Stan's NMR Blog: 2005 entries
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December 30, 2005

Multiple solutions of HR-NMR spin-system spectra

Recently, I had a reason to read again a paper I wrote years ago with Peter Diehl and Jürg Vogt on the automatic analysis of HR-NMR spectra. Apart from the fact that re-reading one's own papers may be very interesting (one often learns a lot), one minor aspect of that study struck me as being of some value for NMR spectroscopy newcomers who often think that fitting a set of parameters (chemical shifts s and coupling constants J) to an HR-NMR spectrum automatically guarantees that the said parameters are 'correct'.

To show that this is not true, consider the two cases shown on the right. In both cases, each with two distinct solutions, the Figure shows stick spectra plotted 'upward' for one solution and 'downward' for the other one. The system of spin-1/2 nuclides is in both cases of the ABC type, one which appears to be most subject to solution multiplicity (more than four-spin systems). Convoluted with a Lorentzian of 0.1 Hz linewidth, the two spectra deviate in both cases less than 1% of the strongest line - a difference which may well be below the noise level.

Case A: Here we have two solutions which give essentially the same transitions with slight position and intensity differences noticeable only in a few very weak outermost lines or in combination lines with unobservable intensity. The parameters of the two spectra are:

Upward:     sA = 8.26, sB = 6.13, sC = 1.00, JAB = 14.23, JAC = -9.69, JBC = 12.14
Downward: sA = 9.04, sB = 4.89, sC = 1.53, JAB = 19.15, JAC = -3.45, JBC = 11.33

Case B: Here the two solutions differ more than in case B, with some almost exactly coalescent lines of one solution splitting into visually resolved doublets in the other solution (the splittings, however, are too small to be resolved in a real experimental spectrum). The parameters of the two solutions are:

Upward:     sA = 1.62, sB = 1.68, sC = -9.72, JAB = 0.49, JAC = 8.16, JBC = -5.16
Downward: sA = 2.91, sB = 0.47, sC = -9.78, JAB = 6.55, JAC = 7.42, JBC = 6.70

The feeling that a solution for a spectrum of a coupled spin system should be always 'correct' is comforted by H. Kummer's uniqueness theorem (Helv.Phys.Acta 36, 901, 1963). That theorem, however, applies only to generic systems with no special symmetries and does not take into account approximate, experimentally un-resolvable multiplicity like the cases shown above.

In special systems with manifest or hidden symmetries, the un-determination of spectral parameters is well known and accepted. In an AB system, for example, the sign of the coupling constant is irrelevant so that we always have two solutions.

In more complex systems like AA'A'', or the ones shown above, one often finds in the multi-dimensional space of spectral parameters one or more continuous subsets (usually segments of one-dimensional 'lines') along which the spectra are approximately the same and experimentally undistinguishable. What, even today, is completely missing is any hint of a theory which, for any given type of spin system, would predict the existence of such subsets, their number and their properties. Such a knowledge would have great impact on deciding which combinations of parameters are strongly determined (small experimental error) and which might be almost undetermined.

Another aspect of the problem which, in my opinion, merits attention is whether - and to which extent - 2D spectroscopy techniques remove the multiplicity of 1D solutions (when present). So far I did not have sufficient time and resources to look into this.

December 7, 2005

What kind of instrument do I need to measure an NMRD profile ?

Bertrand Lo from the GM Lab of National Tsing Hua University (Taiwan) has send me the following query: I read your blog when i was trying to find something about "How to record the NMRD profile". Also, can the regular FT-NMR provide the NMRD profile? Or do I need some specific instrument to measure it ?

Dear Bertrand, I am aware of the fact that modern variable-field NMR relaxometry (VF-MRR) is still a novelty on the NMR scene and many people don't have a clear idea about the required instrument(s) and about their modus operandi. At the same time, there is a lack of up-to-date introductory material. Since I have worked in the field for a few years, I will try to write an educational Note on the topic very soon (please, follow this blog). In the meantime, I advise you to consult the review articles and books listed below. The most recent one, written by Gianni Ferrante and myself, covers technical stuff as well as methodology and applications. In the absence of something less heavy, it is probably the best introductory text.

As far as instruments are concerned, the answers are simple:
1. No, a standard FT-NMR instrument is not capable of measuring NMRD profiles.
2. For modern VF-MRR you need a special fast-field-cycling (FFC) instrument with a low-inductance magnet which can be operated at any magnetic field between 0 and, say, 1 Tesla and switched between any two field levels in about 1 ms. You also need a broad-band NMR console, special gear to control the magnet (400A/15kW switchable power supply and a special cooling system), and special software.
3. You can build such a system yourself (in the past decades, several research groups around the world have done so) or buy one from Stelar, an Italian company which produces commercial FFC equipment for VF-MRR. Typically, a research-grade instrument of this type costs about as much as a HR-NMR 200 MHz spectrometer and occupies about the same laboratory space.

