 DR.S.ARAVAMUDHAN http://www.ugc-inno-nehu.com/ |
 BIODATA CONTACT INFO Curriculum Vitae/Resume webpages_list http://nehuacin.tripod.com Phone Mobile: +919862053872 EMAIL:- inboxnehu_sa@yahoo.com saravamudhan@hotmail.com aram1121944@gmail.com |
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 Dr.S.Aravamudhan Logo "NMRS2009" |  CLICK HERE and find updated [as received from organizers on 6th Jan.2009] list of participants, titles of abstracts, accommodation request and details of their travel.The same information will be posted on webpage (www.nmrs2009.org/linked to image above) Entry Number(S.No) 158 in the list is as below; 158 M DR. ARAVAMUDHAN SANKARAMPADI GUEST PROF. NEH UNIV.,SHILLONG 2 5 Y N inboxnehu_sa@yahoo.com THE NECESSITY FOR A PROTOCOL FOR PROCESSING AFTER EXPERIMENTAL MEASUREMENT OF PROTON SHIELDING TENSOR IN SINGLE-CRYSTAL SPECIMEN posted at Kolkata Airport on 7th Jan.2009 at 3:47 PM |
| S.ARAVAMUDHAN Department of Chemistry NORTH EASTERN HILL UNIVERSITY SHILLONG 793022 Meghalaya The context here is the measurements of Shielding Tensor of protons in solid-state single-crystal specimen. The experiments yield the values of the components and the direction cosines of the principal directions of the Tensor. Further after, In order to obtain the information on the molecular electronic properties (in the case of single crystals of organic molecules) it becomes necessary to properly account for the near neighbor inter molecular contribution to the shielding at a given site; and the bulk susceptibility contribution to the induced fields at this site. Thus, the subsequent processing, required after obtaining the experimentally measured values, has been a discouraging factor in the HR PMR studies using the multiple pulse line narrowing techniques. This has relegated such HR PMR studies even more because of the current day advances in the multi nuclear multi dimensional techniques and the corresponding improvements in the spectrometer features. However, in spite of all such trends and improvements there has been no unequivocal evidence(1) that there would not be situations arising when a structural characteristic can be established only with the HR PMR measurements also made for conclusive evidences. Such situations may not be a routine these days, but still there is a necessity to provide a protocol for the processing after the experimental measurement (2). An enumeration of the results till now is intended in this contribution envisaging a protocol for measurements by HR PMR using multiple pulse line narrowing technique. The various steps taken till now to obtain clarifications(3) on the accounting of bulk susceptibility contributions(4) are enumerated systematically realizing a protocol which would be valid for any shape of the specimen of all molecular systems for which a single crystal can be obtained(5). 1. http://www.geocities.com/saravamudhan1944/eenc_ampere_lille.html#Section_4 2. http://nehuacin.tripod.com/id4.html ) (EUROMAR2007) 3. http://nehuacin.tripod.com/id6.html (FD NMR; Sheet-10 of display sheets) 4. http://nehuacin.tripod.com/id3.html (4th Alpine SSNMR Conference) 5. http://www.geocities.com/inboxnehu_sa/nmrs2009.html |
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VARIATION OF CHEMICAL SHIFTS WITH MOLECULAR GEOMETRY THROUGH THE EQUILIBRIUM CORRESPONDING TO A GEOMETRY OPTIMIZATION S.ARAVAMUDHAN Department of Chemistry NORTH EASTERN HILL UNIVERSITY SHILLONG 793022 Meghalaya When the Geometry Optimization for equilibrium (stable) geometry procedure is explained on the basis of the applicability of variation principle, then the molecule passes through a minimum of potential energy to recognize the most stable structure as corresponding to the minimum. For such a passage through a series of structures on both sides of the minimum energy, if the chemical shifts of the nuclei in the molecule are also calculated for the series of structures, would there be a possibility to recognize the characteristics of the stable structures? This is a pertinent question and since the Computational methods result in the Full Tensor element values (not merely the isotropic, trace value), it is probably worth the while looking into the above question, with the variation of the chemical shift tensor properties tracked through the series of structures encountered during the geometry optimization procedure. For this perspective a beginning can be made with what ever effort is known in the literature to document the chemical shift dependence on the geometry parameters. Since the Solid State High Resolution NMR is gaining in importance in structure determination (small molecules, and polymeric macro molecules also of biologically relevant) a question of the variation of chemical shift with geometry, and explaining the trends on the basis of the electron population analysis would lead to a situation of using full tensor information similar to the way chemists these days interpret the isotropic liquid HR NMR spectra. In this context the consideration in the cited reference (1) for the trends of methyl group proton (isotropic and anisotropic part of the) chemical shift tensor can be viewed from the point of view of the available electronic structure information by the quantum chemical computation for the electron distribution within the molecule. The relevance of such considerations would be highlighted with regard to the HR Single Crystal PMR results as in cited reference (2). REFERENCES: 1. “Die magnetische Abschirmung von Protonen in Methylgruppen und aromatischen Ringen: Multipuls-NMR-Experimente an Molekulkristallen”: Inaugural-Dissertation zur Erlangung der Doctorwürde der Naturwissenschftlich-Mathematichen Gesamtfakultät der Ruprecht-Karls-Universität, Heidelberg. Vorgelect von Dipl.