Through study of observations and coupled climate simulations, it is argued that the mean position of the Inter-Tropical Convergence Zone (ITCZ) north of the equator is a consequence of a northwards ...heat transport across the equator by ocean circulation. Observations suggest that the hemispheric net radiative forcing of climate at the top of the atmosphere is almost perfectly symmetric about the equator, and so the total (atmosphere plus ocean) heat transport across the equator is small (order 0.2 PW northwards). Due to the Atlantic ocean’s meridional overturning circulation, however, the ocean carries significantly more heat northwards across the equator (order 0.4 PW) than does the coupled system. There are two primary consequences. First, atmospheric heat transport is southwards across the equator to compensate (0.2 PW southwards), resulting in the ITCZ being displaced north of the equator. Second, the atmosphere, and indeed the ocean, is slightly warmer (by perhaps 2 °C) in the northern hemisphere than in the southern hemisphere. This leads to the northern hemisphere emitting slightly more outgoing longwave radiation than the southern hemisphere by virtue of its relative warmth, supporting the small northward heat transport by the coupled system across the equator. To conclude, the coupled nature of the problem is illustrated through study of atmosphere–ocean–ice simulations in the idealized setting of an aquaplanet, resolving the key processes at work.
Strong-gravitational lens systems with quadruply imaged quasars (quads) are unique probes to address several fundamental problems in cosmology and astrophysics. Although they are intrinsically very ...rare, ongoing and planned wide-field deep-sky surveys are set to discover thousands of such systems in the next decade. It is thus paramount to devise a general framework to model strong-lens systems to cope with this large influx without being limited by expert investigator time. We propose such a general modelling framework (implemented with the publicly available software lenstronomy) and apply it to uniformly model three-band Hubble Space Telescope Wide Field Camera 3 images of 13 quads. This is the largest uniformly modelled sample of quads to date and paves the way for a variety of studies. To illustrate the scientific content of the sample, we investigate the alignment between the mass and light distribution in the deflectors. The position angles of these distributions are well-aligned, except when there is strong external shear. However, we find no correlation between the ellipticity of the light and mass distributions. We also show that the observed flux-ratios between the images depart significantly from the predictions of simple smooth models. The departures are strongest in the bluest band, consistent with microlensing being the dominant cause in addition to millilensing. Future papers will exploit this rich data set in combination with ground-based spectroscopy and time delays to determine quantities such as the Hubble constant, the free streaming length of dark matter, and the normalization of the initial stellar mass function.
Although wastewater use in irrigation provides one solution to water scarcity, it also presents a threat to the environment. Thus, wastewater treatment prior to irrigation is necessary. Microbial ...Fuel Cell (MFC) is a sustainable technology that treats wastewater and generates electricity simultaneously while leaving low concentrations of nutrients in the effluent. In order to explore the economic returns of using MFC as a pre-irrigation treatment method for wastewater, a case study involving fruit processing wastewater in a semi-arid region was conducted. The potential profit from treated water and produced electricity was estimated. The analysis showed that MFC is a promising technology that appears to be economically feasible and that can reduce water and energy shortages.
Display omitted
•MFC technology is economically feasible to treat wastewater before irrigation.•The technology can be more feasible than conventional wastewater treatment.•MFC can improve water, energy and food security.
We present 5-38 km mid-infrared spectra at a spectral resolution of R - 65-130 of a large sample of 22 starburst nuclei taken with the Infrared Spectrograph (IRS) on board the Spitzer Space ...Telescope. The spectra show a vast range of starburst SEDs. The silicate absorption ranges from essentially no absorption to heavily obscured systems with an optical depth of t sub(9.8) k sub(m) 6 5. The spectral slopes can be used to discriminate between starburst and AGN powered sources. The monochromatic continuum fluxes at 15 and 30 km enable a remarkably accurate estimate of the total infrared luminosity of the starburst. We find that the PAH equivalent width is independent of the total starburst luminosity L sub(IR) as both continuum and PAH feature scale proportionally. However, the luminosity of the 6.2 km feature scales with L sub(IR) and can be used to approximate the total infrared luminosity of the starburst. Although our starburst sample covers about a factor of 10 difference in the Ne III/Ne II ratio, we found no systematic correlation between the radiation field hardness and the PAH equivalent width or the 7.7 km/11.3 km PAH ratio. These results are based on spatially integrated diagnostics over an entire starburst region, and local variations may be "averaged out." It is presumably due to this effect that unresolved starburst nuclei with significantly different global properties appear spectrally as rather similar members of one class of objects.
