Measuring air connectivity between China and Australia

This paper assesses air connectivity between China and Australia for the period 2005–16 using a Connectivity Utility Model. Our direct connectivity measure shows that as a gateway city, Sydney continues to play a key role in facilitating the movements of people and goods between China and Australia. Guangzhou has become the city best connected with Australia since 2011 as measured by direct connectivity. When indirect connections are considered, the largest increases in overall connectivity from 2005 to 2016 can be observed among Australia's major capital cities, particularly Sydney, Melbourne and Brisbane. Chinese carriers are the key drivers behind the increases. There have been rises and falls for airports serving as a hub between China and Australia. Guangzhou has forged its strong status as a transfer hub between Australia and China thanks to the quick expansion of China Southern. The gaps between Guangzhou and other transfer hubs measured by hub connectivity have widened since 2010

The growing influence of low-cost carriers in Northeast Asia and its implications for a regional single aviation market

This paper provides an overview of the development of the low-cost carrier (LCC) sector in China, Japan, and South Korea. It is the first paper that documents LCC contributions to the passenger traffic and cheaper fares in Northeast Asia (NEA)’s intra-markets. We argue that a single aviation market can facilitate the growth of the LCC sector, which in turn will make a significant contribution to the NEA connectivity, mobility, and integration. In addition, with a single aviation market, NEA countries can adopt a proactive, unified approach in negotiating air transport agreements with the major aviation partners to maximize the interests of this region as a whole, which will further provide valuable growth opportunities for the LCCs

The determinants of outward foreign direct investment strategies of Chinese energy firms

This paper investigates the location strategies of Chinese energy firms over the period 2003–2013. The results confirm that market-seeking and resource-seeking are two significant motivations behind Chinese energy firms’ outward foreign direct investment (OFDI). As expected, a higher level of the host country’s energy resource reserves attracts more energy resource related projects and the host country’s renewable energy output influences Chinese firms’ renewable energy investment. However, for OFDI in energy resources, the political stability of the host country is not a significant factor while when investing in renewable energy, it is a significant consideration. Interestingly, for OFDI in energy resources, trade integration measured by the share of exports sold in the host country in China’s total exports, is not statistically significant while for OFDI in renewable energy, trade integration affects the investment decision

COVID-19, air transportation, and international trade in the ASEAN+5 region

This paper provides an in-depth description of the coronavirus disease (COVID-19) pandemic and its interactions with air transportation in the Association of Southeast Asian Nations (ASEAN) + 5 region, and then links the changes in air connectivity to trade using a gravity regression model. We find that almost all the countries probably reacted too late in their decision to reduce flights in the early stage of the pandemic. As the pandemic evolved, most countries have significantly cut the number of flight connections, especially international flights. The reduced connectivity is found to have a significantly negative impact on trade for time-sensitive merchandise that is essential to consumers and businesses. This points to the importance of the region seeking alternative arrangements to restore air connectivity. We offer a way to construct optimal travel bubbles by using the introduced risk indexes. Other policy issues such as uniform standards and regulations, and regional ‘open skies’, are also discussed

Qualitative and Quantitative MRI Analysis in IDH1 Genotype Prediction of Lower-Grade Gliomas: A Machine Learning Approach

Purpose. Preoperative prediction of isocitrate dehydrogenase 1 (IDH1) mutation in lower-grade gliomas (LGGs) is crucial for clinical decision-making. This study aimed to examine the predictive value of a machine learning approach using qualitative and quantitative MRI features to identify the IDH1 mutation in LGGs. Materials and Methods. A total of 102 LGG patients were allocated to training (n=67) and validation (n=35) cohorts and were subject to Visually Accessible Rembrandt Images (VASARI) feature extraction (23 features) from conventional multimodal MRI and radiomics feature extraction (56 features) from apparent diffusion coefficient maps. Feature selection was conducted using the maximum Relevance Minimum Redundancy method and 0.632+ bootstrap method. A machine learning model to predict IDH1 mutation was then established using a random forest classifier. The predictive performance was evaluated using receiver operating characteristic (ROC) curves. Results. After feature selection, the top 5 VASARI features were enhancement quality, deep white matter invasion, tumor location, proportion of necrosis, and T1/FLAIR ratio, and the top 10 radiomics features included 3 histogram features, 3 gray-level run-length matrix features, and 3 gray-level size zone matrix features and one shape feature. Using the optimal VASARI or radiomics feature sets for IDH1 prediction, the trained model achieved an area under the ROC curve (AUC) of 0.779±0.001 or 0.849±0.008 on the validation cohort, respectively. The fusion model that integrated outputs of both optimal VASARI and radiomics models improved the AUC to 0.879. Conclusion. The proposed machine learning approach using VASARI and radiomics features can predict IDH1 mutation in LGGs

Dynamic and visual nomograms to online predict unfavorable outcome of mechanical thrombectomy for acute basilar artery occlusion

