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Topics - shahina

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Science Discussion Forum / ‘Laser whitening' of TEETH
« on: March 09, 2015, 09:39:18 AM »

Tooth whitening can be a very effective way of lightening the natural colour of your teeth without removing any of the tooth surface. It cannot make a complete colour change, but it may lighten the existing shade.

‘Laser whitening', it is not a laser that is used. Gel is painted onto teeth and then a light is shone onto the gel to speed up the whitening reaction.

Science Discussion Forum / Laser telemetry
« on: March 09, 2015, 09:32:53 AM »

Laser telemetry

Laser telemetry is a technique used to determine the distance between an observer on the ground and a laser retroreflector placed on a satellite or on the surface of the Moon.

 A typical station comprises a powerful impulse laser that sends a beam to the target, a telescope to collect the reflected light and a time measuring device that allow to get the two-way duration. CERGA runs three such stations located on the plateau de Calern : the Lunar laser ranging station , the satellite laser ranging station and the ultra-mobile satellite laser station  which all have the capability to range with a centimeter accuracy.


Using lasers to cut a diamond apart atom by atom

One of great challenges of the 21st century has been to develop ways to manipulate matter on smaller and smaller dimensions.

Nanomachines, quantum computing components and ultrafast electronics are all important areas that are benefiting from this extreme push for engineering on the ultra-nanoscale.

EXPERIMENTS SHOW that a laser beam can target specific atoms on the surface, in a way not yet entirely understood, causing their chemical bonds to break before there is any significant dissipation of energy into the surrounding area.

The laser hits the diamond surface and releases the atoms. The significance of the result is that it is possible for lasers to interact with pairs of atoms and cause their separation without disturbing the surroundings. In the case of diamond, light polarisation IS USED to select what atom pairs are targeted by the laser beam.


Th­ere are special techniques that are used to cut and shape a diamond before it gets to the jewelry store. Diamond cutters use these four basic techniques:

1. Cleaving - To cut a rough diamond down to a manageable size, the cutter must cleave it along the diamond's tetrahedral plane, where it is the weakest

2. Sawing - Sometimes, diamonds have to be cut where there is no plane of weakness, which cannot be done with cleaving.

3. Bruiting/Cutting - This technique gives diamonds their shape. When diamonds are cut by hand, the technique is called bruiting -- cutting refers to bruiting by machine.

4. Poli­shing - To create the diamond's finished look, the cutter places it onto the arm above a rotating polishing wheel. The wheel is coated with an abrasive diamond powder that smoothes the diamond as it is pressed against the wheel.



Recognized as one of the top ten technological achievements of the twentieth century.

Lasers are devices that produce intense beams of light which
are monochromatic, coherent, and highly collimated. The wavelength
(color) of laser light is extremely pure (monochromatic) when compared
to other sources of light, and all of the photons (energy) that
make up the laser beam have a fixed phase relationship (coherence)
with respect to one another. Light from a laser typically has very
low divergence. It can travel over great distances or can be focused
to a very small spot with a brightness which exceeds that of the
sun. Because of these properties, lasers lasers are used in a wide variety
of applications in all walks of life.

Science Discussion Forum / LASERINVENTOR
« on: March 09, 2015, 08:58:40 AM »

The inventor of LASER was Theodore Maiman.  An experimental physicist, Maiman launched the ruby laser onto the world stage in 1960, and continued developing it and its uses in the decades since. 

He gained world recognition with awards such as the Wolf Prize, the Japan Prize, and induction into the Inventors' Hall of Fame.  In 2000 he authored The Laser Odyssey, which chronicles the years leading up to his invention, as well as describing his subsequent professional and personal journeys. 


The laser punches a hole in a preplanned spot IN EYE and the eye fluid drains out through the hole. The treatment can be performed in a doctor's office instead of a hospital.

Science Discussion Forum / WHAT IS GLUCOMA?
« on: March 09, 2015, 08:35:03 AM »

 GLAUCOMA, which is buildup of fluid in the eye.

Normally the eye's natural fluids drain away a little at a time, and the eye stays healthy. In eyes impaired with glaucoma the fluid does not drain properly, and the buildup affects vision; blindness can sometimes result. In some cases drugs can be used to treat glaucoma.

Science Discussion Forum / DENTAL LASER: DOES IT HURT? NO, WHY?
« on: March 09, 2015, 08:28:01 AM »

Each burst of laser light from a dental laser lasts only thirty-trillionths of a second, much faster than the amount of time a nerve takes to trigger pain. In other words, the beam would have to last 100 million times longer in order to cause any discomfort. So this sort of treatment requires no anesthetic.

« on: March 09, 2015, 08:16:35 AM »

Plaque is a tough fatty substance that can build up on the inside walls of the arteries. Gradually  the arteries can get so clogged that blood does not flow normally, and the result can be a heart attack or stroke. The traditional method for removing the plaque involves opening the chest and making several incisions, a long and sometimes risky operation. It is also expensive and requires weeks for recovery.

