Electric properties of granitic rocks

The objective of this work is to clarify the role of water content on the charge trans- port mechanisms of different granitic rocks. The mineralogical content of the rocks will also be taken into account. From the electrical point of view these materials are rather insulating porous media where charge injection creates different phenomena like build-up charges, space charge limited currents, surface effects and other behav- iors that resemble much a variety of oxides, like AlO

Isotopic data from the Pomarinho enclave swarm (SW Iberian Chain)

Mafic microgranular enclaves are a common feature of calc-alkaline granitoids (e.g. tonalites and granodiorites) in active continental margins and collisional orogens. They correspond to dark-coloured globules that, although widespread throughout the host rock, usually constitute only a small proportion of the whole volume of the intrusion. When the enclaves occur strongly concentrated in a restricted area, they form an enclave swarm (e.g. Tobish et al. 1997). At Pomarinho, the Granialpa quarry is a privileged exposure of a cluster of dark igneous enclaves that has been targeted for geochemical and geophysical studies (GeoRadar and AMS). The Pomarinho swarm is located in the SW edge of Évora granitoid (Carvalhosa, 1983), in the Portuguese sector of the Ossa-Morena Zone (Iberian Variscides). The enclaves have tonalitic and granodioritic compositions, whereas the host correspond to a very homogeneous light-coloured granodiorite. Preliminary geochemical information, based on major and trace elements (Moita et al., 2011), suggests that the enclaves and the host rock are probably derived from co-genetic magmas. Rb-Sr isotope data now obtained in four enclaves and three host-rock samples yield an isochron corresponding to 335±14Ma (MSWD=0.96), which fits into the spectrum of ages of the Variscan granitoids in the region. Additionally, the homogeneity of both 87Sr/86Sr335 (0.704758 to 0.705133) and εNd335 (-0.10 to 1.13) values corroborates the hypothesis of derivation of the enclaves and the host granodiorite from a common primitive melt through magmatic differentiation. Low 87Sr/86Sr335 and high εNd335 values suggest that ultimately the parental melt is related to a mantle source, with no or only small contribution of metasedimentary crustal materials

Geochemical signature of the Pomarinho enclave swarm (Ossa-Morena Zone, Portugal)

The enclave swarm of Pomarinho is located in the SW edge of Évora granitoid (Carvalhosa, 1983), in the SW sector of the Ossa-Morena Zone (Iberian Variscides). The Granialpa quarry constitutes a privileged exposure of that swarm and, therefore, it was used to collect samples for AMS, petrographic and geochemical studies. The dominant rock in the quarry is a medium-grained granodiorite, composed of plagioclase, quartz, alkali feldspar and biotite. This granodiorite displays a weak N-S planar anisotropy, de-fined by the arrangement of ferromagnesian minerals (mainly biotite). Dark-colored and fine-grained enclaves, that do not exceed 1% volume of the host rock, can be observed scattered throughout the quarry. However, in the NW part of the quarry, there is a cluster of enclaves which, locally, corre-spond to 40-50% of the volume of the host rock. These enclaves exhibit a significant variability in modal composition and texture; therefore, they constitute a heterogeneous swarm, according to Tobish et al. (1997). The enclaves correspond to tonalites and granodiorites, with either equi-granular or porphyritic textures. Their modal compositions comprise essentially the same minerals found in the host granitoid; the major differences are the higher abundances of biotite and plagioclase and the occurrence of small amounts of hornblende, in the enclaves. AMS measurements on both the enclaves and the host rock are very consistent and show that magnetic lineations (K1) have a N-S trend and a plunge of 36º to the South (Moita et al., 2010). Geochemically, the host granodiorite is very homogeneous considering most of the major elements. It is slightly peraluminous (A/CNK~1.03), corresponding to an I-type granite (White & Chapell, 1977). Regarding trace elements, this granodiorite exhibits negative Nb-Ta anomalies [(Th/Nb)N: 8.59-12.08; (La/Ta)N: 1.73-2.18], slightly LREE-enriched patterns [(La/Lu)N: 12.08-16.43] and negative Eu anomalies (EuN/EuN*: 0.73-0.81). The enclaves may be divided into two groups. The first comprises tonalites with SiO2 from 63% to 65%, MgO from 2.2% to 2.4%, Fe2O3t from 5.1% to 5.8%, CaO from 4.1% to 4.8% and TiO2 from 0.7% to 0.9%. Their A/CNK ratios lie in the range 0.98-1.03 and, therefore, they may be considered metaluminous to weakly peraluminous. The trace element geochemistry, similarly to the host, is characterized by the negative Nb-Ta anomalies [(Th/Nb)N: 4.45-6.86; (La/Ta)N: 2.02-2.65] and the slight enrichment in LREE [(La/Lu)N:9.12-11.38]. The second enclave group, with granodioritic compositions, is always slightly peraluminous (A/CNK ~ 1.05), and has higher SiO2 and lower MgO, Fe2O3, CaO and TiO2 values compared to the tonalitic enclaves. Compared to the host rock, the granodioritic enclaves have higher CaO and Na2O and lower K2O contents. The multi-element patterns of the second enclave group also show negative Nb-Ta anomalies [(Th/Nb)N: 9.55 and 10.88; (La/Ta)N: 1.35 and 1,58] and a small LREE enrichment [(La/Lu)N: 9.48 and 12.86]. This preliminary geochemical information suggests that the enclaves and the host rock are probably derived of co-genetic magmas. In such a picture, the tonalitic enclaves and the host granodiorite should represent different degrees of fractionation from the same parental magmas. The granodioritic enclaves, on the other hand, may represent a strong mechanical interpenetra-tion, but chemically incomplete, of the host granodiorite and the less evolved tonalite. Other da-ta, such as isotope geochemistry (in progress) and AMS information, are expected to bring new light to the discussion on the Pomarinho enclave swarm genesis and evolution

