Lead

Lead (/lɛd/) is a chemical element in the carbon group with symbol Pb (from Latin: plumbum) and atomic number 82. It is a soft, malleable and heavy post-transition metal. Freshly cut, solid lead has a bluish-white color that soon tarnishes to a dull grayish color when exposed to air; the liquid metal has shiny chrome-silver luster. Lead is the heaviest (has the highest atomic number) non-radioactive element (two radioactive elements, namely technetium and promethium, are lighter), although the next higher element, bismuth, has one isotope with a half-life that is so long (over one billion times the estimated age of the universe) that it can be considered stable. Lead's four stable isotopes each have 82 protons, a magic number in the nuclear shell model of atomic nuclei. The isotope lead-208 also has 126 neutrons, another magic number, and is hence double magic, a property that grants it enhanced stability: lead-208 is the heaviest known stable nuclide.

Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield.

Cutoff (steam engine)

In a steam engine, cutoff is the point in the piston stroke at which the inlet valve is closed. On a steam locomotive, the cutoff is controlled by the reversing gear.

The point at which the inlet valve closes and stops the entry of steam into the cylinder from the boiler plays a crucial role in the control of a steam engine. Once the valve has closed, steam trapped in the cylinder expands adiabatically. The steam pressure drops as it expands. A late cutoff delivers full steam pressure to move the piston through its entire stroke, for maximum start-up forces. But, since there will still be unexploited pressure in the cylinder at the end of the stroke, this is achieved at the expense of engine efficiency. In this situation the steam will still have considerable pressure remaining when it is exhausted resulting in the characteristic “chuff chuff” sound of a steam engine. An early cutoff has greater thermodynamic efficiency but results in a lower Mean effective pressure so less average force on the piston and is used for running the engine at higher speeds. The steam engine is the only thermodynamic engine design that can provide its maximum torque at zero revolutions per minute.

Lead (disambiguation)

Lead has two different pronunciations and several different meanings, usually related to either the chemical element lead (a heavy metal) or the verb to lead.

When pronounced /ˈlɛd/ (rhymes with "bed")

With this pronunciation, "lead" refers to:

The past tense of the verb to lead is led, pronounced /ˈlɛd/. It is often misspelled as lead.

See also:

When pronounced /ˈliːd/ (rhymes with "need")

With this pronunciation, "lead" generally means "first", "ahead", or "guide":

Soraya

Soraya (Persian: ثريا ) is a feminine given name of Persian origin. It may refer to:

Alphonsus (crater)

Alphonsus is an ancient impact crater on the Moon that dates from the pre-Nectarian era. It is located on the lunar highlands on the eastern end of Mare Nubium, west of the Imbrian Highlands, and slightly overlaps the crater Ptolemaeus to the north. To the northwest is the smaller Alpetragius.

Description

The surface of Alphonsus is broken and irregular along its boundary with Ptolemaeus. The outer walls are slightly distorted and possess a somewhat hexagonal form.

A low ridge system of deposited ejecta bisects the crater floor, and includes the steep central peak designated Alphonsus Alpha (α). This pyramid-shaped formation rises to a height of 1.5 km above the interior surface. It is not volcanic in origin, but rather is made of anorthosite like the lunar highlands.

The floor is fractured by an elaborate system of rilles and contains three smaller craters surrounded by a symmetric darker halo. These dark-halo craters are cinder cone-shaped and are believed by some to be volcanic in origin, although others think they were caused by impacts that excavated darker mare material from underneath the lighter lunar regolith.

Soraya (musician)

Soraya (born Soraya Raquel Lamilla Cuevas; March 11, 1969 – May 10, 2006) was a Colombian-American singer/songwriter, guitarist, arranger and record producer.

A successful Colombian music star, she had two number-one songs on Billboard's Latin Pop Airplay charts. She won a 2004 Latin Grammy Award for the self-titled album "Soraya" as "Best Album by Songwriter", which she produced, and a 2005 Latin Grammy Awards nomination for "Female Pop Vocal Album" for her album El Otro Lado de Mí (literally "The Other Side of Me"). She was the opening act for the 2005 Billboard Latin Music Awards. Her career spanned ten years, and she recorded five albums. Soraya died on May 10, 2006 following a long struggle against breast cancer.

Biography

Early life

She was born Soraya Raquel Lamilla Cuevas in Point Pleasant, New Jersey, a year after her father, mother, and brother moved to the United States from their native Colombia. The family moved back to Colombia when she was a baby, but when Soraya was eight years old, they returned to New Jersey. "Soraya" is a very common name in the Middle East, and its meaning can be translated "rich" or "princess". Soraya's maternal relatives were Lebanese Christians who emigrated from Lebanon to Colombia. Soraya's mother, Yamila Cuevas Gharib, had been a housewife in Colombia. Soraya's father, Gregorio Lamilla, worked for an exporting company in Colombia; in the U.S., life was hard for the family, so to make ends meet, he worked three or four jobs.