The goal of building a multivariate calibration model is to predict a chemical or physical property from a set of predictor variables, e.g. analyte concentration or octane number from a near infrared (NIR) spectrum. A good multivariate calibration model should be able to replace the laborious, possibly imprecise reference method. The quality of a model therefore primarily depends on its predictive ability. Other properties such as interpretability of the model coefficients might also be of interest, but here the focus is on the problem of quantifying the predictive ability.
Gabriel Pinto and Isabel Paz
Departamento de Ingeniería Química Industrial y del Medio Ambiente, E.T.S.I. Industriales, Universidad Politécnica de Madrid, José Gutiérrez Abascal 2, 28006 Madrid, Spain
LURE, centre Universitaire Paris Sud, BP 34, F-91898 Orsay Cédex, France
Mark J. Tobin
CCLRC Daresbury Laboratories, Warrington, Cheshire WA4 4AD, UK
LADIR-UMR 7075 CNRS & Université P. & M. Curie, 2 rue Henry Dunant, 94320 Thiais, France
G.J. Price, G.W. Fraser, J.F. Pearson, I.B. Hutchinson, A.D. Holland, J. Nussey, D. Vernon, D. Pullan and K. Turner
Space Research Centre, Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK. E-mail: [email protected]
David Chenery and Hannah Bowring
Smith & Nephew Group Research Centre, York Science Park, Heslington, York YO10 5DF, UK
Glow Discharge Mass Spectrometry (GDMS) is one of the most powerful solid state analytical methods for the direct determination of traces, impurities and depth profiling of solids.1–5 Glow discharge mass spectrometers, which are commercially available with fast and sensitive electrical ion detection, allow direct trace elemental determination in solid materials with good sensitivity and precision in the concentration range lower than ng g–1.6
Luisa Mannina,a,b Anatoli P. Sobolevb and Annalaura Segreb
aUniversity of Molise, Faculty of Agriculture, 86100 Campobasso, Italy
bInstitute of Chemical Methodologies, CNR, 00016 Monterotondo Staz., Rome, Italy
Moore’s law* dictates microelectronics researchers to make integrated circuit (IC) devices smaller and to put them as close to each other as possible on a chip. This results in a better performance and a larger functionality of the chips. However, these devices also require a good electrical isolation from each other. This is in general done by the formation of a thick local oxide in the “field region” between the devices. In 1970, researchers from Philips1 invented the so-called LOCOS (LOCal Oxidation of Silicon) technique to achieve this isolation. Using a Si3N4 mask, the silicon is thermally oxidised in the nitride-free field regions. Figure 1 (left) shows a typical LOCOS structure. Although LOCOS seemed a perfect solution at that time, it came with a lot of problems, many of them related to mechanical stresses. Thermal oxidation of Si to SiO2 occurs together with a 125% volume expansion. As a result, the oxide grown in the field region, called the “field oxide,” exerts large forces on the surrounding silicon. Another major drawback of this technique is the so-called “bird’s beak,” caused by the lateral growth of the oxide under the nitride mask. This bird’s beak not only affects the intended device length, it also introduces large local mechanical stresses in the silicon, because of volume expansion, and it also deforms the nitride film. These stresses often resulted in the generation of dislocations in the silicon, which are quite harmful for the devices.
S.Y. Luk,a N. Patela and M.C. Daviesb
aMolecular Profiles Ltd, 1 Faraday Building, Nottingham Science & Technology Park, University Boulevard, Nottingham NG7 2QP, UK. E-mail: [email protected]
bLaboratory of Biophysics and Surface Analysis, School of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, UK
Technical Director, Oxford Instruments Superconductivity
Dipl. Chem. FH Ch. Schanzer and Prof. Dr H.G. Bührer
Department of Chemistry, Zurich University of Applied Sciences Winterthur (ZHW), CH-8401 Winterthur, Switzerland
S.E.J. Bell,a* E.S.O. Bourguignon,a A. O’Grady,a J. Villaumiea and A.C. Dennisb
aSchool of Chemistry, The Queen’s University of Belfast, Belfast, BT9 5AG, Northern Ireland, UK
bAvalon Instruments Ltd, 10 Malone Road, Belfast BT9 5BN, Northern Ireland, UK
J. Sabine Becker
Central Department of Analytical Chemistry, Research Centre Jülich, D-52425 Jülich, Germany
The study of the mineralogical phases of archaeological ceramics may be very helpful in unravelling the history of an ancient sherd, particularly by means that investigate the process of its production. Micro-Raman spectroscopy offers advantages as a non-destructive, or even better, a non-sampling technique.
An introduction to photoacoustic spectroscopy.
It is now more than fifty years ago that Felix Bloch and Edward Mills Purcell independently discovered a phenomenon called nuclear magnetic resonance (NMR). Only a few years later, in 1952, both received the Nobel Laureate Physics award for this discovery. Purcell and Bloch were the first to “listen” to the whisperings of hydrogen. They eventually obtained an NMR spectrum representing the different “pitches” of the nuclei, a property, which reflects the physico–chemical (electronic) neighbourhood of the nucleus.