Characterization of a Regional Aquifer System in the Maritimes Basin,Eastern Canada

A regional hydrogeological study was carried out in the Maritimes provinces, in one of the main aquifer systems in Canada. The study area covers a land surface of 10,500 km², of which 9,400 km² is over Carboniferous and younger rocks. The sedimentary fractured bedrock is composed of a sequence of discontinuous strata of highly variable hydraulic properties, and is overlain by a thin layer of glacial till (mostly 4 to 8 m). Depending on areas, 46 to 100% of the population relies on groundwater for water supply. Almost all residential wells are shallow (28 m on average) open holes that are cased only through the surficial sediments. This paper describes a regional hydrogeological investigation based on targeted fieldwork, the integration of a wide variety of existing multisource datasets and groundwater flow numerical modelling. The aim of this paper is to present the current state of understanding of the aquifer system in a representative area of the Maritimes Basin, along with the methodology used to characterize and analyze its distinct behaviour at the regional, local and point scales. This regional hydrogeological system contains confined and unconfined zones, and its aquifer lenticular strata extend only a few kilometers. Preferential groundwater recharge occurs where sandy tills are present. The estimated mean annual recharge rate to the bedrock aquifers ranges between 130 and 165 mm/year. Several geological formations of this Basin provide good aquifers, with hydraulic conductivity in the range of 5 × 10⁻⁶ to 10⁻⁴ m/s. Based on numerical flow modelling, faults were interpreted to play a key role in the regional flow. Pumping test results revealed that the aquifers can locally be very heterogeneous and anisotropic, but behave similarly to porous media. Work performed at the local scale indicated that most water-producing fractures generally have a sub-horizontal dip along a north-east (45°) strike.     

Lost in PubMed. Factors influencing the success of medical information retrieval

With the explosion of information available on the Web, finding specific medical information in an efficient way has become a considerable challenge. PubMed/MEDLINE offers an alternative to free-text searching on the web, allowing searchers to do a keyword-based search using Medical Subject Headings. However, finding relevant information within a limited time frame remains a difficult task. The current study is based on an error analysis of data from a retrieval experiment conducted at the nursing departments of two Belgian universities and a British university. We identified the main difficulties in query formulation and relevance judgment and compared the profiles of the best and worst performers in the test.For the analysis, a query collection was built from the queries submitted by our test participants. The queries in this collection are all aimed at finding the same specific information in PubMed, which allowed us to identify what exactly went wrong in the query formulation step. Another crucial aspect for efficient information retrieval is relevance judgment. Differences between potential and actual recall of each query offered indications of the extent to which participants overlooked relevant citations.The test participants were divided into “worst”, “average” and “best” performers based on the number of relevant citations they selected: zero, one or two and three or more, respectively. We tried to find out what the differences in background and in search behavior were between these three groups.     

The RADTRAN microwave surface emission models

The AFGL RADTRAN microwave atmospheric transmission/brightness temperature computer code has been enhanced by a surface emissivity modeling subpackage. This enhancement will provide realistic calculations of frequency-dependent polarized surface emissivity to support simulations of Earth-viewing microwave sensing systems. These models are appropriate for the frequency range 1-40 GHz. Two distinct modeling approaches have been applied: one based on wave theory for random discrete scatterers, and one based on radiative transfer theory for continuous random media. The former approach is used to model the ocean surface, various forms of sea ice, and snow over land, whereas the latter is used to treat soils and vegetation. Surface emissivity values obtained from these models as functions of polarization, frequency, and look angle are illustrated     

Optimal interpolation analysis of leaf area index using MODIS data

A simple data analysis technique for vegetation leaf area index (LAI) using Moderate Resolution Imaging Spectroradiometer (MODIS) data is presented. The objective is to generate LAI data that is appropriate for numerical weather prediction. A series of techniques and procedures which includes data quality control, time-series data smoothing, and simple data analysis is applied. The LAI analysis is an optimal combination of the MODIS observations and derived climatology, depending on their associated errors σ_o and σ_c. The “best estimate” LAI is derived from a simple three-point smoothing technique combined with a selection of maximum LAI (after data quality control) values to ensure a higher quality. The LAI climatology is a time smoothed mean value of the “best estimate” LAI during the years of 2002-2004. The observation error is obtained by comparing the MODIS observed LAI with the “best estimate” of the LAI, and the climatological error is obtained by comparing the “best estimate” of LAI with the climatological LAI value. The LAI analysis is the result of a weighting between these two errors. Demonstration of the method described in this paper is presented for the 15-km grid of Meteorological Service of Canada (MSC)'s regional version of the numerical weather prediction model. The final LAI analyses have a relatively smooth temporal evolution, which makes them more appropriate for environmental prediction than the original MODIS LAI observation data. They are also more realistic than the LAI data currently used operationally at the MSC which is based on land-cover databases.     

Establishment of rapid detection method of methamidophos in vegetables by surface enhanced Raman spectroscopy

Methamidophos (MAP) is a highly efficient and broad-spectrum organophosphate pesticide. In this study, a rapid method for detecting MAP in vegetables using surface enhanced Raman scattering (SERS) spectroscopy has been established. Density functional theory calculations were performed with Gaussian 03 at RB3LYP level and with the 6-311G (d) basis set. SERS, normal and theoretical Raman spectroscopy were compared to investigate the mechanism of Raman scattering enhancement. The SERS signal of MAP was improved in alkaline conditions with optimum scattering efficiency at pH of 13.46. Furthermore, MAP detection in vegetables by SERS method had a good linear relationship between 0.01 and 1,000?μg/mL. The concentration of MAP in vegetables was detected and chosen for recovery test with three levels: 4, 8, and 15?μg/mL. The results of three level tests were 86.7–96.6?% and their relative standard deviations were between 1.2 and 2.5?%, which shows the good repeatability of this method.