An essential step for a productive infection by the dengue flavivirus (DEN) is translation of the m
7G-capped, nonpolyadenylated positive-sense RNA genome. We have recently identified sequences ...within the DEN 3′ untranslated region (UTR) that modulate viral translation. Here, we show that the DEN type 2 (DEN2) 3′UTR stimulated translation of m
7G-capped DEN2 5′UTR-containing reporter mRNAs in baby hamster kidney (BHK) cells compared to a 3′ vector sequence. Analogous to the 3′ poly(A) tail, the DEN2 3′UTR also enhanced translation of reporter mRNAs containing (i) a nonfunctional A cap, (ii) the 5′UTR of human β-globin, or (iii) a viral internal ribosome entry site (IRES). In all cases, approximately half of the translation efficiency was due to the terminal 3′ stem-loop (3′SL) domain. In addition, the 3′SL domain increased the association of mRNAs with polysomes. Together, these results indicate that the DEN2 3′UTR, mediated in part by the 3′SL domain, enhances translation initiation, possibly after recognition of the 5′ cap structure.
We present ALMA high spatial resolution observations toward two star-forming regions located in one of the most extreme zones of star formation in the Galaxy, the Carina Nebula. One region is located ...at the center of the nebula and is severally affected by the stellar feedback from high-mass stars, while the other region is located farther south and is less disturbed by the massive-star clusters. We found that the region at the center of the nebula is forming less but more massive cores than the region located in the south, suggesting that the level of stellar feedback effectively influences the fragmentation process in clumps. Lines such as HCN, HCO+, and SiO show abundant and complex gas distributions in both regions, confirming the presence of ionization and shock fronts. Jeans analysis suggests that the observed core masses in the region less affected by the massive stars are consistent with thermal fragmentation, but turbulent Jeans fragmentation might explain the high masses of the cores identified in the region in the center of Carina. Consistently, two different analyses in the HCO+ line provided evidence for a higher level of turbulence in the gas more affected by the stellar feedback. The gas column density probability functions, N-pdf's, show lognormal shapes with clear transitions to power-law regimes. We observed a wider N-pdf in the region at the center of the nebula, which provides further evidence for a higher level of turbulence in the material with a higher level of massive stellar feedback.
The PHANGS–MUSE nebular catalogue Groves, B; Kreckel, K; Santoro, F ...
Monthly notices of the Royal Astronomical Society,
02/2023, Letnik:
520, Številka:
4
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
Ionized nebulae provide critical insights into the conditions of the interstellar medium (ISM). Their bright emission lines enable the measurement of physical properties, such as the ...gas-phase metallicity, across galaxy discs and in distant galaxies. The PHANGS–MUSE survey has produced optical spectroscopic coverage of the central star-forming discs of 19 nearby main-sequence galaxies. Here, we use the $\rm {H}\,\alpha$ morphology from this data to identify 30 790 distinct nebulae, finding thousands of nebulae per galaxy. For each nebula, we extract emission line fluxes and, using diagnostic line ratios, identify the dominant excitation mechanism. A total of 23 244 nebulae (75 per cent) are classified as H ii regions. The dust attenuation of every nebulae is characterized via the Balmer decrement and we use existing environmental masks to identify their large-scale galactic environment (centre, bar, arm, interarm, and disc). Using strong-line prescriptions, we measure the gas-phase oxygen abundances (metallicity) and ionization parameter for all H ii regions. With this new catalogue, we measure the radial metallicity gradients and explore second-order metallicity variations within each galaxy. By quantifying the global scatter in metallicity per galaxy, we find a weak negative correlation with global star formation rate and stronger negative correlation with global gas velocity dispersion (in both ionized and molecular gas). With this paper we release the full catalogue of strong line fluxes and derived properties, providing a rich data base for a broad variety of ISM studies.
Significant attention has focused on the potential for increased shipping activity driven by recently observed declines in Arctic sea ice cover. In this study, we describe the first coupled spatial ...analysis between shipping activity and sea ice using observations in the Canadian Arctic over the 1990–2015 period. Shipping activity is measured by using known ship locations enhanced with a least cost path algorithm to generate ship tracks and quantified by computing total distance traveled in kilometers. Statistically significant increases in shipping activity are observed in the Hudson Strait (150–500 km traveled yr−1), the Beaufort Sea (40–450 km traveled yr−1), Baffin Bay (50–350 km traveled yr−1), and regions in the southern route of the Northwest Passage (50–250 km traveled yr−1). Increases in shipping activity are significantly correlated with reductions in sea ice concentration (Kendall's tau up to −0.6) in regions of the Beaufort Sea, Western Parry Channel, Western Baffin Bay, and Foxe Basin. Changes in multiyear ice‐dominant regions in the Canadian Arctic were found to be more influential on changes to shipping activity compared to seasonal sea ice regions.
