Convective condensation of R134a and R1234ze(E) inside microfin tube

Environmental concerns are forcing the replacement of the commonly used refrigerants and finding new fluids is a top priority. The hydro-fluoro-olefin (HFO) R1234ze(E), because of its smaller global warming potential (GWP) and shorter atmospheric lifetime, replaced R134a. Accordingly, for HVAC systems design, a detailed knowledge of the thermo-fluid-dynamic characteristics of the fluids and reliable predictive models are required. To improve the understanding, R134a and R1234ze(E) were employed in convective condensation experiments (saturation temperature Tsat = 35°C, mean quality xm = 0.1~0.9, quality changes Δx = 0.05~0.6, mass flux G = 43~444 kg·m-2s-1) inside a microfin tube (outer diameter D = 9.52 mm, fin number n = 60, fin height H = 0.2 mm). The results were used for two goals: the former is the comparison of the heat transfer features of the two fluids, while the latter aims at testing the performance of prediction models available in the open literature. At the saturation temperature T = 35°C, the two fluids show small differences in the thermal properties so that, as expected, the experiments highlighted a very similar behavior in the typical operating conditions of HVAC systems. In fact, for all the operating conditions marginal differences were observed in the pressure drop, the heat transfer coefficient and the flow pattern maps. The issue of prediction reliability, however, is still open. Actually, not all the models achieving good results for R134a show the same performance for R1234ze(E), especially for the pressure drop

Transcriptional variation of sensory-related genes in natural populations of Aedes albopictus

BACKGROUND: The Asian tiger mosquito, Aedes albopictus, is a highly dangerous invasive vector of numerous medically important arboviruses including dengue, chikungunya and Zika. In four decades it has spread from tropical Southeast Asia to many parts of the world in both tropical and temperate climes. The rapid invasion process of this mosquito is supported by its high ecological and genetic plasticity across different life history traits. Our aim was to investigate whether wild populations, both native and adventive, also display transcriptional genetic variability for functions that may impact their biology, behaviour and ability to transmit arboviruses, such as sensory perception. RESULTS: Antennal transcriptome data were derived from mosquitoes from a native population from Ban Rai, Thailand and from three adventive Mediterranean populations: Athens, Greece and Arco and Trento from Italy. Clear inter-population differential transcriptional activity was observed in different gene categories related to sound perception, olfaction and viral infection. The greatest differences were detected between the native Thai and the Mediterranean populations. The two Italian populations were the most similar. Nearly one million quality filtered SNP loci were identified. CONCLUSION: The ability to express this great inter-population transcriptional variability highlights, at the functional level, the remarkable genetic flexibility of this mosquito species. We can hypothesize that the differential expression of genes, including those involved in sensory perception, in different populations may enable Ae. albopictus to exploit different environments and hosts, thus contributing to its status as a global vector of arboviruses of public health importance. The large number of SNP loci present in these transcripts represents a useful addition to the arsenal of high-resolution molecular markers and a resource that can be used to detect selective pressure and adaptive changes that may have occurred during the colonization process

Transcriptional variation of sensory-related genes in natural populations of Aedes albopictus

BACKGROUND: The Asian tiger mosquito, Aedes albopictus, is a highly dangerous invasive vector of numerous medically important arboviruses including dengue, chikungunya and Zika. In four decades it has spread from tropical Southeast Asia to many parts of the world in both tropical and temperate climes. The rapid invasion process of this mosquito is supported by its high ecological and genetic plasticity across different life history traits. Our aim was to investigate whether wild populations, both native and adventive, also display transcriptional genetic variability for functions that may impact their biology, behaviour and ability to transmit arboviruses, such as sensory perception. RESULTS: Antennal transcriptome data were derived from mosquitoes from a native population from Ban Rai, Thailand and from three adventive Mediterranean populations: Athens, Greece and Arco and Trento from Italy. Clear inter-population differential transcriptional activity was observed in different gene categories related to sound perception, olfaction and viral infection. The greatest differences were detected between the native Thai and the Mediterranean populations. The two Italian populations were the most similar. Nearly one million quality filtered SNP loci were identified. CONCLUSION: The ability to express this great inter-population transcriptional variability highlights, at the functional level, the remarkable genetic flexibility of this mosquito species. We can hypothesize that the differential expression of genes, including those involved in sensory perception, in different populations may enable Ae. albopictus to exploit different environments and hosts, thus contributing to its status as a global vector of arboviruses of public health importance. The large number of SNP loci present in these transcripts represents a useful addition to the arsenal of high-resolution molecular markers and a resource that can be used to detect selective pressure and adaptive changes that may have occurred during the colonization process

