Changes In Velocity Research Articles

Numerical Simulation and Flow Field Analysis of Porous Water Jet Nozzle Based on Fluent

The water jet nozzle is a penetrating drilling tool, which sends the pumped water to the nozzle through a high-pressure hose. It can work in a variety of working environments. When it dredges the blockage in the pipeline, its structural parameters will affect the jet flow field in the pipeline. Taking the self-propelled water jet nozzle as the research object, SolidWorks was used to establish the nozzle model with different parameter structures. Based on Fluent, the k-ε turbulence model was used to simulate the jet of nozzles with different nozzle sizes and arrangements in the pipeline. The distribution of the jet flow field and the change in velocity and displacement of nozzles with different parameters in the pipeline were compared, and then computational fluid dynamics (CFD) were used to process the simulation data for further research. The results show that when the inclination angle of the rear nozzle is 35°, the attenuation of the front jet velocity and the fluctuation of the wall fluid velocity are the smallest. When the nozzle aperture is increased from 2 mm to 3.5 mm, the vortex area inside the pipe is reduced, and the velocity attenuation of the front jet is also reduced, with the velocity attenuation rate decreasing by about 10%. This study provides a reference for the design and parameter optimization of self-propelled water jet nozzles.

Application of iterative elastic reverse time migration to shear horizontal ultrasonic echo data obtained at a concrete step specimen

AbstractThe ultrasonic echo technique is broadly applied in non‐destructive testing (NDT) of concrete structures involving tasks such as measuring thickness, determining geometry and locating built‐in elements. To address the challenge of enhancing ultrasonic imaging for complex concrete constructions, we adapted a seismic imaging algorithm – reverse time migration (RTM) – for NDT in civil engineering. Unlike the traditionally applied synthetic aperture focusing technique (SAFT), RTM takes into account the full wavefield including primary and reflected arrivals as well as multiples. This capability enables RTM to effectively handle all wave phenomena, unlimited by changes in velocity and reflector inclinations. This paper concentrates on applying and evaluating a two‐dimensional elastic RTM algorithm that specifically addresses horizontally polarized shear (SH) waves only, as these are predominantly used in ultrasonic NDT of concrete structures. The elastic SH RTM algorithm was deployed for imaging real ultrasonic echo SH‐wave data obtained at a concrete specimen exhibiting a complex back wall geometry and containing four tendon ducts. As these features are frequently encountered in practical NDT scenarios, their precise imaging holds significant importance. By applying the elastic SH RTM algorithm, we successfully reproduced nearly all reflectors within the concrete specimen. In particular, we were capable of accurately reconstructing all vertically oriented reflectors as well as the circular cross sections of three tendon ducts, which was not achievable with traditional SAFT imaging. These findings demonstrate that elastic SH RTM holds the ability to considerably improve the imaging of complex concrete geometries, marking a crucial advancement for accurate, high‐quality ultrasonic NDT in civil engineering.

A thermal infrared imaging observation system for the measurement of overland flow velocities under controlled laboratory conditions

Flow velocity is an important physical parameter in characterizing the hydraulics of water flow. The accurate measurement of overland flow velocities has great significance for understanding and modeling sediment transport and soil erosion. In this study, a Thermal Infrared Imaging Observation System (TIIOS) based on thermal infrared imaging techniques and computer vision recognition technology was established to measure overland flow velocities under controlled laboratory conditions. TIIOS has three subsystems including thermal tracer control, image acquisition and transmission, and image storage and processing. It can be used to dynamically monitor changes in shallow flow velocity by means of automatic control of thermal tracer, instantaneous image acquisition, image correction, noise removal and centroid determination. The observation precision was high with a standard deviation of 0.004 m·s−1 for flow velocity, a temporal resolution of 1/9th s, and a spatial resolution of 2 mm. The new system achieved higher accuracy compared to the traditional dye tracing and salt tracing techniques in observing the dynamic transport process of thermal tracer movement. The relative errors of the centroid velocity measured by the TIIOS ranged from −9.83 % to 6.40 %; whereas the relative errors of centroid velocity measured by salt tracer ranged from −21.36 % to 17.22 %. Measurements by the established TIIOS under different hydraulic conditions demonstrate that the relative errors of the centroid velocity are all smaller than those of the leading-edge velocity. This observational system provided a reliable way to measure shallow flow velocity for better understanding the mechanisms of water erosion processes and showed its potential to be used in field experiments under natural conditions.

