Height Of Center Research Articles

Kinematic Factors Associated with Hitting Hurdles During the Initial Phase of a 110-m Hurdle Race.

This study aimed to clarify the kinematic factors for the cause and effect of hitting hurdles during the initial phase of a 110-m hurdle run. Nine experienced male hurdlers participated in this study (body height: 1.74 ± 0.04 m, body mass: 67.4 ± 5.9 kg, age: 20.2 ± 1.4 years, personal best: 15.21 ± 0.47 s, seasonal best: 15.33 ± 0.55 s). Hurdlers undertook 12 trials of the initial phase of hurdling from the start to the second hurdle landing. Dual-sided sagittal plane motion was obtained from images from two high-speed cameras operating at 120 Hz. One ‘hit’ trial which had the largest horizontal displacement of markers fixed on the hurdle and one ‘non-hit’ trial which had the fastest time of hurdle clearance were extracted for each participant. Kinematic variables were compared between the two trials. Significantly lower height of the whole-body centre of mass at the take-off was found as a possible cause of hitting hurdles, caused by insufficient swing-up of the lead leg thigh. In contrast to conventional understanding, take-off velocity, take-off distance and the take-off angle were comparable between the ‘hit’ trial and ‘non-hit’ trial. Regarding the effect of hitting hurdles, it was observed that running velocity during hurdling was not substantially reduced. However, several characteristic movements were identified that might induce inefficient motion to re-accelerate running velocity during the following landing steps.

Validation of the Reproducibility of Warm-Season Northeast China Cold Vortices for ERA5 and MERRA-2 Reanalysis

Abstract Reanalysis datasets have been widely used in meteorological research, including studies of Northeast China cold vortices (NCCVs), where these datasets act as effective substitutes for observations. However, to date, no studies have focused on their performance in reproducing NCCVs. To address this knowledge gap, we adopted an automatic three-step identification algorithm (TIA) and used it to detect NCCVs from ERA5 and MERRA-2 reanalysis datasets spanning 39 warm seasons (May–September) during the period from 1980 to 2018. A comparative method was employed for a rough verification of the characteristics of the reproduced NCCVs. Moreover, a dataset derived from 1370 Chinese ground-based observational stations was used to verify the performance of the reanalysis models in reproducing the precipitation and air temperature associated with NCCVs. The results show that the TIA identified the majority of NCCVs, with an accuracy of approximately 90% from ERA5 or MERRA-2. Both reanalysis models can reproduce the characteristics of NCCVs (including location, strength, and duration), and both replicate air temperature better than precipitation. ERA5 and MERRA-2 showed strong consistency in reproducing the central longitude, central latitude, central height, and range of NCCVs, with correlation coefficients of 0.974, 0.972, 0.996, and 0.919, respectively, at the 99.9% significance level. The daily average 2-m temperatures in both reanalysis datasets were in good agreement with observations; however, overestimations of approximately 7°–8°C arose in steep high-altitude regions. In addition, both models tended to overestimate light rain (≤5 mm day−1) by approximately 1.2 mm and underestimate heavy rain (≥20 mm day−1) by over 6.7 mm.

Simulation of ionospheric heating in Iran coordinates with SAMI2 model ‎

In this paper the heating effects was investigated with SAMI2 model. An external Gaussian heating source was considered in electron temperature equation that models the radio frequency heating. The effects of the heating were investigated as a function of the heating period, intensity of the heating source, height of the heating center and different latitude of the heating in Iran coordinates. Results of the simulations show that height of the heating and intensity of the source have main role in the distribution function of the electron density and temperature. This distribution in heating zone and conjugate point was shown. In early time of heating, by increasing the height, the electron temperature was increased dramatically. At low intensity of the heating source, the electron temperature wasn’t increased. However, the electron temperature was increased in heating zone after 30 minutes. Also, the heating distributes the electron density counter which represents the reduction of the electron density and the formation of the duct in heating zone and the growth of the electron density at conjugate point. The results show that at low latitude, electron temperature at heating zone and conjugate point was increased more.

