Taking a fresh look at garlic

Shari Roan (Los Angeles Times)

Few people would want to eat a clove of fresh, odoriferous garlic almost every day for months. But dozens of residents of Palo Alto, California, and surrounding communities are volunteering to do just that in one of the most unusual, and important, studies on garlic ever done.

During the last 20 years, hundreds of studies have attempted, and failed, to establish whether garlic can help lower cholesterol. But Stanford University researcher Christopher Gardner believes that his new study finally will provide some much-needed clarification. Not only will it examine whether garlic supplements, which are among the most popular of all dietary supplements, work. It also may determine whether fresh garlic is better at lowering cholesterol.

Six days a week for six months, 200 healthy adults with moderately high cholesterol will either take one of two popular garlic supplements or eat sandwiches containing fresh garlic. The volunteers will have their cholesterol, blood pressure and antioxidant levels monitored periodically. (Garlic is also purported to help lower blood pressure and raise antioxidant levels.) The study, funded by the National Institutes of Health, will be completed in about two years.

"There is lots of lore about garlic," says Gardner, of Stanford’s Center for Research in Disease Prevention. "But if you look at the (recent research), there is almost nothing on fresh garlic. People swear by it, but you can’t encourage people to try this unless you have the randomized, double-blind trials."

In the 1970s and ’80s, Gardner says, many studies concluded that garlic helped lower cholesterol. But some researchers criticized those studies, saying they were too small or didn’t include a control group. In the 1990s, several scientifically rigorous studies showed that garlic had no effect on lowering cholesterol. However, they were done using garlic supplements, which Gardner thinks may not work as well as fresh garlic.

Stanford biochemist Larry Lawson, a co-investigator with Gardner, has performed chemical analyses on garlic supplements that suggest the way some supplements are made could reduce their potency. For example, the active ingredient in garlic, allicin, sometimes dissolves before it can get into the bloodstream. Or the supplement may pass through the body without dissolving at all.

The Stanford researchers have gone to great lengths to make sure that the chemical composition of the garlic and garlic supplements they’re studying is well understood, Gardner says. "With a lot of these supplements, we don’t even know what the active ingredient is," says Gardner. "We are characterizing what is in each of the three (the two supplements and the fresh garlic in the study). This study may set a precedent on how to look at and evaluate herbs."

Global positioning system 

Saujan Kiran Shrestha

During World War II, several radio based navigation systems were developed. A few ground based radio navigation systems are still in use today. The ground based radio navigation system is not very accurate and does not cover a wide area. To overcome this drawback, the Global Positioning System (GPS) was designed and developed. GPS is a space based radio transmission system that provides three dimensional position, velocity and time.

The pioneer of GPS system, NAVSTAR is still operated by the US Department of Defense. The first GPS satellite, a Block I development model, was launched on February 22, 1979. After that other eleven development model satellites were launched. The first operational satellite was launched in February 1989 and the launch of the 24th satellite in 1994 completed the system. Since then, GPS has been the major component for military, surveyors and researchers. It is playing a vital role in navigation, survey, geodetic control, plate tectonic studies, measurement of atmospheric parameters, etc.

Three segments work together to form a GPS system. They are: (a) Space Segment, (b) Control Segment and (c) User Segment.

Space Segment: The nominal GPS operational constellation consists of 24 satellites which are 20000 km above the Earth, orbiting 12 hours period. These satellites revolve around the Earth in six different orbital planes. Each plane consists of four equally spaced satellites which are inclined at about 55 degrees with respect to the equatorial plane. This constellation provides the user with between five to eight satellites visible from any point on the earth. For a GPS receiver to display the position and time, at least four satellites must be visible to it.

Each satellite contains a high precision atomic clock and constantly transmits radio signals using its own code. The satellite transmits two microwave carrier signals. The L1 (1575.42 MHz) carries Precise (P) code and Coarse Acquisition (C/A) code. The L2 (1227.6 MHz) carries only P code. The navigation message of 50 Hz signal with data bits describes the GPS satellite orbit and clock correction. Other system parameters are also superimposed on these codes. C/A code is a pseudorandom noise code which is a sequence of 1023 bits which repeat after every millisecond. P code is very long pseudorandom noise code which is transmitted at ten times the rate of C/A code and does not repeat for seven days. The P code is precise and encrypted so it is only available to the authorised user and is therefore not available for civilian purpose.

Control Segment: The control segment maintains and monitors the health of satellites, determines their orbits and the behaviours of their atomic clocks. The NAVSTAR control segment consists of five passive monitor stations located at Hawaii and Kwajalein in Pacific ocean; Diego Garcia in Indian ocean, Ascension island in Atlantic ocean and Colorado Spring, Colorado. These stations collect the data from the satellite signal and sent it to the main control station for processing. The main control station, situated at Falcon Air Force Base, 12 miles east of Colorado Springs, receives data from passive control stations. These data are analysed to determine if the satellites are experiencing clock or ephemeris changes and to detect equipment malfunctions. After calculation of new navigational and ephemeris data, it is uploaded to the satellites once or twice a day. The new data and other routine maintenance commands are transmitted to the satellite by ground based uplink antennas in S band frequency.

User Segment: The GPS receiver and its user is the user segment. The GPS receiver, which is small and handy, is a radio receiver that receives and converts the signals from satellite into position, velocity and time. A typical GPS receiver is about the size of a cellular phone and weighs only about 30 ounces.

Although the GPS satellite constellation was completed recently, it has already proved to be the most valuable aid to military, surveyors and scientists. GPS is being used for navigations in ships and aircrafts. During construction of a tunnel under the English Channel, British and French crew started digging from opposite ends. They totally relied on GPS receivers to check their positions along the way and to make sure they meet exactly in the middle. Even in Nepal, GPS is being utilised for various surveys. In 1980, HMG survey department carried out first GPS measurements in order to fix the major control points of the cadastral and topographic mapping. In May 1992, the Chinese National Bureau for surveying and mapping used GPS and LASER to measure the height of Mt. Everest.

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