Application of an Ovate Leaf Shape Model to Evaluate Leaf Bilateral Asymmetry and Calculate Lamina Centroid Location

Leaf shape is an important leaf trait, with ovate leaves common in many floras. Recently, a new leaf shape model (referred to as the MLRF equation) derived from temperature-dependent bacterial growth was proposed and demonstrated to be valid in describing leaf boundaries of many species with ovate leaf shape. The MLRF model’s parameters can provide valuable information of leaf shape, including the ratio of lamina width to length and the lamina centroid location on the lamina length axis. However, the model wasn’t tested on a large sample of a single species, thereby limiting its overall evaluation for describing leaf boundaries, for evaluating lamina bilateral asymmetry and for calculating lamina centroid location. In this study, we further test the model using data from two Lauraceae species, Cinnamomum camphora and Machilus leptophylla, with >290 leaves for each species. The equation was found to be credible for describing those shapes, with all adjusted root-mean-square errors (RMSE) smaller than 0.05, indicating that the mean absolute deviation is smaller than 5% of the radius of an assumed circle whose area equals lamina area. It was also found that the larger the extent of lamina asymmetry, the larger the adjusted RMSE, with approximately 50% of unexplained variation by the model accounted for by the lamina asymmetry, implying that this model can help to quantify the leaf bilateral asymmetry in future studies. In addition, there was a significant difference between the two species in their centroid ratio, i.e., the distance from leaf petiole to the point on the lamina length axis associated with leaf maximum width to the leaf maximum length. It was found that a higher centroid ratio does not necessarily lead to a greater investment of mass to leaf petiole relative to lamina, which might depend on the petiole pattern.

Multi-objective UAV Positioning Mechanism for Sustainable Wireless Connectivity in Environments with Forbidden Flying Zones

Unmanned aerial vehicles (UAVs)-based communication system is a promising solution to meet coverage and capacity requirements of future wireless networks. However, UAV-enabled communications is constrained with its coverage, energy consumption, and flying regulations, and the number of works focusing on the sustainability aspect of UAV-assisted networking has been limited in the literature so far. In this paper, we propose a solution to this limitation; particularly, we design a $Q$-learning-based UAV positioning scheme for sustainable wireless connectivity considering key constraints, that are, altitude regulations, non-flight zones, and transmit power. The objective is to find the optimal position of the UAV base station (BS) and minimize the energy consumption while maximizing the number of users covered. Moreover, a weighting mechanism is developed, where the energy consumption and number of users covered can be prioritized according to network/battery conditions. The proposed Q-learning-based solution is compared to the baseline k-means clustering method, where the UAV BS is positioned at the centroid location that minimizes the cumulative distance between the UAV BS and the users. The results demonstrate that the proposed solution outperforms the baseline k-means clustering-based method in terms of the number of users covered while achieving the desired minimization of the energy consumption.

Tibiofemoral contact and alignment in patients with anterior cruciate ligament rupture treated nonoperatively versus reconstruction

Aims Anterior cruciate ligament (ACL) rupture commonly leads to post-traumatic osteoarthritis, regardless of surgical reconstruction. This study uses standing MRI to investigate changes in contact area, contact centroid location, and tibiofemoral alignment between ACL-injured knees and healthy controls, to examine the effect of ACL reconstruction on these parameters. Methods An upright, open MRI was used to directly measure tibiofemoral contact area, centroid location, and alignment in 18 individuals with unilateral ACL rupture within the last five years. Eight participants had been treated nonoperatively and ten had ACL reconstruction performed within one year of injury. All participants were high-functioning and had returned to sport or recreational activities. Healthy contralateral knees served as controls. Participants were imaged in a standing posture with knees fully extended. Results Participants’ mean age was 28.4 years (SD 7.3), the mean time since injury was 2.7 years (SD 1.6), and the mean International Knee Documentation Subjective Knee Form score was 84.4 (SD 13.5). ACL injury was associated with a 10% increase (p = 0.001) in contact area, controlling for compartment, sex, posture, age, body mass, and time since injury. ACL injury was associated with a 5.2% more posteriorly translated medial centroid (p = 0.001), equivalent to a 2.6 mm posterior translation on a representative tibia with mean posteroanterior width of 49.4 mm. Relative to the femur, the tibiae of ACL ruptured knees were 2.3 mm more anteriorly translated (p = 0.003) and 2.6° less externally rotated (p = 0.010) than healthy controls. ACL reconstruction was not associated with an improvement in any measure. Conclusion ACL rupture was associated with an increased contact area, posteriorly translated medial centroid, anterior tibial translation, and reduced tibial external rotation in full extension. These changes were present 2.7 years post-injury regardless of ACL reconstruction status. Cite this article: Bone Joint J 2021;103-B(9):1505–1513.