References:

  • Ferrante G., Sykora S., Technical Aspects Of Fast Field Cycling in Adv.Inorg.Chem.,
    Editors R.van Eldik, I.Bertini, Vol. 57, 405-470 (2005). Abstract.
  • Kimmich R., Anoardo E., Field-cycling NMR relaxometry in Progress in NMR Spectroscopy, Editors Emsley J.W., Feeney J., Vol.44, 257-320, Elsevier 2004.
  • Anoardo E., Galli G., Ferrante G., Fast-Field-Cycling NMR: Applications and Instrumentation, Appl.Magn.Reson. 20, 365-404 (2001).
  • Kimmich R., NMR Tomography, Diffusometry, Relaxometry, Springer-Verlag 1997.
  • Koenig S.H., Brown R.D.III., Field-cycling relaxometry of protein solutions and tissue: Implications for MRI in Progress in NMR Spectroscopy, Editors Emsley J.W., Feeney J., Sutcliffe L.H., Vol.22, 487-567, Pergamon Press 1990.
  • Noack F., NMR Field-Cycling Spectroscopy: Principles and Applications in Progress in NMR Spectroscopy, Editors Emsley J.W., Feeney J., Sutcliffe L.H.,
    Vol.18, 171-276, Pergamon Press 1986.
  • Noack F., Nuclear Magnetic Relaxation Spectroscopy in NMR - Basic Principles and Progress, Editors Diehl P., Fluck E., Kosfeld R., Vol.3, 83-144, Springer Verlag 1971.

December 1, 2005

NMR and Nanotechnology

For a physicist like me, there is a deep analogy between the two concepts.

The NMR spin systems are an ideal laboratory for the development and testing of quantum mechanical ideas since they fit finite-dimensional Hilbert spaces and can be handled without the severe approximations arising from fitting infinite-dimensional spaces into finite-dimensional computers.

Likewise, nano-particles position themselves between isolated atoms and solid bodies. The latter have, of course, a number of properties which are totally inapplicable to the former. What, for example, is the melting point of an atom? Here, the fascinating aspect is the transition from a single atom to a poly-atomic ensemble and the question of how and when macroscopic (ensemble) properties emerge along the way.

This reflection, however, has been stimulated by a much more down-to-earth March article on Solid-State Nuclear Magnetic Resonance for Studying the Molecular and Atomic Structures of Nano-Level Building Materials which appeared on the Azonano.com news page. It says that Prof.Yoshitaka Ishii, an assistant professor at the University of Illinois at Chicago has received a $558000 NSF specific grant for the development of NMR methods for the characterization of nano-materials. It poes on explaining why NMR should play an important role in developing nanotechnology. Which, of course, I have absolutely no reason to doubt.

On the same page I read that University of Delaware has received $1.3 million for nonotechnology research, etc. Which indicates that there is a lot of money flowing through the US nano-channels and that some of it is earmarked for NMR. Since, lately, I did not hear much about nano-matters from my local NMR friends, I wonder whether perhaps we are not too sleepy on this side on the Atlantic (not to mention Italy).

There might be fat grass growing just beyond the little hill where we can't see it !!!

November 23, 2005

List of Early NMR references: an unwieldy Behemoth split in two

This project started almost as a game, based on the fact that I already had a pretty extensive collection of "historic" articles and reference lists. I now realize that I have perhaps made an error in wanting to include all references up to the end of 1959. As you might have noticed, the count has reached 450 and keeps growing at a steady rate.

Since managing such a long list is becoming a problem, I have decided to split it into two parts: Part I, covering the early period up to 1955 and Part II, covering the years 1956-1959. The break-line coincides with the introduction of the first commercial NMR instrument by Varian Inc.

Keep in mind that the references are at present sorted by year, journal volume (in case of the same journal) and page numbers. This means that, within the same year but across different journals, the order need not be chronologically correct and should not be used to assign priorities. A true chronological sorting based on the submittal dates would require more work than I can at this time afford.

Part I of the list should be now nearly complete but, so far, I can not say the same about Part II. Naturally, your help in bringing this project closer to completion would be most welcome (forgotten or incorrect references, sponsorships, etc...).

In future, I plan to introduce some classification (NMR, NQR, relaxometry, spectroscopy, basic theory, computing, observed nucleus, non-academic applications, ...). If you have any good ideas about which keys are most useful, I would be very glad to know them.

November 8, 2005

Second EuCheMS School on Protein Chemistry

Mario Piccioli informs me that the registration period for this School is now in full progress (to register, click on the title of this entry.). The School will be held January 15-20, 2006, in Alba di Canazei, Italy (Dolomiti) and, as I so far know, is one of two principal NMR events apart from the annual meeting of GIDRM, the national discussion group.

