Terms Of Dilatation Research Articles

An improved detached eddy simulation method for cavitation multiphase flow

The evolution of cavitation flow involves intense transient characteristics and complex multi-scale motions, significantly increasing the difficulty and computational cost of solving in separation zones. This study proposes an Improved Detached Eddy Simulation (IDES) method, based on a single-equation eddy-viscosity model, aimed at enhancing the resolution of small-scale cavitation flows. By incorporating the broad-spectrum von Karman scale concept, the method effectively improves the resolution capability for small-scale flows in separated zones. The performance of the IDES model was validated through three computational cases, and the main conclusions are as follows: The results of the triangular cylinder flows show that the IDES model demonstrates a resolution capability for large-scale turbulence comparable to the Large Eddy Simulation (LES) model. The orifice flow results indicate that activating the LES method with insufficient grid resolution is highly discouraged, whereas the IDES model performs more robustly under such conditions. For hydrofoil flows, the IDES model more accurately captures the temporal evolution of cavitation, avoiding the premature cavity shedding predicted by LES under coarse grid conditions. The decomposition results of the vorticity transport equation show that both the dilatation term and viscous term are significant contributors in the vorticity transport process, with their average contributions to vorticity reaching 49.25% and 39.99%, respectively. Vortices can be considered the primary controllers of cavitation dynamics, while the dilatation term and viscous term can be regarded as the main controllers of vorticity. Overall, the energy compensation mechanism of the IDES model, based on local flow information, gives it unique advantages in handling small-scale turbulence and cavitation phenomena, providing both high computational efficiency and accuracy.

Three-dimensional shock–flame interactions: effect of wall friction

Multi-dimensional numerical simulations were performed to study the interactions between shock wave and premixed flame. The three-dimensional (3D) fully-compressible, reactive Navier–Stokes equations were solved using a high-order numerical method on a dynamically adapting mesh. The effect of wall friction on the shock–flame interaction was examined by varying wall boundary condition on sidewall. The simulations agree with previous experiment in terms of flame perturbation and flame evolution. The results show two effects of wall friction on flame–shock interaction: (1) flame stretching and (2) damping of local flame perturbation very close to the no-slip wall. The stretch effect leads to non-uniform development of the perturbated flame and consequently a significantly higher growth rate in both global flame perturbation and averaged pressure in the no-slip case compared to the free-slip case. By contrast, the damping effect locally moderates the flame perturbation in close proximity to the no-slip wall because less vorticity is deposited on this part of flame during shock–flame interaction. Quantitative analysis of vortex dynamics suggests that vorticity generation that is produced by baroclinic torque and enhanced by the dilation term during shock–flame interaction causes a growth of flame perturbation via Richtmyer–Meshkov instability. Nevertheless, the vorticity generation is greatly weakened in close proximity to the no-slip wall by the viscous torque and viscous dissipation terms due to friction.

Numerical and experimental analysis of the cavitation and flow characteristics in liquid nitrogen submersible pump

In this paper, the cavitation and flow characteristics of the unsteady liquid nitrogen (LN2) cavitating flow in a submersible pump are investigated through both experimental and numerical approaches. The performance curve of the LN2 submersible pump is obtained via experimental measurement. Numerical simulations are performed using a modified shear stress transport k–ω turbulence model, incorporating corrections for rotation and thermal effects as per the Schnerr–Sauer cavitation model. The numerical framework is verified by comparing the cavitation morphology features with previously reported visual data of the LN2 inducer and aligning pump performance data with those obtained from experimental tests of the LN2 submersible pump. The results indicate that cavitation at the designed flow rate predominantly manifests as tip clearance vortex cavitation in the inducer. Increased flow rates exacerbate cavitation, potentially obstructing the flow passage of the impeller. The vortex identification method and the vorticity transport equation are employed to identify the vortex structures and analyze the interaction between cavitation and vortices in the unsteady LN2 cavitating flow. The vortex structures primarily concentrate at the outlet of the impeller flow passage, largely attributed to the vortex dilation term and baroclinic torque. The influence of thermal effects on the cavitation flow of submersible pumps is analyzed. An entropy production analysis model, comprehensively involving various contributing factors, is proposed and utilized to accurately predict the entropy production rate within the pump. This study not only offers an effective numerical approach but also provides valuable insight into the cavitation flow characteristics of the LN2 submersible pump.