Spraying Ethephon Effectively Increased Canopy Light Transmittance of Densely Planted Summer Maize, Thus Achieving Synergistic Improvement in Stalk Lodging Resistance and Grain Yield.

Increasing planting density is an effective way to improve maize yield, but high plant populations often cause a lodging problem. This experiment was conducted to investigate the effect of increasing planting density on stalk lodging resistance and grain yield, and to explore the effects on stalk and yield properties of spraying ethephon in densely planted summer maize. The summer maize hybrid, Xundan20 (XD20), was used as experimental material. It was grown by spraying water (CK) or ethephon (E) at BBCH (BASF, Bayer, Ciba-Geigy and Hoechst) 17 under three different planting densities of 60,000 plants ha−1 (L), 75,000 plants ha−1 (M) and 90,000 plants ha−1 (H) in order to explore the possibility of synergistic improvement in stalk lodging resistance and grain yield. The results from this experiment suggested that the gravity center height of densely planted summer maize was significantly increased, the stem diameter, area and number of vascular bundles were significantly decreased and the dry weight per unit internode was significantly decreased, thereby weakening the stalk rind penetration strength and bending performance, resulting in a significant increase in lodging percentage. The ear height was significantly decreased and the SPAD (soil and plant analysis development) and canopy light transmittance were increased after spraying ethephon; then, the internode dry weight per unit length was increased and the stalk rind penetration strength and bending performance were enhanced so as to significantly reduce the lodging percentage and increase the grain yield. The correlation analysis further showed that lodging percentage was significantly negatively correlated with stem diameter, area and number of vascular bundles and stalk bending performance, but there were no strong relationships with grain yield. This suggested that the synergistic improvement in stalk lodging resistance and grain yield was not contradictory. Under the experiment conditions, the effect of spraying ethephon was most significant when the planting density was 90,000 plants ha−1. At the time, the lodging percentage and grain yield were 12.2% and 11,137.5 kg ha−1, which were decreased by 44.6% and increased by 8.0% compared with the control treatment. Scientific chemical regulation could significantly improve the stalk lodging resistance and grain yield of densely planted summer maize.

Analysis of the causes of residual back pain in the early and late stages after percutaneous vertebral augmentation

To explore the influencing factors of the residual back pain in patient with osteoporotic vertebral compression fractures(OVCFs) in the early and late stages after percutaneous vertebral augmentation(PVA), and analyze the correlation between these factors and the residual back pain after PVA. From March 2018 to December 2019, 312 patients with OVCFs who treated with PVA were collected. According to the inclusion and exclusion criteria, a total of 240 patients were included in this retrospective study. There were 59 males and 181 females, aged from 50 to 95 years old with an average of (76.11±10.72) years old, and 50 cases of fractures located in the thoracic region (T5-T10), 159 cases in the thoracolumbar region (T11-L2), and 31 cases in the lumbar region (L3 and below). The first day after PVA was regarded as the early postoperative period, and the seventh day was regarded as the late postoperative period. According to the visual analogue scale (VAS), the patients were divided into 4 groups:early postoperative pain relief group(group A, VAS≤4 scores), there were 121 patients, including 29 males and 92 females, aged from 50 to 90 years with an average of (75.71±11.00) years;early postoperative pain relief was not an obvious group (group B, VAS >4 scores), there were 119 patients, including 30 males and 89 females, aged from 53 to 95 years with an average of (76.51±10.46) years; late postoperative pain relief group (group C, VAS≤ 4 scores), there were 172 patients, including 42 males and 130 females, aged from 50 to 95 years with an average of (76.20±10.68) years; late postoperative pain relief was not obvious group (group D, VAS>4 scores), there were 68 patients, including 17 males and 51 females, aged from 53 to 94 years old with an average of (75.88±10.91) years old. The age, gender, bone mineral density(BMD), injured vertebral segment, preoperative thoracolumbar fascial condition, surgical methods, single or bilateral puncture, the amount of bone cement injection, anterior vertebral height recovery rate and central vertebral height recovery rate in the 4 groups were analyzed by univariate analysis. The statistically significant factors were put into a Logistic regression to analyze the correlation between these factors and residual back pain after PVA. Univariate analysis showed that the residual back pain in the early stage after PVA was correlated with BMD, preoperative thoracolumbar fascial injury, single or bilateral puncture, the amount of bone cement injection, anterior vertebral height recovery rate and central vertebral height recovery rate(P<0.05). The residual back pain in the late postoperative period was related to BMD, injured vertebral segment, surgical methods, the amount of bone cement injection, anterior vertebral height recovery rate and central vertebral height recovery rate(P<0.05). Multivariate Logistic regression analysis showed that thoracolumbar fascial injury(OR=4.938, P=0.001), single or bilateral puncture(OR=5.073, P=0.002) were positively correlated with the residual back pain in the early stage after PVA(B>0), which were risk factors;the BMD (OR=0.211, P=0.000) and anterior vertebral height recovery rate (OR=0.866, P=0.001) were negatively correlated with the residual back pain in the early stage after PVA(B<0), which were protective factors. In the late stage after PVA, the BMD(OR=0.448, P=0.003), the amount of bone cement injection (OR=0.648, P=0.004) and anterior vertebral height recovery rate (OR=0.820, P=0.000) were negatively correlated with residual back pain(B<0), which were protective factors. The decrease of BMD, injury of the thoracolumbar fascia, single or bilateral puncture, poor recovery of anterior vertebral height and insufficient injection of bone cement are closely related to the occurrence of residual back pain after PVA, which affect the relief of residual back pain in the early and late postoperative periods.

