Liquid drops tend to be in a state of minimum surface energy which is directly related to the surface area. The force, surface tension, which is trying to hold the droplet together, therefore tries to reduce the surface area of the drop. Mathematically only a sphere has the smallest surface area for a given volume, compared to other geometric shapes. Hence, in the absence of external forces, liquid drops tend to be spherical.
Monday, January 14, 2008
How does antidandruff shampoo work?
Dandruff is thought to be caused by overgrowth of yeast such as Pityrosporum ovale which live on normal skin. This overgrowth causes local irritation resulting in hyperproliferation of the cells (keratinocytes) forming the outer layer of the skin. These form scales which accumulate and are shed as dandruff flakes.
Antidandruff shampoos work by three mechanisms. Ingredients such as coal tar are antikeratostatic and they inhibit keratinocyte cell division. Detergents in the shampoo are keratolytic: they break up accumulation of scale. Finally, antifugal agents such as ketoconazole inhibit growth of the yeast itself. Other components such as selenium sulphide also inhibit yeast growth and therefore scaling.
Antidandruff shampoos work by three mechanisms. Ingredients such as coal tar are antikeratostatic and they inhibit keratinocyte cell division. Detergents in the shampoo are keratolytic: they break up accumulation of scale. Finally, antifugal agents such as ketoconazole inhibit growth of the yeast itself. Other components such as selenium sulphide also inhibit yeast growth and therefore scaling.
What is dandruff?
Dandruff is a condition of excessive scaliness of the scalp. There are two varieties - dry and greasy. In the dry variety, the scales are fine, thin, white or greyish, and dry or slightly greasy. Such type of hair lacks lusture. People with this type of hair will have mild to moderate itching. The scales will fall freely on the shoulders.
This dandruff will be more common in winter than in summer. It signifies exaggeration of normal exfoliation of the horny layer of the epidermis, It usually affects people with dry integument and scalp. Such people are rather reluctant to use oil, on their scalp. In the greasy variety both the scalp and the integument are oily. It diffuses all over the scalp. Later the condition also extends to other hairy regions. It may extend typically to the eyebrows, eyelids, beard and other regions. The basic defect in this case is over production and/or change in composition of the sebaceous secretion. Dandruff is common at puberty and it occurs due to endocrine disorders, familial predisposition, unbalanced diet and constipation. Effective treatments for these conditions are prescribed, in siddha medicine, based on commonly available plant products.
This dandruff will be more common in winter than in summer. It signifies exaggeration of normal exfoliation of the horny layer of the epidermis, It usually affects people with dry integument and scalp. Such people are rather reluctant to use oil, on their scalp. In the greasy variety both the scalp and the integument are oily. It diffuses all over the scalp. Later the condition also extends to other hairy regions. It may extend typically to the eyebrows, eyelids, beard and other regions. The basic defect in this case is over production and/or change in composition of the sebaceous secretion. Dandruff is common at puberty and it occurs due to endocrine disorders, familial predisposition, unbalanced diet and constipation. Effective treatments for these conditions are prescribed, in siddha medicine, based on commonly available plant products.
Sunday, January 13, 2008
How are mummies made?
Mummies are embalmed bodies that have been preserved for thousands of years. The dead have been mummified with the help of good drying agents applied all over the body.
Drying agents are other materials were stuffed inside the body to maintain its shape after removing internal organs. The word mummy is derived from the Persian word mummia meaning bitumen because the black resin used for embalming the dead looked like bitumen.
Three techniques of mummification have been discovered by Greek historians. The methodology was the same in all three cases and the differences lie in the process of extraction of internal organs. Mummies belonging to 1570-1070 BC are still found to be in good condition.
Actually in the process of mummification embalmers removed all the internal organs except the heart and kidneys. The brain was removed through the nostril using a hook. They soaked them in natron (a mixture of salt, sodium bi-carbonate and sodium carbonate). It was then bandaged and kept in jars. The internal cavities were stuffed with linen bags of sawdust, natron bags, and resin coated materials.
