Statistical evidence of central moment as fault indicators in ball bearing diagnostics

This paper deals with post processing of vibration data coming from a experimental tests. An AC motor running at constant speed is provided with a faulted ball bearing, tests are done changing the type of fault (outer race, inner race and balls) and the stage of the fault (three levels of severity: from early to late stage). A healthy bearing is also measured for the aim of comparison. The post processing simply consists in the computation of scalar quantities that are used in condition monitoring of mechanical systems: variance, skewness and kurtosis. These are the second, the third and the fourth central moment of a real-valued function respectively. The variance is the expectation of the squared deviation of a random variable from its mean, the skewness is the measure of the lopsidedness of the distribution, while the kurtosis is a measure of the heaviness of the tail of the distribution, compared to the normal distribution of the same variance. Most of the papers in the last decades use them with excellent results. This paper does not propose a new fault detection technique, but it focuses on the informative content of those three quantities in ball bearing diagnostics from a statistical point of view. In this paper, a discriminant function analysis is used, to determine which central moment has a high discrimination power in the diagnostics of ball bearing in stationary conditions

Heterogeneous effects of spinoff foundations on the means of technology transfer: the role of past academic-industry collaborations

Focusing on the Italian population of academic entrepreneurs, we analyze the effect of establishing a spinoff firm on researchers' attitudes towards carrying out other activities in collaboration with firms, namely, co-publishing and co-patenting. We investigate the heterogeneity in this effect in terms of existing collaborations with firms in the pre-spinoff period. Using a counterfactual analysis on subgroups, we verify that academic entrepreneurs with previous publications with firms diminish their co-publishing and increase their co-patenting after founding a spinoff. Conversely, academic entrepreneurs who had no previous publications with firms increase their co-publishing and decrease their co-patenting. We maintain that such results are related to academics' learning processes connected with their previous technology transfer activities. The policy implications are related to technology transfer aims and contradict the idea that promoting spinoffs is an appropriate "one-size-fits-all" initiative

Extension of the predictive policy to a series of mechanical systems

In the literature, a great interest is reserved to complex systems (i.e. serial or parallel or mixed systems), constituted by the interconnection of single elements. The evolution of system reliability depends on its structure as well as on the evolution of the reliability of its individual elements. Maintenance activities on systems strongly affect element aging and system\u2019s operating life. Preventive maintenance, for example, is used to increase system availability reducing, as a consequence, the probability of failure. Generally, maintenance plans are performed with respect to some criteria depending on cost or on reliability/availability requirements. Therefore, the optimum maintenance scheduling of a system can be based on the minimization of the total cost or on the maximization of its availability. Many Authors emphasize the requirement on system reliability. In [1], for example, the concept of reliability equivalence from simple series and parallel systems to some complex systems is presented and reliability equivalence factors of complex systems are obtained. One of the most critical problems in preventive maintenance is the determination of the optimum frequency to perform maintenance actions on systems, in order to ensure a pre-defined level of availability. In this paper the predictive maintenance policy, for a single element, is extended to a system constituted by two series elements, named A and B. The transition from a single unit to a series system is not immediate and presents a great number of problems. Actually, when a maintenance action is scheduled for a system of this kind, the decision maker must decide if it is more convenient (with respect to some chosen criterion) to intervene on element A or B or on both. The proposed methodology deals with this practical problem in the context of the predictive maintenance policy. Research on this topic is in a running state and the methodology is only theoretically presented

System monitoring and maintenance policies: a review

In the industrial context, the main goal of the maintenance team is to avoid sudden failures that can cause the stoppage of the system with a consequent loss of production. This means that each maintenance action must be performed before the degradation level of a system exceeds a critical threshold beyond which the failure probability becomes high. The increasing importance given to maintenance is shown not only by the great deal of literature on the topic, but also by the interest in transforming this area from a managerial area to a branch of applied mathematics (Operational Research or Statistics). Maintenance is now considered as a subject and much research activity is concerned with its mathematical modeling rather than with the management processes relating to maintenance itself. In [1], Scarf evidences the great importance of the mathematical modeling of maintenance and the correlated strategic support given by the maintenance management information systems. Nevertheless, no model can be built without an exhaustive collection of data. By data, Author means not only specific figures regarding, for example, failure times, but all information related to the process under study. With the recent advent of condition monitoring and the development of appropriate decision models, critical components of a system can be tracked through appropriate variable(s) correlated to their degradation process, logistic support (for example, spares inventory) can be provided, maintenance history can be stored, predetermined maintenance activity can be alarmed and management reports can be produced. The use of condition monitoring techniques reduces the uncertainty operators feel about the current state of the plant. For example, knowledge about the vibration levels of a rotating bearing gives engineers confidence about its operation in the short term. Data acquired by monitoring systems, maintenance histories collected for specific components can be considered fundamental resources for the mathematical modeling of the maintenance activities. This paper is the first part of two [2], presenting the transition from preventive maintenance policy to the predictive one. In particular, the paper presents a brief review of the subject and some critical considerations about the two maintenance policies

