434 research outputs found
Temperature affects the silicate morphology in a diatom
No full textTemperature affects the silicate morphology in a diatom Javaheri, N.; Dries, R.M.; Burson, A.M.; Stal, L.J.; Sloot, P.M.A.; Kaandorp, J.A. Published in: Scientific Reports DOI: 10.1038/srep11652 Link to publication Citation for published version (APA): Javaheri, N., Dries, R., Burson, A., Stal, L. J., Sloot, P. M. A., & Kaandorp, J. A. (2015). Temperature affects the silicate morphology in a diatom. Scientific Reports, 5, [11652]. https://doi.org/10.1038/srep11652 General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. , and 23 °C ). We observed three distinct temperature-dependent growth phases. The morphology of silica was investigated using scanning electron microscopy followed by image analysis and supervised learning. The silica in the valves of the same species showed different structures: a mesh-like pattern in silicon-rich cultures and a treelike pattern in silicon-limited cultures. Moreover, temperature affected this silica pattern, especially in silicon-limited cultures. We conclude that cells grown at 14 °C and 18 °C divide more successfully in Si-limited conditions by developing a tree-like pattern (lower silicification)
Uuden niobimikroseostetun keskihiilisen teräksen suunnittelu, termomekaaninen käsittely ja induktiokarkaisu
No full textAbstractThis thesis has been made within the European Industrial Doctorate (EID) project called Mathematics and Materials Science for Steel Production and Manufacturing, abbreviated as MIMESIS, which has five partners: EFD Induction in Norway; SSAB, Outokumpu, and the University of Oulu in Finland; and Weierstrass Institute for Applied Analysis and Stochastics (WIAS) in Germany. The main aim of this work was to develop a steel composition and processing route suitable for making a slurry transportation pipeline with the aid of induction hardening, and to characterize the phase transformations and microstructures involved in the various stages of the processing route.A novel steel chemistry was designed based on metallurgical principles assisted by computational thermodynamics and kinetics. The designed composition is a medium-carbon, low-alloy steel microalloyed with niobium, in wt.% 0.40 C, 0.20 Si, 0.25 Mn, 0.50 Mo, 0.90 Cr, and 0.012 Nb. This was subsequently cast, thermomechanically rolled on a laboratory rolling mill to two bainitic microstructures, and finally subjected to the thermal cycles predicted to be encountered with the internal induction hardening of a typical pipe geometry. The phase transformations and microstructures found at various stages of the simulated production process have been characterized and algorithms developed to enable the optimization of microstructure and hardness through the pipe wall thickness.Original papersOriginal papers are not included in the electronic version of the dissertation.Javaheri, V., Porter, D., & Kuokkala, V.-T. (2018). Slurry erosion of steel – Review of tests, mechanisms and materials. Wear, 408–409, 248–273. https://doi.org/10.1016/j.wear.2018.05.010Self-archived versionJavaheri, V., Nyyssönen, T., Grande, B., & Porter, D. (2018). Computational design of a novel medium-carbon, low-alloy steel microalloyed with niobium. Materials Engineering and Performance, 27, 2978–2992. https://doi.org/10.1007/s11665-018-3376-9Self-archived versionJavaheri, V., Khodaie, N., Kaijalainen, A., & Porter, D. (2018). Effect of niobium and phase transformation temperature on the microstructure and texture of a novel 0.40% C thermomechanically processed steel. Materials Characterization, 142, 295–308. https://doi.org/10.1016/j.matchar.2018.05.056Self-archived versionJavaheri, V., Kolli, S., Grande, B., & Porter, D. (2019). Insight into the induction hardening behavior of a new 0.40% C microalloyed steel: Effects of initial microstructure and thermal cycles. Materials Characterization, 149, 165–183. https://doi.org/10.1016/j.matchar.2019.01.029Self-archived versionJavaheri, V., Pohjonen, A., Asperheim, J.I., Ivanov, D., & Porter, D. (2019). Physically based