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🔗 Environment 🔗 Biology 🔗 Physics 🔗 Guild of Copy Editors 🔗 Energy 🔗 Chemical and Bio Engineering

Artificial photosynthesis is a chemical process that biomimics the natural process of photosynthesis to convert sunlight, water, and carbon dioxide into carbohydrates and oxygen. The term artificial photosynthesis is commonly used to refer to any scheme for capturing and storing the energy from sunlight in the chemical bonds of a fuel (a solar fuel). Photocatalytic water splitting converts water into hydrogen and oxygen and is a major research topic of artificial photosynthesis. Light-driven carbon dioxide reduction is another process studied that replicates natural carbon fixation.

Research of this topic includes the design and assembly of devices for the direct production of solar fuels, photoelectrochemistry and its application in fuel cells, and the engineering of enzymes and photoautotrophic microorganisms for microbial biofuel and biohydrogen production from sunlight.

🔗 Biology 🔗 Women's History 🔗 Anthropology 🔗 Human Genetic History 🔗 Molecular Biology 🔗 Molecular Biology/Molecular and Cell Biology 🔗 Molecular Biology/Genetics

In human genetics, the Mitochondrial Eve (more technically known as the Mitochondrial-Most Recent Common Ancestor, shortened to mt-Eve or mt-MRCA) is the matrilineal most recent common ancestor (MRCA) of all living humans. In other words, she is defined as the most recent woman from whom all living humans descend in an unbroken line purely through their mothers and through the mothers of those mothers, back until all lines converge on one woman.

In terms of mitochondrial haplogroups, the mt-MRCA is situated at the divergence of macro-haplogroup L into L0 and L1–6. As of 2013, estimates on the age of this split ranged at around 155,000 years ago, consistent with a date later than the speciation of Homo sapiens but earlier than the recent out-of-Africa dispersal.

The male analog to the "Mitochondrial Eve" is the "Y-chromosomal Adam" (or Y-MRCA), the individual from whom all living humans are patrilineally descended. As the identity of both matrilineal and patrilineal MRCAs is dependent on genealogical history (pedigree collapse), they need not have lived at the same time. As of 2015, estimates of the age of the Y-MRCA range around 200,000 to 300,000 years ago, roughly consistent with the emergence of anatomically modern humans.

The name "Mitochondrial Eve" alludes to the biblical Eve, which has led to repeated misrepresentations or misconceptions in journalistic accounts on the topic. Popular science presentations of the topic usually point out such possible misconceptions by emphasizing the fact that the position of mt-MRCA is neither fixed in time (as the position of mt-MRCA moves forward in time as mitochondrial DNA (mtDNA) lineages become extinct), nor does it refer to a "first woman", nor the only living female of her time, nor the first member of a "new species".

🔗 Medicine 🔗 Biology 🔗 Skepticism 🔗 Transhumanism 🔗 Alternative Views 🔗 Guild of Copy Editors 🔗 Alternative medicine 🔗 Longevity

Life extension is the idea of extending the human lifespan, either modestly – through improvements in medicine – or dramatically by increasing the maximum lifespan beyond its generally settled limit of 125 years. The ability to achieve such dramatic changes, however, does not currently exist.

Some researchers in this area, and "life extensionists", "immortalists" or "longevists" (those who wish to achieve longer lives themselves), believe that future breakthroughs in tissue rejuvenation, stem cells, regenerative medicine, molecular repair, gene therapy, pharmaceuticals, and organ replacement (such as with artificial organs or xenotransplantations) will eventually enable humans to have indefinite lifespans (agerasia) through complete rejuvenation to a healthy youthful condition. The ethical ramifications, if life extension becomes a possibility, are debated by bioethicists.

The sale of purported anti-aging products such as supplements and hormone replacement is a lucrative global industry. For example, the industry that promotes the use of hormones as a treatment for consumers to slow or reverse the aging process in the US market generated about $50 billion of revenue a year in 2009. The use of such products has not been proven to be effective or safe.

🔗 Mathematics 🔗 Biology 🔗 Physics 🔗 Plants

Tendril perversion, often referred to in context as simply perversion, is a geometric phenomenon found in helical structures such as plant tendrils, in which a helical structure forms that is divided into two sections of opposite chirality, with a transition between the two in the middle. A similar phenomenon can often be observed in kinked helical cables such as telephone handset cords.

The phenomenon was known to Charles Darwin, who wrote in 1865,

A tendril ... invariably becomes twisted in one part in one direction, and in another part in the opposite direction... This curious and symmetrical structure has been noticed by several botanists, but has not been sufficiently explained.

The term "tendril perversion" was coined by Goriely and Tabor in 1998 based on the word perversion found in the 19th Century science literature. "Perversion" is a transition from one chirality to another and was known to James Clerk Maxwell, who attributed it to the topologist J. B. Listing.

Tendril perversion can be viewed as an example of spontaneous symmetry breaking, in which the strained structure of the tendril adopts a configuration of minimum energy while preserving zero overall twist.

Tendril perversion has been studied both experimentally and theoretically. Gerbode et al. have made experimental studies of the coiling of cucumber tendrils. A detailed study of a simple model of the physics of tendril perversion was made by MacMillen and Goriely in the early 2000s. Liu et al. showed in 2014 that "the transition from a helical to a hemihelical shape, as well as the number of perversions, depends on the height to width ratio of the strip's cross-section."

Generalized tendril perversions were put forward by Silva et al., to include perversions that can be intrinsically produced in elastic filaments, leading to a multiplicity of geometries and dynamical properties.