Safety culture to improve accidental events reporting in radiotherapy

The potential for unintended and adverse radiation exposure in radiotherapy is real and should be studied because radiotherapy is a highly complex, multistep process which requires input from numerous individuals from different areas and steps of the radiotherapy workflow. The 'Incident' (I) is a consequence of which are not negligible from the point of view of protection or safety. A 'near miss' (NM) is defined as an event which is highly likely to happen but did not occur. The purpose of this work is to show that through a systematic reporting and analysis of these adverse events, their occurrence can be reduced

Synergism Between Immunotherapy and Radiotherapy in Esophageal Cancer: An Overview of Current Knowledge and Future Perspectives

Background: Esophageal cancer (EC) is an aggressive neoplasm of the gastrointestinal tract that is usually treated with a combination of chemotherapy, radiotherapy (RT), and/or surgery, according to disease status. Despite the availability of multimodal therapeutic strategies, local recurrence is frequently observed. Immunotherapy is a promising therapeutic approach that is currently highly investigated in association to standard therapies, including RT, with the aim to improve patients' outcomes. Materials and Methods: A PubMed search was performed with the following keywords in all fields: "esophageal cancer" and "radiotherapy" and "radiation" and "immunotherapy" and "PD-1" and "PD L1." For an overview of ongoing trials, an additional search on ClinicalTrials.gov website was performed using the keywords "esophageal cancer" and "immunotherapy" and "PD-L1" and "CTLA-4" and "radiation" and "radiotherapy." Emerging data from preclinical and clinical studies are suggesting a synergistic effect between immunotherapy and RT. With the aim to update the knowledge of this synergistic immune-mediated antitumor activity and discuss current challenges, the authors summarize published data concerning the basic mechanisms and the effectiveness and tolerance of the combination between immunotherapy and RT for patients with EC, followed by an overview of ongoing clinical trial. Conclusions: Published results encourage the use of personalized therapeutic approaches for EC patients in the future; results from ongoing studies will help to identify the optimal strategies for patient selection and treatment response evaluation

Diagnostic Value of Choline PET in the Preoperative Localization of Hyperfunctioning Parathyroid Gland(s): A Comprehensive Overview

Hyperparathyroidism is a metabolic disorder characterized by the excessive production of the parathyroid hormone. The diagnosis is based on clinical and laboratory data. In most cases the only treatment is surgery and a correct preoperatory localization of the hyperfunctioning parathyroid gland(s) is essential. Currently, ultrasonography combined with [Tc-99m]Tc-MIBI parathyroid scintigraphy, optionally associated with single photon emission computed tomography/computed tomography (SPECT/CT), represent the standard preoperative imaging. In recent years, a number of studies have evaluated the potential role of choline positron emission tomography (PET) in hyperparathyroidism with promising results. Most of the recent evidence underlined its higher sensitivity and diagnostic accuracy in the localization of hyperfunctioning parathyroid glands. Choline PET has a higher spatial resolution that is useful for the detection of smaller parathyroid glands and it also has shorter examination times and favorable radiation exposure. These are just a few of the aspects that support it to overcome traditional imaging. Moreover, from the preliminary data, the choline uptake mechanism seems to also have an impact on its better performance. For these reasons, if first used as second level imaging in patients with negative or inconclusive traditional imaging results, several authors have supported its use as a first line investigation. This comprehensive overview aims to provide an accurate description of the preliminary results available in the literature about the use of choline PET/CT in hyperparathyroidism and to compare these results with the performance of traditional imaging methods

Heterogeneous response to target therapy in metastatic papillary renal cell carcinoma evaluated by morphologic and metabolic multimodality imaging

