Quick facts on iodine

Iodine is one of the most important mineral salts, which is required by our body. Deficiency of iodine may result in the following problems: 1) Goitre in adults, 2) Early miscarriage and blood anemia in females, 3) Dwarfs and children having low intelligence, and 4) New born babies
with not very well developed organ systems.

Iodine is present in green leafy vegetables. Due to its volatile nature, it must be protected from sunlight and severe heat. It needs to be stored in a cold and dry environment. To get a high concentration of iodine in cooked food, it must be added after the food is cooked.

Nowadays, the Government of Nepal has provided iodized salt packets which are packed with brand names like AAYO, TEJ and SAKTI. The minimum daily requirement of our body is about 20 micrograms. One kilogram packet of salt must contain 50 ppm iodine.

A simple test can be performed at home to check the quality of salt. Take one tea spoonful of the salt. Put it
in a dry clean plate. Pour fresh
lemon juice to cover the salt completely. The colour of the salt changes immediately. The colour intensity displayed is directly proportional to the concentration of iodine present in the salt.

(The author is a B.Sc. student at Trichandra College, Tribhuvan University)

Physics behind swinging cricket balls

As a cricket ball travels air streams past the ball while it spins and creates a sort of whirlpool of rotating air. This causes asymmetrical air layers to be separated on each side of the ball. The separation increases the velocity of air on one side of the ball and decreases it on the other, creating areas of low and high pressure. Consequently, unbalanced forces act on the two hemispheres of the ball and drags the ball into the region of low pressure causing a swinging effect. The best swings are possible when bowlers disrupt the flow of air on one side of the ball with a slightly worn out ball that is shone on one side. Also important is the delicate balance of delivery action, seam angle, tossing speed and throwing speed.

Normal-swing is achieved by keeping one side of the ball polished smooth and shiny, and delivering the ball with the polished side forward. The seam is angled in the direction of the desired swing. The delivery action will maintain a laminar boundary layer air-flow on the shiny side whilst creating turbulent flow on the seam side. For the in-swing delivery, the ball is reversed with the seam pointing to the leg-side and for an out-swing delivery, the ball is delivered in the opposite position.

The amount of swing increases with delivery speed and seam angle. These parameters should not be large so that the boundary layer separates before reaching the seam. This would result in symmetrical separation of the ball and hence zero net force. As a ball with seam angle 20 degrees, speeds past the Reynolds number (108 km per hour speed would correspond to a Reynolds number of approximately 150,000), turbulence will start to develop on the shiny side reducing the net side force. At lower speeds (60 km per hour), a bowler requires a larger seam angle of about 30 degrees. This is why medium pace blowers can generate excellent swings.

Spin of the ball helps stabilise the ball’s seam orientation. When a ball is bowled with a round arm action, there will always be some backspin imparted to it. Too much spin is detrimental which would lead to a negative side force for post critical Reynolds numbers. This is more relevant at higher speeds (speeds greater than 90 km per hour) for which the optimal spin rate is 5 revolutions per second. For this reason, slow bowlers with a high spin rate can produce superior swings.

Late-swing occurs when sideway deviation shows little or no sign of occurring until late in the ball’s flight, usually as it begins to fall downwards. There are two possible causes that could bring this about. The first could be due to the position of the seam relative to the air-flow past the ball. The second reason could be the critical speed of the ball, above which the ball will not swerve at all.

At a critical speed of about 108 km per hour, the air resistance opposing the motion is about half the weight of the ball. But just below it, the opposing force becomes nearly twice the weight of the ball and this would result in a vertical free-fall of the flying ball without horizontal motion. The perfect combination of delivery rhythm and speed produces the best late-swing. Therefore, a skillful medium pace blower can generate a late-swing - an unexpected dip of the ball near the batsman.

Reverse-swing occurs when the ball is bowled very fast with the seam at a slight angle. In this case, the air flow will become turbulent on both sides before it reaches the seam. The ideal ball for reverse-swing has one side rough, the other smooth, with a prominent seam in between. A prominent seam helps in the laminar to turbulence transition process, whereas a smooth and polished surface helps maintain a laminar boundary layer. The roughness of the seam at the front of the ball makes the boundary layer cling more around this side and on the smooth side the layer breaks away early on. This produces an asymmetrical pressure distribution over the surface, and the resulting force makes the ball swerve. The amount of sideways movement depends on the speed of delivery making this swing an effective delivery for fast bowlers.