Full‐waveform inversion as a tool to predict fault zone acoustic properties

AbstractUnderstanding the physical properties of fault zones is essential for various subsurface applications, including carbon capture and geologic storage, geothermal energy and seismic hazard assessment. Although three‐dimensional seismic reflection data can image the geometries of faults in the sub‐surface, it does not provide any direct information on the physical properties of fault zones. We currently cannot use seismic reflection data to infer directly which faults may be leaking or sealing and are reliant instead on shale‐gauge ratio type calculations, which are fraught with uncertainties. In this paper, we propose that full‐waveform inversion P‐wave velocity models can be used to extract information on fault zone acoustic properties directly, which may be a proxy for subsurface fault transmissibility. In this study, we use high‐quality post‐stack depth–migrated seismic reflection and full‐waveform inversion velocity data to investigate the characteristics of fault zones in the Samson Dome in the SW Barents Sea. We analyse the variance attribute of the post‐stack depth migrated and full‐waveform inversion volumes, revealing linear features that consistently appear in both datasets. These features correspond to locations of rapid velocity changes and seismic trace distortions, which we interpret as faults. These observations demonstrate the capability of full‐waveform inversion to recover fault zone velocity structures. Our findings also reveal the natural heterogeneity and complexity of fault zones, with varying P‐wave velocity anomalies within the studied fault network and along individual faults. Our results indicate a correlation between P‐wave velocity anomalies within fault zones and the modern‐day stress orientation. Faults with high P‐wave velocity are the ones that are perpendicular to the present‐day maximum horizontal stress orientation and are likely under compression. Faults with lower P‐wave velocity are the ones more parallel to the present‐day maximum horizontal stress orientation and are likely in extension. We propose that these P‐wave velocity anomalies may indicate differences in how ‘open’ and fluid filled the fault zones are (i.e. faults in extension are more open, more fluid filled and have lower VP) and therefore may provide a promising proxy for fault transmissibility.

Wall-scaling prevention in cryogenic external cooler of ammonium chloride solution by liquid-solid fluidization

A double-tube cooler with liquid-solid circulating fluidization operation and corresponding parameter measuring system are developed to avoid fouling of inner walls of heat exchange tubes in a cryogenic temperature external cooler of ammonium chloride solution in soda ash production. Wall-scaling prevention performance of the cooling process is experimentally evaluated using convection and overall coefficients, enhancement factor, wall temperature and fouling resistance. Effects of different volume fractions of added particles, particle size, superficial liquid velocity, and cooling medium temperature on heat transfer are examined. Under present conditions, convection coefficient of liquid-solid flow inside the tube of external cooler is higher than that of the liquid phase flow, increased by 0.7–2.8 times, enhancing cooling performance obviously. Convection coefficient initially increases and then decreases as the volume fraction of added particles increases, reaching its maximum value at a volume fraction of 2.0%. The wall-scaling prevention effect of glass beads mainly depends on the volume fraction of added particles; optimal anti-fouling effects are achieved when adding particles at a volume fraction of 2.0%, regardless of changes in superficial liquid velocity or cooling medium temperature. This study lays a foundation for industrial applications of this new technique of fluidized bed external coolers.

Influence of impact velocity on the semi-sealed cylindrical shell during water entry

To study the motion characteristics and cavity evolution of the cylindrical shell with different initial velocity, the numerical simulation based on the Star-CCM+ and ABAQUS collaborative simulation method is carried out in this paper. The results show that when the shell penetrates into the water at a lower speed, only a small amount of external fluid can enter into the shell, and the internal fluid shows a reciprocating motion trend. Moreover, the speed of the shell and the force at the bottom wall show a fluctuating trend. As the speed increases, the volume of fluid entering into the interior of the shell gradually increases. After the speed reaches 30 m/s, the fluid can impact the upper wall of the shell, which also causes sudden changes in velocity and displacement. When the initial velocity of the shell reaches 80 m/s, significant deformation occurs at the upper wall of the shell, and the deformation is not fully restored after the fluid leaves the upper wall. As the speed increases, the degree of deformation gradually increases, and the volume of the cavity gradually increases.

