Diffuse-Charge Dynamics in Electrochemical Systems

The response of a model micro-electrochemical system to a time-dependent applied voltage is analyzed. The article begins with a fresh historical review including electrochemistry, colloidal science, and microfluidics. The model problem consists of a symmetric binary electrolyte between parallel-plate, blocking electrodes which suddenly apply a voltage. Compact Stern layers on the electrodes are also taken into account. The Nernst-Planck-Poisson equations are first linearized and solved by Laplace transforms for small voltages, and numerical solutions are obtained for large voltages. The ``weakly nonlinear'' limit of thin double layers is then analyzed by matched asymptotic expansions in the small parameter $\epsilon = \lambda_D/L$, where $\lambda_D$ is the screening length and $L$ the electrode separation. At leading order, the system initially behaves like an RC circuit with a response time of $\lambda_D L / D$ (not $\lambda_D^2/D$), where $D$ is the ionic diffusivity, but nonlinearity violates this common picture and introduce multiple time scales. The charging process slows down, and neutral-salt adsorption by the diffuse part of the double layer couples to bulk diffusion at the time scale, $L^2/D$. In the ``strongly nonlinear'' regime (controlled by a dimensionless parameter resembling the Dukhin number), this effect produces bulk concentration gradients, and, at very large voltages, transient space charge. The article concludes with an overview of more general situations involving surface conduction, multi-component electrolytes, and Faradaic processes.Comment: 10 figs, 26 pages (double-column), 141 reference

Nonlinear electrochemical relaxation around conductors

We analyze the simplest problem of electrochemical relaxation in more than one dimension - the response of an uncharged, ideally polarizable metallic sphere (or cylinder) in a symmetric, binary electrolyte to a uniform electric field. In order to go beyond the circuit approximation for thin double layers, our analysis is based on the Poisson-Nernst-Planck (PNP) equations of dilute solution theory. Unlike most previous studies, however, we focus on the nonlinear regime, where the applied voltage across the conductor is larger than the thermal voltage. In such strong electric fields, the classical model predicts that the double layer adsorbs enough ions to produce bulk concentration gradients and surface conduction. Our analysis begins with a general derivation of surface conservation laws in the thin double-layer limit, which provide effective boundary conditions on the quasi-neutral bulk. We solve the resulting nonlinear partial differential equations numerically for strong fields and also perform a time-dependent asymptotic analysis for weaker fields, where bulk diffusion and surface conduction arise as first-order corrections. We also derive various dimensionless parameters comparing surface to bulk transport processes, which generalize the Bikerman-Dukhin number. Our results have basic relevance for double-layer charging dynamics and nonlinear electrokinetics in the ubiquitous PNP approximation.Comment: 25 pages, 17 figures, 4 table

Vitamin D3 (Cholecalciferol) and Pelvic Pain Caused by Ovarian Endometriosis

Статья посвящена изучению взаимосвязи концентрации витамина D с наличием и интенсивностью тазовой боли у женщин, страдающих эндометриозом яичников. Цель исследования: установить взаимосвязь уровня витамина D и интенсивности тазовой боли у женщин, страдающих эндометриозом яичников. В исследование были включены 190 женщин репродуктивного возраста с верифицированным диагнозом эндометриоз яичников, в возрасте от 20 до 41 года (средний возраст – 29,1±3,3 года). Для определения интенсивности тазовой боли использовали визуальную аналоговую шкалу (ВАШ). Всем пациенткам (n=190) исходно оценку уровня витамина D проводили путем определения уровня общего 25(ОН)D в сыворотке крови методом масс-спектрометрии, адаптированным к клинической практике, согласно международным стандартам, на тандемном масс-спектрометре AB SCIEX QTRAP 5500.The article studies the relation between vitamin D concentration and the presence and intensity of pelvic pain in women suffering from ovarian endometriosis. The aim of the study is to examine the relation between vitamin D levels and intensity of pelvic pain in women with ovarian endometriosis. Study design: cohort, prospective, non-comparative study. The study included 190 women of reproductive age suffering from ovarian endometriosis (OE), aged 20 to 41 years (mean age 29.1±3.3 years). Visual analogue scale (VAS) was used to determine the intensity of pelvic pain.The evaluation of vitamin D level in all patients (n=190) was initially performed by determining the level of total 25 (OH) D in blood serum by the method of mass spectrometry. Study Results: The average vitamin D level in the study was 23.98±6.82 ng/ml. The average concentration of vitamin D in the blood of the patients with low-intensity pelvic pain was 26.7±5.92 ng/ml, with moderate-intensity – 23.06±of 5.55 ng/ml, with high pain intensity – 19.26±6,01 ng/ml. The content of vitamin D in the blood of the patients in the control group was 28.83±6.15 ng/ml, which met the criteria of insufficiency. Аn inverse correlation between the severity of pain based on VAS and vitamin D in women with endometriosis of the main group was established in the study, it amounted to 0.502 (p<0.001)

Chronic pelvic inflammatory disease: controversial issues

Pelvic inflammatory disease (PID) is one of the most common serious infection of nonpregnant women of reproductive age. Goals of the therapy must include the resolution of clinical signs, the eradication of pathogens from genital tract and the prevention of sequelae primarily including the development of chronic inflammation. The paper deals with the currennt problems and contraversial issues of chronic pelvic inflammatory disease. This review presents the results of domestic and foreign studies, and the own view of the issue, the prospects and possible solutions

The microbiota of the female genital organs of women with pelvic inflammatory diseases

Pelvic Inflammatory diseases (PID) is one of the most pressing and debated issues of modern gynecology. A special place is devoted to the study of the microflora of female genital mutilation, where there are many unresolved issues. This review presented the modern data of domestic and foreign researches of microbiota of female genital mutilation in inflammatory diseases

Rehabilitation of reproductive function after surgical treatment of common forms of external genital endometriosis

The study included 155 women of reproductive age with extended forms of genital endometriosis. The developed algorithm of treatment has improved the reproduction health after treatment this disease