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Scientists have known for more than two decades that cancer is a disease of the genes. Something scrambles the DNA inside a nucleus, and suddenly, instead of dividing in a measured fashion, a cell begins to copy itself furiously. Unlike an ordinary cell, it never, stops. But describing the process isn’t the same as figuring it out. Cancer cells are so radically different from normal ones that it’s almost impossible to untangle the sequence of events that made them that way. So for years researchers have been attacking the problem by taking normal cells and trying to determine what changes will turn them cancerous - always Without success. According to a report in the current issue of Nature, a team of scientists based at M. I .T.’s Whitehead Institute for Biomedical Research has finally managed to make human ceils malignant -a feat they accomplished with two different cell types by inserting just three altered genes into their DNA. While these manipulations were done only in lab dishes and won’t lead to any immediate treatment, they appear to be a crucial step in understanding the disease. This is a "landmark paper," wrote Jonathan Weitzman and Moshe Yaniv of the Pasteur Institute in Paris, in an accompanying commentary. The dramatic new result traces back to a breakthrough in 1983, when the Whitehead’s Robert Weinberg and colleagues showed that mouse cells would become cancerous when subjected to two altered genes. But when they tried such alterations on human cells, they didn’t work. Since then, scientists have learned that mouse cells differ from human cells in an important respect: they have higher levels of an enzyme called telomerase. That enzyme keeps caplike structures called telomeres on the ends of chromosomes from getting shorter with each round of cell division. Such shortening is part of a cell’s aging process, and since cancer cells keep dividing forever, the Whitehead group reasoned that making human cells more mouselike might also make them cancerous. The strategy worked. The scientists took connective-tissue and kidney cells and introduce three altered genes—one that makes cells divide rapidly; another that disables two substances meant to rein in excessive division; and a third that promotes the production of telomerase, which made the cells essentially immortal. They’d created a tumor in a test tube. "Some people believed that telomerase wasn’t that important," says the Whitehead’s William Hahn, the study’s lead author. "This allows us to say with some certainty that it is.\ Whitehead’s scientists have succeeded in ______.
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I was introduced to the concept of literacy animator in Oladumi Arigbede’s (1994) article on high illiteracy rates among women and school dropout rates among girls. According to Arigbede, literacy animators view their role as assisting in the self-liberating development of people in the world who are struggling for a more meaningful life. Animators are a family of deeply concerned and committed people whose gut-level rejection of mass human pauperizafion compels them to intervene on the side of the marginalized. Their motivation is not derived from a love of literacy as merely another technical life skill, and they accept that literacy is never culturally or ideologically neutral. Arigbede writes from her experiences as an animator working with women and men in Nigeria. She believes that literacy animators have to make a clear choice about whose culture and whose ideology will be fostered among those with whom they work. Do literacy educators in the United States consider whether the instruction they pursue conflicts with their students’ traditional cultures or community, or fosters illiteracies in learners’ first or home languages or dialects and in their orality Some approaches to literacy instruction represent an ideology of individualism, control, and competition. Consider, for example, the difference in values conveyed and represented when students engage in choral reading versus the practice of having one student read out loud to the group. To identify as a literacy animator is to choose the ideology of "sharing, solidarity, love, equity, co-operation with and respect of both nature and other human beings". Literacy pedagogy that matches the animator ideology works on maintaining the languages and cultures of millions of minority children who at present are being forced to accept the language and culture of the dominant group. It might lead to assessment that examines the performance outcomes of a community of literacy learners and the social significance of their uses of literacy, as opposed to measuring what an individual can do as a reader and writer on a standardized test. Shor(1993) describes literacy animators as problem-posing, community-based, dialogic educators. Do our teacher-education textbooks on reading and language arts promote the idea that teachers should explore problems from a community-based dialogic perspective Arigbede worked with Nigerians probably to ______.
If a mother pushes her small son in a swing, giving only a light force each time he returns, eventually he will be swinging quite high. The child can do this for himself by using his legs to increase the motion, but both the mother’s push and the child’s leg movements must occur at the proper moment, or the extent of the swing will not increase. In physics, increasing the swing is increasing the amplitude; the length of the rope on the swing determines its natural oscillation period. This ability of an object to move periodically or to vibrate when stimulated by a force operating in its natural period is called resonance. Resonance is observed many times without consciously thinking about it; for example, one may find an annoying vibration or shimmy in an automobile, caused by a loose engine mount vibrating with increasing amplitude because of an out-of-round tire. The bulge on the tire slaps the pavement with each revolution; at the natural resonance point of the engine mount, it will begin to vibrate. Such vibrations can result in considerable damage if allowed to persist. Another destructive example of resonance is the shattering of a crystal goblet by the production of a musical tone at the natural resonant point of the goblet. The energy of the sound waves causes vibration in the glass; as its amplitude increases, the motion in the glass exceeds the elasticity of the goblet, and it shatters. An instrument called a tachometer makes use of the principle of resonance. It consists of many tiny bars, loosely fastened together and arranged so that each bar can slide independently of the others. Movement of the bars causes changes in a dial. When placed next to a rotating motor or engine, the tachometer picks up slight vibrations which are transferred to the resonant bars. These bars begin to move, and the resulting dial may be read to find the revolutions per minute of the motor very quickly. An object, if moving rhythmically when stimulated in a natural period, is said to ______.
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