PHYSICS: NUCLEAR PHYSICS
Nuclear Fission- Nuclear fission is a reaction in which the nucleus of an atom splits into smaller parts
- Nuclear fission can either release energy or absorb energy: for nuclei lighter than iron fission absorbs energy, while for nuclei heavier than iron it releases energy
- Energy released can be in the form of electromagnetic radiation or kinetic energy
- The amount of free energy contained in nuclear fuel is about a million times that contained in a similar mass of chemical fuel (like petrol)
- The atom bomb or fission bomb is based on nuclear fission
- Example: fission of Uranium-235 to give Barium, Krypton and neutrons
Nuclear Fusion
- Nuclear fusion is the process by which multiple nuclei join together to form a heavier nucleus
- Nuclear fusion can result in either the release or absorption of energy: for nuclei lighter than iron fusion releases energy, while for nuclei heavier than iron it absorbs energy
- Nuclear fusion is the source of energy of stars.
- Nuclear fusion is responsible for the production of all but the lightest elements in the universe. This process is called nucleosynthesis
- Controlled nuclear fusion can result in a thermonuclear explosion – the concept behind the hydrogen bomb
- The energy density of nuclear fusion is much greater than that of nuclear fission
- Only direct conversion of mass into energy (collision of matter and anti matter) is more energetic than nuclear fusion
- Example: fusion of hydrogen nuclei to form helium
PIONEERS OF NUCLEAR PHYSICS RESEARCH
| Scientist | Nationality | Discovery | Recognition |
| J J Thomson | Britain | Electron (1897) | Nobel in Physics (1906) |
| Henri Becquerel | Belgium | Radioactivity (1896) | Nobel in Physics (1903) |
| Ernest Rutherford | New Zealand | Structure of atom (1907) | Nobel in Chemistry (1908) He is regarded as the father of nuclear physics |
| Franco Rasetti | Italy/USA | Nuclear spin (1929) | |
| James Chadwick | Britain | Neutron (1932) | Nobel in Physics (1935) |
| Enrico Fermi | Italy/USA | Nuclear chain reaction (1942) Neutron irradiation | Nobel in Physics (1938) |
| Hideki Yukawa | Japan | Strong nuclear force (1935) | Nobel in Physics (1949) |
| Hans Bethe | Germany/USA | Nuclear fusion (1939) | Nobel in Physics (1967) |
APPLICATIONS OF NUCLEAR PHYSICS
| Application | Developed by | Working principle | Use |
| Nuclear power | Enrico Fermi (Italy, 1934) | Nuclear fission | Power generation |
| Nuclear weapons | Enrico Fermi (Italy, 1934) Edward Teller (USA, 1952) | Nuclear fission Nuclear fusion | Weapons |
| Radioactive pharmaceuticals | Sam Seidlin (USA, 1946) | Radioactive decay | Cancer, endocrine tumours, bone treatment |
| Medical imaging | David Kuhl, Roy Edwards (USA, 1950s) | Nuclear magnetic resonance (for MRI) Positron emission (for PET) | MRI: Musculosketal, cardiovascular, brain, cancer imaging PET: cancer, brain diseases imaging |
| Radiocarbon dating | Willard Libby (USA, 1949) | Radioactive decay of carbon-14 | Archaeology |
IMPORTANT NUCLEAR RESEARCH FACILITIES
Nuclear research facilities in the world| Facility | Location | Established | Famous for |
| Brookhaven National Lab | New York | 1947 | Until 2008 world’s largest heavy-ion collider |
| European Organization for Nuclear Research (CERN) | Geneva | 1954 | World’s largest particle physics lab Birthplace of the World Wide Web Large Hadron Collider (LHC) |
| Fermilab | Chicago | 1967 | Tevatron – world’s second largest particle accelerator |
| ISIS | Oxfordshire (England) | 1985 | Neutron research |
| Joint Institute for Nuclear Research | Dubna, Russia | 1956 | Collaboration of 18 nations including former Soviet states, China, Cuba |
| Lawrence Berkeley National Lab | California | 1931 | Discovery of multiple elements including astatine, and plutonium |
| Lawrence Livermore National Lab | California | 1952 | |
| Los Alamos National Lab | New Mexico, USA | 1943 | The Manhattan Project |
| National Superconducting Cyclotron lab | Michigan | 1963 | Rare isotope research |
| Oak Ridge National Lab | Tennessee | 1943 | World’s fastest supercomputer – Jaguar |
