The following are given passages.
Passage 1:
Vinko Dvořák
Vinko Dvořák (January 21, 1848 – May 6, 1922) was a Czech-Croatian physicist, professor and academician.He studied mathematics and physics at the Charles University in Prague, and after graduating he became an assistant to professor Ernst Mach. After obtaining his doctorate in Prague in 1873/1874 he came to Zagreb (at the time also part of Austria-Hungary) and founded the Physics Cabinet at the Faculty of Philosophy in 1875.
Dvořák made many important discoveries in the field of experimental acoustics and optics, which are known as the Dvořák-Rayleigh current, the Dvořák acoustic repulsion, and the Dvořák circuit. His work on acoustic radiometers coincided with that of Lord Rayleigh.He was the dean of the Faculty of Philosophy in 1881/82 and again in 1891/92 and the rector of the University of Zagreb in 1893/94.
Professor Dvorak made constant advancements in physics experimentation at the Faculty—in 1896 he obtained a Röntgen radiation device just six months after it was discovered.He became a member of the Academy of Sciences and Arts in 1883 (associate) and 1887 (full member). He was also an associate member of the Czech Academy of Franz Joseph I, a member of the Société francaise de physique (French Physics Society) and the Paris Société internationale des électriciens, and a member of the Royal Czech Society of Sciences in Prague.
Dvořák retired in 1911.
Passage 2:
Boeing VC-25
The Boeing VC-25 is a military version of the Boeing 747 airliner, modified for presidential transport and commonly operated by the United States Air Force (USAF) as Air Force One, the call sign of any U.S. Air Force aircraft carrying the president of the United States.
Only two examples of this aircraft type are in service; they are highly modified Boeing 747-200Bs, designated VC-25A and having tail numbers 28000 and 29000. Although technically the Air Force One designation applies to the aircraft only while the president is on board, the term is commonly used to refer to the VC-25 in general. The two aircraft often operate in conjunction with Marine One helicopters, which ferry the president to airports whenever a vehicle motorcade would be inappropriate. Two new aircraft, based on the Boeing 747-8I and designated VC-25B, have been ordered by the USAF to replace the aging VC-25As.

Development
By 1985, the pair of Boeing 707-based VC-137s used as the presidential aircraft had been in service for 23 and 13 years respectively, and the USAF began searching for an eventual replacement. The Request for Proposal issued stated that the aircraft to be selected should have at least three engines and an unrefueled range of at least 6,000 miles (9,700 km). Both Boeing with its 747 and McDonnell Douglas with the DC-10 were in competition to be selected, with the Boeing entry the eventual winner.  The fabrication of the current 747s began during the presidency of Ronald Reagan (1981–1989).
The VC-25s were completed in 1986 and first flew in 1987.  The interior designs were created by First Lady Nancy Reagan, who used designs reminiscent of the American Southwest. Problems with interior wiring for communication systems delayed delivery of the two aircraft until 1990, during the administration of George H. W. Bush.
The Air Force reported that the operating cost for each VC-25A in 2014 was $210,877 per hour.

Design and configuration
The VC-25 is capable of flying 7,800 miles (12,600 km)—roughly one-third the distance around the world—without refueling. The VC-25A can accommodate more than 70 passengers. Each VC-25A cost approximately $325 million. While the VC-25 has two main decks and a cargo area, like a regular Boeing 747, its 4,000 square feet (370 m2) of floor space has been reconfigured for presidential duties. Its lowest level is mostly cargo space, carrying luggage and the onboard food supply.
The main passenger area is on the second floor or main deck. There are three entrances on board, two on the main and one on the lower deck. Typically the president boards and disembarks from the front, main deck entrance via an airstair, while journalists and other passengers enter at the rear door of the main deck. Facilities for the press and other passengers are configured like an ordinary airliner's first-class cabin.

The "White House"
The front section of the aircraft is informally called the "White House", a reference to the president's official residence in Washington, D.C. The president's executive suite includes sleeping quarters with two couches that can be converted into beds, lavatory and shower, vanity, double sink, and a private office, or the president's "Oval Office aboard Air Force One". If necessary, the president can address the nation from the office. This capability was added after the September 11 attacks, during which the aircraft had to land at Barksdale Air Force Base for President George W. Bush to address the nation. These offices, including the president's suite, are mostly located on the starboard (right) side, and a long corridor runs along the port (left) side. The aircraft also contains a conference room, originally designed as a situation room, but now used for meeting with staff while traveling. This room includes a 50-inch plasma screen television which can be used for teleconferencing. The aircraft has fully equipped office areas with telecommunication systems (including 87 telephones and 19 televisions).On board the VC-25 is a medical annex, which includes a fold-out operating table, emergency medical supplies, and a well-stocked pharmacy. George W. Bush had a treadmill added to Air Force One during his term in office. Every flight is staffed by a doctor and nurse. The aircraft is self-sufficient, such as carrying all the food it will need. Meals are prepared in two galleys, which together are equipped to feed up to 100 people at a time. The president gets a personal menu. An area where guests sit is near the center of the aircraft, outside the "White House".There are separate quarters for guests, senior staff, Secret Service and security personnel, and the news media located in the aft area of the main deck. Protocol states that one may wander aft of one's assigned seat, but not forward of it. Communications equipment and the cockpit are on the upper deck. There are also secure and non-secure voice, fax and data communications facilities. While the aircraft's luggage capacity is adequate to carry the belongings of the passengers, the logistics train of the president means that the aircraft must fly preceded by an aerial convoy of several cargo transports, which carry the helicopters, motorcade vehicles, and other equipment required by the presidential entourage.

Operational history
VC-25A
The VC-25A replaced the VC-137C (a military version of the Boeing 707) as the mainstay of the Air Force One fleet. On some occasions, the VC-25s serve as transport for the US vice president, for which service they use the Air Force Two call sign. The VC-25A aircraft are maintained and operated as military operations by the Presidential Airlift Group, part of Air Mobility Command's 89th Airlift Wing, based at Joint Base Andrews in Camp Springs, Maryland.
The aircraft can also be operated as a military command center in the event of an incident such as a nuclear attack. Operational modifications include aerial refueling capability and countermeasures against anti-aircraft missiles. The electronics on board are connected with approximately 238 miles (383 km) of wiring, twice that of a regular 747. All wiring is covered with heavy shielding for protection from a nuclear electromagnetic pulse in the event of a nuclear attack. The aircraft also has electronic countermeasures (ECMs) to jam enemy radar, flares to avoid heat-seeking missiles, and chaff to avoid radar-guided missiles. All small arms and ammunition stores not in the physical possession of the Secret Service on board the VC-25s are stowed and secured by the Secret Service in separate locked compartments, each with a different locking mechanism for added security.  Many of the VC-25's other capabilities are classified for security reasons.
After a presidential inauguration resulting in a change in office, the outgoing president is provided transport on a VC-25 aircraft to their home destination.  The aircraft for this flight does not use the Air Force One call sign because it is not carrying the president in office.  For both Presidents Bill Clinton and George W. Bush, the flight was known as Special Air Mission 28000, where the number represents the aircraft's tail number.

The VC-25As have also been used to transport deceased former presidents, as the guest area aft of "the White House" has chairs and tables that can be removed and the casket laid in their place. The bodies of Ronald Reagan, Gerald Ford, and George H.W. Bush were transported to Washington for their state funerals, and then on to their final resting places. Colonel Mark Tillman, pilot for President George W. Bush, said, "We'll take care of the president from basically when he's in office to when he lays in state." For the funeral of President Ronald Reagan in 2004, Tillman said that the crew converted the front of the aircraft to look the way it would have appeared when Reagan was president; President and Nancy Reagan's Air Force One jackets were placed on the chairs to "make them feel at home". A specially designed hydraulic lifter (similar to the type used by airline catering) with the presidential seal affixed to the sides lifts the casket up to the portside aft door to enter the VC-25A. The tradition of placing the caskets in the passenger cabin dates back to the assassination of John F. Kennedy, when the crew did not want the president's body placed in the cargo hold, and again during the state funeral of Lyndon B. Johnson.The two VC-25As are slated for retirement by the end of 2025.

