laser

Laser [acronym for light amplification by stimulated emission of radiation] , device for the creation, amplification, and transmission of a narrow, intense beam of coherent light, visible electromagnetic radiation.
Of the entire electromagnetic spectrum, the human eye is sensitive to only a tiny part, the part that is called light.
The coherent light produced by a laser differs from ordinary light in a way that it is made up of waves all of the same wavelength and all in phase; ordinary light contains many different wavelengths and phase relations.
The laser can be explained on the basis of the quantum theory.
The electromagnetic energy is transmitted in discrete amounts (i.e., in units or packets) called quanta.
A quantum of electromagnetic energy is called a photon, the particle composing light and other forms of electromagnetic radiation, sometimes called light quantum.
The energy carried by each photon is proportional to its frequency.
An atom or molecule of a substance usually does not emit energy; it is then said to be in a low-energy or ground state. When an atom or molecule in the ground state absorbs a photon, it is raised to a higher energy state, and is said to be excited.
The substance spontaneously returns to a lower energy state by emitting a photon with a frequency proportional to the energy difference between the excited state and the lower state.
In the simplest case, the substance will return directly to the ground state, emitting a single photon with the same frequency as the absorbed photon.
In a laser, the atoms or molecules are excited so that more of them are at higher energy levels than are at lower energy levels, a condition known as an inverted population.

If a photon whose frequency corresponds to the energy difference between the excited state and the ground state strikes an excited atom, the atom is stimulated to emit a second photon of the same frequency, in phase with and in the same direction as the bombarding photon.
The bombarding photon and the emitted photon may then each strike other excited atoms, stimulating further emissions of photons, all of the same frequency and all in phase.
This produces a sudden burst of coherent radiation as all the atoms discharge in a rapid chain reaction.
Often the laser is constructed so that the emitted light is reflected between opposite ends of a resonant cavity; an intense, highly focused light beam passes out through one end, which is only partially reflecting.
If the atoms are pumped back to an excited state as soon as they are discharged, a steady beam of coherent light is produced.

Characteristics of Lasers

The physical size of a laser depends on the materials used for light emission, on its power output, and on whether the light is emitted in pulses or as a steady beam.
In some lasers, a gas or liquid is used as the emitting medium.

Applications of Lasers

When lasers were invented in 1960, they were called "a solution looking for a problem".

In every section of modern society, including consumer electronics, information technology, science, medicine, industry, law enforcement, entertainment, and the military.

The first application of lasers visible in the daily lives of the general population was the supermarket barcode scanner, introduced in 1974.

The laserdisc player, introduced in 1978, was the first successful consumer product to include a laser, but the compact disc player was the first laser-equipped device to become truly common in consumers' homes, beginning in 1982, followed shortly by laser printers.

Some of the other applications include:

Medicine: Bloodless surgery, laser healing, surgical treatment, kidney stone treatment, eye treatment, dentistry
Industry: Cutting, welding, material heat treatment, marking parts
Defense: Marking targets, guiding munitions, missile defence, electro-optical countermeasures (EOCM), alternative to radar
Research: Spectroscopy, laser ablation, Laser annealing, laser scattering, laser interferometry, LIDAR, Laser capture micro dissection
Product development/commercial: laser printers, CDs, barcode scanners, thermometers, laser pointers, holograms, bubble grams.
Laser lighting displays: Laser light shows
Laser skin procedures such as acne treatment, cellulite reduction, and hair removal.

Digital signature

The digital signature is an electronic signature that can be used to authenticate the identity of the sender of a message or the signer of a document, and possibly to ensure that the original content of the message or document that has been sent is unchanged.

The digital signature is a digital guarantee that information has not been modified, as if it were protected by a tamper-proof seal that is broken if the content were altered.

The two major applications of digital signatures are for setting up a secure connection to a Web site and verifying the integrity of files transmitted.

Digital signatures are easily transportable, cannot be imitated by someone else, and can be automatically time-stamped.

The ability to ensure that the original signed message arrived means that the sender cannot easily repudiate it later.

A digital signature can be used with any kind of message, whether it is encrypted or not, simply so that the receiver can be sure of the sender's identity and that the message arrived intact.


