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| 3. |
- Pålsson, Sara, et al.
(författare)
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Methods for detailed histopathological investigation and localization of biopsies from cervix uteri to improve the interpretation of auto fluorescence data
- 2006
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Ingår i: Journal of Environmental Pathology and Toxicology. - 2162-6537. ; 25:1-2, s. 321-340
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence spectroscopy is one of many optical methods that are potentially clinically useful for noninvasive detection and characterization of disorders on the cervical part of uterus, including precancerous lesions. The cervix uteri exhibits a biologically complex tissue and the morphology of a biopsy is generally not homogenous. The standard histopathological protocol accounts only for the most severe condition found within the biopsy and no information is given on other constituents potentially influencing the recorded fluorescence spectra. Spectra are usually correlated, using multivariate techniques, to the histopathological diagnosis of the biopsies. Since the probe volume of fluorescence spectroscopy is considerably smaller than the extension of the biopsy, this can cause problems in the search for correlation between the fluorescence signals and the pathological structures. In addition, the orientation and location of the biopsies are normally not recorded. We now report on the first detailed histopathological protocol where numerous tissue parameters, such as thickness and type of the epithelium and the number of blood vessels, glands, and inflammatory cells, are tabulated and the orientation and location of the biopsy are recorded as precisely as possible. Hopefully, the use of this protocol together with sophisticated mathematical methods will increase the probability to classify cervical disorders of the uterus, including precancerous lesions, with high sensitivity and specificity.
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| 4. |
- Alnis, J, et al.
(författare)
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Sum-frequency generation with a blue diode laser for mercury spectroscopy at 254 nm
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76:10, s. 1234-1236
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Tidskriftsartikel (refereegranskat)abstract
- Blue diode lasers emitting 5 mW continuous-wave power around 400 nm have recently become available. We report on the use of a blue diode laser together with a 30 mW red diode laser for sum-frequency generation around 254 nm. The ultraviolet power is estimated to be 0.9 nW, and 35 GHz mode-hop-free tuning range is achieved. This is enough to perform high-resolution ultraviolet spectroscopy of mercury isotopes. The possibility to use frequency modulation in the ultraviolet is demonstrated; however, at present the ultraviolet power is too low to give advantages over direct absorption monitoring. Mercury detection at atmospheric pressure is also considered which is of great interest for environmental monitoring. (C) 2000 American Institute of Physics. [S0003-6951(00)02810-2].
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| 5. |
- Gustafsson, U, et al.
(författare)
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Atomic spectroscopy with violet laser diodes
- 2000
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Ingår i: American Journal of Physics. - : American Association of Physics Teachers (AAPT). - 0002-9505 .- 1943-2909. ; 68:7, s. 660-664
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Tidskriftsartikel (refereegranskat)abstract
- Laser spectroscopy with laser diodes can now also be performed in the violet/blue spectral region. a 5 mW commercially available CW laser diode operating at 404 nm was used to perform spectroscopy on potassium atoms with signal detection in absorption as well as fluorescence when operating on a potassium vapor cell and with optogalvanic detection on a potassium hollow cathode lamp. The 4s(2)S(1/2)-5P(2)P(3/2,1/2) transitions were observed at 404.5 and 404.8 nm, respectively. The laser diode was operated with a standard laser diode driver, and with or without an external cavity. The 4s(2)S(1/2)-4p(2)P(1/2) transition at 770.1 nm was also observed with a different laser diode. Here, Doppler-free saturated-absorption signals were also observed, enabling the evaluation of the ground-state hyperfine splitting of about 460 MHz. The data recorded allows an experimental verification of the theory for Doppler broadening at two widely separated wavelengths. (C) 2000 American Association of Physics Teachers.
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| 6. |
- Gustafsson, U, et al.
