Extreme-ultraviolet images from the Solar Dynamics Observatory often show loop-like fine structure to be present where no minority-polarity flux is visible in magnetograms, suggesting that the rate ...of ephemeral region (ER) emergence inside "unipolar" regions has been underestimated. Assuming that this rate is the same inside coronal holes as in the quiet Sun, we show that interchange reconnection between ERs and open field lines gives rise to a solar wind energy flux that exceeds 105 erg cm−2 s−1 and that scales as the field strength at the coronal base, consistent with observations. In addition to providing ohmic heating in the low corona, these reconnection events may be a source of Alfvén waves with periods ranging from the granular timescale of ∼10 minutes to the supergranular/plume timescale of many hours, with some of the longer-period waves being reflected and dissipated in the outer corona. The asymptotic wind speed depends on the radial distribution of the heating, which is largely controlled by the rate of flux-tube expansion. Along the rapidly diverging flux tubes associated with slow wind, heating is concentrated well inside the sonic point (1) because the outward conductive heat-flux density and thus the outer coronal temperatures are reduced, and (2) because the net wave energy flux is dissipated at a rate proportional to the local Alfvén speed. In this "hybrid" solar wind model, reconnection heats the lower corona and drives the mass flux, whereas waves impart energy and momentum to the outflow at greater distances.
Steels containing reverted nanoscale austenite (γRN) islands or films dispersed in a martensitic matrix show excellent strength, ductility and toughness. The underlying microstructural mechanisms ...responsible for these improvements are not yet understood, but are observed to be strongly connected to the γRN island or film size. Two main micromechanical effects are conceivable in this context, namely: (i) interaction of γRN with microcracks from the matrix (crack blunting or arresting); and (ii) deformation-induced phase transformation of γRN to martensite (TRIP effect). The focus here is on the latter phenomenon. To investigate size effects on γRN transformation independent of other factors that can influence austenite stability (composition, crystallographic orientation, defect density, surrounding phase, etc.), a model (TRIP-maraging steel) microstructure is designed with support from diffusion simulations (using DICTRA software) to have the same, homogeneous chemical composition in all γRN grains. Characterization is conducted by in-situ tension and bending experiments in conjunction with high-resolution electron backscatter diffraction mapping and scanning electron microscopy imaging, as well as post-mortem transmission electron microscopy and synchrotron X-ray diffraction analysis. Results reveal an unexpected “smaller is less stable” effect due to the size-dependent competition between mechanical twinning and deformation-induced phase transformation.
Families and genera assigned to Tremellomycetes have been mainly circumscribed by morphology and for the yeasts also by biochemical and physiological characteristics. This phenotype-based ...classification is largely in conflict with molecular phylogenetic analyses. Here a phylogenetic classification framework for the Tremellomycetes is proposed based on the results of phylogenetic analyses from a seven-genes dataset covering the majority of tremellomycetous yeasts and closely related filamentous taxa. Circumscriptions of the taxonomic units at the order, family and genus levels recognised were quantitatively assessed using the phylogenetic rank boundary optimisation (PRBO) and modified general mixed Yule coalescent (GMYC) tests. In addition, a comprehensive phylogenetic analysis on an expanded LSU rRNA (D1/D2 domains) gene sequence dataset covering as many as available teleomorphic and filamentous taxa within Tremellomycetes was performed to investigate the relationships between yeasts and filamentous taxa and to examine the stability of undersampled clades. Based on the results inferred from molecular data and morphological and physiochemical features, we propose an updated classification for the Tremellomycetes. We accept five orders, 17 families and 54 genera, including seven new families and 18 new genera. In addition, seven families and 17 genera are emended and one new species name and 185 new combinations are proposed. We propose to use the term pro tempore or pro tem. in abbreviation to indicate the species names that are temporarily maintained.
