The distribution of pressure coefficient formed when the fluid contacts with the kayak oar blade is not been studied extensively. The CFD technique was employed to calculate pressure coefficient distribution on the front and rear faces of oar blade resulting from the numerical resolution equations of the flow around the oar blade in the steady flow conditions (4 m/s) for three angular orientations of the oar (45°, 90°, 135°) with main flow. A three-dimensional (3D) geometric model of oar blade was modeled and the k-ε turbulent model was applied to compute the flow around the oar. The main results reported that, under steady state flow conditions, the drag coefficient (Cd = 2.01 for 4 m/s) at 90° orientation has the similar evolution for the different oar blade orientation to the direction of the flow. This is valid when the orientation of the blade is perpendicular to the direction of the flow. Results indicated that the angle of oar strongly influenced the Cd with maximum values for 90° angle of the oar. Moreover, the distribution of the pressure is different for the internal and external edges depending upon oar angle. Finally, the difference of negative pressure coefficient Cp in the rear side and the positive Cp in the front side, contributes toward propulsive force. The results indicate that CFD can be considered an interesting new approach for pressure coefficient calculation on kayak oar blade. The CFD approach could be a useful tool to evaluate the effects of different blade designs on the oar forces and consequently on the boat propulsion contributing toward the design improvement in future oar models. The dependence of variation of pressure coefficient on the angular position of oar with respect to flow direction gives valuable dynamic information, which can be used during training for kayak competition.

The aim of the current study was to analyze the hydrodynamics of three kayaks: 97-kg-class, single-rower, flatwater sports competition, full-scale design evolution models (Nelo K1 Vanquish LI, LII, and LIII) of M.A.R. Kayaks Lda., Portugal, which are among the fastest frontline kayaks. The effect of kayak design transformation on kayak hydrodynamics performance was studied by the application of computational fluid dynamics (CFD). The steady-state CFD simulations where performed by application of the k-omega turbulent model and the volume-of-fluid method to obtain two-phase flow around the kayaks. The numerical result of viscous, pressure drag, and coefficients along with wave drag at individual average race velocities was obtained. At an average velocity of 4.5 m/s, the reduction in drag was 29.4% for the design change from LI to LII and 15.4% for the change from LII to LIII, thus demonstrating and reaffirming a progressive evolution in design. In addition, the knowledge of drag hydrodynamics presented in the current study facilitates the estimation of the paddling effort required from the athlete during progression at different race velocities. This study finds an application during selection and training, where a coach can select the kayak with better hydrodynamics.

This work reports on the use of two different Monte Carlo codes (GEANT4 and MCNPX) for assessing the dose reduction using bismuth shields in computer tomography (CT) procedures in order to protect radiosensitive organs such as eye lens, thyroid and breast. Measurements were performed using head and body PMMA phantoms and an ionisation chamber placed in five different positions of the phantom. Simulations were performed to estimate Computed Tomography Dose Index values using GEANT4 and MCNPX. The relative differences between measurements and simulations were <10 %. The dose reduction arising from the use of bismuth shielding ranges from 2 to 45 %, depending on the position of the bismuth shield. The percentage of dose reduction was more significant for the area covered by the bismuth shielding (36 % for eye lens, 39 % for thyroid and 45 % for breast shields).

Purpose: To compare balloon occlusion prostatic artery embolization (bPAE) with conventional microcatheter PAE (cPAE). Materials and methods: In this single-center trial, between November 2017 and November 2018, 89 patients with symptomatic benign prostatic hyperplasia were randomly assigned to cPAE (n = 43) or bPAE (n = 46). All patients received embolization with 300-500 μm Embosphere microspheres and were evaluated before and 1 and 6 months after PAE. Primary outcome measure was change from baseline in International Prostate Symptom Score (IPSS). Student t test was used for between-group comparisons of change from baseline, and paired t test was used for within-group comparisons. Results: At baseline, groups were identical (P > .05). Unilateral PAE was performed in 4 patients receiving cPAE and 3 patients receiving bPAE (9.30% and 6.52%, P = .708). Procedural and fluoroscopy times, dose area product, air kerma, embolic volume, and mean prostate-specific antigen (PSA) 24 hours after PAE did not differ between groups (P > .05). Coils were used in 6 patients receiving cPAE and 4 patients receiving bPAE (14.0% and 8.70%, P = .51). Assessments at 6 months after PAE showed mean IPSS reduction was 7.58 ± 6.88 after cPAE and 8.30 ± 8.12 after bPAE (P = .65); mean prostate volume reduction was 21.9 cm3 ± 51.6 (18.2%) after cPAE and 6.15 cm3 ± 14.6 (7.3%) after bPAE (P = .05); mean PSA reduction was 0.9 ng/mL ± 2.22 after cPAE and 0.22 ng/mL ± 1.65 after bPAE (P = .10). Penile skin lesions (n = 3) and rectal bleeding (n = 2) were documented only in patients receiving cPAE (11.9%, P = .01). No major adverse events occurred. Conclusions: bPAE is as effective as cPAE in treating benign prostatic hyperplasia with a potential to reduce nontarget embolization.

