High-performance Computing using Graphics Processors

Dr. Rekesh Mohan gave a very interesting seminar in our Institute recently. It was about the use of existing hardware used for graphics applications for high performance computing. 

An important recent trend in high-performance computing is the use of hardware originally designed for graphics and games to solve general purpose computing problems. Modern Graphics Processing Units (GPUs) deliver enormous power for arithmetically-intensive computations, at extremely low cost and power consumption as compared to CPU based computing clusters. 

The existing programs need to be modified using the syntax that can be understood by the Graphics Processing units. This requires certain libraries and commands. The speed could be enhanced to 10-100 times, and is cost effective compared to parallel CPU cluster method. 

Check here for two platforms to use for GPU programming:- 

GPGPU General Purpose Graphics Processing Unit 

CUDA Compute Unified Device Architecture

Lectures on General Theory of Relativity

Lectures on General Theory of Relativity, by Prof. T. Padmanabhan have been uploaded here.

T. Padmanabhan is a renowned Physicist who has written excellent books on Theoretical Astrophysics.

Lectures by Prof. V. Balakrishnan

Excellent lectures.

Forming monolayer films

The water contains loosely bound Hydrogen nuclei in bonding with the OH radical. The molecules can have afinity to water depending on their polarity, if a molecule can contribute a positive charge, it would bond very well with OH negative radical. If it has negative polarity, it will be repelled from OH radicals. So any typical molecule will have either a crowding of OH -ve radicals around it or it has H+ ions around it. The situation is special when it comes to bipolar molecules, and if they are sufficiently long, they will attract both OH- or H+ at their ends. If the molecules are long, then they have sufficient space to accommodate different radicals on both ends. Surfactant molecules look like these:-

They are long chain molecules with a "head" that is water-loving :- water philic. the tails are water phobic, and hence in the given surface interface between water and air, they tend to stand upright as shown. Just like when you dip a plate in water, some water clings on the surface of plate, a metal can be dipped into a surfactant solution, and it will come out with a layer of the surfactant molecules. However this needs to be done very slowly. Here is a good article on this method of forming monolayers of one substance on another. Here are some good diagrams of the process.

Heartbeat of the Sun

One of the greatest opportunities in a research Institute is to get to listen to great Scientists. Here is the news article describing how a team of scientists studying Sun is extracting the information of the internal activities of the Sun. 

The studies of Sun using Visible or any other electromagnetic radiation is limited to the photosphere. Only Neutrinos produced in the nuclear reactions at the core of the Sun carry information about the layers inside Sun, to us. In what amounts to finding needle in the hey, the scientists have discovered a subtle ripple in the overall movement of the solar surface. The technique is to get the Fourier transform of the Fourier transform, thus giving an indication to the patterns in the frequency spectrum! It is like finding the octaves in the music of piano, and detecting the presence of piano in a grand symphony. The waves originate at the core of Sun because of gravitational disturbances. Rafael A. Garcia, DSM/DAPNIA/Service  d'Astrophysique, France explained this in a colloquium at our Indian Institute for Astrophysics.

Mysteries in Sound Phenomena

One friend asked, why in the place that is an empty square covered at a sixth floor ceiling and surrounded by classrooms in a college, echos a lot? 

After some discussions, we came to a simple conclusion: they had used that place after college hours, when there is absolutely no-one in the college. During the day-time, when it is flooded with students, it doesn't echo at all! The absence of students here, is giving rise to a lack of any absorbing medium for the sound energy, and it finds it easy to bounce back and forth. This effect can be seen in any empty place, flat, hall, most famous being the hilltops, as the sound seems to come back from distant hills.

Our staircase has hollow pipes as hand railings. I was having fun striking the metal with my metal keys, and it would create quite a sound! I checked striking on different sized pipes, and the sound is so very different! When the metals being stroked the same, why did the sound differ?

The energy of the stroke gives rise to an impulse of vibration in the solid of the pipe. This impulse is a superposition of a huge number of frequencies. These all frequencies get transmitted to the air within the pipe. Due to the size of the pipe, the back and forth oscillations are sustained only at the natural frequencies of that length and radius of the pipe. So the standing waves are dependent on the radius of the pipe, thus giving different sound in different sized pipes.