VC-25B
The VC-25A aircraft are aging and have become less cost-effective to operate. The USAF Air Mobility Command investigated possible replacements, with early press coverage suggesting that the USAF would consider the Boeing 747-8 and the Airbus A380. On 7 January 2009, Air Force Materiel Command issued a new Sources Sought notice for a replacement aircraft to enter service by 2017 with an additional two aircraft to follow in 2019 and 2021. On 28 January 2009, EADS North America representing EADS and its Airbus division confirmed it would not respond to the US Air Force notice, as assembling only three airplanes in the US would not make financial sense. This made Boeing the only aircraft manufacturer interested in supplying the replacement aircraft, and was reported to be exploring a 787 option also. On 28 January 2015, the Air Force announced the selection of the Boeing 747-8 to replace the aging VC-25A for presidential transport.On 10 May 2016, the Air Force posted online an amendment to its Air Force One contract authorizing Boeing to begin preliminary design activities. This version of the contract synopsis confirmed that the government will buy two modified 747-8 aircraft. Boeing was awarded a contract in January 2016 to identify cost reduction opportunities in areas including maintenance, aerial refueling and communications. On 15 July 2016, Boeing received another contract for pre-engineering and manufacturing development (EMD) risk-reduction to address "system specification, the environmental control system, the aircraft interior, the electrical and power system and sustainment and maintenance approaches" to reduce development risks and life-cycle costs.On 1 August 2017, Defense One reported that in an effort to pay less for the replacement program, the USAF entered into a contract to purchase two 747-8 Intercontinentals from Boeing, which had originally been ordered by Transaero, a Russian airline, in 2011. Before they could be delivered, the company filed for bankruptcy and was closed down; the two aircraft were stored at Southern California Logistics Airport in the Mojave desert to prevent corrosion. On 27 February 2018, the White House announced a US$3.9 billion agreement with Boeing to modify the two unsold 747-8s to replace the current VC-25As. The new aircraft will be designated VC-25B. These aircraft are to be retrofitted with telecommunications and security equipment to bring them to the required security level for the presidential aircraft, and are due to be delivered by 2024. Once the new aircraft are delivered, the VC-25As will be retired and placed in museums.In June 2019, President Trump announced his plans to revamp the VC-25's livery from the traditional white and ultramarine shades to one of red, white, and blue. This would have been the first deviation from the Raymond Loewy livery scheme since it was introduced in 1962 on the VC-137C which was first used as Air Force One during the Kennedy administration. The Biden administration abandoned the new design, citing "additional engineering, as well as increased time and cost." A modified version of the traditional scheme was announced in March 2023.The 747s begun undergoing modification work at the Boeing's San Antonio facility in 2020. According to The Wall Street Journal, the development process has been hit by multiple "production mishaps", including the discovery of empty tequila mini-bottles on one of the aircraft, and the use of jacks that were not rated to support the weight of the aircraft. While the jacking did not result in damage to the planes, "the Pentagon's contractor-management agency formally requested Boeing improve its operations." While the initial delivery date was set to 2024, the Pentagon expects the jets to be two to three years late.In April 2022, Boeing's CEO Dave Calhoun revealed that he expects the company to have a loss of $660 million on the VC-25B program, after the contract was renegotiated by President Trump.

Variants
VC-25A
based on Boeing 747-200B
VC-25B
based on Boeing 747-8 Intercontinental, to replace the VC-25As

Operators
United StatesUnited States Air Force
89th Airlift Wing, Presidential Airlift Group (PAG) - Andrews AFB, Maryland

Specifications (VC-25A)
Data from Boeing BDSGeneral characteristics
Crew: 26: 2 pilots, flight engineer, navigator, + cabin crew + mission crew
Capacity: 76 passengers
Length: 231 ft 10 in (70.66 m)
Wingspan: 196 ft 8 in (59.94 m)
Height: 63 ft 5 in (19.33 m)
Max takeoff weight: 833,000 lb (377,842 kg)
Powerplant: 4 × General Electric CF6-80C2B1 turbofan engines, 56,700 lbf (252 kN) thrust eachPerformance

Maximum speed: 547.5 kn (630.1 mph, 1,014.0 km/h) at 35,000 ft (10,668 m)
Maximum speed: Mach 0.92
Cruise speed: 500 kn (580 mph, 930 km/h) / M0.84 at 35,000 ft (10,668 m)
Range: 6,800 nmi (7,800 mi, 12,600 km)
Service ceiling: 45,100 ft (13,700 m)

Notable appearances in media
The VC-25 "Air Force One" is a prominent symbol of the U.S. presidency and its powers; with the White House and presidential seal, it is among the most recognized presidential symbols. Air Force One has often appeared in popular culture and fiction, including the setting of the 1997 action movie Air Force One where the aircraft had an escape pod and a parachute ramp, unlike the actual presidential aircraft.

See also
Air Force One photo op incident
Air Force Two
Air transports of heads of state and governmentRelated development

Boeing 747
Boeing E-4B NightwatchAircraft of comparable role, configuration, and era

VC-137C SAM 26000
VC-137C SAM 27000
Boeing C-32
Boeing C-40 Clipper
Airbus A330 MRTT Vespina
Passage 3:
SOLID
In software engineering, SOLID is a mnemonic acronym for five design principles intended to make object-oriented designs more understandable, flexible, and maintainable. The principles are a subset of many principles promoted by American software engineer and instructor Robert C. Martin, first introduced in his 2000 paper Design Principles and Design Patterns discussing software rot.: 2–3 The SOLID ideas are

The Single-responsibility principle: "There should never be more than one reason for a class to change." In other words, every class should have only one responsibility.
The Open–closed principle: "Software entities ... should be open for extension, but closed for modification."
The Liskov substitution principle: "Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it." See also design by contract.
The Interface segregation principle: "Clients should not be forced to depend upon interfaces that they do not use."
The Dependency inversion principle: "Depend upon abstractions, [not] concretions."The SOLID acronym was introduced later, around 2004, by Michael Feathers.Although the SOLID principles apply to any object-oriented design, they can also form a core philosophy for methodologies such as agile development or adaptive software development.

See also
Code reuse
GRASP (object-oriented design)
Inheritance (object-oriented programming)
List of software development philosophies
Passage 4:
Form I-9
Form I-9, officially the Employment Eligibility Verification, is a United States Citizenship and Immigration Services form. Mandated by the Immigration Reform and Control Act of 1986, it is used to verify the identity and legal authorization to work of all paid employees in the United States. All U.S. employers must ensure proper completion of Form I-9 for each individual they hire for employment in the United States.

Requirements
The Immigration Reform and Control Act of 1986 (IRCA) required employers to verify that all newly hired employees presented facially valid documentation verifying the employee's identity and legal authorization to accept employment in the United States. The I-9 form, or more properly the Employment Eligibility Verification Form, is provided by the federal government for that purpose.Every employee hired after November 6, 1986 must complete an I-9 form at the time of hire. Employees must complete Section 1 of the form upon commencing employment. The employer must complete Section 2 within three days of the employee's starting date at work. The employer is responsible for ensuring that the forms are completed properly and in a timely manner. 
The I-9 is not required for unpaid volunteers or for contractors. However, a company could still find itself liable if it contracts work to a contractor it knows either is or employs unauthorized workers.Multiple versions of Form I-9, Employment Eligibility Verification, have been issued since the form was first introduced in 1987; not all versions are valid for use. Currently, only forms showing the following revision date are valid: "Rev. 07/17/2017 N*".If an employee cannot read or cannot write in English, a translator or preparer may complete the form and sign it on behalf of the employee. The form also requires the employee's own signature.
In October 2004, new legislation made it possible to complete the I-9 electronically.

