Large Magnitude Research Articles

Prediction and suppression of chaos following flutter in wind turbines

Chaotic motion in a fluttering wind turbine blade is investigated by the development of an efficient analytical predictive model that is then used to suppress the phenomenon. Flutter is a dynamic instability of an elastic structure in a fluid, such as an airfoil section of a wind turbine blade. It is presently modelled using generalised two degree of freedom coupled modes of a blade airfoil section (pitch and plunge) combined with local unsteady aerodynamics, based on flutter derivatives and a continuous bilinear lift curve under damping. The mode coupling causes instability and limit cycle flutter due to a Hopf bifurcation. Following the critical flutter speed, the response can transition to chaos through successive other bifurcations like period doubling. New closed-form conservative analytical conditions for chaos following blade flutter are identified and discussed for the wind turbine section taking into account the blade geometry and optimal design of the wind turbine. These predictions are numerically verified for a range of conditions including stall slope and damping. The results confirm that chaos following blade flutter can occur due to nonlinearities in the aerodynamics, i.e. due to a bilinear lift law. This phenomenon is then suppressed to unrealistically high wind speeds and/or eliminated by quantified variation of system parameters using the predictive model. The results show that small changes in tip speed ratio (−15%), and stall slope factor (−17%) can eliminate or suppress chaos following flutter, while, in general, larger magnitude changes in dynamic parameters (i.e. mass, inertia > 81%, stiffness > 97%, damping > 100%) are required to achieve the same, by detuning the coupled plunge and pitch natural frequencies or damping out overlapping parametric resonances. These results also highlight that the analytical predictions can remarkably be generalized to any parameter set and provide almost instantaneous calculations representing many thousands of numerical simulations from many bifurcation diagrams (computational acceleration factor of 107 times). General insight is also provided into the occurrence and suppression of airfoil chaos following flutter in aeroelastic structures like wind turbines.

Dynamic performance of the Mosque-Cathedral of Córdoba under different earthquake scenarios: The Abd al-Rahman I sector

The Mosque-Cathedral of Córdoba is one of the most important monuments in Spain. Owing to its authenticity, its integrity and its influence on later architecture, it was declared as a World Heritage Site by the UNESCO in 1984. The monument is located in Andalusia, in southern Spain. This region presents a moderate seismic hazard, and it is affected by two kinds of seismic sources: a) far away earthquakes of large/very large magnitude; b) close earthquakes of moderate magnitude. Particularly, the Mosque-Cathedral had to endure the well-known 1755 Lisbon's earthquake (Mw = 8.5, at 488 km) and the 1504 Carmona earthquake (Mw = 6.8, at 82 km). This research has analysed its dynamic behaviour under several earthquake scenarios: code-base response spectrum, previous historic earthquakes and fault maximum magnitude earthquakes. However, after the seismic hazard analysis and due to the lack of faults registered surrounding the building, no worst-case scenario considering the maximum expected magnitude has been found. Owing to the complexity of the building, this work has focused on the Abd al-Rahman I sector, which is the most aged part, dating from the VIII century. A refined 3D numerical model has been developed and calibrated through free ambient vibration tests. The distribution of the maximum amplitudes (internal displacements and absolute accelerations) under the different scenarios has been comparatively presented. Also, the seismic performance has been assessed considering the drifts and the damage expected. The results showed that the damage would be concentrated in the contact between the arcades and the courtyard wall. Also, the lower part of the North-South closing wall would be damaged. According to the seismic performance, the building is expected to present moderate damage. In contrast, the analysis of the drifts, according to the codes, suggest that the building would resist each damage limit. Also, it was shown that the far fault earthquake scenario is more demanding than the close fault earthquake scenario. Next, it should be noted that the behaviour of the building for a seismic action of 475-year return period is expected to be similar to the far-fault earthquake scenario. The most demanding earthquake scenario has been the 975-year return period one.

Review: tunable nanophotonic metastructures.