Simplified Criterion for Low Gravity Center Cable-Stayed Bridge Based on Response Spectrum Analyses

The seismic response characteristics of a cable-stayed bridge are closely related to the structural system. At the same time, the influence of the height of the gravity center cannot be ignored in the structural system selection of cable-stayed bridges. For convenience, to make the scheme comparison and structural system selection in the preliminary design stage of a cable-stayed bridge, the judgment criterion of a low gravity center cable-stayed bridge was proposed, based on the simplified calculation of the fundamental frequency of cable-stayed bridges with two kinds of the structural system and combined with the response spectrum analysis method. The comparison of the results of the finite element model and the calculating results of the criterion showed that the judgment criterion has high accuracy and reliability, and can be applied to the preliminary design, the scheme comparison of cable-stayed bridges, and help select structural systems in the preliminary design stage of cable-stayed bridges.

Multiview Fusion 3D Target Information Perception Model in Nighttime Unmanned Intelligent Vehicles

Unmanned technology is an important development project of today’s cutting-edge science and technology, which has a significant impact on social and economic development, national defense construction, and scientific and technological development. The rapid development of industrial information technology has driven the unmanned intelligent vehicle system to innovate and gradually enter the public’s view, and at the same time, the driving safety of unmanned intelligent vehicles is also widely concerned. Target information perception system is the foundation of unmanned system and the fundamental guarantee of safety and intelligence of unmanned vehicles. There are three key problems of target recognition in unmanned driving, namely, target classification, localization, and attitude determination. In the implementation of a networked virtual environment system, a flexible and complete perception model is needed as the guiding model of the system. Since 3D point cloud data can provide more spatial information than 2D RGB image data, it is more beneficial to determine the target category, position, and pose in 3D. In this paper, based on the existing research of unmanned intelligent vehicle perception system, we combine the application of fusion of 3D target information perception model and develop a nighttime unmanned system based on multiview fusion of 3D target information perception model. This system can simultaneously perform the detection of multiple categories of objects and predict the center point, length, width, height, and orientation of the objects, so that the unmanned car can sense the location of the surrounding objects when driving in the actual scene.