Prerequisites for employees
In completing form I-9, prospective employees attest, under penalty of perjury, that they are in one of the following categories:

A U.S. citizen,
A U.S. non-citizen national,
A lawful permanent resident or
An alien authorized to work.

Documentation for proof of identity or employment authorization
With the form, prospective employees must provide documents that prove their eligibility to work. A variety of documents are acceptable. The prospective employee must provide either:

One document that establishes both identity and employment eligibility (on List A on the I-9)
One document that establishes identity (on List B) together with another document that establishes employment eligibility (on List C).All documents must be unexpired

List A
Documents that may be used under "List A" of the I-9 form to establish both identity and employment eligibility include:

An unexpired U.S. Passport,
A U.S. Passport Card,
A Permanent Resident Card (often called a "green card") or Alien Registration Receipt Card with photograph,
An unexpired Temporary Resident Card,
An unexpired foreign passport with an I-551 stamp, or with Form I-94 (For the certain alien who is authorized to work with restrictions. The person should also attach the documents which indicate an unexpired employment authorization.),
An unexpired Employment Authorization Document issued by the United States Department of Homeland Security that includes a photograph (Form I-766) or
An unexpired Employment Authorization Card.

List B
Documents that may be used under "List B" of the I-9 to establish identity include:

Driver's license or identification card issued by a U.S. state or outlying possession of the U.S. provided it contains a photograph or identifying information such as name, date of birth, sex, height, eye color and address;
Federal or state identification card provided it contains a photograph or identifying information such as name, date of birth, sex, height, eye color and address;
School identification card with photograph;
U.S. Armed Services identification card or draft record;
Voter Registration Card;
U.S. Coast Guard Merchant Mariner Card;
Native American tribal document;
Driver's license issued by a Canadian government authority or
Trusted traveler documentation (Global Entry, NEXUS, SENTRI).For individuals under the age of eighteen, the following documents may be used to establish identity:

School record or report card;
Clinic, doctor or hospital record or
Daycare or nursery school record.Employees who supply an item from List B (to establish identity) must also supply an item from List C (to establish employment eligibility).

List C
Documents that may be used under "List C" of the I-9 to establish employment eligibility include:

A U.S. Social Security card issued by the Social Security Administration unless it indicates one of the following:
NOT VALID FOR EMPLOYMENT (generally issued to non-immigrant aliens unauthorized to work)
VALID FOR WORK ONLY WITH INS AUTHORIZATION
VALID FOR WORK ONLY WITH DHS AUTHORIZATION,
A birth certificate issued by the U.S. State Department (Form FS-545 or Form DS-1350),
Original or certified copy of a birth certificate from the U.S. or an outlying possession of the U.S., bearing an official seal,
A Certificate of U.S. Citizenship (Form N-560 or N-561),
A Certificate of Naturalization (Form N-550 or N-570),
Native American tribal document,
U.S. Citizen ID Card (Form I-197),
An ID Card for the use of a Resident Citizen in the United States (Form I-179),
An unexpired employment authorization card issued by the Dept. of Homeland Security (other than those included on List A) or
Consular Report of Birth Abroad (Form FS-240).U.S. citizens who have lost their social security card can apply for a duplicate at the Social Security Administration. 
Employees who supply an item from List C (to establish employment eligibility) must also supply an item from List B (to establish identity).

Reverification
Employers must update or reverify certain ID documents at or prior to their expiration date. This does not apply to already presented and accepted non-expired U.S. Passports or Permanent Resident Cards when they reach their expiration date, nor to any List B documents (e.g., state driver's licenses and state IDs). The USCIS website, in the Employer section, Employer Bulletins, lists the limited requirements and allowed instances for reverification.
For U.S. citizens, I-9s are valid continuously unless a break of more than a year of employment occurs. International employees on F-1 (student), H-1B (specialty occupation), or J-1 (exchange visitor) visas must have their I-9 reverified each time their visa has expired with a new work authorization permit (renewed visa with work authorization, EAD, Permanent Residence Card, etc.).

Retention
Employers must retain a Form I-9 for all current employees. Employers must also retain a Form I-9 for three years after the date of hire, or one year after the date employment ends, whichever is later. Employers must show their employees' I-9 form any time the immigration or labor authority requests it.

Anti-discrimination provisions
The Immigration Reform and Control Act which introduced the requirement leading to the promulgation of the I-9 form also included anti-discrimination provisions. Under the Act, most U.S. citizens, permanent residents, temporary residents, asylees or refugees who are legally allowed to work in the United States cannot be discriminated against on the basis of national origin or citizenship status. This provision applies to employers of three or more workers and covers both hiring and termination decisions. In addition, an employer must accept any valid document or combination of documents specified in the I-9 form as long as the documents appear genuine.For example, an employer could not refuse to hire a candidate because his I-9 revealed that he was a non-citizen (such as a permanent resident or a refugee) rather than a U.S. citizen. For this reason some immigration lawyers advise companies to avoid requiring an I-9 until a candidate is hired rather than risk a lawsuit. As another example, a company could not insist that an employee provide a passport rather than, say, a driver's license and social security card. Another anti-discrimination provision requires that employers must enforce I-9 compliance in a uniform manner. For example, an employer must not require some employees to complete an I-9 before being hired, but allow others to complete the form after starting employment.Employers must not assume that the employee is unauthorized to work just because the individual either could not bring the proof of employment authorization or has brought the unaccepted documents until the start date of the employment. Instead, employers should encourage that employee to bring the acceptable documents which are under the List A, B and C. Employers may terminate the employment only if the employee cannot attest the person's work authorization by bringing the proof after the start date.
The Office of Special Counsel for Immigration-Related Unfair Employment Practices ("OSC") is a section within the Department of Justice's Civil Rights Division that enforces the anti-discrimination provision of the Immigration and Nationality Act ("INA"). The OSC can help workers by calling employers and explaining proper verification practices and, when necessary, by providing victims of discrimination with charge forms. Upon receipt of a charge of discrimination, OSC investigations typically take no longer than seven months. Victims may obtain various types of relief including job relief and back pay.
OSC also has an extensive outreach program. It provides staff to speak at outreach events throughout the country, and has free informational brochures, posters and tapes for distribution.

Types of discrimination
The OSC investigates the following types of discriminatory conduct under the anti-discrimination provision of the Immigration and Nationality Act (INA), 8 U.S.C. § 1324b:

Citizenship or immigration status discrimination
With respect to hiring, firing, recruitment or referral for a fee by employers with four or more employees, employers may not treat individuals differently because they are or are not U.S. citizens or work-authorized individuals. U.S. citizens, recent permanent residents, temporary residents, asylees and refugees are protected from citizenship status discrimination. However, permanent residents who do not apply for naturalization within six months of eligibility are not protected from citizenship status discrimination. Citizenship status discrimination which is otherwise required to comply with law, regulation, executive order or government contract is permissible by law.

National origin discrimination
With respect to hiring, firing, recruitment or referral for a fee by employers with more than three and fewer than fifteen employees, employers may not treat individuals differently because of their place of birth, country of origin, ancestry, native language, accent or because they are perceived as looking or sounding foreign. All U.S. citizens, lawful permanent residents and work authorized individuals are protected from national origin discrimination. The Equal Employment Opportunity Commission has jurisdiction over employers with fifteen or more employees.

Unfair documentary practices
Relating to verifying the employment eligibility of employees, employers may not request more or different documents than are required to verify employment eligibility, reject reasonably genuine-looking documents or specify certain documents over others with the purpose or intent of discriminating on the basis of citizenship status or national origin. U.S. citizens and all work authorized individuals are protected from document abuse.