modelling, characterization and design of an induction hardening process for a new slurry pipeline steel. Materials and Design, 182, 108047. https://doi.org/10.1016/j.matdes.2019.108047Self-archived versionTiivistelmäTämä väitöskirja on tehty osana Euroopan teollisuustohtori (European Industrial Doctorate, EID) -ohjelmaa projektissa eli Matematiikka ja materiaalitiede teräksen valmistuksessa ja käytössä (Mathematics and Materials Science for Steel Production and Manufacturing, MIMESIS). Ohjelmassa on viisi partneria: EFD Induction Norjasta; SSAB, Outokumpu ja Oulun yliopisto Suomesta; ja Weierstrass Institute for Applied Analysis and Stochastics (WIAS) Saksasta. Työn päätavoitteina oli kehittää teräksen koostumusta ja prosessointireittiä, jotka soveltuvat lietteen kuljetusputken valmistukseen induktiokarkaisun avulla, sekä karakterisoida prosessin eri vaiheiden aikana tapahtuvat faasimuutokset ja mikrorakenteet.Uusi teräskoostumus suunniteltiin metallurgisten periaatteiden pohjalta hyödyntämällä laskennallista termodynamiikkaa ja kinetiikkaa. Suunniteltu teräs on niobilla mikroseostettu, matalaseosteinen ja keskihiilinen, eli painoprosentteina 0,40 C, 0,20 Si, 0,25 Mn, 0,50 Mo, 0,90 Cr ja 0,012 Nb. Teräs valettiin, valssattiin ja jäähdytettiin termomekaanisesti laboratoriovalssaimella kahdeksi bainiittiseksi mikrorakenteeksi ja lopulta altistettiin lämpösykleille, joiden ennustettiin olevan tyypillisiä sisäisesti induktiokarkaistulle teräsputkelle. Simuloidun tuotantoprosessin eri vaiheissa havaitut faasimuutokset ja mikrorakenteet on karakterisoitu. Sen lisäksi on kehitetty algoritmit, jotka mahdollistavat mikrorakenteen ja kovuuden optimoinnin putken seinämän paksuuden läpi.OsajulkaisutOsajulkaisut eivät sisälly väitöskirjan elektroniseen versioon.Javaheri, V., Porter, D., & Kuokkala, V.-T. (2018). Slurry erosion of steel – Review of tests, mechanisms and materials. Wear, 408–409, 248–273. https://doi.org/10.1016/j.wear.2018.05.010Rinnakkaistallennettu versioJavaheri, V., Nyyssönen, T., Grande, B., & Porter, D. (2018). Computational design of a novel medium-carbon, low-alloy steel microalloyed with niobium. Materials Engineering and Performance, 27, 2978–2992. https://doi.org/10.1007/s11665-018-3376-9Rinnakkaistallennettu versioJavaheri, V., Khodaie, N., Kaijalainen, A., & Porter, D. (2018). Effect of niobium and phase transformation temperature on the microstructure and texture of a novel 0.40% C thermomechanically processed steel. Materials Characterization, 142, 295–308. https://doi.org/10.1016/j.matchar.2018.05.056Rinnakkaistallennettu versioJavaheri, V., Kolli, S., Grande, B., & Porter, D. (2019). Insight into the induction hardening behavior of a new 0.40% C microalloyed steel: Effects of initial microstructure and thermal cycles. Materials Characterization, 149, 165–183. https://doi.org/10.1016/j.matchar.2019.01.029Rinnakkaistallennettu versioJavaheri, V., Pohjonen, A., Asperheim, J.I., Ivanov, D., & Porter, D. (2019). Physically based modelling, characterization and design of an induction hardening process for a new slurry pipeline steel. Materials and Design, 182, 108047. https://doi.org/10.1016/j.matdes.2019.108047Rinnakkaistallennettu versioAcademic dissertation to be presented with the assent of the Doctoral Training Committee of Technology and Natural Sciences of the University of Oulu for public defence in the OP auditorium (L10), Linnanmaa, on 1 November 2019, at 12 noonAbstract
This thesis has been made within the European Industrial Doctorate (EID) project called Mathematics and Materials Science for Steel Production and Manufacturing, abbreviated as MIMESIS, which has five partners: EFD Induction in Norway; SSAB, Outokumpu, and the University of Oulu in Finland; and Weierstrass Institute for Applied Analysis and Stochastics (WIAS) in Germany. The main aim of this work was to develop a steel composition and processing route suitable for making a slurry transportation pipeline with the aid of induction hardening, and to characterize the phase transformations and microstructures involved in the various stages of the processing route.