A digital certificate contains the digital signature of the certificate-issuing authority so that anyone can verify that the certificate is real.


In cryptography, digital signatures are a method of authenticating digital information often is analogous to a physical signature on paper. Whilst there are analogies, there are also differences which can be important. The term electronic signature, although used for the same thing, has a distinct meaning: it refers to any of several, not necessarily cryptographic, mechanisms for identifying the originator of an electronic message. Commonly such electronic signatures have included cable and Telex addresses, as well as FAX transmission of handwritten signatures on a paper document.


How It Works


Assume you were going to send the draft of a contract to your lawyer in another town. You want to give your lawyer the assurance that it was unchanged from what you sent and that it is really from you.

You copy and paste the contract into an e-mail note.

Using special software, you obtain a message hash of the contract.

You then use a private key that you have previously obtained from a public-private key authority to encrypt the hash.

The encrypted hash becomes your digital signature of the message. At the other end, your lawyer receives the message.

To make sure it's intact and from you, your lawyer makes a hash of the received message.

Your lawyer then uses your public key to decrypt the message hash or summary.
If the hashes match, the received message is valid

TOTAL SOLAR ECLIPSE 2009

On Wednesday, 2009 July 22, a total eclipse of the Sun will be visible from within a narrow corridor that traverses half of Earth which includes most of eastern Asia, and the Pacific Ocean. The total solar eclipse of 22nd of July 2009 will be the longest eclipse of the 21st Century being 6 minutes 38 seconds at the point of maximum eclipse. The occurrences of total solar eclipses are still important, not withstanding the invention of coronagraph in 1930 and number of space instruments launched in space to make the observations of solar corona in EUV, soft X-ray and low resolution broad band images. The total solar eclipses provide minimum of scattered light about 1000 times less than that in the coronagraphs.

The total solar eclipse will be of longest duration during this century. It will be visible in India, some of the Japanese islands, China and Pacific Ocean. The eclipse begins with the sunrise in the western part of India, travels to eastern part of India, crosses to Myna-mar (Burma), small islands of Japan and China. In India Surat, Indore, Bhopal, Jabalpur, Varanasi and Patna are some of the cities lie close to the central part of the totality. In China duration of the totality will be about 5 minutes. In India altitude of the sun will be about 15 degrees in the eastern part at the time of total eclipse and this period is full of rains due to South West monsoon.



What Causes a Solar Eclipse?


An eclipse occurs at those times when the Moon moves into a position of direct alignment with the Sun and the Earth. Not all solar eclipses are total. During a partial solar eclipse, only the penumbra touches our planet. The umbra passes either just above the North Pole or just below the South Pole, completely missing the Earth. No total eclipse is visible -- only partial phases can be seen.

Why is a total solar eclipse such a rare event?


Eclipses do not occur every month during a new Moon or a full Moon. This is because the orbit of the Moon is tilted by about five degrees with respect to the Earth’s orbit, so that usually the Moon passes slightly above or below the line between the Sun and the Earth. Thus at most new and full Moons, the shadows miss their mark and no eclipse occurs.

To see a total solar eclipse, you have to be in the path of totality. With fewer than 70 total eclipses per century, the chance to see one is for most of us a once-in-a-lifetime event.

The sun's outermost region, called the corona, shines like a halo around the moon during a total solar eclipse. Such eclipses occur when a new moon passes in front of the sun. They don't happen often—only about once a year—since the tilted orbits of the sun, moon, and Earth make their alignment rare. Total solar eclipses are of special interest to astronomers because it is the only time the sun's corona can be seen from the Earth's surface.

On Wednesday, 2009 July 22, a total eclipse of the Sun will be visible from within a narrow corridor that traverses half of Earth which includes most of eastern Asia, and the Pacific Ocean. The total solar eclipse of 22nd of July 2009 will be the longest eclipse of the 21st Century being 6 minutes 38 seconds at the point of maximum eclipse. The occurrences of total solar eclipses are still important, not withstanding the invention of coronagraph in 1930 and number of space instruments launched in space to make the observations of solar corona in EUV, soft X-ray and low resolution broad band images. The total solar eclipses provide minimum of scattered light about 1000 times less than that in the coronagraphs.

