Velocity Variables Research Articles

Force-velocity-power variables derived from isometric and dynamic testing: metrics reliability and the relationship with jump performance.

We investigated the convergent validity and intrasession reliability of force, velocity, and power (FVP) variables and the dynamic strength index (DSI) obtained from isometric midthigh pull (IMTP) and squat jump (SJ) testing. Fifteen male combat sports athletes (27 ± 5 years, 77 ± 9 kg, 1.76 ± 0.1 m, 14 ± 6% body fat) participated in a 2-days study. The first day involved testing familiarization, while the second was dedicated to IMTP and SJ testing. Maximal isometric force (Fiso ) was obtained from IMTP, while mean force, mean velocity, jump height, and jump impulse (J) were gathered from SJ. To analyze the FVP, we calculated the linear relationship between force and velocity, which allowed us to obtain the slope of the relationship (SFV ), the theoretical velocity at zero force (V0 ), and the theoretical maximal power (Pmax ). DSI was obtained as a ratio from SJ peak force and Fiso . The convergent validity was investigated using Spearman's ρ coefficients to assess the relationships between jump height and J with Fiso , V0 , SFV , Pmax , and DSI. The intrasession reliability was assessed using intraclass correlation coefficients (ICC) and coefficient of variations (CV). All variables demonstrated acceptable reliability scores. ICC ranged from moderate to excellent, and the mean CV was <10%. We found a "very large" correlation between jump J and Pmax , while jump height was not correlated with any variable. In conclusion, the IMTP and SJ combination is a practical way to determine FVP producing capacities that can be reliably measured (intrasession). The Pmax , derived from FVP, was correlated with jump performance, which might evidence the convergent validity of the method.

Comparison of high-intensity interval training and moderate-intensity continuous training on cardiopulmonary function, cardiac autonomic function and vascular function in adolescent boys with obesity: A randomized controlled trial.

Adolescent obesity can impair cardiopulmonary function, vascular elasticity, endothelial function, and vago-sympathetic balance. While moderate-intensity continuous training (MICT) benefits cardiovascular health in obese adolescents, the effects of high-intensity interval training (HIIT) are less understood. We hypothesize that HIIT may be more effective than MICT in improving VO2peak, vascular elasticity, endothelial function, and vago-sympathetic balance in obese adolescent boys. Forty four participants were randomly assigned to the HIIT (10×1-min at 85%-95% peak HR, intersperse with 2-min active recovery at 60%-70% peak HR) or MICT (35min at 65%-75% peak HR) for an 8-week program. The primary outcome measured was the change in VO2peak with secondary outcomes including brachial-ankle pulse wave velocity (baPWV), flow-mediated dilation (FMD), and heart rate variability (HRV). Forty four adolescent boys with obesity (age, 14±1years old, body mass index, 31.6±1.3kg/m2) were enrolled and 43 (97.73%) completed the 8-week exercise. No significant difference of VO2peak was found between the HIIT and MICT group (p=0.243). There was no significant difference of baPWV between the groups (p=0.789). Change in FMD% was significantly higher in the HIIT group compared to the MICT group (p<0.001). The Change in HRV-high frequency (HRV-HF; p=0.009) and HRV-low frequency/high frequency (HRV-LF/HF; p=0.035) was significantly higher in the HIIT group compared to the MICT group. Among adolescent boys with obesity, 8-week HIIT and MICT had similar effects on improving VO2peak. HIIT may be superior to MICT to improve endothelial function and vago-sympathetic balance.

Novel method to estimate horizontal variability of shear wave velocity through multichannel analysis of surface waves

