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Acidic macromolecules are traditionally considered key to calcium carbonate biomineralisation and have long been first choice in the bio-inspired synthesis of crystalline materials. Here, we challenge this view and demonstrate that low-charge macromolecules can vastly outperform their acidic counterparts in the synthesis of nanocomposites. Using gold nanoparticles functionalised with low charge, hydroxyl-rich proteins and homopolymers as growth additives, we show that extremely high concentrations of nanoparticles can be incorporated within calcite single crystals, while maintaining the continuity of the lattice and the original rhombohedral morphologies of the crystals. The nanoparticles are perfectly dispersed within the host crystal and at high concentrations are so closely apposed that they exhibit plasmon coupling and induce an unexpected contraction of the crystal lattice. The versatility of this strategy is then demonstrated by extension to alternative host crystals. This simple and scalable occlusion approach opens the door to a novel class of single crystal nanocomposites. Calcium carbonate biomineralisation has long been linked to acidic macromolecules. Here, the authors challenge this view and show that a huge number of gold nanoparticles coated with hydroxyl-rich proteins can be incorporated into a calcium carbonate crystal while maintaining single crystal character.

The middepth ocean circulation in the tropical Pacific is dominated by sets of alternating eastward and westward jets. The origin and transport properties of these flow features remain in many ways an open question, all the more crucial since their usual underestimation in ocean global circulation models has been identified as a potential bias for the misrepresentation of the oxygen minimum zones. In this study, we analyze the water mass properties associated with these systems of jets using velocity and hydrographic sections. Data acquired during a dedicated cruise carried out in the western part of the basin and supplemented by cross-equatorial sections from historical cruises in the central and eastern parts are analyzed. While it is confirmed that the near-equatorial jets carry oxygen anomalies, contributing to the ventilation of the eastern tropical Pacific, the data also revealed unexpected features. Tracer distributions (oxygen, salinity, and potential vorticity) show the presence of fronts extending from 500 to 3000 m and flanked by homogeneous regions. These structures define meridional staircase profiles that coincide with the alternating velocity profiles. Historical data confirm their presence in the off-equatorial deep tropical ocean with a zonal and temporal coherence throughout the basin. These observations support existing theoretical studies involving homogenization by isopycnic turbulent mixing in the formation of staircase profiles and maintenance of zonal jets. The effect of other processes on the equilibration of tracer structures is also discussed.

Quantifying physical activity and estimating the metabolic equivalent of tasks based on inertial measurement units has led to the emergence of multiple methods and data reduction approaches known as physical activity metrics. The present study aims to compare those metrics and reduction approaches based on descriptive and high order statistics. Data were obtained from 147 young healthy subjects wearing inertial measurement units at their wrist or ankle during standing, walking and running, labeled as light, medium or vigorous activities. The research question was, first, if those metrics allowed differentiating between light, moderate, and vigorous physical activities, and, secondly, what was the relationship with the metabolic equivalent of the task performed. The results showed that each metric differentiated the level of activity and presented a high correlation with the metabolic equivalent of the task. However, each metric and data reduction approach demonstrated its specific statistical characteristics related to the localization of the sensors. Our findings also confirm the absolute necessity to detail explicitly all calculus and post processing of metrics in order to quantify the level of activity by inertial measurement units.

Understanding how marine taxa will respond to near-future climate changes is one of the main challenges for management of coastal ecosystem services. Ecological studies that investigate relationships between the environment and shell properties of commercially important marine species are commonly restricted to latitudinal gradients or small-scale laboratory experiments. This paper aimed to explore the variations in shell features and growth of the edible bivalve Chamelea gallina from the Holocene sedimentary succession to present-day thanatocoenosis of the Po Plain-Adriatic Sea system (Italy). Comparing the Holocene sub-fossil record to modern thanatocoenoses allowed obtaining an insight of shell variations dynamics on a millennial temporal scale. Five shoreface-related assemblages rich in C . gallina were considered: two from the Middle Holocene, when regional sea surface temperatures were higher than today, representing a possible analogue for the near-future global warming, one from the Late Holocene and two from the present-day. We investigated shell biometry and skeletal properties in relation to the valve length of C . gallina . Juveniles were found to be more porous than adults in all horizons. This suggested that C . gallina promoted an accelerated shell accretion with a higher porosity and lower density at the expense of mechanically fragile shells. A positive correlation between sea surface temperature and both micro-density and bulk density were found, with modern specimens being less dense, likely due to lower aragonite saturation state at lower temperature, which could ultimately increase the energetic costs of shell formation. Since no variation was observed in shell CaCO 3 polymorphism (100% aragonite) or in compositional parameters among the analyzed horizons, the observed dynamics in skeletal parameters are likely not driven by a diagenetic recrystallization of the shell mineral phase. This study contributes to understand the response of C . gallina to climate-driven environmental shifts and offers insights for assessing anthropogenic impacts on this economic relevant species.

Motion is key to health and wellbeing, something we are particularly aware of in times of lockdowns and restrictions on movement. Considering the motion of humans and animals as a biomarker of the performance of the neuro-musculoskeletal system, its analysis covers a large array of research fields, such as sports, equine science and clinical applications, but also innovative methods and workplace analysis. In this Special Issue of Sensors, we focused on human and animal motion-tracking using inertial sensors. Ten research and two review papers, mainly on human movement, but also on the locomotion of the horse, were selected. The selection of articles in this Special Issue aims to display current innovative approaches exploring hardware and software solutions deriving from inertial sensors related to motion capture and analysis. The selected sample shows that the versatility and pervasiveness of inertial sensors has great potential for the years to come, as, for now, limitations and room for improvement still remain.