The total solar eclipse will be of longest duration during this century. It will be visible in India, some of the Japanese islands, China and Pacific Ocean. The eclipse begins with the sunrise in the western part of India, travels to eastern part of India, crosses to Myna-mar (Burma), small islands of Japan and China. In India Surat, Indore, Bhopal, Jabalpur, Varanasi and Patna are some of the cities lie close to the central part of the totality. In China duration of the totality will be about 5 minutes. In India altitude of the sun will be about 15 degrees in the eastern part at the time of total eclipse and this period is full of rains due to South West monsoon.

Imaging of the solar corona has the advantages of providing the information over two dimensional region of the solar corona but it may have the small uncertainty of in the data due to variations in the sky transparency. On the other hand spectroscopy provides data only on the small portion of the solar corona but with spectral purity and is possible to account for the variations in the sky transparency. Line profiles can also yield information about the temperature and non-thermal structure of the solar corona.

Watch solar eclipse with precaution

For protecting the eyes, one must use tested solar filter goggles all through the partial phase, only during the period of totality one can enjoy the total solar eclipse with naked eyes.

The Google Story

" The google story" by David Wise is Quite an eyeopener on how Serjey and Larry managed to make their dreams into a $80 billion giant. The journey from the Stanford lab to the gates building to the garage to googleplex is worth a read.


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1)Google is a mis-spelt word. The original word is Googol which means 1 followed by 100 zeroes.


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2)Larry Page's brother Carl page also sold his internet company during the dot com era for an eye popping $500 million.


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3)Google's ad model was originally developed by a company named Overture ( Now a Yahoo company)


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4)From their original hostel at Stanford, Larry Page and Sergey Brin were shifted to a newly constructed building named William Gates building.


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5)Though a tech company Google followed the practices of media companies during its IPO. To protect itself from unwanted takeover threats the company issued class A and B types of shares. Valued similarly the two classes of shares differed only in their voting rights. The company also developed an auction based system of allotting its stake to prevent unwanted volatility just after listing.


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6)Google had lost the Amazon Europe ad deal to Yahoo. Larry and Serjey were traveling on their private jet when they got this news. With much persuation the founders arranged a secret meeting with Amazon's CEO. Google raised its bid to such a level that Yahoo was eventually forced to back out of the deal saying that it did not make business sense for the latter.


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7)Google's inhouse chef Charlie Ayers is one of the few chefs in the world who became a millionaire by selling personal Google shares given to him.


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8)Its very rare to find Kleiner Perkins and sequoia capital investing in the same venture. Larry and Sergie played a sleek game pitting the two VC'c against each other resulting in the two firms investing $12.5 million each.


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9)Google has a policy where employees are allowed to spend 20% of their time persuing their interests. Googlenews, Gmail and a host of other applications are a result of employee ideas which originated during this 20% time.


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10)Google has one of the largest hardware infrastructure and computing power in the world. This can be gauged from the fact that the company crawl the entire web and saves it in its computers. When a user searches for something, the google computers searches through the saved pages and throws out relevant results within seconds.



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Courtesy: http://www.thegooglestory.com

HIV/AIDS: Knowledge is Power

HIV can never survive in any other liquid medium also other than blood or semen (& please for God sake ... never in Pani Puri wala pani)



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Even if one drinks an HIV infected blood (or semen) of someone

(ingest through Gastro Intestinal track), the virus can not survive in the acidic pH of stomach. Highest extent of acidity is 0 (practically not possible) so imagine 1 as pH which is in our stomach. (This pH can burn

your own finger in less than a second if you dip in that acid).




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Exposure of less than 1 second in AIR KILLS the HIV virus(hence story of needle pricks in Cinema theatres is a crap). Even if blood from a wound (of infected person) dries up (blood clot), the virus diesand can not infect anyone else



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HIV transmission is ONLY an INFECTION i.e.entrance of virus in one's body. It DOES NOT MEAN AIDS.



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An HIV-infected person (after entrance of virus) can progress to a condition of AIDS only after 8 to 10 YEARS (not in 15 days as in the Pani Puri story). In some cases the time span may be 20 yrs. too.



