Leser-Trélat sign: Does it really exist?

Leser-Trelat sign is a rare cutaneous disorder that appears by sudden emergence of seborrheic keratoses and increase in their numbers and size just in weeks or months. Its cooccurence with many kinds of malignancies, especially with adenocarcinoma and lymphoma, has been reported in literature. In this case report, a patient having Leser Trélat sign, without any detected malignancy in spite of a detailed examination and 18 months of follow-up, is presented. The current literature is being discussed whether Leser-Trélat is a paraneoplastic syndrome or not

Effect of biofouling roughness on a marine propeller's performance including cavitation and underwater radiated noise (URN)

This study aims to investigate the effects of biofouling-related roughness on a propeller’s hydrodynamic and underwater radiated noise (URN) performance. Selected benchmark INSEAN E779A propeller operated in uniform & open water flow under non-cavitating and cavitating conditions. The hydrodynamic flow field around the propeller was first solved using RANS (Reynolds-averaged Navier Stokes) solver. The Schnerr-Sauer cavitation model, based on reduced Rayleigh-Plesset equation, was used to model the sheet cavitation on the propeller blades and tip vortex cavitation (TVC) in the propeller’s slipstream. A vorticity-based Adaptive Mesh Refinement (AMR) technique was employed for the observation of TVC. The porous form of the Ffowcs-Williams Hawkings (P-FWH) equation, which is coupled with the RANS solver, was used to predict the URN (or hydroacoustic performance) of the propeller. The propeller performance characteristics, including cavitation, were validated with the available experimental data. Following that, the roughness functions representing the different roughness configurations obtained from the literature were employed using wall function model of Computational Fluid Dynamics (CFD) solver. The results showed that roughness has detrimental impacts on the propeller’s performance characteristics. That is to say that the propeller’s thrust decreases while the torque increases with increasing severity of the roughness. Hence, the efficiency loss of the propeller at the most severe roughness condition can be as high as 30% and 25% at J=0.795 and J=0.71 & σ=1.763, respectively. Unlike its detrimental effects on the hydrodynamic performance, the roughness had some positive effects by reducing the cavitation volume, especially for the TVC and hence on the propeller underwater radiated noise (URN). The results also indicated that the URN levels might be reduced up to 10dB between 1kHz and 2khz. Besides, 2nd and 3rd BPF values decrease between 1 and 7dB under varying roughness configurations in comparison to the smooth case. The study reported the effect of a particular biofouling roughness on the URN levels of a propeller for the first time in model-scale and using the CFD simulations

A CFD study : influence of biofouling on a full-scale submarine

The aim of this study is to investigate the effect of biofouling related hull roughness on a full-scale submarine by taking into consideration the resistance components, effective power, and nominal wakefield using a Computational Fluid Dynamics (CFD) solver. The validation study was first performed for the model scale submarine form in hydraulically smooth (reference) condition with the available experimental data. Following that, roughness functions, representing the different biofouling conditions, were obtained from the literature and then employed in the wall function of a RANS solver. Later on, the full-scale submarine form was investigated both in the smooth and different grades of biofouling related roughness conditions. The scale effects were examined between the model and full-scale submarine forms through the total resistance components and nominal wake fraction in the smooth reference condition. In rough cases, the frictional resistance values of the full-scale submarine form obtained by RANS solver were compared with those of predicted using Granville‘s similarity law analysis based on the flat plate approach. The numerical results showed that the roughness causes a substantial increase in effective power, ranging from ∼36% to ∼112% depending on the roughness height and submarine speed. Furthermore, with an increasing boundary layer thickness (due to the impact of increasing roughness heights), the mean nominal wake fraction values increase ranging from ∼25% to ∼68 compared to the reference wake fraction values in the axial direction at the stern

Nitrate reductase activity in cabbage (Brassica oleracae var. capitata) seedlings affected by the different nitrogen fertilizer forms

The effect of different nitrogen fertilizer (potassium nitrate, ammonium nitrate, ammonium sulphate, urea and farmyard manure) on nitrate reductase activity in cabbage (Brassica oleracea var. capitata) seedlings were studied. pH of the plant growth niedia was higher in the nitrate fertilizer treatment than the ammonium and other fertilizer forms. NO3--N application increased NRA in plant, but NH4+-N decreased NRA in plant. Harvesting date and different fertilizer doses increased NRA while NH4+-N decreased plant nitrate uptake. There was a significant relationship between NRA and fertilizer types

Leser-Trélat sign: Does it really exist?

