322 research outputs found
Investigation of the metabolism of rare nucleotides in plants
Nucleotides are metabolites involved in primary metabolism, and specialized
metabolism and have a regulatory role in various biochemical reactions in all forms of life. While in other organisms, the nucleotide metabolome was characterized
extensively, comparatively little is known about the cellular concentrations of
nucleotides in plants. The aim of this dissertation was to investigate the nucleotide metabolome and enzymes influencing the composition and quantities of nucleotides in plants. For this purpose, a method for the analysis of nucleotides and nucleosides in plants and algae was developed (Chapter 2.1), which comprises efficient quenching of enzymatic
activity, liquid-liquid extraction and solid phase extraction employing a weak-anionexchange resin. This method allowed the analysis of the nucleotide metabolome of plants in great depth including the quantification of low abundant deoxyribonucleotides and deoxyribonucleosides. The details of the method were summarized in an article, serving as a laboratory protocol (Chapter 2.2).
Furthermore, we contributed a review article (Chapter 2.3) that summarizes the
literature about nucleotide analysis and recent technological advances with a focus on plants and factors influencing and hindering the analysis of nucleotides in plants, i.e., a complex metabolic matrix, highly stable phosphatases and physicochemical
properties of nucleotides. To analyze the sub-cellular concentrations of metabolites, a protocol for the rapid isolation of highly pure mitochondria utilizing affinity chromatography was developed (Chapter 2.4).
The method for the purification of nucleotides furthermore contributed to the
comprehensive analysis of the nucleotide metabolome in germinating seeds and in
establishing seedlings of A. thaliana, with a focus on genes involved in the synthesis of thymidilates (Chapter 2.5) and the characterization of a novel enzyme of purine nucleotide degradation, the XANTHOSINE MONOPHOSPHATE PHOSPHATASE (Chapter 2.6). Protein homology analysis comparing A. thaliana, S. cerevisiae, and H. sapiens led to the identification and characterization of an enzyme involved in the metabolite damage repair system of plants, the INOSINE TRIPHOSPHATE PYROPHOSPHATASE (Chapter 2.7). It was shown that this enzyme dephosphorylates deaminated purine nucleotide triphosphates and thus prevents their incorporation into nucleic acids. Lossof-function mutants senesce early and have a constitutively increased content of salicylic acid. Also, the source of deaminated purine nucleotides in plants was investigated and it was shown that abiotic factors contribute to nucleotide damage.Nukleotide sind Metaboliten, die am PrimÀrstoffwechsel und an spezialisierten
StoffwechselvorgÀngen beteiligt sind und eine regulierende Rolle bei verschiedenen
biochemischen Reaktionen in allen Lebensformen spielen. WĂ€hrend bei anderen
Organismen das Nukleotidmetabolom umfassend charakterisiert wurde, ist in Pflanzen
vergleichsweise wenig ĂŒber die zellulĂ€ren Konzentrationen von Nukleotiden bekannt.
Ziel dieser Dissertation war es, das Nukleotidmetabolom und die Enzyme zu
untersuchen, die die Zusammensetzung und Menge der Nukleotide in Pflanzen
beeinflussen. Zu diesem Zweck wurde eine Methode zur Analyse von Nukleotiden und
Nukleosiden in Pflanzen und Algen entwickelt (Kapitel 2.1), die ein effizientes Stoppen
enzymatischer AktivitĂ€t, eine FlĂŒssig-FlĂŒssig-Extraktion und eine
Festphasenextraktion unter Verwendung eines schwachen Ionenaustauschers
umfasst. Mit dieser Methode konnte das Nukleotidmetabolom von Pflanzen eingehend
analysiert werden, einschlieĂlich der Quantifizierung von Desoxyribonukleotiden und
Desoxyribonukleosiden mit geringer Abundanz. Die Einzelheiten der Methode wurden
in einem Artikel zusammengefasst, der als Laborprotokoll dient (Kapitel 2.2).
DarĂŒber hinaus wurde ein Ăbersichtsartikel (Kapitel 2.3) verfasst, der die Literatur
ĂŒber die Analyse von Nukleotiden und die jĂŒngsten technologischen Fortschritte
zusammenfasst. Der Schwerpunkt lag hierbei auf Pflanzen und Faktoren, die die
Analyse von Nukleotiden in Pflanzen beeinflussen oder behindern, d. h. eine komplexe
Matrix, hochstabile Phosphatasen und physikalisch-chemische Eigenschaften von
Nukleotiden.
Um die subzellulÀren Konzentrationen von Metaboliten zu analysieren, wurde ein
Protokoll fĂŒr die schnelle Isolierung hochreiner Mitochondrien unter Verwendung einer
AffinitÀtschromatographie entwickelt (Kapitel 2.4).
