Total Velocity Research Articles

Unveiling the shape: A multi-wavelength analysis of the galaxy clusters Abell 76 and Abell 1307

We analyse the dynamical state of the galaxy clusters Abell 76 and Abell 1307 from the optical point of view, presenting a coherent scenario that responds to the X-ray emissions observed in these structures. Our study is based on 231 and 164 spectroscopic redshifts, for the clusters A76 and A1307, respectively, obtained mostly with the Telescopio Nazionale Galileo, and complemented with others collected from the SDSS DR16 spectroscopic database and the literature. We find that A76 and A1307 are two galaxy clusters at z = 0.0390 and 0.0815, respectively, with a velocity dispersion of 650 ± 56 km s−1 and 863 ± 85 km s−1, and they show velocity distributions following, in practice, Gaussian profiles. From our dynamical analysis, X-ray studies and SZ-Planck emission, we obtain a mean total mass M500 = 1.7 ± 0.6 ⋅ 1014 M⊙ and 3.5 ± 1.3 ⋅ 1014 M⊙ for A76 and A1307, respectively. Using the SDSS DR16 photometric database, we find that the spatial distribution of likely cluster members in the case of A76 is very anisotropic, while A1307 shows a compact distribution of galaxies, but it is double peaked and elongated in the south-north direction. Using XMM-Newton X-ray data, we compared the surface brightness maps with galaxy distributions and noticed that both distributions are correlated. We reconstructed the total mass profile and velocity anisotropy of both clusters by analysing the full projected phase space, through the MG-MAMPOSSt code. Our study reveals a slight indication of radial orbits for A76, while A1307 seems to prefer more isotropic orbits in the whole cluster range. In summary, A76 represents a typical young cluster, in an early stage of formation, with a very low X-ray surface brightness but a high temperature showing a very anisotropic galaxy distribution. A1307 is however more consolidated and massive showing in-homogeneous galaxy distribution and an asymmetric X-ray emission, which suggest a scenario characterised by recent minor mergers.

Numerical simulation and experimental study of microplastic transport under open channel shear flow: Roles of particle physical properties and flow velocities

Microplastic (MP) transport patterns under open channel shear flow remain unclear. This study investigates the transport laws of MPs at various flow velocities, MP densities, sizes and concentrations in the U-shaped experimental flume and the numerical flume based on Lattice Boltzmann Method (LBM). The results indicate that the average horizontal particle velocity and the transport distances of Polyvinyl chloride (PVC) and Polystyrene (PS) particles increase with the average cross-sectional flow velocity, while the average vertical particle velocity decreases with it. The total average particle velocity closely matches the average vertical particle velocity, regardless of the variation in MP size, density and concentration. Formula-based analysis reveals that the acceleration of spherical MP transport mainly depends on the particle size and its consequent relative drag force term (RDFT) under the conditions with a single type of MP particles, but on the particle density and its consequent RDFT and relative gravity term (RGT) in the case concerning different types of MP particles with identical particle sizes. The average horizontal particle velocity maximum of PVC and PS are both strongly correlated with the average flow velocity maximum in the cross-section. This correlation lowers with the MP particle size and concentration, and is independent of MP density. Our findings can provide reference for the prevention and control of MP pollution in rivers.

Effect of Different Semen Extenders on Cat Epididymal Semen Cryopreservation

BACKGROUND: Cryopreservation of spermatozoa is a biotechnology used for fertilization purposes and preservation of genetic material in various domestic species. OBJECTIVE: To determine the efficacy of two different commercial semen diluents in the cryopreservation of epididymal semen of domestic cats. MATERIALS AND METHODS: Twenty male cats aged between 1 - 3 years and weighing 2.5 - 4.5 kg were used in the study. The testicular tissues removed from the cats were immediately brought to the laboratory in physiological saline and the epididymal parts were trimmed in commercial semen extenders (INRA 96, Group I; OPTIXCELL, Group II). Diluted semen samples were cooled to 4°C and filled into 0.25 mL straws. Semen samples were frozen in a programmable semen freezing device and then placed in a liquid nitrogen container at -196 C. Semen samples were thawed at 38°C for 25 s. Thawed semen samples were evaluated in terms of motility and kinematic parameters using CASA. RESULTS: No statistical difference was found between the groups in terms of total motility, progressive motility, and velocity parameters at 4 °C. The rate of spermatozoa at slow speeds was found to be lower in group II. In addition, after freezing and thawing process, no statistical difference was observed between the groups in terms of motility, kinematics, and velocity parameters. CONCLUSION: Both commercial semen extenders can be used for cryopreservation of cat epididymal semen.

