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Search Results: 1 - 10 of 3431 matches for " Sonja-Michaela Gross-Barsnick "
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Influencing the Crystallization of Glass-Ceramics by Ultrashort Pulsed Laser Irradiation after Nucleation  [PDF]
Florian Senn, Ronald Holtz, Sonja-Michaela Gross-Barsnick, Uwe Reisgen
New Journal of Glass and Ceramics (NJGC) , 2018, DOI: 10.4236/njgc.2018.81001
Abstract: An ultra-fast laser with central wavelength at 1064nm and 10ps pulse durationwas used to tightly focus laser radiationwith a microscope objective inside the volume of nucleated Lithium Aluminosilicate (LAS) glass-ceramic. The nonlinear absorptionof the LAS glass-ceramic was measuredfor different laser parameters and a thermal simulation was performed to determine the temperature field inside the laser-modified area. After laser processing,the samples were crystallized in a furnace and the effect of the laser-induced modifications on the microstructure was analyzed with SEM. The SEM analysis shows an increase in the length and size of whisker-shaped?β-spodumene crystals in the laser-modified area. By increasing the dimension of these whisker-shaped crystals, the flexural strength of LAS can be improved locally.Firstfour-point bending flexural tests were performed to examine the influence on the mechanical properties.
Combinatorial degree bound for toric ideals of hypergraphs
Elizabeth Gross,Sonja Petrovi?
Mathematics , 2012,
Abstract: Associated to any hypergraph is a toric ideal encoding the algebraic relations among its edges. We study these ideals and the combinatorics of their minimal generators, and derive general degree bounds for both uniform and non-uniform hypergraphs in terms of balanced hypergraph bicolorings, separators, and splitting sets. In turn, this provides complexity bounds for algebraic statistical models associated to hypergraphs. As two main applications, we recover a well-known complexity result for Markov bases of arbitrary 3-way tables, and we show that the defining ideal of the tangential variety is generated by quadratics and cubics in cumulant coordinates.
PHCpack in Macaulay2
Elizabeth Gross,Sonja Petrovi?,Jan Verschelde
Mathematics , 2011,
Abstract: The Macaulay2 package PHCpack.m2 provides an interface to PHCpack, a general-purpose polynomial system solver that uses homotopy continuation. The main method is a numerical blackbox solver which is implemented for all Laurent systems. The package also provides a fast mixed volume computation, the ability to filter solutions, homotopy path tracking, and a numerical irreducible decomposition method. As the size of many problems in applied algebraic geometry often surpasses the capabilities of symbolic software, this package will be of interest to those working on problems involving large polynomial systems.
Goodness-of-fit for log-linear network models: Dynamic Markov bases using hypergraphs
Elizabeth Gross,Sonja Petrovi?,Despina Stasi
Statistics , 2014,
Abstract: Social networks and other large sparse data sets pose significant challenges for statistical inference, as many standard statistical methods for testing model fit are not applicable in such settings. Algebraic statistics offers a theoretically justified approach to goodness-of-fit testing that relies on the theory of Markov bases and is intimately connected with the geometry of the model as described by its fibers. Most current practices require the computation of the entire basis, which is infeasible in many practical settings. We present a dynamic approach to explore the fiber of a model, which bypasses this issue, and is based on the combinatorics of hypergraphs arising from the toric algebra structure of log-linear models. We demonstrate the approach on the Holland-Leinhardt $p_1$ model for random directed graphs that allows for reciprocated edges.
Maximum likelihood degree of variance component models
Elizabeth Gross,Mathias Drton,Sonja Petrovi?
Statistics , 2011,
Abstract: Most statistical software packages implement numerical strategies for computation of maximum likelihood estimates in random effects models. Little is known, however, about the algebraic complexity of this problem. For the one-way layout with random effects and unbalanced group sizes, we give formulas for the algebraic degree of the likelihood equations as well as the equations for restricted maximum likelihood estimation. In particular, the latter approach is shown to be algebraically less complex. The formulas are obtained by studying a univariate rational equation whose solutions correspond to the solutions of the likelihood equations. Applying techniques from computational algebra, we also show that balanced two-way layouts with or without interaction have likelihood equations of degree four. Our work suggests that algebraic methods allow one to reliably find global optima of likelihood functions of linear mixed models with a small number of variance components.
