Asymmetric Index Research Articles

Reliability and Validity of the Ground Reaction Force Asymmetric Index at Seat-Off as a Measure of Lower Limb Functional Muscle Strength: A Preliminary Study

This study examined the reliability of the newly developed ground reaction force asymmetry index (GRF AI) at seat-off using a low-cost force plate and the validity of this new test by comparing it with other muscle strength-measuring methods and walking speed. This study was a cross-sectional design in general hospital setting. A convenience sample of 47 community-dwelling adults aged ≥40 years was performed. GRF AI is the measurement value obtained by shifting the weight to the right and left while performing sit-to-stand (STS). GRF AI assessed using GRF data at seat-off during an STS test with maximal weight shift to the right and left side and repeated 4 weeks later. Hip and knee extensor strength were measured using hand-held dynamometry; hand grip strength and walking speed were measured using a standardized method. Intrasessional intrarater reliability of the right and left side at Sessions 1 and 2 were high (intraclass correlation coefficients [ICC] = 0.947 and 0.974; 0.931 and 0.970, respectively). In addition, the intersessional intrarater reliability of a single test trial (ICC = 0.911 and 0.930) and the mean of three test trials (ICC = 0.965 and 0.979) was also high. There was a low correlation between right-side GRF AI and right hand grip strength (r = 0.268) and between left-side GRF AI and left hand grip strength (r = 0.316). No significant correlations were found between the GRF AI and other parameters. Although the reliability of the GRF AI was high, the validity was poor. To be clinically useful, this test should be further refined by modifying the test protocol.

Statistical Hypothesis Testing for Asymmetric Tolerance Index

Many of the nominal-the-best quality characteristics of important machine tool components, such as inner or outer diameters, have asymmetric tolerances. An asymmetric tolerance index is a function for the average of the process and the standard deviation. Unfortunately, it is difficult to obtain the 100(1−α)% confidence interval of the index. Therefore, this study adopts Boole’s inequality and DeMorgan’s theorem to find the combined confidence region for the average of the process as well as the standard deviation. Next, using the asymmetric tolerance index for the target function and the combined confidence region for the feasible region, this study applies mathematical programming to find the confidence interval as well as employs this confidence interval for statistical hypothesis testing. Lastly, this study demonstrates the applicability of the proposed approach with an illustrative example.

COVID-19 and asymmetric volatility spillovers across global stock markets

In this study, I improve the assessment of asymmetry in volatility spillovers, and define six asymmetric spillover indexes. Employing Diebold-Yilmaz spillover index, network analysis, and my developed asymmetric spillover index, this study investigates the time-varying volatility spillovers and asymmetry in spillovers across stock markets of the U.S., Japan, Germany, the U.K., France, Italy, Canada, China, India, and Brazil based on high-frequency data from June 1, 2009, to August 28, 2020. I find that the global markets are well connected, and volatility spillovers across global stock markets are time-varying, crisis-sensitive, and asymmetric. Developed markets are the main risk transmitters, and emerging markets are the main risk receivers. Downside risk dominates financial contagion effects, and a great deal of downside risk spilled over from stock markets of risk transmitters into the global markets. Moreover, during the coronavirus recession, the total degree of volatility spillover is staying at an extremely high level, and emerging markets are the main risk receivers in the 2020 stock markets crash.

Finite time asymmetric bipartite consensus for multi‐agent systems based on iterative learning control

AbstractIn this paper, the finite‐time asymmetric bipartite consensus problem of multi‐agent systems with signed digraph is considered. Firstly, an asymmetric index is introduced to describe a desired output relationship of the agents in terms of quantity. Based on the information of the agent's communication and the index, a novel iterative learning control protocol is proposed. By establishing the input and output errors relationship of the agents along the iteration domain, a sufficient condition is derived and a defined leaderless tracking error is proved to be asymptotically convergence as iteration increases. The result shows that the proposed design can ensure the agents achieve the asymmetric bipartite consensus goal in the finite‐time. Moreover, the proposed design is also extended to deal with the problem of the multi‐agent systems with heterogeneous dynamics. Finally, numerical simulation examples verify the effectiveness of the proposed protocol.