Retaliation
Individuals who file charges with OSC; who cooperate with an OSC investigation; who contest action that may constitute unfair documentary practices or discrimination based upon citizenship, immigration status, or national origin; or who assert their rights under the INA's anti-discrimination provision are protected from retaliation.

Penalties
The IRCA includes penalties for I-9 noncompliance. Federal law provides for imprisonment or fines for making false statements or using false documents in connection with the completion of the I-9. An employer who hires an unauthorized worker can be fined between $250 and $5,500 per worker. In addition, such an employer can be barred from federal government contracts for a year. An employee who knowingly accepts fraudulent documentation can also be criminally prosecuted under other immigration laws.An employer who fails to keep proper records that I-9s are properly filed can be fined $110 per missing item for each form, up to $1100 per form, even if the employee is legally authorized to work in the United States. Since 2009, Immigration & Customs Enforcement (ICE) has conducted over 7,500 audits and imposed over $80 million in fines. In 2011 alone, ICE conducted 2,740 audits and assessed over $7 million in fines.An individual who knowingly commits or participates in document fraud may be fined between $375 and $3,200 per document for the first offense and between $3,200 and $6,500 per document for subsequent offenses.

See also
Immigration to the United States
E-Verify
Passage 5:
Mach bands
Mach bands is an optical illusion named after the physicist Ernst Mach. It exaggerates the contrast between edges of the slightly differing shades of gray, as soon as they contact one another, by triggering edge-detection in the human visual system.

Explanation
The Mach bands effect is due to the spatial high-boost filtering performed by the human visual system on the luminance channel of the image captured by the retina. Mach reported the effect in 1865, conjecturing that filtering is performed in the retina itself, by lateral inhibition among its neurons.  This conjecture is supported by observations on other (non-visual) senses, as pointed out by von Békésy.  The visual pattern is often found on curved surfaces subject to a particular, naturally-occurring illumination, so the occurrence of filtering can be explained as the result of learnt image statistics.  The effect of filtering can be modeled as a convolution between a trapezoidal function that describes the illumination and one or more bandpass filters.  A tight approximation is obtained by a model employing 9 even-symmetric filters scaled at octave intervals.The effect is independent of the orientation of the boundary.

In radiology
This visual phenomenon is important to keep in mind when evaluating dental radiographs for evidence of decay, in which grayscale images of teeth and bone are analyzed for abnormal variances of density. A false-positive radiological diagnosis of dental caries can easily arise if the practitioner does not take into account the likelihood of this illusion. Mach bands manifest adjacent to metal restorations or appliances and the boundary between enamel and dentin. Mach bands may also result in the misdiagnosis of horizontal root fractures because of the differing radiographic intensities of tooth and bone.Mach effect can also lead to an erroneous diagnosis of pneumothorax by creating a dark line at the lung periphery (whereas a true pneumothorax will have a white pleural line).

In computer graphics
Mach bands can also appear when there is a discontinuity in the derivative of a gradient, a visual effect common when intensities are linearly interpolated such as in Gouraud shading.
Computer image processing systems use edge-detection in a way analogous to the brain, using unsharp masking to clarify edges in photos for example.

See also
Acutance
Cornsweet illusion
Hermann grid illusion
Lateral inhibition
Optical illusions
Watercolour illusion
Gibbs phenomenon
Passage 6:
Sound barrier
The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first approached the speed of sound, these effects were seen as constituting a barrier, making faster speeds very difficult or impossible. The term sound barrier is still sometimes used today to refer to aircraft approaching supersonic flight in this high drag regime. Flying faster than sound produces a sonic boom.
In dry air at 20 °C (68 °F), the speed of sound is 343 metres per second (about 767 mph, 1234 km/h or 1,125 ft/s). The term came into use during World War II when pilots of high-speed fighter aircraft experienced the effects of compressibility, a number of adverse aerodynamic effects that deterred further acceleration, seemingly impeding flight at speeds close to the speed of sound. These difficulties represented a barrier to flying at faster speeds. In 1947, American test pilot Chuck Yeager demonstrated that safe flight at the speed of sound was achievable in purpose-designed aircraft, thereby breaking the barrier. By the 1950s, new designs of fighter aircraft routinely reached the speed of sound, and faster.

History
Some common whips such as the bullwhip or stockwhip are able to move faster than sound: the tip of the whip exceeds this speed and causes a sharp crack—literally a sonic boom. Firearms made after the 19th century generally have a supersonic muzzle velocity.The sound barrier may have been first breached by living beings about 150 million years ago. Some paleobiologists report that computer models of their biomechanical capabilities suggest that certain long-tailed dinosaurs such as Brontosaurus, Apatosaurus, and Diplodocus could flick their tails at supersonic speeds, creating a cracking sound. This finding is theoretical and disputed by others in the field. Meteorites in the Earth's upper atmosphere usually travel at higher than Earth's escape velocity, which is much faster than sound.

Early problems
The tip speed of a propeller blade depends on the propeller speed and the forward speed of the aircraft. When the aircraft speed is high enough, the tips reach supersonic speeds. Shock waves form at the blade tips and sap the shaft power driving the propeller. To maintain thrust, the engine power must replace this loss, and must also match the aircraft drag as it increases with speed. The required power is so great that the size and weight of the engine becomes prohibitive. This speed limitation led to research into jet engines, notably by Frank Whittle in England and Hans von Ohain in Germany. The jet engine is suitable for two reasons. It produces the required power, in terms of thrust, from a relatively small size compared to the piston engine it replaced. The whirling blades in the front of the jet engine are not adversely affected by high aircraft speeds in the same way as the propeller. 
Nevertheless, propeller aircraft were able to approach their critical Mach number, different for each aircraft, in a dive. Unfortunately, doing so led to numerous crashes for a variety of reasons. Flying the Mitsubishi Zero, pilots sometimes flew at full power into terrain because the rapidly increasing forces acting on the control surfaces of their aircraft overpowered them. In this case, several attempts to fix it only made the problem worse. Likewise, the flexing caused by the low torsional stiffness of the Supermarine Spitfire's wings caused them, in turn, to counteract aileron control inputs, leading to a condition known as control reversal. This was solved in later models with changes to the wing. Worse still, a particularly dangerous interaction of the airflow between the wings and tail surfaces of diving Lockheed P-38 Lightnings made "pulling out" of dives difficult; however, the problem was later solved by the addition of a "dive flap" that upset the airflow under these circumstances. Flutter due to the formation of shock waves on curved surfaces was another major problem, which led most famously to the breakup of a de Havilland Swallow and death of its pilot Geoffrey de Havilland, Jr. on 27 September 1946. A similar problem is thought to have been the cause of the 1943 crash of the BI-1 rocket aircraft in the Soviet Union.
All of these effects, although unrelated in most ways, led to the concept of a "barrier" making it difficult for an aircraft to exceed the speed of sound. Erroneous news reports caused most people to envision the sound barrier as a physical "wall", which supersonic aircraft needed to "break" with a sharp needle nose on the front of the fuselage. Rocketry and artillery experts' products routinely exceeded Mach 1, but aircraft designers and aerodynamicists during and after World War II discussed Mach 0.7 as a limit dangerous to exceed.

Early claims
During WWII and immediately thereafter, a number of claims were made that the sound barrier had been broken in a dive. The majority of these purported events can be dismissed as instrumentation errors. The typical airspeed indicator (ASI) uses air pressure differences between two or more points on the aircraft, typically near the nose and at the side of the fuselage, to produce a speed figure. At high speed, the various compression effects that lead to the sound barrier also cause the ASI to go non-linear and produce inaccurately high or low readings, depending on the specifics of the installation. This effect became known as "Mach jump". Before the introduction of Mach meters, accurate measurements of supersonic speeds could only be made remotely, normally using ground-based instruments. Many claims of supersonic speeds were found to be far below this speed when measured in this fashion.
In 1942, Republic Aviation issued a press release stating that Lts. Harold E. Comstock and Roger Dyar had exceeded the speed of sound during test dives in a Republic P-47 Thunderbolt. It is widely agreed that this was due to inaccurate ASI readings. In similar tests, the North American P-51 Mustang demonstrated limits at Mach 0.85, with every flight over Mach 0.84 causing the aircraft to be damaged by vibration.

