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Elastic collisions of gliders on linear air tracks are often used to explore conservation of energy and momentum. If one is interested in the glider behavior over a long time span, the analysis involves repeated collisions and is complicated by reflections from the track end stops. Here we analyze elastic collisions on a novel circular air track; since such a track lacks end stops, the mathematical analysis of repeated collisions is amenable to our students. Our analysis uncovers a variety of interesting behaviors which depend on the ratio of the glider masses. We examine periodic sequences where the gliders return to their initial conditions and progressions where (when plotted in polar coordinates) the collision positions take on the locus of a spiral. One set of initial conditions produces an "angle trap" where one glider remains within a certain angular range. We also explore making one glider's mass hypothetically negative, which results in a novel "chasing" motion. Our results were obtained using a 3D interactive simulation (created using C++ within the Unreal engine), which we make available as supplementary material. Editor's Note: Students in introductory courses often analyze one-dimensional elastic collisions between carts on wheels or gliders on an air track. If the track possesses end stops, and the system is left undisturbed after the initial contact, multiple collisions will occur. The analysis of repeated collisions can be somewhat complicated due to the end-stop reflections. In this article, the authors consider a clever simplification involving a circular track without end stops. This renders the mathematical analysis more tractable for students, and the system presents a variety of interesting behaviors to explore. Students and instructors will enjoy this entertaining application of linear algebra and can freely make use of online computer simulations provided as supplementary material. [ABSTRACT FROM AUTHOR]

A wave glider with webbed wings (WGWWs) is a new type of unmanned surface robot that combines wave energy and solar energy as its energy supply, driven by flexible webbed wings (FWWs). Wave gliders with webbed wings are already playing an important role in marine science research. Flexible webbed wings are significant components of wave gliders with webbed wings that achieve the absorption and conversion of wave energy through bidirectional fluid–structure coupling with water flow. To address the issues of large deformations and nonconvergence under the strong coupling action of flexible webbed wings, a dynamic model of flexible webbed wings is first established on the basis of an analysis of the motion principle of a wave glider with webbed wings. The Mooney–Rivlin model was subsequently applied to describe the stress–strain relationship of a rubber hyperelastic material for flexible webbed wings. By adopting the overset method and dynamic mesh technology, employing the system coupling interface based on the data interaction platform of the ANSYS Workbench, as well as mechanical and fluid solvers, the transient dynamic characteristics of fluid–structure coupling of flexible webbed wings under different working conditions are obtained. Finally, by setting different sea conditions, the influences of wave height and period on the dynamic characteristics of flexible webbed wings are analyzed. The results indicate that the greater the wave height and the smaller the wave period are, the greater the power output of the flexible webbed wings is. Additionally, the influence of the wave height ratio period on the dynamic characteristics of flexible webbed wings is more pronounced. [ABSTRACT FROM AUTHOR]

Ocean gliders are versatile and efficient passive acoustic monitoring platforms in remote marine environments, but few studies have examined their potential to monitor ship underwater noise. This study investigates a Slocum glider's capability to assess ship noise compared to the ability of fixed observers. Trials were conducted in shallow coastal inlets and deep bays in Newfoundland, Canada, using a glider, hydrophone array, and single-moored system. The study focused on (1) the glider's self-noise signature, (2) range-depth-dependent propagation loss (PL) models, and (3) identifying the location of the vessel to the glider using glider acoustic measurements. The primary contributors to the glider's self-noise were the buoyancy pump and rudder. The pitch-motor noise coincided with the buoyancy pump activation and did not contribute to the glider self-noise in our experiments. PL models showed that seafloor bathymetry and sound speed profiles significantly impacted estimates compared to models assuming flat and range-independent profiles. The glider's performance in recording ship noise was superior to that of other platforms. Using its hydrophones, the glider could identify the bearing from the vessel, although a third hydrophone would improve reliability and provide range. The findings demonstrate that gliders can characterize noise and enhance our understanding of ocean sound sources. [ABSTRACT FROM AUTHOR]

As deep learning has produced dramatic breakthroughs in many areas, it has motivated emerging studies on the combination between neural networks and cache replacement algorithms. However, deep learning is a poor fit for performing cache replacement in hardware implementation because its neural network models are impractically large and slow. Many studies have tried to use the guidance of the Belady algorithm to speed up the prediction of cache replacement. But it is still impractical to accurately predict the characteristics of future access addresses, introducing inaccuracy in the discrimination of complex access patterns. Therefore, this paper presents the LSTM-CRP algorithm as well as its efficient hardware implementation, which employs the long short-term memory (LSTM) for access pattern identification at run-time to guide cache replacement algorithm. LSTM-CRP first converts the address into a novel key according to the frequency of the access address and a virtual capacity of the cache, which has the advantages of low information redundancy and high timeliness. Using the key as the inputs of four offline-trained LSTM network-based predictors, LSTM-CRP can accurately classify different access patterns and identify current cache characteristics in a timely manner via an online set dueling mechanism on sampling caches. For efficient implementation, heterogeneous lightweight LSTM networks are dedicatedly constructed in LSTM-CRP to lower hardware overhead and inference delay. The experimental results show that LSTM-CRP was able to averagely improve the cache hit rate by 20.10%, 15.35%, 12.11% and 8.49% compared with LRU, RRIP, Hawkeye and Glider, respectively. Implemented on Xilinx XCVU9P FPGA at the cost of 15,973 LUTs and 1610 FF registers, LSTM-CRP was running at a 200 MHz frequency with 2.74 W power consumption. [ABSTRACT FROM AUTHOR]

A new dataset from oceanographic cruises in the Western Mediterranean Sea (WMED) was compiled to integrate the previously published regional data product about dissolved inorganic nutrients CNR-DIN-WMED about dissolved inorganic nutrients (https://doi.org/10.1594/PANGAEA.904172 , Belgacem et al., 2019, 2020). The Mediterranean region is experiencing rapid changes, necessitating high-quality and reliable datasets. However, the scarcity of the in-situ observations hinders the understanding of these changes and their impact on biogeochemical cycles. Dissolved oxygen is a vital component of marine ecosystems and plays a fundamental role in governing nutrient and carbon cycles, underscoring the need for accurate and reliable data. To address this, a high resolution, regional-scale data product was developed to understand decadal variability and spatial/temporal patterns of the ventilation process in the WMED. This study presents an extensive collection of unpublished dissolved oxygen data from continuous sensors collected between 2004 and 2023, along with a description of the quality assurance procedures. The quality assurance process involves calibration of CTD measurements against Winkler analyses and the comparison of deep observations with reference datasets, using the crossover analysis. The resulting data product O2WMED can be used as reference for assessing oxygen sensors mounted on biogeochemical Argo (BGC-Argo) floats or Gliders and for regional model validation. [ABSTRACT FROM AUTHOR]

