| 1. |
- Delley, Diane, et al.
(författare)
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ASTER: Developing a Platform to Achieve Microgravity for Low-Cost Experiments
- 2021
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Ingår i: IAC 2021 Congress Proceedings, 72nd International Astronautical Congress (IAC), Dubai, United Arab Emirates. - : International Astronautical Federation, IAF.
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Konferensbidrag (refereegranskat)abstract
- Microgravity is an important field of research, which is vital for the efficient future utilisation of space. It is possible to undertake microgravity experiments on-orbit, however, this is often well outside the available funding range of low-cost experiments. Microgravity experiments undertaken on sounding rockets are more accessible to low-budget institutions and students, and provide longer periods of sustained microgravity than drop towers and parabolic flights. However, unless stabilised, such experiments cannot achieve true microgravity conditions due to residual external forces, such as the centrifugal force of the rocket’s spin, acting on the experiment. Thus, projects that want to carry out experiments in microgravity conditions would first need to design the platform required to achieve true microgravity, making these projects more complex and time intensive.Project ASTER (Attitude STabilised free falling ExpeRiment) is designing and testing such a platform for microgravity research. ASTER is taking advantage of the extended microgravity period of a sounding rocket flight to test a high performance, low-cost Attitude Control System (ACS) solution capable of providing microgravity conditions for experiments. This would greatly benefit both future satellite projects and sounding rocket experiments which require highly accurate stabilisation and pointing capabilities. The design utilises three reaction wheels controlled by a closed loop system to stabilise a Free Falling Unit - ejected from a sounding rocket - within seconds. The platform will be able to perform slewing manoeuvres and accommodate future experiments on easily adaptable mounting points which allow for on-board sensors and cameras. ASTER will be launched on-board REXUS 30 in March 2022, after which it will be recovered and the obtained results will be published on an open source basis to ensure its future availability to student and other low budget research projects, thereby allowing further improvement, optimisation, and customisation. ASTER is aiming to establish a platform which simplifies the development of microgravity experiments, especially for student projects which often face tight schedules and limited resources. ASTER is being developed as part of the 13th Cycle of the German-Swedish student programme REXUS/BEXUS by students of Luleå University of Technology (LTU) at the Kiruna Space Campus.
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| 2. |
- Dierks, Philipp, et al.
(författare)
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Ground- And Excited-State Properties of Iron(II) Complexes Linked to Organic Chromophores
- 2020
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 59:20, s. 14746-14761
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Tidskriftsartikel (refereegranskat)abstract
- Two new bichromophoric complexes, [Fe(bim-ant)2]2+ and [Fe(bim-pyr)2]2+ ([H2-bim]2+ = 1,1′-(pyridine-2,6-diyl)bis(3-methyl-1H-imidazol-3-ium); ant = 9-anthracenyl; pyr = 1-pyrenyl), are investigated to explore the possibility of tuning the excited-state behavior in photoactive iron(II) complexes to design substitutes for noble-metal compounds. The ground-state properties of both complexes are characterized thoroughly by electrochemical methods and optical absorption spectroscopy, complemented by time-dependent density functional theory calculations. The excited states are investigated by static and time-resolved luminescence and femtosecond transient absorption spectroscopy. Both complexes exhibit room temperature luminescence, which originates from singlet states dominated by the chromophore (1Chrom). In the cationic pro-ligands and in the iron(II) complexes, the emission is shifted to red by up to 110 nm (5780 cm-1). This offers the possibility of tuning the organic chromophore emission by metal-ion coordination. The fluorescence lifetimes of the complexes are in the nanosecond range, while triplet metal-to-ligand charge-transfer (3MLCT) lifetimes are around 14 ps. An antenna effect as in ruthenium(II) polypyridine complexes connected to an organic chromophore is found in the form of an internal conversion within 3.4 ns from the 1Chrom to the 1MLCT states. Because no singlet oxygen forms from triplet oxygen in the presence of the iron(II) complexes and light, efficient intersystem crossing to the triplet state of the organic chromophore (3Chrom) is not promoted in the iron(II) complexes.
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| 3. |
- Howner, Katarina, et al.
