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Making beads is an old craft. Bone, stone (turquoise and other semi-precious stones) and shell beads are still made the ancient way, little affected by modern technology. Sea shells, the commonest material for handmade beads, have been important native regional trade items for thousands of years.
The bow and arrow represents one of the great technological advancements in weaponry in the ancient world. In fact, the bow is the first mechanical device that could store energy, as the arrow was held in the string before its release. Recent distance records in flight archery for pulled bows are around one third mile, the longest crossbow shot is 1.16 miles! Bows and arrows were used just about everywhere in the world except Australia where spear throwers were the preferred weapon. Triangular shaped arrow points were one of the most common types of arrow points used on the tips of arrows.
The bow and arrow represents one of the great technological advancements in weaponry in the ancient world. In fact, the bow is the first mechanical device that could store energy, as the arrow was held in the string before its release. Recent distance records in flight archery for pulled bows are around one third mile, the longest crossbow shot is 1.16 miles! Bows and arrows were used just about everywhere in the world except Australia where spear throwers were the preferred weapon. Triangular shaped arrow points were one of the most common types of arrow points used on the tips of arrows.
The Willow Tree series was replaced because of a new technology. Rather than simply using the older hammer striking method Richard Doty has suggested Hull changed to a rocker arm press. The dies needed for a rocker arm press were quite different from dies used in the hammer strike method. A rocker press used large-sized rectangular shaped dies with a curved face so that the die could rock back and forth. The image for the coin was then engraved on the curved face of the rocker, one rocker for the obverse and another for the reverse (click here for picture of rocker dies). The two rocker dies would then be mounted face to face in the press. By pulling a lever the upper and lower rockers would press against each other with a rolling motion (click here for picture of a rocker press). As long as the two dies were properly aligned a blank planchet placed between them would be impressed with the design of the dies.
The Willow Tree series was replaced because of a new technology. Rather than simply using the older hammer striking method Richard Doty has suggested Hull changed to a rocker arm press. The dies needed for a rocker arm press were quite different from dies used in the hammer strike method. A rocker press used large-sized rectangular shaped dies with a curved face so that the die could rock back and forth. The image for the coin was then engraved on the curved face of the rocker, one rocker for the obverse and another for the reverse (click here for picture of rocker dies). The two rocker dies would then be mounted face to face in the press. By pulling a lever the upper and lower rockers would press against each other with a rolling motion (click here for picture of a rocker press). As long as the two dies were properly aligned a blank planchet placed between them would be impressed with the design of the dies.
Red blood cells (RBCs), also called erythrocytes, are the most common type of blood cell and the vertebrate organism’s principal means of delivering oxygen (O2) to the body tissues—via blood flow through the circulatory system] RBCs take up oxygen in the lungs or gills and release it into tissues while squeezing through the body’s capillaries. They are between 6-8 microns in diameter.
The cytoplasm of erythrocytes is rich in hemoglobin, an iron-containing biomolecule that can bind oxygen and is responsible for the red color of the cells. The cell membrane is composed of proteins and lipids, and this structure provides properties essential for physiological cell function such as deformability and stability while traversing the circulatory system and specifically the capillary network.
In humans, mature red blood cells are flexible and oval biconcave disks. They lack a cell nucleus and most organelles, in order to accommodate maximum space for hemoglobin. Approximately 2.4 million new erythrocytes are produced per second in human adults. The cells develop in the bone marrow and circulate for about 100–120 days in the body before their components are recycled by macrophages. Each circulation takes about 20 seconds. Approximately a quarter of the cells in the human body are red blood cells.
Eyes are the organs of vision. They detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.
Agrilus planipennis, commonly known as the emerald ash borer is a green jewel beetle native to eastern Asia that feeds on ash species. In its native range, it is typically found at low densities and is not considered a significant pest.
The presence of scales on the wings of Lepidoptera, comprising moths and butterflies, characterises this order of insects. The name is derived from Ancient Greek λεπίδος (scale) and πτερόν (wing). The wings of Lepidoptera are minutely scaled, which feature gives the name to this order. Scales also cover the head, parts of the thorax and abdomen as well as parts of the genitalia.
We’ve all looked through a microscope, but have you ever wondered what it may look like to look up from under one?
A watch is a small timepiece intended to be carried or worn by a person. It is designed to keep working despite the motions caused by the person’s activities. A wristwatch is designed to be worn on a wrist, attached by a watch strap or other type of bracelet. A pocket watch is designed for a person to carry in a pocket.
A weevil is a type of beetle from the Curculionoidea superfamily. They are usually small, less than 6 millimetres, and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae.
Eyes are the organs of vision. They detect light and convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.
The crested gecko, New Caledonian crested gecko, Guichenot’s giant gecko or eyelash gecko, Correlophus ciliatus, is a species of gecko native to southern New Caledonia. This species was thought extinct until it was rediscovered in 1994. Along with several Rhacodactylus species, it is being considered for protected status by the Convention on the International Trade in Endangered Species of Wild Flora and Fauna. It is popular in the pet trade.
Mastodons are any species of extinct proboscideans in the genus Mammut, distantly related to elephants, that inhabited North and Central America during the late Miocene or late Pliocene up to their extinction at the end of the Pleistocene 10,000 to 11,000 years ago.
Slag is the glass-like by-product left over after a desired metal has been separated (i.e., smelted) from its raw ore. Slag is usually a mixture of metal oxides and silicon dioxide.
Caption by: Enchanted Learning
