| 1. |
- Dahlin, Clas
(författare)
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Surface charge densities and membrane fluidities in thylakoids with different degrees of thylakoid appression after Norflurazon treatment
- 2003
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Ingår i: Photosynthetica (Praha). - : Springer-Verlag. - 0300-3604 .- 1573-9058. ; 41:4, s. 635-639
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Tidskriftsartikel (refereegranskat)abstract
- Wheat seedlings (Triticum aestivum L.) develop plastids (etioplasts and chloroplasts) which exhibit alterations in inner membrane organisation after treatment with Norflurazon (NF), an inhibitor of carotenoid biosynthesis. In dark-grown plants, results in a decreased amount of partitions (contact zones) between prothylakoids. In weak red light, the results in plants containing chloroplasts devoid of grana. Assays have been performed to investigate the membrane surface charge density in these membranes, and relate possible differences to the absence of (pro-)thylakoid overlap after NF teatment. Using the fluorescent probe 9- amino acridine (9-AA), the average surface charge density of isolated PTs was -21.8±3.2 mC m-2 and - 27.4±2.6 mC m-2 in the control and after, respectively. Thylakoid membranes isolated from plants grown in weak red light exhibited slightly more negative values, -23.5±2.9 mC m-2 and -29.0±2.1 mC m-2, in control and after, respectively. The surface charge density of destacked thylakoids from greenhouse-grown untreated plants, containing extensive grana stacking, was -34.3±2.5 mC m-2. Assays using the fluorescent probe of DPH (1,6- diphenyl- 1,3,5- hexatriene) showed that this probe exhibits a higher polarisation value when incorporated into thylakoids from NF- treated plants compared to untreated plants grown in weak red light. The highest polarisation value was found in untreated plants grown in the greenhouse. This indicates a lower rotation transition of the probe in the lipid environment of thylakoids after NF treatment, which can be interpreted as more rigid membranes. These results suggest that the surface charge density and the mobility of membrane components may play a major role for the formation of partitions in dark-grown plants and in the formation of grana in plants grown in weak red light. 23 Additional key words: chloroplasts; etioplasts; (pro-)thylakoids; Triticum; stacking; wheat; 9- amino acridine.
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| 2. |
- Amirjani, M.R., et al.
(författare)
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Red region excitation spectra of protochlorophyllide in dark-grown leaves from plant species with different proportions of its spectral forms
- 2005
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Ingår i: Photosynthetica. - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 44:1, s. 83-92
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Tidskriftsartikel (refereegranskat)abstract
- Etiolated leaves of three different species, maize, wheat, and pea, as well as a pea mutant (lip1) were used to compare the excitation spectra of protochlorophyllide (Pchlide) in the red region. The species used have different composition of short-wavelength and long-wavelength Pchlide forms. The relation between different forms was furthermore changed through incubating the leaves in 5-aminolevulinic acid (ALA), which caused an accumulation of short-wavelength Pchlide forms, as shown by changes in absorption and fluorescence spectra. This is the first time a comprehensive comparison is made between excitation spectra from different species covering an emission wavelength range of 675750 nm using fluorescence equipment with electronic compensation for the variations in excitation irradiance. The different forms of Pchlide having excitations peaks at 628, 632, 637, 650, and 672 nm could be best measured at 675, 700, 710, 725, and 750 nm, respectively. Measuring emission at wavelengths between 675 710 nm gave an exaggeration of the short-wavelength forms and measuring at longer wavelengths gave for the pea leaves an exaggeration of the 672 nm peak. In general, an energy transfer from short-wavelength Pchlide forms to long-wavelength Pchlide forms occurred, but such an energy transfer sometimes seemed to be limited as a result of a discrete location of the Pchlide spectral forms. The excitation spectra resembling the absorption spectrum most were measured at an emission wavelength of 740 nm. Measuring the excitation at 710 nm gave higher intensity of the spectra but the short-wavelength forms were accentuated.
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| 3. |
- Borisov, A. Y., et al.
(författare)
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On oxygen production by photosynthesis : A viewpoint
- 2018
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Ingår i: Photosynthetica. - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 56:1, s. 44-47
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Tidskriftsartikel (refereegranskat)abstract
- In this brief communication we provide an estimate of the part of the incident solar energy used for oxygen evolution as well as the time, in years, needed for the generation of the present amount of molecular oxygen in the biosphere by photosynthesis on land and in the ocean. We find this to be ≈4,000 yr. We also find that the ocean produces 22% more oxygen than the land surface.
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| 4. |
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| 5. |
- Nonomura, Arthur M., et al.
