• Volume 22, Issue 2

February 2017,   pages  101-191

• Editorial

• Vera C Rubin (1928-2016)

• Science Smiles

• On the Trail of WIMPs: Direct Detection of Weakly Interacting Massive Particle Dark Matter

The fundamental particle nature of the Dark Matter (DM)that constitutes more than 80% of the gravitating matter inthe Universe is unknown. There is no suitable candidate forthis DM in the Standard Model (SM) of particle physics. Theso-called Weakly Interacting Massive Particles (WIMPs), predictedin many scenarios of possible new physics beyond theSM, are currently one of the most favoured candidates of theDM. A number of experiments worldwide are trying to directlydetect these WIMPs in underground laboratories. Herewe discuss the basic ideas behind the WIMP hypothesis andbriefly discuss the latest results of such experiments and futureprospects.

The Earth's ionosphere consists of plasma produced by thephotoionization of thin upper atmospheric gases by UV raysand photons of short wavelength from the sun. The upperionosphere is used for radio communication and navigationas it reflects long, medium, as well as short radio waves. Sincesolar radiation is the main cause of the existence of ionosphere,any variation in the radiations can affect the entireradio communication system. This article attempts to brieflyintroduce the readers to the study of ionosphere in the contextof its use as a radio reflector, with particular reference toIndia.

• How Do Wings Generate Lift? 2. Myths, Approximate Theories and Why They All Work

A cambered surface that is moving forward in a fluid generateslift. To explain this interesting fact in terms of simplermodels, some preparatory concepts were discussed in thefirst part of this article. We also agreed on what is an acceptableexplanation. Then some popular models were discussed.Some quantitative theories will be discussed in this concludingpart. Finally we will tie up all these ideas together andconnect them to the rigorous momentum theorem.

• The Inveterate Tinkerer: 1. Salt Oscillator

In this series of articles, the authors discuss various phenomenain fluid dynamics, which may be investigated via tabletopexperiments using low-cost or home-made instruments. Thefirst article in this series is about the salt oscillator – a hydrodynamiccuriosity.

• Understanding Active Metal Reaction Kinetis with Cu-Mg Replacement Reaction

Metal substitution reactions are simple redox reactions. Thesereactions demonstrate the relative activity and the electrochemicalseries of metals. In particular, the purpose of thisstudy is to help students comprehend the displacement reactionamong, Mg metal and solutions containing Cu$^{+2}$, Ni$^{+2}$,Pb$^{+2}$, Cd$^{+2}$, Co$^{+2}$. This study is an important experiment towardsunderstanding reaction kinetics.

• MicroRNAs: Tiny Genetic Switches in Our Genome

Gary Ruvkun is a winner of the 2015 Breakthrough Prize in Life Sciences. He is a codiscoverer of microRNAs (with Victor Ambros, University of Massachusetts), regarded as one of the seminal discoveries of 21st century molecular biology. In addition to the Breakthrough Prize, Ruvkun and Ambros have received the Warren Triennial Prize, the Laskar Foundation Award, and numerous other awards and prizes. Professor Ruvkun obtained his PhD from Harvard University, did his postdoctoral research at MIT, and subsequently accepted a faculty position at Harvard, where he is currently Professor of Genetics. His laboratory conducts research on basic cellular processes, using the worm \italics{C. elegans} as a model system.

• Dark Matter in the Universe

Vera Rubin gave an evening lecture during the 19th General Assembly of the International Astronomical Union, in 1985 at New Delhi, on dark matter. It was a lucid introduction to the issues regarding dark matter, as well as a comprehensive review of the evidences for dark matter. This extraordinary lecture, aimed towards non-specialists, is reprinted below.

• Science Academies' Refresher Course in Quantum Mechanics

• Science Academies' Refresher Course in Experimental Physics

• Science Academies' Refresher Course in Experimental Physics

• Science Academies' Refresher Course in Experimental Physics

• Homi Bhabha Centre for Science Education, Tata Institute of Fundamental Research (A Deemed University)

• \it{Viburnum punctatum} Buch.-Ham.