Food contamination refers to the presence of harmful chemicals and microorganisms in edible items which cause illness. It can come from various sources -Agrochemicals and environmental. The first category is chemicals used by farmers and employees in animal husbandry to further their output, its appearance and maturity cycle. They include pesticides, insecticides, rodenticides, fertilizers and in animals, it includes drugs like nitrofuran and fluoroquinolones. Most of these chemicals are toxic and pose health hazards. Some of them like organophosphates and carbamates present in these fertilizers can affect the nervous system where as others may cause irritation to the skin and eye allergy. Some pesticides affect the hormonal or endocrine system in the body as well.
Now looking at the environmental contaminants, i.e. those chemicals that are present in the food due to the environment where the food is grown, stored, packaged, processed, consumed or in any manner that it may come in contact with contains them. The physical contact with the external environment which is polluted results in food contamination. The sources of contaminants can be radionuclides in air, mercury in water, nitrates, dioxins in soil, tin and lead in packaging material, copper in cooking equipment, petroleum and chemicals in consumer products and various other naturally occurring toxins like mycotoxins. These contaminants can have varied effect on human body. Dioxins can lead to skin lesions, impairment of immune system, reproductive system and nervous system. Mercury acts as a neurotoxin and effects the rain and the nervous system. The presence of chemicals in food like tin, lead, aluminium leads to suppressing the human immune system, depressing the white cell response and leading to brain problems like Alzheimer's. Petroleum chemicals can cause attritional effects to the nervous system and immune system and lead to problems like cancer.
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Besides these, other contaminants like hair, cloth fires can lead to problems like choking and vomiting. Also, the contaminants present on these external materials like hair and cloth fires can cause other health problems.
Name and distinguish the group of bacteria called Cocci. Give examples of characteristics of each.
Cocci (from Greek kókkos, grain, seed) bacteria are groups of bacteria having roughly a circular shape. They can take generally 5 forms with their characteristics in braces:
Monococcus (occur singly)
Diplococci (occur in pairs)
Tetracocci (occur in groups of four)
Streptococci (occur in the form of a filament)
Staphylococci (occur in the form of sheets)
Discuss the group of bacteria called bacillus. Give examples, structure, characteristics and location.
The group of bacteria called bacillus (from Latin baculus, stick) are the rod-shaped bacteria. Following structural forms are commonly observed with respective examples, characteristics and locations:
Agrobacterium tumefaciens (causes crown gall disease in plants)
Lactobacillus bulgaricus (Used in Yogurt, Cheese)
Bacilli in chains
Bacillus anthracis (Causes anthrax)
Mycobacterium tuberculosis (Causes TB)
Bacilli with spores
Bacillus subtilis (Soil bacteria)
Bacillus thuringensis (bactericidal in nature)
Clostridium welchii (Causes gangrene)
Clostridium tetani (Causes lockjaw/tetanus)
Bacilli in flagellated form
Escherichia coli (lies in human gut/colon)
Salmonella typhi (Causes typhoid, food poisoning)
Shigella spp (Causes bacillary dysentery)
What are the various types of immunity and give examples? Include in the discussion humeral and cellular immunity.
Immunity is the resistance of human body to become infected due to an exposure to a microorganism or parasite. The various types of Immunity are as follows:
Immunity acquired actively, as when exposure to a vaccine induces formation of antibodiesÂ that mark foreign substances for destruction. Example - DPT immunization, Exposure to an upper respiratory virus etc.
Immunity transferred to the patient "passively", rather than developed by the patient himself; usually in the form of antibody protein substances. Example - Maternal immunity to infections transferred via bloodstream prior to delivery or in breast milk etc.
Immunity produced by the T-cell lymphocyteÂ white cells of the body; basically, T-cells remember exposure, and tell the B-cells to make the antibodies. Example - Life-long immunity to chickenpox after childhood infection etc.
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Immunity produced by the B-cell lymphocyte white cells of the body; B-cells produce antibodies ("humors") upon direction from the T-cells. Example - Expectant mothers are tested for their antibody levels to rubella to determine if they are immune etc.
It is the protection of any one individual from a disease by the fact that everyone around is immune to the disease and thus never exposed directly. Example - Herd immunity is the principal behind rubella immunization: if all the kids who could possibly transmit the disease to expectant mothers are immune, the expectant mothers will be protected even if their antibodies are low etc.