Leser-Trelat sign is a rare cutaneous disorder that appears by sudden emergence of seborrheic keratoses and increase in their numbers and size just in weeks or months. Its cooccurence with many kinds of malignancies, especially with adenocarcinoma and lymphoma, has been reported in literature. In this case report, a patient having Leser Trélat sign, without any detected malignancy in spite of a detailed examination and 18 months of follow-up, is presented. The current literature is being discussed whether Leser-Trélat is a paraneoplastic syndrome or not

Effect of biofouling roughness on the full-scale powering performance of a submarine

The aim of this study is to investigate the impact of barnacle type biofouling roughness on the full-scale powering performance of a submarine in calm seas. The importance of the diversified biofouling accumulations in terms of hull location is also examined over the submarine hull by implementing homogeneous and heterogenous roughness distribution. In this study, a Reynolds Averaged Navier Stokes (RANS) based CFD model was used for predicting the effects of biofouling roughness on the self-propulsion characteristics for the full-scale submarine form. The powering performance analyses are performed with discretised propeller geometry, and the Moving Reference Frame approach is used to model the rotational motion of the propeller. A proportional-integral (PI) approach is adopted to obtain the self-propulsion point efficiently by modifying the propeller's rotational speed. First, the resistance and the self-propulsion characteristics of the model scale submarine are validated with the experimental and other numerical studies in the literature. Following this validation task, a roughness function model is employed within a CFD software's wall function to represent the rough surfaces over the submarine hull. The results showed that although roughness has a varying effect on the submarine's self-propulsion characteristics depending on the roughness distribution, it increases the hull resistance and, hence, the delivered power overall. Roughness on the forward section of the hull has a more pronounced effect on the resistance and delivered power. The study demonstrated that the presence of partial hull fouling should not be ignored, and required precautions should be taken to prevent losses in submarine performance, especially for the fouling at the forward section of the submarine

Influence of roughness on propeller performance with a view to mitigating tip vortex cavitation

This study explored the effects of uniformly and non-uniformly distributed biofouling roughness on hydrodynamic performance, particularly on the tip vortex cavitation (TVC) for model and full-scale marine propellers. The effect of roughness was investigated on a benchmark propeller belongs to the research catamaran, 'The Princess Royal'. The investigation also explored the potential use of the roughness effect to mitigate this propeller's tip vortex cavitation with uniform, inclined and non-uniform flow conditions. In the numerical calculations, DES (Detached Eddy Simulation) approach was used to simulate the cavitating flow around the propeller. The Schneer-Sauer cavitation model was used to model the sheet and tip vortex cavitation. An advanced meshing technique called V-AMR (Vorticity-based Adaptive Mesh Refinement) was proposed to model the TVC in the propeller slipstream. The modified wall-function approach was utilised to implement the roughness effects in the calculations using the experimentally obtained roughness functions based on one of the authors' recent study. The results showed that the velocity components decreased inside the tip vortex due to roughness, resulting in a pressure increase and TVC mitigation. The suction side of the propeller blade tips was found to be an effective roughness application area for the TVC mitigation with a moderate level of loss in the propeller efficiency. The findings indicated that the cavitation volume reduction, mainly due to the TVC mitigation, was by approximately 6–38%, with a 5–10% efficiency loss in the model scale, while these figures were 4–10% and 2–5%, respectively, for the full-scale propeller under the uniform and non-uniform flow conditions