Friday, September 5, 2008

In A Pinch

One of the most amazing tools of our time are the tongs. A simple device that works in so many ways.

Just take a look.

Tongs are gripping and lifting tools, of which there are many forms adapted to their specific use. Some are merely large pincers or nippers, but the greatest number fall into three classes:
 1. Tongs which have long arms terminating in small flat circular ends of tongs and are pivoted close to the handle, as in the common fire-tongs, used for picking up pieces of coal and placing them on a fire.
 2. Tongs consisting of a single band of metal bent round one or two bands joined at the head by a spring, as in sugar-tongs, asparagus-tongs, and the like.
 3. Tongs in which the pivot or joint is placed close to the gripping ends, such as blacksmith's tongs or crucible-tongs.
The tongs are the most-used cooking utensil when grilling, as they provide a way to move, rotate and turn the food with delicate precision.
A special form of tongs, known as "lazy-tongs," consists of a pair of grippers at the end of a series of levers pivoted together like scissors, the whole being closed or extended by the movement of the handles communicated to the first set of levers and thence to the grippers, the whole forming an extensible pair of tongs for gripping and lifting things at a distance.

Forceps are a handheld, hinged instrument used for grasping and holding objects. Forceps are used when fingers are too large to grasp small objects or when many objects need to be held at one time while the hands are used to perform a task. The term forceps is used almost exclusively within the medical field. Outside medicine, people usually refer to forceps as tweezers, tongs, pliers, clips or clamps.
The singular and plural form of forceps is always forceps, never 'forcep.' Nor is it referred to as a "pair of" as one refers to a pair of scissors. Etymologically, the word derives from the Latin 'Forca,' meaning a snare or trap.
Mechanically, forceps employ the principle of the lever to grasp and apply pressure.
Surgical forceps are commonly made of high-grade carbon steel. Lower quality steel is used in forceps made for other uses. High carbon steel ensure that the instruments can withstand repeated sterilization in high-temperature autoclaves. Some forceps, intended to be used once and then discarded, are made of plastic.
There are two basic types of forceps: non-locking (often called 'thumb forceps' or 'Pick-ups') and locking, though these two types come in dozens of specialized forms for various uses. Non-locking forceps also come in two basic forms, hinged at one end, away from the grasping end (colloquially such forceps are called tweezers, though a medical professional would not likely refer to them a such) and hinged in the middle, rather like scissors (though, unlike scissors, forceps meet on flat, grasping surfaces rather than in interposing blades). Locking forceps are almost always hinged in the middle, though some forms place the hinge very close to the grasping end. Locking forceps use various means to lock the grasping surfaces in a closed position to facilitate manipulation or to independently clamp, grasp or hold an object.
Used in the late century to hold joints. 

Tweezers are tools used for picking up small objects that are not easily handled with the human hands. They are probably derived from tongs, pincers, or scissors-like pliers used to grab or hold hot objects from the dawn of recorded history.
Tweezers make use of two third-class levers connected at one fixed end (the fulcrum point of each lever), with the pincers at the others.
Tweezers have many uses, such as gold panning, in the manual construction or repair of many things such as models, clockwork, surface mount electronics; or in cosmetics for plucking eyebrows.
Two sticks would be used to pinch another stick over a stone age fire. Tweezers are known to have been used in predynastic Egypt. There are drawings of Egyptian craftsmen holding hot pots over ovens with a double-bow shaped tool. Asiatic tweezers, consisting of two strips of metal brazed together were common to Mesopotamia and India about 3000 B.C. These likely served purposes such as catching lice.[1] There is evidence of Roman shipbuilders pulling nails out of construction with plier-type pincers.
Tweezers come in a variety of tip shapes, including pointed, blunt and tapered. There are also various types of specialised forms of tweezers, including:
 • Optical tweezers use light to manipulate microscopic objects as small as a single atom. The radiation pressure from a focused laser beam is able to trap small particles. In the biological sciences, these instruments have been used to apply forces in the pico Newton range and to measure displacements in the nm range of objects ranging in size from 10 nm to over 100 mm.
 • Magnetic tweezers use magnetic forces to manipulate single molecules (such as DNA) via paramagnetic interactions. In practice it is an array of magnetic traps designed for manipulating individual biomolecules and measuring the ultrasmall forces that affect their behavior.
 • Electric tweezers deliver an electrical signal through the tip, intended to damage hair roots and prevent new hair from growing from the same root.
 • Molecular tweezers are noncyclic host molecules that have two arms capable of binding guests molecules through non-covalent bonding.
 • Stamp tweezers or Stamp tongs are specially designed tweezers used for handling postage stamps.

