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Volumetric Rates of Luminous Red Novae and Intermediate-luminosity Red Transients with the Zwicky Transient Facility
No full textLuminous red novae (LRNe) are transients characterized by low luminosities and expansion velocities, and they are associated with mergers or common-envelope ejections in stellar binaries. Intermediate-luminosity red transients (ILRTs) are an observationally similar class with unknown origins, but they are generally believed to be either electron-capture supernovae in super-asymptotic giant branch stars or outbursts in dusty luminous blue variables (LBVs). In this paper, we present a systematic sample of eight LRNe and eight ILRTs detected as part of the Census of the Local Universe (CLU) experiment on the Zwicky Transient Facility (ZTF). The CLU experiment spectroscopically classifies ZTF transients associated with nearby (<150 Mpc) galaxies, achieving 80% completeness for mr < 20 mag. Using the ZTF-CLU sample, we derive the first systematic LRNe volumetric rate of 7.8_(-3.7)^(+6.5) x 10⁻⁵ Mpc⁻³ yr⁻¹ in the luminosity range −16 ≤ Mᵣ ≤ −11 mag. We find that, in this luminosity range, the LRN rate scales as dN/dL ∝ L^(-2.5 ± 0.3) — significantly steeper than the previously derived scaling of L^(−1.4 ± 0.3) for lower-luminosity LRNe (Mᵥ ≥ −10 mag). The steeper power law for LRNe at high luminosities is consistent with the massive merger rates predicted by binary population synthesis models. We find that the rates of the brightest LRNe (Mᵣ ≤ −13 mag) are consistent with a significant fraction of them being progenitors of double compact objects that merge within a Hubble time. For ILRTs, we derive a volumetric rate of 2.6_(-1.4)^(+1.8) x 10^⁻⁶ Mpc⁻³ yr⁻¹ for Mᵣ ≤ −13.5 mag, which scales as dN}/dL ∝ L^(-2.5 ± 0.5). This rate is ∼1%–5% of the local core-collapse supernova rate and is consistent with theoretical ECSN rate estimates
Pyocyanin-dependent electrochemical inhibition of Pseudomonas aeruginosa biofilms is synergistic with antibiotic treatment
No full textPseudomonas aeruginosa biofilms are common in chronic wound infections and recalcitrant to treatment. Survival of cells within oxygen-limited regions in these biofilms is enabled by extracellular electron transfer (EET), whereby small redox active molecules act as electron shuttles to access distal oxidants. Here, we report that electrochemically controlling the redox state of these electron shuttles, specifically pyocyanin (PYO), can impact cell survival within anaerobic P. aeruginosa biofilms and can act synergistically with antibiotic treatment. Prior results demonstrated that under anoxic conditions, an electrode poised at sufficiently oxidizing potential (+100 mV vs Ag/AgCl) promotes EET within P. aeruginosa biofilms by re-oxidizing PYO for reuse by the cells. Here, when a reducing potential (−400 mV vs Ag/AgCl) was used to disrupt PYO redox cycling by maintaining PYO in the reduced state, we observed a 100-fold decrease in colony forming units within these biofilms compared with those exposed to electrodes poised at +100 mV vs Ag/AgCl. Phenazine-deficient Δphz* biofilms were unaffected by the potential applied to the electrode but were re-sensitized by adding PYO. The effect at −400 mV was exacerbated when biofilms were treated with sub-MICs of a range of antibiotics. Most notably, addition of the aminoglycoside gentamicin in a reductive environment almost completely eradicated wild-type biofilms but had no effect on the survival of Δphz* biofilms in the absence of phenazines. These data suggest that antibiotic treatment combined with the electrochemical disruption of PYO redox cycling, either through the toxicity of accumulated reduced PYO or the disruption of EET, or both, can lead to extensive killing
Rubber Banjo Bridge Demo
No full textWondering about what a rubber-topped bridge would do for your banjo? Read on and hear an example
Tidyproteomics: an open-source R package and data object for quantitative proteomics post analysis and visualization
No full textBackground. The analysis of mass spectrometry-based quantitative proteomics data can be challenging given the variety of established analysis platforms, the differences in reporting formats, and a general lack of approachable standardized post-processing analyses such as sample group statistics, quantitative variation and even data filtering. We developed tidyproteomics to facilitate basic analysis, improve data interoperability and potentially ease the integration of new processing algorithms, mainly through the use of a simplified data-object.
Results: The R package tidyproteomics was developed as both a framework for standardizing quantitative proteomics data and a platform for analysis workflows, containing discrete functions that can be connected end-to-end, thus making it easier to define complex analyses by breaking them into small stepwise units. Additionally, as with any analysis workflow, choices made during analysis can have large impacts on the results and as such, tidyproteomics allows researchers to string each function together in any order, select from a variety of options and in some cases develop and incorporate custom algorithms.
Conclusions: Tidyproteomics aims to simplify data exploration from multiple platforms, provide control over individual functions and analysis order, and serve as a tool to assemble complex repeatable processing workflows in a logical flow. Datasets in tidyproteomics are easy to work with, have a structure that allows for biological annotations to be added, and come with a framework for developing additional analysis tools. The consistent data structure and accessible analysis and plotting tools also offers a way for researchers to save time on mundane data manipulation tasks
Isaac Newton, A Radical Whig?