| Sudbury Neutrino Lab | Ontario | 1999 | Located 2 km underground Studies solar neutrinos |
| TRIUMF (Tri University Meson Facility) | Vancouver | 1974 | World’s largest cyclotron |
| Yongbyon Nuclear Scientific Research Centre | Yongbyon, North Korea | 1980 | North Korea’s main nuclear facility |
| Sandia National Lab | New Mexico, USA | 1948 | Z Machine (largest X-ray generator in the world) |
| Institute of Nuclear Medicine, Oncology and Radiotherapy (INOR) | Abbottabad, NWFP (Pakistan) | ||
| Pakistan Institute of Nuclear Science and Technology (PINSTECH) | Islamabad | 1965 |
Nuclear research facilities in India
| Facility | Location | Established | Famous for |
| Bhabha Atomic Research Centre | Bombay | 1954 | India’s primary nuclear research centre India’s first reactor Apsara |
| Variable Energy Cyclotron Centre (VECC) | Calcutta | 1977 | First cyclotron in India |
| Institute for Plasma Research (IPR) | Gandhinagar | 1982 | Plasma physics |
| Indira Gandhi Centre for Atomic Research (IGCAR) | Kalpakkam | 1971 | Fast breeder test reactor (FBTR) KAMINI (Kalapakkam Mini) light water reactor Built the reactor for Advanced Technology Vessel (ATV) |
| Saha Institute for Nuclear Physics | Calcutta | 1949 | |
| Tata Institute for Fundamental Research (TIFR) | Bombay | 1945 |
CHEMISTRY: POLYMERS
Overview- A polymer is a large molecule consisting of repeating structural units
- The repeating units are usually connected by covalent chemical bonds
- Polymers can be of two types
- Natural polymers: shellac, amber, rubber, proteins etc
- Synthetic polymers: nylon, polyethylene, neoprene, synthetic rubber etc
- Synthetic polymers are commonly referred to as plastics
- The first plastic based on a synthetic polymer to be created was Bakelite, by Leo Baekeland(Belgium/USA) in 1906
- Vulcanization of rubber was invented by Charles Goodyear (USA) in 1839. Vulcanization is the process of making rubber more durable by addition of sulphur
- The first plastic to be created was Parkesine (aka celluloid) invented by Alexander Parkes (England) in 1855
Synthesis of polymers
- The synthesis of polymers – both natural and synthetic – involves the step called polymerization
- Polymerization is the process of combining many small molecules (monomers) into a covalently bonded chain (polymer)
- Synthetic polymers are created using of two techniques
- Step growth polymerization: chains of monomers are combined directly
- Chain growth polymerization: monomers are added to the chain one at a time
- Natural polymers are usually created by enzyme-mediated processes, such as the synthesis of proteins from amino acids using DNA and RNA
Categories of polymers
- Organic polymers are polymers that are based on the element carbon. Eg: polyethylene, cellulose etc
- Inorganic polymers are polymers that are not based on carbon. Eg: silicone, which uses silicon and oxygen
- Copolymer is one that is derived from two or more monomeric units. Eg: ABS plastic
- Fluoropolymers are polymers based on fluorocarbons. They have high resistance to solvents, acids and bases. Eg: teflon
TYPES OF BIOPOLYMERS 
DNA as a biopolymer
DNA as a biopolymer
- Structural proteins
- Structural proteins are proteins that provide structural support to tissues
- They are usually used to construct connective tissues, tendons, bone matrix, muscle fibre
- Examples include collagen, keratin, elastin
- Functional proteins
- Proteins that perform a chemical function in organisms
- Usually used for initiate or sustain chemical reactions
- Examples include hormones, enzymes
- Structural polysaccharides
- They are carbohydrates that provide structural support to cells and tissues
- Examples include cellulose, chitin
- Storage polysaccharides
- Carbohydrates that are used for storing energy
- Eg: starch, glycogen
- Nucleic acids
- Nucleic acids are macromolecules composed of chains of nucleotides
- Nucleic acids are universal in living beings, as they are found in all plant and animal cells
- Eg: DNA, RNA
TYPES OF SYNTHETIC POLYMERS
- Thermoplastics
- Thermoplastics are plastics that turn into liquids upon heating
- Also known as thermosoftening plastic
