This study compares the fish assemblages of the permanently open cool-temperate Olifants and warm-temperate Breede estuaries on the west and south coasts of South Africa respectively, and their ...responses to altered freshwater flows. Both estuaries have experienced a >35% reduction
in mean annual runoff (MAR) from a historical reference condition to the present day with a >60% reduction possible under future flow scenarios. With the exception of species that have both marine and estuarine breeding populations, the Olifants Estuary fish assemblage has experienced an
overall 20% decrease in abundance from reference (pristine state) to the present day and will gradually decline to 55% of reference with a predicted future 60% reduction in MAR. Consequently, future reductions in flow are likely to result in the Olifants Estuary progressing towards a low biomass,
low diversity, marine-dominated system. In contrast, reduced freshwater flows in the Breede Estuary are likely to experience an overall reduction in the abundance of species that breed only in estuaries, and in freshwater and catadromous species. Collectively, entirely estuarine-dependent
fish will increase in abundance, but considered individually some important exploited species such as Argyrosomus japonicus and Pomadasys commersonnii will collapse to 50% of historical numbers once there has been a 64% reduction in MAR. Overall, fish abundance in the estuary
has increased by 6% from reference to the present day and is likely to increase to 115% of reference with future reductions in flow. Some species with a preference for fresh and brackish water will be all but lost from the system, but overall diversity is likely to increase with the range
expansion of warm-temperate and subtropical marine species westward. In all, the fish assemblage of the Breede Estuary will experience a gradual change from a relatively high-diversity, low-abundance, freshwater rich system under historical flow conditions to a high diversity, high-abundance,
marine-dominated system with future reductions in flow.
There remains considerable debate over the active form of gold under operating conditions of a recently validated gold catalyst for acetylene hydrochlorination. We have performed an in situ x-ray ...absorption fine structure study of gold/carbon (Au/C) catalysts under acetylene hydrochlorination reaction conditions and show that highly active catalysts comprise single-site cationic Au entities whose activity correlates with the ratio of Au(I):Au(III) present. We demonstrate that these Au/C catalysts are supported analogs of single-site homogeneous Au catalysts and propose a mechanism, supported by computational modeling, based on a redox couple of Au(I)-Au(III) species.
Oxygen evolution from water poses a significant challenge in solar fuel production because it requires an efficient catalyst to bridge the one-electron photon capture process with the four-electron ...oxygen evolution reaction (OER). Here, a new strategy was developed to synthesize nonsupported ultrasmall cobalt oxide nanocubanes through an in situ phase transformation mechanism using a layered Co(OH)(OCH3) precursor. Under sonication, the precursor was exfoliated and transformed into cobalt oxide nanocubanes in the presence of NaHCO3–Na2SiF6 buffer solution. The resulting cobalt catalyst with an average particle size less than 2 nm exhibited a turnover frequency of 0.023 per second per cobalt in photocatalytic water oxidation. X-ray absorption results suggested a unique nanocubane structure, where 13 cobalt atoms fully coordinated with oxygen in an octahedral arrangement to form 8 Co4O4 cubanes, which may be responsible for the exceptionally high OER activity.
This paper presents the results of a study of the methane–deuterium exchange reaction for a range of metal oxides. Interestingly, particularly with respect to their potential dehydrogenation role in ...other catalytic systems, Ga
2O
3 was found to be the most active by a considerable margin followed by ZnO. The results indicate that the oxide basicity may be an important factor in the activation of methane, although basicity arguments cannot be used to rationalise the dataset as a whole.
The term urban heat island (UHI) describes a phenomenon where cities are on average warmer than the surrounding rural area. Trees and greenspaces are recognised for their strong potential to regulate ...urban air temperatures and combat the UHI. Empirical data is required in the UK to inform predictions on cooling by urban greenspaces and guide planning to maximise cooling of urban populations. We describe a 5-month study to measure the temperature profile of one of central London's large greenspaces and also in an adjacent street to determine the extent to which the greenspace reduced night-time UHI intensity. Statistical modelling displayed an exponential decay in the extent of cooling with increased distance from the greenspace. The extent of cooling ranged from an estimated 20m on some nights to 440m on other nights. The mean temperature reduction over these distances was 1.1°C in the summer months, with a maximum of 4°C cooling observed on some nights. Results suggest that calculation of London's UHI using Met Stations close to urban greenspace can underestimate ‘urban’ heat island intensity due to the cooling effect of the greenspace and values could be in the region of 45% higher. Our results lend support to claims that urban greenspace is an important component of UHI mitigation strategies. Lack of certainty over the variables that govern the extent of the greenspace cooling influence indicates that the multifaceted roles of trees and greenspaces in the UK's urban environment merit further consideration.
