173 research outputs found
Ravnoteža sila i momenata sila u diobenom vretenu
No full textIn this thesis, I present results of my work over the last three years, carried out as a member of Pavin Group at the Faculty of Science, University of Zagreb. The mitotic spindle is a complex micro-machine composed of microtubules and associated proteins that must be highly ordered in space and time to function properly. A functional spindle has a distinct shape composed of curved bundles of microtubules twisted around the pole-to-pole axis. There is still a lack of understanding of how linear and rotational forces define the overall shape of the mitotic spindle, as well as how twisted shapes emerge as a result of interactions between microtubules and motor proteins. To answer this, we use a mean-field approach to model the entire spindle, describing the forces and torques along microtubule bundles throughout the spindle. We compare our theoretical modelling to experimentally observed bundle shapes in the mitotic spindle, including both unperturbed and compressed spindles. We conclude that rotational forces are primarily responsible for the observed spindle shape. Furthermore, we discover that the difference in bending forces explains the difference in the shapes of the inner and outer bundles, that the chirality of the spindle is caused by a constant twisting moment and that there exists a preferred direction from microtubules arising out of the centrosome.Diobeno vreteno je stanična struktura koja je odgovorna za raspodjelu genetskog materijala medu stanicama kćeri, a sastoji se od mikrotubula i pridruženih proteina. Funkcionalno diobeno vreteno ima karakterističan oblik, sastojeći se od zakrivljenih svežnjeva mikrotubula, zakrenutih oko osi vretena. Potpuno razumijevanje linearnih i rotacionih sila, koje određuju cjelokupni oblik diobenog vretena te koje interakcije između mikrotubula i motornih proteina ih stvaraju, ostaje otvoreno pitanje. Predstavljamo metodu kojom je moguće izvući relevantne geometrijske parametre iz mikroskopskih slika diobenog vretena. Nadalje, uvodimo teorijski model diobenog vretena u kojem motorni proteini stvaraju sile i momente sila na polovima i duž svežnjeva mikrotubula, time regulirajući oblike svežnjeva mikrotubula. Iz modela dobivamo predviđanje oblika diobenog vretena, odnosno raspodjelu sila u diobenom vretenu, iz kojih možemo zaključiti da razlika u silama savijanja objašnjava razliku u obliku unutarnjih i vanjskih mikrotubula te da je cjelokupni oblik vretena većinski rezultat rotacionih sila. U prvom poglavlju opisana je struktura diobenog vretena, kao i njegova svojstva i uloga. Predstavljen je detaljni pregled biološke grade diobenog vretena i njegove strukture te je uloga diobenog vretena u staničnoj diobi i u stanici razjašnjena. Struktura diobenog vretena je razrađena sa posebnim naglaskom na svežnjeve mikrotubula i motornih proteina, koji svojim djelovanjem stvaraju sile i momente sila u diobenom vretenu. Uvedena je fizikalna teorija elastičnosti, s istaknutim dijelovima koji se koriste u radu za opis svežnjeva mikrotubula te je objašnjena opravdanost korištenja iste za opis stvarnih svežnjeva mikrotubula. Drugo poglavlje posvećeno je kiralnosti diobenog vretena, odnosno opisano je nedavno otkriće da se svežnjevi mikrotubula u diobenom vretenu namotavaju oko glavne osi diobenog vretena, tj. da nisu isključivo ravninski oblici. Objašnjena je pojava zavrnutih mikrotubula u diobenom vretenu, značaj tog uvrnuća za razumijevanje ravnoteže sila i momenata sila u diobenom vretenu te dosadašnji (neuspjeli) pokušaji kvantificiranja ovog uvinuća. Navedeno ujedno služi i kao uvod za opis glavnog cilja radnje, koji uključuje konstrukciju sveobuhvatnog modela diobenog vretena, koristeći aprokismaciju srednjeg polja, te prethodnu potrebu razvijanja metode koja će moći adekvatno izmjeriti uvrnuće svežnjeva mikrotubula u diobenom vretenu, kako bi se eksperimentalni podaci mogli dobro interpretirati te služiti za postavljanje, a potom i verifikaciju modela. U trećem poglavlju razvija se metoda kosog kruga (eng. Oblique Circle Method) koja se koristi služi za mjerenje uvinutosti mikrotubula. Prikazane su pretpostavke metode, ista je sistematički razrađena te u konačnici primijenjena i