-Phys. Bernd Tesche aus Lüdenscheid, Tag der mündliche Prufung 19-07-1995 2. “The proton nuclear magnetic shielding tensors in biphenyl: Experiment and Theory”, Frank Schonborn, Heike Schmitt, Herbert Zimmermann, Ulrich Haeberlen, Clémence Corminboeuf, Gilbert Grossmann, Thomas Heine, J.Mag.Res. 175, (2005), 52-64. Email:- inboxnehu_sa@yahoo.com |
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POSTER SHEETS of NMRS2010 |
| During 27-31 Jan. 2009 Dr. Aravamudhan was at the IGNOU, New Delhi for consultations with the Pro-Vice-Chancellor Prof. K.R. Srivathsan in connection with a "WORKSHOP ON E-LEARNING WITH FOCUS TO EDUCATIONAL INTERNET DOMAINS" to be held at the Computer Centre, N.E.H.U. Some of the considerations on the theme for the workshop are included in the Downloadable link : E-Learning Workshop This document essentially describes the needs as does arise for students with educational backgrounds from the North Eastern Region |
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The materials for presentation in IBS2009 are based essentially on the materials of the IBS2007. This author could not attend the IBS2007 due to turn of events beyond control hence the materials remained unpresented. The Poster materials of IBS2007 can be viwed from HERE,..Click! |
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Find on page 92 of the NCMB-2009 Symposium ABSTRACTA BOOK FULL TENSOR FORM FOR CALCULATING RING CURRENT SHIFTS GENERATING WEIGHT FACTORS OF THE INSTANTANEOUS CHEMICAL SHIFT VALUES FOR AN EFFECTIVE MOTIONAL AVERAGING IN BIOLOGICAL MOLECULES S. ARAVAMUDHAN Department of Chemistry North Eastern Hill University SHILLONG 793022 Meghalaya inboxnehu_sa@yahoo.com
By using the Full Tensor Form of the equation for the aromatic ring current shifts in the , 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. Conventionally, an oscillatory motion (torsion) is satisfactorily taken into account on the basis of the characteristics of Simple Harmonic Motion. In such a case the characteristic resident time for the molecule at a point during the oscillation can determine the weight factor. 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 whatever extent possible a comparison with the approaches as in Reference (3&4) would be presented. Indications to the observable trends in the chemical shifts become evident in the results obtainable in tabular form and or graphical plots. |
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SHEETS-01 to 03 consist of excerpts from an early application of isotropic ring current shift values to the context of macromolecular fluctuations. SHEET-04 describes the efforts initiated for the calculation of FULL TENSOR instead of only the trace. Display SHEETS 05 to 09 contain the results of a calculation as per the considerations of SHM weight factors discussed in the Previous SHEET-03. SHEET-09 consist the essential results as can be summarised till the present. SHEETS 10 to 12 contain the results displayed in the previous years� IBS events on the necessity for the calculation of ring current shits in Full Tensor FORM. The illustrations in this presentation of the considerations on the trends in weight factors while averaging are once again mainly with isotropic calculation trends. But the results as presented indicate well how the differences can improve significantly the conclusions with appropriate option on the specific tensor component should be relevant and for such a specified component how the criteria for relative weight factors can be adapted |
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IN TERMS OF CLASSICAL VECTOR PRECESSION: An effort for the appreciation of Chemists, highlighting similarities and differences in the NMR and NQR Phenomena S.ARAVAMUDHAN Department of Chemistry North Eastern Hill University SHILLONG 793022 Meghalaya inboxnehu_sa@yahoo.com The induced transitions, in presence of the electromagnetic radiations in the Radio Frequency region responsible for Nuclear Quadrupole Resonance (referring explicitly to NQR at zero external magnetic field) are magnetic dipole transitions in nature as much as the NMR transitions are. But, the energy of interactions which cause the energy level splitting in the two cases are different. In the case of NMR it is the magnetic dipole vector interacting with the External Magnetic fields (external to the sample