ReWalk: A Robotic Exoskeleton

Radi Kaiof tests the ReWalk. The inventor of ReWalk, Israeli engineer Amit Goffer, learned the hard way that wheelchair mobility is terribly outdated.  In 1997, he broke his neck as the result of a fall, and the wheelchair's limitations were experienced by Goffer first hand.  He set to work on a design for a wearable exoskeleten, kind of like a battery powered suit of armor for the lower body. 
When he discovered that a whole body device would need too many batteries and be too heavy to be efficient, he decided to build instead a lower body exoskeleten that depended on the use of crutches as well as motors and batteries.  Because Goffer can not use his arms to use the crutches, he will not be able to make use of the ReWalk himself.
The ReWalk is more complicated than it looks.  Its 44 pounds of off-the-shelf components are controlled by hundreds of algorithms and codes and sensors that all enable standing, sitting, walking, and even climbing stairs.   Radi Kaiof, a ReWalk tester had not walked in 20 years, but when he's strapped into the ReWalk, he's a different man.
"I speak eye-to-eye with people, not from the bottom up," he says. "There is one life in a wheelchair, and this is a new life."

Paper and it's development

In this age, paper had been an inseparable part of our life. We need paper every day in the form of anything like book, copy or newspaper. Let’s talk about the development of paper.
Paper had been named ‘paper’ from the Greek word called ‘papyrus’.  It is the name of a long grass found in Greece.  This grass is couple of meters long.  By this type of grass, papers were made by the ancient people of Greece. So paper was first prepared in Greece. But those papers were very different from the paper of today. The paper we are using now-a-days was discovered by Chinese. They firstly prepared paper by the small pieces of bamboo and tree. Further the Arabian kidnapped the people of China who could make paper. And the Arabians forced them to make paper in Arabia. In 9th century, the Arabians too started to make paper. Then it spread to whole European countries in 12th century.
With the purpose of business, the paper was first discovered in Italy (Fabriyano) in the year 1726. So, the most paper is manufactured in Finland with the purpose of business. After the establishment of press in 1450, the manufacture of paper is rapidly growing.

Black Hole

Black holes are the remaining part of star after its death. In the life cycle of star, there is a constant nuclear fusion at its core which generates photons through electromagnetic radiations. The radiation is responsible for the outward pressure that perfectly balances the pull of gravity from the mass of the star. But at the far end of the star’s life, when the nuclear fuel of the star starts diminishing, the outward pressure starts to reduce. Consequently, the inward gravitational pull increases manifold, thereby shrinking the star inward. Eventually, the core of the star collapses and becomes a black hole.
According to Einstein’s theory of relativity, the object falling to the surface of black does not appear ever and never comes out from the black hole, not even the light. Its gravity is so powerful and intense that even time stops in the black hole. The mass and size of the black hole are directly proportional to each other. For instance, if one black hole is 10 times heavier than other black hole, its radius also ought to be 10 times larger than the other. In fact, if there is a black hole with a mass equivalent to Sun, it will have a radius of 3 kilometers only! The radius of this event horizon is also known as the Schwarzschild radius which can be calculated by the formula:
                                   ::     r=2GM/c2 (where G: gravitational force, M: mass and c: speed of light or escape velocity)
The black hole contains two sections: event horizon and singularity. The event horizon is the surface of the black hole and the singularity signifies the core of the black hole. Anything needs to be in the vicinity of the event horizon to get sucked in. Event horizon is also called “point of no return”. Singularity is the sole of suction where the volume is zero and density is maximum. This is the point of infinite spacetime curvature. With time, the black holes keep shrinking in size as they constantly emit X-ray radiations constantly. After some while, they nearly evaporate.
The stars which are 10-15 times bigger than sun only can transform into a black hole. Smaller stars than sun become white dwarfs. Any body, to escape form the black hole is impossible, because the body must have greater velocity than light to escape from the black hole which is not possible till today. There have been a lot of researches ongoing in context of black hole. NASA has established a space telescope, which helps to detect and see the black hole, named as XMM-Newton. This telescope can observe the universe in light containing high energy X-rays that are mostly emissions of black holes, which have also helped scientists a great deal in unraveling facts about the black holes in space. Due to the telescope, the scientists had the experienced the view of the entire process of a star being sucked into the black hole.

Why sea does not freeze?

Water is such a compound that can change its state at any temperature and pressure without changing its chemical properties. It is also called the universal solvent. It can solve anything with its solubility power. The earth is made by 2/3 part of water and 1 part is land. In those 2 parts, the land containing water is divided into 7 oceans. Due to large amount of contained water, those parts covered by water are called oceans and seas.

