Numerical model of the Tikitere geothermal system

The Tikitere geothermal field is one of the 21 high-enthalpy geothermal fields in the Taupo Volcanic Zone (TVZ) in New Zealand. The field is renowned for the tourist attraction Hell’s Gate, which consists of many natural geothermal surface features. Based on geoscientific data from the open-source literature, a conceptual model was set up in Leapfrog Geothermal. A corresponding natural state reservoir model was then set up and calibrated using temperature and heat flux data from fourteen thermal areas. The calibrated numerical model matches the higher temperatures at the locations of some of the surface thermal features but does not match the estimated heat flows

Numerical model of the Tikitere geothermal system

The Tikitere geothermal field is one of the 21 high-enthalpy geothermal fields in the Taupo Volcanic Zone (TVZ) in New Zealand. The field is renowned for the tourist attraction Hell’s Gate, which consists of many natural geothermal surface features. Based on geoscientific data from the open-source literature, a conceptual model was set up in Leapfrog Geothermal. A corresponding natural state reservoir model was then set up and calibrated using temperature and heat flux data from fourteen thermal areas. The calibrated numerical model matches the higher temperatures at the locations of some of the surface thermal features but does not match the estimated heat flows

Climate Change and Biosphere Response: Unlocking the Collections Vault

Natural history collections (NHCs) are an important source of the long-term data needed to understand how biota respond to ongoing anthropogenic climate change. These include taxon occurrence data for ecological modeling, as well as information that can be used to reconstruct mechanisms through which biota respond to changing climates. The full potential of NHCs for climate change research cannot be fully realized until high-quality data sets are conveniently accessible for research, but this requires that higher priority be placed on digitizing the holdings most useful for climate change research (e.g., whole-biota studies, time series, records of intensively sampled common taxa). Natural history collections must not neglect the proliferation of new information from efforts to understand how present-day ecosystems are responding to environmental change. These new directions require a strategic realignment for many NHC holders to complement their existing focus on taxonomy and systematics. To set these new priorities, we need strong partnerships between NHC holders and global change biologists

The physics of indirect estimators of Lyman Continuum escape and their application to high-redshift JWST galaxies

Reliable indirect diagnostics of LyC photon escape from galaxies are required to understand which sources were the dominant contributors to reionization. While multiple LyC escape fraction (fesc) indicators have been proposed to trace favourable conditions for LyC leakage from the interstellar medium of low-redshift ‘analogue’ galaxies, it remains unclear whether these are applicable at high redshifts where LyC emission cannot be directly observed. Using a library of 14 120 mock spectra of star-forming galaxies with redshifts 4.64 ≤ z ≤ 10 from the SPHINX20 cosmological radiation hydrodynamics simulation, we develop a framework for the physics that leads to high fesc. We investigate LyC leakage from our galaxies based on the criteria that successful LyC escape diagnostics must (i) track a high-specific star formation rate, (ii) be sensitive to stellar population age in the range 3.5–10 Myr representing the times when supernova first explode to when LyC production significantly drops, and (iii) include a proxy for neutral gas content and gas density in the interstellar medium. O32, ΣSFR, MUV, and H β equivalent width select for one or fewer of our criteria, rendering them either necessary but insufficient or generally poor diagnostics. In contrast, UV slope (β), and E(B − V) match two or more of our criteria, rendering them good fesc diagnostics (albeit with significant scatter). Using our library, we build a quantitative model for predicting fesc based on direct observables. When applied to bright z > 6 Ly α emitters observed with JWST, we find that the majority of them have esc≲10 per cent⁠

The highest frequency detection of a radio relic : 16 GHz AMI observations of the 'Sausage' cluster

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters. © 2014 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We observed the cluster CIZA J2242.8+5301 with the Arcminute Microkelvin Imager at 16 GHz and present the first high radio-frequency detection of diffuse, non-thermal cluster emission. This cluster hosts a variety of bright, extended, steep-spectrum synchrotron-emitting radio sources, associated with the intracluster medium, called radio relics. Most notably, the northern, Mpc-wide, narrow relic provides strong evidence for diffusive shock acceleration in clusters. We detect a puzzling, flat-spectrum, diffuse extension of the southern relic, which is not visible in the lower radio-frequency maps. The northern radio relic is unequivocally detected and measures an integrated flux of 1.2 ± 0.3 mJy. While the low-frequency (<2 GHz) spectrum of the northern relic is well represented by a power law, it clearly steepens towards 16 GHz. This result is inconsistent with diffusive shock acceleration predictions of ageing plasma behind a uniform shock front. The steepening could be caused by an inhomogeneous medium with temperature/density gradients or by lower acceleration efficiencies of high energy electrons. Further modelling is necessary to explain the observed spectrum.Peer reviewe

The Physics of Indirect Estimators of Lyman Continuum Escape and their Application to High-Redshift JWST Galaxies

