1,025 research outputs found
Sanni Lindroos
No full texthttps://publications.lakeforest.edu/writing_contest_gallery/1012/thumbnail.jp
Rotation periods of Post-T Tauri stars in Lindroos systems
No full textWe present a rotational study of Post-T Tauri stars (PTTSs)
in Lindroos systems, defined as binaries with early type primaries on
the main-sequence (MS) and late-type secondaries on the
pre-main-sequence (PMS) phase. The importance of this study in
comparison with previous ones is that the Lindroos sample is not X-ray
selected so we avoid a possible bias towards fast rotators. In
this preliminary study we have monitored eleven stars in the UBVRI bands during two campaigns of ten consecutive nights each.
Eight of the observed PTTSs show periodic modulations in their
lightcurves and the derived periods range from 1.9 d to 8.0 d. The
comparison of these results with theoretical rotational tracks based
on disk-star locking theory shows that star-disk decoupling times of
1-20 Myr could reproduce the rotational properties of the targets,
assuming an initial rotation period of ~8 d and a mass of
1 . We have studied the rotation-activity relations of
Lindroos PTTSs and compared them with those found in other groups of
PMS and zero-age main-sequence (ZAMS) ~1 stars. The
Lindroos sample displays activity-rotation relations very similar to
those found in TTSs. It contains a mixture of very active stars, with
ratios close to the saturation level of –3,
and less active (unsaturated) stars. This could be the result of
different star-disk decoupling times. Future monitoring of a larger
and unbiased sample of PTTS will be important to confirm the
significance of these results
The role of dopaminergic and cholinergic modulation on the striatal network : a computational investigation
No full textThe famous words from the French philosopher René Descartes (1596-1650), “I think therefore I am”, proclaims that since we are thinking we must also exist. At the time when this was stated, very little was known about the main organ involved in thinking, the nervous system. Today we know that the nervous system consists of interconnected cells, so called neurons that communicate with each other through electro-chemical signals. This has been known for little over a century and during this time we have gathered an impressive amount of detailed data on neurons and the circuits they make up. Despite this, we still don’t have a detailed description of the overall computing mechanism of the central nervous system, the brain, or even single nuclei within the brain. One reason for this is the transient nature of the brain, continuously going in and out of operational modes, or so called brain states. The state of the brain is heavily influenced by neuromodulators – molecules changing the properties of neurons and the connections between them. One area strongly affected by neuromodulators is the striatum, the main input structure of the basal ganglia.The basal ganglia are an evolutionary conserved set of interconnected nuclei tightly connected to the cerebral cortex and thalamus, with which they form a loop. From pathological states like Parkinson’s disease we know that the basal ganglia are involved in motor control. More specifically they have been proposed to drive formation and control of automatic motor response sequences (including habits), but like in the rest of the brain, the modus operandi of the basal ganglia is not known. To bridge the gap between data and function we therefore need models and testable theories.In this thesis I have studied the role of neuromodulation in the striatal microcircuit, with the aim of understanding how subcellular changes affect cellular behavior. The technique used is biophysically detailed computational modelling. The essence of these models tries to mimic the electro-chemical signals within and between neurons using as detailed a description of individual neurons as possible. From this standpoint a good model minimizes the number of assumptions used in construction, by restricting the model to experimentally measured entities. Simulations of the striatal projection neurons in such models show that complex spikes – a particular type of neuronal signal associated with learning in other brain regions – may be triggered following manipulation of certain