In physics, quintessence is a hypothetical form of dark energy, more a scalar field, postulated as an explanation of the observation of an accelerating rate of expansion of the universe. The first example of this scenario was proposed by Peebles; the concept was expanded to more general types of time-varying dark energy and the term "quintessence" was first introduced in a paper by Robert R. Caldwell, Rahul Dave and Paul Steinhardt, it has been proposed by some physicists to be a fifth fundamental force. Quintessence differs from the cosmological constant explanation of dark energy in that it is dynamic. Quintessence can be either attractive or repulsive depending on the ratio of its kinetic and potential energy; those working with this postulate believe that quintessence became repulsive about ten billion years ago, about 3.5 billion years after the Big Bang. Quintessence is a scalar field with an equation of state where wq, the ratio of pressure pq and density ρ q, is given by the potential energy V and a kinetic term: w q = p q ρ q = 1 2 Q ˙ 2 − V 1 2 Q ˙ 2 + V Hence, quintessence is dynamic, has a density and wq parameter that varies with time.

By contrast, a cosmological constant is static, with a fixed energy density and wq = −1. Many models of quintessence have a tracker behavior, which according to Ratra and Peebles and Paul Steinhardt et al. solves the cosmological constant problem. In these models, the quintessence field has a density which tracks the radiation density until matter-radiation equality, which triggers quintessence to start having characteristics similar to dark energy dominating the universe; this sets the low scale of the dark energy. When comparing the predicted expansion rate of the universe as given by the tracker solutions with cosmological data, a main feature of tracker solutions is that one needs four parameters to properly describe the behavior of their equation of state, whereas it has been shown that at most a two-parameter model can optimally be constrained by mid-term future data; some special cases of quintessence are phantom energy, in which wq < −1, k-essence, which has a non-standard form of kinetic energy.

If this type of energy were to exist, it would cause a big rip in the universe due to the growing energy density of dark energy which would cause the expansion of the universe to increase at a faster-than-exponential rate. Holographic dark energy models compared with cosmological constant models, imply a high degeneracy, it has been suggested that dark energy might originate from quantum fluctuations of spacetime, are limited by the event horizon of the universe. Studies with quintessence dark energy found that it dominates gravitational collapse in a spacetime simulation, based on the holographic thermalization; these results show that the smaller the state parameter of quintessence is, the harder it is for the plasma to thermalize. In 2004, when scientists fitted the evolution of dark energy with the cosmological data, they found that the equation of state had crossed the cosmological constant boundary from above to below. A proven no-go theorem indicates this situation, called the Quintom scenario, requires at least two degrees of freedom for dark energy models.

The name comes from quinta essentia so called in Latin starting from the Middle Ages, was the element added by Aristotle to the other four ancient classical elements, because he thought it was the essence of the celestial world. Aristotle called this element aether, which he posited to be a pure and primigenial element. Modern quintessence would be the fifth known "dynamical, time-dependent, spatially inhomogeneous" contribution to the overall mass–energy content of the universe. Of course, the other four components are not the ancient Greek classical elements, but rather "baryons, dark matter, radiation." Although neutrinos are sometimes considered radiation, the term "radiation" in this context is only used to refer to massless photons. Spatial curvature of the cosmos is excluded. Aether Ostriker JP. "The Quintessential Universe". Scientific American. 284: 46–53. Bibcode:2001SciAm.284a..46O. Doi:10.1038/scientificamerican0101-46. PMID 11132422. Lawrence M. Krauss. Quintessence: The Search for Missing Mass in the Universe.

