39,651 research outputs found
Advanced methods for enhanced sensing in biomedical Raman spectroscopy
No full textRaman spectroscopy is a powerful tool in the field of biomedicine for disease
diagnosis owing to its potential to provide the molecular fingerprint of biological
samples. However due to the inherent weak nature of the Raman process, there is a
constant quest for enhancing the sensitivity of this technique for enhanced diagnostic
efficiency. This thesis focuses on achieving this goal by integrating advanced methods
with Raman spectroscopy.
Firstly this thesis explores the applicability of a laser based fluorescence
suppression technique – Wavelength Modulated Raman Spectroscopy (WMRS) - for
suppressing the broad luminescence background which often obscure the Raman peaks.
The WMRS technique was optimized for its applications in single cell studies and tissue
studies for enhanced sensing without compromising the throughput. It has been
demonstrated that the optimized parameter would help to chemically profile single cell
within 6 s. A two fold enhancement in SNR of Raman bands was demonstrated when
WMRS was implemented in fiber Raman based systems for tissue analysis. The
suitability of WMRS on highly sensitive single molecule detection techniques such as
Surface Enhanced Raman Spectroscopy (SERS) and Surface Enhanced Resonance
Raman Spectroscopy (SERRS) was also explored. Further this optimized technique was
successfully used to address an important biological problem in the field of immunology.
This involved label-free identification of major immune cell subsets from human blood.
Later part of this thesis explores a multimodal approach where Raman
spectroscopy was combined with Optical Coherence Tomography (OCT) for enhanced
diagnostic sensitivity (>10%). This approach was used to successfully discriminate
between ex-vivo adenocarcinoma tissues and normal colon tissues.
Finally this thesis explores the design and implementation of a specialized fiber
Raman probe that is compatible with surgical environments. This probe was originally
developed to be compatible with Magnetic Resonance Imaging (MRI) environment. It
has the potential to be used for performing minimally invasive optical biopsy during
interventional MRI procedures
Raman microspectroscopy interrogating 19th and 20th century painted trades union banners
No full textWe have previously developed protocols for the application of Raman microspectroscopy to studies on painted textiles. We have further assessed the value of such microanalyses in the identification of both inorganic and organic constituents, including original components and consolidants used in conservation treatments. This paper presents the results of a recent study on a number of 19th- and 20th-century trades union banners directed at collating a spectral database of inorganic pigments used in the illustrations and at probing the preparative process prior to painting. Such information will contribute to an understanding of the manufacture of such banners and their current condition, leading to the development of optimum conservation procedures.While Raman spectroscopy has the potential to be used in situ and, with the appropriate protocol, is non-destructive, nonetheless we have found that the analysis of resin-embedded cross-sections is to be preferred with microtoming providing the cleanest sample surface. The optimum methodology for acquiring good quality Raman spectra is described including operation in the confocal mode, with consideration of fluorescence, interference from resin, laser-induced photochemistry, and so on
Integrated waveguide and nanostructured sensor platform for surface-enhanced Raman spectroscopy
No full textLimitations of current sensors include large dimensions, sometimes limited sensitivity and inherent single-parameter measurement capability. Surface-enhanced Raman spectroscopy can be utilized for environment and pharmaceutical applications with the intensity of the Raman scattering enhanced by a factor of 106. By fabricating and characterizing an integrated optical waveguide beneath a nanostructured precious metal coated surface a new surface-enhanced Raman spectroscopy sensing arrangement can be achieved. Nanostructured sensors can provide both multiparameter and high-resolution sensing. Using the slab waveguide core to interrogate the nanostructures at the base allows for the emission to reach discrete sensing areas effectively and should provide ideal parameters for maximum Raman interactions. Thin slab waveguide films of silicon oxynitride were etched and gold coated to create localized nanostructured sensing areas of various pitch, diameter, and shape. These were interrogated using a Ti:Sapphire laser tuned to 785-nm end coupled into the slab waveguide. The nanostructured sensors vertically projected a Raman signal, which was used to actively detect a thin layer of benzyl mercaptan attached to the sensors
Revitalization of College Libraries with Computer Assistance
No full textAvailability and utilization in teaching learning process; of up-to-date information on topics dealt in colleges is essential to maintain the quality and relevance of college education. The study observes that presently the college libraries in India are not organized in a way in which they can provide information services of required quality. The collections are not properly classified and catalogued. Reference collections lack required source materials. Qualified and competent staff is not available. Improving the situation is costly and time consuming. The paper examines how library automation process can improve library management, collection development, adding reference sources in electronic media in a cost effective way and introduce new and innovative services. Points out that the effects of computerizing college library will give immediate results in the way in which library delivers information, in modes of preparation of lectures by teachers and in the methods of learning by students
Advanced techniques in Raman tweezers microspectroscopy for applications in biomedicine
No full textThis thesis investigates the use of Raman tweezers microspectroscopy to interrogate the biochemistry of single biological cells. Raman tweezers microspectroscopy is a powerful technique, which combines traditional Raman microspectroscopy and optical trapping, allowing the manipulation and environmental isolation of a biological cell of interest whilst simultaneously probing its biochemistry gleaning a wealth of pertinent information.
