Real-time Adaptive Optics with pyramid wavefront sensors: A theoretical analysis of the pyramid sensor model

We consider the mathematical background of the wavefront sensor type that is widely used in Adaptive Optics systems for astronomy, microscopy, and ophthalmology. The theoretical analysis of the pyramid sensor forward operators presented in this paper is aimed at a subsequent development of fast and stable algorithms for wavefront reconstruction from data of this sensor type. In our analysis we allow the sensor to be utilized in both the modulated and non-modulated fashion. We derive detailed mathematical models for the pyramid sensor and the physically simpler roof wavefront sensor as well as their various approximations. Additionally, we calculate adjoint operators which build preliminaries for the application of several iterative mathematical approaches for solving inverse problems such as gradient based algorithms, Landweber iteration or Kaczmarz methods

Real-time Adaptive Optics with pyramid wavefront sensors: Accurate wavefront reconstruction using iterative methods

In this paper, we address the inverse problem of fast, stable, and high-quality wavefront reconstruction from pyramid wavefront sensor data for Adaptive Optics systems on Extremely Large Telescopes. For solving the indicated problem we apply well-known iterative mathematical algorithms, namely conjugate gradient, steepest descent, Landweber, Landweber-Kaczmarz and steepest descent-Kaczmarz iteration based on theoretical studies of the pyramid wavefront sensor. We compare the performance (in terms of correction quality and speed) of these algorithms in end-to-end numerical simulations of a closed adaptive loop. The comparison is performed in the context of a high-order SCAO system for METIS, one of the first-light instruments currently under design for the Extremely Large Telescope. We show that, though being iterative, the analyzed algorithms, when applied in the studied context, can be implemented in a very efficient manner, which reduces the related computational effort significantly. We demonstrate that the suggested analytically developed approaches involving iterative algorithms provide comparable quality to standard matrix-vector-multiplication methods while being computationally cheaper

eLearning-Tools zur Verbesserung verständlichen Schreibens.

Thema dieses Artikels ist das Schreiben von Texten in verständlicher Form. Die zunehmende digitale und webbasierte Bearbeitung von Texten lässt die für Lehre und Forschung relevante und allgemeine Frage auftauchen, ob oder inwiefern die Qualität des Schreibens sich verändern wird. Innerhalb des eLearning-Projekts "Verständlich Schreiben", welches an der Universität Wien am Institut für Bildungswissenschaft in Kooperation mit dem Institut für Knowledge and Business Engineering durchgeführt wird, wird hier die konkrete Frage gestellt: Wie kann die Qualität des verständlichen Schreibens mittels eLearning-Tools verbessert werden? \ud \u

Early and Middle Holocene Hunter-Gatherer Occupations in Western Amazonia: The Hidden Shell Middens

We report on previously unknown early archaeological sites in the Bolivian lowlands, demonstrating for the first time early and middle Holocene human presence in western Amazonia. Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region. The absence of stone resources and partial burial by recent alluvial sediments has meant that these kinds of deposits have, until now, remained unidentified. We conducted core sampling, archaeological excavations and an interdisciplinary study of the stratigraphy and recovered materials from three shell midden mounds. Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites. In a tropical and geomorphologically active landscape often considered challenging both for early human occupation and for the preservation of hunter-gatherer sites, the newly discovered shell middens provide evidence for early to middle Holocene occupation and illustrate the potential for identifying and interpreting early open-air archaeological sites in western Amazonia. The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region's past and offers a new context within which the late Holocene "Earthmovers" of the Llanos de Moxos could have emerged. © 2013 Lombardo et al

Chronophin regulates active vitamin B6 levels and transcriptomic features of glioblastoma cell lines cultured under non-adherent, serum-free conditions

