Experimental investigation on materials and lubricants for sliding-vane air compressors

Abstract. Positive-displacement compressors and, among them, sliding-vane rotary machines are widely used in the compressed air sector. As in many other industrial fields, the efficient utilization of energy has become a major goal also in this sector. The aim of the present activity is the experimental investigation on the influence of two vanes materials (cast iron and aluminium with anodized surface) and of four commercial lubricants (characterized by different formulations and additives concentrations) on the performance of a mid-capacity sliding-vane rotary compressor in a number of operating pressures. The performance is identified by both the volume flow rate and the absorbed mechanical power, evaluated according to the international standard ISO 5167 and ISO 1217. The campaign indicates that the considered lubricants do not affect appreciably the volumetric flow rate. On the other hand, the specific lubricants determine a variation of about 1% of the mechanical power for both materials, while the specific material a variation between 0.9% and 2.6%. The best performance is achieved by aluminium vanes and a synthetic poly-α-olefin lubricant

The open and clopen Ramsey theorems in the Weihrauch lattice

We investigate the uniform computational content of the open and clopen Ramsey theorems in the Weihrauch lattice. While they are known to be equivalent to ATR_0 from the point of view of reverse mathematics, there is not a canonical way to phrase them as multivalued functions. We identify eight di\ufb00erent multivalued functions (\ufb01ve corresponding to the open Ramsey theorem and three corresponding to the clopen Ramsey theorem) and study their degree from the point of view of Weihrauch, strong Weihrauch, and arithmetic Weihrauch reducibility. In particular one of our functions turns out to be strictly stronger than any previously studied multivalued functions arising from statements around ATR_0

Modeling And Testing The Thermal Effect Of Lubricating Oil Sprayed In Sliding-Vane Air Compressors Using Pressure-Swirl Nozzles

Positive-displacement compressors and, among them, sliding-vane machines are widely used in the compressed air sector. As in many other industrial fields, the efficient utilization of energy has become a major goal also in this sector. The aim of the present activity is the numerical modeling and the experimental testing of the positive thermal effect due to spraying the lubricating oil inside sliding-vane air compressors using pressure-swirl nozzles. The benefits of proper oil atomization in positive-displacement compressors have been documented already by a number of investigations (Singh and Bowman, 1986; Stosic et al., 1988; Fujiwara and Osada, 1995; Valenti et al., 2013; Cipollone et al. 2014). The novelty of this work resides in the extension of a previous model to describe more accurately the quantity and the diameter distribution of the droplets generated by the nozzles and, consequently, to predict more precisely the heat transfer occurring between the liquid and the gas phase within a compression chamber. The model is applied to a pre-commercial mid-size compressor that is equipped with a number of pressure-swirl nozzles. The numerical data are validated successfully against the measurements of the pressure as a function of the angular position. The results indicate that the specific energy of compression is appreciable reduced with respect to the case of an adiabatic process. The model is applied here to a sliding-vane compressor, but it is general in nature and can be promptly modified for another kind of machine. It may be used also for optimizing type, number and position of the nozzles in order to further improve the performances of air compressors

A Dog with Pseudo-Addison Disease Associated with Trichuris vulpis Infection

A female Rottweiler dog was presented with a history of intermittent vomiting and diarrhoea, dysorexia, weakness, and weight loss. Haemocytometry and biochemistry values were within normal ranges except for electrolyte analyses, that demonstrated hyponatremia and hyperkalemia with a decreased sodium/potassium ratio. A diagnosis of hypoadrenocorticism was suspected. Basal and post-ACTH stimulation cortisolemia were within the normal values. Electrocardiography was normal, and thoracic radiography showed no significant modifications. On abdominal ultrasonography, adrenal glands appeared normal, while the bowel was distended, and several thin linear hyperechoic objects floating in the lumen were observed. Two adult female whipworms (Trichuris vulpis) were collected following bowel irrigation. Anthelmintic treatment against the parasite was curative

