N. Lourenço

Synthesis of 2,4,6-Tri-substituted-1,3,5-Triazines

Several specific synthetic protocols were developed for the preparation from cyanuric chloride of a range of symmetric and non-symmetric di- and tri-substituted 1,3,5-triazines containing alkyl, aromatic, hindered, chiral and achiral hydroxyalkyl, ester and imidazole groups via sequential nucleophilic substitution of the C-Cl bond by C-O, C-N and C-S bonds.

Large, deepwater slope failures: Implications for landslide-generated tsunamis

Deepwater landslides are often underestimated as potential tsunami triggers. The North Gorringe avalanche (NGA) is a large (~80 km3 and 35 km runout) newly discovered and deepwater (2900 m to 5100 m depth) mass failure located at the northern fl ank of Gorringe Bank on the southwest Iberian margin. Steep slopes and pervasive fracturing are suggested as the main preconditioning factors for the NGA, while an earthquake is the most likely trigger mechanism. Near-fi eld tsunami simulations show that a mass failure similar to the NGA could generate a wave >15 m high that would hit the south Portuguese coasts in ~30 min. This suggests that deepwater landslides require more attention in geo-hazard assessment models of southern Europe, as well as, at a global scale, in seismically active margins.

Understanding the Ion Jelly Conductivity Mechanism

The properties of the light flexible device, ion jelly, which combines gelatin with an ionic liquid (IL) were recently reported being promising to develop safe and highly conductive electrolytes. This article aims for the understanding of the ion jelly conductive mechanism using dielectric relaxation spectroscopy (DRS) in the frequency range 10(-1)-10(6) Hz; the study was complemented with differential scanning calorimetry (DSC) and pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy. The room temperature ionic liquid 1-butyl-3-methylimmidazolium dicyanamide (BMIMDCA) used as received (1.9% w/w water content) and with 6.6% (w/w) of water content and two ion jellies with two different ratios BMIMDCA/gelatin/water % (w/w), IJ1 (41.1/46.7/12.2) and IJ3 (67.8/25.6/6.6), have been characterized. A glass transition was detected by DSC for all materials allowing for classifying them as glass formers. For the ionic liquid, it was observed that the glass transition temperature decreases with the increase of water content. While in subsequent calorimetric runs crystallization was observed for BMIMDCA with negligible water content, no crystallization was detected for any of the ion jelly materials upon themal cycling. To the dielectric spectra of all tested materials, both dipolar relaxation and conductivity contribute; at the lowest frequencies, electrode and interfacial polarization highly dominate. Conductivity, which manifests much more intensity relative to dipolar reorientations, strongly evidences subdiffusive ion dynamics at high frequencies. From dielectric measures, transport properties as mobility and diffusion coefficients were extracted. Data treatment was carried out in order to deconvolute the average diffusion coefficients estimated from dielectric data in its individual contributions of cations (D(+)) and anions (D(-)). The D(+) values thus obtained for IJ3, the ion jelly with the highest IL/gelatin ratio, cover a large temperature range up to room temperature and revealed excellent agreement with direct measurements from PFG NMR, obeying to the same VFT equation. For BMIMDCA(6.6%water), which has the same water amount as IJ3, the diffusion coefficients were only estimated from DRS measurements over a limited temperature range; however, a single VFT equation describes both DRS and PFG NMR data. Moreover, it was found that the diffusion coefficients and mobility are similar for the ionic liquid and IJ3, which points to a role of both water and gelatin weakening the contact ion pair, facilitating the translational motion of ions and promoting its dissociation; nevertheless, it is conceivable the existence of a critical composition of gelatin that leads to those properties. The VFT temperature dependence observed for the conductivity was found to be determined by a similar dependence of the mobility. Both conductivity and segmental motion revealed to be correlated as inferred by the relatively low values of the decoupling indexes. The obtained results show that ion jelly could be in fact a very promising material to design novel electrolytes for different electrochemical devices, having a performance close to the IL but presenting an additional stability regarding electrical measurements and resistance against crystallization relative to the bulk ionic liquid.

