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Objective: Previous studies on osteoporotic vertebral fractures are usually based on the neutral posture of spine; however, the fractures are usually associated with the flexion posture of spine. Therefore, we aimed to ascertain the relationship between vertebral compression fractures and thoracolumbar hyperflexion Cobb angles (TLHCobb) and determine the clinical cut‐off of the TLHCobb angle. Methods: In this retrospective case–control study, TLHCobbs were collected from 154 postmenopausal women (67.45 ± 6.68 years) with vertebral compression fractures (study group) and 310 postmenopausal women (66.57 ± 8.22 years) without vertebral compression fractures (control group) from June 2017 to July 2019. Demographic data, clinical data, and quantitative computed tomography (QCT) findings were compared between the groups. Chi‐squared tests, unpaired t‐tests, and Mann Whitney U were used to assess the group characteristics and proportions. Logistic regression was used to examine the association between vertebral compression fractures and TLHCobb. The cut‐off of the TLHCobb was determined by ROC curve and Youden's index. Results: Fracture prevalence was higher in the higher TLHCobb study group than that in the control group [OR = 2.81 (2.15–3.67)] after adjusting for age, BMI, and QCT findings. TLHCobbs at and >20.05° were associated with an increased fracture prevalence and ORs of 2.79 (1.82–4.27) and 4.83 (3.24–7.20), respectively. TLHCobb, disk height (semiquantitative grading score) and QCT values differed between the study and control groups (p < 0.001 for all three). There were no significant differences in body mass index (BMI), or coronal TLCobb between the two groups. Conclusion: There was an association between the prevalence of vertebral compression fractures and TLHCobbs in postmenopausal women, and a TLHCobb > 20.05° can be an indicator of vertebral fracture. [ABSTRACT FROM AUTHOR]

Objective: To compare the efficacy and safety of retaining the posterior longitudinal ligament (PLL) with resecting the PLL in inside‐out percutaneous endoscopic transforaminal discectomy (PETD) surgery for lumbar disc herniation (LDH). Method: A total of 135 patients with symptomatic LDH who were treated by inside‐out PETD surgery from January 2015 to January 2017were included in this retrospective analysis. There were 38 males and 30 females in the PLL resection group (mean age = 52.40 ± 8.73 years) and 35 males and 32 females in the PLL retention group (mean age = 53.50 ± 9.24 years). The visual analogue scale (VAS) score, Oswestry disability index (ODI), and modified MacNab criteria were used to evaluate clinical outcomes. Operation time, blood loss, recurrence of LDH, and complications were recorded. Three months after surgery, magnetic resonance imaging was performed to confirm that nerve root compression was relieved. Results: The VAS and ODI scores improved significantly immediately after surgery, at 1 month after surgery, at 3 months after surgery, and at last follow‐up compared with those before surgery (P < 0.01). The scores also improved significantly between immediately after surgery and 1 month after surgery in the two groups (P < 0.001). Multivariate analysis indicated that age ≥ 50 years (odds ratio (OR) = 6.33, 95% confidence interval (CI): 1.64–21.98, P = 0.014), pain duration ≥6 months (OR = 4.68, 95% CI: 1.29–6.51, P = 0.025), pre‐ODI score ≥ 40% (OR = 5.97, 95% CI: 2.41–14.86, P = 0.003) were all associated with poor functional outcomes. There was no significant difference in the excellent/good ratio between the two groups and the mean operation time of the retention group was 71.5% of that of the resection group (82.7 ± 18.5 min vs 115.6 ± 24.6 min, P < 0.01). In the patients, no serious complications, such as dural tear, wound infection, or persistent nerve root injury, were observed during the follow‐up period. There was no significant difference in the complication rate between the two groups (6/68 vs 6/67, P = 0.979). Although the recurrence rate was higher in retention group, there was no significant difference between the two groups (1/68 vs 2/67, P = 0.551). Conclusion: The PLL is recommended to be retained for inside‐out PETD surgery. [ABSTRACT FROM AUTHOR]

