搜索结果：Experiments in fluids

In urban environments, pollutant ingress from outdoor sources poses a significant challenge to indoor air quality. Cross-ventilation, while essential for passive cooling and natural airflow, can also facilitate the entry of outdoor contaminants into indoor spaces. To investigate the dynamics of outdoor-to-indoor pollutant transport, the present study employs an idealized configuration, namely, a hollow cube representing a scaled-down model building with window openings in the upstream and downstream faces, subjected to an upstream passive scalar source within an atmospheric boundary layer. The experiments are conducted in two distinct facilities: a water tunnel using Rhodamine dye as the scalar, and a wind tunnel using propane gas, all performed at a specified flow Reynolds number of Re = U Ref H / ν ≈ 50 , 000 for a fixed boundary layer-to-cube height ratio of about 3; here, U Ref is the streamwise velocity at cube's height (H) measured without the cube. The scalar, released from a ground-level upstream source, is predominantly transported by a streamwise advective flux, while relatively weaker wall-normal advective and turbulent fluxes contribute to vertical dispersion and local mixing. A fraction of the oncoming scalar enters the cube intermittently, through the upstream window. Inside, a central jet-like flow carries the scalar parcels primarily by streamwise advective flux, while also interacting with the upper and lower recirculation regions, enabling scalar exchange across these zones through wall-normal advective and turbulent fluxes. While the time-averaged concentration field inside the cube is nearly uniform, suggesting effective mixing, instantaneous concentration traces exhibit strong intermittency, with sporadic peak events, highlighting the risk of transient peak exposures. The indoor concentration exponentially decays over time once the source is turned off, with a slower decay in the upper recirculation region, implying relatively prolonged exposure near the ceiling region. Both experimental setups produce closely matching values and consistent trends in the spatio-temporal dynamics of scalar concentration, and also highlight their complementary nature, with each offering distinct advantages. The present findings will deepen our understanding of pollutant ingress and mixing in buildings in cross-ventilated flows and also offer valuable insights to future modeling of pollutant exposure in urban indoor spaces.

Peptide hormone-based weight-loss therapeutics have gained increasing attention, driven amongst other reasons, by the clinical and commercial success of semaglutide. Their increasing accessibility raises concerns about their potential misuse in sports, especially in disciplines where weight management is decisive for athletic performance. Semaglutide has been included in the World Anti-Doping Agency's monitoring program since 2024. Given that amylin signalling is a key therapeutic target for next-generation weight-loss drugs, amylin receptor agonists such as pramlintide, cagrilintide and KBP-066 also warrant consideration as to metabolism and detection strategies in sports drug testing programs. This study aimed to characterize the metabolic profiles of pramlintide, cagrilintide and KBP-066, identify analytically suitable metabolites and develop and validate a LC-MS/MS-based detection approach. Comprehensive in vitro models, including human skin S9 fraction, kidney S9 fraction and biological fluids, were used to investigate metabolic pathways. HRMS/MS was employed to characterize metabolites and evaluate their suitability as analytical targets. For comparison, authentic post-administration rat samples were analysed for cagrilintide and respective biotransformation products. All three peptides underwent N-terminal and C-terminal degradation, yielding multiple stable metabolic products suitable as detection targets. Cagrilintide metabolites predicted from in vitro experiments were observed in authentic post administration rat plasma samples, confirming in vivo relevance. Finally, suitable preparation and detection methods were established and validated. This study provides the first systematic metabolic characterization of pramlintide, cagrilintide and KBP-066. The identified metabolites and LC-MS/MS detection approach offer a foundation for future monitoring of emerging weight-loss peptide hormone analogues in anti-doping contexts.

