Utility of the decubitus or the supine rather than the extension lateral radiograph in evaluating lumbar segmental instability.

OBJECTIVE: To determine the superiority of decubitus and supine radiographs for the reduction of olisthesis instead of the extension radiograph, and the inconsistency of the CT scout view, 3D-reconstruction and MR image in evaluating segmental instability. METHODS: A cohort of 154 low-grade lumbar degenerative spondylolisthesis patients with the average age of (60.9 ± 8.6) years were enrolled. Slip percentage was measured on the flexion, upright and extension radiographs, the decubitus lateral radiograph, CT scout view, the supine median sagittal 3D-reconstruction and MR image. The translational range of motion was calculated, and segmental instability was defined as translational motion ≥ 8%. RESULTS: The flexion radiograph showed higher slip percentage than upright radiograph (p < 0.001). The slip percentage of the MR image was lower than CT scout view (p = 0.003) and CT sagittal radiograph (p = 0.001) on the basis of statistical differences among three groups (p = 0.002). The slip percentage of the CT scout view, decubitus radiograph, and extension radiograph was statistically different (p = 0.01). The CT scout view and sagittal reconstruction had lower slip percentage than the extension radiograph (p = 0.042; p = 0.003, respectively). Both the flexion-supine and flexion-decubitus modality had larger translational motion than the flexion-extension modality (p = 0.007; p < 0.001, respectively). CONCLUSION: Many modalities and techniques are used to show the vertebral displacement and its possible change and any cane used in the daily practice. In this study, supine and decubitus lateral radiography have larger reduction of olisthesis than the extension radiograph. The flexion radiograph coupled with a supine or decubitus radiograph reveals greater mobility than the flexion-extension modality.

Recent Progress in Sensing Technology Based on Triboelectric Nanogenerators in Dynamic Behaviors.

Under the trend of the rapid development of the internet of things (IoT), sensing for dynamic behaviors is widely needed in many fields such as traffic management, industrial production, medical treatment, building health monitoring, etc. Due to the feature of power supply independence and excellent working performance under a low-frequency environment, triboelectric nanogenerators (TENGs) as sensors are attracting more and more attention. In this paper, a comprehensive review focusing on the recent advance of TENGs as sensors for dynamic behaviors is conducted. The structure and material are two major factors affecting the performance of sensors. Different structure designs are proposed to make the sensor suitable for different sensing occasions and improve the working performance of the sensors. As for materials, new materials with stronger abilities to gain or lose electrons are fabricated to obtain higher surface charge density. Improving the surface roughness of material by surface engineering techniques is another strategy to improve the output performance of TENG. Based on the advancement of TENG structures and materials, plenty of applications of TENG-based sensors have been developed such as city traffic management, human-computer interaction, health monitoring of infrastructure, etc. It is believed that TENG-based sensors will be gradually commercialized and become the mainstream sensors for dynamic sensing.

Parameter Estimation of Micro-Motion Targets for High-Resolution-Range Radar Using Online Measured Reference.

Micro-motion dynamics produce Micro-range (m-R) signatures which are important features for target classification and recognition, provided that the range resolution of radar signal is high enough. However, dechirping the echo with reference measured by narrow bandwidth radar would generate the residual translational motion, which exhibits as random shifts of envelopes of range profiles. The residual translational motion would destroy the periodicity of m-R signatures and make a challenge to estimate rotational parameter. In this work, we proposed an efficient high-resolution range profile (HRRP)-based method to estimate rotational parameter, in which online measured reference distances are used to dechirp the radar raw echo. Firstly, the deduction for the modified first conditional comment of range profiles (MFCMRP) is introduced in detail, and the MFCMRP contain periodic and random components when dechirped by measured reference, corresponding to the rotational motion and the reference measured errors compared with actual reference. Secondly, the Wavelet Transform (WT) is utilized to separate the measured errors from the MFCMRP. The estimations of measured errors are used to compensate the MFCMRP, and then autocorrelation is performed on the estimated periodic component to obtain the estimation of rotational period. Lastly, the rotational amplitudes and phases are achieved by inverse Radon transform (IRT) of the compensated HRRP. The effectiveness of the proposed method in this paper is verified by synthetic data and measured radar data.