Tunable nanophotonic metastructures offer new capabilities in computing, networking, and imaging by providing reconfigurability in computer interconnect topologies, new optical information processing capabilities, optical network switching, and image processing. Depending on the materials and the nanostructures employed in the nanophotonic metastructure devices, various tuning mechanisms can be employed. They include thermo-optical, electro-optical (e.g. Pockels and Kerr effects), magneto-optical, ionic-optical, piezo-optical, mechano-optical (deformation in MEMS or NEMS), and phase-change mechanisms. Such mechanisms can alter the real and/or imaginary parts of the optical susceptibility tensors, leading to tuning of the optical characteristics. In particular, tunable nanophotonic metastructures with relatively large tuning strengths (e.g. large changes in the refractive index) can lead to particularly useful device applications. This paper reviews various tunable nanophotonic metastructures' tuning mechanisms, tuning characteristics, tuning speeds, and non-volatility. Among the reviewed tunable nanophotonic metastructures, some of the phase-change-mechanisms offer relatively large index change magnitude while offering non-volatility. In particular, Ge-Sb-Se-Te (GSST) and vanadium dioxide (VO2) materials are popular for this reason. Mechanically tunable nanophotonic metastructures offer relatively small changes in the optical losses while offering large index changes. Electro-optically tunable nanophotonic metastructures offer relatively fast tuning speeds while achieving relatively small index changes. Thermo-optically tunable nanophotonic metastructures offer nearly zero changes in optical losses while realizing modest changes in optical index at the expense of relatively large power consumption. Magneto-optically tunable nanophotonic metastructures offer non-reciprocal optical index changes that can be induced by changing the magnetic field strengths or directions. Tunable nanophotonic metastructures can find a very wide range of applications including imaging, computing, communications, and sensing. Practical commercial deployments of these technologies will require scalable, repeatable, and high-yield manufacturing. Most of these technology demonstrations required specialized nanofabrication tools such as e-beam lithography on relatively small fractional areas of semiconductor wafers, however, with advanced CMOS fabrication and heterogeneous integration techniques deployed for photonics, scalable and practical wafer-scale fabrication of tunable nanophotonic metastructures should be on the horizon, driven by strong interests from multiple application areas.

How Costly is Tax Avoidance? Evidence from Structural Estimation

ABSTRACT I develop a structural model to quantify the costs of tax avoidance. In the model, the firm trades off tax savings with tax audit risk, financial reporting considerations, and operational frictions imposed by tax avoidance, the last of which I label as nontax costs. The estimated parameters suggest nontax costs, which are difficult to observe, decrease pretax income by 6.4 percent or $58 million per firm-year. The large magnitude of this estimate can explain why firms appear to underutilize tax avoidance strategies. Through counterfactual analysis, I estimate the effect of tax audit risk and financial reporting considerations to find that financial reporting considerations have an effect on tax avoidance similar to the penalties imposed by tax authorities. Overall, the estimated parameters help explain the “undersheltering puzzle.” JEL Classifications: G14; H21; H25; H26; M41; M48.

Responsiveness and Minimal Important Change of the Arabic Disabilities of the Arm, Shoulder and Hand (DASH) in Patients with Upper Extremity Musculoskeletal Disorders.

The aim of this study was to examine the responsiveness of the Arabic Disabilities of the Arm, Shoulder and Hand (DASH) and to quantify its minimal important change (MIC) for improvement. People with upper extremity musculoskeletal problems who were receiving physical therapy were evaluated at baseline and again during a follow-up appointment, with a median time frame of 7 days between the two testing sessions (range of 6 to 72 days). The participants completed the Arabic DASH, Global Assessment of Function (GAF), Numeric Pain Rating Scale (NPRS) and Global Rating of Change Scale (GRC). The responsiveness of the Arabic DASH was assessed by examining the pre-specified hypotheses. The MIC for improvement was determined using the receiver operating characteristic method (MICROC) and the predictive modeling method (MICpred). As hypothesized, a change in the Arabic DASH demonstrated a significant positive correlation with changes in the GAF (r = 0.69), NPRS (r = 0.68) and GRC (r = 0.73). Consistent with our hypotheses, the DASH change scores could be used to differentiate between participants who improved and those who did not improve (area under the receiver operating characteristic curve = 0.87), and they showed a large magnitude of change (effect size = 1.53, standardized response mean = 1.42) in patients who improved. All the hypotheses specified a priori were supported by the results. The Arabic DASH MICROC and MICpred were estimated to be 14.22 and 14.85. The interaction between the DASH change and baseline score was not a significant predictor of status (improved vs. not improved) (p = 0.75), indicating that the DASH MIC was not baseline-dependent. The Arabic DASH demonstrated sufficient responsiveness, supporting the idea that the Arabic DASH is capable of detecting changes in upper extremity function over time. The value of the Arabic DASH MIC was similar when estimated using the predictive modeling and ROC methods, and the MIC was not dependent on baseline status.

