Altered Arterial Stiffness and Subendocardial Viability Ratio in Young Healthy Light Smokers after Acute Exercise

Studies showed that long-standing smokers have stiffer arteries at rest. However, the effect of smoking on the ability of the vascular system to respond to increased demands (physical stress) has not been studied. The purpose of this study was to estimate the effect of smoking on arterial stiffness and subendocardial viability ratio, at rest and after acute exercise in young healthy individuals.Healthy light smokers (n = 24, pack-years = 2.9) and non-smokers (n = 53) underwent pulse wave analysis and carotid-femoral pulse wave velocity measurements at rest, and 2, 5, 10, and 15 minutes following an exercise test to exhaustion. Smokers were tested, 1) after 12h abstinence from smoking (chronic condition) and 2) immediately after smoking one cigarette (acute condition). At rest, chronic smokers had higher augmentation index and lower aortic pulse pressure than non-smokers, while subendocardial viability ratio was not significantly different. Acute smoking increased resting augmentation index and decreased subendocardial viability ratio compared with non-smokers, and decreased subendocardial viability ratio compared with the chronic condition. After exercise, subendocardial viability ratio was lower, and augmentation index and aortic pulse pressure were higher in non-smokers than smokers in the chronic and acute conditions. cfPWV rate of recovery of was greater in non-smokers than chronic smokers after exercise. Non-smokers were also able to achieve higher workloads than smokers in both conditions.Chronic and acute smoking appears to diminish the vascular response to physical stress. This can be seen as an impaired 'vascular reserve' or a blunted ability of the blood vessels to accommodate the changes required to achieve higher workloads. These changes were noted before changes in arterial stiffness or subendocardial viability ratio occurred at rest. Even light smoking in young healthy individuals appears to have harmful effects on vascular function, affecting the ability of the vascular bed to respond to increased demands

Optimization of cable terminations equipped with non linear stress control tubes

A significant electrical field grading in HV cable terminations can be achieved by using stress control tubes (SCTs), obtained by adding a controlled amount of conducting fillers, as carbon black or silicon carbide, to polymeric insulating matrices. Nevertheless, no data can be found in the literature concerning the influence played by the SCT length, thickness and position around the cable termination on the grading performances of these accessories. The purpose of this paper is to investigate on such interesting aspects by evaluating the electric field distributions inside cable terminations characterized by different arrangements of the SCT. The numerical evaluations of the electric field are carried out by adopting a model based on the electroquasi-static approximation of Maxwell equations

A Galerkin model to evaluate the field distribution in electrical components employing non linear stress grading materials

An effective model is presented for the evaluation of the electric field dynamics inside electrical components, using nonlinear stress grading materials. The model, implemented in a numerical procedure, permits the solution of the Laplace equation and the diffusion equation by adopting the Galerkin method. Two-dimensional domains, even of very complex shapes and the finite thickness of the grading materials are properly taken into account, allowing an accurate evaluation of the electric field distribution and a sound understanding of the influence of the different types of nonlinearities on the stress grading efficiency. The proposed technique has been applied to study the field distributions inside a cable termination equipped with a stress control tube and in a suspension cap-and-pin glass insulator covered with an anti-corona layer. Numerical results for sinusoidal power frequency and standard impulse voltages elucidate the different role of resistive and capacitive contributions in determining the overall potential map

Electrical properties of different composite materials for stress relief in HV cable accessories

In order to ensure optimal electrical performances of high voltage cable accessories an important aspect which determine both the steady-state long-term and impulse performances of the components, resides on the appropriate selection of the grading material. The use of a simple circuital approach, and significant control parameters, allow the evaluation of suitable limits for the values of the resistivity and permittivity of the adopted composite material which should guarantee a reliable operation of the components. In order to supply this significant information and compare the performances of thermosets and rubber based composites, typically adopted in these applications, the electrical properties of carbon black-loaded polyolefins and EPDM materials are analysed for a broad range of applied field and temperature

