Dielectric characteristics and nonlinear properties of ZnO-polypyrrole composites

The nonlinear properties and frequency characteristics of ZnO-polypyrrole composites were investigated at 200 Hz-5 MHz frequency interval with different zinc oxide contents. Samples were prepared using hot press method at 130 ℃. Results show an optimum point for breakdown voltage at ZnO content of 70%. Breakdown voltage decreases from 590 to 380 V and after that tends to increase from 450 to 740 V due to the absence of polypyrrole at grain boundaries. No matter how breakdown voltage behaves, nonlinear coefficient increases from 4.2 to 9 by increasing ZnO content because of the increase in acceptor-like states at grain boundaries by increasing ZnO content. The electrical parameters such as dielectric constant, dielectric loss and series resistance of samples show a strong dependence on frequency especially below 1 k Hz. These parameters fall off by increasing frequency up to 1 k Hz, which is related to charge transportation through the Schottky barrier at grain boundaries. The high dielectric constant of samples below 1 k Hz is related to the Maxwell-Wagner polarization at grain boundaries. The presence of different anomalies at different frequency intervals is related to interfacial polarization because of different structures of grains and intergranular layer with a huge difference in conductivity.

Thermal Therapy in Patients Suffering from Non-Specific Chronic Low Back Pain—A Systematic Review

Thermal therapy is frequently used as an adjunct to treatment in patients suffering from chronic low back pain. It is also an inherent part of patients’ self-administered pain treatment. This review aims to update the evidence for thermal therapy treatments in non-specific chronic low back pain patients and to rate the methodological quality of the corresponding clinical trials. Previous studies have reported contradictory evidence for the effectiveness of thermal therapy. An electronic search on MEDLINE (PubMed), PEDro, CENTRAL and CINHAL databases was conducted between May 2016 and February 2018. Clinical trials comparing local thermal therapy to conservative or no treatment were assessed for eligibility. Pain, physical function and global health were defined as outcome parameters. A total of n = 9 studies met the inclusion criteria. All of them applied an electrophysical agent as the thermal treatment: continuous ultrasound (n = 6), short-wave diathermy (n = 2), microwave diathermy (n = 1). Out of the n = 6 studies on ultrasound treatment, n = 2 reported significant within and between-group results for pain reduction after 4 to 6 weeks of treatment. Both short-wave diathermy studies demonstrated significant between-group results for pain reduction after 3 weeks of treatment. Contradictory results for all other observed outcome parameters were reported regardless of the intervention. Moreover, significant within-group results for the control groups questioned the effectiveness of the intervention treatments. Therefore, the effect of thermal therapy, (electrophysical agents), is not superior to any control treatment except for ultrasound treatment on short-term pain reduction.

Stimulation Therapies and the Relevance of Fractal Dynamics to the Treatment of Diseases

This paper provides an overview of the conventional therapeutic stimulation methodologies and proposes a more effective stimulation approach based on a consideration of the inherently fractal nature of normal biological dynamics. There are varying forms of physiological stimulations including the use of electrical currents, electromagnetic fields, temperature change, ultrasound, light and so forth. These stimulation therapies can be categorized into three main modalities: electrical stimulation modalities, thermal modalities, and non-thermal modalities. Electrical stimulation modalities include therapeutic techniques where electrical current is directly applied to the body of treated subject. Direct application of electrical current to the brain also falls under this category. Thermal modalities consist of stimulations that induce temperature change on the body for therapeutic effects without the direct transfer of electrical current. Non-thermal modalities functions through energy transfer without directly applying electrical current and without the effects of temperature change. A fourth miscellaneous category for stimulation techniques consists of the stimulation effects of music along with physical stimulation as in massage therapy. Common to most of these therapeutic strategies is that the stimulation is delivered at certain fixed periods or frequencies. We introduce some rudiments of fractal dynamics, and the notions of self-similarity, scale-invariance, and long-range correlation or memory in the dynamics of a system. We present evidence that fractal dynamics is commonly observed in healthy physiological systems while unhealthy systems are shown to veer away from fractal dynamics towards periodic or random motion. This difference in dynamics can be observed in many biological signals such as in neural activity, heart rate variations, and breathing patterns. We propose that an optimal stimulation technique should thus be one that encourages an unhealthy, non-fractal pathological system towards a healthy, fractal dynamic. Given the ubiquity of fractality in healthy biological dynamics, we argue that a fractal pattern of stimulation is a more optimal approach to functional restoration than the widely used conventional periodic stimulation, which may further consolidate the existing pathological dynamics.

Ferroelectric solid solutions with perovskite- and columbite-type components: From structures formation to domain and hysteresis phenomena

The paper reports results on the complex study on ferroelectric ceramics that represent solid solutions containing components with a perovskite-type or columbite-type structure.Solid solutions of a three-component(1−x−y)NaNbO_(3)−xKNbO_(3)−yCdNb_(2)O_(6) system are manufactured at x=0.05-0.20 and y=0.10.Domain structures in ceramic grains are studied.The consistency between experimental and calculated results is examined for coexisting phases split into non-180°domains(mechanical twins)in the solid solution with x=0.15.A correlation between the internal structure(crystal,domain,granular,and defect)and fundamental elec­tromechanical and polarization properties is stated for the studied three-component solid solutions.