A novel steel chemistry was designed based on metallurgical principles assisted by computational thermodynamics and kinetics. The designed composition is a medium-carbon, low-alloy steel microalloyed with niobium, in wt.% 0.40 C, 0.20 Si, 0.25 Mn, 0.50 Mo, 0.90 Cr, and 0.012 Nb. This was subsequently cast, thermomechanically rolled on a laboratory rolling mill to two bainitic microstructures, and finally subjected to the thermal cycles predicted to be encountered with the internal induction hardening of a typical pipe geometry. The phase transformations and microstructures found at various stages of the simulated production process have been characterized and algorithms developed to enable the optimization of microstructure and hardness through the pipe wall thickness.Tiivistelmä
Tämä väitöskirja on tehty osana Euroopan teollisuustohtori (European Industrial Doctorate, EID) -ohjelmaa projektissa eli Matematiikka ja materiaalitiede teräksen valmistuksessa ja käytössä (Mathematics and Materials Science for Steel Production and Manufacturing, MIMESIS). Ohjelmassa on viisi partneria: EFD Induction Norjasta; SSAB, Outokumpu ja Oulun yliopisto Suomesta; ja Weierstrass Institute for Applied Analysis and Stochastics (WIAS) Saksasta. Työn päätavoitteina oli kehittää teräksen koostumusta ja prosessointireittiä, jotka soveltuvat lietteen kuljetusputken valmistukseen induktiokarkaisun avulla, sekä karakterisoida prosessin eri vaiheiden aikana tapahtuvat faasimuutokset ja mikrorakenteet.
Uusi teräskoostumus suunniteltiin metallurgisten periaatteiden pohjalta hyödyntämällä laskennallista termodynamiikkaa ja kinetiikkaa. Suunniteltu teräs on niobilla mikroseostettu, matalaseosteinen ja keskihiilinen, eli painoprosentteina 0,40 C, 0,20 Si, 0,25 Mn, 0,50 Mo, 0,90 Cr ja 0,012 Nb. Teräs valettiin, valssattiin ja jäähdytettiin termomekaanisesti laboratoriovalssaimella kahdeksi bainiittiseksi mikrorakenteeksi ja lopulta altistettiin lämpösykleille, joiden ennustettiin olevan tyypillisiä sisäisesti induktiokarkaistulle teräsputkelle. Simuloidun tuotantoprosessin eri vaiheissa havaitut faasimuutokset ja mikrorakenteet on karakterisoitu. Sen lisäksi on kehitetty algoritmit, jotka mahdollistavat mikrorakenteen ja kovuuden optimoinnin putken seinämän paksuuden läpi
Strain rate and mechanical stability in determining deformation behavior of beta Ti alloys
No full textThe effect of strain rate on flow behaviors of three beta Ti alloys with different beta phase stability was studied. The alloys were subjected to compression deformation at four strain rates ranging from 7 × 10−5 to 7 × 10−2 s−1 at room temperature. Microstructure evolution was characterized using laser scanning microscopy and electron backscattered diffraction methods. The effect of strain rate on the yield strength was found to vary between the alloys increasing with increased stability. The microstructural observations showed that the alloys exhibited different deformation mechanisms: deformation induced martensite formation, twinning and slip band formation. The strain hardening exponent (n) depended on the deformation mechanism, i.e., the stability. In the low and intermediate stability alloys showing martensite formation and combination of the deformation mechanisms respectively, n was about 0.07 independent of strain rate. In the alloy with the highest stability it was only 0.01 when the deformation mechanism was dislocation slip at low strain rates but increased significantly to ≈0.13 at high strain rates when also twinning occurred. The strain rate sensitivity factor (m) was about 0.014 and 0.017 for the low and intermediate stability alloy respectively independent of strain, but very low ≈ 0.002 for the highest stability alloy though increasing to ≈ 0.011 with increasing strain. Based on the experiments, the stability-strain rate-mechanism diagram was introduced to predict the effect of phase stability and strain rate on the deformation mechanism of beta Ti alloys
