The geothermal zone of lake Assal (F.T.A.I.), geochemical and experimental studies

A geothermal model of Lake Assal region (F.T.A.I.) was derived from in situ observations and chemical and isotopic studies of hot and cold springs.According to this model, the lake water supply is provided mainly by sea water infiltrating from Ghoubbet el Kharab and, for a small part, by highly mineralized hot spring water of meteoric origin.Temperatures at depth were determined by means of various methods (among them a new one). These temperatures were found to range from 150 to 170°C.A geochemical experimental study of this model is under way.     

The family of lasers: a survey

Operating over a frequency range from audio to ultraviolet, the modern laser may be the most widely applicable active device at the disposal of today's engineer, enabling him to generate, amplify, modulate, transmit, and detect signals at frequencies more than 10000 times higher than was previously possible. Yet despite the almost unlimited potential for new and exotic applications offered by these shorter wavelengths, innovations have not lived up to their rave notices. Reasons for this relative inertia vary according to the application intended but, in general, it can be predicted that progress in the laser art will accelerate with the improvement of laser efficiency, development of auxiliary systems, and an updating of engineering thinking in terms of finding the ``problems' that lasers can solve. This first article in a series deals with the laser devices themselves?their advantages and their deficiencies?and will summarize what is happening in the laser art today. Other parts, scheduled to appear in future issues of IEEE SPECTRUM, will cover applications in materials processing, instrumentation and measurement, optical communication, medicine, holography, data processing and storage, displays, and safety.     

Grafcet revisited with a synchronous data-flow language

The Grafcet (or sequential function charts) language is a graphic language often offered in programmable logic control systems (PLC) used for industrial control-command applications. Modeling of Grafcet by the synchronous data-flow language Signal gives both explicit semantics, and the corresponding simulator. The translation into a graph of tasks makes it possible to execute the Grafcet program on any hardware architecture. Moreover, the use of Signal's proof tools allows verification of Grafcet properties, opening the field of critical applications to this very expressive language     

A combined ecological and epidemiologic investigation of metal exposures amongst Indigenous peoples near the Marlin Mine in Western Guatemala

In August 2009 a combined epidemiological and ecological pilot study was conducted to investigate allegations of human rights abuses in the form of exposures to toxic metals experienced by mine workers and Indigenous Mam Mayan near the Marlin Mine in Guatemala. In the human study there were no differences in blood and urine metals when comparing five mine workers with eighteen non-mine workers, and there were no discernible relationships between metal exposures and self-reported health measures in any study group. On the other hand, individuals residing closest to the mine had significantly higher levels of certain metals (urinary mercury, copper, arsenic, and zinc) when compared to those living further away. The levels of blood aluminum, manganese, and cobalt were elevated in comparison to established normal ranges in many individuals; however, there was no apparent relationship to proximity to the mine or occupation, and thus are of unclear significance. In the ecological study, several metals (aluminum, manganese, and cobalt) were found significantly elevated in the river water and sediment sites directly below the mine when compared to sites elsewhere. When the human and ecological results are combined, they suggest that exposures to certain metals may be elevated in sites near the mine but it is not clear if the current magnitude of these elevations poses a significant threat to health. The authors conclude that more robust studies are needed while parallel efforts to minimize the ecological and human impacts of mining proceed. This is critical particularly as the impact of the exposures found could be greatly magnified by expected increases in mining activity over time, synergistic toxicity between metals, and susceptibility for the young and those with pre-existing disease.