Expansion Axis Research Articles

Megaciudad Buenos Aires: Cartografía de su última expansión y conurbación mediante el procesamiento digital de imágenes satelitales nocturnas

El procesamiento digital de imágenes satelitales nocturnas y el uso de Sistemas de Información Geográfica confirma que la última expansión y conurbación de la Megaciudad Buenos Aires se produjo con el cambio de siglo. Esto se verifica al analizar un período de dos décadas (1992-2012) con centralidad en el año 2002. Si bien la estabilización del crecimiento de la Megaciudad Buenos Aires comenzó hace cinco décadas, el análisis temporal de imágenes y la realización de cartografía temática permitieron representar espacialmente un nuevo proceso de conurbación. Este proceso se desarrolló en cinco ejes de expansión incorporando otras ciudades de la región metropolitana cuya distancia media al centro principal es de 61 km. Las imágenes satelitales nocturnas brindan nuevas perspectivas del espacio urbano al utilizarse los conceptos de megaciudad, expansión urbana, conurbación e infraestructura gris. A través de los elementos que brinda el área urbana consolidada, la urbanización difusa y la mayor densidad y proporción de las vías de comunicación dan la posibilidad de captar configuraciones actuales y disponer de elementos para captar tendencias espaciales futuras.

Comparative Study of the Structure, Composition, and Electrocatalytic Performance of Hydrogen Evolution in MoSx~2+δ/Mo and MoSx~3+δ Films Obtained by Pulsed Laser Deposition.

Systematic and in-depth studies of the structure, composition, and efficiency of hydrogen evolution reactions (HERs) in MoSx films, obtained by means of on- and off-axis pulsed laser deposition (PLD) from a MoS2 target, have been performed. The use of on-axis PLD (a standard configuration of PLD) in a buffer of Ar gas, with an optimal pressure, has allowed for the formation of porous hybrid films that consist of Mo particles which support a thin MoSx~2+δ (δ of ~0.7) film. The HER performance of MoSx~2+δ/Mo films increases with increased loading and reaches the highest value at a loading of ~240 μg/cm2. For off-axis PLD, the substrate was located along the axis of expansion of the laser plume and the film was formed via the deposition of the atomic component of the plume, which was scattered in Ar molecules. This made it possible to obtain homogeneous MoSx~3+δ (δ~0.8–1.1) films. The HER performances of these films reached saturation at a loading value of ~163 μg/cm2. The MoSx~3+δ films possessed higher catalytic activities in terms of the turnover frequency of their HERs. However, to achieve the current density of 10 mA/cm2, the lowest over voltages were −162 mV and −150 mV for the films obtained by off- and on-axis PLD, respectively. Measurements of electrochemical characteristics indicated that the differences in the achievable HER performances of these films could be caused by their unique morphological properties.

Modernidades Industriais do Maranhão

Este artigo tem por objetivo compreender as modernidades industriais do Maranhão, abordando os ciclos econômicos do Estado e desenvolvimento urbano, com destaque a implantação das fábricas da virada do século XIX para o XX e sua influência nas transformações urbanas da capital São Luís, entre o centro e os eixos de expansão urbana do Caminho Grande até o Anil, ressaltando o aparecimento dos bungalows burgueses e dos bairros operários como o Filipinho. Como conclusão, o artigo apresenta uma reflexão sobre toda a trajetória urbano econômica do Estado e sua percepção como patrimônio industrial brasileiro.

Evolution of Dispersal Can Rescue Populations from Expansion Load.

Understanding the causes and consequences of range expansions or range shifts has a long history in evolutionary biology. Recent theoretical, experimental, and empirical work has identified two particularly interesting phenomena in the context of species range expansions: (i) gene surfing and the relaxation of natural selection and (ii) spatial sorting. The former can lead to an accumulation of deleterious mutations at range edges, causing an expansion load and slowing down expansion. The latter can create gradients in dispersal-related traits along the expansion axis and cause an acceleration of expansion. We present a theoretical framework that treats spatial sorting and gene surfing as spatial versions of natural selection and genetic drift, respectively. This model allows us to analytically study how gene surfing and spatial sorting interact and derive the probability of fixation of pleiotropic mutations at the expansion front. We use our results to predict the coevolution of mean fitness and dispersal rates, taking into account the effects of random genetic drift, natural selection, and spatial sorting, as well as correlations between fitness- and dispersal-related traits. We identify a "rescue effect" of spatial sorting, where the evolution of higher dispersal rates at the leading edge rescues the population from incurring expansion load.