Measurements of visual double stars with PISCO2 at the Nice 76‐cm refractor in 2013–2014 (new data) and in 2015

AbstractWe present relative astrometric and photometric measurements of visual double stars made in 2013–2015, with PISCO2 installed at the 76‐cm refractor of Côte d'Azur Observatory in Nice (France). Our observing list contains orbital couples as well as double stars whose motion is still uncertain. Most of the observations were done in 2015, but some other observations of wide couples were done in 2013–2014 (0.3% of the total of the observations). Three different techniques were used for obtaining measurements: lucky imaging, speckle interferometry and the direct vector autocorrelation method. From our observations of 2837 multiple stars, we obtained 5182 new measurements with angular separations in the range of 0.1–32 and an average accuracy of . The mean error on the position angles is 0°.8. Most of the position angles were determined without the usual 180° ambiguity with the application of the direct vector autocorrelation technique and/or by inspection of the Lucky images or the long integration files. We managed to routinely monitor faint systems () with large magnitude difference (up to ). We have thus been able to measure 21 systems containing red dwarf stars that had been poorly monitored since their discovery, from which we estimated the stellar masses thanks to Gaia measurements. We also measured the magnitude difference of the two components of 1079 double stars with an estimated error of 0.2 mag. Except for a few objects that are discussed, our measurements are in good agreement with the ephemerides computed with published orbital elements, even for the double stars whose separation is smaller than the diffraction limit. Thanks to good seeing images and with the use of high‐contrast numerical filters, we have also been able to obtain 196 measurements with an angular separation smaller than the diffraction limit of our instrumentation, and consistent with those obtained with larger telescopes. We also report measurements of the 164 new double stars that we found in the files obtained during the observations. Finally, from a study of the DR3 Gaia release, it is shown that all the objects of the Tycho Double Star Catalog that we did not resolve in 2015 are probably false detections by Tycho.

A novel mathematical approach for gravity-driven granular flows in block caving

This study presents a novel mathematical model aimed at elucidating the distinctive behavior observed in the flow of flat-bottom silos. A scheme analogous to the spot model proposed by Bazant is adopted, in which groups of particles move in relation to a static medium. However, we assume that the movement of the particles is driven by the local change in the tensional state instead of the increment of interstitial space through the diffusion of spots. We propose that the tensional state and gravity might induce a driving force with a larger magnitude than the friction exerted at the boundary of the group of mobilized particles. Thus, the dynamics of the flow is controlled by the driving and frictional force. Finally, we have introduced a dimensionless number (Y) corresponding to the ratio of driving to frictional force to characterize the movement of particles. By assuming that frictional force at the interface has a viscous component proportional to the relative speed of the mobilized particles, we have writen an equation analogous to Darcy's law for the flow of a Bingham fluid in a porous medium. The finite element method is utilized to solve the model, and the numerical findings demonstrate a strong correspondence with experimental results achieved in flat-bottom silos featuring one or two openings. Comparatively, the results of the kinematic model are surpassed, with a notable enhancement in the depiction of the velocity field.

Effects of different forms of explicit instruction on L2 development: A meta‐analysis

AbstractTo determine the effects of explicit instruction (EI) and potential moderators in second/foreign language (L2) teaching, this study meta‐analyzed 28 primary reports (a total of 67 unique samples, N = 3754). The main results show that EI was significantly effective in facilitating L2 development, with effect sizes ranging from moderate to large magnitudes (d = 1.07 and 0.81 for within‐and between‐group contrasts, respectively). Moderator analyses show that EI type, practice type, delivery mode, length and intensity of treatment, the type of outcome measures, as well as the reporting practices of the validity and reliability of outcome measures moderated differentially the effects of EI. The findings offer important pedagogical implications for teacher‐practitioners to enhance the efficacy and efficiency of EI.

Phosphine and Selenoether peri-Substituted Acenaphthenes and Their Transition-Metal Complexes: Structural and NMR Investigations.

