Document Retrieval on Repetitive Collections

Document retrieval aims at finding the most important documents where a pattern appears in a collection of strings. Traditional pattern-matching techniques yield brute-force document retrieval solutions, which has motivated the research on tailored indexes that offer near-optimal performance. However, an experimental study establishing which alternatives are actually better than brute force, and which perform best depending on the collection characteristics, has not been carried out. In this paper we address this shortcoming by exploring the relationship between the nature of the underlying collection and the performance of current methods. Via extensive experiments we show that established solutions are often beaten in practice by brute-force alternatives. We also design new methods that offer superior time/space trade-offs, particularly on repetitive collections.Comment: Accepted to ESA 2014. Implementation and experiments at http://www.cs.helsinki.fi/group/suds/rlcsa

From Theory to Practice: Plug and Play with Succinct Data Structures

Engineering efficient implementations of compact and succinct structures is a time-consuming and challenging task, since there is no standard library of easy-to- use, highly optimized, and composable components. One consequence is that measuring the practical impact of new theoretical proposals is a difficult task, since older base- line implementations may not rely on the same basic components, and reimplementing from scratch can be very time-consuming. In this paper we present a framework for experimentation with succinct data structures, providing a large set of configurable components, together with tests, benchmarks, and tools to analyze resource requirements. We demonstrate the functionality of the framework by recomposing succinct solutions for document retrieval.Comment: 10 pages, 4 figures, 3 table

Investigating thermal properties of gas-filled planetary regoliths using a thermal probe

We introduce a general purpose penetrator, fitted with a heater, for measuring temperature and thermal diffusivity. Due to its simplicity of deployment and operation the penetrator is well suited for remote deployment by spacecraft into a planetary regolith. Thermal measurements in planetary regoliths are required to determine the surface energy balance and to measure their thermal properties. If the regolith is on a planet with an atmosphere a good understanding of the role of convection is required to properly interpret the measurements. This could also help to identify the significant heat and mass exchange mechanisms between the regolith and the atmosphere. To understand the role of convection in our regolith analogues we use a network of temperature sensors placed in the target. In practical applications a penetrator will push material out of the way as it enters a target possible changing its thermal properties. To investigate this effect a custom built test rig, that precisely controls and monitors the motion of the penetrator, is used. The thermal diffusivity of limestone powder and sand is derived by fitting a numerical thermal model to the temperature measurements. Convection seems to play an important role in the transfer of heat in this case. Firstly a diffusion-convection model fits the laboratory data better than a diffusivity-only model. Also the diffusivity derived from a diffusivity-convection model was found to be in good agreement with diffusivity derived using other methods published in the literature. Thermal diffusivity measurements, inspection of the horizontal temperature profiles and visual observations suggests that limestone powder is compacted more readily than sand during entry of the penetrator into the target. For both regolith analogues the disturbance of material around the penetrator was determined to have an insignificant effect on the diffusivity measurements in this case

Propagation of thermal excitations in a cluster of vortices in superfluid 3He-B

We describe the first measurement on Andreev scattering of thermal excitations from a vortex configuration with known density, spatial extent, and orientations in 3He-B superfluid. The heat flow from a blackbody radiator in equilibrium rotation at constant angular velocity is measured with two quartz tuning fork oscillators. One oscillator creates a controllable density of excitations at 0.2Tc base temperature and the other records the thermal response. The results are compared to numerical calculations of ballistic propagation of thermal quasiparticles through a cluster of rectilinear vortices.Comment: 6 pages, 4 figure

ExoMars entry, descent and landing science

The entry, descent and landing of ExoMars offer a rare (once-per-mission) opportunity to perform in situ investigation of the martian environment over a wide altitude range. Entry, Descent and Landing System (EDLS) measurements can provide essential data for atmospheric scientific investigations. We intend to perform atmospheric science measurements by exploiting data from EDLS engineering sensors and exploiting their readings beyond the expected engineering information

Population genomic analyses of early-phase Atlantic Salmon (Salmo salar) domestication/captive breeding

Domestication can have adverse genetic consequences, which may reduce the fitness of individuals once released back into the wild. Many wild Atlantic salmon (Salmo salar L.) populations are threatened by anthropogenic influences, and they are supplemented with captively bred fish. The Atlantic salmon is also widely used in selective breeding programs to increase the mean trait values for desired phenotypic traits. We analyzed a genomewide set of SNPs in three domesticated Atlantic salmon strains and their wild conspecifics to identify loci underlying domestication. The genetic differentiation between domesticated strains and wild populations was low (FST < 0.03), and domesticated strains harbored similar levels of genetic diversity compared to their wild conspecifics. Only a few loci showed footprints of selection, and these loci were located in different linkage groups among the different wild population/hatchery strain comparisons. Simulated scenarios indicated that differentiation in quantitative trait loci exceeded that in neutral markers during the early phases of divergence only when the difference in the phenotypic optimum between populations was large. This study indicates that detecting selection using standard approaches in the early phases of domestication might be challenging unless selection is strong and the traits under selection show simple inheritance patterns

Integrated microfluidics for at-line culture monitoring of proteins and metabolites

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Reported prevalence of health conditions that affect drivers

Drivers' health and fitness are essential factors in order to predict performance outcomes and to promote road safety. It is a demonstrated fact that drivers with (physical and mental) health impairments or illnesses have more probabilities of being involved in traffic crashes and suffering (or causing) several injuries. The general objective of this study was to examine the prevalence of adverse health conditions that may affect Spanish drivers and its perceived impact on driving fitness. It was used a sample of 1200 Spanish drivers (666 men and 534 women). The only selection criteria were to be in possession of any type of driving license for vehicles other than motorcycles and to drive frequently. As a first result, 42% of the participants considered that sometimes they were not in good health conditions to drive and 1.8% considered it frequently. Furthermore, fatigue, alcohol, negative emotions, drowsiness, headaches, respiratory disease, and fever the most prevalent health conditions impairing driver's fitness. Statistical analysis revealed gender differences in reported health and fitness between male and female drivers. The main cause reported to avoid driving task was to suffer illnesses related to physical health (77.6% of drivers). Based on this study, it can be stated that the Administration should work together with the primary health care system in order to improve drivers' awareness on the risk of driving while suffering symptoms of any common physical or mental illness

Oscillatory Shear Flow-Induced Alignment of Lamellar Melts of Hydrogen-Bonded Comb Copolymer Supramolecules

In this work we present the orientational behavior of comb copolymer-like supramolecules P4VP(PDP)1.0, obtained by hydrogen bonding between poly(4-vinylpyridine) and pentadecylphenol, during large-amplitude oscillatory shear flow experiments over a broad range of frequencies (0.001-10 Hz). The alignment diagram, presenting the macroscopic alignment in T/TODT vs ω/ωc, contains three regions of parallel alignment separated by a region of perpendicular alignment. For our material, the order-disorder temperature TODT = 67 °C and ωc, the frequency above which the distortion of the chain conformation dominates the materials’ viscoelasticity, is around 0.1 Hz at 61 °C. For the first time flipping from a pure transverse alignment via biaxial transverse/perpendicular alignment to a perpendicular alignment as a function of the strain amplitude was found.