My Science School

It is a method of farming by which crops are grown without disturbing the soil by tilling. If there is no tilling the crop residue on the soil prevents evaporation of rain water and more water infiltrates the soil. There is better retention of organic matter in the soil and nutrients are well recycled, thereby improving the fertility of the soil. It minimises soil erosion and no ploughing means there is no air-blown dust. It is more profitable as it does away with the labour, irrigation and machinery associated with tilling.

Tilling also damages ancient structures like burial mounds under the earth as archaeologists have found in the UK

It was Edward Faulkner's book "Plowman's Folly" which started the idea of no-till farming in the 1940s. No-till farming is widely practised in the U.S. Indian farmers started adopting the practice in the 1960s. In the Indo-Gangetic plains, rice-wheat cultivation is done using this method. In parts of Andhra Pradesh, rice-maize cultivation is done without tilling.

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Osmosis is the movement of a thinner liquid into a thicker liquid through a semipermeable partition or membrane when physical external pressure is applied. The thinner liquid dilutes the thicker solution.

Osmosis is a process that occurs in our bodies all the time. For example, after the food we eat is broken down in the stomach, it passes through the intestines. The intestines contract to force the nutrients, which are thinner, to pass through the walls of the intestines into the blood, which is a thicker solution.

In reverse osmosis, exactly the opposite happens. Water that has a high concentration of impurities is put under pressure and forced through a semipermeable partition leaving all the larger particles behind. This process renders the impure water as well as salty water (here the process is called desalination) potable enough to drink.

This is why RO is used in water purifiers. In a purifier, water passes through several stages-a sediment filter, activated carbon filter and ultraviolet light. RO is the final stage. The larger molecules cannot pass through these various filters and RO removes the harmful particles, metal ions and bacteria in the water that remains. This cleans the water thoroughly and prevents diseases caused by contaminated water.

Reverse osmosis is also used in the food industry to make concentrated juices. The traditional heat treatment reduces the quality of heat-sensitive fruits such as oranges. RO reduces the quantity of water in the juice, so it doesn't need to be thickened by heating. For instance, in the production of maple syrup, RO is used to remove the water from the sap before it is boiled into a syrup. Dairy industries use RO to make concentrated milk and whey protein powders.

Since RO units are also manufactured in compact sizes, they can be installed easily which is why a number of home water filters come equipped with it.

RO removes almost all the minerals in the water, which leaves it tasteless. Some RO systems come with a remineralisation filter that adds minerals to the water and makes it more flavourful!

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Additive manufacturing, more commonly identified as 3D printing, allows for the fabrication of complex parts from functional or biological materials. As objects are constructed one line or one layer at a time, conventional 3D printing can be a slow process.

Scientists from the Max Planck Institute for Medical Research and the Heidelberg University have demonstrated a new technology to form a 3D object from smaller building blocks in a single step. They utilise the concept of multiple acoustic holograms to generate pressure fields.

Sound exerts force

If you've ever been near a powerful loudspeaker, you would be aware that sound waves exert forces on matter. When high-frequency ultrasound that is inaudible to the human car is used, the wavelengths can be pushed into the microscopic realm. This would allow researchers to manipulate building blocks that are incredibly small, including biological cells.

This research group had previously shown how to form ultrasound using acoustic holograms, which are 30 printed plates made to encode a specific sound field. The scientists had devised a fabrication concept to use these sound fields to assemble materials in 2D patterns.

Holds promise

For this research, the team expanded the concept further by capturing particles and cells freely floating in water and assembling them into 3D shapes. Additionally, the new method works with materials such as glass, hydrogel beads, and biological cells.

Ultrasound affords the advantage that it is gentle for using biological cells and that it can travel deep into tissue. Hence, it can be used to remotely manipulate cells without harm. Scientists believe that their technology of creating 3D objects with sounds holds promise as it can provide a platform for the formation of tissues and cell cultures.

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