(författare)
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The carbon reactions of photosynthesis : role of lectins and glycoregulation
- 2020
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Ingår i: Photosynthetica (Praha). - Prague : Institute of Experimental Botany of the Academy of Sciences of the Czech Republic. - 0300-3604 .- 1573-9058. ; 58:5, s. 1090-1097
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Forskningsöversikt (refereegranskat)abstract
- Modulation of glycoregulation in agriculture is reviewed here with emphasis on the elucidation of previously unknown pathways involving vacuolar lectins as well as a bypass of lectins that direct free sugars toward productivity. The reversible binding sequences of the endogenous lectin cycle are compared to an induced lectin bypass, as follows. (1) In the cycle, carbohydrate ligands, with similar binding specificities that compete for binding sites on lectins, are involved in the natural cycle of sugar exchanges. (2) For the bypass, tightly bound ligands that occupy lectins prevent free sugars from binding, making them available for productivity. This bypass is induced by methyl-α-D-mannopyranoside, a biochemical plant growth regulator for photosynthesis. Integration of this novel technology, with structural elements crucial for ligand binding by the lectins and with nitrogen assimilation, provides the basis for successful modulation of glycoregulation in crops for enhancement of quality and quantity.
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| 6. |
- Novriyanti, E., et al.
(författare)
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Photosynthetic nitrogen- and water-use efficiency of acacia and eucalypt seedlings as afforestation species
- 2012
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Ingår i: Photosynthetica (Praha). - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 50:2, s. 273-281
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Tidskriftsartikel (refereegranskat)abstract
- The ecophysiological traits of acacia and eucalypt are important in assessing their suitability for afforestation. We measured the gas-exchange rate, the leaf dry mass per area (LMA) and the leaf nitrogen content of two acacia and four eucalypt species. Relative to the eucalypts, the acacias had lower leaf net photosynthetic rate (P-N), lower photosynthetic nitrogen-use efficiency (PNUE), higher water-use efficiency (WUE), higher LMA and higher leaf nitrogen per unit area (N-area). No clear differences were observed within or between genera in the maximum rate of carboxylation (V-cmax) or the maximum rate of electron transport (J(max)), although these parameters tended to be higher in eucalypts. PNUE and LMA were negatively correlated. We conclude that acacias with higher LMA do not allocate nitrogen efficiently to photosynthetic system, explaining why their P-N and PNUE were lower than in eucalypts.
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| 7. |
- Sundqvist, Christer, et al.
(författare)
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Obituary: Prof. Dr. Hemming Virgin
- 2008
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Ingår i: Photosynthetica. - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 46:1, s. 1-2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Hemming Ivar Virgin (1918-2005) was a pioneer in plant photobiology.The main topics of his research covered areas such as light effects on viscosity of protoplasm, determination of turgor and elasticity of plant organs, chlorophyll formation and accumulation, plastid development during greening, and phytochrome regulation of physiological processes.
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| 8. |
- Tikhonov, K., et al.
(författare)
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Quantification of bound bicarbonate in photosystem II
- 2018
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Ingår i: Photosynthetica (Praha). - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 56:1, s. 210-216
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we presented a new approach for quantification of bicarbonate (HCO3-) molecules bound to PSII. Our method, which is based on a combination of membrane-inlet mass spectrometry (MIMS) and O-18-labelling, excludes the possibility of "non-accounted" HCO3- by avoiding (1) the employment of formate for removal of HCO3- from PSII, and (2) the extremely low concentrations of HCO3-/CO2 during online MIMS measurements. By equilibration of PSII sample to ambient CO2 concentration of dissolved CO2/HCO3-, the method ensures that all physiological binding sites are saturated before analysis. With this approach, we determined that in spinach PSII membrane fragments 1.1 +/- 0.1 HCO3- are bound per PSII reaction center, while none was bound to isolated PsbO protein. Our present results confirmed that PSII binds one HCO3- molecule as ligand to the non-heme iron of PSII, while unbound HCO3- optimizes the water-splitting reactions by acting as a mobile proton shuttle.
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| 9. |
- Tikhonov, K., et al.
(författare)
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Quantification of bound bicarbonate in photosystem II#
- 2018
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Ingår i: Photosynthetica (Praha). - : Springer. - 0300-3604 .- 1573-9058. ; 56:1, s. 210-216
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we presented a new approach for quantification of bicarbonate (HCO3-) molecules bound to PSII. Our method, which is based on a combination of membrane-inlet mass spectrometry (MIMS) and O-18-labelling, excludes the possibility of "non-accounted" HCO3- by avoiding (1) the employment of formate for removal of HCO3- from PSII, and (2) the extremely low concentrations of HCO3-/CO2 during online MIMS measurements. By equilibration of PSII sample to ambient CO2 concentration of dissolved CO2/HCO3-, the method ensures that all physiological binding sites are saturated before analysis. With this approach, we determined that in spinach PSII membrane fragments 1.1 +/- 0.1 HCO3- are bound per PSII reaction center, while none was bound to isolated PsbO protein. Our present results confirmed that PSII binds one HCO3- molecule as ligand to the non-heme iron of PSII, while unbound HCO3- optimizes the water-splitting reactions by acting as a mobile proton shuttle.
