You might know that mushroom is a type of fungus but, it may be surprising to know that corals and jellies also belong to the group! Researches suggest that fungi are more related to animals than plants and other microorganisms. These organisms depend on others for food and hence, do not need light for their existence. Lichens, fungal association with cyanobacteria or algae, generally grow in very uncongenial environments like rocks, gravestones and tree trunks. Highly sensitive to pollution, they are indicators of air pollution. Fungi are also of great use to mankind; they are used as fermenting agents, medicine, food, pest control and many more. But, all fungi are not beneficial; some of them cause fatal infections in human beings. Learning about the characteristics of fungi would help you understand more about these organisms. Given below are the common morphological (appearance related), anatomical, physiological, pathological and reproductive characteristics of fungi. These characteristics are general; they may vary according to the species. 

General Characteristics Of Fungi

Morphological Characteristics Of Fungi

• The vegetative body of fungi may be either unicellular (yeast) or multicellular.
• Groups of fungi are formed of elongated cells which form filaments called hyphae. These hyphae form a diffuse association of cells. This association of cells is referred to as Mycelium, a word that represents the body of the fungus.
• Fungi produce reproductive hyphae which bear numerous spore-containing structures called sporocarp. This structure is purely for reproductive purposes and has nothing to do with the normal growth and development.
• Like plants, fungi also grow attached to their substratum. They are non-motile and lack locomotory organs like flagella, except for chytrids, which are motile gametes with flagella.
• The surface of fungi is folded into numerous ridges called gills (found under the cap of mushrooms), which are actually adaptations to increase the surface area. They are used for disposal of spores and are extremely important in taxonomy for species identification. 

Anatomical Characteristics Of Fungi

• Fungi are mostly eukaryotic multicellular organisms i.e., they have many cells in their bodies, each cell complete with membrane-bound cell organelles.
• Most of the fungal cells are coenocytic; there is no distinction between cells; the nuclei are distributed throughout the filament.
• Ascomycetes and basidiomycets have filaments that are septate, with numerous septa which separates individual cells from each other. The features of septa are different in different fungi and thus, they have taxonomical importance as well.
• The filaments have cytoplasm and large vacuoles.
• The cell wall of a fungal cell is made of chitin, unlike the cell walls of plants which are made of cellulose and lignin.
• Fungi are non-vascular organisms. 

Physiological Characteristics Of Fungi

• Fungi are heterotrophic; they depend on others for food.
• Unlike plants and animals, fungi first digest the food and then ingest it. This is possible with the help of exoenzymes. Fungi store food as glycogen like animals do.
• The ergosterol found in fungal cells has similar functions to that of mammalian cholesterol.
• Saprophytic fungi depend on non-organic materials for food. They play an important role in recycling of nitrogen, carbon and other essential mineral nutrients.
• Parasitic fungi thrive on organic food derived from a range of hosts including plants and animals.
• Symbiotic relationships are formed between certain types of plants and fungi. Symbiotic associations of plant roots and fungi are called mycorrhizae while fungal associations with plants or cyanobacteria are called lichens. 

Pathological Characteristics Of Fungi

• Fungi can cause diseases in plants and animals, including human beings.
• Fungi are capable of damaging all kind of things, except for some pesticides and plastics.
• They can compete with other pathogens for food by following the complete exclusion principle. According to this, two groups of organisms competing for the same resource cannot co-exist. This characteristic feature of fungi is used for biological pest control.
• Fungi cause many diseases in human beings. Athlete’s Foot is one such disease caused by Trichophyton which includes symptoms like itching, scaling and flaking of the affected skin. Candidiasis or thrush is another serious fungal infection which ranges from superficial infection to systemic and is a potentially life-threatening disease.
• Fungal infections occur in animals and plants too. Such infections in agricultural plants are a major threat faced by farmers across the globe.
• Fungal infections generally occur in moist and warm areas like the area under clothes and shoes. The infections initially occur on the skin surface and then penetrate into deeper parts. They may enter into the body through cuts and injuries as well. 

Reproductive Characteristics

• Fungi have two kinds of reproduction – sexual and asexual.
• Asexual reproduction is done by means of spores. Spores can remain dormant for long time and they germinate during favorable conditions.
• Sexual reproduction involves combination of two compatible nuclei or gametes followed by mitotic division.
• Sex organs are called gametangia and they may be distinguished into male and female, depending on the gametes present. Sometimes, both male and female gametes are present in the same gametangia. 
• Homothallic mycelia do not need other mycelium for sexual reproduction; both male and female gametes are present in them.
• Heterothallic mycelia need other mycelia for sexual reproduction because though both male and female gametes are present in the same mycelium, they are not compatible. 

Fungi belong neither to animal kingdom nor to kingdom plantae. They are a separate kingdom by themselves, though some of their characters are similar to both kingdoms. The characteristics mentioned above are common and hence, may change according to the species.

