Velocity Variables Research Articles

Prediction of floods using improved PCA with one-dimensional convolutional neural network

Forecasting floods have always been a difficult task due to the complexity of the available data. Machine learning techniques have been widely used to predict floods based on precipitation, humidity, temperature, water velocity, and level variables. However, most prior studies have examined the monthly rainfall intensity to determine the likelihood of flooding. As a result, a state's daily and monthly rainfall intensity has been used to train deep-learning models to predict floods. In addition, feature reduction approaches are critical for dealing with data of a large dimensionality and improving classification accuracy. This article utilizes improved Principal Component Analysis (i-PCA), a linear unsupervised statistical transformation, as a feature reduction procedure. A 1D-Convolutional Neural Network (CNN) model forecasts the flood based on the reduced features. The experiments are based on a dataset of daily and monthly rainfall data collected from 1901 to 2021 for Kerala state. Qualitative analysis is performed using precision, accuracy, recall and F1-score parameters. The experiment analysis proves that the proposed algorithm attained 94.24% accuracy, and existing techniques achieved 86% of accuracy performance. The reason is that the proposed model uses the improved PCA for the feature reduction technique.

Entropy generation in bioconvection hydromagnetic flow with gyrotactic motile microorganisms.

Here, the magnetohydrodynamic bioconvective flow of a non-Newtonian nanomaterial over a stretched sheet is scrutinized. The characteristics of convective conditions are analyzed. Irreversibility analysis in the presence of gyrotactic micro-organisms is discussed. Energy expression is assisted with thermal radiation, heat generation and ohmic heating. Buongiorno's model is employed to discuss the characteristics of the nanoliquid through thermophoresis and random diffusions. Nonlinear expressions of the given model are transformed through adequate transformations. The obtained expressions have been computed by the Newton built in-shooting technique. Results of influential variables for velocity, concentration, microorganism field, temperature and entropy rate are graphically studied. Clearly, velocity reduction is witnessed for the bioconvection Rayleigh number and magnetic variable. A higher heat generation variable leads to augmentation of temperature. An increase in the magnetic variable results in entropy and temperature enhancement. A higher Peclet number results in microorganism field reduction. Temperature distribution rises for radiation and the thermal Biot number. A higher solutal Biot number intensifies the concentration. The entropy rate for radiation and diffusion variables is enhanced.

Measurement of Cross-Sectional Velocity Distribution of Pneumatically Conveyed Particles in a Square-Shaped Pipe Through Gaussian Process Regression-Assisted Nonrestrictive Electrostatic Sensing

Online continuous measurement of the cross-sectional velocity distribution of pneumatically conveyed solids in a square-shaped pipe is desirable in monitoring and optimizing circulating fluidized beds, coal-fired power plants, and exhaust pipes. Due to the limitation of nonrestrictive electrostatic sensors in spatial sensitivity, it is difficult to accurately measure the velocity of particles in large-diameter pipes. In this article, a novel approach is presented for the measurement of cross-sectional particle velocity distribution in a square-shaped pipe using sensors and Gaussian process regression (GPR). The electrostatic sensor includes 12 pairs of strip-shaped electrodes. Experimental tests were conducted on a laboratory test rig to measure the cross-sectional particle velocities in a vertical square-shaped pipe under various experimental conditions. The GPR model is developed to infer the relationship between the input variables of velocities and the cross-sectional velocity distribution of particles in nine areas of the pipe cross section, and the performance of the built models was compared with other machine learning models. The relative error of velocities predicted under all the experimental conditions is within ±3%. When the training dataset is not comprehensive enough, the performance of the model is negatively affected, and the relative error range is −9% to +15%. With fewer measurement electrodes (input variables), the relative error of the predicted velocities in each area increases slightly but remains within ±5%. Results obtained suggest that the electrostatic sensor in conjunction with the GPR model is a feasible approach to obtain the cross-sectional velocity distribution of pneumatically conveyed particles in a square-shaped pipe.

