River deltas rank among the most economically and ecologically valuable environments on Earth. Even in the absence of sea-level rise, deltas are increasingly vulnerable to coastal hazards as ...declining sediment supply and climate change alter their sediment budget, affecting delta morphology and possibly leading to erosion
. However, the relationship between deltaic sediment budgets, oceanographic forces of waves and tides, and delta morphology has remained poorly quantified. Here we show how the morphology of about 11,000 coastal deltas worldwide, ranging from small bayhead deltas to mega-deltas, has been affected by river damming and deforestation. We introduce a model that shows that present-day delta morphology varies across a continuum between wave (about 80 per cent), tide (around 10 per cent) and river (about 10 per cent) dominance, but that most large deltas are tide- and river-dominated. Over the past 30 years, despite sea-level rise, deltas globally have experienced a net land gain of 54 ± 12 square kilometres per year (2 standard deviations), with the largest 1 per cent of deltas being responsible for 30 per cent of all net land area gains. Humans are a considerable driver of these net land gains-25 per cent of delta growth can be attributed to deforestation-induced increases in fluvial sediment supply. Yet for nearly 1,000 deltas, river damming
has resulted in a severe (more than 50 per cent) reduction in anthropogenic sediment flux, forcing a collective loss of 12 ± 3.5 square kilometres per year (2 standard deviations) of deltaic land. Not all deltas lose land in response to river damming: deltas transitioning towards tide dominance are currently gaining land, probably through channel infilling. With expected accelerated sea-level rise
, however, recent land gains are unlikely to be sustained throughout the twenty-first century. Understanding the redistribution of sediments by waves and tides will be critical for successfully predicting human-driven change to deltas, both locally and globally.
Climate change is intensifying tropical cyclones, accelerating sea-level rise, and increasing coastal flooding. River deltas are especially vulnerable to flooding because of their low elevations and ...densely populated cities. Yet, we do not know how many people live on deltas and their exposure to flooding. Using a new global dataset, we show that 339 million people lived on river deltas in 2017 and 89% of those people live in the same latitudinal zone as most tropical cyclone activity. We calculate that 41% (31 million) of the global population exposed to tropical cyclone flooding live on deltas, with 92% (28 million) in developing or least developed economies. Furthermore, 80% (25 million) live on sediment-starved deltas, which cannot naturally mitigate flooding through sediment deposition. Given that coastal flooding will only worsen, we must reframe this problem as one that will disproportionately impact people on river deltas, particularly in developing and least-developed economies.
A systematic review was conducted to identify and quality assess how studies published since 1999 have measured and reported the usage of hearing aids in older adults. The relationship between usage ...and other dimensions of hearing aid outcome, age and hearing loss are summarised.
Articles were identified through systematic searches in PubMed/MEDLINE, The University of Nottingham Online Catalogue, Web of Science and through reference checking.
(1) participants aged fifty years or over with sensori-neural hearing loss, (2) provision of an air conduction hearing aid, (3) inclusion of hearing aid usage measure(s) and (4) published between 1999 and 2011.
Of the initial 1933 papers obtained from the searches, a total of 64 were found eligible for review and were quality assessed on six dimensions: study design, choice of outcome instruments, level of reporting (usage, age, and audiometry) and cross validation of usage measures. Five papers were rated as being of high quality (scoring 10-12), 35 papers were rated as being of moderate quality (scoring 7-9), 22 as low quality (scoring 4-6) and two as very low quality (scoring 0-2). Fifteen different methods were identified for assessing the usage of hearing aids.
Generally, the usage data reviewed was not well specified. There was a lack of consistency and robustness in the way that usage of hearing aids was assessed and categorised. There is a need for more standardised level of reporting of hearing aid usage data to further understand the relationship between usage and hearing aid outcomes.