Construct Validity of a Wearable Inertial Measurement Unit (IMU) in Measuring Postural Sway and the Effect of Visual Deprivation in Healthy Older Adults

Inertial Motor sensors (IMUs) are valid instruments for measuring postural sway but their ability to detect changes derived from visual deprivation in healthy older adults requires further investigations. We examined the validity and relationship of IMU sensor-derived postural sway measures compared to force plates for different eye conditions in healthy older adults (32 females, 33 males). We compared the relationship of the center of mass and center of pressure (CoM and CoP)-derived total length, root means square (RMS) distance, mean velocity, and 95% confidence interval ellipse area (95% CI ellipse area). In addition, we examined the relationship of the IMU sensor in discriminating between open- (EO) and closed-eye (EC) conditions compared to the force plate. A significant effect of the instruments and eye conditions was found for almost all the variables. Overall, EO and EC variables within (force plate r, from 0.38 to 0.78; IMU sensor r, from 0.36 to 0.69) as well as between (r from 0.50 to 0.88) instruments were moderately to strongly correlated. The EC:EO ratios of RMS distance and 95% CI ellipse area were not different between instruments, while there were significant differences between total length (p = 0.973) and mean velocity (p = 0.703). The ratios’ correlation coefficients between instruments ranged from moderate (r = 0.65) to strong (r = 0.87). The IMU sensor offers an affordable, valid alternative to a force plate for objective, postural sway assessment.

Self-propulsion performance prediction in calm water based on RANS/TEBEM coupling method

This paper proposes a hybrid RANS/TEBEM method to conduct self-propulsion prediction in calm water with accuracy and improve its efficiency by means of larger time step. In the coupling procedure, the rotating propeller is represented by time-averaged, spatial inhomogeneous body force field obtained from the potential flow solver based on Taylor Expansion Boundary Element Method (TEBEM) in RANS simulation. Effective wake is evaluated by subtracting induced velocities computed by potential solver from total velocities in RANS solver at a coupling plane upstream of propeller plane. The influence of coupling plane position and grid density on the numerical results is also investigated. Through KCS and KVLCC2 cases, it is shown that the predicted value of propeller revolution speed is within 4% of the experimental value, verifying the robustness and reliability of this method.

Optimizing the Pore Structure of Lotus-Type Porous Copper Fabricated by Continuous Casting.

Lotus-type porous copper was fabricated using a continuous casting method in pressurized hydrogen and nitrogen gas atmospheres. This study evaluates the effects of process parameters, such as the hydrogen ratio, total pressure, and transference velocity, on the resulting pore structure. A continuous casting process was developed to facilitate the mass production of lotus-type porous copper. To achieve the desired porosity and pore diameter for large-scale manufacturing, a systematic evaluation of the influence of each process parameter was conducted. Lotus-type porous copper was produced within a hydrogen ratio range of 25-50%, a transference velocity range of 30-90 mm∙min-1, and a total pressure range of 0.2-0.4 MPa. As a result, the porosity ranged from 36% to 55% and the pore size varied from 300 to 1500 µm, demonstrating a wide range of porosities and pore sizes. Through process optimization, it is possible to control the porosity and pore size. The hydrogen ratio and total pressure were found to primarily affect porosity, whereas the hydrogen ratio, transference velocity, and total pressure significantly influenced pore diameter. When considering these parameters together, porosity was most influenced by the hydrogen ratio, whereas the total pressure and transference velocity had a greater influence on pore diameter. Reducing the hydrogen ratio and increasing the transference velocity and total pressure reduced the pore diameter and porosity. This optimization of the continuous casting process enables the control of porosity and pore diameter, facilitating the production of lotus-type porous copper with the desired pore structures.

Acupuncture treatment of diabetic peripheral neuropathy: an overview of systematic reviews based on evidence mapping.