Identification of the magnetization low of the Lucky Strike hydrothermal vent using surface magnetic data

[1] Two surface magnetic surveys, covering the Lucky Strike hydrothermal area, are merged into a single magnetic anomaly description, which, when inverted in the presence of topography, shows a magnetization low at the segment center, close to the central volcano, in the middle of which is located the hydrothermal vent. To test if this magnetization is in any way connected with the hydrothermal vent field, we devised a method to distinguish a ‘‘regional’’ field that can be attributed to the ‘‘normal’’ spreading geometry from the ‘‘local’’ field that can be attributed to the hydrothermal vent area itself. This is achieved by the computation of a three-dimensional regional magnetic field that takes into consideration bathymetry, location of the ‘‘zero-age’’ axis, asymmetry in the half spreading rates, magnetization decay with age, polarity reversals, and the transition between consecutive magnetic blocks. This model was fitted to the observed surface magnetic data, and the ‘‘magnetic residual’’ was inverted to allow a better definition of the magnetization anomalies. We show that as far as surface magnetic data are concerned, the magnetization low has only partial correlation with the hydrothermal field and is the signature of a relatively large area in which bulk magnetization is lower than average.

Ion Jelly Conductive Properties Using Dicyanamide-Based Ionic Liquids

The thermal behavior and transport properties of several ion jellys (IJs), a composite that results from the combination of gelatin with an ionic liquid (IL), were investigated by dielectric relaxation spectroscopy (DRS), differential scanning calorimetry (DSC), and pulsed field gradient nuclear magnetic resonance spectroscopy (PFG NMR). Four different ILs containing the dicyanamide anion were used: 1-butyl-3-methylimidazolium dicyanamide (BMIMDCA), 1-ethyl-3-methylimidazolium dicyanamide (EMIMDCA), 1-butyl-1-methylpyrrolidinium dicyanamide (BMPyrDCA), and 1-butylpyridinium dicyanamide (BPyDCA); the bulk ILs were also investigated for comparison. A glass transition was detected by DSC for all materials, ILs and IJs, allowing them to be classified as glass formers. Additionally, an increase in the glass transition temperature upon dehydration was observed with a greater extent for IJs, attributed to a greater hindrance imposed by the gelatin matrix after water removal, rendering the IL less mobile. While crystallization is observed for some ILs with negligible water content, it was never detected for any IJ upon thermal cycling, which persist always as fully amorphous materials. From DRS measurements, conductivity and diffusion coefficients for both cations (D+) and anions (D-) were extracted. D+ values obtained by DRS reveal excellent agreement with those obtained from PFG NMR direct measurements, obeying the same VFTH equation over a large temperature range (ΔT ≈ 150 K) within which D+ varies around 10 decades. At temperatures close to room temperature, the IJs exhibit D values comparable to the most hydrated (9%) ILs. The IJ derived from EMIMDCA possesses the highest conductivity and diffusion coefficient, respectively, ∼10(-2) S·cm(-1) and ∼10(-10) m(2)·s(-1). For BMPyrDCA the relaxational behavior was analyzed through the complex permittivity and modulus formalism allowing the assignment of the detected secondary relaxation to a Johari-Goldstein process. Besides the relevant information on the more fundamental nature providing physicochemical details on ILs behavior, new doorways are opened for practical applications by using IJ as a strategy to produce novel and stable electrolytes for different electrochemical devices.

Chapter 2 The structure of the Azores Triple Junction: implications for São Miguel Island

Abstract To date, a lack of reliable morphological and geophysical data has been a major limitation to understanding the tectonic and magmatic processes that shape the Azores Triple Junction and the Terceira Rift. This situation has changed recently: for the first time both areas are covered by high-quality swath bathymetry surveys and marine magnetic data with GPS quality positioning. This provides a good description of the surface morphology, and also of magnetic chrons that give fundamental information for the timing of spreading processes in a geological time frame. There is also a large amount of data from GPS stations that provide accurate estimations of present-day velocities for most of the islands. It is shown that only two main rift systems can be found on the plateau, the older one matching the Princess Alice Basin, and the newer one matching Terceira Rift; the shift between the two probably occurs close to c. 3 Ma. It is shown that extension is currently concentrated on the Terceira Rift, progressively attaching Graciosa and Terceira islands to Eurasia, while São Miguel is being strained by rifting. It is also shown that no right lateral strike-slip fault connects the Terceira Rift to the Mid-Atlantic Ridge.

