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Selective transesterification mediated by lanthanum complexes in the copolymerisation of lactide and δ-valerolactone
Get PDFModel category structures on truncated multicomplexes for complex geometry
Get PDFTo a bicomplex one can associate two natural filtrations, the column and row filtrations, and then two associated spectral sequences. This can be generalized to N-multicomplexes. We present a family of model category structures on the category of N-multicomplexes where the weak equivalences are the morphisms inducing a quasi-isomorphism at a fixed page r of the first spectral sequence and at a fixed page s of the second spectral sequence. Such weak equivalences arise naturally in complex geometry. In particular, the model structures presented here establish a basis for studying homotopy types of almost complex manifolds
EP 250108a/SN 2025kg: Observations of the Most Nearby Broad-line Type Ic Supernova Following an Einstein Probe Fast X-Ray Transient
Get PDFWith a small sample of fast X-ray transients (FXTs) with multiwavelength counterparts discovered to date, their progenitors and connections to γ-ray bursts (GRBs) and supernovae (SNe) remain ambiguous. Here, we present photometric and spectroscopic observations of SN 2025kg, the SN counterpart to the FXT EP 250108a. At z = 0.17641, this is the closest known SN discovered following an Einstein Probe (EP) FXT. We show that SN 2025kg’s optical spectra reveal the hallmark features of a broad-lined Type Ic SN. Its light-curve evolution and expansion velocities are comparable to those of GRB-SNe, including SN 1998bw, and two past FXT-SNe. We present JWST/NIRSpec spectroscopy taken around SN 2025kg’s maximum light, and find weak absorption due to He I 1.0830 μm and 2.0581 μm and a broad, unidentified emission feature at ∼4–4.5 μm. Further, we observe broadened Hα in optical data at 42.5 days that is not detected at other epochs, indicating interaction with H-rich material. From its light curve, we derive a 56Ni mass of 0.2–0.6 M⊙. Together with our companion Letter, our broadband data are consistent with a trapped or low-energy (≲1051 erg) jet-driven explosion from a collapsar with a zero-age main-sequence mass of 15–30 M⊙. Finally, we show that the sample of EP FXT-SNe supports past estimates that low-luminosity jets seen through FXTs are more common than successful (GRB) jets, and that similar FXT-like signatures are likely present in at least a few percent of the brightest Type Ic-BL SNe
How can qualitative research enhance and strengthen randomised controlled trials undertaken with children and young people?
No full textDiversity of coatings on hydrothermal vent gastropods
No full textShells of hydrothermal vent gastropods are often covered by inorganic coatings whose chemical composition, formation mechanisms, and possible function remain poorly understood. We investigated the mineral coatings of six vent gastropod specimens (one each of the species Lepetodrilus nux, Cantrainea jamsteci, Desbruyeresia armata, Desbruyeresia marisindica, and two specimens of Alviniconcha marisindica from separate vent sites) from four different localities (Iheya North vent field, Okinawa Trough and Myojin-sho Caldera, Izu-Ogasawara Arc in the Pacific Ocean, and Kairei and Edmond vent fields on the Central Indian Ridge) using SEM/EDS and Raman spectroscopy. The resulting data show that the chemical composition of the coatings corresponds to the chemistry of vent fluids at the respective localities and distance from active venting. There was no evidence of mineral replacement of any of the studied shells. In one specimen the coating was partly overgrown by the shell, showing a contemporary growth of the shell and the coating. The texture of the coating on the Desbruyeresia armata specimen suggests a possible role of microorganisms in its formation. Gastropod fossils from ancient vent sites are preserved by pyrite, with no remaining carbonate shell. We found pyrite only in coatings of the modern gastropods collected near high-temperature vent sites, indicating that close proximity to active venting may be necessary for successful preservation of vent gastropods in the fossil record
LArTPC hit-based topology classification with quantum machine learning and symmetry considerations
