Gravitational signal propagation in the double pulsar studied with the MeerKAT telescope

The double pulsar PSR J0737−3039A/B has offered a wealth of gravitational experiments in the strong-field regime, all of which general relativity has passed with flying colours. In particular, among current gravity experiments that test photon propagation, the double pulsar probes the strongest spacetime curvature. Observations with MeerKAT and, in the future, the Square Kilometre Array (SKA) can greatly improve the accuracy of current tests and facilitate tests of next-to-leading-order (NLO) contributions in both orbital motion and signal propagation. We present our timing analysis of new observations of PSR J0737−3039A, made using the MeerKAT telescope over the last three years. The increased timing precision offered by MeerKAT yields a measurement of Shapiro delay parameter s that it twice as good, and an improved mass measurements compared to previous studies. In addition, our results provide an independent confirmation of the NLO signal propagation effects and already surpass the previous measurement from 16 yr data by a factor of 1.65. These effects include the retardation effect due to the movement of the companion and the deflection of the signal by the gravitational field of the companion. We also investigate the novel effects that have been expected. For instance, we search for potential profile variations near superior conjunctions caused by shifts of the line of sight due to latitudinal signal deflection, and we find insignificant evidence with our current data. With simulations, we find that the latitudinal deflection delay is unlikely to be measured with timing because of its correlation with Shapiro delay. Furthermore, although it is currently not possible to detect the expected lensing correction to the Shapiro delay, our simulations suggest that this effect may be measured with the full SKA. Finally, we provide an improved analytical description for the signal propagation in the double pulsar system that meets the timing precision expected from future instruments such as the full SKA

Constraining the dense matter equation-of-state with radio pulsars

Radio pulsars provide some of the most important constraints for our understanding of matter at supranuclear densities. So far, these constraints are mostly given by precision mass measurements of neutron stars (NS). By combining single measurements of the two most massive pulsars, J0348$+$0432 and J0740$+$6620, the resulting lower limit of 1.98 $M_\odot$ (99% confidence) of the maximum NS mass, excludes a large number of equations of state (EOSs). Further EOS constraints, complementary to other methods, are likely to come from the measurement of the moment of inertia (MOI) of binary pulsars in relativistic orbits. The Double Pulsar, PSR J0737$-$3039A/B, is the most promising system for the first measurement of the MOI via pulsar timing. Reviewing this method, based in particular on the first MeerKAT observations of the Double Pulsar, we provide well-founded projections into the future by simulating timing observations with MeerKAT and the SKA. For the first time, we account for the spin-down mass loss in the analysis. Our results suggest that an MOI measurement with 11% accuracy (68% confidence) is possible by 2030. If by 2030 the EOS is sufficiently well known, however, we find that the Double Pulsar will allow for a 7% test of Lense-Thirring precession, or alternatively provide a $\sim3\sigma$-measurement of the next-to-leading order gravitational wave damping in GR. Finally, we demonstrate that potential new discoveries of double NS systems with orbital periods shorter than that of the Double Pulsar promise significant improvements in these measurements and the constraints on NS matter.Comment: 13 pages, 8 figures. Accepted by MNRA

Computer-Based Redesign of a β Sandwich Protein Suggests that Extensive Negative Design Is Not Required for De Novo β Sheet Design

The de novo design of globular β-sheet proteins remains largely an unsolved problem. It is unclear if most designs are failing because the designed sequences do not have favorable energies in the target conformations or if more emphasis should be placed on negative design, i.e. explicitly identifying sequences that have poor energies when adopting undesired conformations. We tested if we could redesign the sequence of a naturally occurring β-sheet protein, tenascin, with a design algorithm that does not include explicit negative design. Denaturation experiments indicate that the designs are significantly more stable than the wild type protein and the crystal structure of one design closely matches the design model. These results suggest that extensive negative design is not required to create well-folded β-sandwich proteins. However, it is important to note that negative design elements may be encoded in the conformation of the protein backbone which was preserved from the wild type protein

A Gaussian-processes approach to fitting for time-variable spherical solar wind in pulsar timing data