Scale of fluctuations (SOFs) of spatially variable soil properties have been regarded as one of the important parameters for performing reliability-based design in geotechnical engineering. However, the information required to estimate the SOFs in practice is limited, especially in the horizontal direction. In this study, the potential use of Multichannel Analysis of Surface Waves (MASW) to estimate the SOFs of shear wave velocity (VS) in horizontal direction is investigated through a series of numerical investigations. 2D random field models with a vertically increasing trend of VS were first simulated with different levels of variability controlled by the coefficient of variation (COV) and SOF. Afterwards, a large number of numerical MASW tests were performed using a 2D finite difference method, where the survey lines were progressively shifted. Results show that the COV of VS can be determined from the scatter of the dispersion curves, whereas the horizontal SOF of VS can be appropriately estimated from the phase velocity profile presented in the wavelength form. Additionally, in-situ MASW tests were conducted to estimate the horizontal SOF, and the obtained results align with those estimated by different methods. It is highlighted that the accuracy of the estimation depends on survey length. The interpretation using a long array reflects an averaged site condition of the survey area, thus losing the variability information. Favorable predictions are produced when survey length is shorter than 1.0 SOF. However, it should be noted that use of short survey length may limit the depth of investigation.

Ankle torque variance is a better indicator of balance control performance than plantar perceptual sensitivity threshold.

We explored whether ankle torque variability or plantar perceptual threshold explains human balance control more effectively. We hypothesized that ankle torque variance is a better indicator of center of pressure (COP) velocity variance than plantar perceptual sensitivity. Two conditions were tested: loaded (23-kg vest added) and unloaded, as loading should diminish plantar sensitivity and increase COP velocity variability. We created a linear feedback model to assess the noise change in the sensorimotor loop induced by loading. Plantar sensitivity was quantified using a psychophysical approach while participants stood barefoot. A linear motor applied a force impulse on the participant's heel. A "yes-no" method of limits was selected to identify plantar sole sensory thresholds in both conditions. We observed reduced plantar sensitivity in loaded compared with unloaded conditions. In the loaded condition, participants exhibited greater COP velocity variance, with significant positive Pearson's correlations confirming a substantial association between ankle torque and COP velocity variances for both loaded [variance accounted for (VAF): r2 = 44.56%, P = 0.018] and unloaded conditions (VAF: r2 = 58.83%, P = 0.004). No significant correlation existed between COP velocity variance and plantar sensitivity threshold for both loaded (VAF: r2 = 0.002%, P = 0.99) and unloaded conditions (VAF: r2 = 21.81%, P = 0.35). The model confirmed an ∼88% rise in sensorimotor loop noise in the loaded condition. Ankle torque variance assesses the precision of nonperceptual and perceptual detection mechanisms in evaluating whole body motions and the accuracy in converting sensory cues into ankle torque.NEW & NOTEWORTHY Plantar cutaneous information contributes to balance control by modulating motor commands, but plantar perceptual sensitivity is a suboptimal indicator of balance performance. Multiple sensory cues encode whole body dynamics, guiding sensorimotor mechanisms to minimize body sway variability. Ankle torque variance is proposed as a superior measure for explaining balance control performance and evaluating the sensorimotor loop's functioning in balance control.

Breaststroke and butterfly intercycle kinematic variation according to different competitive levels with Statistical Parametric Mapping analysis

Breaststroke and butterfly are complex swimming techniques requiring refined motor skills to perform successfully, with coordinated and consistent interaction between propulsive and resistive forces being decisive when considering swimmers expertise. The current study analysed those techniques intercycle kinematic variation in two swimmers cohorts. Twenty elite and 15 national level swimmers performed one 25 m breaststroke and one 25 m butterfly sprints, with an underwater camera recording images at 120 Hz in the sagittal plane. Mean velocity, maximum and minimum velocities, stroke rate and length, intracycle velocity variation and phases relative duration were calculated for consecutive cycles (elite: five breaststroke/butterfly, national level: eight breaststroke/seven butterfly). The two highest peaks and the lower peak in between in breaststroke were also addressed. Intercycle and inter-groups analysis were performed using ANOVA, ANCOVA and Statistical Parametric Mapping. Elite and national level differed regarding breaststroke mean and maximum velocities, 1st and 2nd peaks and minimum between peaks (1.30 ± 0.02 vs 1.15 ± 0.02 m/s, 2.13 ± 0.05 vs 1.88 ± 0.06 m/s, 1.63 ± 0.05 vs 1.48 ± 0.05 m/s, 2.13 ± 0.05 vs 1.86 ± 0.05 m/s, 1.33 ± 0.04 vs 1.23 ± 0.04 m/s), and butterfly mean, maximum and minimum velocities, stroke rate and intracycle velocity variation, respectively (1.65 ± 0.01 vs 1.50 ± 0.01 m/s, 2.20 ± 0.04 vs 2.09 ± 0.04 m/s, 1.12 ± 0.04 vs 0.79 ± 0.04 m/s, (57.9 ± 0.9 vs 54.9 ± 1.0cycles/min, 18.4 ± 1.3 vs 23.7 ± 1.3 %). Elite and national level swimmers showed consistent breaststroke intercycle kinematic variation, but a butterfly mean velocity decay, with the upper limbs release and recovery, and the outsweep phases originating variability between butterfly cycles. Skill levels contrasted in technical and strategic features at sprint breaststroke and butterfly but showed similar velocity variability between consecutive swimming cycles.