Introduction of interlath reverted austenite is an effective method to design ductile lath martensitic steels. The challenge in this concept is that all reverted austenite films have similar ...mechanical stability, hence, they all undergo transformation-induced plasticity (TRIP) at the same strain level. Here we propose a new thermo-mechanical treatment route to activate the TRIP effect over a broad strain regime and refer to it as ‘spectral TRIP effect’. It aims at spreading the micro-mechanical stability of reverted austenite grains by widening the austenite nucleation barrier in martensite. To validate the proposed thermo-mechanical treatment route, an as-quenched medium-Mn martensitic steel was cold rolled prior to the reversion treatment at 600 °C. Microstructure characterization was carried out by electron backscatter diffraction (EBSD) and electron channeling contrast imaging (ECCI). Mechanical tests show that the approach is effective. The spectral TRIP effect improves both, the strength and the ductility due to the well dispersed size distribution and the associated size-dependent deformation and phase transformation behavior of the reverted austenite grains, extending TRIP-related work hardening over a broad strain range.
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Carbon dioxide (CO2) emissions allocation plays a fundamental role in determining reduction responsibility at economy level or emission permits at firm level. Past decades have seen the development ...and applications of various methods for CO2 emissions allocation. This paper provides a literature review of CO2 emissions allocation with emphasis on the evolution of allocation methods used. It begins with a summary of the most popular allocation principles and criteria that lay a foundation for the development of allocation methods. We then classify the existing allocation methods into four groups, namely indicator, optimization, game theoretic and hybrid approaches. The main features and findings of past studies are identified and summarized. While the fairness principle prevails in earlier studies, the efficiency principle has been found to receive increasing attention recently. We also present a comparison of the empirical results based on ten popular indicator methods to show how indicator choice affects the allocation results. Issues related to selecting appropriate methods in CO2 emissions allocation are finally discussed. Further research may be carried out to strike a balance between fairness and efficiency so that the allocation results become more widely acceptable and economically feasible.
Abstract
The minimum value of the geomagnetic
aa
index has served as a remarkably successful predictor of solar cycle amplitude. This value is reached near or just after sunspot minimum, when both ...the near-Earth solar wind speed and interplanetary magnetic field (IMF) strength fall to their lowest values. At this time, the heliospheric current sheet is flattened toward the heliographic equator and the dominant source of the IMF is the Sun’s axial dipole moment, which, in turn, has its source in the polar fields. As recognized previously, the success of
aa
min
as solar cycle precursor provides support for dynamo models in which the sunspots of a given cycle are produced by winding up the poloidal field built up during the previous cycle. Because they are highly concentrated toward the poles by the surface meridional flow, the polar fields are difficult to measure reliably. Here we point out that the observed value of the radial IMF strength at solar minimum can be used to constrain the polar field measurements, and that this parameter, which is directly proportional to the Sun’s axial dipole strength, may be an even better solar cycle predictor than geomagnetic activity.
COVID‐19 is a novel, rapidly changing pandemic: consequently, evidence‐based recommendations in solid organ transplantation (SOT) remain challenging and unclear. To understand the impact on ...transplant activity across the United States, and center‐level variation in testing, clinical practice, and policies, we conducted a national survey between March 24, 2020 and March 31, 2020 and linked responses to the COVID‐19 incidence map. Response rate was a very high 79.3%, reflecting a strong national priority to better understand COVID‐19. Complete suspension of live donor kidney transplantation was reported by 71.8% and live donor liver by 67.7%. While complete suspension of deceased donor transplantation was less frequent, some restrictions to deceased donor kidney transplantation were reported by 84.0% and deceased donor liver by 73.3%; more stringent restrictions were associated with higher regional incidence of COVID‐19. Shortage of COVID‐19 tests was reported by 42.5%. Respondents reported a total of 148 COVID‐19 recipients from <1 to >10 years posttransplant: 69.6% were kidney recipients, and 25.0% were critically ill. Hydroxychloroquine (HCQ) was used by 78.1% of respondents; azithromycin by 46.9%; tocilizumab by 31.3%, and remdesivir by 25.0%. There is wide heterogeneity in center‐level response across the United States; ongoing national data collection, expert discussion, and clinical studies are critical to informing evidence‐based practices.
In this national survey of transplant centers during the COVID‐19 pandemic, the authors report substantial reduction in transplant activity, wide variation in COVID‐19 testing practices, and use of off‐label or investigational therapies in the treatment of 148 COVID‐19‐SOT recipients.
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