Numerical simulation of cavitation-vortex interaction mechanism in an advanced rotational hydrodynamic cavitation reactor

Hydrodynamic cavitation (HC), a promising technology for enhancing processes, has shown distinct effectiveness and versatility in various chemical and environmental applications. The recently developed advanced rotational hydrodynamic cavitation reactors (ARHCRs), employing cavitation generation units (CGUs) to induce cavitation, have demonstrated greater suitability for industrial-scale applications than conventional devices. However, the intricate interplay between vortex and cavitation, along with its spatial-temporal evolution in the complex flow field of ARHCRs, remains inadequately elucidated. This study investigated the interaction mechanism between cavitation and vortex in a representative interaction-type ARHCR for the first time using the “simplified flow field strategy” and the Q-criterion. The findings reveal that the flow instability caused by CGUs leads to intricate helical and vortex flows, subsequently giving rise to both sheet and vortex cavitation. Subsequently, utilizing the Q-criterion, the vortex structures are identified to be concentrated inside and at CGU edges with evolution process of mergence and separation. These vortex structures directly influence the shape and dimensions of cavities, establishing a complex interaction with cavitation. Lastly, the vorticity transport equation analysis uncovered that the stretching and dilatation terms dominate the vorticity transport process. Simultaneously, the baroclinic term focuses on the vapor-liquid interface, characterized by significant alterations in density and pressure gradients. These findings contribute to a better comprehension of the cavitation-vortex interaction in ARHCRs.

Large Eddy Simulation of the Effect of Hydrogen Ratio on the Flame Stabilization and Blow-Off Dynamics of a Lean CH4/H2/Air Bluff-Body Flame

This study investigated the flame structure and dynamics of a bluff-body flame when numerically close to blow-off conditions. This includes the impact of the hydrogen ratio on lean CH4/H2/air flame stabilization and blow-off characteristics. In this study, we assessed the impacts of four different hydrogen ratios: 0%, 30%, 60%, and 90%. Large eddy simulation (LES) was coupled with a thickened flame (TF) model to determine the turbulent combustion using a 30-species skeletal mechanism. The numerical results were progressively validated using OH-PLIF and PIV techniques. The results obtained from the numerical simulations showed minor differences with the experimental data on the velocity field and flame structure for all conditions. The presented results reveal that the flame is stabilized in higher-strain-rate spots more easily in the presence of high hydrogen ratios. Moreover, the flame location moves away from the concentrated vortex area with an increasing hydrogen ratio. The results of our blow-off investigation indicate that the blow-off sequence of a premixed bluff-body flame can be separated into two stages. The entire blow-off process becomes shorter with an increase in the hydrogen ratio. The primary reason for global extinction is a reduction in the heat release rate, and enstrophy analysis implies that blending hydrogen can reduce the enstrophy values of flames at the downstream locations. The dilatation and baroclinic torque terms decrease close to blow-off, but their decline is not significant in high-hydrogen-ratio conditions.

Numerical investigation of cavitation vortex dynamics in different cavitation patterns coupled implicit large eddy simulation and boundary data immersion method