Hot cell
Shielded containments are commonly referred to as Hot Cells. The word "hot" refers to radioactive. Hot cells are used in both the Nuclear and the Nuclear Medicines Industry. They are required to protect individuals from radioactive isotopes by providing a safe containment box in which they can control and manipulate the equipment required.
Nuclear Industry
Hot cells are used to inspect spent nuclear fuel rods and to work with other items which are high-energy gamma ray emitters. For instance, the processing of medical isotopes, having been irradiated in a nuclear reactor or particle accelerator, would be carried out in a hot cell. Hot cells are of nuclear proliferation concern, as they can be used to carry out the chemical steps used to extract plutonium from reactor fuel. The cutting of the used fuel, the dissolving of the fuel and the first extraction cycle of a nuclear reprocessing PUREX process (highly active cycle) would need to be done in a hot cell. The second cycle of the PUREX process (medium active cycle) could be done in glove boxes.
Nuclear Medicines Industry
Hot cells are commonly used in the Nuclear Medicines industry: - for the production of radiopharmaceuticals, according to GMP guidelines (industry) - for the manipulation and dispense of radiopharmaceuticals (hospitals) The user must never be subject to shine paths that are emitted from the radioactive isotopes and therefore there generally is heavy shielding around the containment boxes, which can be made out of stainless steel 316 or other materials such as PVC or Corian. This shielding can be ensured by the use of lead (common) or materials such as concrete (very large walls are therefore required) or even tungsten. The amount of energy that is being used in the hot cell will prescribe how thick the shielding must be - for the production of molybdenum (which is used for the manufacture of technetium generators) would require 150mm of Pb.
Viewing windows
In order to view what is in the hot cell, cameras can be used (but these require replacing on a regular basis) or most commonly, lead glass is used. There are several densities for lead glass, but the most common is 5.2 g/cc. A rough calculation for lead equivalence would be to multiply the Pb thickness by 2.5 (e.g. 10mm Pb would require a 25mm thick lead glass window)
Telemanipulators or tongs are used for the remote handling of equipment inside hot cells. These are incredibly valuable as they do not require for the user to place his/her arms inside the containment box and be subject to heavy finger/hand doses. The French company la Calhéne's model MA 11-80 is very popular in this industry.[citation needed] EMS are a fabricator of remote manipulation tongs. These need to be used in conjonction with a shielded sphere which can be made by most lead engineering companies (eg. Gravatom)
Lead loaded gloves are often used in conjonction with tongs as they offer better dexterity and can be used in low radiation environments (such as hot cells used in hospital nuclear medicine labs)
Some companies have developed tungsten loaded gloves (eg. Gravatom) which offer greater dexterity than lead loaded gloves alongside with better shielding than their conterparts.
Gloves are regularly changed as the chemicals used for the cleaning/sterilisation process of the containments cause considerable wear & tear.
Clean Room
Hot cells are generally placed in clean rooms with an air classification ranging from D to B (C is the most common).
Different types of hot cells
- Research and Development cells: These cells are often used to test new chemistry units or processes. They are generally fairly large as they require flexibility for the use of varying chemistry units which can greatly vary in size (e.g. synthera and tracerlab). Some cells require remote manipulation.
- Stack mini-cells: This type of hot cell is used purely for production of radiopharmaceuticals. A chemistry unit is placed in each cell, the production process is iniated (receiving the radioactive F18 from the cyclotron) and once finished, the cells are left closed for a minimum of 6 hours allowing the radiation to decrease to a safe level. No Manipulation is necessary here.
- Production and dispense cells: Once the FDG has been produced from the F18 mixing with glucose, a bulk vial will be present in a dispense cell and will therefore need to be carefully dispensed into a number of syringes or vials. Remote manipulation is crucial at this stage

See how a wonderful tool can be so corrupted!

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