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Ternary sulfides and selenides in the distorted-perovskite structure (“chalcogenide perovskites”) are predicted by theory to be semiconductors with band gap in the visible-to-infrared and may be useful for optical, electronic, and energy conversion technologies. Density functional theory can be used in combination with computational thermodynamics to predict the pressure-temperature phase diagrams for chalcogenide perovskites. We report results using the Strongly Constrained and Appropriately Normed (SCAN) and the rVV10 density functionals, and compare to previously-published results using the PBEsol functional. We highlight the windows of thermodynamic equilibrium between solid chalcogenide perovskites and the vapor phase at high temperature and very low pressure. These phase diagrams can guide adsorption-limited growth of ternary chalcogenides by molecular beam epitaxy (MBE).
Ternary sulfides and selenides in the distorted-perovskite structure (“chalcogenide perovskites”) are predicted by theory to be semiconductors with a band gap in the visible-to-infrared and may be useful for optical, electronic, and energy conversion technologies. Here we use computational thermodynamics to predict the pressure–temperature phase diagrams for select chalcogenide perovskites. Our calculations incorporate formation energies calculated by density functional theory, and empirical estimates of heat capacities. We highlight the windows of thermodynamic equilibrium between solid chalcogenide perovskites and the vapor phase at high temperature and very low pressure. These results can guide the adsorption-limited growth of ternary chalcogenides by molecular beam epitaxy.
Roundup is a glyphosate-based herbicide (GBH) widely used in agriculture and may cause toxic effects in non-target organisms. Model organisms, as zebrafish, and analysis of gene expression by reverse transcription-quantitative PCR (RT-qPCR) could be used to better understand the Roundup toxicity. A prerequisite for RT-qPCR is the availability of appropriate reference genes; however, they have not been described for Roundup-exposed fish. The aim of this study was to evaluate the expression stability of six reference genes (rpl8, β-act, gapdh, b2m, ef1α, hprt1) and one expressed repetitive element (hatn10) in organs of males (brain, gill, testis) and females (ovary) of zebrafish exposed to Roundup WG at three concentrations (0.065, 0.65 and 6.5 mg N-(phosphonomethyl) glycine/l) for 7 days. Genes were ranked by geNorm, NormFinder, BestKeeper, Delta Ct and RefFinder, and their best combinations were determined by geNorm and NormFinder programs. The two most stable ranked genes were specific to each organ: gill (β-act; rpl8); brain (rpl8; β-act); testis (ef1α; gapdh); and ovary (rpl8; hprt1). The cat transcript level was used to evaluate the effect of normalization with these reference genes. These are the first suitable reference genes described for the analysis of gene expression in organs of Roundup-exposed zebrafish, and will allow investigations of the molecular mechanisms of Roundup toxicity.
The first analyses of biological components in glaciers of the Chilean lake district are presented based on microalgae biovolume, pollen and other microorganisms detected in shallow (∼10 m) firn/ice cores. Three cores were retrieved, two at Volcán Mocho-Choshuenco (39°55′ S, 72°02′ W; summit at 2422 m a.s.l; east glacier at 2000 m a.s.l.), and one at the summit of Volcán Osorno (41°06′ S, 72°30′ W; 2652 m a.s.l.). Microalgae, protozoa and pollen quantified in the samples obtained from the two summit cores show clear fluctuations interpreted as seasonal signs. In contrast, δD and many chemical species from the summit cores show strong dampening at depth, probably due to water percolation. The limited information provided by isotopic and chemical analyses is used to support the seasonal interpretation of biological parameters from the summit cores, with microorganism maxima inferred to occur in summer and pollen maxima in spring. A good comparison is found between mass-balance estimations from the Volcán Mocho-Choshuenco summit core and values obtained near that site by means of the stake method. It is concluded that biological analyses of firn/ice cores provide reliable estimations of annual and seasonal markers from these temperate glaciers.
Catalyst development is needed to enable the use of renewable electricity to chemically convert carbon dioxide (CO2) and water into fuels and chemicals, a more sustainable, lower-carbon alternative to conventional processes that produce fuels and chemicals based on fossil resources. In this study, the catalytic activity and selectivity of polycrystalline platinum (Pt) is thoroughly characterized for the CO2 reduction reaction, based on an electrochemical cell design that offers high sensitivity for product detection. Thin polyaniline films are then electrodeposited onto polycrystalline Pt foils to form hybrid organic–inorganic surfaces. The addition of the polymer is observed to have an impact on the catalytic chemistry, yielding up to a fivefold enhancement in formate and CO production over pure Pt foils. This work elucidates new strategies to perturb interfacial chemistry in a manner that could help steer CO2 electro-reduction catalysis in desired directions.