Influence of engine oil-infused multi-walled carbon nanotubes and titania nanoparticles on a vertically inclined porous surface

This study analyses the flow of a hybrid nanofluid, combining engine oil with multi-walled carbon nanotubes and titania nanoparticles. The flow occurs over a vertically inclined, electrically conducting, heat-producing/absorbing surface that is both permeable and expanding/contracting. The analysis incorporates influential factors such as buoyancy forces, heat source/sink effects, and convective conditions with Cattaneo-Christov theory and Hamilton-Crosser model. The mathematical model is numerically solved using the bvp4c solver in MATLAB. The expansion/contraction of the surface significantly impacts the boundary layer thickness, leading to changes in velocity, temperature, and various physical parameters. This study is significant due to the nanoparticles’ enhanced optical and mechanical properties, offering potential applications in diverse fields. A notable finding is the reduced fluid velocity and temperature within a porous medium with permeability. These findings present opportunities for enhancing heat and fluid transmission in various systems, including those related to energy storage.

Transient surface pressure of a rectangular cylinder subjected to downburst-like winds

Thunderstorm downbursts are transient in nature and have been responsible for a variety of structural damages in recent years. Currently, the researchers have done several works on the characteristics of downburst wind speed. Nonetheless, rare attention has been placed on the structural aerodynamics characteristics subjected to downburst winds. Based on this, an experimental investigation is performed to reproduce downburst-like winds physically and to study the transient surface pressures (SPs) on a 5:1 rectangular cylinder (RC). The experiment is conducted within a multiple-fan active control wind tunnel (MFACWT) and mainly focuses on simulating the transient characteristics of downburst-like flow, including time-varying mean (TVM) wind speed and nonstationary wind fluctuation. The resulting SPs are measured to understand the influence of transient wind on the aerodynamic behavior of bluff bodies. The spatiotemporal characteristics of the SPs are analyzed using wavelet transform and Priestley's classic spectral theory. The results indicate that the transient nature of the downburst-like flow can be physically reproduced by a MFACWT. The instantaneous pressures of a RC are illustrated by both the turbulence parameters of the transient flow and the flow-separation characteristics. The pressure coefficients normalized by the TVM of the downburst-like winds remain constant, which provides a more appropriate way to estimate the transient gust loading in a quasi-steady manner. Interestingly, the phenomenon of the time-varying phase shift and time-varying correlation of chordwise SPs is observed when the turbulent velocity changes dramatically. In addition, the normalized surface pressure can be regarded as a stationary stochastic process, which provides a significant basis for further establishing the theoretical model of nonstationary gust-loading.

An envelope statistic features and MFO-SVM fusion method for tidal stream turbine blades impact fault diagnosis

Abstract The fault diagnosis of a Tidal Stream Turbine (TST) blade impact fault benefits its stable operation. However, when the stream velocity changes, it is hard to distinguish between different fault severities directly by observing the changes in the signal feature. To address this problem, this paper proposes a blade impact fault diagnosis method based on envelope statistical features and MFO-SVM. The method is divided into two parts. In the first part, the Teager-Kaiser energy operator (TKEO) and sliding window technique are introduced to extract the envelope statistic features of the current signal, and then the local outlier factor (LOF) values of fault sample points are calculated to form a new set of feature samples; in the second part, the fault feature samples are input into the support vector machine (SVM) optimized by moth fame optimization (MFO) for fault diagnosis. The experimental results show that the proposed method is more accurate than traditional fault diagnosis methods.

Flow structures in large-scale bank erosion zone of Lower Yangtze River

The bank erosion process in the densely populated Lower Yangtze River can pose a great threat to riparian residents and industries. It is characterized by rapid development within a few hours, a large-scale soil collapse of 106 m3, and an arc shape. During its development, flow field inside the bank erosion area continuously evolves and interacts with the bank soil. However, the mechanisms behind the bank erosion process are still unclear. Therefore, laboratory experiments were conducted to investigate flow structures and turbulences inside bank erosion areas. A pulsed particle image velocimeter was employed to obtain high-quality velocity data inside the bank erosion zone. Results show that the bank erosion zone can be divided into a backflow zone, a mixing zone, and a mainstream zone, according to variations in flow structure; in the mixing zone, water flow is highly turbulent, and the mixing width gradually increases downstream because of the shear effects between the mainstream and backflow; the backflow zone can be subdivided into a central zone and a peripheral zone, based on the pattern of velocity changes along the radial axis from the backflow center to its periphery. A formula for calculating the flow velocity within the backflow zone was proposed, and we found that the velocity gradient in the peripheral zone was approximately four times higher than that in the central zone. This indicated that shear stress exerted by the flow near the backflow boundary was significantly intensified.

