100 results on '"Sikk P"'
Search Results
2. Action Research to Study Problem Solving Skills of Primary School Physics Students
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Sikk, Jörgen Ivar and Tammets, Kairit
- Abstract
PISA studies have concluded that while the level of knowledge, amongst students in Estonia, is good the level of higher order thinking skills is lower, especially in natural sciences, which is accompanied by lower study motivation. In order to study the level of higher order thinking skills and what influences those skills, an action research was conducted. The research was done in Tallinn 21. school with 90 students from 8th grade. The students studied, using ICT enhanced study material specifically made to increase their higher order thinking skills. In order to study the effects of the study material, student's problem solving skills were measured before and after using the new study material. Also, the students had to answer a questionnaire, which was measuring their study motivation and self-confidence. The research concluded that the study material has an effect on the level of higher order thinking skills, but the statistical evidence was lacking to clearly understand the role of the new study material. [For the full proceedings, see ED621108.]
- Published
- 2021
3. Toponymic surnames and the spatiality of heresy prosecutions: Peter Seila’s register of sentences from the Quercy region (Languedoc), 1241–1242
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Robert L. J. Shaw, Kaarel Sikk, and David Zbíral
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History of scholarship and learning. The humanities ,AZ20-999 ,Social Sciences - Abstract
Abstract Our knowledge of the geography of medieval religious dissent and its repression in the Latin West is limited by a lack of systematic study of locational information in inquisition trial records. Spatial analysis of these rich details has the potential to help build a bottom-up picture of interaction between dissidents and inquisitors that moves beyond institutional perspectives. This task is rendered challenging due to the inconsistencies and uncertainties of what inquisitors and their notaries typically recorded about the spatial associations of suspects. Probably the most common indicator of such associations found in inquisition records are toponymic surnames. They present challenges of coverage (not everybody had a toponymic surname) and interpretation (multiple possible meanings). This study attempts to tackle the challenge of interpreting such surnames within the context of the nine sentencing events held by the inquisitor Peter Seila in 1241 and 1242 in the Quercy region of Languedoc: covering 650 sentenced individuals, the register documenting these events is the earliest extant record of an inquisition of such scale. Rather than taking the interpretative challenges of toponymic surnames as reasons to limit ourselves to qualitative analysis, our approach shows the value of rendering and analysing them as structured data. Firstly, we quantify the context of toponymic surnames, placing them against the background of broader name construction practices and other social factors. Secondly, we plot and analyse the geocoded data derived from toponymic surnames with the benefit of this contextualisation, looking especially at the distance of toponyms from their associated sentencing centres, in order to derive narratives that best explain the generality of their meaning. The results allow us to appraise the actual spatial coverage of the nine sentencing events. The first two, centred on the important towns of Montauban and Moissac, seem most likely to have been primarily urban affairs, with little evidence of rural coverage. The remainder, which took place in castra (fortified villages), appear to have covered more of the surrounding countryside. These results geographically contextualise the reports of dissidence conveyed within Peter’s register, and suggest narratives for how Peter optimised his strategy for impact in the face of constraints.
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- 2024
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4. Psychostimulant-induced aberrant DNA methylation in an in vitro model of human peripheral blood mononuclear cells
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Anier, Kaili, Somelar, Kelli, Jaako, Külli, Alttoa, Margret, Sikk, Kerli, Kokassaar, Raul, Kisand, Kai, and Kalda, Anti
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- 2022
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5. Prevalence of dental fluorosis and dental caries in fluoride endemic areas of Rohtak district, Haryana
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Reena Rani, Ruchi Singhal, Parul Singhal, Ritu Namdev, Neha Sikk, Shruti Jha, and Nancy Goel
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dean's fluorosis index (modified criteria 1942) ,dental caries ,dental fluorosis ,dmft index ,groundwater fluoride concentration ,Dentistry ,RK1-715 - Abstract
Objectives: This study investigates the estimation of the fluoride concentration in drinking water in Rohtak district, Haryana, and quantifies its effect on the prevalence of dental fluorosis and dental caries. Materials and Methods: A cross-sectional survey was conducted among 1262 school children in endemic fluoride areas of Haryana. Using simple random sampling, thirty villages from five blocks of Rohtak districts were selected, and children 6–12 years of age were examined. A questionnaire survey form was filled out to record the demographic details of the samples. Dental caries was recorded according to DMFT (D = Decayed, M = Missing due to caries only, F = Filled, T = Teeth)/deft index (d = decayed, e = extracted due to caries, f = filled, t = teeth). Assessment of Dental Fluorosis was done according to Dean's Fluorosis index, modified in 1942. The data were analyzed using SPSS version 19, and nonparametric tests were used to assess the significance. Results: The study participants included 615 males and 647 females among which Mean DMFT in the area of study ranged from 0.32 to 1.90. Mean deft in the area of study ranged from 0.34 to 1.91. The fluoride concentrations in groundwater are in the range of 0.532–8.802. Out of 1262 children examined, 655 (51.90%) children were having dental fluorosis. 607 (48.10%) of the subjects were free from fluorosis. 16.09%, 13.39%, 9.11%, and 8.16% and 5.15% were having questionable, very mild, mild, moderate, and severe form of fluorosis, respectively. Conclusion: It can be concluded that in Rohtak district, the fluoride levels in drinking water and the prevalence of dental fluorosis are high, so requiring an urgent need to improve the quality of water and institute de-fluoridation of drinking water in affected areas to lower the burden of dental fluorosis in the community.
