The United States of America
is a federal republic
of 50 states
, a capital district
, and a number of other territories. It is located mostly in central North America
. The U.S. has three land borders, two with Canada
and one with Mexico
, and is otherwise bounded by the Pacific Ocean
, the Bering Sea
, the Arctic Ocean
and the Atlantic Ocean
. Of the 50 states, only Alaska
are not contiguous with any other state. The U.S. also has a collection of districts, territories, and possessions
around the world. Each state has a high level of local autonomy according to the system of federalism. The U.S. traces its national origin to the declaration
by 13 British
colonies in 1776
that they were free and independent states. They were recognized as such by the Treaty of Paris
in 1783. Since then, the nation has grown to become a global superpower
and exerts a high level of economic, political, military, and cultural influence.
African American history
is the portion of American history
that specifically discusses the African American
American ethnic group in the United States. Most African Americans are the descendants of captive Africans held in the United States from 1619 to 1865. Blacks from the Caribbean whose ancestors immigrated, or who immigrated to the U.S., also traditionally have been considered African American, as they share a common history of predominantly West African
or Central African
roots, the Middle Passage
It is these peoples, who in the past were referred to and self-identified collectively as the American Negro, who now generally consider themselves African Americans. It is these peoples whose history is celebrated and highlighted annually in the United States during February, designated as Black History Month, and it is their history that is the focus of this article.
Others who sometimes are referred to as African Americans, and who may self-identify as such in US government censuses, include relatively recent Black immigrants from Africa, South America and elsewhere who self-identify as being of African descent.
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Selected society biography
(June 16, 1902 – September 2, 1992) was an American scientist and cytogeneticist
who was awarded the 1983 Nobel Prize in Physiology or Medicine
. McClintock received her PhD
from Cornell University
in 1927. There she started her career as the leader in the development of maize
cytogenetics, the focus of her research for the rest of her life. From the late 1920s, McClintock studied chromosomes
and how they change during reproduction in maize
. She developed the technique for visualizing maize chromosomes
and used microscopic analysis to demonstrate many fundamental genetic ideas. One of those ideas was the notion of genetic recombination
—a mechanism by which chromosomes exchange information. She produced the first genetic map
for maize, linking regions of the chromosome to physical traits. She demonstrated the role of the telomere
, regions of the chromosome that are important in the conservation of genetic information
. She was recognized as among the best in the field, awarded prestigious fellowships, and elected a member of the National Academy of Sciences
During the 1940s and 1950s, McClintock discovered transposition and used it to demonstrate that genes are responsible for turning physical characteristics on and off. She developed theories to explain the suppression and expression of genetic information from one generation of maize plants to the next. Due to skepticism of her research and its implications, she stopped publishing her data in 1953.
Anniversaries for October 31
(, stressed , locally ) is the capital of and the most populous city in the U.S.
state of Georgia
, with a 2010 population of 420,003. Atlanta is the cultural and economic center of the Atlanta metropolitan area
, home to 5,268,860 people and the ninth largest metropolitan area
in the country. Atlanta is the county seat
of Fulton County
, and a small portion of the city extends eastward into DeKalb County
Atlanta was established in 1847 at the intersection of two railroad lines, and the city rose from the ashes of the Civil War to become a national center of commerce. In the decades following the Civil Rights Movement, during which the city earned a reputation as "too busy to hate" for the progressive views of its citizens and leaders, Atlanta attained international prominence. Atlanta is the primary transportation hub of the Southeastern United States via highway, railroad, and air, with Hartsfield–Jackson Atlanta International Airport being the world's busiest airport since 1998. Atlanta is considered an "alpha(-) world city," and, with a gross domestic product of US$270 billion, Atlanta’s economy ranks 15th among world cities and sixth in the nation. Although Atlanta’s economy is considered diverse, dominant sectors include logistics, professional and business services, media operations, government administration, and higher education. Geographically, Atlanta is marked by rolling hills and dense tree coverage. Revitalization of Atlanta's neighborhoods, initially spurred by the 1996 Olympics, has intensified in the 21st century, altering the city's demographics, politics, and culture.
Selected culture biography
was a renowned Russian-American photographer
, best known for capturing on film the culture of Jews
and Eastern Europe
before the Holocaust
Vishniac was an extremely diverse photographer, an accomplished biologist and a knowledgeable collector and teacher of art history. Throughout his life, he made significant scientific contributions to the fields of photomicroscopy and time-lapse photography. Vishniac was very interested in history, especially that of his ancestors. In turn, he was strongly tied to his Jewish roots and was a Zionist later in life.
Roman Vishniac won international acclaim for his photography: his pictures from the shtetlach and Jewish ghettos, celebrity portraits, and images of microscopic biology. He is known for his book A Vanished World, published in 1983, which was one of the first such pictorial documentations of Jewish culture in Eastern Europe from that period and also for his extreme humanism, respect and awe for life, sentiments that can be seen in all aspects of his work.
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