All the living beings are organized into broad categories called kingdoms. Categorizing makes the study about so many different organisms simple. For many years, fungi was placed in the plant kingdom and studied under the same light for a long time. But then it was disputed because of the absence of vascular tissues that are responsible for the growth of stems, leaves and roots. It was then placed in the animal kingdom. That, too, did not fit the fungi properly until they were given a kingdom of their own and categorized separately. This mysterious organism is only partly seen with the naked eyes; only the fruit part is seen, rest of the body is made up of tiny filaments and these filaments are generally hidden in food material or wood or soil. We may never be able to see fungi if it did not grow a fruit at all. Fungi can reproduce both sexually and asexually. There are over million species of fungi, with over two hundred thousand species already identified all over the world. These different species have been identified by the arrangement and spores of the fruiting body. Fruiting bodies generate millions of spores. For example, a single fruiting body of mushroom may produce 10,000 million spores and more. Some fungi have hundreds of gills. The spores grow all over these gills, called lamellae. Some fungi have pores in the fruiting body and the spores develop inside the pores, which increases the surface area. This surface area of the fruiting body comes handy in identifying different kinds of fungi.

 

Different Types of Fungi 

 

Gill Fungi: This type includes the very famous, mushroom. Mostly they have a stem and an umbrella type of cap on the top of it. The lamellae are on the underside of the cap. The ‘Destroying Angel’ or Amanita Verna is a deadly poisonous fungus, under this category. The gilled mushrooms are most famous mushrooms in the world, for their easy availability and taste.

 

Boletes: These fungi also have a stem and a cap on the top of it. But, like gill fungi, boletes do not have lamellae on the undersurface of the cap; instead it has thousands of tubes arranged on the side of the cape, perpendicularly. As a result, the cap looks like it has got a large number of little holes or tubes.

 

Polypores: Polypores have tough and wood-like bodies. Some of these fungi grow on the soil, but most of them attach themselves to rotten trees and plants. These fungi are also called bracket fungi; it looks like a shelf growing out on the side of a tree. The pores are grown on the underside of the cap with lots of spores. It can grow large in size and have rings on it. Its age can be identified through these rings.

 

Stinkhorns: It grows out of an egg like structure and looks extraordinary. It has a bell-shaped head on the top of a stalk. The head is slimy and foul-smelling, full of spores. The smell and slime attracts the flies and these flies later on become the spores’ disperser.

 

Earth Balls and Earth Stars: The spores, in this kind of fungi, are inside a ball like structure. This ball can either be on the ground level or leveled up with a stalk. The spores in the center are hard in the beginning, but later turn into a powdery accumulation. The earth stars have petals forming a star shaped structure, coming out of its outer space. It exposes the inner ball-like structure, containing pores.

 

Jelly Fungi: These are soft, jelly-like structures found growing like blobs, on trees or soil. It shrinks when it is dried, but then with availability of moisture again, it regains its consistency. This type of fungi commonly grows in the fall or summer time. Jelly fungi are usually orange, white, pink, rose, brown or black in color. They can look like corals because of their indefinite shapes.  

 

Cup Fungi: This type of fungi belongs to the Ascomycetes, which makes these fungi ‘spore-shooters’. This has cup shaped structure with a spore sac on its surface. Some cup fungi like ‘monilinia’ are pathogens. Some of these cup fungi are saprobes, found on decaying plants, twigs or cow-dung, etc. In cup fungi like helvella and peziza, spores are shot out like tiny explosions. Pyronema and Anthracobia are also called the fire fungi, because they grow on burned wood and steamed soil.

 

 

Main Divisions Of Fungi

 

Chytridiomycota: It is the division of fungi which contains unreleased pores. These are the most primitive form of fungi. This fungi is responsible of killing amphibians through the disease called chytridiomycosis. It was first discovered in Australia and Panama. This fungi has been the principle cause of decline in the population of amphibian worldwide.

 

Zygomycota: This is the division of fungi that attacks the food products. This fungi forms zygospore during sexual reproduction and many of these are also known as plant root symbionts. It can go through both sexual and asexual reproduction. In its asexual reproduction, spores are formed by separation and thickening of hyphal cells. In sexual reproduction, these fungi either mate through individual species. When hyphae from opposite mating types are met with, progametangia is produced. These structures are dense and multinucleate. Walls of the cell separate from this structure and transform into gametangia. Gametangia is attached to the mating hyphae with the help of remaining spensors. Then the process of plasmogamy takes place, which helps in forming a zygote and later, karyogamy happens within this zygote. This zygote thickens to form zygospore.

 

Glomeromycota: This is the division of fungi, recognized as one of the seven phyla of kingdom of fungi. This type of fungi depends on the symbiotic relationship with the land plants and deduces carbon and energy from it but some of the species can also lead independent existence. These fungi can also be found in the salt-marshes and form an association with the epiphytic plants. Glameromycota undergoes asexual reproduction through balastic development of hyphal tip, producing spores.

