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Ultrasound viscoelastic creep imaging (UVCI) is a newly developed technology aiming to measure the viscoelastic properties of materials. The purpose of this study is to investigate the accuracy of UVCI in measuring the viscoelastic properties of heterogeneous materials that mimic pathological lesions and normal tissues. The finite element simulation is used to investigate the measurement accuracy of UVCI on three material models, including a homogeneous material, a single-inclusion phantom, and a three-layer structure. The measurement accuracy for a viscoelastic property is determined by the difference between the simulated measurement result of that viscoelastic property and its true value defined during the simulation process. The results show that UVCI in general cannot accurately measure the true values of the viscoelastic properties of a heterogeneous material, demonstrating the need to further improve the theories and technologies relevant to UVCI to improve its measurement accuracy on tissue-like heterogeneous materials.

Despite the common use of the standard linear solid model (SLSM) in viscoelasticity, the physical significance as well as the difference between the Maxwell and Kelvin forms of SLSM are still not clear. This paper demonstrates that each parameter of those two models has its specific physical meaning, and introduces the relationships allowing the transformations between those parameters. Regardless of their physical significance, those two models are equivalent in terms of their mathematical properties. Hence, no matter which model is chosen, consistent analysis results can always be obtained as long as the physical meaning of each parameter is accurately interpreted.

This study used Doppler radar data, surface observations, and National Centers for Environmental Prediction reanalysis data to explore the statistical characteristics of Taiwan rainbands (TRs) that formed in the outer region of tropical cyclones (TCs). A comprehensive examination of the available radar measurements from 2002 to 2017 identified a total of 103 TRs from 44 TC events and showed that approximately 47% of all TCs influencing Taiwan could develop TRs. The spatial distribution of TR formation exhibited a substantial offshore extent, with the highest frequency observed ~25–100 km offshore. The TRs tended to be initiated when the northwestward-moving typhoons passed over the oceanic area northeast of Luzon Island (16°–20°N, 122°–127°E), the Philippines. This track characteristic brought stronger easterly onshore flow to the eastern coast of Taiwan and favored the development of a pronounced coastal pressure ridge. In particular, the offshore convergence caused by upstream deceleration of the onshore flow due to orographic blocking was found to be a primary contributor to the initiation of the TRs. The strength of the observed coastal pressure ridge and its high correlation with the intensity of environmental onshore flow associated with outer circulations of TCs were consistent with the theoretical prediction of pressure distributions generated as incident flow interacted dynamically with the Taiwan topography. Results from the study suggest that the typhoon location relative to the Taiwan landmass is a critical factor determining TR initiation.

To explore the subacromial motion metrics in patients with and without subacromial impingement syndrome (SIS) and to investigate whether the abnormality was associated with rotator cuff pathologies.This cross-sectional observational study used dynamic quantitative ultrasonography imaging for shoulder joint assessment.Outpatient rehabilitation clinic.Individuals with SIS on at least 1 shoulder (n=32) and asymptomatic controls (n=32) (N=64).Not applicable.Frame-by-frame, the humeral greater tuberosity against the lateral edge of the acromion was traced to obtain the minimal vertical acromiohumeral distance (AHD). The rotation angle and radius of the humerus were computed using the least-squares curve fitting method.Approximately two-thirds of the shoulders with SIS did not have any sonographically identifiable rotator cuff pathologies. There was a consistent trend of nonsignificantly increased humeral rotation angles in painful shoulders. The generalized estimating equation demonstrated that the decreased minimal vertical AHD was associated with painful subacromial impingement (β coefficient: -0.123cm, 95% confidence interval [CI], -0.199 to -0.047). The area under the curve for the minimal vertical AHD to discriminate painful or impinged shoulders ranged from 0.624-0.676. The increased rotation angle (β coefficient: 10.516°; 95% CI, 3.103-17.929) and decreased rotation radius (β coefficient: -2.903cm; 95% CI, -5.693 to -0.111) were shown to be significantly related to the presence of supraspinatus tendinopathy.Shoulders with SIS were characterized by a decreased minimal vertical AHD during dynamic examination. Abnormal subacromial metrics can develop in patients with mild (or no) rotator cuff pathologies. More prospective cohort studies are warranted to investigate the changes in subacromial motion metrics in populations at risk for painful or impinged shoulders.

