eChapters

Ultraviolet Radiation : Ultraviolet radiation (UV) is one form of radiant energy coming from the sun. The sun emits a range of energy known as the electromagnetic spectrum. The various forms of energy, or radiation, are classified according to wavelength (measured in nanometers (nm) where one nm is a millionth of a millimeter). The shorter the wavelength, the more energetic is the radiation. In order of decreasing energy, the principal forms of radiation are gamma rays, X-rays, UV (ultraviolet radiation), visible light, infrared radiation, microwaves, and radio waves. Ultraviolet, which is invisible, is so named because it occurs next to violet in the visible light spectrum. Ultraviolet radiation contains the wavelengths between 30 and 400 nm. The UV band is divided into three sub-bands in regard to its biological impacts :

Taiga (Boreal Forest) : The open northern part of the coniferous forest. Taiga also refers to sub-polar climate.
 
Tail Wind : The wind that assists the further movement of an object by blowing in the same direction in which the object is actually moving.
 
Tangent Arc : An arc of light tangent to a halo. It forms by refraction of light through ice crystals.
 
Tcu : An abbreviation sometimes used to denote a towering cumulus cloud (cumulus congestus).
 
Teleconnections : A linkage between weather changes occurring in widely separated regions of the world. 

Saffir-Simpson Scale : A scale relating a hurricane’s central pressure and winds to the possible damage it is capable of inflicting.
 
Sand Storm : An ensemble of particles of dust or sand energetically lifted to great heights by a strong and turbulent wind.
 
Santa Ana Wind : A warm, dry wind that blows into southern California from the east off the elevated desert plateau. Its warmth is derived from compressional heating.
 
Satellite Imagery : Images formed from data collected by a weather satellite that reveal visual information on the nature of the atmosphere such as the flow of water vapour, the development and movement of weather systems, or the distribution of the temperatures of cloud tops or the earth’s surface.

Saturated Adiabat : Any statistically valid thermodynamic diagram on a graph related to adiabatic change under saturated conditions of an air parcel. 

Rabi : The winter crop season in India from November to April. Main crops grown in rabi comprise wheat, mustard, etc.

Rad : The ‘rad’ is the unit of radiation dose and is defined as the total absorbed dose of 100 ergs of energy per gram of tissue in a unit time.

Radar : An electronic instrument used to detect objects (such as falling precipitation) by their ability to reflect and scatter microwaves back to a receiver. The radar is used for detecting tropical cyclones and monitoring their course as they approach the coast.
 
Radar sonde : A system in which both meteorological and wind data may be obtained, as in radiosonde.

Radiance : Radiant flux per unit area per unit solid angle. Radiance has unit of watts per meter per meter per steradian. The radiance of a perfectly diffuse surface (Lambertian) is independent of the viewing angle.

Q₁₀ : The number of times the rate of a process (physical, chemical or physiological) increases with a 10^ºC increase in temperature. If the rate of the process is doubled Q₁₀ is 2. Q₁₀ for respiration is 2 to 3.

Quantum : Unit of energy emitted by a photon.

Quantum Flux Density : The number of quanta from a source, incident on a unit area of a small surface situated in a perpendicular direction.

Quantum Irradiance : The number of quanta from a source incident on a unit area of a surface. This differs from the ‘quantum flux density’ as far as direction is concerned.

Pan Coefficient (Kp) : It is the ratio between reference evapotranspiration (ET_o ) and water loss by evaporation from an open water surface of a pan (E_pan ).
    K_p = ET_o / E_pan

Peat soil : An organic soil containing more than 50 per cent organic matter.

Pan Evaporation : is the value of evaporation from an open pan evaporimeter (usually from standard USWB, class ‘A’ pan evaporimeter) during a day or specified period at a place.

Parcel : A volume of air small enough to contain uniform distribution of its meteorological properties and large enough to remain relatively self-contained and respond to all meteorological processes.

Oasis effect : Vertical energy transfer from the air to the crop. It is the exchange of heat between a growing crop and hot air whereby air over the crop is cooled.
 
Observation : In meteorology, the evaluation of one or more meteorological elements, such as temperature, pressure, or wind, that describe the state of the atmosphere, either at the earth’s surface or aloft. An observer is one who records the evaluations of the meteorological elements.
 
