Sunburn

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Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, commonly from the sun. Common symptoms in humans and other animals include red or reddish skin that is hot to the touch, pain, general fatigue, and mild dizziness. An excess of UV radiation can be life-threatening in extreme cases. Excessive UV radiation is the leading cause of primarily non-malignant skin tumors.

Sunburn is an inflammatory response in the skin triggered by direct DNA damage by UV radiation. When the skin cells' DNA is overly damaged by UV radiation, type I cell-death is triggered and the skin is replaced.

Sun protective measures including sunscreen and sun protective clothing is widely accepted to prevent sunburn and some types of skin cancer. Special populations including children are especially susceptible to sunburn and protective measures should be used.

Video Sunburn

Signs and symptoms

Typically, there is initial redness (erythema), followed by varying degrees of pain, proportional in severity to both the duration and intensity of exposure.

Other symptoms can include blistering, swelling (edema), pruritus (itching), peeling skin, rash, nausea, fever, chills, and fainting (syncope). Also, a small amount of heat is given off from the burn, caused by the concentration of blood in the healing process, giving a warm feeling to the affected area. Sunburns may be classified as superficial, or partial thickness burns. Blistering is a sign of second degree sunburn.

Variations

Minor sunburns typically cause nothing more than slight redness and tenderness to the affected areas. In more serious cases, blistering can occur. Extreme sunburns can be painful to the point of debilitation and may require hospital care.

Duration

Sunburn can occur in less than 15 minutes, and in seconds when exposed to non-shielded welding arcs or other sources of intense ultraviolet light. Nevertheless, the inflicted harm is often not immediately obvious.

After the exposure, skin may turn red in as little as 30 minutes but most often takes 2 to 6 hours. Pain is usually most extreme 6 to 48 hours after exposure. The burn continues to develop for 1 to 3 days, occasionally followed by peeling skin in 3 to 8 days. Some peeling and itching may continue for several weeks.

Skin cancer

Ultraviolet radiation causes sunburns and increases the risk of three types of skin cancer: melanoma, basal-cell carcinoma and squamous-cell carcinoma. Of greatest concern is that the melanoma risk increases in a dose-dependent manner with the number of a person's lifetime cumulative episodes of sunburn. It has been estimated that over 1/3 of melanomas in the United States and Australia could be prevented with regular sunscreen use.

Maps Sunburn

Causes

Biological

Sunburn is caused by UV radiation, either from the sun or from artificial sources, such as tanning lamps, welding arcs, or ultraviolet germicidal irradiation. It is a reaction of the body to direct DNA damage from UVB light. This damage is mainly the formation of a thymine dimer. The damage is recognized by the body, which then triggers several defense mechanisms, including DNA repair to revert the damage, apoptosis and peeling to remove irreparably damaged skin cells, and increased melanin production to prevent future damage. Melanin readily absorbs UV wavelength light, acting as a photoprotectant. By preventing UV photons from disrupting chemical bonds, melanin inhibits both the direct alteration of DNA and the generation of free radicals, thus indirect DNA damage.

Sunburn causes an inflammation process, including production of prostanoids and bradykinin. These chemical compounds increase sensitivity to heat by reducing the threshold of heat receptor (TRPV1) activation from 109 °F (43 °C) to 85 °F (29 °C). The pain may be caused by overproduction of a protein called CXCL5, which activates nerve fibres.

Skin type determines the ease of sunburn. In general, people with lighter skin tone and limited capacity to develop a tan after UV radiation exposure have a greater risk of sunburn. The Fitzpatrick's Skin phototypes classification describes the normal variations of skin responses to UV radiation. Persons with type I skin have the greatest capacity to sunburn and type VI have the least capacity to burn. However, all skin types can develop sunburn.

Fitzpatrick's skin phototypes:

• Type I: Pale white skin, burns easily, does not tan
• Type II: White skin, burns easily, tans with difficulty
• Type III: White skin, may burn but tans easily
• Type IV: Light brown/olive skin, hardly burns, tans easily
• Type V: Brown skin, usually does not burn, tans easily
• Type VI: Black skin, very unlikely to burn, becomes darker with UV radiation exposure

Age also affects how skin reacts to sun. Children younger than six and adults older than sixty are more sensitive to sunlight.

There are certain genetic conditions, for example xeroderma pigmentosum, that increase a person's susceptibility to sunburn and subsequent skin cancers. These conditions involve defects in DNA repair mechanisms which in turn decreases the ability to repair DNA that has been damaged by UV radiation.

Medications

The risk of a sunburn can be increased by pharmaceutical products that sensitize users to UV radiation. Certain antibiotics, oral contraceptives, and tranquillizers have this effect.

UV intensity

The UV Index indicates the risk of getting a sunburn at a given time and location. Contributing factors include:

1. The time of day. In most locations, the sun's rays are strongest between approximately 10am and 4pm daylight saving time.
2. Cloud cover. UV is partially blocked by clouds; but even on an overcast day, a significant percentage of the sun's damaging UV radiation can pass through clouds.
3. Proximity to reflective surfaces, such as water, sand, concrete, snow, and ice. All of these reflect the sun's rays and can cause sunburns.
4. The season of the year. The position of the sun in late spring and early summer can cause a more-severe sunburn.
5. Altitude. At a higher altitude it is easier to become burnt, because there is less of the earth's atmosphere to block the sunlight. UV exposure increases about 4% for every 1000 ft (305 m) gain in elevation.
6. Proximity to the equator (latitude). Between the polar and tropical regions, the closer to the equator, the more direct sunlight passes through the atmosphere over the course of a year. For example, the southern United States gets fifty percent more sunlight than the northern United States.

Because of variations in the intensity of UV radiation passing through the atmosphere, the risk of sunburn increases with proximity to the tropic latitudes, located between 23.5° north and south latitude. All else being equal (e.g., cloud cover, ozone layer, terrain, etc.), over the course of a full year, each location within the tropic or polar regions receives approximately the same amount of UV radiation. In the temperate zones between 23.5° and 66.5°, UV radiation varies substantially by latitude and season. The higher the latitude, the lower the intensity of the UV rays. Intensity in the northern hemisphere is greatest during the months of May, June and July -- and in the southern hemisphere, November, December and January. On a minute-by-minute basis, the amount of UV radiation is dependent on the angle of the sun. This is easily determined by the height ratio of any object to the size of its shadow. The greatest risk is at solar noon, when shadows are at their minimum and the sun's radiation passes most directly through the atmosphere. Regardless of one's latitude (assuming no other variables), equal shadow lengths mean equal amounts of UV radiation.

The skin and eyes are most sensitive to damage by UV at 265-275 nm wavelength, which is in the lower UVC band that is almost never encountered except from artificial sources like welding arcs. Most sunburn is caused by longer wavelengths, simply because those are more prevalent in sunlight at ground level.

Ozone depletion

In recent decades, the incidence and severity of sunburn has increased worldwide, partly because of chemical damage to the atmosphere's ozone layer. Between the 1970s and the 2000s, average stratospheric ozone decreased by approximately 4%, contributing an approximate 4% increase to the average UV intensity at the earth's surface. Ozone depletion and the seasonal "ozone hole" have led to much larger changes in some locations, especially in the southern hemisphere.

Tanning

Suntans, which naturally develop in some individuals as a protective mechanism against the sun, are viewed by most in the Western world as desirable. This has led to an overall increase in exposure to UV radiation from both the natural sun and tanning lamps. Suntans can provide a modest sun protection factor (SPF) of 3, meaning that tanned skin would tolerate up to three times the UV exposure as pale skin.

Sunburns associated with indoor tanning can be severe and are the most common indoor-tanning related injury treated in United States emergency departments.

The World Health Organization, American Academy of Dermatology, and the skin cancer foundation recommend avoiding artificial UV sources such as tanning beds, and do not recommend suntans as a form of sun protection.

