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Algorithmic and High-Frequency Trading Strategies: A Literature Review
No full textThe advances in computer and communication technologies have
created new opportunities for improving, extending the application of or
even developing new trading strategies. Transformations have been observed
both at the level of investment decisions, as well as at the order execution
layer. This review paper describes how traditional market participants, such
as market-makers and order anticipators, have been reshaped and how new
trading techniques relying on ultra-low-latency competitive advantage, such
as electronic \front running", function. Also, the natural con
ict between liquidity-consumers and liquidity-suppliers has been taken to another level, due to the proliferation of algorithmic trading and electronic liquidity provision
strategies
Untersuchungen zur Bildung von Rosmarinsäure in Anthoceros agrestis und Melissa officinalis.
No full textRosmarinsäure (RA) ist ein Naturstoff, der in Anthoceros agrestis vorkommt und im Rahmen
dieser Arbeit untersucht wurde, wobei Mengen von bis zu 4 % des Trockengewichts festgestellt
wurden. Der Biosyntheseweg für RA konnte für Plectranthus scutellarioides vollständig
aufgeklärt werden, wobei L-Tyrosin und L-Phenylalanin als Vorläufer dienen. Ein wesentlicher
Schritt in dieser Biosynthese ist die Esterverknüpfung von 4-Cumaroyl-CoA und 4-
Hydroxyphenylmilchsäure durch die Rosmarinsäure Synthase (RAS) zur Bildung von 4-
Cumaroyl-4‘-Hydroxyphenylmilchsäure, die dann weiter hydroxyliert wird, um RA zu bilden.
Für A. agrestis wurde jedoch kein Ortholog zu RAS gefunden. Da RAS eine Acyltransferase der
BAHD-Familie ist, wurde eine Suche nach Sequenzen durchgeführt, die konservierte Motive
enthalten, die für BAHD-Acyltransferasen charakteristisch sind. Dabei wurden mehrere
Sequenzen gefunden, wobei AaHCT6 am ähnlichsten zu RAS von P. scutellarioides ist.
Untersuchungen an der heterolog exprimierten AaHCT6 zeigten jedoch, dass sie nicht die
Reaktion von 4-Cumaroyl-CoA und 4-Hydroxyphenylmilchsäure oder 3,4-
Dihydroxyphenylmilchsäure katalysiert, wie ursprünglich vorgeschlagen. Ein Katalog von 55
potenziellen Akzeptorsubstraten wurde auf Akzeptanz durch AaHCT6 getestet und ergab
Akzeptanz für Shikimat, 3-Hydroxyanthranilat und 2,3-Dihydroxybenzoat mit Caffeoyl-CoA und
4-Cumaroyl-CoA als Donorsubstraten. Enzymkinetische Messungen ergaben die höchste
Affinität für 4-Cumaroyl-CoA als Donorsubstrat und Shikimat als Akzeptorsubstrat, gefolgt von
3-Hydroxyanthranilat und 2,3-Dihydroxybenzoat. Für 3-Hydroxyanthranilat erfolgt die
Produktbildung über eine Amidbindung, während bei Shikimat und 2,3-Dihydroxybenzoat die
Produktbildung über eine Esterbindung erfolgt.
AaHCT1 wurde erfolgreich aus Gesamt-RNA amplifiziert, in verschiedene Expressionsvektoren
ligiert und in prokaryotische und eukaryotische Organismen zur heterologen Expression
eingeführt. Jedoch war eine Expression des entsprechenden Proteins nicht erfolgreich.