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- 2022
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6. Editorial: Party Entry and Exit in Times of Crisis
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Marc van de Wardt, Nicole Bolleyer, and Allan Sikk
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party entry ,party survival ,party system change ,crisis ,new parties ,Political science - Published
- 2022
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7. NanoSolveIT Project: Driving nanoinformatics research to develop innovative and integrated tools for in silico nanosafety assessment
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Antreas Afantitis, Georgia Melagraki, Panagiotis Isigonis, Andreas Tsoumanis, Dimitra Danai Varsou, Eugenia Valsami-Jones, Anastasios Papadiamantis, Laura-Jayne A. Ellis, Haralambos Sarimveis, Philip Doganis, Pantelis Karatzas, Periklis Tsiros, Irene Liampa, Vladimir Lobaskin, Dario Greco, Angela Serra, Pia Anneli Sofia Kinaret, Laura Aliisa Saarimäki, Roland Grafström, Pekka Kohonen, Penny Nymark, Egon Willighagen, Tomasz Puzyn, Anna Rybinska-Fryca, Alexander Lyubartsev, Keld Alstrup Jensen, Jan Gerit Brandenburg, Stephen Lofts, Claus Svendsen, Samuel Harrison, Dieter Maier, Kaido Tamm, Jaak Jänes, Lauri Sikk, Maria Dusinska, Eleonora Longhin, Elise Rundén-Pran, Espen Mariussen, Naouale El Yamani, Wolfgang Unger, Jörg Radnik, Alexander Tropsha, Yoram Cohen, Jerzy Leszczynski, Christine Ogilvie Hendren, Mark Wiesner, David Winkler, Noriyuki Suzuki, Tae Hyun Yoon, Jang-Sik Choi, Natasha Sanabria, Mary Gulumian, and Iseult Lynch
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Nanoinformatics ,Computational toxicology ,Hazard assessment ,Engineered nanomaterials ,(quantitative) Structure–activity relationships ,Integrated approach for testing and assessment ,Biotechnology ,TP248.13-248.65 - Abstract
Nanotechnology has enabled the discovery of a multitude of novel materials exhibiting unique physicochemical (PChem) properties compared to their bulk analogues. These properties have led to a rapidly increasing range of commercial applications; this, however, may come at a cost, if an association to long-term health and environmental risks is discovered or even just perceived. Many nanomaterials (NMs) have not yet had their potential adverse biological effects fully assessed, due to costs and time constraints associated with the experimental assessment, frequently involving animals. Here, the available NM libraries are analyzed for their suitability for integration with novel nanoinformatics approaches and for the development of NM specific Integrated Approaches to Testing and Assessment (IATA) for human and environmental risk assessment, all within the NanoSolveIT cloud-platform. These established and well-characterized NM libraries (e.g. NanoMILE, NanoSolutions, NANoREG, NanoFASE, caLIBRAte, NanoTEST and the Nanomaterial Registry (>2000 NMs)) contain physicochemical characterization data as well as data for several relevant biological endpoints, assessed in part using harmonized Organisation for Economic Co-operation and Development (OECD) methods and test guidelines. Integration of such extensive NM information sources with the latest nanoinformatics methods will allow NanoSolveIT to model the relationships between NM structure (morphology), properties and their adverse effects and to predict the effects of other NMs for which less data is available. The project specifically addresses the needs of regulatory agencies and industry to effectively and rapidly evaluate the exposure, NM hazard and risk from nanomaterials and nano-enabled products, enabling implementation of computational ‘safe-by-design’ approaches to facilitate NM commercialization.
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- 2020
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8. How population size affects party systems and cabinet duration
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Sikk, Allan and Taagepera, Rein
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country size ,electoral change ,electoral systems ,party systems ,predictive models ,Political Science ,Political Science & Public Administration - Abstract
This study develops and tests theoretical formulas for linking country size and party system characteristics. For countries using one-seat electoral districts or nationwide districts, the averages of the largest seat-share, effective number of assembly parties and mean duration of cabinets can be predicted based solely on population. For countries allocating seats by PR in multi-seat districts, the averages of these characteristics can be predicted based on population and district magnitude. We show that first-past-the-post countries of less than one million tend to have highly dominant largest parties and one-and-a-half party assemblies, rather than a balance of two parties. For larger countries, and PR countries of any size, population is not destiny, as far as party system is concerned. © The Author(s) 2012.
- Published
- 2014
9. Activist Localities in the Queer South
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Helis Sikk
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activism ,LGBTQ ,the South ,online communication ,Political science ,Social Sciences - Abstract
Cultural anthropologist Arjun Appadurai’s theories about place link together various surrounding contexts: technology, media, economics, and ideology. He sees locality as a “complex phenomenological quality” (1996, p. 178) that we should not look at as context, but instead focus on how contexts define the boundaries of localities. Appadurai’s theories help to link global and local by taking into account the various surrounding contexts: technology, media, economics, and ideology. This paper uses Appadurai’s theory as a basis to explore how localities emerge in grassroots queer activist practices that combine offline and online tactics in their organizing. I use participant observation, in-depth interviews, and content analysis to gain an understanding of the strengths and weaknesses of networked locality created by LGBTQ activists physically located in Southern United States.
- Published
- 2018
10. Parsimonious Model for Predicting Mean Cabinet Duration On the Basis of Electoral System
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Taagepera, Rein and Sikk, Allan
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causal model ,electoral systems ,party government ,party systems ,Political Science ,Political Science & Public Administration - Abstract
This study joins two existing logical models and tests the resulting predictions of mean cabinet duration (C). One of these models predicts C based on effective number of parties (N): C = k/N2, where k is found to be around 42 years. The other predicts N on the basis of number of seats in the assembly (S) and district magnitude (M). The new combined model leads to a prediction for the mean cabinet duration in terms of these two institutional factors: C = 42 years/(MS)1/3. Three-quarters of the actual mean durations agree with the prediction within a factor of 2. For the purposes of institutional engineering, the model predicts that doubling the district magnitude would reduce the mean cabinet duration by 21 percent ceteris paribus. © 2010 SAGE Publications.
- Published
- 2010
11. Predicting Cytotoxicity of Metal Oxide Nanoparticles Using Isalos Analytics Platform
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Anastasios G. Papadiamantis, Jaak Jänes, Evangelos Voyiatzis, Lauri Sikk, Jaanus Burk, Peeter Burk, Andreas Tsoumanis, My Kieu Ha, Tae Hyun Yoon, Eugenia Valsami-Jones, Iseult Lynch, Georgia Melagraki, Kaido Tämm, and Antreas Afantitis
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cytotoxicity ,metal oxide nanoparticles ,Isalos analytics platform ,computational descriptors ,in silico modelling ,machine learning ,Chemistry ,QD1-999 - Abstract
A literature curated dataset containing 24 distinct metal oxide (MexOy) nanoparticles (NPs), including 15 physicochemical, structural and assay-related descriptors, was enriched with 62 atomistic computational descriptors and exploited to produce a robust and validated in silico model for prediction of NP cytotoxicity. The model can be used to predict the cytotoxicity (cell viability) of MexOy NPs based on the colorimetric lactate dehydrogenase (LDH) assay and the luminometric adenosine triphosphate (ATP) assay, both of which quantify irreversible cell membrane damage. Out of the 77 total descriptors used, 7 were identified as being significant for induction of cytotoxicity by MexOy NPs. These were NP core size, hydrodynamic size, assay type, exposure dose, the energy of the MexOy conduction band (EC), the coordination number of the metal atoms on the NP surface (Avg. C.N. Me atoms surface) and the average force vector surface normal component of all metal atoms (v⊥ Me atoms surface). The significance and effect of these descriptors is discussed to demonstrate their direct correlation with cytotoxicity. The produced model has been made publicly available by the Horizon 2020 (H2020) NanoSolveIT project and will be added to the project’s Integrated Approach to Testing and Assessment (IATA).
