1,721,196 research outputs found
[Screening for cerebral aneurysms in the ADPKD population: mandatory or potentially harmful?]
No full textCerebral aneurysm in autosomal dominant polycystic kidney disease (ADPKD) is an uncommon event (documented in 6-13% of cases) but frequently characterized by severe neurological sequelae and potentially fatal in case of rupture. The arterial vascular wall of the anterior cerebral circulation is most frequently involved. Experimental data showed the expression of polycystins (the proteins modified by the mutation in this disease) in the affected arterial vascular wall and some mutations apparently give rise to greater susceptibility to the complication. The risk factors that cause the predisposition to this condition and the natural history are poorly understood. This lack of information complicates the clinical management of these patients because many pivotal questions still need an answer: Are cerebral aneurysms to be screened for in the ADPKD population? If so, at which intervals? In which cases where an aneurysm has been detected is correction needed? Which type of correction technique is to be preferred, interventional neuroradiology or neurosurgery? The three authors compare their partially discordant positions on this highly controversial topic
The place of cyclical therapy for the treatment of membranous nephropathy in the era of rituximab
No full textPrimary membranous nephropathy (MN) is the most frequent cause of nephrotic syndrome in adults, due to a variety of autoantibodies, most frequently against phospholipase A2 receptor (PLA2R). In severe cases or when spontaneous remission is not achieved, immunosuppression is required. Cyclical therapy, based on glucocorticoids and cyclophosphamide on alternate months for 6 months, has proven effective to induce remission and reduce the risk of end-stage renal disease. Since the early 2000s, rituximab (RTX) has emerged as a key player in the management of MN, showing overall comparable effectiveness and likely better safety compared with the cyclical regimen, despite the lack of adequately powered trials comparing the two approaches head to head. For these reasons, RTX is now considered the agent of choice for most patients with MN. However, there are still uncertainties. Around 20-40% of patients are resistant to RTX, especially in the setting of high anti-PLA2R levels, and this drug remains relatively unexplored in patients with the most severe disease. In these scenarios, although the expanding therapeutic armamentarium is probably going to provide further options, the cyclical regimen still plays a key role as a safety net. The aim of this article is to illustrate the role of cyclical therapy in the RTX era
[Clinical diagnosis of Autosomal Dominant Polycystic Kidney Disease]
No full textAutosomal dominant polycystic kidney disease (ADPKD) is the most common genetic disorder related to kidney. ADPKD is usually easy to diagnose in people who have a family history of ADPKDs developing typical symptoms, including flank, abdominal pain or macroscopic hematuria. In this setting, diagnosis in adults at risk for ADPKD is commonly performed by ultrasonography, which reveals two enlarged kidneys with multiple bilateral cysts. ADPKD may be more difficult to diagnose in the absence of family history or in subjects with atypical presentation, including asymmetric or focal renal imaging findings, discordant disease within family, early onset of ADPKD and development of ESRD before 30 yr of age. The presence of a total of three or more renal cysts for at-risk subjects aged 15-39 years and two cysts or more in each kidney for at-risk subjects aged 40-59 years are sufficient for the diagnosis of ADPKD. The absence of any renal cyst is sufficient for disease exclusion only for at-risk subjects aged 40 years or older. If the family history is negative, the diagnosis of ADPKD can be made in a patient with enlarged kidneys, numerous cysts, presence of liver cysts and absence of findings suggesting a different cystic disease. If the imaging diagnosis is not clear or showing atypical manifestations in subjects, molecular genetic testing should be performed
Modelling and validation of cavitating orifice flow in hydraulic systems
No full textCavitation 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
Theoretical Analysis of Active Flow Ripple Control in Positive Displacement Pumps
Full text linkPositive displacement machines present a well-known major drawback that is the oscillation in delivered flow rate. This paper presents two active solutions for reducing the flow ripple generated by a pump with an external device actuated by means of a piezo-stack actuator. The work is focused on a theoretical analysis, with the aim of collecting information about the performance of the solutions proposed and their main advantages and drawbacks. The active methods proposed involve a cylindrical actuator connected to the delivery line of the pump. The piston could be actuated directly by a piezo-stack actuator or by a differential pressure modulated by a propor-tional piezo actuated valve. The actuators were modelled and a control algorithm based on Least Mean Square algorithm was used to achieve the adaptability for both systems at different oper-ating conditions. The developed mathematical model permits to define the great potential of these solutions that can drastically reduce the flow ripple. The first architecture presented resulted as the best solution, while the second one allowed reduction of the production cost
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Energy Comparison between a Load Sensing System and Electro-Hydraulic Solutions Applied to a 9-Ton Excavator
Full text linkWith the increasingly stringent regulations on air quality and the consequent emission limits for internal combustion engines, researchers are concentrating on studying new solutions for improving efficiency and energy saving even in off-road mobile machines. To achieve this task, pump-controlled or displacement-controlled systems have inspired interest for applications in offroad working machines. Generally, these systems are derived from the union of a hydraulic machine coupled to an electric one to create compact components that could be installed near the actuator. The object of study of this work is a 9-ton excavator, whose hydraulic circuit is grounded on load sensing logic. The validated mathematical model, created previously in the Simcenter Amesim© environment, represents the starting point for developing electro-hydraulic solutions. Electric components have been inserted to create different architectures, both with open-and closed-circuit layouts, in order to compare the energy efficiency of the different configurations with respect to the traditional load sensing system. The simulations of a typical working cycle show the energy benefits of electrohydraulic solutions that allow for drastically reducing the mechanical energy required by the diesel engine and, consequently, the fuel consumption. This is mainly possible because of the elimination of directional valves and pressure compensators, which are necessary in a load sensing circuit, but are also a source of great energy dissipations. The results show that closed-circuit solutions produce the greatest benefits, with higher energy efficiencies than the open-circuit solution. Furthermore, closed-circuit configurations require fewer components, allowing for more compact and lighter solutions, as well as being cheaper
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