Also, on a broader level, immunity can be categorized as:
Innate ability is the natural immunity of an individual that act as barriers or eliminators of a wide range of pathogens. Adaptive immunity is developed when a new disease is encountered and the body is able to develop pathogen-specific immunity.
Adaptive immunity comprises of two major types depending on how that immunity was introduced.
Naturally acquired immunity develops through contact with a disease-causing agent, when there was no intentional contact, whereas artificially acquired immunity develops only through specific intentional actions such as vaccination.
Both these categories can be further subdivided depending on whether immunity is induced in the host or transferred from an immune host passively.
Discuss the tests used in water analysis and the outcome of these tests if they are positive.
Name the various gases in the atmosphere and indicate their percentages. Include the functions of each.
Functions of major gases are as follows:
Nitrogen is widely used to replace air where there might be a risk of explosion. It is also used in food storage units to prevent deterioration of food. Liquid nitrogen (196Â° C) is used in cold storage. Liquid nitrogen is very cheap because it is a by-product of the production of liquid oxygen. The addition of nitrogen to the Earth's surface soils and various water bodies' supplies much needed nutrition for plant growth.
Oxygen is used in respiration and combustion, and also has uses in industry: steel-making, flame-welding etc.
Argon is used in light bulbs and helps to produce an inert atmosphere for welding etc.
Carbon dioxide is used in fire extinguishers, fizzy drinks etc.
Neon is used in to illuminate red lights such as shop displays and advertisements.
Helium is much lighter than air and is used in airships (Although it is more expensive than hydrogen, it is non-flammable). Deep sea divers also use a mixture of oxygen and helium to avoid decompression sickness.
Methane is the principal component in the natural gas and also, used in several industrial chemical processes. It may be transported as a refrigerated liquid (liquefied natural gas, or LNG).
Krypton is used in some high-powered lights.
Hydrogen is extensively used in physics and engineering. It is used as a shielding gas in welding, isolating the weld site from atmospheric gases. Because of its high thermal conductivity, hydrogen is used for cooling rotors in electrical power generators. Liquid hydrogen is cooler than 14 K and hence, is used for research in cryogenics and superconductivity.
Nitrous oxide is commonly used for surgical, food service and recreational purposes. It can be used as an anesthetic for dental surgery. Nitrous oxide chargers are also used to whipping cream and hence used in ice-cream industries. Nitrous oxide is sometimes used in auto racing to speed combustion.
Xenon is used in stroboscopes and various special types of lighting.
Ozone is used for water treatment (both drinking and waste), ultra-pure and de-ionized water systems, fish hatcheries-aquaculture, air treatment, pulp and paper (bleaching and disinfection) and industrial applications.
Discuss in detail the entire spectral range both visible and invisible citing examples of each in your discussion.
Infrared: These wavelengths are longer than visible range up to 1 mm (often measured in microns or micrometers, symbol Î¼m). These radiations can be felt as heat radiated: example - standing in front of fire.
Visible: These wavelengths are between 400 nm (violet light) and 700 nm (red light). The solar radiations are most strongly in this range, and the atmosphere does not absorb it. Visible light may cause chemical reactions (example vision and photosynthesis) but generally does not.
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Ultraviolet: These wavelengths are shorter than visible range down to about 10 nanometers. A UV photon has sufficient energy to damage DNA molecules. If objects are hotter than the sun (example -few massive young stars), they radiate in the UV range. Bees have the ability to see in near UV range and hence it is inferred that flowers have UV colors to attract them.
X rays: These wavelengths lie from several nm to 10 pm. X rays with wavelengths comparable to atomic dimensions are used to find out the structure of crystals. Their energies are enough to ionize atoms and to destroy chemical bonds. They can also be produced by colliding high energy electrons into metal targets: these radiations are used to treat cancer.
Gamma rays: Wavelengths are less than about 10 pm. Gamma rays have very high energy, and often come from deep space, sometimes in bursts from cataclysmic cosmic events, such as the collapse or collision of stars.
What does the audiometer report? Give ranges of hearing. Briefly report the anatomy and function of the ear.
An audiometer is a device used for evaluating hearing loss. An audiometer helps in preparing an audiogram that covers limited range 100Hz to 8000Hz (8Â kHz) which is most important for clear understanding of speech, and they plot the threshold of hearing relative to a standardized curve that represents 'normal' hearing, in dBHL. Audiograms have frequency in hertz (Hz) set on the horizontal axis, most commonly on a logarithmic scale, and a linear dBHL scale on the vertical axis. Normal hearing is classified as being between -10dBHL and 15dBHL, although 0dB from 250Hz to 8 kHz is considered as 'average' normal hearing.