Key Points
First observational coupled spatial analysis of the influence of declining sea ice on increasing ship activity in the Canadian Arctic
Shipping activity increases are significantly correlated to declining sea ice in several regions
The presence of multiyear ice seems to influence shipping activity more than seasonal first‐year ice
In this paper, we identify the patterns of change agency in peripheral regions and the forces shaping them. The following are the main research questions: (a) what are the patterns of local change ...agency like in peripheral regions and (b) what causes patterns of local change agency? We seek answers to these questions by carrying out a detailed analysis of trinity of change agency in Lapland, Finland. We show how the pattern of it evolves in time, and how, in a crisis, new modes of agency surface and key actors need to learn new ways of intervening. Change agents need to build confidence and mobilize resources, capabilities and power. The empirical study follows a longitudinal single case study design. The empirical data were based on 15 interviews of the national and local/regional development agencies as well as from firms and research/educational organizations. Additionally, the written material from the Internet, relevant journals, related newspaper articles and respective policy documents were analysed. The empirical analysis identifies the main phases of path development in Eastern Lapland, key actors in different phases and their agency.
Microbial communities in arctic-alpine soils show biogeographic patterns related to elevation, but the effect of fine-scale heterogeneity and possibly related temperature and soil moisture regimes ...remains unclear. We collected soil samples from different micro-topographic positions and elevational levels in two mountain regions of the Scandes, Central Norway. Microbial community composition was characterized by 16S rRNA gene amplicon sequencing and was dependent on micro-topography and elevation. Underlying environmental drivers were identified by integration of microbial community data with a comprehensive set of site-specific long-term recorded temperature and soil moisture data. Partial least square regression analysis allowed the description of ecological response patterns and the identification of the important environmental drivers for each taxonomic group. This demonstrated for the first time that taxa responding to elevation were indeed most strongly defined by temperature, rather than by other environmental factors. Micro-topography affected taxa were primarily controlled by temperature and soil moisture. In general, 5-year datasets had higher explanatory power than 1-year datasets, indicating that the microbial community composition is dependent on long-term developments of near-ground temperature and soil moisture regimes and possesses a certain resilience, which is in agreement with an often observed delayed response in global warming studies in arctic-alpine regions.
Regional capabilities are regarded a pillar of Smart Specialisation Strategy (S3). There is yet little focus in S3 policy on the role of interregional linkages. This study on 292 NUTS-2 regions in ...Europe finds that interregional linkages have a positive effect on the probability of regions to diversify, especially in peripheral regions. What matters is not being connected to other regions per se, but being connected to regions that provide complementary capabilities. Finally, we propose a new indicator that enables regions to identify other regions as strategic partners in their S3 policy, depending on the presence of complementary capabilities in other regions.
The present study is aimed to validate the occurrence of two species of Diadem or Royal snakes of Genus Spalerosophis Jan, 1865 from the Poonch District of Jammu and Kashmir, India along with the ...presentation of eight different colour morphs and diagnostic characteristics. The eight different colour morphs include four colour morphs of adults of S. d. diadema (Schlegel, 1837), two colour morphs of adults of S. atriceps (Fischer, 1885), one colour morph of subadults of unknown parentage and one colour morph of the adult of S. diadema (Schlegel, 1837) represented by a single individual whose identification at subspecies level (ssp. cliffordii/diadema) is the subject for further investigations for want of more specimens. This solitary specimen shares many similarities with S. d. diadema, but it has less number of sub-caudal scales which point towards the likelihood of S. d. cliffordii (Schlegel, 1837). The distribution, activity, habitat and behaviour have also been reported along with the morphological, morphometric and meristic characters. Between two identified species S. atriceps is a new report from the Poonch District. Reported specimens are mapped across the study area and are depicted here in the distribution map.
Understanding how star formation is regulated requires studying the energy balance between turbulence, magnetic fields, stellar feedback, and gravity within molecular clouds. However, identifying the ...transition region where the gravity takes over remains elusive. Recent studies of the Velocity Gradient Technique (VGT), which is an advanced tool for magnetic field studies, reveal that the gradients of spectroscopic observables change their directions by 90° with respect to the magnetic fields in the regions of gravitational collapse. In this study, we perform 3D MHD numerical simulations. We observe that star formation successfully proceeds in strongly magnetized and fully ionized media. We confirm that the self-gravity induces the change of gradients' orientation and gradients' high amplitude. We explore two ways of identifying collapsing self-gravitating regions through the double-peak feature in the histogram of gradients' orientation and the curvature of gradients. We show that velocity gradients' morphology and amplitude can be synthetically used to trace the convergent inflows. By comparing with the column density Probability Density Functions method, we show that VGT is a powerful new tool for studying the gas dynamics and tracing magnetic field in star-forming regions. By analogy with VGT, we extend the Intensity Gradient Technique (IGT) to locate the gravitational collapsing region and shocks. We demonstrate that the synergy of VGT and IGT can determine the collapsing stages in a star-forming region.
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