Action Video Games Improve Direction Discrimination of Parafoveal Translational Global Motion but Not Reaction Times.

Playing action video games enhances visual motion perception. However, there is psychophysical evidence that action video games do not improve motion sensitivity for translational global moving patterns presented in fovea. This study investigates global motion perception in action video game players and compares their performance to that of non-action video game players and non-video game players. Stimuli were random dot kinematograms presented in the parafovea. Observers discriminated the motion direction of a target random dot kinematogram presented in one of the four visual quadrants. Action video game players showed lower motion coherence thresholds than the other groups. However, when the task was performed at threshold, we did not find differences between groups in terms of distributions of reaction times. These results suggest that action video games improve visual motion sensitivity in the near periphery of the visual field, rather than speed response.

Translation of interacting cavitation bubble in a plane acoustic field.

In a plane acoustic field, a model involving the radial and translational motions of bubble is derived, which is used to numerically investigate the translation of two interacting spherical cavitation bubbles. For the smaller initial distance between bubble centers, we investigate the dynamics of two bubbles, and find that they could come into contact but the velocities of closing to each other are different when the equilibrium radius is different. The results show that when the wavelength of plane acoustic field is much larger than the initial distance, the bubbles are approximately pulsating in phase. Moreover, the velocity of contact process of two bubbles can be changed by adjusting the parameters of plane acoustic field. For increasing in the initial distance, the bubbles would present two translation motions: close to each other for the pulsating in phase and away from each other for the pulsating out of phase, which could be verified by calculating the secondary Bjerknes force. Meanwhile, the larger the initial distance, the smaller the secondary Bjerknes force value is. Understanding the translation of bubble is of great significance for helpful explaining formation of streamer structures in ultrasonic cavitation.

Radial and translational motions of a gas bubble in a Gaussian standing wave field.

Acoustic waves with a finite beam width are widely used in acoustic manipulation and cavitation applications. In view of this, radial oscillation and translational motion of a gas bubble in a Gaussian standing wave field are studied in this work. Dynamic differential equations for the bubble are derived with the axial and transverse motions coupled with each other. A comprehensive numerical study is also carried out in the parameter space of the driving frequency, pressure amplitude, initial coordinate, off-axial distance and beam waist. The results demonstrate that the nonlinear radial oscillation can be intensified by a higher pressure amplitude and a smaller off-axial distance. Whether the driving frequency is much lower than the resonance frequency determines not only the final equilibrium position but also the direction of translational motion for the gas bubble. With the widening of the Gaussian standing wave, the radial oscillation will be weakened and the translational motion will be slowed down due to reduction of the pressure gradient regardless of the driving frequency. The results obtained in this study is of interest for an understanding of the bubble dynamics in non-plane acoustic wave fields.

Transition mechanisms of translational motions of bubbles in an ultrasonic field.

The translation behaviors of oscillating bubbles are closely related to the polymerizations and dispersions between them, which are crucial for the ultrasonic cavitation effect. In this study, six types of translational motion of bubbles with a wide range of sizes (2-100 µm) in the R01-R02 plane are investigated. Our results demonstrate that in addition (to the 2nd order harmonic), the 1/2 order subharmonic can change the bubble pairs from the three states of the attraction, stable after attraction, and repulsion to that of the repulsion, coalescence, and attraction, respectively. Furthermore, within the range of the main resonance radius and the 1/2 order subharmonic resonance radius, the chaotic bubble pairs with alternating attractive and repulsive forces appear in the region between the coalescence pairs and stable pairs after attraction. Finally, the corresponding physical mechanisms of the chaotic translational motions are also revealed.

Effects of translational motion on the Bjerknes forces of bubbles activated by strong acoustic waves.