validirana na stvarnim ljudskim stanicama. Metoda je potom korištena za dobivanje zaključaka o strukturi diobenog vretena u perturbiranim i ne-perturbiranim ljudskim tumorskim stanicama, kao i stanicama amebe. Iz primjene metode dobiveni su zaključci o okomitim i paralelnim silama i momentima sila u diobenom vretenu. U četvrtom poglavlju uvodi se fizikalni model diobenog vretena, koji za cilj ima opis svih svežnjeva mikrotubula u metafaznom diobenom vretenu. Predstavljen je opis sustava od prebrojivo mnogo svežnjeva mikrotubula te je potom aproksimacijom srednjeg polja taj broj pušten u beskonačnost, kako bi se dobio kontinuirani model koji opisuje cjelokupno diobeno vreteno. Iz kontinuiranog modela je izračunata ravnoteža sila i momenata sila u čitavom diobenom vretenu nakon čega su svežnjevi mikrotubula opisani Kirchhoffovom jednadžbom za tanke štapove. Predstavljeni su ulazni i izlazni parametri modela, istražen je parametarski prostor modela te je biološki relevantan dio parametarskog prostora identificiran. U petom poglavlju je teorijski model uspoređen s eksperimentalnim podacima bioloških diobenih vretena, koristeći za usporedbu informacije dobivene uporabom metode kosog kruga na mikroskopske slike diobenog vretena. Teorijski model je uspoređen s više staničnih linija te su za svaku staničnu liniju pronađeni parametri koji ju najbolje opisuju, odnosno, određene su optimalne distribucije sila i momenata sila u diobenom vretenu. Iz distribucije sila i momenata sile, pokazano je da unutarnji i vanjski mikrotubuli imaju znatno različite okomite sile, no slične paralelne sile. Nadalje, model pokazuje da mikrotubuli iz centrosoma izviru pod kutom, odnosno ne ravno poput zraka sunca, već su sve okrenute prema jednoj strani, što je dosad u polju nerazmatran detalj, ali za njega postoje eksperimentalni dokazi, stoga na taj način model sugerira daljnje eksperimente. U šestom poglavlju su reiterirani glavni zaključci doktorskog rada, u vidu rezultata koji su dobiveni korištenjem samo metode kosog kruga, ali i teorijskog modela, te njegove usporedbe s eksperimentalnim podacima
Balance of forces and torques in a mean-field approximation in mitotic spindles
No full textDiobeno vreteno je stanična struktura koja je odgovorna za raspodjelu genetskog materijala medu stanicama kćeri, a sastoji se od mikrotubula i pridruženih proteina. Sile i momenti sila igraju ključnu ulogu u funkcioniranju vretena te su odgovorni za pomicanje kromosoma i održavanje njegove grade, a važnu ulogu igraju elastična svojstva mikrotubula. Međutim, sile i momente nije lako odrediti današnjim eksperimentalnim tehnikama. U ovom teorijskom istraživanju uvodimo model za ravnotežu sila i momenata sila u diobenom vretenu. Korištenjem aproksimacije srednjeg polja opisujemo sve mikrotubule u diobenom vretenu, kao i sile i momente sila koje djeluju na njih. Model daje predvidanja za oblik diobenog vretena. Dobivene rezultate planiramo usporediti s eksperimentalno određenim oblicima koje su dobili naši suradnici. Teorijska predviđanja dobivena ovim modelom, zajedno s eksperimentima, trebala bi odgovoriti na pitanje kolike sile djeluju u diobenom vretenu.The mitotic spindle is a cellular structure which is responsible for the partition of genetic material when a cell divides into two daughter cells. It is comprised of microtubules and accompanying proteins. Forces and torques play a key role in the functioning of the spindle, for they are chiefly responsible for the movement of chromosomes and maintaining the overall shape of the spindle. This is facilitated by the elastic properties of microtubules. The forces and torques are, however, hard to determine with contemporary experimental techniques. In this theoretical research we develop a model for the balance of forces and torques in a mitotic spindle. Using a mean-field approximation we describe all microtubules in a mitotic spindle and the forces acting upon them. The model gives a prediction for the shape of the spindle. The results are to be matched to experimental imaging done by our associates, with the aim of answering what magnitude of forces and torques act in mitotic spindles
Inflöde-bearbetning-utflöde : En studie om språk- och kunskapsutvecklande arbetssätt i internationella klasser.
