| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
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| 3. |
- Axner, Ove, 1957-, et al.
(författare)
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NICE-OHMS – frequency modulation cavity-enhanced spectroscopy : principles and performance
- 2014
-
Ingår i: Cavity-Enhanced Spectroscopy and Sensing. - Berlin : Springer Berlin/Heidelberg. - 9783642400025 - 9783642400032 ; , s. 221-251
-
Bokkapitel (refereegranskat)abstract
- Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is a sensitive technique for detection of molecular species in gas phase. It is based on a combination of frequency modulation for reduction of noise and cavity enhancement for prolongation of the interaction length between the light and a sample. It is capable of both Doppler-broadened and sub-Doppler detection with absorption sensitivity down to the 10−12 and 10−14 Hz−1/2 cm−1 range, respectively. This chapter provides a thorough description of the basic principles and the performance of the technique.
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| 4. |
- Bjurstöm, Helen, et al.
(författare)
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GABA, a natural immunomodulator of T lymphocytes.
- 2008
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Ingår i: Journal of Neuroimmunology. - : Elsevier BV. - 1872-8421 .- 0165-5728. ; 205:1-2, s. 44-50
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Tidskriftsartikel (refereegranskat)abstract
- gamma-aminobutyric acid (GABA) is the main neuroinhibitory transmitter in the brain. Here we show that GABA in the extracellular space may affect the fate of pathogenic T lymphocytes entering the brain. We examined in encephalitogenic T cells if they expressed functional GABA channels that could be activated by the low (nM-1 microM), physiological concentrations of GABA present around neurons in the brain. The cells expressed the alpha1, alpha4, beta2, beta3, gamma1 and delta GABAA channel subunits and formed functional, extrasynaptic-like GABA channels that were activated by 1 microM GABA. 100 nM and higher GABA concentrations decreased T cell proliferation. The results are consistent with GABA being immunomodulatory.
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| 5. |
- Ehlers, Patrick, 1981-, et al.
(författare)
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Doppler broadened NICE-OHMS beyond the triplet formalism : assessment of optimum modulation index
- 2014
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 31:7, s. 1499-1507
-
Tidskriftsartikel (refereegranskat)abstract
- The dependence of Doppler broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) on the modulation index, beta, has been investigated experimentally on C2H2 and CO2, both in the absence and the presence of optical saturation. It is shown that the maximum signals are obtained for beta that produce more than one pair of sidebands: in the Doppler limit and for the prevailing conditions (unsaturated transition and the pertinent modulation frequency and Doppler widths) around 1 and 1.4 for the dispersion and absorption detection phases, respectively. The results verify predictions given in an accompanying work. It is also shown that there is no substantial broadening of the NICE-OHMS signal for beta < 1. The use of beta of unity has yielded a Db-NICE-OHMS detection sensitivity of 4.9 x 10(-12) cm(-1) Hz(-1/2), which is the lowest (best) value so far achieved for NICE-OHMS based on a tunable laser. The number of sidebands that needs to be included in fits of the line-shape function to obtain good accuracy has been assessed. It is concluded that it is enough to consider three pairs of sidebands whenever the systematic errors in a concentration assessment should be below 1% when beta < 2 are used and <1 parts per thousand for beta < 1.5.
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| 6. |
- Ehlers, Patrick, 1981-, et al.
(författare)
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Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry incorporating an optical circulator
- 2014
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 39:2, s. 279-282
-
Tidskriftsartikel (refereegranskat)abstract
- To reduce the complexity of fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry, a system incorporating a fiber-coupled optical circulator to deflect the cavity-reflected light for laser stabilization has been realized. Detection near the shot-noise limit has been demonstrated for both Doppler-broadened and sub-Doppler signals, yielding a lowest detectable absorption and optical phase shift of 2.2 x 10(-12) cm(-1) and 4.0 x 10(-12) cm(-1), respectively, both for a 10 s integration time, where the former corresponds to a detection limit of C2H2 of 5 ppt. (C) 2014 Optical Society of America
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| 7. |
- Ehlers, Patrick, 1981-, et al.
