Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location, not due to deliberate introduction of radiation sources. Background radiation originates from a variety of both natural and artificial; these include both cosmic radiation and environmental radioactivity from occurring radioactive materials, as well as man-made medical X-rays, fallout from nuclear weapons testing and nuclear accidents. Background radiation is defined by the International Atomic Energy Agency as "Dose or dose rate attributable to all sources other than the one specified. So a distinction is made between dose, in a location, defined here as being "background", the dose due to a deliberately introduced and specified source; this is important where radiation measurements are taken of a specified radiation source, where the existing background may affect this measurement. An example would be measurement of radioactive contamination in a gamma radiation background, which could increase the total reading above that expected from the contamination alone.
However, if no radiation source is specified as being of concern the total radiation dose measurement at a location is called the background radiation, this is the case where an ambient dose rate is measured for environmental purposes. Background radiation varies with location and time, the following table gives examples: Radioactive material is found throughout nature. Detectable amounts occur in soil, water and vegetation, from which it is inhaled and ingested into the body. In addition to this internal exposure, humans receive external exposure from radioactive materials that remain outside the body and from cosmic radiation from space; the worldwide average natural dose to humans is about 2.4 mSv per year. This is four times the worldwide average artificial radiation exposure, which in 2008 amounted to about 0.6 millisieverts per year. In some rich countries, like the US and Japan, artificial exposure is, on average, greater than the natural exposure, due to greater access to medical imaging.
In Europe, average natural background exposure by country ranges from under 2 mSv annually in the United Kingdom to more than 7 mSv annually for some groups of people in Finland. The International Atomic Energy Agency states: "Exposure to radiation from natural sources is an inescapable feature of everyday life in both working and public environments; this exposure is in most cases of little or no concern to society, but in certain situations the introduction of health protection measures needs to be considered, for example when working with uranium and thorium ores and other Naturally Occurring Radioactive Material. These situations have become the focus of greater attention by the Agency in recent years." Terrestrial radiation, for the purpose of the table above, only includes sources that remain external to the body. The major radionuclides of concern are potassium and thorium and their decay products, some of which, like radium and radon are intensely radioactive but occur in low concentrations.
Most of these sources have been decreasing, due to radioactive decay since the formation of the Earth, because there is no significant amount transported to the Earth. Thus, the present activity on earth from uranium-238 is only half as much as it was because of its 4.5 billion year half-life, potassium-40 is only at about 8% of original activity. But during the time that humans have existed the amount of radiation has decreased little. Many shorter half-life isotopes have not decayed out of the terrestrial environment because of their on-going natural production. Examples of these are radium-226 and radon-222. Thorium and uranium undergo alpha and beta decay, aren't detectable. However, many of their daughter products are strong gamma emitters. Thorium-232 is detectable via a 239 keV peak from lead-212, 511, 583 and 2614 keV from thallium-208, 911 and 969 keV from actinium-228. Uranium-238 manifests as 609, 1120, 1764 keV peaks of bismuth-214. Potassium-40 is detectable directly via its 1461 keV gamma peak.
The level over the sea and other large bodies of water tends to be about a tenth of the terrestrial background. Conversely, coastal areas may have an additional contribution from dispersed sediment; the biggest source of natural background radiation is airborne radon, a radioactive gas that emanates from the ground. Radon and its isotopes, parent radionuclides, decay products all contribute to an average inhaled dose of 1.26 mSv/a. Radon is unevenly distributed and varies with weather, such that much higher doses apply to many areas of the world, where it represents a significant health hazard. Concentrations over 500 times the world average have been found inside buildings in Scandinavia, the United States and the Czech Republic. Radon is a decay product of uranium, common in the Earth's crust, but more concentrated in ore-bearing rocks scattered around the world. Radon seeps out of these ores into the atmosphere or into ground water or infiltrates into buildings, it can be inhaled into the lungs, along with its decay products, where they will reside for a period of time after exposure.
