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COSMIC’s Large-scale Search for Technosignatures during the VLA Sky Survey: Survey Description and First Results
Get PDFDeveloping algorithms to search through data efficiently is a challenging part of searching for signs of technology beyond our solar system. We have built a digital signal processing system and computer cluster on the backend of the Karl G. Jansky Very Large Array (VLA) in New Mexico in order to search for signals throughout the Galaxy consistent with our understanding of artificial radio emissions. In our first paper, we described the system design and software pipelines. In this paper, we describe a postprocessing pipeline to identify persistent sources of interference, filter out false positives, and search for signals not immediately identifiable as anthropogenic radio frequency interference during the VLA Sky Survey. As of 2024 September 1, the Commensal Open-source Multi-mode Interferometric Cluster had observed more than 950,000 unique pointings. This paper presents the strategy we employ when commensally observing during the VLA Sky Survey and a postprocessing strategy for the data collected during the survey. To test this postprocessing pipeline, we searched toward 511 stars from the Gaia catalog with coherent beams. This represents about 30 minutes of observation during the VLA Sky Survey, where we typically observe about 2000 sources hr–1 in the coherent beamforming mode. We did not detect any unidentifiable signals, setting isotropic power limits ranging from 1011 to 1016 W
Volcano-Tectonic Controls on Magmatic Evolution at Campi Flegrei, Italy: Insights from Thermodynamic Modelling
Get PDFCampi Flegrei caldera (Naples, southern Italy) is one of the most hazardous volcanoes on Earth, having produced >70 eruptions in the past 15 kyr, and currently showing significant signs of unrest within a densely populated part of Europe. Post-15 ka eruptions span a range of eruptive styles and compositions, which broadly correlate with the spatial and structural location of vents within the large caldera: eruptions from vents along the northern and eastern caldera rim faults are typically small and extend to mafic compositions; eruptions from vents in the central and eastern side of the caldera extend to evolved compositions and have produced Plinian columns; and vents along regional faults (also activated by caldera collapse) in the western caldera have produced sub-Plinian eruptions, which are often relatively Na2O-rich and K2O-depleted. These compositional and eruptive differences suggest an intrinsic link between their volcano-tectonic setting and structure and/or processes operating within the sub-volcanic magmatic system. To investigate this, we compare post-15 ka erupted glass major element compositions to liquid lines of descent produced using the rhyolite-MELTS thermodynamic model. To constrain magma storage conditions at Campi Flegrei, we systematically vary the crystallisation conditions in 1800 models before employing a new statistical approach to assess the quality of fit between natural glass compositions and model outputs. In simple (uncontaminated) fractional crystallisation models, we find that glass compositions in each volcano-tectonic setting are best reproduced by similar storage conditions: pressure of 110–160 MPa, liquidus oxygen fugacity of 0–1 log unit above the quartz–fayalite–magnetite buffer, and a liquidus H2O concentration of 2 wt % for the northern, eastern and western caldera eruptions and 3 wt % for the central caldera eruptions. However, the addition of an assimilant further improves the fit between predicted and observed major element compositions, with the amount and type of assimilant varying between volcano-tectonic settings. Best-fit models for vents along the northern and eastern caldera rim faults include small (5–10%) amounts of Palaeozoic metamorphic basement, whereas those for vents in the centre of the caldera or along the western regional faults include larger quantities (~30%) of assimilated syenitic restite. The Fondi di Baia eruption is compositionally anomalous, and its evolution may reflect minor limestone or hydrothermal calcite contamination. Our results demonstrate a novel link between the spatial and structural location of vents within the Campi Flegrei caldera and the physicochemical processes operating within its magmatic system, providing important information for the assessment of future hazard scenarios
Decoding how higher-order network interactions shape contagion dynamics
Get PDFComplex contagion models that involve contagion along higher-order structures, such as simplicial complexes and hypergraphs, yield new classes of mean-field models. Interestingly, the differential equations arising from many such models often exhibit a similar form, resulting in qualitatively comparable global bifurcation patterns. Motivated by this observation, we investigate a generalised mean-field-type model that provides a unified framework for analysing a range of different models. In particular, we derive analytical conditions for the emergence of different bifurcation regimes exhibited by three models of increasing complexity—ranging from three- and four-body interactions to two connected populations which simultaneously includes both pairwise and three-body interactions. For the first two cases, we give a complete characterisation of all possible outcomes, along with the corresponding conditions on network and epidemic parameters. In the third case, we demonstrate that multistability is possible despite only three-body interactions. Our results reveal that single population models with three-body interactions can only exhibit simple transcritical transitions or bistability, whereas with four-body interactions multistability with two distinct endemic steady states is possible. Surprisingly, the two-population model exhibits multistability via symmetry breaking despite three-body interactions only. Our work sheds light on the relationship between equation structure and model behaviour and makes the first step towards elucidating mechanisms by which different system behaviours arise, and how network and dynamic properties facilitate or hinder outcomes
Accessing Metal‐Containing Species in Tin–Lead Perovskite Precursor Solutions via Molecular Strategies Guided by the Hard–Soft Acid–Base Principle