A series of peri-substituted acenaphthene-based phosphine selenoether bidentate ligands Acenap(iPr2P)(SeAr) (L1-L4, Acenap = acenaphthene-5,6-diyl, Ar = Ph, mesityl, 2,4,6-trisopropylphenyl and supermesityl) were prepared. The rigid acenaphthene framework induces a forced overlap of the phosphine and selenoether lone pairs, resulting in a large magnitude of through-space 4JPSe coupling, ranging from 452 to 545 Hz. These rigid ligands L1-L4 were used to prepare a series of selected late d-block metals, mercury, and borane complexes, which were characterized, including by multinuclear NMR and single-crystal X-ray diffraction. The Lewis acidic motifs (BH3, Mo(CO)4, Ag+, PdCl2, PtCl2, and HgCl2) bridge the two donor atoms (P and Se) in all but one case in the solid-state structures. Where the bridging motif contained NMR-active nuclei (11B, 107Ag, 109Ag, 195Pt, and 199Hg), JPM and JSeM couplings are observed directly, in addition to the altered JPSe in the respective NMR spectra. The solution NMR data are correlated with single-crystal diffraction data, and in the case of mercury(II) complexes, they are also correlated with the solid-state NMR data and coupling deformation density calculations. The latter indicate that the through-space interaction dominates in free L1, while in the L1HgCl2 complex, the main coupling pathway is via the metal atom and not through the carbon framework of the acenaphthene ring system.

Magnetic interactions and high-field magnetotransport properties of Ge1-x-ySnxMnyTe epitaxial layers

In this work, we present the structural, magnetic and magnetotransport results of Ge1−x−ySnxMnyTe thin layers with x = 0.076–0.22 and y = 0.051–0.16. The samples were grown via molecular beam epitaxy with thickness ranging from 160 nm to 900 nm. From X-ray diffraction analysis, the layers maintain low symmetry rhombohedral crystal structure inherited from the host lattice. The rhombohedral distortion is well-maintained in alloyed layers even in the sample with the highest Sn and Mn contents, x ≈ 0.22 and y ≈ 0.051. The dc magnetic susceptibility, χdc(T) of all three layers manifests large bifurcation in the field-cooled/zero-field-cooled curves which might represent frustrated magnetic state interpreted as possible cluster-glass order. From high field magnetotransport results, a negative to positive crossover in magnetoresistance is observed for y = 0.11 at T ≈ 36 K. Furthermore, we also present a modified scaling results of anomalous Hall resistivity which displays a large magnitude, ρAH ≈ 4.9 μΩcm at T = 4.2 K for the layer with y = 0.11. The scaling results show that both skew scattering and side-jump mechanisms contribute to the anomalous Hall effect in Ge1−x−ySnxMnyTe samples however; the later seems to be dominant driving mechanism.

Body mass index and inflammation in depression and treatment-resistant depression: a Mendelian randomisation study

BackgroundMajor depressive disorder (MDD) has a significant impact on global burden of disease. Complications in clinical management can occur when response to pharmacological modalities is considered inadequate and symptoms persist (treatment-resistant depression (TRD)). We aim to investigate inflammation, proxied by C-reactive protein (CRP) levels, and body mass index (BMI) as putative causal risk factors for depression and subsequent treatment resistance, leveraging genetic information to avoid confounding via Mendelian randomisation (MR).MethodsWe used the European UK Biobank subcohort (n=451,025), the mental health questionnaire (MHQ) and clinical records. For treatment resistance, a previously curated phenotype based on general practitioner (GP) records and prescription data was employed. We applied univariable and multivariable MR models to genetically predict the exposures and assess their causal contribution to a range of depression outcomes. We used a range of univariable, multivariable and mediation MR models techniques to address our research question with maximum rigour. In addition, we developed a novel statistical procedure to apply pleiotropy-robust multivariable MR to one sample data and employed a Bayesian bootstrap procedure to accurately quantify estimate uncertainty in mediation analysis which outperforms standard approaches in sparse binary outcomes. Given the flexibility of the one-sample design, we evaluated age and sex as moderators of the effects.ResultsIn univariable MR models, genetically predicted BMI was positively associated with depression outcomes, including MDD (beta (95% CI): 0.133(0.072, 0.205)) and TRD (0.347(0.002, 0.682)), with a larger magnitude in females and with age acting as a moderator of the effect of BMI on severity of depression (0.22(0.050, 0.389)). Multivariable MR analyses suggested an independent causal effect of BMI on TRD not through CRP (0.395(0.004, 0.732)). Our mediation analyses suggested that the effect of CRP on severity of depression was partly mediated by BMI. Individuals with TRD (n=2199) observationally had higher CRP and BMI compared with individuals with MDD alone and healthy controls.DiscussionOur work supports the assertion that BMI exerts a causal effect on a range of clinical and questionnaire-based depression phenotypes, with the effect being stronger in females and in younger individuals. We show that this effect is independent of inflammation proxied by CRP levels as the effects of CRP do not persist when jointly estimated with BMI. This is consistent with previous evidence suggesting that overweight contributed to depression even in the absence of any metabolic consequences. It appears that BMI exerts an effect on TRD that persists when we account for BMI influencing MDD.

