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Ceramic–metal composites are an important group of materials that have gained interest recently because of their peculiar properties. There have been numerous studies on the reinforcement of alumina through the incorporation of various ductile metals in it. However, these studies have been limited to determining the effect of the addition of metals on the mechanical properties of ceramics, without determining the effect of these metal additions on other physical properties of the resulting composite. In this way, in agreement with the obtained results, we have that because of the conductive nature of metals, there is a considerable decrease in the electrical resistivity of alumina, mainly when copper is added to it. However, in terms of optical performance, alumina matrix composites showed significant changes in absorbance in the visible spectra. The addition of iron, titanium, and yttrium enhanced the absorbance of alumina, whereas manganese addition significantly decreased the optical absorption.
A Zn/Al LDH with fluorescein intercalated as counterion with fluorescent properties was prepared. Fluorescein was prepared by the reaction between resorcinol and phthalic anhydride using the mixed oxide obtained after the thermal treatment of the LDH as catalyst. The material thus obtained, i.e. fluorescein adsorbed onto the mixed oxide from the calcined LDH, was treated with a mixture of water and pentanol in order to reconstitute the LDH and intercalate the fluorescein in the material. Three mixtures of water/pentanol with volume percent ratios of 100/0, 50/50, 20/80, were used to obtain the LDH with fluorescein intercalated. The best treatment could be determined according to the degree reconstruction and fluorescein intercalated into the LDH.
Here we present a new site in the Sierra de Atapuerca (Burgos, Spain): Galería de las Estatuas (GE), which provides new information about Mousterian occupations in the Iberian Plateau. The GE was an ancient entrance to the cave system, which is currently closed and sealed by a stalagmitic crust, below which a detritic sedimentary sequence of more than 2 m is found. This has been divided into five litostratigraphic units with a rich assemblage of faunal and lithic remains of clear Mousterian affinity. Radiocarbon dates provide minimum ages and suggest occupations older than 45 14C ka BP. The palynological analysis detected a landscape change to increased tree coverage, which suggests that the sequence recorded a warming episode. The macromammal assemblage is composed of both ungulates (mainly red deer and equids) and carnivores. Taphonomic analysis reveals both anthropic, and to a lesser extent, carnivore activities. The GE was occupied by Neanderthals and also sporadically by carnivores. This new site broadens the information available regarding different human occupations at the Sierra de Atapuerca, which emphasizes the importance of this site-complex for understanding human evolution in Western Europe.
A remarkable stela from Montoro, southern Spain, is unique in its morphology, epigraphic traits and landscape context. A programme of chemical characterisation, digital imaging, and geo-lithological and epigraphic analyses were conducted to determine its age and significance, and the results were integrated with data from archaeological investigations of the surrounding area. This multi-faceted approach allowed the stela to be interpreted within the context of early interactions between literate Mediterranean societies of the Late Bronze Age and Iron Age and non-literate Iberian societies. A key outcome of this research is a wider understanding of the complex patterns in the use and perception of early scripts.
The aim of this work was to assess the corrosion and degradation effects of a biofuel on metallic materials tested in an experimental internal combustion engine (ICE). Biodiesel is considered as an alternative fuel for diesel, for industrial applications ranging from boilers to ICE. The experimental vehicle motor, fitted with carbon steel, stainless steel, aluminum alloys and magnesium alloys was operated with local biodiesel. The corrosion performance was evaluated by gravimetric, chemical and electrochemical techniques, following the practices recommended in ASTM and NACE standards for corrosion testing. This work is the result of an international cooperation between the Institute of Engineering, Autonomous University of Baja California, Mexico and the Corrosion Research Center, Sami Shamoon College of Engineering, Israel. The characteristics and conditions of the ICE operated with biodiesel, and the results of the corrosion essays are presented, analyzed and discussed.