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Diagnosis

Differential Diagnosis:

The differential diagnosis of sunburn includes other skin pathology induced by UV radiation including photoallergic reactions, phototoxic reactions to topical or systemic medications, and other dermatologic disorders that are aggravated by exposure to sunlight. Considerations for diagnosis include duration and intensity of UV exposure, use of topical or systemic medications, history of dermatologic disease, and nutritional status.

• Phototoxic reactions: Non-immunological response to sunlight interacting with certain drugs and chemicals in the skin which resembles an exaggerated sunburn. Common drugs that may cause a phototoxic reaction include amiodarone, dacarbazine, fluoroquinolones, 5-fluorouracil, furosemide, nalidixic acid, phenothiazines, psoralens, retinoids, sulfonamides, sulfonylureas, tetracyclines, thiazides, and vinblastine.
• Photoallergic reactions: Uncommon immunological response to sunlight interacting with certain drugs and chemicals in the skin. When in excited state by UVR, these drugs and chemicals form free radicals that react to form functional antigens and induce a Type IV hypersensitivity reaction. These drugs include 6-methylcoumarin, aminobenzoic acid and esters, chlorpromazine, promethazine, diclofenac, sulfonamides, and sulfonylureas. Unlike to photoxic reactions which resemble exaggerated sunburns, photoallergic reactions can cause intense itching and can lead to thickening of the skin.
• Phytophotodermatitis: UV radiation induces inflammation of the skin after contact with certain plants (including limes, celery, and meadow grass). Causes pain, redness, and blistering of the skin in the distribution of plant exposure.
• Polymorphic light eruption: Recurrent abnormal reaction to UVR. It can present in various ways including pink-to-red bumps, blisters, plaques and urticaria.
• Solar urticaria: UVR-induced wheals that occurs within minutes of exposure and fades within hours.
• Other skin diseases exacerbated by sunlight: Several dermatologic conditions can increase in severity with exposure to UVR. These include systemic lupus erythematosus (SLE), dermatomyositis, acne, atopic dermatitis, and rosacea.

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Prevention

Skin

The most effective way to prevent sunburn is to reduce the amount of UV radiation reaching the skin. The World Health Organization, American Academy of Dermatology, and Skin Cancer Foundation recommend the following measures to prevent excessive UV exposure and skin cancer:

• Limit sun exposure between the hours of 10am and 4pm, when UV rays are the strongest
• Seek shade when UV rays are most intense
• Wear sun-protective clothing including a wide brim hat, sunglasses, and tightly-woven, loose-fitting clothing
• Use sunscreen
• Avoid tanning beds and artificial UV exposure

UV intensity:

The strength of sunlight is published in many locations as a UV Index. Sunlight is generally strongest when the sun is close to the highest point in the sky. Due to time zones and daylight saving time, this is not necessarily at 12 noon, but often one to two hours later. Seeking shade including using umbrellas and canopies can reduce the amount of UV exposure, but does not block all UV rays. The WHO recommends following the shadow rule: "Watch your shadow - Short shadow, seek shade!"

Sunscreen:

Commercial preparations are available that block UV light, known as sunscreens or sunblocks. They have a sun protection factor (SPF) rating, based on the sunblock's ability to suppress sunburn: The higher the SPF rating, the lower the amount of direct DNA damage. The stated protection factors are correct only if 2 ?L of sunscreen is applied per square cm of exposed skin. This translates into about 28 mL (1 oz) to cover the whole body of an adult male, which is much more than many people use in practice. Sunscreens function as chemicals such as oxybenzone and dioxybenzone that absorb UV radiation (chemical sunscreens) or opaque materials such as zinc oxide or titanium oxide to physically block UV radiation (physical sunscreens). Chemical and mineral sunscreens vary in the wavelengths of UV radiation blocked. Broad-spectrum sunscreens contain filters that protect against UVA radiation as well as UVB. Although UVA radiation does not primarily cause sunburn, it does contribute to skin aging and an increased risk of skin cancer.

Sunscreen is effective and thus recommended for preventing melanoma and squamous cell carcinoma. There is little evidence that it is effective in preventing basal cell carcinoma. Typical use of sunscreen does not usually result in vitamin D deficiency, but extensive usage may.

Recommended use

Research has shown that the best sunscreen protection is achieved by application 15 to 30 minutes before exposure, followed by one reapplication 15 to 30 minutes after exposure begins. Further reapplication is necessary only after activities such as swimming, sweating, and rubbing. This varies based on the indications and protection shown on the label -- from as little as 80 minutes in water to a few hours, depending on the product selected. The American Academy of Dermatology recommends the following criteria in selecting a sunscreen:

• Broad spectrum: protects against both UVA and UVB rays
• SPF 30 or higher
• Water resistant: sunscreens are classified as water resistant based on time, either 40 minutes, 80 minutes, or not water resistant

Eyes

The eyes are also sensitive to sun exposure at about the same UV wavelengths as skin; snow blindness is essentially sunburn of the cornea. Wrap-around sunglasses or the use by spectacle-wearers of glasses that block UV light reduce the harmful radiation. UV light has been implicated in the development of age-related macular degeneration, pterygium and cataract. Concentrated clusters of melanin, commonly known as freckles, are often found within the iris.

Diet

Dietary factors influence susceptibility to sunburn, recovery from sunburn, and risk of secondary complications from sunburn. Several dietary antioxidants, including essential vitamins, have been shown to have some effectiveness for protecting against sunburn and skin damage associated with ultraviolet radiation, in both human and animal studies. Supplementation with Vitamin C and Vitamin E was shown in one study to reduce the amount of sunburn after a controlled amount of UV exposure. A review of scientific literature through 2007 found that beta carotene (Vitamin A) supplementation had a protective effect against sunburn, but that the effects were only evident in the long-term, with studies of supplementation for periods less than 10 weeks in duration failing to show any effects. There is also evidence that common foods may have some protective ability against sunburn if taken for a period before the exposure.

Protecting Children:

Babies and children are particularly susceptible to UV damage which increases their risk of both melanoma and non-melanoma skin cancers later in life. Children should not sunburn at any age and protective measures can ensure their future risk of skin cancer is reduced.

• Infants 0-6 months: Children under 6mo generally have skin too sensitive for sunscreen and protective measures should focus on avoiding excessive UV exposure by using window mesh covers, wide brim hats, lose clothing that covers skin, and reducing UV exposure between the hours of 10am and 4pm.
• Infants 6-12 months: Sunscreen can safely be used on infants this age. It is recommended to apply a broad-spectrum, water-resistant SPF 30+ sunscreen to exposed areas as well as avoid excessive UV exposure by using wide-brim hats and protective clothing.
• Toddlers and Preschool-aged children: Apply a broad-spectrum, water-resistant SPF 30+ sunscreen to exposed areas, use wide-brim hats and sunglasses, avoid peak UV intensity hours of 10am-4pm and seek shade. Sun protective clothing with a SPF rating can also provide additional protection.

Artificial UV exposure:

The WHO recommends that artificial UV exposure including tanning beds should be avoided as no safe dose has been established . When one is exposed to any artificial source of occupational UV, special protective clothing (for example, welding helmets/shields) should be worn. Such sources can produce UVC, an extremely carcinogenic wavelength of UV which ordinarily is not present in normal sunlight, having been filtered out by the atmosphere.

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Treatment

The primary measure is avoiding further exposure to the sun. The best treatment for most sunburns is time. Most sunburns heal completely within a few weeks.

The American Academy of Dermatology recommends the following for treatment of sunburn:

• For pain relief, take cool baths or showers frequently.
• Use soothing moisturizers that contain aloe vera or soy. Hydrocortisone creams that can be purchased over-the-counter can also be used on areas that are painful, however avoid creams that end in "caine" as these can be more irritating.
• Anti-inflammatory medications such as ibuprofen or aspirin can help with pain.
• Keep hydrated and drink extra water.
• Do not pop blisters on a sunburn. Instead, let them heal on their own.
• Protect sunburned skin with loose clothing when going outside to prevent further damage.