Study of the wave scattering in geological environments for the propagation velocity estimation

Diffraction is a naturally physical phenomenon which plays an extremely key role in forming some theoretical foundations of analyzing geophysical data such as seismic reflection and high frequency electromagnetic, Ground Penetrating Radar to study geological objects. In this phenomenon, when a wave field propagates from a source to an object with small size or a rough surface, its wave energy receivers act as the secondary sources and send their energy parts back to geophones on the ground surface. The relationship between the wave propagation time and the receiver coordinates is formulated as a diffraction hyperbola. This paper reported examples of the high frequency electromagnetic and seismic scattering phenomena with their applications in the study of the wave propagation velocity, location of civil underground objects and seabed depth. The research on scattering phenomenon for the electromagnetic waves has been known and widely applied; however, studying the wave velocity model by the diffraction analysis from the high resolution reflection seismic data for a fixed source receiver distance can be firstly considered in Vietnam and in the world. To determine the two wave velocity types, two graphs of their energy and entropy attributes were built and then calculated from their Kirchhoff migrated data in velocity ranges in order to find out their attributes’ extremes versus velocity variables. Their migrated sections with correct wave velocities could correctly locate diffractors as underground anomalies and produced the maximum energy and minimum entropy values in the peaks of diffraction hyperbolae and the surrounding zones of the diffractors, respectively. These geophysical data were measured at the urban and coastal area of Can Gio district, Ho Chi Minh city, Vietnam.

Boundary Currents at the Northern Edge of the Chukchi Sea at 166°W

AbstractData from two moorings deployed at 166°W on the northern Chukchi shelf and slope from summer 2002 to fall 2004, as part of the Western Arctic Shelf‐Basin Interactions program, are analyzed to investigate the characteristics and variability of the flow in this region. The depth‐mean velocity at the outer‐shelf mooring is northeastward and bottom‐intensified, while that at the upper‐slope mooring is northwestward and surface‐intensified. This, together with results from a high resolution ocean and sea ice reanalysis, indicates that the outer‐shelf mooring sampled the seaward edge of the Chukchi Shelfbreak Jet, while the upper‐slope mooring sampled the shoreward edge of the Chukchi Slope Current. The coupled variability in velocity at both sites is related to the wind stress curl over the Chukchi Sea shelf, likely via Ekman dynamics and geostrophic set up, analogous to the dynamics of both currents closer to Barrow Canyon near 157°W. Hydrographic signals are analyzed to elucidate the origin of the water masses present at this location. It is argued that the annual appearance of Pacific‐origin warm water at the outer‐shelf (upper‐slope) mooring in late‐fall and winter originates from Herald (Barrow) Canyon some months earlier. Our results constitute the first robust evidence that the westward‐flowing Chukchi Slope Current persists this far west of Barrow Canyon.

Preliminary validity of the Draw a Shape Test for upper extremity assessment in multiple sclerosis.

To validate the smartphone sensor-based Draw a Shape Test - a part of the Floodlight Proof-of-Concept app for remotely assessing multiple sclerosis-related upper extremity impairment by tracing six different shapes. People with multiple sclerosis, classified functionally normal/abnormal via their Nine-Hole Peg Test time, and healthy controls participated in a 24-week, nonrandomized study. Spatial (trace accuracy), temporal (mean and variability in linear, angular, and radial drawing velocities, and dwell time ratio), and spatiotemporal features (trace celerity) were cross-sectionally analyzed for correlation with standard clinical and brain magnetic resonance imaging (normalized brain volume and total lesion volume) disease burden measures, and for capacity to differentiate people with multiple sclerosis from healthy controls. Data from 69 people with multiple sclerosis and 18 healthy controls were analyzed. Trace accuracy (all shapes), linear velocity variability (circle, figure-of-8, spiral shapes), and radial velocity variability (spiral shape) had a mostly fair/moderate-to-good correlation (|r|=0.14-0.66) with all disease burden measures. Trace celerity also had mostly fair/moderate-to-good correlation (|r|=0.18-0.41) with Nine-Hole Peg Test performance, cerebellar functional system score, and brain magnetic resonance imaging. Furthermore, partial correlation analysis related these results to motor impairment. People with multiple sclerosis showed greater drawing velocity variability, though slower mean velocity, than healthy controls. Linear velocity (spiral shape) and angular velocity (circle shape) potentially differentiate functionally normal people with multiple sclerosis from healthy controls. The Draw a Shape Test objectively assesses upper extremity impairment and correlates with all disease burden measures, thus aiding multiple sclerosis-related upper extremity impairment characterization.