Reliable indirect diagnostics of LyC photon escape from galaxies are required to understand which sources were the dominant contributors to reionization. While multiple escape fraction ($f_{\rm esc}$) indicators have been proposed to trace favourable conditions for LyC leakage from the interstellar medium of low-redshift ``analog'' galaxies, it remains unclear whether these are applicable at high redshifts where LyC emission cannot be directly observed. Using a library of 14,120 mock spectra of star-forming galaxies with redshifts $4.64 \leq z \leq 10$ from the SPHINX$^{20}$ cosmological radiation hydrodynamics simulation, we develop a framework for the physics that leads to high $f_{\rm esc}$. We investigate LyC leakage from our galaxies based on the criteria that successful LyC escape diagnostics must \textit{i)} track a high specific star formation rate, \textit{ii)} be sensitive to stellar population age in the range $3.5-10$~Myr representing the times when supernova first explode to when LyC production significantly drops, and \textit{iii)} include a proxy for neutral gas content and gas density in the interstellar medium. ${\rm O}_{32}$, $\Sigma_{\rm SFR}$, M$_{\rm UV}$, and H$\beta$ equivalent width select for one or fewer of our criteria, rendering them either necessary but insufficient or generally poor diagnostics. In contrast, UV slope ($\beta$), and ${\rm E(B-V)}$ match two or more of our criteria, rendering them good $f_{\rm esc}$ diagnostics (albeit with significant scatter). Using our library, we build a quantitative model for predicting $f_{\rm esc}$ based on $\beta$, ${\rm E(B-V)}$, H$\beta$, M$_{\rm UV}$, ${\rm R_{23}}$, and ${\rm O_{32}}$. When applied to bright $z > 6$ Ly$\alpha$ emitters observed with JWST, we find that the majority of them have $f_{\rm esc} \lesssim 10\%$.Comment: 16 pages, 15 figures, 1 table, submitted to MNRA

Potential regulatory phosphorylation sites in a Medicago truncatula plasma membrane proton pump implicated during early symbiotic signaling in roots

AbstractIn plants and fungi the plasma membrane proton pump generates a large proton-motive force that performs essential functions in many processes, including solute transport and the control of cell elongation. Previous studies in yeast and higher plants have indicated that phosphorylation of an auto-inhibitory domain is involved in regulating pump activity. In this report we examine the Medicago truncatula plasma membrane proton pump gene family, and in particular MtAHA5. Yeast complementation assays with phosphomimetic mutations at six candidate sites support a phosphoregulatory role for two residues, suggesting a molecular model to explain early Nod factor-induced changes in the plasma membrane proton-motive force of legume root cells

Interactions and dynamics in Li+Li2 ultracold collisions

A potential energy surface for the lowest quartet electronic state (A′4) of lithium trimer is developed and used to study spin-polarized Li+Li2collisions at ultralow kinetic energies. The potential energy surface allows barrierless atom exchange reactions. Elastic and inelastic cross sections are calculated for collisions involving a variety of rovibrational states of Li2. Inelastic collisions are responsible for trap loss in molecule production experiments. Isotope effects and the sensitivity of the results to details of the potential energy surface are investigated. It is found that for vibrationally excited states, the cross sections are only quite weakly dependent on details of the potential energy surface

Model-Constrained Reconstruction Accelerated With Fourier-Based Undersampling for Hyperpolarized [1-13C] Pyruvate Imaging

PURPOSE: Model-constrained reconstruction with Fourier-based undersampling (MoReFUn) is introduced to accelerate the acquisition of dynamic MRI using hyperpolarized [1- METHODS: The MoReFUn method resolves spatial aliasing using constraints introduced by a pharmacokinetic model that describes the signal evolution of both pyruvate and lactate. Acceleration was evaluated on three single-channel data sets: a numerical digital phantom that is used to validate the accuracy of reconstruction and model parameter restoration under various SNR and undersampling ratios, prospectively and retrospectively sampled data of an in vitro dynamic multispectral phantom, and retrospectively undersampled imaging data from a prostate cancer patient to test the fidelity of reconstructed metabolite time series. RESULTS: All three data sets showed successful reconstruction using MoReFUn. In simulation and retrospective phantom data, the restored time series of pyruvate and lactate maintained the image details, and the mean square residual error of the accelerated reconstruction increased only slightly (\u3c 10%) at a reduction factor up to 8. In prostate data, the quantitative estimation of the conversion-rate constant of pyruvate to lactate was achieved with high accuracy of less than 10% error at a reduction factor of 2 compared with the conversion rate derived from unaccelerated data. CONCLUSION: The MoReFUn technique can be used as an effective and reliable imaging acceleration method for metabolic imaging using hyperpolarized [1

Investigating the effects of mobile bottom fishing on benthic biota:A systematic review protocol

Background Mobile bottom fishing, such as trawling and dredging, is the most widespread direct human impact on marine benthic systems. Knowledge of the impacts of different gear types on different habitats, the species most sensitive to impacts and the potential for habitats to recover are often needed to inform implementation of an ecosystem approach to fisheries and strategies for biodiversity conservation. This knowledge helps to identify management options that maximise fisheries yield whilst minimising negative impacts on benthic systems. Methods/design The methods are designed to identify and collate evidence from experimental studies (e.g. before/after, control/impact) and comparative studies (spanning a gradient of fishing intensity) to identify changes in state (numbers, biomass, diversity etc.) of benthic biota (flora and fauna), resulting from a variety of mobile bottom fishing scenarios. The primary research question that the outputs will be used to address is: “to what extent does a given intensity of bottom fishing affect the abundance and/or diversity of benthic biota?” Due to the variety of gear and habitat types studied, the primary question will be closely linked with secondary questions. These include: “how does the effect of bottom fishing on various benthic biota metrics (species, faunal type, trait, taxon etc.) vary with (1) gear type and (2) habitat, and (3) gear type-habitat interactions?” and (4) “how might properties of the community and environment affect the resilience (and recovery potential) of a community to bottom fishing?