Molecule matters Dinitrogen

Dinitrogen (N₂) is a very stable and inert molecule due to the formation of a triple bond between the two atoms. Surprisingly isoelectronic molecules are quite reactive making dinitrogen very useful and unique.     

Quantum computing 1. Building blocks of a quantum computer

In this article we have seen how the principles of quantum physics can be exploited in making a computational device. However, we still haven’t seen the kind of algorithms a quantum computer would use and how they would be different from traditional algorithms. We will look at these issues in the next part of this article, with the help of Shor’s famous factorization algorithm. We will also briefly mention some practical issues and the progress achieved so far.     

Silicon photonics Silicon Raman lasers

The increased use of optoelectronic devicessuch as TV screens and computer monitors in everyday life, calls for a material on which integration of all circuits may be performed. Silicon, the most widely used material in electronics, has limited application in optoelectronics due to its poor light emission property. In this article, the need for silicon photonics in present day ICs, and communication, the reason for its inefficient light emission, and recent breakthrough in the form of Si Raman laser are discussed.     

Fire synthesis Preparation of alumina products

The novel ‘solution combustion method’ or ‘fire synthesis’ has been used to make high temperature synthesised ceramic materials. The process, which can be initiated at low temperature, is self-propagating and gas-producing. Fine-particle alumina and its related oxides can be easily prepared in bulk by the redox mixture method.     

Mangroves The most fragile forest ecosystem

Mangroves, an exclusive group of plants with remarkable ecological importance, inhabit mostly the zones washed by the back and forth movement of tides. They are disappearing rapidly from their natural habitat due to various reasons. Mangroves create a unique ecological environment that is composed of rich assemblages of species. Economic importance of mangroves is also noteworthy.     

Symmetries and conservation laws in classical and quantum mechanics 2. Quantum mechanics

In Part 1 of this two-part article we have spelt out, in some detail, the link between symmetries and conservation principles in the Lagrangian and Hamiltonian formulations of classical mechanics (CM). In this second part, we turn our attention to the corresponding question in quantum mechanics (QM). The generalization we embark upon will proceed in two directions: from the classical formulation to the quantum mechanical one, and from a single (infinitesimal) symmetry to a multi-dimensional Lie group of symmetries. Of course, we always have some definite physical system in mind. We also assume that the reader is familiar with the elements of quantum mechanics at the level of a standard first course on the subject. Operators will be denoted with an overhead caret, e.g., $ \hat A,\hat G,\hat U $ \hat A,\hat G,\hat U , etc., while $ [\hat A,\hat B] = \hat A\hat B - \hat B\hat A $ [\hat A,\hat B] = \hat A\hat B - \hat B\hat A is the commutator of $ \hat A $ \hat A and $ \hat B $ \hat B .     

The Freudenstein equation Design of four-link mechanisms

Ferdinand Freudenstein is widely acknowledged to be the father of modern kinematics of mechanisms and machines. His PhD thesis in 1954 and subsequent research papers by him and his students have influenced academic and industrial research, teaching and practice related to the analysis and design of mechanisms and machines throughout the world. In this article, we revisit Freudenstein’s thesis and the equation named after him. The Freudenstein equation results from an analytical approach towards analysis and design of four-link mechanisms which, along with its variants, are present in a large number of machines used in daily life.     

Irving Langmuir A pioneering industrial physical chemist

This is a biography of one of the most famous industrial chemists of the last century. Irving Langmuir showed that developing new devices leads to fundamental work of the highest order. Langmuir was the first industrial chemist to get the Noble Prize.     

Willis H carrier Father of air conditioning

Willis H Carrier, the Father of Air Conditioning, placed the science of air conditioning on a firmscientific basis in the year 1911, in his paper ‘Rational Psychrometric Formulae’ — widely known also as the ‘Magna Carta of Psychrometrics’. This paper was presented at the annual meeting of American Society of Mechanical Engineers (ASME). The centenary of this historic event happens to be the past year 2011. Amongst his many achievements are his contributions to development of the Psychrometric Chart (which remains essentially the same as the chart presentedmore than a century ago), the Law of Constant Dew-Point Depression, Dew-Point Control and the invention of the Centrifugal Refrigeration Machine.