Occluded Front : Also known as an occlusion, it is a complex front formed when a cold front overtakes a warm front. It develops when three thermally different air masses conflict. The type of frontal boundary they create depends on the manner in which they meet.

Nanometre : The unit of length specifically applied to wavelengths of radiation. This is equal to ten Angstrom units or 10-9 meters.

Net Assimilation Rate (NAR) : It is increase in dry weight of plant per unit leaf area per unit time. NAR is calculated from the following equation : 

Macroclimate : It deals with the study of atmosphere over large areas of the earth and with the large scale atmospheric motions that cause weather. It helps in forecasting weather. OR Climate of a continent or over the complete globe.
 
Macrometeorology : A branch of meteorology concerned with the study of large scale meteorological phenomena over a continent or the entire globe.

Macroscale : The meteorological scale covering an area ranging from the size of a continent to the entire globe.
 
Marine climate : Almost similar and on many occasions used as a synonym to maritime climate. The climate is basically influenced by adjacent seas and oceans.
 
Maritime Climate : The climate experienced in areas and regions near the oceans and seas. It is characterised by hot dry summers and mild wet winters. The diurnal variations of temperature are small and air is with high relative humidity.

Lake Effect : The effect of any lake in modifying the weather and climate along its shore and inland which depends on the size of the lake. In some areas such as the North American Great Lakes, lake effect refers to snowfall generated by the lake on the downwind shore.

Lake Effect Snowfall : Snowfalls along the lee shore of a lake or downwind some distance from the shore caused by the modification of cold, subfreezing air by the relatively warmer lake water. The intensity of the lake-effect snowfall depends upon several factors : the temperature contrast between the lake surface and the air passing over it, the over-water distance the air has traversed (the fetch), and the regional weather situation. 

Katabatic Wind : Downslope gravitational flow of the colder, denser air beneath the warmer, lighter air results and comprises the katabatic wind. It is also known as the drainage wind or mountain wind.

Kelvin Temperature Scale : An absolute temperature scale in which the zero point is absolute zero. The scale is based upon the triple point of pure water and the size of the degree is same as on the celsius scale. So the 273.16 K = 0°C. That means the freezing point of water is 273.16 K and boiling point of water is 373.16 K, etc. This is more commonly called as the absolute.

January Thaw : A period of mild weather, usually following a cold spell, which often occurs in late January in the eastern regions of North America, particularly around the Great Lakes region, New England and the Canadian Maritime Provinces. The thaw is associated with a strong flow of warm air northward from the Gulf of Mexico on southerly winds on the back of a high pressure system.

Jet Stream : A relatively narrow band of high-speed winds, generally greater than 50 knots (57 mph or 93 kmph), found in the upper troposphere above regions of strong horizontal temperature contrasts such as fronts. The major jet streams are the subtropical jet and the polar jet stream.

Joule : The unit of work or energy. In mechanical systems, this is the work done when a force of one Newton displaces the point of application by a distance of one metre in the direction of force. In electrical systems, a joule is the equivalent of moving one coulomb through a potential difference of one volt. One joule is equal to one watt per second

Ice Caps : A perennial ice/snow cover over an extensive area of land or sea, found only around the two geographic poles.

Ice Columns : Ice crystals resembling stubby pencils rather than the delicate branched snowflake shape. Columns typically form in the temperature ranges -5° C to -8° C (23° F to 18° F) and below -25° C ( -13° F). They are long in comparison to their hexagonal cross-section.

Ice Crystals : 1) Hexagonal (6-sided) crystals that form upon freezing of water, may be in one of several shapes : stars, needles, plates, columns or combinations of these forms. 2) Precipitation in the form of slowly falling, singular or unbranched ice needles, columns, or plates, may be called diamond dust.

Ice Fog : Fog composed of minute ice particles that occur in very low temperatures (typically - 30°C or - 22°F & below) under clear, calm conditions in the polar latitudes. 

Haboob : Sudanese name for duststorm or sandstorm with strong winds that carry small particles of dirt or sand into the air, particularly severe in areas of drought.
 
Habitat : A place where a plant or a community of plants or a crop is existing.

