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The photoacoustic effect or optoacoustic effect is the formation of sound waves following light absorption in a material sample. In order to obtain this effect the light intensity must vary, either periodically (modulated light) or as a single flash (pulsed light). The photoacoustic effect is quantified by measuring the formed sound (pressure changes) with appropriate detectors, such as microphones or piezoelectric sensors. The time variation of the electric output (current or voltage) from these detectors is the photoacoustic signal. These measurements are useful to determine certain properties of the studied sample. For example, in photoacoustic spectroscopy, the photoacoustic signal is used to obtain the actual absorption of light in either opaque or transparent objects. It is useful for substances in extremely low concentrations, because very strong pulses of light from a laser can be used to increase sensitivity and very narrow wavelengths can be used for specificity. Furthermore, photoacoustic measurements serve as a valuable research tool in the study of the heat evolved in photochemical reactions (see: photochemistry), particularly in the study of photosynthesis.

Most generally, electromagnetic radiation of any kind can give rise to a photoacoustic effect. This includes the whole range of electromagnetic frequencies, from gamma radiation and X-rays to microwave and radio. Still, much of the reported research and applications, utilizing the photoacoustic effect, is concerned with the near ultraviolet/visible and infrared spectral regions.

🔗 Biography 🔗 France 🔗 Women writers 🔗 Biography/Actors and Filmmakers 🔗 Belgium 🔗 Feminism 🔗 Women artists

Agnès Varda (French: [aɲɛs vaʁda]; born Arlette Varda; 30 May 1928 – 29 March 2019) was a Belgian-born French film director, screenwriter, photographer, and artist. Her pioneering work was central to the development of the widely influential French New Wave film movement of the 1950s and 1960s. Her films focused on achieving documentary realism, addressing women's issues, and other social commentary, with a distinctive experimental style.

Varda's work employed location shooting in an era when the limitations of sound technology made it easier and more common to film indoors, with constructed sets and painted backdrops of landscapes, rather than outdoors, on location. Her use of non-professional actors was also unconventional for 1950s French cinema. Varda's feature film debut was La Pointe Courte (1955), followed by Cléo from 5 to 7 (1962), one of her most notable narrative films, Vagabond (1985), and Kung Fu Master (1988). Varda was also known for her work as a documentarian with such works as Black Panthers (1968), The Gleaners and I (2000), The Beaches of Agnès (2008), Faces Places (2017), and her final film, Varda by Agnès (2019).

Director Martin Scorsese described Varda as "one of the Gods of Cinema". Among several other accolades, Varda received an Honorary Palme d'Or at the 2015 Cannes Film Festival, becoming the first woman to win the award, a Golden Lion for Vagabond at the 1985 Venice Film Festival, an Academy Honorary Award, and a nomination for the Academy Award for Best Documentary Feature for Faces Places, becoming the oldest person to be nominated for a competitive Oscar. In 2017, she became the first female director to win an honorary Oscar.

🔗 Novels 🔗 Novels/Science fiction 🔗 Novels/Short story

"The Murderer" (1953) is a short story by Ray Bradbury, published in his collection The Golden Apples of the Sun.

🔗 London

Lloyd's Coffee House was a significant meeting place in London in the 17th and 18th centuries.

It was opened by Edward Lloyd (c. 1648–15 February 1713) on Tower Street in 1686. The establishment was a popular place for sailors, merchants and shipowners, and Lloyd catered to them by providing reliable shipping news. The shipping industry community frequented the place to discuss maritime insurance, shipbroking and foreign trade. The dealings that took place led to the establishment of the insurance market Lloyd's of London, Lloyd's Register and several related shipping and insurance businesses.

The coffee shop relocated to Lombard Street in December 1691. Lloyd had a pulpit installed in the new premises, from which maritime auction prices and shipping news were announced. Candle auctions were held in the establishment, with lots frequently involving ships and shipping. From 1696–1697 Lloyd also experimented with publishing a newspaper, Lloyd's News, reporting on shipping schedules and insurance agreements reached in the coffee house. In 1713, the year of Edward Lloyd's death, he modified his will to assign the lease of the coffee house to his head waiter, William Newton, who then married one of Lloyd's daughters, Handy. Newton died the following year and Handy subsequently married Samuel Sheppard. She died in 1720 and Sheppard died in 1727, leaving the coffee house to his sister Elizabeth and her husband, Thomas Jemson. Jemson founded the Lloyd's List newspaper in 1734, similar to the previous Lloyd's News. Merchants continued to discuss insurance matters here until 1774, when the participating members of the insurance arrangement formed a committee and moved to the Royal Exchange on Cornhill as the Society of Lloyd's.

🔗 Food and drink 🔗 United Kingdom

A toast sandwich is a sandwich made with two slices of bread in which the filling is a thin slice of toasted bread, which can be heavily buttered. An 1861 recipe says to add salt and pepper to taste.

