Demersal Fish

Sat, 04 Sep 2010 07:09:50 -0500

TypesDemersal fish can be divided into two main types: benthic fish which rest on the sea floor, and benthopelagic fish which float in the water column just above the sea floor.Benthopelagic fish have neutral buoyancy, so they can float at depth without much effort, while benthic fish are more dense, with negative buoyancy so they can lie on the bottom without any effort. Most demersal fish are benthopelagic.As with other bottom feeders, a mechanism to deal with substrate is often necessary. With demersal fish the sand is usually pumped out of the mouth through the gill slit. Most demersal fish exhibit a flat ventral region so as to more easily rest their body on the substrate. The exception may be the flatfish, which are laterally depressed but lie on their sides. Also, many exhibit what is termed an "inferior" mouth, which means that the mouth is pointed downwards; this is beneficial as their food is often going to be below them in the substrate. Those bottom feeder...

Global Maritime Distress Safety System

Fri, 03 Sep 2010 07:25:29 -0500

Components of GMDSSThe main types of equipment used in GMDSS are: Emergency Position-Indicating Radio Beacon EPIRBMain article: Emergency Position-Indicating Radio BeaconCospas-Sarsat is an international satellite-based search and rescue system, established by Canada, France, the United States, and Russia. These four countries jointly helped develop the MHz Emergency Position-Indicating Radio Beacon EPIRB, an element of the GMDSS designed to operate with Cospas-Sarsat system. These automatic-activating EPIRBs, now required on SOLAS ships, commercial fishing vessels, and all passenger ships, are designed to transmit to alert rescue coordination centers via the satellite system from anywhere in the world. The original COSPAS SARSAT system used Polar orbiting satellites but in recent years the system has been expanded to also include GEOSTATIONARY satellites. Newest designs incorporate GPS receivers to transmit highly accurate positions within about met...

Magnetic Levitation

Thu, 02 Sep 2010 07:17:04 -0500

LiftMagnetic materials and systems are able to attract or press each other apart or together with a force dependent on the magnetic field and the area of the magnets, and a magnetic pressure can then be defined.The magnetic pressure of a magnetic field can be calculated by:where Pmag is the force per unit area in Nm, B is the magnetic field in Teslas, and NA is the permeability of the vacuum. StabilityStatic stability means that any small displacement away from a stable equilibrium causes a net force to push it back to the equilibrium point.Earnshaw's theorem proved conclusively that it is not possible to levitate stably using only static, macroscopic, paramagnetic fields. The forces acting on any paramagnetic object in any combination of gravitational, electrostatic, and magnetostatic fields will make the object's position unstable along at least one axis, and can be unstable along all axes. However, several possibilities exist to make levitation viab...

The Muppet Show

Wed, 01 Sep 2010 20:07:26 -0500

HistoryThis section does not cite any references or sources.Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. June Since , Sesame Street had given Jim Henson's Muppet creations exposure; however, Henson began to perceive that he was pigeonholed as a children's entertainer. He sought to create a program that could be enjoyed by young and old. Two specials were produced and aired that are considered pilots for The Muppet Show. Neither led to the sale of a prime-time network series. However, the prime-time access rule had just been enacted, which took the : to pm ET slot from the networks and turned it over to their affiliates. CBS suggested it would be interested in Henson's proposal as a syndicated series it could purchase for its owned-and-operated stations, to run one night a week in that time slot.citation neededLew Grade, head of the British commercial station ATV, offered a ...