Non-steroidal anti-inflammatory drugs (such as ibuprofen or naproxen), and aspirin may decrease redness and pain. Local anesthetics such as benzocaine, however, are contraindicated. Schwellnus et al. states that topical steroids (such as hydrocortisone cream) do not help with sunburns, although the American Academy of Dermatology says they can be used on especially sore areas. While lidocaine cream is often used as a sunburn treatment, there is little evidence for the effectiveness of such use.

Home treatments that may help the discomfort include using cool and wet cloths on the sunburned areas. Applying soothing lotions that contain aloe vera to the sunburn areas was supported by one review. Others have found aloe vera to have no effect. Aloe vera has no ability to protect people from sunburns. Another treatment includes using a moisturizer that contains soy.

A sunburn draws fluid to the skin's surface and away from the rest of the body. Drinking extra water when you are sunburned helps prevent dehydration.

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References

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External links

• Sunburn at Curlie (based on DMOZ)

Source of article : Wikipedia

H&R Block

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H&R Block, Inc., or H&R Block, is an American tax preparation company operating in North America, Australia, and India. The company was founded in 1955 by brothers Henry W. Bloch and Richard Bloch.

As of 2018, H&R Block operates approximately 12,000 retail tax offices staffed by tax professionals worldwide. It also offers consumer tax software as well as online tax preparation and electronic filing from their website. The Kansas City-based company also offers payroll, and business consulting services.

Video H&R Block

History

Early history

During World War II, Henry W. Bloch was a young Army Air Forces navigator who wanted to start a family business with his brothers in Kansas City. Home from the war in 1946, Henry saw a pamphlet suggesting a bright future for companies serving small businesses, and it sparked his imagination. That year, Henry and his older brother, Leon, borrowed $5,000 and opened a small bookkeeping business on Main Street in downtown Kansas City. However, four months later, they had few clients and Leon decided to seek a law degree.

Henry wanted to keep trying with the fledgling business and placed a newspaper ad for help-wanted. He got an unexpected response--from his mother--who proposed that Henry hire his younger brother, Richard, for the job. Henry and Richard Bloch jointly ran their United Business Company, which focused on accounting, bookkeeping and payroll, but also did some income tax work for clients. The brothers took out an ad for its $5 tax services in The Kansas City Star newspaper in 1955. The ad was a success and H&R Block was born. The Bloch brothers chose to spell the name "Block" with a K to ensure the name is not mispronounced "blotch".

In 1956, the Blochs decided to expand and picked New York City. Neither brother wanted to move to New York, so they agreed to sell that regional operation, creating the first H&R Block franchise tax office. In the following years, H&R Block grew and went public in 1962.

In 1980 H&R Block purchased the Compuserve online service. By 1986, Block was handling more than 10 million tax returns annually and had opened offices in Canada and Australia. That year, the company worked with the Internal Revenue Service to introduce electronic filing.

Recent history

H&R Block acquired MECA Software, the company that created the TaxCut software, in 1993. In 1995, H&R Block sold MECA, but retained TaxCut.

The company began to expand in the 1990s into the financial services arena, offering mortgage loans, banking and business services. H&R Block purchased Olde Discount Stockbrokers in 1999 and operated as a full-service securities broker-dealer under the name H&R Block Financial Advisors. In 2008, the company sold its H&R Block Financial Advisors unit to Ameriprise Financial for $315 million. At the time, the unit managed $30 billion in assets and employed 900 financial advisors in the U.S.

RSM McGladrey Business Solutions was created in 1999 when H&R Block acquired the assets of McGladrey & Pullen, aside from its auditors and attest services which remained under ownership of McGladrey's partners. Following the acquisition H&R Block became the sixth-largest accounting firm in the U.S. McGladrey had 100 offices in 25 states and offered accounting, consulting, tax services, and international business services to mid-sized companies. Through an alliance with McGladrey & Pullen and other accountancies, the Block subsidiary operated in 70 countries under the RSM International name. In 2011, H&R Block sold the unit back to McGladrey & Pullen.

In August 2005, H&R Block announced that it had overstated its earnings for 2003 and 2004 by $91.1 million. The company stated that it had "insufficient resources" to identify and report complex transactions in its corporate tax accounting. On February 23, 2006, the company said in its quarterly results that it had miscalculated its own state income taxes for 2005 and 2004, and that it owed an additional $32 million in back taxes.

In December 2005, H&R Block sent its customers free copies of its TaxCut software, and the mailing labels on the packages mistakenly included the recipients' Social Security numbers. The company said it sent the promotional mailing to former customers and people whose names were taken from purchased lists. It said it is legally required to hold on to customers' tax information, including Social Security numbers, for three years. H&R Block said no customer data has been lost or stolen as a result of the mistake, and that less than 3 percent of the mailings were involved.

California Attorney General Bill Lockyer sued H&R Block in February 2006, alleging the company's refund anticipation loan (RAL) business violated state and federal laws in its marketing and providing of high-cost RALs mainly to low-income clients. The company responded that it "believes the refund lending program is both fair and legal, and will vigorously defend against the complaint". On January 2, 2009, California Attorney General Edmund G. Brown Jr. reached a $4.85 million settlement with H&R Block, which prohibits the company from deceptively marketing high-cost refund anticipation loans as early "tax refunds". The company set aside $2.45 million in restitution for customers if they purchased a "refund anticipation loan" or a "refund anticipation check" through H&R Block between January 1, 2001 and December 31, 2008. In addition, H&R Block agreed to pay $500,000 in penalties and $1.9 million in fees and costs. In 2011, H&R Block ceased offering RALs altogether, a move praised by consumer rights activists.

On March 16, 2006, New York Attorney General Eliot Spitzer sued H&R Block, accusing the company of deceptive marketing of its Express IRA retirement accounts. The lawsuit alleged the company assessed fees, including set-up fees, annual fees, and account closing fees that, for 85% of account holders, resulted in the account losing money. However, in July 2007, a New York state judge dismissed much of the lawsuit. Justice Karla Moskowitz of the State Supreme Court excused Block and five of its units from the lawsuit. She let stand the portion of the complaint concerning another unit, H&R Block Financial Advisers, but dismissed allegations of common law fraud. At the time of the ruling, H&R Block said it believed the remaining assertions lacked merit and that it would appeal. On January 6, 2009, a New York state appeals court overruled trial justice Karla Moskowitz's July 2007 ruling and reinstated the lawsuit against H&R Block Inc that accused the company of fraudulently marketing Express IRA retirement accounts to hundreds of thousands of lower-income clients nationwide. The matter was settled in 2009, and H&R Block agreed to pay $11.4 million to $19.4 million of fees to customers and $750,000 in fees and other costs.

H&R Block hired Jeff Jones, a former Target Corporation and Uber executive, as president and CEO on October 9, 2017. He replaced Tom Gerke, who was interim CEO following the retirement of former CEO Bill Cobb. Jones has said he sees H&R Block as a financial services company and a retail company, and aims to grow the company.

Maps H&R Block

Corporate affairs

H&R Block is headquartered at 13th and Main streets, Kansas City, Missouri, in a building constructed downtown in the 2000s as part of an effort to revitalize the city's downtown. The company is governed by an 11-member board of directors. Jeff Jones is CEO. Tony Bowen is CFO. As of April 30, 2018, H&R Block employs approximately 2,700 regular full-time employees, and as many as 90,700 including seasonal employees. It generates over $3 billion annually in revenue. The company also runs The Tax Institute at H&R Block.