The plastic heel cup has been adopted to treat plantar heel problems for years. However, its mechanisms and biomechanical effects are yet to be fully understood. The purpose of this study was to investigate the effects of the plastic heel cup on the microchamber and macrochamber layers of the heel pad by comparing the stiffness (in terms of the shear wave speed) and thickness of these two layers with and without a plastic heel cup during static standing. Fifteen patients with unilateral plantar fasciitis were recruited. The shear wave speed and thickness of the microchamber and microchamber layers of each symptomatic heel pad during standing measured by ultrasound shear wave elastography were compared between conditions with and without a plastic heel cup. It was found that a plastic heel cup reduced the shear wave speed of the microchamber layer to 55.5% and increased its thickness to 137.5% compared with the condition without a plastic heel cup. For the microchamber layer, the shear wave speed was reduced to 89.7%, and thickness was increased to 113.6% compared with the condition without a plastic heel cup. The findings demonstrate that a plastic heel cup can help to reduce the stiffness and increase the thickness for both layers of the heel pad during standing, suggesting that the mechanism of a plastic heel cup, and its resulting biomechanical effect, is to reduce the internal stress of the heel pad by increasing its thickness through confinement.

Direct numerical simulations have been applied to simulate flows with polymer additives. FENE-P (finite-extensible-nonlinear-elastic-Peterlin) dumbbell model solving for the conformation tensor is adopted to investigate the influence of the polymer on the flowfield. Boundary treatments of the conformation tensor on the flowfield are examined first, where boundary condition based on the linear extrapolation scheme provides more accurate results with second-order accurate error norms. Further simulations of the turbulent channel flow at different Weissenberg numbers are also conducted to investigate the influence on drag reduction. Drag reduction increases in tandem with the increase of Weissenberg number and the increase saturates at Weτ~200, where the drag reduction is close to the maximum drag reduction (MDR) limit. At the regime of y+ > 5, the viscous layer thickens with the increase of the Weissenberg number showing a departure from the traditional log-law profile, and the velocity profiles approach the MDR line at high Weissenberg number. The Reynolds stress decreases in tandem with the increase of Weτ, whereas the levels of laminar stress and polymer stress act adversely. However, as the Weissenberg number increases, the proportion of the laminar stress in the total stress increases, and this contributes to the drag reduction of the polymer flow.

Purpose Marin-Amat syndrome is an acquired facial synkinesis manifesting as involuntary eyelid closure on jaw movement. The authors investigate the clinical features, especially the quantitative changes in eyelid parameters of patients with Marin-Amat syndrome. Methods Patients with Marin-Amat syndrome between 2015 and 2017 in a medical center were collected. Clinical features and the change of eyelid parameters, including margin reflex distance 1 (MRD-1), margin reflex distance 2 (MRD-2), and palpebral fissure height, were evaluated. Results There were 5 men and 3 women with a mean age of 76 years. All had a history of facial palsy. The mean time to onset of Marin-Amat syndrome was 4.4 years after facial palsy. Seven patients (87.5%) developed subsequent ipsilateral facial spasm after facial palsy. Most patient complaints were ptosis (62.5%) and ptosis on eating (37.5%). The mean palpebral fissure height of involved eyes decreased from 5.88 to 2 mm on jaw opening (p = 0.011), which resulted from decrease in MRD-1 (from 2.06 to 0.06 mm, p = 0.012) and MRD-2 (from 3.81 to 1.94 mm; p = 0.012). Botulinum toxin A (Botox) injection into the periorbital orbicularis muscle in 6 patients significantly relieved the change of palpebral fissure height on jaw opening compared with that before injection (9.9% vs. 68.6 %, p = 0.027). Conclusions Most patients with Marin-Amat syndrome present with ptosis and might be overlooked or underestimated. The reduction in palpebral fissure height in our patients with Marin-Amat syndrome was due to involuntary orbicularis oculi muscle contraction, resulting in decrease of both the MRD-1 and MRD-2 on jaw opening.