🔗 Computing 🔗 Computer science 🔗 Biology 🔗 Chemistry 🔗 Genetics

DNA computing is a branch of computing which uses DNA, biochemistry, and molecular biology hardware, instead of the traditional silicon-based computer technologies. Research and development in this area concerns theory, experiments, and applications of DNA computing. The term "molectronics" has sometimes been used, but this term has already been used for an earlier technology, a then-unsuccessful rival of the first integrated circuits; this term has also been used more generally, for molecular-scale electronic technology.

🔗 Biology 🔗 Palaeontology 🔗 Geology

The Boring Billion, otherwise known as the Mid Proterozoic and Earth's Middle Ages, is the time period between 1.8 and 0.8 billion years ago (Ga) spanning the middle Proterozoic eon, characterized by more or less tectonic stability, climatic stasis, and slow biological evolution. It is bordered by two different oxygenation and glacial events, but the Boring Billion itself had very low oxygen levels and no evidence of glaciation.

The oceans may have been oxygen- and nutrient-poor and sulfidic (euxinia), populated by mainly anoxygenic purple bacteria, a type of chlorophyll-based photosynthetic bacteria which uses hydrogen sulfide (H₂S) instead of water and produces sulfur instead of oxygen. This is known as a Canfield ocean. Such composition may have caused the oceans to be black- and milky-turquoise instead of blue. (By contrast, during the much earlier Purple Earth phase the photosynthesis was retinal-based.)

Despite such adverse conditions, eukaryotes may have evolved around the beginning of the Boring Billion, and adopted several novel adaptations, such as various organelles, multicellularity, and possibly sexual reproduction, and diversified into plants, animals, and fungi at the end of this time interval. Such advances may have been important precursors to the evolution of large, complex life later in the Ediacaran and Phanerozoic. Nonetheless, prokaryotic cyanobacteria were the dominant lifeforms during this time, and likely supported an energy-poor food-web with a small number of protists at the apex level. The land was likely inhabited by prokaryotic cyanobacteria and eukaryotic proto-lichens, the latter more successful here probably due to the greater availability of nutrients than in offshore ocean waters.

🔗 Biology 🔗 Physics 🔗 Economics 🔗 Philosophy 🔗 Systems 🔗 Philosophy/Philosophy of science 🔗 Philosophy/Epistemology

In philosophy, systems theory, science, and art, emergence occurs when an entity is observed to have properties its parts do not have on their own. These properties or behaviors emerge only when the parts interact in a wider whole. For example, smooth forward motion emerges when a bicycle and its rider interoperate, but neither part can produce the behavior on their own.

Emergence plays a central role in theories of integrative levels and of complex systems. For instance, the phenomenon of life as studied in biology is an emergent property of chemistry, and psychological phenomena emerge from the neurobiological phenomena of living things.

In philosophy, theories that emphasize emergent properties have been called emergentism. Almost all accounts of emergentism include a form of epistemic or ontological irreducibility to the lower levels.

🔗 Biology 🔗 Politics 🔗 Psychology 🔗 Neuroscience 🔗 Genetics 🔗 Physiology 🔗 Physiology/neuro 🔗 Evolutionary biology 🔗 Conservatism

A number of studies have found that biology can be linked with political orientation. This means that biology is a possible factor in political orientation but may also mean that the ideology a person identifies with changes a person's ability to perform certain tasks. Many of the studies linking biology to politics remain controversial and unreplicated, although the overall body of evidence is growing.

🔗 Biology 🔗 Neuroscience 🔗 Physiology 🔗 Science

A microtome (from the Greek mikros, meaning "small", and temnein, meaning "to cut") is a cutting tool used to produce extremely thin slices of material known as sections, with the process being termed microsectioning. Important in science, microtomes are used in microscopy for the preparation of samples for observation under transmitted light or electron radiation.

Microtomes use steel, glass or diamond blades depending upon the specimen being sliced and the desired thickness of the sections being cut. Steel blades are used to prepare histological sections of animal or plant tissues for light microscopy. Glass knives are used to slice sections for light microscopy and to slice very thin sections for electron microscopy. Industrial grade diamond knives are used to slice hard materials such as bone, teeth and tough plant matter for both light microscopy and for electron microscopy. Gem-quality diamond knives are also used for slicing thin sections for electron microscopy.

Microtomy is a method for the preparation of thin sections for materials such as bones, minerals and teeth, and an alternative to electropolishing and ion milling. Microtome sections can be made thin enough to section a human hair across its breadth, with section thickness between 50 nm and 100 μm.

🔗 Biology 🔗 Engineering 🔗 Science

Xenobots, named after the African clawed frog (Xenopus laevis), are synthetic organisms that are automatically designed by computers to perform some desired function and built by combining together different biological tissues.

Xenobots are less than a 1 millimeter (0.039 inches) wide and composed of just two things: skin cells and heart muscle cells, both of which are derived from stem cells harvested from early (blastula stage) frog embryos. The skin cells provide rigid support and the heart cells act as small motors, contracting and expanding in volume to propel the xenobot forward. The shape of a xenobot's body, and its distribution of skin and heart cells, are automatically designed in simulation to perform a specific task, using a process of trial and error (an evolutionary algorithm). Xenobots have been designed to walk, swim, push pellets, carry payloads, and work together in a swarm to aggregate debris scattered along the surface of their dish into neat piles. They can survive for weeks without food and heal themselves after lacerations.