SCIENCE & TECHNOLOGY

Fighting drug-resistant bugs
Radhakrishna Rao
T
HE discovery of first ever antibiotic penicillin by Alexander Fleming was a landmark event that brought about far-reaching changes in tackling a variety of diseases caused by microbes. The introduction penicillin paved the way for developing a string of “miracle drugs” to combat disorders and illness caused by microbes like bacteria and virus.

High-performance concrete
Gurvinder Singh Bedi
C
oncrete is most used building material invented in last century. With increase in its use continued research is being done to have desired results. It has very good compressive strength. But it is poor in tension. In latest IS/456-2000 code concrete is designated by its compressive strength of 150 mm cubes at 28 days in N/mm2

Birds descended from waterfowl
A
set of 110-million-year-old fossils from China is the earliest example of a modern-looking bird and strongly suggests ancestors of all living birds were waterfowl, researchers said.

Prof Yash Pal

Prof Yash Pal

PROF YASH PAL
THIS UNIVERSE
Why water does not have any colour — why is it transparent?
Colour is the sensation we get when some components of the wavelengths our eyes are sensitive to get eliminated, reduced or amplified in what we sense as white light!



Top









Fighting drug-resistant bugs
Radhakrishna Rao

TB microbes
TB microbes

THE discovery of first ever antibiotic penicillin by Alexander Fleming was a landmark event that brought about far-reaching changes in tackling a variety of diseases caused by microbes.

The introduction penicillin paved the way for developing a string of “miracle drugs” to combat disorders and illness caused by microbes like bacteria and virus. However, over the years, the misuse, abuse and overuse of antibiotics has given rise to a new class of “virulent super bugs” that are resistant to one or more antibiotics.

Indeed, a WHO study warns that if people continue to misuse antibiotics, new “super bugs” which resist all drugs could take the world back to the time when minor diseases caused instant death.

Meanwhile, a fact-filled report from the US Government warns that a virtually untreatable form of TB resistant to at least five classes of antibiotics is manifesting slowly across the world. Though, at the moment, the total number of infections by this new strain is quite insignificant, researchers are afraid that it could spread rapidly in areas such as East Europe, India and China.

Incidentally, in 2004, that virulent strain was responsible for more than 10 per cent of all drug resistant TB cases in industrialised countries. “The time to act is now to prevent a new pandemic,” says Dr Marcos Espinal, Executive Secretary of WHO’s Stop TB Partnership.

According to researchers at the Atlanta based Centre for Diseases Control (CDC), the evolution of drug-resistant strains of Mycobacterium tuberculosis is a fallout of both the TB patients’ failure to complete the six-month course of therapy, necessary to cure the disease and physicians’ failure to prescribe proper therapy.

Unfortunately, the drugs that are meant to treat drug resistant TB cases are more toxic, more expensive and less effective. Moreover, they are time consuming in that a course of therapy for multi drug resistant TB may require two years instead of six months.

Biomedical researchers hold the view that indiscriminate prescription of antibiotics by physicians and self-medication could be at the root of many microbes developing resistance to hitherto effective antibiotics.

“Most practitioners are not familiar with rational drug use practices and are often forced to prescribe a slightly high powered drug where a simple one may work”, says Anus Misra, a physician.

Significantly, it was way back in 1977 that Dr Michael Jacobs documented the first-ever case of the resistance shown by streptococcus pneumonia which is responsible for causing pneumonia, ear and sinus infection, to several classes of antibiotics, Amoxicillin, the antibiotic first developed by Glaxo Smithkline is still a preferred drug for tackling this microbe. But then as pointed out by Dr Jacobs, the standard dosage of Amoxicillin has increased fourfold in a quarter of century.

On the other hand, Prof McGavock of Ulster University believes that all antibodies could lose their punch in a decade or so and the resulting crisis could be far more serious than the AIDS crisis.

Even so, very few big pharma companies are interested in developing a new class of antibiotics because it is costly, time consuming and fraught with uncertainties. As such it is now the turn of small biotech companies to focus on antibiotics. According to a spokesman of WHO, “We must take urgent measures to turn back the threat of infectious diseases. We are here to call on the world to mobilise a massive effort for better use of these powerful weapons before the window of opportunities closes and we move further towards the pre antibiotic era”.