 

Ascomycota: This division of fungi includes diverse fungi from unicellular yeasts to complex cup fungi. There are atleast 30,000 species of Ascomycota. Ascomycota includes a reproductive structure called the ascus. Many of these causes tree diseases like dutch elm disease, apple blights, etc. Some of the yeasts from this group are used in the production of breads and alcoholic beverages. The medicine penicillin is produced from the fungi from this group called the Penacillium mold. It can undergo both sexual and asexual reproduction.

 

Basidiomycota: This division includes some of the most familiar fungi like mushrooms, puffballs, shelf fungi, plant rusts and smuts, etc.  This division contains more than 15,000 species and has a peculiar feature of a club-shaped reproductive organ called basidium. Apart from basidium, another peculiar feature to identify Basidiomycota is the degree with which individual cells separate in it. This division has more separated hyphae than Zygomycota, which lets the cutoplasm to flow freely between the cells. This divison undergoes both asexual and sexual reproduction.

Once relegated to science fiction, bioluminescence – or organic bodies that are capable of creating their own light sources, are now a reality. Thanks to projects like GlowingPlant.com, who is currently running a wildly successful Kickstarter campaign, sustainable light sources might be on the not-so-distant horizon. Hailed as being “the first step in creating sustainable natural lighting,” this solution brings about a new glimpse of what is to be expected from later attempts at innovation in the near future.

Some of you may already be familiar with the work of scientists who used luciferin, Latin for “light-bringer”, more than two decades ago to bring the plants to a glowing state, but technology has come a long way since that point in time. Prior to those experiments, the bioluminescence phenomenon, seen in creatures like fireflies, was a mystery to the scientific community. Today, scientists are much better able to manipulate this light source.

The Age of Bioluminescence

One of the coolest aspects of this new ability to genetically alter the plants to a glowing state is the ability for the public to access them for a reasonable fee. This commerce not is not great for the environment, but great for the companies working to make these groundbreaking scientific advances a common household item.

Although GlowingPlant.com plans to sell individual seeds for $40, or a grown glowing plant for $150, orders are not being taking until later in the month of May.

To give a bit of history as to how scientists were able to reach this monumental achievement, the story must begin in 1986. This is when scientists and researchers first added luciferin to the plants to allow them to become illuminated. Later in 1989, researchers were successful in determining the gene sequence for Luciferase-luciferin. It wasn’t until 2010 that scientists were able to create a glowing bacteria as well as plants that were able to as well based off of their genetically-modified make ups.

Taking this knowledge a bit further, they were able to create plants that glowed brightly instead of just dimly in 2013.

Letting the Light In

For those looking to accentuate their gardens in ways that have only been a distant dream, this may be the ultimate scientific discovery. For those that discourage genetic scientific breakthroughs, this may only be a small glimpse of what may be in store for the human race as a whole in a negative way. From what can be gathered by this monumental advancement, careful steps are being taken not to cross the boundaries of what is socially acceptable in terms of toying around with nature. In fact, this discovery may actually save the world from unnecessary power usage that is brought about by home lighting. It may also bring about new methods of facing illumination issues across the world. To think of the problem with a organic solution may be just the step that is needed for the next step of evolution.

There are three common technologies used by 2G cell-phone networks for transmitting information 

• Frequency division multiple access (FDMA)
• Time division multiple access(TDMA)
• Code division multiple access(CDMA)

Although these technologies sound very intimidating, you can get a good sense of how they work just by breaking down the title of each one.

The first word tells you what theaccess method is. The second word,division, lets you know that it splits calls based on that access method.

• FDMA puts each call on a separate frequency.
• TDMA assigns each call a certain portion of time on a designated frequency.
• CDMA gives a unique code to each call and spreads it over the available frequencies.

The last part of each name is multiple access. This simply means that more than one user can utilize each cell.

FDMA

FDMA separates the spectrum into distinct voice channels by splitting it into uniform chunks of bandwidth. To better understand FDMA, think of radio stations: Each station sends its signal at a different frequency within the available band. FDMA is used mainly for analog transmission. While it is certainly capable of carrying digital information, FDMA is not considered to be an efficient method for digital transmission.

TDMA

TDMA is the access method used by the Electronics Industry Alliance and the Telecommunications Industry Association for Interim Standard 54 (IS-54) and Interim Standard 136 (IS-136). Using TDMA, anarrow band that is 30 kHz wide and 6.7 milliseconds long is split time-wise into three time slots.

Narrow band means "channels" in the traditional sense. Each conversation gets the radio for one-third of the time. This is possible because voice data that has been converted to digital information is compressed so that it takes up significantly less transmission space. Therefore, TDMA has three times the capacity of an analog system using the same number of channels. TDMA systems operate in either the 800-MHz (IS-54) or 1900-MHz (IS-136) frequency bands.

TDMA splits a frequency into time slots.

