منابع مشابه
"On guard at the gateway".
TO the general public the work of the Port Health Service is little known with the result that it gets very little publicity except on those rare occasions when a large passenger liner is held up with a case of suspected smallpox on board. Port health authorities whether they are concerned with a seaport or airport have one major function and that is to protect the country of which they are the...
متن کاملGuard cells
What are guard cells? A pair of guard cells surrounds each stoma on the leaf surface. Stomata are important because they regulate the uptake of CO 2 from the atmosphere for photosynthesis and also the loss of water vapour from the plant during transpiration. The aperture of the stomatal pore is controlled by the two guard cells. When the guard cells are fully turgid the pore gapes open, whereas...
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The IPv6 Router Advertisement Guard (RA-Guard) mechanism is commonly employed to mitigate attack vectors based on forged ICMPv6 Router Advertisement messages. Many existing IPv6 deployments rely on RA-Guard as the first line of defense against the aforementioned attack vectors. However, some implementations of RA-Guard have been found to be prone to circumvention by employing IPv6 Extension Hea...
متن کاملA microtome knife guard.
The base sledge microtome presents a hazard to the operator due to the length of blade that is exposed. Manipulation of the carriage requires hand movements close to the knife edge and serious lacerations may result. A simple, effective guard has been devised, suitable for knives which have screw holes for handles at both ends. It consists of two perspex end-pieces (Fig. I), attached to the kni...
متن کاملUniversal Guard Problems
We provide a spectrum of results for the Universal Guard Problem, in which one is to obtain a small set of points (“guards”) that are “universal” in their ability to guard any of a set of possible polygonal domains in the plane. We give upper and lower bounds on the number of universal guards that are always sufficient to guard all polygons having a given set of n vertices, or to guard all poly...
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ژورنال
عنوان ژورنال: Nature Reviews Immunology
سال: 2002
ISSN: 1474-1733,1474-1741
DOI: 10.1038/nri710