Molecules

                                  Molecules

A molecule is defined as a group of two or more atoms arranged in a precise arrangement by means of covalent bonds. A molecule can range in size from two atoms, for example, H 2 (hydrogen), to thousands of atoms in macromolecules such as proteins, nucleic acids or synthetic and natural polymers. It can also occur ionic bonds, hydrogen bonds and other types of chemical bonds between different parts of the molecule, but it is only covalent bonds that are always between atoms in the same molecule.Within the kinetic theory of gases often used the term molecule for all particles in gas regardless of its constituents. According to this definition include noble gases molecules even though they only consist of single unbound atoms. Proteins with quaternary structure consists in fact in many cases by more molecules held together by intermolecular forces, although biochemists often regard them as a single molecule.

                                      Bonding

For a molecule to exist, atoms have to stick together. This happens when two atoms share electrons. Instead of circling just one atom, the electron now circles around two. This is called bonding. The shared electrons are called 'bonds'. Sometimes, more than one electron is shared. The more electrons are shared, the stronger the bond gets and the stronger the atoms stick together. Bonds can also be broken apart. Since most bonds require energy to form, they also give off energy when they are broken. But before most bonds break, the molecule has to be heated. Then the atoms start to move, and when they move too much, the bond breaks. Molecules that require less energy to break than they give off when broken are called fuels. For example, a candle will just sit there and nothing happens. But when you use a match to light it, it will burn for a long time. The match brings the energy to break the first bonds, which release enough energy to break the bonds below them, until the candle has burned down.

I really do hope you found the post informative as well as interesting. Sincerely, William.

Ultrasound

Ultrasound

To understand what ultrasound is and what it’s used for, we must first understand what sound is.

Sound occurs when things vibrate. These vibrations are transferred to the air particles of its surrounding. This causes a chain reaction in the air particle vibrations, causing them to move like waves. These waves are called sound waves and are longitudinal, meaning they travel horizontally. When the sound waves reaches our ears, it vibrates the ear drum. The ear drum sends the vibrations to three small bones that are put together. In this order, they are called the hammer, the     

anvil and the stirrup. This series of bones

amplifies and transports the vibrations

further into the ear, reaching the cochlea. The cochlea transforms the vibrations into electrical impulses which can be understood by the brain. The auditory nerve sends the electrical impulses to the brain.

Sound waves can have different frequencies. A low note has a low frequency and a high note has a high frequency. Frequency means how many waves there are in one second, which we measure in Hz (Hertz). If there is a note with a frequency of 500, there are 500 waves reaching the ear or an oscilloscope in one second. We measure frequency in Hz. Humans can only hear sound between the frequencies of about 27 and 20 000 Hz. A frequency below 27 Hz is called infrasound and a frequency above 20 000 is called ultrasound.

We can’t hear ultrasound or infrasound because our ear isn’t sensitive enough.

Even though we can’t hear ultrasound, it is used to treat many medical issues like looking inside the body(at unborn babies) and breaking down kidney stones. When looking at a fetus you are essentially sending ultrasonic waves towards it using a doppler scanner. The scanner sends out the waves as well as recognizes the changes in the reflected waves as they pass through different tissue. We call the reflected waves echoes. The scanner sends its data to a computer that processes it. The finished image is then shown on a TV screen (images changes as you move the scanner).

Ultrasound scans are much safer and better in some cases than x-rays. Ultrasound scans does not hurt living cells as it's just sound passing through the body. It also gives a better image of soft tissue compared to x-rays which only shows hard organs like bones and tumors. X-rays hurt living cells a lot as it is radioactive rays passing through the body.

- Erik & Leo

Fibre Optics (Total Internal Reflection)

Fibre Optics

Fibre optic cable are a type of cables which works with total internal reflection. Optical fibre is a thin light-pipe. It’s as thin as the human hair and it’s as flexible too. The core is surrounded by cladding which is also made by pure glass. The cladding has a low index which makes the light rays inside the core, totally internal reflected. The edges of the core acts like a mirror and it reflects the right rays through. Outside the cladding, there’s another layer named Buffer Coating (plastic) which protects the cladding and core so they don’t get damaged.

An optic fibre can transfer thousand of phone calls in the same time. A good thing with fibre optics is that they aren’t distracted by electronic or magnetic disorders such as thunders.

The signals used for the internet are electrical so you need a GBIC module because the optical fibre wires use optical signals. The information transmitted is usually digital information generated by computers, telephone systems and cable TV companies. This is a GBIC module (with its cover removed) which is an optical and electrical transceiver/convertor. The electrical connector is at top right, and the optical connectors are at bottom left

Review:

The signals in the optical fibres work with total internal reflection which means that the signal bounces of the surface. It can go on for about 200 km before the signals gets too weak.

The signals from the internet are electrical and the ones in the cable are optical so you need a electrical-optical convertor (GBIC module).

Helpful links and videos:

http://www.youtube.com/watch?v=0MwMkBET_5I

http://en.wikipedia.org/wiki/Fiber-optic_communication

http://www.youtube.com/watch?v=aqazAcE19vw

- Ali