No full textLanguage is the basis for all communication. Man needs a rich and nuanced language to understand and be understood. With a new language is a new culture, a new identity and a new need to be included in a community. Language develops only if it is used. The use of the language through conversation, reading and writing, working in various forms, gives the student capability to process the inflow of a future outflow. Arian Asinger is the author of this essay written at Södertörn University spring semester 2009. Instructor for the paper has been Per Sundgren. The essay has been named "Inflow - processing - output. A study of language- and knowledge based development approach in international classes". This work puts forward four teachers teaching methods in international classes in a school in central Sweden. With international classes meant preparation classes to newly arrived refugees and immigrants with a different mother tongue than Swedish. The main purpose of this study is to present the teaching methods of research considers the promotion of pupils' learning and language skills development. This has been lodged against the teachers working in reality and what teaching methods they use. The material is collected from a qualitative research through interviews. The result is then analyzed against previous research which shows differences in teaching methods and educational philosophy which might depend on teachers' educational background in the subject Swedish as a second language
Inflöde-bearbetning-utflöde : En studie om språk- och kunskapsutvecklande arbetssätt i internationella klasser.
No full textLanguage is the basis for all communication. Man needs a rich and nuanced language to understand and be understood. With a new language is a new culture, a new identity and a new need to be included in a community. Language develops only if it is used. The use of the language through conversation, reading and writing, working in various forms, gives the student capability to process the inflow of a future outflow. Arian Asinger is the author of this essay written at Södertörn University spring semester 2009. Instructor for the paper has been Per Sundgren. The essay has been named "Inflow - processing - output. A study of language- and knowledge based development approach in international classes". This work puts forward four teachers teaching methods in international classes in a school in central Sweden. With international classes meant preparation classes to newly arrived refugees and immigrants with a different mother tongue than Swedish. The main purpose of this study is to present the teaching methods of research considers the promotion of pupils' learning and language skills development. This has been lodged against the teachers working in reality and what teaching methods they use. The material is collected from a qualitative research through interviews. The result is then analyzed against previous research which shows differences in teaching methods and educational philosophy which might depend on teachers' educational background in the subject Swedish as a second language
Industrial Informatics: Emerging Trends and Applications in the Era of Big Data and AI
No full textIndustrial informatics is a rapidly developing scientific field that deals with the knowledge-based automation of industrial design and manufacturing processes. In the last decade, industrial informatics has been strongly influenced by the rapid rise of data-based technologies such as Data Science, Big Data, and artificial intelligence. The goal of this paper is to provide a literature review of academic research analyzing the extensive spectrum of industrial informatics. Articles indexed in Scopus with the term “Industrial Informatics” in the title, abstract, or keywords were extracted since the term emerged in the 1990s, over a period of 29 years. The main journals, conferences, authors and countries were studied using bibliometric analysis. Text mining using VosViewer was used to extract the thematic groups of research related to industrial informatics, which are as follows: (i) Internet of Things, (ii) machine learning, (iii) engineering education, (iv) cyber–physical systems, and (v) embedded systems. We also found that China, Germany, and Brazil dominate research in industrial computing. The results showed that research in industrial informatics is related to the emergence of new methods and tools, and is nowadays shifting towards the application of intelligent methods such as machine learning and Big Data
Roman primacy and the development of the synodal institution in the period of the Arian controversy
No full textThe object of this study is process of evolution of church organization in the 4th century, especially the relationships between Roman primacy and synodal institution in the epoch of the Arian controversy. The author examines evolution of the institution of the Roman synod and practice of participation of the Roman See in church councils outside Rome, focusing on the unsuccessful attempt to convene the general council in Rome in 382. Analysis of historical data shows that the ability of the Roman see to organize in a short time a representative council (mainly of the Italian bishops) allowed Rome to claim for a special status within the church communion. In the same time the Roman See did not become in the 4th century the center of conciliar activity at the universal level. Participation of Rome in Ecumenical and Western councils was quite passive. In the second part of the paper the author attempts to reconstruct various models of church organization, which were typical for the western and the eastern episcopate in the 4th century. The author concludes that the real initiator of the development of universal primacy of Rome was not originally the pope, but the western episcopate (council of Serdica, 343). In the second part of the 4th century pope Damasus developed this conception, putting the principle of primacy of the Roman See as the chair of Peter above principle of synodal consensus. At the same time eastern bishops considered the Roman chair as the center of the West, rather than the head of the whole Church. Sometimes they invited bishop of Rome and other western bishops to act as arbiters in the eastern conflicts, but more often they defended the idea of full autonomy of the East
