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Topic Review
Aerial Photography
Aerial photography (or airborne imagery) is the taking of photographs from an aircraft or other flying object. Platforms for aerial photography include fixed-wing aircraft, helicopters, unmanned aerial vehicles (UAVs or "drones"), balloons, blimps and dirigibles, rockets, pigeons, kites, parachutes, stand-alone telescoping and vehicle-mounted poles. Mounted cameras may be triggered remotely or automatically; hand-held photographs may be taken by a photographer. Aerial photography should not be confused with air-to-air photography, where one or more aircraft are used as chase planes that "chase" and photograph other aircraft in flight.
  • 1.6K
  • 30 Nov 2022
Topic Review
Aerobic Bioreactor Systems Treating Agro-Industrial Wastewaters
The thriving agro-industry sector accounts for an essential part of the global gross domestic product, as the need for food and feed production is rising. However, the industrial processing of agricultural products requires the use of water at all stages, which consequently leads to the production of vast amounts of effluents with diverse characteristics, which contain a significantly elevated organic content. This fact reinforces the need for action to control and minimize the environmental impact of the produced wastewater, and activated sludge systems constitute a highly reliable solution for its treatment.
  • 440
  • 14 Oct 2022
Topic Review
Aerosol Characteristics on the Himalayan Energy Budget
The extensive work on the increasing burden of aerosols and resultant climate implications shows a matter of great concern.
  • 401
  • 11 Jan 2022
Topic Review
Aerosols Deposition and Marine Biota
Atmospheric aerosol deposition (wet and dry) is an important source of macro and micronutrients (N, P, C, Si, and Fe) to the oceans. Most of the mass flux of air particles is made of fine mineral particles emitted from arid or semi-arid areas (e.g., deserts) and transported over long distances until deposition to the oceans. However, this atmospheric deposition is affected by anthropogenic activities, which heavily impacts the content and composition of aerosol constituents, contributing to the presence of potentially toxic elements (e.g., Cu). Under this scenario, the deposition of natural and anthropogenic aerosols will impact the biogeochemical cycles of nutrients and toxic elements in the ocean, also affecting (positively or negatively) primary productivity and, ultimately, the marine biota. 
  • 830
  • 08 Jun 2021
Topic Review
AeroVironment Global Observer
The AeroVironment Global Observer is a concept for a high-altitude, long endurance unmanned aerial vehicle, designed by AeroVironment (AV) to operate as a stratospheric geosynchronous satellite system with regional coverage. Two Global Observer aircraft, each flying for up to a week at an altitude of 55,000 to 65,000 feet (17,000 to 20,000 m), could alternate coverage over any area on the earth, providing a platform for communications relays, remote sensing, or long-term surveillance. In addition to flying above weather and above other conventional aircraft, operation at this altitude permits communications and sensor payloads on the aircraft to service an area on the surface of the earth up to 600 miles (970 km) in diameter, equivalent to more than 280,000 square miles (730,000 km2) of coverage. Global Observer may offer greater flexibility than a satellite and longer duration than conventional manned and unmanned aircraft.
  • 601
  • 20 Nov 2022
Topic Review
African Humid Period
The African humid period (AHP) is a climate period in Africa during the late Pleistocene and Holocene geologic epochs, when northern Africa was wetter than today. The covering of much of the Sahara desert by grasses, trees and lakes was caused by changes in Earth's orbit around the Sun; changes in vegetation and dust in the Sahara which strengthened the African monsoon; and increased greenhouse gases, which may, or may not imply that anthropogenic global warming could result in a shrinkage of the Sahara desert. During the preceding last glacial maximum, the Sahara contained extensive dune fields and was mostly uninhabited. It was much larger than today, but its lakes and rivers such as Lake Victoria and the White Nile were either dry or at low levels. The humid period began about 14,600–14,500 years ago at the end of Heinrich event 1, simultaneously to the Bølling-Allerød warming. Rivers and lakes such as Lake Chad formed or expanded, glaciers grew on Mount Kilimanjaro and the Sahara retreated. Two major dry fluctuations occurred; during the Younger Dryas and the short 8.2 kiloyear event. The African humid period ended 6,000–5,000 years ago during the Piora Oscillation cold period. While some evidence points to an end 5,500 years ago, in the Sahel, Arabia and East Africa the period appears to have taken place in several steps such as the 4.2 kiloyear event. The AHP led to a widespread settlement of the Sahara and the Arabian Deserts, and had a profound effect on African cultures, such as the birth of the Pharaonic civilization. They lived as hunter-gatherers until the agricultural revolution and domesticated cattle, goats and sheep. They left archeological sites and artifacts such as one of the oldest ships in the world, and rock paintings such as those in the Cave of Swimmers and in the Acacus Mountains. Earlier humid periods in Africa were postulated after the discovery of these rock paintings in now-inhospitable parts of the Sahara. When the period ended, humans gradually abandoned the desert in favour of regions with more secure water supplies, such as the Nile Valley and Mesopotamia, where they gave rise to early complex societies.
  • 4.0K
  • 10 Nov 2022
Topic Review
Agate
Agate ‒ a spectacular form of SiO2 and a famous gemstone ‒ is commonly characterized as banded chalcedony. In detail, chalcedony layers in agates can be intergrown or intercalated with macro-crystalline quartz, quartzine, opal-C, opal-CT, cristobalite and/or moganite. In addition, agates often contain considerable amounts of mineral inclusions and water as both interstitial molecular H2O and silanol groups.
  • 1.3K
  • 16 Apr 2021
Topic Review
Age of the Earth
The age of the Earth is estimated to be 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%). This age may represent the age of the Earth's accretion, or core formation, or of the material from which the Earth formed. This dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples. Following the development of radiometric age-dating in the early 20th century, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old. The oldest such minerals analyzed to date—small crystals of zircon from the Jack Hills of Western Australia—are at least 4.404 billion years old. Calcium–aluminium-rich inclusions—the oldest known solid constituents within meteorites that are formed within the Solar System—are 4.567 billion years old, giving a lower limit for the age of the Solar System. It is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites. Because the time this accretion process took is not yet known, and predictions from different accretion models range from a few million up to about 100 million years, the difference between the age of Earth and of the oldest rocks is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.
  • 1.2K
  • 21 Nov 2022
Topic Review
Agri-Environmental Indicators and Stakeholders’ Assessment of Their Quality
The degree to which economic goals have been prioritized over environmental and social objectives has caused dissatisfaction with conventional agricultural practices and stimulated the adoption of sustainable farming methods. One way to consider the multidimensionality of sustainable agriculture is to refer to indicators, more precisely, to agri-environmental indicators (AEIs). 
  • 400
  • 01 Apr 2022
Topic Review
Agri-Food Waste from Apple, Pear, and Sugar Beet
Endothelial damage is recognized as the initial step that precedes several cardiovascular diseases (CVD), such as atherosclerosis, hypertension, and coronary artery disease. It has been demonstrated that the best treatment for CVD is prevention, and, in the frame of a healthy lifestyle, the consumption of vegetables, rich in bioactive molecules, appears effective at reducing the risk of CVD. In this context, the large amount of agri-food industry waste, considered a global problem due to its environmental and economic impact, represents an unexplored source of bioactive compounds. The waste matrices of apple, pear, and sugar beet crops can represent promising starting material for producing “upcycled” products with functional applications, such as the prevention of endothelial dysfunction linked to cardiovascular diseases.
  • 495
  • 22 Sep 2022
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