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- 2020
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12. Quantifying the Use of Stones in the Stone Age Fireplaces of Estonia
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Kaarel Sikk
- Subjects
ugniavietė ,kiekybinė analizė ,pakartotinis duomenų naudojimas ,mezolitas ,neolitas ,Archaeology ,CC1-960 - Abstract
Akmenų naudojimo Estijos akmens amžiaus ugniavietėse nustatymas Ugniavietės ir su jais susiję degę akmenys yra įprastos struktūros, randamos akmens amžiaus gyvenvietėse. Nors informacija apie šiuos objektus pateikiama archeologinėse ataskaitose ir publikacijose, iki šiol nebuvo specialaus jiems skirto tyrimo. Šio straipsnio tikslas yra užpildyti šią spragą ir patikrinti hipotezę, kad ugniaviečių struktūriniai bruožai atskleidžia informaciją apie pragyvenimo gyvenvietėse modelį. Šioje studijoje remiamasi Estijos akmens amžiaus ugniaviečių duomenų baze, kuri sudaryta iš visų prieinamų kasinėtų objektų. Duomenų bazėje yra 167 ugniavietės ir kiekybiniai duomenys apie akmenis jose. Duomenų analizė atskleidė, kad akmenų naudojimas ugniavietėse laikui bėgant smarkiai keitėsi. Daugumoje mezolito laikotarpio ugniaviečių akmenų yra, o neolito laikotarpio ugniavietėse akmenys tapo retenybe. Galima daryti išvadą, kad akmenų naudojimas ugniavietėse susijęs su gyvenviečių ekonomika ir pokyčiai laikui bėgant atspindi bendros gyvenimo strategijos pokyčius.
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- 2017
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13. Gas-Phase Lithium Cation Basicity: Revisiting the High Basicity Range by Experiment and Theory
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Mayeux, Charly, Burk, Peeter, Gal, Jean-Francois, Kaljurand, Ivari, Koppel, Ilmar, Leito, Ivo, and Sikk, Lauri
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- 2014
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14. Villem Tamm (10.02.1942 – 31.08.2011). Majandusküberneetikute Õpetaja ja sõber. Mentor und Freund der Wirtschaftskybernetiker
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Juta Sikk and Kaia Philips
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Economics as a science ,HB71-74 - Abstract
Villem Tamm, who was called also as Tamme Villu or simply Villu, was born on 10th of February 1942 in Viljandi county Kabala. He studied seven years in Villavere school and then in high school in Viljandi. He graduated Tartu State University as „economic cybernetics” (mathematical economists) in 1969. His course mates considered him as a capable and talented person and predicted him successful and fast career as a lecturer and scientist. Villu worked at the Faculty of Economics and Business Administration, University of Tartu, almost 40 years. He started as assistant and continued as senior lecturer, associate professor in the Chair of Economic Cybernetics and Statistics (during the years 1991-1992 he was the head of this chair). During the years 1993-1996 he was professor of statistics and also the head of the Institute of Informatics and Economic Modelling. In the following years he worked as associate professor of statistics and retired in 2007. The new specialisation in the soviet economic education with the name “economic cybernetics” was opened at the Tartu State University in 1967 and there was an urgent need for academic staff who could teach the subjects of specialisation. Villem Tamm was assigned to teach basic principles of “economic cybernetics” and mathematical and statistical methods. He was one of the main lecturers who were teaching the specialisation subjects of “economic cybernetics” and also one of the main supervisors of students’ research papers and Diploma Thesis. He has remarkable contribution in preparation of almost 450 students, who have graduated the specialisation of “economic cybernetics”. In essence he is one of the founders of the new direction in education of economists – “economic cybernetics” - in Estonia. During his career he was teaching different statistical and mathematical planning courses in Estonian and in Russian for stationary students and for Open University students. For those students, who specialised to economic modelling, Villu was teaching subjects like principles of economics prognosis, input-output tables, Leontief’s economic equilibrium models, system analysis in economics, etc. Lot of students from Pärnu and Narva Collage, private universities of Audentes and Veritas can consider him also as their lecturer. Students evaluated him highly as a lecturer, as he was concrete in his taught subjects, he was thought-provoking and the personality to his lectures added his smugly humour. He was innovative and quickly adopted new technics and methods to modernise the teaching process. For example in 1980 he made dozens of dispositive about statistics, prepared punched card test for controlling students’ knowledge. In 2003 together with his colleague he designed a web-based course “Statistics”, which get the first price in the faculty’s competition. In total Villem Tamm has published nine textbooks and voluminous methodological materials for six courses. The way to the candidate (Ph.D) degree was not so quick. He continued his post-graduate studies in 1977 and defended Ph.D thesis (candidate in economics) in 1985. His main research areas have been very diverse: starting from the studies devoted to efficiency and effective use of labour resources, regularity of working processes up to problems and misunderstandings of statistical information. During several decades he was doing research in the field of input-output tables. From his personality Villem Tamm had good leadership abilities and as a head of different structural units he was tolerant, steady and fair leader. He had desire to motivate and direct both students and his colleagues; at the same time being dispassionate in communication and dignified in his behaviour. He was helpful and mindful of others; he had skills to solve complicated situations humanly and peacefully. During his working career he had also to fulfil different administrative obligations. He was 15 years supervisor and leader for different courses, curator of cooperation agreement between economic cybernetics from Vilnius, Latvia and Tartu Universities, member of teaching methodology commission, member of faculty’s council, etc. He was one of the founders of Estonian Statistical Society, alumni society “Hermes”, lecturer of association “Teadus” (“Science”), etc. He was participating in conducting population censuses, where he could implement his statistical knowledge and organiser’s abilities. Since the independence of Estonia he was several times leading the local election commissions during the parliament and local elections. Even if sometimes others could not see active engagement to these named and also to lot of others not mentioned activities, everything was functioning and was done at high quality.