Hadley Cell : A mean thermally driven atmospheric circulation in which warm air rises and flows away from the equator at upper level and descends at the tropics. Wind moves from the tropics back to equator poleward. In many cases this term is also referred to as ‘Hadley circulation’.

Hail : Solid precipitation in the form of balls or pieces if ice (hailstones) with diameter ranging from 5 mm to 50 mm or even more. 
Hailstorm : A storm, often too long and severe, consisting largely of hail or frozen rain drops ranging in diameter from 5 mm to 10 mm or more. 

Gale : Wind of force 8 or above blowing continuously and damaging trees, houses etc.

General Circulation : The average general distribution of wind in motion on the Earth. This general circulation includes the scientific description of atmospheric dynamics not only statistically but also from the point of view of physics. The global wind systems like westerlies, trades, etc., are the examples of general circulation.

General Circulation Model : At present, there are different models in vogue, to explain the general circulation of the atmosphere. If the general circulation is modelled in a three dimensional procedure, then it is known as a general circulation model.

Geopotential : The potential energy per unit mass of a body due to the earth’s gravitational field referred to an arbitrary zero.

Fahrenheit Temperature Scale : A temperature scale having freezing point of water as 32 degrees and the boiling point equal to 212 degrees at standard atmospheric pressure. 
    Degree F = (Degree C x 1.8) + 32
    Degree C = (Degree F - 32)/1.8

Fair Weather : Fine sky. Appearance of cirrus or cumulus cover is in fair amount but not covering the sky totally.

Fetch : The distance over which a wind of nearly constant direction has blown, usually over a consistent surface such as water or a forest or a field. Most often the fetch is applied to a distance over water and used to determine the height of wind-generated waves.
 
Fine Weather : A blue and cloudless sky. Even if a few cirrus clouds are noticed, they do not express any vertical development.

Earthquake : A sudden, transient motion or trembling of the earth’s crust, resulting from the waves in the earth caused by faulting of the rocks or by volcanic activity.
    
Easterlies : Usually applied to the broad patterns of persistent winds with an easterly component, such as the easterly trade winds.

Easterly Wave : A wave like disturbance, of the tropospheric easterlies of low latitude. These are synoptic scale and occur in the region of intertropical convergence zone.

Ecoclimate : Climate under crop canopy is called eco-climate. 

Edaphic : A term pertaining to the influence or relationship of soil or other similar media to plant growth in contrast to atmospheric influences. 

Daily Maximum Temperature : As per the IMD guidelines, the maximum temperature recorded in a 24 hour period at any given place or location.

Daily Mean Temperature : The average of the values observed during a day (at any regular intervals or maximum and minimum) of temperature.

Daily Minimum Temperature : As per the IMD guidelines, the minimum temperature recorded in a 24 hour period at any given place or location.

Daily Range of Temperature : The range of temperature (between maximum and minimum) recorded as per IMD guidelines in 24 hour period.

C3 Plant : A plant in which the first product of CO₂ fixation is the 3-carbon compound; phosphoglyceric acid and is comparatively photosynthetically less efficient than C4 plants e.g. wheat, rice, barley etc. 
C4 Plant : A plant in which the first product of CO₂ fixation is the 4-carbon compound oxalo acetic acid (OAA) and is photosynthetically more efficient than C3 plants e.g. sugarcane, maize etc.
Calibration : Calibration with respect to models refers to the adjustments made to model parameters so as to give the most accurate comparison between simulated results and results obtained from field measurements. 
Calm : Absence of appreciable wind : On the Beaufort Scale of wind force calm is accorded the figure 0 and has a wind speed equivalent or less than 1 knot.

Back-Door Cold Front : A front moving south or southwest along the Atlantic seaboard of the United States.

Backing : A change in wind direction in a counterclockwise manner in the Northern Hemisphere and a clockwise manner in the Southern Hemisphere.
 
Ball Lightning : A rare form of lightning that may consist of a reddish, luminous ball of electricity or charged air.
 
Banner Cloud : A cloud extending downwind from an isolated mountain peak, often on an otherwise cloud-free day.
 
Bar : A unit of pressure, (usually the atmospheric pressure on) one is equivalent to a pressure of one million dynes per centimeter square one hundred kilopascals; 29.53 inches or 750 millimeters of mercury at zero degree Celsius.