Simple Summary: Sugar gliders are exotic animals that have become pets in recent years. As a result, these small marsupials are increasingly coming to the veterinary practices. Marsupials are a group of mammals characterized by their peculiar way of reproduction. This translates into the distinct anatomy of their genital apparatus, both male and female. There are not many references concerning the anatomy of this particular species. The male reproductive system of the Petaurus breviceps follows the general pattern in marsupials, but each species has its own peculiarities that the veterinary clinician should know. It includes two testes, epididymis, and deferent ducts, as well as two types of accessory glands: the prostate and the bulbourethral glands, in addition to the male urethra and the penis, which is bifid at its end. The purpose of this study was to describe the male genital gross anatomy of the sugar gliders (supplemented with some microscopic observations), to provide detailed information to veterinary clinicians to facilitate accurate diagnosis and surgery. The present study provides a detailed macroscopic examination (with some microscopic insights) of the genital apparatus of seven adult and intact male sugar gliders, as well as one castrated individual. The scrotum is pendulous and attached to the ventral abdominal wall, situated in the caudal part of the abdomen and cranial to the cloacal opening. The testes are oval shaped with their long axes oriented vertically. The epididymides are attached along the caudomedial border of their respective testes. The head and tail of the epididymides are in close proximity to the poles of the testes but are not directly attached. The deferent ducts are positioned laterally to their ipsilateral ureter as they run near the dorsal surface of the urinary bladder. The ampulla of the deferent duct is absent. The penis is located post-scrotally, lacks insertion into the bony pelvis, and has a bifid distal end. The crura of the penis originate within the ischiocavernosus muscles, and there are two bulbs of the penis. When flaccid, the entire penis is concealed in the perineal region and externalizes through an orifice situated in the ventral part of the cloaca, traversing its floor towards the cloacal opening. The urethral external orifice is positioned at the point where the bifurcation of the free part of the penis begins. The prostate gland resides in the pelvic cavity and consists of two parts: a macroscopically visible body surrounding the urethra and a microscopically identifiable portion embedded within the walls of the duct. Sugar gliders possess two pairs of bulbous bulbourethral glands, located dorsally and laterally to the rectum, but lack vesicular glands. [ABSTRACT FROM AUTHOR]

Study Design. The study included 2 fresh-frozen cadavers. Objective. To elucidate the positional relationship between surgical instruments and nerve roots during full endoscopic facet-sparing (FE fs-TLIF) and full endoscopic facet-resecting (FE fr-TLIF) transforaminal lumbar interbody fusion and propose safe instrumentation insertion procedures and recommend cage glider designs aimed at protecting nerve roots. Background. Endoscopic surgical techniques are increasingly used for minimally invasive lumbar fusion surgery, with FE fr-TLIF and FE fs-TLIF being common approaches. However, the risk of nerve root injury remains a significant concern during these procedures. Patients and Methods. Eight experienced endoscopic spine surgeons performed uniportal FE fr-TLIF and FE fs-TLIF on cadaveric lumbar spines, totaling 16 surgeries. Postoperation, soft tissues were removed to assess the positional relationship between the cage entry point and nerve roots. Distances between the cage entry point, traversing nerve root, and exiting nerve root were measured. Safe instrumentation design and insertion procedures were determined. Results. In FE fr-TLIF, the mean distance between the cage entry point and traversing nerve root was significantly shorter compared with FE fs-TLIF (3.30 ± 1.35 vs. 8.58 ± 2.47 mm, respectively; P < 0.0001). Conversely, the mean distance between the cage entry point and the exiting nerve root was significantly shorter in FE fs-TLIF compared with FE fr-TLIF (3.73 ± 1.97 vs. 6.90 ± 1.36 mm, respectively; P < 0.0001). For FE fr-TLIF, prioritizing the protection of the traversing root using a 2-bevel tip cage glider was crucial. In contrast, for FE fs-TLIF, a single-bevel tip cage glider placed in the caudal location was recommended. Conclusion. This study elucidates the anatomic relationship between cage entry points and nerve roots in uniportal endoscopic lumbar fusion surgery. Protection strategies should prioritize the traversing root in FE fr-TLIF and the exiting root in FE fs-TLIF, with corresponding variations in surgical techniques. Level of Evidence. Level V. [ABSTRACT FROM AUTHOR]

In May 2018, an unprecedented long and intense seismic-volcanic crisis broke out off the island of Mayotte (Indian Ocean) and was associated with the birth of an underwater volcano (Fani Maoré). Since then, an integrated observation network has been created (REVOSIMA), with the given objective of monitoring and better understanding underwater volcanic phenomena. Recently, an unmanned submarine glider (SeaExplorer glider) has been deployed to supplement the data obtained during a series of oceanographic surveys (MAYOBS) carried out on an annual basis. Operated by ALSEAMAR, the glider performed a continuous monitoring of 30 months of the water column from the sea surface to 1250 meters water depth with the objective to acquire hydrological properties, water currents and dissolved gas concentrations. This monitoring already showed that it is feasible and valuable to measure autonomously, continuously and at a high spatio-temporal scale, physical (temperature, salinity, ocean current) and biogeochemical parameters (O 2, CH 4, CO 2, bubbles/droplets, vertical speeds anomalies related to droplets) over several months from a glider. In particular, innovating sensing capabilities (e.g., MINICO2, ADCP) have shown a great potential in the context of the Mayotte seismic volcano crisis, despite technical challenges (complex algorithms, sensor capabilities, etc.). [ABSTRACT FROM AUTHOR]