GSM

TDM­A is also used as the access technology for Global System for Mobile communications (GSM). However, GSM implements TDMA in a somewhat different and incompatible way from IS-136. Think of GSM and IS-136 as two different operating systems that work on the same processor, like Windows and Linux both working on an Intel Pentium III. GSM systems use encryption to make phone calls more secure. GSM operates in the 900-MHz and 1800-MHz bands in Europe and Asia and in the 850-MHz and 1900-MHz (sometimes referred to as 1.9-GHz) band in the United States. It is used in digital cellular and PCS-basedsystems. GSM is also the basis forIntegrated Digital Enhanced Network (IDEN), a popular system introduced by Motorola and used by Nextel.

GSM is the international standard in Europe, Australia and much of Asia and Africa. In covered areas, cell-phone users can buy one phone that will work anywhere where the standard is supported. To connect to the specific service providers in these different countries, GSM users simply switch subscriber identification module (SIM) cards. SIM cards are small removable disks that slip in and out of GSM cell phones. They store all the connection data and identification numbers you need to access a particular wireless service provider. ­

Unfortunately, the 850MHz/1900-MHz GSM phones used in the United States are not compatible with the international system. If you live in the United States and need to have cell-phone access when you're overseas, you can either buy a tri-band or quad-band GSM phone and use it both at home and when traveling or just buy a GSM 900MHz/1800MHz cell phone for traveling. You can get 900MHz/1800MHz GSM phones from Planet Omni, an online electronics firm based in California. They offer a wide selection ofNokia, Motorola and Ericsson GSM phones. They don't sell international SIM cards, however. You can pick up prepaid SIM cards for a wide range of countries at Telestial.com.

CDMA

CDMA takes an entirely different approach from TDMA. CDMA, after digitizing data, spreads it out over the entire available bandwidth. Multiple calls are overlaid on each other on the channel, with each assigned aunique sequence code. CDMA is a form of spread spectrum, which simply means that data is sent in small pieces over a number of the discrete frequencies available for use at any time in the specified range.

In CDMA, each phone's data has a unique code.

All of the users transmit in the samewide-band chunk of spectrum. Each user's signal is spread over the entire bandwidth by a unique spreading code. At the receiver, that same unique code is used to recover the signal. Because CDMA systems need to put an accurate time-stamp on each piece of a signal, it references the GPS system for this information. Between eight and 10 separate calls can be carried in the same channel space as one analog AMPS call. CDMA technology is the basis forInterim Standard 95 (IS-95) and operates in both the 800-MHz and 1900-MHz frequency bands.

Ideally, TDMA and CDMA are transparent to each other. In practice, high-power CDMA signals raise the noise floor for TDMA receivers, and high-power TDMA signals can cause overloading and jamming of CDMA receivers.

2G is a cell phone network protocol. Click here to learn about network protocols for Smartphones.

3G:

3G technology is the latest in mobile communications. 3G stands for "third generation" -- this makes analog cellular technology generation one and digital/PCS generation two. 3G technology is intended for the true multimedia cell phone -- typically called smartphones -- and features increased bandwidth and transfer rates to accommodate Web-based applications and phone-based audio and video files.

3G comprises several cellular access technologies. The three most common ones as of 2005 are:

• CDMA2000 - based on 2G Code Division Multiple Access (see Cellular Access Technologies)
• WCDMA (UMTS) - Wideband Code Division Multiple Access
• TD-SCDMA - Time-division Synchronous Code-division Multiple Access

3G networks have potential transfer speeds of up to 3 Mbps (about 15 seconds to download a 3-minuteMP3 song). For comparison, the fastest 2G phones can achieve up to 144Kbps (about 8 minutes to download a 3-minute song). 3G's high data rates are ideal for downloading information from the Internet and sending and receiving large, multimedia files. 3G phones are like mini-laptops and can accommodate broadband applications like video conferencing, receiving streaming video from the Web, sending and receiving faxes and instantly downloading e-mail messages with attachments.

Of course, none of this would be possible without those soaring towers that carry cell-phone signals from phone to phone.

3G is a cell phone network protocol. Click here to learn about network protocols for Smartphones.

Millions of people in the United States and around the world usecellular phones. They are such great gadgets -- with a cell phone, you can talk to anyone on the planet from just about anywhere!

These days, cell phones provide an incredible array of functions, and new ones are being added at a breakneck pace. Depending on the cell-phone model, you can:

• Store contact information

• Make task or to-do lists

• Keep track of appointments and set reminders

• Use the built-in calculator for simple math

• Send or receive e-mail

• Get information (news, entertainment, stock quotes) from theInternet

• Play games

• Watch TV

• Send text messages

• Integrate other devices such as PDAs, MP3 players and GPS receivers

In full-duplex radio, the two transmitters use different frequencies, so both parties can talk at the same time. Cell phones are full-duplex.

