| 1. |
- Amcoff, Mirjam, et al.
(författare)
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Sensory exploitation and plasticity in female mate choice in the swordtail characin
- 2013
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Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 85:5, s. 891-898
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Tidskriftsartikel (refereegranskat)abstract
- Despite extensive research in the field of sexual selection, the evolutionary origin and maintenance of preferences for sexual ornaments are still debated. Recent studies have pointed out that plasticity in mate choice might be more common than previously thought, but little is still known about the factors that affect such plasticity. The swordtail characin, Corynopoma riisei, is a tropical fish species in which males use a food-mimicking ornament to attract females. We tested whether ecological factors, more specifically prior foraging experience, can affect female preference for male ornaments. For this, we habituated females on a diet consisting of either red-coloured food or standard-coloured green food items and then we tested whether female preferences for artificially red-coloured male ornaments matched their previous foraging experience. We found a strong effect of food treatment: females trained on red food showed a stronger response to males with red-coloured ornaments than females trained on green food. Our results show that ecological variation can generate divergence of female preferences for male ornaments and that the response in preference to environmental change can be rapid if the bias is partly learnt.
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| 2. |
- Darmastuti, Zhafira, et al.
(författare)
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SiC based field effect transistor for H2S detection
- 2011
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Ingår i: Proc. IEEE Sensors 2011, Limerick, Ireland, October 28-31. - : IEEE. - 9781424492909 ; , s. 770-773
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Konferensbidrag (refereegranskat)abstract
- Experimental characterization and quantum chemical calculations were performed to evaluate the performance of a SiC based Field Effect Transistors with Pt and Ir gates as H2S sensors. The sensors were tested against various concentrations of H2S gas at the operating temperature between 150 and 350 °C. It was observed that Ir was very sensitive and selective to H2S at 350 °C. This phenomenon was studied further by comparing the reaction energy when H2S is exposed to Pt and Ir with density functional theory (DFT) calculations.
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| 3. |
- Darmastuti, Zhafira, et al.
(författare)
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SiC-FET based SO2 sensor for power plant emission applications
- 2014
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 194, s. 511-520
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Tidskriftsartikel (refereegranskat)abstract
- Thermal power plants produce SO2 during combustion of fuel containing sulfur. One way to decrease the SO2 emission from power plants is to introduce a sensor as part of the control system of the desulphurization unit. In this study, SiC-FET sensors were studied as one alternative sensor to replace the expensive FTIR (Fourier Transform Infrared) instrument or the inconvenient wet chemical methods. The gas response for the SiC-FET sensors comes from the interaction between the test gas and the catalytic gate metal, which changes the electrical characteristics of the devices. The performance of the sensors depends on the ability of the test gas to be adsorbed, decomposed, and desorbed at the sensor surface. The feature of SO2, that it is difficult to desorb from the catalyst surface, makes it known as catalyst poison. It is difficult to quantify the SO2 with static operation, even at the optimum operation temperature of the sensor due to low response levels and saturation already at low concentration of SO2. The challenge of SO2 desorption can be reduced by introducing dynamic operation in a designed temperature cycle operation (TCO). The intermittent exposure to high temperature can help to desorb SO2. Simultaneously, additional features extracted from the sensor data can be used to reduce the influence of sensor drift. The TCO operation, together with pattern recognition, may also reduce the baseline and response variation due to changing concentration of background gases (4-10% O-2 and 0-70% RH), and thus it may improve the overall sensor performance. In addition to the laboratory experiment, testing in the desulphurization pilot unit was performed. Desulphurization pilot unit has less controlled environment compared to the laboratory conditions. Therefore, the risk of influence from the changing concentration of background gas is higher. In this study, linear discriminant analysis (LDA) and partial least square (PLS) were employed as pattern recognition methods. It was demonstrated that using LDA quantification of SO2 into several groups of concentrations up to 2000 ppm was possible. Additionally, PLS analysis indicated a good agreement between the predicted value from the model and the SO2 concentration from the reference instrument of the pilot plant.
