Geoelectrical and electromagnetic methods applied to paleolimnological studies: Two examples from desiccated lakes in the Basin of Mexico

Paleolimnological studies require a broad understanding of the geometry and depth of the sedimentary fill of lake basins prior to coring campaigns. Seismic methods are routinely employed for the indirect characterization of lake-bottom sediments. However, the use of seismic methods might occasionally be limited due to surface conditions or poor seismic contrasts between the stratigraphic units, which lead to data quality that is too poor to provide sufficient information for the selection of drill sites. Sources of cultural noise are one of the main reasons why seismic methods fail in study areas near or within large cities, such as Mexico City. Under certain conditions, electrical and electromagnetic methods might be a suitable substitute or complement to seismic exploration, as they respond to different physical properties of the subsurface. To evaluate the applicability of such methods, here we present two recent case studies from the desiccated lakes Chalco and Xochimilco both located in urban areas within the Basin of Mexico where electrical resistivity tomography (ERT), transient electromagnetic (TEM) and magnetotelluric (MT) soundings were conducted for the characterization of lake basement and lacustrine sediments. In both examples, the results of the geophysical exploration contributed valuable stratigraphic information for the following drilling and core recovery, which highlights the potential of electrical and electromagnetic methods in paleolimnological studies

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

Meeting abstrac

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Modelling, simulation and performance evaluation of the IEEE 802.11e protocol with station mobility

In this article, we present a parameterized Colored Petri Net (CPN) model of the IEEE 802.11e protocol for wireless communications with mobile stations. CPNs provide a graphical model for the modeling and analysis of concurrent systems, which can be parameterized by the use of constants, and thus they allow us to create more flexible models. Our CPN model captures the protocol’s behavior, and the specific parameters used for the 802.11e protocol and the scenarios to be evaluated are captured by the CPN parameters. The model presented is flexible enough to cover full customization of traffic types, user mobility and collision avoidance protocols. In this model, there is an access point (AP) which is visible to all the stations, and we assume that due to physical restrictions, there are two range groups. All the stations in the same range group are visible to each other. The impact of mobility is then analyzed by studying a situation in which the stations move in a controlled way to the same range group. The simulation results demonstrate the impact on network performance for sensitive and insensitive traffic types, as well as the role of the RTS/CTS protocol in collision avoidance, especially when users are located in different regions. Specifically, we show how the performance improves in the different scenarios when the stations move to the same area, where they can see each other, and we also study the impact on the performance for each type of traffic

Orígenes y desarrollo

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Framingham risk score for prediction of cardiovascular diseases: a population-based study from southern Europe.

BackgroundThe question about what risk function should be used in primary prevention remains unanswered. The Framingham Study proposed a new algorithm based on three key ideas: use of the four risk factors with the most weight (cholesterol, blood pressure, diabetes and smoking), prediction of overall cardiovascular diseases and incorporating the concept of vascular age. The objective of this study was to apply this new function in a cohort of the general non Anglo-Saxon population, with a 10-year follow-up to determine its validity.MethodsThe cohort was studied in 1992-94 and again in 2004-06. The sample comprised 959 randomly-selected persons, aged 30-74 years, who were representative of the population of Albacete, Spain. At the first examination cycle, needed data for the new function were collected and at the second examination, data on all events were recorded during the follow-up period. Discrimination was studied with ROC curves. Comparisons of prediction models and reality in tertiles (Hosmer-Lemeshow) were performed, and the individual survival functions were calculated.ResultsThe mean risks for women and men, respectively, were 11.3% and 19.7% and the areas under the ROC curve were 0.789 (95%CI, 0.716-0.863) and 0.780 (95%CI, 0.713-0.847) (PConclusionsThe results support the proposal for "reclassification" of Framingham. This study, with a few exceptions, passed the test of discrimination and calibration in a random sample of the general population from southern Europe