One of the most dramatic events in river environments is the natural diversion, or avulsion, of a channel across its floodplain. Though rarely witnessed, avulsions can cause massive floods, and over ...geologic time they create most of the fluvial stratigraphic record. Avulsions exhibit behavior ranging from reoccupying abandoned channels to constructing new channels and splay complexes. To quantify avulsion behavior, or style, we measure avulsion-related floodplain disturbance in modern environments. We show that for 63 avulsions from Andean, Himalayan, and New Guinean basins, avulsion style correlates with channel morphology and changes systematically downstream. Avulsions in braided rivers reoccupy abandoned channels, whereas avulsions in meandering rivers often produce flooding and sediment deposition during channel construction. These downstream changes in avulsion style can explain the abrupt transition from channel-dominated to floodplain-dominated facies commonly observed in foreland basin stratigraphy. These dynamics also explain why some avulsions are more hazardous than others.
Bacterial transition metal homoeostasis or simply 'metallostasis' describes the process by which cells control the intracellular availability of functionally required metal cofactors, from manganese ...(Mn) to zinc (Zn), avoiding both metal deprivation and toxicity. Metallostasis is an emerging aspect of the vertebrate host-pathogen interface that is defined by a 'tug-of-war' for biologically essential metals and provides the motivation for much recent work in this area. The host employs a number of strategies to starve the microbial pathogen of essential metals, while for others attempts to limit bacterial infections by leveraging highly competitive metals. Bacteria must be capable of adapting to these efforts to remodel the transition metal landscape and employ highly specialized metal sensing transcriptional regulators, termed metalloregulatory proteins,and metallochaperones, that allocate metals to specific destinations, to mediate this adaptive response. In this essay, we discuss recent progress in our understanding of the structural mechanisms and metal specificity of this adaptive response, focusing on energy-requiring metallochaperones that play roles in the metallocofactor active site assembly in metalloenzymes and metallosensors, which govern the systems-level response to metal limitation and intoxication.
Can Paris pledges avert severe climate change? Fawcett, Allen A.; Iyer, Gokul C.; Clarke, Leon E. ...
Science (American Association for the Advancement of Science),
12/2015, Letnik:
350, Številka:
6265
Journal Article
Recenzirano
Reducing risks of severe outcomes and improving chances of limiting warming to 2°C
Current international climate negotiations seek to catalyze global emissions reductions through a system of ...nationally determined country-level emissions reduction targets that would be regularly updated. These “Intended Nationally Determined Contributions” (INDCs) would constitute the core of mitigation commitments under any agreement struck at the upcoming Paris Conference of the Parties to the United Nations Framework Convention on Climate Change (UNFCCC) (
1
). With INDCs now reported from more than 150 countries and covering around 90% of global emissions, we can begin to assess the role of this round of INDCs in facilitating or frustrating achievement of longer-term climate goals. In this context, it is important to understand what these INDCs collectively deliver in terms of two objectives. First, how much do they reduce the probability of the highest levels of global mean surface temperature change? Second, how much do they improve the odds of achieving the international goal of limiting temperature change to under 2°C relative to preindustrial levels (
2
)? Although much discussion has focused on the latter objective (
3
–
5
), the former is equally important when viewing climate mitigation from a risk-management perspective.
In this paper, we use observational data and numerical modeling to present a new explanation for the formation of river‐dominated delta networks. Observational data from deltas throughout the world ...show that distributary channel widths, depths, and lengths decrease nonlinearly with successive bifurcations. Trends in width and depth are an outcome of hydraulic geometry scaling. The trend in channel length is a consequence of delta growth. Analyses of serial maps show that the positions of bifurcations are the fossilized locations of river mouth bars (also called middle‐ground and distributary mouth bar) in front of old delta channel mouths. Therefore the trend in channel length can be explained through the mechanics of river mouth bar formation and evolution. We use Delft3D, a coupled hydrodynamic and morphodynamic model, to simulate the process of river mouth bar formation within an expanding turbulent jet in front of distributary channel mouths. Our results describe in detail the formation and evolution of a river mouth bar system and demonstrate that the distance to the river mouth bar is proportional to jet momentum flux and inversely proportional to grain size. Therefore channel length decreases down delta because with each successive bifurcation, the jet momentum flux decreases. These results can be used to predict the future evolution of river‐dominated deltas and can be used to aid in hydrocarbon exploration of these depositional environments.
