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Updated on Sunday, August 27, 2006 at 7:23PM
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NMRS2005-ICMRBS; Hyderabad,Jan.16-21,2005
For more particulars about participation of Dr.S.Aravamudhan CLICK HERE


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Disentangling the Bulk Susceptibility Medium-Effects from the Molecular Local Chemical Shift Changes in
Heterogeneous Biological Systems



S.Aravamudhan
Department of Chemistry
North Eastern Hill University
PO NEHU Campus Mawkynroh Umshing
East Khasi Hills District
SHILLONG 793022 MeghalayaINDIA

EMail: saravamudhan@nehu.ac.in

The importance of having to recognize the bulk susceptibility contributions to the induced fields at a nuclear spin site as distinctly different from the Chemical shift changes arising from the local molecular/atomic electron charge cloud circulation changes is becoming prominent in the studies of biological samples by the NMR techniques [1]. It is also has to be taken into consideration that the sample shape dependence of the Bulk Susceptibility contribution dominates the induced field distribution patterns more than the actual differences in Bulk susceptibility values from one sample to another. This bulk susceptibility contribution if can be tracked well, this can be advantageously used for obtaining the required image-quality in the MRI studies to extract the information on the system critically.

In this context it becomes necessary to have a simple mathematical procedure, which appropriately takes into consideration, the required validity point-dipole approximation by inherently built in the mathematical criteria, which is the basis for the calculation procedure.

An alternative simple summing procedure [instead of the complicated procedures of integration] is possible for the calculation of shape dependent Demagnetization Factors as can be known from the considerations of having to account for the bulk susceptibility effects in HR PMR Solids [2].

A perspective of this above simple summation procedure is that if a suitable polar coordinate axis system can be defined in the sample with the specific nuclear site as origin, then given a radial distance from the nucleus with the polar angular coordinates {謶} it is a simple matter of a pocket calculator calculation to arrive at the induced field contribution at the nuclear site. This calculation inherently generates a conical volume element with the defined origin at the apex. The required dimensions for this cone described this way can be predetermined as per the situational convenient [3].

This simple procedure seems capable of providing induced-field distribution patterns for specified shapes. And, also, if there is any prior information about the possible induced field distributions using these procedures an effort can be possibly made to infer about the shapes, which might be contributing to such patterns. This latter aspect has to be given a better investigation than
what at present was possible. This back and forth procedure might help to iterate and improve the inferences. The discussions in interpreting such bulk susceptibility by workers till now indicate
that this could be worthwhile tool in these contexts.

It is intended to highlight this feature of the summing procedure in this presentation. However only a peripheral reference to applications to actual biological systems would be possible since it is necessary to emphasize and illustrate the simplicity of this mathematical procedure..


    [1] DJ Philip, WA Bubb and PWKuchel, Mag.Res.Med., 51, 441-444 (2004)
    [2]http://geocities.com/inboxnehu_sa/Poster_Sheets_Ampere.html
    [3]http://geocities.com/amudhan20012000/Confview_link.html


CLICK HERE to display particulars of participation at the 17thEENC/32ndAmpere at France,Lille in Sept.2004
View poster site
Click HERE to display Abstract
The SHEETs numbered 7,8,9,and 10 in the poster below can be displayed also from URL: http://geocities.com/amudhan20012000/Confview_link.html  as sheets 3,4,5, and 6 respectively of that 'Confview' poster
SHEET_1
Introduction
SHEET_2
Introduction and index
SHEET_3
Charge Cloud descriptions, Circulatory Movement of Charges,the Current flow
SHEET_4
Charge circulation, magnetic Moments,and the point dipole approximation
SHEET_5
Induced fields due to circulation of electrons causing Shielding deamgnaetization effects
SHEET_6
Definitions of terms encountered while considering bulk susceptibility effects in NMR
SHEET_7
A description of the mathematical procedure-[1]
SHEET_8
A description of the mathematical procedure-[2]
SHEET_9
A description of the mathematical procedure-[3]
SHEET_10
A description of the mathematical procedure-[4]
SHEET_11
Advantages of the simple summation procedure described in the previous sheets
SHEET_12
An illustartion of calculation in specimen with inherently two parts
SHEET_13
Specimen with regional spots of differing susceptibility values
SHEET_14
Calculating the induced field at a point out sied the magnetized sphere
SHEET_15
Specimen shapes other than ellipsoidal
SHEET_16
refrences, summary and conclusions

Related webpages

 CLICK HERE to display the page on the participation in the "Meeting of Indian Biophysical Society" for the Year 2006

Link below is to a Web Page Built by Dr.Aravamudhan on his participation in National Workshop on Bioinformatics and Computational Biology
http://www.geocities.com/saravamudhan2002/BHU_BCB2006.html


Image and link below is that of Biological Magnetic Resonance Data Bank-B.M.R.B.
CLICK on image to display the webpage on Biological Magnetic Resaonance Data Base
The Information about BMRB at Wisconsin University was acquired during the participation in the ICMRBS2005 at Hydrabad, India.

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