Autonomous underwater vehicles are increasingly frequently used in the fields of ocean observation, data collection, and tactical surveillance. Underwater navigation and near real-time communication are the most important factors limiting the performance of these vehicles. In this article, an underwater acoustic communication and positioning system (UACPS) based on heterogeneous gliders is presented. The system consists of an acoustic wave glider and an acoustic underwater glider, and includes an ultrashort baseline and an acoustic modem. The program and communication protocol of the communication and positioning algorithm are independently developed, and the hardware circuit design of the communication and ultra-short baseline positioning, as well as the embedded surface wave gliders and gliders are independently implemented. Sea trial results indicate that the communication distance of the system is more than 3 km and the positioning error is less than 5%. With the further improvement of system performance, the low cost, long time, long distance and near real-time communication characteristics of our UACPS can be used to integrate multiple autonomous unmanned platforms as part of intelligent surveillance robot networks. [ABSTRACT FROM AUTHOR]

The South Scotia Ridge, in the Atlantic sector of the Southern Ocean, is a key region for water mass modification. It is the location of the Weddell‐Scotia Confluence, an area of reduced stratification which separates the Weddell Gyre to the south and the Antarctic Circumpolar Current to the north, and which receives input of shelf waters from the tip of the Antarctic Peninsula. To elucidate the transformations over the ridge, we focus on one of its largest seamounts, Discovery Bank, which has previously been observed as hosting a stratified Taylor column that retains water for months to years, during which time water masses are entrained from north and south of the Weddell Front and steadily mixed. Data from ship‐deployed sensors and autonomous platforms are analyzed to quantify and understand the diapycnal mixing, heat fluxes and water mass transformations over the bank. Ocean glider and free‐profiling drifting float data show that the mid‐depth temperature maximum of the Circumpolar Deep Water (CDW) is eroded between the northern and southern sides of the bank, while diapycnal diffusivity is enhanced by up to an order‐of‐magnitude over its steeply sloping portions. This is accompanied by heat fluxes from the CDW layer being increased by up to a factor of six, which may contribute to a reduction in mid‐depth stratification. Tidal model analysis shows that the southern side of the bank hosts strong barotropic to baroclinic energy conversion (>150 N m−2), emphasizing the role of internal tides in modulating water mass transformations in the Confluence. Plain Language Summary: The Weddell‐Scotia Confluence region, in the South Atlantic sector of the Southern Ocean, is a zone where ocean waters from the Antarctic Circumpolar Current to the north, the Weddell Sea to the south, and the Antarctic Peninsula to the west, come together and interact. In this paper, observations from a research ship, an autonomous underwater glider, and free‐drifting ocean floats are used to characterize the mixing between these different sources of water, and to understand what impact this mixing has on the downstream vertical structure of the water column. The results show that an anticlockwise circulation of waters occurs around a large underwater seamount in the region, causing the waters there to be trapped for months to years. In addition, interaction with the steeply sloping undersea topography generates particularly strong mixing between these different waters through the action of tides, which helps to sustain the characteristic low vertical density gradients present in the region. These processes have important implications for both the movement of mid‐depth waters south into the circulation of the Weddell Sea, and likely also for the supply of nutrients to the productive surface layer of the ocean. Key Points: New observations reveal enhanced mixing rates and mid‐depth heat fluxes over one of the largest seamounts of the South Scotia RidgeThis enhanced mixing may help to sustain the mid‐depth stratification minimum found in the Weddell Scotia ConfluenceResults from a tidal model show high rates of barotropic to baroclinic tidal energy conversion over steeply sloping parts of the bank [ABSTRACT FROM AUTHOR]

Altered fire regimes and the increased frequency and/or severity of wildfires are significant issues for fire‐sensitive species. In the Austral summer of 2019/2020, Australia experienced one of the worst fire seasons in recorded history (known as the 2019/2020 megafires), affecting 12.6 million hectares of eastern Australia. The Endangered southern greater glider (Petauroides volans) inhabits large areas impacted by the 2019/2020 megafires. With increasing fire severity, frequency, and intensity, there is a need to understand where in the landscape southern greater gliders are most impacted by fire, and where the species is most likely to persist in fire‐affected landscapes. This is challenging given the lack of systematic data collected for this species. Maximum entropy modelling (Maxent) is a type of species distribution model with good predictive performance for presence‐only records. We used Maxent to model the distribution of the southern greater glider in the two years prior (2017–2019) and two years post (2020–2022) megafire across the East Gippsland region of Victoria, an area heavily affected by the 2019/2020 megafires. Whilst we found that the predicted short‐term area of occurrence of the southern greater glider remained relatively stable in the two years after megafire, a large area of marginal habitat was considerably reduced. We interpret this result as a potential contraction of suitable habitat where southern greater gliders may become isolated. Post fire, higher elevation areas and locations that experienced comparatively lower fire severity and a lower fire frequency had a higher predicted occurrence of the southern greater glider. Understanding the role of fire in species survival is essential for effective biodiversity conservation and management of species. More comprehensive and systematic monitoring in suitable and unsuitable areas will enhance our understanding of the distribution of the southern greater glider, including areas subject to wildfire. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) is one of the most important drivers of ocean biogeochemical cycles and marine life, and in many areas its concentration has declined due to climate change. In recent decades, a growing number of autonomous oceanographic platforms has been equipped with sensors for direct in situ measurements of oxygen levels. However, to ensure high quality and comparable data, these observations need to be validated or, if necessary, corrected. In this paper, we compiled all the available DO data collected by Argo floats and gliders in the South Adriatic Pit (Mediterranean Sea) between 2014 and 2020. This dataset includes data for which it was not possible to apply conventional quality-control methods. Therefore, we had to apply tailored procedures based on well-established best practices for correction. The aim is to showcase how these tailored procedures allowed us to achieve the best possible quality of data and generate consistent datasets. The drift of the glider DO sensors related to storage was also estimated. The described procedure could be useful in similar cases where the conventional methods are not viable, thus making available potentially useful data. [ABSTRACT FROM AUTHOR]

A 7-y-old, castrated male, leucistic sugar glider (Petaurus breviceps) was presented because of a progressive history of lethargy, ataxia, diarrhea, and anorexia. Abdominal ultrasound revealed fluid in the abdomen and an infiltrative mass in the liver. Due to a poor prognosis, euthanasia was performed. Postmortem examination revealed a focally extensive, infiltrative, off-white, firm mass in the liver with adhesion to the omentum, mesentery, gastric serosa, and diaphragm. The remaining hepatic parenchyma was diffusely yellow. Histologically, the hepatic mass was consistent with metastatic cholangiocarcinoma (cholangiocellular carcinoma) with proliferation of neoplastic epithelial cells surrounded by marked desmoplasia. Neoplastic cells expanded and infiltrated the adjacent omentum, mesentery, and the serosal surfaces of the stomach, kidney, and small and large intestines. To our knowledge, cholangiocarcinoma has not been reported previously in a sugar glider. [ABSTRACT FROM AUTHOR]