The study attempted to evaluate the meta-analyses (MAs) of the acupuncture treatment of diabetic peripheral neuropathy (DPN) to provide a basis for clinical decision-making. Eight databases, such as PubMed, Cochrane Library, Embase, Web of Science, CNKI, Wanfang Data, CQVIP, and CBM, were searched from database creation to December 22, 2023. The MAs of DPN treatment using acupuncture or acupuncture combined with conventional Western medicine were included. AMSTAR-2 and PRISMA 2020 helped evaluate the methodological and reporting quality of the included studies. The GRADE methodology helped assess the evidence quality of outcome indicators. Evidence mapping was performed to display evaluation results. A total of 18 MAs involving 23,240 DPN patients were included. Based on the methodological quality evaluation, four MAs were of "moderate" quality, seven had a quality grade of "low," and another seven were of "critically low" quality. The evidence quality evaluation showed that among studies of acupuncture vs. conventional Western medicine, four had an evidence quality of "moderate," 18 had an evidence quality of "low," and 17 had an evidence quality of "critically low" and that among studies of acupuncture + conventional Western medicine vs. conventional Western medicine, 12 had an evidence quality of "moderate," 29 had an evidence quality of "low," and 33 had an evidence quality of "critically low." Compared with conventional Western medicine, simple acupuncture and acupuncture + conventional Western medicine significantly improved total effective rate (TER) and nerve conduction velocity (NCV). Acupuncture treatment of DPN significantly improves TER and NCV with proven safety. However, the MAs of the acupuncture treatment of DPN must strictly refer to relevant standards and specifications regarding methodological and reporting quality, along with the design, execution, and reporting of primary randomized controlled trials (RCTs).

Numerical Simulation of Fixed-Free End Beam’s Modal Behaviour using Two-Way Coupled Fluid-Structure Interaction Approach

The fluid flow velocity stands as a pivotal parameter with a great influence on the mutual interaction between the fluid domain and structure. This paper focuses on structural deformation, structural velocity, von-Mises stress and frequency response of a fixed-free end beam using two-way coupled fluid-structure interaction within ANSYS Workbench. The parameters such as deformed fluid pressure and velocity were analysed across three diverse flow regimes: laminar, transitional and turbulent – each aligned with distinct fluid velocities. The outcomes show that the total deformation, velocity and von-Mises stress distribution of the fixed-free end beam increase as the inlet fluid velocity increases. As a result, the pressure and velocity distribution in the fluid flow which receiving the resultant or leftover structure deflection also increases as the incoming fluid velocity increases. Furthermore, the analysis probes the frequency response in turbulent flow conditions reveals higher values compared to laminar and transitional flows, albeit within the same natural frequency domain. This observation marks significant vibrational characteristics found in the presence of turbulent flow dynamics.

An equivalent source method for acoustic problems with thermoviscous effects.

This paper presents an equivalent source method (ESM) for analyzing sound propagation in small-scale acoustic structures with thermoviscous effects. The formulations that describe the thermal, viscous, and acoustic modes for thermoviscous acoustic problems are introduced. The concept of ESM is then applied to solve these formulations, resulting in an efficient numerical computation and implementation procedure. Based on two different strategies, the obtained ESM formulations are coupled at the boundary using the isothermal, non-slip, and null-divergence conditions. The coupling based on the first strategy is efficient for solving thermoviscous acoustic problems with few matrices required. However, this procedure faces the evaluation of the tangential derivatives of the boundary velocity. Coupling the ESM formulations directly for each component of the total particle velocity at the boundary has no such problem, which leads to the second strategy. However, it entails a larger memory usage compared to the former. Additionally, the coupled finite element method (FEM)-ESM formulations based on the above strategies are developed for acoustic-structural interaction. The validity of the presented ESM formulations is demonstrated through benchmark examples, and that of the coupled FEM-ESM formulation is illustrated by the numerical analysis of a simplified microphone.