🔗 Africa 🔗 Africa/Ghana 🔗 Food and drink 🔗 Africa/Ivory Coast 🔗 Africa/French Africa

Child labour is a recurring issue in cocoa production. Cote d’Ivoire (also known in English as Ivory Coast) and Ghana, together produce nearly 60% of the world's cocoa each year. During the 2018/19 cocoa-growing season, research commissioned by the U.S. Department of Labor was conducted by NORC at the University of Chicago in these two countries and found that 1.48 million children are engaged in hazardous work on cocoa farms including working with sharp tools and agricultural chemicals and carrying heavy loads. That number of children is significant, representing 43 percent of all children living in agricultural households in cocoa growing areas. During the same period cocoa production in Cote d’Ivoire and Ghana increased 62 percent while the prevalence of child labour in cocoa production among all agricultural households increased 14 percentage points. Attention on this subject has focused on West Africa, which collectively supplies 69% of the world's cocoa, and Côte d'Ivoire, supplying 35%, in particular. The 2016 Global Estimates of Child Labour indicate that one-fifth of all African children are involved in child labour. Nine percent of African children are in hazardous work. It is estimated that more than 1.8 million children in West Africa are involved in growing cocoa. A 2013–14 survey commissioned by the Department of Labor and conducted by Tulane University found that an estimated 1.4 million children aged 5 years old to 11 years old worked in agriculture in cocoa-growing areas, while approximately 800,000 of them were engaged in hazardous work, including working with sharp tools and agricultural chemicals and carrying heavy loads. According to the NORC study, methodological differences between the 2018/9 survey and earlier ones, together with errors in the administration of the 2013/4 survey have made it challenging to document changes in the number of children engaged in child labour over the past five years.

A major study of the issue, published in Fortune magazine in the U.S. in March 2016, concluded that approximately 2.1 million children in West Africa "still do the dangerous and physically taxing work of harvesting cocoa". The report was doubtful as to whether the situation can be improved significantly.

🔗 Physics 🔗 Elements 🔗 Elements/Isotope 🔗 Chemistry

In nuclear physics, the island of stability is a predicted set of isotopes of superheavy elements that may have considerably longer half-lives than known isotopes of these elements. It is predicted to appear as an "island" in the chart of nuclides, separated from known stable and long-lived primordial radionuclides. Its theoretical existence is attributed to stabilizing effects of predicted "magic numbers" of protons and neutrons in the superheavy mass region.

Several predictions have been made regarding the exact location of the island of stability, though it is generally thought to center near copernicium and flerovium isotopes in the vicinity of the predicted closed neutron shell at N = 184. These models strongly suggest that the closed shell will confer further stability towards fission and alpha decay. While these effects are expected to be greatest near atomic number Z = 114 and N = 184, the region of increased stability is expected to encompass several neighboring elements, and there may also be additional islands of stability around heavier nuclei that are doubly magic (having magic numbers of both protons and neutrons). Estimates of the stability of the elements on the island are usually around a half-life of minutes or days; some estimates predict half-lives of millions of years.

Although the nuclear shell model predicting magic numbers has existed since the 1940s, the existence of long-lived superheavy nuclides has not been definitively demonstrated. Like the rest of the superheavy elements, the nuclides on the island of stability have never been found in nature; thus, they must be created artificially in a nuclear reaction to be studied. Scientists have not found a way to carry out such a reaction, for it is likely that new types of reactions will be needed to populate nuclei near the center of the island. Nevertheless, the successful synthesis of superheavy elements up to Z = 118 (oganesson) with up to 177 neutrons demonstrates a slight stabilizing effect around elements 110 to 114 that may continue in unknown isotopes, supporting the existence of the island of stability.

🔗 Computer science

Hoare logic (also known as Floyd–Hoare logic or Hoare rules) is a formal system with a set of logical rules for reasoning rigorously about the correctness of computer programs. It was proposed in 1969 by the British computer scientist and logician Tony Hoare, and subsequently refined by Hoare and other researchers. The original ideas were seeded by the work of Robert W. Floyd, who had published a similar system for flowcharts.

🔗 Norway

The Norwegian butter crisis began in late 2011 with an acute shortage of butter and inflation of its price across markets in Norway. The shortage caused soaring prices and stores' stocks of butter ran out within minutes of deliveries. According to the Danish tabloid B.T., Norway was gripped by smør-panik ("butter panic") as a result of the butter shortage.

🔗 Psychology 🔗 Cognitive science

Functional fixedness is a cognitive bias that limits a person to use an object only in the way it is traditionally used. The concept of functional fixedness originated in Gestalt psychology, a movement in psychology that emphasizes holistic processing. Karl Duncker defined functional fixedness as being a "mental block against using an object in a new way that is required to solve a problem". This "block" limits the ability of an individual to use components given to them to complete a task, as they cannot move past the original purpose of those components. For example, if someone needs a paperweight, but they only have a hammer, they may not see how the hammer can be used as a paperweight. Functional fixedness is this inability to see a hammer's use as anything other than for pounding nails; the person couldn't think to use the hammer in a way other than in its conventional function.

When tested, 5-year-old children show no signs of functional fixedness. It has been argued that this is because at age 5, any goal to be achieved with an object is equivalent to any other goal. However, by age 7, children have acquired the tendency to treat the originally intended purpose of an object as special.