This article investigates the optimal control problem via reinforcement learning for a class of nonlinear discrete‐time systems. The nonlinear system under consideration is assumed to be partially unknown. A new learning‐based algorithm, T‐step heuristic dynamic programming with eligibility traces (T‐sHDP(λ)), is proposed to tackle the optimal control problem for such partially unknown system. First, the concerned optimal control problem is turned into its equivalence problem, that is, solving a Bellman equation. Then, the T‐sHDP(λ) is utilized to get an approximate solution of Bellman equation, and a rigorous convergence analysis is also conducted as well. Instead of the commonly used single step update approach, the T‐sHDP(λ) stores finite step past returns by introducing a parameter, and then utilizes these knowledge to update the value function (VF) of multiple moments synchronously, so as to achieve higher convergence speed. For implementation of T‐sHDP(λ), a neural network‐based actor‐critic architecture is applied to approximate VF and optimal control scheme. Finally, the feasibility of the algorithm is demonstrated by two illustrative simulation examples. [ABSTRACT FROM AUTHOR]

In continuous permafrost environments, understanding complex river‐talik system dynamics is fundamental for the sustainable use of talik aquifers as a source of drinking water in remote communities. A conceptual model of a river‐talik system was previously developed based on field investigations in the floodplain of the Kuuguluk River at Salluit, Nunavik (Quebec), Canada, including geophysical surveys and monitoring of hydraulic heads and riverbed temperatures. This conceptual model is here used to develop a 3D numerical model for simulating the governing cryo‐hydrogeological processes and dynamic system behavior. The numerical simulations, supported by the field data, show that the width and thickness of the river talik is highly correlated to the width of the overlying riverbed. In summer, the river talik is hydraulically connected to the riverbed, and groundwater from the talik aquifer is contributing to river baseflow. In winter, when the river and riverbed freeze, the river talik becomes hydraulically isolated from the riverbed. Under such conditions, the river talik acts as a tube‐like conduit system which focusses groundwater flow. Increasing hydraulic heads at constrictions in the talik can be sufficient to fracture the frozen riverbed and ice cover, leading to groundwater overflows and icing formation. This study presents an integrated field and modeling approach for assessing the potential of talik aquifers as reliable sources of drinking water in northern communities. Plain Language Summary: Finding a reliable source of drinking water in very cold climates is a challenging task for the sustainable development of northern communities. On the one hand, surface water is vulnerable to contamination and can freeze in winter. On the other hand, groundwater stored as ice in permanently frozen ground, called permafrost, is not readily available for use. However, extractable groundwater in permafrost environments can often be found below surface water, including groundwater below rivers. Heat transport from the relatively warmer river water can be enough to maintain a zone of unfrozen ground below the riverbed, called a river talik. For example, the Inuit community of Salluit (Nunavik, Canada) is currently extracting groundwater from a river talik as a source of drinking water. Understanding the dynamics of this complex river‐talik system is fundamental for sustainable use of this natural resource. To improve our understanding of this system, we have undertaken field investigations to monitor water levels and temperatures in the riverbed, and to delineate the river talik using geophysical methods. We have also developed and applied a 3D numerical model to simulate the governing physical processes of groundwater flow and heat transport in and around the river talik. In winter, increases in groundwater pressure at talik constrictions are sufficient to crack the ice cover, which induces groundwater overflow, and enlarges the ice cover. The study presents a useful integrated field and modeling approach for assessing the potential of talik aquifers as reliable sources of drinking water in northern communities. Key Points: Numerical modeling supported by field investigations shows that the size of the river talik is correlated to the width of the river channelThe river talik is hydraulically connected to the riverbed in summer but is hydraulically isolated in winter due to freezing of the riverbed and icing formationWhen the talik is hydraulically isolated in winter, increases in hydraulic head at talik constrictions are enough to fracture the frozen riverbed and overlying ice which leads to groundwater overflows [ABSTRACT FROM AUTHOR]