- Thermoplastics can be remelted and remoulded
- Eg: polyethylene, Teflon, nylon
- Recyclable bottles (such as Coke/Pepsi) are made from thermoplastics
- Thermosetting plastics
- Thermosettings plastics are plastics that do not turn into liquid upon heating
- Thermosetting plastics, once cured, cannot be remoulded
- They are stronger, more suitable for high-temperature applications, but cannot be easily recycled
- Eg: vulcanized rubber, bakelite, Kevlar
- Elastomers
- Elastomers are polymers that are elastic
- Elastomers are relatively soft and deformable
- Eg: natural rubber, synthetic polyisoprene
IMPORTANT NATURAL POLYMERS AND THEIR APPLICATIONS
| Polymer | Application | Notes | |
| Collagen | Connective tissue Gelatine (food) | Most abundant protein in mammals | |
| Keratin | Hair, nails, claw etc | ||
| Enzymes | Catalysis | ||
| Hormones | Cell signalling | ||
| Cellulose | Cell wall of plants Cardboard, paper | Most common organic compound on Earth | |
| Chitin | Cell wall of fungi, insects | ||
| Starch | Energy storage in plants | Most important carbohydrate in human diet | |
| Glycogen | Energy storage in animals | ||
| DNA | Genetic information | ||
| RNA | Protein synthesis | ||
IMPORTANT SYNTHETIC POLYMERS AND THEIR APPLICATIONS
| Polymer | Developed by | Constituent elements | Application | Notes |
| Parkesine | Alexander Parkes (Britain, 1855) | Cellulose | Plastic moulding | First man-made polymer |
| Bakelite | Leo Baekeland (USA, 1906) | Phenol and formaldehyde | Radios, telephones, clocks | First polymer made completely synthetically |
| Polyvinylchloride (PVC) | Henri Regnault (France, 1835) | Vinyl groups and chlorine | Construction material | Third most widely used plastic |
| Styrofoam | Ray McIntre (USA, 1941) | Phenyl group | Thermal insulation | Brand name for polystyrene |
| Nylon | Wallace Carothers (USA, 1935) | Amides | Fabric, toothbrush, rope etc | Family of polyamides First commercially successful synthetic polymer |
| Synthetic rubber | Fritz Hoffman (Germany, 1909) | Isoprene | Tyres, textile printing, rocket fuel | |
| Vulcanized rubber | Charles Goodyear (USA, 1839) | Rubber, sulphur | Tyres | Vulcanized rubber is much stronger than natural rubber |
| Polypropylene | Karl Rehn and Guilio Natta (Italy, 1954) | Propene | Textiles, stationary, automotive components | Second most widely used synthetic polymer |
| Polyethylene | Hans von Pechmann (Germany, 1898) | Ethylene | Packaging (shopping bags) | Most widely used synthetic polymer |
| Teflon | Roy Plunkett (USA, 1938) | Ethylene | Cookware, construction, lubricant | Brand name for polytetrafluoroehtylene (PTFE) Very low friction, non-reactive |
DEGRADATION OF POLYMERS 
Ozone cracking in natural rubber tubing
Ozone cracking in natural rubber tubing
- Degradation of polymers can be desirable as well undesirable: desirable when looking for biological degradation, undesirable when faced with loss of strength, colour etc
- Polymer degradation usually occurs due to hydrolysis of covalent bonds connecting the polymer chain
- Polymer degradation can happen because of heat, light, chemicals and galvanic action
- Ozone cracking is the cracking effect of ozone on rubber products such as tyres, seals, fuel lines etc. Usually prevented by adding antiozonants to the rubber before vulcanization
- Chlorine can cause degradation of plastic as well, especially plumbing
- Resin Identification Code is the system of labelling plastic bottles on the basis of their constituent polymers. This Code helps in the sorting and recycling of plastic bottles
- Degradation of plastics can take hundreds to thousands of years
Biodegradable plastics
- Biodegradable plastics are plastics than can break down upon exposure to sunlight (especially UV), water, bacteria etc
- Biopol is a biodegradable polymer synthesized by genetically engineered bacteria
- Ecoflex is a fully biodegradable synthetic polymer for food packaging
Bioplastics
- They are organic plastics derived from renewable biomass sources such as vegetable oil, corn, starch etc
Oxy-biodegradable plastics