conductances in the cell membrane. In our simulations, the complex spikes were associated with large calcium signals in the dendrites, indicating a more robust form of crosstalk in the soma-to-dendrites direction than following regular action potentials. Together these simulations extend the theory of striatal function and learning.List of scientific papersI. Du, K., Wu, Y., Lindroos, R., et al. (2017). Cell-type–specific inhibition of the dendritic plateau potential in striatal spiny projection neurons. Proc Natl Acad Sci U S A. 114, E7612–E7621. https://doi.org/10.1073/pnas.1704893114 II. R. Lindroos, Dorst, M., Du, K., Filipovic, M., Keller, D., Ketzef, M., Kozlov, A., Kumar, A., Lindahl, M., Nair, A., Perez-Fernandez, J., Grillner, S., Silberberg, G., and Hellgren Kotaleski, J. (2018). Basal ganglia neuromodulation over multiple temporal and structural scales—simulations of direct pathway MSNs investigate the fast onset of dopaminergic effects and predict the role of Kv4.2. Frontiers in Neural Circuits. 12, 3. https://doi.org/10.3389/fncir.2018.00003 III. J. Hjorth, A. Kozlov, I. Carannante, J. Frost Nylén, R. Lindroos, et al. (2020). The microcircuits of striatum in silico. Proc Natl Acad Sci U S A. [Accepted] https://doi.org/10.1038/srep02285 IV. R. Lindroos and J. Hellgren Kotaleski. Predicting complex spikes in striatal projection neurons following neuromodulation by acetylcholine and dopamine. [Manuscript]</p
Conceptual Design Report for a Beta-Beam Facility
No full textLindroos, M. Magistris, A. Mueller, J. Payet, P. Puppel, P. Spiller, A. Tkatchenko, S. Trovati, V. Vlachoudi
Structural maintenance of chromsomes : a complex tale of genomic integrity
No full textGenomic integrity is an absolute requirement for cell survival. Programmed events such as genome rearrangements and DNA replication can cause lesions in the DNA, as can exogenous agents such as radiation and chemicals. One of the most austere types of lesion is DNA double strand breaks (DBSs). In Saccharomyces cerevisiae, budding yeast, they are preferentially repaired by the homologous recombination (HR) pathway using a homologous DNA sequence as template.The Structural maintenance of chromosomes (SMC) family proteins are essential for cell viability and have functions in chromosome condensation, segregation and in DNA repair by HR. The cohesin complex is important for cohesion and correct segregation of sister chromatids. The Smc5/6 complex functions late in the HR process and it has another function, not yet entirely elucidated, that makes the complex essential.We have investigated the chromosomal localization of the Smc5/6 complex and found that the complex associates with specific sites along the chromosome arms in a chromosome length-dependent manner. This association is dependent on the cohesin loading protein Scc2. The complex also localizes to chromosomal regions surrounding a DNA DSB in the G2/M phase. Localization to DSBs is dependent on the damage-sensing HR protein Mre11, but not on Scc2. Smc6 mutants exhibit a delay in chromosome segregation and a closer investigation suggests that this delay is caused by persisting replication forks.The length-dependent distribution of the Smc5/6 complex on chromosomes was found to reflect a function of the complex that is independent of its function in HR. A possible explanation for this length-dependency is the accumulation of replication-induced topological structures on longer chromosomes due to their inability to swivel off the torsional stress. A circular short chromosome is therefore expected to generate more unresolved topological structures than a linear version of the same chromosome. Smc5/6 complex components showed an increase in binding regions on a circular chromosome compared to the linear version. Deletion of Top1, a protein required for release of replication-induced torsional tension in DNA, also shows a similar chromosome length-specific phenotype as the Smc5/6 complex components, indicating that topology is the inherent cause of the Smc5/6 complex association with chromosomes.The main function of the cohesin complex is linking the sister chromatids from S phase until the metaphase-to-anaphase transition. To investigate a role for cohesin in DSB repair, we examined its localization in response to a site-specific DSB. Cohesin is normally