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- 2014
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15. Computational study of the Sonogashira cross-coupling reaction in the gas phase and in dichloromethane solution
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Sikk, Lauri, Tammiku-Taul, Jaana, Burk, Peeter, and Kotschy, András
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- 2012
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16. Direct measurement of energy fluxes from mitochondria into cytoplasm in permeabilized cardiac cells in situ: some evidence for mitochondrial interactosome
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Timohhina, Natalia, Guzun, Rita, Tepp, Kersti, Monge, Claire, Varikmaa, Minna, Vija, Heiki, Sikk, Peeter, Kaambre, Tuuli, Sackett, Dan, and Saks, Valdur
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- 2009
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17. Manganese-Induced Parkinsonism due to Ephedrone Abuse
- Author
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Katrin Sikk, Sulev Haldre, Sten-Magnus Aquilonius, and Pille Taba
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Neurology. Diseases of the nervous system ,RC346-429 - Abstract
During recent years, a syndrome of hypokinesia, dysarthria, dystonia, and postural impairment, related to intravenous use of a “designer” psychostimulant derived from pseudoephedrine using potassium permanganate as the oxidant, has been observed in drug addicts in several countries in Eastern Europe with some cases also in Western countries. A levodopa unresponsive Parkinsonian syndrome occurs within a few months of abusing the homemade drug mixture containing ephedrone (methcathinone) and manganese. The development of this neurological syndrome has been attributed to toxic effects of manganese, but the role of the psychostimulant ephedrone is unclear. This paper describes the clinical syndrome, results of neuroimaging, and therapeutic attempts.
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- 2011
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18. Studies of mitochondrial respiration in muscle cells in situ: Use and misuse of experimental evidence in mathematical modelling
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Seppet, Enn K., Eimre, Margus, Andrienko, Tatiana, Kaambre, Tuuli, Sikk, Peeter, Kuznetsov, Audrey V., and Saks, Valdur
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- 2004
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19. In Memoriam prof. Heiki Müür (1932-1996). Mit Zusammenfassung
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Tiiu Paas, Helje Kaldaru, and Juta Sikk
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Economics as a science ,HB71-74 - Abstract
Professor Heiki Müür had his successful professional career mainly during the soviet period. Heiki Müür was born in 1932 in Tallinn. In 1954, at the age of 22, he received the diploma from the Tallinn Technical University, honouring him as a good specialist in socialist economy. This educational background allowed him to continue the post-graduate studies in the Moscow Institute of Economics. In 1959, he defended PhD thesis (candidate in economics), and in 1976, was approved as the habilitated doctor in Economics. Heiki Müür started his academic career at the Tartu State University in 1956, working initially as a lector and later as a docent and a professor. He published several books in Estonian that were actively used by the students as well as practitioners: Management and Planning, 1964; Prices and Economic Reform, 1971; Economic Planning, 1971; Economics and National Economy (editor of the series of books, 1972-1974; National Balance and Planning (1987, co-author). During his academic career, professor Heiki Müür demonstrated good abilities for leadership working as a vice dean and the dean at Tartu State University, and after 1990s, as a head of the institute of the Faculty of Economics and Business Administration at the University of Tartu. During the years 1981-1986, he was the director of the Research Institute, which worked for the Soviet Estonian government in Tallinn; during these years, he also continued to work as a part-time professor at the university. We, as his students of the field of “economic cybernetics” (mathematical economics) and successors, appreciate particularly highly his activities and success in establishing and promoting education in mathematical economics at the Faculty of Economics of the Tartu State University. The new specialisation in the soviet economic education with the name “economic cybernetics” was opened at the Tartu State University in 1967. Professor Heiki Müür devoted lots of his energy, time and knowledge to create the school of young economists who have good knowledge in applying mathematical and statistical methods for analysing economic problems in Estonia. The knowledge in economics and research methodology of these graduates was not heavily related to the soviet rules of the economic mechanism. In collaboration with the young postgraduates, professor Müür started to develop applied research for the soviet firms examining the relationship between the working conditions and economic outcomes and implementing modern mathematical and statistical methods by conducting economic analysis. He was one of the initiators and organisers of the high scientific level economic conference on applying modern methods for analysing economic processes in Tallinn in 1981. L. Kantorovitš, the only soviet economist who got Nobel Prize (1975) in relation to elaborating and developing linear programming methods, was among the participants of the conference. Professor Heiki Müür was innovative and flexible in starting to restructure the curricula and study process at the University of Tartu after Estonia regains its independence. He was the initiator of offering new study courses in market economy not only for the students of the Faculty of Economics, but also for students from other faculties as well as for practitioners. The graduates, who obtained diploma in “economic cybernetics” and belonged to the school of the Estonian economists established by the significant contribution of professor Heiki Müür continued his work being the initiators and developers of the new economic curricula and of restructuring economic education and research in compliance with high level international requirements
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- 2010
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20. The sets of abstract trigonometric series induced by Lp
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Sikk, Jaak
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- 2000
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21. Developmental changes in regulation of mitochondrial respiration by ADP and creatine in rat heart in vivo
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Tiivel, Toomas, Kadaya, Lumme, Kuznetsov, Andrei, Käämbre, Tuuli, Peet, Nadezhda, Sikk, Peeter, Braun, Urmo, Ventura-Clapier, Renée, Saks, Valdur, and Seppet, Enn K.
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- 2000
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22. Permeabilized cell and skinned fiber techniques in studies of mitochondrial function in vitro
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Veksler, Vladimir I., Kuznetsov, Andrei V., Kay, Laurence, Sikk, Peeter, Tiivel, Toomas, Tranqui, Leone, Olivares, Jose, Winkler, Kirstin, Wiedemann, Falk, and Kunz, Wolfram S.
- Published
- 1998
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23. Concomitant immunocytochemical study of macrophage cells and blood vessels in disc herniation tissue
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Virri, J., Sikk, S., Grönblad, M., Tolonen, J., Seitsalo, S., Kankare, J., and Karaharju, E. O.
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- 1994
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24. Land fragmentation and other determinants of agricultural farm productivity: The case of Estonia.
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Looga, J., Jürgenson, E., Sikk, K., Matveev, E., and Maasikamäe, S.