Viviparity and habitat restrictions may influence the evolution of male reproductive genes in tsetse fly (Glossina) species

11openInternationalInternational coauthor/editorBackground Glossina species (tsetse flies), the sole vectors of African trypanosomes, maintained along their long evolutionary history a unique reproductive strategy, adenotrophic viviparity. Viviparity reduces their reproductive rate and, as such, imposes strong selective pressures on males for reproductive success. These species live in sub-Saharan Africa, where the distributions of the main sub-genera Fusca, Morsitans, and Palpalis are restricted to forest, savannah, and riverine habitats, respectively. Here we aim at identifying the evolutionary patterns of the male reproductive genes of six species belonging to these three main sub-genera. We then interpreted the different patterns we found across the species in the light of viviparity and the specific habitat restrictions, which are known to shape reproductive behavior. Results We used a comparative genomic approach to build consensus evolutionary trees that portray the selective pressure acting on the male reproductive genes in these lineages. Such trees reflect the long and divergent demographic history that led to an allopatric distribution of the Fusca, Morsitans, and Palpalis species groups. A dataset of over 1700 male reproductive genes remained conserved over the long evolutionary time scale (estimated at 26.7 million years) across the genomes of the six species. We suggest that this conservation may result from strong functional selective pressure on the male imposed by viviparity. It is noteworthy that more than half of these conserved genes are novel sequences that are unique to the Glossina genus and are candidates for selection in the different lineages. Conclusions Tsetse flies represent a model to interpret the evolution and differentiation of male reproductive biology under different, but complementary, perspectives. In the light of viviparity, we must take into account that these genes are constrained by a post-fertilization arena for genomic conflicts created by viviparity and absent in ovipositing species. This constraint implies a continuous antagonistic co-evolution between the parental genomes, thus accelerating inter-population post-zygotic isolation and, ultimately, favoring speciation. Ecological restrictions that affect reproductive behavior may further shape such antagonistic co-evolution.openSavini, Grazia; Scolari, Francesca; Ometto, Lino; Rota-Stabelli, Omar; Carraretto, Davide; Gomulski, Ludvik M.; Gasperi, Giuliano; Abd-Alla, Adly M. M.; Aksoy, Serap; Attardo, Geoffrey M.; Malacrida, Anna R.Savini, G.; Scolari, F.; Ometto, L.; Rota-Stabelli, O.; Carraretto, D.; Gomulski, L.M.; Gasperi, G.; Abd-Alla, A.M.M.; Aksoy, S.; Attardo, G.M.; Malacrida, A.R

High promiscuity among females of the invasive pest species Drosophila suzukii

Drosophila suzukii (Matsumura, 1931), the spotted-wing drosophila, is a highly invasive fruit fly that spread from Southern Asia across most regions of Asia and, in the last 15 years, has invaded Europe and the Americas. It is an economically important pest of small fruits such as berries and stone fruits. Drosophila suzukii speciated by adapt ing to cooler, mountainous, and forest environments. In temperate regions, it evolved seasonal polyphenism traits which enhanced its survival during stressful winter population bottlenecks. Consequently, in these temperate regions, the populations undergo seasonal reproductive dynamics. Despite its economic importance, no data are available on the behavioural reproductive strategies of this fly. The presence of polyandry, for example, has not been determined despite the important role it might play in the reproductive dynamics of populations. We explored the presence of poly andry in an established population in Trentino, a region in northern Italy. In this area, D. suzukii overcomes the winter bottleneck and undergoes a seasonal reproductive fluctuation. We observed a high remating frequency in females during the late spring demographic explosion that led to the abundant summer population. The presence of a high degree of polyandry and shared paternity associated with the post-winter population increase raises the question of the possible evolutionary adaptive role of this reproductive behaviour in D. suzuki