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| 10. |
- Voitsekhovskaja, O. V., et al.
(författare)
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Photosynthetic activity as assessed via chlorophyll a fluorescence suggests a role of potassium channels in root to shoot signaling
- 2020
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Ingår i: Photosynthetica (Praha). - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 58:2, s. 608-621
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Tidskriftsartikel (refereegranskat)abstract
- Potassium is indispensable for plant growth. Recently, a role of K+ channels has emerged in sensing and transducing stress and nutrient status. Tetraethylammonium (TEA(+)) is a specific blocker of K+ transport and affects K+ channel gene expression. Two barley varieties with contrasting salinity tolerance, and a chlorophyll b-less mutant, were grown either in the presence of TEA(+) alone or combined with NaCl, at two different concentrations of external K+ and Ca2+, and were analyzed nine days after germination. Chlorophyll a transients monitored via JIP-tests were used to evaluate the state of the photosynthetic machinery. In contrast to reported responses to K+ deficiency, TEA(+) inhibited shoot growth while inducing root growth and increasing photosynthetic performance. Both TEA(+) and NaCl induced the appearance of negative K-bands in OJIP kinetics and an increase in PIABS, indicating a stimulation of photosynthesis by increased sink strength in the context of root to shoot signaling.
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| 11. |
- Björn, Lars Olof
(författare)
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Why are plants green - relationships between pigment absorption and photosynthetic efficiency
- 1976
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Ingår i: Photosynthetica. - 0300-3604. ; 10:2, s. 121-129
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Tidskriftsartikel (refereegranskat)abstract
- The maximum efficiency of an optically thin photosynthetic system in converting solar radiation into chemical energy is theoretically considered as a function of the absorption spectrum of the photon-collecting pigment. The absorption band position giving maximum rate of power conversion is close to 700 nm in full sunlight and at somewhat shorter wavelength in weaker light. The chemical potential obtainable is decreased if the band is too wide. The effect of a 2nd absorption band (or accessory pigment) on potential is rather small.
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| 12. |
- Lazár, Dušan, et al.
(författare)
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Light quality, oxygenic photosynthesis and more.
- 2022
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Ingår i: Photosynthetica. - 0300-3604. ; 60:SI, s. 23-56
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Forskningsöversikt (refereegranskat)abstract
- Oxygenic photosynthesis takes place in thylakoid membranes (TM) of cyanobacteria, algae, and higher plants. Itbegins with light absorption by pigments in large (modular) assemblies of pigment-binding proteins, which thentransfer excitation energy to the photosynthetic reaction centers of photosystem (PS) I and PSII. In green algaeand plants, these light-harvesting protein complexes contain chlorophylls (Chls) and carotenoids (Cars). However,cyanobacteria, red algae, and glaucophytes contain, in addition, phycobiliproteins in phycobilisomes that are attachedto the stromal surface of TM, and transfer excitation energy to the reaction centers via the Chl a molecules in the innerantenna of PSI and PSII. The color and the intensity of the light to which these photosynthetic organisms are exposedin their environment have a great influence on the composition and the structure of the light-harvesting complexes(the antenna) as well as the rest of the photosynthetic apparatus, thus affecting the photosynthetic process and even theentire organism. We present here a perspective on ‘Light Quality and Oxygenic Photosynthesis’, in memory of GeorgeChristos Papageorgiou (9 May 1933–21 November 2020; see notes a and b). Our review includes (1) the influence ofthe solar spectrum on the antenna composition, and the special significance of Chl a; (2) the effects of light quality onphotosynthesis, measured using Chl a fluorescence; and (3) the importance of light quality, intensity, and its durationfor the optimal growth of photosynthetic organisms.
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| 13. |
- Öhlén, Joakim, 1958, et al.
(författare)
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Students’ learning as the focus for shared involvement between universities and clinical practice : a didactic model for postgraduate degree projects
- 2012
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Ingår i: Advances in Health Sciences Education. - Dordrecht : Springer Netherlands. - 1382-4996 .- 1573-1677. ; 17:4, s. 471-487
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Tidskriftsartikel (refereegranskat)abstract
- In an academic programme, completion of a postgraduate degree project could be a significant means of promoting student learning in evidence- and experience-based practice. In specialist nursing education, which through the European Bologna process would be raised to the master’s level, there is no tradition of including a postgraduate degree project. The aim was to develop a didactic model for specialist nursing students’ postgraduate degree projects within the second cycle of higher education (master’s level) and with a specific focus on nurturing shared involvement between universities and healthcare settings. This study embodies a participatory action research and theory-generating design founded on empirically practical try-outs. The 3-year project included five Swedish universities and related healthcare settings. A series of activities was performed and a number of data sources secured. Constant comparative analysis was applied. A didactic model is proposed for postgraduate degree projects in specialist nursing education aimed at nurturing shared involvement between universities and healthcare settings. The focus of the model is student learning in order to prepare the students for participation as specialist nurses in clinical knowledge development. The model is developed for the specialist nursing education, but it is general and could be applicable to various education programmes. © 2011 Springer Science+Business Media B.V.