(författare)
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Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry instrumentation for Doppler-broadened detection in the 10-12 cm-1 Hz-1/2 region
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:6, s. 1305-1315
-
Tidskriftsartikel (refereegranskat)abstract
- A fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry (FL-NICE-OHMS) system for white-noise-limited Doppler-broadened detection down to 5.6 x 10(-12) cm(-1) Hz(-1/2) is demonstrated. The system is based on a previous FL-NICE-OHMS instrumentation in which the locking of the laser frequency to a cavity mode has been improved by the use of an acousto-optic modulator (AOM) and provision of a more stable environment by the employment of a noise-isolating enclosed double-layer table, a temperature regulation of the laboratory, and an ultra-high-vacuum (UHV) gas system. White-noise behavior up to 10 s provides the instrument with a minimum detectable on-resonance absorbance per unit length of 1.8 x 10(-12) cm(-1) and a relative single-pass absorption (Delta I/I) of 7.2 x 10(-11). The system was applied to detection of acetylene on a transition at 1531.588 nm, yielding a detection sensitivity of C2H2 in atmospheric pressure gas of 4 ppt (measured over 10 s). (C) 2012 Optical Society of America
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| 8. |
- Ejlerskov, Patrick, et al.
(författare)
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Lack of Neuronal IFN-β-IFNAR Causes Lewy Body- and Parkinson's Disease-like Dementia.
- 2015
-
Ingår i: Cell. - : Elsevier BV. - 1097-4172 .- 0092-8674. ; 163:2, s. 324-339
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Tidskriftsartikel (refereegranskat)abstract
- Neurodegenerative diseases have been linked to inflammation, but whether altered immunomodulation plays a causative role in neurodegeneration is not clear. We show that lack of cytokine interferon-β (IFN-β) signaling causes spontaneous neurodegeneration in the absence of neurodegenerative disease-causing mutant proteins. Mice lacking Ifnb function exhibited motor and cognitive learning impairments with accompanying α-synuclein-containing Lewy bodies in the brain, as well as a reduction in dopaminergic neurons and defective dopamine signaling in the nigrostriatal region. Lack of IFN-β signaling caused defects in neuronal autophagy prior to α-synucleinopathy, which was associated with accumulation of senescent mitochondria. Recombinant IFN-β promoted neurite growth and branching, autophagy flux, and α-synuclein degradation in neurons. In addition, lentiviral IFN-β overexpression prevented dopaminergic neuron loss in a familial Parkinson's disease model. These results indicate a protective role for IFN-β in neuronal homeostasis and validate Ifnb mutant mice as a model for sporadic Lewy body and Parkinson's disease dementia.
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| 9. |
- Foltynowicz, Aleksandra, et al.
(författare)
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Distributed-feedback-laser-based NICE-OHMS
in the pressure-broadened regime
- 2010
-
Ingår i: Optics Express. - 1094-4087. ; 18:18, s. 18580-18591
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Tidskriftsartikel (refereegranskat)abstract
- A compact noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) system based on a narrow linewidth distributed-feedback laser and fiber-coupled acousto-optic and electro-optic modulators has been developed. Measurements of absorption and dispersion signals have been performed at pressures up to 1/3 atmosphere on weak acetylene transitions at 1551 nm. Multiline fitting routines were implemented to obtain transition parameters, i.e., center frequencies, linestrengths, and pressure broadening coefficients. The signal strength was shown to be linear with pressure and concentration, and independent of detection phase. The minimum detectable on-resonance absorption with a cavity with a finesse of 460 was 2 × 10−10 cm−1 for 1 minute of integration time.
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| 10. |
- Leiding, Thom, et al.
(författare)
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Proton and cation transport activity of the M2 proton channel from influenza A virus.
