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for heart disease and is the primary risk factor for stroke. Prehypertension is a condition that increases a child's risk of developing high blood pressure in the future. Children with hypertension have a higher risk for high blood pressure as adults. High blood pressure in childhood is also correlated with early devel... |
blood pressure reading and corresponds to the pressure in arteries when the heart contracts. Diastolic pressure is the bottom number in a blood pressure reading, and corresponds to the pressure in the arteries between heart beats, when the heart relaxes. The American Academy of Pediatrics recommends that children ages ... |
care provider for routine checkups. Normal blood pressure in children depends on their gender, age, and height. Parents and health care providers encourage children with high blood pressure to make lifestyle changes, such as losing weight. Other changes may include increased exercise and improved diet. A doctor may als... |
and may keep blood pressure in check. Regular exercise means 30 to 60 minutes of moderate physical activity on most days. Sedentary activities should be limited to less than two hours a day. A healthy diet for a child with prehypertension or high blood pressure includes fresh vegetables and fruits, additional fiber, an... |
American Heart Association recommends a maximum daily sodium intake of 1,500 mg/day; however, this number may be lower, depending on your child's age and other health considerations. Please consult your child's pediatrician regarding the recommended sodium intake for your child. |
South Korea (officially, Republic of Korea) encompasses an area of 98,477 sq. km. (38,022 sq. mi.), about the size of state of Indiana. Its capital is Seoul (population 10.3 million); other major cities are: Busan, Daegu, Inchon, Gwangju, Daejeon, and Ulsan. The terrain of South Korea consists of forested mountain |
ranges separated by deep, narrow valleys and cultivated plains along the coasts. South Korea is bordered by North Korea to the North and is surrounded by the Sea of Japan, Korean Strait, and Yellow Sea. An independent Korean state or a collection of states has existed almost continuously for several |
millennia. Between its initial unification in the 7th century, until the 20th century, Korea existed as a single independent country. In 1905, following the Russo-Japanese War, Korea became a protectorate of imperial Japan, and in 1910 it was annexed as a colony. Korea regained its independence following Japan's surren... |
the United States in 1945. After World War II, the Republic of Korea (ROK) was set up in the southern half of the Korean Peninsula. During the Korean War (1950-53), US troops and UN forces fought alongside soldiers from the ROK to defend South Korea from Democratic People's Republic of |
Korea attacks supported by China and the Soviet Union. An armistice was signed in 1953, splitting the peninsula along a demilitarized zone at about the 38th parallel. After 1953, South Korea achieved rapid economic growth. In 1993, Kim Young-sam became South Korea's first civilian president, following 32 years of milit... |
rule. In June 2000, a historic North-South summit took place between South's President Kim Dae-jung and the North's leader Kim Jong Il. The natural hazards facing South Korea consist of occasional typhoons bringing high winds and floods and low-level seismic activity. In 2004, South Korea's oil consumption was 2.149 ba... |
Historical diversification of migration patterns in a passerine bird Förlag: Society for the Study of Evolution Migratory strategies of birds require complex orientation mechanisms, morphological adaptations, and life-history adjustments. From an evolutionary perspective, it is important to know how fast this complex c... |
populations with different migratory behaviors. The sample included sedentary populations in Europe and Atlantic archipelagos and migratory populations with different distances of migration, from regional to intercontinental migrations, and different heading directions (due to a migratory divide in central Europe). The... |
Iberian Peninsula, or the continent), however we found evidence of a genetic structure when comparing populations located on either side of the migratory divide. These findings support an independent evolution of highly divergent migratory strategies in blackcaps, occurring after a postglacial colonization of the conti... |
very small population size, and time estimates dated such an expansion during the last postglacial period. However, the populations in Gibraltar, located in a putative Mediterranean refuge, appeared to be independent of these processes, showing evidence of restricted gene flow with other populations and demonstrating i... |
flow between migratory and sedentary populations is not necessary for the maintenance of such a polymorphism, and that even the most divergent migratory strategies of a bird species are susceptible to evolution in response to historical environmental changes. - Biology and Life Sciences - Molecular Ecology and Evolutio... |