Abiotic Factors : These are physical, chemical and other non-living components of the environment such as light, temperature, moisture, nutrients and other edaphic factors.
 
Absolute Drought : It is defined as a period of consecutive days none of which had rainfall of 2.5 mm or more OR when actual rainfall is less than twice the mean deviation OR actual rainfall is less than half the normal weekly rainfall.
 
Absolute Growth Rate : The rate of increase in size of a growing plant (or part of it) in a given time under specific growing conditions.

Absolute Humidity : Absolute humidity is defined as the actual mass of water vapour present in the given volume of air. It is measured in grams per cubic meter or in terms of partial pressure of water vapour in air in mb or mm.

It has been well established that the risk of health problems rises as the amount of radiation exposure increases. All types of radiation produce changes in the living tissues. The resultant cellular injury causes physiological and pathological changes leading to “Radiation sickness”. The radiation effects may be somatic or genetic. Somatic effects are harmful to a person in his lifetime whereas genetic effects affect generations. Radiation may cause changes in complex molecular systems of living cells, primarily in following two ways :- 

Radiation therapy is the delivery of ionizing radiation to a specific body areas with the goal of obtaining maximum lesion control with minimal complication. Radiation therapy is based on the fact that ionizing radiation is lethal to the cells, particularly rapidly dividing ones. Normal cells in the irradiated area may be as sensitive to ionizing radiation as tumor cells. Therefore, the normal tissue response limits the amount of ionizing radiation that can be tolerated by the patient. Effective use of radiation therapy requires an understanding of the physics of the radiation used and normal cellular and tumor biology as it relates to radiation therapy as well as an appreciation of the clinical application of veterinary radiation therapy.

Diagnostic imaging refers to technologies that doctors use to look inside the body of the patient for clues about any disease condition. A variety of machine and techniques can create pictures of the structures and activities inside the patient body. In India, some of these modalities like digital radiography and ultrasonography are being used at some of the veterinary colleges and reaseach institutes while at some places some of the veterinarians have access to the techniques like computed tomography (CT) and magnetic resoncace imaging (MRI) of the human hospitals. So this is the responsibility of the scientists and researchers engaged in the advancement of the diagnostic imaging and the manufacturing companies to make these facilities cot effective so that an animal of a common man can be benefited with these facilities.

Radiology has been an important diagnostic modality in exotic animals and birds (includes rodents, reptiles and fish). The radiographic equipment needed for radiography of exotic animals and birds is basically the same to that used for domestic animals. A high-milliamperage (mA) X-ray machine, having 200- or 300 mA unit is recommended to allow the use of a short exposure time (1/40 seconds) or less are preferred. Maximum kilovoltage (kVp, 40-75) is less important for avian and exotic radiography than for domestic animal radiography. As with other species, at least two radiographic views at 900 angles to each other are recommended. However, restraining and knowledge of radiographic anatomy of different species of exotic animals and birds are the prerequisite for the modality. Restrain and immobilization:

Contrast radiography: The radiographic technique which employ the use of contrast media to identify a soft tissue structure or an organ and pathological findings which may be difficult or even impossible to visualize clearly in plain films due to lack of contrast with surrounding tissue is known as contrast radiography. This is a special radiographic techniques/procedures may be required to supplement or confirm the information obtained from plain or survey radiography. 
The substances used for this purpose is called contrast agents/medium/materials.

Orthopaedic Radiography
 
Radiography as an aid to diagnosis the orthopaedic cases has become an integral part of every modern hospital. This technique may also be helpful in detecting some previously unrecognized lesions in the area radiographed.

The radiologist must be aware of the radiological anatomy of part being examined, and of its normal variation with age, species and breed. The anatomical features which can be appreciated in a radiograph are:

Artifacts are any unwanted radiographic densities in the form of blemishes arising from improper handling x-ray film, exposure, processing, housekeeping or setting up a technique for an examination. Artifacts will reduce the overall quality of the radiograph and in certain cases may nullify its diagnostic outcome. An idea about the possible errors is desirable in order to adopt corrective measures.