Although radon is occurring, exposure can be enhanced or diminished by human act
The Lees River or Lee's River, shown on federal maps as the Lee River, is a 2.9-mile-long tidal river that forms part of the boundary between Swansea and Somerset, Massachusetts. It flows south to drain into Mount Hope Bay; the first documented local shipyard was established on the river between 1707 and 1712 by Samuel Lee. Today the river is designated as "outstanding resource" water. Southeastern Regional Planning & Economic Development District Environmental Protection Agency Massachusetts Department of Housing and Community Development
East Street in a street located in Fremantle, Western Australia. It runs between Beach Street on the southern shore of the Swan River; the intersection with High Street is at the north east corner of the Monument Hill reserve. It intersects with Ellen Street and Burt Street on its western side, it crosses Canning Highway before a steep drop to the level of Beach Street. Located on the western side of the street is the John Curtin College of the Arts The Swan River end of the street, a jetty known locally as the East Street Jetty, has been the location for a number of events
The Woodlark cuscus is a species of marsupial in the family Phalangeridae endemic to Papua New Guinea on Madau and Woodlark Island, a part of the Milne Bay Province of Papua New Guinea. It happens to be the largest mammal living on Woodlark Island but it is found on the neighboring island of Alcester, 70 kilometers south of Woodlark Island; the generic name, Phalanger, is of Greek origin and means "spider's web." This name is given in reference to their syndactyly. Its specific name, lullulae, is Latin in origin and is the Latin translation of "Woodlark." In a phylogenetic tree published in 1987 by Tim Flannery and his colleagues, Phalanger lullulae was believed to share the same states with Phalanger intercastellanus known as the Eastern common cuscus. A morphological consensus tree shows that the Phalanger lullulae is related to the Mountain cuscus, Phalanger interpositus, Stein's cuscus, the Banggai cuscus; this phylogenetic tree was created by Tim Flannery and his colleagues in 1987 but was reanalyzed by Ruedas and Morales in 2005.
A partial 12S rRNA ML tree by Ruedas and Morales demonstrated the firstly mentioned relationship between the Phalanger lullulae and Phalanger intercastellanus. The Partial 12S rRNA ML tree by Hamilton and Springer demonstrated that the Phalanger lullulae is most related to the Northern common cuscus. An ML tree of the nuclear gene BRCA1 created by Raterman and his colleagues shows the Phalanger lullulae's close relationship to the Phalanger orientalis as well. While these aforementioned phylogenies are more certain, there is another proposed morphological phylogeny by Flannery that demonstrates the uncertainty of the Phalanger lullulae's relationship among the Phalanger orientalis and Phalanger vestitus; the Woodlark cuscus is overall a medium-sized marsupial with dark facial skin small pink colored ears, a pink rhinarium. While they are medium-sized, the females, on average, tend to be larger than the males. What sets these cuscuses apart from other diprotodont marsupials is the back part of the cranium not being so exposed to the mastoid.
Its skull is in the shape of a pear and its widest portion of the skull can be found in the posterior end of its zygomatic arch. While the molars do not undergo strong crenulation, the nasal bones extend and stop where the premaxilla stops, its dentition continues with the cingulum being quite large and well-developed and sitting between the lopids of the lower molars. The backside of the skull where the paroccipital processes are located are longer in comparison to the rest of the skull. What sets this marsupial apart from all of the others is its short fur, marble-like with a mix of white, dark brown, ginger spots on its back and a white underbelly; because the mixture is so varied between each Woodlark cuscus, you will never find two of these marsupials with the same coat pattern on its back. While this is true, the species can be divided into two groups: dark morphs. Light morphs have the lighter color mixture on their coats so they would have more of the white and ginger colors accompanied by small patches of dark fur.