The theme of the School, organized by Paola Turano, Gianfranco Scorrano and Henriette Molinari, is Protein-protein interactions: from genome to function and the goal is to provide qualified background training on the subject for those embarking on academic and industrial applications.

Doubtless, NMR will be much a part of the talks which will focus on the bioinformatics, biochemical, structural, and computational aspects related to the identification and characterization of protein-protein functional interactions.

In case you wonder, the second major NMR event in Italy in 2006 will be the 8th International Bologna Conference on Magnetic Resonance Applications to Porous Media which will be held September 10-14, 2006, in Bologna.

October 31, 2005

Sorted list of over 500 (!) Books on NMR Spectroscopy and Relaxometry

I hate looking up references to books and articles which I have read long time ago and which I can't find any more - especially when all I need is a reference to put into a new manuscript.

This collection of NMR monographs should cover part of that need. In addition it should be useful to students, as well as to people looking for texts describing stuff which is a bit out of their field, or maybe just checking on new texts in their own field. Whichever is the case, I hope that you find the list helpful.

If you have written a book which is not in the list (or just read one), let me know and I will be glad to add it.

October 30, 2005


SEQUELS:
 
30 Dec 2007
13 Jun 2008
22 Mar 2009

W. G. Proctor's Reminiscences of the Early Days of NMR at Stanford

This is a delightful historic recount written around 1967 by Warren G. Proctor, one of the pioneers of NMR and co-discoverer of chemical shifts. I have obtained the document long time ago from L.O.Andersson (then working at the Varian premises in Zug, Switzerland) who had a few notes added to it by Martin Packard. I don't know what was the original purpose of the recount - possibly a presentation or an invited talk somewhere. Internet gives me the possibility to make the recount public since, in my opinion, it was intended to be public and it is most eminently of public interest.

October 28, 2005

References on Early History of NMR

In the June 15 entry of this blog, I have promised to come up with various collections of references on specific NMR/MRI topic. The first such collection was dedicated to physical principles of MRI and at present contains over 180 entries. I am pleased to be able to announce the second collection, dedicated to early history of NMR and containing at present over 500 entries. The list contains titled entries up to 1959 (inclusive). For many entries I have added a one-line note which points out the historic merits of the publication.

I hope that you will find the collection useful and keep an eye on it. In a reasonable it should become complete. For that, I would most welcome your help. If you have a titled reference pertinent to the list, or a title of one which is has been included without the title, or if you spot a mistake or mistype, please, let me know. Together, we can make this page a valuable resource for the NMR/MRI community.

October 26, 2005

New process NMR platform under development

John C.Edwards of Process NMR Associates informs me that they terminated their relationship with Invensys which included development of applications for the FoxboroNMR hardware (see the July 15 entry in this blog). They are now developing further NMR process-control applications on their own.

October 10, 2005

Two coils, two preamps, cooled probes ... ???

This year I could not participate at the EENC meeting but, nevertheless, I have picked up rumors about Company presentations and about an apparent discrepancy between various approaches to improving the S/N ratios of NMR spectrometers which, it seems, have puzzled many of the application-oriented user of NMR spectrometers.

The whole question of spectrometer sensitivity is again in motion and we witness various approaches being tried, alas in a somewhat un-coordinated way. These include two receiver channels (in particular, two preamplifiers), two pick-up coils (possibly in quadrature), cooled coils (cryo-probes) and cooled preamps.

If these aspects of NMR spectroscopy interest you, have a look at my Note NMR Sensitivity: Novel Approaches and Perspectives. I would be also glad to receive - and publish - any comments, be they critical or supportive of my own standpoints.

September 18, 2005

Scuola Nazionale di RMN a Torino (Torino, Italy, September 12-16)

The week-long NMR Spectroscopy School of GIDRM (Italian NMR Discussion Group) was held at the Turin facilities of Fondazione per le Biotecnologie which was also in charge of the event's logistic. Having participated as a Lecturer, I can testify that:

# The 40 attendees (mostly post-graduate students and young researchers) were splendid. Not only were they constantly taking notes and asking questions but, in the whole week, I have not spotted a single napping head!

# The quality of all the lectures (except mine, I am afraid) was excellent. As a technologically-oriented physicist with limited day-to-day exposition to NMR spectroscopy, I was particularly impressed by the pedagogical competence of my colleagues in teaching the subtleties of 1D and 2D NMR techniques to young chemists. They managed, apparently effortlessly, to make beasts like COSY, TOCSY, NOESY, ROESY, HMQC and HMBC appear as innocuous kitties.

