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noirua · 17 January 2008

...how radioisotopes are produced. Isotopes give off alpha, beta and gamma rays - the three kinds of radiation. Radioisotopes are therefore the most convenient source of radiation. They are made by bombarding a sample of non-radioactive isotope with atomic particles. A sample is placed in position by manipulators. A beam of particles is then produced by the cyclotron to strike the sample and change it into a radioisotope.
The radiation is dangerous, the operator of the equipment cannot enter the chamber, and the radioisotopes produced are packed in heavy boxes.

noirua · 19 January 2008

...specific gravity is the density of a substance compared with the density of water at 4degC. If for example, a substance is twice as dense as water, then it has a specific gravity (S.G.) of 2.

2020hindsight · 19 January 2008

noirua said:
...specific gravity is the density of a substance compared with the density of water at 4degC. If for example, a substance is twice as dense as water, then it has a specific gravity (S.G.) of 2.

well if my brother in law drinks anything stronger than H2O - he gets about 3 times as dense as water

Hey noi - how do you weigh Hydrogen? H2

maybe if the same volume of H2O weighs 2000kg
then you just cross off the 'O' and get 200kg? :eek3:

PS ice is less dense that icey water by 9% - just as well otherwise the rocks in your scotch would sink to the bottom.
http://www.simetric.co.uk/si_water.htm

At 4°C pure water has a density (weight or mass) of about 1 g/cu.cm, 1 g/ml,
1 kg/litre, 1000 kg/cu.m, 1 tonne/cu.m or 62.4 lb/cu.ft

At 4°C pure water has a specific gravity of 1. ( Some reference the s.g. base temperature as 60F.)

Water is essential for life. Most animals and plants contain more than 60 % water by volume.

More than 70 % of the Earth's surface is covered with about 1.36 billion cubic kilometers of water / ice

The density of pure water is a constant at a particular temperature, and does not depend on the size of the sample. That is, it is an intensive property. The density of water varies with temperature and impurities.

Water is the only substance on Earth that exists in all three physical states of matter: solid, liquid and gas.

When water freezes it expands rapidly adding about 9 % by volume. Fresh water has a maximum density at around 4° Celsius. Water is the only substance where the maximum density does not occur when solidified. As ice is lighter than water, it floats.

Likewise that little trick of being lighter "either-side-of 4degC temperature-wise" means that lakes freeze from the top down, leaving fish to still swim around and stuff. - (ice "falling out of lakes" etc )

http://en.wikipedia.org/wiki/Water_(molecule)

The solid form of most substances is more dense than the liquid phase; thus, a block of pure solid substance will sink in a tub of pure liquid substance. But, by contrast, a block of common ice will float in a tub of water because solid water is less dense than liquid water. This is an extremely important characteristic property of water. At room temperature, liquid water becomes denser with lowering temperature, just like other substances. But at 4 °C (3.98 more precisely), just above freezing, water reaches its maximum density, and as water cools further toward its freezing point, the liquid water, under standard conditions, expands to become less dense.

.....
Water falling out of lakes

The importance of this property cannot be overemphasized for its role on the ecosystem of Earth. For example, if water were more dense when frozen, lakes and oceans in a polar environment would eventually freeze solid (from top to bottom). This would happen because frozen ice would settle on the lake and riverbeds, and the necessary warming phenomenon (see below) could not occur in summer, as the warm surface layer would be less dense than the solid frozen layer below. It is a significant feature of nature that this does not occur naturally in the environment.

Nevertheless, the unusual expansion of freezing water (in ordinary natural settings in relevant biological systems), due to the hydrogen bond, from 4 °C above freezing to the freezing point offers an important advantage for freshwater life in winter. Water chilled at the surface increases in density and sinks, forming convection currents that cool the whole water body, but when the temperature of the lake water reaches 4 °C, water on the surface decreases in density as it chills further and remains as a surface layer which eventually freezes and forms ice. Since downward convection of colder water is blocked by the density change, any large body of fresh water frozen in winter will have the coldest water near the surface, away from the riverbed or lakebed. This accounts for various little known phenomena of ice characteristics as they relate to ice in lakes and "ice falling out of lakes" as described by early 20th century scientist Horatio D. Craft.

2020hindsight · 19 January 2008

Might as well post this as well - just in case everyone isn't completely confused yet. (Now to read it three times myself - I think it makes more sense read upside down lol)

Density of saltwater and ice
The density of water is dependent on the dissolved salt content as well as the temperature of the water. Ice still floats in the oceans, otherwise they would freeze from the bottom up. However, the salt content of oceans lowers the freezing point by about 2 °C and lowers the temperature of the density maximum of water to the freezing point. That is why, in ocean water, the downward convection of colder water is not blocked by an expansion of water as it becomes colder near the freezing point. The oceans' cold water near the freezing point continues to sink. For this reason, any creature attempting to survive at the bottom of such cold water as the Arctic Ocean generally lives in water that is 4 °C colder than the temperature at the bottom of frozen-over fresh water lakes and rivers in the winter.