Tip vortices generated at the tip of lifting surfaces pose significant challenges in fluid dynamics, causing induced drag, noise, and cavitation erosion risk across aerospace and hydraulic applications. Among the various mitigation strategies, porous tips have been explored with mixed results, showing limited effectiveness in diffusing concentrated vorticity. In this study, we introduce a gyroid-based porous tip as a novel passive flow control device for tip vortex mitigation. A gyroid is a triply periodic minimal surface that forms a smooth and tortuous porous 3D network. A gyroid-based porous insert was attached to an elliptical NACA 16-020 hydrofoil tip (Re ≈ 9 × 105), replacing 3%, 5%, and 9% of the span. Laser Doppler Velocimetry (LDV) measurements revealed that increasing the gyroid portion dramatically reduces maximum tangential velocity while enlarging the vortex core radius. The vortex circulation remains unchanged, indicating a diffusion mechanism that spreads concentrated vorticity over a larger core. At 12° incidence, the 9% gyroid insert reduced peak tangential velocity by a factor of 3.2 alongside a sixfold increase in vortex core radius. Consequently, the minimum pressure coefficient at the vortex center increased from - 1.4 to - 0.1 , reducing significantly the risk of cavitation. Flow visualization confirmed complete suppression of tip vortex cavitation across all tested conditions. The gyroid effectiveness was verified for both tripped and natural boundary layer transitions. Critically, hydrodynamic performance remained essentially unaffected for gyroid inserts spanning up to 5%, with lift and drag coefficients maintained within experimental uncertainty. Tests with blocked permeability demonstrate that the observed effects stem from structural permeability rather than surface roughness. These findings establish gyroid inserts as a promising passive flow control for cavitation mitigation in marine propellers, hydrofoils, and turbomachinery, as well as noise control in aircraft wings and wind turbines, while preserving operational efficiency.

Over the past decade, there has been a tremendously increased interest in understanding the neurophysiology of cerebrospinal fluid (CSF) flow, which plays a crucial role in clearing metabolic waste from the brain. This growing interest was largely initiated by two significant discoveries: the glymphatic system (a pathway for solute exchange between interstitial fluid deep within the brain and the CSF surrounding the brain) and meningeal lymphatic vessels (lymphatic vessels in the layer of tissue surrounding the brain that drains CSF). These two CSF systems work in unison, and their disruption has been implicated in several neurological disorders including Alzheimer's disease, stroke, and traumatic brain injury. Here, we present experimental techniques for in vivo quantification of CSF flow via direct imaging of fluorescent microspheres injected into the CSF. We discuss detailed image processing methods, including registration and masking of stagnant particles, to improve the quality of measurements. We provide guidance for quantifying CSF flow through particle tracking and offer tips for optimizing the process. Additionally, we describe techniques for measuring changes in arterial diameter, which is an hypothesized CSF pumping mechanism. Finally, we outline how these same techniques can be applied to cervical lymphatic vessels, which collect fluid downstream from meningeal lymphatic vessels. We anticipate that these fluid mechanical techniques will prove valuable for future quantitative studies aimed at understanding mechanisms of CSF transport and disruption, as well as for other complex biophysical systems.

Mycoplasma bovis (M. bovis) causes several costly diseases in cattle and has a negative effect on cattle welfare. There is no effective commercial vaccine, and antimicrobial resistance is common. Maintaining a closed herd is the best method to minimize the risk of introduction of M. bovis. Assisted reproduction is crucial in a closed herd to make genetic improvements. M. bovis has been found in commercial semen, and contaminated semen has been the source of disease in naïve dairy herds. The objective of this study was to evaluate M. bovis transmission in bovine in vitro embryo production (IVP) using several possible exposure routes. We used a wild-type M. bovis strain isolated from semen at a final concentration of 106 CFU/mL to infect cumulus-oocyte complexes, spermatozoa, and 5-day-old embryos. We also used naturally contaminated semen in fertilization. Blastocysts were collected on day 7-8 and zona pellucida (ZP)-intact embryos were either washed 12 times, including trypsin washes as recommended by the International Embryo Technology Society (IETS), or left unwashed. Washed and unwashed embryos, follicular fluids, maturation medium, cumulus cells, fertilization medium, and G1 and G2 culture media, as well as all wash media were analyzed using enrichment culture followed by real-time PCR detection of M. bovis. Altogether, 76 pools containing 363 unwashed embryos and 52 pools containing 261 IETS washed embryos were analyzed after oocytes, spermatozoa, or 5-day-old embryos were infected with M. bovis or naturally contaminated semen was used in fertilization. We could not detect M. bovis in any of the embryo pools. M. bovis was not found in any of 12 wash media from different exposure experiments. M. bovis did not affect the blastocyst rate, except when using experimentally infected semen. Contrary to an earlier study, which used a cell co-culture system, we could not demonstrate M. bovis in embryo wash media or tight adherence of M. bovis to ZP-intact embryos. Naturally infected semen did not transmit M. bovis to embryos. We conclude that by using our IVP system, the risk of M. bovis transmission via IVP embryos to recipient cows is very low.