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It is not HIV (virus) that kills a human .....the virus attacks immune cells (cells that fight against foreign pathogens/antigens)

and hence a person's ability to fight against infections & diseases slowly diminishes and person ultimately dies of a disease which could be as simple as TB



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Most importantly, HIV is no longer a dreadful disease ... it is "CHRONIC MANAGEABLE DISEASE" just like Diabetes or Hypertension.



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If there is anything you need to be careful from to prevent HIV is Unsafe sex, Blood transfusion (check before taking) /Blood donation (use sterilized needles only) and any blood contact during an accident or so where amount of bleeding is very high.



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PLZ O PLZ spread this message to avoid rumors and to educate people.


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A letter to Bill Gates from santa singh

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Dear Mr. Bill Gates,


This letter is from Banta Singh from Punjab. We have bought a computer
for our home and we found problems, which I want to bring to your
notice.

1. After connecting to internet we planned to open e-mail account and
whenever we fill the form in Hotmail in the password column, only ******
appears, but in the rest of the fields whatever we typed appears, but
we face this problem only in password field. We checked with hardware
vendor Santa Singh and he said that there is no problem in keyboard.
Because of this we open the e-mail account with password *****. I
request you to check this as we ourselves do not know what the password is.


2. We are unable to enter anything after we click the 'shut down '
button.


3. There is a button 'start' but there is no "stop" button. We request
you to check this.


4. We find there is 'Run' in the menu. One of my friend clicked 'run '
has ran upto Amritsar! So, we request you to change that to "sit", so
that we can click that by sitting.


5. One doubt is that any 're-scooter' available in system? As I find
only 're-cycle', but I own a scooter at my home.


6. There is 'Find' button but it is not working properly. My wife lost
the door key and we tried a lot for tracing the key with this ' find',
but unable to trace. Is it a bug??


7. Every night I am not sleeping as I have to protect my 'mouse' from
CAT, So I suggest u to provide one DOG to kill that cat.


8. Please confirm when u are going to give me money for winning
'HEARTS' (playing cards in games) and when are u coming to my home to collect
ur money.


9. My child learnt 'Microsoft word' now he wants to learn 'Microsoft
sentence', so when u will provide that?

Foods That Boost Your Health

There is evidence that our brain responds to the foods we eat, and that nutrients can trigger neurotransmitters and hormones that impact our mood and improve our mental sharpness. Not only has this been shown in children at school, but studies have also found that adults can help maintain brain health as they age.
The way things are going, I don’t anticipate a break until at least Thanksgiving. So until then, here’s what I’m focusing on during this grueling work-a-thon.


Brains are very hungry


The brain and nervous system are the hungriest organs—meaning that they require a constant supply of energy that can only be delivered in the form of glucose, the end product of carbohydrate metabolism. The brain uses more than 20 times the energy ounce-per-ounce of exercising muscle than any other part of the body; in fact, as we age, it’s the natural loss of gray matter that makes a significant contribution to our drop in metabolism.

What this means is that breakfast is very important, and so is eating every two to three hours throughout the day. The constant stream of glucose to the brain will help keep your concentration and mood elevated. A meal or snack that contains low-glycemic carbohydrates, or combines carbs with lean protein and/or some healthy mono or polyunsaturated fats, will help keep the fuel to the brain steady.


Eat a slow-burn breakfast



Reams of research show that kids who eat a healthy breakfast have improved concentration, and they perform better on tests compared to those that skips out on the a.m. meal. I’m no student, but I do know that eating my low-glycemic steel-cut oats gives me energy to start the day and raises my blood-sugar levels that have plummeted overnight. Other studies have found that a breakfast of low-glycemic-index foods like oatmeal increased mental acuity over high-glycemic-index breakfasts with the same number of same calories.

Eggs with a whole-wheat product—toast are great option to boost brainpower. Eggs contain choline, which helps the body make the memory-boosting chemical acetylcholine.



Eat more fruits and veggies


You’re probably aware of studies showing that blueberries improve the memory and cognitive function of aged animals, but all fruits and veggies are great cerebral choices. In addition to providing carbs to fuel the brain, they supply folic acid, a B-vitamin integral for the nervous system. In addition, they’re loaded with powerful antioxidants that help keep the blood vessels of the brain healthy and more flexible so that the brain gets adequately nourished.
I’m making more of my snacks fresh or dried fruits and veggies. Today I had raisins in my oatmeal, a banana with peanut butter at lunch, and a spinach salad with my dinner.



