving context
awareness is challenging due to data sparsity. We present a probabilistic
suggestion model that is able to account for sequences of previous queries of
arbitrary lengths. Our novel hierarchical recurrent encoder-decoder
architecture allows the model to be sensitive to the order of queries in the
context while avoiding data sparsity. Additionally, our model can suggest for
rare, or long-tail, queries. The produced suggestions are synthetic and are
sampled one word at a time, using computationally cheap decoding techniques.
This is in contrast to current synthetic suggestion models relying upon machine
learning pipelines and hand-engineered feature sets. Results show that it
outperforms existing context-aware approaches in a next query prediction
setting. In addition to query suggestion, our model is general enough to be
used in a variety of other applications.Comment: To appear in Conference of Information Knowledge and Management
(CIKM) 201
Molecular structure and free energy landscape for electron transport in the decahaem cytochrome MtrF
Sensing and control of segmented mirrors with a pyramid wavefront sensor in the presence of spiders
The segmentation of the telescope pupil (by spiders & the segmented M4)
create areas of phase isolated by the width of the spiders on the wavefront
sensor (WFS), breaking the spatial continuity of the wavefront. The poor
sensitivity of the Pyramid WFS (PWFS) to differential piston leads to badly
seen and therefore uncontrollable differential pistons. In close loop
operation, differential pistons between segments will settle around integer
values of the average sensing wavelength. The differential pistons typically
range from one to ten times the sensing wavelength and vary rapidly over time,
leading to extremely poor performance. In addition, aberrations created by
atmospheric turbulence will contain large amounts of differential piston
between the segments. Removing piston contribution over each of the DM segments
leads to poor performance. In an attempt to reduce the impact of unwanted
differential pistons that are injected by the AO correction, we compare three
different approaches. We first limit ourselves to only use the information
measured by the PWFS, in particular by reducing the modulation. We show that
using this information sensibly is important but will not be sufficient. We
discuss possible ways of improvement by using prior information. A second
approach is based on phase closure of the DM commands and assumes the
continuity of the correction wavefront over the entire unsegmented pupil. The
last approach is based on the pair-wise slaving of edge actuators and shows the
best results. We compare the performance of these methods using realistic
end-to-end simulations. We find that pair-wise slaving leads to a small
increase of the total wavefront error, only adding between 20-45 nm RMS in
quadrature for seeing conditions between 0.45-0.85 arcsec. Finally, we discuss
the possibility of combining the different proposed solutions to increase
robustness.Comment: 12 pages, 15 figures, AO4ELT5 Proceedings, Adaptive Optics for
Extremely Large Telescopes 5, Conference Proceeding, Tenerife, Canary
Islands, Spain, June 25-30, 201
Project management success I-C-E model: a work in progress
Project management in software development has shown high rates of failure since the beginning of computation. Over the last years, several studies have sought and proposed solutions for this problem by focusing, for instance, on success critical aspects and evaluation criteria. Although these efforts have provided a significant evolution in how the work is done, project management success rates are in fact still well below the desirable values. This paper presents a work-inprogress based on an integrated approach to project management success and proposes a model that considers jointly the set of success influencers, project characteristics and evaluation criteria of success, from the initiation of a project until its closure
The ‘porin-cytochrome’ model for microbe-to-mineral electron transfer
Many species of bacteria can couple anaerobic growth to the respiratory reduction of insoluble minerals containing Fe(III) or Mn(III/IV). It has been suggested that in Shewanella species electrons cross the outer membrane to extracellular substrates via ‘porin–cytochrome’ electron transport modules. The molecular structure of an outer-membrane extracellular-facing deca-haem terminus for such a module has recently been resolved. It is debated how, once outside the cells, electrons are transferred from outer-membrane cytochromes to insoluble electron sinks. This may occur directly or by assemblies of cytochromes, perhaps functioning as ‘nanowires’, or via electron shuttles. Here we review recent work in this field and explore whether it allows for unification of the electron transport mechanisms supporting extracellular mineral respiration in Shewanella that may extend into other genera of Gram-negative bacteria
Temporal Stream Logic: Synthesis beyond the Bools
Reactive systems that operate in environments with complex data, such as
mobile apps or embedded controllers with many sensors, are difficult to
synthesize. Synthesis tools usually fail for such systems because the state
space resulting from the discretization of the data is too large. We introduce
TSL, a new temporal logic that separates control and data. We provide a
CEGAR-based synthesis approach for the construction of implementations that are
guaranteed to satisfy a TSL specification for all possible instantiations of
the data processing functions. TSL provides an attractive trade-off for
synthesis. On the one hand, synthesis from TSL, unlike synthesis from standard
temporal logics, is undecidable in general. On the other hand, however,
synthesis from TSL is scalable, because it is independent of the complexity of
the handled data. Among other benchmarks, we have successfully synthesized a
music player Android app and a controller for an autonomous vehicle in the Open
Race Car Simulator (TORCS.
