2,466 research outputs found
Climate services for managing societal risks and opportunities
The Earth’s climate and changes to it impact our lives, well-being and economy in numerous ways, some positive and some negative. Managing the risks that arise from changes in the climate over the coming months, years and decades is one of the most pressing challenges that society faces, but there are also some opportunities. The provision and use of climate information in decision-making (i.e. climate services) are central to managing the risks and opportunities. In this article we describe the seemingly complex climate service landscape, the actors in it, what the services are used for, and what next, to help stimulate further action to enable society to reduce risks and realise benefits, particularly timely as the world looks ahead to build a green recovery from the COVID-19 pandemic on the path to net zero emissions. Through a consideration of the value chain for climate services, we emphasise the importance of dialogue and collaboration between those developing, providing and using climate information in decision-making, and stress that a climate service is only worth delivering if it is going to be used by someone to influence an outcome. Co-production can be highly useful for enabling the dialogue and collaborating across the value chain, helping create services based on credible, salient and legitimate knowledge
OT J002656.6+284933 (CSS101212:002657+284933): An SU UMa-Type Dwarf Nova with Longest Superhump Period
We observed the 2016 outburst of OT J002656.6+284933
(CSS101212:002657+284933) and found that it has the longest recorded
[0.13225(1) d in average] superhumps among SU UMa-type dwarf novae. The object
is the third known SU UMa-type dwarf nova above the period gap. The outburst,
however, was unlike ordinary long-period SU UMa-type dwarf novae in that it
showed two post-outburst rebrightenings. It showed superhump evolution similar
to short-period SU UMa-type dwarf novae. We could constrain the mass ratio to
less than 0.15 (most likely between 0.10 and 0.15) by using superhump periods
in the early and post-superoutburst stages. These results suggest the
possibility that OT J002656.6+284933 has an anomalously undermassive secondary
and it should have passed a different evolutionary track from the standard one.Comment: 6 pages, 3 figures, accepted for publication in PASJ (Letters), Note
added in proof has been added. Supplementary Information (si.pdf) is
available in the source fil
Subtidal macrozoobenthos communities from northern Chile during and post El Niño 1997–1998
Despite a large amount of climatic and oceanographic information dealing with the recurring climate phenomenon El Niño (EN) and its well known impact on diversity of marine benthic communities, most published data are rather descriptive and consequently our understanding of the underlying mechanisms and processes that drive community structure during EN are still very scarce. In this study, we address two questions on the effects of EN on macrozoobenthic communities: (1) how does EN affect species diversity of the communities in northern Chile? and (2) is EN a phenomenon that restarts community assembling processes by affecting species interactions in northern Chile? To answer these questions, we compared species diversity and co-occurrence patterns of soft-bottoms macrozoobenthos communities from the continental shelf off northern Chile during (March 1998) and after (September 1998) the strong EN event 1997–1998. The methods used varied from species diversity and species co-occurrence analyses to multivariate ordination methods.
Our results indicate that EN positively affects diversity of macrozoobenthos communities in the study area, increasing the species richness and diversity and decreasing the species dominance. EN represents a strong disturbance that affects species interactions that rule the species assembling processes in shallow-water, sea-bottom environments
The Chandra Source Catalog
The Chandra Source Catalog (CSC) is a general purpose virtual X-ray
astrophysics facility that provides access to a carefully selected set of
generally useful quantities for individual X-ray sources, and is designed to
satisfy the needs of a broad-based group of scientists, including those who may
be less familiar with astronomical data analysis in the X-ray regime. The first
release of the CSC includes information about 94,676 distinct X-ray sources
detected in a subset of public ACIS imaging observations from roughly the first
eight years of the Chandra mission. This release of the catalog includes point
and compact sources with observed spatial extents <~ 30''. The catalog (1)
provides access to the best estimates of the X-ray source properties for
detected sources, with good scientific fidelity, and directly supports
scientific analysis using the individual source data; (2) facilitates analysis
of a wide range of statistical properties for classes of X-ray sources; and (3)
provides efficient access to calibrated observational data and ancillary data
products for individual X-ray sources, so that users can perform detailed
further analysis using existing tools. The catalog includes real X-ray sources
detected with flux estimates that are at least 3 times their estimated 1 sigma
uncertainties in at least one energy band, while maintaining the number of
spurious sources at a level of <~ 1 false source per field for a 100 ks
observation. For each detected source, the CSC provides commonly tabulated
quantities, including source position, extent, multi-band fluxes, hardness
ratios, and variability statistics, derived from the observations in which the
source is detected. In addition to these traditional catalog elements, for each
X-ray source the CSC includes an extensive set of file-based data products that
can be manipulated interactively.Comment: To appear in The Astrophysical Journal Supplement Series, 53 pages,
27 figure
From 10 Kelvin to 10 TeraKelvin: Insights on the Interaction Between Cosmic Rays and Gas in Starbursts
Recent work has both illuminated and mystified our attempts to understand
