Soil hydraulic properties are essential for understanding soil hydrological and erosion processes. The importance of roots on soil hydraulic parameters has been widely recognized, but current studies have focused mainly on the root effect of a single plant species. However, few studies have been carried out to investigate the effect of mixed plant roots on soil hydraulic parameters. Undisturbed soil samples were collected from three natural sampling sites with single plant types and four sites with mixed plant types. Both soil hydraulic parameters were measured: soil saturated hydraulic conductivity (Ks) and soil saturated water content (SW). Then the root effects on Ks and SW were subsequently evaluated. The results showed that the Ks and SW at the sites with mixed plants were higher than those at the sites with a single plant species. At all the sites, Ks and SW both exhibited a decreasing-increasing-decreasing trend with increasing root density. The critical root density for the above change was quantified. When fibrous roots were mixed with tap roots, Ks was mainly affected by tap roots, while SW was mainly affected by fibrous roots. The influence of roots on Ks and SW was mainly achieved by affecting soil organic matter, not by directly affecting Ks and SW. Based on the root density, the herbaceous coverage with optimal saturated hydraulic conductivity and water content was estimated to be 66.71%.
Traditional nonintelligent signal control systems are typically used in road traffic signal systems, which cannot provide optimal guidance and have low traffic efficiency during rush hour. This study proposes a traffic signal phase dynamic timing optimization strategy based on a time convolution network and attention mechanism to improve traffic efficiency at intersections. The corresponding optimization was performed after predicting traffic conditions with different impacts using the digital twinning technique. This method uses a time-convolution network to extract the cross-time nonlinear characteristics of traffic data at road intersections. An attention mechanism was introduced to capture the relationship between the importance distribution and duration of the historical time series to predict the traffic flow at an intersection. The interpretability and prediction accuracy of the model was effectively improved. The model was tested using traffic flow data from a signalized intersection in Shangrao, Jiangxi Province, China. The experimental results indicate that the model generated by training has a strong learning ability for the temporal characteristics of traffic flow. The model has high prediction accuracy, good optimization results, and wide application prospects in different scenarios.
This study investigated the effect of MB oscillations on neuronal activity in the central nervous system (CNS) of mammals. The motor cortex of mouse was subjected to ultrasound (US) stimulation with and without MBs. Electromyogram (EMG) signals were recorded by tungsten electrodes. An immunofluorescence assay with antibodies against c-fos was performed to examine the evoked neuronal activity. The influence of US stimulation with MBs on blood brain barrier (BBB) integrity was also assessed. The presence of MBs significantly increased the success rate of motor response from 6.5% ± 6% to 28% ± 10% at 0.12 MPa acoustic pressure. At 0.25 MPa, the success rate was 38% ± 9% without MBs and it significantly increased to 77% ± 18% with MBs. Compared to the US stimulation alone group, the density of c-fos + cells in the region of stimulation was significantly increased for US+MBs group, which indicated that MBs oscillations would enhance neuronal activity. The examination of BBB integrity showed that 0.12 MPa US stimulation with MBs did not result in disruption of BBB integrity while MB oscillations still produced enhanced effect on ultrasonic neuromodulation, suggesting that the neuromodulatory effects induced by MBs is independent on BBB opening. These findings advance the understanding of the effects of MB oscillation on neuronal activity, and break new avenues for the application of MBs in brain.
