Allethrins are compounds used in household insecticides like mosquito coils because they have low toxicity for humans. They are sourced from chrysanthemum flowers, found in Asia and eastern Europe. These plants are cultivated for ornamental, culinary or insecticide-preparation purposes. The flowers are pulverized and the allethrin compounds found in the seed cells are extracted and sold to insecticide makers.

Frank Sortino, now the director of a pension research institute in San Francisco, developed the Sortino Ratio. Many global Mutual Fund rating agencies prefer this risk-adjusted return measure over the Sharpe Ratio, because it is simple and easy. The Sortino Ratio is similar to the Sharpe Ratio, except that instead of using standard deviation as the denominator, it uses downside …

The solar system along with the universe is balanced and dominated by three universal forces – repulsion, gravitation and retraction. But present science knows only one universal astronomical force – gravitation. The other two forces are still unknown. With efforts spanning over 25 years, the scientific fraternity has devised a new technology called the Sorlod Space System (SSS). With this, …

Boiling Point Depends on Pressure We all know that the boiling point of water is 100 degree Centigrade. But this statement is hardly sufficient. We should add that this is the boiling point at sea-level; in other words, under normal conditions. If we climb a mountain, and so obtain a reduced atmospheric pressure, boiling point will be less than 100 …

Principle of the Helicopter A helicopter differs from every other sort of flying machine because it takes off vertically, the airscrew being on top instead of at the front. Here is a device that will illustrate the way a helicopter works, and if it is properly made it will rise to quite remarkable heights. It is easy to make, and …

How to Make Distilled Water If you are keen on doing chemical experiments, you will often come across instructions telling you to use distilled water. As a rule, water that has been thoroughly boiled and then carefully poured off so that the dregs or sediment are left behind, will serve the same purpose. If the decanted liquid is again boiled …

Punch and Judy Show This is one of the oldest forms of theatrical entertainment and has enthralled and amused countless boys and girls throughout the centuries. The story of Punch and Judy is well known and the authentic play can be bought in printed form very cheaply. The theatre for Punch and Judy can be constructed from wood and curtaining …

Punch and Judy Dolls These quaint characters that have been passed down to us through the years still retain their distinctive appearance and have not deviated at all. The dolls can, of course, be bought at the large stores, but they can also be made very simple by any boy that is clever with his hands and has done a …

Ferry Boat How would you like to make a ferry boat, with paddles, that actually does work and cruise on water? All you will need to make a fine model of this kind is some wood for the hull of the ship, elastic, nails, paper and paints. This is how the ferry boat is made. Cut a piece of soft …

Rocky The Horse Would you like to make a most acceptable present for a young boy? Here is an idea that will not cost you anything in materials, yet will work and really look most attractive. Get a medium sized cork from an old medicine bottle and clean this up with a piece of sandpaper. This is to make the …