In this work, we introduce a MoS2-based field effect transistor that can alternately operate either as a p-type or an n-type semiconductor in the same device. The proposed device is built with an adjustable threshold voltage (Vth), which can be varied by adding a layer of plasma-oxidized dielectric at the top gate structure. This facilitates a surplus of oxygen due to the relatively thin grown dielectric layer and the creation of negative charges in that layer instead of the usual ones of positive polarization in the bottom dielectric layer. Consequently, the Vth shifts and the top gate structure switches from the typical n-type to p-type while the n-type behaviour remains in the application of the bottom-gate voltages. The Vth can be tuned further by applying a gate pulse input at the top gate. Accordingly, we have demonstrated complementary logic inverters with adjustable device characteristics that are controllable by the polarity of charges induced in the device's oxide layer. This is a big step towards the concurrent implementation of both n-type and p-type characteristics in a single device.

Conductive polymers (CPs) have received increasing attention as promising materials for studying electrophysiological signals in cell and tissue engineering. The combination of CPs with electrical stimulation (ES) could possibly enhance neurogenesis, osteogenesis, and myogenesis. To date, research has been prioritized on capitalizing CPs as two-dimensional (2D) structures for guiding the differentiation. In contrast, relatively little is conducted on the implementation of 3D conductive scaffolds. In this research, we report the synergic assembly of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and multi-walled carbon nanotubes (MWCNTs) as a biocompatible, electrically conductive, mechanically robust and structurally porous 3D scaffold. To showcase the bioelectronic utilization, a proof-of-concept demonstration of electrically stimulated cell culture under ES is conducted. The ES effects coupled with the 3D scaffold are promising on pheochromocytoma 12 (PC12), a neuronal cell line, and the ES effect on osteogenesis of human adipose-derived stem cells (hASC) was further studied. PC12 cultured on this PEDOT:PSS/MWCNT 3D scaffolds was induced to differentiate toward a more mature neuronal phenotype with the ES treatment. Furthermore, hASC osteogenesis could be highly promoted in this conductive scaffold with ES. Calcium deposition concentration and osteo-differentiated gene markers were significantly higher with ES. The facile assembly of 3D conductive scaffolds sheds light on both platforms for investigating the 3D microenvironment for electrophysiological simulation of cells and tissues under the ES treatment of in vivo tissue engineering.

Mechanical properties are crucial parameters for scaffold design for bone tissue engineering; therefore, it is important to understand the definitions of the mechanical properties of bones and relevant analysis methods, such that tissue engineers can use this information to properly design the mechanical properties of scaffolds for bone tissue engineering. The main purpose of this article is to provide a review and practical guide to understand and analyze the mechanical properties of compact bone that can be defined and extracted from the stress–strain curve measured using uniaxial tensile test until failure. The typical stress–strain curve of compact bone measured using uniaxial tensile test until failure is a bilinear, monotonically increasing curve. The associated mechanical properties can be obtained by analyzing this bilinear stress–strain curve. In this article, a computer programming code for analyzing the bilinear stress–strain curve of compact bone for quantifying the associated mechanical properties is provided, such that the readers can use this computer code to perform the analysis directly. In addition to being applied to compact bone, the information provided by this article can also be applied to quantify the mechanical properties of any material having a bilinear stress–strain curve, such as a whole bone, some metals and biomaterials. The information provided by this article can be applied by tissue engineers, such that they can have a reference to properly design the mechanical properties of scaffolds for bone tissue engineering. The information can also be applied by researchers in biomechanics and orthopedics to compare the mechanical properties of bones in different physiological or pathological conditions.

