Camera obscura

Camera obscura referred to as pinhole image, is the natural optical phenomenon that occurs when an image of a scene at the other side of a screen is projected through a small hole in that screen as a reversed and inverted image on a surface opposite to the opening. The surroundings of the projected image have to be dark for the image to be clear, so many historical camera obscura experiments were performed in dark rooms; the term "camera obscura" refers to constructions or devices that make use of the principle within a box, tent, or room. Camera obscuras with a lens in the opening have been used since the second half of the 16th century and became popular as an aid for drawing and painting; the camera obscura box was developed further into the photographic camera in the first half of the 19th century when camera obscura boxes were used to expose light-sensitive materials to the projected image. The camera obscura was used as a means to study eclipses without the risk of damaging the eyes by looking into the sun directly.

As a drawing aid, the camera obscura allowed tracing the projected image to produce a accurate representation appreciated as an easy way to achieve a proper graphical perspective. Before the term "camera obscura" was first used in 1604, many others are attested: "cubiculum obscurum", "cubiculum tenebricosum", "conclave obscurum" and "locus obscurus". A camera obscura device without a lens but with a small hole is sometimes referred to as a "pinhole camera", although this more refers to simple lens-less cameras in which photographic film or photographic paper is used. Rays of light travel in straight lines and change when they are reflected and absorbed by an object, retaining information about the color and brightness of the surface of that object. Lit objects reflect rays of light in all directions. A small enough opening in a screen only lets through rays that travel directly from different points in the scene on the other side, these rays form an image of that scene when they are collected on a surface opposite from the opening.

The human eye works much like a camera obscura with an opening, a biconvex lens and a surface where the image is formed. A camera obscura device consists of a tent, or room with a small hole in one side. Light from an external scene passes through the hole and strikes a surface inside, where the scene is reproduced and reversed, but with color and perspective preserved. In order to produce a reasonably clear projected image, the aperture has to be about 1/100th the distance to the screen, or less; as the pinhole is made smaller, the image gets sharper. With too small a pinhole, the sharpness worsens, due to diffraction. In practice, camera obscuras use a lens rather than a pinhole because it allows a larger aperture, giving a usable brightness while maintaining focus. If the image is caught on a semi-transparent screen, it can be viewed from the back so that it is no longer reversed. Using mirrors it is possible to project a right-side-up image; the projection can be diverted onto a horizontal surface.

The 18th-century overhead version in tents used mirrors inside a kind of periscope on the top of the tent. The box-type camera obscura has an angled mirror projecting an upright image onto tracing paper placed on the glass top. Although the image is viewed from the back, it is now reversed by the mirror. There are theories. Distortions in the shapes of animals in many paleolithic cave artworks might be inspired by distortions seen when the surface on which an image was projected was not straight or not in the right angle, it is suggested that camera obscura projections could have played a role in Neolithic structures. Perforated gnomons projecting a pinhole image of the sun were described in the Chinese Zhoubi Suanjing writings; the location of the bright circle can be measured to tell the time of year. In Arab and European cultures its invention was much attributed to Egyptian astronomer and mathematician Ibn Yunus around 1000 CE; some ancient sightings of gods and spirits in temple worship, are thought to have been conjured up by means of camera obscura projections.

The earliest known written record of the camera obscura is found in the Chinese text called Mozi, dated to the 4th century BCE, traditionally ascribed to and named for Mozi, a Han Chinese philosopher and the founder of Mohist School of Logic. These writings explain how the image in a "collecting-point" or "treasure house" is inverted by an intersecting point that collects the light. Light coming from the foot of an illuminated person would be hidden below and form the top part of the image. Rays from the head would be hidden above and form the lower part of the image; this is a remarkably early correct description of the camera obscura. The Greek philosopher Aristotle, or a follower of his ideas, touched upon the subject in the work Problems – Book XV, asking: Why is it that when the sun passes through quadri-laterals, as for instanc

2015 United States E. coli outbreak

The 2015 United States E. coli outbreak is an incident in the United States involving the spread of Escherichia coli O157:H7 through contaminated celery, consumed in chicken salad at various large retailers. A product recall covering more than one dozen states and over 155,000 products has taken place as a result of the incident. Nineteen cases of E. coli were linked to the outbreak, across seven states in the western half of the United States. Of these reported cases, five resulted in hospitalization, with two patients developing hemolytic-uremic syndrome, a type of kidney failure; this outbreak was therefore the second largest to occur in the U. S. in 2015, behind the far more severe Chipotle outbreak, which totaled about sixty cases. A total of 19 cases of E. coli linked to the outbreak were reported, throughout seven states: California, Missouri, Utah and Washington. Recalls of Costco rotisserie chicken salad, deemed the source of the outbreak, occurred throughout the entire United States, with Costco claiming to have removed all infected products by November 20, 2015.

The epidemiologic evidence collected during the outbreak suggested that rotisserie chicken salad made and sold in Costco Wholesale stores in several states was the source of the outbreak

2013–14 UEFA Youth League

The 2013–14 UEFA Youth League was the first season of the UEFA Youth League, a European youth club football competition organised by UEFA. It was contested by the under-19 youth teams of the 32 clubs qualified for the group stage of the 2013–14 UEFA Champions League; the final was played on 14 April 2014 at the Colovray Stadium in Nyon, between Benfica and Barcelona. Barcelona won 3–0 and became the first team to lift the Lennart Johansson Trophy, named after UEFA's honorary president. Players must be born on or after 1 January 1995; the schedule of the competition was. The 32 teams were drawn into eight groups of four, with the group compositions determined by the draw for the 2013–14 UEFA Champions League group stage, held in Monaco on 29 August 2013. In each group, teams played against each other home-and-away in a round-robin format; the matchdays were 17–18 September, 1–2 October, 22–23 October, 5–6 November, 26–27 November, 10–11 December 2013, with the matches played on the same matchday as the corresponding Champions League matches.

The group winners and runners-up advanced to the round of 16. TiebreakersThe teams are ranked according to points. If two or more teams are equal on points on completion of the group matches, the following criteria are applied to determine the rankings: higher number of points obtained in the group matches played among the teams in question. If this procedure does not lead to a decision, criteria 6 to 9 apply. Times up to 26 October 2013 were CEST, thereafter times were CET; the match was cancelled due to the refusal of Ajax players to take the field, as they considered the condition of the pitch not sufficient to ensure the safety of the players. The match was irrelevant for the qualification to the knockout phase. In the knockout phase, teams played against each other over one match. If scores were level after full-time, the match was decided by penalty shoot-out; the mechanism of the draws for each round was as follows: In the draw for the round of 16, the eight group winners were seeded, the eight group runners-up were unseeded.

The seeded teams were drawn with the seeded teams hosting the match. Teams from the same group or the same association could not be drawn against each other. In the draws for the quarter-finals onwards, there were no seedings, teams from the same group or the same association could be drawn against each other; the draw decided the home team for each quarter-final, the "home" team for administrative purposes for each semi-final and final. Times up to 29 March 2014 were CET, thereafter times were CEST; the draw for the knockout phase was held on 16 December 2013. The round of 16 were played on 18, 25 and 26 February 2014; the quarter-finals were played on 11, 16 and 18 March 2014. The semi-finals were played on 11 April 2014 at the Colovray Stadium in Switzerland; the final was played on 14 April 2014 at the Colovray Stadium in Switzerland. 2013–14 UEFA Youth League Final tournament: Nyon 2014