Expression of ATP-sensitive potassium channels in human pregnant myometrium

<p>Abstract</p> <p>Background</p> <p>Potassium channels play critical roles in the regulation of cell membrane potential, which is central to the excitability of myometrium. The ATP-sensitive potassium (KATP) channel is one of the most abundant potassium channels in myometrium. The objectives of this study were to investigate the protein expression of KATP channel in human myometrium and determine the levels of KATP channel in lower and upper segmental myometrium before and after onset of labour.</p> <p>Methods</p> <p>Both lower segmental (LS) and upper segmental (US) myometrial biopsies were collected at cesarean section from pregnant women not-in-labour (TNL) or in-labour (TL) at term. Protein expression level and cellular localization of four KATP channel subunits in US and LS myometrium were determined by Western blot analysis and immunohistochemistry, respectively. The contractile activity of myometrial strip was measured under isometric conditions.</p> <p>Results</p> <p>Four KATP channel subunits, namely Kir6.1, Kir6.2, SUR1 and SUR2B were identified in pregnant myometrium. While found in vascular myocytes, these subunits appear to be preferentially expressed in myometrial myocytes. Diazoxide, a KATP channel opener, inhibited the spontaneous contractility of pregnant myometrium, suggesting that the KATP channels are functional in human pregnant myometrium. Diazoxide was less potent in TL strips than that in TNL strips. Interestingly, expression of SUR1 was greater in TL than TNL tissues, although no differences were found for SUR2B in these two tissues. For both lower and upper segmental myometrium, Kir6.1 and Kir6.2 were less in TL compared with TNL tissues.</p> <p>Conclusions</p> <p>Functional KATP channels are expressed in human pregnant myometrium. Down-regulation of Kir6.1 and Kir6.2 expression in myometrium may contribute to the enhanced uterine contractility associated with the onset of labour.</p

A Multi-Objective Ground Motion Selection Approach Matching the Acceleration and Displacement Response Spectra

For seismic resilience-based design (RBD), a selection of recorded time histories for dynamic structural analysis is usually required. In order to make individual structures and communities regain their target functions as promptly as possible, uncertainty of the structural response estimates is in great need of reduction. The ground motion (GM) selection based on a single target response spectrum, such as acceleration or displacement response spectrum, would bias structural response estimates leading significant uncertainty, even though response spectrum variance is taken into account. In addition, resilience of an individual structure is not governed by its own performance, but depends severely on the performance of other systems in the same community. Thus, evaluation of resilience of a community using records matching target spectrum at whole periods would be reasonable because the fundamental periods of systems in the community may be varied. This paper presents a GM selection approach based on a probabilistic framework to find an optimal set of records to match multiple target spectra, including acceleration and displacement response spectra. Two major steps are included in that framework. Generation of multiple sub-spectra from target displacement response spectrum for selecting sets of GMs was proposed as the first step. Likewise, the process as genetic algorithm (GA), evolvement of individuals previously generated, is the second step, rather than using crossover and mutation techniques. A novel technique improving the match between acceleration response spectra of samples and targets is proposed as the second evolvement step. It is proved computationally efficient for the proposed algorithm by comparing with two developed GM selection algorithms. Finally, the proposed algorithm is applied to select GM records according to seismic codes for analysis of four archetype reinforced concrete (RC) frames aiming to evaluate the influence of GM selection considering two design response spectra on structural responses. The implications of design response spectra especially the displacement response spectrum and GM selection algorithm are summarized

Tunable Adhesion of a Bio-Inspired Micropillar Arrayed Surface Actuated by a Magnetic Field

Bio-inspired functional surfaces attract many research interests due to the promising applications. In this paper, tunable adhesion of a bio-inspired micropillar arrayed surface actuated by a magnetic field is investigated theoretically in order to disclose the mechanical mechanism of changeable adhesion and the influencing factors. Each polydimethylsiloxane (PDMS) micropillar reinforced by uniformly distributed magnetic particles is assumed to be a cantilever beam. The beam's large elastic deformation is obtained under an externally magnetic field. Specially, the rotation angle of the pillar's end is predicted, which shows an essential effect on the changeable adhesion of the micropillar arrayed surface. The larger the strength of the applied magnetic field, the larger the rotation angle of the pillar's end will be, yielding a decreasing adhesion force of the micropillar arrayed surface. The difference of adhesion force tuned by the applied magnetic field can be a few orders of magnitude, which leads to controllable adhesion of such a micropillar arrayed surface. Influences of each pillar's cross section shape, size, intervals between neighboring pillars, and the distribution pattern on the adhesion force are further analyzed. The theoretical predictions are qualitatively well consistent with the experimental measurements. The present theoretical results should be helpful not only for the understanding of mechanical mechanism of tunable adhesion of micropillar arrayed surface under a magnetic field but also for further precise and optimal design of such an adhesion-controllable bio-inspired surface in future practical applications

Probabilistic Generalization of a Comprehensive Model for the Deterioration Prediction of RC Structure under Extreme Corrosion Environments

In some extreme corrosion environments, the erosion of chloride ions and carbon dioxide can occur simultaneously, causing deterioration of reinforced concrete (RC) structures. This study presents a probabilistic model for the sustainability prediction of the service life of RC structures, taking into account that combined deterioration. Because of the high computational cost, we also present a series of simplifications to improve the model. Meanwhile, a semi-empirical method is also developed for this combined effect. By probabilistic generalization, this simplified method can swiftly handle the original reliability analysis which needs to be based on large amounts of data. A comparison of results obtained by the models with and without the above simplifications supports the significance of these improvements

Spontaneous dewetting of a hydrophobic micro-structured surface

Inspired by recent experimental observations and natural phenomena that spontaneous dewetting transition occurs on a hydrophobic micro-structured surface, a thermodynamic model of a condensed water droplet on a micro-pillar arrayed surface is established in order to disclose the mechanical mechanism. Based on a general model of an arbitrary-shaped micro-structured surface, surfaces with conical, rectangular and parabolic micro-pillars are investigated. A critical water droplet volume is found, beyond which dewetting transition can be realized. The effect of the micro-pillar's size and intrinsic contact angle on the free energy difference and critical water droplet volume are further studied. The theoretical model may provide a possible explanation for the abnormal Wenzel wetting state of condensed water droplets on lotus leaves and the anti-fogging behavior of a mosquito's compound eyes. The present results should be very useful for the biomimetic design of functional dewetting surfaces in practical applications