Modelling and Validation of Cavitating Orifice Flow in Hydraulic Systems

Cavitation can occur at the inlet of hydraulic pumps or in hydraulic valves; this phenomenon should be always avoided because it can generate abnormal wear and noise in fluid power components. Numerical modeling of the cavitation is widely used in research, and it allows the regions where it occurs more to be predicted. For this reason, two different approaches to the study of gas and vapor cavitation were presented in this paper. In particular, a model was developed using the computational fluid dynamics (CFD) method with particular attention to the dynamic modeling of both gaseous and vapor cavitation. A further lumped parameter model was made, where the fluid density varies as the pressure decreases due to the release of air and the formation of vapor. Furthermore, the lumped parameter model highlights the need to also know the speed of sound in the vena contracta, since it is essential for the correct calculation of the mass flow during vaporization. A test bench for the study of cavitation with an orifice was set up; cavitation was induced by increasing the speed of the fluid on the restricted section thanks to a pump located downstream of the orifice. The experimental data were compared with those predicted by CFD and lumped parameter models

dynamic modelling of the swash plate of a hydraulic axial piston pump for condition monitoring applications

Abstract In the last years Prognostic and Health Management (PHM) has become one of the challenging topic in the engineering field. In particular, model-based approach for diagnostic relies on the development of a mathematical model of the system representing its flawless status. Once the model has been developed and carefully calibrated on experimental data referred to flawless pump condition the comparison between the model output and the real system output leads to the residual analysis, which gives a diagnosis of the component health. This paper presents the mathematical model of a hydraulic axial piston pump developed in order to replicate the dynamic behavior of the swash plate for PHM applications. The model has been developed on the basis of simplified hypotheses, a friction model between swash plate and bearings has been introduced. A detailed experimental activity was carried out to calibrate and validate the model with step tests and sweep tests. The comparison between numerical and experimental results shows a satisfying agreement and highlights the model capability to reproduce the swash plate dynamics. Future works will include tests with the pump in faulty conditions to evaluate the pump health state through the residual analysis of the swash plate position

CFD Analyses of Textured Surfaces for Tribological Improvements in Hydraulic Pumps

In any hydraulic machine there are lubricated couplings that could become critical beyond certain operating conditions. This paper presents the simulation results concerning textured surfaces with the aim of improving the performance of lubricated couplings in relative motion. The texturing design requires much care to obtain good improvements, and it is essential to analyze both the geometric features of the dimples and the characteristics of the coupled surfaces, like the sliding velocity and gap height. For this purpose, several CFD simulations have been performed to study the behavior of the fluid bounded in the coupling, considering dimples with different shapes, size, and spatial distribution. The simulations consider the onset of gaseous cavitation to evaluate the influence of this phenomenon on the pressure distribution generated by the textured surface. The analyses have pointed out that it is critical to correctly predict the behavior of the textured surface in the presence of local cavitation, in fact, when cavitation occurs, the characteristic time of the transient in which the phase of the fluid change is very rapid and it is comparable to the time taken by the fluid to move from one dimple to the next

CHOLESTEROL CRYSTAL EMBOLISM: A RECOGNIZABLE CAUSE OF RENAL DISEASE

7openopenFrancesco Scolari; Regina Tardanico; Roberta Zani; Alessandra Pola; Battista Fabio Viola; Ezio Movilli; Rosario MaiorcaScolari, Francesco; Regina, Tardanico; Roberta, Zani; Alessandra, Pola; Battista Fabio, Viola; Ezio, Movilli; Rosario, Maiorc

