|SCIENCE & TECHNOLOGY|
Cheap drinking water from
the world’s oceans
The making of a “manimal”
Cheap drinking water from the world’s oceans
Increasing population and other factors like limited and dwindling water resources, changing weather conditions and society’s irresponsible exploitation of these resources are already putting a great deal pressure on the availability of drinking water to common people as well as for irrigation.
It is no exaggeration to say that in the times to come drinking water will be one of the most precious of commodities if thought is not given towards proper conservation and management of this resource and the development of new technologies and methods.
Planners, scientists and technologists are looking towards the vast reservoir of water covering two thirds of the earth’s surface area e- the oceans. But as we know the ocean water is suitable neither for drinking nor for agriculture due to its salinity as well as un-cleanliness.
Various methods have been researched and practiced for desalination of ocean water to make it useful for mankind. Water containing salt is broadly classified into two categories: Saline and Brackish. Saline waters such as sea water contains upto 42000 mg.l-1 of salts, whereas brackish waters contain upwards of 2000 mg.l-1. To be fit for human consumption, water should contain less than 1500 mg.l-1 of salts (usually expressed as Total Dissolved Solids). The process of desalination has been known for a long time and can be accomplished by methods such as:
Thermal Distillation: In distillation, saltwater is heated in one container to make the water evaporate, leaving the salt behind. The desalinated vapor is then condensed to form water in a separate container. Thermal desalination process technologies are mature and are generally applied to seawater desalination and rarely to brackish water desalination, as they are energy intensive.
This technique is very costly, and is usually carried out using solar energy or in conjunction with power generation in order to utilise the waste heat/steam generated at these facilities. Research is focused on performance improvements in these process technologies and simplification of the design.
Ion Exchange: In this method, the water to be treated is passed through beds of Ion Exchange Resins where Cat-ions (such as Sodium, Magnesium, Calcium, Strontium etc) are replaced by exchange with Hydrogen ions attached to the resin, and An-ions (such as Chloride, Sulphate, Bromide etc) are replaced by exchange with Hydroxide ions attached to a different type of resin. The resins require frequent regeneration with Sulphuric Acid and Caustic Soda.
Membrane Separation: By Electro-Dialysis where ions are caused to migrate through a membrane under the influence of an electric charge, or Reverse Osmosis (RO) where the solvent (pure water) is forced through a semi-permeable membrane by applying a high pressure.
Of all the desalination methods available, Reverse Osmosis is the one which has seen the most rapid growth in the last 30 years. A study undertaken (in 1992) showed that the industry was growing by approximately 70 per cent per annum. At that time, almost 4 million cubic meters of water were being produced every day by 9000 desalination plants worldwide -- with 30% of this being produced by RO.
The main reason for this rapid growth has been the technological developments which have occurred in recent years with membrane manufacture. Membrane flux has progressively increased while retaining high salt rejection ratios at progressively lower operating pressures.
Research is focused on the improvement of performance of these processes for seawater and brackish water desalination. Topics under consideration are new membranes, membrane module and process design, energy recovery in RO processes, pretreatment methods, scaling and fouling fundamentals, and process and ancillary equipment design. Research is also focused on development and feasibility studies of new concepts for non-traditional desalination processes and feasibility studies of desalination concepts that have not been fully explored.
Carbon nanotube-based membranes: Nanotubes, special molecules made of carbon atoms in a unique arrangement, are hollow and each is more than 50,000 times thinner than a human hair. Billions of these tubes act as the pores in the membrane. The super-smooth inside of the nanotubes allow liquids and gases to rapidly flow through, while the tiny pore size can block larger molecules. This previously unobserved phenomenon opens a vast array of possible applications. Membranes that have carbon nanotubes as pores could be used in desalination and demineralisation. Salt removal from water, commonly performed through reverse osmosis, uses less permeable membranes, requires large amounts of pressure and is quite expensive. However, these more permeable nanotube membranes could reduce the energy costs of desalination by up to 75 percent compared to conventional membranes used in reverse osmosis, researchers have said. The membranes sort molecules by size and with electrostatic forces. The carbon nanotubes used by the researchers are sheets of carbon atoms rolled so tightly that only seven water molecules can fit across their diameter.