Fetal magnetic resonance imaging of lumbar spine development in vivo: a retrospective study

ObjectiveThe aim of this study is to describe MR imaging appearances of the fetal lumbar spine in vivo at different gestational ages (GAs).MethodsThis retrospective study was approved by the Third Affiliated Hospital of Zhengzhou University. We collected MR images and clinical data of 93 fetuses in our hospital. All the MR images were obtained by 3-T MR. All had the mid-sagittal plane of steady state free precession sequence (Trufi) of the lumbar spine, which could show the lumbar vertebra and conus medullaris (CM). Regression analysis was made between GA and heights of lumbar vertebral body ossification center (LVBOC), lengths of LVBOC, and heights of intervertebral gap (IVG).ResultsThere were good linear correlations between the heights of LVBOC and GA (P < 0.001), lengths of LVBOC and GA (P < 0.001), and heights of IVG and GA (P < 0.001).ConclusionWe showed the different development of each LVBOC and IVG which caused the difference of the shape of LVBOC and IVG.

Estimation of Broadleaf Tree Canopy Height of Wolong Nature Reserve Based on InSAR and Machine Learning Methods

Tree height is an important parameter for calculating forest carbon sink and assessing forest carbon cycle. In order to obtain forest tree height over a large area both efficiently and at a low cost, this study proposed an Interferometric Synthetic Aperture Radar (InSAR) combined with a machine learning method to estimate the tree canopy height. The forest height in the study area was obtained using Unmanned Aerial Vehicle (UAV) photogrammetry, which was considered to be the true canopy height. Two machine learning methods (Random Forest, Multi-layer perceptron) were used to establish the relationship between phase center height calculated by InSAR DEM differential interference method and coherent amplitude method with true canopy height. The topographic factor, backward scattering coefficient and coherence coefficient were introduced into the relationship model. It was found that the accuracy of tree height estimation using random forest and two InSAR methods can reach 0.95 and 0.94. The root-mean-square error was 1.76 m, 1.86 m, respectively. The accuracy of tree height estimation using multi-layer perceptron and two InSAR methods was 0.25 and 0.2. The root-mean-square error was 3.96 m and 4.13 m. The results indicated that the combination of InSAR and machine learning can estimate canopy height efficiently and at a low cost. Moreover, the integrated learning algorithm random forest demonstrated better stability and higher accuracy than the single learning algorithm multi-layer perceptron.

Co-optimization of piston bowl and injector for light-duty GCI engine using CFD and ML

In this study, the piston bowl geometry and injector design of a light-duty GCI engine were co-optimized using computational fluid dynamics (CFD) and advanced machine learning (ML) techniques to maximize the capability of a GCI technology. This study was performed at low- (6 bar), mid- (11 bar) and high-load (22 bar) indicated mean effective pressure (IMEP) conditions. The 3-D CFD setup was first validated against experimental data. Then, the injector and the piston bowl were simultaneously co-optimized. In total, 13 (ten piston- and three injector-related) design parameters were considered. At each load condition, 128 DoE cases were generated, and the features and performance of the top three designs were analyzed. The best DoE solution was selected by defining weighted merit values to provide one best design across all load conditions. The simulated dataset was used for further optimization using advanced ML techniques. It was found that a flatter design with low center height, wide and shallow bowl, and the low lip was preferable in the low- and high-loads. At the low-load partially premixed compression ignition (PPCI) mode, spray targeting the upper lip and divided into the bowl and squish zones for enhanced mixing is preferred. At the high-load mixing-controlled diffusion combustion mode, where injection occurs near the top dead center (TDC) and diffusion burn is the dominant combustion mode, targeting the lower lip is favorable. At the mid-load with a high premixed ratio, the combustion was close to homogeneous charge compression ignition (HCCI), and the piston bowl design had limited effect. Regarding the optimum injector parameters, larger number nozzles with smaller diameters were favorable at low-load to control partially premixed charge. At high-load, larger and fewer number nozzles are recommended. Lastly, the optimum ML design provided similar performance at mid-load but a 3.8–4.5 % reduction in fuel consumption compared to the baseline cases at low- and high-load conditions.