The correlation between porosity characteristics and the crystallographic texture in extruded stabilized aluminium titanate for diesel particulate filter applications

Porous ceramic diesel particulate filters (DPFs) are extruded products that possess macroscopic anisotropic mechanical and thermal properties. This anisotropy is caused by both morphological features (mostly the orientation of porosity) and crystallographic texture. We systematically studied those two aspects in two aluminum titanate ceramic materials of different porosity using mercury porosimetry, gas adsorption, electron microscopy, X-ray diffraction, and X-ray refraction radiography. We found that a lower porosity content implies a larger isotropy of both the crystal texture and the porosity orientation. We also found that, analogous to cordierite, crystallites do align with their axis of negative thermal expansion along the extrusion direction. However, unlike what found for cordierite, the aluminium titanate crystallite form is such that a more pronounced (0 0 2) texture along the extrusion direction implies porosity aligned perpendicular to it.

Dynamics of Land Use and Land Cover Changes in Harare, Zimbabwe: A Case Study on the Linkage between Drivers and the Axis of Urban Expansion

With increasing population growth, the Harare Metropolitan Province has experienced accelerated land use and land cover (LULC) changes, influencing the city’s growth. This study aims to assess spatiotemporal urban LULC changes, the axis, and patterns of growth as well as drivers influencing urban growth over the past three decades in the Harare Metropolitan Province. The analysis was based on remotely sensed Landsat Thematic Mapper and Operational Land Imager data from 1984–2018, GIS application, and binary logistic regression. Supervised image classification using support vector machines was performed on Landsat 5 TM and Landsat 8 OLI data combined with the soil adjusted vegetation index, enhanced built-up and bareness index and modified difference water index. Statistical modelling was performed using binary logistic regression to identify the influence of the slope and the distance proximity characters as independent variables on urban growth. The overall mapping accuracy for all time periods was over 85%. Built-up areas extended from 279.5 km2 (1984) to 445 km2 (2018) with high-density residential areas growing dramatically from 51.2 km2 (1984) to 218.4 km2 (2018). The results suggest that urban growth was influenced mainly by the presence and density of road networks.

Investigation on the material in the plasma phase by high temporally and spectrally resolved emission imaging during pulsed laser ablation in liquid (PLAL) for NPs production and consequent considerations on NPs formation

In this paper experimental temperature and density maps of the laser induced plasma in water during pulsed laser ablation in liquid (PLAL) for the production of metallic nanoparticles (NPs) has been determined. A detection system based on the simultaneous acquisition of two emission images at 515 and 410 nm has been constructed and the obtained images have been processed simultaneously by imaging software. The results of the data analysis show a variation of the temperature between 4000 and 7000 K over the plasma volume. Moreover, by the study of the temperature distribution and of the number densities along the plasma expansion axis it is possible to observe the condensation zone of the plasma where NPs can be formed. Finally, the time associated with the electron processes is estimated and the plasma charging effect on NPs is demonstrated. The set of observations retrieved from these experiments suggests the importance of the plasma phase for the growth of NPs and the necessity of considering the spatial distribution of plasma parameters for the understanding of one of the most important issues of the PLAL process, that is the source of solid material in the plasma phase.

Analysis of lead and copper in soil samples by laser-induced breakdown spectroscopy under external magnetic field

The purpose of the present study was to improve the detection limits of copper and lead in the soil samples by coupling Laser-Induced Plasma Spectrometry (LIPS) with an external magnetic field. The laser-induced plasma was generated using an Nd:YAG laser (532 nm) and the emission spectra were registered using a set of four spectrometers covering the wavelength region from 250 to 870 nm. The application of external magnetic field (0.7 T) perpendicular to the propagation of the plasma plume increases the plasma temperature, electron density, and plasma emission intensity. This enhancement in the plasma parameters is attributed to the plasma confinement. The detection limit of Pb and Cu has been improved from 12 ppm to 4.1 ppm and from 3.9 ppm to 1.4 ppm by applying magnetic field. The plasma temperature and electron number density decays slowly along the plasma expansion axis in the presence of external magnetic field.

Landscape genomics of an obligate mutualism: Concordant and discordant population structures between the leafcutter ant Atta texana and its two main fungal symbiont types.