AaHCT2 wurde erfolgreich in E. coli exprimiert, und Untersuchungen zur Substratakzeptanz
ergaben eine Akzeptanz für zwei kleine Alkanole als Akzeptorsubstrate, Methanol und Ethanol,
mit Caffeoyl-CoA als Donorsubstrat. AaHCT5 wurde erfolgreich in E. coli exprimiert, wie durch
Western Blot verifiziert wurde, jedoch wurde kein Substrat akzeptiert, das in dem Katalog von
55 potenziellen Substraten enthalten war. Die Sequenz, die für AaHCT7 kodiert, wurde zwar in
einem späten Stadium dieser Arbeit entdeckt, konnte jedoch erfolgreich aus Gesamt-RNA
amplifiziert werden. Eine Integration in den Vektor pDrive war erfolgreich, wie durch
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Sequenzierung verifiziert wurde. Eine Integration in den Expressionsvektor pET-15b war jedoch
nicht erfolgreich, da sie in einer umgekehrten Orientierung eingebaut wurde.
Bis heute ist der letzte Schritt des Rosmarinsäure-Biosynthesewegs in A. agrestis noch unklar.
Es besteht die Möglichkeit, dass dieser Schritt von einem Enzym der BAHD-Acyltransferase-
Familie katalysiert wird, wie es für Pflanzen der Lamiaceae-Familie nachgewiesen wurde. Es
kann jedoch nicht ausgeschlossen werden, dass dieser Schritt von einem Enzym einer völlig
anderen Klasse katalysiert wird. Darüber hinaus ist es möglich, dass dieser Schritt von einem
Enzym katalysiert wird, das Acyltransferase-Aktivität aufweist, aber die für BAHD-
Acyltransferasen typischen konservierten Sequenzen fehlen (oder davon abweichen).
Neben der Aufklärung der Funktion und Rolle von HCTs, die in A. agrestis gefunden wurden,
befasst sich diese Arbeit auch mit der Erforschung von Elektrizität als potenziellem Auslöser
für die Steigerung der Produktion von Rosmarinsäure in Suspensionskulturen von Melissa
officinalis. Erste Experimente mit elektrischen Feldern zeigten unterschiedliche Auswirkungen
auf die Metabolitproduktion, was auf die Notwendigkeit weiterer Optimierung und
Untersuchung der Anwendung von elektrischem Strom als Auslöser hinweist. Die Ergebnisse
zeigten jedoch, dass die Anwendung eines chemischen Elicitors, Methyljasmonat, die
Rosmarinsäureproduktion konsequent besser fördert als die elektrische Stimulation, was die
wirtschaftliche Praktikabilität von Methyljasmonat für die Steigerung der Bildung von
Naturstoffen gegenüber komplexen Aufbauten mit elektrischer Verkabelung hervorhebt.Rosmarinic acid (RA) is a natural product found in Anthoceros agrestis with amounts of up to
4 % of dry weight investigated in this work. The biosynthetic pathway for RA has been fully
elucidated for Plectranthus scutellarioides with L-tyrosine and L-phenylalanine serving as
precursors. An essential step in this biosynthesis is the ester linkage of 4-coumaroyl-CoA and
4-hydroxyphenyllactate by rosmarinic acid synthase (RAS) to form
4-coumaroyl-4’-hydroxyphenyllactate which is then further hydroxylated to form RA. However,
for A. agrestis no ortholog to RAS has been found. With RAS being an acyltransferase of the
BAHD family a search for sequences containing conserved motifs characteristic for BAHD
acyltransferases resulted in several sequences, with AaHCT6 being the most similar to RAS
from P. scutellarioides. However, investigations on heterologously expressed AaHCT6 showed,
that it does not catalyze the reaction of 4-coumaroyl-CoA and 4-hydroxyphenyllactate or
3,4-dihydroxyphenyllactate, as it was initially proposed (Petersen et al. 1993; Petersen 1997;
Petersen and Simmonds 2002). A catalogue of 55 potential acceptor substrates was tested for
acceptance by AaHCT6 and resulted in acceptance for shikimate, 3-hydroxyanthranilate and
2,3-dihydroxybenzoate with caffeoyl-CoA and 4-coumaroyl-CoA as donor substrates. Enzyme
kinetic measurements revealed the highest affinity for 4-coumaroyl-CoA as donor substrate
and shikimate as acceptor substrate, followed by 3-hydroxyanthranilate and 2,3-
dihydroxybenzoate. For 3-hydroxyanthranilate the product formation occurs via amide linkage,
173
whereas with shikimate and 2,3-dihydroxybenzoate product formation occurs via ester
linkage.
