Similar Velocity Research Articles

Dryout suppression and significantly enhanced flow boiling heat transfer through the two-tier vertically aligned carbon nanotube channel

It is crucial to design multi-functional structure to improve heat transfer characteristics. Here we report significantly enhanced saturated flow boiling heat transfer of water using the two-tier vertically aligned multiwalled carbon nanotube (VAMWNT) channel (tube diameter: 11.5 nm). The channel size is 10 × 10 × 2 mm3 (height: 2 mm). The tube aggregation-generated large voids act as micropores (10-200 µm) whereas the interstitial spaces between the tubes act as nanopores (< 72 nm). The microcavities at the periphery of aggregated nanotubes increase bubble nucleation sites while constraining bubble size. The high nanotube thermal conductivity induces more uniform bubble nucleation, and departed bubbles are swept away through the micropores. On the other hand, water is effectively replenished through the nanopores by high capillary pumping. Overall, the path separation of bubble departure and water replenish effectively prevents dryout and increases critical heat flux (CHF). The experiment is carried out at 3 different mass velocities (62, 83, and 104 kg m−2 s−1). The VAMWNT channel provides a high heat transfer coefficient (h = 100,666 W m−2 K−1 at 183 W cm−2), even before reaching CHF without any sign of local dryout, compared with microchannels and porous media in literature (under the similar heat flux and mass velocity). In contrast, the CHF condition is observed for a plain channel of the same size without the nanotubes, resulting in smaller h values than those of the VAMWNT channel. The novel two-tier structure separated liquid-vapor pathways, significantly enhancing heat transfer characteristics.

Integration of Electrical Resistivity Tomography and Seismic Refraction Tomography to Investigate Subsiding Sinkholes in Karst Areas

Operational and safety issues associated with subsiding sinkholes in karst areas start with the definition of fractures and joints, causing ground weakness. Conventional geotechnical boreholes and geological mapping must be complemented with indirect subsurface exploration techniques to detail those structures. This work aims to use electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) near-surface geophysical techniques to infer the 2D and 3D geometry of sediment-infilled sinkholes formed by the conjunction of fractures and joints in karst areas. Geophysical surveys were performed in a sediment-infilled sinkhole area with two sectors of different subsiding and infilling degrees formed by the conjunction of two fault systems in an experimental research area in the Sierra de Gádor Mountains in southeastern Spain. The ERT survey delimited the geometry of the sinkhole area, including the main fault-boun4ded limits, other minor faults, buried epikarst forms, and the distribution of coarse and clay-rich infilling. The SRT survey corroborated the structure and disambiguated clay-rich and high-moisture-content structures giving similar velocity fields. The integration of the ERT and SRT techniques provides indirect 2D and 3D visualizations of the ground of interest in predicting weakness-triggering mechanisms associated with the regional karst structure. This trial in an experimental uninhabited area, with the possibility of exploring subsiding karst structures is of special interest for designing operational and safety measures in urban areas, where similar karst structures may go undetected and monitoring capability is often more limited. The technological development of the used techniques enables the periodical geophysical monitoring of karst structures, thus making the identification of structural changes modifying the land safety and hydrological mechanisms feasible over time.

Design principles for selective polarization of PAR proteins by cortical flows.

Clustering of membrane-associated molecules is thought to promote interactions with the actomyosin cortex, enabling size-dependent transport by actin flows. Consistent with this model, in the Caenorhabditis elegans zygote, efficient anterior segregation of the polarity protein PAR-3 requires oligomerization. However, through direct assessment of local coupling between motion of PAR proteins and the underlying cortex, we find no links between PAR-3 oligomer size and the degree of coupling. Indeed, both anterior and posterior PAR proteins experience similar advection velocities, at least over short distances. Consequently, differential cortex engagement cannot account for selectivity of PAR protein segregation by cortical flows. Combining experiment and theory, we demonstrate that a key determinant of differential segregation of PAR proteins by cortical flow is the stability of membrane association, which is enhanced by clustering and enables transport across cellular length scales. Thus, modulation of membrane binding dynamics allows cells to achieve selective transport by cortical flows despite widespread coupling between membrane-associated molecules and the cell cortex.

