Multi-robot spot-welding cells: An integrated approach to cell design and motion planning

The necessity to manage several vehicle models on the same robotized assembly cell has made the cell design and the robot off-line motion planning two fundamental activities. Industrial practice and state-of-the-art methods focus on the technical issues of each activity, but no integrated approach has been yet proposed, resulting in a lack of optimality for the final cell configuration. The paper introduces a formalization of the whole process and proposes a heuristic multi-stage method for the identification of the optimal combination of cell design choices and motion planning. The proposed architecture is depicted through a real case for welding application.     

ADP ribosylation factor regulates spectrin binding to the Golgi complex

Homologues of two major components of the well-characterized erythrocyte plasma-membrane-skeleton, spectrin (a not-yet-cloned isoform, betaI Sigma* spectrin) and ankyrin (AnkG119 and an approximately 195-kDa ankyrin), associate with the Golgi complex. ADP ribosylation factor (ARF) is a small G protein that controls the architecture and dynamics of the Golgi by mechanisms that remain incompletely understood. We find that activated ARF stimulates the in vitro association of betaI Sigma* spectrin with a Golgi fraction, that the Golgi-associated betaI Sigma* spectrin contains epitopes characteristic of the betaI Sigma2 spectrin pleckstrin homology (PH) domain known to bind phosphatidylinositol 4,5-bisphosphate (PtdInsP2), and that ARF recruits betaI Sigma* spectrin by inducing increased PtdInsP2 levels in the Golgi. The stimulation of spectrin binding by ARF is independent of its ability to stimulate phospholipase D or to recruit coat proteins (COP)-I and can be blocked by agents that sequester PtdInsP2. We postulate that a PH domain within betaI Sigma* Golgi spectrin binds PtdInsP2 and acts as a regulated docking site for spectrin on the Golgi. Agents that block the binding of spectrin to the Golgi, either by blocking the PH domain interaction or a constitutive Golgi binding site within spectrin's membrane association domain I, inhibit the transport of vesicular stomatitis virus G protein from endoplasmic reticulum to the medial compartment of the Golgi complex. Collectively, these results suggest that the Golgi-spectrin skeleton plays a central role in regulating the structure and function of this organelle.     

Role of prion protein aggregation in neurotoxicity

In several neurodegenerative diseases, such as Parkinson, Alzheimer's, Huntington, and prion diseases, the deposition of aggregated misfolded proteins is believed to be responsible for the neurotoxicity that characterizes these diseases. Prion protein (PrP), the protein responsible of prion diseases, has been deeply studied for the peculiar feature of its misfolded oligomers that are able to propagate within affected brains, inducing the conversion of the natively folded PrP into the pathological conformation. In this review, we summarize the available experimental evidence concerning the relationship between aggregation status of misfolded PrP and neuronal death in the course of prion diseases. In particular, we describe the main findings resulting from the use of different synthetic (mainly PrP106-126) and recombinant PrP-derived peptides, as far as mechanisms of aggregation and amyloid formation, and how these different spatial conformations can affect neuronal death. In particular, most data support the involvement of non-fibrillar oligomers rather than actual amyloid fibers as the determinant of neuronal death.     

Evaluation of prosthetic-valved devices by means of numerical simulations

The in vivo evaluation of prosthetic device performance is often difficult, if not impossible. In particular, in order to deal with potential problems such as thrombosis, haemolysis, etc., which could arise when a patient undergoes heart valve replacement, a thorough understanding of the blood flow dynamics inside the devices interacting with natural or composite tissues is required. Numerical simulation, combining both computational fluid and structure dynamics, could provide detailed information on such complex problems. In this work, a numerical investigation of the mechanics of two composite aortic prostheses during a cardiac cycle is presented. The numerical tool presented is able to reproduce accurately the flow and structure dynamics of the prostheses. The analysis shows that the vortical structures forming inside the two different grafts do not influence the kinematics of a bileaflet valve or the main coronary flow, whereas major differences are present for the stress status near the suture line of the coronaries to the prostheses. The results are in agreement with in vitro and in vivo observations found in literature.     

A model-based Digital Twin to support responsive manufacturing systems

Manufacturing systems are subject to continuous changing conditions, which are due both to external reasons (e.g. changing demand) and to the natural system evolution, (e.g. machine degradation, operators’ upskilling). At tactical level, production engineers are challenged to continuously improve the system performance. At strategical level, the manufacturing company must monitor the system status and proactively identify reconfiguration actions to ensure system fitness to the evolving competitive scenario. A novel Digital Twin based on an analytical model for performance evaluation of manufacturing system embedding evaluation of joint parameter variations is introduced. In particular this work concentrates on how tactical decision makers can benefit from an integrated system model. The method is proved in a real industrial case in the railway sector.     

The tooling system configuration in a new manufacturing system architecture

A new manufacturing system architecture, called Mod Flex Prod (MFP), has been recently proposed to match the balance between productivity and flexibility required by suppliers of components for the automotive industry. Among the relevant issues that cause the new architecture to be more profitable than transfer lines and flexible manufacturing systems, tooling has been shown to have an important role. Starting from this result, this paper deepens the advantages in tooling attainable with the new architecture. In particular, it presents a new approach for configuring the tooling system (i.e. selecting the number of tool copies for each tool type) which takes into account that tool copies can be required by the machines to perform operations, by the tool carrier to transport tools within the system and by the tool room when inserts have to be reconditioned. With reference to a real case study, the new approach allows one to assess that tooling investment can be reduced by about 20% if the new architecture replaces traditional flexible manufacturing systems.     

Effect of potassium channel openers on the firing rate of hippocampal pyramidal cells and A10 dopaminergic neurons in vitro

The clinical relevance of grading in ependymomas is almost always regarded as controversial. According to the classification of brain tumours revised by the World Health Organization (WHO) in 1993, brain tumours of ependymal origin are differentiated as subependymomas Grade I, ependymomas Grade II, and anaplastic (malignant) ependymomas Grade III. The purpose of the present retrospective study of 126 patients with intracranial ependymomas was to assess the clinical and prognostic significance of the topical classification and grading system by a uni- and multivariate statistical analysis. 87 Grade II ependymomas were predominantly located in the midline and in the fourth ventricle, whereas 39 anaplastic ependymomas Grade III were most often found in the cerebral hemispheres. Excluding the localization-linked operative mortality, progression-free survival (PFS) was significantly dependent on the histological grading. Median PFS time was 7.5 years in Grade II, but only 1.5 years in Grade III ependymomas. Stratifying for the two time intervals 1951-1970 and 1971-1990, and excluding the operative mortality, a multivariate Cox' model analysis of the covariates age, localization, grading, extent of surgery, and radiation therapy revealed that only the histological grading and radiation therapy had a significant impact on PFS. Thus, the WHO grading system has a statistically significant relevance for the long-term prognosis of intracranial ependymomas. However, the therapeutic management including radical tumour resection and additional local irradiation should be independent of the grading.