AaHCT1 was successfully amplified from total RNA, ligated into several expression vectors and
introduced into prokaryotic and eukaryotic organisms for heterologous expression. However,
an expression of the protein of interest was not successful. AaHCT2 was successfully expressed
in E. coli and investigations on substrate acceptance revealed an acceptance for two small
alkanols as acceptor substrates, methanol and ethanol, with caffeoyl-CoA as donor substrates.
AaHCT5 was successfully expressed in E. coli as verified by Western blot. However, no substrate
accepted by this enzyme was found out of the catalogue of 55 potential substrates. The
sequence coding for AaHCT7, although discovered in a late stage of this work, was successfully
amplified from total RNA. An incorporation into the vector pDrive was successful as verified by
sequencing. However, an incorporation into the expression vector pET-15b was not successful
as it was implemented in a reverse orientation as verified by sequencing. To date, the ester-
forming step of the rosmarinic acid pathway for Anthoceros agrestis is still unclear. Chances
are that this step is being catalyzed by an enzyme of the BAHD acyltransferase family, as it is
demonstrated for plants of the Lamiaceae family. However, it cannot be ruled out that this
step might be catalyzed by an enzyme of a completely different class. Furthermore, it is
possible that this step might be catalyzed by an enzyme exhibiting acyltransferase activity but
lacking (or deviating from) the conserved sequences typical for BAHD acyltransferases.
In addition to elucidating the function and role of HCTs found in A. agrestis, this work also
delves into the exploration of electricity as a potential elicitor for the production of the
specialized metabolite rosmarinic acid in suspension cultures of Melissa officinalis. Initial
experiments involving electric fields demonstrated varying effects on metabolite
accumulation, indicating the need for further optimization and investigation into the
application of electric current as an elicitor. However, the results showed that the application
of a chemical elicitor, methyl jasmonate, consistently outperforms electric stimulation in
enhancing RA production, highlighting the economic practicality of methyl jasmonate as a
preferred elicitor for specialized metabolite enhancement rather than complex setups with
electric wiring
Methods for Constraint Satisfaction, Error Handling, and Data Recovery in DNA Data Storage
No full textThe ever-increasing generation of digital data has created unprecedented challenges for data storage and preservation. Since current data storage technologies do not provide means for adequate long-term retention, storage density, resource efficiency, and cost if used for very long time periods, novel solutions are required. Deoxyribonucleic acid (DNA) with its various beneficial properties has emerged as a promising medium for long-term data storage. Due to its superior density, durability, and stability compared to conventional storage technologies, as well as its inherent relevance for humanity, DNA is an interesting medium for long-term data storage. However, the biological nature of DNA introduces unique constraints and error characteristics that must be addressed through computational methods tailored to DNA data storage. Additionally, since research in the field of synthetic biology and DNA sequencing is progressing rapidly, technologies currently deemed error-prone, expensive, or generally infeasible may be attractive in the future. This thesis presents novel contributions to improve the effectiveness and reliability of DNA data storage systems, especially those based on fountain coding schemes. The research in the thesis encompasses three key areas in which significant improvements are presented: simulation of DNA data storage, data encoding/decoding, and postprocessing using various sequence repair and data recovery methods. Since performing in-vitro experiments is still expensive and time-consuming, the use of computer simulations is a feasible approach to accelerate research while allowing comparability and reproducibility. Thus, the first research area presented in this thesis includes a versatile simulation framework for the simulation of each step involved in a typical DNA data storage process. To increase usability, this approach does not only include predefined methods, but supports the simulation of user-defined scenarios. The second research area covered in this thesis