High-intensity focused ultrasound (HIFU) is a rapidly emerging non-invasive technique to selectively and locally produce thermal ablation of tumors located in various tissues, which could produce thermal lesions in periosteal structures for the thermal treatment of bone metastases that has been approved by FDA. In this work we characterized the surface vibration of an ex vivo bovine bone exposed to HIFU and explored the feasibility of using acoustic parameters to evaluate the thermal lesions at bone-soft tissue interface. The vibration of the bone surface was measured using a laser vibrometer when exposed to HIFU under acoustic pulse excitation and continuous sinusoidal excitation. Thermal lesions were formed at normal and oblique acoustic incidence of HIFU to the surface of the bone. 2-D RF data backscattered from the ablated region were captured by a modified diagnostic ultrasound scanner to construct the ultrasonic B-mode ultrasound images, Nakagami images and differential integrated backscatter (DIBS) images simultaneously, as well as the changes of acoustic apparent integrated backscattering (AIB) and integrated reflection coefficient (IRC) due to the thermal lesions on the bone surface. At oblique incidence of HIFU, the amplitudes of the nano-vibration of the bone surface were higher in the opposite direction. The thermal lesion was 20 mm in width and extended along the front surface of the bone to the right of the HIFU focus. The thermal lesions in the soft tissue were visualized as hyperechoic regions in ultrasonic B-mode images, Nakagami images and DIBS images simultaneously. The mean value of AIB in the region of surface thermal lesions was increased by about 35% compared with the normal level in the control groups and the value of IRC was decreased by about 70% on average. This preliminary study suggested that the presence of bone would directionally change the spatial distribution of surface vibration and thermal effects at bone-soft tissue interface for oblique incidence of HIFU. Ultrasonic parameters, AIB and IRC, may have the potential to evaluate the characteristics of surface thermal injury of bone induced by HIFU ablation.
Abstract Artificial total hip arthroplasty (THA) is one of the most effective orthopaedic surgeries that has been used for decades. However, wear of the articulating surfaces is one of the key failure causes limiting the lifetime of total hip implant. In this paper, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were employed to explore the composition and formation mechanism of the tribo-layer on the articulating surfaces of metal-on-polyethylene (MoPE) implants retrieved from patients. Results showed that, in contrast to conventional understanding, the attached tribo-layer contained not only denatured proteins but also a fraction of polymer particles. The formation of the tribo-layer was believed to relate to lubrication regime, which was supposed to be largely affected by the nature of the ultra-high-molecule-weight-polyethylene (UHMWPE). Wear and formation of tribo-layer could be minimized in elasto-hydrodynamic lubrication (EHL) regime when the UHMWPE was less stiff and have a morphology containing micro-pits; whereas the wear was more severe and tribo-layer formed in boundary lubrication. Our results and analyses suggest that enhancing interface lubrication may be more effective on reducing wear than increasing the hardness of material. This finding may shed light on the design strategy of artificial hip joints.
This work investigated and compared the dynamic cavitation characteristics between low and high boiling-point phase-shift nanodroplets (NDs) under physiologically relevant flow conditions during focused ultrasound (FUS) exposures at different peak rarefactional pressures. A passive cavitation detection (PCD) system was used to monitor cavitation activity during FUS exposure at various acoustic pressure levels. Root mean square (RMS) amplitudes of broadband noise, spectrograms of the passive cavitation detection signals, and normalized inertial cavitation dose (ICD) values were calculated. Cavitation activity of low-boiling-point perfluoropentane (PFP) NDs and high boiling-point perfluorohexane (PFH) NDs flowing at in vitro mean velocities of 0-15 cm/s were compared in a 4-mm diameter wall-less vessel in a transparent tissue-mimicking phantom. In the static state, both types of phase-shift NDs exhibit a sharp rise in cavitation intensity during initial FUS exposure. Under flow conditions, cavitation activity of the PFH NDs reached the steady state less rapidly compared to PFP NDs under the lower acoustic pressure (1.35 MPa); at the higher acoustic pressure (1.65 MPa), the RMS amplitude increased more sharply during the initial FUS exposure period. In particular, the RMS-time curves of the PFP NDs shifted upward as the mean flow velocity increased from 0 to 15 cm/s; the RMS amplitude of the PFH ND solution increased from 0 to 10 cm/s and decreased at 15 cm/s. Moreover, amplitudes of the echo signal for the low boiling-point PFP NDs were higher compared to the high boiling-point PFH NDs in the lower frequency range, whereas the inverse occurred in the higher frequency range. Both PFP and PFH NDs showed increased cavitation activity in the higher frequency under the flow condition compared to the static state, especially PFH NDs. At 1.65 MPa, normalized ICD values for PFH increased from 0.93 ± 0.03 to 0.96 ± 0.04 and from 0 to 10 cm/s, then decreased to 0.86 ± 0.05 at 15 cm/s. This work contributes to our further understanding of cavitation characteristics of phase-shift NDs under physiologically relevant flow conditions during FUS exposure. In addition, the results provide a reference for selecting suitable phase-shift NDs to enhance the efficiency of cavitation-mediated ultrasonic applications.
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