МОДЕЛЬ НЕПРЕРЫВНОГО ТРАНСПОРТНОГО ПОТОКА БЕСПИЛОТНЫХ АВТОМОБИЛЕЙ ПРИ ДВИЖЕНИИ НА СЕРПАНТИНЕ С ВИРАЖАМИ С УЧЕТОМ СРЕДНЕЙ СКОРОСТИ ДВИЖУЩИХСЯ ВПЕРЕДИ АВТОМОБИЛЕЙ

The paper proposes a new model of continuous traffic flow of unmanned autonomous cars when travelling on a serpentine with curves, taking into accountthe average speed of the cars ahead. The review of existing traffic flow models, in particular, the models of following the leader, such as the optimal speed model, generalised traffic model, model of total velocity difference is carried out. It is noted that these models do not take into account the peculiarities of traffic on serpentines with turns. On the basis of the existing models, a new model of continuous traffic flow has been developed, the principal difference of which is the consideration of the transverse slope of the road (turn) when travelling on a serpentine. The model takes into account the action of forces on the vehicle, including gravity, driving force and centripetal force. The prospects of using the developed model in the conditions of using intelligent transport systems, when the information about the average speed of vehicles moving ahead is transmitted over the network, are shown. Th proposed model allows to take into account the transverse slope of the road on curvilinear serpentine sections when calculating speed modes, to adequately assess the carrying capacity and identify potentially dangerous sections for optimisation of design decisions when creating unmanned transport.

A new evaluation method for sand control performance of slotted screen

Evaluation method of slotted screen performance is a critical concern for sand control. Despite its significance, comprehensive investigations into quantitative study of sand retaining during the complex flow process need further in-depth study, particularly in numerical simulation research model of the slotted screen. This paper adopts the two-way coupling calculation method of computational fluid dynamics (CFD) and discrete element method (DEM) for the particle movement and fluid flow at the slotted screen and establishes a numerical model of the sand particle migration process through the slotted screen. The sand particle deposition and plugging dynamics on the surface of the sand retaining medium and the micro sand plugging mechanism and blockage pattern are studied. The fractal dimension of formation sand is introduced to characterize different distribution of formation sand. The effects of fluid viscosity, width of the slotted screen, sand production concentration, fluid velocity and particle size distribution on sand production, sand passing rate and particle size distribution of formation sand passing through the slot and plugging behavior are studied. The sand plugging process of slotted screen can be divided into three stages: the beginning of blockage, the intensification of blockage, and the balance of blockage. Under simulated conditions, the initial sand plugging rate is 87%, and as the blockage intensifies, the sand plugging rate gradually increases to 96.5%. Based on the analysis of numerical simulation results, the index of total seepage resistance damage amplitude and velocity, general sand retention ratio and passed-sand size were defined to construct the integrated evaluation method of slotted screen media, which involves the performance of sand retention, anti-plugging and flow ability. A brand new set of ideas on quantifying the integrated evaluation method were introduced to calculate the individual and integrated performance indicators of the slotted screen based on simulated data. The quantitative evaluation of the sand control performance of the slotted screen provides guidance and reference for the parameter design of the slotted screen in the target oil region and the accuracy optimization of the sand control medium.

The role of a medium-term physical exercise program in improving cardiovascular parameters in hypertensive patients

The objective of our study was to evaluate the changes in cardiovascular parameters in patients with hypertension who completed a 3-month physical exercise program. 229 sub-jects with high normal values of blood pressure and stage 1 hypertension (group 1) and 120 patients with stage 2 hypertension (group 2) followed a 3-month physical exercise program. The following parameters were measured: systolic blood pressure, diastolic blood pressure, pulse pressure, heart rate, pulse wave velocity. For group 1 there were sta-tistically significant differences for all the tested parameters after the 3-month program (decreased systolic blood pressure, heart rate, pulse pressure and pulse wave velocity, p< 0.0001; lower diastolic blood pressure, p=0.018)). In group 2 all the tested parameters had decreased values after the 3-month rehabilitation program. However, only for the pulse wave velocity there was recorded a statistically significant reduction after the exercise program (p< 0.001). There were significant direct correlations between total cholesterol and pulse wave velocity for group 1 at both initial (p=0.024) and final assessments (p=0.03), and for group 2 patients at the 3-month assessment (p=0.001). A medium-term physical exercise program improved the cardiovascular parameters (blood pressure, arte-rial stiffness) in hypertensive patients.