An intracooling system for a novel two-stage sliding-vane air compressor

Lube-oil injection is used in positive-displacement compressors and, among them, in sliding-vane machines to guarantee the correct lubrication of the moving parts and as sealing to prevent air leakage. Furthermore, lube-oil injection allows to exploit lubricant also as thermal ballast with a great thermal capacity to minimize the temperature increase during the compression. This study presents the design of a two-stage sliding-vane rotary compressor in which the air cooling is operated by high-pressure cold oil injection into a connection duct between the two stages. The heat exchange between the atomized oil jet and the air results in a decrease of the air temperature before the second stage, improving the overall system efficiency. This cooling system is named here intracooling, as opposed to intercooling. The oil injection is realized via pressure-swirl nozzles, both within the compressors and inside the intracooling duct. The design of the two-stage sliding-vane compressor is accomplished by way of a lumped parameter model. The model predicts an input power reduction as large as 10% for intercooled and intracooled two-stage compressors, the latter being slightly better, with respect to a conventional single-stage compressor for compressed air applications. An experimental campaign is conducted on a first prototype that comprises the low-pressure compressor and the intracooling duct, indicating that a significant temperature reduction is achieved in the duct

Cat Taming in the Western Mediterranean. Issues, Problematics and Unpredictability in the Light of Bio-archaeological Approaches to a Museum Specimen

The vast wealth of cultural artifacts and ancient biological samples can today be investigated using a great variety of methods and technologies. The result is a growing diffusion of studies on DNA, isotopes and morphometrics, and the exponential growth of publications and bio-archaeological discoveries of inestimable value for different areas of interpretation, such as phylogeny, history and archaeology. This paper describes the morphological and molecular study of a rare specimen of Felis from an Early Bronze Age horizon. The report offers the opportunity for a brief discussion on cat taming, on the origin of this practice and on the archaeological importance of this specimen for the reconstruction of taming practices in the Western Mediterranean Basin.Il vasto patrimonio culturale di manufatti e di reperti biologici antichi può attualmente essere investigato con molte metodologie e tecnologie. Ne deriva una crescente diffusione di studi sul DNA, isotopici e morfogeometrici e una crescita esponenziale delle pubblicazioni e dei risultati bio-archeologici di inestimabile valore per ambiti interpretativi diversi, filogenetici, storici, archeologici. Il presente lavoro descrive uno studio morfologico e molecolare di un raro reperto di Felis proveniente da un orizzonte del Bronzo Antico. Il report offre per altro l’occasione per una breve disamina sull’addomesticamento del gatto, la provenienza di tale pratica e sull’importanza zooarcheologica della relazione con Homo nel Mediterraneo occidentale

Experimental investigation into an ORC-based low-grade energy recovery system equipped with sliding-vane expander using hot oil from an air compressor as thermal source

Compressed air production is an energy-intensive sector, thus compressor manufacturers are constantly looking for enhancing the efficiency, by acting on several technological aspects. In an air compressor, about 80-90% of the input electric power used is wasted into the environment through the oil circuit, continuously cooled by ambient air blown via a fan. An interesting way to optimize the overall system efficiency is to exploit this waste heat to produce electrical power. Organic Rankine Cycles (ORCs) are a suitable solution for recovering energy from low-grade heat source. In this paper, an experimental analysis of two low-grade ORC-based recovery systems is presented. The thermal source is the hot lubricant of a mid-size air compressor, while the thermal sink is tap water. The first system is tested in a simple cycle configuration while the second in a recuperative one. An extensive experimental campaign is carried out on a test bench composed by sliding-vane expander, pump and plate heat exchangers. The expander differs in terms of geometry and aspect ratio between the two cycles. R236fa is used as working fluid in both the systems. The expander operating conditions are deeply investigated by using piezoelectric pressure transducers to determine the expansion indicated diagram and the expander mechanical efficiency. Experimental results show that the recuperative cycle has a better performance, in terms of cycle efficiency and expander mechanical efficiency, compared with the simple cycle. For this configuration, two off-design conditions are investigated, acting on the pump rotational speed. Finally, an exergy analysis is conducted, in order to evaluate the irreversible losses produced by each component