Analysis of shock train leading shock structure under oscillatory backpressure

The leading shock in a steady shock train takes one of two forms: oblique or normal. However, the phenomenon and mechanism of the normal-to-oblique transition of the leading shock in a forced shock train have not been widely reported. In this study, leading normal and oblique shocks are experimentally observed at the same position and similar velocities in a forced oscillation shock train with an incoming Mach number of 1.83. The normal-to-oblique transition is found to be closely related to the self-excited oscillation of the shock train. In addition, we find that the direct use of free-interaction theory cannot accurately predict the leading shock angle in a moving shock train. Thus, free-interaction theory requires appropriate correction for this scenario.

Renal denervation reverses ventricular structural and functional remodeling in failing rabbit hearts

Renal denervation (RDN) suppresses the activity of the renin–angiotensin–aldosterone system and inflammatory cytokines, leading to the prevention of cardiac remodeling. Limited studies have reported the effects of renal denervation on ventricular electrophysiology. We aimed to use optical mapping to evaluate the effect of RDN on ventricular structural and electrical remodeling in a tachycardia-induced cardiomyopathy rabbit model. Eighteen rabbits were randomized into 4 groups: sham control group (n = 5), renal denervation group receiving RDN (n = 5), heart failure group receiving rapid ventricular pacing for 1 month (n = 4), and RDN-heart failure group (n = 4). Rabbit hearts were harvested for optical mapping. Different cycle lengths were paced (400, 300, 250, 200, and 150 ms), and the results were analyzed. In optical mapping, the heart failure group had a significantly slower epicardial ventricular conduction velocity than the other three groups. The RDN-heart failure, sham control, and RDN groups had similar velocities. We then analyzed the 80% action potential duration at different pacing cycle lengths, which showed a shorter action potential duration as cycle length decreased (P for trend < 0.01), which was consistent across all groups. The heart failure group had a significantly longer action potential duration than the sham control and RDN groups. Action potential duration was shorter in the RDN-heart failure group than the heart failure group (P < 0.05). Reduction of conduction velocity and prolongation of action potential duration are significant hallmarks of heart failure, and RDN reverses these remodeling processes.

Effects of discharge-to-submergence ratio on evolution of air-core vortex

An air-core vortex is generated in a tidal power station when the discharge increases or the submergence decreases at the intake. To better understand the complex evolution of the air-core vortex, we conduct high-fidelity coupled level-set and volume-of-fluid and wall-modeled large-eddy simulations for various ratios of discharge and submergence. We characterize the air-core vortex evolution process into two stages: the inception stage and the propagation stage. Our results show that the streamwise and spanwise velocity fluctuations exhibit similar distributions and temporal evolutions and are responsible for generating asymmetrical flow transitioned from a completely symmetrical pattern in the inception stage. The turbulence quadrant decomposition analysis in the confluence region quantifies the velocity fluctuation signal and Reynolds shear stress distribution. Under a specific Reynolds shear stress distribution, eddies converge and evolve into a main vortex. We introduce a vortex burst index to quantitatively characterize the contribution of the Reynolds shear stress to the main vortex evolution. The vortex burst index is positively correlated with the discharge-to-submergence ratio. In the propagation stage, the enstrophy stretching mechanism dominates the air-vortex evolution. The tilting terms nearly cancel each other because of the similar tangential velocity distribution in the axial direction. The results show that the increase in the discharge-to-submergence ratio accelerates the formation of the air-core vortex, owing to the increase in the vertical velocity gradient and the enhancement of the stretching effect.