(författare)
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Brain processing of fearful facial expression in mentally disordered offenders
- 2011
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Ingår i: Journal of Behavioral and Brain Science. - Irvine, CA : Scientific Research Publishing. - 2160-5866 .- 2160-5874. ; 1:3, s. 115-123
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Tidskriftsartikel (refereegranskat)abstract
- Emotional facial expressions are important cues for interaction between people. The aim of the present study was to investigate brain function when processing fearful facial expressions in offenders with two psychiatric disorders which include impaired emotional facial perception; autism spectrum disorder (ASD) and psychopathy (PSY). Fourteen offenders undergoing forensic psychiatric assessment (7 with ASD, and 7 psychopathic offenders) and 12 healthy controls (HC) viewed fearful and neutral faces while undergoing functional magnetic resonance imaging (fMRI). Brain activity (fearful versus neutral faces) was compared both between HC and offenders and between the two offender groups (PSY and ASD). Functional co-activation was also investigated. The offenders had increased activity bilaterally in amygdala and medial cingulate cortex as well as the left hippocampus during processing fearful facial expressions compared to HC. The two subgroups of offenders differed in five regions compared with each other. Results from functional co-activation analysis suggested a strong correlation between the amygdala and anterior cingulate cortex (ACC) in the left hemisphere only in the PSY group. These findings suggest enhanced neural processing of fearful faces in the amygdala as well as in other facial processing brain areas in offenders compared to HC. Moreover, the co-activation between amygdala and ACC in the PSY but not the ASD group suggested qualitative differences in amygdala activity in the two groups. Since the sample size is small the study should be regarded as a pilot study.
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| 4. |
- Howner, Katarina, et al.
(författare)
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Thinner cortex in the frontal lobes in mentally disordered offenders
- 2012
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Ingår i: Psychiatry Research. - : Elsevier BV. - 0165-1781 .- 1872-7123 .- 0925-4927. ; 203:2-3, s. 126-131
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Tidskriftsartikel (refereegranskat)abstract
- Antisocial and violent behaviour have been associated with both structural and functional brain abnormalities in the frontal and the temporal lobes. The aim of the present study was to assess cortical thickness in offenders undergoing forensic psychiatric assessments, one group with psychopathy (PSY, n = 7) and one group with autism spectrum disorder (ASD, n = 7) compared to each other as well as to a reference group consisting of healthy non-criminal subjects (RG, n = 12). A second aim was to assess correlation between scores on a psychopathy checklist (PCL-SV) and cortical thickness. Magnetic resonance imaging (MRI) and surface-based cortical segmentation were used to calculate cortical thickness. Analyses used both regions of interest and statistical maps. When the two groups of offenders were compared, there were no differences in cortical thickness, but the PSY group had thinner cortex in the temporal lobes and in the whole right hemisphere compared to RG. There were no differences in cortical thickness between the ASD group and RG. Across subjects there was a negative correlation between PCL-SV scores and cortical thickness in the temporal lobes and the whole right hemisphere. The findings indicate that thinner cortex in the temporal lobes is present in psychopathic offenders and that these regions are important for the expression of psychopathy. However, whether thinner temporal cortex is a cause or a consequence of the antisocial behaviour is still unknown.
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| 5. |
- Lange, Jonathan, et al.
(författare)
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ASTER: Developing a High Performance Attitude Controlled Platform for Low-Cost Experiments
- 2021
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Ingår i: GLEX 2021 Conference Proceedings, IAF Global Space Exploration Conference 2021, St. Petersburg, Russian Federation. - : International Astronautical Federation, IAF.
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Konferensbidrag (refereegranskat)abstract
- An important aspect of the low-cost development of spacecraft components is its verification of the functionality under microgravity conditions. Microgravity is an important field of research, providing a suitable testbed for new technologies, in order to mimic the conditions of such projects. Microgravity experiments undertaken on sounding rockets however, cannot achieve true microgravity conditions unless stabilised due to residual external forces acting on the experiment, such as the rocket’s spin.Project ASTER (Attitude STabilised free falling ExpeRiment) is taking advantage of the extended microgravity period of a sounding rocket flight to test a high performing, low-cost Attitude Control System (ACS) solution. This would greatly benefit both future exploration missions and sounding rocket experiments which require highly accurate stabilisation and pointing capabilities. The proposed design utilises three reaction wheels to stabilise a Free Falling Unit ejected from a sounding rocket within seconds. The platform will be able to perform slewing manoeuvres and accommodate future experiments on easily adaptable mounting points. ASTER will be launched on-board REXUS 30 in March 2022, after which the obtained results will be published on an open source basis to ensure its future availability to student and low budget research projects, thereby allowing further improvement, optimisation, and customisation. ASTER is being developed as part of the 13th Cycle of the German-Swedish student programme REXUS/BEXUS.
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| 6. |
- Lehmann, Christoph, et al.
(författare)
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Increased sensitivity and specificity in mapping task demand in visuo-spatial processing using reaction-time convolved hemodynamic response predictors in rapid event-related fMRI.