Higher abundance of DLD protein in buffalo bull spermatozoa causes elevated ROS production leading to early sperm capacitation and reduction in fertilizing ability

BackgroudBefore fertilization, spermatozoa undergo a crucial maturation step called capacitation, which is a unique event regulates the sperm’s ability for successful fertilization. The capacitation process takes place as the spermatozoa pass through the female reproductive tract (FRT). Dihydrolipoamide dehydrogenase (DLD) protein is a post-pyruvate metabolic enzyme, exhibiting reactive oxygen species (ROS) production which causes capacitation. Additionally, other vital functions of DLD in buffalo spermatozoa are hyperactivation and acrosome reaction. DLD produces the optimum amount of ROS required to induce capacitation process in FRT. Depending on physiological or pathophysiological conditions, DLD can either enhance or attenuate the production of reactive oxygen species (ROS). Aim of this study was to investigate whether changes in the production of ROS in sperm cells can impact their ability to fertilize by triggering the capacitation and acrosome reaction.ResultsIn this study, abundance of DLD protein was quantified between high (n = 5) and low fertile bull (n = 5) spermatozoa. It was found that compared to high-fertile (HF) bulls, low-fertile (LF) bulls exhibited significantly (P < 0.05) higher DLD abundances. Herein, we optimised the MICA concentration to inhibit DLD function, spermatozoa were treated with MICA in time (0, 1, 2, 3, 4, and 5 h) and concentrations (1, 2.5, 5, and 10 mmol/L) dependent manner. Maximum DLD inhibition was found to be at 4 h in 10 mmol/L MICA concentration, which was used for further experimentation in HF and LF. Based on DLD inhibition it was seen that LF bull spermatozoa exhibited significantly (P < 0.05) higher ROS production and acrosome reaction in comparison to the HF bull spermatozoa. The kinematic parameters of the spermatozoa such as percent total motility, velocity parameters (VCL, VSL, and VAP) and other parameters (BCF, STR, and LIN) were also decreased in MICA treated spermatozoa in comparison to the control (capacitated) spermatozoa.ConclusionsThe present study provides an initial evidence explaining the buffalo bull spermatozoa with higher DLD abundance undergo early capacitation, which subsequently reduces their capacity to fertilize.

Association between movement speed and instability catch kinematics and the differences between individuals with and without chronic low back pain

Studies reported the existence of instability catch (IC) during trunk flexion in patients with chronic low back pain (CLBP). However, different movement speeds can cause different neuromuscular demands resulting in altered kinematic patterns. In addition, kinematic characterization corresponding to clinical observation of IC is still limited. Therefore, this study aimed to determine (1) the association between movement speed and kinematic parameters representing IC during trunk flexion and (2) the differences in kinematic parameters between individuals with and without CLBP. Fifteen no low back pain (NoLBP) and 15 CLBP individuals were recruited. Inertial measurement units (IMU) were attached to T3, L1, and S2 spinous processes. Participants performed active trunk flexion while IMU data were simultaneously collected. Total trunk, lumbar, and pelvic mean angular velocity (T_MV, L_MV, and P_MV), as well as number of zero-crossings, peak-to-peak, and area of sudden deceleration and acceleration (Num, P2P, and Area), were derived. Pearson’s correlation tests were used to determine the association between T_MV and L_MV, P_MV, Num, P2P, and Area. An ANCOVA was performed to determine the difference in kinematic parameters between groups using movement speed as a covariate. Significant associations (P < 0.05) were found between movement speed and other kinematic parameters, except for Area. Results showed that L_MV significantly differed from the P_MV (P = 0.002) in the CLBP group, while a significant between-group difference (P = 0.037) was found in the P_MV. Additionally, significant between-group differences (P < 0.05) in P2P and Area were observed. The associations between movement speed and kinematic parameters suggest that movement speed changes can alter kinematic patterns. Therefore, clinicians may challenge lumbopelvic neuromuscular control by modifying movement speed to elicit greater change in kinematic patterns. In addition, the NoLBP group used shared lumbar and pelvic contributions, while the CLBP group used less pelvic contribution. Finally, P2P and Area appeared to offer the greatest sensitivity to differentiate between the groups. Overall, these findings may enhance the understanding of the mechanism underlying IC in CLBP.

