Solar Coronal Plumes

Polar plumes are thin long ray-like structures that project beyond the limb of the Sun polar regions, maintaining their identity over distances of several solar radii. Plumes have been first observed in white-light (WL) images of the Sun, but, with the advent of the space era, they have been identified also in X-ray and UV wavelengths (XUV) and, possibly, even in in situ data. This review traces the history of plumes, from the time they have been first imaged, to the complex means by which nowadays we attempt to reconstruct their 3-D structure. Spectroscopic techniques allowed us also to infer the physical parameters of plumes and estimate their electron and kinetic temperatures and their densities. However, perhaps the most interesting problem we need to solve is the role they cover in the solar wind origin and acceleration: Does the solar wind emanate from plumes or from the ambient coronal hole wherein they are embedded? Do plumes have a role in solar wind acceleration and mass loading? Answers to these questions are still somewhat ambiguous and theoretical modeling does not provide definite answers either. Recent data, with an unprecedented high spatial and temporal resolution, provide new information on the fine structure of plumes, their temporal evolution and relationship with other transient phenomena that may shed further light on these elusive features

Circadian and cyclic environmental determinants of blood pressure patterning and implications for therapeutic interventions

Blood pressure (BP) exhibits significant 24 h variation; in most normotensive and uncomplicated hypertensive persons, BP declines during the first half of nighttime sleep by 10–20% from its daytime mean level, starts rising in the second half of sleep, further increases with commencement of diurnal activity, and peaks in the afternoon or early evening. Environmental 24 h cycles of temperature and noise; behavior-driven nyctohemeral patterning of food, liquid, and stimulant consumption, posture, mental and emotional stress, and physical activity; plus innate circadian rhythms in wake/sleep, autonomic nervous, hypothalamic-pituitary-adrenal, renal hemodynamic, opioid, renin-angiotensin-aldosterone, endothelial, and vasoactive peptide systems constitute the key determinants of the BP day/night variation. The current perspective is the environmental and behavioral cycles are far more influential than the innate circadian ones in determining the BP nyctohemeral profile. Yet, the facts that the: (i) BP 24h pattern of secondary hypertension, e.g., diabetes and other endocrine disorders, renal disease, heart failure, is different -- BP fails to decline as expected during nighttime sleep typically due to pathological alteration of autonomic nervous system and other influential circadian rhythms, and (ii) scheduling of conventional long-acting medications at bedtime, rather than in the morning, results in much better hypertension control and vascular risk reduction, presumably because highest drug concentration coincides closely with the peak of most key circadian determinants of the BP 24h profile, indicates the endogenous rhythmic influences are of much greater importance than previously appreciate