Die Methode zur Analyse von Nukleotiden trug auĂerdem zu einer umfassenden
Analyse des Nukleotidmetaboloms in keimenden Samen und in sich etablierenden
Keimlingen von A. thaliana bei, wobei der Schwerpunkt auf Genen lag, die an der
Synthese von Thymidilaten beteiligt sind (Kapitel 2.5), sowie zu der Charakterisierung
eines neuen Enzyms des Purinnukleotidabbaus, der XANTHOSINE
MONOPHOSPHATE PHOSPHATASE (Kapitel 2.6). Eine Proteinhomologieanalyse, die A. thaliana, S. cerevisiae und H. sapiens
miteinander verglich fĂŒhrte zur Identifizierung und Charakterisierung eines Enzyms,
das an der Reparatur von geschÀdigten Metaboliten in Pflanzen beteiligt ist, der
INOSINE TRIPHOSPHATE PYROPHOSPHATASE (Kapitel 2.7). Es konnte gezeigt
werden, dass dieses Enzym desaminierte Purinnukleotidtriphosphate
dephosphoryliert und so deren Einbau in NukleinsÀuren verhindert.
Funktionsverlustmutanten altern frĂŒh und weisen einen konstitutiv erhöhten Gehalt an SalicylsĂ€ure auf. AuĂerdem wurde die Quelle der desaminierten Purinnukleotide in Pflanzen untersucht, und es wurde gezeigt, dass abiotische Faktoren zur
NukleotidschÀdigung beitragen
Measuring the beam-spin asymmetry Ïâ° production off the neutron with CLAS12
Over the course of the last couple of decades, Generalised Parton Distributions (GPDs) have become a compelling area of focus in both theoretical and experimental research in the field of hadronic structure. GPDs can be indirectly accessed via observables in hard exclusive reactions such as Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP). In these reactions, an incident lepton scatters off an individual quark within the target nucleon via the exchange of a virtual photon, and a real photon (DVCS) or a meson (DVMP) are emitted as a result.
This thesis presents an analysis of Deeply Virtual πâ° Meson Production off the deuteron (nDVπâ°P). The data were taken with the CLAS12 detector, which is housed in the experimental Hall B at the Jefferson National Laboratory (JLab) in Virginia, USA. A longitudinally polarised electron beam delivered by JLabâs Continuous Electron Beam Accelerator Facility (CEBAF), at an energy of 10.2 and 10.6 GeV, was incident on a liquid deuterium target housed within the CLAS12 detector assembly.
The nDVπâ°P channel is sensitive to the lesser-studied chiral-odd transversity GPDs. GPDs are accessed indirectly via observables related to the cross-sections of hard exclusive processes. One such example is the beam-spin asymmetry (𝐴LU) as a function of Trento-ɸ, the angle between the leptonic plane and the hadronic plane which are defined with the beam and scattered electron, and with the recoiling neutron and reconstructed πâ°, respectively. Despite the limited statistics, the observable (𝐴LU) was successfully extracted for eight kinematic bins (four in Mandelstam 𝑡 and two in 𝑥𝐵). This is a first measurement for nDVπâ°P in the phase-space which is now available with CLAS12 in the 12 GeV era of JLab
A Theoretical Approach to Optimize the Pipeline Data Communication in Oil and Gas Remote Locations Using Sky X Technology
Oil, gas, and water distribution networks in remote locations require optimized data transmission from their sources to prevent or detect leakage or improve production flow in their manufacturing units. Remote oil and gas installations frequently encounter substantial obstacles in terms of data connectivity and transfer. Slow data transmission rates, data loss, and decision-making delays can all be caused by a lack of dependable network infrastructure, restricted bandwidth, and severe climatic conditions. The purpose of this research work is to identify critical concerns concerning data communication and data transfer in oil and gas distant areas and to investigate feasible approaches to these challenges. The survey was carried out to gather feedback from oil and gas experts on issues concerning data transmission in remote locations. This study provides a theoretical approach to optimizing data transmission and communication in remote areas using Sky X technology. This study presents a new theoretical method that improves the performance of IP over satellite using the critical aspects of data transmission issues from experts. This technology's contribution can improve the reliability of all users on a satellite network by delivering all features with a successful data transfer rate discreetly. This attempt may also aid oil and gas companies in optimizing data transmission/communication in remote regions
Change-point analysis of time series with evolutionary spectra
First author draf
INTEGRATED PROTONIC CERAMIC ELECTROCHEMICAL CELL FOR SUSTAINABLE ENERGY ECONOMY USING WATER-ENERGY NEXUS FRAMEWORK
Reliance on fossil fuels will continue for the next decades even though there are global pushes away from it to mitigate the overarching climate challenge, most especially by its highest consumers and availability. While there is a hastening global shift away from fossil fuel, integrating its assets into this technology helps limit the risk and future losses of stranded assets and reduce the cost of investment in the new technologies. Moreover, the generation of electricity from intermittent renewable sources like solar and wind has witnessed a significant surge in recent years, leading to a pressing demand for practical energy storage systems. Electrical energy storage is anticipated to play a pivotal role in the future global energy system, facilitating load-leveling operations to support the greater integration of renewable and distributed generation. Reversible electrochemical cells (RECs) offer a promising option for addressing the fossil fuel assets integration and energy storage challenges through the interconversion between electrical and chemical energy and concurrent utilizing carbon emission. In their electrolysis mode, the RECs convert electricity into durable, storable, and portable valuable chemical fuels such as syngas and methane. Conversely, the produced chemical fuels can be used as reactants in the fuel cell mode to generate electricity on demand with minimal (hydrocarbons) or zero when H2 or NH3 is used emissions. However, a challenging goal for this type of technology remains to achieve optimal operation and high roundtrip efficiencies, which has hindered the deployment of previous electrochemical cells. This dissertation demonstrates how reversible protonic ceramic electrochemical cells (RePCECs) can be integrated with fossil fuel power plants and renewable energy sources as a potential energy storage system. In this work, integrated RePCEC systems are designed and examined using computational modeling at scales to determine appropriate system configurations and operating conditions that achieve high roundtrip efficiencies. Cell level design of the PCEC is the first approach, several cells are assembled for the stack level model that is integrated into combined cycle powerplant and solar photovoltaic for the system level model. After critical literature review, this answered the operational and integration research questions proposed to address these challenges. The designed systems perform two functions, utilizing captured CO2 and storing renewable energy through co-electrolysis of steam and CO2.