Flexible Motion Framework of the Six Wheel-Legged Robot: Experimental Results

In complex real-world scenarios, wheel-legged robots with maneuverability, stability, and reliability have addressed growing research attention, especially in material transportation, emergency rescue, as well as the exploration of unknown environments. How to achieve stable high-level movement with payload delivery simultaneously is the main challenge for the wheel-legged robot. In this article, a novel hierarchical framework for the flexible motion of the six wheel-legged robot is considered in experimental results. First, for the wheeled motion, the speed consensus algorithm is implemented to the six-wheeled cooperative control; for the legged motion, three gait sequences, and foot-end trajectory based on the Bezier function are designed. Furthermore, a whole-body control architecture includes the attitude controller, impedance controller, and center height controller is developed for obstacle avoidance, which can ensure the horizontal stability of the body of the robot when it passes through obstacles in different terrain. Finally, extensive experimental demonstrations using the six wheel-legged robot (BIT-6NAZA) are dedicated to the effectiveness and robustness of the developed framework, indicating that it is a superior case of a selectable flexible motion with satisfactory stable performance under the field world environment.

Clinical observation on healing of tarsal plate defect after reconstruction with xenogeneic acellular dermal matrix

ObjectiveTo evaluate the safety, function, and cosmetic outcome of eyelid reconstruction using a xenogeneic acellular dermal matrix as a tarsal plate replacement in the repair of 50 to 100% eyelid defects following excision of large malignant tumours.MethodsA retrospective, non-comparative, interventional study of 21 eyes was performed over 26 months. Fourteen patients were female and seven were male. In all cases, a xenogeneic acellular dermal matrix was used for total or subtotal replacement of the tarsal plate. The central vertical height of the palpebral fissure was measured immediately after eyelid margin incision and at 1 and 6 months postoperatively.ResultsIn patients who underwent surgery, the mean palpebral fissure height (PFH) was not significantly different between immediately and 1 month after incision (8.10 ± 0.562 mm vs 8.17 ± 0.577 mm, respectively; P > 0.05). After 6 months, PFH was 8.26 ± 0.605 mm, which was significantly different from that immediately after incision (P < 0.05). After 6 months of follow-up, all patients had a good aesthetic appearance after eyelid reconstruction, with no obvious graft dissolution or rejection, normal eyelid activity, and normal opening, closing, and lifting function. None of the 21 patients experienced tumour recurrence during postoperative follow-up.ConclusionThe xenogeneic acellular dermal matrix was a successful tarsal plate replacement. This material is readily available, and a second surgical site is avoided. The xenogeneic acellular dermal matrix is considered a promising alternative material for tarsal replacement in future generations.

Application of personalized digital analog assisted acetabular prosthesis precise implantation in Crowe typeⅠand Ⅱ hip dysplasia

To explore the effect of personalized digital analog assisted acetabular prosthesis precise implantation in hip dysplasia. From February 2017 to July 2019, 11 patients(12 hips) with hip dysplasia underwent total hip arthroplasty, including 4 males(5 hips) and 7 females(7 hips), aged from 27 to 61 years old, with an average of (46.64±12.93) years old;Crowe classification:8 hips in typeⅠ and 4 hips in typeⅡ. The preoperative thin-layer CT scan was imported into Mimics 10.01 software. The appropriate size and placement angle of acetabular prosthesis were selected through preoperative simulation, and the acetabular bone defect was understood to determine whether structural bone grafting was needed during the operation. The length of both lower limbs, the anteversion angle of acetabular prosthesis, the abduction angle, the height of acetabular rotation center and the horizontal distance of hip joint center before and after the operation were measured, and the postoperative dislocation, bone graft healing and acetabular cup loosening were observed. The hip Harris score was used to evaluate the joint function. All patients were followed up for 18 to 30 months with an average of (23.45±3.70) months. There was no prosthesis dislocation, loosening and bone graft healing after operation. One case had numbness in the innervation area due to the traction of sciatic nerve during operation, and was treated with neurotrophic drugs and recovered one month after operation. The length difference of both lower limbs decreased from (31.73±5.98) mm before operation to (4.73±1.90) mm 3 months after operation (t=15.268, P<0.01). The anteversion angle of acetabular cup and acetabulum was (17.45±3.62)°and abduction angle was (40.10 ± 2.30)° after operation. In all cases, the abduction angle and anteversion angle were within the safe range of Lewinek. The height of hip rotation center was (20.64±2.58) mm and the horizontal inward displacement of hip was (33.46±3.61) mm. Harris score increased from (45.36±2.34) before operation to (91.27±2.37) 3 months after operation (P<0.05). Through preoperative personalized digital analog reconstruction of acetabulum in patients with hip dysplasia, we can better understand the acetabular defect, help to evaluate the size and placement angle of acetabular prosthesis and whether structural bone grafting is needed, and obtain satisfactory clinical curative effect.