loaded onto DNA in late G1/early S phase, but when a DNA break has been induced in G2/M, cohesin localizes to the break area in a Scc2-dependent manner. In addition, we have demonstrated that cohesin recruited in response to DSBs in G2/M phase can mediate cohesion, supporting the idea that cohesin and sister chromatid cohesion have a role in DNA repair.The damage-induced cohesion can be distinguished from cohesion formed during replication and the regulation and function of this damage-induced cohesion was found to be dependent on Mre11 and the Tel1 and Mec1 kinases. The HR protein Rad52 protein was not required, showing that contrary to S phase-established cohesion, formation of damage-induced cohesion in G2/M phase is independent of DNA synthesis.A single DNA DSB is enough to generate cohesion throughout the entire genome. Mec1, Scc2, Smc6 and the establishment of cohesion protein Eco1 are also required for genome-wide cohesion after DSB induction, and the damage-induced cohesion is required for DNA repair.List of scientific papersI. Lindroos HB, Ström L, Itoh T, Katou Y, Shirahige K, Sjögren C (2006). "Chromosomal association of the Smc5/6 complex reveals that it functions in differently regulated pathways." Mol Cell 22(6): 755-67 https://pubmed.ncbi.nlm.nih.gov/16793545II. Lindroos HB, Kegel A, Zhao X, Shirahige K, Sjögren C (2009). "The Smc5/6 complex acts together with topoisomerase I in the resolution of chromosome length-dependent stress." (Manuscript)III. Ström L, Lindroos HB, Shirahige K, Sjögren C (2004). "Postreplicative recruitment of cohesin to double-strand breaks is required for DNA repair." Mol Cell 16(6): 1003-15 https://pubmed.ncbi.nlm.nih.gov/15610742IV. Ström L, Karlsson C, Lindroos HB, Wedahl S, Katou Y, Shirahige K, Sjögren C (2007). "Postreplicative formation of cohesion is required for repair and induced by a single DNA break." Science 317(5835): 242-5 https://pubmed.ncbi.nlm.nih.gov/17626884</p
Kopparrelaterad fotodegradering i kristallint kisel
No full textUnintentional copper and nickel impurities are common in silicon-based devices due to the abundance of contamination sources in industrial silicon crystallization and wafer processing lines. High solubility and diffusivity result readily in significant impurity concentrations, which cause charge-carrier recombination and reduce the device response. This work confirms that nickel diffuses as fast as copper in silicon, emphasizing the importance of contamination control in silicon-based devices. Copper contamination is known to form recombination-active defects in silicon during illumination, which is observed as copper-related light-induced degradation (Cu-LID). In order to identify the extent of degradation in silicon-based devices, this work focuses on determining the properties of Cu-LID in gallium-doped Czochralski (Cz) silicon, boron-doped Cz-Si, and boron-doped multicrystalline silicon. Cu-LID is determined to be predominantly a bulk recombination effect, and the formed defects are found to be stable at 200°C. Slower Cu-LID is observed in Ga-Si compared to B-Si, suggesting that Cu-LID formation is limited by the effective copper diffusivity. Cu-LID is shown to completely disappear after negative sample surface charging and illumination. The negative surface charge is achieved by corona charging or aluminum oxide deposition. Cu-LID removal is observed to have no impact on classical boron-oxygen-related light-induced degradation (BO-LID), which has previously been shown to recover at 200°C. Unlike BO-LID, the activation energy of Cu-LID is found to depend on the silicon doping concentration. Hence, Cu-LID and BO-LID are concluded to be two different degradation effects, which can occur simultaneously in silicon-based devices.Kiselbaserade elektroniska komponenter är ofta oavsiktligt förorenade av koppar och nickel från otaliga kontaminationskällor i industriella komponentframställningsprocesser. Metallernas höga diffusivitet samt löslighet leder fort till markanta orenhetskoncentrationer, vilka förorsakar rekombination av laddningsbärare och nedsatt komponentrespons. Denna avhandling bekräftar att nickel diffuserar lika fort som koppar i kristallint kisel, vilket betonar vikten av metallorenhetskontroll i kiselbaserade komponenter. Kopparorenheter förorsakar fotodegradadering (Cu-LID) i kisel via formationen av rekombinationsaktiva koppardefekter under illuminering. För att fastställa omfattningen av fotodegradadering i kiselbaserade komponenter, fokuserar denna avhandling på att identifiera egenskaper för Cu-LID i gallium-dopat Czochralski (Cz) kisel, boron-dopat Cz-Si och boron-dopat mångkristallint kisel. Cu-LID finnes orsaka främst bulkrekombination och de formade koppardefekterna är stabila i 200°C. Cu-LID sker långsammare i Ga-Si jämfört med B-Si, vilket antyder att fotodegraderingsprocessen begränsas av den effektiva koppardiffusiviteten. I avhandlingen förhindras kopparrelaterad fotodegradadering fullständigt genom att kombinera negativ kiselytladdning med illuminering. Den negativa ytladdningen skapas via deposition av koronaladdning eller aluminiumoxidtunnfilm. Avlägsning av Cu-LID inverkar inte på klassisk bor-syre-relaterad fotodegraderingen (BO-LID), som förekommer i kisel utan kopparföroreningar och försvinner i 200°C. I motsats till BO-LID beror aktiveringsenergin för Cu-LID på dopingkoncentrationen i kiselmaterialet. Följaktligen fastställs Cu-LID och BO-LID vara två skilda former av fotodegradering, vilka kan förkomma samtidigt i kiselbaserade elektroniska komponenter
Uppslaget med notiser, bokanmälningar, kalender m m
No full textNotiser: Satsning på kulturarvet / Lars Amréus Tredje spåret / Lena Simonsson Svenska hus / Elina Antell Byggnadsvårdsläger Tio vinnare Bokanmälningar: Gunnarsson, AnnMarie, 1943-. - Hus av slagg : byggnadskonst i Bergslagen / Ann Marie Gunnarsson ; [teckningar: Sven Olsson].. - 1994 Lindroos, Bengt, 1918-2010. - Ur den svenska byggnadskonstens magasin / Bengt Lindroos ; [teckningar och foton: författaren ; översättning till engelska: Roger Tanner].. - 1989. - ISBN: 9186050184 Pettersson Jensen, Ing-Marie, 1960-. - Norbergs bergslag : en sammanställning över de bergshistoriska lämningarna i Karbennings, Norbergs, Västerfärnebo och Västervåla socknar samt Fagersta stad / Ing-Marie Pettersson.. - 1994 Darphin, Jean-Paul, 1948-. - Sockrets katedraler : en studie av sockerindustrins historia och arkitektur / Jean-Paul Darphin.. - 1994 - 1. [uppl.]. - ISBN: 9171928944 Svanberg, Jan, 1935-. - Medeltida byggmästare / Jan Svanberg.. - 1994 - [Ny utg.]. - ISBN: 9155040381 Kommentarer: Perspektiv och värderingar / Olof Genbo Kommentar till kommentaren / Bo & Elsbeth Rosé
Sharing Rules and Stability in Coalition Games with Externalities
No full textThis paper examines cooperative sharing rules in fisheries coalition games and develops a new sharing rule that takes into account the stability of cooperation when externalities are present. We contribute to existing knowledge by introducing a connection between cooperative games (sharing rules) and non-cooperative games (stability). As an illustrative example, we describe a discrete-time, deterministic, coalition game model of the major agents who exploit the cod stock in the Baltic Sea.Baltic Sea cod, characteristic function, coalition game, cooperation, fisheries, nucleolus, Shapley value, sharing rules, stability of cooperation, Environmental Economics and Policy, C62, C70, Q22, Q28,
Uppslaget med notiser, bokanmälningar, kalender m m
No full textNotiser: Satsning på kulturarvet / Lars Amréus Tredje spåret / Lena Simonsson Svenska hus / Elina Antell Byggnadsvårdsläger Tio vinnare Bokanmälningar: Gunnarsson, AnnMarie, 1943-. - Hus av slagg : byggnadskonst i Bergslagen / Ann Marie Gunnarsson ; [teckningar: Sven Olsson].. - 1994 Lindroos, Bengt, 1918-2010. - Ur den svenska byggnadskonstens magasin / Bengt Lindroos ; [teckningar och foton: författaren ; översättning till engelska: Roger Tanner].. - 1989. - ISBN: 9186050184 Pettersson Jensen, Ing-Marie, 1960-. - Norbergs bergslag : en sammanställning över de bergshistoriska lämningarna i Karbennings, Norbergs, Västerfärnebo och Västervåla socknar samt Fagersta stad / Ing-Marie Pettersson.. - 1994 Darphin, Jean-Paul, 1948-. - Sockrets katedraler : en studie av sockerindustrins historia och arkitektur / Jean-Paul Darphin.. - 1994 - 1. [uppl.]. - ISBN: 9171928944 Svanberg, Jan, 1935-. - Medeltida byggmästare / Jan Svanberg.. - 1994 - [Ny utg.]. - ISBN: 9155040381 Kommentarer: Perspektiv och värderingar / Olof Genbo Kommentar till kommentaren / Bo & Elsbeth Rosé
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