Python, global function

Python, global function

Problem

1) One want to organize the code using modules (files)

2) One wan packages to see other packages (at least a global function that is aware of all the definition of classes and can be used by all module)

3) One can not using from xx import * in every package

The solution is dynamic importing (which is one of the beauty of Python)

We can

1) define the global function, say, isa() in __ini__.py in the package's root directory

2) import in the METHOD (not __init__ method or as a module import) where you want to use.

Xpy version 1.47 is released

See http://xpydaov.spaces.live.com/

Electric dipole-dipole interaction

Electric dipole-dipole interaction between f electron atoms

Estimate of electric dipole moment:

According to Yen et al.[1], the electric dipole moment can be estimated as:
 
p~e<r>V_c/D,

where e is the elctronic charge, <r>~10^-10 m is the mean radius of the 4f electronic orbit, V_c~500 cm^-1 is the characteristic crystal field splitting, and D~60000 cm^-1 [2] is the energy separation between (4f)ⁿ and (4f)^n-1(5d)' configuration.

Then p~1.3e-31 C.m

Then the dipole-dipole interaction is

W=\frac{ p_1 p_2}{4\pi \epsilon_0 R^3}

For example, if R=0.42 nm, we get

W=1.2 e-5 eV, or 0.01 meV.

[1]    W. M. Yen et al., Physical Review 140, 1188 (1965).
[2]    G. H. Dieke, and H. M. Crosswhite, Applied Optics 2, 675 (1963).

Transfer helium from (100 Liter) Dewa...

Transfer helium from (100 Liter) Dewar to bolometer

In order to transfer helium smoothly, we need to position the bolometer at a good altitude, which depends on the dimensions of the Dewars and the trasfer line. Here is an illustration of how to determine how high the bottom of the bolometer should be.