Reliability of tibiofemoral contact area and centroid location in upright, open MRI

Background Imaging cannot be performed during natural weightbearing in biomechanical studies using conventional closed-bore MRI, which has necessitated simulating weightbearing load on the joint. Upright, open MRI (UO-MRI) allows for joint imaging during natural weightbearing and may have the potential to better characterize the biomechanical effect of tibiofemoral pathology involving soft tissues. However open MRI scanners have lower field strengths than closed-bore scanners, which limits the image quality that can be obtained. Thus, there is a need to establish the reliability of measurements in upright weightbearing postures obtained using UO-MRI. Methods Knees of five participants with prior anterior cruciate ligament (ACL) rupture were scanned standing in a 0.5 T upright open MRI scanner using a 3D DESS sequence. Manual segmentation of cartilage regions in contact was performed and centroids of these contact areas were automatically determined for the medial and lateral tibiofemoral compartments. Inter-rater, test-retest, and intra-rater reliability were determined and quantified using intra-class correlation (ICC3,1), standard error of measurement (SEM), and smallest detectable change with 95% confidence (SDC95). Accuracy was assessed by using a high-resolution 7 T MRI as a reference. Results Contact area and centroid location reliability (inter-rater, test-retest, and intra-rater) for sagittal scans in the medial compartment had ICC3,1 values from 0.95–0.99 and 0.98–0.99 respectively. In the lateral compartment, contact area and centroid location reliability ICC3,1 values ranged from 0.83–0.91 and 0.95–1.00 respectively. The smallest detectable change in contact area was 1.28% in the medial compartment and 0.95% in the lateral compartment. Contact area and centroid location reliability for coronal scans in the medial compartment had ICC3,1 values from 0.90–0.98 and 0.98–1.00 respectively, and in the lateral compartment ICC3,1 ranged from 0.76–0.94 and 0.93–1.00 respectively. The smallest detectable change in contact area was 0.65% in the medial compartment and 1.41% in the lateral compartment. Contact area was accurate to within a mean absolute error of 11.0 mm2. Conclusions Knee contact area and contact centroid location can be assessed in upright weightbearing MRI with good to excellent reliability. The lower field strength used in upright, weightbearing MRI does not compromise the reliability of tibiofemoral contact area and centroid location measures.

Reliability of Tibiofemoral Contact Area and Centroid Location in Upright, Open MRI