Reliability of Force Plate Metrics During Standard Jump, Balance, and Plank Assessments in Military Personnel.

Prevention of musculoskeletal injury is vital to the readiness, performance, and health of military personnel with the use of specialized systems (e.g., force plates) to assess risk and/or physical performance of interest. This study aimed to identify the reliability of one specialized system during standard assessments in military personnel. Sixty-two male and ten female Australian Army soldiers performed a two-leg countermovement jump (CMJ), one-leg CMJ, one-leg balance, and one-arm plank assessments using a Sparta Science force plate system across three testing sessions. Sparta Science (e.g., total Sparta, balance and plank scores, jump height, and injury risk) and biomechanical (e.g., average eccentric rate of contraction, average concentric force, and sway velocity) variables were recorded for all sessions. Mean ± SD, intraclass correlation coefficients (ICCs), coefficient of variation, and bias and limits of agreement were calculated for all variables. Mean results were similar between sessions 2 and 3 (P > .05). The relative reliability for the Sparta Science (ICC = 0.28-0.91) and biomechanical variables (ICC = 0.03-0.85) was poor to excellent. The mean absolute reliability (coefficient of variation) for Sparta Science variables was similar to or lower than that of the biomechanical variables during the CMJ (1-10% vs. 3-7%), one-leg balance (4-6% vs. 9-14%), and one-arm plank (5-7% vs. 12-17%) assessments. The mean bias for most variables was small (<5% of the mean), while the limits of agreement varied with most unacceptable (±6-87% of the mean). The reliability of most Sparta Science and biomechanical variables during standard assessments was moderate to good. The typical variability in metrics documented will assist practitioners with the use of emerging technology to monitor and assess injury risk and/or training interventions in military personnel.

Stochastic dynamics of a discrete-time car-following model and its time-delayed feedback control

In this paper, a discrete-time optimal velocity model (DOVM) is presented by discretizing continuous car-following model into a difference equation. Considering the influences of stochastic disturbance on DOVM, the stochastic stability is studied by using Z-transform and Routh criterion. The theoretical expressions of the velocity oscillation amplitude and stability conditions are derived from the expected variance of the velocity variable. To stabilize the unstable traffic flow in DOVM, the time-delayed feedback control strategies are proposed by considering velocity difference and displacement–velocity–acceleration difference, respectively. Then, the stochastic stability of controlled DOVM and the choose of control parameters are provided. The numerical simulations for different traffic scenes indicate that the proposed control strategies can improve system stability and suppress traffic jams effectively. Based on the actual traffic data provided by NGSIM and quantum particle swarm algorithm, the parameters in DOVM are calibrated to optimize the car-following model. Furthermore, the proposed control methods are verified through the actual measured traffic data.

Mechanical model of the over-stroke displacement behaviour for double concave surface slider anti-seismic devices