This study used radar and surface observations to track a long-lasting outer tropical cyclone rainband (TCR) of Typhoon Jangmi (2008) over a considerable period of time (~10 h) from its formative to mature stage. Detailed analyses of these unique observations indicate that the TCR was initiated on the eastern side of the typhoon at a radial distance of ~190 km as it detached from the upwind segment of a stratiform rainband located close to the inner-core boundary. The outer rainband, as it propagated cyclonically outward, underwent a prominent convective transformation from generally stratiform precipitation during the earlier period to highly organized, convective precipitation during its mature stage. The transformation was accompanied by a clear trend of surface kinematics and thermodynamics toward squall-line-like features. The observed intensification of the rainband was not simply related to the spatial variation of the ambient CAPE or potential instability; instead, the dynamical interaction between the prerainband vertical shear and cold pools, with progression toward increasingly optimal conditions over time, provides a reasonable explanation for the temporal alternation of the precipitation intensity. The increasing intensity of cold pools was suggested to play an essential role in the convective transformation for the rainband. The propagation characteristics of the studied TCR were distinctly different from those of wave disturbances frequently documented within the cores of tropical cyclones; however, they were consistent with the theoretically predicted propagation of convectively generated cold pools. The convective transformation, as documented in the present case, is anticipated to be one of the fundamental processes determining the evolving and structural nature of outer TCRs.

Most biomaterials and tissues are viscoelastic, thus, evaluating viscoelastic properties is important for numerous biomedical applications. Compressional viscoelastography is an ultrasound imaging technique used for measuring the viscoelastic properties of biomaterials and tissues. It analyzes the creep behavior of a material under an external mechanical compression. The aim of this study is to use finite element analysis to investigate how loading conditions (the distribution of the applied compressional pressure on the surface of the sample) and boundary conditions (the fixation method used to stabilize the sample) can affect the measurement accuracy of compressional viscoelastography. The results show that loading and boundary conditions in computational simulations of compressional viscoelastography can severely affect the measurement accuracy of the viscoelastic properties of materials. The measurement can only be accurate if the compressional pressure is exerted on the entire top surface of the sample, as well as if the bottom of the sample is fixed only along the vertical direction. These findings imply that, in an experimental validation study, the phantom design should take into account that the surface area of the pressure plate must be equal to or larger than that of the top surface of the sample, and the sample should be placed directly on the testing platform without any fixation (such as a sample container). The findings indicate that when applying compressional viscoelastography to real tissues in vivo, consideration should be given to the representative loading and boundary conditions. The findings of the present simulation study will provide a reference for experimental phantom designs regarding loading and boundary conditions, as well as guidance towards validating the experimental results of compressional viscoelastography.

We present direct numerical simulation data for turbulent duct flow of a finite-extensibility non-linear elastic dumbbell model with the Peterlin approximation (FENE-P) fluid in the high drag reduction regime. While the secondary flow pattern is qualitatively similar to that in a Newtonian fluid, its magnitude is significantly reduced, resulting in a less uniformly distributed velocity profile and hence smaller gradients at the wall. The Reynolds stress tensor in the polymer-laden flow was found to be increasingly anisotropic with most of the turbulent kinetic energy retained in the streamwise component, [Formula: see text]. We introduce a novel approach for investigating polymer stretching using the anisotropy invariant map of the polymer stress tensor and observe the persistence of both uniaxial and biaxial extension. Analysis of the transport equation for the mean kinetic energy indicates that polymer stretching and relaxation is a highly dissipative process; hence, the introduction of an additional channel for dissipation in a flow is key to drag reduction.

Surface coating with sulfobetaine methacrylate (SBMA) containing polymers is a simple method for reducing non-specific protein adsorption and cell adhesion to biomaterials. It has been shown that c...

