1,924 research outputs found
Properties of synchronization in the systems of non-identical coupled van der Pol and van der Pol - Duffing oscillators. Broadband synchronization
The particular properties of dynamics are discussed for the dissipatively
coupled van der Pol oscillators, non-identical in values of parameters
controlling the Hopf bifurcation. Possibility of a special synchronization
regime in an infinitively long band between oscillation death and quasiperiodic
areas is shown for such system. Features of the bifurcation picture are
discussed for different values of the control parameters and for the case of
additional Duffing-type nonlinearity. Analysis of the abridged equations is
presented.Comment: 19 pages, 9 figure
The Relationship Between Molecular Gas, HI, and Star Formation in the Low-Mass, Low-Metallicity Magellanic Clouds
The Magellanic Clouds provide the only laboratory to study the effect of
metallicity and galaxy mass on molecular gas and star formation at high (~20
pc) resolution. We use the dust emission from HERITAGE Herschel data to map the
molecular gas in the Magellanic Clouds, avoiding the known biases of CO
emission as a tracer of H. Using our dust-based molecular gas estimates,
we find molecular gas depletion times of ~0.4 Gyr in the LMC and ~0.6 SMC at 1
kpc scales. These depletion times fall within the range found for normal disk
galaxies, but are shorter than the average value, which could be due to recent
bursts in star formation. We find no evidence for a strong intrinsic dependence
of the molecular gas depletion time on metallicity. We study the relationship
between gas and star formation rate across a range in size scales from 20 pc to
~1 kpc, including how the scatter in molecular gas depletion time changes with
size scale, and discuss the physical mechanisms driving the relationships. We
compare the metallicity-dependent star formation models of Ostriker, McKee, and
Leroy (2010) and Krumholz (2013) to our observations and find that they both
predict the trend in the data, suggesting that the inclusion of a diffuse
neutral medium is important at lower metallicity.Comment: 24 pages, 14 figures, accepted for publication in ApJ. FITS files of
the dust-based estimates of the H2 column densities for the LMC and SMC
(shown in Figures 2 and 3) will be available online through Ap
Structural basis of rotavirus RNA chaperone displacement and RNA annealing.
Rotavirus genomes are distributed between 11 distinct RNA molecules, all of which must be selectively copackaged during virus assembly. This likely occurs through sequence-specific RNA interactions facilitated by the RNA chaperone NSP2. Here, we report that NSP2 autoregulates its chaperone activity through its C-terminal region (CTR) that promotes RNA-RNA interactions by limiting its helix-unwinding activity. Unexpectedly, structural proteomics data revealed that the CTR does not directly interact with RNA, while accelerating RNA release from NSP2. Cryo-electron microscopy reconstructions of an NSP2-RNA complex reveal a highly conserved acidic patch on the CTR, which is poised toward the bound RNA. Virus replication was abrogated by charge-disrupting mutations within the acidic patch but completely restored by charge-preserving mutations. Mechanistic similarities between NSP2 and the unrelated bacterial RNA chaperone Hfq suggest that accelerating RNA dissociation while promoting intermolecular RNA interactions may be a widespread strategy of RNA chaperone recycling
THE RELATIONSHIP BETWEEN MOLECULAR GAS, H I, AND STAR FORMATION IN THE LOW-MASS, LOW-METALLICITY MAGELLANIC CLOUDS
The Magellanic Clouds provide the only laboratory to study the effects of metallicity and galaxy mass on molecular gas and star formation at high (∼20 pc) resolution. We use the dust emission from HERITAGE Herschel data to map the molecular gas in the Magellanic Clouds, avoiding the known biases of CO emission as a tracer of . Using our dust-based molecular gas estimates, we find molecular gas depletion times () of ∼0.4 Gyr in the Large Magellanic Cloud and ∼0.6 in the Small Magellanic Cloud at 1 kpc scales. These depletion times fall within the range found for normal disk galaxies, but are shorter than the average value, which could be due to recent bursts in star formation. We find no evidence for a strong intrinsic dependence of the molecular gas depletion time on metallicity. We study the relationship between the gas and the star formation rate across a range of size scales from 20 pc to ≥1 kpc, including how the scatter in changes with the size scale, and discuss the physical mechanisms driving the relationships. We compare the metallicity-dependent star formation models of Ostriker et al. and Krumholz to our observations and find that they both predict the trend in the data, suggesting that the inclusion of a diffuse neutral medium is important at lower metallicit
A systematic review of participatory scenario planning to envision mountain social-ecological systems futures
Mountain social-ecological systems (MtSES) provide crucial ecosystem services to over half of humanity. However, populations living in these highly varied regions are now confronted by global change. It is critical that they are able to anticipate change to strategically manage resources and avoid potential conflict. Yet, planning for sustainable, equitable transitions for the future is a daunting task, considering the range of uncertainties and the unique character of MtSES. Participatory scenario planning (PSP) can help MtSES communities by critically reflecting on a wider array of innovative pathways for adaptive transformation. Although the design of effective approaches has been widely discussed, how PSP has been employed in MtSES has yet to be examined. Here, we present the first systematic global review of single- and multiscalar, multisectoral PSP undertaken in MtSES, in which we characterize the process, identify strengths and gaps, and suggest effective ways to apply PSP in MtSES. We used a nine-step process to help guide the analysis of 42 studies from 1989 screened articles. Our results indicate a steady increase in relevant studies since 2006, with 43% published between 2015 and 2017. These studies encompass 39 countries, with over 50% in Europe. PSP in MtSES is used predominantly to build cooperation, social learning, collaboration, and decision support, yet meeting these objectives is hindered by insufficient engagement with intended end users. MtSES PSP has focused largely on envisioning themes of governance, economy, land use change, and biodiversity, but has overlooked themes such as gender equality, public health, and sanitation. There are many avenues to expand and improve PSP in MtSES: to other regions, sectors, across a greater diversity of stakeholders, and with a specific focus on MtSES paradoxes. Communicating uncertainty, monitoring and evaluating impacts, and engendering more comparative approaches can further increase the utility of PSP for addressing MtSES challenges, with lessons for other complex social-ecological systems. © 2020 by the author(s)
First Results from the and ALMA Spectroscopic Surveys of the SMC: The Relationship Between [CII]-bright Gas and CO-bright Gas at Low Metallicity
The Small Magellanic Cloud (SMC) provides the only laboratory to study the
structure of molecular gas at high resolution and low metallicity. We present
results from the Herschel Spectroscopic Survey of the SMC (HS), which
mapped the key far-IR cooling lines [CII], [OI], [NII], and [OIII] in five
star-forming regions, and new ALMA 7m-array maps of CO and CO
with coverage overlapping four of the five HS regions. We detect
[CII] and [OI] throughout all of the regions mapped. The data allow us to
compare the structure of the molecular clouds and surrounding photodissociation
regions using CO, CO, [CII], and [OI] emission at " ( pc)
scales. We estimate Av using far-IR thermal continuum emission from dust and
find the CO/[CII] ratios reach the Milky Way value at high A in the
centers of the clouds and fall to the Milky Way value in
the outskirts, indicating the presence of translucent molecular gas not traced
by bright CO emission. We estimate the amount of molecular gas traced by bright
[CII] emission at low A and bright CO emission at high A. We find
that most of the molecular gas is at low A and traced by bright [CII]
emission, but that faint CO emission appears to extend to where we estimate the
H-to-HI transition occurs. By converting our H gas estimates to a
CO-to-H conversion factor (), we show that is primarily
a function of A, consistent with simulations and models of low
metallicity molecular clouds.Comment: Accepted for publication in Ap
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