4,408 research outputs found
Gold nanoparticles explore cells: cellular uptake and their use as intracellular probes
No full textUnderstanding uptake of nanomaterials by cells and their use for intracellular sensing is important for studying their interaction and toxicology as well as for obtaining new biological insight. Here, we investigate cellular uptake and intracellular dynamics of gold nanoparticles and demonstrate their use in reporting chemical information from the endocytotic pathway and cytoplasm. The intracellular gold nanoparticles serve as probes for surface-enhanced Raman spectroscopy (SERS) allowing for biochemical characterisation of their local environment. In particular, in this work we compare intracellular SERS using non-functionalised and functionalised nanoparticles in their ability to segregate different but closely related cell phenotypes. The results indicate that functionalised gold nanoparticles are more efficient in distinguishing between different types of cells. Our studies pave the way for understanding the uptake of gold nanoparticles and their utilisation for SERS to give rise to a greater biochemical understanding in cell-based therapies
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
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
Raman Spectroscopy of pure and (Nb+In) co-doped TiO2 single crystals
No full textThis research project focused on the study of pure TiO2 rutile crystals and rutile crystals that were 2% co doped with Niobium and Indium TiO2 (2-NITO). There has been a growing interest in co-doped TiO2 due to recent papers published on its “colossal permittivity” in the lower frequency range of 10^2 to 10^6 Hz. The goal of this study was to analyze the impact of co-doping on the Raman modes by using Raman spectroscopy. To determine the Raman shift and Half width at half max from the raman data, the Lorentz fit analysis was applied
The further assessment of a handheld Raman spectroscopy probe for the intraoperative diagnosis of axillary lymph nodes in breast cancer
No full textAxillary sentinel lymph node biopsy plays an important role in breast cancer management
in determining further surgical and medical treatment options. Intraoperative assessment of
the sentinel lymph node might allow immediate axillary surgery, which would incur
benefits to both the patient and healthcare trusts. A handheld Raman spectroscopy probe
has already been shown to be a comparable option for intraoperative assessment through
previous published and unpublished studies, delivering a sensitivity of up to 92% and
specificity of up to 99%.
This research aims to define further the role of the hand-held Raman spectroscopy probe as
an accurate, rapid and non-destructive technique for intra-operative axillary node
assessment, making it a strong competitor in the clinical market. It also looks to improve
the sensitivity of the probe by altering the methodology used in previous studies.
122 lymph node halves were collected intraoperatively from 37 patients diagnosed with
breast cancer and spectra measured using a commercially available handheld Raman
spectroscopy probe. Spectra were then fed into a specialist software programme and
analysed using principal component fed linear discriminant analysis trained by
histopathology results.
A “2 group” training model defining the probe‟s ability to distinguish between benign and
malignant tissue produced an overall performance of 86.4%, with a sensitivity of 71% and
specificity of 91%.
The results were not as impressive as previous studies. This was possibly due to a broken
probe, leading to four different phases of measurements (original probe/failing
probe/temporary replacement/mended probe). Secondly a smaller, less balanced data set, in
terms of spectra per pathology group, was collected and there appeared to be more
fluorescence in some of the data which may have originated from varying blue dye
injection protocols. However, that said further research using a robust, high specification
system may help establish its role as a reliable assessment tool intraoperatively as well as
a non-invasive means of assessing lymph nodes in the initial assessment clinic
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
Towards objective endoscopic diagnosis of Barrett's associated early neoplasia using fibre-optic Raman Spectroscopy
No full textThis translational research evaluates a novel, custom-built Raman probe for potential
application as an in vivo diagnostic tool in the oesophagus. Raman spectroscopy (RS) is a
well established analytical technique which is capable of probing the biochemical changes
associated with neoplastic progression in oesophageal tissue. RS relies on measurement of
subtle inelastic scattering signals following monochromatic laser excitation.
Clinical utilisation of RS within hollow organs requires accurate collection and transmission
of signal through fibre-optic cables. This research aims to evaluate the ability of a custom
built fibre-optic Raman probe, in conjunction with multivariate classification models, to
differentiate between benign and neoplastic oesophageal pathologies ex vivo. The need for
spectral stability and reproducibility are addressed, as are difficulties associated with multisystem
reliability. In addition, the biochemical basis of spectral classification is evaluated and
discussed. Cont/d
A chirped, pulsed laser system and magneto-optical trap for rubidium
No full textThis thesis covers the construction and characterisation of a magneto-optical trap (MOT) for 85Rb from the very beginning. It details both the optical and mechanical aspects from laser diode assembly, tuning and stabilisation to the preparation and assembly of the vacuum system. The MOT construction forms the first goal of the project, the second was to develop a laser system capable of producing custom programmable, amplitude modulated and frequency chirped pulses (on the tens of microseconds timescale) from a continuous wavesource. This involved developing software and computer control for several arbitrary signal generators linked to drivers for acousto-optic and electro-optic modulators. This chirped, pulsed laser system will be used to perform state manipulations on the 85Rb MOT cloud using two-photon Raman transitions in an adiabatic rapid passage regime. The chirped pulse system was initially tested with a rubidium vapour cell in an attempt to perform atomic interferometry that would produce spatial interference fringes along the length of the cell. However, due to the beam power requirements, the beam diameter together with the large Doppler shift at room temperature meant these fringes were not seen and so the vapour cell was replaced with the cold atom cloud in the MOT. Two-photon experiments were attempted with the MOT cloud using the chirped pulse system, however despite greatly improved laser power and detection efficiency, the signal indicating ground state population transfer via a two-photon interaction was not seen. The results indicate that the hyperfine-ground state splitting frequency has been shifted due to the proximity of the ion pump magnet to the vacuum system. Presently, efforts are being directed towards searching for the correct frequency
Intelligent transportation systems (ITS) operational support contracts implementation plan / submitted by Raman K. Patel.
No full textAphelocheirus Westwood 1833
No full textSubgenus Aphelocheirus Westwood, 1833 Type species. Naucoris aestivalis Fabricius, 1794; by original designation.Published as part of PATEL, RAMAN, RANA, RAJENDRA SINGH, NEL, ANDRÉ & ALI, ASHIF, 2023, The oldest aquatic aphelocheirid bug (Heteroptera, Nepomorpha) from the lower Eocene of India, pp. 250-254 in Palaeoentomology 6 (3) on page 251, DOI: 10.11646/palaeoentomology.6.3.7, http://zenodo.org/record/807306
- …