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AGRICULTURAL productivity ,REAL estate development ,CLIMATE change mitigation ,ENVIRONMENTAL protection - Abstract
Highlights • Higher weighted average size of the land parcel increases farm productivity. • Agricultural training, conventional production type increases farm productivity. • Land fragmentation is an important determinant of farm productivity. • Januszewski index has U-shape relation to farm productivity. Abstract The rising population of the world increases the need for raw materials and food. The more efficient production methods help to reduce the shortage of production and to mitigate climate change. This paper analyses the relationship between land fragmentation and farm productivity. The results show that land fragmentation measured using the Januszewski index has U-shape relationship to farm productivity: there are larger farms with many parcels which are productive, but their parcels are scattered and smaller farms, with few parcels that are also productive. We found an indicator which describes the differences in farms' productivity based on their land use – the area-weighted mean size of the parcels of one farm. This indicator is a statistically significant determinant of farm productivity. Other significant variables that are related to higher productivity are farm owners' education, farm size, farming system and production type. Agricultural land policies should consider multiple indicators and analyse different production types to intervene more effectively. [ABSTRACT FROM AUTHOR]
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- 2018
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25. The creatine kinase phosphotransfer network: thermodynamic and kinetic considerations, the impact of the mitochondrial outer membrane and modelling approaches
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Saks, V., Kaambre, T., Guzun, R., Anmann, T., Sikk, P., Schlattner, U., Wallimann, T., Aliev, M., Marko Vendelin, Hamant, Sarah, Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics = Keemilise ja bioloogilise füüsika instituut [Estonie] (NICPB | KBFI), Laboratoire de bioénergétique fondamentale et appliquée (LBFA), Université Joseph Fourier - Grenoble 1 (UJF)-Institut National de la Santé et de la Recherche Médicale (INSERM), Department of Biology, Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology [Zürich] (ETH Zürich)-Institute of Cell Biology, Institute of Experimental Cardiology, and Cardiology Research Center
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MESH: Myocardium ,Phosphocreatine ,MESH: Phosphocreatine ,Models, Biological ,Mitochondria, Heart ,Adenosine Triphosphate ,Oxygen Consumption ,MESH: Adenosine Triphosphate ,[SDV.BBM] Life Sciences [q-bio]/Biochemistry, Molecular Biology ,Animals ,Humans ,MESH: Animals ,[SDV.BBM]Life Sciences [q-bio]/Biochemistry, Molecular Biology ,MESH: Oxygen Consumption ,Creatine Kinase ,MESH: Creatine Kinase ,MESH: Humans ,MESH: Adenosine Diphosphate ,MESH: Kinetics ,Myocardium ,MESH: Energy Metabolism ,MESH: Models, Biological ,Adenosine Diphosphate ,Kinetics ,Thermodynamics ,MESH: Mitochondria, Heart ,MESH: Thermodynamics ,MESH: Mitochondrial ADP, ATP Translocases ,Energy Metabolism ,Mitochondrial ADP, ATP Translocases - Abstract
International audience; In this review, we summarize the main structural and functional data on the role of the phosphocreatine (PCr)--creatine kinase (CK) pathway for compartmentalized energy transfer in cardiac cells. Mitochondrial creatine kinase, MtCK, fixed by cardiolipin molecules in the vicinity of the adenine nucleotide translocator, is a key enzyme in this pathway. Direct transfer of ATP and ADP between these proteins has been revealed both in experimental studies on the kinetics of the regulation of mitochondrial respiration and by mathematical modelling as a main mechanism of functional coupling of PCr production to oxidative phosphorylation. In cells in vivo or in permeabilized cells in situ, this coupling is reinforced by limited permeability of the outer membrane of the mitochondria for adenine nucleotides due to the contacts with cytoskeletal proteins. Due to these mechanisms, at least 80% of total energy is exported from mitochondria by PCr molecules. Mathematical modelling of intracellular diffusion and energy transfer shows that the main function of the PCr-CK pathway is to connect different pools (compartments) of ATP and, by this way, to overcome the local restrictions and diffusion limitation of adenine nucleotides due to the high degree of structural organization of cardiac cells.
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- 2007
26. Intracellular energetic units in red muscle cells
- Author
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Saks, V A, Kaambre, T, Sikk, P, Eimre, M, Orlova, E, Paju, K, Piirsoo, A, Appaix, F, Kay, L, Regitz-Zagrosek, V, Fleck, E, Seppet, E, Bioénergétique fondamentale et appliquée, Université Joseph Fourier - Grenoble 1 (UJF)-Institut National de la Santé et de la Recherche Médicale (INSERM), Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics = Keemilise ja bioloogilise füüsika instituut [Estonie] (NICPB | KBFI), Department of Pathophysiology, University of Tartu, Department of Human Biology and Genetics, Deutsche Herzzentrum, and Hamant, Sarah
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Male ,MESH: Myocardium ,MESH: Rats ,MESH: Microscopy, Electron ,In Vitro Techniques ,Models, Biological ,Biochemistry ,Mitochondria, Heart ,03 medical and health sciences ,0302 clinical medicine ,Animals ,MESH: Animals ,Rats, Wistar ,Muscle, Skeletal ,Molecular Biology ,030304 developmental biology ,0303 health sciences ,MESH: Muscle, Skeletal ,MESH: Adenosine Diphosphate ,MESH: Creatine ,MESH: Kinetics ,Myocardium ,MESH: Energy Metabolism ,MESH: Models, Biological ,MESH: Mitochondria, Muscle ,Heart ,Cell Biology ,MESH: Rats, Wistar ,Creatine ,MESH: Male ,Mitochondria, Muscle ,Rats ,Adenosine Diphosphate ,MESH: Heart ,Kinetics ,Microscopy, Electron ,MESH: Mitochondria, Heart ,Energy Metabolism ,030217 neurology & neurosurgery ,Research Article - Abstract
International audience; The kinetics of regulation of mitochondrial respiration by endogenous and exogenous ADP in muscle cells in situ was studied in skinned cardiac and skeletal muscle fibres. Endogenous ADP production was initiated by addition of MgATP; under these conditions the respiration rate and ADP concentration in the medium were dependent on the calcium concentration, and 70-80% of maximal rate of respiration was achieved at ADP concentration below 20 microM in the medium. In contrast, when exogenous ADP was added, maximal respiration rate was observed only at millimolar concentrations. An exogenous ADP-consuming system consisting of pyruvate kinase (PK; 20-40 units/ml) and phosphoenolpyruvate (PEP; 5 mM), totally suppressed respiration activated by exogenous ADP, but the respiration maintained by endogenous ADP was not suppressed by more than 20-40%. Creatine (20 mM) further activated respiration in the presence of ATP and PK+PEP. Short treatment with trypsin (50-500 nM for 5 min) decreased the apparent K(m) for exogenous ADP from 300-350 microM to 50-60 microM, increased inhibition of respiration by PK+PEP system up to 70-80%, with no changes in MgATPase activity and maximal respiration rates. Electron-microscopic observations showed detachment of mitochondria and disordering of the regular structure of the sarcomere after trypsin treatment. Two-dimensional electrophoresis revealed a group of at least seven low-molecular-mass proteins in cardiac skinned fibres which were very sensitive to trypsin and not present in glycolytic fibres, which have low apparent K(m) for exogenous ADP. It is concluded that, in oxidative muscle cells, mitochondria are incorporated into functional complexes ('intracellular energetic units') with adjacent ADP-producing systems in myofibrils and in sarcoplasmic reticulum, probably due to specific interaction with cytoskeletal elements responsible for mitochondrial distribution in the cell. It is suggested that these complexes represent the basic pattern of organization of muscle-cell energy metabolism.