To explore landscape genomics at the range limit of an obligate mutualism, we use genotyping-by-sequencing (ddRADseq) to quantify population structure and the effect of host-symbiont interactions between the northernmost fungus-farming leafcutter ant Atta texana and its two main types of cultivated fungus. Genome-wide differentiation between ants associated with either of the two fungal types is of the same order of magnitude as differentiation associated with temperature and precipitation across the ant's entire range, suggesting that specific ant-fungus genome-genome combinations may have been favoured by selection. For the ant hosts, we found a broad cline of genetic structure across the range, and a reduction of genetic diversity along the axis of range expansion towards the range margin. This population-genetic structure was concordant between the ants and one cultivar type (M-fungi, concordant clines) but discordant for the other cultivar type (T-fungi). Discordance in population-genetic structures between ant hosts and a fungal symbiont is surprising because the ant farmers codisperse with their vertically transmitted fungal symbionts. Discordance implies that (a) the fungi disperse also through between-nest horizontal transfer or other unknown mechanisms, and (b) genetic drift and gene flow can differ in magnitude between each partner and between different ant-fungus combinations. Together, these findings imply that variation in the strength of drift and gene flow experienced by each mutualistic partner affects adaptation to environmental stress at the range margin, and genome-genome interactions between host and symbiont influence adaptive genetic differentiation of the host during range evolution in this obligate mutualism.

Microtubule bundling by MAP65-1 protects against severing by inhibiting the binding of katanin.

The microtubule-severing enzyme katanin (KTN1) regulates the organization and turnover of microtubule arrays by the localized breakdown of microtubule polymers. In land plants, KTN1 activity is essential for the formation of linearly organized cortical microtubule arrays that determine the axis of cell expansion. Cell biological studies have shown that even though KTN1 binds to the sidewalls of single and bundled microtubules, severing activity is restricted to microtubule cross-over and nucleation sites, indicating that cells contain protective mechanisms to prevent indiscriminate microtubule severing. Here, we show that the microtubule-bundling protein MAP65-1 inhibits KTN1-mediated microtubule severing in vitro. Severing is inhibited at bundled microtubule segments and the severing rate of nonbundled microtubules is reduced by MAP65-1 in a concentration-dependent manner. Using various MAP65-1 mutant proteins, we demonstrate that efficient cross-linking of microtubules is crucial for this protective effect and that microtubule binding alone is not sufficient. Reduced severing due to microtubule bundling by MAP65-1 correlated to decreased binding of KTN1 to these microtubules. Taken together, our work reveals that cross-linking of microtubules by MAP65-1 confers resistance to severing by inhibiting the binding of KTN1 and identifies the structural features of MAP65-1 that are important for this activity.

Spectroscopy Measurements of Laser-Induced Molybdenum Plasma

Molybdenum plasma in air at atmospheric pressure was carried out by utilizing Nd-YAG laser at fundamental wavelength 1064 nm, 0.206 mJ input energy, 5 ns pulse duration and repetition rate 10 Hz. After plasma formation, the optical fiber was used to collect plasma emission. The spectral analysis was displayed in the Local Thermal Equilibrium (LTE) state. Electron temperature was estimated by Boltzmann plot method and electron density was calculated from Stark broadening and compared with electron density of Hα-line at 656.3 nm which has reliable values. The temperature of plasma and density were evaluated for different positions along the expansion axis. The influence of the input power on plasma was studied. The electron density varied from 5 ×1018 to 3.5×1019 cm-3. These parameters are important in environmental and industrial application. At distance of 10 mm from the target, the electron temperature has a minimum value while the electron density shows a maximum value.

Hydration of an Acid Anhydride: The Water Complex of Acetic Sulfuric Anhydride.

The complex formed from acetic sulfuric anhydride (CH3COOSO2OH, ASA) and water has been observed by pulsed nozzle Fourier transform microwave spectroscopy. ASA was formed in situ in the supersonic jet via the reaction of SO3 and CH3COOH, and subsequently complexed with water using a concentric, dual injection needle that allows reagents to be introduced at different points along the expansion axis. Spectroscopic constants for the parent, fully deuterated, and CH313COOSO2OH species are reported. Both A and E internal rotor states have been observed and analyzed. The fitted internal rotation barrier of the methyl group is 219.598(21) cm-1 for the parent species, indicating that complexation with water lowers the internal rotation barrier of the methyl group by 9% relative to that of the free ASA. M06-2X/6-311++G(3df,3pd) calculations predict at least two distinct isomeric forms of ASA···H20. Spectroscopic constants for the observed species agree with those for the lower energy isomer in which the water inserts into the intramolecular hydrogen bond of the ASA monomer. CCSD(T)/CBS(D-T) calculations place the binding energy of this isomer at 13.3 kcal/mol below that of the isolated ASA and H2O monomers. The calculations further indicate that the doubly hydrogen bonded complex CH3COOH···H2SO4, which contains the hydrolysis products of ASA, lies even lower in energy, but this species was not observed in this study. This system represents the first stage of microsolvation of an acid anhydride, and the results indicate that a single water molecule does not induce spontaneous hydrolysis in a cold molecular cluster.