Modeling trajectories of human speech articulators using general Tau theory

This paper presents an application of general Tau theory to the modeling and analysis of articulatory trajectories in speech. We evaluated the model using electromagnetic articulometry data from 12 native speakers of English reading a common text, where trajectories of the following sensors were fitted: lower and upper lips, jaw, and three tongue sensors. Additionally, we analyzed trajectories of the lip aperture signal. Our experiments show that the general Tau theory model gives a better fit than existing (i) methods based on critically damped oscillators, and (ii) a method based on sequential target approximation. These findings support the hypothesis of Tau-guided movements of articulators during speech production. In the second part of the paper, our Tau theory analysis shows that articulatory movements follow similar velocity profile distributions across speakers. In particular, the value of the shape parameter κ of the Tau theory equation is identically distributed across speakers, following a unimodal distribution. The statistical mode of the distribution corresponds to the value of κ that generates a symmetric velocity profile. The analysis of the statistical distribution of κ values also reveals that its variance decreases when greater articulatory effort is required, such that produced articulatory effort remains close to that predicted by the theoretical minimal cost function based on forces acting on the moving articulator. This provides new evidence that articulatory effort is optimized during speech production.

Positive correlation between wet-day frequency and intensity linked to universal precipitation drivers

Understanding precipitation is essential for quantifying weather and climate-related risks. Changes in precipitation climatology are typically based on independent analysis of precipitation frequency and intensity. Here we show that where it rains more often, it also rains harder. When grouping global precipitation reanalysis data and observations from the past 40 years into regions of similar wet-day frequency, regardless of geographical separation, there is a strong correlation with wet-day intensity distributions. These wet-day-frequency regions are also more physically coherent than regions based on geographical location. We find the coherent relationship between wet-day frequency and intensity distributions is partially explained by wet-day-frequency regions having similar vertical velocity and convective available potential energy distributions, once polar regions are excluded. These represent dynamic and thermodynamic processes that indicate how conducive wet-day-frequency regions are to large-scale and convective precipitation. This suggests that the main drivers of precipitation are universal. We also show that extreme-precipitation metrics are dependent on wet-day frequency within our framework. Our results imply that wet-day frequency could be used to derive estimates of extreme-precipitation climate indices and corresponding uncertainties, these uncertainties being related to local processes.

Experiments on upstream induction and wake flow for multirotor wind turbines

Multirotor wind turbine concepts are increasingly discussed as cost-effective alternatives for floating wind energy installations. When multiple smaller rotors are installed next to each other, the individual rotors experience local blockage from their neighbours. Depending on the rotor arrangement, the flow through and around the multirotors will differ leading to a local variation in axial forcing and power output on the individual rotors. In this lab-scale experiment, we investigate how the spacing between the single rotors in a multirotor of seven actuator discs affects the upstream flow, thrust force distribution and downstream wake flow. Reducing the inter-rotor spacing is observed to cause larger zones of upstream velocity reductions, both in streamwise and lateral direction. Consequently, the difference in thrust force between a locally blocked central rotor and the surrounding rotors also increases for smaller rotor spacing. Measurements of the downstream wake flow behind a multirotor model indicate a lower initial velocity deficit compared to a single rotor. Reduced rotor spacing is found to increase the wake’s initial velocity deficit and turbulence levels. Consequently, the wake recovers faster, resulting in similar velocity deficits independent of the rotor-spacing in the far wake region.

Determining 3D Distributions of Pulsatile Blood Flow Using Orthogonal Simultaneous Biplane High-Speed Angiography (SB-HSA) with 1000 fps CdTe Photon Counting Detectors for 3D X-ray Particle Image Velocimetry (3D-XPIV) compared to Results Using Computational Fluid Dynamics (CFD).