The nostrils and eyes were stuffed with linen rolls. Cedar oil, natron and purgatives were then smeared were then smeared on the body to close the pores. After this, the body was wrapped in long sheets of fine linen. Toes, fingers and limbs were separately wrapped in long sheets of fine linen. Toes, fingers and limbs were separately wrapped and then the torso was wrapped up in several layers.
A mask revealing the external features, made of pliable linen treated with resin was fixed on the face. According to ancient texts, a complete treatment could take about 70 days. Though resin has burnt the skin of the dead body in many cases, the hairs were seen to be intact.
Drying agents are other materials were stuffed inside the body to maintain its shape after removing internal organs. The word mummy is derived from the Persian word mummia meaning bitumen because the black resin used for embalming the dead looked like bitumen.
Three techniques of mummification have been discovered by Greek historians. The methodology was the same in all three cases and the differences lie in the process of extraction of internal organs. Mummies belonging to 1570-1070 BC are still found to be in good condition.
Actually in the process of mummification embalmers removed all the internal organs except the heart and kidneys. The brain was removed through the nostril using a hook. They soaked them in natron (a mixture of salt, sodium bi-carbonate and sodium carbonate). It was then bandaged and kept in jars. The internal cavities were stuffed with linen bags of sawdust, natron bags, and resin coated materials.
The nostrils and eyes were stuffed with linen rolls. Cedar oil, natron and purgatives were then smeared were then smeared on the body to close the pores. After this, the body was wrapped in long sheets of fine linen. Toes, fingers and limbs were separately wrapped in long sheets of fine linen. Toes, fingers and limbs were separately wrapped and then the torso was wrapped up in several layers.
A mask revealing the external features, made of pliable linen treated with resin was fixed on the face. According to ancient texts, a complete treatment could take about 70 days. Though resin has burnt the skin of the dead body in many cases, the hairs were seen to be intact.
Why does boiling milk overflow but boiling water does not?
The major component of milk is water (83-87%). Its other constituents are protein (3.5%) , sugar (5%), and fat (4-7.4%). When heated, fat being lighter than water, floats as a creamy layer on the top and water vapor, in the form of steam bubbles, is trapped under it. Further heating results in the formation of more number of bubble. These bubbles expand and lift the creamy layer causing it to overflow. In the case of water, the steam bubbles break as they reach the surface.
Is there any significance in using gravel on railway tracks?
Yes. Gravel used on railway tracks is known as ballast. It is used to dissipate the vibration produced by trains traveling at high speeds. In effect, the gravel layer acts as a cushion and damps the vibrations so that they do not travel long distances. If the rails are laid on a solid base, these vibrations can travel long distances and lead to cracks on the base as well as on nearby buildings.
The ballast provides a foundation for the sleepers, distributes the pressure on to the formation and helps in diverting the rain water. In a typical ballast, voids constitute 20 to 30 percent of the volume.
The ballast provides a foundation for the sleepers, distributes the pressure on to the formation and helps in diverting the rain water. In a typical ballast, voids constitute 20 to 30 percent of the volume.
How fast is the Earth moving through space?
The Earth is speeding like a top and like a merry-go-round horse on a carousel that is itself riding on a larger carousel, and the whole amusement park is moving through space.
The Earth rotates on its axis at about 460 meters per second at the equator. The speed of a trip around the Sun is about 30 km per second. Meanwhile, the solar system is in a more-or-less circular orbit around the center of the galaxy at an average velocity of about 220 kilometers a second, according to Facts on File Dictionary of Astronomy, and the galaxy is moving at about 19.4 kilometers a second, toward a point in the constellation Hercules called the solar apex. Some authorities believe that there is also a general drift by the Milky Way and some neighboring upper clusters towards the Southern Cross at a speed of more than a million miles an hour.
The Earth rotates on its axis at about 460 meters per second at the equator. The speed of a trip around the Sun is about 30 km per second. Meanwhile, the solar system is in a more-or-less circular orbit around the center of the galaxy at an average velocity of about 220 kilometers a second, according to Facts on File Dictionary of Astronomy, and the galaxy is moving at about 19.4 kilometers a second, toward a point in the constellation Hercules called the solar apex. Some authorities believe that there is also a general drift by the Milky Way and some neighboring upper clusters towards the Southern Cross at a speed of more than a million miles an hour.
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