# The students particularly enjoyed the hands-on exercise sessions held on a networked array of twenty PC's equipped with the MestReC NMR software package. They were guided through the exercises in a gentle but firm manner which enhanced their impact. Moreover, since Mestrec has kindly provided all attendees with a special four-months demo version of the software, they will have ample possibility to expand at home on the lessons they learned at school.

# Thanks to the organizing committee, to the lodging and catering facilities of Villa Gualino and to the care of Dr.ssa Martina Di Paolo, the organization was flawless (the worst mishap was a mulfunction of an overhead projector which was promptly replaced). The program included even a guided tour of Turin and a countryside dinner with local dishes and excellent Piemont wines.

September 9, 2005

950 MHz (22.31 Tesla) HR-NMR magnet is operative !

In August, Oxford Instruments has energized and tested the first-ever commercially available 22.31 Tesla magnet suitable for High-Resolution NMR spectroscopy. The corresponding proton Larmor frequency is 950 MHz, 50 MHz more than the last record. The magnetic field drift of the device is about 5 Hz/hour, which places it into the category of fully persistent magnets. At this moment, it should be already delivered to the Oxford University's Department of Biochemistry.

The news opens bets on who and when will puncture the 1 GHz barrier (23.486 Tesla). If you want to try a guess, send me an e-mail and I will publish it together with all others in a section of this blog.

Note: Has it occurred to you that, superconductivity being a quantum phenomenon, supercon magnets are genuine quantum devices? I have once put it that way to a European Union sub-Commissar for Science and he appeared to be genuinely surprised by the fact. Without Planck, Schrödinger and the rest of them we would be still plodding along at the 2.3 Tesla maximum of iron-based electromagnets!

September 4, 2005

NMR in Microbiology by Jean-Philippe Grivet

I rarely promote new books but this one, published by Horizon Scientific Press, I really like. The above link points to an extensive and well-written resumè which, especially for a non-specialist, represents in itself a valuable briefing on both NMR spectroscopy and microbiology. It is laced with numerous further links and terminates with a nice list of serious links to Molecular Biology and Genomic matters.

September 2, 2005

Contrast Media & Molecular Imaging - a new MRI/NMR Journal

The appearance of a new scientific journal dedicated primarily to MRI and/or NMR is certainly of great interest to all readers of this blog. The CMMI, published by Wiley-Interscience, is just kicking-off.

MRI contrast media are of course all about NMR relaxation and their development requires, among other things, the use of fast-field-cycling NMR relaxometers. Since I have dedicated years of my life to the development of such instruments, the appearance of this journal can not but please me. It is also of particular interest to Stelar, Srl which is the only Company producing commercially available FFC-NMR Relaxometers.

The name of the new journal goes beyond plain contrast agents and hints at contrast media with specific binding properties. Such substances are soon going to become MRI relaxation probes allowing the acquisition of MRI images whose contrast stems from concentration differences of specific molecules or classes of molecules. This, I believe is a new scientific frontier with a very bright future, as well as an exciting challenge for chemists and bio-chemists.

For an almost complete Directory of NMR/MRI journals, click here.

July 27, 2005

Are you sure you know what is N.M.R. ?

So far I knew that whenever I read NMR, it meant either Nuclear Magnetic Resonance or No More Research. That certainty, however, fell today when, scavenging the Net, I have hit on a NMR 2004 Workshop and clicked the link. Moments later, my brain was badly scorched and I was squirming in agony!

It turns out that NMR is an established acronym for Non-Monotonic Reasoning, an Artificial Intelligence discipline which, I believe, has something to do with taking decisions based on very limited data which, on top of it, might be plain lies. Those who ponder these matters wallow knee-deep in belief-dynamics, individually-inconsistent-data-bases, answer-set-algorithms, belief-change-operators, etc.

Since the discipline is essentially a branch of mathematics, be particularly careful when you hear about, say, Novel Computational Aspects of NMR - it might have nothing to do with NOE and proteins!

There is a much more frequent but inocuous confusion related to the acronym FFC (Fast-Field-Cycling) which, in Net searches, brings up all kinds of bicycle clubs and/or events. To avoid the problem, use it always together with either NMR or MRR (Magnetic Resonance Relaxometry).

July 20, 2005

NMR of solid urea - an unsolved mystery

Looking through some year-old data of mine, I have revived my memory of an experimental NMR mystery which I would like to share with others and keep alive until a plausible explanation is found. It regards NMR relaxometry of solid urea which, it turns out, is at present IMPOSSIBLE to do at the acquisition frequencies which are available to me (<50 MHz). My attempt to measure a 1H-NMRD relaxation profile of solid urea failed and raised some very disquiting questions.