The Challenge of Diagnosing Atheroembolic Renal Disease

Background— Atheroembolic renal disease (AERD) is caused by showers of cholesterol crystals released by eroded atherosclerotic plaques. Embolization may occur spontaneously or after angiographic/surgical procedures. We sought to determine clinical features and prognostic factors of AERD. Methods and Results— Incident cases of AERD were enrolled at multiple sites and followed up from diagnosis until dialysis and death. Diagnosis was based on clinical suspicion, confirmed by histology or ophthalmoscopy for all spontaneous forms and for most iatrogenic cases. Cox regression was used to model time to dialysis and death as a function of baseline characteristics, AERD presentation (acute/subacute versus chronic renal function decline), and extrarenal manifestations. Three hundred fifty-four subjects were followed up for an average of 2 years. They tended to be male (83%) and elderly (60% >70 years) and to have cardiovascular diseases (90%) and abnormal renal function at baseline (83%). AERD occurred spontaneously in 23.5% of the cases. During the study, 116 patients required dialysis, and 102 died. Baseline comorbidities, ie, reduced renal function, presence of diabetes, history of heart failure, acute/subacute presentation, and gastrointestinal tract involvement, were significant predictors of event occurrence. The risk of dialysis and death was 50% lower among those receiving statins. Conclusions— Clinical features of AERD are identifiable. These make diagnosis possible in most cases. Prognosis is influenced by disease type and severity

Apolipoprotein E in idiopathic nephrotic syndrome and focal segmental glomerulosclerosis

Apolipoprotein E in idiopathic nephrotic syndrome and focal segmental glomerulosclerosis.BackgroundHyperlipemia characterizes nephrotic syndrome (NS) and contributes to the progression of the underlying nephropathy. The data in the literature support an implication of apolipoprotein E (apoE) in both hyperlipemia and focal segmental glomerulosclerosis (FSGS), a malignant condition associated with NS.MethodsThe apoE genotype was determined in 209 nephrotic patients, who were classified according to age and their response to steroids as resistant children (N = 96) and adults (43), and steroid dependent (33) and steroid responder (37) children. A total of 123 presented the histological features of FSGS. In a subgroup of 28 patients, serum and urinary levels of apoE and renal deposits were evaluated by immunofluorescence.ResultsThe allelic frequencies of the three major haplotypes γ2, γ3, and γ4 were the same in nephrotic patients versus controls, and homozygosity for γ3γ3 was comparably the most frequent genotype (70 vs. 71%) followed by γ3γ4, γ2γ3, γ2γ4, γ4γ4. Serum levels of apoE were fivefold higher in NS and in FSGS patients than in controls, with a direct correlation with hypercholesterolemia and proteinuria. ApoE genotypes did not influence serum levels. Urinary levels were 1/10,000 of serum with an increment in nephrotic urines. Finally, immunofluorescence demonstrated the absence of apoE in sclerotic glomeruli, while comparably nephrotic patients with membranous nephropathy had an increased glomerular expression of apoE.ConclusionsApoE is dysregulated in NS with a marked increment in serum, which is a part of the complex lipid metabolism. Down-regulation of glomerular apoE instead is a peculiarity of FSGS and may contribute to the pathogenesis of the disease. The normal distribution of apoE genotypes in nephrotic patients with FSGS excludes a pathogenetic role of genetic variants

Vitreous pharmacokinetics and electroretinographic findings after intravitreal injection of acyclovir in rabbits

OBJECTIVES: Acute retinal necrosis is a rapidly progressive and devastating viral retinitis caused by the herpesvirus family. Systemic acyclovir is the treatment of choice; however, the progression of retinal lesions ceases approximately 2 days after treatment initiation. An intravitreal injection of acyclovir may be used an adjuvant therapy during the first 2 days of treatment when systemically administered acyclovir has not reached therapeutic levels in the retina. The aims of this study were to determine the pharmacokinetic profile of acyclovir in the rabbit vitreous after intravitreal injection and the functional effects of acyclovir in the rabbit retina. METHODS: Acyclovir (Acyclovir; Bedford Laboratories, Bedford, OH, USA) 1 mg in 0.1 mL was injected into the right eye vitreous of 32 New Zealand white rabbits, and 0.1 mL sterile saline solution was injected into the left eye as a control. The animals were sacrificed after 2, 9, 14, or 28 days. The eyes were enucleated, and the vitreous was removed. The half-life of acyclovir was determined using high-performance liquid chromatography. Electroretinograms were recorded on days 2, 9, 14, and 28 in the eight animals that were sacrificed 28 days after injection according to a modified protocol of the International Society for Clinical Electrophysiology of Vision. RESULTS: Acyclovir rapidly decayed in the vitreous within the first two days after treatment and remained at low levels from day 9 onward. The eyes that were injected with acyclovir did not present any electroretinographic changes compared with the control eyes. CONCLUSIONS: The vitreous half-life of acyclovir is short, and the electrophysiological findings suggest that the intravitreal delivery of 1 mg acyclovir is safe and well tolerated by the rabbit retina.CNPq [150614/2009-8, 1A]CNPqFAPESP [2010/08331-8, 2011/06924-4, 2008/58731-2]FAPES