Allosteric communication between two ligand-binding sites in a protein is a central aspect of biological regulation that remains mechanistically unclear. Here we show that perturbations in ...equilibrium picosecond–nanosecond motions impact zinc (Zn)-induced allosteric inhibition of DNA binding by the Zn efflux repressor CzrA (chromosomal zinc-regulated repressor). DNA binding leads to an unanticipated increase in methyl side-chain flexibility and thus stabilizes the complex entropically; Zn binding redistributes these motions, inhibiting formation of the DNA complex by restricting coupled fast motions and concerted slower motions. Allosterically impaired CzrA mutants are characterized by distinct nonnative fast internal dynamics “fingerprints” upon Zn binding, and DNA binding is weakly regulated. We demonstrate the predictive power of the wild-type dynamics fingerprint to identify key residues in dynamics-driven allostery. We propose that driving forces arising from dynamics can be harnessed by nature to evolve new allosteric ligand specificities in a compact molecular scaffold.
Representative Concentration Pathway (RCP) 4.5 is a scenario that stabilizes radiative forcing at 4.5 W m
−2
in the year 2100 without ever exceeding that value. Simulated with the Global Change ...Assessment Model (GCAM), RCP4.5 includes long-term, global emissions of greenhouse gases, short-lived species, and land-use-land-cover in a global economic framework. RCP4.5 was updated from earlier GCAM scenarios to incorporate historical emissions and land cover information common to the RCP process and follows a cost-minimizing pathway to reach the target radiative forcing. The imperative to limit emissions in order to reach this target drives changes in the energy system, including shifts to electricity, to lower emissions energy technologies and to the deployment of carbon capture and geologic storage technology. In addition, the RCP4.5 emissions price also applies to land use emissions; as a result, forest lands expand from their present day extent. The simulated future emissions and land use were downscaled from the regional simulation to a grid to facilitate transfer to climate models. While there are many alternative pathways to achieve a radiative forcing level of 4.5 W m
−2
, the application of the RCP4.5 provides a common platform for climate models to explore the climate system response to stabilizing the anthropogenic components of radiative forcing.
•Examined risk factors for later health anxiety during the COVID-19 pandemic.•COVID-19 affective risk associated with multiple health anxiety dimensions.•Intolerance of uncertainty (IU) associated ...with all health anxiety dimensions.•Affective risk positively associated with health anxiety at mean and low IU levels.•Results highlight risk factors for and targets for preventing severe health anxiety.
The COVID-19 pandemic is likely to increase risk for the development of health anxiety. Given that elevated health anxiety can contribute to maladaptive health behaviors, there is a need to identify individual difference factors that may increase health anxiety risk. This study examined the unique and interactive relations of COVID-19 affective risk assessments (worry about risk for contracting/dying from COVID-19) and intolerance of uncertainty to later health anxiety dimensions. A U.S. community sample of 364 participants completed online self-report measures at a baseline assessment (Time 1) and one month later (Time 2). Time 1 intolerance of uncertainty was uniquely associated with the Time 2 health anxiety dimension of body vigilance. Time 1 affective risk assessments and intolerance of uncertainty were uniquely associated with later perceived likelihood that an illness would be acquired and anticipated negative consequences of an illness. The latter finding was qualified by a significant interaction, such that affective risk assessments were positively associated with anticipated negative consequences of having an illness only among participants with mean and low levels of intolerance of uncertainty. Results speak to the relevance of different risk factors for health anxiety during the COVID-19 pandemic and highlight targets for reducing health anxiety risk.
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