For double concave curved surface slider (DCCSS) isolators with a flat rim and lacking restrainers, such as those most commonly used in Europe, the rigid slider can exceed the geometrical capability of the housing plate during earthquakes stronger than those produced in simulations. During this over-stroke displacement, DCCSSs preserve the ability to support superstructure gravity loads and the capacity to dissipate energy. There are currently no applicable hysteresis rules or available algebraic solutions that can be used to predict over-stroke behaviour for response-history analysis. This study presents an algebraic solution to extend basic theories for estimating the actual limit displacement of DCCSS devices with over-stroke capacity. DCCSS behaviour in the over-stroke sliding regime was modelled with a focus on geometrical compatibility and kinematics. The proposed analytical formulation was calibrated on the basis of experimental controlled-displacement tests performed on single DCCSS devices. A case study of a six-storey reinforced concrete frame isolated building was modelled using a combination of non-linear elements that are currently available in several structural analysis software packages and able to correctly model over-stroke displacement behaviour for non-linear time history analyses. The DCCSS model was augmented with a friction model capable of accounting for torsional effects, axial load, and velocity variabilities. Comparison with non-linear dynamic analysis outcomes shows that the forces and displacements in the over-stroke sliding regime are predictable and therefore useful for the designer.

Two substellar survivor candidates: one found and one missing

ABSTRACT This study presents observations of two possible substellar survivors of post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy of GD 1400 reveals a 9.98 h orbital period, where the benchmark brown dwarf has M2 = 68 ± 8 MJup, Teff ≈ 2100 K, and a cooling age under 1 Gyr. A substellar mass in the lower range of allowed values is favoured by the gravitational redshift of the primary. Synthetic brown dwarf spectra are able to reproduce the observed CO bands, but lines below the bandhead are notably overpredicted. The known infrared excess towards PG 0010+281 is consistent with a substellar companion, yet no radial velocity or photometric variability is found despite extensive searches. Three independent stellar mass determinations all suggest enhanced mass-loss associated with binary evolution, where the youngest total age for an isolated star is 7.5 ± 2.5 Gyr. A possible solution to this conundrum is the cannibalization of one or more giant planets, which enhanced mass-loss post-main sequence, but were ultimately destroyed. PG 0010 + 281 is likely orbited by a debris disc that is comfortably exterior to the Roche limit, adding to the growing number of non-canonical discs orbiting white dwarfs. At present, only L-type (brown) dwarfs are known to survive direct engulfment during the post-main sequence, whereas T- and Y-type substellar companions persist at wide separations. These demographics indicate that roughly 50 MJup is required to robustly avoid post-main sequence annihilation, suggesting all closely orbiting giant planets are consumed, which may contribute to mass-loss and magnetic-field generation in white dwarfs and their immediate progenitors.

Improving the accuracy of discretisations of the vector transport equation on the lowest-order quadrilateral Raviart-Thomas finite elements

Within finite element models of fluids, vector-valued fields such as velocity or momentum variables are commonly discretised using the Raviart-Thomas elements. However, when using the lowest-order quadrilateral Raviart-Thomas elements, standard finite element discretisations of the vector transport equation typically have a low order of spatial accuracy. This paper describes two schemes that improve the accuracy of transporting such vector-valued fields on two-dimensional curved manifolds.The first scheme that is presented reconstructs the transported field in a higher-order function space, where the transport equation is then solved. The second scheme applies a mixed finite element formulation to the vector transport equation, simultaneously solving for the transported field and its vorticity. An approach to stabilising this mixed vector-vorticity formulation is presented that uses a Streamline Upwind Petrov-Galerkin (SUPG) method. These schemes are then demonstrated, along with their accuracy properties, through some numerical tests. Two new test cases are used to assess the transport of vector-valued fields on curved manifolds, solving the vector transport equation in isolation. The improvement of the schemes is also shown through two standard test cases for rotating shallow-water models.