- Plastics to which a small amount of metals salts have been added
- As long as the plastic has access to oxygen the metal salts speed up process of degradation
- Degradation process is shortened from hundreds of years to months
BIOLOGY: GENETIC DISORDERS
About genetic disorders
Huntington's disease is inherited in the autosomal dominant fashion
- Genetic disorders are disorders that are passed on from generation to generation
- They are caused by abnormalities in genes or chromosomes
- Some genetic disorders may also be influenced by non-genetic environmental factors. Eg: cancer
- Most genetic disorders are relatively rare and only affect one person in thousands or millions
- To recollect, males have XY chromosome pairs while females have XX pairs
Single Gene Disorders
- Single gene disorders result from the mutation of a single gene
- They can be passed onto subsequent generations in multiple ways
- Single gene disorders include sickle cell disease, cystic fibrosis Huntington disease
Multiple gene disorders
- Multiple gene disorders result from mutation on multiple genes in combination with environmental factors
- They do not have a clear pattern of inheritance, which makes it difficult to assess risk of inheriting a particular disease
- Examples include heart disease, diabetes, hypertension, obesity, autism
TYPES OF SINGLE GENE GENETIC DISORDERS
- Autosomal dominant
Sickle cell disease is inherited in the autosomal recessive pattern
- Only one mutated copy of the gene is necessary for inheritance of the mutation
- Each affected person usually has one affected parent
- There is a 50% chance that the child will inherit the mutated gene
- Autosomal dominant disorders usually have low penetrance i.e. although only one mutated copy is needed, only a small portion of those who inherit that mutation will develop the disorder
- Eg: Huntington’s disease, Marfan syndrome
- Only one mutated copy of the gene is necessary for inheritance of the mutation
- Autosomal recessive
- Two copies of the gene must be mutated for a person to be affected
- An affected person usually has unaffected parents who each have one mutated gene
- There is a 25% chance that the child will inherit the mutated gene
- Eg: Cystic fibrosis, sickle cell disease, Tay-Sachs disease, dry earwax, Niemann-Pick disease
- Two copies of the gene must be mutated for a person to be affected
- X-linked dominant
- X-linked dominant disorders are caused by mutations on the X chromosome
- Males and females are both affected by such disorders. However, males are affected more severely
- For a man with a X-linked dominant disorder, his sons will all be unaffected (since they receive their father’s Y chromosome) while his daughters will all be affected (since they receive his X chromosome)
- A woman with a X-linked dominant disorder has a 50% chance of passing it on to progeny
- Eg: Hypophosphatemic rickets, Rett syndrome, Aicardi syndrome
- X-linked recessive
X-linked recessive with a carrier mother
- Caused by mutations on the X-chromosome
- Males are affected more frequently than females
- The sons of a man affected by a X-linked recessive disorder will not be affected, while his daughters will carry one copy of the mutated gene
- The sons of a woman affected by a X-linked recessive disorder will have have a 50% chance of being affected by the disorder, while the daughters of the woman have a 50% chance of becoming carriers of the disorder
- Eg: colour blindness, muscular dystrophy, hemophilia A
- Y-linked disorders
- Caused by mutations on the Y chromosome
- Y chromosomes are present only in males
- The sons of a man with Y-linked disorders will inherit his Y chromosome and will always be affected while the daughters will inherit his X chromosome and will never be affected
- Eg: male infertility
- Mitochondrial disorders
- These disorders are caused by mutations in the mitochondrial DNA
- Only mothers can pass on mitochondrial disorders to children, since only egg cells (from the mother) contribute mitochondria to the developing embryo
- Eg: Leber’s Heriditary Optic Neuropathy
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