Outcrop Groundwater Prospecting, Drilling, and Well Construction in Hard Rocks in Semi-arid Regions

This chapter presents some recommendations for prospecting, drilling and well construction in hard rocks in semi-arid regions. Considering that these conditions are present in many countries where technology is not always available, the chapter concentrates on the most basic and simple methods to plan where best to drill and maximize success through the direct observation of rock types, weathering and fracturing. The advantage for the geologist and hydrogeologist in an arid or semi-arid environment is that vegetation is normally scarce and the weathering layer thin, allowing a direct view of the rock in circumstances impossible in other climate regions of the world. The close observation of the weathering material, and especially of the fracture network, mainly the fracture density, dip, extension and interconnection, can provide important information for a field hydrogeologist who can then plan the best place for drilling. The most appropriate drilling technique, if available in the area, is rotary percussion, also designated as down-the-hole drilling, with drilling rates that can achieve 100 m per day in normal circumstances. This allows a well to be constructed in about two days, essential in the case of disaster relief. Finally, some information is given about well construction, careful planning of the work, protection to preserve the water quality, avoiding problems of partial or total collapse of the hole during construction or of the well and after completion, and how to avoid direct contact between the surface or sub-surface waters with the aquifer along the walls of the well to protect the well and the aquifer against contamination

A visual processing advantage for young-adolescent deaf observers: Evidence from face and object matching tasks

It is unresolved whether the permanent auditory deprivation that deaf people experience leads to the enhanced visual processing of faces. The current study explored this question with a matching task in which observers searched for a target face among a concurrent lineup of ten faces. This was compared with a control task in which the same stimuli were presented upside down, to disrupt typical face processing, and an object matching task. A sample of young-adolescent deaf observers performed with higher accuracy than hearing controls across all of these tasks. These results clarify previous findings and provide evidence for a general visual processing advantage in deaf observers rather than a face-specific effect

Changes in Early Cortical Visual Processing Predict Enhanced Reactivity in Deaf Individuals

Individuals with profound deafness rely critically on vision to interact with their environment. Improvement of visual performance as a consequence of auditory deprivation is assumed to result from cross-modal changes occurring in late stages of visual processing. Here we measured reaction times and event-related potentials (ERPs) in profoundly deaf adults and hearing controls during a speeded visual detection task, to assess to what extent the enhanced reactivity of deaf individuals could reflect plastic changes in the early cortical processing of the stimulus. We found that deaf subjects were faster than hearing controls at detecting the visual targets, regardless of their location in the visual field (peripheral or peri-foveal). This behavioural facilitation was associated with ERP changes starting from the first detectable response in the striate cortex (C1 component) at about 80 ms after stimulus onset, and in the P1 complex (100–150 ms). In addition, we found that P1 peak amplitudes predicted the response times in deaf subjects, whereas in hearing individuals visual reactivity and ERP amplitudes correlated only at later stages of processing. These findings show that long-term auditory deprivation can profoundly alter visual processing from the earliest cortical stages. Furthermore, our results provide the first evidence of a co-variation between modified brain activity (cortical plasticity) and behavioural enhancement in this sensory-deprived population

Relevance of plasma fibrinogen estimation in obstetric complications.

We present a study of fibrinogen levels in 133 patients who were prone to develop disseminated intravascular coagulation as a result of an underlying complication of pregnancy such as abruptio placentae, pregnancy-induced hypertension, missed abortion, septic abortion, intrauterine fetal death, vesicular mole and amniotic fluid embolism. A high incidence of hypofibrinogenemia was found in cases of abruptio placentae (43.9%) and pregnancy-induced hypertension (25%). Hypofibrinogenemia occurred in 10% cases of intrauterine fetal death within 4 weeks of fetal demise. The use of this simple investigation makes possible the diagnosis of hemostatic failure and also helps to guide replacement therapy during the fibrinopenic state. There were 4 maternal deaths and 12 perinatal losses in this study

Practical aspects of applied optimised survey design for electrical resistivity tomography

The use of optimised resistivity tomography surveys to acquire field data imposes extra constraints on the design strategy beyond maximising the quality of the resulting tomographic image. In this paper, methods are presented to 1) minimise electrode polarisation effects; 2) make efficient use of parallel measurement channels; and 3) incorporate data noise estimates in the optimisation process. 1) A simulated annealing algorithm is used to rearrange the optimised measurement sequences to minimise polarisation errors. The method is developed using random survey designs, and is demonstrated to be effective for use with single and multi-channel optimised surveys. 2) An optimisation algorithm is developed to design surveys by successive addition of multi-channel groups of measurements rather than individual electrode configurations. The multi-channel surveys are shown to produce results nearly as close to optimal as equivalent single channel surveys, while reducing data collection times by an order of magnitude. 3) Random errors in the data are accounted for by weighting the electrode configurations in the optimisation process according to a simple error model incorporating background and voltage-dependent noise. The use of data weighting produces optimised surveys that are more robust in the presence of noise, while maintaining as much of the image resolution of the noise-free designs as possible. All the new methods described in this paper are demonstrated using both synthetic and real data, the latter having been measured on an active landslide using a permanently installed geoelectrical monitoring system