The studies carried out in this thesis can be split into two broad categories: firstly, the exploitation of Raman tweezers microspectroscopy to study biological cells and secondly developments to the Raman tweezers microspectroscopy technique that extend its capabilities and the range of samples that can be studied. In the application of Raman tweezers, the stacking and interrogation of multiple cells is reported allowing a rapid representative Raman signal to be recorded from a small cell population with improved signal to noise. Also demonstrated is the ability of Raman spectroscopy to identify and grade the development of Human Papillomavirus induced cervical neoplasia with sensitivities of up to 96 %. These studies demonstrate the potential of Raman spectroscopy to study biological cells but it was noted that the traditional Raman tweezers system struggled to manipulate large cells thus a decoupled Raman tweezers microspectroscopy system is presented where a dual beam fibre optical trap is used to perform the trapping function and a separate Raman probe is introduced to probe the biochemical nature of the trapped cell. This development allowed the trapping and examination of very large cells whilst opening up the possibility of creating Raman maps of trapped objects. Raman tweezers microspectroscopy could potentially become an important clinical diagnostic and biological monitoring tool but is held back by the long signal integration times required due to the weak nature of Raman scattering. The final study presented in this thesis examines the potential of wavelength modulated Raman spectroscopy to improve signal to noise ratios and reduce integration times.
All these studies aim to demonstrate the potential and extend the performance of Raman tweezers microspectroscopy
Stimulated terahertz emission due to electronic Raman scattering in silicon
No full textSilicon-based semiconductors are intensively investigated over the past years as promising candidates for optoelectronic devices at terahertz (THz) frequencies [1]. Optically pumped intracenter silicon lasers, realized in the past decade in the THz range, are based on direct optical transitions between shallow levels of different shallow donors [2]. Recently, terahertz Raman laser emission has been demonstrated in silicon doped by antimony [3] and phosphorus [4].
We report on realization of terahertz lasers based on intracenter electronic Raman scattering in silicon doped by arsenic (Si:As, frequency range 4.8 – 5.1 THz and 5.9 – 6.5 THz) and silicon doped by bismuth (Si:Bi, 4.6 – 5.9 THz) under optical excitation by infrared frequency-tunable free electron laser at low lattice temperatures. The Stokes shift of the observed laser emission is equal to the Raman-active donor electronic transition between the ground 1s(A1) and the excited 1s(E) donor states. Raman terahertz gain of the lasers is similar to those observed for the donor-type terahertz silicon donor lasers
Forensic applications of raman spectroscopy
No full textThe forensic applications of Raman spectroscopy have been explored and extended using the development of novel sampling techniques and task-specific instrumentation described in this thesis.
The phenomenon of Raman scattering, enhanced Raman scattering and their relevance in forensic investigations was reviewed. Particular emphasis was placed on current applications, experimental considerations relevant to in-situ Raman sampling and the deficiencies of instrumentation commercially available at the time. It was concluded that the development of novel, optimised instrumentation was
essential in the application of Raman spectroscopy to portable forensic applications.
The feasibility of achieving molecularly-specific and sensitive detection of TNT vapour using waveguide-enhanced, surface-enhanced resonance Raman spectroscopy was investigated using reference spectra measured using a calibrated optical system provided by a collaborator. Improvements in signal-to-noise ratio afforded by employing waveguide-enhanced sampling, higher excitation power,
long integration times and an improved spectrometer design were modelled, experimentally verified, and used to predict a detection limit of 10-16g for saturated vapour-phase TNT. The theoretical performance of the optical instrument is
described and verified using experimentally measured data.