3D hemodynamic distributions are useful for the diagnosis and treatment of aneurysms. Detailed blood-flow patterns and derived velocity maps can be obtained using 1000 fps High Speed Angiography (HSA). The novel orthogonal Simultaneous Biplane High-Speed Angiography (SB-HSA) system enables flow information to be quantified in multiple planes, and with additional components of flow at depth, accurate 3D flow distributions are available. Computational Fluid Dynamics (CFD) is the current standard for derivation of volumetric flow distributions, but obtaining solution convergence is computationally expensive and time intensive. More importantly, matching in-vivo boundary conditions is non-trivial. Therefore, an experimentally derived 3D flow distribution method could offer realistic results with less computation time. Using SB-HSA image sequences, 3D X-Ray Particle Image Velocimetry (3D-XPIV) was explored as a new method for assessing 3D flow. 3D-XPIV was demonstrated using an in-vitro setup, where a patient-specific internal carotid artery aneurysm model was attached to a flow loop, and an automated injection of iodinated microspheres was used as a flow tracer. Two 1000 fps photon-counting detectors were placed orthogonally with the aneurysm model in the FOV of both planes. Frame-synchronization of the two detectors made correlation of single-particle velocity components at a given timepoint possible. With frame-rates of 1000 fps, small particle displacements between frames resolved realistic time varying flow, where accurate velocity distributions depended on near-instantaneous velocities. 3D-XPIV velocity distributions were compared to CFD velocity distributions, where the simulation boundary conditions matched the in-vitro setup. Results showed similar velocity distributions between CFD and 3D-XPIV.

An unusually powerful and long-lasting water maser flare phenomenon in IRAS 16293-2422

Aims. Our goal is to obtain new detailed observational data on the water maser flare phenomenon, unprecedented in power and duration, that occurred in IRAS 16293-2422 and determine the physical characteristics of the individual flares. Methods. We used the ground-based 22 m radio telescope to conduct long-term observations of the water maser features near – 1.5 km s−1 in IRAS 16293-2422. The movement of the radio telescope, collection of observational data, and processing were performed automatically. We used spectral-temporal data analysis to identify water maser flares in a complex flare phenomenon and determine their physical parameters. Results. The detected maser emission came from the largest structure of maser spots, the high density of which resulted in their partial overlap in time. There were a total of ten individual powerful flares in the phenomenon. The existence of such a complex configuration of emitting maser spots with very similar radial velocities has been confirmed for the first time. We were able to determine that masers of the powerful flares were in an unsaturated state due to a cascade pumping of radiation from several masers located in the observer’s line of sight. We obtained new important physical parameters of maser flares: the detailed shape of flares, the state of the water maser during flares, the H2O kinetic temperature, the density of the medium, the degree of ionization, and the velocities of the maser spots responsible for the flares.

Geophysical transects in the Abitibi greenstone belt of Canada from the mineral-exploration-oriented Metal Earth project

The Metal Earth project integrates geophysics, geology, geochemistry, and geochronology to improve the understanding of metal endowment in Precambrian terranes. Magnetics (airborne), gravity, magnetotellurics, and reflection seismic methods are the primary geophysical tools employed. Data were collected along 13 transects in the initial phase of the project. All geophysical tools are crucial for understanding the structure of the shallow, middle, and deeper crust and identifying pathways along which the constituents of critical minerals might have migrated from a source to a deposit. The magnetic data are used predominantly to help map the geology away from the transects, and the gravity data are useful for extending the near-surface geology to depths up to 8 km. The magnetotelluric data show the upper Archean crust to about 10 km as highly resistive, except for some conductive subvertical zones that correspond to major deformation zones, many of which are known to be metalliferous. This suggests that these conductive zones could have been hydrothermal fluid pathways feeding the mineral deposits. These zones can be traced to larger horizontal conductive zones in the midcrust. The seismic reflection data are consistent with and complement this: the upper crust is primarily nonreflective; however, the midcrust shows many horizontal reflectors, usually with a consistent dip to the north. Processing crooked-line seismic data is problematic, and techniques have been developed to improve the imaging, including multifocusing, 3D processing, full-waveform inversion, and cross-dip moveout methods. Passive seismic data have also been collected. Ambient-noise surface-wave tomography can be used to infer broad zones of similar seismic velocity between major reflectors, while receiver function analysis has been used to identify deeper structures such as horizontal features at or below the Moho and a dipping structure evident to about 70 km depth.

