Context. Large cavities in disks are important testing grounds for the mechanisms proposed to drive disk evolution and dispersion, such as dynamical clearing by planets and photoevaporation. Aims. We ...aim to resolve the large cavity in the disk around HD 34282, whose presence has been predicted by previous studies modeling the spectral energy distribution of the disk. Methods. Using ALMA band 7 observations we studied HD 34282 with a spatial resolution of 0.10″ × 0.17′′ at 345 GHz. Results. We resolve the disk around HD 34282 into a ring between 0.24′′ and 1.15′′ (78+7-11 and 374+33-54 au adopting a distance of 325+29-47 pc). The emission in this ring shows azimuthal asymmetry centered at a radial distance of 0.46′′ and a position angle of 135° and an azimuthal FWHM of 51°. We detect CO emission both inside the disk cavity and as far out as 2.7 times the radial extent of the dust emission. Conclusions. Both the large disk cavity and the azimuthal structure in the disk around HD 34282 can be explained by the presence of a 50 Mjup brown dwarf companion at a separation of ≈0.1′′.
A hepatitis A outbreak has occurred in Chile since November 2016. Men are predominantly affected, with a large proportion of men who have sex with men (MSM). We describe 12 consecutive unrelated ...confirmed cases who presented at our healthcare institution in Santiago Metropolitan Area. Nine were men, all reporting having had sex with men. Ten viral sequences, genotyped as IA, clustered with the V16-25801 strain causing outbreaks mostly in MSM in Europe since mid-2016.
Models of planet formation and disc evolution predict a variety of observables in the dust structure of protoplanetary discs. Here, we present Atacama Large Millimeter/submillimeter Array (ALMA) ...Band-6 and Band-7 observations of the transition disc Sz 91 showing that the continuum emission at 870 μm, which is dominated by emission from large dust grains, is localized in an optically thin narrow ring. We find that most of the emission (∼95 per cent) is concentrated in a ring located at 110 au from the central star that is only about 44 au wide. In contrast, the 12CO (2–1) emission peaks closer to the star and is detected up to ∼488 au from the star. The concentration of large grains in a ring-like structure while the gas disc extends much further in and further out is in qualitative agreement with predictions of hydrodynamical models of planet–disc interactions including radial drift and gas drag.
Taylor orientation factors for strain hardening in textured and random polycrystals of magnesium were derived from the ratio of the strain hardening rates of polycrystals to that of single crystals ...deforming by equivalent polyslip. For polycrystals with textures that inhibit basal and prismatic slip while favouring pyramidal polyslip, the Taylor factor is estimated to be between 2.1 and 2.5, increasing to about 4.5 for randomly textured polycrystals. The micromechanics of strain hardening in polycrystals are discussed.
The hemagglutinin (HA) stem region is a major target of universal influenza vaccine efforts owing to the presence of highly conserved epitopes across multiple influenza A virus (IAV) strains and ...subtypes. To explore the potential impact of vaccine-induced immunity targeting the HA stem, we examined the fitness effects of viral escape from stem-binding broadly neutralizing antibodies (stem-bnAbs). Recombinant viruses containing each individual antibody escape substitution showed diminished replication compared to wild-type virus, indicating that stem-bnAb escape incurred fitness costs. A second-site mutation in the HA head domain (N129D; H1 numbering) reduced the fitness effects observed in primary cell cultures and likely enabled the selection of escape mutations. Functionally, this putative permissive mutation increased HA avidity for its receptor. These results suggest a mechanism of epistasis in IAV, wherein modulating the efficiency of attachment eases evolutionary constraints imposed by the requirement for membrane fusion. Taken together, the data indicate that viral escape from stem-bnAbs is costly but highlights the potential for epistatic interactions to enable evolution within the functionally constrained HA stem domain.
Influenza A virus (IAV) genetic exchange through reassortment has the potential to accelerate viral evolution and has played a critical role in the generation of multiple pandemic strains. For ...reassortment to occur, distinct viruses must co-infect the same cell. The spatio-temporal dynamics of viral dissemination within an infected host therefore define opportunity for reassortment. Here, we used wild type and synonymously barcoded variant viruses of a pandemic H1N1 strain to examine the within-host viral dynamics that govern reassortment in guinea pigs, ferrets and swine. The first two species are well-established models of human influenza, while swine are a natural host and a frequent conduit for cross-species transmission and reassortment. Our results show reassortment to be pervasive in all three hosts but less frequent in swine than in ferrets and guinea pigs. In ferrets, tissue-specific differences in the opportunity for reassortment are also evident, with more reassortants detected in the nasal tract than the lower respiratory tract. While temporal trends in viral diversity are limited, spatial patterns are clear, with heterogeneity in the viral genotypes detected at distinct anatomical sites revealing extensive compartmentalization of reassortment and replication. Our data indicate that the dynamics of viral replication in mammals allow diversification through reassortment but that the spatial compartmentalization of variants likely shapes their evolution and onward transmission.
