Physically Constrained Neural Networks and Regularization of Inverse Problems

The solution to a variety of engineering problems entails the simulation of a physical system. The main component of a simulator is a model that must accurately depict the system behaviour. There are two approaches to build such a model: to describe the functioning of the system with the help of physical laws; or to obtain a representation from observations of actual experiments. Theoretical models may have great precision and high generalisation capabilities; however, it is not possible to guarantee that every aspect of a physical phenomenon is represented into the equations. Obtaining agreement with a real system is a hard task: a bad estimate for a material parameter suffices to invalidate a prediction. Models based on measurements are not concerned with the complex system structure that gave rise to the data. In addition they are generally fast: a representation like a neural network is evaluated in a fraction of the time needed by a differential equation solver. On the other side, the obtention of a representation is an ill-posed problem; the resulting model is unable to extrapolate the predictions to regions not covered during data gathering. This paper considers the combination of both sources of information to construct a model, in a manner similar in concept to data assimilation. The equations of the theoretical model are used as restrictions in the training of neural networks; this is done in the framework of regularization techniques. The procedure is illustrated with situations as convection-diffusion, prismatic bar, plate and two dimensional flow

In Vitro Activity of Nisin A Against Staphylococci Isolated from Periprosthetic Joint Infection

Background/Objectives: Staphylococci are the most common causes of periprosthetic joint infection (PJI); new antimicrobials are needed to manage these difficult infections. Nisin A is a lantibiotic peptide derived from Lactococcus lactis that has antimicrobial activity against Gram-positive bacteria, including staphylococci, and is an FDA-approved preservative used in the food and dairy industry. Here, the in vitro nisin A susceptibility of PJI-associated staphylococci was assessed. Methods: The minimum inhibitory concentrations (MICs), minimum biofilm inhibitory concentrations (MBICs), and minimum biofilm bactericidal concentrations (MBBCs) of nisin A were measured by broth microdilution against 106 staphylococcus isolates isolated from PJI. MICs were assessed using 5 × 105 CFU/mL plus nisin A. For MBICs, biofilms were grown on pegged lids for 6 h, followed by 20 h of treatment. For MBBCs, pegged lids were transferred to plates containing media only for 20 h. The results were determined as the lowest concentrations with no visual growth. Two-dimensional MICs with nisin A and vancomycin were assessed for 20 isolates. Fractional inhibitory concentrations (FICs) were calculated to determine synergistic, additive, antagonistic, or indifferent interactions. Results: The MIC that inhibited 90% of S. aureus and S. epidermidis was 4 µg/mL, apart from for the MRSA subset (8 µg/mL). The MBIC that inhibited 90% of isolates was 4 µg/mL. The MBBCs ranged from 4 to 256 µg/mL. When tested together, nisin A and vancomycin yielded an FIC between 1.25 and 1.5, indicative of indifference, except for one isolate each of MRSA and MSSA, for which an additive effect (FIC of 1) was observed. Conclusions: Nisin A showed inhibitory activity against staphylococci that cause PJI

The relationship between non-alcoholic fatty liver disease and acute coronary syndrome severity: is non-alcoholic fatty liver disease a risk marker of coronary atherosclerotic disease?

Abstract Background/Introduction Non-alcoholic fatty liver disease (NAFLD) has been significantly associated with atherosclerotic disease independent of classical risk factors. However, the role of NAFLD in this context remains unclear. The systemic inflammation described in NAFLD related to liver disease progression may be one factor that can influence the progression and instability of atherosclerotic disease and, consequently, in the clinical characteristics of acute coronary syndrome (ACS). Purpose To assess the potential relationship between NAFLD and ACS severity. Methods We performed a retrospective study in adult patients with ACS who presented to the emergency room of a quaternary care medical centre between March 2015 and March 2016 and selected 99 patients without previously known coronary artery disease or liver disease, without a history of significant alcohol consumption, terminal disease, other acute illness, use of statins, amiodarone, or other steatogenic drugs. The diagnostic criteria for acute myocardial infarction (AMI) with ST-segment elevation (STEMI) were ST elevation ≥1mm in ≥2 contiguous leads (2mm for leads V1 to V3). The acute myocardial infarction without ST-segment elevation (NSTEMI) diagnostic was established in patients who did not meet the criteria for STEMI and who had elevated necrosis markers (creatine kinase-MB isoform and troponin I). Unstable angina (UA) diagnostic was established in patients who did not meet the criteria for STEMI and NSTEMI but had more than three cardiovascular risk factors and typical thoracic pain. The presence of steatosis and its degrees was assessed using ultrasound, and the diagnosis of NAFLD was based on the presence of steatosis and clinical history. Results The diagnosis of UA, NSTEMI and STEMI was established in 40, 33 and 26 patients, respectively, and NAFLD was observed in 30%, 66.6% and 76.9% of these patients. NAFLD patients were 5.8 times more likely to have a diagnosis of AMI than UA (p&amp;lt;0.001), were 7.88 times more likely to have a diagnosis of STEMI than UA (p&amp;lt;0.001) and were 4.7 times more likely to have a diagnosis of NSTEMI than UA (p&amp;lt;0.01). Patients with grades 2 and 3 liver steatosis were 4.2 times more likely to have a diagnosis of AMI than UA (p&amp;lt;0.01) and were 8.2 times more likely to have a diagnosis of STEMI than UA (p&amp;lt;0.01). There was no significant relationship between other variables evaluated and the clinical presentation of ACS. Conclusion(s) In this study, the frequency of AMI presentation in NAFLD patients with ACS was significantly higher than the frequency of UA, suggesting a significant relationship between NAFLD and the severity of ACS, independent of the classic risk factors assessed. The results also suggest that the steatosis degree can proportionally influence this context. Therefore, NAFLD could be considered a potential risk marker for coronary atherosclerotic disease progression and instability. Funding Acknowledgement Type of funding sources: None. </jats:sec

HSQ Lithography for Nanowire First Integration: an Interesting Alternative for Gate Last Fabrication of Sub-7nm Stacked Nanowire FETs.

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