TheoryA theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may be scientific, belong to a non-scientific discipline, or no discipline at all. Depending on the context, a theory's assertions might, for example, include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several related meanings.
Embryonic stem cellEmbryonic stem cells (ESCs) are pluripotent stem cells derived from the inner cell mass of a blastocyst, an early-stage pre-implantation embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells. Isolating the inner cell mass (embryoblast) using immunosurgery results in destruction of the blastocyst, a process which raises ethical issues, including whether or not embryos at the pre-implantation stage have the same moral considerations as embryos in the post-implantation stage of development.
Adult stem cellAdult stem cells are undifferentiated cells, found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells (from Greek σωματικóς, meaning of the body), they can be found in juvenile, adult animals, and humans, unlike embryonic stem cells. Scientific interest in adult stem cells is centered around two main characteristics.
Stem-cell nicheStem-cell niche refers to a microenvironment, within the specific anatomic location where stem cells are found, which interacts with stem cells to regulate cell fate. The word 'niche' can be in reference to the in vivo or in vitro stem-cell microenvironment. During embryonic development, various niche factors act on embryonic stem cells to alter gene expression, and induce their proliferation or differentiation for the development of the fetus.
SkyscraperA skyscraper is a tall, continuously habitable building having multiple floors. Modern sources currently define skyscrapers as being at least or in height, though there is no universally accepted definition, other than being very tall high-rise buildings. Historically, the term first referred to buildings with between 10 and 20 stories when these types of buildings began to be constructed in the 1880s. Skyscrapers may host offices, hotels, residential spaces, and retail spaces.
Stem-cell lineA stem cell line is a group of stem cells that is cultured in vitro and can be propagated indefinitely. Stem cell lines are derived from either animal or human tissues and come from one of three sources: embryonic stem cells, adult stem cells, or induced stem cells. They are commonly used in research and regenerative medicine. Stem cell By definition, stem cells possess two properties: (1) they can self-renew, which means that they can divide indefinitely while remaining in an undifferentiated state; and (2) they are pluripotent or multipotent, which means that they can differentiate to form specialized cell types.
Arts and Crafts movementThe Arts and Crafts movement was an international trend in the decorative and fine arts that developed earliest and most fully in the British Isles and subsequently spread across the British Empire and to the rest of Europe and America. Initiated in reaction against the perceived impoverishment of the decorative arts and the conditions in which they were produced, the movement flourished in Europe and North America between about 1880 and 1920.
Stem cellIn multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage. They are found in both embryonic and adult organisms, but they have slightly different properties in each. They are usually distinguished from progenitor cells, which cannot divide indefinitely, and precursor or blast cells, which are usually committed to differentiating into one cell type.
Beaux-Arts architectureBeaux-Arts architecture (boʊz_ˈɑɹ , boz‿aʁ) was the academic architectural style taught at the École des Beaux-Arts in Paris, particularly from the 1830s to the end of the 19th century. It drew upon the principles of French neoclassicism, but also incorporated Renaissance and Baroque elements, and used modern materials, such as iron and glass. It was an important style in France until the end of the 19th century. The Beaux-Arts style evolved from the French classicism of the Style Louis XIV, and then French neoclassicism beginning with Style Louis XV and Style Louis XVI.
ResearchResearch is "creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular attentiveness to controlling sources of bias and error. These activities are characterized by accounting and controlling for biases. A research project may be an expansion on past work in the field. To test the validity of instruments, procedures, or experiments, research may replicate elements of prior projects or the project as a whole.