Get PDFThe properties of metal‐centred species in metal halide perovskite precursor solutions substantially influence the formation and evolution of colloidal particles, which in turn dictate the crystallisation process and the film quality. In this work, we assess the “hard” and “soft” Lewis acid characteristics of Sn2+ and Pb2+ cations as a strategy to modulate the chemical environment of these metal‐containing species in mixed‐metal tin–lead perovskite precursor solutions. We observe enhanced simultaneous access to both metal centres upon adding compounds with functional groups suggested by the hard–soft acid–base principle. Theoretical calculations suggest that the hard base carboxyl group preferentially interacts with Sn2+‐based species, while the softer base thiol group also targets Pb2+‐based species. By effectively accessing and manipulating possible classes of inorganic species and their colloidal particle properties in the precursor solutions, we achieve 1.26 eV perovskite polycrystalline films exhibiting enhanced structural and optoelectronic quality, giving the best quasi‐Fermi level splitting values of up to 0.95 eV. As a result, the solar cell devices demonstrate efficiency values of up to 23.3% with an extended operational lifetime, retaining 80% of their initial efficiency after over 280 and 180 h of maximum power point tracking under simulated AM1.5G illumination at 25 and 65 °C, respectively
Optimal control of multiple myeloma assuming drug resistance and off-target effects
Get PDFMultiple myeloma (MM) is a plasma cell cancer that occurs in the bone marrow. A leading treatment for MM is the monoclonal antibody Daratumumab, targeting the CD38 receptor, which is highly overexpressed in myeloma cells. In this work we model drug resistance via loss of CD38 expression, which is a proposed mechanism of resistance to Daratumumab treatment. We develop an ODE model that includes drug resistance via two mechanisms: a direct effect in which CD38 expression is lost without cell death in response to Daratumumab, and an indirect effect in which CD38 expression switches on and off in the cancer cells; myeloma cells that do not express CD38 have lower fitness but are shielded from the drug action. The model also incorporates competition with healthy cells, death of healthy cells due to off-target drug effects, and a Michaelis-Menten type immune response. Using optimal control theory, we study the effect of the drug resistance mechanisms and the off-target drug effect on the optimal treatment regime. We identify a general increase in the duration and costs of optimal treatment, as a result of these added mechanisms. Several distinct optimal treatment regimes are identified within the parameter space
FYI: predicate insubordination with ἵνα in documentary post-Classical Greek
Get PDFThis chapter examines insubordinate ἵνα in the disclosure formula (‘I want you to know that’) and the future-open conditional sequence (‘if the weather is nice, I will go for a walk’) in the documentary papyri. The future-open conditional sequence with ἵνα as an apodosis-initial signpost appears in the Ptolemaic and Roman periods and seems to disappear afterwards. The disclosure formula in the form ἵνα μάθῃς / μάθητε / ἰδῇς ὅτι ‘know that’ appears in the early Byzantine period only. While in the former ἵνα seems to act as a discourse marker in the left periphery of the sentence, in the latter ἵνα seems to cliticise to the verb. Unlike the adverbial insubordinate ‘just so you know’ which is attested throughout the history of Greek and cross-linguistically common, insubordinate ἵνα in the future-open conditional sequence and the disclosure formula appear to be context-specific developments that diachronically constitute dead ends
Information, skills and job search
Get PDFI use a Bayesian hierarchical model to estimate the general average treatment effect of reducing information frictions for jobseekers in low- and middle-income urban labour markets. I find that information provision generates a small and reasonably certain increase in private employment, but has an uncertain average effect on earnings. Reducing information frictions is particularly beneficial to individuals who previously lacked a method to credibly communicate their skills to firms. I examine the estimate heterogeneity to establish whether the general average effect is informative of the labour market effects of reducing information frictions in similar low- and middle-income countries. I find that the estimates are mutually informative and therefore likely to generalise to other settings well. These findings suggest that information provision interventions offer fairly certain increases in employment for low- and middle-income labour markets, particularly if individuals who are unable to credibly communicate their skills to firms are targeted with the policy
HotRock datasets: experimental field and lab simulation data for rock-surface and biomimetic temperatures
No full textRaw datasets corresponding to six field days (3 sites) and six laboratory simulations (3 scenarios) of rock-surface temperatures and biomimetic temperatures, focussing on extreme thermal events (heatwaves) in Southern England rocky shores
The structure of sets with cube‐avoiding sumsets
Get PDFSuppose G is a finite abelian group, Z 0 ⊂ G is not contained in any strict coset in G , and E , F are dense subsets of G n such that the sumset E + F avoids Z 0 n . We show that E and F are almost entirely contained in sets defined by a bounded number of coordinates, that is, sets E ′ × G I c and F ′ × G I c , where the size of I ⊂ [ n ] is non‐zero and independent of n , and E ′ , F ′ are subsets of G I such that E ′ + F ′ avoids Z 0 I . Furthermore, we show that this result extends to any finite group and d summands for any d ⩾ 2
Measuring the effectiveness of keyword lists in digital forensics
Get PDFKeyword searching is fundamental to digital forensics and therefore there is a clear need to validate results. This paper demonstrates an approach that can be used to measure the effectiveness of generic wordlists used for specific crime types (e.g. drugs, child abuse, terrorism) that complement specific keywords chosen for individual cases. This approach allows measurement of error associated with this use of case-type based wordlists, and facilitates development of a new research area in digital forensics: optimising keyword lists. The paper demonstrates this experimentally and shows that this important technique can now be evaluated in a scientific manner and concludes with a proposed implementation for deploying this within a forensic lab