An attempt to design a universal specimen for any multiaxial loading conditions

The design of the multiaxial testing specimen is a challenging for the arbitrary loading conditions. We find that the stress of the inner thin region of biaxial/multiaxial testing specimen is not in proportion to one of the outer thick region. Therefore, a large magnitude of anisotropy in strength of the biaxial/multiaxial testing specimen may result in its failure before realizing the required stress state. Moreover, it makes the design of the multiaxial testing specimen unreliable for the arbitrary loading conditions. We have first attempted to obtain a universal design of a standard biaxial/multiaxial testing specimen for all materials which can also be employed to realize any stress state at its center, and found it impossible. Alternatively, we have adopted a typical composite material and optimized its geometry to realize widely representative stress modes at the center of a testing specimen. We have focused on obtaining the less number of biaxial/multiaxial testing specimen that can be employed for all stress modes. Overall, this work can be used as a guideline of specimen design for a reliable failure prediction of the composite structures under complex loading conditions.

Literacy Measures That Leverage the Strengths of Spanish-Speaking Latino Kindergarteners

Researchers largely rely on child language and literacy measures to determine the effectiveness of interventions for Latino dual language learners. However, some of these measures may miss certain strengths of these students. This study identified two unstandardized language and literacy tasks (IDELA food and animal vocabulary and personal narratives) that might leverage some eco-cultural assets of Latino children; it also examined concurrent associations between these tasks and standardized language and literacy tests. Participants were 237 Latino kindergarteners ( M age = 67.22 months, SD = 4.12; 51% female). Positive associations were found between standardized tests and the IDELA food and animal vocabulary ( β = 0.92–1.40; large magnitude) and personal narrative tasks ( β = 0.28–0.46; medium magnitude), controlling for important covariates, including the language of administration of assessment. Further research might use these tasks as complementary assessments to gauge the impact of interventions on the language and literacy skills of Latino dual-language learners in kindergarten.

Velocity Changes Associated to the 2019 Ambon 6.5 Mw Earthquake Using Ambient Seismic Noise

Seismic velocity changes which occurred before, during and after large magnitude earthquake carry information about damage fault surrounding the area. Research focused on Ambon 6.5 Mw earthquake on September 26, 2019. We use ambient noise cross-correlation technique to compute empirical Green’s Function between station pairs from January to December 2019. We use doublet method to determine perturbation calculated in frequency domain by using Moving Windows Cross Spectrum in frequency between 0.1 to 1.0 Hz. Our results show no obvious significant velocity change before the mainshock. Velocity fluctuation average about ±0.1% caused by non-isotropic of noise source around the area. Sudden velocity decrease occurred and reached average value of -0.35% in 7 days after mainshock. After reaching its lowest value, velocity gradually increased about +0.4% in 14 days. Velocity fluctuations about ±0.2% also occurred for three months after the earthquake which may caused by the aftershocks around the earthquake epicentre. Following the large magnitude mainshock, velocity reduction may be induced by cracks opening and fractures due to deformation. While the velocity increase may caused by post-seismic relaxation due to elastic behaviour and crack healing of the fault throughout the surrounding region.