Expose is a multi-user instrument for astrobiological and astrochemical experiments in space. Installed at the outer surface of the International Space Station, it enables investigators to study the impact of the open space environment on biological and biochemical test samples. Two Expose missions have been completed so far, designated as Expose-E (Rabbow et al. 2012) and Expose-R (Rabbow et al. this issue). One of the space-unique environmental factors offered by Expose is full-spectrum, ultraviolet (UV)-rich electromagnetic radiation from the Sun. This paper describes and analyses how on Expose-R, access of the test samples to Solar radiation degraded during space exposure in an unpredicted way. Several windows in front of the Sun-exposed test samples acquired a brown shade, resulting in a reduced transparency in visible light, UV and vacuum UV (VUV). Post-flight investigations revealed the discolouration to be caused by a homogenous film of cross-linked organic polymers at the inside of the windows. The chemical signature varied per sample carrier. No such films were found on windows from sealed, pressurized compartments, or on windows that had been kept out of the Sun. This suggests that volatile compounds originating from the interior of the Expose facility were cross-linked and photo-fixed by Solar irradiation at the rear side of the windows. The origin of the volatiles was not fully identified; most probably there was a variety of sources involved including the biological test samples, adhesives, plastics and printed circuit boards. The outer surface of the windows (pointing into space) was chemically impacted as well, with a probable effect on the transparency in VUV. The reported analysis of the window contamination on Expose-R is expected to help the interpretation of the scientific results and offers possibilities to mitigate this problem on future missions – in particular Expose-R2, the direct successor of Expose-R.
Four distinct fossil turtle assemblages (Chelonia) are recognized from the Panama Canal Basin. The oldest, from the late Eocene–early Oligocene Gatuncillo Formation, is dominated by podocnemidid pleurodires. The early Miocene Culebra Formation includes both podocnemidids and trionychids. The early to middle Miocene Cucaracha Formation includes taxa classified in Geoemydidae (including Rhinoclemmys panamaensis n. sp.), Kinosternidae (represented by Staurotypus moschus n. sp.), large testudinids, trionychids, and podocnemidids, and finally, the late Miocene Gatun Formation records cheloniid sea turtles. These fossils include the oldest known representatives of Rhinoclemmys, the oldest record of kinosternids in Central America with a more extensive southern paleodistribution for Staurotypus and staurotypines in general, early occurrences of giant tortoises in the Neotropics, the oldest occurrence of soft-shell turtles in the tropics, the oldest late Eocene–early Oligocene Neotropical occurrences of podocnemidids. The Panamanian fossil turtles represent clades that are primarily endemic to North America, showing their very early arrival into the Neotropics prior to the complete emergence of the Isthmus of Panama, as well as their first contact with Caribbean-South American pleurodires by the early Miocene.
The design and construction of an instrumentation for NOX degradation in a dielectric-barrier discharge reactor (DBDR) is presented. This is endowed with a parallel plane electrode glass-glass (GG) circular geometry configuration. A solid-state multi-cellular power supply was produced in order to generate the plasma discharge. The power supply is based on a full-bridge voltage inverter commanded by three 4.33 kHz square-wave signals. Thus, the output converter signal is filtered by a resonant LC circuit, providing a 13 kHz sine wave to the DBDR. Initial results showing high removal efficiencies of about 97% have been obtained by means of this instrumentation.
A dielectric barrier discharge (DBD) has been successfully applied to studying, both theoretically and experimentally, phenol degradation in waste water aqueous solutions. A coaxial reactor was selected where the liquid waste constitutes a part of the internal electrode itself, the liquid solution flowing up inside the hollow internal electrode impelled by a submersible pump. Thus, the solution falls by gravity on the external surface of the internal electrode. The DBD gas flows in parallel to the surface of the liquid. The cold plasma was generated from Ar-O2 mixture and O2 pure with the inclusion of moisture from the same solution. Two power supplies were compared delivering potentials up to 23 kV at 1.5 kHz, and up to 12 kV at 15.6 kHz respectively. The initial concentration of phenol was around 5 × 10−3 mol/L and efficiencies up to 99% were obtained after 1 h of treatment. Finally, a simplified kinetics model was developed where the temporal evolution of the compounds generated in the phenol degradation process was analyzed. Hydroquinone, catechol and resorcinol were obtained as byproducts and H2O, CO2 and some light carboxylic acids as final products.
This contribution presents the results obtained by a Mexican laboratory in the Asia-Pacific Economy Cooperation Interlaboratory Comparison (IC) on mechanical properties by nanoindentation from 2008 using fused silica and polycarbonate as samples. Reduced modulus and indentation hardness are the parameters asked to be measured and compared. The aim for this paper is to show and to discuss the so called “indentation size effect” (ISE) on the indentation hardness of fused silica. Using the spherical formulation of the ISE model for crystalline materials, the macroscopic hardness and material length scale of fused silica are determined as (7.34 ± 0.085) GPa and (166.36 ± 14) nm, respectively.
