University of Waterloo

About: University of Waterloo is a education organization based out in Waterloo, Ontario, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 36093 authors who have published 93906 publications receiving 2948139 citations. The organization is also known as: UW & uwaterloo.

A survey of top-k query processing techniques in relational database systems

Abstract: Efficient processing of top-k queries is a crucial requirement in many interactive environments that involve massive amounts of data. In particular, efficient top-k processing in domains such as the Web, multimedia search, and distributed systems has shown a great impact on performance. In this survey, we describe and classify top-k processing techniques in relational databases. We discuss different design dimensions in the current techniques including query models, data access methods, implementation levels, data and query certainty, and supported scoring functions. We show the implications of each dimension on the design of the underlying techniques. We also discuss top-k queries in XML domain, and show their connections to relational approaches.

Supernova constraints and systematic uncertainties from the first three years of the supernova legacy survey

Abstract: We combine high redshift Type Ia supernovae from the first 3 years of the Supernova Legacy Survey (SNLS) with other supernova (SN) samples, primarily at lower redshifts, to form a high-quality joint sample of 472 SNe (123 low-$z$, 93 SDSS, 242 SNLS, and 14 {\it Hubble Space Telescope}). SN data alone require cosmic acceleration at >99.9% confidence, including systematic effects. For the dark energy equation of state parameter (assumed constant out to at least $z=1.4$) in a flat universe, we find $w = -0.91^{+0.16}_{-0.20}(\mathrm{stat}) ^{+0.07}_{-0.14} (\mathrm{sys})$ from SNe only, consistent with a cosmological constant. Our fits include a correction for the recently discovered relationship between host-galaxy mass and SN absolute brightness. We pay particular attention to systematic uncertainties, characterizing them using a systematics covariance matrix that incorporates the redshift dependence of these effects, as well as the shape-luminosity and color-luminosity relationships. Unlike previous work, we include the effects of systematic terms on the empirical light-curve models. The total systematic uncertainty is dominated by calibration terms. We describe how the systematic uncertainties can be reduced with soon to be available improved nearby and intermediate-redshift samples, particularly those calibrated onto USNO/SDSS-like systems.

GLIM Criteria for the Diagnosis of Malnutrition: A Consensus Report From the Global Clinical Nutrition Community

Abstract: Summary Rationale This initiative is focused on building a global consensus around core diagnostic criteria for malnutrition in adults in clinical settings Methods In January 2016, the Global Leadership Initiative on Malnutrition (GLIM) was convened by several of the major global clinical nutrition societies GLIM appointed a core leadership committee and a supporting working group with representatives bringing additional global diversity and expertise Empirical consensus was reached through a series of face-to-face meetings, telephone conferences, and e-mail communications Results A two-step approach for the malnutrition diagnosis was selected, ie, first screening to identify “at risk” status by the use of any validated screening tool, and second, assessment for diagnosis and grading the severity of malnutrition The malnutrition criteria for consideration were retrieved from existing approaches for screening and assessment Potential criteria were subjected to a ballot among the GLIM core and supporting working group members The top five ranked criteria included three phenotypic criteria (non-volitional weight loss, low body mass index, and reduced muscle mass) and two etiologic criteria (reduced food intake or assimilation, and inflammation or disease burden) To diagnose malnutrition at least one phenotypic criterion and one etiologic criterion should be present Phenotypic metrics for grading severity as Stage 1 (moderate) and Stage 2 (severe) malnutrition are proposed It is recommended that the etiologic criteria be used to guide intervention and anticipated outcomes The recommended approach supports classification of malnutrition into four etiology-related diagnosis categories Conclusion A consensus scheme for diagnosing malnutrition in adults in clinical settings on a global scale is proposed Next steps are to secure further collaboration and endorsements from leading nutrition professional societies, to identify overlaps with syndromes like cachexia and sarcopenia, and to promote dissemination, validation studies, and feedback The diagnostic construct should be re-considered every 3–5 years

How does water get through roots

Abstract: uptake of water. On the contrary, at low rates of transpiration such as during the night or during stress conOn the basis of recent results with young primary ditions (drought, high salinity, nutrient deprivation), maize roots, a model is proposed for the movement of the apoplastic path will be less used and the hydraulic water across roots. It is shown how the complex, ‘com- resistance will be high. The role of water channels posite anatomical structure’ of roots results in a ‘com- (aquaporins) in the transcellular path is in the fine posite transport’ of both water and solutes. Parallel adjustment of water flow or in the regulation of uptake apoplastic, symplastic and transcellular pathways play in older, suberized parts of plant roots lacking a suban important role during the passage of water across stantial apoplastic component. The composite transthe different tissues. These are arranged in series port model explains how plants are designed to within the root cylinder (epidermis, exodermis, central optimize water uptake according to demands from the cortex, endodermis, pericycle stelar parenchyma, and shoot and how external factors may influence water tracheary elements). The contribution of these struc- passage across roots. tures to the root’s overall radial hydraulic resistance is examined. It is shown that as soon as early metaxy- Key words: Composite transport model, endodermis, exolem vessels mature, the axial (longitudinal) hydraulic dermis, hydraulic conductivity, reflection coefficient, root, resistance within the xylem is usually not rate-limiting. water, water channels. According to the model, there is a rapid exchange of water between parallel radial pathways because, in contrast to solutes such as nutrient ions, water per- Introduction meates cell membranes readily. The roles of apoplastic One of the essential functions of roots is to supply the barriers (Casparian bands and suberin lamellae) in the shoot with water from the soil. The process of water root’s endo- and exodermis are discussed. The model