Shallow submarine and subaerial, low-enthalpy hydrothermal manifestations in Punta Banda, Baja California, Mexico: Geophysical and geochemical characterization

The low-enthalpy geothermal system at Punta Banda (NW Baja California Peninsula, Mexico) has been studied because it might provide heat to future desalination plants in the city of Ensenada. Utilization of subaerial, intertidal and submarine hot springs is evaluated based on geochemical and geophysical data. The results of the geochemical studies show that the geothermal fluids have a major meteoric water component because seawater is not present at the subaerial springs and hot wells. The highest estimated reservoir temperature (140 °C) calculated using a silica geothermometer corresponds to the Agua Caliente intertidal manifestation, a promising area also identified by geophysics. Geothermometric calculations applied to the computed composition of the thermal end member yield a reservoir temperature of 137 °C. Cl/B ratios indicate that the thermal fluids discharged by the intertidal vents and subaerial springs are similar, but they differ from those of submarine vents. Geoelectrical models depict an anomalous conductive trend from the La Jolla well to the Agua Caliente manifestation, suggesting the presence of a fault that allows upflow of hot water from depth. Lastly, integration of geochemical and geophysical data identified the best site for future exploration drilling at Punta Banda.     

Integration of absorption cooling systems into micro gas turbine trigeneration systems using biogas: Case study of a sewage treatment plant

Absorption chillers can help to increase the performance of biogas-driven micro gas turbine (MGT) cogeneration plants. In this paper we analyse various integrated configurations of several types of commercially available absorption cooling chillers and MGT cogeneration systems driven by biogas. MGTs are fuelled with biogas and their waste heat is used to drive absorption chillers and other thermal energy users. The chillers considered in this study include single- and double-effect water/LiBr and ammonia/water chillers. The exhaust gas from the MGT can be used directly to drive the chiller or indirectly to produce hot water to drive the chiller. In this paper we conduct a case study for an existing sewage treatment plant. Chilled water is used to reduce humidity in the biogas pre-treatment process and cool the combustion air of the MGT. We identify the most interesting integrated configurations for trigeneration systems that use biogas and micro gas turbines. We analyse these configurations and compare them with conventional configurations using operational data from an existing sewage treatment plant. The best configurations are those that completely replace the existing system with a trigeneration plant that uses all the available biogas and additional natural gas to completely meet the heating demands of the sewage treatment plant.     

Outlier exploration and diagnostic classification of a multi-centre H-MRS brain tumour database

Non-invasive techniques such as magnetic resonance spectroscopy (MRS) are often required for assisting the diagnosis of tumours. Radiologists are not always accustomed to make sense of the biochemical information provided by MRS and they may benefit from computer-based support in their decision making. The high dimensionality of the MR spectra obscures atypical aspects of the data that may jeopardize their classification. In this study, we describe a method to overcome this problem that combines nonlinear dimensionality reduction, outlier detection, and expert opinion. MR spectra subsequently undergo a feature selection process followed by classification. The impact of outlier removal on classification performance is assessed.     

Simultaneous quantitative analysis of anionic, cationic, and nonionic surfactants in water by electrospray ionization mass spectrometry with flow injection analysis

A rapid method is described for the quantitative analysis of anionic, cationic, and nonionic surfactants in water samples by flow injection analysis coupled to electrospray ionization mass spectrometry (FIA/ESI-MS). All surfactants were isolated by liquid-liquid extraction and quantified using labeled triethoxylated nonylphenol ([13C6]-NP3EO) and sodium dibutylnaphthalenesulfonate as internal standards. FIA/ESI-MS was performed by alternating both positive and negative ionization modes, which allows simultaneous analysis of most common surfactants in a short time. Quality parameters of the method, such as linear range, repeatability, reproducibility, and limits of detection were studied. This method was applied to the analysis of wastewater treatment plant effluents from Catalonia (NE Spain).     

Pulmonary embolism in patients using estrogen-progestagen contraceptives

OBJECTIVES: The risk of thromboembolism in patients taking estrogen-progestagen oral contraceptive drugs has apparently increased since the introduction of third-generation progestagens (desogestrel, gestodene). We examined the clinical features, risk factors and outcome of pulmonary embolism in this context. PATIENTS AND METHODS: We reviewed 11 cases of thromboembolism in patients on oral contraception and hospitalized in emergency situations in 1995 and 1996 for pulmonary embolism in order to determine the gravity of the thromboembolic event, risk factors and type of drug used. RESULTS: Early clinical signs had preceded the onset of embolism by 2 to 164 days. PaO2 was below 70 mmHg in 4 patients. Diagnosis was achieved with pulmonary scintigraphy (11 cases), spiral CT (3 cases) and angiopneumography (2 cases). Duplex Doppler visualized the phlebitis in 7 patients. Given heparin (with fibrinolysis in 3 cases) then anti-vitamin K, and after withdrawal of the oral contraceptive, outcome was favorable in all cases. There were no recurrences. The nature of the oral contraceptive varied. Five patients were taking third-generation progestagens. In two cases, embolism had occurred following a change from a second-generation to a third-generation progestagen. Family history of phlebitis and/or abnormal laboratory findings were observed in 6 patients: resistance to activated protein C (2 patients), protein C deficiency (2 patients), anticardiolipin (2 patients) and low-titre antinuclear antibodies (2 patients). CONCLUSION: Pulmonary embolism in patients on oral contraceptives persists despite changes in the hormone content of the drugs. Diagnosis is often delayed. Family history of thrombosis or biological risk factors are often found.     

A Negotiation Meta Strategy Combining Trade-off and Concession Moves

In this paper we present a meta strategy that combines two negotiation tactics. The first one based on concessions, and the second one, a trade-off tactic. The goal of this work is to demonstrate by experimental analysis that the combination of different negotiation tactics allows agents to improve the negotiation process and as a result, to obtain more satisfactory agreements. The scenario proposed is based on two agents, a buyer and a seller, which negotiate over four issues. The paper presents the results and analysis of the meta strategy’s behaviour.     

Potential Environmental Applications of Pure Zeolitic Material Synthesized from Fly Ash

A pure 4A∕X (60∕40) zeolite product was synthesized from silica extracts of the Meirama fly ash in northwestern Spain. A high cation-exchange capacity (4.7 meq∕g) was obtained for the zeolitic material. The potential application of this coal fly ash conversion product for decontamination of high heavy metal waters was evaluated using three high heavy metal waters from acid mine drainage around the pyrite Huelva belt. The results were compared with those obtained with an equivalent pure commercial synthetic zeolite. A considerable reduction in the heavy metal content was attained (Zn from 174 to <0.1 mg∕L, Cu from 36 to 0.1 mg∕L, Fe from 444 to 0.8 mg∕L, Mn from 74 to <0.1 mg∕L, Pb from 1.5 to <0.1 mg∕L, and Cd from 0.4 to <0.1 mg∕L), even in high Ca and Fe waters using zeolite doses from 5 to 30 mg∕L. Both precipitation and cation-exchange processes accounted for the reduction in the pollutant concentration in the treated waters. Leachable hazardous elements from coal fly ash, such as Mo, B, As, V, and Cr, were not fixed in the synthesis of pure zeolites from the silica extracts. Consequently, they did not restrict the potential applications of this material as an ion exchanger, unlike the zeolitic material obtained from fly ash by direct alkaline conversion.