Expression pattern of matrix metalloproteinases in human gynecological cancer cell lines
Andrea Schr?pfer, Ulrike Kammerer, Michaela Kapp, Johannes Dietl, Sonja Feix, Jelena Anacker
BMC Cancer , 2010, DOI: 10.1186/1471-2407-10-553
Abstract: In total, cell lines from three endometrium carcinomas (Ishikawa, HEC-1-A, AN3 CA), three cervical carcinomas (HeLa, Caski, SiHa), three chorioncarcinomas (JEG, JAR, BeWo), two ovarian cancers (BG-1, OAW-42) and one teratocarcinoma (PA-1) were examined. The expression of MMPs was analyzed by RT-PCR, Western blot and gelatin zymography.We demonstrated that the cell lines examined can constitutively express a wide variety of MMPs on mRNA and protein level. While MMP-2, -11, -14 and -24 were widely expressed, no expression was seen for MMP-12, -16, -20, -25, -26, -27 in any of the cell lines. A broad range of 16 MMPs could be found in the PA1 cells and thus this cell line could be used as a positive control for general MMP experiments. While the three cervical cancer cell lines expressed 10-14 different MMPs, the median expression in endometrial and choriocarcinoma cells was 7 different enzymes. The two investigated ovarian cancer cell lines showed a distinctive difference in the number of expressed MMPs (2 vs. 10).Ishikawa, Caski, OAW-42 and BeWo cell lines could be the best choice for all future experiments on MMP regulation and their role in endometrial, cervical, ovarian or choriocarcinoma development, whereas the teratocarcinoma cell line PA1 could be used as a positive control for general MMP experiments.Tumor invasion and metastasis define malignancy and are the principal causes of cancer associated death. Tumor cells are surrounded by the extracellular matrix (ECM) comprising of proteoglycanes and non-proteoglycanic matrix components (collagen, laminin, fibronectin and elastin). Degradation of the extracellular matrix allows tumor cells to detach from the primary tumor mass, invade local tissue, intravasate, extravasate and build new metastatic formations [1]. Currently, four classes of proteinases are known as being capable of breaking down nearly all components of the extracellular matrix: serine proteinases, aspartatic proteases, cystein proteinases and matr
CD7 in acute myeloid leukemia: correlation with loss of wild-type CEBPA, consequence of epigenetic regulation
Sonja R?hrs, Michaela Scherr, Julia Romani, Margarete Zaborski, Hans G Drexler, Hilmar Quentmeier
Journal of Hematology & Oncology , 2010, DOI: 10.1186/1756-8722-3-15
Abstract: As already described for primary AML cells, the majority of AML cell lines tested were either C/EBPα+/CD7- or C/EBPα-/CD7+. However, the existence of isolated CD7+ cell lines expressing wild-type C/EBPα challenges the notion that C/EBPα acts as a unique repressor of CD7. Furthermore, ectopic expression of CEBPA did not reduce CD7 in CD7+ cells and knock-down of C/EBPα failed to induce CD7 in CD7- cells. In contrast, the DNA demethylating agent Aza-2'deoxycytidine triggered CD7 expression in CD7- AML and in T-cell lines suggesting epigenetic regulation of CD7. Bisulfite sequencing data confirmed that CpGs in the CD7 exon1 region are methylated in CD7- cell lines, and unmethylated in CD7+ cell lines.We confirmed an inverse correlation between the expression of wild-type CEBPA and of CD7 in AML cells. Our results contradict the hypothesis that C/EBPα acts as repressor for CD7, and instead show that epigenetic mechanisms are responsible for CD7 regulation, in AML cells as well as in T-cells, the typical CD7 expressing cell type.CCAAT/enhancer binding factor alpha (CEBPA), located on chromosome 19q13.1 encodes a transcription factor that is of importance for granulocytic differentiation [1]. C/EBPα is upregulated during myelomonocytic development and positively affects expression of granulocyte differentiation related genes such as the G-CSF receptor (GCSFR), myeloperoxidase and neutrophil elastase (ELA2) [2-4]. CEBPA mutations are found in 5 - 14% of acute myeloid leukemia (AML) cases [5]. C/EBPα mutant proteins block the effect of wild-type C/EBPα on target genes in a dominant-negative manner [6]. This might be the reason why patients with CEBPA mutations and those with a silenced CEBPA promoter are found in the same AML subclass according to gene expression profiling [7]. Also expression of the T-cell marker CD7 has been associated with CEBPA mutations and with CEBPA hypermethylation [7,8].CD7 is expressed in 30% of AML cases and CD7 positivity is linked with poor pro