After the patient has been radiographed, the exposed X-ray film is processed to produce the consistent quality radiographs. Film processing can be manually, or use an automatic film processor.  Manual film processing is a multi-stage process involving five basic steps in processing X-ray film: 
    i)    Developing 
    ii)    Rinsing 
    iii)    Fixing
    iv)    Washing
    v)    Drying. 

The X-ray film is the major element that record the image of part exposed with X-rays. Although the situation is changing with the introduction of new technologies in recent years. The film can be exposed by the direct action of X-rays, but more commonly the X-ray energy is converted into light by intensifying screens and this light is used to expose the film. The X-ray film is somewhat similar to photographic film in its basic composition. However unlike photographic film, the light (or radiation) sensitive emulsion is usually coated on both sides of the base of X- ray film so that it can be used with intensifying screens. Because of its importance to medicine, X-ray film is manufactured with consistent uniformity and quality, which facilitates standardization of exposure and processing.

One of the most important pieces of information in the field of  X-rays is a radiographic technique chart. If one select exposure factors from a good rating chart, consistent radiographic examinations of diagnostic quality will be obtained. In addition, there will be a saving of X-ray films because waste from repeated exposures will be avoided.

There are several types of techniques chart that can be formulated, each type must be formulated with the goat of maximum potential of a particular X-ray machine. Perhaps the most popular type of technique chart used by veterinarians is a variable kilovoltage technique chart. A variable mA second chart is probably more appropriate for the most powerful X-ray machine. However, combination of variable kilovoltage and mAs technique chart is best. Such charts take into consideration the need to adopt a technique chart for different body systems, such as a thoracic and abdominal study, as well as examination involving the musculoskeletal system. The principle of how to prepare a variable kilovoltage technique chart along with an example of such a chart is given.

A diagnostic radiograph is defined as one showing the tissues adequately penetrated, sharply outlined, and the variations in tissue opacity sufficiently demonstrated. An ideal diagnostic radiograph should have excellent detail, correct density and proper scale of contrast. The sharpness of the image determines the detail or definition of an image. There are two factors in radiographic quality control, viz: photographic and the geometric effect.  Density, contrast and detail are photographic aspects of radiographic quality. Detail and distortion are geometric aspects of radiographic quality. Because a radiograph is a two-dimensional (2-D) image of a three-dimensional (3-D) object, the appearance of a radiographic image varies with the patient’s orientation in relation to the primary X-ray beam. 

The radiographic appearance of various tissues is influenced by a number of factors which determine the character of X-rays.  Various exposure factors control the radiographic dentsity, detail and contrast: milliamperage (mA), time (sec), kilovoltage (kV), focal spot/film distance (FFD) and object-film distance (OFD), thickness and nature of the part radiogaphed, speed and type of film and intensifying screens, temperature and time of developing, grid type, incoming line voltage, make and type of X-ray machine. Of these, first five exposure factors (milliamperage (mA), time (sec), kilovoltage (kV), focal spot/film distance (FFD) and object-film distance (OFD) are very important as radiographic technique chart may be worked out by varying one or more of the five factors.  These exposure factors are integral to image quality and should, therefore, to be adjusted appropriately in order to achieve a diagnostic radiograph of optimal quality (image contrast, brightness and clarity).

Handling

X-ray film is delicate and should not be handled carelessly or roughly. Avoid touching its surfaces, holding it as near the edges as possible with clean, dry hands. It is sensitive to maltreatment of any kind; heat and light adversely affect the emulsion. It can be handled safely and rapidly for all radiographic purposes as long as the X-ray specialist uses precaution to avoid the production of foreign marks (artifacts) on the film. 

To set up of an X–ray (radiology) section following points should be considered while planning:
 
    1.    Anticipated present work load (number of cases and species of animals to be X-rayed) and future requirement in the next 10-15 years.
    2.    Financial resources available.
    3.    Type of equipment to be installed for radiographic work.
    4.    Requirement of radiation safety enforcing agencies e.g. of Bhaba Atomic Research Centre, Mumbai.
The overall set up of radiology section should consider the following requirements:

    1.    X-ray beam collimators: Comprised of 2 independently-acting sets of adjustable lead shutters. These are the devices made of lead and are used to restrict X-ray beam up to a desire area. In diagnostic radiology they are essential for safety of the patients, and persons and also to prevent fogging of films due to unnecessary radiations. The collimator is the most effective of beam limiting devices.

