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Variability of Known Exoplanet Host Stars Observed by TESS
No full textAbstract
Both direct and indirect methods of exoplanet detection rely upon detailed knowledge of the potential host stars. Such stellar characterization allows for accurate extraction of planetary properties, as well as contributing to our overall understanding of exoplanetary system architecture. In this analysis, we examine the photometry of 264 known exoplanet host stars (harboring 337 planetary companions) that were observed during the Transiting Exoplanet Survey Satellite (TESS) Prime Mission. We identify periodic signatures in the lightcurves of these stars and make possible connections to stellar pulsations and their rotation periods, and compare the stellar variability to the published planetary orbital periods. From these comparisons, we quantify the effects of stellar variability on exoplanet detection, confirming that exoplanets detection is biased toward lower variability stars, but larger exoplanets dominate the population of exoplanets around variable stars. Exoplanet detection methods represented among these systems are distinct between stellar spectral types across the main sequence, though notable outliers exist. In addition, biases present in both the sourced data from TESS and the host star selection process, which strongly influences the representation of both stellar and planetary characteristics in the final populations. We also determine whether the host stars photometric variability affects or mimics the behavior or properties of the system’s planets. These results are discussed in the context of how the behavior of the host star is responsible for how we observe exoplanet characteristics, most notably their radii and atmospheric properties, and how the activity may alter our measurements or impact the evolution of planetary properties.</jats:p
Virtually the Same? Evaluating the Effectiveness of Remote Undergraduate Research Experiences
No full text Undergraduates participating in remote research programs experienced gains in scientific self-efficacy similar those observed in in-person research. Students experienced gains in scientific identity, graduate and career intentions, and perceptions of benefits and costs of doing research only if they started their remote undergraduate research experiences at lower levels. </jats:p
Steps of actin filament branch formation by Arp2/3 complex investigated with coarse-grained molecular dynamics
No full textThe nucleation of actin filament branches by the Arp2/3 complex involves activation through nucleation promotion factors (NPFs), recruitment of actin monomers, and binding of the complex to the side of actin filaments. Because of the large system size and processes that involve flexible regions and diffuse components, simulations of branch formation using all-atom molecular dynamics are challenging. We applied a coarse-grained model that retains amino-acid level information and allows molecular dynamics simulations in implicit solvent, with globular domains represented as rigid bodies and flexible regions allowed to fluctuate. We used recent electron microscopy structures of the inactive Arp2/3 complex bound to NPF domains and to mother actin filament for the activated Arp2/3 complex. We studied interactions of Arp2/3 complex with the activating VCA domain of the NPF Wiskott-Aldrich syndrome protein, actin monomers, and actin filament. We found stable configurations with one or two actin monomers bound along the branch filament direction and with CA domain of VCA associated to the strong and weak binding sites of the Arp2/3 complex, supporting prior structural studies and validating our approach. We reproduced delivery of actin monomers and CA to the Arp2/3 complex under different conditions, providing insight into mechanisms proposed in previous studies. Simulations of active Arp2/3 complex bound to a mother actin filament indicate the contribution of each subunit to the binding. Addition of the C-terminal tail of Arp2/3 complex subunit ArpC2, which is missing in the cryo-EM structure, increased binding affinity, indicating a possible stabilizing role of this tail.</jats:p
The Impact of What Others Do, Approve Of, and Expect You to Do: An In-Depth Analysis of Social Norms and Self-Disclosure on Social Media
No full text There are many factors that account for disclosure of private information on social network sites, but a potentially powerful determinant that remains understudied is social norms, which refer to perceptions of what other people do, approve of, and expect us to do on social media. To address this gap, we conducted an in-depth analysis of descriptive, injunctive, and subjective norms for verbal and visual disclosure on Facebook and Instagram, using a preregistered survey study with 863 participants. We further analyzed whether critical media literacy and media-related self-reflection could buffer against uncritical adoption of these norms. The findings revealed that all three types of norms positively and independently predicted self-disclosure, regardless of the platform or type of self-disclosure (visual vs. verbal), while controlling for other common predictors of self-disclosure, including perceived benefits and risks of self-disclosure. Self-reflection and critical media literacy neither directly predicted disclosure, nor accounted for differences in norm-behavior relationships. </jats:p
Accelerating the Plonk zkSNARK Proving System using GPU Architectures