As the surface of salt water begins to freeze (at −1.9 °C for normal salinity seawater, 3.5%) the ice that forms is essentially salt free with a density approximately equal to that of freshwater ice. This ice floats on the surface and the salt that is "frozen out" adds to the salinity and density of the seawater just below it, in a process known as brine rejection. This more dense saltwater sinks by convection and the replacing seawater is subject to the same process. This provides essentially freshwater ice at −1.9 °C on the surface. The increased density of the seawater beneath the forming ice causes it to sink towards the bottom.

noirua · 21 January 2008

...salt (sodium) increases the electolyte concentration in the blood, so that water is retained, effectively increasing the blood volume and thereby increasing blood pressure.

noirua · 22 January 2008

... Nero: Roman Emperor (born AD 37), reigned (AD54-68), notorious for his vanity, cruelty, and corruption. He was eventually overthrown by a military revolt and committed suicide.

Happy · 22 January 2008

noirua said:
...salt (sodium) increases the electolyte concentration in the blood, so that water is retained, effectively increasing the blood volume and thereby increasing blood pressure.

Blood pressure lowering medicine allows people continue to ingest insane amount of salt and live on a time bomb of organs failure, other than heart.

noirua · 23 January 2008

...the Gila Monster is a large lizard from the desert region of America. There are only two poisonous lizards in the world and the Gila is one of them. Coloured pink, brown and orange, the Gila is a stocky creature about 60 cms long: the poison gland is in its bottom jaw.

noirua · 24 January 2008

...Medici: An Italian family and rulers of Florence from the 1300's to the 1700's, the Medici derived their power from their wealth, made in commerce and banking. Lorenzo the Magnificient (1449-1492) was a famous patron of the arts. His son became Pope Leo X (1475-1521). Both Catharine (1519-1589) and Marie de' Medici (1573-1642) became Queens of France.

2020hindsight · 24 January 2008

noirua said:
...salt (sodium) increases the electolyte concentration in the blood, so that water is retained, effectively increasing the blood volume and thereby increasing blood pressure.

I think the concentration of salt in the blood is about the same as in the ocean

PS beware of Hyponatremia (water intoxication) !

http://sportsmedicine.about.com/od/hydrationandfluid/a/Sodium_Salt.htm

High salt (sodium) diets have been linked to a number of health risks in many Americans. However, some athletes, due to their increased activity and excessive sweat production, are actually at risk of having too little sodium in their blood stream during training and competition and may have special sodium requirements. Because sodium is lost in sweat, it is more important for individuals who exercise at high intensity to get adequate sodium before, during and after exercise. This is even more critical during ultra-endurance competition.

Risks of Hyponatremia | Water Intoxication
Hyponatremia, a low concentration of sodium in the blood, has become more prevalent in ultra-endurance athletes. The Hawaii Ironman Triathlon routinely sees finishers with low blood sodium concentrations. Adequate sodium balance is necessary for transmitting nerve impulses and proper muscle function, and even a slight depletion of this concentration can cause problems. Ultra distance running events that take place in hot, humid conditions, and have athletes competing at high intensity have conditions prime for hyponatremia to develop

This starts to read like an ad for Gatorade

Causes of Hyponatremia
During high intensity exercise, sodium is lost along with sweat. An athlete who only replaces the lost fluid with water will contribute to a decreased blood sodium concentration. As an example, consider a full glass of salt-water. If you dump out half of the contents of the glass (as is lost in sweat), and replace that with water only, the sodium concentration of in the glass is far less and the water is more dilute. This often occurs in the bloodstream of an athlete who only hydrates with water during excessive sweating. The result is hyponatremia.

Studies have shown that ultra-endurance athletes can lose 1-2 grams of salt per liter of sweat. If you consider that athletes may lose up to a liter (or more) of sweat each hour, you can see that over a long endurance event (12 hour race), it is not unimaginable that an athlete could sweat out a huge amount of sodium. Replacing this loss of sodium during the event is critical to performance and safety.

Symptoms of Hyponatremia
The early warning signs are often subtle and may be similar to dehydration; nausea, muscle cramps, disorientation, slurred speech, confusion, and inappropriate behavior. At this point, many athletes get into trouble by drinking water because they think they are dehydrated. In fact, water alone will increase the problem of hyponatremia. At the most extreme an athlete may experience seizures, coma, or death.