Get PDFWe present a new approach to separate tracklike and showerlike topologies in liquid argon time projection chamber (LArTPC) experiments for neutrino physics using quantum machine learning. Effective reconstruction of neutrino events in LArTPCs requires accurate and granular information about the energy deposited in the detector. These energy deposits can be viewed as 2D images. Simulated data from the MicroBooNE experiment and a simple custom dataset are used to perform pixel-level classification of the underlying particle topology. Images of the events have been studied by creating small patches around each pixel to characterize its topology based on its immediate neighborhood. This classification is achieved using convolution-based learning models, including quantum-enhanced architectures known as quanvolutional neural networks. The quanvolutional networks are extended to symmetries beyond translation. Rotational symmetry has been incorporated into a subset of the models. This study demonstrates that quantum-enhanced models perform better than their classical counterparts with a comparable number of parameters, but are outperformed by classical models with two orders of magnitude more parameters. The inclusion of rotation symmetry appears beneficial only in a small number of cases and remains to be explored further. Possible future use of quantum machine learning in the reconstruction phase is discussed, with emphasis on future LArTPC experiments such as Deep Underground Neutrino Experiment (DUNE)-far detector (FD)
Typhoid toxin of Salmonella Typhi elicits host antimicrobial response during acute typhoid fever
Get PDFSalmonella Typhi secretes typhoid toxin that activates cellular DNA damage responses (DDR) during acute typhoid fever. Human infection challenge studies revealed that the toxin suppresses bacteraemia via unknown mechanisms. Using quantitative proteomic analysis on the plasma of bacteraemic participants, we demonstrate that wild-type toxigenic Salmonella induced secretion of lysozyme (LYZ) and apolipoprotein C3 (APOC3). Recombinant typhoid toxin or Salmonella infection recapitulated LYZ and APOC3 secretion in cultured cells, which involved ATM/ATR-dependent DDRs and confirmed observations in typhoid fever. LYZ caused spheroplast formation, inhibited the Salmonella type 3 secretion system, and intracellular infections. LYZ expression was regulated by p53 in a cell type-specific manner and driven by mitochondrial oxidative stress that caused nuclear DDRs and p53-mediated senescence responses. Addition of LYZ inhibited oxidative DNA damage and resulting senescence responses caused by typhoid toxin. Our findings may indicate that toxin-induced DDRs elicit antimicrobial responses, which suppress Salmonella bacteraemia during typhoid fever
The Kangaroo’s First Hop: The Early Fast Cooling Phase of EP250108a/SN 2025kg
Get PDFFast X-ray transients are a rare and poorly understood population of events. Previously difficult to detect in real time, the launch of the Einstein Probe with its Wide-field X-ray Telescope has led to a rapid expansionof the sample and allowed the exploration of these transients across the electromagnetic spectrum. EP250108a is a recently detected example linked to an optical counterpart, SN 2025kg, or “the kangaroo.” Together with a companion Letter we present our observing campaign and analysis of this event. In this letter, we focus on the early evolution of the optical counterpart over the first 6 days, including our measurement of the redshift of z = 0.17641. We compare to other supernovae and fast transients showing similar features, finding significant similarities with SN 2006aj and SN 2020bvc, and show that the source is well modelled by a rapidly expanding cooling blackbody. We show the observed X-ray and radio properties are consistent with a collapsar-powered jet that is low energy (≲1051 erg) and/or fails to break out of the dense material surrounding it. While we examine the possibility that the optical emission emerges from the shock produced as the supernova ejecta expand into a dense shell of circumstellar material, due to our X-ray and radio inferences, we favour a model where it arises from a shocked cocoon resulting from a trapped jet. This makes SN 2025 one of the few examples of this currently observationally rare event
13: Making the decision of project termination during the delivery stage: the Keystone XL pipeline
No full textThis case study delves into the complex decision of project termination during the construction stage and its implications for project management. Despite the general belief that, once started, projects are rarely terminated, relevant examples show that this is not always the case and happens more often than we are comfortable with. Construction projects face a variety of challenges that can trigger termination, including political polarisations, financial or regulatory constraints, or changes in strategic priorities. This case study analyses a construction project in which the student should understand the context, assess the information provided, decide whether the project should be terminated, and explain the reasoning. The case study shows the need for robust decision-making and adaptive project management strategies to respond to evolving project dynamics in changing political environments, ensuring that project termination does not necessarily translate into wasted resources or compromised reputation
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