The problem is linked to a very strong piezoelectricity of solid urea. This has been observed long time ago by Prof.R.Kimmich who mentions somewhere that the piezoelectric disturbance persists up to excitation/acquisition frequencies of about 80 MHz. Kimmich, just like me, was evidently driven by the desire to see the nitrogen T1 relaxation glitches expected somewhere in the region of relaxation fields comprised between 0.5 and 3 MHz. There should be four marrow relaxation-rate peaks and, in the case of solid urea, they should be fabulously strong. In both cases, however, the fast field cycling (FFC) NMR experiments designed to achieve this goal failed miserably. In fact, you will not find any low-field longitudinal relaxation data on solid urea anywhere in the literature.

What left me really puzzled, however, is not so much the fact that urea is piezoelectric. There are many more piezoelectric solids than what most people would believe and, yes, piezoelectricity does interfere with NMR measurements, especially at low fields. What I find puzzling are the following points:

  • The effect appears to be extremely strong and yet, except for the single-sentence mention by Kimmich, I have not found in the literature any other datum on urea piezoelectricity (if you hit on some, please let me know, since I probably do not know where to look).
  • The strong piezoelectric transient signal has nothing to do with NMR since it is present even in the absence of magnetic field. At NMR resonance field, however, it is substantially weaker than the expected proton NMR signal so that it should appear as a disturbance superposed over normal NMR FID. Yet, this is not what happens - there is simply no trace of the NMR signal. Where and why did the NMR signal disappear?

If you are looking for an experimental mystery involving solid-state physics, NMR and interactions of solids with RF fields, here is a realy nice one waiting for a solution. Personally, time permitting, I plan to return to the matter and keep you informed.

For more details about my experiments up to this point, click here.

July 15, 2005

Is this an NMR Instrument?

I do not discover many new NMR Companies these days. Yet, there are still some that escaped my attention. The latest one I have ferreted out is Foxboro NMR, a Massachussets Company which, if I got it right, is part of the UK Invensys Group. They prefer to call their products MRA (Magnetic Resonance Analyzers) and they produce them specifically for low-resolution industrial process-control applications (primarily crude/petrol plants). It is sort of funny that I have so far never heard about them, considering that they seem to have installations all over the world (there is a link to an installations map at the bottom of their home page).

July 10, 2005

GIDRM: Scuola Nazionale di RMN a Torino

Non so voi, ma io faccio fatica a seguire le continue variazioni dell'indirizzo web della Scuola. Quello riportato sopra sembra funzionare e spero che non cambi più!

Dato che vi sono coinvolto come docente (cenni sulla strumentazione), metterò la mia lezione e tutti i relativi materiali su questo sito a partire dal 20 Agosto. Chi desidera prepararsi in anticipo è invitato a dare un'occhiata a questa pagina dopo tale data.

June 15, 2005

Collections of thematic NMR references

As an NMR/MRI community service, I intend to set-up a series of pages with Collections of thematic literature references. As a kick-off I have prepared a collection of references dedicated to physical principles of MRI which I have had more or less ready. Other thematic pages will follow before the end of August, so stay in tune. Imminent plans include variable-field NMR relaxometry, T1 and T2 measurement methodology, relaxation decays evaluation, NMR of oriented molecules, NMR spectra simulation, and historic NMR papers.

Unlike references in traditional exact-sciences journals, mine are complete with full-length titles and, with only a few exceptions, a complete list of Authors (this, alas, does not mean that I have actually read all of them). Another difference consists in the fact that the Collections are continuously growing, becoming cumulatively ever more complete and useful (another reason why you should periodically check on them).

If you think that this is a good initiative, mail me any additional references you feel should be included in a particular Collection. These may include your own papers. After all, in this age of publish or perish a bit of self-advertisement is not out of place.

May 29, 2005

FC-NMR, FFC-NMR, NMRD, FFC-NMRD, VF-NMR, VF-MRR, ???

The conference on FC-NMR Relaxometry in Torino (see below) was a good platform from which to admire the new Tower of Babel we seem to be erecting in the NMR relaxometry countryside. I refer to the use of terms such as those listed in the header of this entry. By their nature, NMR relaxation rates are both temperature- and field-dependent. While, surprisingly, the temperature dependence did not lead to any special terms or acronyms, the field dependence seems to be very prolific in that direction.

The term Field-Cycling NMR seems to have been born in the early days of mechanical shuffling of samples between two magnets (Ramsey and Pound, 1950) which makes it older than, for example, HR-NMR. It seems, however, that the use of the acronym FC-NMR is much more recent. The acronym NMRD is probably much older and has the advantage of being linked to a phenomenon rather than to a technology. The "D" in fact reminds us of dispersion curves or, as they are called nowadays, dispersion profiles which plot relaxation rates against the applied magnetic field.