Papillary renal cell carcinoma (PRCC) accounts for about 15% to 20% of renal cell carcinoma and is histologically distinguished in type I and type II. The last one is associated with poorer prognosis. Treatment options for PRCC patients are surgery, immunotherapy, revolutionized by Nivolumab, and other target-therapy with an improvement in overall survival. Heterogenous response and a pseudo-progression may be observed in the initial phase of biological treatment that could induce premature discontinuation. Patient concerns: We present the case of a 44-year-old woman with left cervical palpable mass increased in size and without concomitant disease or previous surgery. Diagnosis: Neck ultrasonography, contrast-enhanced Computed Tomography, and 18F-FDG PET/CT were performed with the detection of lymph nodes involvement and a left renal lesion. Interventions: The patients underwent left radical nephrectomy and homolateral cervical and para-aortic lymphadenectomy, with histological diagnosis of PRCC, type II. After disease relapse, the inter-aortocaval lymph node was laparoscopically removed. Following the detection of further disease relapse in several lymph nodes and the lung, several lines of target-therapy were started; then disease progression and worsening of clinical and hematological status led us to start Nivolumab as last-line therapy. Outcomes: A heterogeneous response to therapies was documented with morphological and nuclear medicine imaging, however the concomitant deterioration of performance status and liver function led to discontinuation of Nivolumab; then the patient died, 30 months after diagnosis. Lessons: Here we describe the clinical case and radiological and nuclear medicine imaging investigations performed by our patient, highlighting that 18F-FDG PET/CT shows greater adequacy in assessing the response to therapy, avoiding premature drug discontinuation, and ensuring better management of a patient with advanced PRCC

18F-FDGPET/CT: diabetes and hyperglycaemia

BACKGROUND: Some patients who undergo 18F-FDG PET/CT for neoplastic or benign disease are also affected by diabetes or hyperglycaemia. We propose different preparation procedures in patients (pts) with hyperglycaemia (acute, temporary or chronic) or diabetes (type 1 or 2) at the time of the 18F-FDG injection, in order to improve the diagnostic scheduling of 18F-FDG PET/CT. MATERIAL AND METHODS: We evaluated a sample of 13,063 pts, examined in two different PET/CT centres, one with a stationary scanner (94.4%) and the other with a mobile device (5.6%). High blood sugar was present in 1,698 patients (13%) at the time of the 18F-FDG injection (hyperglycaemia was defined as fasting blood glucose > 11.1 mmol/l). We considered all 18F-FDG PET/CT tests performed over a period of 4 years (2006-2009). In the first 2 years (6,236 tests), scheduling was done directly by the administrative secretary. In the next two years, 6,827 pts underwent a preliminary visit to assess the test indications, medical history, and therapy as well as pre-test preparation. We evaluated different preparation protocols for hyperglycaemic or diabetic pts, especially those recommended in the guidelines of the European Association of Nuclear Medicine (EANM) and Society of Nuclear Medicine (SNM). RESULTS: In the four-year period, 713/13,063 patients (5.45%) were rescheduled; of these, 78.8% were rescheduled in the two years before the implementation of our preparation protocols and 21.2% in the next two years. Before the implementation of our preparation protocols, 562 patients (9%) presented occasional, acute or chronic hyperglycaemia (56.7%), or diabetes (43.3%), requiring postponement of the test to a later date. The test was not performed in 17 of 6,236 pts (0.27%) because of blood glucose levels above 11.1 mmol/l for several days, while in 16/6236 pts (0.26%) the 18F-FDG injection was performed despite high blood glucose levels, in view of the clinical urgency. After the implementation of the preparation protocols, 2.2% of pts were rescheduled because of occasional, acute or chronic hyperglycaemia (79%), or diabetes (21%); 0.1% of pts did not undergo the test because of chronic high blood glucose levels. Although the administration of insulin is recommended in the EANM and SNM guidelines, in our new preparation procedures experience it was not necessary, because we reduced the numbers of hyperglycaemic pts thanks to screening at the preliminary visit and a subsequent good preparation of the patient before scheduling. CONCLUSIONS: The application of our preparation protocols improves the on-time performance and diagnostic accuracy, and increases patients' compliance. Copyright © 2013 Via Medica

Diagnostic Value of the Early Heart-to-Mediastinum Count Ratio in Cardiac 123I-mIBG imaging for Parkinson's Disease

Early diagnosis of Parkinson's disease (PD) is of primary importance. The delayed (3-4 h after injection) Iodine-123-Metaiodobenzylguanidine (123I-mIBG) scintigraphy has been proven to be effective in early differential diagnosis for Lewy body disease. But early imaging (15-30 min after injection) has only been marginally studied for its possible diagnostic role. In this prospective study a thresholdfor the early Heart-to-Mediastinum (H/M) count ratio has been investigated, obtaining a diagnostic accuracy analogous to conventional, delayed imaging