involves contributions towards efficient, constraint-adhering, and error-resilient data coding schemes for DNA data storage. This involves the creation of novel coding schemes based on fountain codes, as well as the optimization of fountain codes for DNA data storage. Furthermore, since state-of-the-art DNA data storage systems are error-prone and the presence of errors in such a biological medium can never be fully avoided, various methods for postprocessing, sequence repair, and recovery of corrupted data are introduced in the third research area of this thesis. The methods presented in this work thus represent key building blocks for realizing practical, large-scale DNA data storage systems.Die ständig wachsende Erzeugung digitaler Daten stellt die Datenspeicherung und -aufbewahrung vor nie dagewesene Herausforderungen. Da die derzeitigen Technologien zur Speicherung von Daten keine Mittel für eine angemessene langfristige Aufbewahrung, Speicherdichte, Ressourceneffizienz und Kosten bei sehr langer Nutzung bieten, sind neue Lösungen erforderlich. Die Desoxyribonukleinsäure (DNS – eng.: DNA) mit ihren verschiedenen vorteilhaften Eigenschaften hat sich als vielversprechendes Medium für die langfristige Datenspeicherung erwiesen. Aufgrund ihrer im Vergleich zu herkömmlichen Speichertechnologien überlegenen Dichte, Haltbarkeit und Stabilität sowie ihrer inhärenten Bedeutung für die Menschheit ist die DNA ein interessantes Medium für die langfristige Datenspeicherung. Die biologische Natur der DNA bringt jedoch einzigartige Einschränkungen und Fehlereigenschaften mit sich, die von auf die DNA-Datenspeicherung zugeschnittenen Kodierungsmethoden berücksichtigt werden müssen. Da die Forschung auf dem Gebiet der synthetischen Biologie und der DNASequenzierung sehr schnell voranschreitet, könnten Technologien, die derzeit als fehleranfällig, teuer oder generell nicht praktikabel gelten, in Zukunft attraktiv sein. In dieser Arbeit werden neue Beiträge zur Verbesserung der Effektivität und Zuverlässigkeit von DNA-Datenspeichersystemen vorgestellt, insbesondere von solchen, die Fountain Codes verwenden. Die Forschung in dieser Arbeit konzentriert sich auf drei Schlüsselbereiche, in denen signifikante Verbesserungen vorgestellt werden: Simulation der DNA-Datenspeicherung, Kodierung/Dekodierung von Daten und Nachbearbeitung mit verschiedenen Sequenzreparaturund Datenwiederherstellungsmethoden. Da die Durchführung von In-vitro-Experimenten nach wie vor teuer und zeitaufwändig ist, ist der Einsatz von Computersimulationen ein geeigneter Ansatz, um die Forschung zu beschleunigen und gleichzeitig Vergleichbarkeit und Reproduzierbarkeit zu gewährleisten. Der erste Forschungsbereich, der in dieser Arbeit vorgestellt wird, umfasst daher einen flexiblen Ansatz für die Nachbildung der einzelnen Schritte eines typischen DNA-Speicherprozesses. Um die Benutzbarkeit zu erhöhen, enthält dieser Ansatz dabei nicht nur vordefinierte Methoden, sondern unterstützt auch die Simulation von benutzerdefinierten Szenarien. Der zweite in dieser Arbeit behandelte Forschungsbereich umfasst Beiträge zur Erforschung effizienter, Bedingungen einhaltender und fehlerresistenter Kodierungsverfahren für die Speicherung von Daten in DNA. Dies beinhaltet die Entwicklung neuartiger auf Fountain Codes basierender Kodierungsschemata sowie die Optimierung dieser Kodierungen für DNADatenspeicher. Da moderne DNA-Speichersysteme fehleranfällig sind und das Vorhandensein von Fehlern in einem solchen biologischen Medium nie vollständig vermieden werden kann, werden außerdem verschiedene Methoden zur Nachbearbeitung, Sequenzreparatur und Wiederherstellung von beschädigten Daten im dritten Forschungsbereich dieser Dissertation vorgestellt. Die in dieser Arbeit vorgestellten Methoden stellen somit wichtige Bausteine für die Realisierung von in der Praxis nutzbaren DNA-Speichersysteme für große Datenmengen dar
Does the ECB’s Monetary Policy Affect Personal Finances and Economic Inequality? A Household Perspective from Germany