One of the highest recorded instrumented Mach numbers attained for a propeller aircraft is the Mach 0.891 for a Spitfire PR XI, flown during dive tests at the Royal Aircraft Establishment, Farnborough in April 1944. The Spitfire, a photo-reconnaissance variant, the Mark XI, fitted with an extended "rake type" multiple pitot system, was flown by Squadron Leader J. R. Tobin to this speed, corresponding to a corrected true airspeed (TAS) of 606 mph. In a subsequent flight, Squadron Leader Anthony Martindale achieved Mach 0.92, but it ended in a forced landing after over-revving damaged the engine.Hans Guido Mutke claimed to have broken the sound barrier on 9 April 1945 in the Messerschmitt Me 262 jet aircraft. He states that his ASI pegged itself at 1,100 kilometres per hour (680 mph). Mutke reported not just transonic buffeting, but the resumption of normal control once a certain speed was exceeded, then a resumption of severe buffeting once the Me 262 slowed again. He also reported engine flame-out.This claim is widely disputed, even by pilots in his unit. All of the effects he reported are known to occur on the Me 262 at much lower speeds, and the ASI reading is simply not reliable in the transonic. Further, a series of tests made by Karl Doetsch at the behest of Willy Messerschmitt found that the plane became uncontrollable above Mach 0.86, and at Mach 0.9 would nose over into a dive that could not be recovered from. Post-war tests by the RAF confirmed these results, with the slight modification that the maximum speed using new instruments was found to be Mach 0.84, rather than Mach 0.86.In 1999, Mutke enlisted the help of Professor Otto Wagner of the Munich Technical University to run computational tests to determine whether the aircraft could break the sound barrier. These tests do not rule out the possibility, but are lacking accurate data on the coefficient of drag that would be needed to make accurate simulations. Wagner stated: "I don't want to exclude the possibility, but I can imagine he may also have been just below the speed of sound and felt the buffeting, but did not go above Mach-1."One bit of evidence presented by Mutke is on page 13 of the "Me 262 A-1 Pilot's Handbook" issued by Headquarters Air Materiel Command, Wright Field, Dayton, Ohio as Report No. F-SU-1111-ND on January 10, 1946:

Speeds of 950 km/h (590 mph) are reported to have been attained in a shallow dive 20° to 30° from the horizontal. No vertical dives were made. At speeds of 950 to 1,000 km/h (590 to 620 mph) the air flow around the aircraft reaches the speed of sound, and it is reported that the control surfaces no longer affect the direction of flight. The results vary with different airplanes: some wing over and dive while others dive gradually. It is also reported that once the speed of sound is exceeded, this condition disappears and normal control is restored.
The comments about restoration of flight control and cessation of buffeting above Mach 1 are very significant in a 1946 document. However, it is not clear where these terms came from, as it does not appear the US pilots carried out such tests.In his 1990 book Me-163, former Messerschmitt Me 163 "Komet" pilot Mano Ziegler claims that his friend, test pilot Heini Dittmar, broke the sound barrier while diving the rocket plane, and that several people on the ground heard the sonic booms. He claims that on 6 July 1944, Dittmar, flying Me 163B V18, bearing the Stammkennzeichen alphabetic code VA+SP, was measured traveling at a speed of 1,130 km/h (702 mph). However, no evidence of such a flight exists in any of the materials from that period, which were captured by Allied forces and extensively studied. Dittmar had been officially recorded at 1,004.5 km/h (623.8 mph) in level flight on 2 October 1941 in the prototype Me 163A V4. He reached this speed at less than full throttle, as he was concerned by the transonic buffeting. Dittmar himself does not make a claim that he broke the sound barrier on that flight and notes that the speed was recorded only on the AIS. He does, however, take credit for being the first pilot to "knock on the sound barrier".The Luftwaffe test pilot Lothar Sieber (7 April 1922 – 1 March 1945) may have inadvertently become the first human to break the sound barrier on 1 March 1945. This occurred while he was piloting a Bachem Ba 349 "Natter" for the first crewed vertical takeoff of a rocket in history. In 55 seconds, he traveled a total of 14 km (8.7 miles). The aircraft crashed, and he perished violently in this endeavor.There are a number of unmanned vehicles that flew at supersonic speeds during this period. In 1933, Soviet designers working on ramjet concepts fired phosphorus-powered engines out of artillery guns to get them to operational speeds. It is possible that this produced supersonic performance as high as Mach 2, but this was not due solely to the engine itself. In contrast, the German V-2 ballistic missile routinely broke the sound barrier in flight, for the first time on 3 October 1942. By September 1944, V-2s routinely achieved Mach 4 (1,200 m/s, or 3044 mph) during terminal descent.

Breaking the sound barrier
In 1942, the United Kingdom's Ministry of Aviation began a top-secret project with Miles Aircraft to develop the world's first aircraft capable of breaking the sound barrier. The project resulted in the development of the prototype Miles M.52 turbojet-powered aircraft, which was designed to reach 1,000 mph (417 m/s; 1,600 km/h) (over twice the existing speed record) in level flight, and to climb to an altitude of 36,000 ft (11 km) in 1 minute 30 seconds.
A huge number of advanced features were incorporated into the resulting M.52 design, many of which hint at a detailed knowledge of supersonic aerodynamics. In particular, the design featured a conical nose and sharp wing leading edges, as it was known that round-nosed projectiles could not be stabilised at supersonic speeds. The design used very thin wings of biconvex section proposed by Jakob Ackeret for low drag. The wing tips were "clipped" to keep them clear of the conical shock wave generated by the nose of the aircraft. The fuselage had the minimum cross-section allowable around the centrifugal engine with fuel tanks in a saddle over the top.

Another critical addition was the use of a power-operated stabilator, also known as the all-moving tail or flying tail, a key to supersonic flight control, which contrasted with traditional hinged tailplanes (horizontal stabilizers) connected mechanically to the pilots control column. Conventional control surfaces became ineffective at the high subsonic speeds then being achieved by fighters in dives, due to the aerodynamic forces caused by the formation of shockwaves at the hinge and the rearward movement of the centre of pressure, which together could override the control forces that could be applied mechanically by the pilot, hindering recovery from the dive. A major impediment to early transonic flight was control reversal, the phenomenon which caused flight inputs (stick, rudder) to switch direction at high speed; it was the cause of many accidents and near-accidents. An all-flying tail is considered to be a minimum condition of enabling aircraft to break the transonic barrier safely, without losing pilot control. The Miles M.52 was the first instance of this solution, which has since been universally applied.
Initially, the aircraft was to use Frank Whittle's latest engine, the Power Jets W.2/700, which would only reach supersonic speed in a shallow dive. To develop a fully supersonic version of the aircraft, an innovation incorporated was a reheat jetpipe – also known as an afterburner. Extra fuel was to be burned in the tailpipe to avoid overheating the turbine blades, making use of unused oxygen in the exhaust. Finally, the design included another critical element –  the use of a shock cone in the nose to slow the incoming air to the subsonic speeds needed by the engine.
Although the project was eventually cancelled, the research was used to construct an unmanned missile that went on to achieve a speed of Mach 1.38 in a successful, controlled transonic and supersonic level test flight; this was a unique achievement at that time, which validated the aerodynamics of the M.52.
Meanwhile, test pilots achieved high velocities in the tailless, swept-wing de Havilland DH 108. One of them was Geoffrey de Havilland, Jr., who was killed on 27 September 1946 when his DH 108 broke up at about Mach 0.9. John Derry has been called "Britain's first supersonic pilot" because of a dive he made in a DH 108 on 6 September 1948.

