741 research outputs found

    Assessing the relationship between spectral solar irradiance and stratospheric ozone using Bayesian inference

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    We investigate the relationship between spectral solar irradiance (SSI) and ozone in the tropical upper stratosphere. We find that solar cycle (SC) changes in ozone can be well approximated by considering the ozone response to SSI changes in a small number individual wavelength bands between 176 and 310 nm, operating independently of each other. Additionally, we find that the ozone varies approximately linearly with changes in the SSI. Using these facts, we present a Bayesian formalism for inferring SC SSI changes and uncertainties from measured SC ozone profiles. Bayesian inference is a powerful, mathematically self-consistent method of considering both the uncertainties of the data and additional external information to provide the best estimate of parameters being estimated. Using this method, we show that, given measurement uncertainties in both ozone and SSI datasets, it is not currently possible to distinguish between observed or modelled SSI datasets using available estimates of ozone change profiles, although this might be possible by the inclusion of other external constraints. Our methodology has the potential, using wider datasets, to provide better understanding of both variations in SSI and the atmospheric response.Comment: 21 pages, 4 figures, Journal of Space Weather and Space Climate (accepted), pdf version is in draft mode of Space Weather and Space Climat

    Preliminary investigation of the diseases of willows (Salix spp.)

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    Willows were introduced into New Zealand by the early European settlers (van Kraayenoord, 1968a). Several species and hybrids have become naturalised and are usually found growing by riverbanks or in other moist situations. The use willows and poplars to control erosion on the steep country and highly erodible soils frequently found in New Zealand, was first implemented during the early days of settlement of the Colony (van Kraayenoord, 1968a). Willows now play a significant role in erosion control, particularly in the South Island catchments, the central North Island pumice country and East Coast North Island papa country. With the extensive use of willows in riverbank and erosion control New Zealand, the disease factor could play a significant role, especially in those areas where planting of a single species has been adopted. The main object of this investigation was to study stem and leaf diseases of Salix spp. incited by micro-organisms and may be summarised this:- (1) To carry out a survey of the extent and severity of the disease factor in New Zealand. (2) To isolate, study in culture and prove the pathogenicity of organisms considered important in the death and dieback of willows. (3) To describe and identify the causal organisms. (4) To determine if possible, factors influencing the spread and degree of infection of the diseases

    Field-level inference of cosmic shear with intrinsic alignments and baryons

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    We construct a field-based Bayesian Hierarchical Model for cosmic shear that includes, for the first time, the important astrophysical systematics of intrinsic alignments and baryon feedback, in addition to a gravity model. We add to the BORG-WL framework the tidal alignment and tidal torquing model (TATT) for intrinsic alignments and compare them with the non-linear alignment (NLA) model. With synthetic data, we have shown that adding intrinsic alignments and sampling the TATT parameters does not reduce the constraining power of the method and the field-based approach lifts the weak lensing degeneracy. We add baryon effects at the field level using the enthalpy gradient descent (EGD) model. This model displaces the dark matter particles without knowing whether they belong to a halo and allows for self-calibration of the model parameters, which are inferred from the data. We have also illustrated the effects of model misspecification for the baryons. The resulting model now contains the most important physical effects and is suitable for application to data

    Natural Variability and Warming Signals in Global Ocean Wave Climates

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    地球全体の波浪特性の変化傾向と自然変動の関係を解明 --地球温暖化の沿岸域への影響を定量化--. 京都大学プレスリリース. 2021-06-15.This paper presents a multivariate classification of the global wave climate into types driven by atmospheric circulation patterns. The primary source of the net long-term variability is evaluated based on historical wave simulations. Results show that the monsoon, extratropical, subtropical, and polar wave climate types of the Pacific and North Atlantic Oceans are dominated by natural variability, whereas the extratropical and subtropical wave climate types in the Indian Ocean, and the tropical wave climate types of the Atlantic and Pacific Oceans exhibit a global warming signal. In the Pacific sector of the Southern Ocean, strong natural variability may mask a global warming signal that is yet to emerge as being statistically significant. In addition, wave climate teleconnections were found across the world that can provide a framework for joint strategies to achieve the goals of climate adaption for resilient coastal communities and environments