- 2006
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Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119. ; 31:2, s. 505-512
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Tidskriftsartikel (refereegranskat)abstract
- Searching for the neural correlates of visuospatial processing using functional magnetic resonance imaging (fMRI) is usually done in an event-related framework of cognitive subtraction, applying a paradigm comprising visuospatial cognitive components and a corresponding control task. Besides methodological caveats of the cognitive subtraction approach, the standard general linear model with fixed hemodynamic response predictors bears the risk of being underspecified. It does not take into account the variability of the blood oxygen level-dependent signal response due to variable task demand and performance on the level of each single trial. This underspecification may result in reduced sensitivity regarding the identification of task-related brain regions. In a rapid event-related fMRI study, we used an extended general linear model including single-trial reaction-time-dependent hemodynamic response predictors for the analysis of an angle discrimination task. In addition to the already known regions in superior and inferior parietal lobule, mapping the reaction-time-dependent hemodynamic response predictor revealed a more specific network including task demand-dependent regions not being detectable using the cognitive subtraction method, such as bilateral caudate nucleus and insula, right inferior frontal gyrus and left precentral gyrus.
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| 7. |
- Vannini, Patrizia, et al.
(författare)
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Failure to modulate neural response to increased task demand in mild Alzheimer's disease : fMRI study of visuospatial processing
- 2008
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Ingår i: Neurobiology of Disease. - : Elsevier BV. - 0969-9961 .- 1095-953X. ; 31:3, s. 287-297
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease (AD) is characterized by disturbances of visuospatial cognition. Given that these impairments are closely related to metabolic and neuropathological changes, our study aimed to investigate the functional competency of brain regions in the visuospatial networks responsible for early clinical symptoms in AD using event-related functional magnetic resonance imaging (fMRI). Participants (13AD patients with mild symptoms and 13 age- and education-matched controls) performed an angle discrimination task with varying task demand. Using a novel approach that modeled the dependency of the blood oxygenation level-dependent (BOLD) signal on the subject's reaction time allowed us to investigate task demand-dependent signal changes between the groups. Both groups demonstrated overlapping neural networks engaged in angle discrimination, including the parieto-occipital and frontal regions. In several network regions, AD patients showed a significantly weaker and sometimes no BOLD signal due to increased task demand compared with controls, demonstrating failure to modulate the neural response to increased task demand. A general task demand-independent increase of activation in AD patients compared with controls was found in right middle temporal gyrus. This latter finding may indicate an attempt to compensate for dysfunctional areas in the dorsal visual pathway. These results confirm deficits in visuospatial abilities, which occur early in AD, and offer new insights into the neural mechanisms underlying this impairment.
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| 8. |
- Vannini, Patrizia, et al.
(författare)
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Reduced neuronal efficacy in progressive mild cognitive impairment : A prospective fMRI study on visuospatial processing
- 2007
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Ingår i: Psychiatry Research. - : Elsevier BV. - 0925-4927 .- 1872-7506 .- 0165-1781. ; 156:1, s. 43-57
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Tidskriftsartikel (refereegranskat)abstract
- Mild cognitive impairment (MCI) often refers to the preclinical stage of dementia, where the majority develop Alzheimer's disease (AD). Given that neurodegenerative burden and compensatory mechanisms might exist before accepted clinical symptoms of AD are noticeable, the current prospective study aimed to investigate the functioning of brain regions in the visuospatial networks responsible for preclinical symptoms in AD using event-related functional magnetic resonance imaging (fMRI). Eighteen MCI patients were evaluated and clinically followed for approximately 3 years. Five progressed to AD (PMCI) and eight remained stable (SMCI). Thirteen age-, gender- and education-matched controls also participated. An angle discrimination task with varying task demands was used. Brain activation patterns as well as task demand-dependent and -independent signal changes between the groups were investigated by using an extended general linear model including individual performance (reaction time [RT]) of each single trial. Similar behavioral (RT and accuracy) responses were observed between MCI patients and controls. A network of bilateral activations, e.g. dorsal pathway, which increased linearly with increasing task demand, was engaged in all subjects. Compared with SMCI patients and controls, PMCI patients showed a stronger relation between task demand and brain activity in left superior parietal lobules (SPL) as well as a general task demand-independent increased activation in left precuneus. Altered brain function can be detected at a group level in individuals that progress to AD before changes occur at the behavioral level. Increased parictal activation in PMCI could reflect a reduced neuronal efficacy due to accumulating AD pathology and might predict future clinical decline in patients with MCI.
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