Large magnetocaloric effect and magnetic properties of EuRhO3

We report on the structural, magnetic, and magnetocaloric properties of EuRhO3 powders. The oxidation states of Eu and Rh ions were studied using X-ray photoelectron spectroscopy (XPS). It is found that the Eu ions are mainly in the divalent oxidation state while the Rh ions have +4 state. EuRhO3 powders are found to be antiferromagnetic with a second order magnetic transition at Néel temperature (TN = 2.9 K). Analysis of the magnetic susceptibility versus temperature data in terms of the Curie–Weiss law: (χ = C/(T–θW)) for T > TN, yields θW = −3.1 K and effective magnetic moment μeffexp = 7.72 μB, which is close to the theoretical value μefftheo = 7.94 μB. The magnetic entropy change (–ΔSM), was determined by employing the thermodynamic Maxwell's relation. At μ0H = 5 T and near TN, (–ΔSMMax) and relative cooling power (RCP) exhibit large values of 33.7 J/(kg⋅K) and 238 J/kg, respectively. The large magnitude of –ΔSM and RCP show that the EuRhO3 compound could be a potential candidate to be used in cryogenic magnetic refrigeration.

Poster Session: Peripheral blur may provide the eye with a cue for the sign of defocus.

The sign of defocus is used by the retina to guide emmetropization. However, the means by which the eye determines whether light is focused in front of, or behind the retina, remains elusive. In the current study, we propose a new cue for the sign of defocus: the orientation of the anisotropic peripheral blur. Previously published [1] population averages of wavefront aberrations across the horizontal visual field in hyperopes, emmetropes and myopes were used to assess peripheral optical quality and blur orientation. Due to the large magnitudes of off-axis astigmatism and coma, the peripheral retinal image quality was dominated by anisotropic blur, whose direction was also correlated with refractive error (vertically elongated peripheral blur in myopic eyes and horizontally elongated peripheral blur in emmetropic and hyperopic eyes). The differences in groups may be due to the interaction between peripheral wavefront aberrations and globe shape (i.e. peripheral axial length). We also found an interaction between longitudinal chromatic aberration and off-axis astigmatism, wherein peripheral blur orientation is wavelength dependent, raising additional questions pertaining to the nature of chromatic cues. The orientation of peripheral blur may provide the retina with an optical cue for the sign of defocus, potentially playing an important role in emmetropization. [1] Romashchenko et al., "Peripheral refraction and higher order aberrations." Clin Exp Optom 103.1 (2020): 86-94.

Evidence of a Transient Aseismic Slip Driving the 2017 Valparaiso Earthquake Sequence, From Foreshocks to Aftershocks

AbstractFollowing laboratory experiments and friction theory, slow slip events and seismicity rate accelerations observed before mainshocks are sometimes interpreted as evidence of a nucleation phase. However, such precursory observations still remain scarce and are associated with different time and length scales, raising doubts about their actual preparatory nature. We study the 2017 Valparaiso Mw = 6.9 earthquake, which was preceded by aseismic slip accompanied by an intense seismicity, suspected to reflect its nucleation phase. We complement previous observations, which have focused only on precursory activity, with a continuous investigation of seismic and aseismic processes from the foreshock sequence to the post‐mainshock phase. By building a high‐resolution earthquake catalog and searching for anomalous seismicity rate increases compared to aftershock triggering models, we highlight an over‐productive seismicity starting within the foreshock sequence and persisting several days after the mainshock. Using repeating earthquakes and high‐rate GPS observations, we highlight a transient aseismic perturbation starting 1‐day before the first foreshock and continuing after the mainshock. The estimated slip rate over time is lightly impacted by large magnitude earthquakes and does not accelerate toward the mainshock. Therefore, the unusual seismic and aseismic activity observed during the 2017 Valparaiso sequence might be interpreted as the result of a slow slip event starting before the mainshock and continuing beyond it. Rather than pointing to a possible nucleation phase of the 2017 Valparaiso mainshock, the identified slow slip event acts as an aseismic loading of nearby faults, increasing the seismic activity, and thus the likelihood of a large rupture.

Single crystal piezoelectric motor operating with both inertia and ultrasonic resonance drives

This study presents a novel piezoelectric motor based on a single crystal material with orthorhombic mm2 symmetry class, in which piezoelectric coupling coefficients in sign and magnitude at transverse directions are different, implying that the value of d32 is positive whilst d31 is negative. The single crystal piezoceramic plate in the shape of a truncated rhombus has three conducting electrodes. While two active electrodes dividing one main surface into two equal sections, the common electrode covers the other main surface uniformly. When a signal is applied between one of the active and the common electrodes, the excited section expands and contracts with a larger magnitude. The expansion and shrinkage on one side causes an oblique movement of the side surface, on which a friction tip is attached. The oblique movement is then transferred to a moving element through frictional coupling. The proposed piezoelectric motor design is simpler and less susceptible to manufacturing tolerances as it does not rely on dimensional aspect ratios to couple two eigenmodes to get a useful movement at the friction tip of the stator. The motor can be operated both inertia (stick–slip) and resonance drive principals. In the case of sawtooth voltage excitation, the smallest motion steps are in the range of 100 nm. Using the ultrasonic excitation of both single source and dual source dual frequency resonance (DSDFR) drives, the piezoelectric motor reached a maximum no load velocity higher than 220 mm/s, and a push–pull force capacity of 2.5 N.

