CPE analysis by local electrochemical impedance spectroscopy

Constant-phase elements (CPE) are used extensively in equivalent electrical circuits for fitting of experimental impedance data. The CPE behavior is generally attributed to distributed surface reactivity, surface inhomogeneity, roughness or fractal geometry, electrode porosity, and to current and potential distributions associated with electrode geometry. In this work, different electrochemical systems showing the CPE dependence in the high-frequency range for the overall impedance were considered. Local electrochemical impedance spectroscopy was found to provide a good means for assessing the influence of local variations on the CPE behavior seen in global impedance measurements. A separation between 2D and 3D distributions could be easily observed. In the case of a 2D distribution (AZ91 Mg alloy), the origin of the CPE behavior was the distribution of high-frequency resistance associated with the geometry of the disk electrode; whereas, the capacitance was independent of position. In the case of the aluminium electrode, the CPE behavior could be attributed to a combination of 3D and 2D distributions. Geometric distributions can play a significant role in the impedance response of electrochemical systems, and these distributions can lead to CPE behavior

Creep motion of a model frictional system

We report on the dynamics of a model frictional system submitted to minute external perturbations. The system consists of a chain of sliders connected through elastic springs that rest on an incline. By introducing cyclic expansions and contractions of the springs we observe a reptation of the chain. We account for the average reptation velocity theoretically. The velocity of small systems exhibits a series of plateaus as a function of the incline angle. Due to elastic e ects, there exists a critical amplitude below which the reptation is expected to cease. However, rather than a full stop of the creep, we observe in numerical simulations a transition between a continuous-creep and an irregular-creep regime when the critical amplitude is approached. The latter transition is reminiscent of the transition between the continuous and the irregular compaction of granular matter submitted to periodic temperature changes

3D Modelling for the Dispersion of Sediments Dredged in the Port of La Rochelle with Open TELEMAC-MASCARET

Hydrodynamic

Fluctuations of the Casimir-like force between two membrane inclusions

Although Casimir forces are inseparable from their fluctuations, little is known about these fluctuations in soft matter systems. We use the membrane stress tensor to study the fluctuations of the membrane-mediated Casimir-like force. This method enables us to recover the Casimir force between two inclusions and to calculate its variance. We show that the Casimir force is dominated by its fluctuations. Furthermore, when the distance d between the inclusions is decreased from infinity, the variance of the Casimir force decreases as -1/d^2. This distance dependence shares a common physical origin with the Casimir force itself.Comment: 5 pages, 3 figure

On a fourth order nonlinear Helmholtz equation

In this paper, we study the mixed dispersion fourth order nonlinear Helmholtz equation $\Delta^2 u -\beta \Delta u + \alpha u= \Gamma|u|^{p-2} u$ in $\mathbb R^N$ for positive, bounded and $\mathbb Z^N$-periodic functions $\Gamma$. Using the dual method of Evequoz and Weth, we find solutions to this equation and establish some of their qualitative properties

“They Love Their Patients”: Client Perceptions of Quality of Postabortion Care in North and South Kivu, the Democratic Republic of the Congo

Background: Postabortion care (PAC) is a lifesaving intervention that, when accessible and of good quality, can prevent the majority of abortion-related deaths. However, these services are only sporadically available and often of poor quality in humanitarian settings. CARE International, the International Rescue Committee, and Save the Children strengthened the Congolese Ministry of Health to provide PAC, including voluntary contraceptive services, in North and South Kivu, DRC. Objective: We aimed to gain understanding of the demographic and clinical characteristics of PAC clients, the experiences of women who sought PAC at supported health facilities, and the women’s perceptions of the quality of care received. We also explored how client perspectives can inform future PAC programming. Methods: A PAC register review extracted sociodemographic and clinical data on all PAC clients during a 12-month period between 2015 and 2016 at 69 supported facilities in 6 health zones. In-depth interviews were conducted between September 2016 and April 2017 with 50 women who sought PAC in the preceding 3 months at supported health facilities. Interviews were recorded, transcribed, and translated into French for analysis. Thematic content analysis was subsequently used as the data analytic approach. Results: In 12 months, 1,769 clients sought PAC at supported facilities; 85.2% were at less than 13 weeks gestation. Over 80% of PAC clients had a uterine evacuation, and of these, 90% were treated with manual vacuum aspiration. The majority (75.2%) of PAC clients chose voluntary postabortion contraception. All but one interview participant reported seeking PAC for a spontaneous abortion, although most also reported their pregnancy was unintended. Clients were mostly made aware that PAC was available by community health workers or other community members. Experiences at the supported facilities were mostly positive, particularly in regards to client-provider interactions. Most women received contraceptive counseling during PAC and selected a modern method of contraception immediately after treatment. However, knowledge about different methods of contraception varied. Nearly all women said that they would advise another woman experiencing abortion complications to seek PAC at a supported health facility. Conclusions: The findings demonstrate the successful implementation of good-quality, respectful PAC in North and South Kivu. Overall, they suggest that the organizations’ support of health workers, including competency-based training and supportive supervision, was successful