Marketing

The brand has undertaken several high-profile marketing campaigns, including television commercials featuring actor Jon Hamm and NBA player Anthony Davis. H&R Block's "Get Your Billions Back, America" campaign started in 2014. It featured Richard Gartland, a real H&R Block tax professional known for wearing bow ties. The campaign focused on urging taxpayers to seek their full potential refund at tax time. Anthony Davis, a power forward and center with the New Orleans Pelicans, became a spokesman for H&R Block in 2015. The company first aired ads featuring Mad Men actor Jon Hamm in 2017, using the tagline "Get your taxes won", in a 12-spot campaign that was the largest in H&R Block's history. Hamm returned as H&R Block's spokesman in 2018 with a new campaign throughout the tax season.

From 2009 to 2016, the company did not advertise during the Super Bowl. It returned in 2017 with an ad featuring H&R Block's partnership with IBM Watson at its retail locations.

Corporate social responsibility

The company partners with United Way MyFreeTaxes to offer its software for free state and federal tax returns. H&R Block is also a member of the Free File Alliance, a consortium of commercial tax preparers and the IRS offering free-tax-prep for low-income and moderate-income taxpayers, and Military One Source, which lets members of the military service file for free.

As part of its corporate social responsibility initiatives, in 2014 H&R Block launched an online game for high school students called the Budget Challenge. The challenge is part of the company's Dollars & Sense financial literacy effort, and offers college scholarships for teenage students who win the game.

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Business areas

Retail and digital tax services

H&R Block has 70,000 tax pros in its 10,000 U.S. retail tax offices. In addition to the company's traditional retail tax offices, it offers digital tax preparation programs and software. It filed 23 million tax returns worldwide in 2016.

The company's services Tax Pro Review and Tax Pro Go were launched in 2017. Tax Pro Review is an updated version of its former service Best of Both, where clients enter their information and do their returns online and are matched with Block tax professional reviews for help. H&R Block Tax Pro Go is marketed to online filers who do not want to or cannot visit an H&R Block office.

H&R Block's tax software comes in different versions. In addition to the free edition, there are Deluxe, Premium and Self-Employed editions. Users can log on using various devices, import photos of their W-2 forms and use a searchable knowledge base. The Deluxe and Premium editions include free online chat with a tax professional.

Block Advisors

In January 2016, H&R Block launched Block Advisors, a service that provides year-round consumer tax preparation. The company has opened about 350 Block Advisor offices. Its advisors include certified public accountants, enrolled agents, or have been certified by H&R Block as master tax advisors.

Partnerships

The company signed a deal with Walmart in 2018, to make H&R Block software the only desktop tax preparation software sold at the retailer's stores. H&R Block also created a deal with Amazon.com in 2017 for better product placement of its suite of software products.

In 2017, H&R Block partnered with IBM to bring IBM Watson technology into its retail offices. Under the partnership, H&R Block tax pros received access to IBM's artificial intelligence system to help tax pros prepare better tax returns for clients.

In 2018, H&R Block partnered with LendingTree to allow customers credit score access via MyBlock.

Other products and services

Following research on the potential expat market in 2013, H&R Block began its Expat Tax Services program to offer tax advice to U.S. citizens living outside the country.

H&R Block maintains financial services products, including the Emerald Card pre-paid debit card and Emerald Advance line of credit. Additionally, the company's Tax Identity Shield offers identity theft protection.

Former business areas

The H&R Block Bank was chartered in 2006 and offered low-cost services to its low- to moderate-income customers. In September 2015, H&R Block sold H&R Block Bank to BofI Holding Inc. The two companies reached an agreement for BofI to serve as the bank for H&R Block-branded financial services products including the Emerald MasterCard, Refund Anticipation Checks, and Emerald Advance lines of credit.

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References

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External links

• H&R Block
• H&R Block Canada
• H&R Block India
• H&R Block Australia
• Block Advisors

Source of article : Wikipedia

Block scheduling

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Block scheduling is a type of academic scheduling used in schools in the American K-12 system, in which each pupil has fewer classes per day. It is more common in middle and high schools than in primary schools. Each class is scheduled for a longer period of time than normal (e.g. 90 minutes instead of 50). In one form of block scheduling, a single class will meet every day for a number of days, after which another class will take its place. In another form, daily classes rotate through a changing daily cycle.

Blocks offer more concentrated experiences of subjects, with fewer, usually half as many if going through a schedule transfer, classes daily.

Video Block scheduling

Description

Under a traditional American schedule, pupils in a High School will study seven subjects a day for 45 minutes for each day of the week for a semester. There will be two semesters in the year so 14 subjects could be studied. Some pupils will not study all seven subjects. There was great variety as each school board was free to decide the requirement.

Conversion to block scheduling became a relatively widespread trend in the 1990s for middle schools and high schools in the United States. Prior to that, many schools scheduled classes such that a student saw every one of their teachers each day. Classes were approximately 40-60 minutes long, but under block scheduling, they became approximately 90 minutes long.

Maps Block scheduling

Schedules

Many forms of block scheduling were devised.

A/B Block Scheduling

One variety of block scheduling, called A/B block scheduling, is shown in the example table. Instead of taking six classes every day, students attend three classes every other day and spend double the amount of continuous time in each class. Students can take 4 classes during one semester and another 4 the next. The example given reverts to a six-period day on Fridays.

4x4 Block Scheduling

A method called 4×4 block scheduling splits the academic year into quarters, and uses a four-period day. This leaves eight slots available for classes during a semester (four classes in each of two quarters). The 4×4 method is somewhat more flexible in that students can take two sequential classes (such as Algebra 1 and 2) in the same semester (in different quarters), which would not be possible on a traditional schedule. This also allows students in their final year to fail a third-quarter class but repeat it in the fourth quarter in order to graduate.

2 Core 2 Electives

Another common block system exists in which students spend up to 100 minutes per class, and earn four credits each semester. Excluding very rare occasions, students at schools using this system take two core classes and two electives per semester. Some schools modify this system further to use one of the mid-day periods for students to take optional year-long classes (usually band) that take half of the period length and take another year-long class during the rest of the period (such as math or journalism). Under such a system most of the classes taken on a year-long basis have all students participating, however it is not uncommon for journalism or yearbook classes to operate under the normal system and only have a few students who leave or arrive halfway through the period. It is also not uncommon for these classes to be scheduled as two credits, and taken both semesters.

Waldorf blocking

Waldorf schools traditionally employ a mixed approach. Certain academic subjects are taught in intensive three to five week blocks known as main lesson blocks, while other subjects are taught in regularly meeting skills classes.

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Colleges and Universities

Within the context of post K-12 establishments, such as in medical school or other intensive university program, a block schedule may mean taking one class at a time, all day, every day, until all of the material is covered. A normal university course might then be completed in three or four weeks of focused effort on a single topic. This is sometimes called "One Course At A Time" ("OCAAT") (see Colorado College and Cornell College). When used as a supplement change instead of the normal schedule, this approach is sometimes called a mini-mester.

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Effectiveness

"Where we were able to combine data to produce summary effect sizes, we found that 4 x 4 block scheduling resulted in higher cross subject achievement than traditional schedules. However, the outcome average cross-subject achievement could conceal worsening performance in some subjects and better performance in others."

Some schools have compensated for this by making AP courses last for the entire school year, providing essentially double the instruction time of normal classes, but this results in a dramatic reduction in the number of courses a student can take. Some schools that make AP courses year long offset this by having students always choose a pair of AP courses during class registration. The student will go to the first AP class one day, and the other AP course the next day. Therefore, the student takes the same number of courses as other students, but both AP classes last for the duration of the year.

A systematic review on Block Scheduling was also conducted by Dickson et al. (2010) at the EPPI-Centre which asserts that there is no conclusive evidence to support the introduction of policy guidance on the use of block scheduling in secondary schools in the UK. Although the findings do not indicate that participating in block schedules would produce negative outcomes for pupils across subjects, neither are the positive effects of block scheduling strong enough to recommend their implementation.

src: citadel.sjfc.edu

Criticism

Some critics believe that certain subjects suffer from a lack of daily exposure to subject matter and practice that occurs with an A/B block schedule. Courses like mathematics, foreign languages, and music may benefit from daily practice and suffer from a lack thereof. Block scheduling can result in gaps of a day or days (or even weeks or months in some circumstances) where students are receiving no reinforcement of instruction in a specific subject like math or history, and critics say this results in retention problems and the need for more remedial review. Some observers similarly feel that summer vacation has a similar effect of interrupting the learning and retention process forcing a need to repeat material at the start of a new school year in the Fall.

