Vapor pressure measurements over supercooled water in the temperature range from −10 1 °C to +10 −2 °C

An accurate measurement of saturation vapor pressure of supercooled water is a strong challenge in metrology, mainly due to difficulties concerning keeping water at a liquid state at temperatures well below the melting point; thus few experimental data covering limited temperature ranges (down to about 253 K) are reported in literature. For this reason, an investigation of the water vapor – supercooled water equilibrium along the saturation line is carried out at Istituto Nazionale di Ricerca Metrologica (INRIM). Measurements cover the temperature range from 261.26 K to 273.25 K, corresponding to a saturation vapor pressure from about 244 Pa to 611 Pa. The experimental apparatus includes a borosilicate glass sample cell, kept in a liquid bath at a constant temperature with millikelvin stability and connected to a manifold where the pressure is measured using a capacitive diaphragm pressure gauge. In this work, the water sample preparation, the measuring method and measurement corrections are reported; moreover, a comparison between experimental and literature data is conducted along with the most used vapor pressure formulations. Measurement results are discussed and uncertainty sources estimated. The resulting expanded relative uncertainty (k = 2) varies from 0.085% at 261.26 K to 0.039% at 273.25 K

Application of plate heat exchangers to the development of portable high-pressure humid gas generators

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.The preliminary design and testing of a portable, high-pressure humidity generator based on a corrugated-plate heat exchanger (PHE) is described. It resulted in a very simple system, consisting of a bubbling pre-saturator followed by the PHE used as a condenser. The PHE does not need to be hosted in a liquid bath, resulting in a very compact design whose operation is largely independent from a specific bath - which may be available on site – used to condition the temperature of a circulating counter-flow fluid. Experimental tests were performed on a prototype in order to demonstrate the principle and validate at an early stage the system operation. The efficiency of the PHE as condenser was assessed over a temperature range from 0 °C to 65 °C by varying input and influence parameters, such as the dew point temperature, the gas flow rate and its pressure up to 0.5 MPa. The saturation temperature of the humid gas flow compared favourably with the dew-point temperature as measured by a chilled-mirror hygrometer calibrated against a primary humidity standard. The temperature deviations were below 0.02 °C, with a maximum deviation of 0.04 °C, over the whole range of investigated temperatures and pressures.cf201

A phylogeographical perspective on the ex situ conservation of Aylacostoma (Thiaridae, Gastropoda) from the High Paraná River (Argentina-Paraguay)

AylacostomaSpix, 1827, contains species that are the subject of focused conservation efforts under the auspices of the 'AylacostomaProject', the only ex situ conservation programme for freshwater gastropods in South America. Two species from the High Paraná River (Argentina-Paraguay) are included in this programme (Aylacostoma chloroticumHylton Scott, 1954 and Aylacostoma brunneumVogler & Peso, 2014), as their habitats have disappeared as a consequence of the filling of the Yacyretá Reservoir in the 1990s. At present, A.chloroticum is restricted to only one known wild population in a small and fragile habitat, and wild populations of A.brunneum are presumed to have gone extinct. We used partial sequences of the cytochrome oxidase subunit I gene to provide the first phylogeographical perspective on these species from a limited dataset containing representatives of several wild populations that are successfully being bred in captivity. We found low genetic diversity and two haplotypes in A.chloroticum, and absence of variation with one haplotype in A.brunneum. The reservoir's entry zone was identified to be of great interest for conservation, and is where we suggest re-introductions and translocations should be targeted, to preserve the future evolutionary potential of the extant diversity.Facultad de Ciencias Naturales y Muse

Threatened Neotropical mollusks: Analysis of shape differences in three endemic snails from High Paraná River by geometric morphometrics

Variation in shape among a living and 2 extinct aquatic snails of the genus Aylacostoma, using a geometric morphometric method of thin plate splines and multivariate analysis was investigated. The analysis was performed to evaluate the diagnostic capability of this method and to explore shell shape differences, due to the lack of other data, in an attempt to answer why only 1 of the species persisted in the wild. Sixteen landmarks in a bi-dimensional space for 32 shells of type, paratype and reference specimens deposited in museums of Argentina were defined. Analysis was successful in assigning individual specimens to particular species. Statistically significant differences in last whorl, aperture, and spire were found for the first 4 non-uniform components explaining an 85% of local variation observed. Differences could be related to a differential use of habitat and/or to the degree of exposure to water current. More globose shell found in the extinct species could be associated to habitats and substrata with the highest water currents, whereas the more stylized shell in the third species could be related to a preference for more protected habitats, like those where it presently occurs.Facultad de Ciencias Naturales y Muse

Threatened Neotropical mollusks: Analysis of shape differences in three endemic snails from High Paraná River by geometric morphometrics

Variation in shape among a living and 2 extinct aquatic snails of the genus Aylacostoma, using a geometric morphometric method of thin plate splines and multivariate analysis was investigated. The analysis was performed to evaluate the diagnostic capability of this method and to explore shell shape differences, due to the lack of other data, in an attempt to answer why only 1 of the species persisted in the wild. Sixteen landmarks in a bi-dimensional space for 32 shells of type, paratype and reference specimens deposited in museums of Argentina were defined. Analysis was successful in assigning individual specimens to particular species. Statistically significant differences in last whorl, aperture, and spire were found for the first 4 non-uniform components explaining an 85% of local variation observed. Differences could be related to a differential use of habitat and/or to the degree of exposure to water current. More globose shell found in the extinct species could be associated to habitats and substrata with the highest water currents, whereas the more stylized shell in the third species could be related to a preference for more protected habitats, like those where it presently occurs.Facultad de Ciencias Naturales y Muse