MP53-13 DOES THE PRESENCE OF PRESSURE "POP-OFFS" IMPACT VOIDING EFFICIENCY AND BLADDER OUTCOMES IN POSTERIOR URETHRAL VALVES?

You have accessJournal of UrologyCME1 Apr 2023MP53-13 DOES THE PRESENCE OF PRESSURE "POP-OFFS" IMPACT VOIDING EFFICIENCY AND BLADDER OUTCOMES IN POSTERIOR URETHRAL VALVES? Adree Khondker, Priyank Yadav, Jin Kyu Kim, Michael Chua, Natasha Brownrigg, Juliane Richter, Joana Dos Santos, Armando Lorenzo, and Mandy Rickard Adree KhondkerAdree Khondker More articles by this author , Priyank YadavPriyank Yadav More articles by this author , Jin Kyu KimJin Kyu Kim More articles by this author , Michael ChuaMichael Chua More articles by this author , Natasha BrownriggNatasha Brownrigg More articles by this author , Juliane RichterJuliane Richter More articles by this author , Joana Dos SantosJoana Dos Santos More articles by this author , Armando LorenzoArmando Lorenzo More articles by this author , and Mandy RickardMandy Rickard More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003301.13AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The protective role of pressure pop-offs, consisting of vesicoureteral reflux (VUR) and ipsilateral kidney dysplasia, in posterior urethral valve (PUV) is controversial. While there has been significant emphasis on exploring the non-significant association between “pop-offs” and kidney function, there is paucity of data on the impact of this mechanism on bladder function. Here, we analyzed this association by examining the role of pressure pop-offs on long-term bladder outcomes in PUV patients. METHODS: A retrospective chart review was conducted for toilet-trained children with PUV managed at our institution between 2000 and 2022, only excluding cases without recorded uroflowmetry studies. Patients were stratified by the presence of pressure pop-offs (high-grade VUR+ipsilateral kidney dysplasia). Outcomes included uroflowmetry parameters and initiation of clean-intermittent catheterization (CIC). Survival analysis was conducted to calculate hazard ratios (HR). RESULTS: We identified a total of 101 patients who met study inclusion criteria, with a median follow-up of 114 months (IQR 67, 169). The median age of first and last uroflowmetry was 57 months (IQR 48, 82) and 120 months (IQR 89, 160), respectively. Patients with pressure pop-offs had similar flow velocity, post-void residuals, and bladder voiding efficiency to other PUV patients at last follow-up uroflowmetry. On survival analysis, patients with pressure pop-offs had no significant difference in risk of requiring CIC compared to patients without pop-offs (HR 1.92, p=0.06). Kidney dysplasia was independently associated with increased risk of CIC (HR 3.16, p=0.02) while VUR was not (HR 1.85, p=0.07). CONCLUSIONS: We show that boys with pressure pop-offs are not at higher risk of poorer voiding and intermittent catheterization than others with PUV. By extension, VURD syndrome does not confer protection against poorer bladder function. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e717 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Adree Khondker More articles by this author Priyank Yadav More articles by this author Jin Kyu Kim More articles by this author Michael Chua More articles by this author Natasha Brownrigg More articles by this author Juliane Richter More articles by this author Joana Dos Santos More articles by this author Armando Lorenzo More articles by this author Mandy Rickard More articles by this author Expand All Advertisement PDF downloadLoading ...