Maternal Neurofascin-Specific Autoantibodies Bind to Structures of the Fetal Nervous System during Pregnancy, but Have No Long Term Effect on Development in the Rat
Sonja Hochmeister, Thomas Pekar, Maren Lindner, Maja Kitic, Michaela Haindl, Maria Storch, Franz Fazekas, Christopher Linington
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0085393
Abstract: Neurofascin was recently reported as a target for axopathic autoantibodies in patients with multiple sclerosis (MS), a response that will exacerbate axonal pathology and disease severity in an animal model of multiple sclerosis. As transplacental transfer of maternal autoantibodies can permanently damage the developing nervous system we investigated whether intrauterine exposure to this neurofascin-specific response had any detrimental effect on white matter tract development. To address this question we intravenously injected pregnant rats with either a pathogenic anti-neurofascin monoclonal antibody or an appropriate isotype control on days 15 and 18 of pregnancy, respectively, to mimic the physiological concentration of maternal antibodies in the circulation of the fetus towards the end of pregnancy. Pups were monitored daily with respect to litter size, birth weight, growth and motor development. Histological studies were performed on E20 embryos and pups sacrificed on days 2, 10, 21, 32 and 45 days post partum. Results: Immunohistochemistry for light and confocal microscopy confirmed passively transferred anti-neurofascin antibody had crossed the placenta to bind to distinct structures in the developing cortex and cerebellum. However, this did not result in any significant differences in litter size, birth weight, or general physical development between litters from control mothers or those treated with the neurofascin-specific antibody. Histological analysis also failed to identify any neuronal or white matter tract abnormalities induced by the neurofascin-specific antibody. Conclusions: We show that transplacental transfer of circulating anti-neurofascin antibodies can occur and targets specific structures in the CNS of the developing fetus. However, this did not result in any pre- or post-natal abnormalities in the offspring of the treated mothers. These results assure that even if anti-neurofascin responses are detected in pregnant women with multiple sclerosis these are unlikely to have a negative effect on their children.
Adsorption Organic Cationic Dyes of Oxycelluloses and Linters  [PDF]
Michaela Filipi, Miloslav Milichovsky
Journal of Encapsulation and Adsorption Sciences (JEAS) , 2014, DOI: 10.4236/jeas.2014.41001
Abstract: Natural cellulose and oxycellulose are heterogeneous highly hydrated substances. They have the same chemical composition, but different size of molecules and representation of COOH groups organized into complex supramolecular structure. The oxycellulosic adsorption capacity of organic cationic dyes increases with increasing -COOH group content and distinctly increases with other competitive ions in the aqueous solution.
Separation of Fe(II) by the DEMI and TEMPO Oxidized Cellulose  [PDF]
Michaela Filipi, Miloslav Milichovsky
Journal of Encapsulation and Adsorption Sciences (JEAS) , 2015, DOI: 10.4236/jeas.2015.53008
Abstract: The description of some adsorption properties and behaviour of oxycellulose with Fe2+ ions is presented. Filter media from oxycelluloses materials have enormous sorption activity. There is described a sorption mechanism of poly 1,4-β-D anhydroglucuronic acid (PAGA). Utilisation of UV-VIS spectroscopy is shown on the adsorption process of optimalisation of oxycelluloses application. Supporting influence is demonstrated on the adsorption isotherms of Fe2+ ions in the competitive environment of NaCl, MgCl2.
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