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Search Results: 1 - 10 of 1835 matches for " Susanne Dorn "
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The focus of light - linear polarization breaks the rotational symmetry of the focal spot
Ralf Dorn,Susanne Quabis,Gerd Leuchs
Physics , 2003, DOI: 10.1080/09500340308235246
Abstract: We experimentally demonstrate for the first time that a linearly polarized beam is focussed to an asymmetric spot when using a high-numerical aperture focussing system. This asymmetry was predicted by Richards and Wolf [Proc.R.Soc.London A, 253, 358 (1959)] and can only be measured when a polarization insensitive sensor is placed in the focal region. We used a specially modified photodiode in a knife edge type set up to obtain highly resolved images of the total electric energy density distribution at the focus. The results are in good agreement with the predictions of a vectorial focussing theory.
The Wnt Pathway Target Gene CCND1 Changes Mitochondrial Localization and Decreases Mitochondrial Activity in Colorectal Cancer Cell Line SW480  [PDF]
Annica Vlad-Fiegen, Natalie Veronika Freytag, Susanne Dorn, Oliver Müller, Sonja Eberth
Journal of Biosciences and Medicines (JBM) , 2016, DOI: 10.4236/jbm.2016.412017
Abstract: Mutations leading to constitutive activation of the Wnt pathway and its target genes are frequently observed in cancer. The Wnt pathway promotes cell proliferation and increasing evidence supports its role also in cancer cell metabolism. This study aims to elucidate the role of the Wnt/β-catenin target gene CCND1 in these processes in colorectal cancer. We analyzed whether knock-down of CCND1 affects cell cycle progression and energy metabolism in a colorectal cancer cell line. Down-regulation of CCND1 led to retardation of the cell cycle. The proportion of cells in the G0 phase increased, while the amount of cells in the S- and G2/M phase decreased. Interestingly, knock-down of CCND1 changed the perinuclear localization of mitochondria into a homogeneous distribution within the cytosol. In addition CCND1 knock-down led to an increase of the intracellular ATP level indicating that cyclin D1 reduced mitochondrial activity. Our findings suggest that in addition to its role in cell cycle regulation, the Wnt target gene CCND1 regulates mitochondrial localization and inhibits mitochondrial activity in colorectal cancer cells.
Determinants in Pay-What-You-Want Pricing Decisions—A Cross-Country Study  [PDF]
Tim Dorn, Augustin Suessmair
American Journal of Industrial and Business Management (AJIBM) , 2017, DOI: 10.4236/ajibm.2017.72010
Abstract: Pay-what-you-want (PWYW) pricing has attracted much attention recently. Current research focused on influencing factors and their power across social contexts and countries. This article empirically examines a comprehensive list of 10 empirically tested factors that influence individual price-setting but never have been investigated holistically. Results indicate: (1) some previously assumed influencing factors have stronger moderating effects than do others, and (2) these influences must be interpreted as influential clusters rather than individually, as not all constructs are of significantly differing influence on an individual’s pricing decision. Satisfaction (Cluster 1), price consciousness, and fairness (both Cluster 2) constitute the most crucial moderators, regardless of context. Four country contexts (i.e., Australia, Germany, Poland, United States) revealed further insights about the intercultural perspective of PWYW pricing: Whereas most of the influencing factors/clusters are of comparable importance across the tested countries, loyalty and reputation (Cluster 6) significantly differed in importance depending on country.
The Anti-Diabetic Drug Metformin Reduces BACE1 Protein Level by Interfering with the MID1 Complex
Moritz M. Hettich, Frank Matthes, Devon P. Ryan, Nadine Griesche, Susanne Schr?der, Stephanie Dorn, Sybille Krauβ, Dan Ehninger
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0102420
Abstract: Alzheimer’s disease (AD), the most common form of dementia in the elderly, is characterized by two neuropathological hallmarks: senile plaques, which are composed of Aβ peptides, and neurofibrillary tangles, which are composed of hyperphosphorylated TAU protein. Diabetic patients with dysregulated insulin signalling are at increased risk of developing AD. Further, several animal models of diabetes show increased Aβ expression and hyperphosphorylated tau. As we have shown recently, the anti-diabetic drug metformin is capable of dephosphorylating tau at AD-relevant phospho-sites. Here, we investigated the effect of metformin on the main amyloidogenic enzyme BACE1 and, thus, on the production of Aβ peptides, the second pathological hallmark of AD. We find similar results in cultures of primary neurons, a human cell line model of AD and in vivo in mice. We show that treatment with metformin decreases BACE1 protein expression by interfering with an mRNA-protein complex that contains the ubiquitin ligase MID1, thereby reducing BACE1 activity. Together with our previous findings these results indicate that metformin may target both pathological hallmarks of AD and may be of therapeutic value for treating and/or preventing AD.