(författare)
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Compact fiber-optic fluorosensor using a continuous-wave violet diode laser and an integrated spectrometer
- 2000
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 71:8, s. 3004-3006
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Tidskriftsartikel (refereegranskat)abstract
- A compact fluorosensor with a fiber-optic measurement probe was developed, employing a continuous-wave violet diode laser as an exciting source and an integrated digital spectrometer for the monitoring of fluorescence signatures. The system has the dimensions 22x13x8 cm(3), and features 5 nm spectral resolution and an excellent detectivity. Results from measurements on vegetation and human premalignant skin lesions are reported, illustrating the potential of the instrument. (C) 2000 American Institute of Physics. [S0034-6748(00)04508-1].
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| 7. |
- Gustafsson, U, et al.
(författare)
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Frequency-modulation spectroscopy with blue diode lasers
- 2000
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Ingår i: Applied Optics. - 2155-3165. ; 39:21, s. 3774-3780
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Tidskriftsartikel (refereegranskat)abstract
- Frequency-modulation spectroscopy provides ultrasensitive absorption measurements. The technique is especially adaptable to diode lasers, which can be modulated easily, and has been used extensively in the near-infrared and infrared spectral regions. The availability of blue diode lasers now means that the accessible wavelength region can be increased. We successfully demonstrate wavelength-modulation spectroscopy and two-tone frequency-modulation spectroscopy for the weak second resonance line of potassium at 404.8 nm and for the transition at 405.8 nm in lead, starting from the thermally populated 6p(2) P-3(2) metastable level, information on the modulation parameters is obtained with a fitting procedure. Experimental signal-to-noise ratios: at different absorption levels are compared with theoretical signal-to-noise ratios and show good agreement. Detection sensitivities of 2 x 10(-6) and 5 x 10(-6) for wavelength and two-tone frequency-modulation spectroscopy, respectively, for a 120-Hz bandwidth are demonstrated. (C) 2000 Optical Society of America.
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| 8. |
- Gustafsson, U, et al.
(författare)
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Simultaneous detection of methane, oxygen and water vapour utilising near-infrared diode lasers in conjunction with difference-frequency generation
- 2000
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 71:6, s. 853-857
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Tidskriftsartikel (refereegranskat)abstract
- An all-diode-laser-based spectrometer is used for the simultaneous detection of methane, oxygen and water vapour. This is accomplished using a 760-nm diode laser and a 980-nm diode laser in conjunction with difference-frequency generation to 3.4 mum in a periodically poled lithium niobate crystal. Each of the output wavelengths is resonant with one of the molecular species. Simultaneous recordings over a 15-m open path of laboratory air are demonstrated. The recording scheme shows the wide applicability of a diode-laser-based difference-frequency spectrometer for the detection of molecular species in different wavelength ranges. By increasing the frequency of the 760-nm diode laser and decreasing the frequency of the 980-nm diode laser, a maximum continuous tuning range in the mid infrared of 3.6 cm(-1) is achieved. This enables the recording of several methane lines at atmospheric pressure. Pressure-dependence studies of methane lineshapes are also performed in an absorption cell. An indoor-air methane background level of 3 ppm is measured. The signal-to-noise ratio in the recorded methane spectra indicates that sub-ppm detection of methane at atmospheric pressure is feasible.
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| 9. |
- Somesfalean, Gabriel, et al.
(författare)
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Long-path monitoring of NO2 with a 635 nm diode laser using frequency-modulation spectroscopy
- 2005
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Ingår i: Applied Optics. - 2155-3165. ; 44:24, s. 5148-5151
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Tidskriftsartikel (refereegranskat)abstract
- In situ monitoring of traffic-generated nitrogen dioxide (NO2) emissions using long-path absorption spectroscopy is reported. High-sensitivity detection of NO2 is achieved by employing two-tone frequencymodulation spectroscopy at a visible absorption band using a tunable high-power diode laser operated around 635 nm. A real-time absorption spectrometer is accomplished by repetitively applying a rectangular current pulse to the diode-laser operating current, allowing detection of isolated NO2 absorption lines. A detection limit of 10 mu g/m(3) for NO2 at atmospheric pressure using a 160 m absorption path is demonstrated. Continuous monitoring of NO2 over a road intersection at peak traffic is performed.
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