American biomedical researchers have found that leprosy bacterium is developing resistance to Depson, once thought to be a potent drug to treat this disease. Cases of MRSA — Methicillin Resistant Staphylococus Auris — have been reported from many third world countries.

Some of the antibiotics have become ineffective in fighting many of the viral strains responsible for causing diarrohea. It is surmised that excessive exposure to antibiotics have brought about a genetic change in disease causing microbes and made them resistant to known antibiotics.

Against such a bleak medical scenario, endeavours are being made to develop a whole new class of drugs called “Ramp” antimicrobials which may address the rapidly spreading problem of antibiotic immunity. These drugs are basically designed to work in the same way as the human body is fighting off bacterial infection.

On another front, biomedical researchers are busy developing two innovative methods to fight microbes without using antibiotics. One method falls back on deploying a viral enzyme named bacteriophage to annihilate the bacteria with a high degree of precision. In the second method researchers use components derived from one bacteria to neutralise another. Each of these methods clearly illustrates the new way of fighting the threat of antibiotic resistance developed by super bugs.

All said and doe, chances of bugs evading these innovative techniques in the long run cannot be ruled out. Precaution should be the key word in implementing this new strategy to surmount the problem of drug resistance that has become both rampant and widespread.

Top

High-performance concrete
Gurvinder Singh Bedi

Concrete is most used building material invented in last century. With increase in its use continued research is being done to have desired results. It has very good compressive strength. But it is poor in tension. In latest IS/456-2000 code concrete is designated by its compressive strength of 150 mm cubes at 28 days in N/mm2

The classification of grades has been done as M 10 to M 20 ordinary concrete;

M 25 to M 55 standard concrete; M 60 to M 80 High performance concrete;

And now new grade has also been developed as ultra high performance concrete

High Performance Concrete is often called durable concrete because its strength and impermeability to chloride penetration makes it last much longer than conventional PCC. The concrete mix is engineered with the typical elements of water, portland cement, and fine and coarse aggregates, but with admixtures which enhance performance. High-performance concrete is not just about high-strength mix, but also enhanced durability.

HPC mix designs were developed in the 1980s to protect reinforced concrete high-rise buildings and bridges from chlorides, sulfates, and alkali-silica reactivity and to quell concrete shrinkage and creep.

In HPC, materials and admixtures are carefully selected and proportioned (optimised) to form high early strengths, high ultimate strengths and high durability beyond conventional concrete.

Some industrial waste materials of a few decades ago now are integral elements of this new-engineered concrete. These admixtures, such as coal flyash, silica fume, and ground granulated blast furnace slag, add both strength and durability to the concrete, and enhance its marketability as an environmentally friendly product.

Providentially, these materials also produce a lower heat of hydration, which can minimise shrinkage cracking produced by higher temperatures. minimising shrinkage cracks can limit ingress of chlorides.

HPC provides enhanced mechanical properties in precast concrete structural elements, including higher tensile and compressive strengths, and heightened modulus of elasticity (stiffness). In frost-prone regions the benefits of HPC are great. The enhanced durability of HPC helps it resist penetration of chloride-laden snow and icemelt water. This results in longer life for the reinforcing steel within, and a reduction in spalling, cracking, and associated repairs.

The proportions in which fundamental components are mixed, and the admixtures that are used, constitute the main difference between conventional PCC and HPC. A high-range water-reducing admixture may provide a required low water/cement ratio, perhaps as low as 0:35.

When strength of concrete is more than M 80 it is called ultra high performance concrete. It is also called as reactive powder concrete (RPC). It is a high strength ductile material formulated by combining Portland cement, silica fumes, quartz flour, fine silica sand, high water reducing agent, water, and steel or organics fibers. The material provides compressive strength up to 200 Mpa and flexural strength up to 50 Mpa.

Top

Birds descended from waterfowl

A set of 110-million-year-old fossils from China is the earliest example of a modern-looking bird and strongly suggests ancestors of all living birds were waterfowl, researchers said.