Researchers at Lawrence Livermore National Laboratory (LLNL) USA, have measured water flow rates up to 10,000 times faster than would be predicted by classical equations. The surprising results might be due to the smooth interior of the nanotubes.
Scientists estimate that these membranes could be brought to market within the next five to ten years. The challenge is to scale up in order to produce usable amounts of these membrane materials for desalination. Eventually, the membranes could be adapted for a variety of applications, ranging from pharmaceuticals to the food industry, where they could be used to separate sugars.
Thus, there is hope that such scientific and technological developments will help to secure the future survival of mankind on the planet Earth.
The writer is with the Department of Physics, S.L.I.E.T., Longowal
The making of a “manimal”
If you’ve been laughing at those Neanderthal US presidential candidates who still don’t believe in evolution, it’s time to sober up. Every serious scientist knows we evolved from animals. The question now is whether to put our DNA and theirs back together.
We’ve been transplanting baboon hearts, pig valves and other animal parts into people for decades. We’ve derived stem cells by inserting human genomes into rabbit eggs. We’ve created mice that have human prostate glands. We’ve made sheep that have half-human livers.
Recently, Britain’s Academy of Medical Sciences reported that scientists have created “thousands of examples of transgenic animals” carrying human DNA. According to the report, “the introduction of human gene sequences into mouse cells in vitro is a technique now practiced in virtually every biomedical research institution across the world.”
Why have we done this? To save lives. If you can’t get a human heart valve, a pig valve will do. If you can’t get human eggs to clone embryos for stem cell research, rabbit eggs will do. If you can’t use people as guinea pigs in gruesome but necessary experiments on human tissue, guinea pigs will do. All you have to do is put -- or grow -- the human tissue in the guinea pigs. You’re free to inflict any disease or drug on a human system, as long as that human system lives in an animal.
In stem cell research, moreover, human cells are the therapy. Under US FDA rules, they must be tested in animals before they’re tested in people. That means implanting them to see how they change the animals. Meanwhile, we’re using hamster cells to make a human protein to treat anemia. We’re using mice to make humanized antibodies that produce cancer drugs. We’ve grown human kidney tissue in rats.
So far, our mixtures are modest. To make humanised animals really creepy, you’d have to do several things. You’d increase the ratio of human to animal DNA. You’d transplant human cells that spread throughout the body. You’d do it early in embryonic development, so the human cells would shape the animals’ architecture, not just blend in. You’d grow the embryos to maturity. And you’d start messing with the brain.
We’re doing all of these things.
According to the British academy’s report, “researchers have constructed ever more ambitious transgenic animals”-- some with an entire human chromosome--and it’s “likely that the process of engineering ever larger amounts of human DNA into mice will continue.” We’re transplanting pluripotent stem cells, which proliferate and grow many kinds of human tissue. We’re doing it early in mouse embryogenesis, and we’re implanting the resulting embryos in “foster mice” so they can develop.
We’re not doing these things because they’re creepy. We’re doing them because they’re logical. The more you humanise animals, the better they serve their purpose as lab models of humanity. That’s what’s scary about species mixing. It’s not some crazy Frankenstein project. It’s the future of medicine.
Now comes the brain. Neurological disorders affect 1 billion people and kill nearly 7 million per year. To study these disorders, we’re doing to brain tissue what we’ve done to liver and kidney tissue: We’re replicating it in animals. We’ve made humanized mice with Alzheimer’s symptoms. We’ve put human neural stem cells in monkey brains.
