Utility of chest CT in diagnosis of COVID-19 pneumonia

PURPOSEWe aimed to explore the imaging findings of computed tomography (CT) in diagnosing coronavirus disease 2019 (COVID-19) and its clinical value for further evaluation of suspected cases.METHODSFiles of 155 patients visiting the fever clinics at our hospital and affiliated hospitals from January 20th to February 9th, 2020 were searched. Among them, 140 cases (including 82 males and 58 females) were included as suspected COVID-19 cases based on clinical and epidemiological history; the CT image features of 70 cases with suggestive findings on CT, confirmed by positive nucleic acid test were analyzed and evaluated. The sensitivity and specificity of CT in diagnosing COVID-19 were evaluated in patients with epidemiological history.RESULTSOf the 70 patients, 84.3% showed bilateral lung involvement on CT; 27 cases (38.6%) showed ground-glass opacity (GGO), which was mostly distributed in the subpleural area (55.7%), and this sign was mainly observed in early COVID-19 patients. In addition, 41 cases (58.6%) manifested GGO combined with focal consolidation opacity, 2 (2.8%) had flake-like consolidation opacity, with involvements of the periphery of lung field and the central zone (44.3%), and this sign was mostly observed in severe or critical patients. Concomitant signs such as pleural effusion and mediastinal lymph node enlargement were rare. Among patients with epidemiological history, the sensitivity of CT in diagnosing COVID-19 was 89.7% (70/78), and the specificity was 88.7% (55/62).CONCLUSIONCT shows high sensitivity and specificity in diagnosing COVID-19. CT is an important examination method in evaluation of suspected cases and assessment of disease severity

Unequal impact of climate warming on meat yields of global cattle farming

Abstract Climate warming affects global livestock productivity. The meat yield from cattle farming (cattle meat per animal) represents livestock productivity at the individual level. However, the impact of warming on cattle meat yield at a global scale is not well understood. In this study, we combine country-level data on the annual meat yield from cattle farming and socioeconomic data from 1961 to 2020 with climate projections from General Circulation Models. The findings show that cattle meat yield increases as temperatures rise from low to medium and then decreases when annual average temperatures exceed 7 °C; this repose is pronounced in the grassland-based livestock system. Further, we show that warming creates unequal impacts between high- and low-income countries due to the divergent baseline temperature conditions. Future warming aggravates these unequal burdens between countries, with the most pronounced effects observed under the upper-middle emissions scenario

Spray combustion characteristics of a gas-liquid pintle injector with variable swirl intensities

The present paper experimentally verified and computationally explained an improved design concept of the spray combustion of a gas-liquid pintle injector with variable swirl intensities. By pintle injector, we mean a promising injector for the throttleable engines with variable thrust capacities, which features the moveable pintle continuously controlling the mass flow rates of fuel and oxidizer where the radial and axial flows encounter to form a spray cone and spray atomization. First, the cold flow test was conducted to study the swirl effects on the spray angle, followed by the combustion test to study the total pressure and the specific impulse under different swirl intensities. The results show that the swirl enhances the combustion performance by increasing the total pressure and specific impulse. Second, the swirl-assisted spray was numerically simulated based on a validated volume-of-fluid method to explain the experimental findings. The diameter distribution and spatial distribution of dispersed droplets were analyzed by the Sauter mean diameter (SMD) and the Voronoi tessellation, respectively. The results show that the swirl significantly promotes the breakup of liquid jet or film, producing smaller SMDs and a more uniform spatial distribution of dispersed droplets. The consolidated correlation between the non-reacting spray characteristics and the combustion performance suggests that the proposed methodology can be used to fast prescreen pintle injector designs

A soft-margin support vector machine based on normal convex hulls

Finding the closest points in the two normal convex hulls (NCH) gives an intuitive geometry explanation to support vector machine (SVM) in hard-margin case. However, the reduced convex hull (RCH) introduced in soft-margin case is difficult to understand and explain because it cuts off some boundary points of NCH, which probably become support vectors. This paper proposes a soft-margin SVM model still based on NCH, named as L2-SVC-NCH. L2-SVC-NCH can be interpreted as finding two closest points in the two NCHs on a feature space and the punishment parameter C for empirical risk can be viewed as a trade off between the ordinary kernel function and Kronecker delta kernel function, which makes that L2-SVC-NCH is more perfect and easier to understand and explain than the SVM model based on RCH. In addition, L2-SVC-NCH obtains many additional advantages, such as the good feasible region, the strictly convex objective function and many optional geometric algorithms. The relationships between L2-SVC-NCH and some commonly used SVM models are also illustrated. The comparative experiments on five benchmark datasets show that L2-SVC-NCH is effective and competitive