Characterizing Diaschisis-Related Thalamic Perfusion and Diffusion After Middle Cerebral Artery Infarction

Ipsilateral thalamic diaschisis (ITD) initially describes functional depression of the thalamus ipsilateral to a supratentorial lesion, but accumulating evidence has shown morphological changes also occur. Therefore, we aimed to characterize thalamic perfusion and diffusion related to ITD over time and their inter-relationships after middle cerebral artery infarction. Eighty-five patients with middle cerebral artery infarction who underwent diffusion kurtosis imaging and arterial spin labeling were retrospectively included. ITD was diagnosed as ipsilateral thalamic hypoperfusion present on ≥2 cerebral blood flow maps. The thalamic asymmetrical index was calculated as (ipsilateral value-contralateral value)/contralateral value×100%. Finally, the inter-relationships of thalamic perfusion and diffusion were analyzed. ITD was present in 56/85 patients (65.9%, ITD+). In ITD+ patients, larger abnormal perfusion volume, higher perfusion-infarct mismatch and lower rates of focal hyperperfusion were observed than ITD- patients. Infarction affecting the corona radiata were more frequent among ITD+ patients. Mean kurtosis were slightly but significantly increased within the ipsilateral thalamus compared with the contralateral one in ITD+ patients of subacute and chronic groups, while fractional anisotropy was significantly increased in subacute group but decreased in chronic group for both ITD+ and ITD- patients. Mean diffusivity was significantly increased in ITD+ patients of chronic group. Furthermore, the AICBF was negatively and significantly correlated with AIMK and AIFA in ITD+ patients in subacute group, and AIMD, even after adjustment for abnormal perfusion volume and days from symptoms onset, in chronic group. ITD+ patients had significantly higher National Institutes of Health Stroke Scale and modified Rankin Scale scores at admission and discharge and also showed a trend to independent association with clinical outcome at discharge. The combination of arterial spin labeling and diffusion kurtosis imaging can reveal early, time-specific thalamic perfusion and diffusion changes after middle cerebral artery infarction. ITD-related hypoperfusion was significantly correlated with underlying microstructural alterations.

A Maintenance Model Applying Loss Function Based on the Cpm+ in the Process Mean Shift Problem in Which the Production Volume Decreases

Machines and facilities are physically or chemically degenerated by continuous usage. The representative type of the degeneration is the wearing of tools, which results in the process mean shift. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore, a preventive maintenance is necessary at some point . The problem of determining the maintenance period (or wear limit) which minimizes the total cost is called the ‘process mean shift problem’. The total cost includes three items: maintenance cost (or adjustment cost), non-conforming cost due to the non-conforming products, and quality loss cost due to the difference between the process target value and the product characteristic value among the conforming products. In this study, we set the production volume as a decreasing function rather than a constant. Also we treat the process variance as a function to the increasing wear rather than a constant. To the quality loss function, we adopted the Cpm+, which is the left and right asymmetric process capability index based on the process target value. These can more reflect the production site. In this study, we presented a more extensive maintenance model compared to previous studies, by integrating the items mentioned above. The objective equation of this model is the total cost per unit wear. The determining variables are the wear limit and the initial process setting position that minimize the objective equation.

Analysis of light coupling in AlxGa1-xAs waveguide arrays.

Light propagation in arrays of AlxGa1-xAs waveguides is studied. The power coupling constant between two adjacent waveguides is precisely measured as waveguide material and structure is varied. Aluminum concentration contrast between waveguide core/cladding layers and waveguide width/height produce an asymmetric effective refractive index between linearly polarized modes, which in turn causes a polarization dependence of the coupling constants. Experimental measurement results agree well with an analytical model. The sensitivity of coupling constant to the waveguide parameters is analyzed. Through a careful geometric design, comparable coupling constants can be achieved in three waveguide arrays with different structure. Similar formation processes of discrete spatial optical solitons are observed respectively, confirming that the parameterization in the discrete nonlinear Schrödinger equation characterizes waveguide arrays.