Variability of the coastal currents, waves and wind surge along the shore of the South-Eastern Baltic (Kaliningrad Oblast, Russian Federation)

The coastline of the Kaliningrad Oblast is an area of the South-East Baltic, which continues from the Vistula Spit to the Curonian Spit via Sambia Peninsula. The coastline has been subject to severe erosion over the past years. The goal of the paper is to analyse whether the alongshore variations of the storm surge water level, field of waves and currents are the reason for the erosion alongshore variability. The numerical simulations were carried out using the quasi-stationary approach for the model wind. The offshore wave breaking distance and the non-linear dependence between wind surge and wind speed were estimated for four typical coastline sites. The alongshore velocity on most of the coastline was enough powerful to transport the fine, medium and coarse sands. West, northern-west and north winds were defined as the most dangerous for coastal erosion. The convergence and divergence of alongshore currents as well as the vortex zones were identified for each wind direction. The results were used to analyse the alongshore current velocity, wind surge, and significant wave height variability against the shore erosion characteristics. The hypothesis that the places of convergence and divergence of alongshore currents correspond to the accumulative and erosion zones was not confirmed with one exception on the western shore of the Sambia Peninsula. Three options were supposed to explain the absence of correlation between the monitoring results on coastal erosion and modelled hydrodynamic conditions: the studied shore has not had enough free sand to demonstrate the typical behaviour of dissipative shores; the erosion characteristics depend on the very local conditions which were not resolved by numerical model; the main erosion has happened at the short term event basis when waves reach the shore at the background of a general Baltic Sea high-water level and is not a result of the general alongshore distribution of waves, wave surge and current characteristics.

Cognitive functioning and simulated driving in older adults with and without cognitive impairment

AbstractBackgroundAge‐related changes in cognitive functions affect complex task engagement such as driving. Studies have demonstrated high occurrences of driving errors and crashes among older adults, particularly those with mild cognitive impairment (MCI). We have previously demonstrated that fatigue contributes to detriments in driving ability, especially among MCI, and that attention‐maintenance tasks (AMT) improve older cognitively normal (OCN) but not MCI performance. This study considers which cognitive deficits predict driving performance across AMT conditions.MethodsParticipants included 34 OCN and 21 MCI adults age 60+ years diagnosed through consensus conference, who completed tests of memory (HVLT‐R delayed recall), executive functioning (Trail Making Test B; TMB), working memory (CogState One Back Test, ONB), simple reaction time (CogState Detection Test, DET), and choice reaction time (CogState Identification Test, IDN). Computerized driving scenarios were presented on a 45” flat screen monitor, which included a 50‐minute simulated drive designed to induce fatigue, followed by four 10‐minute sessions alternating between driving with and without AMT. Lane position, velocity, lane and velocity variability, and driving errors (e.g., leaving the road, crossing midline) were compared across 10‐minute driving segments. Cognitive measures and diagnosis were used to predict driving performance.ResultsParticipants with MCI 1) maintained significantly slower average speed, 2) demonstrated higher variability in lane‐keeping, and 3) had greater velocity variability, only in the non‐AMT condition. OCN participants performed significantly better on all cognitive measures, except DET. Linear regressions showed that TMB, alone, predicted average velocity during the AMT driving condition with no significant predictors for the non‐AMT. Velocity variability during the non‐AMT driving condition was predicted by the main effect of Diagnosis, TMBxDiagnosis, and ONBxDiagnosis interactions. TMB and HVLT‐R predicted velocity variability during the AMT condition. Lane variability during both driving conditions was predicted by DETxDiagnosis and IDNxDiagnosis.ConclusionsPerformance on TMB and its interactions are predominantly important predictors for velocity‐related driving conditions. Reaction time decrements among those with MCI predict lane variability. This suggests that executive functions are particularly needed in maintaining velocity, while monitoring is critical for maintaining lane position. Our findings demonstrate that higher cognitive burden likely accentuates driving difficulty, especially in MCI.

A new seismic tomography system for geotechnical centrifuges

Seismic tomography has been extensively used in geophysics for different purposes, including geological mapping, characterisation of inner earth structure and prospecting for oil and gas. In geophysics, seismic or electromagnetic waves are commonly used to provide tomographic information. In the geotechnical area, seismic tomography is emerging as a promising technique that can be used to determine the spatial variability of shear wave velocities and hence the small strain stiffness of geomaterials, especially when used in the centrifuge where in-situ stress conditions can be mimicked closely. This paper describes the development of a seismic tomography technique in the centrifuge. This technology can be used to image variations of soil stiffness under various mechanical, chemical and physical conditions. The paper describes the various components of the system, which includes arrays of small-size bender elements, hardware and software used to transmit, receive and acquire the shear wave signals during a centrifuge test. The paper illustrates the performance of the system at both 1g and in the centrifuge. Results of tomographic inversion performed on travel-time data obtained from these tests are discussed.

