This paper identifies new ways of moving from land degradation towards sustainable land management through the development of economic mechanisms. It identifies new mechanisms to tackle land ...degradation based on retaining critical levels of natural capital whilst basing livelihoods on a wider range of ecosystem services. This is achieved through a case study analysis of the Kalahari rangelands in southwest Botswana. The paper first describes the socio-economic and ecological characteristics of the Kalahari rangelands and the types of land degradation taking place. It then focuses on bush encroachment as a way of exploring new economic instruments (e.g. Payments for Ecosystem Services) designed to enhance the flow of ecosystem services that support livelihoods in rangeland systems. It does this by evaluating the likely impacts of bush encroachment, one of the key forms of rangeland degradation, on a range of ecosystem services in three land tenure types (private fenced ranches, communal grazing areas and Wildlife Management Areas), before considering options for more sustainable land management in these systems. We argue that with adequate policy support, economic mechanisms could help reorient degraded rangelands towards more sustainable land management.
•To tackle degradation, retain critical natural capital & base livelihoods on a wider range of eco-services.•Economic mechanisms are identified to move from land degradation to sustainable land management.•There is a need to move beyond purely monetary valuation of ecosystem services.•Mechanisms must tackle economic causes of land degradation and benefit rich and poor.•These points are illustrated with a case study from the Kalahari, Botswana.
The 1.28 GHz MeerKAT Galactic Center Mosaic Heywood, I.; Rammala, I.; Camilo, F. ...
Astrophysical journal/The Astrophysical journal,
02/2022, Volume:
925, Issue:
2
Journal Article
Peer reviewed
Open access
Abstract
The inner ∼200 pc region of the Galaxy contains a 4 million M
⊙
supermassive black hole (SMBH), significant quantities of molecular gas, and star formation and cosmic-ray energy densities ...that are roughly two orders of magnitude higher than the corresponding levels in the Galactic disk. At a distance of only 8.2 kpc, the region presents astronomers with a unique opportunity to study a diverse range of energetic astrophysical phenomena, from stellar objects in extreme environments, to the SMBH and star-formation-driven feedback processes that are known to influence the evolution of galaxies as a whole. We present a new survey of the Galactic center conducted with the South African MeerKAT radio telescope. Radio imaging offers a view that is unaffected by the large quantities of dust that obscure the region at other wavelengths, and a scene of striking complexity is revealed. We produce total-intensity and spectral-index mosaics of the region from 20 pointings (144 hr on-target in total), covering 6.5 square degrees with an angular resolution of 4″ at a central frequency of 1.28 GHz. Many new features are revealed for the first time due to a combination of MeerKAT’s high sensitivity, exceptional
u
,
v
-plane coverage, and geographical vantage point. We highlight some initial survey results, including new supernova remnant candidates, many new nonthermal filament complexes, and enhanced views of the Radio Arc bubble, Sagittarius A, and Sagittarius B regions. This project is a South African Radio Astronomy Observatory public legacy survey, and the image products are made available with this article.
We present a measurement of the cosmic-ray electron+positron spectrum between 7 GeV and 2 TeV performed with almost seven years of data collected with the Fermi Large Area Telescope. We find that the ...spectrum is well fit by a broken power law with a break energy at about 50 GeV. Above 50 GeV, the spectrum is well described by a single power law with a spectral index of 3.07±0.02(stat+syst)±0.04(energy measurement). An exponential cutoff lower than 1.8 TeV is excluded at 95% CL.
The 1.28 GHz MeerKAT DEEP2 Image Cotton, W. D.; Matthews, A. M.; Abbott, T. D. ...
Astrophysical journal/The Astrophysical journal,
01/2020, Volume:
888, Issue:
2
Journal Article
Peer reviewed
Open access
We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one primary-beam area with θ = 7 6 FWHM resolution and rms noise. Its J2000 center position = 04h 13m 26 4, δ = −80° 00′ 00″ was ...selected to minimize artifacts caused by bright sources. We introduce the new 64-element MeerKAT array and describe commissioning observations to measure the primary-beam attenuation pattern, estimate telescope pointing errors, and pinpoint (u, v) coordinate errors caused by offsets in frequency or time. We constructed a 1.4 GHz differential source count by combining a power-law count fit to the DEEP2 confusion P(D) distribution from 0.25 to 10 Jy with counts of individual DEEP2 sources between 10 Jy and 2.5 mJy. Most sources fainter than S ∼ 100 Jy are distant star-forming galaxies (SFGs) obeying the far-IR/radio correlation, and sources stronger than 0.25 Jy account for ∼93% of the radio background produced by SFGs. For the first time, the DEEP2 source count has reached the depth needed to reveal the majority of the star formation history of the universe. A pure luminosity evolution of the 1.4 GHz local luminosity function consistent with the Madau & Dickinson model for the evolution of SFGs based on UV and infrared data underpredicts our 1.4 GHz source count in the range .