• Full-duplex vs. half-duplex - Both walkie-talkies and CB radios are half-duplex devices. That is, two people communicating on a CB radio use the same frequency, so only one person can talk at a time. A cell phone is a full-duplex device. That means that you use one frequency for talking and a second, separate frequency for listening. Both people on the call can talk at once.

• Channels - A walkie-talkie typically has one channel, and a CB radio has 40 channels. A typical cell phone can communicate on 1,664 channels or more!

• Range - A walkie-talkie can transmit about 1 mile (1.6 km) using a 0.25-watt transmitter. A CB radio, because it has much higher power, can transmit about 5 miles (8 km) using a 5-watt transmitter. Cell phones operate within cells, and they can switch cells as they move around. Cells give cell phones incredible range. Someone using a cell phone can drive hundreds of miles and maintain a conversation the entire time because of the cellular approach.

Cell-phone Channels

• A cell-phone carrier typically gets 832 radio frequencies to use in a city.

• Each cell phone uses two frequencies per call -- a duplex channel -- so there are typically 395 voice channels per carrier. (The other 42 frequencies are used for control channels -- more on this later.)

• The transmissions of a base station and the phones within its cell do not make it very far outside that cell. Therefore, in the figure above, both of the purple cells can reuse the same 56 frequencies. The same frequencies can be reused extensively across the city.

• The power consumption of the cell phone, which is normally battery-operated, is relatively low. Low power means small batteries, and this is what has made handheld cellular phones possible.

Cell-phone Codes

• When you first power up the phone, it listens for an SID (see sidebar) on the control channel. The control channel is a special frequency that the phone and base station use to talk to one another about things like call set-up and channel changing. If the phone cannot find any control channels to listen to, it knows it is out of range and displays a "no service" message.

• When it receives the SID, the phone compares it to the SID programmed into the phone. If the SIDs match, the phone knows that the cell it is communicating with is part of its home system.

• Along with the SID, the phone also transmits a registration request, and the MTSO keeps track of your phone's location in a database -- this way, the MTSO knows which cell you are in when it wants to ring your phone.

• The MTSO gets the call, and it tries to find you. It looks in its database to see which cell you are in.

• The MTSO picks a frequency pair that your phone will use in that cell to take the call.

• The MTSO communicates with your phone over the control channel to tell it which frequencies to use, and once your phone and the tower switch on those frequencies, the call is connected. Now, you are talking by two-way radio to a friend.

• As you move toward the edge of your cell, your cell's base station notes that your signal strength is diminishing. Meanwhile, the base station in the cell you are moving toward (which is listening and measuring signal strength on all frequencies, not just its own one-seventh) sees your phone's signal strength increasing. The two base stations coordinate with each other through the MTSO, and at some point, your phone gets a signal on a control channel telling it to change frequencies. This hand off switches your phone to the new cell.

• As you travel, the signal is passed from cell to cell.

Analog Cell PhonesAlong Comes Digital
nside a Digital Cell Phone

• An amazing circuit board containing the brains of the phone

• An antenna

• A liquid crystal display (LCD)

• A keyboard (not unlike the one you find in a TV remote control)

• A microphone

• A speaker

• A battery

The SIM card on the circuit board

But have you ever wondered how a cell phone works? What makes it different from a regular phone? What do all those terms like PCS, GSM, CDMA and TDMA mean? In this article, we will discuss the technology behind cell phones so that you can see how amazing they really are.

To start with, one of the most interesting things about a cell phone is that it is actually a radio -- an extremely sophisticated radio, but a radio nonetheless. The telephone was invented by Alexander Graham Bell in 1876, and wireless communication can trace its roots to the invention of the radio by Nikolai Tesla in the 1880s (formally presented in 1894 by a young Italian named Guglielmo Marconi). It was only natural that these two great technologies would eventually be combined.

Cell-phone Frequencies

In the dark ages before cell phones, people who really needed mobile-communications ability installedradio telephonesin their cars. In the radio-telephone system, there was one central antenna tower per city, and perhaps 25 channels available on that tower. This central antenna meant that the phone in your car needed a powerful transmitter -- big enough to transmit 40 or 50 miles (about 70 km). It also meant that not many people could use radio telephones -- there just were not enough channels.

The genius of the cellular system is the division of a city into small cells. This allows extensive frequency reuse across a city, so that millions of people can use cell phones simultaneously.

A good way to understand the sophistication of a cell phone is to compare it to a CB radio or a walkie-talkie.

In a typical analog cell-phone system in the United States, the cell-phone carrier receives about 800 frequencies to use across the city. The carrier chops up the city into cells. Each cell is typically sized at about 10 square miles (26 square kilometers). Cells are normally thought of as hexagons on a bighexagonal grid, like this:

Because cell phones and base stations use low-power transmitters, the same frequencies can be reused in non-adjacent cells. The two purple cells can reuse the same frequencies.

Each cell has a base station that consists of a tower and a small building containing the radio equipment. We'll get into base stations later. First, let's examine the "cells" that make up a cellular system.