Adequate extracorporeal membrane oxygenation support in the adult requires cannulae permitting blood flows up to 6-8 L/minute. In accordance with Poiseuille's law, flow is proportional to the fourth power of cannula inner diameter and inversely proportional to its length. Poiseuille's law can be applied to obtain the pressure drop of an incompressible, Newtonian fluid (such as water) flowing in a cylindrical tube. However, as blood is a pseudoplastic non-Newtonian fluid, the validity of Poiseuille's law is questionable for prediction of cannula properties in clinical practice. Pressure-flow charts with non-Newtonian fluids, such as blood, are typically not provided by the manufacturers. A standardized laboratory test of return (arterial) cannulae for extracorporeal membrane oxygenation was performed. The aim was to determine pressure-flow data with human whole blood in addition to manufacturers' water tests to facilitate an appropriate choice of cannula for the desired flow range. In total, 14 cannulae from three manufacturers were tested. Data concerning design, characteristics, and performance were graphically presented for each tested cannula. Measured blood flows were in most cases 3-21% lower than those provided by manufacturers. This was most pronounced in the narrow cannulae (15-17 Fr) where the reduction ranged from 27% to 40% at low flows and 5-15% in the upper flow range. These differences were less apparent with increasing cannula diameter. There was a marked disparity between manufacturers. Based on the measured results, testing of cannulae including whole blood flows in a standardized bench test would be recommended.

The use of extracorporeal life support devices such as extracorporeal membrane oxygenation in adults requires cannulation of the patient's vessels with comparatively large diameter cannulae to allow circulation of large volumes of blood (>5 L/min). The cannula diameter and length are the major determinants for extracorporeal membrane oxygenation flow. Manufacturing companies present pressure-flow charts for the cannulae; however, these tests are performed with water. Aims of this study were 1. to investigate the specified pressure-flow charts obtained when using human blood as the circulating medium and 2. to support extracorporeal membrane oxygenation providers with pressure-flow data for correct choice of the cannula to reach an optimal flow with optimal hydrodynamic performance. Eighteen extracorporeal membrane oxygenation drainage cannulae, donated by the manufacturers (n = 6), were studied in a centrifugal pump driven mock loop. Pressure-flow properties and cannula features were described. The results showed that when blood with a hematocrit of 27% was used, the drainage pressure was consistently higher for a given flow (range 10%-350%) than when water was used (data from each respective manufacturer's product information). It is concluded that the information provided by manufacturers in line with regulatory guidelines does not correspond to clinical performance and therefore may not provide the best guidance for clinicians.

Background: Adherence to wrist-hand orthoses in patients with musculoskeletal conditions, such as Carpal Tunnel Syndrome, is crucial for effective rehabilitation. However, objective methods for monitoring wear time and pressure distribution remain limited. Purpose: This study presents the Ortho-Monitorizer, a portable 3D-printed sensor-integrated device designed to provide real-time, quantitative monitoring of temperature and pressure in upper limb orthoses. The objective is to evaluate the system's feasibility in detecting patient adherence and identifying critical pressure points. Study design: A descriptive and cross-sectional study was conducted to develop and validate the device, including sensor integration and data acquisition. Methods: Using a 3D scanner and Fusion 360 software, the orthoses were customized and printed in thermoplastic polyurethane. Data from healthy participants (n = 55) and patients with Carpal Tunnel Syndrome (n = 2) were collected through the Ortho-Monitorizer's application, using six sensors (three temperature and three pressure sensors) placed at clinically relevant anatomical points. Data were acquired over five hand positions, and normal reference values were established. Results: Mean temperature values ranged between 29.5∘C and 32.5∘C, while pressure values varied from 0.00 MPa to 0.08 MPa across different hand positions. One CTS patient exhibited pressure values above normal thresholds in specific positions, correlating with discomfort and numbness reports. The device achieved a System Usability Scale (SUS) score of 86.8% (healthy participants) and 92.5% (CTS patients), indicating high usability and acceptance. Conclusions: The Ortho-Monitorizer provides a non-invasive, objective method for monitoring patient adherence to orthotic treatments. By offering real-time tracking of critical parameters, it enhances clinical decision-making and patient outcomes. Future research should explore wireless integration and long-term clinical validation to further optimize its applicability.

Bone histomorphometry is defined as a quantitative evaluation of bone micro architecture, remodelling and metabolism. Bone metabolic assessment is based on a dynamic process, which provides data on bone matrix formation rate by incorporating a tetracycline compound. In the static evaluation, samples are stained and a semi-automatic technique is applied in order to obtain bone microarchitectural parameters such as trabecular area, perimeter and width. These parameters are in 2D, but they can be extrapolated into 3D, applying a stereological formula. Histomorphometry can be applied to different areas; however, in recent decades it has been a relevant tool in monitoring the effect of drug administration in bone. The main challenge for the future will be the development of noninvasive methods that can give similar information. In the herein review paper we will discuss the general principles and main applications of bone histomorphometry.