# Gargoyle-in paris

Have you seen mystical characters at top of Gothic cathedrals in and around paris? I always wondered what these creatures were, it seemed so out of place being placed at the top of a place which seems to be holy.It was some kind of pagan belief that had been carried on to the cathedrals, as one of the artist writes in his website.I did a quick search about them and here is what I came up with. A
• Often made from hard stones such as granite ,etc.(long lasting.?)
• They are endowed with magical and mystical appearance and demonic looks, created in the image of animals humans etc.
• Normally placed at the top of the cathedral, where they are used to drain rain water.The construction adds a pagan look to the cathedral.
• In mythological context ,Gargoyles are neither mammals, nor reptiles, nor birds. They are part of a biological class called gargates, presumably descended from the great reptiles of the Mesozoic Era or the late Paleozoic Era. The only other known species in this group is the gargoyle beasts, which were domesticated by gargoyles as companions millennia ago.
• The most prominent biological feature of gargoyles is that they turn to “stone” in the daytime.
• Folk history:The origin of gargoyles traces back to france.It alleges that in the 6th century, the town of Rouen was threatened by a dragon named Gargouille that arose out of the river Seine. Gargouille laid the lands around the town waste and devoured everyone in his path, until Archbishop Romanus defeated and slew him. He then consigned the dragon’s body to the flames, but Gargouille’s head and neck were too toughened by its fiery breath to be consumed. So the Archbishop had Gargouille’s head mounted upon the walls of the town as a commemoration of the dragon’s defeat.
• The legend of gargoyle have its wings spread to Maya, China, India, Mesopotamia, Persia, ancient Egypt, and even ancient Greece and Rome.

Why are they there?

• No possible obvious reasons.But can be explained with respect to some assumptions
• They appeal to our imagination and the subconscious. They take human characteristics, exaggerate, change them, blend them with animal characteristics, so they can symbolize any aspect of our personalities. Humans are differentiated from the animals by our imagination, creativity, humor, and an appreciation of art. Gargoyles fit in that realm, and are part of what make us human. Artists can express humanity and emotion in a creative fashion by using distorted or fantastic forms.
• In Gothic churches they are there to ward off evil
• Some similatities with the weeping angels of Dr Who?
• Beware children at night!!!!

So next time you go to bed just dont remeber the gargoyle hanging down the cathedral and please dont combine the weeping angels and the gargoyle , its a nasty thing to do. Good night:)

References and Online resources:

# Hall Effect- a different outlook for seeing Hall coefficient

Hall effect is an extraordinary phenomena which involves generation of a subsidiary Electric field $V_H$ when a electric field and magnetic field is applied to a conductor. You can get a basic introduction from wiki. If you are not familiar with it

But familiar Hall effect introduces it through a bound rectangular boundary, which limits the current destity in y direction to zero in steady state. In brief the Hall coefficient is defined as $R_H=\frac{E_y}{J_x B}=\frac{1}{ne}$

where ”$J_x$” is the current density of the carrier electrons, and $E_y$ is the induced electric field,” n” is the carrier charge density and e is the carrier charge.

But consider the Hall effect in a 2D ring.The electric field applied in the ends if inner and outer ring and the magnetic field in the transverse direction.Then solving the Lorentz force equation along with Drude theory model (eqn 1)we get a 2 coupled equation,which can be solved directly

$\frac{dp}{dt}=-e(E+v\times B)-\frac{p}{\tau}$—–(1)

which gives from drude theory (see Ascroft Mermin)

$\sigma_0 E_x=\omega_c \tau J_y+J_x ----(2) \\ \sigma_0 E_y=-\omega_c \tau J_x+J_y----(3)$

Solving the two equations by multiplying the equations successively by $p_x,p_y$ and adding/sutracting we get

$\sigma_0 (E\times J)_z=\omega_c \tau J.J$—-(4)

and

$\sigma_0 (E. J)_{xy}= J.J$—-(5)

where $\sigma_0 (E\times J)_z=E_xJ_y-E_yJ_x$—-(6)

$\sigma_0 (E. J)_{xy}=J_xE_x+J_yE_y$—-(7)

So we can define $tan (\theta_H)=\omega_c\tau$

which in common terms is the hall angle

where $\omega_c=\frac{eH}{m}$

Therefore the relation can be written in a more generally

$\frac{tan (\theta_H)}{H}=\frac{\sigma}{ne} \\using \\ \sigma=\frac{ne^2\tau}{m}$

The hall coefficient would then be defined by

$R_H=\frac{tan (\theta_H)}{\sigma H}=\frac{1}{ne}$

The angle between the net electric field and the net current is given by the angle $tan (\theta)$

This to me is a more general statement for Hall coefficient which reduces to the normal hall coefficient if we consider appropriate boundaries and noticing tan(theta) must be dimensionless and considering $E_x< we get

$R_H=\frac{E_y}{J_x H}=\frac{1}{ne}$

which is the usual hall-coeficient.