Arts and Artisans of Early 19th-Century Portland Text by William David Barry and John Mayer Images from Maine Historical Society, the Maine State Museum Portland's growth began in 1786 when citizens changed the name of the town from Falmouth Neck. Between then and the middle of the nineteenth century, the footprint of ... |
and the population increased dramatically. Newly enriched merchants and community leaders from Portland's middle and upper classes provided support for itinerant and local artisans. By the early nineteenth century, products made by native born and locally trained artists replaced those of itinerants and the work of the... |
in city schools, theaters, and academies. The demand for the arts helped native born and locally trained decorative painters, gilders, silversmiths, potters, furniture and cabinetmakers, tinsmiths, and other artisans thrive in Portland in the early nineteenth century. Fashionable costumes and stately poses rendered wit... |
with exotic or colorful materials illustrate changes over time in taste, design, and craftsmanship. These works represent the distinctive nature of the arts and artisans of Portland. This two-part online exhibit is based on an exhibit featured from June to December 2005 at the Maine Historical Society Museum. The exhib... |
Talking About Economic Troubles Download MP3 (Right-click or option-click the link.) I'm Susan Clark with the Special English program WORDS AND THEIR STORIES. In the nineteen thirties, a song, "Brother, Can You Spare a Dime?," was very popular in the United States. It was the time of the big Depression. The song had me... |
is a piece of money whose value is one-tenth of a dollar. Today, a dime does not buy much. But it was different in the nineteen thirties. A dime sometimes meant the difference between eating and starving. The American economy today is much better. Yet, many workers are concerned about losing their jobs as companies re-... |
troubles. People in businesses may say they feel the pinch. Or they may say they are up against it. Or, if things are really bad, they may say they have to throw in the towel. A pinch is painful pressure. To feel the pinch is to suffer painful pressure involving money. The expression, feel the pinch, has been used sinc... |
famous English writer William Shakespeare wrote something very close to this in his great play "King Lear." King Lear says he would accept necessity's sharp pinch. He means he would have to do without many of the things he always had. Much later, the Times of London newspaper used the expression about bad economic time... |
having been spent ... All classes felt the pinch." Worse than feeling the pinch is being up against it. The saying means to be in a lot of trouble. Word expert James Rogers says the word "it" in the saying can mean any and all difficulties. He says the saying became popular in the United States and Canada in the late n... |
George Ade used it in a book called "Artie." He wrote, "I saw I was up against it." Sometimes a business that is up against it will have to throw in the towel. This means to accept defeat or surrender. Throwing in the towel may mean that a company will have to declare bankruptcy. The company will have to take legal ste... |
people know it has no money to pay its debts. Word expert Charles Funk says an eighteen seventy-four publication called the Slang Dictionary explains throwing in the towel. It says the words probably come from the sport of boxing, or prizefighting. The book says the saying began because a competitor's face was cleaned ... |
was thrown, it meant he was admitting defeat. Most businesses do not throw in the towel. They just re-organize so they can compete better. This WORDS AND THEIR STORIES was written by Jeri Watson. I'm Susan Clark. |
Frilled Sharks, Chlamydoselachus anguineus Taxonomy Animalia Chordata Elasmobranchii Hexanchiformes Chlamydoselachidae Chlamydoselachus anguineus Description & Behavior Frilled sharks, Chlamydoselachus anguineus (Garman, 1884), aka frill sharks, frill-gilled sharks, Greenland sharks, scaffold sharks, and silk sharks ar... |
other existing sharks), and no nictitating membranes (protective third eyelids). The frilled shark, Chlamydoselachus anguineus, is currently one of only two known species of frilled sharks. The southern African frill shark, C. africana, was recently discovered (2009) off southern Angola, Namibia and South Africa. They ... |
own order Chlamydoselachiformes in the near future. Frilled sharks, Chlamydoselachus anguineus, are deepwater eel-like sharks that reach lengths up to 2 m and are thought to reach sexual maturity when they are 1.35 to 1.5 m long. They are dark brown or gray in color above, sometimes lighter below, and have six pairs of... |
under their jaws forming a sort of collar. Frilled sharks' heads are broad and flattened with short, rounded snouts. Their nostrils are vertical slits, separated into incurrent and excurrent openings by a leading flap of skin. The moderately large eyes are horizontally oval (like a cat's). Their mouth is located at the... |
