Liquidity crises on different time scales

We present an empirical analysis of the microstructure of financial markets and, in particular, of the static and dynamic properties of liquidity. We find that on relatively large time scales (15 min) large price fluctuations are connected to the failure of the subtle mechanism of compensation between the flows of market and limit orders: in other words, the missed revelation of the latent order book breaks the dynamical equilibrium between the flows, triggering the large price jumps. On smaller time scales (30 s), instead, the static depletion of the limit order book is an indicator of an intrinsic fragility of the system, which is related to a strongly nonlinear enhancement of the response. In order to quantify this phenomenon we introduce a measure of the liquidity imbalance present in the book and we show that it is correlated to both the sign and the magnitude of the next price movement. These findings provide a quantitative definition of the effective liquidity, which proves to be strongly dependent on the considered time scales

Combined lung and brain ultrasonography for an individualized “brain-protective ventilation strategy” in neurocritical care patients with challenging ventilation needs

When intracranial hypertension and severe lung damage coexist in the same clinical scenario, their management poses a difficult challenge, especially as concerns mechanical ventilation management. The needs of combined lung and brain protection from secondary damage may conflict, as ventilation strategies commonly used in patients with ARDS are potentially associated with an increased risk of intracranial hypertension. In particular, the use of positive end-expiratory pressure, recruitment maneuvers, prone positioning, and protective lung ventilation can have undesirable effects on cerebral physiology: they may positively or negatively affect intracranial pressure, based on the final repercussions on PaO2and cerebral perfusion pressure (through changes in cardiac output, mean arterial pressure, venous return, PaO2and PaCO2), also according to the baseline conditions of cerebral autoregulation. Lung ultrasound (LUS) and brain ultrasound (BUS, as a combination of optic nerve sheath diameter assessment and cerebrovascular Doppler ultrasound) have independently proven their potential in respectively monitoring lung aeration and brain physiology at the bedside. In this narrative review, we describe how the combined use of LUS and BUS on neurocritical patients with demanding mechanical ventilation needs can contribute to ventilation management, with the aim of a tailored “brain-protective ventilation strategy.

A methodology for including suspension dynamics in a simple context of rail vehicle simulations

The running behaviour of rail vehicles is highly influenced by suspension components. Dealing with ride comfort, secondary suspensions are adopted to reduce the vibrations transmitted to the carbody. In this context, the dynamics of the suspension elements themselves has to be properly included in multibody system. This paper proposes a strategy for modelling the passive vertical secondary suspension in the frequency domain. To this aim, a mathematical model is defined and its parameters are tuned to be representative of a real system. Then, a sensitivity analysis over the model parameters is proposed to discuss the suspension performances in terms of dynamic stiffness. Finally, a finite element model of the carbody is considered and coupled to the rear and front suspensions. The model is adopted to simulate the vehicle running on a rail track irregularity in the frequency domain, in the 0-30 Hz frequency range

Pulmonary artery acceleration time accuracy for systolic pulmonary artery pressure estimation in critically ill patients

Background: Estimation of pulmonary pressures is of key importance in acute cardiovascular and respiratory failure. Pulmonary artery acceleration time (PAAT) has emerged as reliable parameter for the estimation of systolic pulmonary artery pressure (sPAP) in cardiological population with preserved right ventricular function. We sought to find whether PAAT correlates with sPAP in critically ill patients with and without right ventricular (RV) systolic dysfunction.Methods: Observational study. We measured sPAP using continuous-wave Doppler analysis of tricuspid regurgitation velocity peak method and we assessed the validity of PAAT in estimating sPAP in patients admitted to adult intensive care unit (ICU) for acute cardiovascular and respiratory failure.Results: We enrolled 236 patients admitted to cardiothoracic ICU for cardiovascular and respiratory failure (respectively: 129, 54.7% and 107, 45.3%). 114 (48.3%) had preserved RV systolic function (defined as TAPSE >= 17 mm), whilst 122 (51.7%) had RV systolic impairment (defined as TAPSE < 17 mm). A weak inverse correlation between PAAT and sPAP (rho-0.189, p 0.0035) was observed in overall population, which was confirmed in those with preserved RV systolic PAAT and sPAP (rho-0.361, p 0.0001). In patients with impaired RV systolic function no statistically significant correlation between PAAT and sPAP was demonstrated (p 0.2737). Adjusting PAAT values for log(10), heart rate and RV ejection time did not modify the abovementioned correlations.Conclusions: PAAT measurement to derive sPAP is not reliable in cardiothoracic critically ill patients, particularly in the coexistence of RV systolic impairment

Lung hyperaeration assessment by computed tomography: Correction of reconstruction-induced bias