We present a catalog of sources detected above 10 GeV by the Fermi Large Area Telescope (LAT) in the first 7 years of data using the Pass 8 event-level analysis. This is the Third Catalog of Hard ...Fermi-LAT Sources (3FHL), containing 1556 objects characterized in the 10 GeV-2 TeV energy range. The sensitivity and angular resolution are improved by factors of 3 and 2 relative to the previous LAT catalog at the same energies (1FHL). The vast majority of detected sources (79%) are associated with extragalactic counterparts at other wavelengths, including 16 sources located at very high redshift (z > 2). Of the sources, 8% have Galactic counterparts and 13% are unassociated (or associated with a source of unknown nature). The high-latitude sky and the Galactic plane are observed with a flux sensitivity of 4.4 to 9.5 × 10−11 ph cm−2 s−1, respectively (this is approximately 0.5% and 1% of the Crab Nebula flux above 10 GeV). The catalog includes 214 new γ-ray sources. The substantial increase in the number of photons (more than 4 times relative to 1FHL and 10 times to 2FHL) also allows us to measure significant spectral curvature for 32 sources and find flux variability for 163 of them. Furthermore, we estimate that for the same flux limit of 10−12 erg cm−2 s−1, the energy range above 10 GeV has twice as many sources as the range above 50 GeV, highlighting the importance, for future Cherenkov telescopes, of lowering the energy threshold as much as possible.
The region around the Galactic Center (GC) is now well established to be brighter at energies of a few GeV than what is expected from conventional models of diffuse gamma-ray emission and catalogs of ...known gamma-ray sources. We study the GeV excess using 6.5 yr of data from the Fermi Large Area Telescope. We characterize the uncertainty of the GC excess spectrum and morphology due to uncertainties in cosmic-ray source distributions and propagation, uncertainties in the distribution of interstellar gas in the Milky Way, and uncertainties due to a potential contribution from the Fermi bubbles. We also evaluate uncertainties in the excess properties due to resolved point sources of gamma rays. The GC is of particular interest, as it would be expected to have the brightest signal from annihilation of weakly interacting massive dark matter (DM) particles. However, control regions along the Galactic plane, where a DM signal is not expected, show excesses of similar amplitude relative to the local background. Based on the magnitude of the systematic uncertainties, we conservatively report upper limits for the annihilation cross-section as a function of particle mass and annihilation channel.
We present the fourth Fermi Large Area Telescope catalog (4FGL) of γ-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range ...from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse γ-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4 significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.
Summary Background Basal-cell carcinoma is the most common form of skin cancer and its incidence is increasing worldwide. We aimed to assess the effectiveness of imiquimod cream versus surgical ...excision in patients with low-risk basal-cell carcinoma. Methods We did a multicentre, parallel-group, pragmatic, non-inferiority, randomised controlled trial at 12 centres in the UK, in which patients were recruited between June 19, 2003, and Feb 22, 2007, with 3 year follow-up from June 26, 2006, to May 26, 2010. Participants of any age were eligible if they had histologically confirmed primary nodular or superficial basal-cell carcinoma at low-risk sites. We excluded patients with morphoeic or recurrent basal-cell carcinoma and those with Gorlin syndrome. Participants were randomly assigned (1:1) via computer-generated blocked randomisation, stratified by centre and tumour type, to receive either imiquimod 5% cream once daily for 6 weeks (superficial) or 12 weeks (nodular), or surgical excision with a 4 mm margin. The randomisation sequence was concealed from study investigators. Because of the nature of the interventions, masking of participants was not possible and masking of outcome assessors was only partly possible. The trial statistician was masked to allocation until all analyses had been done. The primary outcome was the proportion of participants with clinical success, defined as absence of initial treatment failure or signs of recurrence at 3 years from start of treatment. We used a prespecified non-inferiority margin of a relative risk (RR) of 0·87. Analysis was by a modified intention-to-treat population and per protocol. This study is registered as an International Standard Randomised Controlled Trial ( ISRCTN48755084 ), and with ClinicalTrials.gov , number NCT00066872. Findings 501 participants were randomly assigned to the imiquimod group (n=254) or the surgical excision group (n=247). At year 3, 401 (80%) patients were included in the modified intention-to-treat group. At 3 years, 178 (84%) of 213 participants in the imiquimod group were treated successfully compared with 185 (98%) of 188 participants in the surgery group (RR 0·84, 98% CI 0·78–0·91; p<0·0001). No clear difference was noted between groups in patient-assessed cosmetic outcomes. The most common adverse events were itching (211 patients in the imiquimod group vs 129 in the surgery group) and weeping (160 vs 81). We recorded serious adverse events in 99 (40%) of 249 participants in the imiquimod group and 97 (42%) of 229 in the surgery group had serious adverse events, but none were regarded as related to treatment. 12 (5%) participants in the imiquimod group withdrew because of adverse events compared with four (2%) in the surgery group. Interpretation Imiquimod was inferior to surgery according to our predefined non-inferiority criterion. Although excisional surgery remains the best treatment for low-risk basal-cell carcinoma, imiquimod cream might still be a useful treatment option for small low-risk superficial or nodular basal-cell carcinoma dependent on factors such as patient preference, size and site of the lesion, and whether the patient has more than one lesion. Funding Cancer Research UK.
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