and they have small tricuspid teeth in both jaws. Their rows of teeth are rather widely spaced, numbering 19–28 teeth in their upper jaws and 21–29 teeth in their lower jaws. Each tooth is small, with three slender, needle-like cusps alternating with two cusplets. Their very long jaws are positioned terminally (at the ... |
most sharks. They have a small lobe-like dorsal fin set far back over their pelvic fins with an anal fin that is larger than their dorsal fin. Their pectoral fins are small and paddle-shaped and their very long caudal fin (tail fin) has a small ventral lobe and without a subterminal notch. Frilled sharks also have a pa... |
function (possibly to help allow for expansion when digesting larger prey) running along their bellies, separated by a groove, and their midsections are relatively longer in females than in males. Frilled shark differs from their southern African relative, C. africana, by having more vertebrae (160–171 vs 147) and more... |
proportional measurements such as a longer head and shorter gill slits. The maximum known length is 1.7 m for males and 2.0 m for females. Frilled sharks are highly specialized for life in the deep sea with reduced, poorly-calcified skeletons and enormous livers filled with low-density lipids, which allows them to main... |
the few sharks with an "open" lateral line, in which the mechanoreceptive hair cells are positioned in grooves that are directly exposed to the surrounding seawater. This configuration is thought to be the most primitive in sharks and may enhance their sensitivity to minute movements of prey in their proximity. Many fr... |
predatory attacks by other shark species. These sharks, or a proposed giant relative, have been suggested as a source for reports of sea serpents. World Range & Habitat Frilled sharks, Chlamydoselachus anguineus, are an uncommon "primitive" shark species typically found near the sea floor in waters over outer continent... |
but up to 1,570 m and occasionally even at the surface. Frilled sharks are thought to have a wide though patchy distribution (74°N - 58°S, 169°W - 180°E) in the Atlantic and Pacific Oceans. In Suruga Bay, Japan they are most common at depths between 50 m and 200 m. In the western Indian Ocean they are found off South A... |
In the western Pacific, frilled sharks are known to live off Japan and south to New Zealand, New South Wales and Tasmania in Australia. In the eastern/central Pacific they have been observed off Hawaii, southern California to northern Chile. Frilled sharks have also been observed in the eastern Atlantic from waters off... |
Good Hope in South Africa. In the central Atlantic, they have been caught at several locations along the Mid-Atlantic Ridge, from north of the Azores to the Rio Grande Rise off southern Brazil, as well as over the Vavilov Ridge off West Africa. In the western Atlantic, it has been reported from off New England, Georgia... |
anguineus, feed on cephalopods (mainly squid), other sharks, and bony fishes. Feeding behavior has not yet been observed by this weak-swimming species, though they are thought to capture active, fast-moving squid by taking advantage of injured squid or those that are exhausted and dying after spawning. Alternatively, t... |
fins, and launching quick strikes forward like a snake. They may also be able to close their gill slits creating negative internal pressure to suck prey quickly into their mouth. They have many small, sharp, rear-pointing (recurved) teeth that function much like squid jigs which could easily snag the body or tentacles ... |
are protruded. Observations of captive frilled sharks swimming with their mouths open might also suggest that the small teeth, light against their dark mouths, may even fool squid into attacking and entangling themselves. Using their long, extremely flexible jaws they should be able to swallow large prey (up to half it... |
futile. Examining the length and articulation of their jaws appears to show that frilled sharks cannot deliver as strong a bite as more conventionally built sharks. Most captured individuals have been found with no or barely identifiable stomach contents, suggesting that they have a fast digestion rate and/or long inte... |
swallowed an entire 590 g Japanese catshark, Apristurus japonicus. Squid comprise some 60% of the diet of these sharks in Suruga Bay and this includes not only slow-moving, deep-dwelling squid such as Chiroteuthis and Histioteuthis, but also relatively large, powerful swimmers of the open ocean such as Onychoteuthis, S... |
from their egg capsules inside their mother's uterus and are nourished by their yolk until birth. Frilled sharks' gestation period may be as long as three and a half years, the longest of any vertebrate. Between 2 and 15 young are born at a time (average is 6) measuring 40–60 cm long, and there appears to be no distinc... |
as these sharks inhabits depths at which there is little to no seasonal influence). Male frill sharks attain sexual maturity at 1.0–1.2 m long and females at 1.3–1.5 m. A possible mating aggregation of 15 male and 19 female frilled sharks was recorded over a seamount on the Mid-Atlantic Ridge. Conservation Status & Com... |