Demographic profile and epidemiology of injury in Mthatha, South Africa
Objective: To determine the magnitude, socio-demographic and epidemiological characteristics of injury at a Provincial referral hospital.Methods: This review was conducted on all trauma patients admitted at the Mthatha Hospital Complex and Nelson Mandela Academic Hospital from the 1st January 1997 to the 31st December 2000.Results: The incident rate of injuries was 3.2% (n=2460/75,833 total admissions). Injured patients were mostly black (80%) and males (ratio: 5 men: 1 woman). Only 8.1% of injured patients were transported to hospital by ambulances. The leading causes of injuries were inter-personal violence accounting for 60% of cases, and motor vehicle accidents accounting for 19%; of them 38% were due to poor visibility, over speeding, and fatigue. The overall mortality was 33% (n=821) independently predicted by poverty (OR=8.2 95%CI 6-11.1; P40 years(OR=7.8 95%CI 7.7-12.1;P<0.0001).Conclusion: The burden of injury is a mass issue that warrants regional attention with quality of care and training.Keywords: Injuries, violence, poverty, mortality, South AfricaAfrican Health Sciences 2013; 13(4): 1144 - 114
Counting with DNA in metabarcoding studies: How should we convert sequence reads to dietary data?
Advances in DNA sequencing technology have revolutionized the field of molecular analysis of trophic interactions, and it is now possible to recover counts of food DNA sequences from a wide range of dietary samples. But what do these counts mean? To obtain an accurate estimate of a consumer's diet should we work strictly with data sets summarizing frequency of occurrence of different food taxa, or is it possible to use relative number of sequences? Both approaches are applied to obtain semi-quantitative diet summaries, but occurrence data are often promoted as a more conservative and reliable option due to taxa-specific biases in recovery of sequences. We explore representative dietary metabarcoding data sets and point out that diet summaries based on occurrence data often overestimate the importance of food consumed in small quantities (potentially including low-level contaminants) and are sensitive to the count threshold used to define an occurrence. Our simulations indicate that using relative read abundance (RRA) information often provides a more accurate view of population-level diet even with moderate recovery biases incorporated; however, RRA summaries are sensitive to recovery biases impacting common diet taxa. Both approaches are more accurate when the mean number of food taxa in samples is small. The ideas presented here highlight the need to consider all sources of bias and to justify the methods used to interpret count data in dietary metabarcoding studies. We encourage researchers to continue addressing methodological challenges and acknowledge unanswered questions to help spur future investigations in this rapidly developing area of research
Optical dispersive shock waves in defocusing colloidal media
The propagation of an optical dispersive shock wave, generated from a jump discontinuity in light intensity, in a defocusing colloidal medium is analysed. The equations governing nonlinear light propagation in a colloidal medium consist of a nonlinear Schrödinger equation for the beam and an algebraic equation for the medium response. In the limit of low light intensity, these equations reduce to a perturbed higher order nonlinear Schrödinger equation. Solutions for the leading and trailing edges of the colloidal dispersive shock wave are found using modulation theory. This is done for both the perturbed nonlinear Schrödinger equation and the full colloid equations for arbitrary light intensity. These results are compared with numerical solutions of the colloid equations
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