- 2010
-
Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 107:35, s. 15409-15414
-
Tidskriftsartikel (refereegranskat)abstract
- The M2 protein is a small, single-span transmembrane (TM) protein from the influenza A virus. This virus enters cells via endosomes; as the endosomes mature and become more acidic M2 facilitates proton transport into the viral interior, thereby disrupting matrix protein/RNA interactions required for infectivity. A mystery has been how protons can accumulate in the viral interior without developing a large electrical potential that impedes further inward proton translocation. Progress in addressing this question has been limited by the availability of robust methods of unidirectional insertion of the protein into virus-like vesicles. Using an optimized procedure for reconstitution, we show that M2 has antiporter-like activity, facilitating K(+) or Na(+) efflux when protons flow down a concentration gradient into the vesicles. Cation efflux is very small except under conditions mimicking those encountered by the endosomally entrapped virus, in which protons are flowing through the channel. This proton/cation exchange function is consistent with the known high proton selectivity of the channel. Thus, M2 acts as a proton uniporter that occasionally allows K(+) to flow to maintain electrical neutrality. Remarkably, as the pH inside M2-containing vesicles (pH(in)) decreases, the proton channel activity of M2 is inhibited, but its cation transport activity is activated. This reciprocal inhibition of proton flux and activation of cation flux with decreasing pH(in) first allows accumulation of protons in the early stages of acidification, then trapping of protons within the virus when low pH(in) is achieved.
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| 11. |
- Liu, Jian-Jun, et al.
(författare)
-
Sulindac induces apoptosis, inhibits proliferation and activates caspase-3 in Hep G2 cells
- 2002
-
Ingår i: Anticancer research. - 1791-7530. ; 22:1A, s. 263-266
-
Tidskriftsartikel (refereegranskat)abstract
- Background: It has recently been reported that sulindac has an apoptotic effect on KYN-2 cells, an undifferentiated hepatoma cell line. The present work investigates whether sulindac also has an apoptotic effect on well-differentiated hepatoma cells and what its potential mechanism might be. Materials and Methods: Hep G2 cells were treated with sulindac at different concentrations. Apoptosis rate, cell proliferation and 3H-thymidine incorporation were measured. The activities of caspase-3, acid and neutral sphingomyelinase and the changes of sphingomyelin content were also assayed. Results: Sulindac dose-dependently induced apoptosis in Hep G2 cells; both sulindac sulfone and sulfide had similar effects. The apoptosis was accompanied by an increase 3 of caspase-3 activity and a decrease of cell proliferation and H-3-thymidine incorporation. No significant change could be observed for the activity of sphingomyelinase and sphingomyelin content. Conclusion: Sulindac induces apoptosis and inhibits proliferation in Hep G2 cells. The effect may, be mediated by, a pathway related to caspase-3 activation but independent of sphingomyelin metabolism.
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| 12. |
- Liu, Zihe, et al.
(författare)
-
Yeast synthetic biology advances biofuel production
- 2022
-
Ingår i: Current Opinion in Microbiology. - : Elsevier BV. - 1369-5274 .- 1879-0364. ; 65, s. 33-39
-
Forskningsöversikt (refereegranskat)abstract
- Increasing concerns of environmental impacts and global warming calls for urgent need to switch from use of fossil fuels to renewable technologies. Biofuels represent attractive alternatives of fossil fuels and have gained continuous attentions. Through the use of synthetic biology it has become possible to engineer microbial cell factories for efficient biofuel production in a more precise and efficient manner. Here, we review advances on yeast-based biofuel production. Following an overview of synthetic biology impacts on biofuel production, we review recent advancements on the design, build, test, learn steps of yeast-based biofuel production, and end with discussion of challenges associated with use of synthetic biology for developing novel processes for biofuel production.
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| 13. |
- Silander, Isak, 1980-, et al.