by the IUCN Red List: "A generally rare to uncommon deepwater species, with a few localities where it is taken more commonly as bycatch in several fisheries. Not an important target species, but a regular though small bycatch in many bottom trawl, midwater trawl, deep-set longline, and deep-set gillnet fisheries. As by... |
kept in aquaria (Japan). There is some concern that expansion of deepwater fisheries effort (geographically and in depth range) will increase the levels of bycatch. Although little is known of its life history, this deepwater species is likely to have very little resilience to depletion as a result of even non-targeted... |
meet the Vulnerable A2d+A3d+4d criteria." On August 27, 2004, the first observation of this species in its natural habitat was made by the ROV Johnson-Sea-Link II, on the Blake Plateau off the southeastern United States (see the first photo above). On January 21, 2007, a Japanese fisherman discovered a 1.6 m long femal... |
from the warm water. It was brought to Awashima Marine Park in Shizuoka, where it died after a few hours (see the video above). Garman, and numerous authors since, have advanced the frilled shark as an explanation for sea serpent sightings. Because of the shark's modest size, some cryptozoologists have posited the exis... |
of marine conservation issues and their solutions, and support marine conservation scientists and students involved in the marine life sciences. Join the MarineBio Conservation Society or make a donation today. We would like to sincerely thank all of our members, donors, and sponsors, we simply could not have achieved ... |
Ancient secrets of Merlin’s Barrow unearthed The Wiltshire landscape around Avebury and Silbury Hill is at the heart of prehistoric Britain, and has World Heritage designation. Now another monument can |
be added to its archaeological treasures: the Marlborough Mound. The Mound lies in the heart of the grounds of Marlborough College, and has been interwoven with local folklore for hundreds |
of years. The town’s motto, Ubi nunc sapientis ossa Merlini (‘Where now are the bones of wise Merlin?’), echoes the myth which convinced generations that Merlin’s bones were buried under |
the Mound. These were the seductive Arthurian legends that may have drawn the interest of Tennyson and William Morris back to their connections with Marlborough and its Mound – or |
‘Merlin’s Barrow’, as the burghers of the town claimed. Not only has the Mound stimulated some of the region’s most enduring threads of mythology, it has also been recognised as |
a feature of considerable historical significance. It was the motte on which the keep of Marlborough Castle was built fifty years after the Norman Conquest. Subsequently, it became the centrepiece |
of a major seventeenth century garden. The latest research, however, has extended its history back by three millennia. Recent coring of the Mound at Marlborough College has produced four samples |
of charcoal, allowing radiocarbon dating for the first time. The samples, which came from different levels in the Mound, were taken from two bore holes through the height of the |
19m monument, showing that it was built in the years around 2400 BC. This is the first positive evidence proving the theory that the castle motte is in fact a |
re-used prehistoric structure of the highest national standing. Jim Leary, who led the recent archaeological investigations for English Heritage at the nearby Silbury Hill, and is co-author of the recently |
published ‘The Story of Silbury Hill’ coordinated EH’s contribution, which also included radiocarbon dating. He says, “This is an astonishing discovery. The Marlborough Mound has been one of the biggest |
mysteries in the Wessex landscape. For centuries people have wondered whether it is Silbury’s little sister; and now we have an answer. This is a very exciting time for British |
prehistory.” The Master of Marlborough College is equally enthusiastic: ‘We are thrilled at the discovery of another aspect of our rich history, and one which can be added to the |
educational opportunities at the school.’ The work is part of a major conservation programme being undertaken by the Marlborough Mound Trust, specially formed at the invitation of the College. The |
chairman of the Trust says that ‘the inspiration for this was our founder Eric Elstob, a former pupil at the College, whose generous legacy has provided the means for this |
work. He would have been totally delighted by this news.’ Note: As part of the College grounds, the Mound is strictly on private property. For further details please contact: Donald |
A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware component responsible for handling accesses to memory requested by the CPU. Its functions include |
translation of virtual addresses to physical addresses (i.e., virtual memory management), memory protection, cache control, bus arbitration and in simpler computer architectures (especially 8-bit systems) bank switching. Modern MMUs typically |