The objective of this paper is to investigate the flow characteristics of different cavitation flow patterns around a NACA (National Advisory Committee for Aeronautics) 66 hydrofoil by applying the BDIM (boundary data immersion method) and ILES (implicit large eddy simulation) with an artificial code. Meanwhile, an artificial compressibility method is also employed to consider the effects of compressibility on cavitating flow. The results present that the numerical method can effectively capture different cavitation patterns, which agrees well with the previous experimental data. Subsequently, the detailed analysis of vortex structures and dynamics for the non-cavitation (σ = 3.0), sheet cavitation (σ = 2.0), and cloud cavitation (σ = 1.6) cases with the Liutex method and the vortex enstrophy transport equation have been investigated. When cavitation occurs, the degree of turbulence and the enstrophy in the flow field have been enhanced, due to the disturbance of the velocity field. For sheet cavitation, complex vortex structures appear in the attached cavity region with high-intensity enstrophy causing by the highly intense velocity and density gradient. As the cavitation pattern transits from the sheet cavitation to the cloud cavitation, more complex vortex structures can be observed in the cavitation region. Furthermore, the value and the fluctuation amplitude of enstrophy intensity increase significantly under the effect of reentrant jet. Analysis of the enstrophy transport equation indicates that the vortex stretching term and dilatation term for cloud cavitation increase relatively significantly with the movement of the reentrant flow and are highly dependent on the cavitation evolution. In addition, the region affected by the baroclinic torque also increases.

Variability in the Distinctive Features of Silica Sands in Central Europe

Quality quartz sand is globally utilized in construction due to its availability and economic factors, especially in the production of composite cements. Despite its positive properties, quartz sand also has several disadvantages. The dilation of quartz sand can be technologically significant for certain high-temperature applications. This dilation has a non-continuous character with sharp volume change caused by the phase transformation from β to α SiO2 at temperatures around 573 °C. The extent of dilation depends on various factors such as compaction, grain size, the quantity of sand, as well as the shape and character of the grain and chemical purity, particularly the SiO2 content. In this study, six types of quartz sand from different locations in Central Europe were examined, and the influence of chemical composition and grain shape was correlated with the final dilation of these samples. Evaluation methods included X-ray fluorescence spectroscopy (XRFS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), differential thermal analysis (DTA), and linear thermal expansion analysis. It was found that angular grains, despite their chemical purity, may exhibit minimal dilation. Conversely, the least suitable combination in terms of dilation appears to be a high SiO2 content and high roundness of grains with a smooth surface.

Ordinary state-based peridynamic model for out-of-plane deformation and damage analysis of composite laminates

An ordinary state-based peridynamic (PD) model for predicting out-of-plane mechanical behaviour of composite laminates has been proposed, in which three types of PD bonds are used to describe the reinforcement properties. The non-local strain energy density and peridynamic formulations are obtained based on the principle of virtual work by using Total Lagrange formulation, and the force density is reformulated by interpolation technique. Since the Mindlin plate is regarded as the research object of this PD model, the transverse shear deformation of laminates is considered. Also, the dilatation term is included in the force density vector, and flaws in Poisson's ratio of materials can be overcome. In the proposed PD, the critical strain energy density rather than the critical curvature is adopted as the failure criterion. The capability of the developed PD model was demonstrated by the bending examples of composite laminates with different fiber orientations, and damage analysis was further conducted to demonstrate the strong capability of proposed PD model in replicating the damage process of laminates. In addition, a single-layer material point model (SLMPM) can be implemented in the proposed PD algorithm, and the computational efficiency of numerical models will be greatly improved.

Research on the Unsteady Flow and Vortex Characteristics of Cavitation at the Tongue in Centrifugal Pump

In order to study the unsteady flow and vortex characteristics of tongue cavitation, numerical calculation is carried out for the whole flow channel given different conditions. Then, the calculation results are verified experimentally. The results show that after the occurrence of tongue cavitation in the centrifugal pump, it deteriorates with the decrease of NPSHa. However, when NPSHa is reduced to 3.78 m, it does not change significantly anymore with the decrease of NPSHa. The extrusion of fluid by the vapor at the tongue promotes the formation of the separation vortex, and the re-jet flow caused by the separation vortex leads to vapor shedding. The frequency of cavitation shedding is consistent with the frequency of vortex shedding. In the vorticity transport equation, the relative vortex stretching term and the relative vortex dilatation term dominate the vapor shedding by controlling the change in vorticity. The baroclinic torque term mainly affects the change of vorticity at the vapor-liquid interface, but to a much lesser extent than the first two terms.