Abstract Background The evidence of mechanical thrombectomy (MT) in basilar artery occlusion (BAO) was limited. This study aimed to develop dynamic and visual nomogram models to predict the unfavorable outcome of MT in BAO online. Methods BAO patients treated with MT were screened. Preoperative and postoperative nomogram models were developed based on clinical parameters and imaging features. An independent dataset was collected to perform external validation. Web‐based calculators were constructed to provide convenient access. Results A total of 127 patients were included in the study, and 117 of them were eventually included in the analysis. The nomogram models showed robust discrimination, with an area under the receiver operating characteristic (ROC) of 0.841 (preoperative) and 0.916 (postoperative). The calibration curves showed good agreement. The preoperative predictors of an unfavorable outcome were previous stroke, the National Institutes of Health Stroke Scale (NIHSS) at admission, and the posterior circulation Alberta Stroke Program Early Computed Tomography Score (pc‐ASPECTS). The postoperative predictors were previous stroke, NIHSS at 24 h, and pc‐ASPECTS. Conclusion Dynamic and visual nomograms were constructed and validated for the first time for BAO patients treated with MT, which provided precise predictions for the risk of an unfavorable outcome. The preoperative model may assist clinicians in selecting eligible patients, and the postoperative model may facilitate individualized poststroke management

Application of a Simplified Method for Estimating Perfusion Derived from Diffusion-Weighted MR Imaging in Glioma Grading

Purpose: To evaluate the feasibility of a simplified method based on diffusion-weighted imaging (DWI) acquired with three b-values to measure tissue perfusion linked to microcirculation, to validate it against from perfusion-related parameters derived from intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging, and to investigate its utility to differentiate low- from high-grade gliomas.Materials and Methods: The prospective study was approved by the local institutional review board and written informed consent was obtained from all patients. From May 2016 and May 2017, 50 patients confirmed with glioma were assessed with multi-b-value DWI and DCE MR imaging at 3.0 T. Besides conventional apparent diffusion coefficient (ADC0,1000) map, perfusion-related parametric maps for IVIM-derived perfusion fraction (f) and pseudodiffusion coefficient (D*), DCE MR imaging-derived pharmacokinetic metrics, including Ktrans, ve and vp, as well as a metric named simplified perfusion fraction (SPF), were generated. Correlation between perfusion-related parameters was analyzed by using the Spearman rank correlation. All imaging parameters were compared between the low-grade (n = 19) and high-grade (n = 31) groups by using the Mann-Whitney U test. The diagnostic performance for tumor grading was evaluated with receiver operating characteristic (ROC) analysis.Results: SPF showed strong correlation with IVIM-derived f and D* (ρ = 0.732 and 0.716, respectively; both P < 0.001). Compared with f, SPF was more correlated with DCE MR imaging-derived Ktrans (ρ = 0.607; P < 0.001) and vp (ρ = 0.397; P = 0.004). Among all parameters, SPF achieved the highest accuracy for differentiating low- from high-grade gliomas, with an area under the ROC curve value of 0.942, which was significantly higher than that of ADC0,1000 (P = 0.004). By using SPF as a discriminative index, the diagnostic sensitivity and specificity were 87.1% and 94.7%, respectively, at the optimal cut-off value of 19.26%.Conclusion: The simplified method to measure tissue perfusion based on DWI by using three b-values may be helpful to differentiate low- from high-grade gliomas. SPF may serve as a valuable alternative to measure tumor perfusion in gliomas in a noninvasive, convenient and efficient way

Evaluation of skeletal muscle microvascular perfusion of lower extremities by cardiovascular magnetic resonance arterial spin labeling, blood oxygenation level-dependent, and intravoxel incoherent motion techniques

Abstract Background Noninvasive cardiovascular magnetic resonance (CMR) techniques including arterial spin labeling (ASL), blood oxygenation level-dependent (BOLD), and intravoxel incoherent motion (IVIM), are capable of measuring tissue perfusion-related parameters. We sought to evaluate and compare these three CMR techniques in characterizing skeletal muscle perfusion in lower extremities and to investigate their abilities to diagnose and assess the severity of peripheral arterial disease (PAD). Methods Fifteen healthy young subjects, 14 patients with PAD, and 10 age-matched healthy old subjects underwent ASL, BOLD, and IVIM CMR perfusion imaging. Healthy young and healthy old participants were subjected to a cuff-induced ischemia experiment with pressures of 20 mmHg and 40 mmHg above systolic pressure during imaging. Perfusion-related metrics, including blood flow, T2* relaxation time, perfusion fraction f, diffusion coefficient D, and pseudodiffusion coefficient D*, were measured in the anterior, lateral, soleus, and gastrocnemius muscle groups. Friedman, Mann-Whitney, Wilcoxon signed rank, and Spearman rank correlation tests were used for statistical analysis. Results In cases of significant differences determined by the Friedman test (P  0.05). Blood flow and T2* values showed significant positive correlations with transcutaneous oxygen pressure measurements (ρ = 0.465 and 0.522, respectively; both P ≤ 0.001), while f values showed a significant negative correlation in healthy young subjects (ρ = − 0.351; P = 0.018). T2* was independent of age in every muscle group. T2* values were significantly decreased in PAD patients compared with healthy old subjects and severe PAD patients compared with mild-to-moderate PAD patients (all P < 0.0125). Significant correlations were found between T2* and ankle–brachial index values in all muscle groups in PAD patients (ρ = 0.644–0.837; all P < 0.0125). Other imaging parameters failed to show benefits towards the diagnosis and disease severity evaluation of PAD. Conclusions ASL, BOLD, and IVIM provide complementary information regarding tissue perfusion. Compared with ASL and IVIM, BOLD may be a more reliable technique for assessing PAD in the resting state and could thus be applied together with angiography in clinical studies as a tool to comprehensively assess microvascular and macrovascular properties in PAD patients