Erosion Prediction of Gas Turbine Compressor Blades Subjected to Water Washing Process

Technical BriefsBlade fouling is a relevant problem in turbomachinery applications. It affects both compressors and turbines. In the first case, fouling can be generated by the presence of dust, ashes or brackish air (in offshore applications). In turbines, fouling is mainly generated by residual of combustion process. Blade fouling generally leads to a reduction of the performance due to an increase on profile losses. Here we focus on the fouling due to salt deposition on naval/off-shore applications referring to machines that are part of the fleet of gas turbines manufacturers. In such applications, it is common to introduce on-line washing devices aiming at removing fouling from the early stages of the compressors. The water is sprayed upstream of the first rotor, it impacts on the rotor blades and thus dissolving the deposited salt. However, this procedure possibly leads to blade erosion and/or corrosion. A clear comprehension of the erosion mechanism is the main objective of the present work. To this end, we propose an integrated multi-phase CFD tool. The multi-phase flow is analyzed by adopting a one-way coupling, thus assuming water droplets to be drag by the carrier flow without influencing the main flow. The droplets are dispersed and tracked singularly by adopting a Lagrangian approach. As for the erosion, well-known and widely accepted models are used. The capability of a Lagrangian code, P-Track, developed and validated at the Department of Mechanical & Aerospace Engineering, Sapienza University in Rome, is presented. The code is able to predict the droplets trajectories, as well as to simulate the impact on the solid walls and the erosion mechanism. Simulations were performed using 25 and 100 ?m droplet size. Results, expressed in terms of normalized erosion rate, show the erosion patterns and erosive effect of the two size classes. Erosive capacity is proportional to droplet size, and the most eroded part of the blade is the leading edge, which is in qualitative agreement with measurements

Environmental Genomics: A Tale of Two Fishes

The influence of the environment on two congeneric fishes, Gillichthys mirabilis and Gillichthys seta, that live in the Gulf of California at temperatures of 10-25 degrees C, and up to 42-44 degrees C, respectively, was addressed by analyzing their genomes. Compared with G. mirabilis, G. seta showed some striking features. Substitution rates in the mitochondrial genes were found to be extremely fast, in fact faster than in noncoding control regions (D-loops), from which a divergence time of less than 0.66-0.75 Mya could be estimated. In the nuclear genome, 1) both AT --> GC/GC --> AT and transversion: transition ratios in coding sequences (CDSs) were relatively high; moreover, the ratios of nonsynonymous/synonymous changes (Ka/Ks) suggested that some genes were under positive selection; 2) DNA methylation showed a very significant decrease; and 3) a GC-rich minisatellite underwent a 4-fold amplification in the gene-rich regions. All these observations clearly indicate that the environment (temperature and the accompanying hypoxia) can rapidly mold the nuclear as well as the mitochondrial genome. The stabilization of gene-rich regions by the amplification of the GC-rich minisatellite and by the GC increase in nuclear CDSs is of special interest because it provides a model for the formation of the GC-rich and gene-rich isochores of the genomes of mammals and birds

Erosion Prediction of Gas Turbine Compressor Blades Subjected to Water Washing Process

Technical BriefsBlade fouling is a relevant problem in turbomachinery applications. It affects both compressors and turbines. In the first case, fouling can be generated by the presence of dust, ashes or brackish air (in offshore applications). In turbines, fouling is mainly generated by residual of combustion process. Blade fouling generally leads to a reduction of the performance due to an increase on profile losses. Here we focus on the fouling due to salt deposition on naval/off-shore applications referring to machines that are part of the fleet of gas turbines manufacturers. In such applications, it is common to introduce on-line washing devices aiming at removing fouling from the early stages of the compressors. The water is sprayed upstream of the first rotor, it impacts on the rotor blades and thus dissolving the deposited salt. However, this procedure possibly leads to blade erosion and/or corrosion. A clear comprehension of the erosion mechanism is the main objective of the present work. To this end, we propose an integrated multi-phase CFD tool. The multi-phase flow is analyzed by adopting a one-way coupling, thus assuming water droplets to be drag by the carrier flow without influencing the main flow. The droplets are dispersed and tracked singularly by adopting a Lagrangian approach. As for the erosion, well-known and widely accepted models are used. The capability of a Lagrangian code, P-Track, developed and validated at the Department of Mechanical & Aerospace Engineering, Sapienza University in Rome, is presented. The code is able to predict the droplets trajectories, as well as to simulate the impact on the solid walls and the erosion mechanism. Simulations were performed using 25 and 100 ?m droplet size. Results, expressed in terms of normalized erosion rate, show the erosion patterns and erosive effect of the two size classes. Erosive capacity is proportional to droplet size, and the most eroded part of the blade is the leading edge, which is in qualitative agreement with measurements

