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51.
Kohler A Bertrand D Martens H Hannesson K Kirschner C Ofstad R 《Analytical and bioanalytical chemistry》2007,389(4):1143-1153
In this paper we present an algorithm for analysing sets of FTIR microscopic images of tissue sections. The proposed approach
allows one to investigate sets of many FTIR tissue images both with respect to sample information (variation from image to
image) and spatial variations of tissues (variation within the image). The algorithm is applied to FTIR microscopy images
of beef loin muscles containing myofibre and connective tissue regions. The FTIR microscopy images are taken of sub-samples
from five different beef loin muscles that were aged for four different lengths of time. The images were investigated regarding
variation due to the ageing length and due to the homogeneity of the connective tissue regions. The presented algorithm consists
of the following main elements: (1) pre-processing of the spectra to overcome large quality differences in FTIR spectra and
differences due to scatter effects, (2) identification of connective tissue regions in every image, (3) labelling of every
connective tissue spectrum with respect to its location in the connective tissue region, and (4) analysis of variations in
the FTIR microscopic images in regard to ageing time and pixel position of the spectra in the connective tissue region. Important
spectral parameters characterising collagen and proteoglycan structure were determined.
Figure Effective optical path length estimated by EMSC 相似文献
52.
V. N. Grigor’ev O. V. Dorofeev K. L. Litvinenko V. G. Lysenko S. I. Onishchenko K. Leo B. Rosam K. Kohler 《Journal of Experimental and Theoretical Physics》2000,91(4):791-800
An investigation is made of the absorption spectra of a GaAs(82 Å)/Al0.07Ga0.93As(37 Å) superlattice at 10 K in electric fields between 0 and 60 kV/cm. By comparing the experimental absorption spectra with calculations of the energies and oscillator strengths of transitions between states of the Wannier-Stark ladder it is established that in strong electric fields above-barrier states do not form a structureless continuum but a fan of states. Intersection of electric-field-localized electron states with the fan of above-barrier states leads to broadening, splitting, and nonmonotonic changes in the intensity of an intrawell transition band. The additional absorption band observed can be attributed to intrawell transitions between states in the left and right quantum wells of the superlattice. 相似文献
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Mario Thevis Andreas Thomas Maxie Kohler Simon Beuck Wilhelm Schänzer 《Journal of mass spectrometry : JMS》2009,44(4):442-460
The number of compounds and doping methods in sports is in a state of constant flux. In addition to ‘traditional’ doping agents, such as anabolic androgenic steroids or erythropoietin, new therapeutics and emerging drugs have considerable potential for misuse in elite sport. Such compounds are commonly based on new chemical structures, and the mechanisms underlying their modes of action represent new therapeutic approaches arising from recent advances in medical research; therefore, sports drug testing procedures need to be continuously modified and complementary methods developed, preferably based on mass spectrometry, to enable comprehensive doping controls. This tutorial not only discusses emerging drugs that can be categorized as anabolic agents (selective androgen receptor modulators, SARMs), gene doping [hypoxia‐inducible factor stabilizers, peroxisome‐proliferator‐activated receptor (PPAR)δ‐agonists] and erythropoietin‐mimetics (Hematide) but also compounds with potentially performance‐enhancing properties that are not classified in the current list of the World Anti‐Doping Agency. Compounds such as ryanodine‐calstabin‐complex modulators (benzothiazepines) are included, their mass spectrometric properties discussed, and current approaches in sports drug testing outlined. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
55.
Primus T Primus TM Kohler DJ Johnston JJ Sugihara RT Pitt WC 《Journal of chromatographic science》2006,44(1):1-5
A reversed-phase ion-pair liquid chromatographic analysis combined with a solid-phase extraction clean-up method is used to assess the quantity of diphacinone residue found in invertebrates. Three invertebrate species are exposed to commercially available diphacinone-fortified bait used for rat control. The invertebrate samples are collected, frozen, and shipped to the laboratory. The samples are homogenized after cryogenic freezing. A portion of the homogenized samples are extracted with acidified chloroform-acetone, followed by cleanup with a silica solid-phase extraction column. Diphacinone is detected by UV absorption at 325 nm after separation by the chromatographic system. The method limit of detection (MLOD) for snail and slug samples averaged 0.055 and 0.066 mg/kg, respectively. Diphacinone residues in snail tissue ranges from 0.83 to 2.5 mg/kg for Oxychilus spp. The mean recoveries from snails at 0.20 and 2.0 are 97 +/- 21% and 84 +/- 6%. Diphacinone residues in slug tissue ranges from 1.3 to 4.0 mg/kg for Deroceras laeve and < MLOD to 1.8 mg/kg for Limax maximus, respectively. The mean recoveries from slugs at 0.20 and 2.0 mg/kg are 91% +/- 15% and 86% +/- 5%. 相似文献
56.
Bassan P Sachdeva A Kohler A Hughes C Henderson A Boyle J Shanks JH Brown M Clarke NW Gardner P 《The Analyst》2012,137(6):1370-1377
Transmission and transflection infrared microscopy of biological cells and tissue suffer from significant baseline distortions due to scattering effects, predominantly resonant Mie scattering (RMieS). This scattering can also distort peak shapes and apparent peak positions making interpretation difficult and often unreliable. A correction algorithm, the resonant Mie scattering extended multiplicative signal correction (RMieS-EMSC), has been developed that can be used to remove these distortions. The correction algorithm has two key user defined parameters that influence the accuracy of the correction. The first is the number of iterations used to obtain the best outcome. The second is the choice of the initial reference spectrum required for the fitting procedure. The choice of these parameters influences computational time. This is not a major concern when correcting individual spectra or small data sets of a few hundred spectra but becomes much more significant when correcting spectra from infrared images obtained using large focal plane array detectors which may contain tens of thousands of spectra. In this paper we show that, classification of images from tissue can be achieved easily with a few (<10) iterations but a reliable interpretation of the biochemical differences between classes could require more iterations. Regarding the choice of reference spectrum, it is apparent that the more similar it is to the pure absorption spectrum of the sample, the fewer iterations required to obtain an accurate corrected spectrum. Importantly however, we show that using three different non-ideal reference spectra, the same unique correction solution can be obtained. 相似文献
57.
Robert Kohler Rainer Alex Renate Brielmann Bernhard Ausperger 《Macromolecular Symposia》2006,244(1):89-96
Summary: Some natural fibres like flax, hemp and others show excellent mechanical properties which make them a promising choice for the reinforcement of polymers. For natural fibre reinforced composites, hydrophilicity is a problem with respect to dimensional changes, fibre to matrix adhesion and long term stability. The interaction of differently prepared and modified fibres with water vapour has been investigated by dynamic vapour sorption. It has been found that the sorption and desorption kinetics of cellulosic fibres can be excellently fitted by assuming two parallel, independent first order processes. This empirical model, defined here as the “Parallel Exponential Kinetics” model (PEK-model), reveals two distinct mechanisms with slow and fast exchange of water vapour respectively, related to different sorption sites. The specific sorption mechanisms are represented by individual sorption-desorption isotherms as components of the total isotherms. The results suggest a relation to the differing types of amorphous regions in the fibres and/or to the different states of “bound” or “free” water, discussed for hydrophilic materials. The PEK-model proved to be consistently applicable for sorption and desorption over the whole humidity range, and also for all tested cellulose fibres. It is especially useful for a clearer distinction of different fibre types or modifications and can be successfully used for an extended fibre characterization. 相似文献
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