(författare)
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Frequency modulation background signals from fiber-based electro optic modulators are caused by crosstalk
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:5, s. 916-923
-
Tidskriftsartikel (refereegranskat)abstract
- Frequency modulated spectroscopy (FMS) performed by the use of fiber-coupled electro optic modulators (FC-EOMs) is often plagued by background signals that bring in noise and, by their temperature dependence, cause severe drifts. These signals cannot be zeroed out by the conventional technique of using a carefully adjusted polarizer that can be applied to free space electro optic modulators (EOMs). This can limit the use of FC-EOMs in high performance detection techniques. Here we provide an explanation to these background signals that is based upon crosstalk between various polarization directions of light in the fixed mounted polarization-maintaining fibers and the electro optic crystal. The description provides a basis for the previously demonstrated technique that utilizes an EOM regulated simultaneously by temperature and DC voltage to eliminate background signals from systems encompassing FC-EOMs. (C) 2012 Optical Society of America
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| 14. |
- Tian, Xiaohe, et al.
(författare)
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Probe for simultaneous membrane and nucleus labeling in living cells and in vivo bioimaging using a two-photon absorption water-soluble Zn(II) terpyridine complex with a reduced pi-conjugation system
- 2017
-
Ingår i: Chemical Science. - : ROYAL SOC CHEMISTRY. - 2041-6520 .- 2041-6539. ; 8:1, s. 142-149
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Tidskriftsartikel (refereegranskat)abstract
- Small, biocompatible and water-soluble molecules with high two-photon absorption (2PA) cross-section values (delta) are in high demand for specific bioimaging applications. Here, two novel terpyridine derivative ligands with donor-acceptor (D-A) (L1) and donor-pi-acceptor (D-pi-A) (L2) models, and their corresponding Zn(II) complexes are designed and characterized. It was found that the two-photon absorption cross section values (d) in the near-infrared region (NIR, about 800 nm) are significantly enhanced for complexes 1 and 2 compared to their free D-A type ligand L1, while those of complexes 3 and 4 were greatly decreased relative to their free ligand L2, thus confirming that the smaller ligand (D-A type) displays a suitable Turn-ON fluorescence pair for two-photon fluorescence microscopy (2PFM). Firstly, the potential of simultaneously labeling a live cell plasma membrane and nucleus using complex 1 is demonstrated. In addition, live larval and adult zebrafish incubated with an optimal concentration of 1 demonstrated clear brain uptake. Lastly and importantly, using such a probe to visualize the blood-brain- barrier (BBB) capillary endothelial cells and penetrate the BBB into the central nervous system (CNS) intravenously in a mouse model is also explored.
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| 15. |
- Wang, Hua, et al.
(författare)
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Clamping force integrated computer aided tolerancing in composite assembly
- 2021
-
Ingår i: Journal of Composite Materials. - : SAGE Publications. - 1530-793X .- 0021-9983. ; 55:10, s. 1405-1417
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Tidskriftsartikel (refereegranskat)abstract
- Traditional computer aided tolerancing method could not accomplish the tolerancing and variation simulation well in composite assembly. The paper presents a clamping force integrated computer aided tolerancing method for composite assembly. The stochastic variations and the stackup of variations are affected by clamping forces. The clamping force modified probability distribution is used to represent the modification based on the verified FEA model of the composite assembly. The clamping forces are coordinated based on the main deformation mode extracted by the principal component analysis to satisfy the coaxial tolerance requirements of the composite assembly. The assembly of an aircraft composite elevator is considered to illustrate the computational aspects of the proposed methods. The computer aided tolerancing method involving clamping forces outlined in the paper is found to be effective for composite assembly.