La disclosure volontaria del modello di business nel prospetto informativo di quotazione: un’analisi comparative

How do companies to be listed actually deal with voluntary disclosure of their business model? Is it true that firms with greater knowledge-based resources and technological innovation endowments have a lower propensity to adopt fully open communication behaviors? This paper aims to identify the voluntary disclosure policies adopted by three Italian companies in their Initial Public Offering (IPO) prospectuses in order to investigate whether any differences may depend on the type of innovation underlying each business model. A series of interviews conducted with the top management made it possible to understand more deeply the business model of each company. Further, a content analysis has been developed to compute a measure of disclosure and to point out the strategic concepts and their relevance. We provide evidence that companies with a business model based on technology-push innovation have a lower propensity to the full disclosure of their intangible components, particularly of those mainly based on knowledge as these are also invisible. Our study adds to the literature of business and financial reporting by focusing on a new object of inquiry, that is the business model. The business model plays an important role in allowing external actors to understand a company’s value, thus companies’ strategic communication should be shaped accordingly. The results suggest the need to address the issue of voluntary disclosure of the business model by first distinguishing “visible” intangible resources from those that are “invisible” (both to financial and competitive markets). The study aims to make a contribution to the ongoing debate on business and financial reporting practice

Therapeutic aspects of Sydenham's Chorea: an update

Sydenham's Chorea (SC) is a hyperkinetic movement disorder associated with neuropsychiatric manifestations. It is believed to be caused by the autoimmune response following a group A beta-hemolytic streptococcal (GABHS) pharyngitis, and it is one of the major diagnostic criteria for Acute Rheumatic Fever (ARF) diagnosis. Despite having been known and studied for centuries, there are still no standardized therapies or official guidelines for SC treatment, so that it is necessarily left to physicians' clinical experience. Antibiotic treatment, symptomatic therapies, and immunomodulatory treatment are the three pillars upon which SC patients' management is currently based, but they still lack a solid scientific basis. The aim of this writing is precisely to review the state of the art of SC's treatment, with an overview of the advances made in the last 5 years. However, since the therapeutic uncertainties are a mere reflection of the severe gap of knowledge that concerns SC's pathogenesis and manifestations, the importance of high-quality research studies based on homogenized methodologies, instruments, and measured outcomes will also be stressed

Association between Vitamin D Receptor Gene Polymorphisms and Periodontal Bacteria: A Clinical Pilot Study

Abstract: Background: Periodontitis is an inflammatory disease caused by microorganisms involving the supporting tissues of the teeth. Gene variants may influence both the composition of the biofilm in the oral cavity and the host response. The objective of the study was to investigate the potential correlations between the disease susceptibility, the presence and the quantity of periodontopathogenic oral bacterial composition and the VDR gene polymorphisms. Methods: Fifty (50) unrelated periodontal patients and forty-one (41) healthy controls were selected for genomic DNA extraction. DNA concentration was measured and analyzed. The periodontopathogenic bacterial species were identified and quantified using a Real Time PCR performed with species-specific primers and probes. Results: Genotype distribution showed a different distribution between the groups for BsmI rs1544410 genotypes (p = 0.0001) with a prevalence of the G(b) allele in periodontal patients (p = 0.0003). Statistical significance was also found for VDR TaqI rs731236 (p ≤ 0.00001) with a prevalence of the T(T) allele in periodontal patients (p ≤ 0.00001). The average bacterial copy count for the periodontitis group was significantly higher than that of control group. Dividing patients into two groups based on high or low bacterial load, FokI rs2228570 T allele (f) was statistically more represented in patients with high bacterial load. Conclusions: The findings of the study suggest the involvement of the VDR gene BsmI and TaqI polymorphisms in periodontal disease, while FokI and BsmI may be involved in determining an increased presence of periodontopathogens

