The value of valuing nature Adams, W. M.
Science (American Association for the Advancement of Science),
10/2014, Letnik:
346, Številka:
6209
Journal Article
Recenzirano
The complex ways in which humans depend on their natural environment are increasingly expressed in terms of ecosystem services, which are often assigned economic values to assist decision-making. The ...key attraction of the ecosystem services concept to conservationists lies in the potential for win-win outcomes (1), where the value of an ecosystem service depends on high biological diversity and cannot be increased by modifying it. Such outcomes are possible. For example, in Costa Rican coffee plantations, retention of forest patches doubled pest control of coffee berry borer beetle by birds, with substantial economic benefits to coffee farmers (2). However, attention to ecosystem services does not automatically lead to the conservation of biodiversity (3). A series of factors challenge the creation of synergies between ecosystem services and biodiversity conservation (see the figure).
Context.
Repeating fast radio bursts (FRBs) present excellent opportunities to identify FRB progenitors and host environments as well as to decipher the underlying emission mechanism. Detailed ...studies of repeating FRBs might also hold clues as to the origin of FRBs as a population.
Aims.
We aim to detect bursts from the first two repeating FRBs, FRB 121102 (R1) and FRB 180814.J0422+73 (R2), and to characterise their repeat statistics. We also want to significantly improve the sky localisation of R2 and identify its host galaxy.
Methods.
We used the Westerbork Synthesis Radio Telescope to conduct extensive follow-up of these two repeating FRBs. The new phased-array feed system, Apertif, allows one to cover the entire sky position uncertainty of R2 with fine spatial resolution in a single pointing. The data were searched for bursts around the known dispersion measures of the two sources. We characterise the energy distribution and the clustering of detected R1 bursts.
Results.
We detected 30 bursts from R1. The non-Poissonian nature is clearly evident from the burst arrival times, which is consistent with earlier claims. Our measurements indicate a dispersion measure (DM) of 563.5(2) pc cm
−3
, suggesting a significant increase in DM over the past few years. Assuming a constant position angle across the burst, we place an upper limit of 8% on the linear polarisation fraction for the brightest burst in our sample. We did not detect any bursts from R2.
Conclusions.
A single power-law might not fit the R1 burst energy distribution across the full energy range or widely separated detections. Our observations provide improved constraints on the clustering of R1 bursts. Our stringent upper limits on the linear polarisation fraction imply a significant depolarisation, either intrinsic to the emission mechanism or caused by the intervening medium at 1400 MHz, which is not observed at higher frequencies. The non-detection of any bursts from R2, despite nearly 300 h of observations, implies either a highly clustered nature of the bursts, a steep spectral index, or a combination of the two assuming that the source is still active. Another possibility is that R2 has turned off completely, either permanently or for an extended period of time.
Super massive black holes at the centres of galaxies can cycle through periods of activity and quiescence. Characterising the duty cycle of active galactic nuclei (AGN) is crucial for understanding ...the impact of the energy they release on the host galaxy. For radio AGN, this can be done by identifying dying (remnant) and restarted radio galaxies from their radio spectral properties. Using the combination of the images at 1400 MHz produced by Apertif, the new phased-array feed receiver installed on the Westerbork Synthesis Radio Telescope, and images at 150 MHz provided by LOFAR, we have derived resolved spectral index images (at a resolution of ~15 arcsec) for all the sources within an approximately 6 deg
2
area of the Lockman Hole region. In this way, we were able to select 15 extended radio sources with emission (partly or entirely) characterised by extremely steep spectral indices (steeper than 1.2). These objects represent cases of radio sources in the remnant or the restarted phases of their life cycle. Our findings confirm that these objects are not as rare as previously thought, suggesting a relatively fast cycle. They also show a variety of properties that can be relevant for modelling the evolution of radio galaxies. For example, the restarted activity can occur while the remnant structure from a previous phase of activity is still visible. This provides constraints on the duration of the “off” (dying) phase. In extended remnants with ultra-steep spectra at low frequencies, the activity likely stopped a few hundred megayears ago, and they correspond to the older tail of the age distribution of radio galaxies, in agreement with the results of simulations of radio source evolution. We find remnant radio sources with a variety of structures (from double-lobed to amorphous), possibly suggesting different types of progenitors. The present work sets the stage for exploiting the powerful tool of low-frequency spectral index studies of extended sources by taking advantage of the large areas common to the LOFAR and the Apertif surveys.