The term Fast-Field-Cycling NMR, or FFC-NMR, came about when people started switching up and down the current in their magnets and found out that, if they tried hard, they could do it much faster than shuffling the samples. That, however, left out those who did not have such machinery but, having connections, had access to many different instruments, each with a different field. They coined the term Variable-Field NMR, sometimes intending not just relaxometry but also spectroscopy and even imaging.

I feel that the most fitting terms are MRR for Magnetic Resonance Relaxometry and VT-MRR (Variable-Temperature Magnetic Resonance Relaxometry) and VF-MRR (Variable-Field Magnetic Resonance Relaxometry) for its two main branches. They have a chance to be accepted also in the imaging field and they cover even the electron-relaxation aspects of the discipline. Consequently, I am going to promote these terms and acronyms on this site.

If you have any other proposal about how to reduce the linguistic confusion, let me know and I will be glad to publish it here.

May 28, 2005

4th Conference on Field Cycling NMR Relaxometry (Torino, Italy, May 26-28)

These Conferences are dedicated to NMR relaxometry in all its aspects. Due to the recent rapid technical developments in field-cycling (FC) and fast-field-cycling (FFC) NMR, the attention presently tends to focus on the variable-field (VF) aspects of NMR relaxation phenomena but other aspects, such as temperature and pH dependencies are kept in mind and often crop-up.

The first Conference of the series was organized in 1998 in Berlin by Rainer Kimmich, one of the fathers of the FFC technique (this year he was awarded the Conference Prize). The second meeting was held in 2001 in Ivrea, close to Turin, Italy, organized by the group of Silvio Aime and his colleagues. At the third meeting in 2003, held at Villa Gualino in Turin, it was decided to meet every second year at the same location.

I have found this year's edition very stimulating. The number of participants (83) was not overwhelming, permitting the development of a nice, informal atmosphere. The participants came from 15 countries: Argentina (1), Belgium (4), Brazil (3), France (2), Germany (10), Ireland (4), Italy (33), Japan (1), Portugal (1), Russia (1), Slovenia (2), Sweden (5), Switzerland (7), UK (3) and USA (6). Many, of course, were of a nationality different from the country where they momentarily work, or of a mixed one.

Organization of the logistic aspects (handled by people from the NMR lab of Uni Torino and from Stelar) as well as of the scientific contents was faultless. For this, thanks are due to the organizers, namely S.Aime, R.G.Bryant, G.Ferrante, R.Müller, J.P.Korb and M.Vilfan. The Conference was sponsored by Stelar Srl and Bracco Imaging spa.

The 28 oral contributions (30 minutes each) and the 24 posters were of excellent quality and there was not a single one which would not be well presented and which I would not find deeply interesting. Compared with the preceding editions, there was an unquestionable increase in the number of tackled applications, combined with a large mass of new experimental data (clearly due to a growing base of FFC-NMR instruments) and profound improvements in the depth of understanding of the observed phenomena. On the other hand, the talks confirmed my long-standing impression that every accounted-for relaxation phenomenon comes in a company of two unexplained mysteries. For me, that's what really makes the whole field interesting.

I am tempted to comment on many of the oral contributions and posters but, alas, it can't be done for lack of space and time and, besides, the abstracts are available at the conference Web site. Let me just list some of the applications and systems which came up in the talks:

  • Molecular dynamics in constraint geometries (pores, cavities, surfaces)
  • Protein solutions of many types, studied by different ways
  • Solutions of lipid-protein systems
  • Biological tissues
  • Protein quantification in MRI (exploiting 14N glitches)
  • Aqueous gels
  • Sugar glasses
  • Polymers (solid bulk as well as melts)
  • Liquid crystals
  • Acoustically stimulated relaxation
  • Cement (hardening kinetics and structure)
  • Paramagnetics (ions and ion complexes)
  • Fullerene derivatives with trapped paramagnetic ions (Gd)
  • Proton tunneling in hydrogen bonds
  • Fast localization of 14N NQR frequencies
  • NMR well-logging methodology
  • Ex-situ characterization of materials (NMR mouse)
  • Reaction kinetics using variable-field CIDNP
  • Ionic crystals with dipolar and quadrupolar spins
  • Vitrified solutions of inorganic salts

Stelar User's meeting

The Conference was preceded by a meeting of the User's of Stelar instruments at which Stelar people (including myself) described new technical developments of their commercial FFC NMR relaxometers (we also had several posters dedicated to this topic). Stelar hopes that the advances will eventually lead to even more interesting FC-NMR conferences and, based on past experience, the hope is certainly justified. This year's set of novel features includes, apart from a number of minor items, an FFC magnet model (over 1T) with improved cooling (continuous operation even at 1T), fully digital SOC (System-on-Chip) NMR Console, a zero-field accessory and an innovative family of null-biased FFC sequences.