A University of Virginia study of 8,000 college students found that students who had block scheduling in high school performed worse in university science courses.

Students who miss a block-scheduled day can miss a considerable amount of material in a single subject, possibly making it more difficult to catch up. One way this can be mitigated is by making course material available online, which allows students to catch up outside of school, and another way is by using a flipped classroom system.

Some students are better able to manage their time with nightly homework in every class, while other students do better with larger homework assignments that are spaced out over several days. Some subjects may benefit from daily drills while other subjects may lend themselves to less frequent homework projects. Mid-term transfers between schools with different schedules can be problematic in cases where the schedules are different.

src: trinityhs.org

See also

• Academic term

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References

src: humanbiomrt.weebly.com

External links

• "Block Scheduling Revisited" by J. Allen Queen (Original link no longer available. Redirected to the Internet Archive)
• Collection of web links about block scheduling
• Block Scheduling - by Karen Irmsher of the ERIC Clearinghouse on Educational Management
• Block Scheduling: Is this Right for America's Public Schools?- by John W. Cooper
• Block Scheduling: Discussion and links at the Illinois Loop website

Source of article : Wikipedia

Local anesthetic nerve block

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Local anesthetic nerve block (local anesthetic regional nerve blockade, or often simply nerve block) is a short-term nerve block involving the injection of local anesthetic as close to the nerve as possible for pain relief. The local anesthetic bathes the nerve and numbs the area of the body that is innervated by that nerve. The goal of the nerve block is to prevent pain by blocking the transmission of pain signals from the surgical site. The block provides pain relief during and after the surgery. The advantages of nerve blocks over general anesthesia include faster recovery, monitored anesthesia care vs. intubation with an airway tube, and much less postoperative pain.

Video Local anesthetic nerve block

Mechanism of action

Local anesthetics act on the voltage-gated sodium channels that conduct electrical impulses and mediate fast depolarization along nerves. Local anesthetics also act on potassium channels, but they block sodium channels more.

Lidocaine preferentially binds to the inactivated state of voltage-gated sodium channels, but has also been found to bind potassium channels, G protein-coupled receptors, NMDA receptors, and calcium channels in vitro. The duration of the block is mostly influenced by the amount of time the anesthetic is near the nerve. Lipid solubility, blood flow in the tissue, and presence of vasoconstrictors with the anesthetic all play a role in this. A higher lipid solubility makes the anesthetic more potent and have a longer duration of action; however, it also increases the toxicity of the drug.

Maps Local anesthetic nerve block

Toxicity and nerve injury

Local anesthetic toxicity is indicated by numbness and tingling around the mouth, metallic taste, or ringing in the ears. Additionally, this may lead to seizures, arrhythmias, and may progress to cardiac arrest. This reaction may stem from an allergy, excessive dose, or intravascular injection. Other complications include nerve injury which has an extremely low rate of 0.029-0.2%. Some research even suggests that ultrasound lowers the risk to 0.0037%. The use of ultrasound and nerve stimulation has greatly improved practitioners' ability to safely administer nerve blocks. Nerve injury most often occurs from ischaemia, compression, direct neurotoxicity, or needle laceration, and inflammation.

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Common local anesthetics and adjuvants

Local anesthetics are broken down into 2 categories: ester-linked and amide-linked drugs. The esters include benzocaine, procaine, tetracaine, and chloroprocaine. The amides include lidocaine, mepivacaine, prilocaine, bupivacaine, ropivacaine, and levobupivacaine. Chloroprocaine is a short-acting drug (45-90 minutes), lidocaine and mepivacaine are intermediate duration (90-180 minutes), and bupivacaine, levobupivacaine, and ropivacaine are long-acting (4-18 hours). Drugs commonly used for peripheral nerve blocks include lidocaine, ropivacaine, bupivacaine, and mepivacaine. These drugs are often combined with adjuvants (additives) with the end goal of increasing the duration of the analgesia or shortening time of onset. Additives may include epinephrine, clonidine, and dexmedetomidine. Vasoconstriction caused by local anesthetic may be further enhanced synergistically with the addition of epinephrine, the most widely used additive. Epinephrine increases the length of analgesic duration and decreases blood flow by acting as an agonist at the ?1-adrenoceptor. Dexmedetomidine is not as widely used as epinephrine. Studies in humans indicate improved onset time and increased duration of analgesia.

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Duration of nerve block

The duration of the nerve block depends on the type of local anesthetics used and the amount injected around the target nerve. There are short acting (45-90 minutes), intermediate duration (90-180 minutes), and long acting anesthetics (4-18 hours). Block duration can be prolonged with use of a vasoconstrictor such as epinephrine, which decreases the diffusion of the anesthetic away from the nerve.

There are various types of nerve blocks currently performed. Therapeutic blocks may be used for acute pain patients, diagnostic blocks are used to find pain sources, prognostic blocks are used to determine subsequent pain management options, preemptive blocks minimize postoperative pain, and some blocks can be used in place of surgery. Certain surgeries may benefit from placing a catheter that stays in place for 2-3 days postoperatively. Catheters are indicated for some surgeries where the expected postoperative pain lasts longer than 15-20 hours. Pain medication can be injected through the catheter to prevent a spike in pain when the initial block wears off. Nerve blocks may also reduce the risk of developing persistent postoperative pain several months after surgery.

Local anesthetic nerve blocks are sterile procedures that can be performed with the help of anatomical landmarks, ultrasound, fluoroscopy (a live X-ray), or CT. Use of any one of these imaging modalities enables the physician to view the placement of the needle. Electrical stimulation can also provide feedback on the proximity of the needle to the target nerve.

src: pocketdentistry.com

Upper extremity nerve blocks

The brachial plexus is a bundle of nerves innervating the shoulder and arm and can be blocked at different levels depending on the type of upper extremity surgery being performed. Interscalene brachial plexus blocks can be done before shoulder, arm, and elbow surgery. The interscalene block is done at the neck where the brachial plexus emerges between the anterior and middle scalene muscles. Lidocaine is injected first to numb the skin and then a blunt needle is used to protect the nerves from damage as the physician places the needle very close to the nerves. The needle goes in about 3-4 cm and a single shot of local anesthetic is injected or a catheter is placed. The most common local anesthetics used at the site of the nerves are bupivicaine, mepivicaine, and chloroprocaine. There is a very high chance that the phrenic nerve, which innervates the diaphragm, will be blocked so this block should only be done on patients who have use of their accessory respiratory muscles. The block may not affect the C8 and T1 roots which supply part of the hand, so it is usually not done for hand surgeries.

The supraclavicular and infraclavicular blocks can be performed for surgeries on the humerus, elbow, and hand. These blocks are indicated for the same surgeries but they provide different views of the nerves, so it depends on the individual patient's anatomy to determine which block should be performed. A pneumothorax is a risk with these blocks, so the pleura should be checked with ultrasound to make sure the lung was not punctured during the block.

The axillary block is indicated for elbow, forearm, and hand surgery. It anesthetizes the median, ulnar, and radial nerves. This block is useful because it has less risk than the interscalene (spinal cord or vertebral artery puncture) or supraclavicular (pneumothroax) brachial plexus blocks.

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Lower extremity nerve blocks

Fascia iliaca block is indicated for pain relief for hip fractures in adults and femoral fractures in children. It works by affecting the femoral, obturator and the lateral cutaneous nerves.

3-in-1 nerve block is indicated for pain relief for hip fractures.

