Continuous estimation of power system inertia using convolutional neural networks.

Inertia is a measure of a power system's capability to counteract frequency disturbances: in conventional power networks, inertia is approximately constant over time, which contributes to network stability. However, as the share of renewable energy sources increases, the inertia associated to synchronous generators declines, which may pose a threat to the overall stability. Reliably estimating the inertia of power systems dominated by inverted-connected sources has therefore become of paramount importance. We develop a framework for the continuous estimation of the inertia in an electric power system, exploiting state-of-the-art artificial intelligence techniques. We perform an in-depth investigation based on power spectra analysis and input-output correlations to explain how the artificial neural network operates in this specific realm, thus shedding light on the input features necessary for proper neural-network training. We validate our approach on a heterogeneous power network comprising synchronous generators, static compensators and converter-interfaced generation: our results highlight how different devices are characterized by distinct spectral footprints - a feature that must be taken into account by transmission system operators when performing online network stability analyses.

Awareness: An empirical model.

In this work, we face the time-honored problem of the contraposition/integration of analytical and intuitive knowledge, and the impact of such interconnection on the onset of awareness resulting from human decision-making processes. Borrowing the definitions of concepts like intuition, tacit knowledge, uncertainty, metacognition, and emotions from the philosophical, psychological, decision theory, and economic points of view, we propose a skeletonized mathematical model grounded on Markov Decision Processes of these multifaceted concepts. Behavioral patterns that emerged from the solutions of the model enabled us to understand some relevant properties of the interaction between explicit (mainly analytical) and implicit (mainly holistic) knowledge. The impact of the roles played by the same factors for both styles of reasoning and different stages of the decision process has been evaluated. We have found that awareness emerges as a dynamic process allowing the decision-maker to switch from habitual to optimal behavior, resulting from a feedback mechanism of self-observation. Furthermore, emotions are embedded in the model as inner factors, possibly fostering the onset of awareness.

Intraneural Ultrasound-guided Sciatic Nerve Block: Minimum Effective Volume and Electrophysiologic Effects.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Both extra- and intraneural sciatic injection resulted in significant axonal nerve damage. This study aimed to establish the minimum effective volume of intraneural ropivacaine 1% for complete sensory-motor sciatic nerve block in 90% of patients, and related electrophysiologic variations. METHODS: Forty-seven consecutive American Society of Anesthesiologists physical status I-II patients received an ultrasound-guided popliteal intraneural nerve block following the up-and-down biased coin design. The starting volume was 15 ml. Baseline, 5-week, and 6-month electrophysiologic tests were performed. Amplitude, latency, and velocity were evaluated. A follow-up telephone call at 6 months was also performed. RESULTS: The minimum effective volume of ropivacaine 1% in 90% of patients for complete sensory-motor sciatic nerve block resulted in 6.6 ml (95% CI, 6.4 to 6.7) with an onset time of 19 ± 12 min. Success rate was 98%. Baseline amplitude of action potential (mV) at ankle, fibula, malleolus, and popliteus were 8.4 ± 2.3, 7.1 ± 2.0, 15.4 ± 6.5, and 11.7 ± 5.1 respectively. They were significantly reduced at the fifth week (4.3 ± 2.1, 3.5 ± 1.8, 6.9 ± 3.7, and 5.2 ± 3.0) and at the sixth month (5.9 ± 2.3, 5.1 ± 2.1, 10.3 ± 4.0, and 7.5 ± 2.7) (P < 0.001 in all cases). Latency and velocity did not change from the baseline. No patient reported neurologic symptoms at 6-month follow-up. CONCLUSIONS: The intraneural ultrasound-guided popliteal local anesthetic injection significantly reduces the local anesthetic dose to achieve an effective sensory-motor block, decreasing the risk of systemic toxicity. Persistent electrophysiologic changes suggest possible axonal damage that will require further investigation.

Bronchial blocker positioning: learning curve and confidence in its use.

BACKGROUND: Despite being simple and safe to use and cheap, EZ blocker (EZB) remains underused probably because it requires particular skills in recognizing airway and in using fiber-bronchoscopy to check the exact position of their cuffs. Thus, we planned an education training program on the use of EZB for novices in anesthesia and evaluated the number of procedures required for the acquisition of the skills of this technique. METHODS: The educational training program included three different phases as follows. The first phase included a lecture on the utility of one-lung ventilation in thoracic surgery, on the use of the fiber- bronchoscopy and on the characteristics of EZB. The second phase consisted in a practical teaching course performed on a manikin model to acquire the skills in EZB. The third phase was a clinical training where each participant performed a defined number in patients scheduled for thoracic surgery procedures. The acquisition of dexterity and satisfaction were then statistically valuated. RESULTS: The dexterity in placing EZB significantly increased after six attempts (P<0.1). Participants acquired skills in correcting position EZB after 15 attempts. Participants increased their level of confidence with EZB (score 5.7±1.3) and were highly satisfied with the training received (score 5.8±1.6). CONCLUSIONS: EZB is a valid strategy for obtaining one lung ventilation. Thus, it should be included in the armamentarium of all anesthetists interested in the field of thoracic surgery. Our teaching course seems to be a valuable method to instill easily and speedily in training novices in anesthesia the skills in placing EZB.

Surgical Management of Intramyocardial Left Anterior Descending Artery.

An intramyocardial left anterior descending artery can be found in up to 30% of patients undergoing coronary artery bypass graft procedures. We review the various techniques available to identify an intramyocardial left anterior descending artery.

Double-Orifice Mitral Valve in an Eight-Year-Old Boy.

