How does the camel walk in the desert easily?

The camel is dubbed the `ship of the desert'. It can adapt itself easily to the hot conditions due to various reasons. Its special adaptation features are its hump, long legs, long hair and special eyelids.

The hump enables it to store food. Long hair on its body helps it keep warm in the cold desert nights.

The long legs of the camel are strong and have powerful muscles allowing it to carry heavy loads for long distances. It walks at a medium speed. It has two toes on each foot. A hoof that looks like a toenail grows at the front of each toe. The camel walks on a broad pad that connects its two toes. This cushion like pad spreads when the camel places its foot on the ground.

The pad supports the animal on loose sand in much the same way that a snowshoe helps a person walk on snow. The pad enables the animal to firmly grasp the earth. The toenails protect the feet from damages resulting from a bump. In the camel both legs on the same side rise and fall together. This leg action produces a swaying, rocking motion. Taller animals like the camel snap into a rotary walk more often than short animals.

This helps them to shift the balance on one side of a body while the long legs on the other side are in a suspended phase. In the rotary motion on one side they put both legs forward and on the other side they are both back. Thick, broad sole pads and thick callosities on the joints of the legs and on the chest, upon which it rests in a kneeling position, enable it to withstand the heat of the desert sand. It is also able to close its nostrils against flying dust and its eyes are shielded by eyelashes.

The camel has three eyelids and two layers of eyelashes to protect itself from dust and sun. To protect their eyes, camels have long eyelashes that catch most of the sand when desert winds blow sand on to their eyes.

If sand gets into an eye a camel has a third eyelid to get it out. The extra eyelid moves from side to side and wipes the sand away. As the eyelid is very thin the camel can see through it. So a camel can find its way through a sandstorm with its eyes closed.


How do pharmaceutical companies arrive at expiry dates for medicines?

Most of the drugs used in modern medicine are organic molecules, which have, apart from their pharmacological properties, diverse physical and chemical properties. The utility of a drug depends on the availability of the active molecule in blood circulation for curing or controlling the disease. Due to various factors including the structure of the molecule, the formulation the packing and environmental factors these molecules undergo decomposition and degradation over time.

To determine the period over which the degradation will lead to reduction in the availability of the drug to levels below what is required, studies are conducted under what are called accelerated stability tests.

These tests simulate the long term effects of these factors on the stability of the active drug and the formulation in acute experiments lasting up to 45 days at temperatures of 45 degrees or more and humidity of 70 per cent or more. From the correlative data available, it is possible to predict the stability of the drug over long periods of even up to five years.


How do touch screens work?

Touch screen monitors — where you can use your finger on the computer screen to navigate through the contents — have become more and more commonplace over the past decade, particularly at public information kiosks. A basic touch screen has three main components: a touch sensor, a controller, and a software driver. The touch screen is an input device, so it needs to be combined with a display and a PC to make a complete touch input system.

The Touch Sensor has a textured coating across the glass face. This coating is sensitive to pressure and registers the location of the user's finger when it touches the screen. The controller is a small PC card that connects the touch sensor to the PC. It takes information from the touch sensor and translates it into information that PC can understand. The Software Driver is a software update for the PC system that allows the touchscreen and computer to work together. It tells the computer's operating system how to interpret the touch event information that is sent from the controller.

There are three basic systems that are used to recognise a person's touch — Resistive, Capacitive and Surface acoustic wave.

The resistive system consists of a normal glass panel that is covered with a conductive and a resistive metallic layer. These layers are held apart by spacers, and a scratch-resistant layer is placed on top of the whole set up. An electrical current runs through the two layers while the monitor is operational. When a user touches the screen, the two layers make contact in that spot. The change in electrical field is noted and coordinates of the point of contact are calculated. Once the coordinates are known, a special driver translates the touch into something that the operating system can understand, much as a computer mouse driver translates a mouse's movements into a click or drag.

In the capacitive system, a layer that stores electrical charge is placed on the glass panel of the monitor. When a user touches the monitor with his or her finger, some of the charge is transferred to the user, so the charge on the capacitive layer decreases. This decrease is measured in circuits located at each corner of the monitor. The computer calculates, from the relative differences in charge at each corner, exactly where the touch event took place and then relays that information to the touch screen driver software. One advantage of the capacitive system is that it transmits almost 90 per cent of the light from the monitor, whereas the resistive system only transmits about 75 per cent. This gives the capacitive system a much clearer picture than the resistive system.

The surface acoustic wave system uses two transducers (one receiving and one sending) placed along the x and y axes of the monitor's glass plate. Also placed on the glass are reflectors — they reflect an electrical signal sent from one transducer to the other. The receiving transducer is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly. The wave setup has no metallic layers on the screen, allowing for 100-percent light throughput and perfect image clarity. This makes the surface acoustic wave system best for displaying detailed graphics (both other systems have significant degradation in clarity).

Another area in which the systems differ is which stimuli will register as a touch event. A resistive system registers a touch as long as the two layers make contact, which means that it doesn't matter if you touch it with your finger or a rubber ball. A capacitive system, on the other hand, must have a conductive input, usually your finger, in order to register a touch. The surface acoustic wave system works much like the resistive system, allowing a touch with almost any object — except hard and small objects like a pen tip.


Does frequent switching on/off of a fluorescent lamp reduce its life?

The life of a fluorescent lamp is essentially determined by life of the cathode filament it uses. A conventional fluorescent lamp employs closely wound coil of tungsten wire as filament. Upon switching on the lamp, electric current passing through the filament will raise the temperature of the filament that in turn will generate thermions (electrons generated by a thermal process). Thermions are necessary to initiate electric-discharge through the column of the fluorescent lamp.

Frequent switching on/off the fluorescent lamp occurs through several cycles of filament heating and cooling. If the cycles of heating and cooling of the filament are too frequent this may result in tremendous loss of oxide coating (at the rate of 10-20 micro-grams/cm{+2} per cycle).

The loss of oxide coating in the cathode filament through rapid on/off (heating/cooling) operations will lead to poor performance of the filament in generating thermions to initiate the discharge process. This in turn will reduce the life of the fluorescent lamp. Life of a conventional fluorescent lamp usually rated for several thousand hours of continuous burning can be halved or made still less, just by frequent switching on/off.

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"Life is either a daring adventure or nothing."
Helen Keller