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Participation in NMRS2008
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Page CONTENTS: The Three Events for 2007: 1)NSC-9 2)NMRS2007 3)IBS2007
Page Navigation:There are links at convenient places on this page to "Jump" among the sections, i.e., from one event to the other and to the top of page
For each event, at the end of the documentation of the TEXT of the Abstract, a link is provided to display a page containing the poster materials.
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GO TO 2nd Midyear CRSI Symposium IIT/Guwahati, 21-07-2007
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CLICK HERE for a profile of Dr.S.Aravamudhan
NSC9 - CRSI:
Abstract
Feb. 1-4, 2007 University of Delhi
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NMRS2007 Go to IBS2007 Go to top of page
Arrival: New Delhi Railway Station at 19:30 hrs on 31/01/’07 by 2505/NE Express PNR: 6200542984
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participation
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Aravamudhan S---Poster PP-8
A Perspective for Recognizing Discreteness
distinctly from Continuum:
Validity of Point Dipole Approximation to Set
the Distance Scale.
Sankarampadi
ARAVAMUDHAN
Department of Chemistry, North Eastern Hill University, Shillong 793022 Meghalaya
saravamudhan@nehu.ac.in
The materials in any state of matter are made up of discrete units and depending
upon when and how it becomes relevant and possible to count the units as
individual entities is when the term discreteness is applicable. However, mostly
when ensemble properties are considered and the material as a bulk is what can
be tangible for consideration, the term continuum is applicable. But there are
instances when the given specimen has to have within itself demarcations as
discrete region and continuum. Such are the contexts when it becomes necessary
to consider critically and quantitatively a criterion to draw a boundary line
within the medium which is otherwise homogeneous and does not have any
distinctions characteristically associated with the constituents or the way the
constituent units are organized within the material medium which in this context
can be special arrangements and the inter unit distances.
The example of a single crystal of organic molecule would present the
disposition of the molecules as described above; and, the applicability of
magnetic point dipole model for induced field values at specified sites within
the single crystal specimen would be clarifying the extent to which the material
has to be considered as discrete or as a continuum. This subject of the point
dipole approximation and its validity in the contexts of chemist’s use in
interpreting spectroscopic results has been pointed out in the references 1-4
cited below.
It would be further elucidated that the magnitude of the susceptibility of the
molecular unit, the intermolecular distance, and the distance of the specified
site from the contributing units determines where the demarcation can be located
between ‘discrete’ region and the ‘continuum’. With typical values for the
quantities the trends would be illustrated as graphical results, and
diagrammatic illustration of the relative distances within the specimen and the
related properties to together with the graphical results would be presented to
comprehend the terms and defining boundary lines when it is necessary. A typical
diagram which would be part of the illustration is displayed below.
1.
http://www.geocities.com/saravamudhan1944/crsi_6nsc_iitk.html
2.
http://www.geocities.com/inboxnehu_sa/crsi_nsc8_iitb.html
3.
http://www.angelfire.com/art3/saravamudhan/iitm_crsi_ismar_ca98.html
4.
http://nehuacin.tripod.com/pre_euromar_compilation/
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NSC-9
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NMRS2007
Abstract
Feb.4-8, 2007 NCL, Pune
Arrival PUNE Airport 21.00 hrs on 04/02/’07 by Jet Air Flight 9W 363 PNR: 9W7ENCMCT
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HERE PROGRAMME & Index to posters NMRS2007 ARAVAMUDHAN S---Poster: P-30
Day-4 Thursday 8-2-2007 16:00 to 18:00 hrs Session VIII Biomedical NMR Chairman: S ARAVAMUDHAN
BULK SUSCEPTIBILITY
EFFECTS AND NMR CHEMICAL SHIFTS:
THE PERSPECTIVE FOR
MOLECULES TO MATERIALS
S.Aravamudhan
Department of Chemistry, North Eastern
Hill
University,
Shillong, 793022 Meghalaya
India
It is a
well established practice to properly account for Bulk Susceptibility effects in
the measurements of NMR Chemical shifts (proton chemical shifts in particular)
accurately. While accounting for this bulk medium effect, it becomes necessary
to consider an Inner Volume Element (I.V.E) described closer to the molecular
site surrounding it which is excluded from contributions accounted for by the
Bulk Medium, but the contributions within must be accounted for separately and
added to the remaining contributions so that no part of the material medium gets
an undue exemption from contributing to the chemical shifts. Once the above two
are taken into account then the molecular contribution is determined from the
experimentally measured values. The contribution from the neighbor molecules in
the I.V.E. can be termed intermolecular in nature and to some extent is
dependent upon the specific orientation dispositions of the neighbors, and the
neighbor-molecule electronic structure. This is simply a discrete summation from
individual neighbors in the case of the static orientation in Solid state single
crystals. However what happens in such an I.V.E. in liquids is yet to be
ascertained since even within this I.V.E., the molecules are under constant
motion.