Prevalence and etiologies of macrosomia and low birth weight in 1000 neonates at Javaheri hospital in Tehran
No full textBackground and aimLow birth weight is one of the important problems in many societies especially developing ones. The survival rate of infants has a direct relationship with their birth weight. The aim of This cross-sectional study was to determine the prevalence and etiologies of Prevalence and etiologies of macrosomia and low birth weight in 1000 neonates of low birth weight (LBW) as well as macrosomia and their possible etiologies. Materials and methods1000 neonates were sequentially selected by nonrandom sampling method over 6 months in 2006 at Javaheri hospital in Tehran. By reviewing their medical records, the birth weight of the subjects and other variables of the study were assessed. Independent T and Qui-square tests were used for data analysis. FindingsIn this study cross sectional- study mean weigh of the neonates was 2957±910 gr. 7% of the subjects suffered from low birth weight (mean=2371±260) and 3% had macrosomia (mean=4247±240). A significant relationship was found between birth weight and gestational age of the neonates. 10% of mothers having neonates with macrosomia had gestational diabetes. The etiology of macrosomia was not known in most cases. The most common causes of low birth weight included premature rupture of membranes, twin gestation, fetal distress and maternal conditions. ConclusionAppropriate gestational care, risk factor detection before pregnancy and improvement of quantity as well as quality of maternal child health services can reduce the number of low- birth-weight infants. Keywords: Macrosomia, Low birth weight, Prevalence, Etiology. *Corresponding Author: Dr. Masoomeh, Hematyar. Islamic Azad University, College of Medicine, Tehran, Iran. E-mail: [email protected]
Filtering in Finance.
No full textIn this article we present an introduction to various Filtering algorithms and some of their applications to the world of Quantitative Finance. We shall first mention the fundamental case of Gaussian noises where we obtain the well-known Kalman Filter. Because of common nonlinearities, we will be discussing the Extended Kalman Filter.Commodity Prices; Term Structure; Stock Prices; Kalman Filter;
Hypercyclic abelian semigroup of matrices on Cn and Rn and k-transitivity (k ≥ 2)
No full textWe prove that the minimal number of matrices on Cn required to forma hypercyclic abelian semigroup on Cn is n+1. We also prove that theaction of any abelian semigroup finitely generated by matrices on Cnor Rn is never k-transitive for k 2. These answer questions raised byFeldman and Javaheri
Generating CRISPR-dCas9 System in Clostridium difficile Bacteria
No full textThe increasing incidence of Clostridium difficile-associated disease, and its resistance to a number of antibiotics, highlight the need for additional countermeasures. The main issue that hampers the design of antibiotics is a lack of appropriate tools to study the molecular biology of C.difficile in great detail. Insight into the function of DNA replication genes and the protein they encode might eventually lead to the development of specific inhibitors that can be exploited as drugs. By means of CRISPR-dCas9 system, we designed and engineered a construct that is capable of targeting specific replication genes and silence those genes. Our design is composed of a nuclease-deactivated Cas9 (dCas9) protein and a customized single-guided RNA (sgRNA) with a 20-basepair complementary region to target replication genes in C.difficile. Co-expression of dCas9 and sgRNA can efficiently block transcription by interfering with DNA replication process. We developed a set of conjugative plasmids that carries appropriate Pveg-sgRNA targets to repress CD0001 (dnaA) and CD1214 (spo0A) genes in C.difficile. We also built a construct with dCas9 and its inducible promoter (Pcpr) that can be conjugated into C.difficile. Once both constructs are transformed into C.difficile 630 erm, we will be able to analyze and detect potential phenotypes expressed in the presence of dCas9.Biomedical ElectronicsBiomedical EngineeringMechanical, Maritime and Materials Engineerin