Multiphase flow characteristics and gas loss in the shear layer on a ventilated supercavity wall

The shear flow on the large-scale gas–water wall inside a ventilated supercavity exhibits gas entrainment mode and determines the change law of the supercavity's gas loss, significantly impacting the shape and dynamics of the supercavity. Therefore, to develop an accurate prediction model and a ventilation control method for a supercavity under complex motion conditions, it is required to systematically and quantitatively study the shear flow characteristics and rules. This study calculates and comparatively analyzes the shear layers on either side of the supercavity wall based on numerical simulations of ventilated supercavitating flows in an unbounded field using the gas–vapor–water multi-fluid model. It is shown that the external shear layer with a very irregular outer boundary is considerably thinner than the internal shear layer. We further analyze the flow and distribution characteristics of all the phases in the shear layers with and without the influence of gravity. Our analysis confirms that all the phases exhibit a similar velocity change rule along the supercavity radial direction in the shear layer, whereas gas and water phases exhibit opposite radial phase distribution trends. It was also seen when natural cavitation occurs that the vapor phase is mainly distributed in the head of the supercavity. Moreover, at the same radial position, it was seen that the vapor velocity was higher than the gas velocity and slightly lower than the water velocity. Using the shear flow and phase distribution characteristics, a shear-layer gas loss model is established and validated for ventilated supercavitating flows.

Single Cell Analysis of Inertial Migration by Circulating Tumor Cells and Clusters

Single-cell analysis provides a wealth of information regarding the molecular landscape of the tumor cells responding to extracellular stimulations, which has greatly advanced the research in cancer biology. In this work, we adapt such a concept for the analysis of inertial migration of cells and clusters, which is promising for cancer liquid biopsy, by isolation and detection of circulating tumor cells (CTCs) and CTC clusters. Using high-speed camera tracking live individual tumor cells and cell clusters, the behavior of inertial migration was profiled in unprecedented detail. We found that inertial migration is heterogeneous spatially, depending on the initial cross-sectional location. The lateral migration velocity peaks at about 25% of the channel width away from the sidewalls for both single cells and clusters. More importantly, while the doublets of the cell clusters migrate significantly faster than single cells (~two times faster), cell triplets unexpectedly have similar migration velocities to doublets, which seemingly disagrees with the size-dependent nature of inertial migration. Further analysis indicates that the cluster shape or format (for example, triplets can be in string format or triangle format) plays a significant role in the migration of more complex cell clusters. We found that the migration velocity of a string triplet is statistically comparable to that of a single cell while the triangle triplets can migrate slightly faster than doublets, suggesting that size-based sorting of cells and clusters can be challenging depending on the cluster format. Undoubtedly, these new findings need to be considered in the translation of inertial microfluidic technology for CTC cluster detection.

The circumgalactic medium of Milky Way-like galaxies in the TNG50 simulation – II. Cold, dense gas clouds and high-velocity cloud analogs

ABSTRACT We use the TNG50 simulation of the IllustrisTNG project to study cold, dense clouds of gas in the circumgalactic media (CGM) of Milky Way-like galaxies. We find that their CGM is typically filled with of order one hundred (thousand) reasonably (marginally) resolved clouds, possible analogs of high-velocity clouds (HVCs). There is a large variation in cloud abundance from galaxy to galaxy, and the physical properties of clouds that we explore – mass, size, metallicity, pressure, and kinematics – are also diverse. We quantify the distributions of cloud properties and cloud-background contrasts, providing cosmological inputs for idealized simulations. Clouds characteristically have subsolar metallicities, diverse shapes, small overdensities (χ = ncold/ nhot ≲ 10), are mostly inflowing, and have sub-virial rotation. At TNG50 resolution, resolved clouds have median masses of ∼ $10^6\, \rm {M_\odot }$ and sizes of ∼10 kpc. Larger clouds are well converged numerically, while the abundance of the smallest clouds increases with resolution, as expected. In TNG50 MW-like haloes, clouds are slightly (severely) underpressurized relative to their surroundings with respect to total (thermal) pressure, implying that magnetic fields may be important. Clouds are not distributed uniformly throughout the CGM but are clustered around other clouds, often near baryon-rich satellite galaxies. This suggests that at least some clouds originate from satellites, via direct ram-pressure stripping or otherwise. Finally, we compare with observations of intermediate and high velocity clouds from the real Milky Way halo. TNG50 shows a similar cloud velocity distribution as observations and predicts a significant population of currently difficult-to-detect low velocity clouds.

