Dresses that resist radiation
Shirish Joshi

After eight years of in-depth research, Dr Ronald F. DeMeo, a Florida based doctor and his colleagues, have developed a unique polymer composite-based fabric, called Demron, which not only blocks x-rays and nuclear emissions (gamma rays, alpha particles and beta particles) as effectively as currently used lead-based apparel does; but is also significantly more flexible and wearable.

In addition, the new fabric is impermeable to deadly chemical and biological warfare agents. It can be used in dresses of hazardous materials emergency workers and disaster handling workers. American army experts are currently evaluating Demron’s effectiveness against common chemical warfare agents such as mustard gas, nerve gas and sarin.

The new material could also be used for making radiation-proof tents, linings for aircraft and spacecraft, covers for sensitive equipment, and medical shielding garments.

To start with, the researchers in DeMeo’s worked on embedding metal particles in fabric. Then they tried to find polymers that attenuate radiation.

After considerable research they came up with a polymer composite of polyurethane and polyvinylchloride (PVC) that incorporates a variety of particles of organic and inorganic compounds, which block radiation. Constituents of these compounds have high atomic numbers so they tend to arrest radiation more effectively.

Demron looks and behaves like a heavy, dense rubber. It works in two ways, depending on the type of radiation. When x-rays or gama rays meet these dispersed particles, they are either absorbed and their energy dissipated through the generation of heat, or they are scattered and then absorbed or deflected by surrounding particles.

This process of absorption and scattering stops harmful radiation from penetrating to body tissues. When alpha and beta particles strike Demron, electrons in the compounds deflect and slow them down, whereupon they are absorbed into the material.

The polymer composite can be made in two forms: as thin film sheets or as injection-moulded shapes.

Demron is produced by laminating the film between two layers of fabric-one woven, the other non-woven. The resulting material is about 0.43 millimeter thick and has a density of about 0.11 gram per square centimetre.

Demron readily bends, creases and folds. The thin, yielding fabric has proved itself against both x-ray and nuclear emission in tests at various laboratories.

It is not yet clear, however, whether demron degrades when subjected to extended radiation for a very long time. The material is impermeable to air and fluids and can withstand at least eight hours of exposure to corrosive chlorine and ammonia gas.

Because it allows heat to radiate, Demron feels cool to the touch. It can be used to cover 100 per cent of the human body surface.

Demron has gone a long way towards proving that a thin, highly flexible and wearable radiation shield is a technical possibility.

Male contraceptives: many hurdles
Radhakrishna Rao

For decades women’s groups across the world have been protesting over the abuse of females for fertility control. But the global efforts to develop male contraceptive devices continues to be bedeviled by “uncertainties”. For the researchers involved in developing male contraceptives, the biggest hurdle is the complexity of the reproductive process in the men. Significantly, in women pregnancy can be averted by preventing the release of an egg once a month. However with men researchers have to grapple with sustained production of millions of spermatazoa. Not surprisingly many projects aimed at developing male contraceptives had to be abandoned midway.

This is not to suggest that all is quiet on the male contraceptive research front. Scientists at the pharma giant Organon are now close to realising a male pill that would inhibit the production of sperms and prevent pregnancy of the female partner. “Latest information shows that male equivalent of a pill could be available in five years” says Dr Kostas. I. Papadopoulos, a researcher with Organon. According to him, normally men produce around 120-million sperms per ejaculation. This works out to around 20-million sperms per milliliter of semen. The male pill seeks to limit the production of sperms to 1-million per milliliter.

On the other hand researchers at Anzac Research Institute in Sydney are experimenting with the hormonal treatment which involves a combination of implant under the skin coupled with an injection. This implies that men do not have to remember to take a pill every day. The treatment is a combination of implant containing male sex hormone testosterone which would be replaced every fourth month and three-monthly injection of progestin, a hormone forming part of the female birth control pill.” This is the first time a reversible male contraceptive that will suppress sperm production reliably and reversibly has been fully tested. This shows the way for a final product to be a single injection containing testosterone and progestin which will easily be given by local doctors on a three-four monthly basis and still maintain sexual health”.

However, the production of an indigenous injectible made contraceptive has been bogged down in controversy following the reports of the side-effects experienced by the volunteers who were given trial doses of the contraceptive. The one shot of this contraceptive, it is claimed, would be effective for two years. But Prof Sujoy K. Guha, the architect of this reversible contraceptive, is optimistic of overcoming the hurdles on the way to developing a safe male contraceptive.