No full textZero-knowledge proofs (ZKPs) are cryptographic primitives that enable a prover to convince a verifier that a statement about some secret is true without leaking information about the secret. The prover ultimately does not reveal anything beyond the validity of the statement itself to the verifier. In recent years, blockchains have been leveraging the properties of zero-knowledge proofs for private transactions and verifiable outsourced computation, leading to improved privacy and scalability for various systems and applications. The specific problem is that the cost of generating proofs is a computationally intensive task which remains a bottleneck for proving systems, while verifying proofs is computationally inexpensive and fast. However, the proof generation process is primarily dominated by operations such as multi-scalar multiplication (MSM) and number theoretic transforms (NTT), which happen to be embarrassingly parallel. This paper describes the hardware acceleration techniques and challenges for constructing zero-knowledge proofs using NVIDIA GPUs in the CUDA programming language
Interaction between Virtual and Reality: Real-Time Collision Detection for UAVs in VR scenario
No full textAbstractRobot swarm experiments in laboratory scenarios are often constrained by the limitations of the experimental site, and researchers always suffer from many problems such as the small experimental space, the difficulty of matching the obstacles in the experiments with those in real scenarios, and the difficulty of simulating specific environments in the laboratory. Based on this background, the author has constructed a virtual-reality collision detection feedback experiment platform for UAVs in the laboratory under the guidance. The platform is based on a motion capture system [1] as well as the ROS system [2], and is able to provide real-time feedback on the collision between a flying real UAV and an obstacle in the virtual environment with a low latency time. The author\u27s experiments are divided into two major sections. In the first section, the author focuses on familiarizing the operating principle of the motion capture system and the ROS system and sets up a collision feedback model with extremely high speed although sacrificing some accuracy. This part of the approach draws on the ideas of the AABB algorithm [3] [4], with the prior import and loading of the obstacle map, to be able to respond to the data release frequency of more than 1000Hz. In this process, the author also created a program module used to simulate the data distribution module of the motion capture system and visualize experimental results. The focus of this part of the work is to familiarize the author with the experimental tools such as the Optitrack system, as well as the ROS system, meanwhile to verify the feasibility of the experimental design ideas. The goal of the second section is to optimize the model from the first section further. In this section, the author further enhances the accuracy of the collision detection model without introducing too much time complexity. Before conducting the experiments in this section, the author reviewed some papers and chose to use the OBB algorithm [4], GJK algorithm [5], and attitude solver [6] to accurately determine the collision between the volume of a real UAV and the volume of a virtual obstacle, no matter how complex the shape of the UAV and the obstacle is [4] [7]. And while the accuracy is significantly improved, the response data release frequency can still be stable up to 500Hz-1000Hz. At the end of the experiment, the author visualizes the experimental results and gives an outlook on future research
A Preliminary Study on the Solidification Cracking and Stress Relief Cracking Susceptibility of Various Compositions of 10 Weight Percent Nickel Steel
No full textResearch involving the mechanical properties of 10 weight percent nickel steel has recently exemplified its great ballistic resistance and toughness at low temperatures. These superior mechanical properties support the candidacy of this steel to be used in naval combatant ships and other military components that are exposed to low sea temperatures. Despite its potential uses for such applications, limited research has been conducted on the mechanical stability during and after welding, which is essential for the fabrication of military parts. During the weld thermal cycle, the heat affected zone of the steel becomes exposed to very high temperature changes over a short amount of time. This thermal gradient across the span of the HAZ subjects it to high internal stresses after welding. To relieve these stresses, a post-weld heat treatment must be employed, which requires plastic deformation at elevated temperatures. During this process, localized deformation along the grain boundaries can result in low ductility failures, a process known as stress-relief cracking. Another common failure mechanism in steel welds is called solidification cracking, which is a result of non-equilibrium solidification and solute segregation. The solidification cracking and stress-relief cracking susceptibility of three 10 weight percent nickel alloy with varying compositions was investigated using Gleeble, Varestraint, and microscopy techniques. The cracking susceptibility of HY-100, a well-established steel currently being used in ship hull material was also investigated and compared to the 10 weight percent nickel alloys. It was found that the stress relief cracking response largely depend on the carbon content and the post-weld heat treatment temperature, while the trends in solidification cracking susceptibility also depend on the content of tramp elements such as P and S, however further investigation will be necessary to confirm these trends. This investigation provides a reasonable approach to identifying the most suitable composition to be used in hull structure material while avoiding failure via these two mechanisms, and identifies a good post-weld heat treatment temperature to be used after welding this alloy
