994 resultados para stimulated Raman scatting


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In this investigation Raman spectroscopy was shown to be a method that could be used to monitor the polymerisation of PMMA bone cement. Presently there is no objective method that orthopaedic surgeons can use to quantify the curing process of cement during surgery. Raman spectroscopy is a non-invasive, non-destructive technique that could offer such an option. Two commercially available bone cements (Palacos® R and SmartSet® HV) and different storage conditions (4 and 22°C) were used to validate the technique. Raman spectroscopy was found to be repeatable across all conditions with the completion of the polymerisation process particularly easy to establish. All tests were benchmarked against current temperature monitoring methods outlined in ISO and ASTM standards. There was found to be close agreement with the standard methods and the Raman spectroscopy used in this study.

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The main curative therapy for patients with nonsmall cell lung cancer is surgery. Despite this, the survival rate is only 50%, therefore it is important to more efficiently diagnose and predict prognosis for lung cancer patients. Raman spectroscopy is useful in the diagnosis of malignant and premalignant lesions. The aim of this study is to investigate the ability of Raman microscopy to diagnose lung cancer from surgically resected tissue sections, and predict the prognosis of these patients. Tumor tissue sections from curative resections are mapped by Raman microscopy and the spectra analzsed using multivariate techniques. Spectra from the tumor samples are also compared with their outcome data to define their prognostic significance. Using principal component analysis and random forest classification, Raman microscopy differentiates malignant from normal lung tissue. Principal component analysis of 34 tumor spectra predicts early postoperative cancer recurrence with a sensitivity of 73% and specificity of 74%. Spectral analysis reveals elevated porphyrin levels in the normal samples and more DNA in the tumor samples. Raman microscopy can be a useful technique for the diagnosis and prognosis of lung cancer patients receiving surgery, and for elucidating the biochemical properties of lung tumors. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3323088]

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We report the formation of highly scattering silver complexes of adenine, deoxyadenosine and 5'-dAMP under alkaline pH conditions in the colloidal silver solutions which are used for surface-enhanced Raman spectroscopy. These complexes, and other pH-dependent phenomena, help to explain the diversity of previously reported adenine SERS spectra. Using conditions which promote complex formation allows nucleotides to be detected at <1 ppm, even in solutions with high salt concentrations.

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Prokaryotes represent one-half of the living biomass on Earth, with the vast majority remaining elusive to culture and study within the laboratory. As a result, we lack a basic understanding of the functions that many species perform in the natural world. To address this issue, we developed complementary population and single-cell stable isotope (C-13)-linked analyses to determine microbial identity and function in situ. We demonstrated that the use of rRNA/mRNA stable isotope probing (SIP) recovered the key phylogenetic and functional RNAs. This was followed by single-cell physiological analyses of these populations to determine and quantify in situ functions within an aerobic naphthalene-degrading groundwater microbial community. Using these culture-independent approaches, we identified three prokaryote species capable of naphthalene biodegradation within the groundwater system: two taxa were isolated in the laboratory (Pseudomonas fluorescens and Pseudomonas putida), whereas the third eluded culture (an Acidovorax sp.). Using parallel population and single-cell stable isotope technologies, we were able to identify an unculturable Acidovorax sp. which played the key role in naphthalene biodegradation in situ, rather than the culturable naphthalene-biodegrading Pseudomonas sp. isolated from the same groundwater. The Pseudomonas isolates actively degraded naphthalene only at naphthalene concentrations higher than 30 mu M. This study demonstrated that unculturable microorganisms could play important roles in biodegradation in the ecosystem. It also showed that the combined RNA SIP-Raman-fluorescence in situ hybridization approach may be a significant tool in resolving ecology, functionality, and niche specialization within the unculturable fraction of organisms residing in the natural environment.

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The monomeric GTPase Rap1 controls functional activation of beta2 integrins in leukocytes. In this article, we describe a novel mechanism by which the chemoattractant fMLP activates Rap1 and inside-out signaling of beta2 integrins. We found that fMLP-induced activation of Rap1 in human polymorphonuclear leukocytes or neutrophils and differentiated PLB-985 cells was blocked by inhibitors of the NO/guanosine-3',5'-cyclic monophosphate-dependent protein kinase (cGKI) pathway [N-(3-(aminomethyl)benzyl)acetamidine, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, DT-3 peptide, 8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphothioate, Rp-isomer triethylammonium salt-guanosine-3',5'-cyclic monophosphate], indicating that the downstream signaling events in Rap1 activation involve the production of NO and guanosine-3',5'-cyclic monophosphate, as well as the activation of cGKI. Silencing the expression of vasodilator-stimulated phosphoprotein (VASP), a substrate of cGKI, in resting PLB-985 cells or mice neutrophils led to constitutive activation of Rap1. In parallel, silencing VASP in differentiated PLB-985 cells led to recruitment of C3G, a guanine nucleotide exchange factor for Rap1, to the plasma membrane. Expression of murine GFP-tagged phosphodeficient VASP Ser235Ala mutant (murine serine 235 of VASP corresponds to human serine 239) in PLB-985 cells blunted fMLP-induced translocation of C3G to the membrane and activation of Rap1. Thus, bacterial fMLP triggers cGKI-dependent phosphorylation of human VASP on serine 239 and, thereby, controls membrane recruitment of C3G, which is required for activation of Rap1 and beta2 integrin-dependent antibacterial functions of neutrophils.

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Raman and spreading resistance profiling have been used to analyze defects in germanium caused by hydrogen and helium implants, of typical fluences used in layer transfer applications. Beveling has been used to facilitate probing beyond the laser penetration depth. Results of Raman mapping along the projection area reveal that after post-implant annealing at 400°C, some crystal damage remains, while at 600°C, the crystal damage has been repaired. Helium implants create acceptor states beyond the projected range, and for both hydrogen and helium, 1×1016 acceptors/cm2 remain after 600°C. These are thought to be vacancy-related point defect clusters.

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Surface-enhanced Raman scattering (SERS) spectra from molecules adsorbed on the surface of vertically aligned gold nanorod arrays exhibit a variation in enhancement factor (EF) as a function of excitation wavelength that displays little correlation with the elastic optical properties of the surface. The key to understanding this lack of correlation and to obtaining agreement between experimental and calculated EF spectra lies with consideration of randomly distributed, sub-10 nm gaps between nanorods forming the substrate. Intense fields in these enhancement “hot spots” make a dominant contribution to the Raman scattering and have a very different spectral profile to that of the elastic optical response. Detailed modeling of the electric field enhancement at both excitation and scattering wavelengths was used to quantitatively predict both the spectral profile and the magnitude of the observed EF.