The femoral nerve block is indicated for femur, anterior thigh, and knee surgery. It is performed slightly inferior to the inguinal ligament, and the nerve is under the fascia iliaca.

The sciatic nerve block is done for surgeries at or below the knee. The nerve is located in the gluteus maximus muscle. The popliteal block is done for ankle, achilles tendon, and foot surgery. It is done above the knee on the posterior leg where the sciatic nerve starts splitting into the common peroneal and tibial nerves.

The saphenous nerve block is often done in combination with the popliteal block for surgeries below the knee. The saphenous nerve is numbed at the medial part of the lower thigh under the sartorius muscle.

The lumbar plexus block is an advanced technique indicated for hip, anterior thigh, and knee surgery. The lumbar plexus is composed of nerves originating from L1 to L4 spinal roots such as the iliohypogastric, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, and obturator nerves. Since the plexus is located deep, there is an increased risk of local anesthetic toxicity, so less toxic anesthetics like chloroprocaine or mepivacaine mixed with ropivacaine are often recommended. A curvilinear ultrasound probe can be used but it is often difficult to see the plexus, so a nerve stimulator is used to locate it.

src: www.aafp.org

Paravertebral nerve block

The paravertebral block is versatile and can be used for various surgeries depending on the vertebral level it is done. A block at the neck in the cervical region is useful for thyroid gland and carotid artery surgery. At the chest and abdomen in the thoracic region, blocks are used for breast, thoracic, and abdominal surgery. A block at the hip in the lumbar region is indicated for hip, knee, and anterior thigh surgeries. The paravertebral block provides unilateral analgesia, but bilateral blocks can be performed for abdominal surgeries. Since it is a unilateral block, it may be chosen over epidurals for patients who can't tolerate the hypotension that follows bilateral sympathectomy. The paravertebral space is located a couple centimeters lateral to the spinous process and is bounded posteriorly by the superior costotransverse ligament and anteriorly by the parietal pleura. Complications include pneumothorax, vascular puncture, hypotension, and pleural puncture.

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References

Source of article : Wikipedia

Block programming

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Block programming or television block is the arrangement of programs on radio or television so that several items of one general class, such as soap operas or popular music, occur in sequence.

Video Block programming

Overview

Block programming involves scheduling a series of related shows which are likely to attract and hold a given audience for a long period of time. Notable examples of overt block programming were NBC's Thursday evening "Must See TV" lineup, which included two hours of sitcoms and one hour of ER, and Channel 4's "T4" program which often ran sitcoms like Friends back-to-back for an hour or more. Reruns on cable television are often assembled into similar blocks to fill several hours of generally little-watched daytime periods. A particularly long program block, especially one that does not air on a regular schedule, is known as a marathon.

Block programming in radio also refers to programming content that appeals to various demographics in time blocks, usually corresponding to the top or bottom of the hour or the quarter-hour periods. For example, various musical genres might be featured, such as a country music hour, a three-hour afternoon block of jazz, or a four-hour Saturday night '70s disco show.

Generally speaking, block programming is anathema to modern competitive commercial radio, which traditionally uses uniform formats, other than a handful of speciality shows in off-peak hours such as weekends (for instance, the infamous beaver hours in Canadian radio). The general rationale for not using block programming is that listeners expect a certain type of music when they tune into a radio station and breaking from that format will turn those listeners away from the station; likewise, a station that airs its programming in hodgepodge blocks will have difficulty building listener loyalty, as listeners' music will only be on for a few hours of the day. This argument for homogenized radio was also a driving force behind the effective death of freeform radio in the late 20th century. The case of talk radio is indicative of the decline of block programming: prior to the 1980s, it was not uncommon to mix various blocks of talk programming together on one station, but this has declined dramatically in the late 1990s and beyond. A listener to a conservative talk radio station will have little interest in a progressive talk radio, sports radio or hot talk block, which reaches a different demographic; stations that have attempted the block strategy have historically been unsuccessful. Block programming of this nature is alive and well on outlets like public radio (such as NPR, BBC, or the CBC) and in multicultural radio serving broad ethnic and cultural audiences, although even in this realm the idea of block programming is declining due to competition for donations.

Some programming blocks have become so popular that they have been transformed to full-fledged 24-hour channels. Current channels which started as program blocks include TeenNick (originally a program block on Nickelodeon); Disney Junior (which is still a program block on the Disney Channel); Nick Jr. (which still airs on Nickelodeon); Boomerang (which was once a program block on Cartoon Network); and PBS Kids, a 24/7 channel, which PBS member stations are able to provide in addition to their current children's programming on the primary PBS channel. In addition, TV Land airs older shows that were once aired on sister channel Nickelodeon's Nick at Nite program block.

Maps Block programming

See also

• List of television programming blocks
• Strip programming
• Broadcast programming
• Dayparting
• Marathon (television)

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References

Source of article : Wikipedia

New Kids on the Block Live

src: www.aceshowbiz.com

The New Kids on the Block Live was the fifth concert tour by American band New Kids on the Block and the first in 14 years since the group broke up after their last tour in 1994. In April 2008, the group reunited on the Today Show, announcing a new album and tour. The tour visited North America and Europe. The tour took place from the fall of 2008 through the summer of 2010. Each year, the tour was revamped with new staging, setlist and tour name. In 2009, the tour was acknowledged as The "Full Service Tour" and in 2010, the tour was known as the "Casi-NO Tour".

Video New Kids on the Block Live

Opening acts

• Natasha Bedingfield (North America) (select venues)
• Lady Gaga (North America) (select venues)
• Tami Chynn (North America) (select venues)
• Shontelle (Europe) (select venues)
• JabbaWockeeZ (North America) (select venues)
• Colby O'Donis (North America) (select venues)
• Jesse McCartney (North America) (select venues)

Maps New Kids on the Block Live

Setlist

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Tour dates

Music festivals and other miscellaneous performances

^A This concert was a part of Borderfest Music Festival 2009.

^B These concerts were a part of the New Kids on the Block Cruise 2009.

^C This concert was a part of Virgin Festival Canada.

^D This concert was a part of a Toys for Tots Benefit.

^E These concerts were a part of the New Kids on the Block Cruise 2010.

Cancellations and rescheduled dates

• October 14, 2008 Albuquerque Tingley Coliseum
• November 24, 2008 Portland Rose Garden Arena
• June 7, 2009 Bristow Nissan Pavilion at Stone Ridge was rescheduled to Fairfax, Virginia  Patriot Center
• July 13, 2009 El Paso Don Haskins Center
• August 1, 2009 Perth Burswood Dome
• August 3, 2009 Adelaide Adelaide Entertainment Centre
• August 4, 2009 Melbourne Rod Laver Arena
• August 6, 2009 Newcastle, New South Wales Newcastle Entertainment Centre
• August 8, 2009 Boondall Brisbane Entertainment Centre
• August 10, 2009 Sydney Acer Arena
• August 15, 2009 Wollongong WIN Entertainment Centre

Box office score data

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Broadcasts and recordings

The 2008-2009 tour was chronicled on the documentary, "Coming Home". The film featured a behind the scenes process of the group making the latest studio album, "The Block" and preparation for the upcoming tour. The footage is interlaced with performances of their biggest hits. It also features a new song "Coming Home", which was a potential addition to the album. The song was performed for the first time at the Toys for Tots benefit show. The group describes the fill as "a love letter to the fans". As a part of the promotion of releasing the documentary, NKOTB held a "Demand Us!" contest where fans could "demand" that NKOTB come to their city and host a DVD screening party at a local theatre. The cities that won were New York, Seattle, and Wheeling, West Virginia. A DVD was released on February 10, 2010, followed by showings on Palladia HD.

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References

Source of article : Wikipedia

H-index

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The h-index is an author-level metric that attempts to measure both the productivity and citation impact of the publications of a scientist or scholar. The index is based on the set of the scientist's most cited papers and the number of citations that they have received in other publications. The index can also be applied to the productivity and impact of a scholarly journal as well as a group of scientists, such as a department or university or country. The index was suggested in 2005 by Jorge E. Hirsch, a physicist at UCSD, as a tool for determining theoretical physicists' relative quality and is sometimes called the Hirsch index or Hirsch number.