We identified 100 scientific questions that, if answered, would have the greatest impact on conservation practice and policy. Representatives from 21 international organizations, regional sections ...and working groups of the Society for Conservation Biology, and 12 academics, from all continents except Antarctica, compiled 2291 questions of relevance to conservation of biological diversity worldwide. The questions were gathered from 761 individuals through workshops, email requests, and discussions. Voting by email to short-list questions, followed by a 2-day workshop, was used to derive the final list of 100 questions. Most of the final questions were derived through a process of modification and combination as the workshop progressed. The questions are divided into 12 sections: ecosystem functions and services, climate change, technological change, protected areas, ecosystem management and restoration, terrestrial ecosystems, marine ecosystems, freshwater ecosystems, species management, organizational systems and processes, societal context and change, and impacts of conservation interventions. We anticipate that these questions will help identify new directions for researchers and assist funders in directing funds.
ABSTRACT
We report the detection of a bright fast radio burst, FRB 191108, with Apertif on the Westerbork Synthesis Radio Telescope. The interferometer allows us to localize the FRB to a narrow 5 ...arcsec × 7 arcmin ellipse by employing both multibeam information within the Apertif phased-array feed beam pattern, and across different tied-array beams. The resulting sightline passes close to Local Group galaxy M33, with an impact parameter of only 18 kpc with respect to the core. It also traverses the much larger circumgalactic medium (CGM) of M31, the Andromeda Galaxy. We find that the shared plasma of the Local Group galaxies could contribute ∼10 per cent of its dispersion measure of 588 pc cm−3. FRB 191108 has a Faraday rotation measure (RM) of +474 $\pm \, 3$ rad m−2, which is too large to be explained by either the Milky Way or the intergalactic medium. Based on the more moderate RMs of other extragalactic sources that traverse the halo of M33, we conclude that the dense magnetized plasma resides in the host galaxy. The FRB exhibits frequency structure on two scales, one that is consistent with quenched Galactic scintillation and broader spectral structure with Δν ≈ 40 MHz. If the latter is due to scattering in the shared M33/M31 CGM, our results constrain the Local Group plasma environment. We found no accompanying persistent radio sources in the Apertif imaging survey data.
A KINETIC DATABASE FOR ASTROCHEMISTRY (KIDA) Wakelam, V; Herbst, E; Loison, J-C ...
The Astrophysical journal. Supplement series,
03/2012, Letnik:
199, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We present a novel chemical database for gas-phase astrochemistry. Named the KInetic Database for Astrochemistry (KIDA), this database consists of gas-phase reactions with rate coefficients and ...uncertainties that will be vetted to the greatest extent possible. Submissions of measured and calculated rate coefficients are welcome, and will be studied by experts before inclusion into the database. Besides providing kinetic information for the interstellar medium, KIDA is planned to contain such data for planetary atmospheres and for circumstellar envelopes. each year, a subset of the reactions in the database (kida.uva) will be provided as a network for the simulation of the chemistry of dense interstellar clouds with temperatures between 10 K and 300 K. We also provide a code, named Nahoon, to study the time-dependent gas-phase chemistry of zero-dimensional and one-dimensional interstellar sources.
Do you speak lion? Adams, W. M.
Science (American Association for the Advancement of Science),
08/2016, Letnik:
353, Številka:
6302
Journal Article
Recenzirano
Problems in biodiversity conservation tend to be highly complex, encompassing both biological and social systems and their interactions (1). Many have argued for multidisciplinary research in ...conservation, particularly a more effective engagement of the human sciences (2). But even when multidisciplinary, research may not be able to deliver the insights needed to solve a conservation problem. Recent studies help to elucidate these challenges and show how research can be effective in underpinning conservation decisions (2-5).
Despite a substantial genetic component, efforts to identify common genetic variation underlying depression have largely been unsuccessful. In the current study we aimed to identify rare genetic ...variants that might have large effects on depression in the general population. Using high-coverage exome-sequencing, we studied the exonic variants in 1265 individuals from the Rotterdam study (RS), who were assessed for depressive symptoms. We identified a missense Asn396Ser mutation (rs77960347) in the endothelial lipase (LIPG) gene, occurring with an allele frequency of 1% in the general population, which was significantly associated with depressive symptoms (P-value=5.2 × 10
, β=7.2). Replication in three independent data sets (N=3612) confirmed the association of Asn396Ser (P-value=7.1 × 10
, β=2.55) with depressive symptoms. LIPG is predicted to have enzymatic function in steroid biosynthesis, cholesterol biosynthesis and thyroid hormone metabolic processes. The Asn396Ser variant is predicted to have a damaging effect on the function of LIPG. Within the discovery population, carriers also showed an increased burden of white matter lesions (P-value=3.3 × 10
) and a higher risk of Alzheimer's disease (odds ratio=2.01; P-value=2.8 × 10
) compared with the non-carriers. Together, these findings implicate the Asn396Ser variant of LIPG in the pathogenesis of depressive symptoms in the general population.
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