The feasibility of conducting specific and sensitive long-range stand-off covert observation operations against unsuspecting targets in compliance with the UK Regulation of Investigative Powers act was established using a task-optimised laboratory simulation. Using a 5mW visible excitation, short integration times (under 20s) and multiplex detection it was possible to detect and identify a tagged object from a range of up to 50m. The feasibility study yielded a robust prototype handheld system comprising a modified telephoto camera with the integrated capability of sample discrimination using Raman spectroscopy. The instrument design is described
Modulated Raman spectroscopy for enhanced identification of bladder tumor cells in urine samples
No full textStandard Raman spectroscopy (SRS) is a noninvasive technique that is used in the biomedical field to discriminate between normal and cancer cells. However, the presence of a strong fluorescence background detracts from the use of SRS in real-time clinical applications. Recently, we have reported a novel modulated Raman spectroscopy (MRS) technique to extract the Raman spectra from the background. In this paper, we present the first application of MRS to the identification of human urothelial cells (SV-HUC-1) and bladder cancer cells (MGH) in urine samples. These results are compared to those obtained by SRS. Classification using the principal component analysis clearly shows thatMRS allows discrimination between Raman spectra of SV-HUC-1 andMGH cells with high sensitivity (98%) and specificity (95%). MRS is also used to distinguish between SV-HUC-1 and MGH cells after exposure to urine for up to 6 h.We observe a marked change in the MRS of SV-HUC-1 and MGH cells with time in urine, indicating that the conditions of sample collection will be important for the application of this methodology to clinical urine samples.Peer reviewe
Chirped pulse Raman amplification in plasma
No full textRaman amplification in plasma has been proposed to be a promising method of amplifying short radiation pulses. Here, we investigate chirped pulse Raman amplification (CPRA) where the pump pulse is chirped and leads to spatiotemporal distributed gain, which exhibits superradiant scaling in the linear regime, usually associated with the nonlinear pump depletion and Compton amplification regimes. CPRA has the potential to serve as a high-efficiency high-fidelity amplifier/compressor stage
Infrared and Raman studies of thin polymer films
No full text[Keywords:- Waveguide; Raman; Attenuated Total Reflection; Infrared; Polymer Films; Barrier Films; Epoxy; Diffusion; Isocyanate; Crosslinking Agents; Cure Time; Kinetics; Urethane; Film Quality]This thesis describes the experimental work carried out between October l(^st), 1990 and 30th September, 1993, in the Chemistry Department of the University of Durham, in association with Courtaulds Coatings plc, m partial fulfilment of the requirements for the degree of Doctor of Philosophy. The thesis is divided into three sections, namely Theoretical Considerations (three Chapters), Experimental Results (three Chapters) and Discussion of Results (one Chapter). There are also three appendices. The theoretical section presents a working description of Paint Chemistry, Vibrational spectroscopy, Waveguide Raman Spectroscopy, Attenuated Total Reflection Fourier Transform Infrared Spectroscopy and Diffusion Processes. The experimental section is divided into three chapters. The first describes methods of film preparation and characterisation and includes methods of film thickness determination and the development of an off-line waveguiding rig at the University of Durham. Raman spectroscopic results are detailed in the second chapter, and include waveguide experiments on both single polymer films and laminate systems, some of which are reported for the first time, along with some FT-Raman results, also reported for the first time. The FT-IR ATR spectroscopic results are presented in the third chapter and include some barrier film studies on polymeric laminate systems, plus the study of certain diffusion processes, along with an estimation of the associated diffusion coefficients and some kinetic parameters, occurring in epoxy resins, which are reported for the first time. The discussion section concentrates on a full elucidation of the results, and conclusions that may be drawn from them, and ends with suggestions for future work. Refractive indices quoted, unless otherwise stated, refer to indices measured usmg 632.8 nm radiation, and have been estimated either using previous literature, or with the off-line rig. It is accepted that electric field calculations performed with these values will be slightly different to the actual fields observed in the Raman experiments, due to slightly different refractive indices at 514.5 nm. T in tables, unless otherwise stated, refers to band intensities in absorbance units. Finally, the attention of the reader is drawn to the fact that some of the materials used in the course of this project have no precise structure given. This is due to the fact that some of the substances used are of either a highly complicated and/or confidential nature
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