First records of four exotic slugs in Argentina

Fil: Gutiérrez Gregoric, Diego Eduardo. División Zoología Invertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Beltramino, Ariel Aníbal. División Zoología Invertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Vogler, Roberto Eugenio. División Zoología Invertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Cuezzo, María G.. Instituto de Biodiversidad Neotropical. Facultad de Ciencias Naturales. Universidad Nacional de Tucumán. Tucumán; ArgentinaFil: Núñez, María Verónica. División Zoología Invertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Gomes, Suzete R.. National Malacology Laboratory. USDA APHIS PPQ NIS. Academy of Natural Sciences. Philadelphia; USAFil: Virgillito, Marisol. División Invertebrados. Museo Argentino de Ciencias Naturales Bernardino Rivadavia. Buenos Aires; ArgentinaFil: Miquel, Sergio Eduardo. División Invertebrados. Museo Argentino de Ciencias Naturales Bernardino Rivadavia. Buenos Aires; Argentin

Threatened gastropods under the evolutionary genetic species concept: redescription and new species of the genus Aylacostoma (Gastropoda: Thiaridae) from High Paraná River (Argentina–Paraguay)

The genus Aylacostoma Spix, 1827, is mainly endemic to South America, and comprises about 30 nominal species, most of which were described based solely on conchological features following the typological approaches of most of the 19th and the mid-20th century authors. Here, we redescribe Aylacostoma chloroticum Hylton Scott, 1954, and describe Aylacostoma brunneum sp. nov. from the High Paraná River (Argentina–Paraguay) by means of morphological and molecular characters. Both are threatened species currently included into an ongoing ex situ conservation programme, as their habitats have disappeared because of damming and the filling up of the Yacyretá Reservoir in the early 1990s. We used DNA sequences from cytochrome b and cytochrome oxidase subunit I (COI) genes to estimate their genetic distances, and the COI sequences were also used to assess their specific status under the evolutionary genetic species concept by means of the K/θ method. Our results clearly demonstrate that both must be recognized as evolutionary genetic species, despite only minor differences in morphological characters other than in the shells.Facultad de Ciencias Naturales y Muse

Hidden diversity in waterfall environments: The genus <i>Acrorbis</i> (Gastropoda: Planorbidae) from the Upper-Paraná Atlantic Forest

High-energy freshwater environments such as rapids and waterfalls in the Upper-Paraná Atlantic Forest are home to highly endemic minute freshwater snails of the genus Acrorbis. Only one species, Acrorbis petricola, is currently included within this genus, whose geographical distribution is restricted to three known populations, one in Brazil and the other two in Argentina. Because of habitat specificity and limited geographical distribution, the species is considered vulnerable in Argentina and endangered in Brazil. In this work, we identify five new populations of A. petricola in southern Upper-Paraná Atlantic Forest, exclusively found on waterfalls from the Misiones Province, Argentina. Based on these populations and on specimens of one of the two historical populations from the Misiones Province, we explored the morphological features of shells and reproductive system of specimens from each location and provide the first molecular data on the species. We used DNA sequences from cytochrome c oxidase subunit I (COI) and 16S-rRNA genes to investigate the molecular diversity, genetic distances and genealogical relationships among populations. We verified the existence of intra- and interpopulation morphological variability, with the greatest variation being found in spire, spiral sculpture, penis sheath, flagella, prostatic diverticula and bursa copulatrix. We found interpopulation genetic diversity, with no intrapopulation variation, and identified six geographically structured genetic lineages with maximum genetic distances of up to 2.3%. Different combinations of morphological characters with the same genetic background within each locality were observed. The finding of new populations genetically differentiated not only broadens the known distribution of the species, but also illustrates that waterfall environments in the Atlantic Forest harbour a hidden diversity of Acrorbis that still remains to be discovered. This scenario suggests a complex evolutionary history that needs to be unveiled and taken into account for future development of conservation strategies in this endemic genus.Facultad de Ciencias Naturales y MuseoCentro de Estudios Parasitológicos y de Vectore

Estudio de las prestaciones de cabezales arroceros con sistema draper

65-78En un establecimiento arrocero de la provincia de Corrientes se evaluó el desempeño de una cosechadora axial equipada con un cabezal de 25 pies con sistema draper. Se realizó cuatro tratamientos: cosechadora con cabezal 625D a velocidad 3 km-h (T1); 3,5 km-h (T2); 4 km-h (T3); 4,5 km-h (T4). Las variables en estudios (variables respuestas) fueron: pérdidas por cola, daño mecánico al grano, ruido. Las determinaciones de daño mecánico se realizó en cuatro lugares: draper, sinfines alimentadores del cilindro axial, extremo inferior de noria y tolva de almacenamiento. Para las determinaciones de ruido se realizó mediciones de acuerdo con las normas sugeridas por el Instituto de Ingeniería Rural del INTA Castelar. Conclusiones: 1) Los daños ocasionados a los granos, medidos como grano quebrado, tienen como principal responsable al mecanismo alimentador de sinfines. 2) El sistema draper se comportó en forma eficiente produciendo el conjunto draper, molinete y cuchillas de corte daños mínimos. 3) Los sistemas de alimentación (cabezal) y el sistema de trilla axial no mostraron saturación aún a las velocidades más altas de 4,5 km-h comportándose eficientemente. 4) A partir de los 3,2 km-h el sistema de separación y el de limpieza comenzaron a mostrar saturación elevándose las pérdidas en forma no proporcional. 5) El ruido para el operador dentro de la cabina satisface las normativas para realizar jornadas completas de labor demostrando un alto nivel de insonorización respecto del ruido exterior de la máquina