The vortex dynamics characteristics in a pump-turbine: A rigid vorticity analysis while varying guide vane openings in turbine mode

In off-design conditions, pump-turbines generate vortex structures of varying scales and intensities, jeopardizing energy conversion due to unstable flow phenomena. While off-design pump-turbine internal flow dynamics have been analyzed, understanding the spatiotemporal evolution of complex vortex structures within runner blade passages, which are prone to inducing hydraulic instabilities, has to be still addressed properly. This paper applies the rigid vorticity theory, also known as Liutex, to explore vortex characteristics in the pump-turbine under different guide vane openings during turbine mode operation. The investigation focuses on three main aspects: i) spatial distribution characteristics, ii) temporal evolution characteristics, and iii) vortex morphological features along with deformation mechanisms. Results showed that the suction surface side of the blade's trailing edge commonly experiences significant shear effects, while vortices tend to emerge on both pressure and suction surface sides. Under small Guide Vane Opening (GVO) condition, vortices in blade passages show periodic evolution, and Enstrophy of the Rigid Vorticity Dilatation Term (ERDT) predominantly contributes to the helical deformation of these vortices. Conversely, under large GVO condition, vortices maintain high helicity and remain stable. This study provides insights to reduce hydraulic instability in pump-turbines and optimize energy conversion efficiency. The proposed Reynolds-averaged transport equation for enstrophy of the rigid vorticity and the relative streamline coordinate system provide advanced tools for analyzing unstable flow structures.

Additionalintracervical prostaglandin reduces induction to calving time in buffaloes affected with incomplete cervical dilatation post-uterine detorsion.

Conventional induction protocol (CIP) of calving in buffaloes employs the intramuscular (IM) administration of dexamethasone (40mg) and cloprostenol sodium (500μg). If there is no progression in terms of cervical dilatation, then a second dose of cloprostenol sodium (500μg) is administered intramuscularly. This protocol possesses certain demerits: (1) a wide range of response time intervals, and (2) increased risk of fetal membrane retention. Considering the cervix as a caudal continuation of the myometrium with its own contractile potential, and the limitations of CIP, we developed intracervical (IC) drug administration route in buffaloes. The proposed technique was evaluated for its use in a total of 22 cases of incomplete cervical dilatation in uterine torsion-affected buffaloes (IC-14 and IM-8). In addition to CIP, the IC group received an intracervical injection of cloprostenol sodium (500μg) at the start of the experiment whereas the IM group received an extra intramuscular dose of cloprostenol sodium (500μg) either after 24h or when no progression in cervical dilatation is noticed. Surprisingly, the average response time during the experiment in the IC group was 5.8h shorter (p < 0.000) than in the IM group (IC-5.7 ± 0.17h vs. IM-11.9 ± 0.74h). The duration from calving to fetal membrane expulsion (IC-12.8 ± 0.60h vs. IM-17.5 ± 1.40h; p < 0.002) and incidence of retentionof fetal membrane were also less in the IC group (57.1% vs. 87.5%). The proposed intracervical drug administration potentiates cervical dilatation and can be regarded as a safe, effective, and feasible technique for attaining reliable results.

Active‐Source Seismic Imaging of Fault Re‐Activation and Leakage: An Injection Experiment at the Mt Terri Rock Laboratory, Switzerland

AbstractWe conducted a time‐lapse seismic experiment utilizing automated active seismic source and sensor arrays to monitor a reactivated fault within the Opalinus clay formation at the Mont Terri Rock Laboratory (Switzerland), an analog caprock for geologic carbon storage. A series of six brine injections were conducted into the so‐called Main Fault to reactivate it. Seismic instrumentation in five monitoring boreholes on either side of the fault was used to continuously probe changes in P‐wave travel‐times associated with fault displacement and leakage. We performed time‐lapse travel‐time tomography on five hundred sequential data sets; this revealed a zone of decreased P‐wave velocity, up to 16 m/s, during each injection cycle, followed by a velocity increase during shut‐in. These results demonstrate varying elastic property perturbations, both spatially and temporally, along the fault plane during reactivation. We then interpreted these velocity changes in terms of fault dilation induced by pressurized fluids along the fault.