Fast method for skeletal tissue gene expression analysis

open9Several chronic diseases have been associated with bone alteration in the last few years. Despite the wealth of information provided by the analysis of the transcriptome in affected tissues, only a limited number of studies evaluated gene expression in bone tissue due to the difficulty to obtain high quality RNA. Therefore, skeletal pathologies have been often associated to a defective maturation process that occurs during recruitment of progenitor stem cells. In order to explore the possibility of analysing the gene expression during osteogenic differentiation in skeletal tissue, a single-step method to extract well-preserved RNA from bone specimens was performed. A comparison between this technique and a traditional method was made by analysing the quality and yield of RNA obtained. In addition, RNAs were assayed by reverse transcription-quantitative polymerase chain reaction to analyse the expression levels of the bone genes associated with the differentiation process in a mouse model. The present data showed that good quality RNA can be obtained from bone tissue by a simple single-step method allowing the expression analysis of the genes encoded by skeletal tissue. In conclusion, the present study allows the possibility to easily obtain good quality RNA from bone tissue that is suitable for gene expression studies of bone diseases.openDalle Carbonare, Luca; Vilei, Maria Teresa; Stranieri, Chiara; Innamorati, Giulio; Rosato, Antonio; Boldrin, Elisa; Sella, Stefania; Giannini, Sandro; Valenti, Maria TeresaDALLE CARBONARE, LUCA GIUSEPPE; Vilei, MARIA TERESA; Stranieri, Chiara; Innamorati, Giulio; Rosato, Antonio; Boldrin, Elisa; Sella, Stefania; Giannini, Sandro; Valenti, Maria Teres

New Insights into the Runt Domain of RUNX2 in Melanoma Cell Proliferation and Migration

The mortality rate for malignant melanoma (MM) is very high, since it is highly invasive and resistant to chemotherapeutic treatments. The modulation of some transcription factors affects cellular processes in MM. In particular, a higher expression of the osteogenic master gene RUNX2 has been reported in melanoma cells, compared to normal melanocytes. By analyzing public databases for recurrent RUNX2 genetic and epigenetic modifications in melanoma, we found that the most common RUNX2 genetic alteration that exists in transcription upregulation is, followed by genomic amplification, nucleotide substitution and multiple changes. Additionally, altered RUNX2 is involved in unchecked pathways promoting tumor progression, Epithelial Mesenchymal Transition (EMT), and metastasis. In order to investigate further the role of RUNX2 in melanoma development and to identify a therapeutic target, we applied the CRISPR/Cas9 technique to explore the role of the RUNT domain of RUNX2 in a melanoma cell line. RUNT-deleted cells showed reduced proliferation, increased apoptosis, and reduced EMT features, suggesting the involvement of the RUNT domain in different pathways. In addition, del-RUNT cells showed a downregulation of genes involved in migration ability. In an in vivo zebrafish model, we observed that wild-type melanoma cells migrated in 81% of transplanted fishes, while del-RUNT cells migrated in 58%. All these findings strongly suggest the involvement of the RUNT domain in melanoma metastasis and cell migration and indicate RUNX2 as a prospective target in MM therapy

Physical activity modulates miRNAs levels and enhances MYOD expression in myoblasts

Stem cells functions are regulated by different factors and non-conding RNAs, such as microRNA. MiRNAsplay an important role in modulating the expression of genes involved in the commitment and differentiation of progenitor cells. MiRNAs are post transcriptional regulators which may be modulated by physical exercise. MiRNAs, by regulating different signaling pathways, play an important role in myogenesis as well as in muscle activity. MiRNAs quantification may be considered for evaluating physical performance or muscle recovery. With the aim to identify specific miRNAs potentially involved in myogenesis and modulated by physical activity, we investigated miRNAs expression following physical performance in Peripheral Blood Mononuclear Cells (PBMCs) and in sera of half marathon (HM) runnners. The effect of runners sera on Myogenesis in in vitro cellular models was also explored. Therefore, we performed Microarray Analysis and Real Time PCR assays, as well as in vitro cell cultures analysis to investigate myogenic differentiation. Our data demonstrated gender-specific expression patterns of PBMC miRNAs before physical performance. In particular, miR223-3p, miR26b-5p, miR150-5p and miR15-5p expression was higher, while miR7a-5p and miR7i-5p expression was lower in females compared to males. After HM, miR152-3p, miR143-3p, miR27a-3p levels increased while miR30b-3p decreased in both females and males: circulating miRNAs mirrored these modulations. Furthermore, we also observed that the addition of post-HM participants sera to cell cultures exerted a positive effect in stimulating myogenesis. In conclusion, our data suggest that physical activity induces the modulation of myogenesis-associated miRNAs in bothfemales and males, despite the gender-associated different expression of certain miRNAs, Noteworthy, these findings might be useful for evaluating potential targets for microRNA based-therapies in diseases affecting the myogenic stem cells population