The water of those seas is different from the water we use daily. Because of the cold blooded aquatic animals inside the water, the water of sea contains huge amount of salt. According to the chemical property of water, it freezes at 0°C and boils at 100°C. But due to presence of salt, the freezing point of water decreases. Therefore, the water of sea does not freezes at the winter season too.

Ozone Layer

The ozone layer lies at between 12 to 24 km above the surface of the earth. Ozone is a gas with a fishy smell. Its molecules are made of three oxygen atoms linked together (o3). Ozone is a formed from normal oxygen in ultraviolet light. It can also be broken down in ultraviolet light. In the upper atmosphere the making and breaking down of ozon balance each other out so the amount of ozone does not change appreciably.

The layer of ozone in the upper atmosphere stops too much ultraviolet rays of the sun from reaching the earth’ surface. Ultraviolet rays can damage cells, causing mutations of the body cells. It may also cause skin cancer.

This protective ozone layer is being destroyed slowly by substances called chloro-fluoro-carbons (CFCs) which are being used in aerosols in making fast food cartoons and in insulating cavity walls, in refrigeration system and in air conditioning. These CFCs slowly diffuse up to the upper layer of the atmosphere, where the ultraviolet light from the sum reacts with them producing chlorine. The chlorine produced then reacts with ozone and breaks it down. This has formed a hole in the ozone layer. It appears over the Antarctic zone and its sizes reaches maximum in the spring season.

If the ultraviolet light is not cut down by the ozone layer, we will be in trouble as we are now.

Scientists and people in general who are conscious of this situation are trying hard to stop further worsening of this situation.

The amount of CFCs used is being reduced. In October 1987, an international agreement was signed in Canada to reduce CFCs emission by 50% of the 1986 levels by 1999. recently, it has been reported that the hole in the ozone layer is smaller now than it was before. However, CFCs may exist in the atmosphere for centuries.

Homologous Chromosomes

Under the vast and fascinating field of biology, comes the branch called genetics which studies genes, heredity and organism variations. One of the primary units of the study of  is human genitics the chromosome. The human body is made up of billions of cells - each human cell is made up of 46 homologous chromosomes, which are paired, to make 23 pairs. Of these 23 pairs, 22 are non-sex homologous chromosomes or autosomes, whereas one single pair is a sex chromosome. In females, all 23 pairs of chromosomes are identical, that is, each pair is made up of 2 X chromosomes. In males however, the sex chromosome is made up of one X and one Y chromosome, which pair up to form an XY sequence. At the genetic level, this is the difference between the male and female of the species.

HOW TO PRODUCE ELECTRICITY?

Electricity 

Electricity is a form of energy. It consists of electrons - tiny particles that come from atoms. Each electron carries a tiny electric charge which is an amount of electricity. When you switch on a light, electrons move through the bulb every second. Cables hidden in walls and ceilings carry electricity around houses and factories, providing energy at the flick of a switch. Electricity also provides portable power. Batteries produce electricity from chemicals, and solar cells provide electricity from the energy in sunlight. Lamps, motors and dozens of other machines use electricity as their source of power.

The device used for producing electricity is called a ‘dynamo’ or ‘generator’. The dynamo consists of a huge magnet called field magnet. In between the two poles of the magnet a rectangular coil made of copper wires is made to rotate. The two ends of the coil are connected to two metal rings, which keep on touching two carbon brushes. Wires carrying electric current are connected to these brushes. When the rectangular coil is rotated between the two poles of the magnet, electric current is produced in the coil because of electromagnetic induction. This current is brought to our houses and factories with the help of wires. 

In general two techniques are used to rotate the coil in between the poles of the magnet of a generator. In the first, water is accumulated by building dams across rivers and then it is allowed to fall from large heights over the blades of a turbine by which it starts rotating. The axle of the turbine is connected to the rotation mechanism of the copper coil of the dynamo. The movement of the turbine, thus rotates the coils and electricity is generated. Power-houses producing electricity by this technique are called hydel-power stations. 

In another process coal is burnt to boil water and convert it into steam. The steam so produced is used to rotate the turbine blades which in turn rotate the copper coil in the dynamo, thus producing electricity. Power houses producing electricity by this technique are called ‘thermal-power stations.’ Besides these two famous techniques, atomic energy is also being used to produce electricity. Installations producing electricity by this technique are called ‘atomic power reactors’. In view of the ever increasing demands of electricity, scientists are also constantly engaged in developing new techniques to generate electricity from solar energy and wind power.