Video H-index

Definition and purpose

The definition of the index is that a scholar with an index of h has published h papers each of which has been cited in other papers at least h times. Thus, the h-index reflects both the number of publications and the number of citations per publication. The index is designed to improve upon simpler measures such as the total number of citations or publications. The index works properly only for comparing scientists working in the same field; citation conventions differ widely among different fields.

Maps H-index

Calculation

Formally, if f is the function that corresponds to the number of citations for each publication, we compute the h index as follows. First we order the values of f from the largest to the lowest value. Then, we look for the last position in which f is greater than or equal to the position (we call h this position). For example, if we have a researcher with 5 publications A, B, C, D, and E with 10, 8, 5, 4, and 3 citations, respectively, the h index is equal to 4 because the 4th publication has 4 citations and the 5th has only 3. In contrast, if the same publications have 25, 8, 5, 3, and 3, then the index is 3 because the fourth paper has only 3 citations.

f(A)=10, f(B)=8, f(C)=5, f(D)=4, f(E)=3 -> h-index=4

f(A)=25, f(B)=8, f(C)=5, f(D)=3, f(E)=3 -> h-index=3

If we have the function f ordered in decreasing order from the largest value to the lowest one, we can compute the h index as follows:

h-index (f) = ${\displaystyle \max _{i}\min(f(i),i)}$

The Hirsch index is equivalent to the Eddington number, an earlier metric used for evaluating cyclists. The h-index serves as an alternative to more traditional journal impact factor metrics in the evaluation of the impact of the work of a particular researcher. Because only the most highly cited articles contribute to the h-index, its determination is a simpler process. Hirsch has demonstrated that h has high predictive value for whether a scientist has won honors like National Academy membership or the Nobel Prize. The h-index grows as citations accumulate and thus it depends on the "academic age" of a researcher.

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Input data

The h-index can be manually determined using citation databases or using automatic tools. Subscription-based databases such as Scopus and the Web of Science provide automated calculators. Harzing's Publish or Perish program calculates the h-index based on Google Scholar entries. From July 2011 Google have provided an automatically-calculated h-index and i10-index within their own Google Scholar profile. In addition, specific databases, such as the INSPIRE-HEP database can automatically calculate the h-index for researchers working in high energy physics.

Each database is likely to produce a different h for the same scholar, because of different coverage. A detailed study showed that the Web of Science has strong coverage of journal publications, but poor coverage of high impact conferences. Scopus has better coverage of conferences, but poor coverage of publications prior to 1996; Google Scholar has the best coverage of conferences and most journals (though not all), but like Scopus has limited coverage of pre-1990 publications. The exclusion of conference proceedings papers is a particular problem for scholars in computer science, where conference proceedings are considered an important part of the literature. Google Scholar has been criticized for producing "phantom citations," including gray literature in its citation counts, and failing to follow the rules of Boolean logic when combining search terms. For example, the Meho and Yang study found that Google Scholar identified 53% more citations than Web of Science and Scopus combined, but noted that because most of the additional citations reported by Google Scholar were from low-impact journals or conference proceedings, they did not significantly alter the relative ranking of the individuals. It has been suggested that in order to deal with the sometimes wide variation in h for a single academic measured across the possible citation databases, one should assume false negatives in the databases are more problematic than false positives and take the maximum h measured for an academic.

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Comparing results across fields and career levels

Little systematic investigation has been done on how the h-index behaves over different institutions, nations, times and academic fields/disciplines, but it is clear that differences between disciplines can be at a factor of x10 and more. Also, h values have gone up in recent decades. An academic with h 20 may thus be a modest scientist, or a leader in their field.

Comparing results between individuals will have to take into account (a) career stage, (b) publication frequency in the field, and (c) citation frequency in the field. An individual (a) at a more senior career stage will have published more and the publications will have had more time to accumulate citations. How many publications a person authors or co-authors per year (b), and many citations a publication attracts per year (c) differs greatly between academic fields. How much more a senior person (a) is cited differs from field to field - e.g. in lab sciences it is common to always cite the director of the lab. How citations are distributed over time (c) is different - e.g. medical science publications attract many citations in the first years, while humanities publications have a slower but more lasting citation pattern. Finally, the correlation between publications and "success" differs widely between fields and other social factors (e.g. Oxford/Cambridge dons used to care about peer recognition, but not publications or citations).

Hirsch suggested that, for physicists, a value for h of about 12 might be typical for advancement to tenure (associate professor) at major [US] research universities. A value of about 18 could mean a full professorship, 15-20 could mean a fellowship in the American Physical Society, and 45 or higher could mean membership in the United States National Academy of Sciences.

For the most highly cited scientists in the period 1983-2002, Hirsch identified the top 10 in the life sciences (in order of decreasing h): Solomon H. Snyder, h = 191; David Baltimore, h = 160; Robert C. Gallo, h = 154; Pierre Chambon, h = 153; Bert Vogelstein, h = 151; Salvador Moncada, h = 143; Charles A. Dinarello, h = 138; Tadamitsu Kishimoto, h = 134; Ronald M. Evans, h = 127; and Axel Ullrich, h = 120. Among 36 new inductees in the National Academy of Sciences in biological and biomedical sciences in 2005, the median h-index was 57. However, he points out that values of h will vary between different fields.

Among the 22 scientific disciplines listed in the Thomson Reuters Essential Science Indicators Citation Thresholds [thus excluding non-science academics], physics has the second most citations after space science. During the period January 1, 2000 - February 28, 2010, a physicist had to receive 2073 citations to be among the most cited 1% of physicists in the world. The threshold for space science is the highest (2236 citations), and physics is followed by clinical medicine (1390) and molecular biology & genetics (1229). Most disciplines, such as environment/ecology (390), have fewer scientists, fewer papers, and fewer citations. Therefore, these disciplines have lower citation thresholds in the Essential Science Indicators, with the lowest citation thresholds observed in social sciences (154), computer science (149), and multidisciplinary sciences (147).

Numbers are very different in social science disciplines: The Impact of the Social Sciences team at London School of Economics found that social scientists in the United Kingdom had lower average h-indices. The h-indices for ("full") professors, based on Google Scholar data ranged from 2.8 (in law), through 3.4 (in political science), 3.7 (in sociology), 6.5 (in geography) and 7.6 (in economics). On average across the disciplines, a professor in the social sciences had an h-index about twice that of a lecturer or a senior lecturer, though the difference was the smallest in geography.

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Advantages

Hirsch intended the h-index to address the main disadvantages of other bibliometric indicators, such as total number of papers or total number of citations. Total number of papers does not account for the quality of scientific publications, while total number of citations can be disproportionately affected by participation in a single publication of major influence (for instance, methodological papers proposing successful new techniques, methods or approximations, which can generate a large number of citations), or having many publications with few citations each. The h-index is intended to measure simultaneously the quality and quantity of scientific output.

src: blog.scopus.com

Criticism

There are a number of situations in which h may provide misleading information about a scientist's output: Most of these however are not exclusive to the h-index.