The asymptotic preserving unified gas kinetic scheme for the multi-scale kinetic SIR epidemic model

In this paper, we present an asymptotic preserving scheme for the two-dimensional space-dependent and multi-scale kinetic SIR epidemic model which is widely used to model the spread of infectious diseases in populations. The scheme combines a discrete ordinate method for the velocity variables and finite volume method for the spatial and time variables. The idea of unified gas kinetic scheme (UGKS) is used to construct the numerical boundary fluxes which needs the formal integral solutions of the model. Due to the coupling of the three transfer equations in the SIR model, it is difficult to obtain these integral solutions dependently. We decouple the system by constructing the fluxes in a separate way. Then following the framework of UGKS we can obtain the macro auxiliary quantities which is needed in the scheme. Thus the SIR model can be solved in the sequential way. In addition, we can show numerically that the scheme is second-order accurate both in space and time. Moreover, it can not only capture the solution of the diffusion limit equations without requiring the cell size and time step being related to the smallness of the scaling parameters, but also resolve the solution in hyperbolic regime in a natural way. Furthermore, the positive property of the UGKS is analyzed in detail, and through adding time step constraint conditions and applying nodal limiters together, the positive UGKS, called PPUGKS2−order, is obtained. Moreover, in order release the time step constraints in the diffusion regime, a temporal first-order accuracy positive preserving UGKS, called PPUGKS1−order, is proposed. Finally, several numerical tests are included to validate the performance of the proposed schemes.

Full Abundance Study of Two Newly Discovered Barium Giants

Barium (Ba) stars are chemically peculiar stars that show enhanced surface abundances of heavy elements produced by the slow-neutron-capture process, the so-called s-process. These stars are not sufficiently evolved to undergo the s-process in their interiors, so they are considered products of binary interactions. Ba stars form when a former Asymptotic Giant Branch (AGB) companion, which is now a white dwarf, pollutes them with s-process-rich material through mass transfer. This paper presents a detailed chemical characterization of two newly discovered Ba giants. Our main goal is to confirm their status as extrinsic s-process stars and explore potential binarity and white dwarf companions. We obtained high-resolution spectra with UVES on the Very Large Telescope to determine the chemical properties of the targets. We perform line-by-line analyses and measure 22 elements with an internal precision up to 0.04 dex. The binary nature of the targets is investigated through radial velocity variability and spectral energy distribution fitting. We found that both targets are enhanced in all the measured s-process elements, classifying our targets as Ba giants. This is the first time they are classified as such in the literature. Additionally, both stars present a mild enhancement in Eu, but less than in pure s-process elements, suggesting that the sources that polluted them were pure s-process sources. Finally, we confirmed that the two targets are RV variable and likely binary systems. The abundances in these two newly discovered polluted binaries align with classical Ba giants, providing observational constraints to better understand the s-process in AGB stars.

Building an emulator for sea surface temperature

We are interested in the problem of predicting sea surface temperature with machine learning methods using only the relevant climate factors. We tried to resolve the cost inefficiency of the temperature predicting model using over a million of data[1] that is observed by about 6300[2] NASA weather stations, a typical model that prominent agencies like NASA uses. First of all, we minimized the required computing power by using only velocity and pressure variables. Moreover, we minimized the usage of data by using only 14GB of NASA-GISS data and supplemented the minimized data by comparing four different machine learning models to predict global sea surface temperature. In addition, beyond predicting the global sea surface temperature, we also wanted to delve into predicting each region’s temperature. Thus, we gridded the earth into 64,800 regions, based on latitudes and longitudes. However, the accuracy drastically decreased since the data was also divided into 64,800 parts. Therefore, we applied the Gaussian filter to our predicted outcomes, and it made a breakthrough in accuracy. This will have a huge impact on temperature prediction because it will astoundingly decrease the expense and the amount of data needed for predicting temperature.