Assessment of Upper Limb Nerves in Coronary Artery Disease Patients Undergoing Coronary Artery Bypass Graft.

Background Many patients experience pain in their upper limbs following surgical procedures involving median sternotomy, particularly those undergoing coronary artery bypass grafting (CABG). This type of pain, commonly reported by CABG patients, is often overlooked in hospital settings. Our study aims to address this issue by utilizing electrodiagnostic studies to understand this postoperative discomfort better. Objectives Cardiovascular procedures are standard and are trending toward endovascular interventions. Through this study, we aim to assess the occurrence of neurological issues in the upper limbs after CABGby comparing patients' preoperative and postoperative electrophysiological studies of the upper limb nerves. Materials and methods A prospective study was performed on 32 coronary artery disease (CAD) patients undergoing CABG to determine the effects of surgery on the upper limb nerves (median and ulnar nerves). We performed nerve conduction studies (NCS) and analyzed different parameters of both median and ulnar nerves pre and post-surgery. Results A change was noted in different NCS parameters of the median and ulnar nerves when we comparedthe pre and post-surgical values. The meanlatency of the median nerve sensory increased from a minimum of 3.01 millisecondsat the preoperative level to a maximum of 3.60 milliseconds when assessedtwo weeks post-surgery. The mean amplitude decreased from 16.49 microvolts to a minimum of 12.30 microvolts when assessed two weeks post-surgery. The meanvelocity decreased from 55.83 m/s at the preoperative value to a minimum of 45.03 m/sat the two weeks post-surgery assessment. The ulnar nerve also underwent similar changes. Conclusion The observed changes in latency, amplitude, and velocity might be attributed to various factors, including surgical trauma, inflammation, or alterations in the physiological state post-surgery. The sternotomy technique and the position and extent of opening the sternal retractor determine the prevalence of complications by causing injury to the medial and lateral cords of the brachial plexusafter CABG. Careful preoperative and postoperative assessments of patients may aid in preventing, minimizing, and treating these often undiagnosed complications.

Investigating the dynamics and interactions of surface features on Pine Island Glacier using remote sensing and deep learning

Pine Island Glacier (PIG), the largest glacier in the Amundsen Sea Embayment of West Antarctica, has contributed to over a quarter of the observed sea level rise around Antarctica. In recent years, multiple observations have confirmed its continuous retreat, ice flow acceleration and profound surface melt. Understanding these changes is crucial for accurately monitoring ice mass discharge and future Antarctic contributions to sea level rise. Therefore, it is essential to investigate the complex interactions between these variables to comprehend how they collectively affect the overall stability of the intricate PIG system. In this study, we utilized high-resolution remote sensing data and deep learning method to detect and analyze the spatio-temporal variations of surface melt, ice shelf calving, and ice flow velocity of the PIG from 2015 to 2023. We explored the correlations among these factors to understand their long-term impacts on the glacier's stability. Our findings reveal a retreat of 26.3 km and a mass loss of 1001.6 km2 during 2015–2023. Notably, extensive surface melting was observed, particularly in the 2016/2017 and 2019/2020 melting seasons. Satellite data vividly illustrate prolonged and intense melting periods, correlating with a significant retreat in the glacier's terminus position in 2019/2020. Furthermore, the comprehensive analysis of surface melting and the cumulative retreat of the ice shelf from 2017 to 2020 on the PIG shows a temporal relationship with subsequent significant changes in ice flow velocity, ranging from 10.9 to 12.2 m d−1, with an average acceleration rate of 12%. These empirical findings elucidate the intricate relationship among surface melt, ice flow velocity, and consequential glacier dynamics. A profound understanding of these interrelationships holds paramount importance in glacier dynamic changes and modeling, providing invaluable insights into potential glacier responses to global climate change.