divide the virtual address space (the range of addresses used by the processor) into pages, each having a size which is a power of 2, usually a few kilobytes, but |
they may be much larger. The bottom n bits of the address (the offset within a page) are left unchanged. The upper address bits are the (virtual) page number. The |
MMU normally translates virtual page numbers to physical page numbers via an associative cache called a translation lookaside buffer (TLB). When the TLB lacks a translation, a slower mechanism involving |
hardware-specific data structures or software assistance is used. The data found in such data structures are typically called page table entries (PTEs), and the data structure itself is typically called |
a page table. The physical page number is combined with the page offset to give the complete physical address. A PTE or TLB entry may also include information about whether |
the page has been written to (the dirty bit), when it was last used (the accessed bit, for a least recently used page replacement algorithm), what kind of processes (user |
mode, supervisor mode) may read and write it, and whether it should be cached. Sometimes, a TLB entry or PTE prohibits access to a virtual page, perhaps because no physical |
random access memory has been allocated to that virtual page. In this case the MMU signals a page fault to the CPU. The operating system (OS) then handles the situation, |
perhaps by trying to find a spare frame of RAM and set up a new PTE to map it to the requested virtual address. If no RAM is free, it |
may be necessary to choose an existing page (known as a victim), using some replacement algorithm, and save it to disk (this is called "paging"). With some MMUs, there can |
also be a shortage of PTEs or TLB entries, in which case the OS will have to free one for the new mapping. In some cases a "page fault" may |
indicate a software bug. A key benefit of an MMU is memory protection: an OS can use it to protect against errant programs, by disallowing access to memory that a |
particular program should not have access to. Typically, an OS assigns each program its own virtual address space. An MMU also reduces the problem of fragmentation of memory. After blocks |
of memory have been allocated and freed, the free memory may become fragmented (discontinuous) so that the largest contiguous block of free memory may be much smaller than the total |
amount. With virtual memory, a contiguous range of virtual addresses can be mapped to several non-contiguous blocks of physical memory. In some early microprocessor designs, memory management was performed by |
a separate integrated circuit such as the VLSI VI475 (1986) or the Motorola 68851 (1984) used with the Motorola 68020 CPU in the Macintosh II or the Z8015 (1985) used |
with the Zilog Z8000 family of processors. Later microprocessors such as the Motorola 68030 and the Zilog Z280 placed the MMU together with the CPU on the same integrated circuit, |
as did the Intel 80286 and later x86 microprocessors. While this article concentrates on modern MMUs, commonly based on pages, early systems used a similar concept for base-limit addressing, that |
further developed into segmentation. Those are occasionally also present on modern architectures. The x86 architecture provided segmentation rather than paging in the 80286, and provides both paging and segmentation in |
the 80386 and later processors (although the use of segmentation is not available in 64-bit operation). Most modern systems divide memory into pages that are 4 - 64 kB in |
size, often with the possibility to use huge pages from 2 MB to 512 MB in size. Page translations are cached in a TLB. Some systems, mainly older RISC designs, |
trap into the OS when a page translation is not found in the TLB. Most systems use a hardware-based tree walker. Most systems allow the MMU to be disabled; some |
disable the MMU when trapping into OS code. VAX pages are 512 bytes, which is very small. An OS may treat multiple pages as if they were a single larger |
page, for example Linux on VAX groups 8 pages together, thus the system is viewed as having 4 kB pages. The VAX divides memory into 4 fixed-purpose regions, each 1 |
GB in size. They are: Page tables are big linear arrays. Normally this would be very wasteful when addresses are used at both ends of the possible range, but the |
page table for applications is itself stored in the kernel's paged memory. Thus there is effectively a 2-level tree, allowing applications to have sparse memory layout without wasting lots of |
space on unused page table entries. The VAX MMU is notable for lacking an accessed bit. OSes which implement paging must find some way to emulate the accessed bit if |
they are to operate efficiently. Typically, the OS will periodically unmap pages so that page-not-present faults can be used to let the OS set an accessed bit. ARM architecture based |
application processors implement an MMU defined by ARM's Virtual Memory System Architecture. The current architecture defines PTEs for describing 4 kB and 64 kB pages, 1 MB sections and 16 |
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