No full textDespite a growing academic literature on the distributional effects of monetary policy (MP), little is known about how laypersons perceive the effects of MP on their own economic situation and national economic inequality. This study examines laypersons' perceptions in Germany of the impact of the ECB's MP on (i) their personal economic situation and (ii) national economic inequality, using representative survey data collected in 2018. I review the existing academic literature, which identifies various characteristics of individuals that could potentially render them susceptible to the effects of monetary policy, such as savings, wealth, home ownership, debt, unemployment, or age. I then investigate whether these characteristics align with layperson’s perceptions. Ordered logit analysis shows that, contrary to the economic literature, most variables - with the exception of 'savers' - appear to be irrelevant to laypersons' perceptions. Instead, factors such as objective knowledge of monetary policy, trust in the ECB, party affiliation and residence in East Germany emerge as significant factors
COVID-19 and Financial Markets: A Panel Analysis for European Countries
No full textIn order to fight the economic consequences of the COVID-19 pandemic, monetary and fiscal policy announced a large variety of support packages which are often unprecedented in size. In this paper, we provide an empirical analysis of the responses of European financial markets to these policy announcements. The key contribution is a very granular set of policy announcements, both at the national and the European level. We also differentiate between the first announcement in a series of policies and the subsequent announcements because the initial steps were often seen as bad news about the state of the economy. In a panel model we find that monetary policy, in particular through asset purchases, is effective in supporting the real economy and easing the pressure on governmental finances. Across all subsets of polices, it seems that monetary policy is more effective in supporting the stock market than national fiscal policy, though markets clearly distinguish between different types of policies
Math Skill Growth and Learning Differences in Higher Education. Can Lower-Skilled Students Catch up?
No full textStudies determining students' success in higher education mostly rely on students' predetermined baseline variables like high school GPA or ACT scores and, therefore, describe skill differences at the beginning of college but not the development of these differences over time. Whether ex-ante lower-skilled students can catch up or higher-skilled students may expand their initial lead remains unclear. We investigate the students' learning growth in a business math course and analyze if the gap between initially higher and lower-skilled students changes. Also, we provide possible reasons for different skill growth rates using panel data and mixed-effects models. The results suggest that ex-ante higher-skilled students become disproportionately better (cumulative learning pattern). However, we find evidence that this is only because of engagement effects. In other words, ex-ante lower-skilled students cannot catch up and fall behind even more because they seem less engaged in their studies than higher-skilled students
Cognitive Ability and Corruption: Rule of Law (still) Matters
No full textThis study shows that the “longer time horizon” argument proposed by Potrafke (2012) with regard to the negative effect of a higher national average cognitive ability on corruption holds only in countries with a relatively high quality of rule of law
Health Behaviors of Colombian First-Semester University Students in Association with Behaviors of Close Social Ties, Living Arrangement, and Time Spent with Peers
No full textObjective: in Colombia, many first-year university students consume unhealthy food, are physically inactive, and drink regularly, which can be associated with the behavior of social ties, living with social ties, and time with peers. The present cross-sectional study assessed the association between health behaviors of first-semester students and these factors. Method: N = 189 (Mage = 18.79; SD = 1.07; female = 68.8%) first-semester students in Colombia completed an online questionnaire investigating current and expected health behaviors as well as influencing factors. ANCOVAs, bivariate correlations, moderation analyses, and hierarchical regressions were used to analyze the data. Results: expected food consumption (stronger among participants who live with parents) as well as current and expected heavy drinking and binge drinking (stronger among participants who do not live with parents) were significantly correlated to the respective parental behavior. Current and expected drinking was significantly correlated to partners’ drinking. Expected physical activity was correlated with peers’ physical activity. Partners’ attempts to encourage drinking moderated the association between participants’ current and expected drinking with partners’ drinking. Time spent with peers was related to heavy drinking and engaging in more physical activity. Conclusion: in Colombia, parents appear to play a significant role in their offspring’s health behaviors during their first semester at university, particularly regarding food consumption and alcohol use. Partners’ drinking and time spent with peers are strongly related to heavy drinking.Gefördert durch den Open-Access-Publikationsfonds der UB Marburg
