Uniqueness and Non-uniqueness in the Einstein Constraints

The conformal thin sandwich (CTS) equations are a set of four of the Einstein equations, which generalize the Laplace-Poisson equation of Newton's theory. We examine numerically solutions of the CTS equations describing perturbed Minkowski space, and find only one solution. However, we find {\em two} distinct solutions, one even containing a black hole, when the lapse is determined by a fifth elliptic equation through specification of the mean curvature. While the relationship of the two systems and their solutions is a fundamental property of general relativity, this fairly simple example of an elliptic system with non-unique solutions is also of broader interest.Comment: 4 pages, 4 figures; abstract and introduction rewritte

Strategies towards sustainability environmental from the local areas and the university

El propósito del presente trabajo es explorar un posible arreglo socioambiental pensado desde lo local que propicie el desarrollo sustentable, por medio del privilegio de la articulación de lo social (ciudadanía y educación) con el medio ambiente (capacidad de renovación). El planteamiento central es que ante un modelo social dominante que es insustentable, en el sentido que refuerza la desigualdad socioeconómica y el deterioro ambiental; se demanda pensar y actuar en formas novedosas e integradoras de lo social con la natural y del presente con el futuro para hacer posible sentar bases para un desarrollo sustentable de largo plazo. Para tal fin, se formula un arreglo que articule lo social (ciudadanía y educación) con el medio ambiente (capacidad de renovación) desde ámbitos locales, por medio de estrategias de acción gestionadas socialmente.The aim of this paper is to explore and present a suitable socio-environmental proposal conducive to sustainable development considering the local aspects emphasizing on the joint between the social (citizenship and education) with the environmental (renewability). The rationale of the study is that having a dominant unsustainable social model that reinforces socioeconomic inequality and environmental degradation, a need of developing more integrative and innovative ways to cope with the social and the natural as well as the present and the future is required in order to lay the foundations for a more long-term sustainable development. To that end, a suitable arrangement is presented in order to articulate the social aspects (citizenship and education) to the environmental ones (renewability) from a local perspective, managed through social action strategies.Fil: González López, Sergio. Universidad Autónoma del Estado de México. Instituto de Estudios sobre la Universidad.Fil: Salvador Benítez, J. Loreto. Universidad Autónoma del Estado de México. Instituto de Estudios sobre la Universidad.Fil: Arand a Sánchez, José María. Universidad Autónoma del Estado de México. Instituto de Estudios sobre la Universidad

2-Isopropoxyethanol – Determination of 2-isopropoxyethanol in workplace air using gas chromatography (GC-FID)

This analytical method is a validated measurement procedure for the determination of 2-isopropoxyethanol [109-59-1] in workplace air in a concentration range of one tenth up to twice the currently valid occupational exposure limit value (OELV) in Germany of 44 mg/m3. For sampling a defined volume of air is drawn through a sorbent tube (for thermal desorption) filled with Chromosorb 106. The flow rate is set to 5 ml/min and sampling is performed over 2 hours (which corresponds to a sampling volume of 600 ml). The samples to which cyclooctane is added as internal standard are thermally desorbed. The quantitative determination is based on a calibration function, whereby the 2-isopropoxyethanol concentration of the calibration standard is plotted against the intensities, calculated over the internal cyclooctane standard. The limit of quantification is 4.48 mg/m3 based on an air sample volume of 600 ml. The mean recovery is 92% and the expanded uncertainty for the validation range of 4.62 to 83.08 mg/m3 is 28.4

Glyphosate – Determination of glyphosate and AMPA in urine by GC-MS/MS

The working group “Analyses in Biological Materials” of the Permanent Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area developed and verified the presented biomonitoring method. Glyphosate (N-phosphonomethylglycine) is a synthetic phosphonic acid derivative which has been used as a broad spectrum herbicide since 1974. Its only known metabolite is aminomethylphosphonic acid (AMPA). Exposure in occupational settings is predominantly due to inhalation and dermal contact with glyphosate. The general population is exposed to glyphosate and AMPA via both dietary (plant and animal products) and environmental (soils, surface water, and groundwater) exposure. The aim of this work was to develop a selective method for the determination of glyphosate and AMPA in urine. The method has been comprehensively validated, and the reliability data have been confirmed by replication and verification of the procedure in a second, independent laboratory. The analytes are directly derivatised in the dried urine sample with trifluoroacetic anhydride and trifluoroethanol without an initial extraction step. Calibration is performed using aqueous calibration standards processed analogously to the samples. As internal standards, glyphosate-d2 and 13C,15N-AMPA are added to the urine samples and calibration standards. The derivatives are measured after capillary gas-chromatographic separation with tandem mass-spectrometric detection (GC-MS/MS) using negative chemical ionisation (NCI). The good precision and accuracy data show that the method provides reliable and accurate analytical results. The method is both selective and sensitive, and the quantitation limit of 0.1 μg/l urine for glyphosate and AMPA is sufficient to determine occupational exposure as well as higher background levels in the general populatio