323,232 research outputs found
Hierarchy of sigmoid growth models - towards justification of sigmoid treatment of nucleation data
Get PDFIn the poster we provide a brief introduction to the general problem of fitting the nucleation data – the so called N-t curves, with an hierarchy of sigmoid growth models [1] (HSGM). The special focus of such a treatment is to be on the principal mechanisms of nucleation that could give raise to a positive feedback as demonstrated in the supelinear regime (before the inflection point) of N-t curves.
In the introductory part, we continue the mothodological development of the HSGM by identifying a novel quantitative criterium for “sigmoidness” based on the idea of catastrophe. Here we will use examples of population dynamics.
In the course of implementing the HSGM-approach we revisit several typical datasets reporting sigmoid data [2] and more. A novel tool used in the course of this revisit is the so called Multiple Fitting of a Single Dataset (MFSDS) as first proposed in [3]. Here we also make further refinements of the approach by including datasets generated by the Richards model and Cellular Automata.
In collaboration with: Daniela Tsekova and Feyzim Hodzhaoglu
References
[1] V. Kleshtanova, V. Ivanov, F. Hodzhaoglu, J. Prieto, and V. Tonchev, Heterogeneous Substrates Modify Non-Classical Nucleation Pathways: Reanalysis of Kinetic Data from the Electrodeposition of Mercury on Platinum Using Hierarchy of Sigmoid Growth Models, Crystals 13, 1690 (2023).
[2] C. N. Nanev and V. D. Tonchev, Sigmoid kinetics of protein crystal nucleation, Journal of Crystal Growth 427, 48 (2015).
[3] V. V. Ivanov, C. Tielemann, K. Avramova, S. Reinsch, and V. Tonchev, Modelling crystallization: When the normal growth velocity depends on the supersaturation, Journal of Physics and Chemistry of Solids 181, 111542 (2023)
Hierarchy of sigmoid growth models - towards justification of sigmoid treatment of nucleation data
Get PDFIn the poster we provide a brief introduction to the general problem of fitting the nucleation data – the so called N-t curves, with an hierarchy of sigmoid growth models [1] (HSGM). The special focus of such a treatment is to be on the principal mechanisms of nucleation that could give raise to a positive feedback as demonstrated in the supelinear regime (before the inflection point) of N-t curves.
In the introductory part, we continue the mothodological development of the HSGM by identifying a novel quantitative criterium for “sigmoidness” based on the idea of catastrophe. Here we will use examples of population dynamics.
In the course of implementing the HSGM-approach we revisit several typical datasets reporting sigmoid data [2] and more. A novel tool used in the course of this revisit is the so called Multiple Fitting of a Single Dataset (MFSDS) as first proposed in [3]. Here we also make further refinements of the approach by including datasets generated by the Richards model and Cellular Automata.
In collaboration with: Daniela Tsekova and Feyzim Hodzhaoglu
References
[1] V. Kleshtanova, V. Ivanov, F. Hodzhaoglu, J. Prieto, and V. Tonchev, Heterogeneous Substrates Modify Non-Classical Nucleation Pathways: Reanalysis of Kinetic Data from the Electrodeposition of Mercury on Platinum Using Hierarchy of Sigmoid Growth Models, Crystals 13, 1690 (2023).
[2] C. N. Nanev and V. D. Tonchev, Sigmoid kinetics of protein crystal nucleation, Journal of Crystal Growth 427, 48 (2015).
[3] V. V. Ivanov, C. Tielemann, K. Avramova, S. Reinsch, and V. Tonchev, Modelling crystallization: When the normal growth velocity depends on the supersaturation, Journal of Physics and Chemistry of Solids 181, 111542 (2023)
The autophagy regulators Ambra1 and Beclin 1 are required for adult neurogenesis in the brain subventricular zone
Get PDFAutophagy is a conserved proteolytic mechanism required for maintaining cellular homeostasis. The role of this process in vertebrate neural development is related to metabolic needs and stress responses, even though the importance of its progression has been observed in a number of circumstances, both in embryonic and in postnatal differentiating tissues. Here we show that the proautophagic proteins Ambra1 and Beclin 1, involved in the initial steps of autophagosome formation, are highly expressed in the adult subventricular zone (SVZ), whereas their downregulation in adult neural stem cells in vitro leads to a decrease in cell proliferation, an increase in basal apoptosis and an augmented sensitivity to DNA-damage-induced death. Further, Beclin 1 heterozygosis in vivo results in a significant reduction of proliferating cells and immature neurons in the SVZ, accompanied by a marked increase in apoptotic cell death. In sum, we propose that Ambra1- and Beclin 1-mediated autophagy plays a crucial role in adult neurogenesis, by controlling the survival of neural precursor cells
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
A proof of the Jungnickel-Tonchev conjecture on quasi-multiple quasi-symmetric designs
No full textA proof of the following conjecture of Jungnickel and Tonchev on quasi-multiple quasi-symmetric designs is given: Let D be a design whose parameter set (v',b',r',k',λ') equals (v,sv,sk,k, sλ) for some positive integer s and for some integers v,k,λ that satisfy λ(v-1) = k(k-1) (that is, these integers satisfy the parametric feasibility conditions for a symmetric (v,k,λ)-design). Further assume that D is a quasi-symmetric design, that is D has at most two block intersection numbers. If (k,λ (s-1)) = 1, then the only way D can be constructed is by taking multiple copies of a symmetric (v,k,λ)-design
LiNbO<sub>3</sub> optical waveguides deposited on sapphire by electric-field-assisted pulsed laser deposition
No full textOriented LiNbO3 films have been grown on sapphire (1 1 0 2) substrates by low electric-field-assisted pulsed laser deposition. KrF excimer laser (248 nm) has been utilized for the ablation of monocrystalline stoichiometric target. The deposition was performed at all substrate temperatures in the range of 550–800°C in an oxygen atmosphere. The ablation threshold of 2.5 J/cm2 for the monocrystalline target was determined from the experimental results presenting ablation rate vs. laser fluence dependence. Electro-optical properties of these films appeared to be strongly dependent on the process parameters (substrate temperature, oxygen partial pressure, electric field), demonstrating the importance of the epitaxial growth control during the deposition. The films structure and morphology were characterized by XRD and AFM, respectively. The waveguide properties of the films were studied experimentally
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Waveguide Mach-Zehnder Intensity Modulator produced via Proton Exchange Technology in LiNbO3
No full textElectro-optic effect in proton exchanged LiNbO3 and LiTaO3 waveguides
No full textElectro-optic properties of proton-exchanged (PE) waveguide layers in LiTaO3 and LiNbO3 are studied and related to their optical characteristics. The proton-exchange process induces a degradation of the electro-optic activity in both types of waveguides, PE LiNbO3 and PE LiTaO3. The measured electrooptic effect is close to the detection sensitivity even when the exchange regime is performed at low temperatures for short periods of time, The PE samples have been annealed (APE waveguides) and the changes of their tau(33) electro-optic coefficient has been followed at successively higher temperatures and periods of time, Subjected to annealing at temperatures between 265-420 degrees C, the LiTaO3 layers show a partially recovered tau(33) coefficient, the recovering being different for quick and slow cooling of the samples, In thin APE LiNbO3 waveguiding layers a restoration of tau(33) UP to 75% of the bulk value is observed due to the annealing at temperatures between 200-340 degrees C
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