The aim of this study is to compare the corrosion rate of aluminum alloys for ornamental pieces. Three Fe/Cu relationships were tested in order to improve hardness and brightness in aluminum pieces since these alloys are used in the making of ornamental pieces. The variation on Fe/Cu content could result in modification on corrosion rate, since a metallographic characterization must be carried out identifying the presence of intermetallic phases. The presence of these elements could result in increasing corrosion rate, or even in modification of corrosion morphology, so localized corrosion could be expected.
The assessment of corrosion rate was carried out in saline media, since chlorides are ions that promote localized corrosion. Electrochemical techniques (polarization curves and Tafel plots) were used in order to evaluate the attack in aluminum pieces; electrochemical impedance spectroscopy was also employed with voltage amplitude of 10 mV rms, and a frequency range from 10,000 Hz to 0.01 Hz. A typical three electrodes cell was used, exposing an area of one cm2. Before polarization, open circuit potential was monitored for an hour looking for a steady state. All conditions were tested for triplicate.
The behavior of open circuit potential vs. time, and polarization curves was analyzed; a corrosion mechanism is proposed according to the electrochemical control. Polarization rate was calculated by using Tafel plots and, an electrochemical impedance spectroscopy analysis by using equivalent electric circuits is shown. Electrochemical impedance will yield information about corrosion morphology that is backed with microscopic inspection.
The objective of this study is to compare the corrosion rate of aluminum alloys for ornamental pieces in order to determine the effect of the relationship Fe/Cu on the corrosion mechanism in aluminum parts for ornamental pieces.
Chitosan is biocompatible polymer has a great commercial interest because it can be processed in a sort of devices varying in shape and size, such as membranes, gels and nanoparticles. Mostly, the cell’s attachment and proliferation are very positive on nanostructurated materials with a three-dimensional formation. An irreversible network can be produced by covalently binding the polymer to the cross-linker molecules. Chitosan nanoparticles were prepared using glutaraldehyde as cross-linker. This crosss-liker mostly reacts with chitosan amino groups. In order to control and understand the physical characteristics of chitosan nanoparticle, in this work is showed the molecular behavior of chitosan/glutaraldehyde from the viewpoint of molecular interactions base in a series of molecular dynamics (MD) computer simulation. The results indicated the conformations of both molecules, which had a significant influence on the molecular association. The chitosan chains were uniformly distributed presenting a high flexibility and preference for the relaxed two-fold helix. This was due to the various associations such as intramolecular chitosan interactions –O-H···O-C-. While the chitosan-glutaraldehyde associations were due to the positive net charge density of hydrogens in the chitosan plus - H2N···C=O associations. In solid state chitosan nano and microparticles were analyzed by scanning electron microscopy (SEM). According to the micrographs results, the nanoparticles presented a monomorphism with piles of particles arranged in linear order which was consistent with the conformations determined by simulation.
Aluminum titanium oxynitride (TiAlNO) coatings were deposited on 316 steel substrates by the sputtering technique, varying the nitrogen flow from 2.5, 5, 7.5 to 10 sccm, and maintaining constant at 12 sccm the flow argon gas. We used targets of titanium and alumina with 99.995% purity. The hardness and tribological analyses were determined by Vickers microhardness and tribology (tribometer pin-disc), respectively. The results show that the coating with a nitrogen flow of 10 sccm had the lowest volumetric wear (2.047738693 mm3) and the maximum value of hardness (11.2 GPa). Analysis of X-ray diffraction evidenced the presence of three crystalline phases: Ti2N, Al2O3 and TiO2. It can be observed that by increasing the nitrogen flow, the portion of semi-Ti2N phase increases, Al2O3 decreases and TiO2 remains almost constant, and also producing a change in crystallographic orientation with reference to the Ti2N phase. Crystal grain sizes were estimated by X-ray diffraction Fourier line profile analysis using Warren–Averbach method. This analysis showed a grain size between 5 and 15 nm. Raman spectroscopy results show the presence of the TiO2 phase which corroborated the X-ray diffraction results.