Evaluation of the SALTMED model for tomato crop production in unheated greenhouses

The SALTMED model is one of the few available generic models that can be used to simulate crop growth with an integrated approach considering water, crop, soil and field management. It is a physically based model using the well-known water and solute transport, evapotranspiration, and water uptake equations. The possibility of using models able to simulate crop growth with this integrated approach can be very useful for farmers as a decision support tool, helping with decisions such as: what crop/variety to use, when to plant and harvest, when and how much to irrigate, what yield to expect under a specific irrigation system or strategy, when using a certain water quality, and also to allow increasing water use efficiency and crops productivity. The SALTMED model has been calibrated and validated for several field crops, in several parts of the world, including field tomato. However, the greenhouse environment has specific conditions that are not always easy to simulate with generic crop growth models. The objective of this work was to evaluate SALTMED model for a tomato crop grown in unheated greenhouse conditions. Climatic data and crop parameters were recorded during two years, in two greenhouses with different ventilation management, and three different sets of data were used to calibrate and to validate the model. The results showed that the model can accurately simulate soil grown tomato crop yield under Mediterranean unheated greenhouse conditions

SEISMO-ELECTROMAGNETIC PHENOMENA IN TECTONICALLY ACTIVE REGIONS

This work presents a research plan that aims to monitor seismo-electromagnetic signals in seismic active regions. Two effects will be considered: electromagnetic field emissions and radio broadcastings. Our study will be focused in the analysis of low magnitude earthquakes almost completely disregarded in literature. We aim to collect novel seismo-electromagnetic emission data emerging from seismic activity. We expect to address the time variation of electromagnetic properties of the crust in relation with the strain field and complement it with the development of proper models. Experimental studies based on the electrical properties of rocks will also be done aiming the understanding of pressure stimulated currents and voltages that produce detectable electromagnetic radiation and can be a cause for seismo-electromagnetic signals

Greenhouse Energy Consumption for Tomato Production in the Iberian Peninsula Countries