Basic Books. ISBN 978-0465037414

Following the simultaneous federal elections and regional elections of 26 May 2019, negotiations started to form a new Federal Government as well as new regional governments: a Flemish, French Community and Brussels Government. A Government of the German-speaking Community was formed only a few days after the elections. King Philippe appointed Didier Reynders and Johan Vande Lanotte as informateurs, they are tasked with looking for possibilities to form a government coalition. On 8 October, the King appointed two preformateurs: Geert Bourgeois and Rudy Demotte, each being a former minister-president and member of the largest party in Flanders and Wallonia; the remaining parties in the negotiations were N-VA, PS, sp.a, CD&V, Open Vld and MR. Two weeks both Green parties were invited again, they did not succeed in finding a coalition of parties, upon which the King appointed PS leader Paul Magnette as informateur on 5 November. Two coalitions are: "Purple-yellow": socialists + liberals + Flemish nationalists "Purple-green": socialists + liberals + Greens A negotiation paper of Magnette leaked to the media on 27 November, which contained left-leaning proposals, indicating a push for a purple-green coalition.

On 1 December, it turned out that those parties held a meeting unbeknownst to N-VA and CD&V. The paper was unacceptable to many within Open Vld. On 10 December 2019, the King appointed Joachim Coens and Georges-Louis Bouchez as informateurs. Both had at that moment become leader of their respective party only days earlier, they concluded that both coalitions were not yet sufficiently viable and other options needed to be considered as well. In January 2020, federal representative Emir Kir was excluded from the PS, leaving the purple-green without a majority. Hence, CD&V has become incontournable for political reasons to form such coalition. In a move seen as his own initiative, King Philippe appointed federal minister of Justica and senior CD&V politician Koen Geens as “Royal assignment holder” with the task to look for any possible coalitions. However, his party ruled out joining a purple-green coalition, which left Geens focussing on bringing PS and N-VA closer together to form a “purple-yellow” coalition, with CD&V taking Open VLD’s place therein.

It is said that progress to this purpose was made and several amicable meetings took place between Paul Magnette and Bart De Wever, the presidents of the two antagonized parties. On 10 February, Geens' assignment was prolonged for one week. In a sudden change of events, PS president Paul Magnette staunchly ruled out a coalition with N-VA on all media platforms of the country. Seeing his task as no longer purposeful, Geens returned to the King that evening and was relieved of his duties. On 16 February, Geens vehemently disapproved the PS' statements from Friday and blamed them for bringing the stability of the country in danger. On 12 August, N-VA released a starting note intended to form the basis of a continued governing coalition of N-VA, CD&V and Open Vld. Jan Jambon will become Minister-President; the government was not formed in time for the traditional "September Declaration", when the Minister-President gives a speech to the Flemish Parliament at the start of the parliamentary year. A few days after the elections, the incumbent coalition of ProDG, SP and PFF agreed to continue governing.

Oliver Paasch remained Minister-President. On Monday 17 June 2019, the four ministers took the oath in front of the Parliament of the German-speaking Community and the next day the Minister-President took the oath in front of King Philippe. 2019 Belgian federal election 2019 Belgian regional elections

A radial tree, or radial map, is a method of displaying a tree structure in a way that expands outwards, radially. It is one of many ways to visually display a tree, with examples extending back to the early 20th century. In use, it is a type of information graphic. In a simple case, the first node is at the top, the linked nodes are beneath; as each node has more than one child, the resulting shape is triangular. In a radial layout, instead of each successive generation being displayed a row below, each generation is displayed in a new, outer orbit. Since the length of each orbit increases with the radius, there tends to be more room for the nodes. A radial tree will spread the larger number of nodes over a larger area as the levels increase. We use the terms depth interchangeably; the number of nodes increases exponentially with the distance from the first node, whereas the circumference of each orbit increases linearly, so, by the outer orbits, the nodes tend to be packed together. The overall distance "d" is the distance between levels of the graph.