May 15, 2005

A new site combines NMR with Rheology

I have just discovered a new site, started in April of this year. It is called Rheo-NMR and was set-up by Magritek of Wellington, New Zealand (though they do not say so very loudly). It includes a news section ragarding everything that has to do with NMR of rheological phenomena, such as polymers and other systems with heavy molecular entanglement and retarded shear-induced effects. There is an extensive list of references to articles about NMR on such systems (I counted 78 of them - so far). Needles to say, the name of Paul Callaghan meets the eye very often which, as far as I am concerned, is a sufficient proof of the site's quality.

May 14, 2005

A headache! How should I manage the growing database of NMR links

Today I have decided that it was more comfortable for all of you to have a new page opened when you click on any of my external (and many internal) links, rather then using all the time the same browser page. When implementing the modification, I have noticed - to my own amazement - that there are already 377 links in Stan's NMR Links and 400 links in the general-science Stan's Links. That adds up to a total of 777 (a lucky number) but it is rapidly becoming intractable without some sort of organization (only the Manufacturers, split into six sub-groups, account for about 110 links). The NMR and MRI links are now grouped into 23 broad categories which, however, need to be reorganized. I will think about it and try a new branching scheme which should make it possible to reach any desired site in not more than 4 clicks. I wonder whether it is possible at all, but it certainly is a challange. If you have any helpful suggestion, I beg you to let me know.

May 11, 2005

NMR history links

I have started a new Section in Stan's NMR Links (Dec.1, 2005: it is now an indepenednt page). It is intended to list all Web pages which are in any way concerned with NMR and/or MRI history. I hope that you will find the Section interesting. Naturally, should you know of any links which I have missed so far (there must be tens of them), I would be most grateful if you could let me know.

May 9, 2005

Early MAS in Prague

Browsing through the NMR Webland, I have stumbled on an interesting article about early (1967-1971) attempts at developping a MAS (magic angle spinning) 1H NMR apparatus at the Institute of Macromolecular Chemistry in Prague.

The article was written by Danica Doskocilova and Bohdan Schneider, two persons who played a particularly important role in my own life, since the former guided my post-graduate work, while the latter headed the department where, in 1964, I started doing NMR. Though the Authors mention the very Jeol instrument which I, too, have used, the developments they describe took place mostly after 1968 - the year when Soviet Union brutally invaded Czechoslovakia, sending in over 800 thousand troops in less than ten days (in comparison, the USA don't have the slightest idea about what a 'serious' invasion means) . Soon after the invasion, I have emigrated and so did about a quarter of the scientists working at the Institute. Doskocilova and Schneider modestly do not mention the fact, but I have no doubt that life got much harder for those who remained in the country than for those who left it. Trying to develop anything of scientific value in the grey years after 1968 must have been a hell and it is no wonder that their efforts ended up in a kind of limbo. When you read that article, please, keep this in mind.

May 3, 2005 

We all know that ∇ ≡ {∂/∂x, ∂/∂y, ∂/∂z} 

but do you know how to script the thing in HTML and be sure that most browsers will display it correctly? If you have doubts then you are just like me - and you are probably fed up looking through manuals every time you are editing a Web document and need to insert a math symbol (or a German name like Schrödinger). That is why I have collected all the HTML entities into a table which shows their codes as well as their actual glyphs. Initially I have compiled the table for my own use but, since it is useful, it would be too selfish if I did not to share it with you. So click here and see whether you can use it.

April 27, 2005

What is this ...

I am starting this blog in a bit too much hurry (it is 1:20 AM, April 27, 2005), prodded by my friend Mauro Cremonini who would like me to use all kinds of fancy Web tricks suitable for publishing whole newspapers. I will occasionally place here my personal reflections on current problems (no politics, don't worry), reports from meetings I attend, announcements pertinent to my site/work, communications regarding my involvement in things like the forthcoming Scuola Nazionale di RMN organized by GIDRM, etc.

I will also use this blog to answer questions from friends and foes, provided that (i) I am in a position to do so and (ii) the answers are reasonably short (since I have to earn my living, too, full-scale on-line courses imply a fee).

Depending upon context, the entries may be in English, Italian or Czech.

April 12, 2005

[it] Domanda a bruciapelo su spazio-K da Mauro Cremonini

Per passare dallo spazio reale a quello inverso (k space) ci vuole la FT. Bene, ma come si applica la FT in 3D? Ovvero, in NMR si fanno FT in 3D, ma in modo successivo. Prima si fa lungo la dimensione del FID e poi lungo la prima dimensione indiretta e infine lungo la seconda indiretta, ma questo solo perche' il segnale e' costruito in modo che i segnali contenuti nel fid oscillino in modo dipendente da due diversi fattori.