An experimental study is conducted of the fluid-thermal-structural interaction of a clamped compliant panel exposed to the intense shock-wave/boundary-layer interaction (SWBLI) induced by a compression ramp at Mach 10. Initial measurements of the underlying flowfield with a rigid ramp showed the incoming boundary layer to be transitional, and the SWBLI was observed to vary from attached to fully separated as the ramp angle was increased from 10 ∘ to 30 ∘ . For the compliant panel, a sealed cavity behind the panel allowed the effects of pressure-differential induced strains to be studied in the context of characterizing surface response to the aero-thermal load. Full-field, time-resolved panel deformations were measured using high-speed photogrammetry enabled by a new high-fidelity marker-tracking routine, which was shown to outperform existing methods. Substantial static panel deformations (of the order of several times the panel thickness) were produced by the intense aero-thermal loading environment. These deformations, combined with induced thermal and pressure gradients across the panel, were found to significantly modify the nature of existing panel modes (both the frequency and the displacement distributions) and introduce new, irregular mode shapes not predicted by classical clamped-plate theory; SolidWorks® simulations were performed to demonstrate that these new mode shapes were a result of the underlying panel curvature. Increasing the ramp angle resulted in a wider variety of panel modes becoming excited, while increasing the pressure differential across the panel typically produced further increases in modal frequencies and decreases in vibrational amplitudes. The transient panel response was characterized and it was found that the lower frequency mode shapes tended to gradually increase in vibrational frequency as the panel heated up and further deformed; however, higher frequency modes ( f ≳ 3 kHz ) generally showed the opposite behavior. Furthermore, as the panel deformed through the test time, the average vibrational spectra root-mean-square power was generally found to monotonically decrease.

Thymosin β4 (Tβ4) was reported to exert various beneficial bioactivities such as tissue repair, anti-inflammation, and reduced scar formation, and it is listed on the prohibited substances in sports by the World Anti-Doping Agency. However, no metabolism studies of Tβ4 were reported yet. Previously, our lab reported in in vitro experiment that a total of 13 metabolites were found by using multiple enzymes, and six metabolites (Ac-Tβ31-43 , Ac-Tβ17-43 , Ac-Tβ1-11 , Ac-Tβ1-14 , Ac-Tβ1-15 , and Ac-Tβ1-17 ) were confirmed by comparing with the synthetic standards. This study was aimed at identifying new metabolites of Tβ4 leucine aminopeptidase (LAP), human kidney microsomes (HKM), cultured huvec cells, and rats after administration of Tβ4 protein to develop biomarkers for detecting doping drugs in sports. A method for detecting and quantifying Ac-Tβ1-14 was developed and validated using Q-Exactive orbitrap mass spectrometry. The limit of detection (LOD) and limit of quantification (LOQ) of the Ac-Tβ1-14 were 0.19 and 0.58 ng/mL, respectively, and showed a good linearity (r2  = 0.9998). As a result, among the six metabolites above, Ac-Tβ1-14 , as a common metabolite, was found in LAP, HKM, huvec cells exposed to Tβ4, and the urine of rats intraperitoneally treated with 20-mg/kg Tβ4. And the metabolite Ac-Tβ1-14 was quantitatively determined by 48 h in rats, with the highest concentration occurring between 0 and 6 h. Ac-Tβ1-14 was not detected in non-treated control groups, including human blank urine. These results suggest that Ac-Tβ1-14 in urine is a potential biomarker for screening the parent Tβ4 in doping tests.