The carbonic anhydrase (CA; EC 4.2.1.1) superfamily is a class of ubiquitous metallo-enzymes that catalyse the reversible hydration of carbon dioxide. The α-CA family, present in all metazoan clades, is a key enzyme involved in a wide range of physiological functions including pH regulation, respiration, photosynthesis, and biocalcification. This paper reviews the evolution of the α-CA family, with an emphasis on metazoan α-CA members involved in biocalcification. Phylogenetic analyses reveal a complex evolutionary history of α-CAs, and suggest α-CA was independently co-opted into a variety of skeleton forming roles (e.g. as a provider of HCO₃⁻ions, a structural protein, a nucleation activator, etc.) in multiple metazoan lineages. This evolutionary history is most likely the result of multiple gene duplications coupled with the insertion of repetitive or non-repetitive low-complexity domains (RLCDs/LCDs). These domains, of largely unknown function, appear to be lineage-specific, and provide further support for the hypothesis of independent recruitment of α-CAs to diverse metazoan biocalcification processes. An analysis of α-CA sequences associated with biocalcification processes indicates that the domains involved in the activity and conformation of the active site are extremely conserved among metazoans.

Back mobility is a criterion of well-being in a horse. Veterinarians visually assess the mobility of a horse’s back during a locomotor examination. Quantifying it with on-board technology could be a major breakthrough to help them. The aim of this study was to evaluate the accuracy of a method of quantifying the back mobility of horses from inertial measurement units (IMUs) compared to motion capture (MOCAP) as a gold standard. Reflective markers and IMUs were positioned on the withers, eighteenth thoracic vertebra, and pelvis of four sound horses. The horses performed a walk and trot in straight lines and performed a gallop in circles on a soft surface. The developed method, based on the three IMUs, consists of calculating the flexion/extension angle of the thoracolumbar region. The IMU method showed a mean bias of 0.8° (±1.5°) (mean (±SD)) and 0.8° (±1.4°), respectively, for the flexion and extension movements, all gaits combined, compared to the MOCAP method. The results of this study suggest that the developed method has a similar accuracy to that of MOCAP, opening up possibilities for easy measurements under field conditions. Future studies will need to examine the correlations between these biomechanical measures and clinicians’ visual assessment of back mobility defects.

The development of on-board technologies has enabled the development of quantification systems to monitor equine locomotion parameters. Their relevance among others relies on their ability to determine specific locomotor events such as foot-on and heel-off events. The objective of this study was to compare the accuracy of different methods for an automatic gait events detection from inertial measurement units (IMUs). IMUs were positioned on the cannon bone, hooves, and withers of seven horses trotting on hard and soft straight lines and circles. Longitudinal acceleration and angular velocity around the latero-medial axis of the cannon bone, and withers dorso-ventral displacement data were identified to tag the foot-on and a heel-off events. The results were compared with a reference method based on hoof-mounted-IMU data. The developed method showed bias less than 1.79%, 1.46%, 3.45% and −1.94% of stride duration, respectively, for forelimb foot-on and heel-off, and for hindlimb foot-on and heel-off detection, compared to our reference method. The results of this study showed that the developed gait-events detection method had a similar accuracy to other methods developed for straight line analysis and extended this validation to other types of exercise (circles) and ground surface (soft surface).

Sit-to-stand tests are used in geriatrics as a qualitative issue in order to evaluate motor control and stability. In terms of measured indicators, it is traditionally the duration of the task that is reported, however it appears that the use of the kinetic energy as a new quantitative criterion allows getting a better understanding of musculoskeletal deficits of elderly subjects. The aim of this study was to determine the feasibility to obtain the measure of kinetic energy using magneto-inertial measurement units (MIMU) during sit-to-stand movements at various paces. 26 healthy subjects contributed to this investigation. Measured results were compared to a marker-based motion capture using the correlation coefficient and the normalized root mean square error (nRMSE). nRMSE were below 10% and correlation coefficients were over 0.97. In addition, errors on the mean kinetic energy were also investigated using Bland-Altman 95% limits of agreement (0.63 J–0.77 J), RMSE (0.29 J–0.38 J) and correlation coefficient (0.96–0.98). The results obtained highlighted that the method based on MIMU data could be an alternative to optoelectronic data acquisition to assess the kinetic energy of the torso during the sit-to-stand test, suggesting this method as being a promising alternative to determine kinetic energy during the sit-to-stand movement.

The variability of sea surface temperature (SST) in the equatorial Atlantic is characterized by strong cooling in May–June and a secondary cooling in November–December. A numerical simulation of the tropical Atlantic is used to diagnose the different contributions to the temperature tendencies in the upper ocean. Right at the equator, the coolest temperatures are observed between 20°W and 10°W due to enhanced turbulent heat flux in the center of the basin. This results from a strong vertical shear at the upper bound of the Equatorial Undercurrent (EUC). Cooling through vertical mixing exhibits a semiannual cycle with two peaks of comparable intensity. During the first peak, in May–June, vertical mixing drives the SST while during the second peak, in November–December, the strong heating due to air‐sea fluxes leads to much weaker effective cooling than during boreal summer. Seasonal cooling events are closely linked to the enhancement of the vertical shear just above the core of the EUC, which appears to be not driven directly by the strength of the EUC but by the strength and the direction of the surface current. The vertical shear is maximum when the northern branch of the South Equatorial Current is intense. The surface cooling in the eastern equatorial Atlantic is not as marked as in the center of the basin. Mean thermocline and EUC rise eastward, but a strong stratification, caused by the presence of warm and low‐saline surface waters, limits the vertical mixing to the upper 20 m and disconnects the surface from subsurface dynamics. Key Points Heat budget in a model of the tropical Atlantic Key role of vertical mixing for equatorial SST seasonal cycle Surface currents drive the shear and the turbulent heat flux