Evaluation of particle tracking codes for dispersing particles in porous media

Particle tracking (PT) is a popular technique in microscopy, microfluidics and colloidal transport studies, where image analysis is used to reconstruct trajectories from bright spots in a video. The performance of many PT algorithms has been rigorously tested for directed and Brownian motion in open media. However, PT is frequently used to track particles in porous media where complex geometries and viscous flows generate particles with high velocity variability over time. Here, we present an evaluation of four PT algorithms for a simulated dispersion of particles in porous media across a range of particle speeds and densities. Of special note, we introduce a new velocity-based PT linking algorithm (V-TrackMat) that achieves high accuracy relative to the other PT algorithms. Our findings underscore that traditional statistics, which revolve around detection and linking proficiency, fall short in providing a holistic comparison of PT codes because they tend to underpenalize aggressive linking techniques. We further elucidate that all codes analyzed show a decrease in performance due to high speeds, particle densities, and trajectory noise. However, linking algorithms designed to harness velocity data show superior performance, especially in the case of high-speed advective motion. Lastly, we emphasize how PT error can influence transport analysis.

Seasonal Variability of Ice Motion for Hubbard and Valerie Glaciers, Alaska

Hubbard Glacier is a large fast-flowing tidewater-terminating glacier in the St. Elias Mountains and is connected at its terminus to Valerie Glacier. Although Hubbard Glacier has been shown to experience large intra-annual velocity changes and a long-term deceleration, previous seasonality studies have had limited timescale without a dense record of motion. Valerie Glacier’s variability has also been understudied, with only one study reporting its seasonal behaviour. The goal of this study was to combine ITS_LIVE, RADARSAT-2, RADARSAT Constellation Mission, and TerraSAR-X/TanDEM-X derived velocity data to create the densest record of motion ever constructed for Hubbard and Valerie glaciers from July 2013-April 2022 in order to explore seasonal velocity variability of both glaciers. Air temperature (NCEP-NCAR Reanalysis) was used to estimate surface melt on the glaciers, which was explored as a potential driver for seasonal velocity changes. Valerie Glacier had a seasonal pattern of fast flow in May, with minimum flow between August-November before accelerating again. Hubbard Glacier displayed a unique seasonal pattern that has not been previously observed on this glacier, with two periods of fast motion: one in May and one in December-February. It is inferred that the spring peaks and late summer/fall minimums on both glaciers are due to meltwater reaching the glacier bed and influencing the subglacial hydrology. The cause of the winter peak and slight velocity drop before the spring peak on Hubbard Glacier has not been determined and should be a topic for future studies, although it is hypothesized to influenced by its geometry.

Associations between pain-related fear and lumbar movement variability during activities of daily living in patients with chronic low back pain and healthy controls

Low back pain (LBP) is a global issue involving biological, psychological, and social factors. Pain-related fear has been shown to influence movement behavior, however, its association with some measures of movement behavior, such as spinal movement variability, remains inconclusive. To further investigate this, spinal kinematics during various activities of daily living (i.e., walking, running, lifting, and stair climbing) of 49 patients with chronic LBP and a group of 51 sex-, age-, and BMI-matched healthy controls were used to calculate lumbar spine movement variability which was quantified using different indices (i.e., coefficient of variation, coupling angle variability in vector coding, deviation phase of the continuous relative phase and an angle-angular velocity variability). General and task-specific pain-related fear was assessed using the Tampa Scale of Kinesiophobia and the Photograph Series of Daily Activities—Short Electronic Version, respectively. Linear regression analyses showed no significant association between movement variability and pain-related fear, however, the sample consisted of younger individuals with moderate disability and with low levels of pain and pain-related fear. In addition, the different variability indices were weakly correlated and varied greatly depending on the method used and the task performed. Therefore, comparisons between studies with different movement variability calculation methods or different activities should be treated with caution.