- Published
- 2001
27. Quantifying the Use of Stones in the Stone Age Fireplaces of Estonia.
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Sikk, Kaarel
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FIREPLACE design & construction ,STONE Age ,PREHISTORIC settlements - Abstract
Copyright of Archaeologia Lituana is the property of Vilnius University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2016
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28. Ultra performance liquid chromatography analysis of adenine nucleotides and creatine derivatives for kinetic studies
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Sikk, P, primary, Käämbre, T, primary, Vija, H, primary, Tepp, K, primary, Tiivel, T, primary, Nutt, A, primary, and Saks, V, primary
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- 2009
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29. Metabolic consequences of functional complexes of mitochondria,myofibrils and sarcoplasmic reticulum in muscle cells
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Andrienko, T., primary, Kuznetsov, A. V., additional, Kaambre, T., additional, Usson, Y., additional, Orosco, A., additional, Appaix, F., additional, Tiivel, T., additional, Sikk, P., additional, Vendelin, M., additional, Margreiter, R., additional, and Saks, V. A., additional
- Published
- 2003
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30. The Creatine Kinase Phosphotransfer Network: Thermodynamic and Kinetic Considerations, the Impact of the Mitochondrial Outer Membrane and Modelling Approaches.
- Author
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Harris, J. Robin, Biswas, B.B., Quinn, P., Salomons, Gajja S., Wyss, Markus, Saks, Valdur, Kaambre, Tuuli, Guzun, Rita, Anmann, Tiia, Sikk, Peeter, Schlattner, Uwe, Wallimann, Theo, Aliev, Mayis, and Vendelin, Marko
- Abstract
In this review, we summarize the main structural and functional data on the role of the phosphocreatine (PCr) -- creatine kinase (CK) pathway for compartmentalized energy transfer in cardiac cells. Mitochondrial creatine kinase, MtCK, fixed by cardiolipin molecules in the vicinity of the adenine nucleotide translocator, is a key enzyme in this pathway. Direct transfer of ATP and ADP between these proteins has been revealed both in experimental studies on the kinetics of the regulation of mitochondrial respiration and by mathematical modelling as a main mechanism of functional coupling of PCr production to oxidative phosphorylation. In cells in vivo or in permeabilized cells in situ, this coupling is reinforced by limited permeability of the outer membrane of the mitochondria for adenine nucleotides due to the contacts with cytoskeletal proteins. Due to these mechanisms, at least 80% of total energy is exported from mitochondria by PCr molecules. Mathematical modelling of intracellular diffusion and energy transfer shows that the main function of the PCr -- CK pathway is to connect different pools (compartments) of ATP and, by this way, to overcome the local restrictions and diffusion limitation of adenine nucleotides due to the high degree of structural organization of cardiac cells [ABSTRACT FROM AUTHOR]
- Published
- 2007
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31. Comparative DFT study of americium and europium complexation with 2,9-bis(1,2-diazin-3-yl)-1,10-phenanthroline ligand in gas phase.
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Burk, Jaanus, Sikk, Lauri, Tämm, Kaido, and Burk, Peeter
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EUROPIUM ,AMERICIUM ,RARE earth metals ,METALWORK ,COMPLEXATION reactions ,COMPARATIVE studies - Abstract
[Display omitted] • Comparative study of americium and europium complexation with BTPhen-CH was done. • Both pure cation and its tetraaquatrinitrato complex were used as reactants. • Five different reactions were studied. • In case of pure cation europium forms the more stable complexes. • In case of tetraaquatrinitrato complex americium form the more stable complexes. 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenantroline (BTPhen) based ligands have shown great promise in separation of trivalent lanthanides and actinides. Although many experimental studies have shown that americium is forming stronger complexes with the BTPhen ligands than europium, most theoretical studies have thus far failed to reproduce these results. In the current study, two different metal forms (the naked cation and its tetraaquatrinitrato complex) were used to study five different complexation reactions. It was shown that in case of naked cations europium forms the most stable complex with the 2,9-bis(1,2-diazin-3-yl)-1,10-phenanthroline (BTPhen-CH) ligand in all of the compared reactions. In case of tetraaquatrinitrato complex it was shown that europium gets a higher stabilizing effect and thus americium complexes with BTPhen-CH become the more stable form, as can be seen in the experimental studies. [ABSTRACT FROM AUTHOR]
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- 2022
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32. VILLEM TAMM: (10.02.1942 -31.08.2011).
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Sikk, Juta and Philips, Kaia
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- 2014
33. The 27.5 kD protein appears to control the oxidative phosphorylation in slow twitch muscle cells
- Author
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Seppet, E.K., primary, Kadaya, L., additional, Peet, N., additional, Käämbre, T., additional, Sikk, P., additional, and Saks, V.A., additional
- Published
- 1998
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34. A CHEMOENZYMATIC APPROACH TO THE PREPARATION OF OPTICALLY ACTIVE α-BROMO-ω-HYDROXY ALDEHYDE HEMIACETALS
- Author
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Parve, O, primary, Vallikivi, I, primary, Lahe, L, primary, Sikk, P, primary, Käämbre, T, primary, and Lille, Ü, primary
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- 1997
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35. Theoretical Modeling of HPV: QSAR and Novodesign with Fragment Approach
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G. Pillai, Girinath, Sikk, Lauri, Tamm, Tarmo, Karelson, Mati, Burk, Peeter, and Tamm, Kaido
- Abstract
Structure-activity relationships in a data set of HPV6-E1 helicase ATPase inhibitors were investigated based on two different sets of descriptors. Statistically significant four parameter Quantitative Structure-Activity Relationships (QSAR) models were constructed and validated in both cases (R2=0.849; R2 cv=0.811; F=52.20; s2=0.25; N=42). A Fragment based QSAR (FQSAR) approach was applied for developing a fragment-QSAR equation, which enabled the construction of virtual structures for novel ATPase inhibitors with desired or pre-defined activity.
- Published
- 2014
36. Computational Study of Copper-Free Sonogashira Cross-Coupling Reaction.
- Author
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Lauri Sikk, Jaana Tammiku-Taul, and Peeter Burk
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- 2011
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37. Computational Study on the Reactivity of Tetrazines toward Organometallic Reagents.
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Lőrincz, Krisztián, Kotschy, \András, Tammiku-TauI, Jaana, Sikk, Lauri, and Burk, Peeter
- Published
- 2010
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38. PROFESSOR HEIKI MÜÜR (1932-1996) -- UUE SUUNA RAJAJA NÕUKOGUDEAEGSETE MAJANDUSTEADLASTE KOOLITAMISEL.