(The author is an academician at RONAST)

Internet telephony

What is the cost of calling your friend in USA? If you make a call through the telephone lines, it will cost around Rs. 150 per minute but, if you use an internet protocol is costs around Rs.10. The possibility of voice communications traveling over the internet was first introduced in 1995 when Vocaltec Inc. launched its internet phone software. Designed to run on a 486/33 MHz computer equipped with a sound card, modem microphone and speakers, the software compressed voice signals and translated it into IP packets for transmission over the internet. This PC- to- PC net telephony only worked, however, if both parties were using the internet phone’s software.

With the new technology emerging up in the field of voice and data transmission, internet telephony is not a new term. Just with a multimedia computer and a modem you can be familiar with internet telephony or internet calls. To facilitate your PC with internet calls, you require an internet connection and a headset. You also need to visit the Internet Service Provider [ISP] and subscribe.

The technology behind internet telephony is rapidly advancing. Many software developers now offer PC telephony software but, most importantly, gateway servers are emerging to act as an interface between the internet and the PSTN. Equipped with voice-processing cards, these gateway servers enable users to communicate via standard telephones over great distances without using the long distance telephone network.

Recently, the Indian government has allowed ISPs for the VoIP enabling ISD calls at very low costs. So, what is VoIP? VoIP is the technology that enables telephone calls and faxes to be sent over IP-based data networks with a suitable quality of service (QoS) at a low cost. Nepal too needs to realise the need for the internet telephone as there is an increasing number of internet phone users.

An estimated 6,000 people are expected to have internet connections in Nepal. Recently, sites like www.dialpad.com and www.mediaring.com provide services that allow internet users to make long distant calls to any number in the U.S. or Canada from their personal computers. Having noticed that long distance telephone calls are being made virtually free through the internet, Nepal Telecommunication Authority (NTA), the telecom governing body issued warnings to all the ISPs to block websites on the internet that allowed this facility. However, even if sites that allow free internet phone calls  are blocked, one does not know how many such sites are available. Thus, it is difficult to put and end to free internet telephone calls.

Water scarcity prompts scientists to look down

With Earth’s inventory of clean, fresh water dwindling fast, scientists who once looked to the clouds are increasingly looking downward for new sources of the life-giving resource. What’s tempting them is a mysterious world of deep underground aquifers—huge rivers and lakes far beneath the surface, some of them containing "fossil" water as much as a million years old.

Recent mapping efforts suggest that some of these aquifers hold enough ‘‘blue gold" to support billions of people for centuries. But the lean and thirsty looks engendered by that enormous wealth of water have made some hydrologists, economists and political scientists nervous. Little is known about the ecological impact of deep aquifer pumping. Moreover, of the hundreds of water treaties and shared-use agreements forged by nations in recent decades, none applies to underground aquifers. With scores of major aquifers crossing international boundaries, the potential is rising for conflict and a greedy "race to the pumps."

Only 2.5 percent of the world’s water is fresh, and the vast majority of that is frozen in glaciers and icecaps. All told, less than three-tenths of 1 percent of the planet’s fresh water is in the lakes and rivers that have served as the major sources of water through most of human history, and much of that is drying up or becoming spoiled.

"There are all kinds of signs that this level of use is not sustainable," said Sandra Postel, director of the Global Water Policy Project in Amherst, Mass., pointing to falling water tables in many parts of the world. Already, about 8 percent of the food that feeds the world’s 6 billion people is being grown by taking water that is not being replenished. "If that’s the case now," Postel said, "what are we going to do when we need to feed 8 or 9 billion people?"

One answer is to go underground, where there is 100 times the amount of water found on the surface. Until recently, it wasn’t worth trying to get at that water but with shortages now looming globally- a comprehensive report released by the United Nations last week predicts crippling water shortages in the next few decades-that equation is changing.

"The water in these aquifers is of much better quality nowadays than in almost any of the rivers or lakes," said Alice Aureli, head of the United Nations Educational, Scientific and Cultural Organization’s transboundary aquifer project. "It’s an invisible resource. But it’s most probably the resource our children will depend on."