We’ve added human stem cells to the brains of fetal mice and grown them into adult mice with human neurons. According to the British academy, it’s now standard practice to test human neural stem cells by assessing whether they “integrate appropriately into mouse or rat brain.”
Last month, ethicists from Stanford University and the University of Wisconsin detailed a proposal by a Stanford scientist to substitute human brain stem cells for dying neurons in fetal mice. “The result would be a mouse brain, the neurons of which were mainly human in origin,” they reported.
The payoff, if the fetuses survived, would be “a laboratory animal that could be used for experiments on living, in vivo, human neurons.” Imagine that: a humanoid brain network you can treat like a lab animal, because it is a lab animal.
The Stanford experiment wouldn’t actually produce a human brain. Most brain cells aren’t neurons, and the experiment called for inserting human cells after the mice had constructed their brain architecture. But last year in the journal Developmental Biology, researchers proposed to insert human stem cells in mice before this architectural stage. The resulting “mouse/human chimeras,” they argued, “would be of considerable value for the modeling of human development and disease in live animals.”
When Stanford’s ethicists first heard the proposal for humanized mouse brains, they were grossed out. But after thinking it over, they tentatively endorsed the idea and decided that it may not be bad to endow mice with “some aspects of human consciousness or some human cognitive abilities.” The British academy and the U.S. National Academy of Sciences have likewise refused to permanently restrict the humanisation of animals.
— LA-Times-Washington Post
— The Independent
— The Independent
THIS UNIVERSE I congratulate you for discovering this question. I am using the word discovering because it did not occur to me till now. It is quite possible that a lot of people have already discovered it and most of them even know the answer. The extent to which we become used to accepting the world without ever asking why is truly amazing. I will try guessing the answer to your query. There might be some other considerations that come in. If you think of something let me know. I will also think a little more about it. We smell things because actual molecules travel out and reach the receptors in our nose. These receptors are like locks that accept only specific keys. They are very particular. When a reception occurs a signal travels out to our brain giving us the feeling of a specific smell. There are a thousand or more types of receptors, each giving a slightly different sense of smell. In addition there might be smells we sense through combinations of different sets of receptors firing. Let me not go on talking about this amazing capability we have to enjoy this world and return to your question. Now the basic answer is easy. Molecules can diffuse out if they belong to a material that is volatile – like alcohol or petrol that evaporate away even at room
temperature. The number of molecules coming out would depend on the vapour pressure. Vapour pressure – or rate of evaporation – increases with temperature. (We know this because we can dry our wet clothes faster if we hang them out in the sun). So at low temperature the volatiles of the fruit or the flower would come out at a lower rate. Smell is nothing but sensing of volatiles. Hence it would be reduced if the fruit or the flower were cold.
I congratulate you for discovering this question. I am using the word discovering because it did not occur to me till now. It is quite possible that a lot of people have already discovered it and most of them even know the answer. The extent to which we become used to accepting the world without ever asking why is truly amazing.
I will try guessing the answer to your query. There might be some other considerations that come in. If you think of something let me know. I will also think a little more about it.
We smell things because actual molecules travel out and reach the receptors in our nose. These receptors are like locks that accept only specific keys. They are very particular.
When a reception occurs a signal travels out to our brain giving us the feeling of a specific smell. There are a thousand or more types of receptors, each giving a slightly different sense of smell.
In addition there might be smells we sense through combinations of different sets of receptors firing. Let me not go on talking about this amazing capability we have to enjoy this world and return to your question. Now the basic answer is easy. Molecules can diffuse out if they belong to a material that is volatile – like alcohol or petrol that evaporate away even at room temperature.
The number of molecules coming out would depend on the vapour pressure. Vapour pressure – or rate of evaporation – increases with temperature. (We know this because we can dry our wet clothes faster if we hang them out in the sun). So at low temperature the volatiles of the fruit or the flower would come out at a lower rate. Smell is nothing but sensing of volatiles. Hence it would be reduced if the fruit or the flower were cold.