A deep learning framework for 18F-FDG PET imaging diagnosis in pediatric patients with temporal lobe epilepsy

PurposeEpilepsy is one of the most disabling neurological disorders, which affects all age groups and often results in severe consequences. Since misdiagnoses are common, many pediatric patients fail to receive the correct treatment. Recently, 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) imaging has been used for the evaluation of pediatric epilepsy. However, the epileptic focus is very difficult to be identified by visual assessment since it may present either hypo- or hyper-metabolic abnormality with unclear boundary. This study aimed to develop a novel symmetricity-driven deep learning framework of PET imaging for the identification of epileptic foci in pediatric patients with temporal lobe epilepsy (TLE).MethodsWe retrospectively included 201 pediatric patients with TLE and 24 age-matched controls who underwent 18F-FDG PET-CT studies. 18F-FDG PET images were quantitatively investigated using 386 symmetricity features, and a pair-of-cube (PoC)-based Siamese convolutional neural network (CNN) was proposed for precise localization of epileptic focus, and then metabolic abnormality level of the predicted focus was calculated automatically by asymmetric index (AI). Performances of the proposed framework were compared with visual assessment, statistical parametric mapping (SPM) software, and Jensen-Shannon divergence-based logistic regression (JS-LR) analysis.ResultsThe proposed deep learning framework could detect the epileptic foci accurately with the dice coefficient of 0.51, which was significantly higher than that of SPM (0.24, P < 0.01) and significantly (or marginally) higher than that of visual assessment (0.31–0.44, P = 0.005–0.27). The area under the curve (AUC) of the PoC classification was higher than that of the JS-LR (0.93 vs. 0.72). The metabolic level detection accuracy of the proposed method was significantly higher than that of visual assessment blinded or unblinded to clinical information (90% vs. 56% or 68%, P < 0.01).ConclusionThe proposed deep learning framework for 18F-FDG PET imaging could identify epileptic foci accurately and efficiently, which might be applied as a computer-assisted approach for the future diagnosis of epilepsy patients.Trial registrationNCT04169581. Registered November 13, 2019Public site: https://clinicaltrials.gov/ct2/show/NCT04169581

An Efficient Organization Method for Large-Scale and Long Time-Series Remote Sensing Data in a Cloud Computing Environment

Historical earth observation (EO) data have played an important role in long-term scientific and environmental monitoring. The effective organization of large-scale and long-term remote-sensing data to achieve efficient retrieval and access has become one of the important issues. However, inherent big data characteristics, such as a large scale, and asymmetrical temporal and spatial distributions, have caused problems with the efficiency of data retrieval and access. Therefore, this study proposes an efficient data organization method for use in a cloud-computing environment that has two aims. First, it addresses the problem of low retrieval efficiency. An asymmetrical index model for the image metadata is constructed that is based on a unified spatio-temporal grid coding; a prepartitioning mechanism under the HBase architecture is established to realize the uniform storage of the metadata with an asymmetrical spatiotemporal distribution and to avoid retrieval efficiency bottlenecks caused by a load imbalance. Second, it addresses low access efficiency. By dividing the remote-sensing image into tiles, a unified spatio-temporal code is established for each tile, and a consistent hash operation is performed; tiles with similar hash values are stored in the same or adjacent Hadoop Distributed File System nodes. In this way, tiles with temporal or spatial correlations can be gathered and stored, and lots of disk seeks can be avoided during retrieval, thereby greatly improving the data access efficiency. Comparative experiments showed that the data organization method can effectively improve the retrieval and access efficiencies of large-scale and long time-series remote-sensing data in a cloud-computing environment.