Treating Hyponatremia
At the first sign of nausea, muscle cramps, disorientation, an athlete should drink a sodium containing sports drink, such as Gatorade, or eat salty foods. If possible, an athlete should plan ahead and estimate his or her fluid loss and need for sodium replacement during the event, and stay on a hydration schedule during the race. If the symptoms are extreme, a medical professional should be seen.

Preventing Hyponatremia
The best way for an athlete to avoid such problems is to plan ahead. Tips and recommendations include:

Use a sodium containing sports drinks during long distance, high intensity events.
Eat salty foods before and during competition if possible. ... etc

"In fact, water alone will increase the problem of hyponatremia. At the most extreme an athlete may experience seizures, coma, or death" - sheesh!
I think VB and XXXX have a bit of salt as well

2020hindsight · 24 January 2008

and speaking of salt concentration this link talks about people preferring to swim in salt water than fresh - and in turn sounds like an ad for salt water chorination systems

They say to aim at making the pool the same concentration as blood - (assuming I read this correctly) - or as saline solution used in blood drips in hospital for that matter. Expensive way to fill a pool you'd think

http://watermaid.com/help/alltopics/why_install_a_watermaid.htm

WHY I SHOULD INSTALL A SALT WATER CHLORINATOR ON MY POOL
in preference to
A POOL USING OZONE, LIQUID OR POWDERED CHLORINE OR OTHER CHEMICAL MEANS AS THE SIMPLE BIOCIDE.

WHY SHOULD I USE AN ISOTONIC POOL WATER SOLUTION?
WHY SHOULD I INSTALL A WATERMAID?

There are three states of water conditioning for use in pools that are of interest to swimmers and pool owners. These are isotonic solutions, hypotonic solutions and hypertonic solutions.

Isotonic solutions of pool water. This water condition has an osmotic pressure that is equal to the osmotic pressure of blood serum and other body fluids. The body’s cell tissue is sensitive to changes in osmotic pressure. In pool water that is isotonic with blood serum and other body fluids, the osmotic pressure is equal on each side of the cell membrane. There isn’t a net transfer of fluids across the cell membrane.

The saline solution used as an intravenous drip in hospitals is an isotonic solution.

An isotonic solution is an ideal pool water condition that provides maximum comfort for people swimming in the pool. Swimmers feel good when they are swimming in isotonic pool water. Stretching and wrinkling of the skin at the fingertips, stretching and wrinkling of the skin on the underside of the toes and irritation of the eyes are noticeably reduced or eliminated. Children get the most benefit. They spend long periods of time in the pool.

A pool with a sodium chloride salt concentration of 9000 ppm is isotonic with blood serum and body fluids.
etc etc

noirua · 25 January 2008

...Balbao, Vasco Nubez De, Spanish explorer and conquistador (1475-1517) was the first European to see the Pacific Ocean.

noirua · 25 January 2008

...each Australian uses the energy from 200 tonnes of coal during their lifetime.

noirua · 26 January 2008

..."The Worlds weirdest 20 court cases": http://business.timesonline.co.uk/tol/business/law/article2741049.ece

noirua · 28 January 2008

Ships emit twice as much CO2 as planes.
A bear named Voytek helped carry ammunition for Polish troops in World War 2. A campaign has been launched to raise a permanent memorial.
Using a mobile phone before bedtime can delay you getting to sleep.
Super-fast broadband fibres are laid in the sewers.

TheAbyss · 28 January 2008

Do you know the name of the England captain who did three tours of Australia and failed to score a single run?

noirua · 29 January 2008

...Coulomb: The SI UNIT of electric charge. It is the amount of electricity that flows through a conductor carrying a current of one AMPERE for one second. Coulombs are represented by the symbol C.

nioka · 29 January 2008

You use twice as many muscles to frown as to smile.

noirua · 30 January 2008

...that Jang Yeong-Sil was a Korean Scientist and Astronomer who lived between 1390 and 1470, in Hanseong (now Seoul), the exact dates of his birth and death are not known. He lived during the reign of King Sejong during the Joseon Dynasty.

Jang Yeong-Sil invented the celestial globe, sundial, rain guage, water guage and iron printing press. Virtually unknown in the West he was one of the most important and perhaps greatest Scientists and Astronomers who ever lived: http://en.wikipedia.org/wiki/Jang_Young_Sil

2020hindsight · 30 January 2008

TheAbyss said:
Do you know the name of the England captain who did three tours of Australia and failed to score a single run?

david beckham? (or was that one tour?)
PS haven't got a clue m8

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