    Program Management versus Portfolio Management in Defense Acquisition

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    Program Management / Faculty ReportAcquisition Research Program Sponsored Report SeriesSponsored Acquisition Research & Technical ReportsThis research performed a gap analysis on the existing Department of Defense (DoD) program management competency standards to determine if changes are required to fully adopt product portfolio management (PPM) strategies in defense acquisition. Current DoD program management standards are compared to the Project Management Institute's Portfolio Management Professional certification standards to analyze alignment and gaps between the standards. Barrier to Implementation (BTI) scores are assigned to address the identified gaps in the DoD standard. The study found that the DoD program management competencies are on average 41% aligned with portfolio management industry standards. The DoD program management competencies are least aligned with the portfolio management domains of governance and strategic alignment. The composite BTI score indicates low to medium level of implementation barriers for most of the gaps. Results indicate that the DoD is capable of conducting PPM, and further research is needed to fully align the current competency standards with industry best practices. Defense acquisition senior leaders should consider formulating DoD portfolio management career field functional competencies to address congressional mandates for portfolio management implementation within the DoD.Approved for public release; distribution is unlimited

    Constraining Quasar and IGM Properties Through Bubble Detection in Redshifted 21-cm Maps

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    The infrared detection of a z>7 quasar has opened up a new window to directly probe the IGM during the epoch of reionization. In this paper we theoretically consider the possibility of detecting the ionized bubble around a z=8 quasar using targeted redshifted 21-cm observations with the GMRT. The apparent shape and size of the ionized bubble, as seen by a distant observer, depends on the parameters \dot{N}_{phs}/C, x_HI/C and \tau_Q where \dot{N}_{phs}, \tau_Q, x_HI and C are respectively the photon emission rate, age of the quasar, the neutral fraction and clumping factor of the IGM.Here we have analytically estimated the shape and size of a quasar's ionized bubble assuming an uniform IGM and ignoring other ionizing sources besides the quasar, and used this as a template for matched filter bubble search with the GMRT visibility data. We have assumed that \dot{N}_{phs} is known from the infrared spectrum and C from theoretical considerations, which gives us two free parameters x_HI and \tau_Q for bubble. Considering 1,000 hr of observation, we find that there is a reasonably large region of parameter space where a 3\sigma detection is possible. We also find that it will be possible to place lower limits on x_HI and \tau_Q with this observation. Deeper follow up observations can place upper limits on \tau_Q and x_HI. Value of C affect the estimation of x_HI but the estimation of \tau_Q remains unaffected.We have used a semi-numerical technique to simulate the apparent shape and size of quasar ionized bubbles considering the presence of other ionizing sources and inhomogeneities in the IGM. The presence of other sources increase the size of the quasar bubble, leading to underestimation of x_HI. Clustering of other ionizing sources around the quasar can produce severe distortions in bubble's shape. However, this does not severely affect parameter estimation in the bubbles that are large.Comment: 18 pages, 16 figures, 3 tables. Minor change in text. Accepted for publication in MNRA

    Extreme water levels, waves and coastal impacts during a severe tropical cyclone in northeastern Australia: a case study for cross-sector data sharing

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    Severe tropical cyclone (TC) Debbie made landfall on the northern Queensland coast of Australia on 27 March 2017 after crossing the Great Barrier Reef as a slow-moving Category 4 system. Groups from industry, government and academia collected coastal hazard and impact data before, during and after the event and shared these data to produce a holistic picture of TC Debbie at the coast. Results showed the still water level exceeded the highest astronomical tide by almost a metre. Waves added a further 16&thinsp;% to water levels along the open coast, and were probably unprecedented for this area since monitoring began. In most places, coastal barriers were not breached and as a result there was net offshore sand transport. If landfall had occurred 2&thinsp;h earlier with the high tide, widespread inundation and overwash would have ensued. This paper provides a case study of effective cross-sector data sharing in a natural hazard context. It advocates for a shared information platform for coastal extremes in Australia to help improve the understanding and prediction of TC-related coastal hazards in the future.</p

    Molecular evolution of HoxA13 and the multiple origins of limbless morphologies in amphibians and reptiles

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    Developmental processes and their results, morphological characters, are inherited through transmission of genes regulating development. While there is ample evidence that cis-regulatory elements tend to be modular, with sequence segments dedicated to different roles, the situation for proteins is less clear, being particularly complex for transcription factors with multiple functions. Some motifs mediating protein-protein interactions may be exclusive to particular developmental roles, but it is also possible that motifs are mostly shared among different processes. Here we focus on HoxA13, a protein essential for limb development. We asked whether the HoxA13 amino acid sequence evolved similarly in three limbless clades: Gymnophiona, Amphisbaenia and Serpentes. We explored variation in ω (dN/dS) using a maximum-likelihood framework and HoxA13sequences from 47 species. Comparisons of evolutionary models provided low ω global values and no evidence that HoxA13 experienced relaxed selection in limbless clades. Branch-site models failed to detect evidence for positive selection acting on any site along branches of Amphisbaena and Gymnophiona, while three sites were identified in Serpentes. Examination of alignments did not reveal consistent sequence differences between limbed and limbless species. We conclude that HoxA13 has no modules exclusive to limb development, which may be explained by its involvement in multiple developmental processes
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