Recent
results on these aspects of effect of the bulk medium in the case of diamagnetic
specimen seem to provide a much clear perspective on the significance of the
chemical shift determinations getting the purview from molecular to material
properties of the specimen. A summary of results which highlights this
significance would be given along with the specific queries to which those
results stand out as clarifications.
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NMRS2007
Participation in NMRS2008
IBS2007
Abstract
Feb.13-15, 2007 AIIMS, New Delhi
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NMRS2007 Go to IBS2007 Go to top of page
NOT ATTENDING IBS2007 "Schedule" Link above
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particulars of participation
Aromatic Ring Current Shifts in Biological
Macromolecules:
Generating Weight Factors for the Instantaneous
Shift Values for an Effective Motional Averaging
Sankarampadi ARAVAMUDHAN
Department of Chemistry
North Eastern Hill
University
Shillong 793022 Meghalaya India
saravamudhan@nehu.ac.in
By using the Full Tensor Form of
the equation for the aromatic ring current shifts in the NMR spectra of
Biological Macromolecules, it has been possible to show (1) that there are
definite advantages of calculating the full shielding tensor for such cases of
molecules in motion, rather than merely using the equations for the isotropic
shift values. However, in the model calculation presented (2) equal weights were
given for the shift values sampled at the several instantaneous dispositions
during the motion while arriving at a average value. Based on the experiences
till now on this type of approach, it is possible now to further investigate for
the possible improvements that may result if one uses weight factors generated
by specifying the characteristics of the motion and the nature of the shift
dependences along the motional paths.
Conventionally, an oscillatory
motion (torsion) is satisfactorily taken into account on the basis of the
characteristics of Simple Harmonic Motion. In such a case it is also known that
depending on the frequency of oscillation and the swing amplitudes, the resident
time for the molecule at the equilibrium (mean) position is small compared to
the times at the maxima for the amplitude. Hence the shift values at the
extremes would be effective more than the shift values corresponding to the mean
positions. Hence the weight factor must be more for the values corresponding to
the extremes of oscillations than to that at the mean position. Such criteria if
it gets built in to the averaging procedure, then the results could have better
confidence indices. An approach of this type would be illustrated and to what
ever extent possible a comparison with the approaches as in Reference (3) would
be presented.
References:
(1).
http://www.geocities.com/sankrampadi/ForIbs2006.html
Poster Sheet_11: A
specific hypothetical case of how the Tensor Form can be useful when the
isotropic values cannot be indicative of the motional state of the system. And
further results as captions for graphical plots in the subsequent sheets.
This sheet contains the main conclusions which resulted from the Calculations
made at this instance of IBS2006.
(2).
http://www.geocities.com/sankarampadi/ForIbs2006.html Poster
Sheets 10 & 11
(3). “Fluctuations and Averaging of Proton Chemical Shifts in the
Bovine Pancreatic Trypsin Inhibitor”, Jeffrey C. Hoch, Christopher M.
Dobson, and Martin Karplus, Biochemistry 21, 1118-1125 (1982)
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IBS2007
Events in 2007 after the Februrary series
announcements
CLICK HERE to display a webpage on the intended presence of Dr.Aravamudhan at the Venue of EUROMAR2007, Terragona, Spain
A POSTER presentation by Dr.S.Aravamudhan at the 2nd Midyear Meeting of CRSI at IIT Guwahati on 21st July 2007 has been included in the Programme for this meeting
INDEX to POSTER SHEET CONTENTS
Sheet-1 : Sample shape criteria for Homogeneous and Inhomogeneous magnetization
Sheet-2 : Division of specimen while calculating induced fields.
Sheet-3 : Further illustrations for sample divisions of magnetized specimen
Sheet-4 : Validity of point dipole approximation and distance scales
Sheet-5 : Recapitulation of topics in Solid State
Sheet-6 : Consequences of Homogeneous and Inhomogeneous magnetization:Illustartion
Sheet-7 : Calculated results for Inhomogeneous magnetization
Sheet-8 : Illustration of the trends on the basis of calculations
Sheet-9 : The necessity of discrete summing at off-centre points within IVE
Sheet-10 : The contents of Sheet-9 further illustarted
Sheet-11 : A hypothetical lattice with a rigorous octahedral symmetry
Sheet-12 : Results of discrete summation at the (centre) origin of the lattice
Sheet-13 : Induced fields at points other than the origin within the lattice as above
Sheet-14 : Graphical plots of the values in the table of Sheet-13
Sheet-15 : Further illustration of trends noticed in Sheet-14
Sheet-16 : Conclusions
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POSTER for 2nd Mid-year CRSI Symposium, IIT Guwahati, 21st July 2007
