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Contraction of soil during desiccation gives rise to polygon-patterned cracking. This phenomenon was investigated by continuous full-strain measurements on soil sample surfaces using digital image correlation techniques. The results show that desiccation cracking was of the mode I variety and can be reliably predicted through strain field analyses: the observed cracking was restricted mostly to high stretching domains. The observed high stretching stems from either external restraint or internal flaws of the shrinking soil. The cracks redistribute the stress in their vicinity and lead neighboring cracks to intersect them mostly orthogonally. As desiccation proceeds, the surface strain field ceases to provide useful information for predicting crack locations. Further analysis indicates that although drying occurs from exposed material surfaces, late-generation cracks actually initiate in the subsurface and express themselves subsequently at the surface. These observations offer insights into the intrinsic mechanisms of drying-induced crack growth in soils.

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To elucidate possible ionic mechanisms of antimyocardial ischemia and antiarrythmia of tetramethyl pyrazine (TP), we studied L-type Ca2+ currents (I(Ca.L)) in adult rat ventricular myocytes using the whole-cell patch-clamp technique. The results showed: (i) under physiological conditions, 0.25 mmol/L TP decreased amplitude of I(Ca.L) to 60.6% and this inhibition was increased with increasing concentration of TP. ID50 was 0.20 mmol/L. (ii) The Ca2+-antagonistic effect of TP was voltage-dependent. A marked negative shift of the steady-state inactivation curve was observed with long (10 s) conditioning prepulses, but not with short (350 ms) ones. (iii) The time course of inhibition during TP treatment was increased with an increase in drug concentration, and recovery from TP-induced inactivation of I(Ca.L) was slower than in control cases. (iv) Tonic block and use-dependent block with TP treatment, which was induced by increasing the frequency of stimulation, occurred. We suggest that TP inhibits the I(Ca.L) mainly by binding to inactivated Ca2+ channels. The high affinity of TP for the inactivated state of I(Ca.L) may play an important role in developing therapies for pathological conditions.

Background: Hypokalemia (LK) was associated with peritonitis in peritoneal dialysis (PD) patients, while the role of its degree and duration have not been fully established. Here, we conducted a retrospective cohort study to identify the relationships of LK degree and duration with peritonitis in PD patients.Methods: A total of 602 PD patients in our department from Jan 1st, 2009 to Dec 31st, 2019 entered the last analysis. Data were collected from their medical records.Serum potassium (SK) levels, degree of hypokalemia, and duration of hypokalemia were analysed with peritonitis. The time association of hypokalemia and peritonitis was also analysed.Results: There were totally 320 (53.7%) and 123 (20.7%) patients who had ever suffered from LK and serious hypokalemia (SLK) in the cohort. Only 6.82% and 0.5% of patients had LK and SLK at baseline, while the incidence increased and kept in