Time evolutions of information entropies in a one-dimensional Vlasov–Poisson system

A one-dimensional Vlasov–Poisson system is considered to elucidate how the information entropies of the probability distribution functions of the electron position and velocity variables evolve in the Landau damping process. Considering the initial condition given by the Maxwellian velocity distribution with the spatial density perturbation in the form of the cosine function of the position, we derive linear and quasilinear analytical solutions that accurately describe both early and late time behaviors of the distribution function and the electric field. The validity of these solutions is confirmed by comparison with numerical simulations based on contour dynamics. Using the quasilinear analytical solution, the time evolutions of the velocity distribution function and its kurtosis indicating deviation from the Gaussian distribution are evaluated with the accuracy of the squared perturbation amplitude. We also determine the time evolutions of the information entropies of the electron position and velocity variables and their mutual information. We further consider Coulomb collisions that relax the state in the late-time limit in the collisionless process to the thermal equilibrium state. In this collisional relaxation process, the mutual information of the position and velocity variables decreases to zero, while the total information entropy of the phase-space distribution function increases by the decrease in the mutual information and demonstrates the validity of Boltzmann's H-theorem.

Velocity Variables: Determining Predictive Metrics During The Bench Press To Failure At Different Relative Intensities

Velocity Variables: Determining Predictive Metrics During The Bench Press To Failure At Different Relative Intensities

A Detailed Study of Jupiter’s Great Red Spot over a 90-day Oscillation Cycle

Jupiter’s Great Red Spot (GRS) is known to exhibit oscillations in its westward drift with a 90-day period. The GRS was observed with the Hubble Space Telescope on eight dates over a single oscillation cycle in 2023 December to 2024 March to search for correlations in its physical characteristics over that time. Measured longitudinal positions are consistent with a 90-day oscillation in drift, but no corresponding oscillation is found in latitude. We find that the GRS size and shape also oscillate with a 90-day period, having a larger width and aspect ratio when it is at its slowest absolute drift (minimum date-to-date longitude change). The GRS’s UV and methane gas absorption-band brightness variations over this cycle were small, but the core exhibited a small increase in UV brightness in phase with the width oscillation; it is brightest when the GRS is largest. The high-velocity red collar also exhibited color changes, but out of phase with the other oscillations. Maximum interior velocities over the cycle were about 20 m s−1 larger than minimum velocities, slightly larger than the mean uncertainty of 13 m s−1, but velocity variability did not follow a simple sinusoidal pattern as did other parameters such as longitude width or drift. Relative vorticity values were compared with aspect ratios and show that the GRS does not currently follow the Kida relation.

Factors Controlling Mud Floc Settling Velocity in a Highly Turbid Macrotidal Fluvial‐Estuarine System

AbstractThis study assesses the settling dynamics of suspended sediments along the hyper‐turbid Gironde Garonne fluvial‐estuarine system, with an innovative optical SCAF instrument (System of Characterization of Aggregates and Flocs). Two fields campaigns were carried out to determine the settling velocity and properties of suspended sediments during a semi‐diurnal tidal cycle, as well as hydrodynamic conditions and water properties. The two sampling stations were representative of two regions: a tidal river dominated by fresh water and an estuary affected by salty or brackish waters. A high spatial variability of the settling velocity was observed along the fluvial‐estuarine system and vertically along the water column. Settling velocities ranged from 0.02 to 0.4 mm/s. This study confirms that in hyper‐turbid systems, the suspended sediment concentration (SSC) is predominantly driving the settling dynamics of suspended sediment. Threshold concentrations have been defined for the flocculation and hindered regimes where the settling velocity may vary by one order of magnitude. Although in natural environments it is difficult to distinguish between the effects of SSC and turbulence (as they are correlated), in the Gironde‐Garonne system the turbulent shear G seems to affect the settling of suspended sediment to a lower extent. Settling velocity variations cannot be directly correlated to salinity or organic matter content. Despite differences in hydrodynamic and environmental conditions in fluvial and estuarine regions, a common prediction law has been found to estimate settling velocity of suspended sediment as a function of suspended sediment concentration.