Research on free falling particles has predominantly focused on wake dynamics and vortex shedding of individual particles in quiescent flow. However, when these particles fall collectively, the wakes of neighboring particles alter the flow fields. To investigate how the settling and wake dynamics of particles are affected by the wakes of other settling particles, we conducted volumetric experiments using the Shake-The-Box technique. Negatively buoyant 12 mm particles of four different geometries (sphere, flat cuboid, circular, and square cylinders) were first released individually into quiescent water. Subsequently, the particles were released individually into the bulk wakes of 20 monodisperse particles. Using four high-speed cameras and LEDs, we simultaneously captured both 3D particle and fluid motions in the terminal velocity regime. The imaging domain measured 90 mm × 90 mm × 40 mm. Our results show that all trailing particles settling through the bulk wakes gain additional downward momentum from the turbulent wakes, causing them to fall faster than in quiescent flow. However, when the induced velocity of the preceding wakes is subtracted, the relative settling velocity was found to be essentially the same as the particle falling in quiescent fluid. Upstream of the particle, the vortices in the bulk wake interact with the developing shear layer along the particle. The wake downstream of the trailing particle also appears more chaotic than that in quiescent flow.

In this study, the capability of Event-based Vision Sensor (EVS) cameras for measuring simultaneously bubble motion, size, and shape in complex bubbly flows has been assessed. This assessment initially focused on benchmark evaluation of the accuracy of an EVS camera in tracking the motion and size of precisely manufactured naturally buoyant particles in quiescent water. Experiments were carried out in synchronization with a conventional high-speed (HS) camera, enabling quantitative comparison. The synchronized measurements obtained from both cameras agreed well with differences of less than 0.65% in measured particle velocities and 2.4% in measured diameters, demonstrating the EVS camera's capability to precisely measure motion and dimensions. Following this validation, the assessment expanded to characterize bubbles generated by injecting compressed air at various pressures at the bottom of a quiescent water tank. The EVS camera demonstrated comparable performance to the HS camera in measuring bubble size and velocity at low to moderate injection pressures. The bubble tracks uniquely captured by the EVS camera, due to its adjustable accumulation time, can be leveraged to extract trajectory and velocity information, as well as instances of partial bubble visual overlap in the camera view. However, event saturation is observed at the EVS camera for several events generated by bubble motion that surpasses a critical threshold (e.g., dense bubbly flow). Subsequently, the increased latency at both pixel levels and read-out leads to temporal misalignment relative to the flow bubble dynamics. This challenge was addressed by employing a pulsed illumination source, which allowed the camera to capture dense bubbly flows, as the increased presence of bubbles corresponds to a reduced number of EVS recorded events. Overall, the assessment highlights that EVS cameras offer comparable performance to conventional HS cameras in characterising bubbly flows with two additional unique advantages. (i) Ability to record bubble tracks, which can be directly used for bubble velocimetry. (ii) An instantaneous EVS camera image records events at a significantly reduced data rate, which enables real-time bubble EVS imaging at higher speeds than conventional HS cameras. The online version contains supplementary material available at 10.1007/s00348-026-04272-5.

In aircraft engines, thermoacoustic oscillations in the combustion chamber contribute significantly to noise emissions, which, like all other emissions, must be drastically reduced. Thermoacoustic oscillations are not only a concern, they can also be beneficial in hydrogen combustion. This work demonstrates that thermoacoustic density oscillations with amplitudes at least an order of magnitude smaller than those resulting from density gradients in a turbulent flame can be detected using laser interferometric vibrometry. This improvement was made possible by heterodyning a carrier fringe system in background-oriented schlieren (BOS) recordings, which were subsequently analyzed using techniques commonly used for holographic interferometry. In comparison with other BOS evaluation techniques, the filtering of the individual frames in the Fourier domain offers a more efficient computational approach, as it allows for phase averaging of a high number of single recordings to reduce noise from turbulence. To address fringe pattern distortions and cross talk in the Fourier domain, which both have been observed by other authors, we propose background subtraction methods and an optimized background pattern. Additionally, the procedure provides a visualization tool for marking the high turbulence regions of heat release by the variations in fringe amplitude. Finally, the line-of-sight data are reconstructed using the inverse Abel transform, with the data calibrated by laser interferometric techniques, resulting in local values for density oscillations.