Bats are the only mammals capable of powered flight and have correspondingly specialized body plans, particularly in their limb morphology. The origin of bat flight is still not fully understood due to an uninformative fossil record but, from the perspective of a functional transition, it is widely hypothesized that bats evolved from gliding ancestors. Here, we test predictions of the gliding-to-flying hypothesis of the origin of bat flight by using phylogenetic comparative methods to model the evolution of forelimb and hindlimb traits on a dataset spanning four extinct bats and 231 extant mammals with diverse locomotor modes. Our results reveal that gliders exhibit adaptive trait optima (1) toward relatively elongate forelimbs that are intermediate between those of bats and non-gliding arborealists, and (2) toward relatively narrower but not longer hindlimbs that are intermediate between those of non-gliders and bats. We propose an adaptive landscape based on limb length and width optimal trends derived from our modeling analyses. Our results support a hypothetical evolutionary pathway wherein glider-like postcranial morphology precedes a bat-like morphology adapted to powered-flight, setting a foundation for future developmental, biomechanical, and evolutionary research to test this idea. [ABSTRACT FROM AUTHOR]

In this study, we exploit autonomous underwater glider data to infer internal-tide dynamics south of New Caledonia, an internal-tide-generation hot spot in the southwestern tropical Pacific. By fitting a sinusoidal function to vertical displacements at each depth using a least-squares method, we simultaneously estimate diurnal and semidiurnal tides. Our analysis reveals regions of enhanced tidal activity, strongly dominated by the semidiurnal tide. To validate our findings, we compare the glider observations to a regional numerical simulation that includes tidal forcing. This comparison assesses the simulation's realism in representing tidal dynamics and evaluates the glider's ability to infer internal-tide signals and their signature in sea surface height (SSH). The glider observations and a pseudo glider, simulated using hourly numerical model output with identical sampling, exhibit similar amplitude and phase characteristics along the glider track. Existing discrepancies are in large part explained by tidal incoherence induced by eddy–internal-tide interactions. We infer the semidiurnal internal-tide signature in steric SSH by the integration of vertical displacements. Within the upper 1000 m, the pseudo glider captures roughly 78 % of the steric SSH total variance explained by the full water column signal. This value increases to over 90 % when projecting the pseudo glider's vertical displacements onto climatological baroclinic modes and extrapolating to full depth. Notably, the steric SSH from glider observations aligns closely with empirical estimates derived from satellite altimetry, highlighting the internal tide's predominant coherent nature during the glider's sampling. [ABSTRACT FROM AUTHOR]

Despite major economic and technological advances, much of the ocean remains unexplored, which has led to the use of remotely operated vehicles (ROVs) and gliders for surveying. ROVs and underwater gliders are essential for ocean data collection. Gliders, which control their own buoyancy, are particularly effective unmanned platforms for long-term observations. The traditional method of recovering the glider on a small boat is a risky operation and depends on the skill of the workers. Therefore, a safer, more efficient, and automated system is needed to recover them. In this study, we propose a lightweight artificial neural network for underwater glider detection that is efficient for learning and inference. In order to have a smaller parameter size and faster inference, a convolutional neural network (CNN) vision encoder in an artificial neural network splits an image of a glider into a number of elongated patches that overlap to better preserve the spatial information of the pixels in the horizontal and vertical directions. Global max-pooling, which computes the maximum over all the spatial locations of an input feature, was used to activate the most salient feature vectors at the end of the encoder. As a result of the inference of the glider detection models on the test dataset, the average precision (AP), which indicates the probability that an object is located within the predicted bounding box, shows that the proposed model achieves AP = 99.7%, while the EfficientDet-D2 model for comparison of detection performance achieves AP = 69.2% at an intersection over union (IOU) threshold of 0.5. Similarly, the proposed model achieves an AP of 78.9% and the EfficientDet-D2 model achieves an AP of 50.5% for an IOU threshold of 0.75. These results show that accurate prediction is possible within a wide range of recall for glider position inference in a real ocean environment. [ABSTRACT FROM AUTHOR]

The diurnal variability of mixed layer (ML) overturning instabilities remains poorly understood due to the challenge in capturing their rapid evolutions across large spatiotemporal ranges. Using high‐resolution data from 52 gliders in the South China Sea, we examine the diurnal modulations of ML overturning instabilities. The results of the 3‐month field observation show that negative potential vorticity occupies ∼16% of the ML and facilitates several types of forced overturning instabilities, especially symmetric instability (SI). Surface heat fluxes are identified to primarily modulate the diurnal variability of these overturning cells, where nighttime surface cooling is found to energize SI with an ∼2‐hr phase lag. As a result, over 60% of forced submesoscale overturning cells tend to restratify the ML at night. These findings quantitatively highlight the modulation of diabatic atmospheric forcing in submesoscale restratification, which should be considered in submesoscale parameterizations of ocean and climate models. Plain Language Summary: The diurnal cycle of submesoscale motions has been explored in high‐resolution simulations and observations, but the understanding for the variability of associated overturning instability remains limited. Here, we present new observational evidence of the diurnal variability of forced overturning instabilities using high‐resolution data from a 3‐month glider array observation. The results show that this diurnal variability is primarily modulated by surface heat fluxes rather than wind friction. Among the identified instabilities, symmetric instability is significantly energized by the surface cooling and tends to drive stronger submesoscale restratification at night. Given their frequent occurrence in the upper ocean, enhanced submesoscale vertical exchange due to nighttime surface cooling may play an important role in oceanic mixed layer restratification, potentially modulating the climate system and marine ecosystem. Key Points: New evidence for the diurnal variability of mixed layer (ML) overturning instabilities is provided by a glider array observationSurface heat fluxes are found to primarily modulate the diurnal variability of ML overturning cells in the realistic oceanMore than 60% of observed submesoscale overturning cells are energized by nighttime surface cooling and act to restratify the ML [ABSTRACT FROM AUTHOR]