Therefore the definition of Hall coefficient should be the tangent of Hall angle between the net Electric field and current in the conductor per unit applied magnetic field per unit conductivity.

Also this would help to resolve some issues regarding energy conservation in hall effect.

Suggestions are welcome.

Aritra Kundu

PS:here is an interesting article regarding hall effect in circular geometry http://www.jstor.org/stable/983911?seq=4

# High magnetic Field white dwarfs exceeding Chandrashekhar Mass Limit

In winter last year, I studied the effects of high magnetic field on Astrophysical objects ,specially related to the mass of a white dwarf.The origin of high magnetic field is stated briefly by http://www.iiap.res.in/meet/chandra/Chandra_files/Tout.pdf. Where it is briefly discussed about the origin of such high magnetic field white dwarfs and observational statistics.
In the article about super chadrasheker supernova from WD,they state that”Chandrasekhar’s 1931 model of stellar collapse was elegant and powerful; it won him the Nobel Prize,” says Nugent. “But it was a simple one-dimensional model. Just by adding rotation one can exceed the Chandrasekhar mass, as he himself recognized.”

Some readups on the topic/news are:
http://www.lbl.gov/Science-Articles/Archive/Phys-weird-supernova.html
http://iopscience.iop.org/0004-637X/744/1/69

In my analysis, I used quantized hall effect-like phenomena for the relativistic electron degeneracy pressure, and calculated the mass limit analytically.As a function of the residual magnetic field, the mass of white dwarf seemed to exceed the chandrashekhar mass limit.
here is my analysis: http://arxiv.org/abs/1204.1463v1
here is the computational (more detailed) analysis of the problem by my guides PhD student later.

http://arxiv.org/pdf/1204.1262.pdf

# TIPS for preparing input file for Molecular dymnamics simulations using DL_POLY

DL_POLY is a classical Molecular dynamics software by http://simx.epfl.ch/simx/en/dl_poly.html

,which is tweaked to work best with large macro molecules.It best simulates Organic molecules and thus is of use in pharmaceutical purpose of drug design etc

The preparation of the input file i.e the CONFIG file is one of the most troublesome episodes that I had.

Firstly, use aten to prepare the basic setup box.You can read throught their manual ,but the disorder button didnt work much for me from the GUI.I had to write script, i.e. use it from commandline to make the disorder work.

Check the output file,such that the output is in sequence,i.e. it follows some definite pattern.

Ensure that you dont have molecules towards the edges of the box, if you are usin periodic boundary condition, as these will culminate in errors during simulation.

If the resulting CONFIG is not in sequence, adjust some molecules and regenerate file again.Check using a program that you have ordering/pattern
as you need to specify the pattern in your FORCE file.

once this is done identify the pattern and write the FORCE field file, with the parameters of potential appropriately chosen from different models(CHARAMM, AMBER,etc etc.)

# DL_POLY a quick user guide-Installation to first simulation in Molecular Dynamics

This summer I spend my time in Ecole Centrale Paris, trying to run a computer simulation on NPLIN.I will post about that later, but this was my first introduction to molecular dynamics simulation,  and there I faced many problems.So I thought to write up a bit, in case it might be of help for someone in future.I am posting this , but you sure can find help from the DISCO forums.And yes, read through the manual!!

