Knowledge N Fact4u

Why is lead used in pencils even though lead is poisonous ? •The core of a pencil does not contain lead and never has. Pencils contain a form of solid carbon known as graphite.  •According to a study, the graphite pencil was first developed and popularized in the 1600's.  •The first users of graphite simply dug this mineral out of the hills and discovered it could be sawed into sticks and used as an excellent writing tool.  •During the 1600's, no one knew the chemical nature of this material, as chemistry itself was still in its infancy. •Since this writing material behaved similar to metallic lead, but had a darker color, people began calling it "black lead".  •Eventually, the name of the core of the pencil got shortened to "lead". In 1779, German chemist K. W. Scheele finally determined pencil lead to be composed of pure carbon.  •A decade later, A. G. Werner decided that this carbon material needed a new name and proposed the name "graphi...

Why don't dark-skinned people get sunburns ? •Dark-skinned people do get sunburns. While it's true that the higher pigment levels that make certain people's skin look dark helps protect against sunlight, the pigments do not block 100% of the light. •The skin pigment melanin is produced by special skin cells called melanocytes to protect the body from the damaging effects of ultraviolet light.  •Higher levels of melanin means less sunburn and less skin cancer. •But even the darkest-skinned person is not protected 100% from sunlight. •A study found that 13% of black women and 9% of black men reported getting at least one sunburn in the past year.  •Furthermore, 38% of Hispanic women and 32% of Hispanic men reported getting at least one sunburn in the past year.  •For comparison purposes, the average value across all ethnicities and genders was 50.1%. While dark-skinned people definitely get fewer sunburns, they still get them.  •When a dark-skinned person g...

Why does chocolate cause acne ? •Chocolate does not cause acne. Acne is caused by overactive sebaceous glands.  •Sebaceous glands are microscopic glands connected to the hair follicles.  •Their job is to secrete skin oil (sebum), which travels up the shaft of the hair and out onto the skin in order to waterproof the body.  •If the glands secrete too much skin oil, the channel along the hair's shaft becomes clogged.  •As a result, a buildup of skin oil and dead cells occurs in the glands and the hair follicle.  •This stagnant, clogged mass just below the skin's surface becomes infected with bacteria and turns into a pimple.  •Sebaceous glands accelerate their secretions in response to high levels of sex hormones, such as present during puberty.  •The causes of acne are therefore: 1) elevated sex hormones, 2) sebaceous glands that are overly sensitive to sex hormones, and 3) the presence of bacteria that take advan...

Find out how these versatile plugand-play devices can store data Similar in nature to a conventional hard drive, a fl ash drive is a very convenient device capable of not only storing data, but also transferring it quickly between computers and digital devices. A form of solid-state storage (electronic, with no moving parts), fl ash drives are both robust and small enough to fit in your pocket and yet can hold vast quantities of data depending on how great their storage capacity. Flash memory is a type of EEPROM (Electrically Erasable Programmable Read-Only Memory) stored as small blocks. The chunks of data stored using fl ash memory can be erased and re-programmed electronically, making it a quick, effective way of transferring files. When you insert the fl ash drive into the computer’s USB port, the computer automatically detects the device. It then acts like an external hard drive, allowing you to immediately begin storing and retrieving data. The internal workings of a fl ash dr...

Only a few years ago, seeing in 3-D meant peering through a pair of red-and-blue glasses, or trying not to go cross-eyed in front of a page of fuzzy dots. It was great at the time, but 3-D technology has moved on. Scientists know more about how our vision works than ever before, and our computers are more powerful than ever before -- most of us have sophisticated components in our computer that are dedicated to producing realistic graphics. Put those two things together, and you'll see how 3-D graphics have really begun to take off. Most computer users are familiar with 3-D games. Back in the '90s, computer enthusiasts were stunned by the game Castle Wolfenstein 3D, which took place in a maze-like castle. It may have been constructed from blocky tiles, but the castle existed in three dimensions -- you could move forward and backward, or hold down the appropriate key and see your viewpoint spin through 360 degrees. Back then, it was revolutionary and quite amazing. Nowaday...

HOW IS FIBRE OPTIC BROADBAND USHERING IN A NEW ERA OF COMMUNICATION? Remember dial-up internet? Most of us do and it’s not so very long ago that speeds of 56K were considered fast when it came to accessing the delights of the world wide web. And while it may have been fine for checking GeoCities pages and bulletin boards, as our demands and uses of the internet became more complex so higher speeds became more necessary, can you imagine using iTunes or YouTube on a 56K modem? Neither could the service providers who now vie for our attention, trying to find the balance between faster connections and lower prices. Currently the fastest speed on offer in the UK and US and most of Europe lie somewhere between 2MB and 10MB while China, South Korea and Japan lead the way in ‘fibre-to-the-home’ broadband lines. However many western nations such as America, Sweden and Romania are following close behind. Over the next few pages we’ll be explaining fibre optics, the amazing technology behind the n...

Seen by many to be the next stage in the evolution of music distribution and reproduction, Spotify is bringing music to the world of cloud computing.  Spotify is a new application that is available for PC and Mac – along with many modern smartphones – which allows you to stream music from a vast catalogue distributed through the Spotify central hub and sourced from every other Spotify user. To use Spotify you would first need to download the Spotify software from www.spotify.com. Once installed, Spotify looks a lot like other media players such as iTunes, but there is a big difference. With Spotify, you don’t have to download the music in order to listen to it (although this is also possible). Instead you can simply stream it over your internet connection.  To use Spotify you would fi rst need to download the Spotify software from www.spotify.com. Once installed, Spotify looks a lot like other media players such as iTunes, but there is a big difference. With Spotif...