Armed with seismic and core-drilling technologies long used by the oil industry, and with funding from several international agencies, the International Association of Hydrogeologists has begun a massive underground mapping project to determine the outlines and volumes of the world’s larger aquifers. Among the bigger bodies of water under study are the Guarani aquifer, shared by Argentina, Brazil, Paraguay and Uruguay, which could provide 27 gallons of water a day to 5.5 billion people for 200 years. Another is the Kalahari/Karoo aquifer, shared by Namibia (the driest nation south of the Sahara), Botswana and South Africa. Others underlie the Middle East, North Africa and the Caucasus.

(LA Times/Washington Post)

Noise pollution high in Kathmandu

Noise is defined as the unwanted sound, which may cause mental and physical disturbances in human beings. Sources of indoor noise are household appliances and electronic media such as radio, television and musical instruments. Machinery noise can be found in factory and construction. Different traffic systems such as road rail and air; human activities such as religious, public and leisure are sources of noise.

Noise affects human health in several ways such as temporary and permanent hearing losses, decreased efficiency, sleep disturbance, annoyance, fatigue and difficulty in general conversation. People working in very high noise environments are found to experience heart, digestion and neurotic troubles. Prolonged exposure to vibration may also lead to the development of vibration disease in human being. Exposure to excessive noise during pregnancy may result in high frequency hearing loss in newborns and may be associated with prematuarity and intra uterine growth retardation. Several studies have reported spasms of peripheral blood vessels, neurotism, ulcer, colitis, and endocrine and biochemical disorders in human being due to excessive exposure.

Recently, a study on traffic noise and its mental health problems in Kathmandu valley was carried out. Along with the author, Dr Trinetra Man Pradhananga, Senior Scientist of the Royal Nepal Academy of Science and Technology (RONAST) and Dr Shisir Kumar Regmi, Psychiatrist of Institute of Medicine, Maharajgunj were involved. A total of 24 sites were selected in which 16 sites were selected from high vehicle pressure areas. The remaining 8 sites were selected from least vehicle pressure areas. The mean noise levels in Kathmandu city were found to be 79 decibels (dB) and 112 dB, which were higher than the noise levels of major cites in India. The rate of increase of noise level in Kathmandu City was found to be 1 dB per year.

The permissible level for road traffic noise is 70 dB. During a early study, Sapkota in 1997 listed RNAC, Kupondol height, Thapathali, Sahidgate, Koteshwor, Gwarko, Gongabu and Gyaneshwor as hazardous areas where noise levels were found to be beyond 80 dB. However, the present study indicated that noise levels in Kathmandu were found to be beyond permissible values.

Comparing the present noise levels with the permissible value, three different types of noise areas were identified in the Kathmandu valley.

< Noise levels below 70 dB are listed as low noisy areas in which all least vehicle pressure sites of the study were included.

< Levels between 70 dB and 80 dB were listed as moderate noisy areas which include Hotel Shangrila, Gairidhara, Galkhupakha, Gausala, Satdobato, Balkhu, Swoyambhu , Pulchwok and Maitidevi.

< The present study also listed hazardous sites in Kathmandu City which are; Putalisadak, New Baneshwore, Kalanki, Narayan Gopal Chowk, Tripureshwor, Kalimati and Koteshwore where noise levels were found beyond 80 dB.

The survey of the mental health problem was also carried out in which 100 men were selected from different noise observed sites. Mental health problems were found in 95 percent from hazardous area, 88 percent from moderate noisy areas and 62 percent from low noisy areas. Some kind of mental health problems were reported from hazardous area such as; strain, unhappiness, depression and decision making problems. Among these people 52 percent of them responded as sleep disturbance, felt unhappy, lost confidence and unable to enjoy daily activities.

In conclusion, there is an immediate need to set up noise standards in the country to control the noise pollution. The present study indicated that mental health problems in city people could also be due to noise pollution. Therefore it is necessary to undertake further investigation of the status of noise levels and related health problems in different parts of the country. There is also an immediate need of setting regulations of vehicular movement in Kathmandu City on the basis of road capacity. Some other suggestions such as improvement of road and parking system, control of honking and over taking, discouragement of high sound producing vehicles and public awareness would also be helpful in reduction of the present noise level in Kathmandu Valley.

(The author is a lecturer at the Department of Environmental Science, Tribhuvan University)

HEADLINE | RECOLLECTIONS