Background:Imaging cannot be performed during natural weightbearing in biomechanical studies using conventional closed-bore MRI, which has necessitated simulating weightbearing load on the joint. Upright, open MRI (UO-MRI) allows for joint imaging during natural weightbearing and may have the potential to better characterize the biomechanical effect of tibiofemoral pathology involving soft tissues. However open MRI scanners have lower field strengths than closed-bore scanners, which limits the image quality that can be obtained. Thus, there is a need to establish the reliability of measurements in upright weightbearing postures obtained using UO-MRI.Methods:Knees of five participants with prior anterior cruciate ligament (ACL) rupture were scanned standing in a 0.5T upright open MRI scanner using a 3D DESS sequence. Manual segmentation of cartilage regions in contact was performed and centroids of these contact areas were automatically determined for the medial and lateral tibiofemoral compartments. Inter-rater, test-retest, and intra-rater reliability were determined and quantified using intra-class correlation (ICC3,1), standard error of measurement (SEM), and smallest detectable change with 95% confidence (SDC95). Accuracy was assessed by using a high-resolution 7T MRI as a reference.Results:Contact area and centroid location reliability (inter-rater, test-retest, and intra-rater) for sagittal scans in the medial compartment had ICC3,1 values from 0.95-0.99 and 0.98-0.99 respectively. In the lateral compartment, contact area and centroid location reliability ICC3,1 values ranged from 0.83-0.91 and 0.95-1.00 respectively. The smallest detectable change in contact area was 1.28% in the medial compartment and 0.95% in the lateral compartment. Contact area and centroid location reliability for coronal scans in the medial compartment had ICC3,1 values from 0.90-0.98 and 0.98-1.00 respectively, and in the lateral compartment ICC3,1 ranged from 0.76-0.94 and 0.93-1.00 respectively. The smallest detectable change in contact area was 0.65% in the medial compartment and 1.41% in the lateral compartment. Contact area was accurate to within a mean absolute error of 11.0 mm2.Conclusions:Knee contact area and contact centroid location can be assessed in upright weightbearing MRI with good to excellent reliability. The lower field strength used in upright, weightbearing MRI does not compromise the reliability of tibiofemoral contact area and centroid location measures.

Lattice Boltzmann Model Simulation of Bubble Deformation and Breakup Induced by Micro-Scale Couette Flow

Understanding the morphology of transformation of a single bubble immersed in a liquid undergoing a shear flow is essential in predicting bubble deformation and breakup phenomena commonly found in applications involving complex liquid-gas multiphase flow. In this study, the deformation and breakup of a single bubble released in a fully developed laminar Couette flow in a micro-scale domain are evaluated under different spanwise positions, as well as under different initial diameters. The simulation is carried out using a multiphase Shan-Chen Lattice Boltzmann Model (SC-LBM). The transition between deformation and breakup experienced by the bubble is described under different Capillary (Ca) numbers, viscosity ratios and relative initial spanwise positions with respect to the channel centreline. A critical Ca number, Cac = 0.31, was found at the onset of breakup, with bubble centroid location varying as a function of the remaining parameters. The results obtained with the SC-LBM are in excellent agreement with those published in the literature.

Reliability of Tibiofemoral Contact Area and Centroid Location in an Upright, Open MRI (UO-MRI)

Background: In biomechanical studies using conventional closed-bore MR, imaging cannot be performed during natural weightbearing which has necessitated simulating weightbearing load on the joint. Upright, open MRI (UO-MRI) allows for joint imaging during natural weightbearing and may have the potential to better characterize the biomechanical effect of tibiofemoral pathology involving soft tissues. However open MRI scanners have lower field strengths than closed-bore scanners, which limits the image quality that can be obtained. Thus, there is a need to establish the reliability of measurements in upright weightbearing postures obtained via the UO-MRI.Methods: Manual segmentation of cartilage regions in contact from participants with prior anterior cruciate ligament (ACL) rupture was performed and centroids of those contact areas were automatically determined for the medial (MC) and lateral (LC) tibiofemoral compartments. To assess reliability, inter-rater, test-retest, and intra-rater reliability were determined by intra-class correlation (ICC3,1), standard error of measurement (SEM), smallest detectable change with 95% confidence (SDC95). Accuracy was assessed by using a high-resolution, 7T MRI as a reference and determined by mean absolute error (MAE).Results: Contact area and centroid location reliability (inter-rater, test-retest, and intra-rater) for sagittal scans in the MC demonstrated ICC3,1 values from 0.95-0.99 and 0.98-0.99 respectively, and in the LC from 0.83-0.91 and 0.95-1.00 respectively. The smallest detectable change in contact area was 1.28% in the MC and 0.95% in the LC. Contact area and centroid location reliability for coronal scans in the MC demonstrated ICC3,1 values from 0.90-0.98 and 0.98-1.00 respectively, and in the LC from 0.76-0.94 and 0.93-1.00 respectively. The smallest detectable change in contact area was 0.65% in the MC and 1.41% in the LC. Contact area segmentation was accurate to within a MAE of 11.0 mm2.Conclusions: Knee contact area and contact centroid location can be assessed in upright weightbearing MRI with good to excellent reliability. The lower field strength used in upright, weightbearing MRI does not compromise the reliability of tibiofemoral contact area and centroid location measures.