Greenhouse climate models are a powerful tool which allows the simulation of inside environmental conditions as a function of external conditions, construction and environmental control equipments characteristics. They also permit to evaluate the energy consumption necessary to obtain the predefined conditions. A theoretical study of the greenhouse energy requirements for all year round tomato production in Portugal and Spain is presented. A Greenhouse Climate Simulator (GCS) was used to analyse the energetic behaviour in different regions. GCS uses mensal mean weather data of several years of solar radiation, temperature, wind speed and relative humidity. A climate generator computes the mean hourly climatic data of a typical day for each month and location. As inputs GCS requires data related with the greenhouse characteristics, environmental control equipment and the crop. For the energy balance a static complex model is used which is based on the physics of heat and mass transfer. The results show the energy consumption due to the heating system in each of the studied locations, as well the heat dissipated by the cooling system along a characteristic year, for year round production in plastic greenhouses. This is used to estimate energy consumption indicators which allow generating predictive maps. It is an interesting tool which may contribute to the grower’s decision making and to the reduction of energy consumption, helping to lower production costs and environmental impacts

Temperature-responsive nanomagnetic logic gates for cellular hyperthermia

While a continuous monitoring of temperature at the micro- and nano-scales is clearly of interest in many contexts, in many others a yes or no answer to the question "did the system locally exceed a certain temperature threshold?" can be more accurate and useful. This is the case of hard-to-detect events, such as those where temperature fluctuations above a defined threshold are shorter than the typical integration time of micro/nanothermometers and systems where fluctuations are rare events in a wide time frame. Herein we present the synthesis of iron selenide magnetic nanoplatelets and their use as non-volatile logic gates recording the near infrared (NIR) dose that triggers a temperature increase above a critical temperature around 42 °C in prostate cancer cell cultures. This use is based on the bistable behavior shown by the nanoplatelets below a magnetic phase transition at a tunable temperature T C and on their photothermal response under NIR light. The obtained results indicate that the synthesized nanomagnets may be employed in the future as both local heaters and temperature monitoring tools in a wide range of contexts involving systems which, as cells, are temperature-sensitive around the tunable T C

Chaotic behaviour of seismic mechanisms: observation and models

Today, it is impractical work modelling the dynamics of failure, given the high complexity of the systems involved. As soon, it is important to identify models, as simples as possible, with qualitatively similar to the failures. The first model introducing is it the mechanical block-spring model, given by Burrigde-Knopoff [1]. In this work the subject was treated by experimental means. For that purpose it was developed and designed a mechanical system similar it that used in the numerical modulations, the so called earthquake machine (shown in Figure 1). We have equipped the springs of the machine with a set of force sensors connected to a data acquisition system (DAQ), linked in turn to a computer. The data recorded in the mechanical prototype consists of temporal series of tensions measured by the sensors that correspond to the sequence of tension accumulation and drop taking place in the springs. Data processing followed two distinct methodologies. The first treated the data according to the techniques used in seismology with field measurements. In the second methodology, we tried to use the series recorded in the context of chaos theories to investigate the behaviour of prototype

Influence of chlorhexidine and zinc oxide in calcium hydroxide pastes on pH changes in external root surface

The objective of this study was to assess the influence of chlorhexidine (liquid and gel) and zinc oxide in calcium hydroxide (CH) pastes on root pH in simulated external resorption. One hundred human anterior teeth with a single root canal were selected. After decoronation and root canal instrumentation, the specimens were divided into 4 experimental groups and 1 control group (without intracanal paste): CH + saline (CH+S), CH + 2% chlorhexidine liquid (CH+ CHX), CH + 2% chlorhexidine gel (CH+ CHXg), and CH + 2% chlorhexidine gel + zinc oxide (CH+ CHXg+ZnO). pH was measured using a microelectrode at 3 and 24 h, and 1, 2, 3, and 4 weeks after inserting intracanal pastes. Data were analyzed statistically using an ANOVA and Tukey's test (p < 0.05). The CH+CHXg+ZnO group had the highest pH values throughout (p < 0.05). The CH+S and CH+ CHX groups had the highest pH values after 1 week and the CH+ CHXg group after 2 weeks. CH+ CHXg maintained the highest pH until the fourth week compared with CH+ CHX (p < 0.05). The control group remained at a neutral pH at all evaluated times. It can be concluded that chlorhexidine solution or gel maintained the alkaline pH of CH, and chlorhexidine gel allowed a slower decrease in pH over time. CH+ CHXg+ZnO showed the highest pH values and was an effective intracanal medication for maintaining alkaline root pH in the area of resorption3