Magnetic nanoparticles (MNPs) are a class of materials that can be manipulated under the influence of an external magnetic field. Thanks to the ability of the MNPs to be guided by an external magnetic field that is like "action at a distance", combined with their low cytotoxicity and the intrinsic penetrability of magnetic fields into human tissue, opens up many applications involving the transport and/or immobilization of biological entities [1, 2].
This work is focused on the synthesis of magnetite nanoparticles by varied methods, their functionalization with nickel tetrasulfonated phthalocyanine, and the corresponding physicochemical characterization and colloidal stability studies in biologically compatible media. The in vitro production of singlet oxygen by these nanoparticles through photochemical stimulation in ultraviolet and visible region was evaluated, resulting in 4.5 and 4 µM respectly to magnetite synthetized in the group. The increase reactive oxygen species concentration in the cellular environment can result in modification and damage of cellular components, and potentially, cell death and necrosis. Therefore, these materials offer the promise of revolutionary tools for photodynamic therapy and hyperthermia, which are attractive strategies for cancer therapy without systemic toxicity.
Chitin nanowhiskers were obtained with the purpose to be used as astaxanthin protectors against the photo and thermal degradation. These nanostructures were generated by a freezing/thawing procedure using two stirring methods: mechanical and sonication, which were named as FTM and FTS respectively. Morphological and spectroscopic studies were carried out on chitin nanowhiskers by scanning electronic microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Through a SEM analysis, chitin fibers were found uniformly spaced and oriented with the width ranged from of 20-40 nm. Furthermore, the nanowhiskers obtained by FTM showed long and flattened structures and bundles of homogeneous sizes, which have the capacity of being sites of stress concentration. In contrast, by FTS, the nanowhiskers showed coarse fibers exhibiting numerous peaks. By comparing the two methods is appreciated that FTS method provides more surface area, giving more sites for functionalization. Fourier transform infrared spectroscopy (FTIR) allowed the determination of free movement of functional groups on the surface of samples obtained by FTM and FTS methods. Significant differences of signals in the spectra indicate that there were more unassociated amides in the nanowhiskers obtained by FTS than by FTM.
Carbon nanotubes (CNTs) were synthesized by Chemical Vapor Deposition (CVD) from diethyl ether, butanol, hexane and ethyl acetate. A quartz tube with a stainless steel tube catalyst core with 0.019 m diameter and 0.6 m large formed the reactor. To avoid combustion, argon was used as the carrier gas. Time process ranged 30 to 60 min. The range of CNTs synthesis temperature was 680-850 °C for different precursors. Scanning Electron Microscopy micrographs have demonstrated tangled CNTs growth in all samples, thus presenting difficult length measurement. The CNTs diameters from diethyl ether are 45-200 nm, butanol diameter range from 55-230 nm, hexane diameter range is 50-130 nm and ethyl acetate range from 100 to 300 nm. Carbon content for all samples was higher than 93 %, CNTs from butanol showed carbon concentration up to 99%. FTIR, Raman and X-Ray Spectroscopies spectra for all samples demonstrated the characteristics signals present in carbon nanotubes. This research proposes a simple, effective and innovative method to synthesize CNTs by CVD on iron stainless steel catalyst in combination with diethyl ether, ethyl acetate, butanol and hexane as precursors by applying the principles of green chemistry, sustainability and its ease to be scaled.