Experimental Investigation of Abrupt Change in a Scramjet with Variable Mach-Number Flow

To study an abrupt phenomenon of a scramjet in the Mach-number variation process, a scramjet model was tested in the simulated acceleration and deceleration conditions between the flight Mach numbers of 5.0 and 6.0. The results showed that once the flame stabilization changes, the pressure and thrust will meet the abrupt change simultaneously, while three typical flame stabilization and two types of transformation processes were found. One is the switching between the jet-wake flame and the cavity shear-layer flame directly, accompanied by one abrupt change. The other is the switching of the first two flame stabilizations, combined with the cavity shear-layer/recirculation flame, accompanied by two abrupt changes. The reduction in the range of the equivalence ratio and the process of increasing the Mach number will promote the appearance of the second type with two abrupt changes, and the process of increasing equivalence ratio and decreasing Mach number makes the first type with only one abrupt change more likely to occur. In other words, the characteristics of the abrupt change during the flame stabilization transition process are determined by the combined effect of the changing paths of the incoming flow condition and the equivalence ratio. The actual process of Mach- number variation has an obvious historical effect on the flame stabilization transition

Experimental investigation of combustion-induced starting hysteresis in the scramjet

Understanding the hypersonic inlet starting characteristics is the prerequisite for avoiding the abnormal unstart state. To make the work close to the actual situation, an experimental study was performed on a scramjet model at a simulated freestream Mach number of 6.0 with pressure and thrust measurements. The inlet working status is determined by the heat release of the injected ethylene with reciprocating variations. The results show that the critical equivalence ratio of the restart state is lower than that of the unstart state, which means that the combustion weakens the inlet restart capability and raises the unstart/restart hysteresis phenomena. Specifically, two novel unstart/restart hysteresis phenomena are found: one may come from the dual-solution characteristics of the shock-combustion interaction and the other may come from the historical effect of reverse flow. Compared to the former type, the latter type requires greater downstream heat release and generates a larger hysteresis loop. In addition, the engine thrust characteristics of the whole unstart and restart processes are analyzed. The thrust increment in the shock-combustion interaction type exhibits nearly linearly. However, the thrust increment meets abrupt changes and strong oscillations in the reverse flow type, accompanied by the reverse flow's formation and disappearance, making the engine more difficult to restart. Published under an exclusive license by AIP Publishing

A new pruning method for decision tree based on structural risk of leaf node

Natural Science Foundations of Fujian Province of China [2011J01373]; Foundation of Key Laboratory of System Control and Information Processing, Ministry of Education, P.R. China [SCIP2011004]Pruning is an effective technique in improving the generalization performance of decision tree. However, most of the existing methods are time-consuming or unsuitable for small dataset. In this paper, a new pruning algorithm based on structural risk of leaf node is proposed. The structural risk is measured by the product of the accuracy and the volume (PAV) in leaf node. The comparison experiments with Cost-Complexity Pruning using cross-validation (CCP-CV) algorithm on some benchmark datasets show that PAV pruning largely reduces the time cost of CCP-CV, while the test accuracy of PAV pruning is close to that of CCP-CV

Combined cardiac, lung, and diaphragm ultrasound for predicting weaning failure during spontaneous breathing trial

Abstract Background Weaning from invasive mechanical ventilation (MV) is a complex and challenging process that involves multiple pathophysiological mechanisms. A combined ultrasound evaluation of the heart, lungs, and diaphragm during the weaning phase can help to identify risk factors and underlying mechanisms for weaning failure. This study aimed to investigate the accuracy of lung ultrasound (LUS), transthoracic echocardiography (TTE), and diaphragm ultrasound for predicting weaning failure in critically ill patients. Methods Patients undergoing invasive MV for > 48 h and who were readied for their first spontaneous breathing trial (SBT) were studied. Patients were scheduled for a 2-h SBT using low-level pressure support ventilation. LUS and TTE were performed prospectively before and 30 min after starting the SBT, and diaphragm ultrasound was only performed 30 min after starting the SBT. Weaning failure was defined as failure of SBT, re-intubation, or non-invasive ventilation within 48 h. Results Fifty-one patients were included, of whom 15 experienced weaning failure. During the SBT, the global, anterior, and antero-lateral LUS scores were higher in the failed group than in the successful group. Receiver operating characteristic curve analysis showed that the areas under the curves for diaphragm thickening fraction (DTF) and global and antero-lateral LUS scores during the SBT to predict weaning failure were 0.678, 0.719, and 0.721, respectively. There was no correlation between the LUS scores and the average E/e’ ratio during the SBT. Multivariate analysis identified antero-lateral LUS score > 7 and DTF  7 and DTF < 31% during the SBT were associated with weaning failure. Graphical Abstrac