Evolution of submarine eruptive activity during the 2011–2012 El Hierro event as documented by hydroacoustic images and remotely operated vehicle observations

Submarine volcanic eruptions are frequent and important events, yet they are rarely observed. Here we relate bathymetric and hydroacoustic images from the 2011 to 2012 El Hierro eruption with surface observations and deposits imaged and sampled by ROV. As a result of the shallow submarine eruption, a new volcano named Tagoro grew from 375 to 89 m depth. The eruption consisted of two main phases of edifice construction intercalated with collapse events. Hydroacoustic images show that the eruptions ranged from explosive to effusive with variable plume types and resulting deposits, even over short time intervals. At the base of the edifice, ROV observations show large accumulations of lava balloons changing in size and type downslope, coinciding with the area where floating lava balloon fallout was observed. Peaks in eruption intensity during explosive phases generated vigorous bubbling at the surface, extensive ash, vesicular lapilli and formed high-density currents, which together with periods of edifice gravitational collapse, produced extensive deep volcaniclastic aprons. Secondary cones developed in the last stages and show evidence for effusive activity with lava ponds and lava flows that cover deposits of stacked lava balloons. Chaotic masses of heterometric boulders around the summit of the principal cone are related to progressive sealing of the vent with decreasing or variable magma supply. Hornitos represent the final eruptive activity with hydrothermal alteration and bacterial mats at the summit. Our study documents the distinct evolution of a submarine volcano and highlights the range of deposit types that may form and be rapidly destroyed in such eruptions.

The Tectonic Evolution of the Azores Based on Magnetic Data

The Azores attracted the interest of geoscientists since the beginning of the XX century. In the late 60s, when plate tectonics was established as the basic geodynamic paradigm, the peculiar morphology of the Azores Islands and the surrounding plateau, located close to the Mid-Atlantic ridge, were early interpreted as the result of the separation between the Eurasian and the North-America plates. Nevertheless, a number of particular geological features were targeted for explanation: (i) the long active fault going from Gibraltar to the Azores (now called Gloria Fault), (ii) the existence of a large but inactive fracture on the North-American plate, offset tenths of kilometres to the north with respect to Gloria Fault, (iii) the curvilinear succession of islands marked by pervasive volcanic and seismic activity, (iv) the development of a plateau, partially split by the Mid-Atlantic Ridge. These questions remained elusive for a long time, despite the large amount of geological and geophysical data available, as most of the conventional approaches were not as fruitful as expected, and new identified features raise new unknowns or revealed uncommon geological environments. Here, we present a review of the progress made in the understanding of the tectonic evolution of the Azores, mainly based on the interpretation of magnetic and morphological data and we present an updated interpretative scheme for the genesis and evolution of the Azores triple junction.

Enzymatic Kinetic Resolution of Secondary Alcohols Using an Ionic Anhydride Generated In Situ

We developed a method for the resolution of secondary alcohols using an ionic anhydride acylating agent prepared directly in the reaction medium containing the biocatalyst Candida antarctica lipase B (CALB). NMR studies showed that mixing all components at the same time does not interfere with the coupling reaction or the enzymatic activity. After optimization of the reaction conditions, the method allowed the resolution of a number of substrates in very high conversions (46-48 %) and enantiomeric ratios (E>170) along with an easy recovery of both enantiomers without the need for preparative chromatographic separation. Additionally, both the starting ionic acid and the biocatalyst could be recovered and reused up to nine cycles without significant loss of enantioselectivity.

Shallow geoelectric structure of eastern part of Terceira Island (Acores) from AMT soundings

The Terceira Island is located at the plate boundary between the Eurasian and African plates. This plate boundary usually referred to as the Terceira axis, is a highly complex, non conventional ridge system morphologically defined by a succession of deep rhombic basins and shallow volcanic banks or islands materializing domains of higher magmatic budget (Lourenco et al., 1998).