Propagation effects are one of the main sources of noise in high-precision pulsar timing. For pulsars below an ecliptic latitude of 5°, the ionized plasma in the solar wind can introduce dispersive delays of order 100 µs around solar conjunction at an observing frequency of 300 MHz. A common approach to mitigate this assumes a spherical solar wind with a time-constant amplitude. However, this has been shown to be insufficient to describe the solar wind. We present a linear, Gaussian-process piecewise Bayesian approach to fit a spherical solar wind of time-variable amplitude, which has been implemented in the pulsar software RUN_ENTERPRISE. Through simulations, we find that the current EPTA+InPTA data combination is not sensitive to such variations; however, solar wind variations will become important in the near future with the addition of new InPTA data and data collected with the low-frequency LOFAR telescope. We also compare our results for different high-precision timing data sets (EPTA+InPTA, PPTA, and LOFAR) of 3 ms pulsars (J0030+0451, J1022+1001, J2145−0450), and find that the solar-wind amplitudes are generally consistent for any individual pulsar, but they can vary from pulsar to pulsar. Finally, we compare our results with those of an independent method on the same LOFAR data of the three millisecond pulsars. We find that differences between the results of the two methods can be mainly attributed to the modelling of dispersion variations in the interstellar medium, rather than the solar wind modelling

Kopplung solarer p und g Moden

Solare g Moden sind potenziell wichtig für die Erforschung des Sonnenkerns, aber die Erkennung von g Moden ist aufgrund ihrer kleinen Amplituden an der Oberfläche sehr schwierig. Eine aktuelle Studie berichtete über die Messung von g Moden durch ihre Interaktion mit solaren p Moden. In dieser Arbeit zielen wir darauf ab, eine theoretische Grundlage für die Auswirkungen von g Moden auf p Moden zu legen, die im Moment fehlt. Dabei wird davon ausgegangen, dass g Moden eine statische Störung eines Referenz-Hintergrundmodells verursachen und ihre Auswirkungen auf die p-Modus-Frequenzen werden in erster Ordnung berechnet. Die Auswirkungen von g Moden auf p Moden sind sehr gering, und nur g Moden mit harmonischem Grad l und azimuthaler Ordnung m = 0 beeinflussen p-Modus-Frequenzen. Diese können die Detektion von g Moden nicht erklären. Darüber hinaus ist die dominante Wechselwirkung zwischen g und p Moden an der Oberfläche.Solar gravity modes (g modes) are potentially important for probing the solar core, however the detection of g modes is notoriously difficult due to their small amplitudes at the surface. A recent study reported the detection of g modes through their interaction with solar pressure modes (p modes). In this thesis, we aim at establishing a theoretical basis for the effects of g modes on p modes, which is missing at the moment. To do so, g modes are assumed to cause a static perturbation to a reference solar background model, and their effects on p-mode frequencies are computed to first order. The effects of g modes on p modes are very small, with the largest frequency shift about 1.45 nHz, and only g modes with even harmonic degree l and azimuthal order m = 0 affect p-mode frequencies. These results can not explain the recent solar g mode detection. In addition, the dominant interaction of g modes with p modes is at the surface.vorgelegt von Huanchen Hu aus ChinaZusammenfassung in deutscher SpracheUniversität Innsbruck, Masterarbeit, 2018Georg-August-Universität Göttingen, Masterarbeit, 2018(VLID)283376

A Fault Diagnosis Support System Using Agents

Fault diagnosis within airplane is a complex and time consuming task. Both the efficiency and the effect of fault diagnosis are increasingly important for airplane flying on timetable and flight security. In this paper, we propose a fault diagnosis support system (FDSS) by using agent technology to support ground crew in process of airplane fault diagnosis. This FDSS consists of four kinds of agents: management agent, interface agent, diagnosis agent and data agent. Management agent serves as an agent name server and keeps the all agents’ information, such as name, location, capabilities. Interface agent is the interface of FDSS. Fault diagnosis user and expert have their own interface agent to interact with the FDSS. Diagnosis agent encapsulates a diagnosis method. Data agent gets the required signals for fault diagnosis. All agents have the capabilities of communication and cooperation with each other. We study the FDSS architecture, and discuss the development technology of FDSS.The original publication is available at JAIST Press http://www.jaist.ac.jp/library/jaist-press/index.htmlIFSR 2005 : Proceedings of the First World Congress of the International Federation for Systems Research : The New Roles of Systems Sciences For a Knowledge-based Society : Nov. 14-17, 2028, Kobe, JapanSymposium 3, Session 1 : Intelligent Information Technology and Applications Men and Computin