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| 14. |
- Pettersson, Helen, et al.
(författare)
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Arsenic trioxide and neuroblastoma cytotoxicity.
- 2007
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Ingår i: Journal of Bioenergetics and Biomembranes. - : Springer Science and Business Media LLC. - 1573-6881 .- 0145-479X. ; 39:1, s. 35-41
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Forskningsöversikt (refereegranskat)abstract
- The majority of aggressive forms of the childhood tumor neuroblastoma can with current treatment protocols not be cured and possess a major challenge in pediatric oncology. After initial rounds of chemotherapy, surgery and irradiation, which in most cases result in tumor regression, these aggressive neuroblastomas relapse and frequently develop drug resistance. As approximately 50% of the children with neuroblastoma have an aggressive form, there is a compelling demand for new treatment strategies. Arsenic trioxide has the capacity to kill multidrug-resistant neuro-blastoma cells in vitro and in vivo and the drug is currently being evaluated in clinical trials. In this report we discuss the background to the use of arsenic trioxide in cancer therapy and the currently known mechanisms by which arsenic trioxide kills human neuroblastoma cells.
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| 15. |
- Angere, Staffan
(författare)
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The defeasible nature of coherentist justification
- 2007
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Ingår i: Synthese. - : Springer Science and Business Media LLC. - 0039-7857 .- 1573-0964. ; 157:3, s. 321-335
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Tidskriftsartikel (refereegranskat)abstract
- The impossibility results of Bovens and Hartmann (2003, Bayesian epistemology. Oxford: Clarendon Press) and Olsson (2005, Against coherence: Truth, probability and justification. Oxford: Oxford University Press.) show that the link between coherence and probability is not as strong as some have supposed. This paper is an attempt to bring out a way in which coherence reasoning nevertheless can be justified, based on the idea that, even if it does not provide an infallible guide to probability, it can give us an indication thereof. It is further shown that this actually is the case, for several of the coherence measures discussed in the literature so far. We also discuss how this affects the possibility to use coherence as a means of epistemic justification.
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| 16. |
- Dachs, B., et al.
(författare)
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The Innovative Performance of Foreign-owned Enterprises in Small Open Economies
- 2008
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Ingår i: Journal of Technology Transfer. - : Springer Science and Business Media LLC. - 0892-9912 .- 1573-7047. ; 33:4, s. 393-406
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Tidskriftsartikel (refereegranskat)abstract
- This paper compares the innovative performance of foreign-owned and domestically owned enterprises in five European countries. We look at innovation inputs, outputs, and examine how strong foreign-owned enterprises are embedded in the innovations systems of their host countries. We find that foreign ownership is associated with similar levels of innovation input, but higher levels of innovation output and higher labour productivity compared to domestic ownership. In four of the five countries, affiliates of foreign multinationals show a similar or even a higher propensity to co-operate with domestic partners than domestically owned enterprises.
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| 17. |
- Weise, Cornelia, et al.
(författare)
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Stability of physiological variables in chronic tinnitus sufferers
- 2008
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Ingår i: Applied Psychophysiology and Biofeedback. - : Springer. - 1090-0586 .- 1573-3270. ; 33:3, s. 149-159
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Tidskriftsartikel (refereegranskat)abstract
- The etiological tinnitus models propose that suffering can be caused and aggravated by heightened physiological arousal. Therefore psychophysiological treatments are applied. Stability of the measured parameters is essential for the use of biofeedback as well as to permit the attribution of changes to the administered treatment. The aim of our study was to investigate the 3-month reproducibility of psychophysiological parameters in 60 tinnitus patients. Using a repeated-measures design, the activity of these parameters was assessed twice during various stress and relaxation trials. The results showed that the measurements of frontalis, masseter and trapezius muscles were stable, while for the sternocleidomastoid, the skin conductance level (SCL) and the skin temperature retest-stability could not be evidenced. For all parameters, test-retest stability was weak for the relative scores. In conclusion, our study has important implications for applied psychophysiology research: (1) the measurement of EMG assessed in a clinical sample is stable over a 3-month interval; (2) in contrast, the measurements of SCL and skin temperature as well as all relative scores are less stable; and (3) the stability of EMG-parameters in our sample gives first hints that physiological changes can be attributed to an administered biofeedback treatment but further research is required. © 2008 Springer Science+Business Media, LLC.
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