Real-Time Hybrid Simulation of Complex Structural Systems Subjected to Multi-natural Hazards
No full textThe overall objective of this dissertation is to develop new computational algorithms for application to real-time hybrid simulation (RTHS) of complex structural systems subjected to multi-natural hazards. Resiliency of structural systems under natural hazards is of interest. Real-Time Hybrid Simulation (RTHS) is a testing tool that can be used to assess the resiliency of such systems. In a RTHS the complete system is considered, where selected components for which computational models exist are modeled numerical and the remaining components are modeled physically in the laboratory. The former is referred to as the analytical substructure while the latter the experimental substructure. It is necessary to expand RTHS to accommodate large complex structural systems that reflect real world problems. The current state-of-the-art includes modeling systems as two-dimensional planar problems with a limited number of degrees of freedom that excludes soil-foundation-structural system interaction effects. It is necessary to expand RTHS to three dimensional structural systems, to include soil-foundation-structural system interaction effects, to develop computationally efficient algorithms to enable the real-time numerical integration of the equations of motion of a system with a large number of degrees of freedom, and to deal with systems that possess many response modification devices (e.g., nonlinear viscous dampers) while only a limited number of experimental testbeds are available for a RTHS. Expanding RTHS to investigate the resiliency of large and complex renewable energy generation structures, such as offshore wind turbines, is also investigated and RTHS is proven to be a viable tool to understand the long- and short-term behavior of their piled foundation
PUTTING WORDS TO VISIONS: Linguistic Encoding of the Oriental Sublime in the Essays of Joseph Addison
No full textJoseph Addison in his daily Periodical, The Spectator, engages with the literary reproductions of Eastern tales, and through this engagement both contributes to, and benefits from the ongoing process of Orientalism in the West, specifically England. He uses the East as a point of reference in order to aid the pedagogical self-conception within his English readers, who are asked to both learn from the East, while emphasizing the difference and distance between the two geographies. Although this engagement furthers the construction of the East by an English writer writing for English audiences, it however also necessitates the inclusion of the Orient–its tropes, vocabularies, myths, fables, characters and literary modes–into English sensibility. These, in turn, not only enter the trove of collective or shared British knowledge, but are also reproduced by Romantic poets as quintessential and identifiable Romanticist ideas and tropes. Among these are notions of sublimity, terror, excess, beauty and mystical considerations of life, death and afterlife. Addison\u27s widely read and circulated paper then becomes a site of inquiry into not only how constructions and reproductions of the Orient contribute to what we understand as Orientalsim, but also how the shadow of the Orient provides the language through which English identity and literature are negotiated, examined, compared to, and studied against. This paper explores three of such essays written by Addison for The Spectator, and examines the ways in which the Orient features in a periodical which states that it is primarily interested in issues and knowledge of the English self
Co-encapsulation and delivery of an efflux pump inhibitor and antibiotic to overcome antibiotic resistance gained from the overexpression of efflux pumps in Pseudomonas aeruginosa.
No full textAntibiotic resistance is a growing issue due to the widespread misuse of antibiotics. The United States Centers for Disease Control and Prevention estimates that 35,000 people die due to antibiotic resistant bacteria in the United States each year. New antibiotics are difficult to create and bring to market; therefore, new solutions using existing antibiotics should be looked at as possible solutions to overcome antibiotic resistance. One mechanism of antibiotic resistance is the overexpression of efflux pumps. Efflux pump inhibitors (EPIs) have been discovered, yet there has been little to no clinical success for these drugs. EPIs have had little clinical use due to a few factors; mammalian cell cytotoxicity, difficulty in getting the EPI into the bacterial cytosol where it is active, and differences in pharmacokinetics between antibiotics and EPIs. Coencapsulation should address all three of these problems. Using existing nanoparticle delivery technology, we seek to overcome the overexpression of efflux pumps by codelivering antibiotics and EPIs encapsulated in liposomes. We hypothesize this codelivery will increase effectiveness of the antibiotic against the resistant bacterium Pseudomonas aeruginosa. This method of delivery could hold potential as a future treatment method for antibiotic resistant bacterial infections