Naturalists and scientists have been captivated by the diversity of marine larval forms since they were discovered following the advent of the microscope. Because they often bear little resemblance ...to adults, larvae were identified initially as new life forms, classified into different groups based on the similarity of their body plans and given new names that are still with us today. The radically different body plans and lifestyles of marine larvae and adults have led most investigators historically to study the two phases of complex life cycles in isolation. More recently, important ecological insights have sprung from taking a holistic view of marine life cycles. Meanwhile, the evolutionary (phenotypic and genetic) links among life-history phases remain less appreciated. In this review, our objective is to evaluate the evolutionary links within marine life cycles, and explore their ecological and evolutionary consequences. We provide a brief overview of marine life histories, discuss the phenotypic and genetic links between the two phases of the life cycle and pose challenges to advance our understanding of the evolutionary constraints acting on marine life histories.
During austral spring 2016 Antarctic sea ice extent (SIE) decreased at a record rate of 75 × 103 km2 d−1, which was 46% faster than the mean rate and 18% faster than in any previous spring season ...during the satellite era. The decrease of sea ice area was also exceptional and 28% greater than the mean. Anomalous negative retreat occurred in all sectors of the Antarctic but was greatest in the Weddell and Ross Seas. Record negative SIE anomalies for the day of year were recorded from 3 November 2016 to 9 April 2017. Rapid ice retreat in the Weddell Sea took place in strong northerly flow after an early maximum ice extent in late August. Rapid ice retreat occurred in November in the Ross Sea when surface pressure was at a record high level, with the Southern Annular Mode at its most negative for that month since 1968.
Key Points
During austral spring 2016 total Antarctic sea ice extent decreased at a record rate that was 18% faster than previously observed
The most anomalous sea ice retreat took place during November and in the Weddell and Ross Sea sectors
Record surface pressure anomalies occurred during spring, with the most negative November Southern Annular Mode index since 1968
Understanding variation in metabolic rate Pettersen, Amanda K; Marshall, Dustin J; White, Craig R
Journal of experimental biology,
01/2018, Letnik:
221, Številka:
Pt 1
Journal Article
Recenzirano
Odprti dostop
Metabolic rate reflects an organism's capacity for growth, maintenance and reproduction, and is likely to be a target of selection. Physiologists have long sought to understand the causes and ...consequences of within-individual to among-species variation in metabolic rates - how metabolic rates relate to performance and how they should evolve. Traditionally, this has been viewed from a mechanistic perspective, relying primarily on hypothesis-driven approaches. A more agnostic, but ultimately more powerful tool for understanding the dynamics of phenotypic variation is through use of the breeder's equation, because variation in metabolic rate is likely to be a consequence of underlying microevolutionary processes. Here we show that metabolic rates are often significantly heritable, and are therefore free to evolve under selection. We note, however, that 'metabolic rate' is not a single trait: in addition to the obvious differences between metabolic levels (e.g. basal, resting, free-living, maximal), metabolic rate changes through ontogeny and in response to a range of extrinsic factors, and is therefore subject to multivariate constraint and selection. We emphasize three key advantages of studying metabolic rate within a quantitative genetics framework: its formalism, and its predictive and comparative power. We make several recommendations when applying a quantitative genetics framework: (i) measuring selection based on actual fitness, rather than proxies for fitness; (ii) considering the genetic covariances between metabolic rates throughout ontogeny; and (iii) estimating genetic covariances between metabolic rates and other traits. A quantitative genetics framework provides the means for quantifying the evolutionary potential of metabolic rate and why variance in metabolic rates within populations might be maintained.