Enjoy caffeine and tea


affeine has been shown to improve concentration in studies, and tea has also been shown to have a compound, L-thiamine that impacts alpha waves in the brain. Alpha waves are supposed to help the brain focus when it is bombarded with all kinds of competing tasks (read: nonstop emails and phone calls). The combination of L-thiamine and caffeine in tea is akin to rebooting my mind to help me focus on finishing one task at a time, instead of being completely frazzled by a long to-do list all day.


Be a (healthy) fat head


Yes, your brain is a muscle, but about 70% of its gray and white matter is composed of fat. And it’s not just any fat; it’s the long-chain polyunsaturated fats that are part of the cell membranes and crucial messenger system of the brain.
These beneficial fats are called DHA and EPA, and you can find them in fish and algae-based supplements. Research shows that adults who eat the most tuna and other fish rich in DHA have healthier brain mass as they age, compared to those who eat the least amount of fish. But there’s one caveat: Interestingly, fried fish consumption does not provide the same brain-boosting benefits.

Make mental moves


nothing goes better with a healthy diet than a healthy lifestyle. To keep the blood and nutrients flowing to your brain, strive to get daily exercise. Exercise also clears your mind, gives you a natural endorphin rush, and staves off depression. Research also shows that among older adults, those who exercise the most have better cognition and improved mental states compared to those who move the least.

The Green Chemistry

What is Green Chemistry?


The Green Chemistry is defined as invention, design, development and application of chemical products and processes to reduce or to eliminate the use and generation of substances hazardous to human health and environment. While this short definition appears straightforward, it marks a significant departure from the manner in which environmental issues have been considered or ignored in the upfront design of the molecules and molecular transformations that are at the heart of the chemical enterprise.

Looking at the definition of green chemistry, the first thing one sees is the concept of invention and design. By requiring that the impacts of chemical products and chemical processes are included as design criteria, the definition of green chemistry inextricably links hazard considerations to performance criteria.

Another aspect of the definition of green chemistry is found in the phrase “use and generation”. Rather than focusing only on those undesirable substances that might be inadvertently produced in a process, green chemistry also includes all substances that are part of the process.

Therefore, green chemistry is a tool not only for minimizing the negative impact of those procedures aimed at optimizing efficiency, although clearly both impact minimization and process optimization are legitimate and complementary objectives of the subject.

Green chemistry, however, also recognizes that there are significant consequences to the use of hazardous substances, ranging from regulatory, handling and transport, and liability issues, to name a few. To limit the definition to deal with waste only, would be to address only part of the problem.


Principles of Green Chemistry


The twelve principles of green chemistry embrace these aims, as well as those of waste prevention, the use of renewable raw materials, the minimization of derivatives and better control of chemical processes. The Royal Society of Chemistry has established the Green Chemistry Network to promote green chemistry and now publishes a journal, Green Chemistry , devoted to the subject.


1) It is better to prevent waste than to treat or clean up waste after it is formed.
2) Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
3) Wherever practicable, synthetic methodologies should be designed to use and generate substances that posses little or no toxicity to human health and the environment.
4) Chemical products should be designed to preserve efficacy of function while reducing toxicity.
5) The use of auxiliary substances (e.g. solvents, separation agents etc.) should be made unnecessary wherever possible and, innocuous when used.
6) Energy requirements should be recognized for their environmental and economic impacts and should be minimized. Synthetic methods should be conducted at ambient temperature and pressure.
7) A raw material feedstock should be renewable rather than depleting whenever technically and economically practical.
8) Unnecessary derivatization (blocking group, protection/deprotection, and temporary modification of physical/chemical processes) should be avoided whenever possible.
9) Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
10) Chemical products should be designed so that at the end of their function they do not persist in the environment and break down into innocuous degradation products.
11) Analytical methodologies need to be further developed to allow for real-time in-process monitoring and control prior to the formation of hazardous substances.
12) Substances and the forms of the substance used in chemical reaction should be chosen so as to minimize the potential of chemical accidents, including releases, explosions, and fires.