Bed inventory balance and stability of dual circulating fluidized bed systems

Experiments and modelling are conducted for general understanding on the imbalance phenomenon and for discussion on the strategies to improve the bed inventory balance and stability of a dual circulating fluidized bed (DCFB) system. The experiments are carried out in a 15.5 m high pilot-scale DCFB cold test system. A fluid-dynamic DCFB model is developed based on a 1.5-dimensional semi-empirical model of an industrial CFB boiler, validated by experimental data. The effects of control methods and operation conditions on the bed inventory balance and on the stability of the pilot- and large-scale DCFB systems are discussed. A “stable-unbalanced” state, where the system reaches a steady state, consisting of unbalanced bed inventories, is observed in both experiments and model simulation. To maintain a balanced state and similar bed inventory in the DCFB systems with similar cross-sectional areas, it is recommended to keep similar total pressure drops or gas velocities in both reactors.

Analysis of MHD torsional nanofluid flow through concentric cylinders with nonlinear thermal radiation

ABSTRACT By applying torque, turning effects are produced on the flow of the fluids flowing between the two concentric cylinders, which have different radii and are moving in the same or opposite directions with similar or variable velocities. This kind of flow is called torsional flow. In this article, different cases are taken into account to study the variation in heat transfer for the flow of nanofluid between the two concentric cylinders. The influence of magnetic fields and nonlinear thermal radiation is also examined. After non-dimensionalizing the formulated equations, the bvp4c (boundary value problem of order) MATLAB function is utilized to determine the impact of different parameters on flow rate and fluid temperature. The graphical interpretation helps to show the behavior of emerging parameters.

Does VURD syndrome impact voiding efficiency in posterior urethral valves?

There is debate regarding the effect of VURD syndrome, consisting of vesicoureteral reflux (VUR) and ipsilateral kidney dysplasia, on long-term outcomes in boys with posterior urethral valve (PUV). Here, we assessed whether VURD syndrome played a "protective" role on long-term bladder outcomes and voiding efficiency in boys with PUV. A retrospective chart review was conducted for toilet-trained children with PUV managed at our institution between 2000 and 2022, only excluding cases without recorded uroflowmetry studies. Patients were stratified by VUR status and by the presence of VURD syndrome (high-grade VUR+ipsilateral kidney dysplasia). Outcomes included initial and final uroflowmetry parameters, and initiation of clean-intermittent catheterization (CIC). We identified a total of 101 patients who met study inclusion criteria, with an overall median follow-up of 114 months (IQR 67, 169). The median age of first and last uroflowmetry was 57 months (IQR 48, 82) and 120 months (IQR 89, 160), respectively. Patients with VURD syndrome had similar flow velocity, post-void residuals, and bladder voiding efficiency to other PUV patients at last follow-up uroflowmetry. On survival analysis, patients with VURD syndrome had no significant difference in risk of requiring CIC compared to patients without pop-offs (p=0.06). Like more contemporary studies on pressure pop-offs, we show that this population is not at higher risk of poorer voiding and intermittent catheterization than others. VURD syndrome does not confer protection against poorer bladder function. Instead, our study suggests an independent association between kidney dysplasia and bladder outcomes which requires further attention. Among boys with PUV, VURD syndrome was not associated with significantly different uroflowmetry findings or rates of CIC by last follow-up.

First Ejection from the PSR B1259-63/LS 2883 High Mass Gamma-Ray Binary Detected During the 2021–2024 Binary Cycle

LS 2883/PSR B1259-63 is a high mass, eccentric gamma-ray binary that has previously been observed to eject X-ray emitting material. We report the results of recent Chandra observations near binary apastron in which a new X-ray emitting clump of matter was detected. The clump has a high projected velocity of v ⊥ ≈ 0.07c and hard X-ray spectrum, which fits an absorbed power-law model with Γ = 1.1 ± 0.3. Although clumps with similar velocities and spectra were detected in some of the previous binary cycles, no resolved clumps were seen near apastron in the preceding cycle of 2017–2021.