Velocities derived from AVISO sea‐surface height observations, adjusted to be nondivergent, are used to simulate the evolution of passive tracers at the ocean surface. Eddy mixing rates are derived ...from the tracer fields in two ways. First, the method of Nakamura is applied to a sector in the East Pacific. Second, the Osborn‐Cox diffusivity is calculated globally to yield estimates of diffusivity in two dimensions. The results from the East Pacific show weak meridional mixing at the surface in the Southern Ocean (<1000 m2 s−1, consistent with previous results) but higher mixing rates (~3000–5000 m2 s−1) in the tropical ocean. The Osborn‐Cox diagnostic provides a global picture of mixing rates and agrees reasonably well with the results from the East Pacific. It also shows extremely high mixing rates (~104 m2 s−1) in western boundary current regions. The Osborn‐Cox diffusivity is sensitive to the tracer initialization, which we attribute to the presence of anisotropic mixing processes. The mixing rates are strongly influenced by the presence of a mean flow nearly everywhere, as shown by comparison with an eddy‐only calculation, with the mean flow absent. Finally, results are compared with other recent estimates of mixing rates using Lagrangian and inverse methods.
Key Points
SSH‐derived velocities can be used to simulate the evolution of passive tracers.
Mixing of passive tracers is highly inhomogeneous in space.
The mean flow plays an important role in shaping the mixing rates.
Summary
Background
The impact of peri‐operative use of TNFα antagonists on post‐operative complications such as infection and wound healing is controversial.
Aim
To conduct a systematic review and ...meta‐analysis to assess the impact of peri‐operative use of TNFα antagonists on post‐operative complications such as infection and wound healing in patients with inflammatory bowel disease (IBD).
Methods
A literature search identified studies that investigated post‐operative outcomes in patients with IBD using TNFα antagonists. The primary outcome was the rate of post‐operative infectious complications. Secondary outcomes included the rates of non‐infectious complications and total complications. Odds ratios (OR) with 95% confidence intervals (CI) are reported.
Results
Overall, 18 studies with 4659 participants were eligible for inclusion. Patients with IBD using preoperative anti‐TNFα therapies had significant increases in post‐operative infectious OR 1.56 (95% CI, 1.09–2.24), non‐infectious OR 1.57 (95% CI, 1.14–2.17) and total complications OR 1.73 (95% CI, 1.23–2.43). Studies limited to patients with Crohn's disease demonstrated a statistically significant increase in infectious (OR 1.93, 95% CI 1.28–2.89) and total (OR 2.19, 95% CI 1.69–2.84) complications, and a trend towards increase in non‐infectious complications (OR 1.73, 95% CI 0.94–3.17). Studies of patients with ulcerative colitis did not demonstrate significant increases in infectious (OR 1.39, 95% CI 0.56–3.45), non‐infectious (OR 1.40, 95% CI 0.68–2.85), or total complications (OR 1.10, 95% CI 0.81–1.47).
Conclusion
Anti‐TNFα therapies appear to increase the risk of post‐operative complications. The increase in risk is small, and may well reflect residual confounding rather than a true biological effect. Nevertheless, physicians should exercise caution when continuing biological therapies during the peri‐operative period.
We report the results of a systematic search for ultra-faint Milky Way satellite galaxies using data from the Dark Energy Survey (DES) and Pan-STARRS1 (PS1). Together, DES and PS1 provide multi-band ...photometry in optical/near-infrared wavelengths over ∼80% of the sky. Our search for satellite galaxies targets ∼25,000 deg2 of the high-Galactic-latitude sky reaching a 10 point-source depth of 22.5 mag in the g and r bands. While satellite galaxy searches have been performed independently on DES and PS1 before, this is the first time that a self-consistent search is performed across both data sets. We do not detect any new high-significance satellite galaxy candidates, recovering the majority of satellites previously detected in surveys of comparable depth. We characterize the sensitivity of our search using a large set of simulated satellites injected into the survey data. We use these simulations to derive both analytic and machine-learning models that accurately predict the detectability of Milky Way satellites as a function of their distance, size, luminosity, and location on the sky. To demonstrate the utility of this observational selection function, we calculate the luminosity function of Milky Way satellite galaxies, assuming that the known population of satellite galaxies is representative of the underlying distribution. We provide access to our observational selection function to facilitate comparisons with cosmological models of galaxy formation and evolution.
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