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1. the entire gaseous envelope surrounding the earth and subject to the earth's gravitational field.
2. the air or climate in a particular place. adj., atmospher´ic.
3. a unit of pressure, being that exerted by the earth's atmosphere at sea level; equal to 1.01325 × 105pascals (approximately 760 mm Hg). Abbreviated atm.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


Farlex Partner Medical Dictionary © Farlex 2012


Ataxia telangiectasia mutated. A checkpoint kinase which transduces genomic stress signals to stop cell cycle progression and promote DNA repair, acting via p53, a tumour suppressor protein. Its cognate gene, ATM (see below), is mutated in ataxia telangiectasia, a rare neurodegenerative disease characterised by ataxia telangiectasias, increased chromosome fragility when exposed to ionising radiation and predisposition to lymphomas.

ATM (Gene)
A gene on chromosome 11q22-q23, which encodes a PI3/PI4 cell-cycle checkpoint kinase that phosphorylates, thereby regulating a broad range of downstream proteins—e.g., tumor suppressor proteins p53 and BRCA1, checkpoint kinase CHK2, checkpoint proteins RAD17 and RAD9, and DNA repair protein NBS1.

Mutated in
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


Abbreviation for standard atmosphere.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
References in periodicals archive ?
"While working at the United Kingdom's National Physical Laboratory, Donald's invention of packet switching made the internet, and ultimately the world wide web, possible.
Without packet switching, it is unlikely the likes of Google or Facebook would ever have been invented.
Alcatel-Lucent Bell Labs and NTT Photonics will, through the agreement, cooperate in investigations on optical packet switching technology, including transport multi-protocol label switching (T-MPLS), the first version of MPLS Transport.
During the past decade, a great deal of technology advancement has occurred that attempts to use the same packet switching technique for voice telephone calls.
The primary reason that low cost can be achieved is attributable to an architecture based on data, which takes advantage of the statistical multiplexing advantages of packet switching and enables a flat decentralized network design, leveraging the benefits of open IP standards.
GPRS networks, which are still in the pre-commercial phase, use mobile rapid packet switching data transmission techniques like the Internet.
This capability results from the use of open standards and development tools inherent in "Voice over Internet Protocol" or VoIP and through the international acceptance of certain voice compression and packet switching standards.
However, the minuscule costs and accordingly "free" nature of the packet switching of email might create a millennium of "free" interpersonal communication via the electronic post.
By contrast, the Internet uses "packet switching." The term "packet" refers to the fact that the data stream from your computer is broken into packets of about 200 bytes (on average), which are then sent out onto the network.
The dreamwork is a kind of packet switching. On the Internet, digital information is broken up into units or packets, and allowed to take whatever route is open through the rhizome of the Net.
A private packet switching setup serves as the backbone of the system, with 24-hour monitoring provided by the telephone company.
X.25 packet switching has moved from public data networks to the nucleus of private networks.