| 1. |
- Axner, Ove, 1957-, et al.
(författare)
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Assessing bacterial adhesion on an individual adhesin and single pili level using optical tweezers
- 2011
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Ingår i: Bacterial adhesion. - Berlin : Springer Berlin/Heidelberg. ; , s. 301-313
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Bokkapitel (refereegranskat)abstract
- Optical tweezers (OT) are a technique that, by focused laser light, can both manipulate micrometer sized objects and measure minute forces (in the pN range) in biological systems. The technique is therefore suitable for assessment of bacterial adhesion on an individual adhesin-receptor and single attachment organelle (pili) level. This chapter summarizes the use of OT for assessment of adhesion mechanisms of both non-piliated and piliated bacteria. The latter include the important helix-like pili expressed by uropathogenic Escherichia coli (UPEC), which have shown to have unique and intricate biomechanical properties. It is conjectured that the large flexibility of this type of pili allows for a redistribution of an external shear force among several pili, thereby extending the adhesion lifetime of bacteria. Systems with helix-like adhesion organelles may therefore act as dynamic biomechanical machineries, enhancing the ability of bacteria to withstand high shear forces originating from rinsing flows such as in the urinary tract. This implies that pili constitute an important virulence factor and a possible target for future anti-microbial drugs.
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| 2. |
- Foltynowicz-Matyba, Aleksandra, 1981-, et al.
(författare)
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Reduction of background signals in fiber-based NICE-OHMS
- 2011
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - Washington, D.C. : Optical Society of America. - 0740-3224 .- 1520-8540. ; 28:11, s. 2797-2805
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Tidskriftsartikel (refereegranskat)abstract
- Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) based on a fiber-coupled electro-optic modulator (EOM) provides a compact and versatile experimental setup. It has, however, been limited by background signals originating from an imbalance of the phase modulated triplet created by a cross-coupling between the principal axes of the polarization maintaining fibers and the extraordinary axis of the EOM. Two strategies for reducing these background signals are investigated: (i) using an EOM with a titanium diffused waveguide, in which the balance of the triplet is controlled by active feedback, and (ii) using an EOM with a proton exchanged waveguide that does not support light propagation along the ordinary axis. It is shown that both approaches significantly reduce drifts and noise in the system. Using a cavity with a finesse of 5700, an absorption sensitivity of 3: 2 x 10(-12) cm(-1) in 1 min of integration time (i.e., 1: 8 x 10(-11) cm(-1) Hz(-1/2)) is demonstrated for Doppler-broadened detection, the lowest reported so far for Doppler-broadened NICE-OHMS. For sub-Doppler detection, a minimum detectable optical phase shift of 1: 3 x 10(-12) cm(-1) in 400s of integration time is obtained. (C) 2011 Optical Society of America
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| 3. |
- Kluczynski, Pawel, et al.
(författare)
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Faraday rotation spectrometer with sub-second response time for detection of nitric oxide using a cw DFB quantum cascade laser at 5.33 µm
- 2011
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Ingår i: Applied physics. B, Lasers and optics (Print). - : Springer. - 0946-2171 .- 1432-0649. ; 103:2, s. 451-459
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Tidskriftsartikel (refereegranskat)abstract
- A Faraday modulation spectrometer for sensitive and fast detection of nitric oxide at 5.33 μm utilizing a room temperature continuous wave distributed feedback quantum cascade laser and a Peltier cooled MCT detector is presented. The magnetic field was modulated at 7.4 kHz whereas the laser wavelength was scanned at 20 Hz across the most favorable rotational-vibrational transition for FAMOS, Q3/2(3/2), at 5.33 μm. Using a 15 cm optical path and lineshape fitting, the spectrometer provides a detection limit of 4.5 ppb for a response time of 1 s. An Allan variance analysis demonstrates that the system has an excellent stability, up to several hours of operation.
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| 4. |
- Lathdavong, Lemthong, 1964-, et al.
(författare)
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Methodology for detection of carbon monoxide in hot, humid media by telecommunication distributed feedback laser-based tunable diode laser absorption spectrometry
- 2011
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 50:17, s. 2531-2550
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Tidskriftsartikel (refereegranskat)abstract
- Detection of carbon monoxide (CO) in combustion gases by tunable diode laser spectrometry is often hampered by spectral interferences from H2O and CO2. A methodology for assessment of CO in hot humid media using telecommunication DFB lasers is presented. By addressing the R14 line at 6395.4 cm-1, and using a dual-species-fitting technique that incorporates fitting of both a previously measured water background reference spectrum and a 2f-wavelength modulation lineshape function, %-level concentrations of CO can be detected in media with tens percent of water (c(H2O) ≤ 40 %) at ≤ 1000 °C with an accuracy of a few percent by the use of a single reference water spectrum for background correction
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| 5. |
- Wang, Junyang, et al.
(författare)
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Dicke narrowing in the dispersion mode of detection and in noise-immune cavity-enhanced optical heterodyne molecular spectroscopy-theory and experimental verification
- 2011
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - Washington, D. C. : The Optical Society of America. - 0740-3224 .- 1520-8540. ; 28:10, s. 2390-2401
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Tidskriftsartikel (refereegranskat)abstract
- Dicke narrowing in both the absorption and dispersion modes of detection have been scrutinized by noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) using an isolated transition in the v(1) + v(3) + v(4)(1) - v(4)(1) band of acetylene [P(e)(33) at 6439.371 cm(-1)] at room temperature. The results represent the first (to our knowledge) demonstration of Dicke narrowing detected in dispersion, as well as by NICE-OHMS, and the paper provides thereby the first comparison of the Dicke narrowing phenomenon for the two modes of detection. It is shown that Dicke narrowing in dispersion can be described by the dispersive counterparts to the conventional Galatry and Rautian absorption line-shape functions, which are explicitly given. Spectroscopic parameters for the targeted transition were extracted in both absorption and dispersion and found to be in agreement with those previously reported for other lines and bands. The shortcomings of the Galatry model to provide physically relevant parameters in this pressure range are discussed.
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| 6. |
- Westberg, Jonas, et al.
(författare)
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Analytical expression for the nth Fourier coefficient of a modulated Lorentzian dispersion lineshape function
- 2011
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Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 112:9, s. 1443-1449
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Tidskriftsartikel (refereegranskat)abstract
- Modulated spectroscopic detection techniques that rely on dispersion, e.g. Faraday modulation/rotation spectroscopy and wavelength-modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy, are often described in terms of Fourier coefficients of a modulated dispersion lineshape function. This work derives a non-complex analytical expression for the nth Fourier coefficient of a modulated Lorentzian dispersion lineshape function. The expression is easier to implement, and orders of magnitude faster to execute, than previous approaches involving numerical calculations of integrals. The first six Fourier coefficients are explicitly given and illustrated for their optimum modulation amplitudes, which are also given
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