In this work, we study the jetting dynamics of individual cavitation bubbles using x-ray holographic imaging and high-speed optical shadowgraphy. The bubbles are induced by a focused infrared laser pulse in water near the surface of a flat, circular glass plate, and later probed with ultrashort x-ray pulses produced by an x-ray free-electron laser (XFEL). The holographic imaging can reveal essential information of the bubble interior that would otherwise not be accessible in the optical regime due to obscuration or diffraction. The influence of asymmetric boundary conditions on the jet's characteristics is analysed for cases where the axial symmetry is perturbed and curved liquid filaments can form inside the cavity. The x-ray images demonstrate that when oblique jets impact the rigid boundary, they produce a non-axisymmetric splash which grows from a moving stagnation point. Additionally, the images reveal the formation of complex gas/liquid structures inside the jetting bubbles that are invisible to standard optical microscopy. The experimental results are analysed with the assistance of full three-dimensional numerical simulations of the Navier-Stokes equations in their compressible formulation, which allow a deeper understanding of the distinctive features observed in the x-ray holographic images. In particular, the effects of varying the dimensionless stand-off distances measured from the initial bubble location to the surface of the solid plate and also to its nearest edge are addressed using both experiments and simulations. A relation between the jet tilting angle and the dimensionless bubble position asymmetry is derived. The present study provides new insights into bubble jetting and demonstrates the potential of x-ray holography for future investigations in this field. The online version contains supplementary material available at 10.1007/s00348-023-03759-9.

This paper investigates the characteristics and control of tip vortices generated by a finite wing, focusing on the impact of the novel grooved-tip designs. Tip vortices can lead to flow loss, noise, vibration and cavitation in hydrodynamic systems. We propose and develop a grooved-tip design, featuring multiple grooves distributed along the wing tip to alter the tip vortex structure and dynamics. Four grooved-tip designs, including tilted and shrinking grooves, were experimentally investigated. Streamwise and cross-flow particle image velocimetry (PIV) measurements were employed to visualise the flow fields near the wing tip and along the primary tip vortex trajectory. The PIV results demonstrate that the grooved-tip designs significantly reduce the velocity magnitude within the primary tip vortex. This velocity deficit is attributed to the decreased suction within the vortex core. Furthermore, cross-flow PIV measurements reveal that the tip separation vortex is substantially suppressed, and the strength of the primary tip vortex is significantly mitigated. Downstream of the wing, the grooved tips lead to a reduction in vortex swirling strength and an enlargement of the vortex dimensions, suggesting enhanced diffusion and a reduction of the pressure drop of approximately 40%, based on the estimation from a reduced-order model linking pressure to vortex swirling strength. Our findings highlight the potential of these grooved-tip designs to effectively modify tip vortex behaviour and mitigate the pressure drop within the tip vortex region, with negligible changes to the lift and drag performance. This work can inform advanced passive vortex control strategies in wing- and blade-based systems, with potential applications in hydrofoils of marine vessels and underwater vehicles, as well as in turbines and propellers.

The so-called 're-entrant jet' is fundamental to periodic cloud shedding in partial cavitation. However, the exact physical mechanism governing this phenomenon remains ambiguous. The complicated topology of the re-entrant flow renders whole-field, detailed measurement of the re-entrant flow cumbersome. Hence, most studies in the past have derived a physical understanding of this phenomenon from qualitative analyses of the re-entrant jet. Thus, quantitative studies are scarce in the literature. In this work, we present a methodology to experimentally measure the re-entrant flow below the vapour cavity in an axisymmetric venturi. The axisymmetry of the flow geometry is exploited to image tracer particles in the near-wall re-entrant flow. The main objective of employing tomographic imaging and subsequent velocimetry is to resolve the thickness and the velocity of the re-entrant flow. Additionally, phase-averaging conditioned on cavity length sheds light on the temporal evolution of re-entrant flow in a shedding cycle. The measured re-entrant film is as thick as ∼ 1.2 mm for a maximum cavity length of ∼ 0.9 D t , where D t is the venturi throat diameter. However, the re-entrant film thickness at higher cavitation number is measured to be about 0.5 mm. Further, the re-entrant flow is seen to attain a maximum velocity up to half the throat velocity as the vapour cavity grows in time and the re-entrant flow thickens. We observe that a complex spatio-temporal evolution of re-entrant flow is involved in the cavity detachment and periodic cloud shedding. Finally, we apply the demonstrated methodology to study the evolution of the near-wall liquid flow, below the vapour cavity in different cavity shedding flow regimes. The role of two main mechanisms responsible for cloud shedding, i.e. (i) the adverse-pressure gradient driven re-entrant jet, and (ii) the bubbly shock wave emanating from the cloud collapse are quantitatively assessed. We observe that the thickness of the re-entrant liquid film with respect to the cavity thickness can influence the cavity shedding behaviour. Further, we show that both the mechanisms could be operating at a given flow condition, with one of them dominating to dictate the cloud shedding behaviour. The online version contains supplementary material available at 10.1007/s00348-022-03417-6.