This work deals with gliding motion of bacteria over a non-Newtonian slime layer attached to a solid substrate. The surface of a glider is approximated with a simple wavy two-dimensional sheet while the sticky slime is modeled as Carreau–Yasuda fluid. The classical Navier–Stokes equations are transformed by using Galilean transformation and dimensionless variables. Flow beneath the organism is creeping and the lubrication assumption is also valid in this scenario, hence the equation is reduced to fourth-order BVP in terms of stream function. The basic purpose is to compute the gliding speed and flow rate of the slime which are present in the boundary conditions. MATLAB built-in bvp5c solver is utilized to calculate the numerical solution of the stream function. Further, unknowns (flow rate and cell speed) are refined by using modified Newton–Raphson method (MNRT). Further, these pairs are employed in the formula of energy expended. Velocity and stream function is also plotted for these computed pairs. This study is motivated by scientific interest and the desire to understand the dynamics of gliding bacteria. The findings of this study are thought to be beneficial in the development of artificial crawlers. [ABSTRACT FROM AUTHOR]

Thermal soaring, a technique used by birds and gliders to utilize updrafts of hot air, is an appealing model-problem for studying motion control and how it is learned by animals and engineered autonomous systems. Thermal soaring has rich dynamics and nontrivial constraints, yet it uses few control parameters and is becoming experimentally accessible. Following recent developments in applying reinforcement learning methods for training deep neural-network (deep-RL) models to soar autonomously both in simulation and real gliders, here we develop a simulation-based deep-RL system to study the learning process of thermal soaring. We find that this process has learning bottlenecks, we define a new efficiency metric and use it to characterize learning robustness, we compare the learned policy to data from soaring vultures, and find that the neurons of the trained network divide into function clusters that evolve during learning. These results pose thermal soaring as a rich yet tractable model-problem for the learning of motion control. Thermal soaring, inspired by gliding birds, is an appealing model behavior for understanding motion control and how it is learned by animals and engineered autonomous systems. The authors propose a deep reinforcement learning framework to study the learning process of thermal soaring under horizontal wind conditions. [ABSTRACT FROM AUTHOR]

Blended-wing-body underwater gliders (BWBUGs) are a new generation of underwater vehicles that have been successfully applied to long-range missions. It is generally recognized that shapes with a high aspect ratio have a higher lift–drag ratio (LDR) and superior fluid performance. However, the pursuit of higher LDR cannot achieve the optimal overall performance, and there are complex design factors. It is necessary but difficult to conduct a thorough examination of shape layout, energy-carrying and other issues. In this article, the layout and energy models are established, and the causal graph is used as a multidisciplinary analysis method to show the interaction between system variables. A shape design method based on surrogate models and causal graphs is proposed that incorporates knowledge into optimization by combing the information flow and finding the relationship between variables. The results show that causal-assisted optimization can mine the characteristics of variables and discover more valuable shape designs. [ABSTRACT FROM AUTHOR]

This study evaluates the feasibility of applying the Estimating the Circulation and Climate of the Ocean (ECCO) data assimilation (DA) framework to a submesoscale-resolving model [Massachusetts Institute of Technology General Circulation Model (MITgcm), at 1-km grid resolution]. This is in preparation for future studies to understand and assimilate the novel swath measurements of sea surface height from the Surface Water and Ocean Topography (SWOT) satellite mission. The model domain is centered at the SWOT calibration/validation (CalVal) site, located 300 km offshore of Monterey Bay, California. We assimilate vertical profiles of temperature and salinity from a linear array of three SWOT prelaunch CalVal moorings, between September and December 2019. Two model solutions are analyzed: 1) a nonassimilating forward simulation termed "first-guess" and 2) an optimized solution that assimilates the in situ observations. Both runs are nested within the global 1/12° Hybrid Coordinate Ocean Model that uses Navy Coupled Ocean Data Assimilation (HYCOM/NCODA) analysis. We evaluate the performance by comparing the two model solutions against assimilated and withheld in situ observations. We show that by assimilating hydrographic data, the model performance over the first-guess solution is improved with an error-to-observation reduction of 30%–45% for temperature, 14%–41% for salinity, and 44%–56% for steric height. Over the study period, the average steric height error at the three assimilated moorings was 1.27 cm for the optimized solution versus 2.6 cm for the first-guess solution. A comparison to withheld glider observations shows that the optimized solution outperforms the first-guess solution with an error-to-observation reduction of approximately 38% in steric height (1.5 versus 2.4 cm). This study indicates, for the first time, that the MITgcm–ECCO framework can be successfully applied to the reconstruction of submesoscale ocean variability, via the nesting of a high-resolution regional domain into a global outer domain. [ABSTRACT FROM AUTHOR]

Polar systems are experiencing major changes that has significant implications for ocean circulation and global biogeochemistry. While these changes are accelerating, access to polar systems is decreasing as ships and logistical capabilities are declining. Autonomous underwater buoyancy gliders have proven to be robust technologies that are capable of filling sampling gaps. Gliders have also provided a more sustained presence in polar seas than ships are able. Along the West Antarctic Peninsula, one of the most rapidly warming regions on this planet, gliders have proven to be a useful tool being used by the international community to link land research stations without requiring major research vessel ship support. The gliders are capable of adaptive sampling of subsurface features not visible from satellites, sustained sampling to characterize seasonal dynamics, and they increasingly play a central role in themanagement of natural resources. Future challenges to expand their utility include: (A) developing robust navigation under ice, which would allow gliders to provide a sustained bridge between the research stations when ship support is declining, and (B) expanding online resources to provide the international community open access to quality data in near real time. These advances will accelerate the use of gliders to fill critical sampling gaps for these remote ocean environments. [ABSTRACT FROM AUTHOR]

The rapid acquisition of flow field characterization information is crucial for closed-loop active flow control. The proper orthogonal decomposition (POD) method is a widely used flow field downscaling modeling method to obtain flow characteristics effectively. Based on the POD method, a flow field reduced-order model (ROM) is constructed in this paper for the flow field control of a hydrofoil of a blended-wing-body underwater glider (BWB-UG) with stabilized suction and blowing forces. Compared with the computational fluid dynamics (CFD) simulation, the computational time required to predict the target flow field using the established POD-ROM is only about 0.1 s, which is significantly less than the CFD simulation time. The average relative error of the predicted surface pressure is not more than 6.9%. These results confirm the accuracy and efficiency of the POD-ROM in reconstructing flow characteristics. The timeliness problem of fast flow field prediction in BWB-UG active flow control is solved by establishing a fast prediction model in an innovative way. [ABSTRACT FROM AUTHOR]

