SCIENCE & TECHNOLOGY

T-rays, more versatile than X-rays
By Dr. S. S. Verma
Terahertz radiation was discovered in 1896. Unless they’re at a temperature of absolute zero (–273.160 C), all objects, animate and inanimate, give off terahertz radiation (called T-rays), the heat from molecular vibrations. This “black-body” radiation is emitted at such low intensities – typically less than a millionth of a watt per square centimeter – that we’re unaware of it.

Genetic defects behind common human diseases
By Steve Connor
When the human genome was fully decoded at the turn of the 21st Century, one scientist described it as the biggest discovery since the invention of the wheel. It has taken some years for medical research to live up to the initial expectations attached to the deciphering of the human genome.

Prof Yash Pal

Prof Yash Pal

THIS UNIVERSE
PROF YASH PAL
When we breathe out slowly, with our mouth open, the air is warm on the back of our hand. But when we blow with our lips compressed, the air feels cooler. Why this difference?
The body temperature of a healthy human being is very close to 37 degrees Celsius. This is fairly uniform within the body, kept the same through circulation of our blood. The air that goes through our lungs is also at that temperature.



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T-rays, more versatile than X-rays
By Dr. S. S. Verma

A T-ray machine used by the US government for homeland security
A T-ray machine used by the US government for homeland security. www.physics.nist.gov

Terahertz radiation was discovered in 1896. Unless they’re at a temperature of absolute zero (–273.160 C), all objects, animate and inanimate, give off terahertz radiation (called T-rays), the heat from molecular vibrations. This “black-body” radiation is emitted at such low intensities – typically less than a millionth of a watt per square centimeter – that we’re unaware of it.

T-rays can go through just about anything except metal and water. This ability of T-rays, which is a result of their short wavelengths, make them ideal candidates for certain types of medical imaging. The T-ray imaging technique is notable in that it can distinguish between different chemical compositions inside a material even when the object looks uniform in visible light.

Molecule fingerprinting: Basically the way this is done with T-rays is to blast the molecule with many T-rays all at once and see which frequencies got absorbed by the molecule and which didn’t. Each molecule has its own characteristic vibrational resonances and measurement of these vibrations can identify one molecule from another called the molecule’s fingerprinting.

T-rays can discriminate for example between anthrax and salt in an envelope because the anthrax molecule will have different vibrational frequencies to the salt molecule. So by blasting the envelope with many different T-ray frequencies all at once and seeing which frequencies get absorbed and which don’t gives us a unique fingerprint of anthrax.

Screening: T-rays have enormous potential for security screening -- complementing rather than replacing X-ray technology. T-rays can reveal the contents of packaging in a way X-rays can’t, so they could be the way of the future for security screening. T-rays can effectively see through packaging – as paper, plastic, clothing, even wood appear transparent under terahertz radiation which distinguishes between properties that are broadly defined as wet and dry.

The X-ray scan only tells the shape of the object in there so if it’s the shape of a gun, we’ll see a gun. Whereas the T-rays won’t just give the shape of the image, it will give the molecular fingerprint. So it will be possible to detect maybe if there’s plastic explosives in there and things like that that wouldn’t normally detect with the X-ray.

T-ray endoscopy: T-rays interact in a unique way with the sea of electrons flowing across the surface of a metal wire. A similar variation in wave velocity is well-documented for higher frequency radiation in the visible portion of the spectrum but no one had predicted it for such low frequencies. Scientists discovered that propagation of T-rays down bare metal wires has allowed them to make T-ray endoscopes that can carry T-rays around corners and into tight places – like pipes and metal containers – where it hasn’t been feasible to place a T-ray generator.

In all T-wave applications today, the beam must be aimed directly from the wave generator at the spot to be sensed. Anything that needs to be scanned has to be moved in front of the beam. Moving the beam isn’t practical because the beam has to be fine-tuned each time it’s set up, and worse, the whole apparatus is very sensitive to bumps and vibrations, which can easily knock the beam out of alignment but endoscope technology can be helpful. . It is a discovery that could extend the reach of terahertz-based sensors for applications as wide-ranging as explosives detection, cancer screening and industrial and post-production quality control. Thoughts of using T-rays to help airline pilots peer through fog or help manufacturers check the number of raisins in cereal have been on hold because of the inability to make sufficiently powerful - and relatively cheap - rays.

Unlike X-rays, T-rays are safe for human application because they’re non-ionizing radiation. Because X-ray photons are such high energy they blast right through soft tissue in the human body so we don’t get much contrast in the skin and in the soft tissue. For detecting cancer in the surface X-rays are not that good whereas T-rays are more gentle and will give you more contrast in detecting cancers near the surface. It turns out that somewhere between 50 and 80 per cent of cancers tend to be surface cancers and so this is the niche where T-rays will win over X-rays.