An effective alternative is to use a laser beam to burn away the plaque. The key to making this work is the doctor's ability to see inside the artery and direct the beam, another area in which fiber optics and lasers are combined into a modern wonder tool. An optic fiber that has been connected to a tiny television camera can be inserted into an artery. These elements now become a miniature sensor that allows the doctor and nurses to see inside the artery while a second fiber is inserted to carry the bursts of light that will burn away the plaque.

Science Discussion Forum / What is felt After LASIK Surgery
« on: March 08, 2015, 03:14:00 PM »
Immediately after the procedure, eye may burn, itch, mild pain, tear or water, vision will probably be hazy or blurry. Rubbing eye could dislodge the flap. Patients may experience sensitivity to light, glare, starbursts or haloes around lights, or the whites of eye may look red or bloodshot.

These symptoms should improve considerably within the first few days after surgery. Patient may also be advised to use artificial tears to help lubricate the eye and not to use wearing a contact lens in the operated eye, even if vision is blurry.
During the first few months after surgery, vision may fluctuate.
•   It may take up to three to six months for vision to stabilize after surgery.
•   Glare, haloes, difficulty driving at night, and other visual symptoms may also persist during this stabilization period.

Science Discussion Forum / During LASIK Surgery
« on: March 08, 2015, 03:03:09 PM »
During LASIK Surgery

The surgery TAKES around less than 30 minutes.

1.   The patient  lies on back in a reclining chair in an exam room containing the laser system. The laser system includes a large machine with a microscope attached to it and a computer screen.
2.   A numbing drop will be placed in eye, the area around eye will be cleaned, and an instrument called a lid speculum will be used to hold eyelids open
3.   Very high pressures will be applied to create suction to the cornea. Vision will dim while the suction ring is on and this time the pressure and some discomfort is felt during this part of the procedure. A cutting instrument or laser, is attached to the suction ring. Doctor will use the blade of the microkeratome to cut a flap in cornea.
4.   Laser energy is focused inside the cornea tissue, creating thousands of small bubbles of gas and water that expand and connect to separate the tissue underneath the cornea surface, creating a flap. The plate is then removed.
5.   The patient is able to see but experiences fluctuating degrees of blurred vision during the rest of the procedure. The doctor will then lift the flap and fold it back on its hinge, and dry the exposed tissue.
6.   The laser will be positioned over eye
7.   is experienced. A computer controls the amount of laser energy delivered to eye. Before the start of surgery,  doctor will have programmed the computer to vaporize a particular amount of tissue based on the measurements taken at initial evaluation. After the pulses of laser energy vaporize the corneal tissue, the flap is put back into and patient is asked to stare at a light.
8.   When eye is in the correct position, doctor will start the laser. As the laser removes corneal tissue, new sounds and smells position.
9.   A shield should be placed over eye at the end of the procedure as protection, since no stitches are used to hold the flap in place.


First, a mechanical surgical tool called a femtosecond laser to create a thin, circular "flap" in the cornea. The surgeon then folds back the hinged flap to access the underlying cornea and removes some corneal tissue using an excimer laser. This highly specialized laser uses a cool ultraviolet light beam to remove microscopic amounts of tissue from the cornea to reshape it so it more accurately focuses light on the retina for improved vision.

a.   For nearsighted people, the goal is to flatten the cornea;
b.   With farsighted people, a steeper cornea is desired.
c.   Excimer lasers also can correct astigmatism by smoothing an irregular cornea into a more normal shape.

After the laser reshapes the cornea, the flap is then laid back in place, covering the area where the corneal tissue was removed. Then the cornea is allowed to heal naturally.
Laser eye surgery requires only anesthetic drops, and no bandages or stitches are required.

Science Discussion Forum / Potential Side Effects of LASIK Eye Surgery
« on: March 08, 2015, 09:43:33 AM »
What Are the Potential Side Effects of LASIK Eye Surgery?

Some patients experience discomfort in the first 24 to 48 hours after LASIK eye surgery. Other side effects, although rare, may include:
•   Glare
•   Seeing halos around images
•   Difficulty driving at night
•   Fluctuating vision
•   Dry eyes

Science Discussion Forum / Some disadvantages to LASIK eye surgery:
« on: March 08, 2015, 09:41:49 AM »
What Are the Disadvantages of LASIK Eye Surgery?

Some disadvantages to LASIK eye surgery:
•   Changes made to the cornea cannot be reversed after LASIK.
•   LASIK is technically complex. Problems may occur when the doctor creates the flap, which can permanently affect vision.
•   LASIK can rarely cause a loss of "best" vision. Your best vision is the highest degree of vision that you achieved while wearing your contacts or eyeglasses.


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