Background/Purpose: To compare shear modulus of heel pad microchamber and macrochamber layers between young and elderly people using shear wave ultrasound elastography (SWUE), with the intent to clarify age-related changes. Methods: This single-center prospective cross-sectional study was conducted between March, 2014 and March, 2016. Shear modulus of entire heel pad (Gentire), macrochamber layer (Gmac), and microchamber layer (Gmic) were measured with SWUE. Results: Elderly participants (15 men, 15 women; age = 66.9 ± 6.2 years) had significantly higher Gmic (103.8 ± 20.7 vs. 60.1 ± 9.8 kPa; p

Ultrasound viscoelastic creep imaging is a noninvasive technique that has potential to measure the internal spatial distribution of viscoelastic properties of materials, based on inducing the creep response of the material and using a viscoelastic mechanical model to analyze the creep response. Since how viscoelastic creep imaging can be applied to accurately measure the viscoelastic properties of heterogeneous materials is still unclear, the purpose of this study is to use finite element computer simulation to quantitatively investigate the accuracy of compressional viscoelastography (viscoelastic creep imaging using external mechanical compression as the source of excitation) on measuring the viscoelastic properties of a single-inclusion phantom. The study intends to answer a question: can compressional viscoelastography accurately measure the viscoelastic properties of the inclusion as well as the background material within a single-inclusion phantom? Based on the simulation results, compressional viscoelastography could not accurately measure the viscoelastic properties of the inclusion. The measurement of a viscoelastic property (modulus of elasticity or relaxation time constant) of the inclusion is accurate if and only if the difference in that property between the inclusion and background material is very small, less than around 10%. On the other hand, compressional viscoelastography can accurately measure the viscoelastic properties of the background material regardless of the difference in the viscoelastic properties between the inclusion and background material. In a real biological tissue, the mechanical behaviors are much more complicated and unpredictable than those in a single-inclusion phantom like the one used in the present study. Hence, based on the simulation results of the present study, it could be more challenging to apply compressional viscoelastography to accurately measure the viscoelastic properties of a mass or a target tissue within a real biological tissue. The findings of the present study based on compressional viscoelastography may also be applicable to acoustic-radiation-force-based viscoelastic creep imaging. In the future, experiments are needed to justify the simulation results found in the present study.

Yung-Chih Kuo,1 Che-Yu Lin,1 Jay-Shake Li,2 Yung-I Lou3 1Department of Chemical Engineering, 2Department of Psychology, National Chung Cheng University, Chia-Yi, 3Department of Accounting, Providence University, Taichung, Taiwan, Republic of China Abstract: Curcumin (CRM) and nerve growth factor (NGF) were entrapped in liposomes (LIP) with surface wheat germ agglutinin (WGA) to downregulate the phosphorylation of kinases in Alzheimer’s disease (AD) therapy. Cardiolipin (CL)-conjugated LIP carrying CRM (CRM-CL/LIP) and also carrying NGF (NGF-CL/LIP) were used with AD models of SK-N-MC cells and Wistar rats after an insult with β-amyloid peptide (Aβ). We found that CRM-CL/LIP inhibited the expression of phosphorylated p38 (p-p38), phosphorylated c-Jun N-terminal kinase (p-JNK), and p-tau protein at serine202 and prevented neurodegeneration of SK-N-MC cells. In addition, NGF-CL/LIP could enhance the quantities of p-neurotrophic tyrosine kinase receptor type 1 and p-extracellular signal-regulated kinase 5 for neuronal rescue. Moreover, WGA-grafted CRM-CL/LIP and WGA-grafted NGF-CL/LIP significantly improved the permeation of CRM and NGF across the blood–brain barrier, reduced Aβ plaque deposition and the malondialdehyde level, and increased the percentage of normal neurons and cholinergic activity in the hippocampus of AD rats. Based on the marker expressions and in vivo evidence, current LIP carriers can be promising drug delivery systems to protect nervous tissue against Aβ-induced apoptosis in the brain during the clinical management of AD. Keywords: liposome, Alzheimer’s disease, β-amyloid, neurodegeneration, blood–brain barrier, wheat germ agglutinin