T-rays production machine is portable in terms of the size of a photocopier and it’s affordable in terms of medical instrumentation. It’s a lot cheaper than X-ray machines and MRI machines and surgery as well.

At the moment X-rays are huge big machines, they’re dangerous, so we don’t see x-rays in the home – it’s always in hospitals. Whereas with T-rays because it’s safe and because it has the potential of becoming very compact, we could envisage a future T-ray machine of smaller size in everybody’s home one day for doing regular health check-ups ourselves.

The writer is from the Department of Physics, S.L.I.E.T., Longowal
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Genetic defects behind common human diseases
By Steve Connor

When the human genome was fully decoded at the turn of the 21st Century, one scientist described it as the biggest discovery since the invention of the wheel.

It has taken some years for medical research to live up to the initial expectations attached to the deciphering of the human genome. Recent announcements go some way to addressing the rationale for decoding the entire 3 billion "letters" of the human DNA code.

It is now possible to use the framework of the human genome as a global atlas to find our way around the individual genomes of real people with real medical problems.

Knowing why some people are born with a set of genes that confers a higher-than-expected risk of developing a particular disease could in theory revolutionise medicine.

A genetic fault resulting from the tiniest change or mutation of a person's DNA might be all that it takes to increase his or her risk of a lethal disease by a small but nevertheless significant amount.

Knowing that a fault in a gene is associated with a disorder could help scientists to understand the molecular basis of that condition, leading to better treatment and possibly even a cure for something that was previously incurable.

Until recently, medical genetics had to focus on often rare conditions resulting from defects in single genes. There are some 5,000 of these disorders, such as sickle-cell anaemia, cystic fibrosis and Huntington's disease.

Now the emphasis is on more common diseases where the genetic element may be small but the effect is still significant, especially in combination with other genes. Heart disease, for instance, affects many millions of people and it is influenced by several genes, or more accurately defects in several genes.

We are all born with genetic predispositions, whether they are to rare disorders or to common diseases. The new science of mass DNA analysis promises to tease apart the inherited traits to learn more about how they can trigger a severe illness or a premature death.

Ultimately the hope is that it may be possible to analyse all our genomes at a fraction of the current cost. It will usher in the era of personalised medicine, when doctors can study our genetic makeup to come to better decisions about which drugs will work best based on the DNA we were born with.

In theory it could actually save money because it would mean that we would be given only the drugs that are known to work, instead of the current practice of prescribing the same drug for everyone.

However, the reality is that this is still a long way off. Nevertheless, scientists are on the cusp of some great discoveries about the fundamental nature of human disease. 

By arrangement with The Independent
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THIS UNIVERSE
PROF YASH PAL

When we breathe out slowly, with our mouth open, the air is warm on the back of our hand. But when we blow with our lips compressed, the air feels cooler. Why this difference?

The body temperature of a healthy human being is very close to 37 degrees Celsius. This is fairly uniform within the body, kept the same through circulation of our blood. The air that goes through our lungs is also at that temperature. On the other hand, our skin is perhaps a wee bit cooler because one of its functions is to lose the heat generated through metabolism in the body.

Its cooling might be due to slight evaporation of perspiration - one of the mechanisms for temperature control of our bodies. This perhaps is the reason that the slow breath from our mouth feels a little warm at the back of our hand.

On the other hand, when we blow out through a narrow opening between our lips we are simultaneously making the air compressed within our mouth expand suddenly. The expansion of the air cools it. During expansion, molecules lose some of their random velocities while overcoming the intermolecular forces of attraction. Most gases cool when they are made to expand. This is good old Boyle’s law working. You can test it by feeling the air released from the valve of an automobile tire when you press the pin of the valve.

I marvel at the sophistication of the biochemical machinery within us that maintains our temperature with such accuracy. If it rises by a degree, a mere touch of the person’s hand tells us that he/she has a little fever. The thermostat of my air conditioner seldom works that well.

There are uncounted millions/billions of birds world wide. So how is it that we hardly, if ever, see a dead one?

Once I was asked a similar question about the near absence of dead flies when they are so abundant in some parts of our towns and villages. The answer to both these questions is similar. Dead birds and dead flies are excellent food for a lot of other living things, including a variety of insects and bacteria. They are carried away and consumed very quickly. Sad, but inevitable.

When we heat glass it cracks. But when it is heated to high temperature it converts into a liquid state. Why?

We know that glass is not a good conductor of electricity. We also know that glass expands when heated. If some part of a glass vessel is heated, it tries to expand. The neighbouring parts, being cooler, resist that expansion. Since glass is brittle, unlike metal, it shatters. If, on the other hand, the heating is slow and uniform, we can heat glass to a high temperature without it shattering.

Turning into liquid would happen irrespective of whether the piece of glass shattered on the way. Usually such heating is done gradually, sometimes in a furnace and sometimes over a flame when the sample is continuously rotated.
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