X-ray Machines
 
There are many factors to consider when choosing X-ray equipment. The need of an individual practice varies depending on the species majority and case work load.
Types of X-ray machines: 
X-ray machines can be grouped into 3 categories:

I. Portable X-ray Machine

    ·    Is one that can be carried to the animal.
    ·    Portable X-ray machines are widely used in veterinary practice.
    ·    The maximum output is 15 to 35 mAs and kV ranges from 70-110 kVp.
    ·    Cost is less and easy to move around and transport. 
    ·    Suitable for X-raying of thin and small parts (limbs below stifle and elbow of large animals and can be used taking 
X-rays of abdomen an skeletal systems of small animals).

X-ray photons are produced as a result of electrons hitting metal while extremely rapidly moving at high speed. This is achieved through the application of an electric current to a cathode (negative electrode) via a high voltage power source (electricity) which enables electrons to be released from the cathode into the X-ray tube. These electrons, being negatively charged, are attracted to the anode (positive electrode or target). When the electrons strike the metallic target (anode) in the tube, X-rays and heat are produced. Basically the process of producing an X-ray involves a source that produces X-rays and radiating them through a body or object, where they are absorbed at different rates until they are detected by a sensitive film or cassette. It should be mentioned at this point that most of the energy of the electrons is not converted into X-rays but is dissipated as heat. In fact 99% of the energy dissipated in the target is lost as heat, and only 1% is converted to X-ray energy.

A tube rating chart is a guide regarding operational limits of the X-ray tube for single and multiple exposures and permissible heat load of the anode and the tube housing. It is an essential component for obtaining diagnostic X-ray examinations is a consistent way.
 
The tube rating chart provides important information on the maximum safe exposure time that can be used with specific mA and kV setting. If lower than designated exposure times are used, tube damage may occur. The size of the anode focal spot determines the rating of the tube because size controls the amount of energy it can absorbs and convert into X-rays and heat. Therefore, one should never use an X-ray chart formulated for another X-ray machine (even those made by the same manufacture) without making appropriate changes. Knowledge of three charts is important to extend tube life and includes tube rating chart, anode heat cooling chart and housing cooling chart.

    ·    An X-ray tube is an energy converter. It receives electrical energy and converts it into two other forms: X-radiation and heat.

    ·    It is a source of X-rays used in diagnostic radiology.

    ·    Designed and constructed to maximize X-ray production and to dissipate heat as rapidly as possible.

    ·    It is a thermo ionic diode type electronic vacuum tube where X-rays are produced.
 
    ·    A basic element of an X-ray tube (Figure) consists of the cathode, anode, glass tube and tube housing.

To understand how radiographs are produced by using X-rays, an understanding of how photons of diagnostic range can interact with matter is necessary in five possible mechanism of interaction:
    ·    Coherent scattering.
    ·    Photoelectric absorption.
    ·    Compton scattering.
    ·    Pair production.
    ·    Photodisintegration.

Structure of matter: every structure is made up of elements. Elements can join together to make compounds. The smallest particle of a compound is a molecule. The periodic table gives details of all elements.

Nucleus: the center of atom containing protons and neutrons and hence almost whole mass of the atom. 

Atom: the smallest units of matter composed of electrons are negatively charged, protons have a positive charged and neutrons are neutral. If there are more electrons atom will be negatively charged, if there are more protons it will be positively charged. The total charge of electrons is equal to protons and hence the atom is electrically neutral.

Radiographic positioning refers to placement of the body in respect to linear alignment of X-ray tube and film. Correct positioning is a most important prerequisite to obtain a diagnostic radiograph. Misinterpretations can result from inaccurate positioning.  Label the film before exposure with anatomical lead markers/ X-rite tape. The anatomical markers should be placed in close proximity to the area of interest without overlying important structures. At least two exposures of the part at 900 to each other should be taken to get complete anatomical information of the part.