Electrical properties of different composite materials for stress relief in HV cable accessories

In order to ensure optimal electrical performances of high voltage cable accessories an important aspect which determine both the steady-state long-term and impulse performances of the components, resides on the appropriate selection of the grading material. The use of a simple circuital approach, and significant control parameters, allow the evaluation of suitable limits for the values of the resistivity and permittivity of the adopted composite material which should guarantee a reliable operation of the components. In order to supply this significant information and compare the performances of thermosets and rubber based composites, typically adopted in these applications, the electrical properties of carbon black-loaded polyolefins and EPDM materials are analysed for a broad range of applied field and temperature

Effect of thermal and mechanical stresses on the electrical properties of stress grading materials

The electrical properties of two cold-shrink stress control tube based on ethylene propylene diene monomer (EPDM) and silicon rubber were analyzed to determine the suitable expressions for the electrical parameters to be used in numerical programs. The influence of the polymeric matrix, the elastic deformation due to the different shrinkage diameter and temperature on the properties of the materials were considered. The elastic deformation induced by the different shrinkage diameter produced some modifications especially in the characteristics of EPDM based composites. A non-monotonic behaviour of either the resistivity or the permittivity versus the shrinkage diameter was shown for these materials

Interaction between neuroanatomical and psychological changes after mindfulness-based training

Several cross-sectional studies have documented neuroanatomical changes in individuals with a long history of meditation, while a few evidences are available about the interaction between neuroanatomical and psychological changes even during brief exposure to meditation. Here we analyzed several morphometric indexes at both cortical and subcortical brain level, as well as multiple psychological dimensions, before and after a brief -8 weeks- Mindfulness Based Stress Reduction (MBSR) training program, in a group of 23 meditation naı¨ve-subjects compared to age-gender matched subjects. We found a significant cortical thickness increase in the right insula and the somatosensory cortex of MBSR trainees, coupled with a significant reduction of several psychological indices related to worry, state anxiety, depression and alexithymia. Most importantly, an interesting correlation between the increase in right insula thickness and the decrease in alexithymia levels during the MBSR training were observed. Moreover, a multivariate pattern classification approach allowed to identify a cluster of regions more responsive to MBSR training across subjects. Taken together, these findings documented the significant impact of a brief MBSR training on brain structures, as well as stressing the idea of MBSR as a valuable tool for alexithymia modulation, also originally providing a plausible neurobiological evidence of a major role of right insula into mediating the observed psychological changes

Polarization and depolarization currents in carbon-black loaded polyolefins

In this paper the first results concerning an experimental investigation of the conduction mechanism in heat shrinkable carbon black-loaded polyolefins are reported by considering the dependence of charging and discharging currents on the adopted electrode material and specimen dimensions. Data concerning applied electrical stresses comparable with those encountered in service are discussed by considering models proposed in the literatur

Impulse performances of cable terminations employing stress grading accessories

Stress control tubes (SCTs), made out of materials characterized by nonlinear electric properties, are widely adopted for the realization of cable terminations, in order to achieve a significant stress control. The influence played on the electric field distribution around the cable termination by SCTs parameters (e.g. length, thickness and position) has been studied only in the case of sinusoidal power frequency applied voltage, while no data can be found in the literature concerning applied standard impulse voltages. The purpose of this paper is to investigate on such interesting aspect by evaluating the potential distributions taking place under impulse voltages in cable terminations characterized by different arrangements of the SCT

Non linear model for cap and pin insulators equipped with anti-corona coating

In order to study the field distribution in a suspension cap and pin glass insulator covered with an anti-corona layer a numerical procedure has been developed, which relies on the solution of the Laplace equation and the diffusion equation in a two dimensional domain by the Galerkin method. Numerical results concerning the case of applied sinusoidal power frequency voltage are presented and discussed allowing to gain a better understanding of the influence played by the presence of the non linear conducting coating on the electric field distribution