Relationship of lower limb geometrics with femorotibial osteoarthritis in the toei cohort

Osteoarthritis (OA) is a common disease of joints that is more common in females than in males. It is characterized by severe knee degeneration, damaged cartilage and appearance of osteophytes. Hip geometry and morphometric parameters in the knee joint vary between the sexes and depend on the severity of OA and the presence of osteophytes. Very few studies have assessed this phenomenon; therefore in this study, we assessed the difference in hip geometry and morphometric parameters in the lower limbs of males and females and evaluated the association of the differences with the presence or absence of osteophytes. Three hundred and six knees volunteers (104 male knees and 202 female knees) from the Toei region were included in the study between 2012 and 2018. The parameters measured were from the anteroposterior and lateral views of the hip and anteroposterior view of the knee. The participants were divided into 4 groups based on the assessment for osteophytes: Group 1 had no osteophytes, Group 2 had lateral compartment osteophytes, Group 3 had medial compartment osteophytes, and Group 4 had osteophytes in both compartments. Males had an increased femoral neck-shaft angle, femoral-tibial angle, and plateau angle, and a decreased femoral offset, femoral neck length, fibular-tibial angle, and knee rotation index than females. Group 2 had a greater height of the hip center, the angle between the femoral mechanical axis and the femoral shaft axis, condylar-hip angle, and plateau angle than Group 1. Group 3 showed an increased abductor angle, the angle between the femoral mechanical axis and the femoral shaft axis. Group 4 showed an increased angle between the femoral mechanical axis and the femoral shaft axis, femoral-tibial angle, and a decreased patellar shift index and knee rotation index. The angle between the femoral mechanical axis and the femoral shaft axis, condylar-hip angle, femoral-tibial angle, plateau angle, patellar shift index, and knee rotation index were different in both sexes and may be dependent on the presence or absence of osteophytes.

Investigation of the mechanism of casein protein to enhance 3D printing accuracy of cassava starch gel

This work evaluated the potential mechanism of casein protein (CP) in enhancing the 3D printing performance of cassava starch (CS) gel in terms of the multi-scale structure of starch and gel properties. The addition of CP could increase the average molecular weight (−Rh) of starch after thermal processing, which reduced the line width and increased the centre height of the 3D-printed product, despite the reduction of the structural recovery of the gel system. In addition, the increase in CS content caused a decrease in the short-range ordered structure of starch, resulting in a decline in relaxation time and an increase in free water content (A23), which in turn provided the gel system with a greater elastic modulus and ultimately increased the printing precision of 3D printed products. This study presented meaningful information for the application of 3D printing to starch-protein complex foods.

Transient Elastohydrodynamic Lubrication of Rough Contact Surface for Intermittent Motion