The effect of phase stability on the grain growth behavior of beta titanium alloys
No full textAbstractThe grain growth kinetics of two beta titanium alloys, Ti–4733 and Ti–5553 was studied over a temperature range of 850 °C–1000 °C. The more stable alloy i.e. Ti–4733, showed a smaller average grain size and slower growth rate compared to Ti–5553 at a same annealing condition. The results showed that the uniformity of grain size decreased initially dawn to a minimum and then increased with increasing temperature. The grain growth exponent (n) and activation energy (Q) were calculated and it was revealed that n is mainly affected by temperature and Q is generally influenced by time. The n value for Ti–4733 was found to be lower than that for Ti–5553 while a higher Q was calculated for Ti–4733. The lower n values and the higher Q were attributed to the solute drag effect and the high Mo content with low diffusivity in Ti matrix.Abstract
The grain growth kinetics of two beta titanium alloys, Ti–4733 and Ti–5553 was studied over a temperature range of 850 °C–1000 °C. The more stable alloy i.e. Ti–4733, showed a smaller average grain size and slower growth rate compared to Ti–5553 at a same annealing condition. The results showed that the uniformity of grain size decreased initially dawn to a minimum and then increased with increasing temperature. The grain growth exponent (n) and activation energy (Q) were calculated and it was revealed that n is mainly affected by temperature and Q is generally influenced by time. The n value for Ti–4733 was found to be lower than that for Ti–5553 while a higher Q was calculated for Ti–4733. The lower n values and the higher Q were attributed to the solute drag effect and the high Mo content with low diffusivity in Ti matrix
On a property of plane curves
No full textAbstractLet γ:[0,1]→[0,1]2 be a continuous curve such that γ(0)=(0,0), γ(1)=(1,1), and γ(t)∈(0,1)2 for all t∈(0,1). We prove that, for each n∈N, there exists a sequence of points Ai, 0⩽i⩽n+1, on γ such that A0=(0,0), An+1=(1,1), and the sequences π1(AiAi+1→) and π2(AiAi+1→), 0⩽i⩽n, are positive and the same up to order, where π1, π2 are projections on the axes
Biosilicification mechanisms: An investigation using computational modeling and experimentation
No full textBiomineralization is the deposition of minerals by living organisms. The question of how and by which mechanisms nature has developed biominerals can be addressed via several complementary approaches. This dissertation investigates these mechanisms from several perspectives using both computational and experimental methods. The emphasis of this work is on silicification in diatoms, eukaryotic unicellular algae, with a complex biosilica structure. One of the approaches taken in this thesis is to study the events that lead to silica formation, such as reactions and the transportation of chemical components. For this purpose a computational model with several cell compartments was designed, on which parameter estimation methods were applied. This model explains the different regimes in silicon uptake by cells that were previously observed in experiments. The presented computational framework was also used to investigate the silicon uptake regulation in close relation with other cell processes such as silicification. Moreover, an experiment was performed on the same species of diatom under different temperatures and different levels of silicic acid supply to address the effect of physical and chemical control on the silica morphology. Using SEM imaging and machine learning analysis on the data extracted from images of silica, it was concluded that the different temperatures changed the cell population dynamics and, consequently, the silica pattern
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