Determination of Karyological Properties of Different Buckwheat (Fagopyrum esculentum Moench) Varieties

In this study, the karyological characteristics of two different varieties (Aktaş and Güneş) of buckwheat (Fagopyrum esculentum) were determined. The study was carried out in Kahramanmaraş Sutcu Imam University, Faculty of Agriculture, Department of Field Crops in 2021. The chromosome number of both varieties was determined as 2n=2x=16 and haploid karyotype formulas as 6 m + 2 sm. Chromosome length ranges from 3.35 µm to 4.78 µm in the Aktaş variety examined, while it varied between 2.89 µm and 3.33 µm in the Güneş variety. While the arm ratio varied between 1.30 and 1.75 in Aktaş variety, it was observed that it varied between 1.22 and 1.86 in Güneş variety. Chromosome length, arm lengths and ratio, relative length, centromere index, centromere state and asymmetric index values of these two varieties were determined. Also, pictures of the metaphase chromosomes of the varieties were taken, measurements were made and idiograms were drawn. Since both types of Fagopyrum esculentum used are bred, they are similar in terms of karyology.

Karyotypic diversity among eight Zea mays L. varieties

Staining property of interphase nuclei and prophase chromosomes, diploid chromosome number, total chromosome length (TCL), symmetric and asymmetric indices of karyotype were studied in eight maize varieties released by BARI. 2n = 20 chromosomes were found in Barnali, Mohor, Khoi Vhutta, BS-1, B-5 and BM-7 whereas 2n = 22 chromosomes in China and 2n = 24 chromosomes in B-73 were observed. TCL was highest in Mohor (190.49 ± 5.61 μm) and lowest in B-73 (69.30 ± 2.51 μm). These varieties showed significant variation in cytogenetical parameters. Results obtained are expected to supplement genetic identification of maize varieties in variety conservation efforts.

In-Fiber Hybrid Cladding Waveguide by Femtosecond Inscription for Two-Dimensional Vector Bend Sensing

A 2D vector bending fiber sensor is demonstrated based on a femtosecond (fs) laser inscribed hybrid cladding waveguide (CWG) structure, which is mainly composed of two eccentric cladding waveguides distributed oppositely in a single mode fiber (SMF). The structure can enable light in the central core to efficiently couple into different CWGs under respective resonant conditions, thereby providing two separate local dips in response to the two CWGs in the transmission spectrum. When the bending is applied, the two CWGs will suffer asymmetric effective refractive index (RI) variation, resulting in that the wavelength shift for each dip differs significantly. The curvature sensitivity can be enhanced by tracking the wavelength interval between the two dips, reaching up to -14.25 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and +14.80 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> at the 0° and 180° orientations ranging from 0 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> to 8 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , respectively. Featured with comparatively high sensitivity, relatively large curvature range, 2D orientation identification, compact size, and reduced temperature crosstalk, the proposed structure offers the opportunity to be applied from public infrastructure health monitoring to wearable artificial devices.

Non-diffraction surface wave with controllable deflection angle by using metasurfaces

A planar metasurface Bessel lens has been proposed for non-diffraction surface wave deflection, which is composed of a planar flat lens and an asymmetric gradient refractive index lens. According to the desired refractive index distribution of the two lenses, a metasurface, consisting of sub-wavelength metallic square rings of different sizes, is constructed to realize the planar Bessel lens. Through the planar Bessel lens, the cylindrical-like surface wave radiated from a point source is converted to an inclined non-diffraction surface wave. The planar Bessel lens is fabricated, and the measurement results show good agreement with the full-wave simulation results, which would verify the correctness of the proposed theory.

Delayed Motor Development and Infant Obesity as Risk Factors for Severe Deformational Plagiocephaly: A Matched Case–Control Study