It is chosen. Layouts are generated by working outward from root; the first level is a special case. The nodes for level 1 can be distributed evenly, or weighted depending on the number of children they have. For subsequent levels, the children are positioned within sectors of the remaining space, so that child nodes of one parent do not overlap with others. There are many extensions to this algorithm to create more visually balanced layouts, to allow a user to navigate from node to node, or accommodate node labels and mix force-directed layouts with radial layouts; the layout has some similarities to a hyperbolic tree, though a key difference is that hyperbolic trees are based on hyperbolic geometry, whereas in a radial tree the distance between orbits is linear. MindManager and MindMapper are mindmapping systems, which can make radial-like layouts, though are not radial beyond the 2nd level. SpicyNodes was an approach to visualizing hierarchies. Comprehensive survey and bibliography of Tree Visualization techniques WikiViz: Visualizing Wikipedia by Chris Harrison Radial maps at "Visual Complexity" site

Christian Geiger is an Australian Alpine skier, Paralympic alpine ski coach and sighted guide for visually impaired skiers. He was Jessica Gallagher's guide skier at the 2014 Winter Paralympics in Sochi, winning a bronze medal, he represented Australia at the 2008 World Junior Alpine Skiing Championships and the 2009 FIS Alpine World Ski Championships, but his career was cut short when he was injured in a traffic collision in 2009. He became Jessica Gallagher's sighted guide in 2013, guided her to silver medals in women's slalom and giant slalom at the 2013 IPC Alpine Skiing World Cup in Thredbo. Geiger was Melissa Perrine's guide and coach at the 2018 Winter Paralympics where she won two bronze medals. Geiger was born on 29 March 1988 in St Leonards, New South Wales, but lived in Austria until he was eight. On 26 September 2009, he was involved in a car crash; the vehicle he was travelling in as a passenger slammed into a tree just 30 metres from his family's home in Bright, Victoria. He suffered severe injuries to his arm and liver as well as serious brain trauma.

As a result, he was in an induced coma for a week. It took months before he could walk and eat independently again; as of August 2011, he had extensive physiotherapy and speech therapy. Geiger began skiing at the age of two in Austria, made the national team in 2006, he won numerous Australian Championships during his teenage years, represented Australia at the 2008 World Junior Alpine Skiing Championships and the 2009 FIS Alpine World Ski Championships. This changed after his 2009 accident. "I tried to get back to able bodied but couldn't quite get back to where I was, let alone where I wanted to go," he explained, "so I had to hang it up."In 2013, Australian Paralympic Alpine Head Coach Steve Graham asked Geiger to replace Eric Bickerton as Jessica Gallagher's sighted guide. In their first competition, the 2013 IPC Alpine Skiing World Cup in Thredbo, New South Wales, he guided Gallagher to silver medals in women's slalom and giant slalom. Gallagher gave an insight on taking on Geiger as a guide.

She said: Every run that we are spending together at the moment, Christian is learning new things about the way that I ski, about the things that I need to be told when I'm going down the hill in terms of the things that I'm not seeing and the things that may throw me and test me as an athlete because at the end of the day his role as a guide is to get me down to the bottom as fast as possible, but as safe as possible. It just happens with time really. Geiger was guide to Gallagher at the 2014 Winter Paralympics in Sochi, where they won a bronze medal in the women's giant slalom visually impaired event, they came seventh in the women's slalom visually impaired. In 2015, he was Head Coach of Australia’s Para-Alpine Skiing program. Following Gallagher's move to para-cycling, Geiger became sighted guide to Melissa Perrine. At the 2018 Winter Paralympics in Pyeongchang, Geiger guided Perrine to bronze medal wins in the women's super combined and giant slalom visually impaired events; the pair placed fourth in the slalom and fifth in the downhill and super-G visually impaired.

In November 2018, Geiger won the New South Wales Institute of Sport 7News Spirit of Sport Award, as voted by the public, for his act of generosity in flying Perrine’s family to PyeongChang, allowing them to watch her compete at the Winter Paralympics. At the 2019 Australian Ski and Snowboard Awards, Geiger with Ryan Pearl was named Coach of the Year. Christian Geiger at the International Ski Federation Christian Geiger at the International Paralympic Committee Christian Geiger at Paralympics Australia Christian Geiger: Days off.. Quick Tour at the Mountain Paralympic Village on YouTube Christian Geiger: tractor guiding at the Mountain Village on YouTube