Background: Computed tomography (CT) reconstruction parameters, such as slice thickness and convolution kernel, significantly affect the quantification of hyperaerated parenchyma (VHYPER%). The aim of this study was to investigate the mathematical relation between VHYPER% calculated at different reconstruction settings, in mechanically ventilated and spontaneously breathing patients with different lung pathology. Methods: In this retrospective observational study, CT scans of patients of the intensive care unit and emergency department were collected from two CT scanners and analysed with different kernel-thickness combinations (reconstructions): 1.25 mm soft kernel, 5 mm soft kernel, 5 mm sharp kernel in the first scanner; 2.5 mm slice thickness with a smooth (B41s) and a sharp (B70s) kernel on the second scanner. A quantitative analysis was performed with Maluna® to assess lung aeration compartments as percent of total lung volume. CT variables calculated with different reconstructions were compared in pairs, and their mathematical relationship was analysed by using quadratic and power functions. Results: 43 subjects were included in the present analysis. Image reconstruction parameters influenced all the quantitative CT-derived variables. The most relevant changes occurred in the hyperaerated and normally aerated volume compartments. The application of a power correction formula led to a significant reduction in the bias between VHYPER% estimations (p 0.15 in all cases). Conclusions: Hyperaerated percent volume at different reconstruction settings can be described by a fixed mathematical relationship, independent of lung pathology, ventilation mode, and type of CT scanner

An in plane flexible ring model for the analysis of the free and forced response of a rolling tyre

The increased demand for vibroacoustic comfort as well as regulations on noise and vibration levels made the NVH performances of a vehicle one of the fundamental design criteria. Therefore, predictive models for the analysis of noise and vibration transmission mechanisms represent interesting tools to support the R&D department of the automotive companies. Focusing the attention on passenger’s comfort, the vibrations induced by the tyre/road interaction propagate from the contact area to the hub and finally inside the cockpit through structure-borne transmission paths. This can be regarded as one of the major contributors to car cabin interior noise at low frequencies (20-500 Hz). Simplified models able to interpret the waves propagating inside the tyre structure and influenced by the angular speed may support the studies in this research field. To this end, an analytical model based on the theory of the flexible ring on elastic foundation was developed. It allows analysing the tyre dynamics in both static and rotating conditions. Model parameters were calibrated based on an Experimental Modal Analysis of the static tyre. The free response of the tyre shows the bifurcation effect at different rotating speeds, while a cleat test simulation allows investigating the forced response of the tyre

A deep Natural Language Inference predictor without language-specific training data

In this paper we present a technique of NLP to tackle the problem of inference relation (NLI) between pairs of sentences in a target language of choice without a language-specific training dataset. We exploit a generic translation dataset, manually translated, along with two instances of the same pre-trained model - the first to generate sentence embeddings for the source language, and the second fine-tuned over the target language to mimic the first. This technique is known as Knowledge Distillation. The model has been evaluated over machine translated Stanford NLI test dataset, machine translated Multi-Genre NLI test dataset, and manually translated RTE3-ITA test dataset. We also test the proposed architecture over different tasks to empirically demonstrate the generality of the NLI task. The model has been evaluated over the native Italian ABSITA dataset, on the tasks of Sentiment Analysis, Aspect-Based Sentiment Analysis, and Topic Recognition. We emphasise the generality and exploitability of the Knowledge Distillation technique that outperforms other methodologies based on machine translation, even though the former was not directly trained on the data it was tested over.Comment: Conference: ICIAP202

Mid-term results of complex distal humeral fractures.

The aim of this study was to assess outcomes following open reduction and internal fixation in complex fractures of the distal humerus. Between 2000 and 2006, 34 patients were operated for complex fractures of the distal humerus. Bone fixation was obtained with a reverse Y-shaped reconstruction plate in 13 cases and with double plating in 21 cases. At final follow-up, all the patients were assessed with the Mayo Elbow Performance Score. Satisfactory results were observed in 71% of the cases despite a high rate of complications. Age over 65 years is correlated with increased risk for an inferior postoperative result. Complex distal humeral fractures are difficult to treat and are associated with a high incidence of complications. It is therefore mandatory to obtain good anatomical reduction and a stable fixation of lateral and medial columns of the distal humerus. The results observed in older patients suggest that an alternative treatment for these patients may be joint replacement

REAL-TIME ELASTOGRAPHY IN THE ASSESSMENT OF LIVER FIBROSIS: A REVIEW OF QUALITATIVE AND SEMI-QUANTITATIVE METHODS FOR ELASTOGRAM ANALYSIS

Despite its invasiveness, liver biopsy is still considered the gold standard for the assessment of hepatic fibrosis. Non-invasive ultrasound-based techniques are increasingly employed to assess parenchymal stiffness and the progression of chronic diffuse liver diseases. Real-time elastography is a rapidly evolving technique that can reveal the elastic properties of tissues. This review examines qualitative and semi-quantitative methods developed for analysis of real-time liver elastograms, to estimate parenchymal stiffness and, indirectly, the stage of fibrosis. Qualitative analysis is the most immediate approach for elastogram analysis, but this method increases intra- and inter-observervariability,whichisseenasamajorlimitationofreal-timeelastography.Semi-quantitativemethods include analysis of the histogram derived from color-coded maps, as well as calculation of the elastic ratio and fibrosis index. (E-mail: [email protected]) 2014 World Federation for Ultrasound in Medicine & Biology