The current study aims to study the characteristics of transient elastohydrodynamic lubrication of smooth and rough surface contacts subjected to intermittent motion for different inactive periods of motion and deceleration/acceleration periods to fulfill an identified need for such conjunction. In this case, the non-steady Reynolds’ equation, the film thickness equation with elastic deformation and taking into account the influence of surface roughness, and the load balance equation are simultaneously solved using the Newton-Raphson with Gauss-Seidel iterations method to determine the film profile and pressure distribution at various time steps. Surface contact of sinusoidal waves is presented with different amplitudes and wavelengths. The results indicated that surface waviness causes random oscillations in pressure and film profiles at different time steps. The greater the amplitude of the waviness, the more pressure and film profile variations occur. The magnitude of the pressure and film profile fluctuations becomes little noticeable as the wavelength of a wavy surface rises. The findings of this investigation also revealed that increasing the inactive duration for wavy surfaces results in zero minimum film thickness and surface contact. Squeezing action is ineffective in conveying loading capacity in this circumstance. The central and maximum pressure heights increase during the stop time interval as stop time increases. The centre film thickness increases at the end of the deceleration phase when the deceleration/acceleration period is reduced, but the minimum film thickness is unaffected. In fact, the minimum film thickness tends to be zero at the end of the deceleration phase, regardless of the deceleration/acceleration period. The central and maximum pressure increase during the stop time interval with the decrease of the deceleration/acceleration period. The difference between the results for smooth and wavy surface contacts is the appearance of fluctuations in film and pressure profiles, as well as the reduction of the film thickness and increase in pressure for the wavy surface when compared to contact with a smooth surface.

Oil-recovery performance of a sponge-covered drum skimmer

Oil spill recovery by means of a rotating drum skimmer covered with a sponge layer was investigated experimentally for a wide range of operating conditions. Tests were conducted on two drums of diameters D = 300 mm and D = 200 mm and lengths L = 300 mm and L = 455 mm, respectively. The examined operating conditions encompassed oil viscosity, rotational speed, slick thickness and centre height above the oil/water interface. The results indicate the superiority of the sponge covered surface in oil recovery over the standard steel surface regardless of the viscosity of oil collected. The sponge-covered drum collected 24% more oil than the plain steel drum, when both were operated under the same conditions. The porous cover improves the skimmer performance due to its ability to absorb oil. The increase in oil slick thickness from 10 to 25 mm led to enhanced recovery rate by 59% in case of sponge-covered drum compared to17.5% with plain steel drum. The study paves the way to applying different types of porous sorbent materials to cover the oleophilic skimmers to achieve higher efficiency and oil recovery rate.

Orbital Aging: A Computed Tomography-Based Study of 240 Orbits.

Previous studies have attempted to explain age-related changes to the orbit in isolation, often producing conflicting results. The authors used highly accurate imaging software to analyze computed tomographic scans to characterize changes related to age objectively. In this case-control study, patients seen in an ear, nose, and throat clinic were screened for study entry. Male and female participants were divided into two age groups (20 to 30 years and 60 to 75 years). Primary outcomes included measurement of bony orbital dimensions, volume of soft tissues (muscle and fat volume), and anterior globe position. Three-dimensional reconstructions were created of each orbit allowing these measurements. The generalized estimating equation was used so that both orbits from each patient could be included without any bias. The final sample included 240 orbits from 120 patients. There were 30 patients in each age group. Among female participants, the bony orbital volume ( p < 0.05), fat volume ( p < 0.01), and central width ( p < 0.001) of the bony orbit increased with age. The anterior globe position was significantly greater in older female participants ( p < 0.01). For male participants, the fat volume ( p < 0.0001) and central height ( p < 0.03) increased with age; the lateral rim moved posteriorly with age ( p < 0.007). The anterior globe position was not different between the age groups in male participants ( p = 0.56). The female bony orbit expands with age and is associated with a more anterior position of the globe; the male bony orbital volume remains the same and the lateral rim moves posteriorly.

Height restoration and sustainability using bilateral vertebral augmentation systems for vertebral compression fractures: a cadaveric study