Mi sembrerebbe che nel caso del passaggio da R a 1/R invece, si debba fare la FT in modo diverso...ma come'? Hai un riferimento o un link? Grazie e ciao, Mauro

La domanda era nata in seguito alla mia Nota K-space formulation of MRI. FT, ovviamente, sta per Trasformata Fourier.

Risposta: Se guardi l'equazioni (1) e (3) della nota, vedrai che sono formulate a posta in forma libera (senza ricorso ad un particolare sistema di coordinate). L'equazione (2) per il prodotto scalare è scritta in un sistema Cartesiano perchè è così che la gente la conosce di più. In realtà il prodotto scalare k.r è invariante rispetto al gruppo di rotazioni e traslazioni e può essere scritto anche esso in forma libera, tipo k.r = |k|.|r|.cos(φ). Con la scelta di coordinate Cartesiane, la FT a nD si RIVELA identica alla applicazione successiva delle FT a 1D (se vuoi, ciò reppresenta un teorema). Ovviamente, essa potrebbe essere riformulata in modo equivalente anche in altre coordinate (sferiche, cilindriche, elittiche, etc) ma la cosa è abbastanza priva di interesse pratico.

Esistono algoritmi che tentano di fare le FFT a 2D e 3D ancora più veloci di una successione delle FFT a 1D, ma il guadagno è troppo esiguo rispetto alla maggiore complessità. Che io sappia, nella MRI fanno IN PRATICA esattamente come voi nella spettroscopia, salvo per l'uso sempre più esteso degli array processor pre-cablati e quindi tempi di calcolo molto più corti. Non vi sono misteri aggiuntivi.

April 6, 2005

20th NMR Valtice: Meeting of Central European NMR Discussion Groups

This little known meeting is held every year (a week after Easter) by an informal Czech and Slovak NMR discussion group. The meeting place is always in the same Liechtenstein castle in the little town of Valtice, the capital of South-Moravian vine production.

For those who are not strong in geography, Moravia (capital town Brno) is one of the two macro-regions of Czech Republic (the other one is Bohemia with Prague as capital). Valtice is located about 60km north of Vien, just beyond the Czech-Austrian border and within the newly promising triangle formed by Vien, Brno and Bratislava. I flew from Milano (Orio airport) to Bratislava (SkyEurope 160 Euro round trip), then took a train to Breclav (5 Euro) and rode the last 10 km in taxi (10 Euro). That amounted to just 5 hours from my home close to Milano to a bed in Valtice.

The particularity of this years' meeting was its international character. It was organized jointly by several Central-European NMR discussion groups. The participants came from Czech Republic (58), Austria (14), Slovakia (5), Bulgaria (2), Germany (2), Poland (2), Finland (1) and Italy (1,myself). Somewhat strangely, no Hungarian subscribed, presumably because they had a meeting of their own NMR discussion group in roughly the same period. The official language, as always, was English.

Absolute majority of the verbal contributions were of chemical and/or biochemical nature, centering mostly on structural and stoechiometric features of particular molecules. To a physicist like me, this is not particularly attractive but, of course, that is a matter of personal orientation and I am sure that the contributions were of high quality within their fields. Personally, I have found very interesting the talk by H.Stepankova about 57Fe ferromagnetic resonance (no external field required) in pure and substituted magnetite crystals - nice spectra, looking just like high resolution, but spreading from 15 to over 80 MHz! Another contribution which I enjoyed was presented by T.Liptaj and regarded the exploitation of residual dipolar couplings in weakly oriented solvents (it reminded me of the youthful crimes I have committed ages ago with P.Diehl in Basel). Personally, I have talked about progress in variable-field relaxometry and, last but not least, there were several contributions dealing with special sequences aimed at in-vivo spectroscopy and spectroscopic imaging. Abstracts of all talks are still available from the conference web site.

Since Varian and Bruker representatives were present (both gave a Company talk), I did some spying and found out that each Company has at present about ten systems installed within the area of the old Czechoslovakia. Adding that the highest available fields are 600 MHz, this gives you some idea about the current NMR capacity in that part of the world. Since we talk about 15M inhabitants, it is not really bad - and it keeps getting better.

The meeting included a pleasant social event, namely an afternoon excursion to the nearby town of Mikulov, known for its magnificent castle. Now restored, the castle was mined and blown to pieces in 1945 by angry German soldiers (just before Mikulov was taken over by the Red Army). With the castle went on fire a vast collection of looted artistic treasures (including many from Italy and, in particular, from Vien museums). For many centuries, Mikulov had a strong Jewish community and its schools trained most European rabis. It has the most extensive Jewish cemetery in Europe (over 20 ha).

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