A parametric investigation of Dual-throat nozzle bypass channel configurations for advanced Aviation applications

The Bypass Dual-Throat Nozzle (BDTN) has garnered growing attention due to its remarkable thrust vectoring capabilities. This type of nozzle boasts broad application prospects as it achieves deflection control of the jet stream merely through regulating the opening and closing of bypass channels. Our comprehensive study delves deeply into the intricate parameterization of the bypass channel within the BDTN. Research has demonstrated that utilizing Fluent software in conjunction with the Realizable k-epsilon turbulence model, standard wall functions, and the Sutherland formula for viscosity coefficient approximation can yield a relatively accurate representation of the vector flow field structure within the BDTN. Following the validation of the numerical computation methodology employed in this study, we have investigated the influence of factors such as bypass channel radius, precise valve positioning, and actuation direction on the nozzle's vectoring performance. Key findings indicate that, due to the relatively small proportion of secondary flow, the radius of the bypass channel has minimal impact on the thrust vector angle. The positioning of the valve and its opening direction are critical in determining the thrust vector angle, requiring careful consideration during the design and optimization process. Fully opening the bypass channel does not necessarily yield the maximum thrust vector angle. Moreover, the total pressure, velocity, position, and direction of the secondary flow within the bypass channel exert a more profound influence on the nozzle's vector performance compared to the mere presence of the secondary flow itself. Notably, the forward opening method of the valve emerges as the preferred choice, as it facilitates more precise later vector control.

Geodetic Evidence for Distributed Shear Below the Brittle Crust of the Walker Lane, Western United States

AbstractModels of active deformation of the Earth's crust are predominantly represented with dislocations having a downdip continuation into the lower crust, where the fault slips continuously. This model predicts surface strain accumulation concentrated near the fault during the interseismic period. In an alternative model, faults do not extend beneath the elastic portion of the crust and are accompanied by a wide zone of distributed shear underneath, predicting a more constant strain rate lacking concentrations at the faults. We use high‐precision GPS data collected across the northern and central Walker Lane, USA— a region of complex faulting near the western edge of the Basin and Range Province to evaluate which model is appropriate. Despite the existence of dense continuous and semi‐continuous geodetic networks that have been surveyed for ∼20 years, the horizontal velocities reveal no evidence of localized strain accumulation across the fault surface expressions. Instead, deformation within the Walker Lane is uniformly linear, suggesting that the surface deformation reflects distributed shear within the ductile crust rather than focused deformation at faults. This suggests no downdip extension of the faults below the seismogenic layer. The shear zone is 172 ± 6 km wide in the northernmost Walker Lane narrowing to 116 ± 4 km in the central Walker Lane. The total velocity budget across the shear zone is 7.2 ± 0.1 mm/yr in the north, increasing to 10.1 ± 0.1 mm/yr in the central Walker Lane. We conclude that assuming the presence of lower crustal dislocations when estimating geodetic faults slip rates may be inappropriate.

Optimizing pollen germination and subcellular dynamics in pollen tube of Torreya grandis

Torreya grandis, a dioecious Taxaceae species of significant economic value in southeast China, presents challenges for natural pollination due to asynchronous maturation of its sex organs and low pollen vitality. In order to enhance fertilization success through artificial pollination of T. grandis, this study investigated the optimal conditions for in vitro pollen germination and pollen tube growth of T. grandis. The optimal in vitro growth medium was found to contain 29 mM sucrose, 0.8 mM H3BO3, 0.72 mM CaCl2, and 0.32 mM MgSO4, supplemented with 4 μM NAA, 2 μM GA3, and 5 μM 2,4-D at pH=5.6. Under these conditions, we achieved a maximum pollen germination ratio of 69.99 ± 5.17 % and a pollen tube length of 34.38 ± 6.04 µm after 6 days germination at 28°C. FM4–64 dye and Mitotracker Red staining revealed highly dynamics of vesicles and mitochondria during germination, which were accumulated at the tip of pollen tube and exhibited biphasic movement patterns. The total number, motion rate, and movement velocity of vesicles as well as mitochondria showed an initially increase followed by a gradual decrease pattern. The presence of sucrose in the medium significantly increased the dynamics and metabolic activity of both vesicles and mitochondria, which may relate with higher pollen germination ratio and faster pollen tube growth compared to sucrose-depleted conditions. Thus, these findings shed light on the physiological characteristics of Torreya pollen germination and provide scientific information for improving Torreya fruit yield through artificial pollination.