cosmic rays (CRs) in starburst galaxies. I discuss my new research exploring
how CRs interact with the ISM in starbursts. Molecular clouds provide targets
for CR protons to produce pionic gamma rays and ionization, but those same
losses may shield the cloud interiors. In the densest molecular clouds, gamma
rays and Al-26 decay can provide ionization, at rates up to those in Milky Way
molecular clouds. I then consider the free-free absorption of low frequency
radio emission from starbursts, which I argue arises from many small, discrete
H II regions rather than from a "uniform slab" of ionized gas, whereas
synchrotron emission arises outside them. Finally, noting that the hot
superwind gas phase fills most of the volume of starbursts, I suggest that it
has turbulent-driven magnetic fields powered by supernovae, and that this phase
is where most synchrotron emission arises. I show how such a scenario could
explain the far-infrared radio correlation, in context of my previous work. A
big issue is that radio and gamma-ray observations imply CRs also must interact
with dense gas. Understanding how this happens requires a more advanced
understanding of turbulence and CR propagation.Comment: Conference proceedings for "Cosmic-ray induced phenomenology in
star-forming environments: Proceedings of the 2nd Session of the Sant Cugat
Forum of Astrophysics" (April 16-19, 2012). 16 pages, 5 figure
Combining microscopic and macroscopic probes to untangle the single-ion anisotropy and exchange energies in an S=1 quantum antiferromagnet
The magnetic ground state of the quasi-one-dimensional spin-1 antiferromagnetic chain is sensitive to the relative sizes of the single-ion anisotropy (D) and the intrachain (J) and interchain (J') exchange interactions. The ratios D/J and J'/J dictate the material's placement in one of three competing phases: a Haldane gapped phase, a quantum paramagnet and an XY-ordered state, with a quantum critical point at their junction. We have identified [Ni(HF)2(pyz)_2]SbF6, where pyz = pyrazine, as a rare candidate in which this behavior can be explored in detail. Combining neutron scattering (elastic and inelastic) in applied magnetic fields of up to 10~tesla and magnetization measurements in fields of up to 60~tesla with numerical modeling of experimental observables, we are able to obtain accurate values of all of the parameters of the Hamiltonian [D = 13.3(1)~K, J = 10.4(3)~K and J' = 1.4(2)~K], despite the polycrystalline nature of the sample. Density-functional theory calculations result in similar couplings (J = 9.2~K, J' = 1.8~K) and predict that the majority of the total spin population resides on the Ni(II) ion, while the remaining spin density is delocalized over both ligand types. The general procedures outlined in this paper permit phase boundaries and quantum-critical points to be explored in anisotropic systems for which single crystals are as yet unavailable
General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes
Black hole (BH) accretion flows and jets are qualitatively affected by the
presence of ordered magnetic fields. We study fully three-dimensional global
general relativistic magnetohydrodynamic (MHD) simulations of radially extended
and thick (height to cylindrical radius ratio of )
accretion flows around BHs with various dimensionless spins (, with BH
mass ) and with initially toroidally-dominated (-directed) and
poloidally-dominated ( directed) magnetic fields. Firstly, for toroidal
field models and BHs with high enough , coherent large-scale (i.e. ) dipolar poloidal magnetic flux patches emerge, thread the BH, and generate
transient relativistic jets. Secondly, for poloidal field models, poloidal
magnetic flux readily accretes through the disk from large radii and builds-up
to a natural saturation point near the BH. For sufficiently high or low
the polar magnetic field compresses the inflow into a geometrically
thin highly non-axisymmetric "magnetically choked accretion flow" (MCAF) within
which the standard linear magneto-rotational instability is suppressed. The
condition of a highly-magnetized state over most of the horizon is optimal for
the Blandford-Znajek mechanism that generates persistent relativistic jets with
% efficiency for . A magnetic Rayleigh-Taylor
and Kelvin-Helmholtz unstable magnetospheric interface forms between the
compressed inflow and bulging jet magnetosphere, which drives a new jet-disk
quasi-periodic oscillation (JD-QPO) mechanism. The high-frequency QPO has
spherical harmonic mode period of for
with coherence quality factors . [abridged]Comment: 32 pages + acks/appendix/references, 22 figures, 10 tables. MNRAS in
press. High-Res Version: http://www.slac.stanford.edu/~jmckinne/mcaf.pdf .
Fiducial Movie: http://youtu.be/V2WoJOkIin
Science and Ideology in Economic, Political, and Social Thought
This paper has two sources: One is my own research in three broad areas: business cycles, economic measurement and social choice. In all of these fields I attempted to apply the basic precepts of the scientific method as it is understood in the natural sciences. I found that my effort at using natural science methods in economics was met with little understanding and often considerable hostility. I found economics to be driven less by common sense and empirical evidence, then by various ideologies that exhibited either a political or a methodological bias, or both. This brings me to the second source: Several books have appeared recently that describe in historical terms the ideological forces that have shaped either the direct areas in which I worked, or a broader background. These books taught me that the ideological forces in the social sciences are even stronger than I imagined on the basis of my own experiences.
The scientific method is the antipode to ideology. I feel that the scientific work that I have done on specific, long standing and fundamental problems in economics and political science have given me additional insights into the destructive role of ideology beyond the history of thought orientation of the works I will be discussing
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