Combined application of FTAN and cross-spectra analysis to ambient noise recorded by a microseismic monitoring network

A case study of seismic interferometry applied to a small microseismic monitoring network is here presented. The main objectives of this study are (i) to quantify the lateral variability of shear-wave velocities in the studied area, and (ii) to investigate the bias produced by noise directionality and non-stationarity in the velocity estimate. Despite the limited number of stations and the short-period character of the seismic sensors, the empirical Green’s functions were retrieved for all station pairs using two years of passive data. Both group and phase velocities were derived, the former using the widespread frequency-time analysis, the latter through the analysis of the real part of the cross-spectra. The main advantage of combining these two methods is a more accurate identification of higher modes, resulting in a reduction of ambiguity during picking and data interpretation. Surface wave tomography was run to obtain the spatial distribution of group and phase velocities for the same wavelengths. The low standard deviation of the results suggests that the sparse character of the network does not limit the applicability of the method, for this specific case. The obtained maps highlight the presence of a lower velocity area that extends from the centre of the network towards southeast. Group and phase velocity dispersion curves have been jointly inverted to retrieve as many shear-wave velocity profiles as selected station pairs. While the average model can be used for a more accurate location of the local natural seismicity, the associated standard deviations give us an indication of the lateral heterogeneity of seismic velocities as a function of depth. Finally, the same velocity analysis was repeated for different time windows in order to quantify the error associated to variations in the noise field. Errors as large as 4% have been found, related to the unfavorable orientation of the receiver pairs with respect to strongly directional noise sources, and to the very short time widows. It was shown that using a one-year time window these errors are reduced to 0.3%.

Evaluation of wave-based parameterizations of air–sea CO2 gas transfer over global oceans

The parameterization of air–sea CO2 transfer velocity employed in the estimation of bulk fluxes over global ocean is typically established on wind speed but could suffer from the deviations induced by sea states. In this study, the effectiveness of wave-based formulations are substantiated by reproducing climatological air–sea CO2 flux and gas transfer velocity. Sea states play a significant role in facilitating CO2 transfer, particularly in mid to high latitude regions with high wind speeds. The variability in transfer velocity induced by sea states is estimated up to 19% at the wind speed of 15 m/s. The two wave-based formulations used in this study are combined using a critical value of the Reynolds number. The combined formulation further improves estimates of the CO2 gas transfer velocity.

Microjet Flow Control on an Airfoil Flap: Particle Image Velocimetry Characterization

Normal-blowing microjets near the trailing edge of a flap can improve the aerodynamic performance of high-lift systems, potentially without some of the system-integration drawbacks of traditional systems. Previous two-dimensional simulations and a preliminary wind-tunnel test demonstrated the effectiveness of the microjet concept on a deployed flap. To further validate microjet effectiveness, this study uses a specially developed particle image velocimetry technique to estimate the momentum injected by a microjet on a deployed Fowler flap of a two-element NLR7301 airfoil while simultaneously measuring the lift enhancement provided by the microjet via surface pressure taps. The test results are broadly consistent with numerical simulations that predict lift increases proportionally to the square root of momentum injection. Within the experimental uncertainties, the test results show slightly less lift benefit for a given level of estimated momentum injection compared to the simulations, possibly due to three-dimensional effects such as spanwise variability and spanwise velocity components of the injected air, which could not be measured with the current instrumentation.

Are lithium-rich giants binaries? A radial velocity variability analysis of 1400 giants