Consistent energy-based framework of amplification mechanisms for the second mode in hypersonic boundary layers

The second mode is of general interest in hypersonic boundary layer flows due to its underlying responsibilities for transition to turbulence. However, a long-term debate exists on the detailed energy sources that sustain the modal exponential growth. Currently, three influential energy-based approaches appear to show different significant energy sources due to dissimilar mathematical formulations, including the momentum potential theory, the inviscid Lagrangian energy analysis, and the relative phase analysis. In this study, these three fundamental approaches are employed and examined in conjunction with direct numerical simulations. The purpose is to seek a possible unified explanation of the source terms that dominate the exponential evolution of the second mode. In the considered Mach 6 flow state, all three approaches consistently point to the same local energy amplification route driven by two pronounced source terms: the dilatation term in the near-wall region and the Reynolds thermal stress term or heat exchange term across the outer layer region, depending on the selection of the specific energy norm. The mathematical forms of the corresponding sources are derived or discussed explicitly. Theoretical and simulation results provide a unified understanding of the local energy amplification mechanisms of the second mode.

Large eddy simulations of cavitation around a pitching–plunging hydrofoil

In this study, we numerically examine the behavior of the NACA (National Advisory Committee for Aeronautics) 66 hydrofoil under combined oscillatory motion, considering different cavitation numbers. The large eddy simulation method is used for the turbulence modeling. The vertical oscillation (combined oscillation) creates an effective angle of attack, leading to reduced drag force. Our findings indicate that increasing the speed of hydrofoil oscillation leads to a delayed onset and increased production of cavity clouds. Moreover, an increase in the angle of attack during combined oscillatory motion decreases the detachment length of cavitation bubbles. Further investigations show that cavitation on the hydrofoil's surface can accelerate the shift from a laminar to turbulent boundary layer, reinforcing the turbulent boundary layer's strength and thereby delaying the onset of flow separation. Additionally, we accurately examine the terms of the vorticity transport equation in this research. It is evident that the vorticity dilatation term forms near the boundary layers close to the hydrofoil surface and correlates well with the vapor volume fraction. This term plays a vital role in the cavitation inception process.

On isolated singularities of mappings with finite length distortion

Here we give a survey of various integral criteria in terms of inner dilatations $K_{I}$ for the removability of isolated singularities of mappings with finite length distortion in $\mathbb{R}^{n}$, $n\geq 2$, that are a natural extension of the well-known Martio-Vaisal a mappings with bounded length distortion. In particular, the survey includes many effective integral criteria of the types of BMO, bounded mean oscillation by John-Nirenberg, FMO, finite mean oscillation, Calderon-Zygmund, Lehto, and Orlicz.

Assessment of Right Ventricular Reverse Remodeling in Infants with Critical Pulmonary Stenosis after Balloon Pulmonary Valvuloplasty Using 3D Echocardiography