The case is described of an eight-year-old boy who required an operation for moderate mitral regurgitation due to a double-orifice mitral valve (DOMV). The DOMV, which was clearly demonstrated by transthoracic echocardiography, had a central fibrous bridge. Mitral valve repair using a 5/0 Prolene suture placed at the level of the superior commissure of each hole to stabilize the valve, and ring annuloplasty with Edwards Physio ring, was successfully performed. Intraoperative real-time transesophageal echocardiography showed the repaired DOMV to be without regurgitation or stenosis.

Role of xenotransplantation in cardiac transplantation.

This review will discuss the history and development of the field of genetic modification, up to the most recent scientific discoveries, and will also consider the current uses of genetic therapy.

Biomarkers for the diagnosis of aortic dissection.

This review discusses the role of biomarkers for both diagnoses and disease monitoring before, during, and after treatment of aortic dissection.

Endovascular stent graft repair of suture-line pseudoaneurysm following ascending aorta replacement.

Ascending aorta pseudoaneurysm (AAPA) is an uncommon complication following replacement of the ascending aorta with a prosthetic graft, carry a high risk of rupture, and warrant urgent intervention. The open surgical procedure "gold standard" of care is not always favorable, as the reoperations are technically more difficult or patient's general condition doesn't allow proceeding. Case discussed is an 80-year-old male patient who presented with worsening cough and hemoptysis. He underwent ascending aorta replacement 10 years ago. Computed tomography (CT) scan revealed a contrast-filled mediastinal mass communicating with the ascending aorta and extended into the right lung. Due to the patient's advanced age, friability and clinical condition, combined with the position of the AAPA behind the sternum, surgery was deemed to be high risk. However, favorable anatomical conditions provided a safe landing zone for an endovascular stent. The patient underwent closed procedure. Postprocedure CT showed complete obliteration of the AAPA.

Lyapunov exponents computation for hybrid neurons.

Lyapunov exponents are a basic and powerful tool to characterise the long-term behaviour of dynamical systems. The computation of Lyapunov exponents for continuous time dynamical systems is straightforward whenever they are ruled by vector fields that are sufficiently smooth to admit a variational model. Hybrid neurons do not belong to this wide class of systems since they are intrinsically non-smooth owing to the impact and sometimes switching model used to describe the integrate-and-fire (I&F) mechanism. In this paper we show how a variational model can be defined also for this class of neurons by resorting to saltation matrices. This extension allows the computation of Lyapunov exponent spectrum of hybrid neurons and of networks made up of them through a standard numerical approach even in the case of neurons firing synchronously.

The successful introduction of an adapted form of the mini extra corporeal circulation used for cardiac surgery in an obese patient.

Obese patients undergoing cardiac surgery have been shown to have a high risk of developing postoperative complications, specifically: increased length of hospital stay, readmission to intensive care unit, acute renal failure, deep sternal wound infections and new onset of atrial fibrillation.A custom-made circuit was created to allow the use of Mini Extra Corporeal Circulation (MECC) but permitting the switch to a closed siphon drainage system in the case of difficulties.To limit artificial surface contact a small oxygenating device (Admiral, Eurosets) was employed in spite of the patients size. This adapted circuit permits a feasible and safer approach to using MECC. This report suggests that smaller oxygenators could be integrated into clinical practice in an adult MECC configuration, even for more obese patients, limiting artificial surface contact.

Different ways to repair the mitral valve with artificial chordae: a systematic review.

Myxomatous mitral regurgitation (type II Carpentier's functional classification) affects about 1-2% of the population. This represents a very common indication for valve surgery resulting in a low percentage of repairs compared to replacement which is actually performed. In the last decades, several methods for mitral valve repair have been developed, to make the surgical feasibility easier, improve the long-term follow-up thus avoiding the need for reoperations. A very interesting method is represented by the combination of various valve repair techniques, depending on the involvement of the anterior, posterior, or both leaflets, and the use of PTFE artificial chordae tendineae when excessive chordal elongation or rupture due to myxomatous degeneration co-exists. The aim of this review is to summarize the evolution of these techniques from the beginning till now.

Cardiogenic shock as a complication of acute mitral valve regurgitation following posteromedial papillary muscle infarction in the absence of coronary artery disease.

A 48 year old man was transferred to our department with cardiogenic shock, pyrexia, a high white cell count and significant serum troponin T level. Clinical evaluation revealed severe mitral regurgitation secondary to a flail of both mitral valve leaflets. An emergency cardiac catheterisation did not reveal any significant coronary artery disease. Left ventricular angiogram and echocardiography demonstrated a good left ventricular function and massive mitral regurgitation. Blood cultures were negative for aerobics, anaerobics and fungi. The patient underwent emergency mitral valve replacement with a mechanical valve. Intraoperatively, the posteromedial papillary muscle was found to be ruptured. Histology of the papillary muscle revealed myocardial necrosis with no signs of infection. Cultures obtained from a mitral valve specimen were negative. The patient's recovery was uneventful and he was discharged on the 6th postoperative day.

A modular supervised algorithm for vessel segmentation in red-free retinal images.

In this paper, a supervised algorithm for vessel segmentation in red-free images of the human retina is proposed. The algorithm is modular and made up of two fundamental blocks. The optimal values of two algorithm parameters are found out by maximizing proper measures of performances (MOPs) able to evaluate from a quantitative point of view the results provided by the proposed algorithm. The choice of the MOP allows one to tailor the solution to the specific image features to be emphasized. The performances of the algorithm are compared with those of other methods described in the literature. The simulation results show a good trade-off between quality and processing speed times. For instance, in terms of the maximum average accuracy (MAA), K value, and specificity (SP), the best performance outcomes are 0.9587, 0.8069 and 0.9477, respectively.