Energy dependent morphology of the pulsar wind nebula HESS J1825-137 with Fermi-LAT

Aims. Taking advantage of more than 11 years of Fermi-LAT data, we perform a new and deep analysis of the pulsar wind nebula (PWN) HESS J1825-137. Combining this analysis with recent H.E.S.S. results we investigate and constrain the particle transport mechanisms at work inside the source as well as the system evolution. Methods. The PWN is studied using 11.6 years of Fermi-LAT data between 1 GeV and 1 TeV. In particular, we present the results of the spectral analysis and the first energy-resolved morphological study of the PWN HESS J1825-137 at GeV energies, which provide new insights into the γ-ray characteristics of the nebula. Results. An optimised analysis of the source returns an extended emission region larger than 2°, corresponding to an intrinsic size of about 150 pc, making HESS J1825-137 the most extended γ-ray PWN currently known. The nebula presents a strong energy dependent morphology within the GeV range, moving from a radius of ∼1.4° below 10 GeV to a radius of ∼0.8° above 100 GeV, with a shift in the centroid location. Conclusions. Thanks to the large extension and peculiar energy-dependent morphology, it is possible to constrain the particle transport mechanisms inside the PWN HESS J1825-137. Using the variation of the source extension and position, as well as the constraints on the particle transport mechanisms, we present a scheme for the possible evolution of the system. Finally, we provide an estimate of the electron energy density and we discuss its nature in the PWN and TeV halo-like scenario.

Reliability of Tibiofemoral Contact Area and Centroid Location in an Upright, Open MRI (UO-MRI)

Background: Biomechanical studies are often performed using conventional closed-bore MR, which has necessitated simulating weightbearing load on the joint. The clinical applicability of these biomechanical findings is unclear because of the limitations of simulating weightbearing. Upright, open MRI (UO-MRI) can be used to assess knee joint mechanics, in particular contact area and centroid location. However, it is not clear how reliably measurements of contact area and centroid location can be made in upright weightbearing postures. Methods: Manual segmentation of cartilage regions in contact was performed and centroids of those contact areas were automatically determined for the medial (MC) and lateral (LC) tibiofemoral compartments. To assess reliability, inter-rater, test-retest, and intra-rater reliability were determined by intra-class correlation (ICC 3,1 ), standard error of measurement (SEM), smallest detectable change with 95% confidence (SDC 95 ). Accuracy was assessed by using a high-resolution, 7T MRI as a reference and determined by measurement error (%). Results: Contact area and centroid location reliability (inter-rater, test-retest, and intra-rater) for sagittal scans in the MC demonstrated ICC 3,1 values from 0.95-0.99 and 0.98-0.99 respectively, and in the LC from 0.83-0.91 and 0.95-1.00 respectively. The smallest detectable change in contact area was 1.28% in the MC and 0.95% in the LC. Contact area and centroid location reliability for coronal scans in the MC demonstrated ICC 3,1 values from 0.90-0.98 and 0.98-1.00 respectively, and in the LC from 0.76-0.94 and 0.93-1.00 respectively. The smallest detectable change in contact area was 0.65% in the MC and 1.41% in the LC. Contact area segmentation was accurate to within 4.81% measurement error. Conclusions: Knee contact area and contact centroid location can be assessed in upright weightbearing MRI with good to excellent reliability and accuracy within 5%. The lower field strength used in upright, weightbearing MRI does not compromise the reliability of tibiofemoral contact area and centroid location measures.