A single cell in an analog cell-phone system uses one-seventh of the available duplex voice channels. That is, each cell (of the seven on a hexagonal grid) is using one-seventh of the available channels so it has a unique set of frequencies and there are no collisions:

Therefore, each cell has about 56 voice channels available. In other words, in any cell, 56 people can be talking on their cell phone at one time. Analog cellular systems are considered first-generation mobile technology, or 1G. With digital transmission methods (2G), the number of available channels increases. For example, a TDMA-based digital system (more on TDMA later) can carry three times as many calls as an analog system, so each cell has about 168 channels available. ­

Cell phones have low-power transmitters in them. Many cell phones have two signal strengths: 0.6 watts and 3 watts (for comparison, most CB radios transmit at 4 watts). The base station is also transmitting at low power. Low-power transmitters have two advantages:

The cellular approach requires a large number of base stations in a city of any size. A typical large city can have hundreds of towers. But because so many people are using cell phones, costs remain low per user. Each carrier in each city also runs one central office called the Mobile Telephone Switching Office(MTSO). This office handles all of the phone connections to the normal land-based phone system, and controls all of the base stations in the region

All cell phones have special codes associated with them. These codes are used to identify the phone, the phone's owner and the service provider.

Let's say you have a cell phone, you turn it on and someone tries to call you. Here is what happens to the call:

Let's say you're on the phone and you move from one cell to another -- but the cell you move into is covered by another service provider, not yours. Instead of dropping the call, it'll actually be handed off to the other service provider.

If the SID on the control channel does not match the SID programmed into your phone, then the phone knows it is roaming. The MTSO of the cell that you are roaming in contacts the MTSO of your home system, which then checks its database to confirm that the SID of the phone you are using is valid. Your home system verifies your phone to the local MTSO, which then tracks your phone as you move through its cells. And the amazing thing is that all of this happens within seconds.

The less amazing thing is that you may be charged insane rates for your roaming call. On most phones, the word "roam" will come up on your phone's screen when you leave your provider's coverage area and enter another's. If not, you'd better study your coverage maps carefully -- more than one person has been unpleasantly surprised by the cost of roaming. Check your service contract carefully to find out how much you're paying when you roam.

Note that if you want to roam internationally, you'll need a phone that will work both at home and abroad. Different countries use different cellular access technologies. More on those technologies later. First, let's get some background on analog cell-phone technology so we can understand how the industry has developed.

In 1983, the analog cell-phone standard called AMPS (Advanced Mobile Phone System) was approved by the FCC and first used in Chicago. AMPS uses a range of frequencies between 824 megahertz (MHz) and 894 MHz for analog cell phones. In order to encourage competition and keep prices low, the U. S. government required the presence of twocarriers in every market, known as A and B carriers. One of the carriers was normally the local-exchange carrier (LEC), a fancy way of saying the local phone company.

Carriers A and B are each assigned 832 frequencies: 790 for voice and 42 for data. A pair of frequencies (one for transmit and one for receive) is used to create one channel. The frequencies used in analog voice channels are typically 30 kHz wide -- 30 kHz was chosen as the standard size because it gives you voice quality comparable to a wired telephone.

The transmit and receive frequencies of each voice channel are separated by 45 MHz to keep them from interfering with each other. Each carrier has 395 voice channels, as well as 21 data channels to use for housekeeping activities like registration and paging.

A version of AMPS known as Narrowband Advanced Mobile Phone Service (NAMPS) incorporates some digital technology to allow the system to carry about three times as many calls as the original version. Even though it uses digital technology, it is still considered analog. AMPS and NAMPS only operate in the 800-MHz band and do not offer many of the features common in digital cellular service, such as e-mail and Web browsing.

Digital cell phones are the second generation (2G) of cellular technology. They use the same radio technology as analog phones, but they use it in a different way. Analog systems do not fully utilize the signal between the phone and the cellular network -- analog signals cannot be compressed and manipulated as easily as a true digital signal. This is the reason why many cable companies are switching to digital -- so they can fit more channels within a given bandwidth. It is amazing how much more efficient digital systems can be.

Digital phones convert your voice into binary information (1s and 0s) and then compress it (see How Analog-Digital Recording Works for details on the conversion process). This compression allows between three and 10 digital cell-phone calls to occupy the space of a single analog call.

Many digital cellular systems rely on frequency-shift keying (FSK) to send data back and forth over AMPS. FSK uses two frequencies, one for 1s and the other for 0s, alternating rapidly between the two to send digital information between the cell tower and the phone. Clever modulation and encoding schemes are required to convert the analog information to digital, compress it and convert it back again while maintaining an acceptable level of voice quality. All of this means that digital cell phones have to contain a lot of processing power.

Let's take a good look inside a digital cell phone.

On a "complexity per cubic inch" scale, cell phones are some of the most intricate devices people use on a daily basis. Modern digital cell phones can process millions of calculations per second in order to compress and decompress the voice stream.