Within a few weeks after November 8, 1895, Wilhelm Conrad Roentgen made the discovery of X-rays, they were being used in medicine and many sophisticated medical applications. This single discovery of X-rays revolutionized the entire medical field and developed into a separate discipline in the diagnostic and therapeutic applications in human beings and animals. On 10 December, 1901, Roentgen received the first Nobel Prize for Physics in recognition for discovery of X-rays. Radiography in veterinary practice may not always be used to arrive at a final diagnosis of the disorders. In the last few years, various types of X-ray scanners have been developed that allow highly detailed views of a particular section of the body. One type, known as a computerized tomography (CT) scanner, sends narrow beams of X- rays at various angles through a patient’s body. The information obtained from the X-rays is processed by a computer to produce an image of a cross-section of the body. The image shows much more detail than an ordinary X-ray picture. A section of the body can be studied in three dimensions by producing a series of adjacent cross-sectional images. Nevertheless, radiography remains a valuable modality in diagnostic purposes and has significantly extended the usefulness in medicine and research.

    ·    Radiology (Roentgenology): the science, which deals with diagnostic (radio-diagnosis) and therapeutic applications (radiotherapy) of radiant energy particularly of X-rays.

    ·    Veterinary radiology: the science, which deals with the uses of radiant energy for diagnostic (radio-diagnosis) and therapeutic applications (radiotherapy) in domestic, zoo, laboratory, exotic animals and birds.

    ·    Veterinary radiologist: a qualified person in radio-diagnosis and radiotherapy.

    ·    Radiography: is the making of film records (radiographs) of internal structures of the body by passing X-rays through the body to act on specially sensitized film.

Pulses are recognized as an integral part of Bengali as well as Indian diet and the ideal supplement of cereals by virtue of their high protein and essential amino acid content.  Pulses are inseparable ingredients of vegetarian diet and one of the cheapest sources of dietary nutrition protein in the state. The present emphasis on soil health, environmental quality and economic consideration, has stimulated a paradigm shift in cropping patterns leading to pulse based cropping systems. Any cropping system can become compatible and complete only when a pulse crop is included in it. Pulses won a strategic position in intensive as well as subsistence agriculture, as they are excellent source of dietary protein for millions of people, nutritional feed for livestock and having profound ameliorative effect on soil.

Pulses are an essential source of protein in the diet of the vegetarian population. Cultivation of pulses has been a long-standing tradition in Uttarakhand, where the availability of alternative sources of protein such as meat and milk is barely sufficient to fulfill the daily dietary requirements. Pulses assume big importance in these rainfed and environmentally harsh regions by being an ideal crop for the prevalent low-input agricultural conditions. In Uttarakhand, pulses not only form the major constituents of the staple diet but also serve as an important source of feed and fodder for the livestock. Pulses also improve the soil health by fixing atmospheric nitrogen as well as by increasing soil organic matter

Pulse crops provide nutritious food, feed and fodder and thrive well in fragile eco-systems where other crops often fail. They have the ability to trap atmospheric nitrogen in their root nodules in association with Rhizobium, bringing qualitative improvement in soil health i.e. physical, chemical and biological properties of the soil.  These virtues enable pulse crops to remain an integral part of subsistence farming system of semi-arid tropics as well as of Indo-gangatic plains. The role of pulses has also been recognized for sustaining soil productivity under intensive cropping systems in irrigated conditions.

Tamil Nadu state is situated at the south-eastern extremity of the Indian peninsula bounded on the north by Karnataka and Andhra Pradesh, in the east by Bay of Bengal, in the south by Indian Ocean and in the west by Kerala state.  The state has a coastal line of 922 km and a land boundary of 1200 km. Tamil Nadu lies between 8°5’ and 13° 35’N latitude and 76°15’ and 80°20’E longitude. The total geographical area of Tamil Nadu is 13.03 m ha.

The average productivity of pulses (Table 1) is only 460 kg/ha but it ranges from 199 kg/ha (Moth bean) to 1719 kg/ha (Field pea). Year to year fluctuation in productivity of different pulses was also observed. The highest productivity i.e. 1067 kg/ha was observed during the year 2006-07 & the lowest productivity i.e. 497 kg/ha was recorded during the year 2008-09. The trend of area under pulse crop during the last ten years has also shown a wide fluctuation. Year to year and crop to crop variations are most pronounced.  The crop wise major pulse growing districts in Rajasthan are as follows.