Multiprobe characterization of plasma flows for space propulsion

Plasma engines for space propulsion generate plasma jets (also denominated plasma plumes) having supersonic ion groups with typical speeds in the order of tens of kilometers per second, which lies between electron and ion thermal speeds. Studies of the stationary plasma expansion process using a four-grid retarding field energy analyzer (RFEA), an emissive probe (EP) and a Langmuir probe (LP), all mounted on a three dimensionally (3D) displaced multiprobe structure are discussed. Specifically, the determination of plasma beam properties from the RFEA current-voltage (IV) characteristic curves is presented. The experimental results show the ion energy spectra to be essentially unchanged over 300 mm along the plasma-jet expansion axis of symmetry. The measured ion velocity distribution function (IVDF) results from the superposition of different ion groups and has two dominant populations: A low-energy group constituted of ions from the background plasma is produced by the interaction of the plasma jet with the walls of the vacuum chamber. The fast-ion population is composed of ions from the plasma beam moving at supersonic speeds with respect to the low-energy ions. The decreasing spatial profiles of the plasma-jet current density are compared with those of the low-energy ion group, which are not uniform along the axis of symmetry because of the small contributions from other ion populations with intermediate speeds.

‘As we all know’: Examining Chinese EFL learners' use of interpersonal grammatical metaphor in academic writing

This article investigates Chinese EFL learners' use of evaluation and stance in academic texts by exploring their deployment of interpersonal grammatical metaphors (IGM), a construct mapped within Systemic Functional Linguistics (SFL; Halliday, 1985; e.g., I believe, it is evident, etc.). The data is drawn from the Chinese Longitudinal Learner Corpus (CLLC), a two-year diachronic study into university learners' development of academic literacy (Liardet, 2014a). When examining IGM, it is important to distinguish which metaphors of modality achieve the registers valued in academic discourse, namely, epistemic metaphors construed objectively (Hyland, 1998a; Schleppegrell, 2002). In the analysis of the CLLC, a widely used construction emerged, that of as we all know (e.g., it is known to all, as we know, etc.). To account for this construct, an additional axis has been mapped across Halliday's (1985) model of IGM. Building on SFL's framework of Appraisal and specifically, the system of ‘engagement’, the axis of expansion is used here to distinguish expressions that expand the ‘dialogic space’ (e.g., it is suggested; Martin & White, 2005; see also, Hyland, 2000, 2002) from those that contract this space (e.g., it is certain). In addition to the Chinese EFL learners' reliance on such deontic, contracting metaphors, this paper explores their preference for subjective realizations and identifies key areas for pedagogical intervention.

Joa?o Pessoa (PB) and Aracaju (SE): about modernization and modern architecture

The 1950s and 1960s represent an important moment of Brazilian development, in which medium-sized cities went through an intense process of modernization driven by a developmental project that has particular impact in the Northeast. The development discourse propelled the modernization process of many northeastern capitals was based on symbols such as the automobile, the skyscraper and the spread of the vocabulary of modern architecture. Cities like Joa?o Pessoa and Aracaju promoted important urban transforma- tions aimed at legitimizing a condition of progress and modernity creating new axes of urban expansion, erecting tall buildings and renewing the urban landscape through the receiving architectural elements such as butter ies roofs, prismatic volumes and pillars “V“. This communication aims to analyze the possible approaches between the discourse and modernization processes performed in these northeastern capitals. The focus of this communication sets the process of di usion and reception of modern architecture in Brazil within the time frame mentioned above, through a compar- ative analysis of the production of this architecture in the cities of Joa?o Pessoa and Aracaju. The production of modern architecture in Joa?o Pessoa is, to some extent, related with architects from Recife making projects to clients in Joa?o Pessoa (e.g. Aca?cio Gil Borsoi) and architects from Parai?ba graduated by the School of Fine Arts of Pernambuco, in addition to the intellectual and cultural life of this capital. On the other hand, the production of modern architecture in Aracaju although it was carried out largely through the work of designers and engineers, despite the proximity of Salvador (BA), another important cultural center in the Northeast, has elements of the same modern vocabulary - a process which was intensi ed Post-Brasilia. So, how circulated the ideas that drove the desire and the search for modernization, that resulted in a certain image of modernity in two northeastern capital midsized?