The pigeon-sized bird probably resembled a tern or a loon, the researchers said. Called Gansus yumensis, it would have been an accomplished flyer and diver and could well be one of the ancestors of modern birds, the researchers report in the journal Science.

“Every bird living today, from ostriches...to bald eagles, probably evolved from Gansus-like ancestor,” Matthew Lamanna of Carnegie Natural History Museum in Pittsburgh told a news conference.

Peter Dodson, professor of anatomy at the University of Pennsylvania, who oversaw the research, said: “Gansus is very close to a modern bird and helps fill in the big gap between clearly non-modern birds and the explosion of early birds that marked the Cretaceous period, the final era of the Dinosaur Age.”

The five skeletons come from an exceptionally rich fossil bed in China’s Gansu Province, in a poor farming area near Changma, 2,000 km west of Beijing.

In the Cretaceous period, 100 million years ago, it would have been a lake, surrounded by lush plant life, filled with crocodiles and fish, and with dinosaurs and early mammals prowling on land. Now the lake bed survives as layers of rock.

“You can walk up to a rock and peel off sheet after sheet like paper until you get to a fossil,” said Jerald Harris of Dixie State College of Utah.

Hai-lu You of the Chinese Academy of Geological Sciences was studying at the University of Pennsylvania when many earlier fossil birds were discovered in China’s northeastern Liaoning Province. He remembered that the rock beds in Gansu were similar and took an expedition there.

They struck paleontological gold and quickly gathered five nearly complete fossils of the early bird.

A computer programme reconstructed the bird evolutionary tree and suggests the birds that gave rise to modern birds were waterfowl. Gansus looks more like a modern bird than some birds that lived later in the Cretaceous period.

Its wings, legs and webbed feet closely resemble those of living loons and diving ducks, with a few exception.

The birds had not yet evolved the hollow, air-filled bones that make modern birds to light and nimble, and it still had tiny claws at the end of its wings that probably would have made it slightly clumsy in flight, Harris said. — Reuters

Top

PROF YASH PAL
THIS UNIVERSE

Why water does not have any colour — why is it transparent?

Colour is the sensation we get when some components of the wavelengths our eyes are sensitive to get eliminated, reduced or amplified in what we sense as white light!

I know this sentence that I have just crafted is a mouthful. This is intentional mischief. This is to highlight the fact that when we see we are doing a sophisticated but limited scattering experiment using the humanly selected set of colours, or wavelengths of electromagnetic radiation we call light. We are entitled to this bias.

But we should recognise that water is not transparent at all wavelengths. X-rays and infrared do not travel well through water, nor does ultraviolet. “Transparency” of water is due to the fact that the molecular and atomic structure of water is such that up to shallow depths it seems transparent to us. In actual fact it is not.

If we were to look down into the depths of the ocean after putting our head in water we will not see very far. It is nearly pitch dark at the bottom of the ocean, because the light from above all gets scattered or absorbed.

You could also ask the question: why is the atmosphere so transparent? It is marvelous that our sun puts out most of its energy in the narrow visible band of light to which over atmosphere is almost transparent and for which our eyes have the maximum sensitivity.

The sun, the earth and its atmosphere seem to have been specially created for us. More likely is the fact that we are a product of evolution suited to the environment in which we came to be.

Furthermore, just as in the case of water it is marvellous that our atmosphere is not completely and equally transparent to all the colours we can see. If it were we would not have had any sky.

Or, more correctly, the sky would have been black! The beauty of the blue skies and orange sunsets would have been denied to us. Clouds would have created some spectacle across the black sky and the rainbows would have still existed — but no twilights and no blue skies.

So our air is transparent but to our delight not uniformly and completely so. I think we live in the best of the possible worlds. I hope we realize it and not make it ugly and miserable through our actions.

Please tell me: when people die of electric shock, what kills them—current or voltage?

The answer to this question is: the current, but this can be a bit misleading. The current depends on the resistance of the body, along with that of the apparel, shoes and whether the skin is a bit wet or not. It also depends linearly on voltage. Current as small as some milliamps can be dangerous. It can interfere with heart functioning, slow down or stop flow of blood to the brain, cause paralysis and interfere with breathing. High current causes serious internal burns.


HOME PAGE

Top