Evaluating the influence of a constraint manipulation on technical, tactical and physical athlete behaviour.

Evaluating practice design is an important component of supporting skill acquisition and improving team-sport performance. Constraint manipulations, including creating a numerical advantage or disadvantage during training, may be implemented by coaches to influence aspects of player or team behaviour. This study presents methods to evaluate the interaction between technical, tactical and physical behaviours of professional Australian Football players during numerical advantage and disadvantage conditions within a small-sided game. During each repetition of the game, team behaviour was manually annotated to determine: repetition duration, disposal speed, total disposals, efficiency, and disposal type. Global Positioning System devices were used to quantify tactical (surface area) and physical (velocity and high intensity running) variables. A rule association and classification tree analysis were undertaken. The top five rules for each constraint manipulation had confidence levels between 73.3% and 100%, which identified the most frequent behaviour interactions. Specifically, four advantage rules involved high surface area and medium high intensity running indicating the attacking team's frequent movement solution within this constraint. The classification tree included three behaviour metrics: surface area, velocity 1SD and repetition duration, and identified two unique movement solutions for each constraint manipulation. These results may inform if player behaviour is achieving the desired outcomes of a constraint manipulation, which could help practitioners determine the efficacy of a training task. Further, critical constraint values provided by the models may guide practitioners in their ongoing constraint manipulations to facilitate skill acquisition. Sport practitioners can adapt these methods to evaluate constraint manipulations and inform practice design.

Dynamic iterative approximate deconvolution model for large-eddy simulation of dense gas compressible turbulence

We study large-eddy simulation of compressible decaying isotropic turbulence of dense gas at initial turbulent Mach numbers of 0.4 and 0.8. The unclosed subgrid-scale (SGS) terms are approximated by the dynamic iterative approximate deconvolution (DIAD) model proposed by Yuan et al. [“Dynamic iterative approximate deconvolution models for large-eddy simulation of turbulence,” Phys. Fluids 33, 085125 (2021)], and compared with the dynamic Smagorinsky (DSM) model. In an a priori test, the correlation coefficients of the DIAD model for most SGS terms are larger than 0.98, and the relative errors are smaller than 0.2, except for the SGS internal energy flux. In an a posteriori test, the DIAD model can well predict the probability density functions (PDFs) of SGS terms involving thermodynamic variables. Moreover, the DIAD model shows greater advantages than the DSM model in predicting various statistics and structures of compressible turbulence of dense gas, including spectra of velocity and thermodynamic variables, PDFs of SGS kinetic energy flux, deviatoric SGS stress and normalized strain-rate tensor, and the instantaneous spatial structures of vorticity.

Searching for Compact Objects in Binaries with Gaia DR3

We search for compact objects in binaries based on Gaia DR3. A sample of 10 targets is derived under the following conditions: the radial velocity variable, low temperature (T eff < 6000 K), high mass function (f(M 2) > 1M ⊙), and ellipsoidal-like light curves. Two targets have LAMOST spectroscopic observations, one of which is a double-lined spectroscopic binary. The observational data of seven targets are not self-consistent, since their photometric periods are even shorter than the theoretical minimum orbital periods calculated by the stellar parameters from Gaia DR3. After excluding these seven inconsistent targets and another target contaminated by a near-bright star, the remaining two targets may contain compact objects worth follow-up observations. This work may serve as an example to demonstrate the feasibility of searching for compact objects in the massive Gaia data.

Blood Pressure Responses During Exercise: Physiological Correlates and Clinical Implications.