Three-dimensional numerical simulation of two-phase flow in a proton exchange membrane electrolysis cell and study of the effect of flow channel depth

Abstract The flow channel play a critical role in water-gas transfer within an electrolysis cell, directly impacting its mass and heat transfer capacity. While most studies concentrate on the overall shape and structure of the flow channel, limited attention has been given to its dimensions. This paper investigates the influence of various operational conditions and changes in flow channel depth on the electrolytic cell using a three-dimensional numerical model of PEMEC. Results indicate that higher temperatures enhance electrolysis cell performance, whereas the impact of water inlet velocity on the polarization curve is insignificant. Under constant inlet velocity, increasing the depth of the flow channel improves mass and heat transfer as well as electrolysis performance, whereas, under constant water flow rate, changes in inlet velocity have a greater effect than alterations in flow channel depth.

Low-Density Lipoprotein Cholesterol, Type 2 Diabetes and Progression of Aortic Stenosis: The RED-CARPET Heart Valve Subgroup Cohort Study.

Low-density lipoprotein cholesterol (LDL-C) and type 2 diabetes (T2DM) are both independent risk factors for aortic stenosis (AS). In AS patients, whether LDL-C or T2DM is associated with fast AS progression (FASP) and their interaction is unknown. This study aims to test the hypothesis that there is a heightened risk of FASP when elevated LDL-C coexists with T2DM. The Real-world Data of Cardiometabolic Protections (RED-CARPET) study enrolled participants with mild (peak aortic velocity = 2-3 m/s), moderate (3-4 m/s) and severe ( 4 m/s) AS between January 2015 and December 2020 at a single center. Participants were further stratified by baseline LDL-C joint T2DM, follow-up echocardiography was performed after 6 months, and the primary outcome was FASP, defined as the annual change in aortic peak velocity ( 0.3 m/s/year). Among the 170 participants included, 45.3% had mild AS, 41.2% had moderate AS, and 13.5% had severe AS. The mean age was 66.84 12.64 years, and 64.1% were women. During the follow-up period of 2.60 1.43 years, 35 (20.6%) cases of FASP were identified. Using non-T2DM with LDL-C 2.15 mmol/L as reference, FASP risk was 1.30 [odds ratio (OR), 95% CI (0.99-7.78, p = 0.167)] for non-T2DM with LDL-C 2.15-3.14 mmol/L, 1.60 [OR, 95% CI (1.17-3.29, p = 0.040)] for non-T2DM with LDL-C 3.14 mmol/L, 2.21 [OR, 95% CI (0.49-4.32, p = 0.527)] for T2DM with LDL-C 2.15 mmol/L, 2.67 [OR, 95% CI (1.65-7.10, p = 0.004)] for T2DM with LDL-C 2.15-3.14 mmol/L, and 3.20 [OR, 95% CI (1.07-5.34, p = 0.022)] for T2DM with LDL-C 3.14 mmol/L. LDL-C joint T2DM was associated with FASP. This investigation suggests that fast progression of AS may develop if LDL-C is poorly managed in T2DM. Additional research is needed to validate this finding and explore the possible biological mechanism to improve the cardiometabolic management of T2DM and seek possible prevention for AS progression for this population. ChiCTR2000039901 (https://www.chictr.org.cn).

On-demand jetting of high-viscosity liquid by jet tube impact

The on-demand jetting of high-viscosity liquid has significant applications in fields such as electronic packaging and bioprinting. Conventional methods for high-viscosity liquid jetting often employ a needle propelling the liquid rapidly, which demands high precision in the manufacturing and assembly of the needle and nozzle, and can potentially damage biomaterials. In this study, a novel method utilizing jet tube impact for on-demand high-viscosity liquid jetting is proposed, leveraging the inherent inertia of the liquid to generate the pressure pulse necessary for on-demand jetting. This method reduces the precision requirements for the device, enables device simplification, and avoids harm to biomaterials. The feasibility of this approach for on-demand high-viscosity liquid jetting is validated through experiments, and by combining numerical simulations, the jetting mechanism is revealed and primary factors influencing jetting performance are investigated. It is found that the water hammer pressure wave induced by the liquid inertia during the sudden velocity change of the jet tube is the predominant driving force for jetting, and the peak pressure can exceed 1 MPa and the peak jet velocity can exceed 15 m/s. An increase in the jet tube impact velocity and an extension of the acceleration duration at the same impact velocity both lead to an increase in the pressure wave amplitude. In addition, a decrease in the liquid level height shortens the period of the pressure wave. These factors all have an influence on the jetting performance. This study provides a new insight and theoretical foundation for the on-demand high-viscosity liquid jetting.