Dark morphs have the darker color mixture on their coats, sporting more of the dark brown along with some patches of white fur. While both morphs are adorned with a dark dorsal stripe on their backs, it is more recognizable on the light morphs; the fur continues on along the tail of this possum but abruptly stops once the distal portion of the tail is reached to reveal a hairless tail. This naked part of the tail is dark much like its face and is a bit rugose but since it is prehensile, it allows for the tail to be used for gripping; this possum lives its arboreal life in primary and secondary tropical forests with a preference for the dry lowland forest. The hunters on Woodlark Island claim that the Phalanger lullalae finds shelter under the epiphytes and inside tree hollows during the day. Since the dry lowland forest makes up the Eastern half of Woodlark Island, there is a higher prominence of these possums here compared to the dense rain forests of the Western half of the Island; the behaviors that occur among male and female Woodlark cuscus before and after mating have not yet been observed.
However, the capture of five female Woodlark cuscuses in August 1987 led to the following interesting observations: one of the females were parous but did not have any young while another was lactating. Two others had its naked young in their pouches; this transition from the pouch of the mother to the back of the mother as the young age is typical in the Phalanger lullulae because they are metatherians and this transition is typical metatherian behavior. The various states of the young and female cuscuses were in demonstrate that the breeding season most happens over a long period of time, it has been noted that they give birth to single young. Another aspect of the Woodlark cuscus' metatherian identity can be seen the composition of the mother's milk; as the young grow, the carbohydrate and protein compositions in the mother's milk fluctuates in accordance to the stage the young Phalanger lullulae is in as it grows. The tiny young will feed on milk, dilute and composted of simple sugars while the older ones feed on more concentrated milk.
Thanks to Oxford University's journey to Woodlark Island, they were able to note and monitor the behavior of the Woodlark cuscus by using radio tracking techniques. These studies revealed that the cuscus is a solitary animal and the activities of the cuscus surround the few sleeping trees they come in contact with
Cleveland is an unincorporated community in suburban northwestern Johnston County, North Carolina, United States. It lies at an elevation of 243 feet; the settlement is known as Cleveland Crossings, Cleveland Community, Cleveland School or 40/42, so named for the intersection of I-40 and NC 42 at the northeastern edge of the community, which serves as the primary commercial hub of the area. NC 50 skirts the western edge of the community; the community's population is concentrated along Cleveland Road in Johnston County. While unincorporated, postal addresses for the community lie in Garner and Benson; the community is named for a former K-12 school lying on Cleveland Road. Nearby unincorporated communities include McGee's Crossroads to the south along NC 50 and Willow Spring to the west along NC 42. There have been several efforts to incorporate the fast-growing community, though the issue was tabled by the North Carolina General Assembly in 1999. Since there is a town known as Cleveland, North Carolina elsewhere in the state, the name of the proposed incorporated town has been a minor point of contention.
Thousands of new homes have been built in the community, making it one of the faster-growing areas in Johnston County. Its location at a major interchange along Interstate 40 has made it a burgeoning business center. Public education for the Cleveland community is provided by the Johnston County School District; the following schools serve residents of the Cleveland community: Cleveland Elementary School Polenta Elementary School Westview Elementary School Cleveland Middle School Swift Creek Middle School Cleveland High School West Johnston High School Johnston Community College's Cleveland Center Greater Cleveland Chamber of Commerce Cleveland Post
Μ Tauri, Latinized as Mu Tauri, is a single star in the equatorial constellation of Taurus. It has a blue-white hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.27. The star is located 490 light years distant from the Sun based on parallax, is drifting further away with a radial velocity of +16 km/s; this object has a stellar classification of B3IV, matching a B-type subgiant star. In the past this star was thought to have a variable radial velocity, but is now considered constant, it is spinning with a projected rotational velocity of 89 km/s. The star has 6.7 times the mass of the Sun and is radiating 462 times the Sun's luminosity from its photosphere at an effective temperature of 16,980 K. It is emitting an infrared excess at a wavelength of 18 μm, making it a candidate host of a faint warm debris disk