Abstract Aim and Objectives The aim of this study is to identify role of 3D echocardiographic assessment of RV volumes and function in infants with critical pulmonary stenosis undergoing balloon pulmonary valvuloplasty pre and post dilatation, the immediate and intermediate term outcome of relieving obstruction on RV volumes Patients and Methods The study included all infants who were referred for elective or urgent BPV in the congenital and structural heart disease Unit, Cardiology department, Ain Shams University because of critical pulmonary stenosis and are followed for 3-6 months after the procedure since first of December 2020 till end of august 2021. Results sixty infants with critical PS with a median age of 8.5 months were subjected to BPV, immediately after the procedure there was significant reduction in RVSP (P &amp;lt; 0.01), there was significant increase in TAPSE, Annulus and FAC by 2D echocardiography immediately post procedure and at 3-6 month follow up (P &amp;lt; 0.01), while there was significant decrease in PG immediately post procedure and throughout a follow up period of 3-6 month (P &amp;lt; 0.01), The indexed RV wall thickness and indexed RA area showed no significant change between pre and immediately post procedure while there was significant decrease at 3-6 month than pre and immediately post (P &amp;lt; 0.01), The indexed End-Diastolic and End systolic volumes by 3D Echocardiography decreased insignificantly immediately post procedure (P = 0.421) (P = 0.317) respectively while it decreased significantly at 3-6 month follow up (P &amp;lt; 0.05), The right ventricle Ejection fraction, FAC and TAPSE by 3D echocardiography increased significantly immediately post procedure and throughout a follow up period of 3-6 month (P &amp;lt; 0.01), The Basal RV dimension by 3D echocardiography decreased insignificantly immediately post procedure (P = 0.057)while there was significant decrease at 3-6 month than pre and immediately post (P &amp;lt; 0.01), The mid RV dimension and Longitudinal RV dimension by 3D Echocardiography decreased significantly immediately post procedure and at 3-6 month follow up (P &amp;lt; 0.01). Conclusion BPV is safe and effective to relieve critical PS. The balloon promotes advantageous changes in pulmonary annulus RVSP, PG and FAC by two dimensional echo across the RVOT. In addition, the Doppler gradient observations during the follow-up support the expectation that BPV is a ‘curative’ therapy and Three-dimensional echocardiography is an effective method to assess RV volumes and function Abbreviations RV: Right ventricle; CHD: Congenital heart disease; BPV: Balloon pulmonary valvuloplasty; LV: Left ventricle; PS: Pulmonary stenosis; HF: Heart failure; RVSP: Right ventricle systolic pressure; ASD: Atrial septal defect; TAPSE: Tricuspid annular peak systolic excursion; PFO: patent foramen ovale; FAC: Fractional area change; VSD: Ventricular septal defect; PG: Pressure gradient; PDA: patent ductus arterioses; RA: Right atrium; RVES: Right ventricle end systole; RVOT: Right ventricle outflow tract; RVED: Right ventricle end diastole; CMR: Cardiac magnetic resonance

Functional, biological, and radiological evaluation of the pancreaticojejunal anastomosis 1 year after pancreatoduodenectomy: a prospective study

PurposeThis prospective study aimed to analyze the functional, biological, and radiological aspects of the pancreatic anastomosis 1 year after pancreatoduodenectomy (PD).MethodsFrom 2016 to 2019, patients with PD indication were screened. Questionnaires about pancreas insufficiency, fecal elastase tests, and magnetic resonance imaging (MRI) were performed before and 1 year after PD.ResultsTwenty patients were prospectively included. The only difference between pre- and postoperative questionnaires was constipation (less frequent 1 year after PD). Median pre- and postoperative fecal elastase levels were 96 μg/g (IQR 15–196, normal value > 200) and 15 μg/g (IQR 15–26, p = 0.042). There were no significant differences in terms of main pancreatic duct (MPD) size (4, IQR 3–5 vs. 4 mm, IQR 3–5, p = 0.892), border regularity, stenosis, visibility, image improvement, and secondary pancreatic duct dilation before and after secretin injection. All patients but one (2 refused and 2 were lost to follow-up, 15/16, 94%) had a patent pancreaticojejunal anastomosis on 1-year MRI.ConclusionAlthough median 1-year fecal elastase was significantly lower than preoperatively, suggesting that exocrine secretion was altered, the anatomical outcome as assessed by MRI was excellent showing high patency rate (15/16, 94%) at 1 year. This emphasizes the difference between anatomy and function.

Development and evolution mechanism of streamwise vortex in an inward-turning inlet

