Particle trajectories and size sorting above a rippled bed under standing water waves.

Particle trajectories and size sorting above an artificial rippled bed under standing surface waves are experimentally and theoretically studied. It is observed that fine particles may be trapped in a very thin region near the ripple crests. When the surface waves damp, fine particles concentrate on the top of ripple crests forming narrow strips, while coarse particles settle more uniformly along the rippled bed. Measurements of particle concentrations before their deposition confirm this size segregation. The present experimental results are explained with a theoretical approach.

Dynamics of propagating front into sand ripples under regular waves.

The results of an experimental study of pattern formation on sandy bottom under the action of regular harmonic surface waves are reported. It is found that two modes of pattern formation occur: sand ripples form uniformly on the whole bottom or from localized nucleation sites. In the second regime, the ripples appear in isolated regions (patches) increasing in size, and front propagation speed is measured. A simple dynamical model based on the Ginzburg-Landau equation is proposed to explain the characteristics of patches.

Segregation of sedimenting grains of different densities in an oscillating velocity field of strongly nonlinear surface waves.

This paper reports the results of an experimental and theoretical study of the segregation of heavy (sand) and light [polyvinyl chloride (PVC)] grains under the action of intense nonlinear water waves, solitons. The tests are carried out with initially carefully mixed grains at the bottom of a wave flume used in resonant mode. Ripples form on the bed and the segregation process is considered after the stopping of the wave paddle. The waves are damped and the PVC grains concentrate in a narrow region close to the ripple crest. A theoretical model explaining this grain density segregation is developed.

Expression levels of the nerve growth factor receptors TrkA and p75 in effusions and solid tumors of serous ovarian carcinoma patients.

PURPOSE: The purpose of this study was to analyze the expression of the high- and low-affinity nerve growth factor (NGF) receptors TrkA and p75 in effusions and in primary and metastatic tumors of serous ovarian carcinoma patients, as well as to evaluate their association with clinicopathological parameters and disease outcome. EXPERIMENTAL DESIGN: Sections from 77 malignant effusions and 78 primary and metastatic lesions were evaluated for protein expression of TrkA and p75 using immunohistochemistry (IHC). Expression of the phosphorylated form of TrkA (p-TrkA) was evaluated in 75 effusions using IHC. TrkA and p75 mRNA expression was studied in 44 effusions using reverse transcription-PCR (RT-PCR). RESULTS: TrkA protein membrane expression was detected in carcinoma cells in 30 of 77 (39%) effusions and 64 of 78 (82%) solid tumors. The decrease in TrkA expression in effusions approached, but did not reach, statistical significance when only corresponding lesions were analyzed (P = 0.06 in the comparison of effusions and primary tumors, P = 0.09 for effusions and metastases). Conversely, p75 protein membrane expression was more common in effusions, which was detected in 16 of 77 (21%) effusions as compared with 6 of 78 (8%) solid tumors (P > 0.05 in analysis of corresponding lesions). Expression of p-TrkA in carcinoma cells was limited to 5 of 75 effusions. Interestingly, 11 of 16 p75-positive effusions were also immunoreactive for the antibody against TrkA (P = 0.001), suggesting NGF activation using two signaling pathways. TrkA and p75 protein expression in tumor cells was similar in pleural and peritoneal effusions (P > 0.05). Using reverse transcription-PCR, TrkA mRNA was detected in 2 of 45 effusions, whereas p75 mRNA was present in 3 of 45 specimens. TrkA and p75 showed no association with tumor grade, Fédération Internationale des Gynaecologistes et Obstetristes stage, chemotherapy status, the extent of residual disease, or survival (P > 0.05). CONCLUSIONS: TrkA and p75 are both expressed in advanced-stage ovarian carcinoma, but whereas p75 expression is elevated in effusions, TrkA shows an opposite trend. The different expression of NGF receptors in effusions may relate to the different microenvironment and growth factor availability in body cavities, as also supported by the infrequent activation of TrkA in effusions. The similar expression of TrkA and p75 in carcinoma cells in pleural and peritoneal effusions provides further evidence for our hypothesis that there are few, if any, phenotypic differences between ovarian carcinoma cells at these two sites. TrkA and p75 expression in effusions does not appear to be a predictor of disease outcome in advanced-stage serous ovarian carcinoma.