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51.
Bush CE Goldston RJ Scott SD Fredrickson ED McGuire K Schivell J Taylor G Barnes CW Bell MG Boivin RL Bretz N Budny RV Cavallo A Efthimion PC Grek B Hawryluk R Hill K Hulse RA Janos A Johnson DW Kilpatrick S Manos DM Mansfield DK Meade DM Park H Ramsey AT Stratton B Synakowski EJ Towner HH Wieland RM Zarnstorff MC Zweben S 《Physical review letters》1990,65(4):424-427
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Yablonovitch E. Gmitter T. J. Leung K. M. Meade R. D. Rappe A. M. Brommer K. D. Joannopoulos J. D. 《Optical and Quantum Electronics》1992,24(2):S273-S283
Three-dimensionally periodic dielectric structures, (photonic crystals), possessing a forbidden gap for electromagnetic wave propagation, (a photonic bandgap), are now known. If the perfect 3-dimensional periodicity is broken by a local defect, then local electromagnetic modes can occur within the forbidden bandgap. The addition of extra dielectric material locally, inside the photonic crystal, produces donor modes. Conversely, the local removal of dielectric material from the photonic crystal produces acceptor modes. It will now be possible to make high-Q electromagnetic cavities of volume 1 cubic wavelength, for short wavelengths at which metallic cavities are useless. These new dielectric cavities can cover the range all the way from millimeter waves, down to ultraviolet wavelengths. 相似文献
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Poon KW Lyng FM Knief P Howe O Meade AD Curtin JF Byrne HJ Vaughan J 《The Analyst》2012,137(8):1807-1814
Fibrinogen assays are commonly used as part of clinical screening tests to investigate haemorrhagic states, for detection of disseminated intravascular coagulation and as a predictor of a variety of cardiovascular events. The Clauss assay, which measures thrombin clotting time, is the most commonly used method for measuring fibrinogen levels. Nevertheless, inconsistencies are present in inter-manufacturer reagent sources, calibration standards and methodologies. Automated coagulation analysers, which measure changes in optical density during the prothrombin time (PT-Fg), have found use in many hospitals. However, the PT-Fg method is found to give falsely elevated values due to varying choices of calibrants, reagents and analysers. As an alternative, Raman spectroscopy has previously been applied to the analysis of blood and its various constituents to determine various analyte concentrations such as glucose, urea, triglycerides and cholesterol. In this study, Raman spectroscopy was investigated for its ability to accurately quantify fibrinogen concentration in blood plasma. Samples collected from 34 patients were analysed by Raman spectroscopy and the resultant spectra were fitted with a Partial Least Squares Regression model using target values obtained through a pre-calibrated Clauss fibrinogen assay. Various spectral pre-processing methods were utilised to prepare data to be entered into a calibration model. A root mean square error of prediction of 0.72 ± 0.05 g/L was achieved with as few as 25 spectra. In this pilot study, Raman spectroscopy has been demonstrated to be a robust technique providing rapid and reagent-free quantification of fibrinogen levels in blood plasma and a potential alternative to the Clauss assay. 相似文献
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Bonnier F Knief P Lim B Meade AD Dorney J Bhattacharya K Lyng FM Byrne HJ 《The Analyst》2010,135(12):3169-3177
Three dimensional collagen gels have been used as matrices for the imaging of live cells by Raman spectroscopy. The study is conducted on a human lung adenocarcinoma (A549) and a spontaneously immortalized human epithelial keratinocyte (HaCaT) cell line. The lateral resolution of the system has been estimated to be <1.5 μm making it possible to access the subcellular organization. Using K-means clustering analysis, it is shown that the different subcellular compartments of individual cells can be identified and differentiated. The biochemical specificity of the information contained in the Raman spectra allows the visualization of differences in the molecular signature of the different sub-cellular structures. Furthermore, to enhance the chemical information obtained from the spectra, principal component analysis has been employed, allowing the identification of spectral windows with a high variability. The comparison between the loadings calculated and spectra from pure biochemical compounds enables the correlation of the variations observed with the molecular content of the different cellular compartments. 相似文献
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Aidan D. Meade Colin Clarke Florence Draux Ganesh D. Sockalingum Michel Manfait Fiona M. Lyng Hugh J. Byrne 《Analytical and bioanalytical chemistry》2010,396(5):1781-1791
The in vitro study of cellular species using Raman spectroscopy has proven a powerful non-invasive modality for the analysis
of cell constituents and processes. This work uses micro-Raman spectroscopy to study the chemical fixation mechanism in three
human cell lines (normal skin, normal bronchial epithelium, and lung adenocarcinoma) employing fixatives that preferentially
preserve proteins (formalin), and nucleic acids (Carnoy’s fixative and methanol–acetic acid). Spectral differences between
the mean live cell spectra and fixed cell spectra together with principal components analysis (PCA), and clustering techniques
were used to analyse and interpret the spectral changes. The results indicate that fixation in formalin produces spectral
content that is closest to that in the live cell and by extension, best preserves the cellular integrity. Nucleic acid degradation,
protein denaturation, and lipid leaching were observed with all fixatives and for all cell lines, but to varying degrees.
The results presented here suggest that the mechanism of fixation for short fixation times is complex and dependent on both
the cell line and fixative employed. Moreover, important spectral changes occur with all fixatives that have consequences
for the interpretation of biochemical processes within fixed cells. The study further demonstrates the potential of vibrational
spectroscopy in the characterization of complex biochemical processes in cells at a molecular level. 相似文献
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