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Topic Review
Venus In Situ Atmospheric and Geochemical Explorer
Venus In Situ Atmospheric and Geochemical Explorer (VISAGE) is a proposed Venus lander mission that would perform atmospheric and surface science investigations. The mission was proposed in 2017 to NASA's New Frontiers program to compete for funding and development, but it was not selected.
  • 286
  • 07 Nov 2022
Topic Review
Venus in Culture
Venus, as one of the brightest objects in the sky, has been known since prehistoric times and has been a major fixture in human culture for as long as records have existed. As such, it has a prominent position in human culture, religion, and myth. It has been made sacred to gods of many cultures, and has been a prime inspiration for writers and poets as the morning star and evening star.
  • 4.9K
  • 14 Nov 2022
Topic Review
Venus (Planet)
Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. After Earth's Moon, it is the brightest object in the night sky, reaching an apparent magnitude of −4.6. As an inferior planet from Earth it never appears to venture far from the Sun, and its elongation reaches a maximum of 47.8°. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, and is often referred to as the Morning Star or as the Evening Star. A terrestrial planet, it is sometimes called Earth's "sister planet", as the two are similar in size and bulk composition. The planet is covered with an opaque layer of highly reflective clouds and its surface cannot be seen from space in visible light, making it a subject of great speculation until some of its secrets were revealed by planetary science in the 20th century. Venus has the densest atmosphere of the terrestrial planets, consisting mostly of carbon dioxide, and the atmospheric pressure at the planet's surface is 90 times that of the Earth. Venus' surface has been mapped in detail only in the last 20 years. It shows evidence of extensive volcanism, and some of its volcanoes may still be active today. In contrast to the constant crustal movement seen on Earth, Venus is thought to undergo periodic episodes of plate tectonics, in which the crust is subducted rapidly within a few million years separated by stable periods of a few hundred million years. The planet is named after Venus, the Roman goddess of love, and most of its surface features are named after famous and mythological women. The adjective Venusian is commonly used for items related to Venus, though the Latin adjective is the rarely used Venereal; the now-archaic Cytherean is still occasionally encountered.
  • 982
  • 01 Nov 2022
Topic Review
Vector Beam with Longitudinally Varying Polarization during Propagation
The vector optical beam with longitudinally varying polarization during propagation in free space has attracted significant attention in recent years. Compared with traditional vector optical beams with inhomogeneous distribution of polarization in the transverse plane, manipulating the longitudinal distribution of polarization provides a new dimension for the expansion of the applications of vector optical beams in volume laser machining, longitudinal detection, and in vivo micromanipulation. 
  • 760
  • 29 Nov 2021
Topic Review
Vat Purnima
Vat Purnima or pournima chavan or Wat Purnima (वट पूर्णिमा, vaṭapūrṇimā, also called Vat Savitri is a celebration observed by married women in the Western Indian states of Gujarat, Maharashtra, Goa and some regions of eastern Uttar Pradesh. On this Purnima or "full moon" during the three days of the month of Jyeshtha in the Hindu calendar (which falls in May-June in the Gregorian calendar) a married woman marks her love for her husband by tying a ceremonial thread around a banyan tree. The celebration is based on the legend of Savitri and Satyavan as narrated in the epic Mahabharata.
  • 380
  • 15 Nov 2022
Topic Review
Vascular Endothelial Dysfunction-Related Disease
Oxidative stress and chronic inflammation play an important role in the pathogenesis of atherosclerosis. Atherosclerosis develops as the first step of vascular endothelial dysfunction induced by complex molecular mechanisms. Vascular endothelial dysfunction leads to oxidative stress and inflammation of vessel walls, which in turn enhances vascular endothelial dysfunction. Vascular endothelial dysfunction and vascular wall oxidative stress and chronic inflammation make a vicious cycle that leads to the development of atherosclerosis.
  • 487
  • 03 Feb 2023
Topic Review
Vallis (Planetary Geology)
Vallis or valles /ˈvælɪs/ (plural valles /ˈvæliːz/) is the Latin word for valley. It is used in planetary geology to name landform features on other planets. Scientists used vallis for old river valleys they discovered when they sent the first probes to Mars. The Viking Orbiters caused a revolution in our ideas about water on Mars; finding huge river valleys in many areas. Space craft cameras showed that floods of water broke through dams, carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. Some valles on Mars (Mangala Vallis, Athabasca Vallis, Granicus Vallis, and Tinjar Valles) clearly begin at graben. On the other hand, some of the large outflow channels begin in rubble-filled low areas, called chaos or chaotic terrain. It has been suggested that massive amounts of water were trapped under pressure beneath a thick cryosphere (layer of frozen ground), then the water was suddenly released, perhaps when the cryosphere was broken by a fault.
  • 524
  • 23 Nov 2022
Topic Review
Valley Network
Valley networks are branching networks of valleys on Mars that superficially resemble terrestrial river drainage basins. They are found mainly incised into the terrain of the martian southern highlands, and are typically - though not always - of Noachian age (approximately four billion years old). The individual valleys are typically less than 5 kilometers wide, though they may extend for up to hundreds or even thousands of kilometers across the martian surface. The form, distribution, and implied evolution of the valley networks are of great importance for what they may tell us about the history of liquid water on the martian surface, and hence Mars' climate history. Some authors have argued that the properties of the networks demand that a hydrological cycle must have been active on ancient Mars, though this remains contentious. Objections chiefly arise from repeated results from models of martian paleoclimate suggesting high enough temperatures and pressures to sustain liquid water on the surface have not ever been possible on Mars. The advent of very high resolution images of the surface from the HiRISE, THEMIS and Context (CTX) satellite cameras as well as the Mars Orbital Laser Altimeter (MOLA) digital terrain models have drastically improved our understanding of the networks in the last decade.
  • 331
  • 25 Oct 2022
Biography
Valery Rubakov
Valery Anatolyevich Rubakov (Russian: Валерий Анатольевич Рубаков, born 16 February 1955 in Moscow, USSR) is a Russian theoretical physicist. His scientific interests include quantum field theory, elementary particle physics, and cosmology. He is affiliated with the Institute for Nuclear Research (INR) of the Russian Academy of Sciences in Moscow. Rubakov studied phys
  • 581
  • 15 Nov 2022
Topic Review
Valence-shell Electron-pair Repulsion Model
There are the following main assumptions of the Valence-shell Electron-pair Repulsion (VSEPR) model. - The arrangement of covalent bonds of the atom centre analyzed depends on the number of electron pairs in its valence shell: bonds and nonbonding pairs as lone electron pairs. - The arrangement of valence electron pairs around the centre considered is to maximize their distances apart. - The non-valence electrons - inner electrons with nucleus (i.e. the core) possess the spherical symmetry (or at least it is in force for the main groups elements). It is worth to note that the intra- and intermolecular interactions influence on electronic and molecular structures in accordance with this VSEPR model.
  • 953
  • 06 Sep 2021
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