Predictive Maintenance in Industry 4.0 for the SMEs: A Decision Support System Case Study Using Open-Source Software
No full textPredictive maintenance is one of the most important topics within the Industry 4.0 paradigm. We present a prototype decision support system (DSS) that collects and processes data from many sensors and uses machine learning and artificial intelligence algorithms to report deviations from the optimal process in a timely manner and correct them to the correct parameters directly or indirectly through operator intervention or self-correction. We propose to develop the DSS using open-source R packages because using open-source software such as R for predictive maintenance is beneficial for small and medium enterprises (SMEs) as it provides an affordable, adaptable, flexible, and tunable solution. We validate the DSS through a case study to show its application to SMEs that need to maintain industrial equipment in real time by leveraging IoT technologies and predictive maintenance of industrial cooling systems. The dataset used was simulated based on the information on the indicators measured as well as their ranges collected by in-depth interviews. The results show that the software provides predictions and actionable insights using collaborative filtering. Feedback is collected from SMEs in the manufacturing sector as potential system users. Positive feedback emphasized the advantages of employing open-source predictive maintenance tools, such as R, for SMEs, including cost savings, increased accuracy, community assistance, and program customization. However, SMEs have overwhelmingly voiced comments and concerns regarding the use of open-source R in their infrastructure development and daily operations
Oblique circle method for measuring the curvature and twist of mitotic spindle microtubule bundles
No full textThe highly ordered spatial organization of microtubule bundles in the mitotic spindle is crucial for its proper functioning. The recent discovery of twisted shapes of microtubule bundles and spindle chirality suggests that the bundles extend along curved paths in three dimensions, rather than being confined to a plane. This, in turn, implies that rotational forces, i.e., torques, exist in the spindle in addition to the widely studied linear forces. However, studies of spindle architecture and forces are impeded by a lack of a robust method for the geometric quantification of microtubule bundles in the spindle. In this work, we describe a simple method for measuring and evaluating the shapes of microtubule bundles by characterizing them in terms of their curvature and twist. By using confocal microscopy, we obtain three-dimensional images of spindles, which allows us to trace the entire microtubule bundle. For each traced bundle, we first fit a plane and then fit a circle lying in that plane. With this robust method, we extract the curvature and twist, which represent the geometric information characteristic for each bundle. As the bundle shapes reflect the forces within them, this method is valuable for the understanding of forces that act on chromosomes during mitosis
Biographies of ancient and modern celebrated freethinkers : reprinted from an English work, entitled "Half-hours with the freethinkers" /
No full textOn cover: Half hours with freethinkers.Thomas Hobbes.--Lord Bolingbroke.--Condorcet.--Spinoza.--Anthony Collins.--Des Cartes.--M. de Voltaire.--John Toland.--Compte de Volney.--Charles Blount.--Percy Byssche Shelley.--Claude Arian Helvetius.--Frances W. D'Arusmont.--Epicurus.--Zeno.--Matthew Tindal.--David Hume.--Dr. Thomas Burnet.--Thomas Paine.--Baptiste de Mirabaud.--Baron d'Holbach.--Robert Taylor.--Joseph Barker.Mode of access: Internet
Sustained epidermal growth factor receptor levels and activation by tethered ligand binding enhances osteogenic differentiation of multi-potent marrow stromal cells
No full textAuthor Manuscript 2011 April 29.Epidermal growth factor receptor (EGFR)-mediated signaling helps regulate bone development and healing through its effects on osteogenic cells. Here, we show how EGFR activity and osteogenic differentiation responses in primary human bone marrow-derived multipotent stromal cells (MSCs) are influenced by presenting covalently tethered epidermal growth factor (tEGF) on the culture substratum, a presentation mode that reduces EGFR internalization and restricts signaling to the cell surface. In both absence and presence of tEGF, MSCs increase expression levels of EGFR and its heterodimerization partner HER2 during the course of osteogenic differentiation. tEGF substrata increased levels of phosphorylated EGFR and phosphorylated extracellular regulated kinase (ERK) compared to control substrata, and these elevations were associated with a twofold enhancement of MSC alkaline phosphatase activity at day 7 and matrix mineralization at day 21. Surprisingly, addition of soluble EGF (sEGF) to cells cultured on tEGF substrata reduces osteogenic differentiation, even though EGFR signaling is more strongly activated in acute, short-term manner by sEGF treatment than by tEGF treatment. A striking concomitant result of the sEGF effects is near-complete downregulation of EGFR and HER2, demonstrating that the tEGF/EGFR interaction is dynamically reversible even though temporally sustained. Taken together, our results show that enhanced MSC osteogenic differentiation corresponds to a sustained combination of receptor expression and ligand presentation, both of which are maintained by tEGF.National Institutes of Health (U.S.) (Grant R01-GM059870-07)National Institutes of Health (U.S.) (Grant R01-DE 019523-10)National Institutes of Health (U.S.) (Grant P40RR017447)United Negro College Fund (Merck Postdoctoral Fellowship)Georgia Institute of Technology (FACES Fellowship)National Center for Research Resources (U.S.) (Grant P40RR017447
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