Improving the pharmacokinetics, biodistribution and plasma stability of monobodies
No full textCancer is a leading cause of death worldwide. Several targeted anticancer drugs
entered clinical practice and improved survival of cancer patients with selected
tumor types, but therapy resistance and metastatic disease remains a challenge. A
major class of targeted anticancer drugs are therapeutic antibodies, but their use
is limited to extracellular targets. Hence, alternative binding scaffolds have been
investigated for intracellular use and better tumor tissue penetration. Among
those, monobodies are small synthetic protein binders that were engineered to
bind with high affinity and selectivity to central intracellular oncoproteins and
inhibit their signaling. Despite their use as basic research tools, the potential of
monobodies as protein therapeutics remains to be explored. In particular, the
pharmacological properties of monobodies, including plasma stability, toxicity
and pharmacokinetics have not been investigated. Here, we show that
monobodies have high plasma stability, are well-tolerated in mice, but have a
short half-life in vivo due to rapid renal clearance. Therefore, we engineered
monobody fusions with an albumin-binding domain (ABD), which showed
enhanced pharmacological properties without affecting their target binding:
We found that ABD-monobody fusions display increased stability in mouse
plasma. Most importantly, ABD-monobodies have a dramatically prolonged in
vivo half-life and are not rapidly excreted by renal clearance, remaining in the
blood significantly longer, while not accumulating in specific internal organs. Our
results demonstrate the promise and versatility of monobodies to be developed
into future therapeutics for cancer treatment. We anticipate that monobodies
may be able to extend the spectrum of intracellular targets, resulting in a
significant benefit to patient outcome.Gefördert durch den Open-Access-Publikationsfonds der UB Marburg
Using GEDI as training data for an ongoing mapping of landscape-scale dynamics of the plant area index
No full textLeaf or plant area index (LAI, PAI) information is frequently used to describe vegetation structure
in environmental science. While field measurements are time-consuming and do not scale to
landscapes, model-based air- or space-borne remote-sensing methods have been used for many
years for area-wide monitoring. As of 2019, NASA’s Global Ecosystem Dynamics Investigation
(GEDI) mission delivers a point-based LAI product with 25 m footprints and periodical repetition.
This opens up new possibilities in integrating GEDI as frequently generated training samples with
high resolution (spectral) sensors. However, the foreseeable duration of the system installed on the
ISS is limited. In this study we want to test the potential of GEDI for regional comprehensive LAI
estimations throughout the year with a focus on its usability beyond the lifespan of the GEDI
mission. We study the landscape of Hesse, Germany, with its pronounced seasonal changes.
Assuming a relationship between GEDI’s PAI and Sentinel-1 and -2 data, we used a Random Forest
approach together with spatial variable selection to make predictions for new Sentinel scenes. The
model was trained with two years of GEDI PAI data and validated against a third year to provide a
robust and temporally independent model validation. This ensures the applicability of the
validation for years outside the training period, reaching a total RMSE of 1.12. Predictions for the
test year showed the expected seasonal and spatial patterns indicated by RMSE values ranging
between 0.75 and 1.44, depending on the land cover class. The overall prediction performance
shows good agreement with the test data set of the independent year which supports our
assumption that the usage of GEDI’s PAI beyond the mission lifespan is feasible for regional studies.Gefördert durch den Open-Access-Publikationsfonds der UB Marburg