Relating Hydro‐Mechanical and Elastodynamic Properties of Dynamically Stressed Tensile‐Fractured Rock in Relation to Applied Normal Stress, Fracture Aperture, and Contact Area

AbstractWe exploit nonlinear elastodynamic properties of fractured rock to probe the micro‐scale mechanics of fractures and understand the relation between fluid transport and fracture aperture under dynamic stressing. Experiments were conducted on rough, tensile‐fractured Westerly granite subject to triaxial stresses. We measure fracture permeability for steady‐state fluid flow with deionized water. Pore pressure oscillations are applied at amplitudes ranging from 0.2 to 1 MPa at 1 Hz frequency. During dynamic stressing we transmit ultrasonic signals through the fracture using an array of piezoelectric transducers (PZTs) to monitor evolution of interface properties. We examine the influence of fracture aperture and contact area by conducting measurements at effective normal stresses of 10–20 MPa. Additionally, the evolution of contact area with stress is characterized using pressure sensitive film. These experiments are conducted separately with the same fracture and map contact area at stresses from 9 to 21 MPa. The measurements are a proxy for “true” contact area for the fracture surface and we relate them to elastic properties using the calculated PZT sensor footprints via numerical modeling of Fresnel zones. We compare the elastodynamic response of the fracture using the stress‐induced changes in ultrasonic wave velocities for transmitter‐receiver pairs to image spatial variations in contact properties. We show that nonlinear elasticity and permeability enhancement decrease with increasing normal stress. Additionally, post‐oscillation wave velocity and permeability exhibit quick recoveries toward pre‐oscillation values. Estimates of fracture contact area (global and local) demonstrate that the elastodynamic and permeability responses are dominated by fracture topology.

An Insight into Perfusion Anisotropy within Solid Murine Lung Cancer Tumors.

Blood vessels are essential for maintaining tumor growth, progression, and metastasis, yet the tumor vasculature is under a constant state of remodeling. Since the tumor vasculature is an attractive therapeutic target, there is a need to predict the dynamic changes in intratumoral fluid pressure and velocity that occur across the tumor microenvironment (TME). The goal of this study was to obtain insight into perfusion anisotropy within lung tumors. To achieve this goal, we used the perfusion marker Hoechst 33342 and vascular endothelial marker CD31 to stain tumor sections from C57BL/6 mice harboring Lewis lung carcinoma tumors on their flank. Vasculature, capillary diameter, and permeability distribution were extracted at different time points along the tumor growth curve. A computational model was generated by applying a unique modeling approach based on the smeared physical fields (Kojic Transport Model, KTM). KTM predicts spatial and temporal changes in intratumoral pressure and fluid velocity within the growing tumor. Anisotropic perfusion occurs within two domains: capillary and extracellular space. Anisotropy in tumor structure causes the nonuniform distribution of pressure and fluid velocity. These results provide insights regarding local vascular distribution for optimal drug dosing and delivery to better predict distribution and duration of retention within the TME.

CFD study of heat transfer in power‐law fluids over multiple corrugated circular cylinders in a heat exchanger