Traumatic brain injury (TBI) poses a major public health challenge. No proven therapies for the condition exist so protective equipment that prevents or mitigates these injuries plays a critical role in minimizing the societal burden of this condition. Our ability to optimize protective equipment depends on our capacity to relate the mechanics of head impact events to morbidity and mortality. This capacity, in turn, depends on correctly identifying the mechanisms of injury. For several decades, a controversial theory of TBI biomechanics has attributed important classes of injury to cavitation inside the cranial vault during blunt impact. This theory explains counter-intuitive clinical observations, including the coup-contre-coup pattern of injury. However, it is also difficult to validate experimentally in living subjects. Also, blunt impact TBI is a broad term that covers a range of different head impact events, some of which may be better described by cavitation theory than others. This review surveys what has been learned about cavitation through mathematical modeling, physical modeling, and experimentation with living tissues and places it in context with competing theories of blunt injury biomechanics and recent research activity in the field in an attempt to understand what the theory has to offer the next generation of innovators in TBI biomechanics.

The performance of a wavelet-based optical flow velocimetry (wOFV) algorithm in extracting high accuracy and high-resolution velocity fields from tracer particle images in wall-bounded turbulent flows is assessed. wOFV is first evaluated using synthetic particle images generated from a channel flow DNS of a turbulent boundary layer. The sensitivity of wOFV to the regularization parameter ( λ ) is quantified and results are compared to cross-correlation-based PIV. Results on synthetic particle images indicated different sensitivity to under-regularization or over-regularization depending on which region of the boundary layer is being analyzed. Nonetheless, tests on synthetic data revealed that wOFV can modestly outperform PIV in vector accuracy across a broad λ range. wOFV showed clear advantages over PIV in resolving the viscous sublayer and obtaining highly accurate estimates of the wall shear stress and thus normalizing boundary layer variables. wOFV was also applied to experimental data of a developing turbulent boundary layer. Overall, wOFV revealed good agreement with both PIV and a combined PIV + PTV method. However, wOFV was able to successfully resolve the wall shear stress and correctly normalize the boundary layer streamwise velocity to wall units where PIV and PIV + PTV showed larger deviations. Analysis of the turbulent velocity fluctuations revealed spurious results for PIV in close proximity to the wall, leading to significantly exaggerated and non-physical turbulence intensity in the viscous sublayer region. PIV + PTV showed only a minor improvement in this aspect. wOFV did not exhibit this same effect, revealing that it is more accurate in capturing small-scale turbulent motion in the vicinity of boundaries. The enhanced vector resolution of wOFV enabled improved estimation of instantaneous derivative quantities and intricate flow structure both closer to the wall and more accurately than the other velocimetry methods. These aspects show that, within a reasonable λ range that can be verified using physical principles, wOFV can provide improvements in diagnostics capability in resolving turbulent motion occurring in the vicinity of physical boundaries.

Pollutant dispersion by a tall-building cluster within a low-rise neighbourhood of Beijing is investigated using both full-scale Large-Eddy Simulation and water flume experiments at 1:2400 model-to-full scale with Particle Image Velocimetry and Planar Laser-Induced Fluorescence. The Large-Eddy Simulation and flume results of this realistic test case agree remarkably well despite differences in the inflow conditions and scale. Tall buildings have strong influence on the local flow and the development of the rooftop shear layer which dominates vertical momentum and scalar fluxes. Additional measurements using tall-buildings-only models at both 1:2400 and 1:4800 scales indicates the rooftop shear layer is insensitive to the scale. The relatively thicker incoming boundary layer affects the Reynolds stresses, the relative size of the pollutant source affects the concentration statistics and the relative laser-sheet thickness affects the spatially averaged results of the measured flow field. Low-rise buildings around the tall building cluster cause minor but non-negligible offsets in the peak magnitude and vertical location, and have a similar influence on the velocity and concentration statistics as the scale choice. These observations are generally applicable to pollutant dispersion of realistic tall building clusters in cities. The consistency between simulations and water tunnel experiments indicates the suitability of both methodologies.