Background: The phosphatase chronophin (CIN/PDXP) has been shown to be an important regulator of glioma cell migration and invasion. It has two known substrates: p-Ser3-cofilin, the phosphorylated form of the actin binding protein cofilin, and pyridoxal 5′-phosphate, the active form of vitamin B6. Phosphoregulation of cofilin, among other functions, plays an important role in cell migration, whereas active vitamin B6 is a cofactor for more than one hundred enzymatic reactions. The role of CIN has yet only been examined in glioblastoma cell line models derived under serum culture conditions. Results: We found that CIN is highly expressed in cells cultured under non-adherent, serum-free conditions that are thought to better mimic the in vivo situation. Furthermore, the substrates of CIN, p-Ser3-cofilin and active vitamin B6, were significantly reduced as compared to cell lines cultured in serum-containing medium. To further examine its molecular role we stably knocked down the CIN protein with two different shRNA hairpins in the glioblastoma cell lines NCH421k and NCH644. Both cell lines did not show any significant alterations in proliferation but expression of differentiation markers (such as GFAP or TUBB3) was increased in the knockdown cell lines. In addition, colony formation was significantly impaired in NCH644. Of note, in both cell lines CIN knockdown increased active vitamin B6 levels with vitamin B6 being known to be important for S-adenosylmethionine biosynthesis. Nevertheless, global histone and DNA methylation remained unaltered as was chemoresistance towards temozolomide. To further elucidate the role of phosphocofilin in glioblastoma cells we applied inhibitors for ROCK1/2 and LIMK1/2 to our model. LIMK- and ROCK-inhibitor treatment alone was not toxic for glioblastoma cells. However, it had profound, but antagonistic effects in NCH421k and NCH644 under chemotherapy. Conclusion: In non-adherent glioblastoma cell lines cultured in serum-free medium, chronophin knockdown induces phenotypic changes, e.g. in colony formation and transcription, but these are highly dependent on the cellular background. The same is true for phenotypes observed after treatment with inhibitors for kinases regulating cofilin phosphorylation (ROCKs and LIMKs). Targeting the cofilin phosphorylation pathway might therefore not be a straightforward therapeutic option in glioblastoma

Introduction of data spaces – Status and recommendations for action

Data sovereignty is paramount in the digital era, and data spaces are often viewed as a means for organizations to cultivate this essential digital competency. However, the adoption of data spaces by organizations remains limited. Furthermore, current perspectives on data spaces tend to emphasize technical aspects while overlooking their socio-technical complexity. What\u27s lacking are recommendations for establishing federated data spaces. To bridge this gap, the study advocates the development of recommendations through expert interviews. Targeting both academia and industry, this research employs coding techniques akin to grounded theory to offer insights and propose four key categories of recommendations: Community, Infrastructure, Interoperability, and Governance. Leveraging data spaces for data sovereignty can provide organizations with a competitive edge

China's Water Market - Opportunities for Foreign Investors

China has undergone a remarkable transformation process and rapid economic development. However, the resources that such growth demands have raised deep concerns about the long-term sustainability and hidden costs of China’s development. Many of these concerns are associated with the state of China’s water resources. As demand for water has increased, so too have problems with water shortages, pollution, falling groundwater tables, and flood/drought damages. To tackle these challenges, the Chinese government increasingly encourages foreign companies to engage in the country’s water market. Market research studies claim that this market holds promising business opportunities for both domestic and foreign companies. This article analyses this statement from a foreign investor’s perspective. It evaluates key factors influencing the reform policy of the Chinese government and introduces the main policy and investment implications. It shows that in spite of the remaining market barriers, the Chinese water market indeed holds business opportunities. In fact, a key role in solving China’s water crisis should be played by international companies and governments

The Sharing Of Anthropological Collections: Cooperation With Third World Museums

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98267/1/mua.1980.4.5.5.pd

University museums and collections of natural history

Natural history museums and collections at American universities have been in decline for the past 30 years, due in part to increasing constraints on the financial support framework and the perception that natural history museums may be no longer central to the mission of universities. This paper disputes the validity of this assumption and suggests strategies for strengthening the position of natural history museums within the academic structure