Researchers working on antifertility devices have also found that neem and proteins derived from plants like tobacco and brinjal can work as antifertility agents. Being plant derivatives, these proteins are quire inexpensive and completely devoid of animal proteins which may have side-effects. A joint Indo-German research team headed by Dr G.P. Talwar, one of the pioneers of contraceptive research in India, is currently studying the possibility of using plant proteins as potential antifertility agents.

UNDERSTANDING THE UNIVERSE
WITH PROF YASH PAL

We are blind to ultraviolet radiations while bees can detect the same. So, how would the sun look to bees?

Bees also see in visible light. Their vision towards the red end of the spectrum is poor to the extent that what is red would be black for them. They certainly can see much further beyond the violet towards shorter wavelengths. That they can see in the visible light and also differentiate between different colours has been established. The sun would be visible very well. The hues would be different. The ultraviolet must give them some advantage. I do not know whether bees derive aesthetic pleasure from an abundance of illumination during the day. If they do have a name for the light that comes through scattering from air molecules, something that gives us our blue skies, their sky would be rather “ultraviolety” blue! On the other hand they would be deprived of orange sunsets or the red globe of the setting sun.

In addition the bees do share with many birds a faculty that we do not have. This is the ability to detect, the plane of polarisation of skylight. (The blue colour of the sky, along with its polarisation, is a result of scattering). This capability can be used to know the direction of the sun even during a cloudy day if a bit of the blue sky is visible. This is extremely useful for navigation.

It is definite that bees are quite sensitive to ordinary light. When they come to the hive after detecting a source of food they communicate the information about their find to other bees through a dance wherein the direction is indicated with respect to the direction of the sun at that time. If the hive is darkened and illuminated with a light bulb, they change the direction of the dance assuming the direction of the bulb as the direction of the sun.

Why is the colour of soil different at different places?

Soil is formed through physical, chemical and biological transformation of the material of the earth crust. Grinding and breakup of rocks of various types due to weathering and other physical processes provides the primary material. Some of the rocks are sedimentary rocks, others are igneous and volcanic, and yet others metamorphic. There are granites and lime stones. Breakup and disintegration of these rocks contributes varied chemical composition and trace elements to soils. Things that begin to grow on these soils also make a difference and bacterial activity adds to differentiation. The rainfall and availability of water, often carrying sediment from far away also play a crucial role. All these factors and processes naturally lead to different quality and colour of soils. Soils are also denuded sometime through erosion and run off and therefore change their characteristics. It is, therefore, not surprising that all these differences in origin and history would also lead to different colours. Just remember that the originating rocks are also different in colour.

New products & discoveries

Chemistry lab in your hand

Collaboration between NASA’s Marshall Space Flight Center and an industry partner has resulted in development of a portable vacuum X-ray fluorescent analyser that performs on-the-spot chemical analyses — a task previously only possible in a chemical laboratory.

Marshall engineers in Huntsville, Ala., teamed with KeyMaster Technologies of Kennewick, Wash., to develop a “chemistry lab in your hand” that weighs about 2 kg and is capable of detailed material analysis, even under field conditions. This capability promises to be a boon to the aerospace community because of unique requirements — for instance, the need to analyse Space Shuttle propulsion systems on the launch pad. Those systems provide the awe-inspiring rocket power that propels the Space Shuttle from earth into orbit in mere minutes.

The newly developed vacuum X-ray fluorescent analyser can identify and characterise a wide range of elements, and is capable of detecting chemical elements with low atomic numbers — such as sodium, aluminum and silicon. It is the only hand-held product on the market with that capability. Aluminum alloy verification is of particular interest to NASA because vast amounts of high-strength aluminum alloys are used in the Space Shuttle propulsion system - the External Tank, Main Engine and Solid Rocket Boosters.

NASA Aura around earth

On June 19, NASA will launch Aura, a next generation Earth-observing satellite. Aura will supply the best information yet about the health of earth’s atmosphere.

Aura will help scientists understand how atmospheric composition affects and responds to earth’s changing climate. The satellite will help reveal the processes that connect local and global air quality. It will also track the extent earth’s protective ozone layer is recovering.

Aura will carry four instruments each designed to survey different aspects of earth’s atmosphere. The instruments will provide an unprecedented and complete picture of the composition of the atmosphere. Aura will survey the atmosphere from the troposphere, where mankind lives, through the stratosphere, where the ozone layer resides and protects life on earth.

Aura’s space-based view of the atmosphere and its chemistry will complete the first series of NASA’s Earth Observing System satellites. The other satellites are, Terra, which monitors land, and Aqua, which observes earth’s water cycle.