The co-electrolysis reaction involves endothermic water electrolysis and exothermic methanation reaction. To enhance high roundtrip efficiency, there is a need for thermal balance and management in the electrolysis mode. This involves operating the RePCEC stack under conditions that favor methane production to balance out heat needed by water electrolysis, it crucial for the RePCEC system operation. Methanation is enhanced by low temperatures. Leveraging on fabricated BCZYYb-electrolyte RePCEC, the cell model designed revealed that the optimum temperature for methane production is 450â at atmospheric pressure. Thus, to achieve optimum system performance, operating in the temperature range 450-525â is recommended at the given configuration, combining between the optimum temperature for methane production and temperature for the optimum stack roundtrip efficiency. Configuration with carbon capture system and purge stream is the optimum configuration from the seven conceptualized and evaluated.
The modeling outcomes include a thermodynamic examination of integrated RePCEC systems, calibration of cell and stack level models, and steady-state simulation and integration into a 600MW combined cycle power plant retrofitted with two two-stage membrane-based carbon capture system and a wastewater treatment and recovery unit. At 100% powerplant loading, the stack and system roundtrip efficiencies are 72% and 51.37% respectively. Adding a purge stream for produced hydrogen at the system downstream improves the efficiencies to 74 and 55.48% respectively. At atmospheric pressure and 525â, the system model suggests that a stack roundtrip of 82% is achievable, and overall system efficiency increases by reducing the energy consumption by the balance of plant components for steam generation and storage. Economic analysis of the process gives levelized cost of methane as 3.46/MMBtu and $9.85/MMBtu. The lifecycle analysis shows that the global warming potential for the production of methane and hydrogen from the RePCEC system is 3.83 kg CO2 eq which is lower than 9.35 kg CO2 eq emission during steam methane reforming for hydrogen production. This answered both the environmental and economic concerns in the raised research question.
The proposed RePCEC configuration and analysis carried out in this dissertation to address the surge in renewable energy and challenges with PCEC technology hold significant potential in achieving large-scale energy storage while simultaneously reducing carbon emissions. These advancements, coupled with suitable governmental policies and incentive programs, have the potential to economically disrupt the natural gas industries by using RePCEC systems for methane production, thereby making them more favorable for eventual implementation and commercialization
Sum-of-squares representations for copositive matrices and independent sets in graphs
A polynomial optimization problem asks for minimizing a polynomial function (cost) given a set of constraints (rules) represented by polynomial inequalities and equations. Many hard problems in combinatorial optimization and applications in operations research can be naturally encoded as polynomial optimization problems. A common approach for addressing such computationally hard problems is by considering variations of the original problem that give an approximate solution, and that can be solved efficiently. One such approach for attacking hard combinatorial problems and, more generally, polynomial optimization problems, is given by the so-called sum-of-squares approximations. This thesis focuses on studying whether these approximations find the optimal solution of the original problem.We investigate this question in two main settings: 1) Copositive programs and 2) parameters dealing with independent sets in graphs. Among our main new results, we characterize the matrix sizes for which sum-of-squares approximations are able to capture all copositive matrices. In addition, we show finite convergence of the sums-of-squares approximations for maximum independent sets in graphs based on their continuous copositive reformulations. We also study sum-of-squares approximations for parameters asking for maximum balanced independent sets in bipartite graphs. In particular, we find connections with the LovĂĄsz theta number and we design eigenvalue bounds for several related parameters when the graphs satisfy some symmetry properties.<br/
LIPIcs, Volume 261, ICALP 2023, Complete Volume
LIPIcs, Volume 261, ICALP 2023, Complete Volum
Proving Termination of C Programs with Lists
There are many techniques and tools to prove termination of C programs, but
up to now these tools were not very powerful for fully automated termination
proofs of programs whose termination depends on recursive data structures like
lists. We present the first approach that extends powerful techniques for
termination analysis of C programs (with memory allocation and explicit pointer
arithmetic) to lists.Comment: Full version of a paper which appeared in the Proceedings of CADE
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