The prevalence of deformational plagiocephaly (DP) has increased since the recommendation of positioning infants to their back during sleeping and is affected by various biological and environmental factors. This study aimed to investigate associations between DP and perinatal or infant characteristics, including obesity. This case–control study included 135 infants (81 males) aged 2–12 months who were diagnosed with DP using calculated cranial vault asymmetric index and cranial index and 135 age- and sex-matched controls. Motor development was evaluated using the Alberta Infant Motor Scale, and obesity was defined by body mass index. Univariate and multivariate logistic regression models were used to assess potential risk factors for DP and its severity. One hundred thirty-five infants with DP were divided into the following three subgroups according to severity indicated by the cranial vault asymmetry index: mild to moderate group (n = 87, 64.4%), severe group (n = 48, 35.6%), and a combined plagiocephaly and brachycephaly group (n = 79, 58.5%). Independent risk factors significantly associated with development of DP were bottle-only feeding (adjusted odds ratio (aOR) = 4.65; 95% CI: 2.70–8.00), little tummy time when awake (aOR = 3.51, 95% CI: 1.71–7.21), delay of motor development (aOR = 2.85, 95% CI: 1.08–7.49), and obesity at diagnosis (aOR = 2.45, 95% CI: 1.02–5.90). Among these risk factors, delay of motor development (aOR = 4.91, 95% CI: 1.46–16.51) and obesity at diagnosis (aOR = 4.10, 95% CI: 1.42–11.90) were particularly related to severe DP. In conclusion, this study confirms that DP risk is positively associated with bottle-only feeding, infrequent tummy time, and delayed development of motor milestones. Notably, this study demonstrates infant obesity as a new risk factor for DP. Our findings suggest that obesity should be identified early and managed comprehensively in infants with DP.

Flow physics of normal and abnormal bioprosthetic aortic valves

Flow physics of transvalvular flows in the aorta with bioprosthetic valves are investigated using computational modelling. For the efficient simulations of flow-structure-interaction in transvalvular flows, a simplified, reduced degree of freedom valve model is employed with a sharp interface immersed boundary based incompressible flow solver. Simulations are performed for normal as well as abnormal valves with reduced leaflet motion that models the effect of early leaflet thrombosis. The structure of the aortic jet and the hemodynamic stresses on the aortic wall are analysed to understand the hemodynamic impacts and possible long-term clinical implications of sub-clinical, reduced leaflet motion. The simulation results have shown that the reduced leaflet motion tilts the direction of aortic jet and generates stronger flow separation and re-attachment on the aortic wall downstream from the reduced motion leaflets. The modified flow pattern increases the wall pressure fluctuation and average wall shear stress on the downstream aortic wall, and results in the asymmetric oscillatory shear index distributions, which may have long-term clinical implications such as aortic wall damage and remodelling.

Coherent multi-mode dynamics in a quantum cascade laser: amplitude- and frequency-modulated optical frequency combs.

We cast a theoretical model based on effective semiconductor Maxwell-Bloch equations and study the dynamics of a multi-mode mid-infrared quantum cascade laser in a Fabry-Perot configuration with the aim to investigate the spontaneous generation of optical frequency combs. This model encompasses the key features of a semiconductor active medium, such as asymmetric, frequency-dependent gain and refractive index as well as the phase-amplitude coupling of the field dynamics provided by the linewidth enhancement factor, and some specific resonator features, such as spatial hole burning. Our numerical simulations are in excellent agreement with recent experimental results, showing broad ranges of comb formation in locked regimes, separated by chaotic dynamics when the field modes unlock. In the former case, we identify self-confined structures travelling along the cavity, while the instantaneous frequency is characterized by a linear chirp behaviour. In such regimes, we show that OFCs are characterized by concomitant and relevant amplitude and frequency modulation.

Change of direction asymmetry across different age categories in youth soccer.

BackgroundIn youth, the development of change of direction (COD) and sprint performance is a key component for successfully competing in soccer across age. During a COD, the presence of directional asymmetries may be detrimental due to the unpredictable nature of the sport. Therefore, the aims of the study were to investigate asymmetries in COD ability and to examine the differences in COD and sprint performance across age in young soccer players.MethodsSixty-eight sub-elite soccer players of different age categories (U18, U17, U16, U15) were tested on a 10-m linear sprint test and 90°COD (5-m entry and exit) test in both directions. Asymmetric index (AI) of COD deficit was obtained for dominant (fastest) and non-dominant directions (slowest).ResultsThe results showed that U16 were more asymmetrical than U18, U17, and U15 from large to moderate effects. The sprint time improved linearly across age with U18 and U15 displaying the fastest and slowest 10-m sprint performance (p < 0.01), respectively. Moreover, COD ability measured by COD deficit did not change across age (p > 0.05).ConclusionGiven the results of this study, practitioners are encouraged to assess asymmetries between dominant and non-dominant directions rather than solely players’ COD ability in young soccer players.