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| 16. |
- Wang, Junyang, 1983-
(författare)
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Dicke narrowing and speed-dependent effects in dispersion signals : Influence on assessment of concentration and spectral parameters by noise-immune cavity-enhanced optical heterodyne molecular spectrometry
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Laser spectroscopic techniques have, during the last decades, demonstrated an extraordinary capability for sensitive detection of molecular constituents in gas phase. Since spectra from such techniques constitute unique and characteristic signatures for each type of species, these techniques enable investigations of molecular structures as well as detection of the presence of species in a gas mixture. They are therefore used for a variety of application, from fundamental studies to the assessment of gas concentrations. In fact, quantitative assessments of gas concentrations by laser-based techniques are constantly gaining in popularity, primarily due to properties such as high sensitivity and selectivity and an ability to perform non-invasive measurement. Moreover, investigations of isolated molecular transitions under different conditions provide excellent means to obtain a comprehensive understanding of spectral broadening mechanisms, which is of importance for, for example, environmental sciences and remote sensing applications. In fundamental studies, spectroscopic parameters are often retrieved from fits of a model function of the technique used, which in turn is based upon a suitable lineshape function. In order to obtain parameter values with highest possible accuracy, it is of importance to use the lineshape model that most correctly can predict the measured spectra. Even though the Voigt function is the most commonly used lineshape model when both Doppler and collision broadenings are present, it is not always suitable when spectroscopic parameters are to be assessed with high precision.This thesis represents a thorough investigation of Dicke narrowing and speed-dependent effects, which are phenomena that are not accounted for by the conventional Voigt profile. For the first time, it is demonstrated that both these effects take place not only in absorption but also in the dispersion mode of detection. Their dispersion lineshape functions are first theoretically presumed and explicitly given before they are validated experimentally by the noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS). By using the models developed, it is also shown that although the two modes of detection, absorption and dispersion, both can provide good quality of fits, they do not always provide identical spectroscopic parameters. A detailed analysis under which conditions they do so, and subsequent recommendations of their use, are presented.It also describes the instrumental implementation of a distributed-feed-back (DFB) laser-based NICE-OHMS instrumentation, which constitutes an important step towards the further development of this technique. Due to the wide tunability of the DFB laser, the setup is capable of extending the working range of NICE-OHMS into the collision broadening region, which, in turn, allows for precise spectroscopic studies. The use of a fiber-coupled DFB laser also provides a compact NICE-OHMS system. The minimum detectable on-resonance absorption was assessed to 2× 10-10 cm-1 for a 70 s integration time.
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| 17. |
- Wang, Junyang, et al.
(författare)
-
Dicke narrowing in the dispersion mode of detection and in noise-immune cavity-enhanced optical heterodyne molecular spectroscopy-theory and experimental verification
- 2011
-
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
-
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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| 18. |
- Wang, Junyang, et al.
(författare)
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On the accuracy of the assessment of molecular concentration and spectroscopic parameters by frequency modulation spectrometry and NICE-OHMS
- 2014
-
Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 136, s. 28-44
-
Tidskriftsartikel (refereegranskat)abstract
- Frequency modulation spectrometry (FMS), and thereby also noise immune cavity enhanced optical heterodyne molecular spectrometry (NICE-OHMS), can detect both absorption and dispersion signals, and can therefore, by curve fitting, extract molecular parameters from both these types of signals. However, parameters evaluated from the two modes of detection have been previously shown not to be identical. Their accuracy is affected by both the type of lineshape used by the fit and the accuracy of the detection phase. A thorough study is presented of the influence of three lineshape functions [Voigt, Rautian, and speed-dependent Voigt (SDV)] and errors in the detection phase on the retrieval of various molecular parameters, in particular the signal strength, which provides information about the concentration of molecules in a gas, from reference spectra in the 10-260 Torr region. It was found that for data detected and evaluated at pure absorption or dispersion phase by a system calibrated in the Doppler limit the signal strength can be underestimated at higher pressures by up to 45% if the evaluation is made using the Voigt profile. If the detection is plagued by phase errors additional inaccuracies, often in the order of percent per degree phase error (%/deg), can occur. More reliable parameters can be obtained if an appropriate lineshape function is used and the detection phase is considered a free parameter. However, despite this, none of the evaluation procedures can retrieve the molecular parameters fully correctly; the most accurate assessments of the signal strength, obtained when the data is detected close to absorption phase and evaluated by the SDV lineshape function, are still associated with an error of a few percent. (C) 2013 Elsevier Ltd. All rights reserved.