Salamanca lies on the right bank of the river Tormes, a tributary of the Douro, on the northern sub-plateau of the Iberian peninsula (fig. 1). Although hardly mentioned in Roman historical sources, it is a reference point for work on Roman territory because the surveyor Frontinus (De Agrorum Qualitate [ed. Thulin 1971] 1–2) used Salmantica (in Lusitania) and Palantia (in Citerior) to exemplify ager per extremitatem mensura comprehensus, the system of land organization characteristic of stipendiary cities. Frontinus was writing in Flavian times, but the creation of ager mensura comprehensus in Lusitania occurred in the Augustan period, as is confirmed by remarkable epigraphic documentation. In N Lusitania, a total of 11 boundary-stones (termini Augustales) are known, nine from the reign of Augustus (and two of these provide explicit reference to Salmantica) and two from that of Claudius. The dates provided by Augustus’ tribunicia potestas allow us to date the surveying operations delimiting the urban territories to between A.D. 4–5 (the inscriptions from Peroviseu and Ul) and A.D. 5–6 (the inscriptions from Sao Salvador, Ledesma, Ciudad Rodrigo, and the new one from Jarandilla de la Vera). The Augustan ager mensura comprehensus may have conditioned the model of the subsequent rural settlement by creating a framework for territorial occupation being organized around the villa from the Flavian period on. The villa would dominate the rural countryside, until it disappeared around the first decades of the 5th c. as part of a process that can be associated with the breaking down of imperial authority and the arrival of the Germanic peoples in the year 409. Almost nothing is known about Salamanca’s territory during the Islamic occupation until the first official repopulation took place under the king of Leon, Ramiro II, in 939–49. The lack of attested settlements in the Douro valley between the 8th and 10th c. is a key question for the organization of the border area between the Islamic state of Al-Andalus and the kingdom of Leon, but scholars generally reject the thesis formulated in 1966 by C. Sánchez Albornoz, which tended to present the lands of the Douro valley as practically depopulated.
Little is known about the clustering patterns of lifestyle behaviours in adult populations. We explored clusters in multiple lifestyle behaviours including physical activity (PA), smoking, alcohol use and eating habits in a sample of adult population. A cross-sectional and multi-centre study was performed with six participating groups distributed throughout Spain. Participants (n 1327) were part of the Lifestyles and Endothelial Dysfunction (EVIDENT) study and were aged between 20 and 80 years. The lifestyle and cardiovascular risk (CVR) factors were analysed using a clustering method based on the HJ-biplot coordinates to understand the variables underlying these groupings. The following three clusters were identified. Cluster 1: unhealthy, 677 subjects (51 %), with a slight majority of men (58·7 %), who were more sedentary and smokers with higher consumption of whole-fat dairy products, bigger waist circumference as well as higher TAG levels, systolic blood pressure (SBP) and CVR. Cluster 2: healthy/PA, 265 subjects (20 %), including 24·0 % of males with high PA. Cluster 3: healthy/diet, including 29 % of the participants, with a higher consumption of olive oil, fish, fruits, nuts, vegetables and lower alcohol consumption. Using the unhealthy cluster as a reference, and after adjusting for age and sex, the multiple regression analysis showed that belonging to the healthy/PA cluster was associated with a lower waist circumference, body fat percentage, SBP and CVR. In summary, the three clusters were identified according to lifestyles. The ‘unhealthy’ cluster had the least favourable clinical parameters, the ‘healthy/PA’ cluster had good HDL-cholesterol levels and low SBP and the ‘healthy/diet’ cluster had lower LDL-cholesterol levels and clinical blood pressure.
Angola is a large country with a relatively small population and abundant natural resources, including oil reserves. The high price fetched by oil, the mainstay of the Angolan economy, on international markets has helped this leading producer attain growth rates that are among the highest in the world. However, Angola is also noted for its unequal distribution of wealth and notorious political corruption. This article seeks to explore this paradox within the framework of the so-called resource curse theory and analyze the role played by the oil industry in the process.
The trace-fossil name Tubotomaculum has been extensively used to refer to spindle-shaped pellet-filled tubes present in Upper Cretaceous to Miocene deep-marine deposits of the western Mediterranean region. However, it has never been formally diagnosed, and accordingly it was regarded as a nomen nudum. In this paper, we formally introduce the ichnogenus Tubotomaculum, including the new ichnospecies Tubotomaculum mediterranensis. Bioglyphs, represented by scratch traces that may be present on the basal and lateral surfaces of the structure, suggesting production by crustaceans. The functional meaning of these structures challenges the simple model of a mining strategy. Instead, the storing of pellets to use them as a bacteria-enriched resource during times when organic detritus was scarce is suggested. The association with chemoautothrophic bacteria in modern analogs of Tubotomaculum provides a crucial piece of evidence to support the cache model. Integration of information from modern environments and the fossil record points to a connection between Tubotomaculum, mud volcanism, fluid venting, and hydrocarbon seeps. The presence of bioglyphs suggests firmgrounds that may have resulted from bottom current scouring of the sea sediment, leading to erosional exhumation of previously buried compacted sediment, which was therefore available for colonization by the infauna. However, an alternative scenario involves enriched fluids related to mud-volcanism resulting in reducing conditions that favored carbonate precipitation and nodule formation just a few centimeters below the sediment-water interface.