•Trees help regulate urban air temperatures and combat the urban heat island effect.•We describe cooling of London's heat island by one large greenspace over 5months•Cooling of up to 4°C over 440m distance from the park was observed on single nights.•The park cooled London when cooling was most needed, on warm still nights.
Over-exploitation and subsequent collapse of marine fishes has focused
attention on the ability of affected populations to recover to former abundance
levels and on the degree to which their ...persistence is
threatened by extinction. Although potential for recovery
has been assessed indirectly, actual changes in population
size following long-term declines have not been examined empirically. Here
I show that there is very little evidence for rapid recovery from prolonged
declines, in contrast to the perception that marine fishes are highly resilient
to large population reductions. With the possible exception
of herring and related species that mature early in life and are fished with
highly selective equipment, my analysis of 90 stocks reveals that many gadids
(for example, cod, haddock) and other non-clupeids (for example, flatfishes)
have experienced little, if any, recovery as much as 15 years after 45-99%
reductions in reproductive biomass. Although the effects of overfishing on
single species may generally be reversible, the actual time
required for recovery appears to be considerable. To exempt marine fishes
from existing criteria used to assign extinction risk would
be inconsistent with precautionary approaches to fisheries management and
the conservation of marine biodiversity.
G protein-coupled receptors (GPCRs) play key roles in many biological functions and are linked to many diseases across all therapeutic areas. As such, GPCRs represent a significant opportunity for ...antibody-based therapeutics.
The structure of the major GPCR families is summarized in the context of choice of antigen source employed in the drug discovery process and receptor biology considerations which may impact on targeting strategies. An overview of the therapeutic GPCR-antibody target landscape and the diversity of current therapeutic programs is provided along with summary case studies for marketed antibody drugs or those in advanced clinical studies. Antibodies in early clinical studies and the emergence of next-generation modalities are also highlighted.
The GPCR-antibody pipeline has progressed significantly with a number of technical developments enabling the successful resolution of some of the challenges previously encountered and this has contributed to the growing interest in antibody-based therapeutics addressing this target class.
Total concentrations of Cu, Pb, As, Cd, Zn, Fe, Ni and Mn were determined for 81 soil samples using two types of field portable X-ray fluorescence (FPXRF) system; dual isotope and X-ray tube. FPXRF ...metal concentrations were statistically compared with analytical results from aqua regia extractions followed by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP–OES) analysis. The ability of each FPXRF instrument to produce analytical results comparable to the reference method was assessed by linear regression. A high degree of linearity was found for Fe and Pb with the X-ray tube instrument and for Fe, Cu, Pb, Zn, Cd and Mn with the dual source instrument. FPXRF analyser performance improved with increased analysis time for Cu, Mn and Pb, whilst Fe, Zn, Cd, Ni and As showed no significant improvement. Particle size did not influence FPXRF analyser performance. Both the dual isotope and the X-ray tube FPXRF instruments are effective tools for rapid, quantitative assessment of soil metal contamination and for monitoring the efficacy of remediation strategies.
Portable X-ray fluorescence instruments can provide an accurate, rapid and cost-effective means of assessing soil contamination and for monitoring the efficacy of remediation strategies.
Glycerol is an important byproduct of biodiesel production, and it is produced in significant amounts by transesterification of triglycerides with methanol. Due to the highly functionalized nature of ...glycerol, it is an important biochemical that can be utilized as a platform chemical for the production of high-added-value products. At present, research groups in academia and industry are exploring potential direct processes for the synthesis of useful potential chemicals using catalytic processes. Over the last 10 years, there has been huge development of potential catalytic processes using glycerol as the platform chemical. One of the most common processes investigated so far is the catalytic oxidation of glycerol at mild conditions for the formation of valuable oxygenated compounds used in the chemical and pharmaceutical industry. The major challenges associated with the selective oxidation of glycerol are (i) the control of selectivity to the desired products, (ii) high activity and resistance to poisoning, and (iii) minimizing the usage of alkaline conditions. To address these challenges, the most common catalysts used for the oxidation of glycerol are based on supported metal nanoparticles. The first significant breakthrough was the successful utilization of supported gold nanoparticles for improving the selectivity to specific products, and the second was the utilization of supported bimetallic nanoparticles based on gold, palladium, and platinum for improving activity and controlling the selectivity to the desired products. Moreover, the utilization of base-free reaction conditions for the catalytic oxidation of glycerol has unlocked new pathways for the production of free-base products, which facilitates potential industrial application. The advantages of using gold-based catalysts are the improvement of the catalyst lifetime, stability, and reusability, which are key factors for potential commercialization. In this Account, we discuss the advantages of the using supported gold-based nanoparticles, preparation methods for achieving highly active gold-based catalysts, and parameters such as particle size, morphology of the bimetallic particle, and metal–support interactions, which can influence activity and selectivity to the desired products.
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