This paper utilizes spectrally efficient carrierless amplitude and phase (CAP) modulation and four wavelength division multiplexing channels in formulation of a high-capacity transmission system. The dispersion and loss associated with a single-mode fiber of 60 km can result in severe power fading and insufficient loss budget, respectively. This study employed high launch power to overcome these issues and thereby achieve long-reach transmission without the need for dispersion compensation or an optical inline amplifier. Modified Volterra filtering is used to deal with the linear and nonlinear distortions within the system. This allowed for the inclusion of cost-effective 10-GHz-class electro-absorption modulators and p-i-n detectors for 4- $\lambda$ 224-Gb/s 32-CAP 60-km transmission with a loss budget of 26 dB/channel. The proposed system provides support for the 64 optical network units (ONUs) with downstream transmission of $>$ 3 Gb/s/ONU for future long-reach passive optical networks. We also examined the transmission performance of each channel under various launch powers. Increasing launch power from 9 to 18 dBm/channel increases the loss budget by 9 dB and expands the total capacity by 42%.

Bulk Czochralski silicon crystals were decorated with Cu and characterized by transmission electron microscopy (TEM) with energy-dispersive spectroscopy (EDS), atomic force microscopy (AFM), optical microscopy (OM), scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). The vacancy-type core, oxidation-induced stacking faults (OISF) ring, nearly defect-free ring, and self-interstitial-type rich outer ring were delineated in the Si crystal wafer. At the surface of the Si crystal, vertical-horizontal line (V-H line) defects and windmill defects (W-defects) were formed instead of OISF. The families of growth planes and directions were expressed as {011} and for the V-H line and {010} and for W-defects, respectively. In addition to V-H line defects and W-defects, pits or voids and Si oxide with dissolved Cu were found in the Si crystal wafer.

Tropical cyclone rainbands (TCRs) are not only one of the most striking and persistent features of tropical cyclones (TCs) but also one of the major causes for extreme floods as TCs approach or encounter the land area. TCRs have been traditionally considered as manifestations of atmospheric waves initiated near the eyewall or close to the TC center. However, the limited evidence from recent studies showed the possibility for TCRs to develop squall-line-like characteristics in the outer region of TCs. In this study, the degree of the prevalence for this similarity is explored by radar and surface observations from a large set of 50 outer TCRs associated with 22 TCs as they approached Taiwan. The results indicate that around 58% of outer TCRs are similar to squall lines. These outer TCRs are generally characterized by convective precipitation, an obvious convergence zone between the band-relative rear-to-front flow and front-to-rear flow at low levels, either frontward or rearward tilting updrafts, and a surface cold pool signature. The frequent similarity between the outer TCRs and squall lines documented provides important insights into the formation of organized, heavy precipitation associated with TCs.

Most transient ultrasound elastography methods use high-intensity ultrasound “push” pulses that generate a shear wave with a wide frequency spectrum. However, it is difficult to control how the energy of the wave is distributed within that spectrum. For this reason, the shear-wave group velocity may not match that of harmonic methods like magnetic resonance elastography (MRE). The objective of this study was to introduce a narrowband shear wave generation method produced by “push” pulses with sinusoidally modulated intensity. The method, named harmonic shear wave imaging (HSWI), successively transmits a series of push pulses with a periodic change in duration. The excited shear waves form a continuous shear wave with a known main frequency that can be controlled by the user. Push pulses are interleaved with imaging pulses so only one clinical transducer is used to generate and record the shear waves. The proposed method was compared to MRE and a transient shear wave elastography method using phantoms and in vivo measurements. It was found that HSWI produces narrowband waves with a speed that closely matches that measured by MRE. Measurement of the acoustic output parameters indicated that the acoustic intensities in HSWI are suitable for clinical applications. The ability of HSWI to generate narrowband shear waves using a single linear array transducer makes it amenable for clinical translation. HSWI can potentially use the same thresholds as MRE for diagnosis of diseases affecting the stiffness of soft tissues.