The purpose of this work was to study the relationship between self-focused
attention and mindfulness in participants prone to hallucinations and others who
were not. A sample of 318 healthy participants, students at the universities of
Sevilla and Almería, was given the Launay-Slade Hallucinations
Scale-revised (LSHS-R, Bentall & Slade, 1985). Based on this sample, two groups were formed:
participants with high (n = 55) and low proneness
(n = 28) to hallucinations. Participants with a
score higher than a standard deviation from the mean in the LSHS-R were included
in the high proneness group, participants with a score lower than a standard
deviation from the mean in the LSHR-R were included in the second one. All
participants were also given the Self-Absorption Scale (SAS, McKenzie
& Hoyle, 2008) and the
Southampton Mindfulness Questionnaire (SMQ, Chadwick et al., 2008). The results showed that
participants with high hallucination proneness had significantly higher levels
of public (t(80) = 6.81, p
< .001) and private (t(77) = 7.39,
p < .001) self-focused attention and lower levels
of mindfulness (t(81) = -4.56, p
< .001) than participants in the group with low hallucination
proneness. A correlational analysis showed a negative association between
self-focused attention (private and public) and mindfulness (r
= -0.23, p < .001; r
= -0.38, p < .001 respectively). Finally,
mindfulness was found to partly mediate between self-focused attention and
hallucination proneness. The importance of self-focused attention and
mindfulness in understanding the etiology of hallucinations discussed and
suggest some approaches to their treatment.
The effect of mechanical activation (MA) of the precursor mixture of raw materials and/or the parent glass, on the microstructure and physical and mechanical properties of iron-rich glass-ceramic materials of the system SiO2-B2O3-BaO-Fe2O3, has been studied. MA of the materials is conducted for 0, 2 or 6h using a high energy attrition milling device. Crystallization treatments are given to the parent glass at 650, 750 or 850°C for 5h. Crystallization of the samples is promoted by increased treatment temperature, and especially also by double MA at 850°C. With increasing crystallization temperature, both the density and the compressive strength increase, while porosity decreases. However, at 850°C, prolonged MA decreases both the density and the compressive strength due to an increment in porosity caused by the growth of the BaFe12O19 crystals.
The benefits of iodine supplements during pregnancy remain controversial in areas with a mild-to-moderate iodine deficiency. The aim of the present study was to determine the effect of improving iodine intakes, with iodised salt (IS) or iodine supplements, in pregnant Spanish women. A total of 131 pregnant women in their first trimester were randomly assigned to three groups: (1) IS in cooking and at the table, (2) 200 μg potassium iodide (KI)/d or (3) 300 μg KI/d. No differences were found in thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3) or thyroid volume (TV) between the three groups. Regardless of the group in which women were included, those who had been taking IS for at least 1 year before becoming pregnant had a significantly lower TV in the third trimester (P= 0·01) and a significantly higher urinary iodine in the first (173·7 (sd 81·8) v. 113·8 (sd 79·6) μg/l, P= 0·001) and third trimesters (206·3 (sd 91·2) v. 160·4 (sd 87·7) μg/l, P= 0·03). Also, no differences were seen in TSH, FT4 or FT3. Children's neurological development was not significantly associated with the consumption of IS for at least 1 year before becoming pregnant and no differences were found according to the treatment group. In conclusion, in pregnant women with insufficient iodine intake, the intake of IS before becoming pregnant was associated with a better maternal thyroid function. The form of iodide intake was not associated with maternal thyroid function or children's neurological development.