- Author
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Paas, Tiiu, Kaldaru, Helje, and Sikk, Juta
- Published
- 2010
39. Computational Study of Cesium Cation Interactions with Neutral and Anionic Compounds Related to Soil Organic Matter.
- Author
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Peeter Burk, Jaana Tammiku-Taul, Sven Tamp, Lauri Sikk, Kaido Sillar, Charly Mayeux, Jean-François Gal, and Pierre-Charles Maria
- Published
- 2009
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40. Metabolic consequences of functional complexes of mitochondria, myofibrils and sarcoplasmic reticulum in muscle cells.
- Author
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Andrienko, T., Kuznetsov, A.V., Kaambre, T., Usson, Y., Orosco, A., Appaix, F., Tiivel, T., Sikk, P., Vendelin, M., Margreiter, R., and Saks, V.A.
- Subjects
MUSCLE cells ,MITOCHONDRIA ,SARCOPLASMIC reticulum - Abstract
Regulation of mitochondrial respiration both by endogenous and exogenous ADP in the cells in situ was studied in isolated and permeabilized cardiomyocytes, permeabilized cardiac fibers and 'ghost' fibers (all with a diameter of 10-20 µm) at different (0-3 µmol 1[sup -1]) free Ca[sup 2+] concentrations in the medium. In all these preparations, the apparent K[sub m] of mitochondrial respiration for exogenous ADP at free Ca[sup 2+] concentrations of 0-0.1 µmol l[sup -1] was very high, in the range of 250-350 µmol 1[sup -1], in contrast to isolated mitochondria in vitro (apparent K[sub m] for ADP is approximately 20 µmol l[sup -1]). An increase in the free Ca[sup 2+] concentration (up to 3 µmol l[sup -1], which is within physiological range), resulted in a very significant decrease of the apparent K[sub m] value to 20-30 µmol l[sup -1], a decrease of V[sub max] of respiration in permeabilized intact fibers and a strong contraction of sarcomeres. In ghost cardiac fibers, from which myosin was extracted but mitochondria were intact, neither the high apparent K[sub m] for ADP (300-350 µmol 1[sup -1]) nor V[sub max] of respiration changed in the range of free Ca[sup 2+] concentration studied, and no sarcomere contraction was observed. The exogenous-ADP-trapping system (pyruvate kinase + phosphoenolpyruvate) inhibited endogenous-ADP-supported respiration in permeabilized cells by no more than 40%, and this inhibition was reversed by creatine due to activation of mitochondrial creatine kinase. These results are taken to show strong structural associations (functional complexes) among mitochondria, sarcomeres and sarcoplasmic reticulum. Inside these complexes, mitochondrial functional state is controlled by channeling of ADP, mostly via energy- and phosphoryltransfer networks, and apparently depends on the state of sarcomere structures. [ABSTRACT FROM AUTHOR]
- Published
- 2003
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41. Force Mineure? The Effects of the EU on Party Politics in a Small Country: The Case of Estonia
- Author
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Sikk, Allan
- Abstract
Assessing the first four years of EU membership on Estonian party politics indicates that following accession EU perspectives on policies and European policy specialists in small countries may remain sidelined in the decision-making processes within political parties because of the mechanical effects of small numbers of such specialists. At the same time, European parliament elections add an additional event to the electoral calendar and the novel role of MEPs has a potential to affect domestic political competition. However, the constraints posed by common policies may be weakened by the overwhelming domestic concerns of political parties as an analysis of the anatomy of the failure to adopt the single currency shows.
- Published
- 2009
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42. Comparing contemporaneous hunter-gatherer and early agrarian settlement systems with spatial point process models: Case study of the Estonian Stone Age
- Author
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Sikk, Kaarel, Caruso, Geoffrey, Rosentau, Alar, and Kriiska, Aivar
- Abstract
•Quantitative comparison of settlement systems with first order point process models.•Usable area by Corded Ware culture increased compared to hunter-fisher-gatherer.•Larger usable land made possible the migration of early agrarian society.•Overlap of suitable residential areas could have led to competition for space.•Spatial land use structure was more homogeneous for early agrarian population.•Differing model performance can be caused by social structure or land-use patterns.
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- 2022
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43. From private organizations to democratic infrastructure: Political parties and the state in Estonia
- Author
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Sikk, Allan
- Abstract
Estonia, one of the first former Soviet republics to regain independence, had to start the processes of party and state development from scratch, beginning with the development of a legal framework for political parties, establishing a regime of public party financing, and training and deploying elites in party and state administrations. In the case of the last element, a variety of career patterns has emerged as individuals have moved between political and administrative roles. The question of the neutrality of county governors and administrative department secretaries-general has been particularly contentious in what has become a close and strengthening relationship between parties and the state. This is visible in the legal status of parties, their growing reliance on public subsidies, and the substantial circulation of people between administrative and political echelons. This can partly be explained by patronage and the particular legacies of communism and state-building, but the small size of the country may have had an independent effect.
- Published
- 2006
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44. Heterogeneity of ADP Diffusion and Regulation of Respiration in Cardiac Cells
- Author
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Saks, Valdur, Kuznetsov, Andrey, Andrienko, Tatiana, Usson, Yves, Appaix, Florence, Guerrero, Karen, Kaambre, Tuuli, Sikk, Peeter, Lemba, Maris, and Vendelin, Marko
- Abstract
Heterogeneity of ADP diffusion and regulation of respiration were studied in permeabilized cardiomyocytes and cardiac fibers in situ and in silico. Regular arrangement of mitochondria in cells was altered by short-time treatment with trypsin and visualized by confocal microscopy. Manipulation of matrix volumes by changing K+and sucrose concentrations did not affect the affinity for ADP either in isolated heart mitochondria or in skinned fibers. Pyruvate kinase (PK)-phosphoenolpyruvate (PEP) were used to trap ADP generated in Ca,MgATPase reactions. Inhibition of respiration by PK-PEP increased 2–3 times after disorganization of regular mitochondrial arrangement in cells. ADP produced locally in the mitochondrial creatine kinase reaction was not accessible to PK-PEP in intact permeabilized fibers, but some part of it was released from mitochondria after short proteolysis due to increased permeability of outer mitochondrial membrane. In in silico studies we show by mathematical modeling that these results can be explained by heterogeneity of ADP diffusion due to its restrictions at the outer mitochondrial membrane and in close areas, which is changed after proteolysis. Localized restrictions and heterogeneity of ADP diffusion demonstrate the importance of mitochondrial functional complexes with sarcoplasmic reticulum and myofibrillar structures and creatine kinase in regulation of oxidative phosphorylation.