Actuators based on soft elastomers offer significant advantages to the field of robotics, providing greater adaptability, improving collision resilience, and enabling shape‐morphing. Thus, soft fluidic actuators have seen an expansion in their fields of application. Closed‐cycle hydraulic systems are pressure agnostic, enabling their deployment in extremely high‐pressure conditions, such as deep‐sea environments. However, soft actuators have not been widely adopted on unmanned underwater vehicle control surfaces for deep‐sea exploration due to their unpredictable hydrodynamic behavior when camber‐morphing is applied. This study presents the design and characterization of a soft wing and investigates its feasibility for integration into an underwater glider. It is found that the morphing wing enables the glider to adjust the lift‐to‐drag ratio to adapt to different flow conditions. At the operational angle of attack of 12.5°, the lift‐to‐drag ratio ranges from −70% to +10% compared to a rigid version. Furthermore, it reduces the need for internal moving parts and increases maneuverability. The findings lay the groundwork for the real‐world deployment of soft robotic principles capable of outperforming existing rigid systems. With the herein‐described methods, soft morphing capabilities can be enabled on other vehicles. [ABSTRACT FROM AUTHOR]

A wave glider is an ocean observation platform that utilizes wave energy to drive and solar energy to power. Its metal structure will generate related electromagnetic fields due to corrosion and underwater motion. In the detection of weak electromagnetic field signals underwater, its own electromagnetic field characteristics will have an impact on signal detection. To study the applicability of electric field sensors and magnetic field sensors on wave glider platforms, the structural characteristics of the wave glider were analyzed, and the installation positions of electric field sensors and magnetic field sensors were designed based on the different motion states of the water surface mother body and underwater towing body. The measured electromagnetic field data of the wave glider platform were measured, and the measured data were analyzed. It was determined that the interference electric field energy under typical working conditions of the wave glider was mainly concentrated within 1 Hz, which decreased with increasing frequency, and the magnitude was mV/m. The magnitude of the interference magnetic field is several tens of nT, indicating that the electromagnetic field interference is significant during the working state of the wave glider. Installing an electric field sensor directly at the bottom of the wave glider will cause significant noise interference, while installing the magnetic field sensor directly at the bottom of the tractor will affect the servo and the shaking-induced magnetic field. Moreover, wave gliders should not use electric field signals below 1 Hz as signal sources, but they can utilize axial frequency electromagnetic fields to detect weak electromagnetic signals underwater. [ABSTRACT FROM AUTHOR]

Objectives: The article's aim is to test if rotary or reciprocating glide path influences the overall performance of WaveOne Gold in S-shaped canals. Methods: Sixty endo training blocks with an S-shape curvature were divided into three groups based on the glide path method used: no glide path; glide path preparation with ProGlider; glide path preparation with WaveOne Gold Glider. All blocks were then shaped with WaveOne Gold Primary. The time for shaping, the incidence in reaching working length and the number of pecking motions were recorded. ANOVA with Turkey's test was used, and the p-value was set to 0.05. Results: WaveOne Gold Primary reached working length faster in the control group when comparing total working times. No significant differences in the ability of the WaveOne Gold Primary to reach working length in all groups (p > 0.05). The mean number of pecking motions was higher in the control group compared to other groups. Conclusions: No significant differences in the time needed to achieve a glide path between Proglider and WaveOne Gold Glider. WaveOne Gold Primary can shape a double curved canal faster if a glide path is present but takes less time to reach length if it is the only file used. No difference in the ability to reach working length. [ABSTRACT FROM AUTHOR]

The West Antarctic Ice Sheet is experiencing rapid thinning of its floating ice shelves, largely attributed to oceanic basal melt. Numerical models suggest that the Bellingshausen Sea has a key role in setting water properties in the Amundsen Sea and further downstream. Yet, observations confirming these pathways of volume and tracer exchange between coast and shelf break and their impact on inter‐sea exchange remain sparse. Here we analyze the circulation and distribution of glacial meltwater at the boundary between the Bellingshausen Sea and the Amundsen Sea using a combination of glider observations from January 2020 and hydrographic data from instrumented seals. Meltwater distributions over previously unmapped western regions of the continental shelf and slope reveal two distinct meltwater cores with different optical backscatter properties. At Belgica Trough, a subsurface meltwater peak is linked with hydrographic properties from Venable Ice Shelf. West of Belgica Trough, the vertical structure of meltwater concentration changes, with peak values occurring at greater depths and denser isopycnals. Hydrographic analysis suggests that the western (deep) meltwater core is supplied from the eastern part of Abbot Ice Shelf, and is exported to the shelf break via a previously‐overlooked bathymetric trough (here named Seal Trough). Hydrographic sections constructed from seal data reveal that the Antarctic Coastal Current extends west past Belgica Trough, delivering meltwater to the Amundsen Sea. Each of these circulation elements has distinct dynamical implications for the evolution of ice shelves and water masses both locally and downstream, in the Amundsen Sea and beyond. Plain Language Summary: Floating ice shelves in West Antarctica are thinning, which is largely due to melting of the ice shelf base by the ocean. Here, measurements of ocean temperature, salinity, and dissolved oxygen, collected by a remotely‐controlled underwater vehicle (a glider), are used to estimate the amount of ice shelf meltwater released in the Bellingshausen Sea. Distinct cores of meltwater can be distinguished by the amount of suspended material that is present in the water, which we attribute to meltwater following different circulation pathways after entering the ocean. Historical data from seals equipped with temperature and salinity sensors provide additional information about how the meltwater circulates in the region. The seal data show the presence of a narrow coastal current that brings meltwater from the Bellingshausen Sea into the Amundsen Sea. The pathways of meltwater revealed in this study suggest an important influence of the Bellingshausen Sea on ice shelves throughout West Antarctica. Key Points: Hydrographic observations identify both shelf‐break and coastal meltwater pathways from the western Bellingshausen Sea into the Amundsen SeaDifferences in optical backscatter properties associated with meltwater are related to distinct coast‐to‐shelf break pathwaysThe main pathway to the shelf break is via Seal Trough, identified as the de facto western boundary of the Bellingshausen Sea [ABSTRACT FROM AUTHOR]