In vitro and ex vivo retina angiogenesis assays

Pathological angiogenesis of the retina is a key component of irreversible causes of blindness, as observed in proliferative diabetic retinopathy, age-related macular degeneration, and retinopathy of prematurity. Seminal studies in the early 1980 s about the angiogenic activity exerted by mammalian retinal tissue extracts on the chick embryo chorioallantoic membrane and the later discovery of vascular endothelial growth factor (VEGF) accumulation in eyes of patients with diabetic retinopathy paved the way for the development of anti-angiogenic VEGF blockers for the treatment of retinal neovascularization. Since then, numerous preclinical and clinical studies about diabetic retinopathy and other retinal disorders have opened new lines of angiogenesis inquiry, indicating that limitations to anti-VEGF therapies may exist. Moreover, the production of growth factors other than VEGF may affect the response to anti-VEGF approaches. Thus, experimental models of retinal angiogenesis remain crucial for investigating novel anti-angiogenic therapies and bringing them to patients. To this aim, in vitro and ex vivo angiogenesis assays may be suitable for a rapid screening of potential anti-angiogenic molecules before in vivo validation of the putative lead compounds. This review focuses on the different in vitro and ex vivo angiogenesis assays that have been developed over the years based on the isolation of endothelial cells from the retina of various animal species and ex vivo cultures of neonatal and adult retina explants. Also, recent observations have shown that eye neovascularization in zebrafish (Danio rerio) embryos, an in vivo animal platform experimentally analogous to in vitro/ex vivo models, may represent a novel target for the identification of angiogenesis inhibitors. When compared to in vivo assays, in vitro and ex vivo models of retina neovascularization, including zebrafish embryo, may represent cost-effective and rapid tools for the screening of novel anti-angiogenic therapeutics

Pharmacogenetic-Based Interactions between Nutraceuticals and Angiogenesis Inhibitors

Background: Angiogenesis inhibitors (AIs) have become established as an effective cancer treatment. Whereas their interactions with antineoplastic drugs have extensively been investigated, little is known of the effect of their co-administration with nutraceuticals/dietary supplements (N/DSs), which are often self-prescribed. N/DSs comprise a wide range of products such as herbs, nutrients, vitamins, minerals, and probiotics. Assessment of their interactions with cancer drugs, particularly AIs, is hampered by the difficulty of gauging the amount of active substances patients actually take. Moreover, there is no agreement on which approach should be used to determine which N/DSs are most likely to influence AI treatment efficacy. We present a comprehensive review of the metabolic routes of the major AIs and their possible interactions with N/DSs. Methods: The PubMed and Cochrane databases were searched for papers describing the metabolic routes of the main AIs and N/DSs. Results: Data from the 133 studies thus identified were used to compile a diagnostic table reporting known and expected AI-N/DS interactions based on their metabolization pathways. AIs and N/DSs sharing the cytochrome P450 pathway are at risk of negative interactions. Conclusions: Recent advances in pharmacogenetics offer exceptional opportunities to identify prognostic and predictive markers to enhance the efficacy of individualized AI treatments. The table provides a guide to genotyping patients who are due to receive AIs and is a promising tool to prevent occult AI-N/DS interactions in poor metabolizers. N/DS use by cancer patients receiving AIs is a topical problem requiring urgent attention from the scientific community

Outbreak of fatal nitrate toxicosis associated with consumption of fennels (Foeniculum vulgare) in cattle farmed in Campania Region (Southern Italy)

Nitrate and nitrite are toxicants which have become increasingly significant environmental chemicals. An increase in environmental distribution of nitrogenous compounds, especially in surface and ground water has been attributed to the intensive use of nitrate as agricultural fertilizers and to increasing amounts of nitrogenous wastes produced by municipalities, industries and feedlots. The purpose of this study is to illustrate a fatal nitrate toxicosis in cattle associated with the consumption of fennels (Foeniculum vulgare). Fifteen cows from the same farm suddenly developed weakness, muscular tremors, respiratory distress and finally anoxic convulsions. Affected animals died within 24 to 48 hours from the onset of the clinical signs. Five cows underwent a complete post-mortem examination. In all examined animals, gross lesions included presence of dark uncoated blood around the nostrils and the anal region, moderate inflammation of the gastrointestinal mucosa, and brown discoloration of the skeletal muscles and kidneys. The histological examination showed tubular degeneration and congestion of glomerular vessels in the kidney. Toxicological analysis detected high levels of nitrates in the fennels used to feed the animals. The source of exposure to nitrates was identified in the fennels. The fennels were grown in a polluted area of Campania region and distributed in a public market for human consumption. The waste from the sale of the fennels were collected and fed the cows. The accumulation of nitrates in some vegetables pose a risk not only for animal health but also for human and environmental safety