Effects of attentional focus on quiet standing balance control in individuals with non-specific chronic low back pain

Despite the widespread research about the effects of attentional focus on balance control in different populations, to the best of our knowledge, no study has yet investigated the effects of attentional focus instructions on balance control in individuals with chronic low back pain (CLBP). Therefore, this study was aimed to compare the effects of internal focus (IF) and external focus (EF) of attention on quiet standing balance control between individuals with CLBP and healthy controls. Twenty individuals with CLBP and 20 healthy controls were enrolled in this quasi-experimental study. The participants were asked to stand still with eyes open and eyes closed while performing three tasks: baseline standing with no focus instructions, internally focusing on their feet, and externally focusing on two markers were placed on the force platform. Statistical analyses showed a significant main effect of group for mean total velocity (p = 0.02), area (p = 0.01), and displacement in mediolateral (ML) direction (p = 0.003). Moreover, a significant main effect of vision was observed for mean total velocity (p < 0.001), area (p < 0.001), and displacement in anteroposterior (AP) (p < 0.001) and ML directions (p < 0.001). Also, the results revealed a significant main effect of attentional focus for mean total velocity (p < 0.001), area (p < 0.001), and displacement in AP (p < 0.001) and ML directions (p = 0.01). Our results showed that in both healthy controls and individuals with CLBP, EF led to improve quiet standing balance control compared to IF and control conditions. From a clinical perspective, it may be useful for physical therapists to consider the use of instruction cues that direct performer's attention away from the body for improving quiet standing balance control in individuals with CLBP.

Numerical Analysis of the Dynamic Properties of Bionic Raster Ceilings.

In this study, a numerical dynamic analysis of ceiling raster panels was performed. The analysis was conducted on panels designed with inspiration from bionics. The purpose of the analysis was to enable optimisation of the location of the holes in the designed slabs in order to achieve the preferred dynamic properties, including the natural frequencies of the slabs and an appropriate airflow to avoid the occurrence of resonance. Three different types of panels were used and a total of fifteen panels were designed in terms of their geometry, with circular, elliptical, and hexagonal perforations, made of different materials: polypropylene PP, wood, and aluminium. Then, using the finite element method and ANSYS 2023 R1 software, the airflow over the ceiling panels and their natural frequencies and vibration modes were analysed. The analysis took into account not only the shape of the openings, but also their percentage area relative to the total panel area and different airflow velocities. In addition, the results were compared in an analytical way with those obtained for a solid slab. The results obtained include findings on the mode shapes and values of the vibration frequencies of the plates, air pressure maps, histograms, and plots of the pressure dependence on the surface area of the plate openings.

Primeval very low-mass stars and brown dwarfs – VIII. The first age benchmark L subdwarf, a wide companion to a halo white dwarf

Abstract We report the discovery of five white dwarf + ultracool dwarf systems identified as common proper motion wide binaries in the Gaia Catalogue of Nearby Stars. The discoveries include a white dwarf + L subdwarf binary, VVV 1256−62AB, a gravitationally-bound system located 75.6$^{+1.9}_{-1.8}$ pc away with a projected separation of 1375$^{+35}_{-33}$ au. The primary is a cool DC white dwarf with a hydrogen dominated atmosphere, and has a total age of $10.5^{+3.3}_{-2.1}$ Gyr, based on white dwarf model fitting. The secondary is an L subdwarf with a metallicity of [M/H] = $-0.72^{+0.08}_{-0.10}$ (i.e. [Fe/H] = −0.81 ± 0.10) and Teff = 2298$^{+45}_{-43}$ K based on atmospheric model fitting of its optical to near infrared spectrum, and likely has a mass just above the stellar/substellar boundary. The subsolar metallicity of the L subdwarf and the system’s total space velocity of 406 km/s indicates membership in the Galactic halo, and it has a flat eccentric Galactic orbit passing within 1 kpc of the centre of the Milky Way every ∼0.4 Gyr and extending to 15-31 kpc at apogal. VVV 1256−62B is the first L subdwarf to have a well-constrained age, making it an ideal benchmark of metal-poor ultracool dwarf atmospheres and evolution.