Grain Size Hardening in Mg and Mg-Zn Solid Solutions Caceres, C. H.; Mann, Gemma E.; Griffiths, J. R.
Metallurgical and materials transactions. A, Physical metallurgy and materials science,
07/2011, Volume:
42, Issue:
7
Journal Article
Peer reviewed
Open access
Cast specimens of Mg and of several Mg-Zn binary alloys with a wide range of grain sizes were deformed in tension and compression. The
k
values calculated from the Hall–Petch (H-P) plots of the ...tensile 0.2 pct proof stress increased with the Zn content, from 0.24 MPa m
1/2
for pure Mg to ~0.66 MPa m
1/2
for the 2.3 at. pct Zn alloy;
k
values measured from compression tests were larger, typically by 0.05 MPa m
1/2
. When the strength measurements were corrected for the pseudoelastic strain resulting from elastic twinning, the
k
values generally increased, and the difference between tension and compression was eliminated. This showed that the larger
k
values obtained in compression using uncorrected data were an artifact of the pseudoelastic effect. The apparent friction stress varied between about 14 MPa for pure Mg to very low or negative values for the most dilute alloy, increasing again to about 8 MPa for the most concentrated alloy. The use of strength data corrected for pseudoelasticity effects is necessary for a consistent analysis of the grain size hardening.
Context.
Characterizing the evolution of protoplanetary disks is necessary to improve our understanding of planet formation. Constraints on both dust and gas are needed to determine the dominant disk ...dissipation mechanisms.
Aims.
We aim to compare the disk dust masses in the Chamaeleon II (Cha II) star-forming region with other regions with ages between 1 and 10 Myr.
Methods.
We use ALMA band 6 observations (1.3 mm) to survey 29 protoplanetary disks in Cha II. Dust mass estimates are derived from the continuum data.
Results.
Out of our initial sample of 29 disks, we detect 22 sources in the continuum, 10 in
12
CO, 3 in
13
CO, and none in C
18
O (
J
= 2−1). Additionally, we detect two companion candidates in the continuum and
12
CO emission. Most disk dust masses are lower than 10
M
⊕
, assuming thermal emission from optically thin dust. Including non-detections, we derive a median dust mass of 4.5 ± 1.5
M
⊕
from survival analysis. We compare consistent estimations of the distributions of the disk dust mass and the disk-to-stellar mass ratios in Cha II with six other low mass and isolated star-forming regions in the age range of 1–10 Myr: Upper Sco, CrA, IC 348, Cha I, Lupus, and Taurus. When comparing the dust-to-stellar mass ratio, we find that the masses of disks in Cha II are statistically different from those in Upper Sco and Taurus, and we confirm that disks in Upper Sco, the oldest region of the sample, are statistically less massive than in all other regions. Performing a second statistical test of the dust mass distributions from similar mass bins, we find no statistical differences between these regions and Cha II.
Conclusions.
We interpret these trends, most simply, as a sign of decline in the disk dust masses with time or dust evolution. Different global initial conditions in star-forming regions may also play a role, but their impact on the properties of a disk population is difficult to isolate in star-forming regions lacking nearby massive stars.
Influenza A (FLUAV) and influenza B (FLUBV) viruses are human and/or animal pathogens widely studied due to their importance to public health and animal production. Both FLUAV and FLUBV possess a ...genome composed of eight viral gene segments. For reverse genetics of influenza viruses, transcription of the mRNA for the viral proteins is typically done from a plasmid encoding an RNA polymerase II (pol II) promoter element upstream of cloned viral cDNA and expressed like host mRNA. On the other side, the synthesis of the negative-sense, single-stranded, uncapped vRNAs can be accomplished by the host's RNA polymerase I (pol I). The reverse genetics for influenza has allowed the manipulation of influenza genomes incorporating heterogeneous sequences into different segments of the influenza genome, such as reporter genes. In this chapter, we outline the protocol from the generation of reverse genetic plasmid that can be applied for the cloning of any of the segments of FLUAV or FLUBV. Furthermore, we describe a protocol for generating FLUAV or FLUBV recombinant viruses carrying Nanoluciferase (NLuc) in the PB1 gene using reverse genetics. Finally, we delineate a microneutralization protocol using FLUAV-NLuc or FLUBV-NLuc viruses optimized for the use of antibodies from different sources (mice, ferrets, avian, etc.), which provides a more sensitive, reliable, and avidity-independent method to assess the presence of neutralizing antibodies against FLUAV or FLUBV.
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