The first aircraft to officially break the sound barrier
The British Air Ministry signed an agreement with the United States to exchange all its high-speed research, data and designs and Bell Aircraft company was given access to the drawings and research on the M.52, but the U.S. reneged on the agreement, and no data was forthcoming in return. Bell's supersonic design was still using a conventional tail, and they were battling the problem of control.

They utilized the information to initiate work on the Bell X-1. The final version of the Bell X-1 was very similar in design to the original Miles M.52 version. Also featuring the all-moving tail, the XS-1 was later known as the X-1. It was in the X-1 that Chuck Yeager was credited with being the first person to break the sound barrier in level flight on 14 October 1947, flying at an altitude of 45,000 ft (13.7 km). George Welch made a plausible but officially unverified claim to have broken the sound barrier on 1 October 1947, while flying an XP-86 Sabre. He also claimed to have repeated his supersonic flight on 14 October 1947, 30 minutes before Yeager broke the sound barrier in the Bell X-1. Although evidence from witnesses and instruments strongly imply that Welch achieved supersonic speed, the flights were not properly monitored and are not officially recognized. The XP-86 officially achieved supersonic speed on 26 April 1948.On 14 October 1947, just under a month after the United States Air Force had been created as a separate service, the tests culminated in the first crewed supersonic flight, piloted by Air Force Captain Charles "Chuck" Yeager in aircraft #46-062, which he had christened Glamorous Glennis. The rocket-powered aircraft was launched from the bomb bay of a specially modified B-29 and glided to a landing on a runway. XS-1 flight number 50 is the first one where the X-1 recorded supersonic flight, with a maximum speed of Mach 1.06 (361 m/s, 1,299 km/h, 807.2 mph).
As a result of the X-1's initial supersonic flight, the National Aeronautics Association voted its 1947 Collier Trophy to be shared by the three main participants in the program. Honored at the White House by President Harry S. Truman were Larry Bell for Bell Aircraft, Captain Yeager for piloting the flights, and John Stack for the NACA contributions.Jackie Cochran was the first woman to break the sound barrier, which she did on 18 May 1953, piloting a plane borrowed from the Royal Canadian Air Force, with Yeager accompanying her.On December 3, 1957, Margaret Chase Smith became the first woman in Congress to break the sound barrier, which she did as a passenger in an F-100 Super Sabre piloted by Air Force Major Clyde Good.In the late 1950s, Allen Rowley, a British journalist, was able to fly in a Super Sabre at 1000mph one of the few non-American civilians to exceed the speed of sound and one of the few civilians anywhere to make such a trip.On 21 August 1961, a Douglas DC-8-43 (registration N9604Z) unofficially exceeded Mach 1 in a controlled dive during a test flight at Edwards Air Force Base, as observed and reported by the flight crew; the crew were William Magruder (pilot), Paul Patten (co-pilot), Joseph Tomich (flight engineer), and Richard H. Edwards (flight test engineer). This was the first supersonic flight by a civilian airliner, achieved before the Concorde or the Tu-144 flew.

The sound barrier understood
As the science of high-speed flight became more widely understood, a number of changes led to the eventual understanding that the "sound barrier" is easily penetrated, with the right conditions. Among these changes were the introduction of thin swept wings, the area rule, and engines of ever-increasing performance. By the 1950s, many combat aircraft could routinely break the sound barrier in level flight, although they often suffered from control problems when doing so, such as Mach tuck. Modern aircraft can transit the "barrier" without control problems.By the late 1950s, the issue was so well understood that many companies started investing in the development of supersonic airliners, or SSTs, believing that to be the next "natural" step in airliner evolution. However, this has not yet happened. Although the Concorde and the Tupolev Tu-144 entered service in the 1970s, both were later retired without being replaced by similar designs. The last flight of a Concorde in service was in 2003.
Although Concorde and the Tu-144 were the first aircraft to carry commercial passengers at supersonic speeds, they were not the first or only commercial airliners to break the sound barrier. On 21 August 1961, a Douglas DC-8 broke the sound barrier at Mach 1.012, or 1,240 km/h (776.2 mph), while in a controlled dive through 41,088 feet (12,510 m). The purpose of the flight was to collect data on a new design of leading edge for the wing.

Breaking the sound barrier in a land vehicle
On 12 January 1948, a Northrop unmanned rocket sled became the first land vehicle to break the sound barrier. At a military test facility at Muroc Air Force Base (now Edwards AFB), California, it reached a peak speed of 1,019 mph (1,640 km/h) before jumping the rails.On 15 October 1997, in a vehicle designed and built by a team led by Richard Noble, Royal Air Force pilot Andy Green became the first person to break the sound barrier in a land vehicle in compliance with Fédération Internationale de l'Automobile rules. The vehicle, called the ThrustSSC ("Super Sonic Car"), captured the record 50 years and one day after Yeager's first supersonic flight.

Breaking the sound barrier as a human projectile
Felix Baumgartner
In October 2012 Felix Baumgartner, with a team of scientists and sponsor Red Bull, attempted the highest sky-dive on record. The project would see Baumgartner attempt to jump 120,000 ft (36,580 m) from a helium balloon and become the first parachutist to break the sound barrier. The launch was scheduled for 9 October 2012, but was aborted due to adverse weather; subsequently the capsule was launched instead on 14 October. Baumgartner's feat also marked the 65th anniversary of U.S. test pilot Chuck Yeager's successful attempt to break the sound barrier in an aircraft.Baumgartner landed in eastern New Mexico after jumping from a world record 128,100 feet (39,045 m), or 24.26 miles, and broke the sound barrier as he traveled at speeds up to 833.9 mph (1342 km/h, or Mach 1.26). In the press conference after his jump, it was announced that he was in freefall for 4 minutes 18 seconds, the second longest freefall after the 1960 jump of Joseph Kittinger for 4 minutes 36 seconds.

Alan Eustace
In October 2014, Alan Eustace, a senior vice president at Google, broke Baumgartner's record for highest sky-dive and also broke the sound barrier in the process. However, because Eustace's jump involved a drogue parachute, while Baumgartner's did not, their vertical speed and free-fall distance records remain in different categories.

Legacy
David Lean directed The Sound Barrier, a fictionalized retelling of the de Havilland DH 108 test flights.

See also
Sonic boom
Vapor cone
Passage 7:
Global Alliance in Management Education
CEMS - The Global Alliance in Management Education or CEMS (formerly the Community of European Management Schools and International Companies) is a cooperation of leading business schools and universities with multinational companies and NGOs. The CEMS Global Alliance includes 34 academic institutions on every continent, nearly 70 corporate partners and eight social partners (NGOs) from around the globe. CEMS administers the delivery of the CEMS MIM degree in its member schools, supports the CEMS Alumni Association (CAA) and facilitates general cooperation among its members.

CEMS MIM
CEMS Master in International Management (CEMS MIM) is a one-year degree program for a select group of students at the member institutions,  taught jointly by CEMS business schools and universities. Created in 1988 by founding members from the University of Cologne, HEC Paris, ESADE and the Bocconi University, it was the first supra-national MSc. The aim of CEMS is to develop knowledge and provide education that is essential in the multilingual, multicultural and interconnected business world.The MIM Programme consists of three terms: two academic terms and one internship term. The two academic terms must be consecutive, while the internship term can take place at any time during the graduate period of studies. Students must spend at least two out of the three terms abroad. In addition to completing one's home degree, graduation from CEMS also requires completion of a business project, skill seminars, an international internship, and two foreign language exams.
Each CEMS academic member has a limited number of places available. In many cases, schools have prerequisites to be admitted into the selection process, including a high-grade average and proof of language skills. The selection process typically requires the student to already be enrolled or selected for a Master of Business degree with a member university before applying for the CEMS MIM. CEMS graduates receive a degree from their home institution as well as from CEMS.