The three-dimensional flows in an inward-turning inlet were numerically investigated at different incoming flow conditions. When the incoming flow conditions change, the shock angle and the shock interaction form of the external compression wave change, and the development of the near-wall low-energy fluid and the streamwise vortex is also affected. The impingement of the shock wave leads to a sharp increase in the vorticity of the low kinetic energy fluid. Under the pressure gradient caused by the shock wave, the high-vorticity fluid migrates from the cowl to the ramp and entrains the mainstream fluid to form a streamwise vortex, for which the velocity gradient ( ∂v/ ∂y + ∂w/ ∂z) along the vortex axis can accurately determine the rotation direction and the Hopf bifurcation position. By considering high Reynolds number flows, the pressure gradient along the vortex axis is developed to estimate the simplified dilation term (velocity gradient) due to its ease of measurement. However, the pressure gradient ( ∂p/ ∂x) along the vortex axis can lead to bias when evaluating the cross-flow state of the streamwise vortex, with the shock wave structure and high-vorticity fluid leading to under- and overestimation, respectively. This study provides a theoretical basis for an accurate determination of the flow state of a streamwise vortex in an inward-turning inlet and thus lays the foundation for effective vortex control.

Pre-induction cervical ripening and hygroscopic cervical dilators in pre-labor induction

Introduction Induction of labor (IOL) is becoming a universal topic in Obstetrics, when the risk of continuing a pregnancy outweighs the benefits. Preinduction is a more recent tool to prepare the cervix when the BISHOP-score is low. About one-third of IOL cases require cervical ripening, which is the physical softening, thinning, and dilation of the cervix in preparation for labor and birth. We report a single center experience regarding the use of hygroscopic dilators in the pre-labor phase to obtain cervical ripening before labor induction. Materials & Methods We conducted a retrospective observational study comparing patient records from the Gynecology and Obstetrics Unit in “Santo Stefano” Hospital in Prato, Tuscany. The inclusion criteria for participants were women who had undergone pre-labor induction because of a BISHOP-score < 3. The gestational age of all the pregnant women was at term (> 37 weeks). Results From January 2022 to April 2022, a total of 581 women delivered at term of gestational age at the Gynecology and Obstetrics Unit in “Santo Stefano” Hospital. Cervical ripening was necessary for 82 women with a Bishop score < 3 and hygroscopic cervical dilators were used in 35/82 (42.7%) patients. All patients showed a change in Bishop-score upon removal of the dilators. All 35 patients (100%) reported an increase in terms of consistency and dilation of the cervix but not in terms of length. None of the patients reported discomfort during the 24 h that they kept the hygroscopic dilators in place. No patients reported uterine tachysystole on cardiotocographic tracing, vaginal bleeding, rupture of membranes or cervical tears. Conclusions Our results are in line with those in the literature, demonstrating the validity of hygroscopic dilators in cervical maturation of pregnancies at term and their efficacy was again highlighted in terms of both maternal and fetal safety and patient satisfaction.

Effect of Melatonin on Increasing the Effectiveness of Liver Preservation Solution.

Various tissue preservation solutions are used during the removal of the organ and during transplantation to protect the normal histological and biochemical characteristics of tissue while performing a successful liver transplant. In our study, it was aimed to investigate the effects of intraperitoneal melatonin administration on liver preservation damage before transplantation. In our study, the histological and biochemical characteristics of University of Wisconsin+melatonin group rats treated with melatonin 45 minutes before hepatectomy were compared between serum physiologic group and University of Wisconsin group. When hematoxylin and eosin staining was evaluated in terms of hydropic degeneration, sinusoidal dilatation, and hepatocyte necrosis, there was no statistically significant difference. Caspase 3 immunohistochemical staining showed a significant increase in Caspase 3 immunoreactivity positivity at the 12th-hour University of Wisconsin group compared to University of Wisconsin+melatonin group. As a result of biochemical analysis, the malondialdehyde and total oxidant status levels in the University of Wisconsin+melatonin group decreased significantly compared to the University of Wisconsin group. When the reduced glutathione activity and total antioxidant capacity level were compared, a significant increase was observed in the University of Wisconsin+melatonin group compared to the University of Wisconsin group at the 12th hour. It was also found that aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase levels decreased significantly in the University of Wisconsin+melatonin 12th-hour group compared to the University of Wisconsin 12th hour and control group. When the findings were evaluated, intraperitoneal administration of melatonin, a cytoprotective antioxidant, was found to play an effective role in preserving immunohistochemical and biochemical properties of liver tissue integrity and hepatocytes in University of Wisconsin solution.