Osteosarcoma (OS) is a sarcoma with high rates of pulmonary metastases and mortality. The mechanisms underlying tumour generation and development in OS are not well‐understood. Haematopoietic cell kinase (HCK), a vital member of the Src family of kinase proteins, plays crucial roles in cancer progression and may act as an anticancer target; however, the mechanism by which HCK enhances OS development remains unexplored. Therefore, we investigated the role of HCK in OS development in vitro and in vivo. Downregulation of HCK attenuated OS cell proliferation, migration and invasion and increased OS cell apoptosis, whereas overexpression of HCK enhanced these processes. Mechanistically, HCK expression enhanced OS tumorigenesis via the mitogen‐activated protein kinase (MEK)/extracellular signal‐regulated kinase (ERK) pathway; HCK upregulation increased the phosphorylation of MEK and ERK and promoted epithelial‐mesenchymal transition, with a reduction in E‐cadherin in vitro. Furthermore, HCK downregulation decreased the tumour volume and weight in mice transplanted with OS cells. In conclusion, HCK plays a crucial role in OS tumorigenesis, progression and metastasis via the MEK/ERK pathway, suggesting that HCK is a potential target for developing treatments for OS. [ABSTRACT FROM AUTHOR]

Icing occurs each winter along the floodplain of the Kuuguluk River in the continuous permafrost zone at Salluit in Nunavik (Quebec), Canada. The source of successive water overflows which thicken and enlarge this ice cover over time is suprapermafrost groundwater discharging from a talik below the riverbed. Electrical resistivity tomography was used to delineate the talik, while water level and temperature dataloggers were used to assess the thermo‐hydraulic conditions of the riverbed. The mean annual riverbed temperature was 1.8°C in 2016 while the mean annual air temperature was −6.0°C. Hydraulic heads below the ice cover as high as 2.8 m and events of abrupt decreases in hydraulic head due to suprapermafrost groundwater overflow through cracks in the ice cover were monitored. An analytical solution based on beam mechanics theory was used to assess the water pressure‐induced stresses which are sufficient to fracture the ice cover. A detailed conceptual model of the talik and icing dynamics is proposed to explain the cryo‐hydrogeological processes taking place in this complex groundwater–river system. The groundwater pressure buildup in the talik during the winter is due to constricted flow of suprapermafrost groundwater in the talik. These results have implications for understanding the dynamics of river taliks and their use as potential water supplies in northern communities. [ABSTRACT FROM AUTHOR]

Predicting and mapping high water table elevation in coastal landscapes is critical for both science application projects like inundation risk analysis and engineering projects like pond design and maintenance. Previous studies of water table mapping focused on the application of geostatistical methods, which cannot predict values beyond an observation spatial domain or generate an ideal pattern for regions with sparse measurements. In this study, we evaluated the multiple linear regression (MLR) and support vector machine (SVM) techniques for high water table prediction and mapping using fine spatial resolution lidar‐derived Digital Elevation Model (DEM) data, and designed an application protocol of these two techniques for high water table mapping in a coastal landscape where groundwater, tide, and surface water are related. Testing results showed that SVM largely improved the high water table prediction with a mean absolute error (MAE) of 1.22 feet and root mean square error (RMSE) of 2.22 feet compared to the application of the ordinary Kriging method which could not generate a reasonable water table. MLR was also promising with a MAE of around 2 feet and RMSE of around 3 feet. The study suggests that both MLR and SVM are valuable alternatives to estimate high water table elevation in Florida. Fine resolution lidar DEMs are beneficial for high water table prediction and mapping. Article impact statement: Predicting high water table elevation using multiple linear regression and support vector machine approach in Florida coastal landscapes. [ABSTRACT FROM AUTHOR]

Migraine comorbid with depression is common and is often encountered in clinical practice. The comorbidity may lead to more serious conditions with other symptoms and a longer duration of treatment and it may impose heavy economic and social burdens, directly or indirectly, on patients and their families. Numerous studies have been published on the association of migraine with depression. Numerous literature have showed that the comorbidity may have a common complicated pathogenic mechanism involving biopsychosocial characteristics, including abnormal brain development and shared genetic basis, as well as neurotransmitters, sex hormones and stress. In addition, some studies have identified the multiple, bidirectional relationship between migraine and depressive disorder. We searched the literature for the possible common mechanisms between migraine and depression and classified the research results. [ABSTRACT FROM AUTHOR]