America Y2K: The Obsolescence of Educational Reforms
Sherman Dorn
Education Policy Analysis Archives , 2000,
Abstract: The passing of the deadline for fulfillment of the national education goals in the United States (the beginning of 2000) reflects the frequently hyperbolic statements of objectives and the manic pace of school reform efforts over the past two decades. The domination by schools of child and family life has combined with a longstanding reliance on schools to solve social problems to make school reform a politically opportune as well as visible issue. Thus, even if the phrasing of national education goals in the U.S. changes to reflect the passing of the nominal deadline, those pressures will remain.
Comment on Ng's "Wealth Redistribution, Race & Southern Public Schools, 1880-1910"
Sherman Dorn
Education Policy Analysis Archives , 2001,
Abstract: Wherein the author raises criticisms and advances qualifications to the conclusions reached by Kenneth Ng is his article "Wealth Redistribution, Race and Southern Public Schools, 1880-1910.
The Political Legacy of School Accountability Systems
Sherman Dorn
Education Policy Analysis Archives , 1998,
Abstract: The recent battle reported from Washington about proposed national testing program does not tell the most important political story about high stakes tests. Politically popular school accountability systems in many states already revolve around statistical results of testing with high-stakes environments. The future of high stakes tests thus does not depend on what happens on Capitol Hill. Rather, the existence of tests depends largely on the political culture of published test results. Most critics of high-stakes testing do not talk about that culture, however. They typically focus on the practice legacy of testing, the ways in which testing creates perverse incentives against good teaching. More important may be the political legacy, or how testing defines legitimate discussion about school politics. The consequence of statistical accountability systems will be the narrowing of purpose for schools, impatience with reform, and the continuing erosion of political support for publicly funded schools. Dissent from the high-stakes accountability regime that has developed around standardized testing, including proposals for professionalism and performance assessment, commonly fails to consider these political legacies. Alternatives to standardized testing which do not also connect schooling with the public at large will not be politically viable.
High-Stakes Testing and the History of Graduation
Sherman Dorn
Education Policy Analysis Archives , 2003,
Abstract: An historical perspective on high-stakes testing suggests that tests required for high school graduation will have mixed results for the putative value of high school diplomas: (1) graduation requirements are likely to have indirect as well as direct effects on the likelihood of graduating; (2) the proliferation of different exit documents may dilute efforts to improve the education of all students; and (3) graduation requirements remain unlikely to disentangle the general cultural confusion in the U.S. about the purpose of secondary education and a high school diploma, especially confusion about whether the educational, exchange, or other value of a diploma is most important.
No more aggregate NAEP studies? [editorial].
Sherman Dorn
Education Policy Analysis Archives , 2006,
Abstract: This editorial reviews recent studies of accountability policies using National Assessment of Educational Progress (NAEP) data and compares the use of aggregate NAEP data to the availability of individual-level data from NAEP. While the individual-level NAEP data sets are restricted-access and do not give accurate point-estimates of achievement, they nonetheless provide greater opportunity to conduct more appropriate multi-level analyses with state policies as one set of variables. Policy analysts using NAEP data should still look at exclusion rates and the non-longitudinal nature of the NAEP data sets.
The mass term in non-Abelian gauge field dynamics on matrix D-branes and T-duality in the $σ$-model approach
H. Dorn
Physics , 1998, DOI: 10.1088/1126-6708/1998/04/013
Abstract: The formal extension of the T-duality rules for open strings from Abelian to non-Abelian gauge field background leads in a well known manner to the notion of matrix valued D-brane position. The application of this concept to the non-Abelian gauge field RG $\beta $-function of the corresponding $\sigma $-model yields a mass term in the gauge field dynamics on the matrix D-brane. The direct calculation in a corresponding D-brane model does $not$ yield such a mass term, if the Dirichlet boundary condition is implemented as a constraint on the integrand in the defining functional integral. However, the mass term arises in the direct calculation for a D-brane model with dynamically realized boundary condition.
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