• The h-index does not account for the typical number of citations in different fields. It has been stated that citation behavior in general is affected by field-dependent factors, which may invalidate comparisons not only across disciplines but even within different fields of research of one discipline.
• The h-index discards the information contained in author placement in the authors' list, which in some scientific fields is significant.
• The h-index has been found in one study to have slightly less predictive accuracy and precision than the simpler measure of mean citations per paper. However, this finding was contradicted by another study by Hirsch.
• The h-index is a natural number that reduces its discriminatory power. Ruane and Tol therefore propose a rational h-index that interpolates between h and h + 1.
• The h-index can be manipulated through self-citations, and if based on Google Scholar output, then even computer-generated documents can be used for that purpose, e.g. using SCIgen.
• The h-index does not provide a significantly more accurate measure of impact than the total number of citations for a given scholar. In particular, by modeling the distribution of citations among papers as a random integer partition and the h-index as the Durfee square of the partition, Yong arrived at the formula ${\displaystyle h\approx 0.54{\sqrt {N}}}$, where N is the total number of citations, which, for mathematics members of the National Academy of Sciences, turns out to provide an accurate (with errors typically within 10-20 percent) approximation of h-index in most cases.

src: blog.scopus.com

Alternatives and modifications

Various proposals to modify the h-index in order to emphasize different features have been made. As the variants have proliferated, comparative studies have become possible showing that most proposals are highly correlated with the original h-index, although alternative indexes may be important to decide between comparable CVs, as often the case in evaluation processes.

• An individual h-index normalized by the number of author has been proposed: ${\displaystyle h_{I}=h^{2}/N_{a}^{(T)}}$, with ${\displaystyle N_{a}^{(T)}}$ being the number of authors considered in the ${\displaystyle h}$ papers. It was found that the distribution of the h-index, although it depends on the field, can be normalized by a simple rescaling factor. For example, assuming as standard the hs for biology, the distribution of h for mathematics collapse with it if this h is multiplied by three, that is, a mathematician with h = 3 is equivalent to a biologist with h = 9. This method has not been readily adopted, perhaps because of its complexity. It might be simpler to divide citation counts by the number of authors before ordering the papers and obtaining the h-index, as originally suggested by Hirsch.
• The m-index is defined as h/n, where n is the number of years since the first published paper of the scientist; also called m-quotient.
• There are a number of models proposed to incorporate the relative contribution of each author to a paper, for instance by accounting for the rank in the sequence of authors.
• A generalization of the h-index and some other indices that gives additional information about the shape of the author's citation function (heavy-tailed, flat/peaked, etc.) has been proposed.
• A successive Hirsch-type-index for institutions has also been devised. A scientific institution has a successive Hirsch-type-index of i when at least i researchers from that institution have an h-index of at least i.
• Three additional metrics have been proposed: h² lower, h² center, and h² upper, to give a more accurate representation of the distribution shape. The three h² metrics measure the relative area within a scientist's citation distribution in the low impact area, h² lower, the area captured by the h-index, h² center, and the area from publications with the highest visibility, h² upper. Scientists with high h² upper percentages are perfectionists, whereas scientists with high h² lower percentages are mass producers. As these metrics are percentages, they are intended to give a qualitative description to supplement the quantitative h-index.
• The g-index can be seen as the h-index for an averaged citations count.
• It has been argued that "For an individual researcher, a measure such as Erd?s number captures the structural properties of network whereas the h-index captures the citation impact of the publications. One can be easily convinced that ranking in coauthorship networks should take into account both measures to generate a realistic and acceptable ranking." Several author ranking systems such as eigenfactor (based on eigenvector centrality) have been proposed already, for instance the Phys Author Rank Algorithm.
• The c-index accounts not only for the citations but for the quality of the citations in terms of the collaboration distance between citing and cited authors. A scientist has c-index n if n of [his/her] N citations are from authors which are at collaboration distance at least n, and the other (N - n) citations are from authors which are at collaboration distance at most n.
• An s-index, accounting for the non-entropic distribution of citations, has been proposed and it has been shown to be in a very good correlation with h.
• The e-index, the square root of surplus citations for the h-set beyond h², complements the h-index for ignored citations, and therefore is especially useful for highly cited scientists and for comparing those with the same h-index (iso-h-index group).
• Because the h-index was never meant to measure future publication success, recently, a group of researchers has investigated the features that are most predictive of future h-index. It is possible to try the predictions using an online tool. However, later work has shown that since h-index is a cumulative measure, it contains intrinsic auto-correlation that led to significant overestimation of its predictability. Thus, the true predictability of future h-index is much lower compared to what has been claimed before.
• The h-index has been applied to Internet Media, such as YouTube channels. The h-index is defined as the number of videos with >= h × 10⁵ views. When compared with a video creator's total view count, the h-index and g-index better capture both productivity and impact in a single metric.
• The i10-index indicates the number of academic publications an author has written that have at least ten citations from others. It was introduced in July 2011 by Google as part of their work on Google Scholar.
• The h-index has been shown to have a strong discipline bias. However, a simple normalization ${\displaystyle h/\langle h\rangle _{d}}$ by the average h of scholars in a discipline d is an effective way to mitigate this bias, obtaining a universal impact metric that allows comparison of scholars across different disciplines. Of course this method does not deal with academic age bias.
• The h-index can be timed to analyze its evolution during one's career, employing different time windows.
• The o-index corresponds to the geometric mean of the h-index and the most cited paper of a researcher.

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See also

• Bibliometrics
• Comparison of research networking tools and research profiling systems

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References

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Further reading

• Alonso, S.; Cabrerizo, F. J.; Herrera-Viedma, E.; Herrera, F. (2009). "h-index: A Review Focused in its Variants, Computation and Standardization for Different Scientific Fields". Journal of Informetrics. 3 (4): 273-89. doi:10.1016/j.joi.2009.04.001. 
• Ball, Philip (2005). "Index aims for fair ranking of scientists". Nature. 436 (7053): 900. Bibcode:2005Natur.436..900B. doi:10.1038/436900a. PMID 16107806. 
• Iglesias, Juan E.; Pecharromán, Carlos. "Scaling the h-index for different scientific ISI fields" (PDF). 
• Kelly, C. D.; Jennions, M. D. (2006). "The h index and career assessment by numbers". Trends Ecol. Evol. 21 (4): 167-70. doi:10.1016/j.tree.2006.01.005. PMID 16701079. 
• Lehmann, S.; Jackson, A. D.; Lautrup, B. E. (2006). "Measures for measures". Nature. 444 (7122): 1003-04. Bibcode:2006Natur.444.1003L. doi:10.1038/4441003a. PMID 17183295. 
• Panaretos, J.; Malesios, C. (2009). "Assessing Scientific Research Performance and Impact with Single Indices". Scientometrics. 81 (3): 635-70. arXiv:0812.4542 . doi:10.1007/s11192-008-2174-9. 
• Petersen, A. M.; Stanley, H. Eugene; Succi, Sauro (2011). "Statistical Regularities in the Rank-Citation Profile of Scientists". Scientific Reports. 181: 1-7. arXiv:1103.2719 . Bibcode:2011NatSR...1E.181P. doi:10.1038/srep00181. 
• Sidiropoulos, Antonis; Katsaros, Dimitrios; Manolopoulos, Yannis (2007). "Generalized Hirsch h-index for disclosing latent facts in citation networks". Scientometrics. 72 (2): 253-80. doi:10.1007/s11192-007-1722-z. 
• Soler, José M. (2007). "A rational indicator of scientific creativity". Journal of Informetrics. 1 (2): 123-30. arXiv:physics/0608006 . doi:10.1016/j.joi.2006.10.004. 
• Symonds, M. R.; et al. (2006). Tregenza, Tom, ed. "Gender differences in publication output: towards an unbiased metric of research performance". PLoS ONE. 1 (1): e127. Bibcode:2006PLoSO...1..127S. doi:10.1371/journal.pone.0000127. PMC 1762413 . PMID 17205131. 
• Taber, Douglass F. (2005). "Quantifying Publication Impact". Science. 309 (5744): 2166a. doi:10.1126/science.309.5744.2166a. PMID 16195445. 
• Woeginger, Gerhard j. (2008). "An axiomatic characterization of the Hirsch-index". Mathematical Social Sciences. 56 (2): 224-32. doi:10.1016/j.mathsocsci.2008.03.001. 

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External links

• Google Scholar Metrics
• H-index for economists
• H-index for computer science researchers
• H-index for astronomers

Source of article : Wikipedia