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Ajay Kumar Saxena Laxmi Publications PDF


Bonding in Solids


In any solid, the mutual interatomic forces are basically electrostatic in nature, and the primary differences among different types of solids depend on the ways in which the valence electrons of the constituent elements are distributed, i.e. it depends on the type of bonding. Thus, on the basis of bonding type, we have the following five categories of solids:

(i) Ionic solids (e.g. alkali halides, alkaline oxides etc.)

(ii) Covalent solids (diamond, silicon etc.)

(iii) vander Waal bonded molecules (O2, H2, solid-He, Kr, Xe)

(iv) Hydrogen-bonded solids (ice, some fluorides and compounds having water of crystallisation)

(v) Metallic solids (various metals and alloys). Different physical, chemical and electrical properties of a material is determined by particular type of bonding present in it.

Before discussing various types of binding, we will consider general nature of atomic bond between two atoms in a solid.


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Dr. Rashmi Tyagi Laxmi Publications PDF





ll biotechnological processes are performed within bioreactors (may be a culture vessel, an open tank or sophisticated fermenters) containing correct medium provided with optimum growth conditions, like pH, temperature, aeration, light (for photosynthetic organisms), etc., The growth of the organisms is the increase of cell material that can be measured in terms of many parameters, like mass (dry weight or fresh weight), total amount of proteins, photosynthetitic pigments, number of cells, etc., Doubling time is the period required for doubling the biomass

(due to cell division as well as due to cell growth) which varies from organism to organism, e.g., for bacteria it is about 0.25–1.00 h, for yeast 1–2 h, for plant cells 20–70 h and for animal cells 15–48 h

(generation time is the time period required for doubling of the cell number due to cell division).

Plant cells (similar to microorganisms) are mainly grown in liquid or solidified nutrient medium for various purposes, like artificial micropropagation of certain plants, production of valuable compounds

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Prof. Rachna Sharma and Prof. Sudipto Das Laxmi Publications PDF

Congestion Control and QoS






As Internet can be considered as a Queue of packets, where transmitting nodes are constantly adding packets and some of them (receiving nodes) are removing packets from the queue. So, consider a situation where too many packets are present in this queue (or internet or a part of internet), such that constantly transmitting nodes are pouring packets at a higher rate than receiving nodes are removing them. This degrades the performance, and such a situation is termed as Congestion. The main reason of congestion is that more number of packets are introduced into the network than it can handle.

So, the objective of congestion control can be summarized as to maintain the number of packets in the network below the level at which performance falls off dramatically. The nature of a Packet switching network can be summarized in following points:

∑ A network of queues

∑ At each node, there is a queue of packets for each outgoing channel

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D. Napolean; B. Balaji Sathya Narayanan Laxmi Publications PDF



1. Naresh K. Malhotra, Marketing Research � An Applied Orientation, Ed.4, Pearson Education

Inc., New Delhi, 2004.

2. C.R.Kothari, Research Methodology � Methods & Techniques, Ed. 2, New Age International

(P) Ltd., New Delhi, 2004.

3. M.G.Parameswaran, Understanding Consumer Building Powerful Brands Using Consumer

Research, Ed. 1, Tata McGraw-Hill Publishing Company Limited, New Delhi, 2003.

4. P.K. Vishwathan, Business Statistics � An Applied Orientation, Ed.1, Pearson Education Inc.,

New Delhi, 2003.

5. R.P. Hooda, Statistics for Business & Economics, Ed.3, McMillan India Limited, New Delhi,


6. Philip Kotler, Marketing Management, Ed.11, Pearson Education Inc., New Delhi, 2004.

7. Amir D. Aczel and Jayavel Sounderpandian, Complete Business Statistics, Ed.5, Tata McGrawHill Publishing Company Limited, New Delhi, 2002.

8. Rajan Saxena, Marketing Management, Ed.2, Tata McGraw-Hill Publishing Company Limited,

New Delhi, 2002.

9. Thomas M. Heffernan, A student�s guide to studying psychology, Ed.3, Psychology Press, page - 66 to 76.

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Dipak Chandra Ghosh, Nripesh Chandra Ghosh, and Prabir Kumar Haldar Laxmi Publications PDF




Isaac Newton

Classical Mechanics



Mechanics is the branch of physical science which treats of the simplest form of motion of matter�the mechanical motion. Such motion is made up of the changes in the relative positions of bodies

(or their parts) in space in the course of time.

Bodies are macroscopic systems consisting of a very large number of molecules or atoms, so that the sizes of these systems are many times larger than the intermolecular distances.

Classical or Newtonian Mechanics deals with the motions of bodies travelling at velocities that are very much less than that of light in vacuum (which is 3 ´ 10+10 cm/sec). The investigation of the motion of bodies travelling with velocities very close to that of the velocity of light in vacuum is taken up in Relativistic Mechanics which is based on the theory of relativity. Specific features of the motion of microparticles are dealt within Quantum Mechanics. Microparticles are those particles whose rest mass (i.e., the mass of the particle measured in the co-ordinate system with respect to which the particle is stationary) is very close to or smaller than the rest mass of atoms.

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