If you take a basic digital cell phone apart, you find that it contains just a few individual parts:

The circuit board is the heart of the system. The analog-to-digital and digital-to-analog conversion chips translate the outgoing audio signal from analog to digital and the incoming signal from digital back to analog. You can learn more about A-to-D and D-to-A conversion and its importance to digital audio in How Compact Discs Work. The digital signal processor (DSP) is a highly customized processor designed to perform signal-manipulation calculations at high speed. ­

The microprocessor handles all of the housekeeping chores for the keyboard and display, deals with command and control signaling with the base station and also coordinates the rest of the functions on the board.

The ROM and Flash memory chips provide storage for the phone's operating system and customizable features, such as the phone directory. The radio frequency (RF) and power section handles power management and recharging, and also deals with the hundreds of FM channels. Finally, the RF amplifiershandle signals traveling to and from the antenna.

The display has grown considerably in size as the number of features in cell phones have increased. Most current phones offer built-in phone directories, calculators and games. And many of the phones incorporate some type of PDA or Web browser.

Some phones store certain information, such as the SID and MIN codes, in internal Flash memory, while others use external cards that are similar toSmartMedia

 cards.

Cell phones have such tiny speakers and microphones that it is incredible how well most of them reproduce sound. As you can see in the picture above, the speaker is about the size of a dime and the microphone is no larger than the watch battery beside it. Speaking of the watch battery, this is used by the cell phone's internal clock chip.

What is amazing is that all of that functionality -- which only 30 years ago would have filled an entire floor of an office building -- now fits into a package that sits comfortably in the palm of your hand!

Women live longer than men partly because their immune systems age more slowly, a new study has claimed.

As the body’s defences weaken over time, men’s increased susceptibility to disease shortens their lifespans, according to Japanese scientists.

Tests of immune function could give an indication of true biological age, they said.

The immune system protects the body from infection and cancer, but causes disease when not properly regulated.

The Japanese study set out to investigate the controversial question of whether age-related changes in the immune system could be responsible for the difference in average life expectancy between men and women, the BBC reported.

Prof Katsuiku Hirokawa of the Tokyo Medical and Dental University and colleagues analysed blood samples from 356 healthy men and women aged between 20 and 90.

They measured levels of white blood cells and molecules called cytokines which interact with cells of the immune system to regulate the body’s response to disease.

In both sexes, the number of white blood cells per person declined with age as expected from previous studies.

However, closer examination revealed differences between men and women in two key components of the immune system - T-cells, which protect the body from infection, and B-cells, which secrete antibodies.

The rate of decline of most T-cell and B-cell lymphocytes was faster in men, while men also showed a more rapid age-related decline in two cytokines.

Two specific types of immune system cell that attack invaders - CD4 T-cells and natural killer cells - increased in number with age, with a higher rate of increase in women than in men.

The researchers believe a person’s immunological parameters could provide an indication of their true biological age.

“Age-related changes in various immunological parameters differ between men and women,” Prof Hirokawa and colleagues said.

“Our findings indicate that the slower rate of decline in these immunological parameters in women than that in men is consistent with the fact that women live longer than do men,” they added.

FACEBOOK’S and Google’s founders set aside their rivalries to create the “Breakthrough Prize” for science that’s worth more than double the value of the Nobel prize.

Facebook creator Mark Zuckerberg and his wife Priscilla Chan, and Google co-founder Sergey Brin and his wife Anne Wojcicki have joined forces to launch the Breakthrough in Life Sciences Award, worth $3 million, The Daily Mail reports.

The prize will be awarded to those with the best ideas in science, medicine, and technology and foundation, lead by the winner, is intended to fund scientists working on research aimed at curing intractable diseases and extending human life.

“Our society needs more heroes who are scientists, researchers and engineers,” Zuckerberg said in a statement. “We need to celebrate and reward the people who cure diseases, expand our understanding of humanity and work to improve people’s lives…At $3 million per prize, it’s the largest prize for this work in the world. I’m hopeful this serves as a blueprint for prizes and philanthropy in other fields as well.” Agencies

If you’ve seen even a few minutes of any documentary on sharks, then chances are you’ve seen a remora. They’re the smaller fish that hitch rides on sharks by sucking onto them. Not only are the remoras able to achieve a seal against their hosts’ rough, sandpaper-like skin, but they also don’t appear to harm that skin in the process. Researchers from the Georgia Tech Research Institute are now studying how the remoras manage this, in hopes of applying their findings to the development of next-generation adhesives.

Remoras are thought to latch onto sharks for three main reasons – it’s easier than swimming that same distance themselves, predators aren’t too likely to approach them with their toothy host nearby, and they get to eat the food scraps that the shark creates while tearing into unfortunate sea creatures.

They’re able to hold on not by using their mouths, but with a sucker on their back. That structure is actually a dorsal fin, that through the course of evolution has flattened. It has a lip of fleshy tissue around its perimeter to create a seal against the shark skin, but it also has an oval disk in the middle, made up of rows of louvered plates known as lamellae.