Menstrual extraction is a type of manual vacuum aspiration technique developed by feminist activists, Lorraine Rothman and Carol Downer, to pass the entire menses at once. The non-medicalized technique has been used in small feminist self-help groups since 1971 and has a social role of allowing access to early abortion without needing medical assistance or legal approval. ME usage declined after 1973, when Wade legalized abortion in the United States. There has been renewed interest in the technique, in the 1990s and more in the 2010s, due to increased restrictions on abortion. In some countries where abortion is illegal, such as Bangladesh, the terms “menstrual regulation” or “menstrual extraction” are used as euphemisms for early pregnancy terminations. In 1971, members of a feminist reproductive health self-help group, Lorraine Rothman and Carol Downer modified equipment found in an underground abortion clinic, developed for a new non-traumatic, manually-operated-suction abortion technique.

They took the thin, flexible plastic Karman cannula, the syringe, added a one-way bypass valve, to fix two main problems. The contraption could prevent air from being pumped into the uterus, suctioned uterine contents directly into the syringe, thus limiting the amount that could be removed, they added two lengths of clear plastic tubing, one from the cannula to the collection jar and another to go from the collection jar to the syringe. With this new set-up, the contents of the uterus went directly into the jar, allowing for the extraction of more material, the two-way bypass valve diverted any air that may have been inadvertently pushed back toward the body to exit harmlessly into the air. Rothman and Downer dubbed the new invention the "Del Em." By making it possible for more than one person to operate the device, the skill level of the operators was reduced. One person could concentrate on guiding the sterile cannula through the vaginal cavity into the cervical os while another could pump the syringe to develop the vacuum.

The Del Em made the procedure more comfortable, with personal control of the suction. Downer considers the teaching and usage of menstrual extraction to be a key radical feminist action to ensure women's reproductive sovereignty. ME was developed and used before the Roe v. Wade Supreme Court decision legalized abortion in 1973. In order to avoid legal issues and Rothman downplayed the device's potential use as an abortion method, they called new technique "menstrual extraction" or "ME" to highlight its harmless use in suctioning out menstrual blood and tissue. To further emphasize the innocuousness of ME, "the procedure was only performed when a woman’s period was due, they wouldn't take a pregnancy test beforehand; that way, everyone had plausible deniability."Since 1971, groups performing menstrual extractions have had an excellent safety record, obviating any opportunity for legal action culminating in the prosecution of any individual. However, the possibility of legal troubles continues to exist, because of that many of these self-help groups have sought legal advice and researched the laws in the states in which they perform ME.

Additionally, many of these self-help groups do not publicize themselves or offer menstrual extraction to those outside of their tight-knit groups, in order to protect themselves and their techniques from legal investigations. There is one instance, it is well known as the "Yogurt Defense" case, in which Downer was arrested while at her self-help group and charged with practicing medicine without a license because she inserted yogurt into the vagina of Z. Budapest, another member of the group, as treatment for a yeast condition. Downer went to trial and was acquitted, as the jury did not see inserting yogurt as practicing medicine. ME made its debut at the National Organization for Women conference in Santa Monica, California in August 1971. To Rothman and Downer's dismay, the organizers of the conference were "so appalled that they refused to give the women exhibit space." Instead and Rothman hung flyers around the conference, announcing a demonstration in their hotel room. The attendees were given a plastic speculum to begin their education.

From the extensive mailing list collected during these demonstrations and Rothman began a national tour, going all over the country teaching the new technique. According to the National Women's Health Network, "the early self-helpers advocated that women join self-help groups and practice extracting each others' menses around the time of their expected periods." The Roe v. Wade Supreme Court decision made abortion legal in 1973. After that, menstrual extraction was practiced much less, it did begin to regain in popularity in the late 1980s and early 1990s, when the U. S. Supreme Court ruled on Webster v. Reproductive Health Services, which limited access to abortion by state of residence and type of medical insurance. Self-helpers reprised the 1971 tour, traveling around the U. S. sharing self-examination and menstrual extraction techniques. Menstrual extraction has regained popularity once again in the 2010s, in addition to other self-induced abortion methods; these self-helpers are following the 1970s methods of teaching by meeting in other women's homes, performing cervix examinations on each other, learning menstrual extraction directly from other women.