The motion of a small cavitation bubble is influenced by a neighboring large bubble, and these two bubbles can be mutually attractive or repulsive. The state of the bubble pair is strongly related to the secondary Bjerknes force in a strong acoustic field. Non-spherical oscillations are easily observed when a small cavitation bubble approaches a large bubble. The effects of translational motion and non-spherical oscillations of the small cavitation bubble on the secondary Bjerknes force are considered numerically in this paper, at large (greater than20 µm) and small (3 µm) bubble pair sizes. We show that the radial oscillation of the cavitation bubble is suppressed by the large bubble when the two are close to each other, and the magnitude and direction of the secondary Bjerknes force on the cavitation bubble are significantly different to those predicted results without considering translational motion. With the increase in size of the large bubble, the value of the secondary Bjerknes force varies from negative to positive, implying a transition between attraction and repulsion. The secondary Bjerknes force is sensitive to changes in the size of the large bubble, as there are many spikes in the curve in the range 20 µm < R10 < 100 µm. Moreover, the cavitation bubble is slightly repulsed when the large bubble is larger than 100 µm. There is a critical distance that can lead to a transition between mutual attraction and repulsion of bubbles. Cavitation bubbles can be driven toward the larger bubble by increasing acoustic pressure. The findings presented here will be helpful in understanding the complex behavior of cavitation bubbles in practical applications in which large bubbles exist and may interact with cavitation.

Radial oscillation and translational motion of a gas bubble in a micro-cavity.

According to classical nucleation theory, a gas nucleus can grow into a cavitation bubble when the ambient pressure is negative. Here, the growth process of a gas nucleus in a micro-cavity was simplified to two "events", and the full confinement effect of the surrounding medium of the cavity was considered by including the bulk modulus in the equation of state. The Rayleigh-Plesset-like equation of the cavitation bubble in the cavity was derived to model the radial oscillation and translational motion of the cavitation bubble in the local acoustic field. The numerical results show that the nucleation time of the cavitation bubble is sensitive to the initial position of the gas nucleus. The cavity size affects the duration of the radial oscillation of the cavitation bubble, where the duration is shorter for smaller cavities. The equilibrium radius of a cavitation bubble grown from a gas nucleus increases with increasing size of the cavity. There are two possible types of translational motion: reciprocal motion around the center of the cavity and motion toward the cavity wall. The growth process of gas nuclei into cavitation bubbles is also dependent on the compressibility of the surrounding medium and the magnitude of the negative pressure. Therefore, gas nuclei in a liquid cavity can be excited by acoustic waves to form cavitation bubbles, and the translational motion of the cavitation bubbles can be easily observed owing to the confining influence of the medium outside the cavity.

Contrast sensitivity and motion discrimination in cannabis users.

RATIONALE: Cannabis use impairs visual attention; however, it is unclear whether cannabis use also impairs low level visual processing or whether low level visual deficits can be related to lower dopaminergic functioning found in cannabis users. OBJECTIVES: To investigate whether spatiotemporal contrast sensitivity and motion discrimination under normal and low luminance conditions differ in cannabis users and non-users. METHODS: Control (n = 20) and cannabis (n = 21) participants completed a visual acuity test, a saliva test and self-report measures. Spatial and temporal contrast thresholds, motion coherence thresholds for translational and radial motion and the spontaneous eye blink rate were then collected. RESULTS: Cannabis users showed decreased spatial contrast sensitivity under low luminance conditions and increased motion coherence thresholds under all luminance levels tested compared to non-users. No differences in temporal contrast sensitivity were found between the groups. Frequency of cannabis use correlated significantly and negatively with contrast sensitivity, both spatial and temporal, in the cannabis group and higher motion coherence thresholds for radial motion were also associated with more frequent cannabis use in this group. The eye blink rate was significantly lower in cannabis users compared to non-users. CONCLUSIONS: The present study shows that cannabis use is associated with deficits in low level visual processing. Such deficits are suggested to relate to lower dopamine, in a similar manner as in clinical populations. The implications for driving safety under reduced visibility (e.g. night) in abstaining cannabis users are discussed.