Each lamella, in turn, incorporates rows of tooth-like structures called spinules. The scientists noted that the spacing between the spinules was very similar to the spacing of the scales of the mako shark, allowing the spinules to non-destructively fit between those scales. This, needless to say, allows for excellent adhesion between the two – that said, remoras are also pretty good at sucking onto other things, such as sea turtles.

If the remoras need to exert physical effort to maintain their hold, then the practicality of an adhesive based on their lamellae might be quite limited. By dissecting and examining the muscle tissue around the suction disk, however, the scientists discovered that the fish utilize a passive form of adhesion – they just latch on and relax. In fact, it’s likely that drag created by the passing water causes the spinules and scales to mesh together more firmly.

Lead scientists Jason Nadler and Allison Mercer, along with their colleagues, are now looking into human applications for what they’ve learned. “We are not trying to replicate the exact remora adhesion structure that occurs in nature,” said Nadler. “We would like to identify, characterize and harness its critical features to design and test attachment systems that enable those unique adhesive functions. Ultimately, we want to optimize a bio-inspired adhesive for a wide variety of applications that have capabilities and performance advantages over adhesives or fasteners available today.”

More specifically, it has been suggested that such an adhesive could be used to create bandages that don’t cause pain or leave behind residue when they’re removed, to attach sensors in marine or military environments, as a replacement for surgical clamps, and as a means of helping robots climb vertical surfaces. Interestingly, some or all of those applications have also been suggested for adhesives based on porcupine quills and gecko feet.

A glow-in-the-dark shark scares off predators with "lightsaber-like" spines on its back, a study suggests.

The research was carried out on the velvet belly lanternshark, a small species found in the deep waters of the Atlantic Ocean and Mediterranean Sea.

The scientists believe that while the light-up spines can be seen by larger, potentially dangerous fish, they are harder for the shark's prey to spot.

It also has a glowing belly, which it uses to camouflage itself, as Dr Julien Claes, a shark biologist from the Catholic University of Louvain in Belgium explains.

According to recent estimates by the United Nations about 2.6 billion people in the world have little or no access to clean drinking water and most of these people reside in underdeveloped parts of the world, where infrastructure to produce drinking water by desalination are not present. Similar is the case in Peru, where people usually source water from wells, which is often polluted and not at all fit for drinking. To better conditions in such areas, UTEC, the University of Engineering and Technology in Lima, Peru, has collaborated with Mayo DraftDCB to develop an innovative billboard that can quench the third of many families.

The billboard, which is the first of its kind in the world, includes advanced water capturing and filtration systems that convert humidity in the air to clean drinking water. Since the average atmospheric humidity in the area reaches almost 98 percent, but rainfall is scarce, the billboard is able to produce up to 96-liters of potable water that is stored in reserve tanks. Local residents can simply approach the billboard and turn the tap for clean water. Head over to Designboom for some more images.

China's environment ministry appears to have acknowledged the existence of so-called "cancer villages" after years of public speculation about the impact of pollution in certain areas.

For years campaigners have said cancer rates in some villages near factories and polluted waterways have shot up.

But the term "cancer village" has no technical definition and the ministry's report did not elaborate on it.

There have been many calls for China to be more transparent on pollution.

The latest report from the environment ministry is entitled "Guard against and control risks presented by chemicals to the environment during the 12th Five-Year period (2011-2015)".

It says that the widespread production and consumption of harmful chemicals forbidden in many developed nations are still found in China.

"The toxic chemicals have caused many environmental emergencies linked to water and air pollution," it said.

The report goes on to acknowledge that such chemicals could pose a long-term risk to human health, making a direct link to the so-called "cancer villages".

"There are even some serious cases of health and social problems like the emergence of cancer villages in individual regions," it said.

Beijing smog

The BBC's Martin Patience in Beijing says that as China has experienced rapid development, stories about so-called cancer villages have become more frequent.

And China has witnessed growing public anger over air pollution and industrial waste caused by industrial development.

Media coverage of conditions in these so-called "cancer villages" has been widespread. In 2009, one Chinese journalist published a map identifying dozens of apparently affected villages.

In 2007 the BBC visited the small hamlet of Shangba in southern China where one scientist was studying the cause and effects of pollution on the village.

He found high levels of poisonous heavy metals in the water and believed there was a direct connection between incidences of cancer and mining in the area.

Until now, there has been little comment from the government on such allegations.

Environmental lawyer Wang Canfa, who runs a pollution aid centre in Beijing, told the AFP news agency that it was the first time the "cancer village" phrase had appeared in a ministry document.

Last month - Beijing - and several other cities - were blanketed in smog that soared past levels considered hazardous by the World Health Organisation.

The choking pollution provoked a public outcry and led to a highly charged debate about the costs of the country's rapid economic development, our correspondent says.