Integrated platform for detecting pathogenic DNA via magnetic tunneling junction-based biosensors

In recent years, the development of portable platforms for performing fast and point-of-care analyses has drawn considerable attention for their wide variety of applications in life science. In this framework, tools combining magnetoresistive biosensors with magnetic markers have been widely studied in order to detect concentrations of specific molecules, demonstrating high sensitivity and ease of integration with conventional electronics. In this work, first, we develop a protocol for efficient hybridization of natural DNA; then, we show the detection of hybridization events involving natural DNA, namely genomic DNA extracted from the pathogenic bacterium Listeria monocytogenes, via a compact magnetic tunneling junction (MTJ)-based biosensing apparatus. The platform comprises dedicated portable electronic and microfluidic setups, enabling point-of-care biological assays. A sensitivity below the nM range is demonstrated. This work constitutes a step forward towards the development of portable lab-on-chip platforms, for the multiplexed detection of pathogenic health threats in food and food processing environment

Autoantibodies against type I IFNs in patients with life-threatening COVID-19

Interindividual clinical variability in the course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is vast. We report that at least 101 of 987 patients with life-threatening coronavirus disease 2019 (COVID-19) pneumonia had neutralizing immunoglobulin G (IgG) autoantibodies (auto-Abs) against interferon-w (IFN-w) (13 patients), against the 13 types of IFN-a (36), or against both (52) at the onset of critical disease; a few also had auto-Abs against the other three type I IFNs. The auto-Abs neutralize the ability of the corresponding type I IFNs to block SARS-CoV-2 infection in vitro. These auto-Abs were not found in 663 individuals with asymptomatic or mild SARS-CoV-2 infection and were present in only 4 of 1227 healthy individuals. Patients with auto-Abs were aged 25 to 87 years and 95 of the 101 were men. A B cell autoimmune phenocopy of inborn errors of type I IFN immunity accounts for life-threatening COVID-19 pneumonia in at least 2.6% of women and 12.5% of men

Rare predicted loss-of-function variants of type I IFN immunity genes are associated with life-threatening COVID-19

Background: We previously reported that impaired type I IFN activity, due to inborn errors of TLR3- and TLR7-dependent type I interferon (IFN) immunity or to autoantibodies against type I IFN, account for 15–20% of cases of life-threatening COVID-19 in unvaccinated patients. Therefore, the determinants of life-threatening COVID-19 remain to be identified in ~ 80% of cases. Methods: We report here a genome-wide rare variant burden association analysis in 3269 unvaccinated patients with life-threatening COVID-19, and 1373 unvaccinated SARS-CoV-2-infected individuals without pneumonia. Among the 928 patients tested for autoantibodies against type I IFN, a quarter (234) were positive and were excluded. Results: No gene reached genome-wide significance. Under a recessive model, the most significant gene with at-risk variants was TLR7, with an OR of 27.68 (95%CI 1.5–528.7, P = 1.1 × 10−4) for biochemically loss-of-function (bLOF) variants. We replicated the enrichment in rare predicted LOF (pLOF) variants at 13 influenza susceptibility loci involved in TLR3-dependent type I IFN immunity (OR = 3.70[95%CI 1.3–8.2], P = 2.1 × 10−4). This enrichment was further strengthened by (1) adding the recently reported TYK2 and TLR7 COVID-19 loci, particularly under a recessive model (OR = 19.65[95%CI 2.1–2635.4], P = 3.4 × 10−3), and (2) considering as pLOF branchpoint variants with potentially strong impacts on splicing among the 15 loci (OR = 4.40[9%CI 2.3–8.4], P = 7.7 × 10−8). Finally, the patients with pLOF/bLOF variants at these 15 loci were significantly younger (mean age [SD] = 43.3 [20.3] years) than the other patients (56.0 [17.3] years; P = 1.68 × 10−5). Conclusions: Rare variants of TLR3- and TLR7-dependent type I IFN immunity genes can underlie life-threatening COVID-19, particularly with recessive inheritance, in patients under 60 years old