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| 19. |
- Wang, Junyang, et al.
(författare)
-
Speed-dependent effects in dispersion mode of detection and in noise-immune cavity-enhanced optical heterodyne molecular spectrometry : experimental demonstration and validation of predicted line shape
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - Washington : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:10, s. 2980-2989
-
Tidskriftsartikel (refereegranskat)abstract
- Speed-dependent effects (SDEs) in both the absorption and dispersion modes of detection have been detected and scrutinized by the noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) technique. The present paper achieves four objectives: (i) it provides the first demonstration of SDEs detected in dispersion, (ii) it validates the expression for a speed-dependent Voigt (SDV) dispersion line-shape function that is derived in an accompanying paper, (iii) it illustrates the influence of SDEs on the NICE-OHMS technique, and (iv) it gives the first experimental comparison of SDEs for the absorption and dispersion modes of detection. Experiments were performed 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)] in the 100-250 Torr range at room temperature. It is shown that SDEs appear in both the absorption and dispersion modes of detection, that they can be well described by the suggested SDV dispersion line-shape function, and that they need to be taken into account if NICE-OHMS signals detected under optimal pressures are to be properly assessed. (c) 2012 Optical Society of America
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| 20. |
- Wang, Junyang, et al.
(författare)
-
Speed-dependent Voigt dispersion line-shape function : applicable to techniques measuring dispersion signals
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - Washington : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:10, s. 2971-2979
-
Tidskriftsartikel (refereegranskat)abstract
- An analytical expression for a Voigt dispersion line-shape function that incorporates speed-dependent effects (SDEs) on the collision broadening, applicable to spectroscopic techniques that measure dispersion signals, is presented. It is based upon a speed-dependent Voigt (SDV) model for absorption spectrometry that assumes that the molecular relaxation rate has a quadratic dependence on molecular speed. The expression is validated theoretically in the limit of small SDEs by demonstration that it reverts to the ordinary Voigt dispersion line-shape function and experimentally in a separate work by experiments performed by the noise-immune cavity-enhanced optical heterodyne molecular spectrometry technique. A comparison is given between the SDEs in the SDV absorption and dispersion line-shape functions. It is shown that both line shapes are affected significantly but differently by SDEs. The expression derived provides, for the first time to our knowledge, a possibility also for the techniques that measure dispersion signals to handle SDEs. (c) 2012 Optical Society of America
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| 21. |
- Wang, Junyang, et al.
(författare)
-
Synthetic biology advanced natural product discovery
- 2021
-
Ingår i: Metabolites. - : MDPI AG. - 2218-1989 .- 2218-1989. ; 11:11
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Forskningsöversikt (refereegranskat)abstract
- A wide variety of bacteria, fungi and plants can produce bioactive secondary metabolites, which are often referred to as natural products. With the rapid development of DNA sequencing technology and bioinformatics, a large number of putative biosynthetic gene clusters have been reported. However, only a limited number of natural products have been discovered, as most biosynthetic gene clusters are not expressed or are expressed at extremely low levels under conventional laboratory conditions. With the rapid development of synthetic biology, advanced genome mining and engineering strategies have been reported and they provide new opportunities for discovery of natural products. This review discusses advances in recent years that can accelerate the design, build, test, and learn (DBTL) cycle of natural product discovery, and prospects trends and key challenges for future research directions.
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| 22. |
- Westberg, Jonas, et al.