Analysis of the relationship between the facet fluid sign and lumbar spine motion of degenerative spondylolytic segment using Kinematic MRI.

PURPOSE: To investigate the relationship between the facet fluid sign (FFS) and kinematics of affected lumbar segment in patients with low-grade, single-level lumbar degenerative spondylolisthesis using kinematic magnetic resonance imaging (kMRI).Materials and methods Ninety-two patients diagnosed with low-grade (Grade 1 or 2), single level lumbar degenerative spondylolisthesis L3 to S1. Angular and translational motion, whole lumbar motion, slip percentage, and facet angle were measured. Disc degeneration and degrees of osteoarthritis were graded, facet effusion was evaluated and classified as Positive or Negative FFS (PosFFS or NegFFS).Results There were significant differences in the facet degeneration, translational motion, percentage of total angular motion, and flexion-extension slip difference between the PosFFS and NegFFS group. 28.3% of the patients in PosFFS group had anterolisthesis in flexion, but not extension.There was a significant difference in the incidence of FFS between the dynamic and static spondylolisthesis (75% vs 35%, p < 0.001). If FFS was present on kMRI, a positive predictive value for dynamic spondylolisthesis was 75.6%. with the sensitivity and specificity of 0.75 and 0.65 for posFFS to diagnose dynamic DS. The likelihood ratio for dynamic slips in the presence of FFS was 2.1, and the likelihood ratio for static slips in the presence of FFS was 1.1.Conclusion Facet fluid sign was present in weight-bearing neutral position, and the presence of FFS in kMRI increased the probability of having dynamic spondylolisthesis.

Kinematic analysis of diseased and adjacent segments in degenerative lumbar spondylolisthesis.

BACKGROUND CONTEXT: Degenerative spondylolisthesis is a common pathologic condition that leads to lumbar instability and significant clinical symptoms. The effect of this pathology on adjacent lumbar motion segments, however, has not yet been studied. PURPOSE: To characterize the motion characteristics of lumbar degenerative spondylolisthesis at both the diseased and adjacent levels in patients with low-grade, single-level lumbar degenerative spondylolisthesis using kinetic magnetic resonance imaging (kMRI). STUDY DESIGN: Retrospective study of patient kMRIs. PATIENT SAMPLE: One-hundred twelve patient MRIs with low-grade, single-level lumbar spondylolisthesis were included. OUTCOME MEASURES: Angular and translational motion. METHODS: This study compared 112 patients diagnosed with low-grade (Grade 1 or 2), single-level lumbar degenerative spondylolisthesis at L3-L4, L4-L5, or L5-S1 with 296 control patients without spondylolisthesis. Angular and translational motion were measured using patient kMRIs. The level of slip was graded according to the Meyerding classification system, and disc degeneration was classified according to the Pfirrmann system. Instability was defined as translational motion greater than 4 mm. RESULTS: Lumbar hypomobility was often present regardless of the level of degenerative spondylolisthesis. A slip at L3-L4 resulted in the largest decrease in lumbar range of motion. Instability at the diseased level was most common at L3-L4 (36%), followed by L5-S1 (31%) and L4-L5 (30%). Instability at the adjacent segments was most frequent at L4-L5 (49%), followed by L5-S1 (34%) and L3-L4 (23%). Patients with stable spondylolisthesis generally had decreased angular motion at all lumbar levels. Translational motion at the diseased level was consistently increased. Disc degeneration was significantly greater at the level of slip for the L3-L4 and L4-L5 spondylolisthesis groups and equal to the control group in the L5-S1 group. There was no significant difference in disc degeneration at adjacent segments in L3-L4 and L4-L5 degenerative spondylolisthesis patients, but there was a significant decrease with an L5-S1 slip. CONCLUSIONS: There were a similar percentage of patients in each degenerative spondylolisthesis group with lumbar instability. Angular motion decreased at the diseased level with L3-L4 and L5-S1 spondylolisthesis, but increased with L4-L5 spondylolisthesis. Translational motion, however, increased at the diseased level in all three groups. There was compensatory hypermobility at adjacent levels in patients with unstable spondylolisthesis at L3-L4 and L4-L5, but not at L5-S1.