Global ranking
The CEMS MIM has consistently ranked among the top 10 in the Masters in Management Ranking since 2005 by the Financial Times.

Academic members
Schools offering the CEMS Master's in International Management (CEMS MIM):

Corporate partners
Nearly 70 corporate partners contribute financially on an annual basis and provide the programme with human resources and input into the curriculum itself in each country they are based. They chart skills courses, give lectures or invite CEMS students to company activities where students learn about corporate practices or solve cases. These connections are very useful to promote the company to the students, while the students gain insight into real-world problems and solution approaches.
Students are advised to be responsible and arrange by themselves an internship partner which will accept the student intern for at least ten consecutive weeks. There are student visa requirements that each student takes responsibility to abide by, and the regulation varies by each local government.

Social partners
The first CEMS social partners joined the organisation in December 2010. These are the first in a series of non-profits and NGOs that contribute to the alliance in a way identical to corporate partners (selection and admission of students, governance, curriculum delivery, proposal of internships and employment opportunities). This new initiative is part of a major sustainability drive from within CEMS. In the same vein, CEMS has also signed the PRME (Principles for Responsible Management Education) declaration.

Alumni association
The CEMS Alumni Association (CAA), founded in 1993 by CEMS graduates, is an international network of CEMS graduates throughout the world. To date, there are nearly 16,000 CEMS alumni. The Graduation Ceremony takes place each year during the CEMS Annual Events (usually at the end of November) which is hosted by one of the CEMS member schools.The CAA is led by an alumni board and is present in many countries through local committees of CEMS alumni. The local committees are responsible for keeping in contact with CEMS alumni and organizing professional and social activities. They meet regularly to discuss the activities and development of the association. The alumni board comprises the CAA President, the CEMS Executive Director, a representative of the CEMS Student Board, a representative of CEMS member schools, three local committee representatives, two senior alumni and two junior alumni. It proposes and develops initiatives to foster career and personal development opportunities for its alumni members and represents alumni interests on the CEMS Executive Board.
While students stay at partner universities, there are support groups called CEMS clubs through which CEMS students share their identities. The extended network of CEMS students spans schools across the world.

Footnotes
Notes
Passage 8:
Confederation of Finnish Industries
The Confederation of Finnish Industries (EK, Finnish: Elinkeinoelämän Keskusliitto, Swedish: Finlands Näringsliv) is the largest employers' association in Finland. It was formed at the beginning of 2005 when the two employers' associations Palvelutyönantajat (Employers of the Service Sector) and Teollisuuden ja Työnantajain Keskusliitto (Union of Industries and Employers) merged. EK's member companies collectively contribute over 70% of Finland's GDP, and over 95% of Finland's exports. It has considerable negotiating power, since Finland has universal validity of collective labour agreements, and often a national income policy agreement is reached.
EK focuses its activity on the following goals:

A business environment which stimulates growth and success for companies
Securing the competitiveness of Finnish work
Ways to benefit from the opportunities offered by globalisation
Economic policies promoting competitiveness
Efficient member servicesThe organisation consists of:

43 branch associations
About 15,000 member companies, 96% of which are small and medium enterprises (SMEs)
About 900,000 employees

External links
The Confederation of Finnish Industries  Official site
Passage 9:
Mach's principle
In theoretical physics, particularly in discussions of gravitation theories,  Mach's principle (or Mach's conjecture) is the name given by Einstein to an imprecise hypothesis often credited to the physicist and philosopher Ernst Mach. The hypothesis attempted to explain how rotating objects, such as gyroscopes and spinning celestial bodies, maintain a frame of reference. 
The proposition is that the existence of absolute rotation (the distinction of local inertial frames vs. rotating reference frames) is determined by the large-scale distribution of matter, as exemplified by this anecdote:

You are standing in a field looking at the stars. Your arms are resting freely at your side, and you see that the distant stars are not moving. Now start spinning. The stars are whirling around you and your arms are pulled away from your body. Why should your arms be pulled away when the stars are whirling? Why should they be dangling freely when the stars don't move?

Mach's principle says that this is not a coincidence—that there is a physical law that relates the motion of the distant stars to the local inertial frame. If you see all the stars whirling around you, Mach suggests that there is some physical law which would make it so you would feel a centrifugal force. There are a number of rival formulations of the principle, often stated in vague ways like "mass out there influences inertia here". A very general statement of Mach's principle is "local physical laws are determined by the large-scale structure of the universe".Mach's concept was a guiding factor in Einstein's development of the general theory of relativity. Einstein realized that the overall distribution of matter would determine the metric tensor which indicates which frame is stationary with respect to rotation. Frame-dragging and conservation of gravitational angular momentum makes this into a true statement in the general theory in certain solutions. But because the principle is so vague, many distinct statements have been made which would qualify as a Mach principle, and some of which are false. The Gödel rotating universe is a solution of the field equations that is designed to disobey Mach's principle in the worst possible way. In this example, the distant stars seem to be revolving faster and faster as one moves further away. This example does not completely settle the question of the physical relevance of the principle because it has closed timelike curves.

History
Mach put forth the idea in his book The Science of Mechanics (1883 in German, 1893 in English). Before Mach's time, the basic idea also appears in the writings of George Berkeley. After Mach, the book Absolute or Relative Motion? (1896) by Benedict Friedlaender and his brother Immanuel contained ideas similar to Mach's principle.

Einstein's use of the principle
There is a fundamental issue in relativity theory: if all motion is relative, how can we measure the inertia of a body? We must measure the inertia with respect to something else. But what if we imagine a particle completely on its own in the universe? We might hope to still have some notion of its state of motion. Mach's principle is sometimes interpreted as the statement that such a particle's state of motion has no meaning in that case.
In Mach's words, the principle is embodied as follows:
[The] investigator must feel the need of... knowledge of the immediate connections, say, of the masses of the universe. There will hover before him as an ideal insight into the principles of the whole matter, from which accelerated and inertial motions will result in the same way.
Albert Einstein seemed to view Mach's principle as something along the lines of:
...inertia originates in a kind of interaction between bodies...
In this sense, at least some of Mach's principles are related to philosophical holism. Mach's suggestion can be taken as the injunction that gravitation theories should be relational theories. Einstein brought the principle into mainstream physics while working on general relativity. Indeed, it was Einstein who first coined the phrase Mach's principle. There is much debate as to whether Mach really intended to suggest a new physical law since he never states it explicitly.
The writing in which Einstein found inspiration was Mach's book The Science of Mechanics (1883, tr. 1893), where the philosopher criticized Newton's idea of absolute space, in particular the argument that Newton gave sustaining the existence of an advantaged reference system: what is commonly called "Newton's bucket argument".
In his Philosophiae Naturalis Principia Mathematica, Newton tried to demonstrate that one can always decide if one is rotating with respect to the absolute space, measuring the apparent forces that arise only when an absolute rotation is performed. If a bucket is filled with water, and made to rotate, initially the water remains still, but then, gradually, the walls of the vessel communicate their motion to the water, making it curve and climb up the borders of the bucket, because of the centrifugal forces produced by the rotation. This experiment demonstrates that the centrifugal forces arise only when the water is in rotation with respect to the absolute space (represented here by the earth's reference frame, or better, the distant stars) instead, when the bucket was rotating with respect to the water no centrifugal forces were produced, this indicating that the latter was still with respect to the absolute space.
Mach, in his book, says that the bucket experiment only demonstrates that when the water is in rotation with respect to the bucket no centrifugal forces are produced, and that we cannot know how the water would behave if in the experiment the bucket's walls were increased in depth and width until they became leagues big. In Mach's idea this concept of absolute motion should be substituted with a total relativism in which every motion, uniform or accelerated, has sense only in reference to other bodies (i.e., one cannot simply say that the water is rotating, but must specify if it's rotating with respect to the vessel or to the earth). In this view, the apparent forces that seem to permit discrimination between relative and "absolute" motions should only be considered as an effect of the particular asymmetry that there is in our reference system between the bodies which we consider in motion, that are small (like buckets), and the bodies that we believe are still (the earth and distant stars), that are overwhelmingly bigger and heavier than the former.
This same thought had been expressed by the philosopher George Berkeley in his De Motu. It is then not clear, in the passages from Mach just mentioned, if the philosopher intended to formulate a new kind of physical action between heavy bodies. This physical mechanism should determine the inertia of bodies, in a way that the heavy and distant bodies of our universe should contribute the most to the inertial forces. More likely, Mach only suggested a mere "redescription of motion in space as experiences that do not invoke the term space".  What is certain is that Einstein interpreted Mach's passage in the former way, originating a long-lasting debate.
Most physicists believe Mach's principle was never developed into a quantitative physical theory that would explain a mechanism by which the stars can have such an effect. Mach himself never made his principle exactly clear.: 9–57  Although Einstein was intrigued and inspired by Mach's principle, Einstein's formulation of the principle is not a fundamental assumption of general relativity, although the principle of equivalence of gravitational and inertial mass is most certainly fundamental.