One new underground network, made up of women knowledgeable on ME and other self-induced abortion methods, has performed over 2,000 abortions between 2015 and 2018. The women involved in this network ran

Still in the stage of development, local flexibility markets for electricity will enable distributed energy resources to provide their flexibility in electricity demand or production/feed-in for the system operator or another counterparty at a local level. As there are different purposes for the use of this flexibility, there exist a variety of different market designs, comprising different actors and role models. Several local market models aim to efficiently tackle the widespread issue of grid congestion; this category of local markets is described further in this article. The rapid expansion of Renewable Energies accelerated in recent years; this is the case in Germany, more so in its Northern regions. Nearly 50GW of installed wind capacity generated over a third of Germanys electricity demand in 2017; as an example, the Land of Schleswig-Holstein was able to cover 95% of its electricity demand by wind-generated energy. Slow grid expansion causes congestions For transportation to the consumer via the electricity grid, these strong amounts of energy require accordingly developed grid capacities.

But while the expansion of wind energy happened fast due to the EEG-incentives, the expansion of the grid happened much slower, since the regulation behind grid expansion requires extensive bureaucratic efforts. This fact causes a sophisticated problem: in times of strong wind energy generation, the amount of electricity is too high to get properly feed in and distributed through the grid; the limited grid capacities are not constructed to transport such high amounts of energy at once, the result is congestions: Solving congestions through feed-in management Today, system operators are given only one possible tool to encounter this problem and to secure grid stability: in times of strong wind, certain wind turbines are shut down. This is called Feed-In Management, but stopping wind turbines when their energy output is at its highest, comes at high cost: both ecologically and economically: Ecologically, because for every curtailed kWh of wind energy, another power plant must be activated to offset the now missing volumes, since they have been traded in the market.

Because the supplementing power plant must be ramped up rather and the first and only choice are combined cycle gas turbines. This practice of balancing energy generation by activating certain power plants on the one hand, shutting down certain generation capacities on the other is called Redispatch. Feed-in management comes at high economic costs for two reasons: first, the redispatched CCGT must be remunerated. Second, the wind turbine operator or owner must be remunerated for every kWh he would otherwise have produced; these costs are not paid directly by the system operator. The system operator is entitled to pass on the costs to the end consumer, meaning that at the end, society pays. Annual costs for feed-in management in Germany were €373m in 2016, €550m in 2017, are to increase up to €5bn until 2025. New solution: Local Flexibility Markets Local Flexibility Markets provide system operators with a new possibility instead of feed-in management; this new kind of market makes it possible to use local flexibility potential, meaning an increase/decrease in consumption/production at specific points in the grid.

This means that higher electricity volumes can be used locally, hence the amount of energy that needs to be transported over long distances via the grid is reduced. Regional trading of electricity enables the system operator to optimize local electricity flows in the grid; the condition for this is an examination of each DER, where the market operator assesses the physical impact of the DER on the grid, based on the location and the provided flexibility capacity. Regional pricing of electricity creates a financial incentive for flexibility providers to adapt their electricity demand or consumption to the current situation in the grid, which alleviates congestions in a market based manner. In recent years, a variety of concepts regarding the roles and actors in local markets were developed; this article highlights the following concept, which refers to a flexibility market used by Transmission and Distribution System Operators for the purpose of alleviating grid congestions in a market based manner.

It was developed within the EU H2020 project Smartnet. It is operated by an neutral third party. System Operator: act as single buyer of energy volumes and are therefore counterpart in every trade; the execution of every trade therefore remains subject to the System Operator. The System Operator is responsible for the financial remuneration of the flexibility providers. Market Operator: a neutral third party that operates the market, including pre-defined profile exchange, operation of order books, clearing activities. Flexible resource owner: offers its flexibility to the system operator. Either downward flexibility or upward flexibility can be offered. Potential flexibility providers are: s