Littoral Drift Impoundment at a Sandbar Breakwater: Two Case Studies along the Bight of Benin Coast (Gulf of Guinea, West Africa)

This study assessed the deposition of sediment and shoreline evolution at two newly constructed port facilities in the Bight of Benin, West Africa. Based on the Building with Nature approach, the concept of a sandbar breakwater was implemented at the study sites. The coastal system of the bight is characterized by a sand barrier-lagoon system and a uniform prevailing wave climate, making it a favorable location for this innovative port solution. The case studies were undertaken at the Port of Lomé, Togo, and the Lekki Deep Sea Port (Dangote Sea Port), Nigeria, using remotely sensed shoreline positions and the one-line coastline change model for different periods. After construction of the breakwater, we estimated that the updrift coastline at the two locations accreted in the range of 10–23 m/year and the rates of sediment deposition were estimated to be in the magnitude of 1.0–7.0 × 105 m3/year. The comparative study conducted also showed that these rates could further reach a magnitude of 106 m3/year at other sediment-accreting landforms within the bight. We found that these large magnitudes of longshore sediment transport generated from very oblique incident waves (10°–20°) and sediment input from rivers (in orders of 106 m3/year) have enabled the realization of expected morphodynamic changes on the updrift shoreline of the ports. From these results, downdrift morphological changes should not be underestimated due to potential imbalances induced in the sedimentary budget along the coastline. Future developmental plans within the bight should also continuously aim to adopt nature-based solutions to protect the ecosystem while mitigating unforeseen implications.

Ultrasonographic measurements of fascicle length overestimate adaptations in serial sarcomere number.

Ultrasound-derived measurements of muscle fascicle length (FL) are often used to infer increases (chronic stretch or training) or decreases (muscle disuse or aging) in serial sarcomere number (SSN). Whether FL adaptations measured via ultrasound can truly approximate SSN adaptations has not been investigated. We casted the right hindlimb of 15 male Sprague-Dawley rats in a dorsiflexed position (i.e., stretched the plantar flexors) for 2weeks, with the left hindlimb serving as a control. Ultrasound images of the soleus, lateral gastrocnemius (LG), and medial gastrocnemius (MG) were obtained with the ankle at 90° and full dorsiflexion for both hindlimbs pre and post-cast. Following post-cast ultrasound measurements, legs were fixed in formalin with the ankle at 90°, then muscles were dissected and fascicles were teased out for measurement of sarcomere lengths via laser diffraction and calculation of SSN. Ultrasound detected an 11% increase in soleus FL, a 12% decrease in LG FL, and an 8-11% increase in MG FL for proximal fascicles and at full dorsiflexion. These adaptations were partly reflected by SSN adaptations, with a 6% greater soleus SSN in the casted leg than the un-casted leg, but no SSN differences for the gastrocnemii. Weak relationships were observed between ultrasonographic measurements of FL and measurements of FL and SSN from dissected fascicles. Our results showed that ultrasound-derived FL measurements can overestimate an increase in SSN by ∼5%. Future studies should be cautious when concluding a large magnitude of sarcomerogenesis from ultrasound-derived FL measurements, and may consider applying a correction factor. NEW FINDINGS: What is the central question of this study? Measurements of muscle fascicle length via ultrasound are often used to infer changes in serial sarcomere number, such as increases following chronic stretch or resistance training, and decreases with ageing: does ultrasound-derived fascicle length accurately depict adaptations in serial sarcomere number? What is the main finding and its importance? Ultrasound detected an ∼11% increase in soleus fascicle length, but measurements on dissected fascicles showed the actual serial sarcomere number increase was only ∼6%; therefore, measurements of ultrasound-derived fascicle length can overestimate serial sarcomere number adaptations by as much as 5%.