containing the ensemble of spins) which causes energy level splitting. On the other hand the basic interaction for the NQR is the Nuclear Quadrupole Moment Tensor with the Electric Field Gradient Tensor within the specimen, but external to the particular nucleus. The classical vector precession picture can be conveniently used to convince in the Chemistry class rooms to get convinced about the parameters which are relevant to chemists. But a similar visualization is not possi9ble for NQR as can be found from several sources. Efforts were made to use the classical vector description for the Bulk Magnetization in the context of NQR, but the classical vector description of the type of nuclear spin precession to describe NQR phenomenon is totally absent. It is because the nuclear quadrupole moment is described and discussed under nuclear physics and the Tensor interactions are describable conveniently by mathematical expressions but visualization of �tensors� is not as easy as the visualization of �vector� quantities. In this paper the tensor interactions and the differences between Magnetic Field Vectors, and the Electric Field Gradient Tensors are being discussed by schematically representing the fields and field gradients in terms of the trends of the �lines of forces� representing the fields. Then the association of the magnetic moment with the spin angular momentum is compared with the difficult task of associating the spin angular momentum vector with the Nuclear Quadrupole Moment Tensor. After arriving at a �equivalent� description of an association of an effective line to represent quadrupole property (even though in reality such a line may not exist) that line is �supposed� to hold a fixed orientation with respect to the Spin angular momentum, by virtue of which a classical vector precession picture becomes tangible. And, this would really enable the necessary basics about the interactions in NQR to be grasped with an awareness as to why the descriptions cannot be as simple. Even though, even without such a study, pulsed NQR experiments are being performed and described in terms of density matrices and the utility of the phenomenon has been so well established. But the appreciation of the pulsed NQR experiments by the Chemists who use this technique remains only vague and elusive for the grasp. Hence descriptions as basic as that of dipole moments1 would be presented for the quadrupole moment to bring the phenomenon under better grasp. An indications to what this approach would be has been made available2 for viewing. Reference:- |
SHEET-01 CONTENTS INDEX SHEET-02 & SHEET-03 INTRODUCTORY NQR SHEET-04 DESCRIBING FIELD GRADIENTS SHEET-05 Nuclear Charge Distribution: Spherical versus Non Spherical Non Spherical distribution of charge and the Quadrupole moment; The possibility of a linear arrangement for the Quadrupole SHEET-06 Nucleus; Nuclear Quadrupole moment; and the Nuclear Spin Angular Momentum SHEET-07 Interaction of the Dipole with Uniform Field and the Quadrupole with Uniform (linear) Field Gradient SHEET-08 Disposition of the various vector quantities and the linear quadrupole moment of nucleus SHEET-09 Quantization of Angular momentum while Quadrupole moment Interacts with Field Gradient SHEET-10 A Energy Level Diagram for Comparing NMR and NQR interactions SHEET-11 Envisaging a Precession Picture for NMR and NQR SHEET-12 What is right and What is wrong with the Question in this Sheet ? |
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AND POPULATIONS, MAGNETIZATION AND COHERENCES S. ARAVAMUDHAN Department of Chemistry NORTH EASTERN HILL UNIVERTSITY PO NEHU Campus SHILLONG 793022 Meghalaya INDIA In the previous presentation (1, 2) the feasibility of a classical vector precession description was considered for NQR and a provisional illustration could be worked out for such a single spin description for the case of the basic NQR interaction of Electric Field Gradients interacting with Nuclear Quadrupole Moment. The further consequence which can be looked for is the possibility of describing the Resonance Phenomenon using the single spin description and envisage a coverage of the description of terms like Population, Magnetization and Coherences and the description of evolution of the spin system in accordance with the classical vector single spin precession under nuclear quadrupole interactions. These terms have a well formulated description for the case of NMR of spin ½ nuclei like protons. A description for the NMR of Spin >1 nuclei (with three equidistant energy levels for Spin=1 unlike the two level system for spin ½) and the corresponding NQR level descriptions have to be considered for a convincing development of the meaning of the terms like populations, magnetization, and the coherences arising out of superposition of levels under short intense pulses applied to the spin system.
This aspect would be considered and the credible alternatives for NMR and NQR would be attempted when the nuclear spin is >1
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POSTER SHEETS of NSC12 |