No full textIsaac Newton’s credentials as a staunch Whig have been taken for granted at least since 1848 when Macaulay hailed him as ‘the glory of the Whig party’.¹ Newton’s defiant stance during the Alban Francis affair, when he defended liberty and Protestantism against the dispensing power of James II—a stand that earned him a place in the Cambridge delegation summoned to appear before Lord Chancellor George Jeffreys—purportedly showed him to be a resolute opponent of the monarch’s policies long before the Revolution of 1688. Newton, in fact, is perceived not only as a veritable Whig delegate to the Convention Parliament, but one closely associated with the radical wing of that party.² Hitherto, however, the evidentiary basis for such seemingly sterling credentials have barely been scrutinized. And though such scrutiny is not possible in a brief note, it is possible to complicate the received view by suggesting that Newton’s voting record during the 1689 parliament sits at odds with the image of a resolute Whig
Revealing the Spectral State Transition of the Clocked Burster, GS 1826-238, with NuSTAR StrayCats
No full textWe present the long-term analysis of GS 1826-238, a neutron star X-ray binary known as the Clocked Burster, using data from NuSTAR StrayCats. StrayCats, a catalog of NuSTAR stray light data, contains data from bright, off-axis X-ray sources that have not been focused by the NuSTAR optics. We obtained stray light observations of the source from 2014–2021, reduced and analyzed the data using nustar-gen-utils Python tools, demonstrating the transition of the source from the island atoll state to a banana branch. We also present the light-curve analysis of Type I X-ray bursts from the Clocked Burster and show that the bursts from the banana/soft state are systematically shorter in duration than those from the island/hard state and have a higher burst fluence. From our analysis, we note an increase in the mass accretion rate of the source, and a decrease in burst frequency with the transition
Storage, evolution, and mixing in basaltic eruptions from around the Okataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa New Zealand
No full textThe Okataina Volcanic Centre (OVC) is the most recently active caldera system in the Taupō Volcanic Zone, Aotearoa New Zealand. Although best known for its high rates of explosive rhyolitic volcanism, there are several examples of basaltic to basaltic-andesite contributions to OVC eruptions. These range from minor involvement of basalt in rhyolitic eruptions to the exclusively basaltic 1886 C.E. plinian eruption of Tarawera. To explore the basaltic component supplying this dominantly rhyolitic area, we analyse the textures and compositions (minerals and melt inclusions) of four basaltic eruptions from within and around the OVC that have similar whole rock chemistry, namely: Terrace Rd, Rotomakariri, Rotokawau, and Tarawera. Data from these basaltic deposits provide constraints on the conditions of magma evolution and ascent in the crust prior to eruption, revealing that eruptions sample multiple distinct reservoirs during ascent to the surface. The most abundant basaltic component is generated by cooling-induced crystallisation of a common, oxidised, volatile-rich basaltic melt at various depths within the crust that mixes upon ascent. Despite similar bulk compositions, these four eruptions are texturally distinct from each other as a result of their wide variation in eruption style
Payload concepts for investigations of electrostatic dust motion on the lunar surface
No full textSignificant experimental and computational investigations have explored the feasibility of electrostatically-motivated dust motion on the lunar surface. The motion of lunar dust influences our understanding of the evolution of the surface and may also present a hazard to future exploration vehicles and astronauts. The possibility of a sustained exploration presence on the lunar surface opens the door to long-term experiments on the lunar surface, akin to the science facilities on the International Space Station. We have identified four measurements/observations that would significantly advance our understanding of dust-plasma interactions on the lunar surface. In this context, we provide conceptual designs for payloads to obtain these observations: a Langmuir probe, dust deposit witness plate, regolith charge measurement instrument, and cameras to look for evidence of horizon glow. These payloads could deploy independently and sequentially, or together as a suite. The proposed payloads would provide key observations that would inform future modeling efforts and direct future in situ experiments to understand the dust-plasma environment, both for planetary science and spacecraft design applications
Behaviors of a Polymer Chain in Channels: From Zimm to Rouse Dynamics
No full textThe effects of confinement and hydrodynamic interactions on single-chain diffusion behaviors are studied by using a combination of molecular dynamics and multiparticle collision dynamics simulations. For polymers in free space, the simulation results showed that the diffusion coefficient D∞ for long chains scales with the chain length N as D_∞ ∼ N^(–ν) (ν = 0.588), consistent with the Zimm dynamics, but it deviates from the Zimm dynamics for short chains. For polymers confined in channels with width H, the diffusion coefficient is found to follow two different scaling relations. The observed behaviors could be understood by introducing a microscopic hydrodynamic length ξₕ, below which the overall effect of hydrodynamic interactions becomes less important. For a confined chain, the diffusion behavior exhibits a crossover from Zimm (nondraining) to Rouse (free draining) dynamics as the channel size H decreases. When H is larger than ξₕ, the confinement experienced by the polymer chain is weak and the diffusion coefficient scales as D ∼ H^(0.7), in accordance with the prediction of blob theory; when H is smaller than ξₕ, D becomes independent of H, implying a free draining condition. A general analytical expression of D is derived by extending the partially permeable sphere model to the blob scale, which gives a quantitative description of the transition from Zimm to Rouse dynamics as H decreases
Recurring summer and winter droughts from 4.2-3.97 thousand years ago in north India
No full textThe 4.2-kiloyear event has been described as a global megadrought that transformed multiple Bronze Age complex societies, including the Indus Civilization, located in a sensitive transition zone with a bimodal (summer and winter) rainfall regime. Here we reconstruct changes in summer and winter rainfall from trace elements and oxygen, carbon, and calcium isotopes of a speleothem from Dharamjali Cave in the Himalaya spanning 4.2–3.1 thousand years ago. We find a 230-year period of increased summer and winter drought frequency between 4.2 and 3.97 thousand years ago, with multi-decadal aridity events centered on 4.19, 4.11, and 4.02 thousand years ago. The sub-annually resolved record puts seasonal variability on a human decision-making timescale, and shows that repeated intensely dry periods spanned multiple generations. The record highlights the deficits in winter and summer rainfall during the urban phase of the Indus Civilization, which prompted adaptation through flexible, self-reliant, and drought-resistant agricultural strategies