Articles
Tony (A.M.C.) Davies starts a review of the chemometric ideas that have most excited him over the last 30 years. In this column, he looks at the use of Fourier transformation for data compression. FT can also provide the side benefit of reducing high-frequency noise.
Chemical modification of wood by methods such as acetylation is required to improve characteristics such as photosensitivity and combustibility, and to provide harmonisation of wood properties in order to avoid swelling and shrinking and to improve biodegradability. The authors describe the use of mid and near infrared spectroscopies to monitor chemical changes due to acetylation is described.
Tony (A.M.C.) Davies and Tom Fearn describe an enhancement of the popular partial least squares (PLS) technique, powered partial least squares (PPLS), that has shown significantly better results.
Tony Davies makes sure we understand “What IS and what is NOT chemometrics” and why it matters.
“Measuring brain activity using functional near infrared spectroscopy: a short review” by Felix Scholkmann and Martin Wolf looks at the various methods for performing fNIRS and some applications that demonstrate why this non-invasive, safely applicable, portable and cost-effective method is now an integral part of the techniques used in neuroscience.
The Tony Davies Column once again contains a contribution from Karl Norris, who is widely regarded as the “father of NIR spectroscopy”. Karl continues to produce innovative ideas about the field and this article is no different. Building on the previous article concerning fourth derivatives, Karl has investigated the effect of varying gap sizes with some remarkable results.
This Tony Davies Column is contributed by Karl Norris, known to many as “The father of near infrared spectroscopy”. He introduces his calculation method for fourth derivatives and shows how it can be used to extract instrument noise.
With the threat of climate change, understanding the workings of our atmosphere is of crucial importance. Ozone is the most important trace gas in the stratosphere and troposphere and it is monitored by both satellite-borne and ground-based instruments. Accurate knowledge of ozone absorption cross-sections is vital for this work and described in this article.
Tea is harvested from the bud, the first leaf and the first three leaves up to a maximum of four leaves. Quality decreases from the bud down as the parts become older. This study looks at the use of NIR spectroscopy to determine optimal production using the harvested material.
Tony (A.M.C.) Davies is again telling us to “Always look at the spectrum”. This time he uses an example from the development of a NIR spectrometer to demonstrate that one doesn’t really know what’s going on until one has “looked at the spectrum”.
This article shows that NIR spectroscopy offers the potential for bioprocess manufacturing companies to limit the variability in the biological production process, thereby increasing the yield and reducing the number of errors.
Anaerobic digestion is a good solution to the joint problems of dealing with organic waste and producing “clean” energy. However, running the digesters at optimum performace is a complex business. NIR spectroscopy offers a solution to monitor a number of analytes within the reactor and in real time.
Tony (A.M.C.) Davies stresses the importance of always looking at the spectrum, even if you [think you] know there’s nothing to learn. He relates his experience with noise in NIR spectra and what he has learnt from it. He would like us all to examine spectra for abnormality before relying on automated methods.
As nanotechnology grows in importance, the need for rapid, easy and automated analytical methods to investigate new nanomaterials increases. Near infrared (NIR) spectroscopy has the potential to replace numerous methods for the investigation of a wide range of nanostructured materials and with particular potential in the area of PAT.
Tony Davies and Tom Fearn present “A digression on regression”. They turn their attention to one of the simpler regression techniques, Classical Least Squares (CLS). As well as an explanation of the basics, they explain why it is not often used in spectroscopy, and give the pros and cons of various regression techniques.
Roumiana Tsenkova introduces us to the field of “Aquaphotomics” which she has pioneered. The potential information held by water in biological systems coupled with NIR spectroscopy’s ability to extract a large amount of information at once, means that Aquaphotomics may be of great importance in the study of living organisms.
The counterfeiting of medicines is an increasing world wide problem as a great danger to public health. Counterfeit medicines are imitations of their authentic counterparts so that both physical characterisation and chemical analysis are required to discriminate between them. In this respect, near infrared (NIR) spectroscopy is ideally suited to screening for counterfeit medicines because it is non-destructive, fast, requires no sample preparation, and provides a fingerprint of the physical and chemical composition of a product.
I recently “discovered” a very interesting radio programme on BBC Radio 4. It is “devoted to the powerful, sometimes beautiful, often abused but ever ubiquitous world of numbers”. A few weeks ago we were asked to say what we were doing while listening to the programme. The next week we were told that nearly 2000 e-mails had been received and this data had been given to information designer David McCandless to turn into a graphic. When this was trailed I got the impression that something new and exciting was going to be displayed and I thought that the graphic would include sound. The graphic is good but rather “ordinary” and I was disappointed. This got me thinking about how we display information. Have we made any advance in the last 25 years? Could sound be used!
<p>In last year’s <a href="https://www.spectroscopyeurope.com/td-column/and-now-something-complete…">August/September</a> issue of <em>Spectroscopy Europe</em> I wrote a column about my “discovery” of computational chemistry and asked if anyone was interested. A satisfying number of readers answered the on-line survey with very positive comments but none more so than Patrik Johansson who e-mailed me about his delight with the column and to assure me that there was “indeed a bunch of scientists out there that do work on IR (and Raman) using both experimental and computational techniques—I am one of them”! This column is the first result of the ensuing e-mail conversation and is due to Patrik. I remain excited by the possibilities of computational chemistry particularly as Patrik thinks that an approach to NIR spectroscopy is indeed possible.
A.M.C. Davies
Norwich Near Infrared Consultancy, 75 Intwood Road, Cringleford, Norwich NR4 6AA, UK. E-mail: [email protected]
Tom Fearn
Department of Statistical Science, University College London, Gower Street, London WC1E 6BT, UK. E-mail: [email protected]