Oxygen transfer across a deforming air-water interface is studied using a synergy of particle image velocimetry and laser-induced fluorescence (LIF). Such approaches have previously been limited to flat interfaces. We develop simultaneous measurements of velocity fields, dissolved oxygen (DO) concentration fields, and interface positions for spatial and temporal tracking. The imaging process begins after the DO in the water has been chemically depleted and continues until the water is saturated with DO. The oxygen LIF intensity field is calibrated using measurements from an optical oxygen probe to ensure accurate conversion into physical unit (mg/L). A canonical air turbulent channel flow, with a centerline velocity of 6.6 m/s (Reynolds number based on channel height of 21,700), develops for more than 100 heights before the bottom boundary condition is changed from a solid wall to a water surface. This induces transient and wavy structures on the air-water interface and generates velocity fluctuations and vorticity on the water side, which drives DO transport. The spatial evolution of DO concentration reveals steep gradients near the interface that diminish with depth, while the temporal evolution shows a reduction in concentration differences between the bulk and interface from about 35% to less than 5% as the water saturates. Concentration fluctuations are lower near the interface compared to the bulk and diminish in time as the system approaches saturation. Turbulent scalar transport analysis shows high vertical flux near the interface, and this too changes as the bulk DO concentration evolves, emphasizing that the observed phenomena are transient and should be treated as such.

Since early 2024, a multistate outbreak of highly pathogenic avian influenza H5N1 has been affecting dairy cattle in the USA. The influenza viral RNA concentrations in milk make it an ideal matrix for surveillance purposes. However, viral RNA detection in multi-component fluids such as milk can be complex, and optimization of influenza detection methods is thus required. Raw bulk tank milk and mastitis milk samples were artificially contaminated with an avian influenza strain and subjected to five extraction methods. HCoV-229E and synthetic RNA were included as exogenous internal process controls. Given the high viral load usually observed in individual raw milk samples, four out of five tested methods would enable influenza detection in milk with normal texture, over a time window of at least 2 weeks post-onset of clinical signs. Nevertheless, sample dilution 1:3 in molecular transport medium prior to RNA extraction provided the best results for dilution of inhibitory substances and a good recovery rate of influenza RNA, that reached 12.5 ± 1.2% and 10.4 ± 3.8% in two independent experiments in bulk milk and 11.2 ± 3.6% and 10.0 ± 2.9% on two cohorts of mastitis milk samples. We have also shown compatibility of an influenza RT-qPCR system with synthetic RNA detection for simultaneous validation of the RNA extraction and RT-qPCR processes.

In spite of many attempts to establish an in vitro fertilization (IVF) technique in the equine, no efficient conventional IVF technique is available. The presence of oviductal fluid or oviductal cells during IVF helps to improve embryo production in vitro but is not sufficient to reach high fertilization rates. Thus, our aim was to perform equine IVF either after sperm pre-incubation with oviductal fluid or in the presence of oviductal cells, and to evaluate the effect of cumulus removal from the oocyte or sperm pre-incubation with progesterone. In experiments 1 and 2, IVF was performed in the presence of porcine oviduct epithelial cells. The removal of cumulus cells from equine oocytes after in vitro maturation tended to increase the percentage of fertilization when fresh sperm was used (1/33 vs. 4/31, p > 0.05) but had no effect when frozen sperm was used (1/32 vs. 1/32). Equine sperm pre-incubation with progesterone did not significantly influence the fertilization rate when fresh or frozen sperm was used (2/14 vs. 2/18 for fresh, 1/29 vs. 1/25 for frozen). In experiments 3 and 4, IVF was performed after pre-incubation of sperm with porcine oviductal fluid. The removal of cumulus cells tended to increase the percentage of fertilization when fresh sperm was used (1/24 vs. 3/26, p > 0.05). Sperm pre-incubation with progesterone did not significantly influence the fertilization rate when fresh or frozen sperm was used (2/39 vs. 2/36 for fresh, 2/37 vs. 1/46 for frozen), but two 3-4 cell stage zygotes were obtained with fresh sperm pre-incubated with progesterone. This is an encouraging result for the setting up of an efficient IVF procedure in equine.