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Radio is the wireless transmission of signals through free space by electromagnetic radiation of a frequency significantly below that of visible light, in the radio frequency range, from about 30 kHz to 300 GHz. These waves are called radio waves. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space.
Information, such as sound, is carried by systematically changing (modulating) some property of the radiated waves, such as their amplitude, frequency, phase, or pulse width. When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor. The information in the waves can be extracted and transformed back into its original form.
The etymology of "radio" or "radiotelegraphy" reveals that it was called "wireless telegraphy," which was shortened to "wireless" in Britain. The prefix radio- in the sense of wireless transmission, was first recorded in the word radioconductor, a description provided by the French physicist Édouard Branly in 1897. It is based on the verb to radiate (in Latin "radius" means "spoke of a wheel, beam of light, ray").
The word "radio" also appears in a 1907 article by Lee De Forest. It was adopted by the United States Navy in 1912, to distinguish radio from several other wireless communication technologies, such as the photophone. The term became common by the time of the first commercial broadcasts in the United States in the 1920s. (The noun "broadcasting" itself came from an agricultural term, meaning "scattering seeds widely.") The term was adopted by other languages in Europe and Asia. British Commonwealth countries continued to commonly use the term "wireless" until the mid-20th century, though the magazine of the BBC in the UK has been called Radio Times ever since it was first published in the early 1920s.
In recent years the more general term "wireless" has gained renewed popularity through the rapid growth of short-range computer networking, e.g., Wireless Local Area Network (WLAN), Wi-Fi, and Bluetooth, as well as mobile telephony, e.g., GSM and UMTS. Today, the term "radio" specifies the actual type of transceiver device or chip, whereas "wireless" refers to the lack of physical connections; one talks about radio transceivers, but about wireless devices and wireless sensor networks.
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El Nino, an abnormal warming of surface ocean waters in the eastern tropical Pacific, is one part of what's called the Southern Oscillation. The Southern Oscillation is the see-saw pattern of reversing surface air pressure between the eastern and western tropical Pacific; when the surface pressure is high in the eastern tropical Pacific it is low in the western tropical Pacific, and vice-versa. Because the ocean warming and pressure reversals are, for the most part, simultaneous, scientists call this phenomenon the El Nino/Southern Oscillation or ENSO for short. South American fishermen have given this phenomenon the name El Nino, which is Spanish for "The Christ Child," because it comes about the time of the celebration of the birth of the Christ Child-Christmas.
To really understand the effects of an El Nino event, compare the normal conditions of the Pacific region and then see what happens during El Nino below.
Scientists do not really understand how El Nino forms. It is believed that El Nino may have contributed to the 1993 Mississippi and 1995 California floods, drought conditions in South America, Africa and Australia. It is also believed that El Nino contributed to the lack of serious storms such as hurricanes in the North Atlantic which spared states like Florida from serious storm related damage.
Unfortunately not all El Nino's are the same nor does the atmosphere always react in the same way from one El Nino to another. This is why NASA's Earth scientists continue to take part in international efforts to understand El Nino events. Hopefully one day scientists will be able to provide sufficient warning so that we can be better prepared to deal with the damages and changes that El Nino causes in the weather.
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DEFINITIONS AND DIMENSIONS
Homeless youth are individuals under the age of eighteen who lack parental, foster, or institutional care. These young people are sometimes referred to as "unaccompanied" youth.
The number of the homeless youth is estimated by the Office of Juvenile Justice and Delinquency Prevention in the US Department of Justice. Their most recent study, published in 2002, reported there are an estimated 1,682,900 homeless and runaway youth. This number is equally divided among males and females, and the majority of them are between the ages of 15 and 17 (Molino, 2007). According to the U.S. Conference of Mayors, unaccompanied youth account for 1% of the urban homeless population, (U.S. Conference of Mayors, 2007). According to the National Network of Runaway and Youth Services, six percent of homeless youth are gay, lesbian, bisexual, or transgender (GLBT) (Molino, 2007). The number of homeless teenagers who are pregnant is estimated to be somewhere between six and twenty-two percent. (Health Resources and Services Administration 2001) According to the National Alliance to End Homelessness, five to seven percent of American youths become homeless in any given year. (NAEH, 2007)
CAUSES
Causes of homelessness among youth fall into three inter-related categories: family problems, economic problems, and residential instability.
Many homeless youth leave home after years of physical and sexual abuse, strained relationships, addiction of a family member, and parental neglect. Disruptive family conditions are the principal reason that young people leave home: in one study, more than half of the youth interviewed during shelter stays reported that their parents either told them to leave or knew they were leaving and did not care (U.S. Department of Health and Human Services (a), 1995). In another study, 46% of runaway and homeless youth had been physically abused and 17% were forced into unwanted sexual activity by a family or household member (U.S. Department of Health and Human Services (c), 1997).
Some youth may become homeless when their families suffer financial crises resulting from lack of affordable housing, limited employment opportunities, insufficient wages, no medical insurance, or inadequate welfare benefits. These youth become homeless with their families, but are later separated from them by shelter, transitional housing, or child welfare policies (Shinn and Weitzman, 1996).
Residential instability also contributes to homelessness among youth. A history of foster care correlates with becoming homeless at an earlier age and remaining homeless for a longer period of time (Roman and Wolfe, 1995). Some youth living in residential or institutional placements become homeless upon discharge -- they are too old for foster care but are discharged with no housing or income support (Robertson, 1996). One national study reported that more than one in five youth who arrived at shelters came directly from foster care, and that more than one in four had been in foster care in the previous year (National Association of Social Workers, 1992).
CONSEQUENCES
Homeless youth face many challenges on the streets. Few homeless youth are housed in emergency shelters as a result of lack of shelter beds for youth, shelter admission policies, and a preference for greater autonomy (Robertson, 1996). Because of their age, homeless youth have few legal means by which they can earn enough money to meet basic needs. Many homeless adolescents find that exchanging sex for food, clothing, and shelter is their only chance of survival on the streets. In turn, homeless youth are at a greater risk of contracting AIDS or HIV-related illnesses. Estimates for percentages of homeless youth infected with HIV are generally around 5%, but one study in San Francisco found that 17% of homeless youths were infected (Health Resources and Services Administration 2001). It has been suggested that the rate of HIV prevalence for homeless youth may be as much as 2 to 10 times higher than the rates reported for other samples of adolescents in the United States (National Network for Youth, 1998).
Homeless adolescents often suffer from severe anxiety and depression, poor health and nutrition, and low self-esteem. In one study, the rates of major depression, conduct disorder, and post-traumatic stress syndrome were found to be 3 times as high among runaway youth as among youth who have not run away (Robertson, 1989).
Furthermore, homeless youth face difficulties attending school because of legal guardianship requirements, residency requirements, improper records, and lack of transportation. As a result, homeless youth face severe challenges in obtaining an education and supporting themselves emotionally and financially.
PROGRAM AND POLICY ISSUES
Homeless youth benefit from programs that meet immediate needs first and then help them address other aspects of their lives. Programs that minimize institutional demands and offer a range of services have had success in helping homeless youth regain stability (Robertson, 1996). Educational outreach programs, assistance in locating job training and employment, transitional living programs, and health care especially designed for and directed at homeless youth are also needed. In the long term, homeless youth would benefit from many of the same measures that are needed to fight poverty and homelessness in the adult population, including the provision of affordable housing and employment that pays a living wage. In addition to these basic supports, the child welfare system must make every effort to prevent children from ending up on the streets.
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