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| 4. |
- Darmastuti, Zhafira
(författare)
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SiC-FET Gas Sensors Developed for Control of the Flue Gas Desulfurization System in Power Plants Experimental and Modeling : Experimental and Modeling
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electricity and power generation is an essential part of our life. However, powergeneration activities also create by-products (such as sulphur oxides, nitrogen oxides,carbon monoxide, etc), which can be dangerous when released to the atmosphere.Sensors, as part of the control system, play very vital role for the fluegas cleaning processes in power plants. This thesis concerns the development ofSilicon Carbide Field Effect Transistor (SiC-FET) gas sensors as sensors for sulfurcontaining gases (SO2 and H2S) used as part of the environmental control systemin power plants. The works includes sensor deposition and assembly, sensinglayer characterization, operation mode development, performance testing of thesensors in a gas mixing rig in the laboratory and field test in a desulfurization pilotunit, and both experimental and theoretical studies on the detection mechanismof the sensors.The sensor response to SO2 was very small and saturated quickly. SO2 is a verystable gas and therefore reaction with other species requires a large energy input.SO2 mostly reacts with the catalyst through physisorption, which results in lowresponse level. Another problem was that once it finally reacted with oxygen andadsorbed on the surface of the catalyst in form of a sulfate compound, it is desorbedwith difficulty. Therefore, the sensor signal saturated after a certain timeof exposure to SO2. Different gate materials were tested in static operation (Pt,Ir, Au), but the saturation phenomena occurred in all three cases. Dynamic sensoroperation using temperature cycling and multivariate data analysis could mitigatethis problem. Pt-gate sensors were operated at several different temperatures in acyclic fashion. One of the applied temperatures was chosen to be very high for ashort time to serve as cleaning step. This method was also termed the virtual multisensor method because the data generated could represent the data from multiplesensors in static operation at different temperatures. Then, several features of thesignal, such as mean value and slope, were extracted and processed with multivariatedata analysis. Linear Discrimination Analysis (LDA) was chosen since itiiiallows controlled data analysis. It was shown that it was possible to quantify SO2with a 2-step LDA. The background was identified in the first step and SO2 wasquantified in the second step. Pt sensors in dynamic operation and 2-step LDAevaluation has also demonstrated promising results for SO2 measurement in thelaboratory as well as in a desulfurization pilot unit. For a commercial sensor, algorithmhave to be developed to enable on-line measurement in real time.It was observed that Ir-gate sensors at 350oC were very sensitive to H2S. The responseobtained by Ir sensors to H2S was almost five times larger than that of Ptsensors, which might be due to the higher oxygen coverage of Ir. Moreover, Irsensors were also more stable with less drift during the operation as a result ofhigher thermal stability. However, the recovery time for Ir sensors was very long,due to the high desorption energy. Overall, the Ir sensors performed well whentested for a leak detection application (presence of oxygen and dry environment).The geothermal application, where heat is extracted from the earth, requires thesensor to be operated in humid condition in the absence (or very low concentration)of oxygen, and this poses a problem. Temperature cycle operation and smartdata evaluation might also be an option for future development.Along with the sensor performance testing, a study on the detection mechanismwas also performed for SO2 sensor, both experimentally and theoretically. The experimentincluded the study of the species formed on the surface of the catalystwith DRIFT (diffuse reflectance infrared frourier transform) spectroscopy and theanalysis of the residual gas with mass spectroscopy. Explanatory investigation ofthe surface reactions was performed using quantum-chemical calculations. Theoreticalcalculations of the infrared (IR) vibration spectra was employed to supportthe identification of peaks in the DRIFT measurement. Based on the study on theresidual gas analysis and quantum-chemical calculations, a reaction mechanismfor the SO2 molecule adsorption on the sensor surface was suggested.