Mach's principle in general relativity
Because intuitive notions of distance and time no longer apply, what exactly is meant by "Mach's principle" in general relativity is even less clear than in Newtonian physics and at least 21 formulations of Mach's principle are possible, some being considered more strongly Machian than others.: 530   A relatively weak formulation is the assertion that the motion of matter in one place should affect which frames are inertial in another.
Einstein, before completing his development of the general theory of relativity, found an effect which he interpreted as being evidence of Mach's principle.  We assume a fixed background for conceptual simplicity, construct a large spherical shell of mass, and set it spinning in that background.  The reference frame in the interior of this shell will precess with respect to the fixed background.  This effect is known as the Lense–Thirring effect.  Einstein was so satisfied with this manifestation of Mach's principle that he wrote a letter to Mach expressing this:

it... turns out that inertia originates in a kind of interaction between bodies, quite in the sense of your considerations on Newton's pail experiment...  If one rotates [a heavy shell of matter] relative to the fixed stars about an axis going through its center, a Coriolis force arises in the interior of the shell; that is, the plane of a Foucault pendulum is dragged around (with a practically unmeasurably small angular velocity).
The Lense–Thirring effect certainly satisfies the very basic and broad notion that "matter there influences inertia here".  The plane of the pendulum would not be dragged around if the shell of matter were not present, or if it were not spinning.  As for the statement that "inertia originates in a kind of interaction between bodies", this, too, could be interpreted as true in the context of the effect.
More fundamental to the problem, however, is the very existence of a fixed background, which Einstein describes as "the fixed stars".  Modern relativists see the imprints of Mach's principle in the initial-value problem.  Essentially, we humans seem to wish to separate spacetime into slices of constant time.  When we do this, Einstein's equations can be decomposed into one set of equations, which must be satisfied on each slice, and another set, which describe how to move between slices.  The equations for an individual slice are elliptic partial differential equations.  In general, this means that only part of the geometry of the slice can be given by the scientist, while the geometry everywhere else will then be dictated by Einstein's equations on the slice.In the context of an asymptotically flat spacetime, the boundary conditions are given at infinity.  Heuristically, the boundary conditions for an asymptotically flat universe define a frame with respect to which inertia has meaning.  By performing a Lorentz transformation on the distant universe, of course, this inertia can also be transformed.
A stronger form of Mach's principle applies in Wheeler–Mach–Einstein spacetimes, which require spacetime to be spatially compact and globally hyperbolic.  In such universes Mach's principle can be stated as the distribution of matter and field energy-momentum (and possibly other information) at a particular moment in the universe determines the inertial frame at each point in the universe (where "a particular moment in the universe" refers to a chosen Cauchy surface).: 188–207 There have been other attempts to formulate a theory that is more fully Machian, such as the Brans–Dicke theory and the Hoyle–Narlikar theory of gravity, but most physicists argue that none have been fully successful. At an exit poll of experts, held in Tübingen in 1993, when asked the question "Is general relativity perfectly Machian?", 3 respondents replied "yes", and 22 replied "no".  To the question "Is general relativity with appropriate boundary conditions of closure of some kind very Machian?" the result was 14 "yes" and 7 "no".: 106 However, Einstein was convinced that a valid theory of gravity would necessarily have to include the relativity of inertia:

So strongly did Einstein believe at that time in the relativity of inertia that in 1918 he stated as being on an equal footing three principles on which a satisfactory theory of gravitation should rest:
The principle of relativity as expressed by general covariance.
The principle of equivalence.
Mach's principle (the first time this term entered the literature): … that the gµν are completely determined by the mass of bodies, more generally by Tµν.In 1922, Einstein noted that others were satisfied to proceed without this [third] criterion and added, 
"This contentedness will appear incomprehensible to a later generation however."

It must be said that, as far as I can see, to this day, Mach's principle has not brought physics decisively farther. It must also be said that the origin of inertia is and remains the most obscure subject in the theory of particles and fields. Mach's principle may therefore have a future – but not without the quantum theory.

Inertial induction
In 1953, in order to express Mach's Principle in quantitative terms, the Cambridge University physicist Dennis W. Sciama proposed the addition of an acceleration dependent term to the Newtonian gravitation equation. Sciama's acceleration dependent term was 
  
    
      
        F
        =
        G
        
          
            
              
                m
                
                  A
                
              
              
                m
                
                  B
                
              
              
                
                  a
                
              
            
            
              r
              
                c
                
                  2
                
              
            
          
        
         
      
    
    {\textstyle F=G{\frac {m_{A}m_{B}{\bf {a}}}{rc^{2}}}\ }
   where r is the distance between the particles, G is the gravitational constant, a is the relative acceleration and c represents the speed of light in vacuum. Sciama referred to the effect of the acceleration dependent term as Inertial Induction.

Variations in the statement of the principle
The broad notion that "mass there influences inertia here" has been expressed in several forms.
Hermann Bondi and Joseph Samuel have listed eleven distinct statements that can be called Mach principles, labelled Mach0 through Mach10.  Though their list is not necessarily exhaustive, it does give a flavor for the variety possible.

Mach0: The universe, as represented by the average motion of distant galaxies, does not appear to rotate relative to local inertial frames.
Mach1: Newton's gravitational constant G is a dynamical field.
Mach2: An isolated body in otherwise empty space has no inertia.
Mach3: Local inertial frames are affected by the cosmic motion and distribution of matter.
Mach4: The universe is spatially closed.
Mach5: The total energy, angular and linear momentum of the universe are zero.
Mach6: Inertial mass is affected by the global distribution of matter.
Mach7: If you take away all matter, there is no more space.
Mach8: 
  
    
      
        Ω
         
        
          
            
              
                =
              
              
                def
              
            
          
        
         
        4
        π
        ρ
        G
        
          T
          
            2
          
        
      
    
    {\displaystyle \Omega \ {\stackrel {\text{def}}{=}}\ 4\pi \rho GT^{2}}
   is a definite number, of order unity, where 
  
    ρ
    \rho
   is the mean density of matter in the universe, and 
  
    T
    T
   is the Hubble time.
Mach9: The theory contains no absolute elements.
Mach10: Overall rigid rotations and translations of a system are unobservable.

See also

Answer the question based on the given passages. Only give me the answer and do not output any other words.

Question: Who is the employer of the person Mach's principle was named after?



Answer: Charles University