Asymmetric-waveguide, short cavity designs with a bulk active layer for high pulsed power eye-safe spectral range laser diodes

It is shown, by calculations calibrated against the authors’ recent experimental data, that an eye-safe wavelength range InGaAsP/InP high pulsed power laser design using a bulk active layer, which has a large refractive index step with respect to the optical confinement layer and is located close to the p-cladding, can provide substantial performance improvement compared to the best results achieved so far for this operating regime and wavelength. The dependence of the laser performance on the design parameters such as the thicknesses of the active layer and the waveguide, as well as the cavity length, are analysed. It is shown that the relatively thick bulk active layer in such InGaAsP/InP lasers allows the use of short cavity lengths (∼1 mm or even shorter), for achieving high pulsed power while maintaining a low p-cladding series resistance (making for high efficiency) and a narrow far field (making for high brightness). A single-asymmetry structure with the asymmetric active layer location but symmetric optical confinement layer/cladding refractive index steps gives performance only marginally inferior to that of a double-asymmetric one including asymmetric refractive index steps.

Agreement Between Dribble and Change of Direction Deficits to Assess Directional Asymmetry in Young Elite Football Players

This study aimed to examine the agreement between asymmetries of dribble and change of direction (COD) deficits and to determine their potential difference to each other. Sixteen young elite football players were recruited and tested for sprint (over 10 m), dribbling (90°CODdribbling) and COD (90°CODrunning) performance in dominant (fastest) and non-dominant (slowest) directions. Dribble and COD deficits were computed to express dribbling and COD ability without the influence of acceleration. The asymmetric index (AI%) of both dribble and COD deficits were obtained for both directions. The level of agreement between dribble and COD deficits was assessed by Cohen’s kappa statistic (κ). Results showed that AI% measured by dribble and COD deficits presented a poor level of agreement (κ = −0.159), indicating their imbalance did not favor the same direction. Moreover, AI% of the dribble deficit was significantly higher than those of the COD deficit. This study demonstrated that asymmetries in dribbling and change of direction performance (measured by dribble and COD deficit) were not in agreement to favor the same direction, also displaying a significant difference to each other. Practitioners should consider the task-specificity of asymmetry to reduce the imbalance in dribbling and COD performance.

Asymmetric spread of heart rate variability

ObjectiveThe variability related to acceleration and deceleration of heart rate contributes unevenly to the overall heart rate variability (HRV). Thus, the spread of heart rate is asymmetric. Despite developing several heart rate asymmetry (HRA) measures, none examines this disparity in HRV. Therefore, a new HRA measure, asymmetric spread index (ASI), is proposed to measure asymmetry in the variability of heart rate associated with acceleration and deceleration. HRA generally arises due to cardiac autonomic modulation. However, the exact underlying phenomenon is unknown. Therefore, the study of HRA is performed in cardiac pathologies, synthetic HRV signals, and meditation. MethodsLike other HRA measures, ASI is defined by using the Poincaré plot. The surrogate data analysis was performed to examine that ASI represents a physiological phenomenon and not an artifact of the method. Statistical analysis and receiver operating characteristic analysis were performed for evaluating the performance of HRA indices. ResultsHRA is found increased in patients with heart failure and arrhythmia. Synthetic HRV signals show less asymmetry than real HRV signals. The HRA increases during meditation. Experimental results indicate that variability shifts from the acceleration part to the deceleration part during meditation, and vice versa. ConclusionThe ASI quantifies the uneven spread of heart rate that would remain unexplored with existing asymmetric measures. It shows better discriminating power than existing HRA. SignificanceSince HRA is a new area, further studies are required to establish its clinical significance. The ASI may help in understanding the underlying mechanism of HRA.