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| 5. |
- Darmastuti, Zhafira
(författare)
-
SiCFET gassensors : theory, developent, and applications to flue gas cleaning processes in power plants
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Environmental and health concerns lead to stricter regulations on power plant emission. Sensors play an important role, not only as part of the process control to ensure that the effluent stays under the regulated values, but also to increase the pollution removal efficiency and to decrease the reagent consumption.Previous studies, on the use of SiC based Field Effect Transistors (FET) as NH3 sensors in Tekniska Verken power plants and as CO sensors for the control of the domestic boilers, have shown promising results. Moreover, these sensors can withstand high temperature operation and are considerably cheaper than most conventional sensors used in power plants. The price of the sensors enable the installation of multiple sensors in one flue gas duct section, which lead to better monitoring of the flue gas uniformity. Based on that argument, this study is performed to determine whether it is possible to expand the possible application of SiC-FET sensors for the detection of other pollutants emitted by power plants. This thesis reports the characterization and performance testing of SiC-FET sensors towards other selected air pollutants: H2S, methanol as a product of CO2 hydrogenation, and SO2.The study is performed by I-V characterization of the sensors toward the test gas in different background gases and studies of the detection mechanism. Detection mechanism studies include DRIFT spectroscopy, mass spectroscopy, and theoretical study of the surface reaction with Density Functional Theory (DFT).Ir-gate SiC-FET sensors at 350oC show a very high sensitivity to H2S. The large response reduces the possibility of cross-sensitivity from other gases. Pt-gate sensors offer very fast response with decent response magnitude at 200oC for methanol. The presence of oxygen improves the response to methanol, which is favorable for the leak detection application. Besides oxygen, the influence of hydrogen, propene, and water vapor is also observed in the experiment with methanol. The detection mechanism and different sensing behavior of Pt and Ir gates are illustrated with model reaction mechanisms on the surface of the metals. Sensor characterization has been performed for SO2 with several catalytic metal gates: Pt, Ir, Cu, and Au. The results suggest that a single sensor with any of Pt, Ir, Cu, and Au gates is able to detect the presence of SO2 in the air or nitrogen background. However, they are unable to measure different SO2 concentration. Moreover, the response level to SO2 is so small, that it will probably disappear if there is any other gas present in the mixture.
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| 6. |
-
EUROSLA Yearbook 12 (2012)
- 2012
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Ingår i: EUROSLA Yearbook. - Amsterdam : John Benjamins Publishing Company. - 1568-1491.
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Samlingsverk (redaktörskap) (refereegranskat)
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| 7. |
- Harun-Or-Rashid, Mohammad, et al.
(författare)
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Transactivation of EGF Receptors in Chicken Muller Cells by α2A-Adrenergic Receptors Stimulated by Brimonidine
- 2014
-
Ingår i: Investigative Ophthalmology and Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 0146-0404 .- 1552-5783. ; 55:6, s. 3385-3394
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: α2-Adrenergic receptor agonists are used in glaucoma treatment and have been shown to have some neuroprotective effects. We performed this study to test the hypothesis that epidermal growth factor receptors on chicken Müller cells are transactivated by α2-adrenergic receptors and we focused on the extracellular signal-activated kinases 1/2 (ERK) pathway. Methods: Embryonic chicken retina and cultures of primary Müller cells were stimulated by α2-adrenergic receptor agonist brimonidine. Immunostaining, qRT-PCR and western blot techniques in combination with Src-, epidermal growth factor receptor kinase-, and matrix metalloproteinase inhibitors were used for analysis of the cellular responses. Results: Our results showed that Müller cells express α2A-adrenergic receptors in vivo and in vitro and that brimonidine triggered a robust and transient phosphorylation of ERK1/2. This ERK-response was Src-kinase dependent, associated with tyrosine phosphorylation of epidermal growth factor receptors (phospho-Y1068, Y1173) and was mediated by matrix metalloproteinase-activity on the Müller cells. Conclusions: Müller cells express the α2A-adrenergic receptor and brimonidine triggers both Src-kinase- and matrix metalloproteinase-mediated autocrine ligand-dependent activation of epidermal growth factor receptors on Müller cell. This response is consistent with transactivation of epidermal growth factor receptors by stimulation of α2-adrenergic receptors.
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| 8. |
- Harun-Or-Rashid, Mohammad, et al.