Preparation and monitoring of small animals in renal MRI

Renal diseases remain devastating illnesses with unacceptably high rates of mortality and morbidity worldwide. Animal models are essential tools to better understand the pathomechanism of kidney-related illnesses and to develop new, successful therapeutic strategies. Magnetic resonance imaging (MRI) has been actively explored in the last decades for assessing renal function, perfusion, tissue oxygenation as well as the degree of fibrosis and inflammation. This chapter aims to provide an overview of the preparation and monitoring of small animals before, during, and after surgical interventions or MR imaging. Standardization of experimental settings such as body temperature or hydration of animals and minimizing pain and distress are essential for diminishing nonexperimental variables as well as for conducting ethical research.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers

Liquid holdup measurement for gas-liquid stratified flows by means of resistive probes and image processing

Flow patterns exert a fundamental influence on the behaviour of multiphase flows, and they must be brought into play when dealing with their modelling. This is usually done by means of summarizing quantities as the phase holdups and the interfacial area concentration. Many techniques have been designed during the years to measure them, among which the use of probes relying on electrical resistance is one of the simplest and less expensive. While having these points of strength, resistive probes are intrusive devices. This work is therefore devoted to a comparison between liquid height (and derived quantities) measurements - for stratified and stratified-wavy air-water flows - performed using a conventional resistive probe and by means of an image-based technique. Validation of the latter was performed using computer-generated flow images. Then, an experimental campaign was carried out for flows with liquid superficial velocities in the range 0.03 ÷ 0.06 m/s and gas superficial velocities in the range 0.77 ÷ 2.31 m/s. Results showed that the two methods give answers within very few percent of difference, which is more than satisfactory in this field. The results are also in good agreement with some of the most credited literature models and correlations

Liquid holdup optical measurements for horizontal stratified flows with an opaque fluid layer

This study presents a method to measure the void fraction in presence of a stratified three-phase flow with an opaque fluid like foam. The commonly used resistive probes, which were successfully applied for air-water flows, fail in detecting the liquid/foam interface due to the variable conductivity of foam. To overcome this problem, a new optical method was developed. A probe consisting of a steel rod covered in red vinyl plastic with a black measuring scale having 1 mm resolution was introduced radially into the flow; the foam layer, being opaque, can be easily identified against the measuring scale in a side view of the flow. The behavior over time of the liquid-foam interface was thus recorded through a video camera. A couple of small LED lamps provided the lighting to record the scene. The videos were then processed to count the measuring scale marks below the foam layer in order to get the instantaneous values of liquid layer depth. Measurements were performed at different pipe sections. The results were compared to those obtained for air-water flows at the same superficial velocities, with the latter ranging from 0.76 to 2.30 m/s for air and 0.03 to 0.06 m/s for water respectively. A liquid loading reduction up to 41 % was detected at the lowest gas superficial velocity, i.e. 1 m/s, while when the gas superficial velocity increases the difference in the liquid holdup lowers and becomes negligible at 2.30 m/s, regardless the value of the liquid superficial velocity. Since no specific model exists for foamy flows, as a first attempt the Zuber and Findlay drift-flux model was finally adopted to correlate the data

Pressure drop and void fraction in horizontal air-water stratified flows with smooth interface at atmospheric pressure

This work presents and analyses the results of an experimental activity aimed at the characterization of stratified air-water flow conditions, which have been poorly analyzed in previous studies although they are significant for industrial applications. Tests were performed in a 24 m long, 60 mm inner diameter PMMA pipe; the superficial velocities ranged between 0.03 m/s and 0.06 m/s for the water and between 0.41 m/s and 2.31 m/s for air. The pressure gradient along the pipeline was determined and compared to the one obtained implementing two-fluid models available in the literature. Fair agreement with the models was found only at high values of the superficial gas velocities, i.e., above 1.31 m/s. Moreover, the void fraction was measured through a resistive probe and compared with the values predicted by available models. Since none of them was able to satisfactorily predict the void fraction in the whole range of superficial velocities, a drift flux model was successfully implemented. Eventually, with both the measured pressure gradient and the void fraction, a two-fluid model was implemented in order to determine the interfacial shear stress and to compare the outcome with the literature, emphasizing the influence of the operating conditions on the prediction performance