McGill University

About: McGill University is a education organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 72688 authors who have published 162565 publications receiving 6966523 citations. The organization is also known as: Royal institution of advanced learning & University of McGill College.

Respiration rates in bacteria exceed phytoplankton production in unproductive aquatic systems

Abstract: PLANKTONIC bacteria are a fundamental component of the organic carbon cycle in aquatic systems1. Organic carbon consumption by planktonic bacteria is the sum of bacterial production (BP) and bacterial respiration (BR). It is now estimated that 30–60% of phytoplankton production (the amount of inorganic carbon fixed by phytoplankton photosynthesis, corrected for phytoplankton respiration) in marine and freshwater systems is processed by bacteria1–3. These estimates of carbon flow through bacteria are conservative, however, because losses due to bacterial respiration are seldom directly measured4,5. We report here that bacterial respiration is generally high, and tends to exceed phytoplankton net production in unproductive systems (less than 70 to 120 μg carbon per litre per day). A large proportion of the world's aquatic systems have phytoplankton productivities below this value6. Bacterial growth efficiency (BGE) is the result of BP and BR[BGE = BP/(BR + BP)]. Comparisons of our models of bacterial respiration with published models of bacterial secondary production1,7 show that bacterial growth efficiency must range from less than 10% to 25% in most freshwater and marine systems, well below the values commonly assumed in many current ecological models1,2,8,9. The imbalance between bacterial respiration and phytoplankton production suggests that in unproductive aquatic systems, the biological system is a net source of CO2.

Statistical practice in high-throughput screening data analysis

Abstract: High-throughput screening is an early critical step in drug discovery. Its aim is to screen a large number of diverse chemical compounds to identify candidate 'hits' rapidly and accurately. Few statistical tools are currently available, however, to detect quality hits with a high degree of confidence. We examine statistical aspects of data preprocessing and hit identification for primary screens. We focus on concerns related to positional effects of wells within plates, choice of hit threshold and the importance of minimizing false-positive and false-negative rates. We argue that replicate measurements are needed to verify assumptions of current methods and to suggest data analysis strategies when assumptions are not met. The integration of replicates with robust statistical methods in primary screens will facilitate the discovery of reliable hits, ultimately improving the sensitivity and specificity of the screening process.

The supplementary motor area of the cerebral cortex; a clinical and experimental study.

Abstract: JUST IN front of the motor area of the cerebral cortex of man there is a supplementary representation of movements. This supplementary area is rather well circumscribed and is situated largely within the longitudinal interhemispheral fissure (Fig. 1). During the past several years we have seen a number of patients whose difficulties have necessitated surgical exploration and cortical stimulation within the longitudinal fissure. The findings cast new light upon the problem of cortical representation of motor and sensory function. This paper is an analysis of our observations on the properties of the superior and mesial intermediate precentral cortex in man. The results of local electrical stimulation and the patterns of focal seizures due to discharge in the area are presented, and an attempt is made to interpret the findings in terms of function. In addition, the results of an experimental approach to the analogous area in monkeys is reported. HISTORICAL