In this, I explain how we can run DL_POLY in parallel.It really did a 30 minuite simulation in 30 seconds in my 4X2 core processor in laptop

Installation:
2.Obtain Liscense by mailing the authors for home/personal/educational use
3.Unzip,Untar,Unencrypt
4.In Linux install open mpi by typing
$sudo apt-get install libopenmpi-dev openmpi-bin openmpi-doc$ sudo apt-get install ssh
Generate keys and add to ssh
$ssh-keygen -t dsa$ cat id_dsa.pub >> authorized_keys

Test program:
#include <stdio.h>
#include <mpi.h>

int main(int argc, char** argv)

{
int myrank, nprocs;

MPI_Init(&argc, &argv);
MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
for (;;){
printf(“Hello from processor %d of %d\n”, myrank, nprocs);
}
MPI_Finalize();
return 0;
}

Testing:
$mpicc MPI_Hello.c -o MPI_Hello$ mpiexec -n 5 MPI_Hello         #specify to run on 5 processors,press Ctrl+Z to exit
You can install htop to see if the process is really parallel [sudo apt-get install htop]
Compiling DL_POLY for Laptop Dell XPS 15z
Requires fortran to be installed.[sudo apt-get install gfortran]
1.In the DL_POLY directory>Build>copy “Makefile_MPI” to source directory and rename to “make”
2.In terminal type “sudo make hpc”
3.The process will create a DLPOLY.Z in the execute directory. Which also has a JAVA gui which can be used.(Personally I find using GUI a bit cumbersome and problematic,so I run using terminal)
4. Terminal >browse to DL_POLY execcute directory> type \$./gui to invoke gui

Running sample scripts:
Some example and basic examples can be found online in
http://www.ccp5.ac.uk/DL_POLY/TUTORIAL/EXERCISES/

Although they used GUI, I am going to use a mixture of both

DLPOLY requires some necessary files to run a simulation,The CONTROL,CONFIG,FIELD files.I am going to explain them as we go,but first lets see if its working!
Download the files for EXERCISE 1 which finds out the phase transition for KCl.
The CONFIG file lists the system in brief,it gives the coordinates and velocities of all atoms in the system in initial condition.
The CONTROL file is important,it determins the thermodynamics of the system.The temperature, pressure, cutoff, and configuration like NVT,NPT etc.
FIELD defines any other field which cannot be characterised by concrete mathematical formulas

The CONFIG file uses its own self-consistent set of units.

 physical quantity symbol unit value time t0 1×10−12 seconds (picoseconds) length l0 1×10−10 metres (Angstroms) mass m0 1.66054×10−27 kilograms (amu) charge q0 1.60218×10−19 Coulombs (electron charge) energy E0=m0(l0/t0)2 1.66054×10−23 Joules = 10 J mol−1 pressure p0=E0/l30 1.66054×107 Pascal = 166.054 bar Planck constant ℏ 6.35078E0t0 Boltzmann constant kB 0.83145E0/K

The others can be found from the user manual(Page 7 of DL_POLY_4_USER_MANUAL)

will learn the process through a process through the first example of DL_POLY guide.i.e. phase transition of KCl

http://www.ccp5.ac.uk/DL_POLY/TUTORIAL/EXERCISES/expmt1.html

This exercise studies a well-known phase transition in potassium chloride using constant pressure molecular dynamics. The objective is to develop the best practice in using such algorithms and to learn how phase transitions can be induced, detected and monitored in a simulation.

The CONFIG file:

 DL_POLY: Potassium Chloride Test Case                                           #heading 2         3      2000    0.5000000000E-02 !levcfg(0-2,2 :position,velocity,forces included in file) ! imcon(periodic boundary condition:0,1,2,3,6) !megatm(total number of particles) !crystallographic information for periodic boundary(x,y,z component of a,b,c cell vector) 18.6960000000        0.0000000000        0.0000000000 0.0000000000       18.6960000000        0.0000000000 0.0000000000        0.0000000000       18.6960000000 !since levcfg = 2 each record will contain 3 data position,veocity,force K+               1                            #atom name, index -7.608595309        -7.897790000        -7.892053559    #position 1.056610291        -1.218664448         3.345828610    #velocity -1979.558687         739.7961625         1027.996603    #force K+               2 -4.678562643        -4.509858530        -7.813252872 -0.7078383910         1.220785303       -0.9440783885 212.7300659        -4290.721728         1363.866117 K+               3 -7.821414265        -4.635443539        -4.732164540 2.637614561        0.5778767520E-01    -1.704765568 150.3309776        -812.6932914         1429.413120 K+               4 -4.577735234        -7.808222424        -4.540282303 4.950411107         3.576253827        0.2276058039 -782.7309730         1322.553499        -205.1240756 Cl-              5 -7.810782981        -4.845250366        -7.815286768 1.643324971       -0.6479194620         3.393130560 407.2394357         1675.508460         748.2506938 …