The sub‐seasonal CO2 flux (FCO2) variability across the Southern Ocean is poorly understood due to sparse observations at the required temporal and spatial scales. Twinned surface and profiling gliders experiments were used to investigate how storms influence FCO2 through the air‐sea gradient in partial pressure of CO2 (ΔpCO2) in the sub‐Antarctic zone. Winter‐spring storms caused ΔpCO2 to weaken (by 22–37 μatm) due to mixing/entrainment and weaker stratification. This weakening in ΔpCO2 was in phase with the increase in wind stress resulting in a reduction of the storm‐driven CO2 uptake by 6%–27%. During summer, stronger stratification explained the weaker sensitivity of ΔpCO2 to storms, instead temperature changes dominated the ΔpCO2 variability. These results highlight the importance of observing synoptic‐scale variability in ΔpCO2, the absence of which may propagate significant biases to the mean annual FCO2 estimates from large‐scale observing programmes and reconstructions. Plain Language Summary: The sub‐Antarctic zone of the Southern Ocean is a region that mostly experiences carbon dioxide (CO2) uptake because of its low temperature, strong winds and lower CO2 content. The wind can influence the CO2 uptake through two pathways: the speed of CO2 transfer between the air‐sea interface (kw) and the difference in CO2 concentration in the surface ocean and overlying atmosphere (ΔpCO2). Using autonomous robots that can measure hourly air and water conditions simultaneously, we show that not resolving ΔpCO2 during a storm event can lead to overestimating the CO2 uptake. This is particularly important during winter and spring when the ocean's surface layers are less stratified. The warmer temperatures during summer meant a more stratified surface layer resulting in a weaker and delayed impact of storms on the ΔpCO2. This study shows that the various annual CO2 uptake estimation methods used by the research community should not neglect ΔpCO2 responses during storms. Key Points: Hourly glider observations show that the impact of storms on both kw and ΔpCO2 simultaneously modulates the ocean CO2 uptake variabilityWinter‐spring storms weaken ΔpCO2 through enhanced entrainment and mixing, partially counteracting the increase in CO2 uptake due to kw aloneBy not accounting for the storm‐linked positive feedback in ΔpCO2, the cumulative seasonal CO2 uptake was found to be overestimated by ∼6% [ABSTRACT FROM AUTHOR]

Determination of the glide path is recommended before using rotary instruments. This study aimed to evaluate the dynamic cyclic fatigue resistance of new and used glider rotary instruments in up to 6 root canals. Seventy-two TruNatomy Glider files were used for the preparation of root canals of extracted lower molars, which were then submitted to the dynamic cyclic fatigue test carried out in a curved metallic artificial canal. The instruments were divided into 4 groups (n = 18): Control group, new instruments without any use in the root canal; Group 2U, instruments used in 2 mesial canals; Group 4U, instruments used in 4 mesial canals; Group 6U, instruments used in 6 mesial canals. The time to failure (TF) of the instrument was recorded, and the number of cycles to failure (NCF) was calculated. The data were submitted to 1-way analysis of variance and to the Games-Howell test for multiple comparisons, adopting a significance level of 5%. TF and NCF were significantly affected by the number of file uses. The Games-Howell test revealed that TF and NCF were significantly greater in the control group than in Group 4U. In Group 2U, TF and NCF were intermediate and not significantly different from the control group. Group 6U had significantly lower TF and NCF than all other groups. The TruNatomy Glider can be used as a glide path for up to 2 mesial canals of mandibular molars, whereas its use on 4 or 6 root canals is not suggested. [ABSTRACT FROM AUTHOR]

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Engaging with the engineering design process can capture students' curiosity and serve as motivation to do, and learn, more. Set in a fourth-grade classroom, this article shares a fun way to introduce students to the engineering design process. Capturing students' attention by using a video of a real-life stow-away cat, students are challenged to make a glider out of common household supplies and help the stow-away cat land safely. Embedded in the three-day activity are some of the essential engineering practices and the opportunity to practice measuring and data collection. Throughout the experience, students are encouraged to examine how their glider performed and collaboratively brainstorm how the design can be improved. Students work in pairs to complete the task while the teacher assesses both informally and using a holistic teacher-created rubric. Ideas for differentiating to meet students' needs are shared. [ABSTRACT FROM AUTHOR]

As one of the most vocal marsupials in Australia, conservation of the yellow-bellied glider (Petaurus australis brevirostrum) (YBG) could benefit from the extraction of more information from their calls during acoustic monitoring. This pilot study investigates the variability of syllable components of full calls and identifies acoustic parameters that underlie variability in recorded calls from wild YBGs in North Queensland, Australia. Full calls with three syllables and with two syllables were distinguished. Using batch correlations and principal component analyses (PCAs), it was found that syllable two and syllable three show high variability in their duration and that maximum frequency is the strongest contributing sound parameter to the observed variability. However, because data collection was done in wild populations, the identity of call emitters remained unknown during call analyses, demanding further studies. Further subdivision of calls, and investigation into further acoustic parameters, could aid in decoding sexual, seasonal and individual-based meanings of calls. In Far North Queensland, passive acoustic monitoring has been used to study the yellow-bellied glider, a species threatened by habitat loss and fragmentation. However, because this species is very vocal, it is likely that more information – related to gender, season or individual-specific parameters – can be extracted from its calls. We present an attempt to analyse acoustic parameters and their variability in components of full calls of this species as a basis for more meaningful acoustic monitoring. [ABSTRACT FROM AUTHOR]

The recent and still controversial claim of phosphine detection in the venusian atmosphere has reignited consideration of whether microbial life might reside in its cloud layers. If microbial life were to exist within Venus' cloud deck, these microorganisms would have to be multi-extremophiles enclosed within the cloud aerosol particles. The most straightforward approach for resolving the question of their existence is to obtain samples of the cloud particles and analyze their interior. While developing technology has made sophisticated in situ analysis possible, more detailed information could be obtained by examining samples with instrumentation in dedicated ground-based facilities. Ultimately, therefore, Venus Cloud-level Sample Return Missions will likely be required to resolve the question of whether living organisms exist in the clouds of Venus. Two multiphase mission concepts are currently under development for combining in situ analyses with a sample return component. The Venus Life Finder architecture proposes collection of cloud particles in a compartment suspended from a balloon that floats for weeks at the desired altitude, while the Novel solUtion for Venus explOration and Lunar Exploitation (NUVOLE) concept involves a glider that cruises within the cloud deck for 1200 km collecting cloud aerosol particles through the key regions of interest. Both architectures propose a rocket-driven ascent with the acquired samples transported to a high venusian orbit as a prelude to returning to Earth or the Moon. Both future conceptual missions with their combined phases will contribute valuable information relative to the habitability of the clouds at Venus, but their fulfillment is decades away. We suggest that, in the meantime, a simplification of a glider cloud-level sample collection scenario could be accomplished in a shorter development time at a lower cost. Even if the cloud particles are not organic and show no evidence of living organisms, they would reveal critical insights about the natural history and evolution of Venus. [ABSTRACT FROM AUTHOR]