Abnormal blood pressure (BP) responses to exercise can predict adverse cardiovascular outcomes, but their optimal measurement and definitions are poorly understood. We combined frequently sampled BP during cardiopulmonary exercise testing with vascular stiffness assessment to parse cardiac and vascular components of exercise BP. Cardiopulmonary exercise testing with BP measured every two minutes and resting vascular tonometry were performed in 2858 Framingham Heart Study participants. Linear regression was used to analyze sex-specific exercise BP patterns as a function of arterial stiffness (carotid-femoral pulse wave velocity) and cardiac-peripheral performance (defined by peak O2 pulse). Our sample was balanced by sex (52% women) with mean age 54±9 years and 47% with hypertension. We observed variability in carotid-femoral pulse wave velocity and peak O2 pulse across individuals with clinically defined exercise hypertension (peak systolic BP [SBP] in men ≥210 mm Hg; in women ≥190 mm Hg). Despite similar resting SBP and cardiometabolic profiles, individuals with higher peak O2 pulse displayed higher peak SBP (P≤0.017) alongside higher fitness levels (P<0.001), suggesting that high peak exercise SBP in the context of high peak O2 pulse may in fact be favorable. Although both higher (favorable) O2 pulse and higher (adverse) arterial stiffness were associated with greater peak SBP (P<0.0001 for both), the magnitude of association of carotid-femoral pulse wave velocity with peak SBP was higher in women (sex-carotid-femoral pulse wave velocity interaction P<0.0001). In sex-specific models, exercise SBP measures accounting for workload (eg, SBP during unloaded exercise, SBP at 75 watts, and SBP/workload slope) were directly associated with the adverse features of greater arterial stiffness and lower peak O2 pulse. Higher peak exercise SBP reflects a complex trade-off between arterial stiffness and cardiac-peripheral performance that differs by sex. Studies of BP responses to exercise accounting for vascular and cardiac physiology may illuminate mechanisms of hypertension and clarify clinical interpretation of exercise BP.

Spectral Gap Formation to Kinetic Equations with Soft Potentials in Bounded Domain

It has been unknown in kinetic theory whether the linearized Boltzmann or Landau equation with soft potentials admits a spectral gap in the spatially inhomogeneous setting. Most of existing works indicate a negative answer because the spectrum of two linearized self-adjoint collision operators is accumulated to the origin in case of soft interactions. In the paper we rather prove it in an affirmative way when the space domain is bounded with an inflow boundary condition. The key strategy is to introduce a new Hilbert space with an exponential weight function that involves the inner product of space and velocity variables and also has the strictly positive upper and lower bounds. The action of the transport operator on such space-velocity dependent weight function induces an extra non-degenerate relaxation dissipation in large velocity that can be employed to compensate the degenerate spectral gap and hence give the exponential decay for solutions in contrast with the sub-exponential decay in either the spatially homogeneous case or the case of torus domain. The result reveals a new insight of hypocoercivity for kinetic equations with soft potentials in the specified situation.

Mutagenesis alters sperm swimming velocity in Astyanax cave fish

We investigated the hypothesis that intra ejaculate sperm competition screens against the transmission of deleterious alleles, including new mutants, from male parent to offspring. Recent investigations have established that sperm haploid genotypes can have major effects on sperm traits such as cellular robustness, longevity, and fertilization success. However, there is no evidence that new mutations can meaningfully affect sperm phenotypes. We tested this directly by comparing sperm from mutagenized and non-mutagenized control males in Astyanax fish. We used N-ethyl-N-nitrosourea (ENU) to induce single base substitutions in spermatogonial stem cells. We looked at swimming velocity, an important factor contributing to fertilization success, and flagellar length. Variability in swimming velocity was significantly higher in sperm from mutagenized males than in control sperm, reflecting their increased allelic diversity. In contrast, flagellar length, which is fixed during diploid stages of spermatogenesis, was unaffected by ENU treatment. We briefly discuss the implications of intra-ejaculate screening for maintenance of anisogamy and for outcomes of assisted reproductive technology.