The details about preparing this file with other packages(Athen) will be discussed
Next we prepare the CONTROL file:

 **–begins here––** DL_POLY: Potassium Chloride Test Case    !heading temperature      600.0                !system temperature in Kelvin pressure         144.0                !system pressure steps             4000                !maximum no of steps,2000 is enough equilibration      500                  !time for the system to equlibrate timestep         0.005 multiple             1 print               10 stats               10 scale               10 restart scale rdf                 10             !write radial distribution function at 10 timescale interval print rdf cutoff             7.0                !define cutoff for interactions to 7 Angstorms rvdw               7.0 delr               1.0 ewald precision  1.e-6 ensemble nst hoover 0.1 1.0            !Ensemble trajectory 20 30 0                !write history file job time          3600                !set job time close time         100 finish                        !control file ends

FIELD FILE:

 DL_POLY: Potassium Chloride Test Case UNITS eV    !energy units MOLECULES 1    ! number of molecule type Potassium Chloride    !Molecule name nummols 27        !number of molecules atoms 8        ! no of atoms in this molecular type K+           39.0983       0.994    4 Cl-          35.4530      -0.994    4 finish VDW 3            !number of van der wall interactions K+      K+      buck      3796.9      0.2603      124.90 Cl-     Cl-     buck      1227.2      0.3214      124.90 K+      Cl-     buck      4117.9      0.3048      0.0000 CLOSE

RUNNING DLPOLY:

To run the program make sure the CONFIG,CONTROL,FIELD files are there in the execute folder, from terminal invoke dlpoly

./dlpoly.z

This will run the simulation and write the output files

ANALYZING OUTPUTS:

1. We will visualize the resulting system.This can be done through GUI by plotting the REVCON file(which is the system at the end of simulation)
You can also visualize the CONFIG file.
Another better alternative of visualizing the files is to convert the CONFIG file to XYZ files and plotting them on VMD

2. Checking the Diffusion coefficient in OUTPUT file, if it is less than 10-5then it is liquid state.A value of zero suggests it to be solid state.

3. Now we will analyze the output from the simulation using the RDFDAT file that was created.From GUI plot the RDF -> select the atom types K+ and Cl-

This will extract the RDF for K+ and Cl- from the RDFDAT file and create a separate XY file.For various simulation parameters you can create different RDF files and merge them together and plot so that you can compare where the system is heading to and draw good conclusions.I have written a small script in python to do that.

 # Import modules import sys import matplotlib.pyplot as plt import numpy as np ”’ to be invoked as plot_rdf option -m merges the given number of files using single X cordinates and y coordinate.Option -p plots the given file eg plot_rdf -m 2 RDF_100.XY RDF_14.XY merges the two files ”’ #import pylab as pl option=sys.argv[1] no_of_options=int(sys.argv[2]) index=3 l_index=index+no_of_options #process data if(option==’-m’):    data=np.loadtxt(sys.argv[index])    shape_data=data.shape    while(index ‘)    yaxis_label = raw_input(‘Y-axis label > ‘)    # Show the plot    plt.ylabel(yaxis_label)    plt.xlabel(xaxis_label)    plt.show() #Stop

The RDF is the measure of how the probability deviates from an uniform distribution.From the radial distribution function a number of parameters can be determined.We can also identify the phase transition from the change in pattern in the RDF

Picture stolen from Jacek Dziedzic,Gdansk University of Technology,Computational nanotechnology

# Diracs Puzzle

I will post here with some musings I came across another blog:
http://www.minustwofish.com/Here is a question that was made to Dirac, the great genius !Here is it

Three fishermen come back from the sea. Each collapses in their respective tent. Fisherman #1 wakes up and decides to get his share of the catch. He counts the fish, realizes it is not a number divisible by three, throws away one fish to the sea correcting the situation, and takes a third of the remaining fish into his tent. Fisherman #2 wakes up later and also decides he is going to get his share of the catch. Fisherman #2 wants a third of the fish he sees. It is not a multiple of three, but he throws away one fish and takes a third of the fish and goes to sleep. Fisherman #3 wakes up after, and does the same: he throws away one fish, takes a third of the fish, and goes into his tent.
What is the smallest number of fish for which this would happen?

Ah its simple isnt it?