(författare)
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Fast and non-approximate methodology for calculation of wavelength-modulated Voigt lineshape functions suitable for real-time curve fitting
- 2012
-
Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - Oxford : Elsevier. - 0022-4073 .- 1879-1352. ; 113:16, s. 2049-2057
-
Tidskriftsartikel (refereegranskat)abstract
- Wavelength modulation (WM) produces lock-in signals that are proportional to various Fourier coefficients of the modulated lineshape function of the molecular transition targeted. Unlike the case for the Lorentzian lineshape function, there is no known analytical expression for the Fourier coefficients of a modulated Voigt lineshape function; they consist of nested integrals that have to be solved numerically, which is often time-consuming and prevents real-time curve fitting. Previous attempts to overcome these limitations have so far consisted of approximations of the Voigt lineshape function, which brings in inaccuracies. In this paper we demonstrate a new means to calculate the lineshape of nf-WM absorption signals from a transition with a Voigt profile. It is shown that the signal can conveniently be expressed as a convolution of one or several Fourier coefficients of a modulated Lorentzian lineshape function, for which there are analytical expressions, and the Maxwell-Boltzmann velocity distribution for the system under study. Mathematically, the procedure involves no approximations, wherefore its accuracy is limited only by the numerical precision of the software used (in this case similar to 10(-16)) while the calculation time is reduced by roughly three orders of magnitude (10(-3)) as compared to the conventional methodology, i.e. typically from the second to the millisecond range. This makes feasible real-time curve fitting to lock-in output signals from modulated Voigt profiles. (C) 2012 Elsevier Ltd. All rights reserved.
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| 23. |
- Westberg, Jonas, et al.
(författare)
-
Methodology for fast curve fitting to modulated Voigt dispersion lineshape functions
- 2014
-
Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 133, s. 244-250
-
Tidskriftsartikel (refereegranskat)abstract
- Faraday rotation spectroscopy (FAMOS) as well as other modulated techniques that rely on dispersion produce lock-in signals that are proportional to various Fourier coefficients of modulated dispersion lineshape functions of the molecular transition targeted. In order to enable real-time curve fitting to such signals a fast methodology for calculating the Fourier coefficients of modulated lineshape functions is needed. Although there exist an analytical expression for such Fourier coefficients of modulated Lorentzian absorption and dispersion lineshape functions, there is no corresponding expression for a modulated Voigt dispersion function. The conventional computational route of such Fourier coefficients has therefore so far either consisted of using various approximations to the modulated Voigt lineshape function or solving time-consuming integrals, which has precluded accurate real-time curve fitting. Here we present a new methodology to calculate Fourier coefficients of modulated Voigt dispersion lineshape functions that is significantly faster (several orders of magnitude) and more accurate than previous approximative calculation procedures, which allows for real-time curve fitting to FAMOS signals also in the Voigt regime.
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| 24. |
- Zhang, Fan, et al.
(författare)
-
Effects of Ni and Al on precipitation behavior and mechanical properties of precipitation-hardened CoCrFeNi high-entropy alloys
- 2022
-
Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 839, s. 142879-
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Tidskriftsartikel (refereegranskat)abstract
- Morphology and volume fraction of precipitates are crucial for mechanical properties of precipitation-hardened high-entropy alloys (HEAs). In this study, we systematically examined the effects of Ni and Al on precipitation behavior and mechanical properties of (FeCoCr)(98-x-y) NixTi2Aly (x = 25, 30, 35; y = 4, 6, 8) HEAs. It was found that an increase of Ni and Al can effectively promote the formation of coherent gamma' precipitates, but an incoherent Heusler phase (Ni2AlTi) also inevitably appeared once the Al content exceeds 6%. Both gamma' and the Heusler phases could strengthen the materials, however, since they shared the same constituent elements, the two phases produced synergistic effects. For instance, excessive Heusler phase not only restrains the formation of gamma', but also reduces the ductility. Our analysis indicated that the ratio of Ni over Al played a pivotal role on the Heusler phase formation, and the Heusler phase could be completely eliminated when the Ni/Al ratio is larger than 5. In such a case, the maximum volume fraction of gamma' in (FeCoCr)(57)Ni35Ti2Al6 reaches 33% and the alloy exhibits tensile strength over 1 GPa with a decent ductility of about 35%. Our findings provide a useful guideline for the optimal design of precipitation-hardened HEAs, it also shed light on understanding precipitation behavior in highly concentrated alloys.
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