Procedure to Approximately Estimate the Uncertainty of Material Ratio Parameters due to Inhomogeneity of Surface Roughness

Roughness parameters that characterize contacting surfaces with regard to friction and wear are commonly stated without uncertainties, or with an uncertainty only taking into account a very limited amount of aspects such as repeatability of reproducibility (homogeneity) of the specimen. This makes it difficult to discriminate between different values of single roughness parameters. Therefore uncertainty assessment methods are required that take all relevant aspects into account. In the literature this is scarcely performed and examples specific for parameters used in friction and wear are not yet given. We propose a procedure to derive the uncertainty from a single profile employing a statistical method that is based on the statistical moments of the amplitude distribution and the autocorrelation length of the profile. To show the possibilities and the limitations of this method we compare the uncertainty derived from a single profile with that derived from a high statistics experiment.Comment: submitted to Meas. Sci. Technol., 12 figure

Glomus Tumor of the Stomach Simulating a Gastrointestinal Stromal Tumor: A Case Report and Review of Literature

Glomus tumor is an infrequent and in most cases benign mesenchymal neoplasia which affects subcutaneous/submucosal tissue and occurs in the gastrointestinal tract, solid organs (e.g. liver, kidney) and the extremities. Visceral glomus tumor of the stomach generally presents with non-specific epigastric pain, loss of appetite and GI bleeding (melaena), often without haemodynamic instability. Macroscopic appearances on upper GI endoscopy are non-diagnostic. Endosonographic appearances are generally heterogenous and poorly-reflective, hence fail to differentiate glomus tumor from other potential diagnoses. Histological confirmation of the diagnosis is only possible when a fine needle biopsy is inclusive of abnormal tissue. These difficulties in diagnosis mean that in many cases, only immunohistochemical analysis of surgically resected tissue can distinguish glomus tumor from several possible differentials. Therefore, endoscopically-assisted laparoscopic curative wedge-resection of a lesion suspicious for glomus tumor of the upper gastrointestinal tract must be considered first-line in terms of a combined investigative and curative approach

Serum contains a potent factor that decreases β\beta-adrenergic receptor-stimulated L-type Ca2+^{2+} current in cardiac myocytes

No abstract availabl

Intracellular Ca2+ release contributes to automaticity in cat atrial pacemaker cells

The cellular mechanisms governing cardiac atrial pacemaker activity are not clear. In the present study we used perforated patch voltage clamp and confocal fluorescence microscopy to study the contribution of intracellular Ca2+ release to automaticity of pacemaker cells isolated from cat right atrium.In spontaneously beating pacemaker cells, an increase in subsarcolemmal intracellular Ca2+ concentration occurred concomitantly with the last third of diastolic depolarization due to local release of Ca2+ from the sarcoplasmic reticulum (SR), i.e. Ca2+ sparks. Nickel (Ni2+; 25–50 μM), a blocker of low voltage-activated T-type Ca2+ current (ICa,T), decreased diastolic depolarization, prolonged pacemaker cycle length and suppressed diastolic Ca2+ release.Voltage clamp analysis indicated that the diastolic Ca2+ release was voltage dependent and triggered at about -60 mV. Ni2+ suppressed low voltage-activated Ca2+ release. Moreover, low voltage-activated Ca2+ release was paralleled by a slow inward current presumably due to stimulation of Na+–Ca2+ exchange (INa-Ca). Low voltage-activated Ca2+ release was found in both sino-atrial node and latent atrial pacemaker cells but not in working atrial myocytes.These findings suggest that low voltage-activated ICa,T triggers subsarcolemmal Ca2+ sparks, which in turn stimulate INa-Ca to depolarize the pacemaker potential to threshold. This novel mechanism indicates a pivotal role for ICa,T and subsarcolemmal intracellular Ca2+ release in normal atrial pacemaker activity and may contribute to the development of ectopic atrial arrhythmias