In humans the audible range of frequencies is usually said to be 20 Hz to 20 kHz (20,000 Hz).
The ears are sensory organs that comprise auditory system, involved in the detection of sound, and the vestibular system, involved with maintaining body balance/ equilibrium.
The ear is divided anatomically and functionally into three regions: the external ear, the middle ear, and the inner ear. All three regions are involved in hearing but only the inner ear functions in the vestibular system.
Anatomy of the Ear
The external ear (or pinna, the part you can see) serves to protect the tympanic membrane (eardrum), as well to collect and direct sound waves through the ear canal to eardrum. About 1Â¼ inches long, the canal contains modified sweat glands which secrete cerumen, or earwax.
The middle ear, separated from the external ear by the eardrum, is an air-filled cavity (tympanic cavity) carved out of the temporal bone that connects to the throat/nasopharynx via the Eustachian tube. This connection makes the ear susceptible to infection (otitis media). The eustachian tube acts to equalize air pressure on both sides of the eardrum. Normally the tube walls are collapsed. The tube to allow air in or out, as needed for equalization during swallowing and chewing actions.
The three linked, movable bones called "ossicles" convert the sound waves striking the eardrum into mechanical vibrations and are the smallest bones in human body.
The inner ear consists of a maze of fluid-filled tubes, that run through the temporal bone of the skull. The bony tubes, the bony labyrinth, are filled with perilymph fluid. Within this bony labyrinth is a second series of cellular tubes, called the membranous labyrinth, filled with fluid known as endolymph. This membranous labyrinth contains actual hearing cells, the hair cells of the Corti. There are three major sections of the bony labyrinth:
The front portion, the snail-shaped cochlea, helps in hearing
The rear part, the semicircular canals, maintains balance
The vestibule interconnects cochlea and semicircular canals, containing the sense organs, utricle and saccule, responsible for balance.
What is meant by desalinization of water? Discuss its steps.
Desalination is a process by which salty water can be made drinkable. Important process steps in desalination plants are:
Pre-Treatment precedes all the important treatment steps that have to be done before the reverse osmosis treatment. This helps in lengthening plant life time and minimizing chemical cleaning and membrane replacement.
The reverse osmosis process can be build with one/two passes, depending on the product water specifications and salinity and temperature of the seawater. In most cases, one pass is sufficient to reach the drinking water standards, especially regarding boron content (1 mg/L). Though, it should be passed through a second filter to reach WHO boron guideline (0.5mg/L).
The energy recovery device determines the plant electrical costs and is dependent on the local energy costs and environment policies.
Post-treatment and/or polishing steps are needed for conditioning the water after the reverse osmosis membrane treatment for making it suitable for a specific purpose.
Brine disposal can be an economical and environmental issue in some areas where the local ecosystem is sensitive to local seawater salinity increase.
Combine the following terms into a discussion of sound: pitch, dB, loudness, Hz, amplitude and ultrasound.
Sound is a wave which is an oscillation of pressure transmitted through a medium composed of frequencies within the range of hearing and at a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by these vibrations.
Pitch differentiates between low and high sounds and is dependent on the frequency of the sound wave. Frequency is the number of wavelengths per unit of time and is measured in Hz. Amplitude or height of sound waves is a measure of energy. A higher energy wave has higher amplitude.
Pressure or the amplitude of sound is defined as loudness. Loudness of the sound wave is measured in decibels, dB.
When the frequency of a sound is too high be processed by human ears, they are called Ultrasonic sound waves.
Organize the following into a logical discussion of radiation: atomic number, mass number, isotope, electron, and neutron.
Atomic Number of an element is defined as the no. of protons in an atom's nucleus.
Mass Number of an element is defined the sum of the number of neutrons and protons in the nucleus of an atom.
Isotopes are two or more atoms which have the same atomic number, thus constitute the same element, but are different in the mass number. Isotopes of a given element have the same number of protons but differing numbers of neutrons.
Electron is a fundamental particle with a unit electrical charge and a mass 1/1837 of a proton. Electrons bound the atom's positively charged nucleus and decide the atom's chemical properties.
Neutron is a fundamental particle of an atom with no electrical charge and has about the same weight as a proton.