Liquid-phase characterization of molecular interactions in polyunsaturated and n-fatty acid methyl esters by (1)H low-field nuclear magnetic resonance.

BACKGROUND: To identify and develop the best renewable and low carbon footprint biodiesel substitutes for petroleum diesel, the properties of different biodiesel candidates should be studied and characterized with respect to molecular structures versus biodiesel liquid property relationships. In our previous paper, (1)H low-field nuclear magnetic resonance (LF-NMR) relaxometry was investigated as a tool for studying the liquid-phase molecular packing interactions and morphology of fatty acid methyl esters (FAMEs). The technological potential was demonstrated with oleic acid and methyl oleate standards having similar alkyl chains but different head groups. In the present work, molecular organization versus segmental and translational movements of FAMEs in their pure liquid phase, with different alkyl chain lengths (10-20 carbons) and degrees of unsaturation (0-3 double bonds), were studied with (1)H LF-NMR relaxometry and X-ray, (1)H LF-NMR diffusiometry, and (13)C high-field NMR. RESULTS: Based on density values and X-ray measurements, it was proposed that FAMEs possess a liquid crystal-like order above their melting point, consisting of random liquid crystal aggregates with void spaces between them, whose morphological properties depend on chain length and degree of unsaturation. FAMEs were also found to exhibit different degrees of rotational and translational motions, which were rationalized by chain organization within the clusters, and the degree and type of molecular interactions and temperature effects. At equivalent fixed temperature differences from melting point, saturated FAME molecules were found to have similar translational motion regardless of chain length, expressed by viscosity, self-diffusion coefficients, and spin-spin (T 2) (1)H LF-NMR. T 2 distributions suggest increased alkyl chain rigidity, and reduced temperature response of the peaks' relative contribution with increasing unsaturation is a direct result of the alkyl chain's morphological packing and molecular interactions. CONCLUSIONS: Both the peaks' assignments for T 2 distributions of FAMEs and the model for their liquid crystal-like morphology in the liquid phase were confirmed. The study of morphological structures within liquids and their response to temperature changes by (1)H LF-NMR has a high value in the field of biodiesel and other research and applied disciplines in numerous physicochemical- and organizational-based properties, processes, and mechanisms of alkyl chains, molecular interactions, and morphologies.

An asymmetry of translational biological motion perception in schizophrenia.

BACKGROUND: Biological motion perception is served by a network of regions in the occipital, posterior temporal, and parietal lobe, overlapping areas of reduced cortical volume in schizophrenia. The atrophy in these regions is assumed to account for deficits in biological motion perception described in schizophrenia but it is unknown whether the asymmetry of atrophy found in previous studies has a perceptual correlate. Here we look for possible differences in sensitivity to leftward and rightward translation of point-light biological motion in data collected for a previous study and explore its underlying neurobiology using functional imaging. METHODS: n = 64 patients with schizophrenia and n = 64 controls performed a task requiring the detection of leftward or rightward biological motion using a standard psychophysical staircase procedure. six control subjects took part in the functional imaging experiment. RESULTS: We found a deficit of leftward but not rightward biological motion (leftward biological motion % accuracy patients = 57.9% ± 14.3; controls = 63.6% ± 11.3 p = 0.01; rightward biological motion patients = 62.7% ± 12.4; controls = 64.1% ± 11.7; p > 0.05). The deficit reflected differences in distribution of leftward and rightward accuracy bias in the two populations. Directional bias correlated with functional outcome as measured by the Role Functioning Scale in the patient group when co-varying for negative symptoms (r = -0.272, p = 0.016). Cortical regions with preferential activation for leftward or rightward translation were identified in both hemispheres suggesting the psychophysical findings could not be accounted for by selective atrophy or functional change in one hemisphere alone. CONCLUSION: The findings point to translational direction as a novel functional probe to help understand the underlying neural mechanisms of wider cognitive dysfunction in schizophrenia.