Spatial structure of ion beams in an expanding plasma

We report spatially resolved perpendicular and parallel, to the magnetic field, ion velocity distribution function (IVDF) measurements in an expanding argon helicon plasma. The parallel IVDFs, obtained through laser induced fluorescence (LIF), show an ion beam with v ≈ 8000 m/s flowing downstream and confined to the center of the discharge. The ion beam is measurable for tens of centimeters along the expansion axis before the LIF signal fades, likely a result of metastable quenching of the beam ions. The parallel ion beam velocity slows in agreement with expectations for the measured parallel electric field. The perpendicular IVDFs show an ion population with a radially outward flow that increases with distance from the plasma axis. Structures aligned to the expanding magnetic field appear in the DC electric field, the electron temperature, and the plasma density in the plasma plume. These measurements demonstrate that at least two-dimensional and perhaps fully three-dimensional models are needed to accurately describe the spontaneous acceleration of ion beams in expanding plasmas.

A Brief Overview about Laser-Ablated Molybdenum Plasma Properties

First step in molybdenum isotope separation for medical purposes project, based in laser ablation followed by electromagnetic separation methods, is the characterization of ablated plasma plume. In this work, a depth profile emission spectroscopy study of laser-ablated molybdenum plasma expanding on air at atmospheric pressure was performed, considering Local Thermodynamic Equilibrium and one-dimensional uniform expanding models. Plasma temperature, electron density, electron population distribution and electron impact width parameter were evaluated along plasma expansion axis and reach average values of 15000 K,1018cm-3, 1% of electron populationat 4d45s6sstate and (0.017±0.008) nm, respectively. Furthermore, mean velocity of (5.0±0.7) km/sand the plasma lifetime that was (160± 14)ns for length equal to (1.80±0.05) mm weremeasured. So, this work includes a description of mainly plasma plume parameters, which permits a discussion for isotope separation methods related to laser ablation.

Retention of gene diversity during the spread of a non-native plant species.

Spatial expansion, which is a crucial stage in the process to successful biological invasion, is anticipated to profoundly affect the magnitude and spatial distribution of genetic diversity in novel colonized areas. Here, we show that, contrasting common expectations, Pyrenean rocket (Sisymbrium austriacum), retained SNP diversity as this introduced plant species descended in the Meuse River Basin. Allele frequencies did not mirror between-population distances along the predominant expansion axis. Reconstruction of invasion history based on the genotypes of historical herbarium specimens indicated no influence of additional introductions or multiple points of entry on this nongradual pattern. Assignment analysis suggested the admixture of distant upstream sources in recently founded downstream populations. River dynamics seem to have facilitated occasional long-distance dispersal which brought diversity to the expansion front and so maintained evolutionary potential. Our findings highlight the merit of a historical framework in interpreting extant patterns of genetic diversity in introduced species and underscore the need to integrate long-distance dispersal events in theoretical work on the genetic consequences of range expansion.

Time resolved anisotropic emission from an aluminium laser produced plasma

The polarisation anisotropy of the emission from a laser produced aluminium plasma has been studied using time and polarisation resolved spectroscopy at various background pressures of air. A Wollaston prism was used to resolve the emission from the plasma into polarisation components that are parallel and orthogonal to the plasma expansion axis. Spectroscopy reveals that as the background pressure is increased, strongly polarised continuum emission dominates at early stages of the plasma formation. The results are compared and contrasted to similar experiments and discussed in the framework of a recombining plasma.

Electron density and temperature measurements in a magnetized expanding hydrogen plasma.

We report measurements of electron densities, n_{e}, and temperatures, T_{e}, in a magnetized expanding hydrogen plasma performed using Thomson scattering. The effects of applying an axial magnetic field and changing the background pressure in the plasma vessel on n_{e} and T_{e} along the expansion axis are reported. Magnetic field strengths (B field) up to 170 mT were applied, which are one order of magnitude larger than previously reported. The main effect of the applied B field is the plasma confinement, which leads to higher n_{e}. At B fields larger than 88 mT the electron density along the expansion axis does not depend strongly on the magnetic field strength. However, T_{e} is susceptible to the B field and reaches at 170 mT a maximum of 2.5 eV at a distance of 1.5 cm from the exit of the cascaded arc. To determine also the effect of the arc current through the arc, measurements were performed with arc currents of 45, 60, and 75 A at background pressures of 9.7 and 88.3 Pa. At constant magnetic field n_{e} decreases from the exit of the arc along the expansion axis when the arc current is decreased. At 88.3 Pa n_{e} shows a higher value close to the exit of the arc, but a faster decay along the expansion axis with respect to the 9.7 Pa case. T_{e} is overall higher at lower pressure reaching a maximum of 3.2 eV at the lower arc current of 45 A. The results of this study complement our understanding and the characterization of expanding hydrogen plasmas.