AbstractThe heat transfer in power‐law fluids across three corrugated circular cylinders placed in a triangular pitch arrangement is studied computationally in a confined channel. Continuity, momentum, and energy balance equations were solved using ANSYS FLUENT (Version 18.0). The flow is assumed to be steady, incompressible, two‐dimensional, and laminar. A square domain of side 300Dh is selected after a detailed domain study. An optimized grid with 98,187 cells is used in the study. The convergence criteria of 10−7 for the continuity, x‐momentum, and y‐momentum balances and 10−12 for the energy equation were used. Constant density and non‐Newtonian power‐law viscosity modules were used. The diffusive term is discretized using a central difference scheme. Convective terms are discretized using the Second‐Order Upwind scheme. Pressure–velocity coupling between continuity and momentum equations was implemented using the semi‐implicit method for pressure‐linked equation scheme. Streamlines show wake development behind the cylinders, which is very dominant at large ReN and n. Isotherm contours are cramped at higher values of ReN and PrN, implying higher heat transfer. Global parameters, like, Cd and Nu, are computed for the wide ranges of controlling dimensionless parameters, such as power‐law index (0.3 ≤ n ≤ 1.5), Reynolds (0.1 ≤ ReN ≤ 40), and Prandtl (0.72 ≤ PrN ≤ 500) numbers. The NuLocal plot attains a pitch near the corrugation of the surface due to abrupt changes in velocity and temperature gradients. Nu increases with ReN and/or PrN and decreases with n under ot herwise identical situations. Nu is correlated with pertinent parameters, namely, ReN, PrN, and n.

Age and dose dependent changes to the bone and bone marrow microenvironment after cytotoxic conditioning with busulfan.

Preparative regimens before Hematopoietic Cell Transplantation (HCT) damage the bone marrow (BM) microenvironment, potentially leading to secondary morbidity and even mortality. The precise effects of cytotoxic preconditioning on bone and BM remodeling, regeneration, and subsequent hematopoietic recovery over time remain unclear. Moreover, the influence of recipient age and cytotoxic dose have not been fully described. In this study, we longitudinally investigated bone and BM remodeling after busulfan treatment with low intensity (LI) and high intensity (HI) regimens as a function of animal age. As expected, higher donor chimerism was observed in young mice in both LI and HI regimens compared to adult mice. Noticeably in adult mice, significant engraftment was only observed in the HI group. The integrity of the blood-bone marrow barrier in calvarial BM blood vessels was lost after busulfan treatment in the young mice and remained altered even 6weeks after HCT. In adult mice, the severity of vascular leakage appeared to be dose-dependent, being more pronounced in HI compared to LI recipients. Interestingly, no noticeable change in blood flow velocity was observed following busulfan treatment. Ex vivo imaging of the long bones revealed a reduction in the frequency and an increase in the diameter and density of the blood vessels shortly after treatment, a phenomenon that largely recovered in young mice but persisted in older mice after 6weeks. Furthermore, analysis of bone remodeling indicated a significant alteration in bone turnover at 6weeks compared to earlier timepoints in both young and adult mice. Overall, our results reveal new aspects of bone and BM remodeling, as well as hematopoietic recovery, which is dependent on the cytotoxic dose and recipient age.

Saccadic "inhibition" unveils the late influence of image content on oculomotor programming.

Image content is prioritized in the visual system. Faces are a paradigmatic example, receiving preferential processing along the visual pathway compared to other visual stimuli. Moreover, face prioritization manifests also in behavior. People tend to look at faces more frequently and for longer periods, and saccadic reaction times can be faster when targeting a face as opposed to a phase-scrambled control. However, it is currently not clear at which stage image content affects oculomotor planning and execution. It can be hypothesized that image content directly influences oculomotor signal generation. Alternatively, the image content could exert its influence on oculomotor planning and execution at a later stage, after the image has been processed. Here we aim to disentangle these two alternative hypotheses by measuring the frequency of saccades toward a visual target when the latter is followed by a visual transient in the central visual field. Behaviorally, this paradigm leads to a reduction in saccade frequency that happens about 90 ms after any visual transient event, also known as saccadic "inhibition". In two experiments, we measured occurrence of saccades in visually guided saccades as well as microsaccades during fixation, using face and noise-matched visual stimuli. We observed that while the reduction in saccade occurrence was similar for both stimulus types, face stimuli lead to a prolonged reduction in eye movements. Moreover, saccade kinematics were altered by both stimulus types, showing an amplitude reduction without change in peak velocity for the earliest saccades. Taken together, our experiments imply that face stimuli primarily affect the later stages of the behavioral phenomenon of saccadic "inhibition". We propose that while some stimulus features are processed at an early stage and can quickly influence eye movements, a delayed signal conveying image content information is necessary to further inhibit/delay activity in the oculomotor system to trigger eye movements.