BACKGROUND CONTEXTThe treatment of vertebral compression fractures using percutaneous augmentation is an effective method to reduce pain and decrease mortality rates. Surgical methods include vertebroplasty, kyphoplasty, and vertebral augmentation with implants. A previous study suggested that a titanium implantable vertebral augmentation device (TIVAD) produced superior height restoration compared to balloon kyphoplasty (BKP) but was based on a less clinically relevant biomechanical model. Moreover, the introduction of high pressure balloons and directional instruments may further aid in restoring height. PURPOSEThe objective was to evaluate three procedures (BKP, BKP w/ Kyphon Assist (KA; directional instruments), and TIVAD) used for percutaneous augmentation of vertebral fractures with respect to height restoration and sustainability post-operatively. STUDY DESIGN/SETTINGThis is an in vitro cadaver study performed in a laboratory setting. METHODSFive osteoporotic female human cadaver thoracolumbar spines (age: 63–77 years, T-score: -2.5 to -3.5, levels: T7–S1) were scanned using computed tomography and dissected into 30 two-functional spine units (2FSUs). Vertebral wedge compression fractures were created by reducing the anterior height of the vertebrae by 25% and holding the maximum displacement for 15 minutes. Post-fracture, surgery was performed on each 2FSU with a constant 100 N load. Surgeries included BKP, BKP w/ KA, or TIVAD (n=10 per treatment group). Post-surgery, cyclic loading was performed on each 2FSU for 10,000 cycles at 600 N (walking), followed by 5,000 cycles at 850 N (standing up/sitting down), and 5,000 cycles at 1250 N (lifting a 5-10kg weight from the floor). Fluoroscopic images were taken and analyzed at the initial, post-fracture, post-surgery, and post-loading timepoints. Anterior, central, and posterior heights, Beck Index, and angle between endplates were assessed. RESULTSNo difference in height restoration was observed among treatment groups (p=.72). Compared to the initial height, post-surgery anterior height was 96.3±8.7% for BKP, 94.0±10.0% for BKP w/ KA, and 95.3±5.8% for TIVAD. No difference in height sustainability in response to 600 N (p=.76) and 850 N (p=.20) load levels was observed among treatment groups. However, after 1250 N loading, anterior height decreased to 93.8±6.8% of the post-surgery height for BKP, 95.9±6.4% for BKP w/ KA, and 86.0±6.6% for TIVAD (p=.02). Specifically, the mean anterior height reduction between post-surgery and post-1250 N loading timepoints was lower for BKP w/ KA compared to TIVAD (p=.02), but not when comparing BKP to TIVAD (p=.07). No difference in Beck Index or angle between endplates was observed at any timepoint among the treatment groups. CONCLUSIONSThe present study, utilizing a clinically relevant biomechanical model, demonstrated equivalent height restoration post-surgery and at relatively lower-level cyclic loading using BKP, BKP w/ KA, and TIVAD, contrary to results from a previous study. Less anterior height reduction in response to high-level cyclic loading was observed in the BKP w/ KA group compared to TIVAD. CLINICAL SIGNIFICANCEAll three treatments can restore height similarly after a vertebral compression fracture, which may lead to pain reduction and decreased mortality. BKP w/ KA may exhibit less height loss in higher-demand patients who engage in physical activities that involve increased weight resistance.

Numerical Simulation of Ionospheric Disturbances Due to Rocket Plume and Its Influence on HF Radio Waves Propagation

In this paper, the ionospheric disturbances of CO2, which is released by rocket exhaust plumes, was simulated. The effect of this disturbance on the propagation of high-frequency (HF) radio waves at different incident frequencies was also simulated by using three-dimensional digital ray tracing technique. The results show that CO2 can effectively dissipate the background electrons and form ionospheric holes after being released in the ionosphere. At the peak height of ionospheric electron density (about 300 km), the electrons are dissipated fastest and the radius of ionospheric hole is also largest. This is due to the fact that the diffusion coefficient of CO2 usually increases with height while the electron density just increases before reaching its peak height and then decreases with height, and the chemical reaction rate between ions and CO2 also becomes largest at the peak height of electron density (about 300 km). Around 100 s after the release of CO2, when the radio waves at a frequency of 8 MHz pass through the ionosphere with an elevation range of 85~95°, the “secondary focusing effect” can occur, and we believe that this is due to the reflection of HF shortwaves on the walls of the ionospheric holes. With time going on, this phenomenon disappears at 300 s and only one focus is left at this time. For the HF shortwaves at same incident frequency, the focusing effect of waves displays a weakening trend with time increasing, and the height of focus center also ascends gradually. At the same time after CO2 releasing, with the increasing of radio waves frequency, the focusing effect also becomes weaker and the focus center displays an ascending trend.