We examined the changes in the ocean’s upper layer structure involved in the formation of the subtropical mode water in the South Atlantic. Here we present the results from a survey done in the region of formation between 37°W and 32°W and 34°S and 37°S from July–October 2018, using high-resolution measurements obtained from an underwater glider. From its records, the mode water development was observed for the first time in the South Atlantic as localized chimney-like patterns in the temperature, salinity, and potential vorticity (PV) measurements with a horizontal scale of (7 ± 2) km, associated with wintertime oceanic convective processes. Over time, these submesoscale structures tend to expand and dominate the region as a large volume of mode water. These vertical structures present highly homogeneous temperature and salinity values. The observed PV was on the order of 5.0 × 10−11 m−1 s−1, which is one order of magnitude smaller than the pre-existent mode water at the lower layers; negative values were observed, indicating active convection. A 1-D vertical model was used to predict the depth of the mixed layer conditioned by the surface fluxes and triggered by its changes in winter to late spring. Comparisons of the sea surface temperature measured from satellite collocated with the glider’s measurements showed a very good agreement. From this analysis, we were able to establish the decorrelation scales that characterize mode water formation. Further inspection of the glider data yielded temporal decorrelation scales indicative of convection modified by planetary rotation. [ABSTRACT FROM AUTHOR]

There is an immediate need to better understand and monitor shelf sea dissolved oxygen (O 2) concentrations. Here we use high-resolution glider observations of turbulence and O 2 concentrations to directly estimate the vertical O 2 flux into the bottom mixed layer (BML) immediately before the autumn breakdown of stratification in a seasonally stratified shelf sea. We present a novel method to resolve the oxycline across sharp gradients due to slow optode response time and optode positioning in a flow "shadow zone" on Slocum gliders. The vertical O 2 flux to the low-O 2 BML was found to be between 2.5 to 6.4 mmol m -2 d -1. Episodic intense mixing events were responsible for the majority (up to 90 %) of this oxygen supply despite making up 40 % of the observations. Without these intense mixing events, BML O 2 concentrations would approach ecologically concerning levels by the end of the stratified period. Understanding the driving forces behind episodic mixing and how these may change under future climate scenarios and renewable energy infrastructure is key for monitoring shelf sea health. [ABSTRACT FROM AUTHOR]

An adaptive finite-time composite control (AFTCC) scheme is designed for the pitch angle trajectory tracking control of Underwater Glider (UG) with actuator physical constraints, uncertain dynamics and external disturbances. Firstly, a novel nonsingular fast terminal sliding mode control (NFTSMC) law is designed that can avoid singular problems, significantly reduce chattering, and achieve finite-time convergence of the system states. Secondly, a novel fixed-time extended state observer (FxTESO) is established to estimate the pitch angular velocity and lumped disturbances within a fixed time. Furthermore, a novel adaptive fixed-time saturation compensation system (AFxTSCS) is proposed to mitigate the effect caused by actuator saturation, and it can adjust the parameter adaptively when the actuator is in saturation or out of saturation. Finally, the AFTCC scheme, which is based on the NFTSMC framework and combines FxTESO and AFxTSCS, is designed to achieve the pitch angle trajectory tracking of UG, and the finite-time convergence of the whole closed-loop system is proved by the Lyapunov stability theory, and the simulations verify the availability and superiority of the proposed AFTCC scheme. • A simplified underwater glider model is established. • A novel FxTESO is constructed to estimate lumped disturbances. • A novel AFxTSCS is designed to mitigate the effect caused by actuator saturation. • An AFTCC scheme is designed to track the pitch angle of underwater glider. [ABSTRACT FROM AUTHOR]

Gliding is only present in six extant groups of mammals-interestingly, despite divergent evolutionary histories, all mammalian gliders are strictly nocturnal. Gliding mammals also seem to have relatively high rates of ultrasound use and ultravioletinduced photoluminescence (UVP) in contrast with their close relatives. Therefore, we hypothesized that, despite diverging lineages, gliding mammals use similar modes of cryptic communication compared to their non-gliding counterparts. We developed two datasets containing the vocal range (minimum-maximum of the dominant harmonic; kHz) and UVP of 73 and 82 species, respectively; we report four novel vocal repertoires and 57 novel observations of the presence or absence of UVP. We complemented these datasets with information about body size, diel activity patterns, habitat openness, and sociality to explore possible covariates related to vocal production and UVP. We found that the maximum of the dominant harmonic was significant higher in gliding mammals when vocalizing than their non-gliding relatives. Additionally, we found that nocturnality was the only significant predictor of UVP, consistent with the previous hypothesis that luminophores primarily drive UVP in mammal fur. In contrast, however, we did not find UVP ubiquitous in nocturnal mammals, suggesting that some unknown process may contribute to variation in this trait. [ABSTRACT FROM AUTHOR]

A 5‐year 6‐month‐old, neutered, male sugar glider (Petaurus breviceps) presented for lethargy. Plasma biochemistry revealed severely elevated alkaline phosphatase and moderate hypercholesterolemia. A heterogenous liver and a right abdominal mass were noted on abdominal ultrasonography. Computed tomography revealed an enlarged liver with ill‐defined hypoattenuating regions and a heterogenous mass arising from the caudate lobe. Cytology of the liver was consistent with low‐grade mixed lipid and hydropic vacuolar change and mild to moderate mixed to mature lymphocytic infiltrate. Liver biopsies were declined, and the patient was managed with silymarin and prednisolone. Serial bloodwork and abdominal ultrasonography revealed persistently elevated alkaline phosphatase and progressive heterogenous hepatomegaly and hepatic nodules. The sugar glider died over 2 years after original presentation. On postmortem examination, there was a poorly differentiated hepatic neoplasm, with immunohistochemistry most consistent with a carcinosarcoma. In future cases, hepatic biopsies could be considered for sugar gliders presenting with hepatic masses when cytology is unrewarding. [ABSTRACT FROM AUTHOR]