In this chapter we study the structure of the fiscal system of the Viceroyalty of New Granada toward the end of the colonial period. Then we discuss how the tax system inherited from the Spanish Empire evolved over the period 1821–50.
The conclusion that emerges from the review of the evidence is that the new republic was successful in improving the tax regime it had received from Spain. By 1850, the Republic of New Granada possessed a fiscal system that was much more fair, efficient, and neutral than it had been in 1810.
In 1717 the Captaincy-General of New Granada was raised to the status of viceroyalty. However, six years later New Granada was again declared to be a Captaincy-General. Finally, in 1739 the Viceroyalty of New Granada was reestablished. The viceroyalty included basically the territory of what is now the Republic of Colombia plus Panamá; the Captaincy-General of Venezuela, over which it had very little control; and the Presidency of Quito. In this chapter, when we refer to the Viceroyalty of New Granada we only include the territory of the present republics of Colombia and Panamá.
In the 1810s, when most of the Spanish American colonies achieved their independence, the former territories of the Viceroyalty of New Granada formed the Republic of Colombia, comprising modern Venezuela, Colombia, Panamá, and Ecuador. However, by 1831 it had broken up into three separate republics: Venezuela, Ecuador, and New Granada.
In the spring of 2000, the department of political science at the University of Colorado received a Preparing Future Faculty (PFF) grant through the American Political Science Association. Grant funds were used to sponsor discussions about how best to prepare young political scientists to meet their professional and scholarly responsibilities as members of the discipline (see <www.preparing-faculty.org>). A central theme of a recent PFF meeting at Colorado was the importance of mentoring relationships in the process of graduate student education and faculty preparation.
We investigate the best order of smoothness of
Lp(Lq). We prove
in particular that
there exists a [Cscr ]∞-smooth bump function on
if and only if p and q are even
integers and p is a multiple of q.
Below-ground herbivores have been poorly studied regardless of their importance for the establishment and composition of plant communities. In a subalpine grassland associated with a 3200-m-elevation pine forest in central Mexico, the composition and vertical and horizontal distribution of the macroarthropod root-feeding community was studied for 14 months. The root-feeding community included six species of Coleoptera and one species of Diptera. The dominant species were Phyllophaga spp. (subgenus Phytallus, "macrophylla" group) and Trachyploeomimus aff. spurcus Champion. Mean density and biomass of this community were 101 individuals and 3 g per square metre, respectively. These values were low when compared with those reported for other communities. Species were most abundant in the first 10 cm of the soil all year around. Dominant species showed a clumped horizontal distribution most of the year.
A non-destructive method for determining water, protein, lipid and ash content along with lean body
mass (LBM; total body mass – total lipid mass) in live channel catfish was evaluated. This non-invasive technique involved placing the fish within a low-frequency electromagnetic field and measuring the total body electrical conductivity (TOBEC) based on the distinct electrical
characteristics of body fat and fat-free tissues. The correlations between TOBEC and whole-body composition were examined using age-1+ channel catfish ranging from 44 to 175 g. Significant linear relationships between TOBEC, body weight, and total length, or combinations of these parameters, and LBM, ash, lipid, protein, and water content were found; r2 values ranged from 0.863 to 0.998. Equations for predicting body composition from TOBEC and morphometric measurements were developed. Analysis of an independent group of fish demonstrated TOBEC equations to be reliable predictors of body composition. This technique should allow successive monitoring of body composition of individual fish at different times and provide additional insight into
the body composition dynamics of channel catfish.
Insomnia is widely accepted as a leading feature of that illness designated by the number 301.1 in the International Classification of Diseases. The name given varies—“endogenous depression”, “manic-depressive psychosis/depressive type”, “melancholia” or “depressive illness”. The present generation of laymen (not to say some psychiatrists) use the word “depression” so freely in order to describe an unpleasant, unhappy mood, whether lasting or transient, that one may prefer the term melancholia, or at least “depressive illness”, to signify that condition which justifies the number 301.1. The adjective “endogenous” implies for many that environmental stress plays little or no part in the onset of the illness; we cannot accept that this is always so. The term “reactive” is used in several ways, generally to indicate that the state of unhappiness arises out of some external circumstance and that it would end when circumstances improved or the individual accepted the realities of practical life. The patients used in the present study were suffering from an illness of a kind which we believe may sometimes develop in the absence of severe environmental stress, while in others it may be clearly provoked by circumstances, but the illness, as it develops, may take on a form which becomes largely independent of the environmental circumstances and may continue even when the provoking factors are past; it has become an autonomous melancholia. It will be apparent that by autonomous melancholia we mean an illness shown by clinical experience to respond especially well to electroplexy.
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