Guess what was Dirac’s answer -2! no wonder he came up with the idea of filled negative electrons in Dirac sea

# Hello !

Hello all, i am shifting blogs from blogspot to wordpress, because of its ease with LaTeX and inconsistency of google,I dd not like the new getup of blogspot.Also I believed Google kept blogspot just for timepass, and wasnt serious about it.Also loved wordpress getup , simple and elegant…so here I come wordpress..

# Two important things to carry while travelling(repairing your glasses and belt)

Few days back,I had some strange problems while I was traveling to Belgium.
1. somehow the clip from the buckle of my belt broke off.
2. my friends spectacles support came off.

Now it was very difficult to find a shop in and around and specially when you are travelling you dont know where the shops are and adding salt to it some said mending would be quite expensive.I was unwilling to pay 3 euros for a ‘small’ mend. Buying a new belt would have costed me about 8 euros, so it was out of question!

I thought a way out, it was really a hotfix, fixing the belt with a straightened paper clip(pic).
In the axle in the end of the buckle,just wrap around the metal rod (straight paper clip),so that it can move freely.
You can also cut the remaining part of the clip if you have a cutter handly.I didn’t have one.
I just realized this could be used for fixing many things which had long attachements,and would be very useful to carry along.

Here is the pic of the mended belt

Now after coming back from the tour, the next morning my friends reading glasses support (one over the ears)came off ,Now he started worrying about his spectacles, and the money to be spend for repair. I couldnt fix this with a paper clip it was too thick and long,(and i dont have a cutter).I thought for a while and looked around for things, when I noticed a stapler pin(pic).This was just perfect to just get in the small screw hole of the glasses.

The fix worked like a charm and it got fixed like never before…and best of it you could never tell a difference from outside..:)

I would always carry these small things always with me from next time:)

# In paris with street artists..

Hey friends ,

Now that I am travelling in france i will post some pictures and videos about paris and france,kind of travel log,and information,when i will have time.
Paris is a city full of art,architecture,and culture.Dont get swayed away by the beauty of the city as it is not that safe here.
I made a short video about the street artists in france,they were really wonderful to watch…

# google ngram observation

I was experimenting with the Google Ngram
Its a wonderful tool that i came across after watching the video on “what we learned from 5 million books”from TedX

For a time now i had wondered when this new age saga for Aliens begin,and the term UFO and Flying saucer are closely related to the controversy of aliens ,So I did a quick Ngram search on UFO and aliens.The results pointed to interesting results.The use of these words started round about 1950’s,but critically the word UFO was more convinient and ahd the mysterious feeing which made it take over the word flying saucer.The heights of the UFO alien visit was in 2000’s when (both the words show a peak) .Well I still guess aliens are out there,
Daleks will be coming to earth one day,and Dr.Who where are you????

SETI institute should be funded for better research for time travel and communication with ET’s

Toward Politics:
The two main groups and thought of interest in this world and its shaping to its current state have been the capitalist and the communist.The Ngram tells us communism was old concept than the cpitalist at least in words dating back at least to 1880.it hasd a slow rise among mass till in 1960’s  it achieved a peak, owing to the fast changing culture and socity in russia china and india
Where as The capitaisit community was at peak in US round about 1940’s  during the war ,but with the rise of communism in 60’s the interest shifts to communusm.
But soon america became overpowerful and decied upon capitalism to bring forth power and trade .
The current trend seems a fast declining capitalism compared to communism.
Will the age of communism rise again?
Viva La revolution!

Ah ha here is another interesting stuff,cinema and movie..which came first and what is more common ?
surprisingly both were born round about the birth of film industry round about 1910.
The number of movies produced after 1960’s became large and also by the invention of color telivision the media was moved out to masses.
and well movie won with cinema..which was more awkward term more reserved for cinematographer. while movie was a sweet,short ,birsk word ready to be used in a date and with friends…
movies on rise..with time and pride…

Communism on its heights roun about 60’s!!

History of fuck:
In its modern sense it started it social outrage from little before 1960’sand then on rise ever…

An embarrassing comparison for google..yahoo seemed more written about till 2008..yes of course it should have been..any doubt????

Graviton research:
80’s!!!

Billion vs trillion:
I guess I was thinking in terms of money.we see with time more is being taked about heigher numbers.Are we heading towards society of more rich and profit?

Tracking history :
Discovery of pluto. round about 1940+-5 years for research to take place.Wiki says 1930’s wow close!!!