Context. The existence of low-mass giants with large amounts of lithium (Li) in their surfaces has challenged stellar evolution for decades. One of the possibilities usually discussed in the literature to explain these Li-rich giants involves the interaction with a close binary companion, a scenario that predicts that, when compared against their non-enriched counterparts, Li-rich giants should preferentially be found as part of binary systems. Aims. We aim to assemble the largest possible sample of low-mass giants with well-measured Li abundances, to determine with high statistical significance the close binary fractions of Li-rich and Li-normal giants, and thus test the binary interaction scenario for the emergence of Li-rich giants. Methods. We developed a method that uses radial velocities (RVs) at three different epochs to quantify the degree of RV variability, which we used as a proxy for the presence of a close binary companion. The method was tested and calibrated against samples of known RV standard stars and known spectroscopic binaries. We then assembled a sample of 1418 giants with available RVs from RAVE, GALAH, and Gaia, as well as stellar parameters and Li abundances from GALAH, to which we applied our variability classification. We could determine an evolutionary state for 1030 of these giants. We also compared the results of our RV variability analysis with binarity indicators from the Gaia mission. Results. When applying our methodology to the control samples, we found that the accuracy of the classification is controlled by the precision of the RVs used in the analysis. For the set of RVs available for the giants, this accuracy is 80–85%. Consistent with seismic studies, the resulting sample of giants contains a fraction of Li-rich objects in the red clump (RC) that is twice as large as that in the first ascent red giant branch (RGB). Among RC giants, the fractions of Li-rich objects with a high RV variability and with no RV variability are the same as those for Li-normal objects, but we find some evidence that these fractions may be different for giants in the first-ascent RGB. Analysis of binary indicators in Gaia DR3 shows a smaller fraction of binary giants than our criteria, but no relation can be seen between Li enrichment and binarity either. Conclusions. Our RV variability analysis indicates that there is no preference for Li-rich giants in the RC to be part of binary systems, thus arguing against a binary interaction scenario for the genesis of the bulk of Li-rich giants at that evolutionary stage. On the other hand, Li-rich giants in the RGB appear to have a small but measurable preference for having close companions, something that deserves further scrutiny with more and better data. Additional measurements of the RVs of these giants at a higher RV precision would greatly help in confirming and more robustly quantifying these results.

Intercomparison of fast airborne ozone instruments to measure eddy covariance fluxes: spatial variability in deposition at the ocean surface and evidence for cloud processing

Abstract. The air–sea exchange of ozone (O3) is controlled by chemistry involving halogens, dissolved organic carbon, and sulfur in the sea surface microlayer. Calculations also indicate faster ozone photolysis at aqueous surfaces, but the role of clouds as an ozone sink is currently not well established. Fast-response ozone sensors offer opportunities to measure eddy covariance (EC) ozone fluxes in the marine boundary layer. However, intercomparisons of fast airborne O3 sensors and EC O3 fluxes measured on aircraft have not been conducted before. In April 2022, the Technological Innovation Into Iodine and GV Environmental Research (TI3GER) field campaign deployed three fast ozone sensors (gas chemiluminescence and a combination of UV absorption with coumarin chemiluminescence detection, CID) together with a fast water vapor sensor and anemometer to study iodine chemistry in the troposphere and stratosphere over Colorado and over the Pacific Ocean near Hawaii and Alaska. Here, we present an instrument comparison between the NCAR Fast O3 instrument (FO3, gas-phase CID) and two KIT Fast AIRborne Ozone instruments (FAIRO, UV absorption and coumarin CID). The sensors have comparable precision &lt; 0.4 % Hz−0.5 (0.15 ppbv Hz−0.5), and ozone volume mixing ratios (VMRs) generally agreed within 2 % over a wide range of environmental conditions: 10 &lt; O3 &lt; 1000 ppbv, below detection &lt; NOx &lt; 7 ppbv, and 2 ppmv &lt; H2O &lt; 4 % VMR. Both instrument designs are demonstrated to be suitable for EC flux measurements and were able to detect O3 fluxes with exchange velocities (defined as positive for upward) as slow as −0.010 ± 0.004 cm s−1, which is in the lower range of previously reported measurements. Additionally, we present two case studies. In one, the direction of ozone and water vapor fluxes was reversed (vO3 = +0.134 ± 0.005 cm s−1), suggesting that overhead evaporating clouds could be a strong ozone sink. Further work is needed to better understand the role of clouds as a possibly widespread sink of ozone in the remote marine boundary layer. In the second case study, vO3 values are negative (varying by a factor of 6–10 from −0.036 ± 0.006 to −0.003 ± 0.004 cm s−1), while the water vapor fluxes are consistently positive due to evaporation from the ocean surface and spatially homogeneous. This case study demonstrates that the processes governing ozone and water vapor fluxes can become decoupled and illustrates the need to elucidate possible drivers (physical, chemical, or biological) of the variability in ozone exchange velocities on fine spatial scales (∼ 20 km) over remote oceans.