Monthly Archives: February 2014
Many laboratories use timers for various purposes – timing heating applications, cooling periods, cycling events, enzyme tests, viscosity measurements, animal studies, and other timed lab tests etc..
When choosing the best timer or stopwatch for your lab you should take into consideration ease-of-programming as well as ease-of-use. You can select from a variety of models based on timing modes, timing capacities, count directions, resolution, and accuracy. General -purpose timers can time the length of events with an alarm function for your laboratory. They are generally available in several styles – single channel, multi channel, count up, count down etc..
|VWR Traceable Timers|
Labs these days need to have traceable results and the introduction of Traceable® timers has proved popular initially in America and more recently in Europe.
P&R Labpak are able to offer VWR Brand Traceable® timers and also some traceable tools.
Items are individually serialised, calibrated and certified, traceable to NIST.
via Blogger http://ift.tt/NbVqwt
Lead is a chemical element in the carbon group with symbol Pb (derived from the Latin: plumbum) and has the atomic number 82. It is a soft and malleable metal and has a bluish-white colour after being freshly cut, but soon tarnishes to a dull grey colour when exposed to air. It has a shiny chrome-silver luster when it is melted into a liquid. Lead rarely occurs in its elemental form in the wild. It is typically found in ores along with copper, and in smaller quantities with zinc and silver.
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. It was also commonly used in pipes for many hundreds of years, giving rise to the English words, “plumbing”, “plumber”, “plumb”, and “plumb-bob” — words derived from the same Latin root with lead.
If ingested, lead is poisonous to animals, including humans. It damages the nervous system and causes brain disorders. Excessive lead also causes blood disorders in mammals. Like the element mercury, another heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bones. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China.
Lead pigments were used in lead paint for white as well as yellow, orange, and red. Most uses have been discontinued due of the dangers of lead poisoning. Lead chromate is still in industrial use. Lead carbonate (white) is the traditional pigment for the priming medium for oil painting, but it has been largely displaced by the zinc and titanium oxide pigments. It was also quickly replaced in water-based painting mediums. Lead carbonate white was used by the Japanese geisha and in the West for face-whitening make-up, which was detrimental to health.
Tetraethyllead was used in leaded fuels to reduce engine knocking, but this practice has been phased out across many countries of the world in efforts to reduce toxic pollution that affected humans and the environment.
Lead is a highly poisonous metal (regardless if inhaled or swallowed), affecting almost every organ and system in the body. The main target for lead toxicity is the nervous system, both in adults and children. Long-term exposure of adults can result in decreased performance in some tests that measure functions of the nervous system. Long-term exposure to lead or its salts (especially soluble salts or the strong oxidant PbO2) can cause nephropathy, and colic-like abdominal pains. It may also cause weakness in fingers, wrists, or ankles.
For more information visit:-
via Blogger http://ift.tt/1p11g2c
36 years ago on this day, Texas Instruments patented the first “micro on a chip”.
It was actually the first speech synthesizer chip and was used in TI’s famous Speak and Spell toy.
In 1976 TI began a feasibility study memory intensive applications for bubble memory then being developed. They soon focused on speech applications. This resulted in the development the TMC0280 one-chip Linear predictive coding (LPC) speech synthesizer which was the first time a single silicon chip had electronically replicated the human voice.
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small plate (“chip”) of semiconductor material, normally silicon.
Integrated circuits are used in virtually all electronic equipment today and have revolutionised the world of electronics. Computers, mobile phones, and other digital home appliances are now inextricable parts of the structure of modern societies, made possible by the low cost of producing integrated circuits.
ICs can be made very compact, having up to several billion transistors and other electronic components in an area the size of a fingernail. The width of each conducting line in a circuit can be made smaller and smaller as the technology advances; in 2008 it dropped below 100 nanometres and in 2013 it is expected to be in the tens of nanometres.
ICs have consistently migrated to smaller feature sizes over the years, allowing more circuitry to be packed on each chip. This increased capacity per unit area can be used to decrease cost and/or increase functionality.
Chips are used in everything now from Kettles and toasters to mobile phones and TV’s. They are an incredible invention which continue to develop and evolve.
via Blogger http://ift.tt/1f0MFPX
On this day in 1984….
The first untethered spacewalk was made by American Bruce McCandless II on February 7, 1984, during Challenger mission STS-41-B, utilising the Manned Maneuvering Unit. He was subsequently joined by Robert L. Stewart during the 5 hour 55 minute spacewalk. Such a self-contained spacewalk was first attempted by Eugene Cernan in 1966 on Gemini 9A, but Cernan could not reach the maneuvering unit without tiring.
|Untethered U.S. astronaut Bruce McCandless uses a manned maneuvering unit. photo taken by Robert “Hoot” Gibson|
The Manned Maneuvering Unit (MMU) is an astronaut propulsion unit that was used by NASA on three Space Shuttle missions in 1984. The MMU allowed the astronauts to perform untethered EVA spacewalks at a distance from the shuttle. The MMU was used in practice to retrieve a pair of faulty communications satellites, Westar VI and Palapa B2. Following the third mission the unit was retired from use. A smaller successor, the Simplified Aid for EVA Rescue (SAFER), was first flown in 1994, and is intended for emergency use only.
While orbiting around the Earth at a speed of 17,500 miles per hour, McCandless floated from the cargo bay into outer space, 150 nautical miles above Earth, an experience he described as “a heck of a big leap.” Mission specialist Robert L. Stewart, an Army lieutenant colonel, also flew the MMU on shuttle mission 41-B.
While flying the MMU, these men were in a journalistic phrase of the time “human satellites.” They checked out the equipment, maneuvered within the cargo bay, flew away from and back to the orbiter, performed docking exercises, recharged the MMU nitrogen tanks, and collected engineering data. The MMU, according to Martin Marietta’s post mission report, “performed as expected and no anomalies were reported.
Gaseous nitrogen was used as the propellant for the MMU. Two aluminium tanks with Kevlar wrappings contained 5.9 kilograms of nitrogen each, enough propellant for a six-hour EVA depending on the amount of manoeuvring done. Typical MMU delta-v (velocity change) capability was about 80 feet per second (24.4 m/s).
There were 24 nozzle thrusters placed at different locations on the MMU. To operate the propulsion system, the astronaut used his fingertips to manipulate hand controllers at the ends of the MMU’s two arms. The right controller produced rotational acceleration for roll, pitch, and yaw. The left controller produced translational acceleration for moving forward-back, up-down, and left-right. Coordination of the two controllers produced intricate movements in the unit. Once a desired orientation was achieved, the astronaut could engage an automatic attitude-hold function that maintained the inertial attitude of the unit in flight. This freed both hands for work.
Yet the MMU has not been used since 1984. There are several reasons for this. First, most extravehicular activities were effective without use of the MMU. Tethers, safety grips, hand bars, and other restraints allowed astronauts to work in the open cargo bay. Furthermore, the maneuverability of the Space Shuttle itself and the utility of the shuttle’s robotic manipulator arm had proved capable of rescuing satellites-the primary function for which the MMU had been designed.
via Blogger http://ift.tt/1b8SxYz