- Published
- 2003
- Full Text
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45. Metabolic Control of Contractile Performance in Isolated Perfused Rat Heart. Analysis of Experimental Data by Reaction:Diffusion Mathematical Model
- Author
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Dos Santos, Pierre, Aliev, Mayis K, Diolez, Philippe, Duclos, François, Besse, Pierre, Bonoron-Adèle, Simone, Sikk, Peeter, Canioni, Paul, and Saks, Valdur A
- Abstract
P. Dos Santos, M. K. Aliev, P. Diolez, F. Duclos, P. Besse, S. Bonoron-Adèle, P. Sikk, P. Canioni and V. A. Saks. Metabolic Control of Contractile Performance in Isolated Perfused Rat Heart. Analysis of Experimental Data by Reaction:Diffusion Mathematical Model. Journal of Molecular and Cellular Cardiology(2000) 32, 1703–1734. The intracellular mechanisms of regulation of energy fluxes and respiration in contracting heart cells were studied. For this, we investigated the workload dependencies of the rate of oxygen consumption and metabolic parameters in Langendorff-perfused isolated rat hearts.31P NMR spectroscopy was used to study the metabolic changes during transition from perfusion with glucose to that with pyruvate with and without active creatine kinase system. The experimental results showed that transition from perfusion with glucose to that with pyruvate increased the phosphocreatine content and stability of its level at increased workloads. Inhibition of creatine kinase reaction by 15-min infusion of iodoacetamide decreased the maximal developed tension and respiration rates by a factor of two.31P NMR data were analyzed by a mathematical model of compartmentalized energy transfer, which is independent from the restrictions of the classical concept of creatine kinase equilibrium. The analysis of experimental data by this model shows that metabolic stability—constant levels of phosphocreatine, ATP and inorganic phosphate—at increased energy fluxes is an inherent property of the compartmentalized system. This explains the observed substrate specificity by changes in mitochondrial membrane potential. The decreased maximal respiration rate and maximal work output of the heart with inhibited creatine kinase is well explained by the rise in myoplasmic ADP concentration. This activates the adenylate kinase reaction in the myofibrillar space and in the mitochondria to fulfil the energy transfer and signal transmission functions, usually performed by creatine kinase. The activity of this system, however, is not sufficient to maintain high enough energy fluxes. Therefore, there is a kinetic explanation for the decreased maximal respiration rate of the heart with inhibited creatine kinase: i.e. a kinetically induced switch from an efficient energy transfer pathway (PCr–CK system) to a non-efficient one (myokinase pathway) within the energy transfer network of the cell under conditions of low apparent affinity of mitochondria to ADP in vivo. This may result in a significant decrease in the thermodynamic affinity of compartmentalized ATPase systems and finally in heart failure.
- Published
- 2000
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46. DFT study of 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenanthroline (BTPhen) and its derivatives complexation with lanthanide series.
- Author
-
Burk, Jaanus, Adamson, Aiko, Sikk, Lauri, Tämm, Kaido, Pupart, Anni, and Burk, Peeter
- Subjects
RARE earth metals ,COMPLEXATION reactions ,ATOMIC number ,DENSITY functional theory ,CHEMICAL bond lengths - Abstract
• Five BTPhen derivatives were studied to better understand lanthanide complextion. • Studied complexes contained two ligands and one lanthanide 3+ ion. • Substituting the outer nitrogen of triazine group increases the complex stability. • Substituting the inner nitrogen of triazine group lowers the complex stability. The complexation reactions between lanthanide 3
+ cations and 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenanthroline and its derivatives were studied with density functional theory Perdew-Burke-Ernzerhof functionals. The complexes consisted of one lanthanide cation and two ligand molecules. Complexation reactions were found to be exothermic and spontaneous in the gas phase. Absolute values of complextion energy and enthalpy increase in the lanthanide series and follow linear trends of lanthanide atomic number. All the bond lengths decrease in the lanthanide series with increasing charge density. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
47. Irreversible inhibition of pancreatic lipase by bis- p-nitrophenyl methylphosphonate
- Author
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Sikk, P., Osa, A., and Aaviksaar, A.
- Abstract
The reaction of porcine pancreatic lipase with an organophosphorus compound bis- p-nitrophenyl methylphosphonate (BNMP) resulted in the complete and irreversible inhibition of lipase activity on tributyrin emulsion (25°C, pH 7.5, 40 mM Na-veronal-HCl buffer) whereas the activity of the enzyme on p-nitrophenyl acetate solution remained unchanged. The BNMP-modified enzyme did not bind on hydrophobic interfaces (siliconized glass beads). Tyr 49 was presumed to be the modification site, and the conclusion has been made that this residue is implicated in the interface recognition site of pancreatic lipase.
- Published
- 1985
- Full Text
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48. Lipase-catalysed enantioselective hydrolysis: Interpretation of the kinetic results in terms of frontier orbital localisation
- Author
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Parve, Omar, Vallikivi, Imre, Metsala, Andrus, Lille, Ülo, Tõugu, Vello, Sikk, Peeter, Käämbre, Tuuli, Vija, Heiki, and Pehk, Tõnis
- Abstract
The initial velocities of the enantioselective hydrolysis of the esters derived from mono- and bicyclic alcohols and hemiacetals catalysed by Lipolase™ in water have been determined. The differences in hydrolysis rates within groups of sterically similar substrates have been interpreted in terms of frontier orbital localisation.
- Published
- 1997
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49. Eye symptoms, visual evoked potentials and EEG during intravenous infusion of glycine
- Author
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Hahn, R. G., Andersson, T., and Sikk, M.
- Abstract
Disturbance of vision is a complication that may occur from absorption of the glycine solution used to irrigate the bladder during transurethral operations. We examined for a possible dose‐response relationship between glycine dose, eye symptoms and neurophysiological changes after repeated intermittent intravenous infusions of 4.4 g of glycine for up to 22 g over 1 h in 10 male volunteers. The serum glycine concentration increased from 230±75 to 5,232±1,088 μmol/1 (mean±s.d.) during the infusions. We found an increase in diastolic arterial pressure but no significant changes in systolic pressure, heart rate or mental status. Five of the volunteers developed blurring of vision which lasted for 10 30 min. The visual evoked potentials (VEP) of these subjects showed an increase of the P100 and N70 latencies which started after no more than 4.4 g of glycine had been administered. The amplitude of the VEP was preserved and the main frequency of the EEG did not change, indicating that VEP changes were not due to cortical dysfunction. There was no dose‐response relationship between glycine infusion and eye symptoms but a sub‐group of volunteers responded with both visual disturbances and VEP changes.
- Published
- 1995
- Full Text
- View/download PDF
50. Calcium-induced contraction of sarcomeres changes the interaction between mitochondria and ATPases in permeabilized cardiac cells
- Author
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Seppet, E.K., Eimre, M., Paju, K., Orlova, E., Piirsoo, A., Sikk, P., Kaambre, T., and Saks, V.A.
- Published
- 2006
- Full Text
- View/download PDF
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