An Agent based Human Resource Management Information System

Human resource means the most to an organization, even the organization is small or large. Human resource management is a critical type of management in the organization. In this paper, we propose an agent based human resource management information system. It comprises a web service and three kinds of agents. The web service provides functions for human resource routine management, such as maintaining basic data, checking on working attendance, calculating salaries and so on. Three kinds of agents are information gathering agent (IGA), personnel evaluating agent (PEA) and decision supporting agent (DSA). When a new employee is recruited in the organization, the IGA will create his website. Three types of persons can visit his webpage, these are himself, colleagues in the same branch and relative management staffers. For himself visiting, he can update his personal information and progress of his work. For colleagues visiting of his webpage, they can make comments on his attitude, capability, effect and efficiency of the work he is doing or has done. And for relative management staff, they can also express their viewpoints about him. All information about him can be gathered by the IGA. The PEA can mine the information gathered by the IGA for specified purposes such as capability evaluation and pre-examination of promotion. The PEA uses the information and evaluation models to perform evaluating tasks. The DSA can help the manager to plan the human resource, including right person at right position, personnel training, employee recruiting and employee dismissing.The original publication is available at JAIST Press http://www.jaist.ac.jp/library/jaist-press/index.htmlIFSR 2005 : Proceedings of the First World Congress of the International Federation for Systems Research : The New Roles of Systems Sciences For a Knowledge-based Society : Nov. 14-17, 2027, Kobe, JapanSymposium 3, Session 1 : Intelligent Information Technology and Applications Men and Computin

Insights into the Underlying Mechanism of Ochratoxin A Production in Aspergillus niger CBS 513.88 Using Different Carbon Sources

Aspergillus niger produces carcinogenic ochratoxin A (OTA), a serious food safety and human health concern. Here, the ability of A. niger CBS 513.88 to produce OTA using different carbon sources was investigated and the underlying regulatory mechanism was elucidated. The results indicated that 6% sucrose, glucose, and arabinose could trigger OTA biosynthesis and that 1586 differentially expressed genes (DEGs) overlapped compared to a non-inducing nutritional source, peptone. The genes that participated in OTA and its precursor phenylalanine biosynthesis, including pks, p450, nrps, hal, and bzip, were up-regulated, while the genes involved in oxidant detoxification, such as cat and pod, were down-regulated. Correspondingly, the activities of catalase and peroxidase were also decreased. Notably, the novel Gal4-like transcription factor An12g00840 (AnGal4), which is vital in regulating OTA biosynthesis, was identified. Deletion of AnGal4 elevated the OTA yields by 47.65%, 54.60%, and 309.23% using sucrose, glucose, and arabinose as carbon sources, respectively. Additionally, deletion of AnGal4 increased the superoxide anion and H2O2 contents, as well as the sensitivity to H2O2, using the three carbon sources. These results suggest that these three carbon sources repressed AnGal4, leading to the up-regulation of the OTA biosynthetic genes and alteration of cellular redox homeostasis, ultimately triggering OTA biosynthesis in A. niger

High-altitude Magnetospheric Emissions from Two Pulsars

We discover three new weak pulse components in two known pulsars, one in PSR J0304+1932 and two in PSR J1518+4904. These components are emitted about halfway between the main emission beam and the interpulse beam (beam from the opposite pole). They are separated from their main pulse peak by 99° ± 3° for J0304+1932 and 123.°6 ± 0.°7 (leading) and 93° ± 0.°4 (trailing) for J1518+4904. Their peak-intensity ratios to main pulses are ∼ 0.06% for J0304+1932 and ∼0.17% and ∼0.83% for J1518+4904. We also analyzed the flux fluctuations and profile variations of the emissions for the two pulsars. The results show correlations between the weak pulses and their main pulses, indicating that these emissions come from the same pole. We estimated the emission altitude of these weak pulses and derived a height of about half of the pulsar’s light-cylinder radius. These pulse components are a unique sample of high-altitude emissions from pulsars, and challenge the current pulsar emission models