(författare)
-
α2-Adrenergic receptors are expressed on chicken Müller glia cells and stimulate the MAPkinase pathway in-vivo and in-vitro
- 2013
-
Konferensbidrag (refereegranskat)abstract
- Muller cells are the principle glia cells of the retina that maintain the integrity and function of the retina and are thought to support and protect neurons during various insults. α2-adrenergic receptor agonists have been shown to be neuroprotective and Mu[[unable to display character: ̈]]ller cells are suggested to take part in these effects. The purpose of this project was to study the expression of α2-adrenergic receptors and the effects of α2-adrenergic agonists on Mu[[unable to display character: ̈]]ller cell-activation and to investigate the signaling pathway that mediates this activation. Retina from embryonic day (E) 18 White-Leghorn chicken and primary Mu[[unable to display character: ̈]]ller cell cultures, established from E14 chick retinas were used for expression analysis. We studied immunoreactivity (IR) and mRNA levels of α2A, 2B and 2C adrenergic receptors in Müller cells. Retinas and Müller cell culture were analyzed by using immunohistochemistry, qRT-PCR and western blot techniques. The results showed that cell soma positive for Müller cell markers, 2M6 and Sox2 in the inner nuclear layer and processes at the outer limiting membrane were positive for α2A receptors. Analysis of primary cultures for IR and mRNA expression confirmed that Müller cells were positive for the α2A receptor. No or very low α2B or α2C expression was detected. Next we analyzed the effect of an α2-adrenergic agonist: Brimonidine (BMD). BMD was tested by injection into E18 chicken eyes or by treatment of the Mu[[unable to display character: ̈]]ller cells in culture. We observed activation of Müller cells after injection of BMD as demonstrated by phospho-ERK1/2 IR in Müller cells with a distinct increase of IR within 2 hours and a gradual decrease to background levels by 24 hours. In-vitro, phospho-ERK1/2 IR was seen already within 5 minutes after BMD addition to the Müller cell culture with peak-levels at 15 minutes and a gradual decrease to pre-exposure levels by 60 minutes. In conclusion, our results show that chick Müller cells mainly expresses α2A adrenergic receptors and that stimulation of the α2-adrenergic receptors triggers the MAPK signaling pathway both in-vivo and in cultured Müller cells in-vitro.
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| 9. |
- Lindqvist, Niclas, et al.
(författare)
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Multiple receptor tyrosine kinases are expressed in adult rat retinal ganglion cells as revealed by single-cell degenerate primer polymerase chain reaction
- 2010
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Ingår i: Upsala Journal of Medical Sciences. - : Uppsala Medical Society. - 0300-9734 .- 2000-1967. ; 115:1, s. 65-80
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: To achieve a better understanding of the repertoire of receptor tyrosine kinases (RTKs) in adult retinal ganglion cells (RGCs) we performed polymerase chain reaction (PCR), using degenerate primers directed towards conserved sequences in the tyrosine kinase domain, on cDNA from isolated single RGCs univocally identified by retrograde tracing from the superior colliculi. RESULTS: All the PCR-amplified fragments of the expected sizes were sequenced, and 25% of them contained a tyrosine kinase domain. These were: Axl, Csf-1R, Eph A4, Pdgfrbeta, Ptk7, Ret, Ros, Sky, TrkB, TrkC, Vegfr-2, and Vegfr-3. Non-RTK sequences were Jak1 and 2. Retinal expression of Axl, Csf-1R, Pdgfrbeta, Ret, Sky, TrkB, TrkC, Vegfr-2, and Vegfr-3, as well as Jak1 and 2, was confirmed by PCR on total retina cDNA. Immunodetection of Csf-1R, Pdgfralpha/beta, Ret, Sky, TrkB, and Vegfr-2 on retrogradely traced retinas demonstrated that they were expressed by RGCs. Co-localization of Vegfr-2 and Csf-1R, of Vegfr-2 and TrkB, and of Csf-1R and Ret in retrogradely labelled RGCs was shown. The effect of optic nerve transection on the mRNA level of Pdgfrbeta, Csf-1R, Vegfr-2, Sky, and Axl, and of the Axl ligands Gas6 and ProteinS, was analysed. These analyses show transection-induced changes in Axl and ProteinS mRNA levels. CONCLUSIONS: The repertoire of RTKs expressed by RGCs is more extensive than previously anticipated. Several of the receptors found in this study, including Pdgfrbeta, Csf-1R, Vegfr-2, Sky, and Axl, and their ligands, have not previously been primarily associated with retinal ganglion cells.
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| 10. |
- Lloyd Spetz, Anita, et al.
(författare)
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Chemical sensor systems for environmental and emission control
- 2013
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Ingår i: Proc. SPIE Defence, Security + Sensors. - : SPIE.
-
Konferensbidrag (refereegranskat)abstract
- Focusing on environment and health aspects, the importance of monitoring and controlling dangerous gases and particulate matter increases. For this purpose we present a new version of silicon carbide based gas sensors with improved properties and suitable for high temperature and harsh environments such as power plants or car exhausts. Development of sulfur dioxide sensors for a power plant application is described as well as sensors for detection of ammonia in connection with the SCR process where urea is converted to ammonia, which reduces nitric oxide components in the exhausts. We also describe progress on nanoparticle detection, especially related to detection of the content of adsorbed particles through heating and detection of emitted molecules by a sensor array. Some results are also presented from impedance spectroscopy for detection of the concentration of nanoparticles but with the potential to reveal more details about the particles such as shape and kind of particles. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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