Gold

Gold is a chemical element with symbol Au (from Latin: aurum) and atomic number 79. In its purest form, it is a bright, slightly reddish yellow, dense, soft, malleable and ductile metal. Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements, and is solid under standard conditions. The metal therefore occurs often in free elemental (native) form, as nuggets or grains, in rocks, in veins and in alluvial deposits. It occurs in a solid solution series with the native element silver (as electrum) and also naturally alloyed with copper and palladium. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides).

Gold's atomic number of 79 makes it one of the higher atomic number elements that occur naturally in the universe. It is thought to have been produced in supernova nucleosynthesis from the collision of two neutron stars and to have been present in the dust from which the Solar System formed. Because the Earth was molten when it was just formed, almost all of the gold present in the early Earth probably sank into the planetary core. Therefore, most of the gold that is present today in the Earth's crust and mantle is thought to have been delivered to Earth later, by asteroid impacts during the late heavy bombardment, about 4 billion years ago.

Metal detector

A metal detector is an electronic instrument which detects the presence of metal nearby. Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects buried underground. They often consist of a handheld unit with a sensor probe which can be swept over the ground or other objects. If the sensor comes near a piece of metal this is indicated by a changing tone in earphones, or a needle moving on an indicator. Usually the device gives some indication of distance; the closer the metal is, the higher the tone in the earphone or the higher the needle goes. Another common type are stationary "walk through" metal detectors used for security screening at access points in prisons, courthouses, and airports to detect concealed metal weapons on a person's body.

The simplest form of a metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, eddy currents will be induced in the metal, and this produces a magnetic field of its own. If another coil is used to measure the magnetic field (acting as a magnetometer), the change in the magnetic field due to the metallic object can be detected.

Metal

A metal (from Greek μέταλλον métallon, "mine, quarry, metal") is a material (an element, compound, or alloy) that is typically hard, opaque, shiny, and has good electrical and thermal conductivity. Metals are generally malleable — that is, they can be hammered or pressed permanently out of shape without breaking or cracking — as well as fusible (able to be fused or melted) and ductile (able to be drawn out into a thin wire). About 91 of the 118 elements in the periodic table are metals, the others are nonmetals or metalloids. Some elements appear in both metallic and non-metallic forms.

Astrophysicists use the term "metal" to collectively describe all elements other than hydrogen and helium. Thus, the metallicity of an object is the proportion of its matter made up of chemical elements other than hydrogen and helium.

Many elements and compounds that are not normally classified as metals become metallic under high pressures; these are formed as metallic allotropes of non-metals.

Structure and bonding

Calochortus luteus

Calochortus luteus, or Yellow mariposa lily, is a mariposa lily endemic to California.

Description

The primarily bright deep yellow flower is 3-5cm across and perianth bulb-shaped, lined red-brown inside, often also with central red-brown blotch and sparse hair inside.

Distribution

This species is found on coastal prairie, grasslands and some open forest floors. Its range is along the coastal ranges from region to the northern Santa Barbara County Channel Islands and mainland, Northwestern California, the Sacramento Valley, and the Sierra Nevada foothills from there to the Tehachapi Mountains.

Cultivation

Calochortus luteus is used in landscape design, with "non-habitat sourced" bulbs available from native plant nurseries and societies, to grow as an ornamental plant in gardens and for restoration projects.Plants for a FutureCalochortus luteus

References

External links

Media related to Calochortus luteus at Wikimedia Commons

Philippines

Coordinates: 13°N 122°E / 13°N 122°E / 13; 122

The Philippines (ⁱ/ˈfɪlᵻpiːnz/; Filipino: Pilipinas [ˌpɪlɪˈpinɐs]), officially known as the Republic of the Philippines (Filipino: Republika ng Pilipinas), is a sovereign island country in Southeast Asia situated in the western Pacific Ocean. It consists of about 7,500 islands that are categorized broadly under three main geographical divisions: Luzon, Visayas, and Mindanao. The capital city of the Philippines is Manila and the most populous city is Quezon City; both are part of Metro Manila.

To the north of the Philippines across the Luzon Strait lies Taiwan; Vietnam sits west across the South China Sea; southwest lies Malaysia in the island of Borneo across the Sulu Sea, and to the south the Celebes Sea separates it from other islands of Indonesia; while to the east it is bounded by the Philippine Sea and the island-nation of Palau. Its location on the Pacific Ring of Fire and close to the equator makes the Philippines prone to earthquakes and typhoons, but also endows it with abundant natural resources and some of the world's greatest biodiversity. At approximately 300,000 square kilometers (115,831 sq mi), the Philippines is the 72nd-largest country in the world.