569 research outputs found
Changes to the airâsea flux and distribution of radiocarbon in the ocean over the 21st century
We investigate the spatiotemporal evolution of radiocarbon (Î14C) in the ocean over the 21st century under different scenarios for anthropogenic CO2 emissions and atmospheric CO2 and radiocarbon changes using a 3âD ocean carbon cycle model. Strong decreases in atmospheric Î14C in the highâemission scenario result in strong outgassing of 14C over 2050â2100, causing Î14C spatial gradients in the surface ocean and vertical gradients between the surface and intermediate waters to reverse sign. Surface Î14C in the subtropical gyres is lower than Î14C in Pacific Deep Water and Southern Ocean surface water in 2100. In the lowâemission scenario, ocean Î14C remains slightly higher than in 1950 and relatively constant over 2050â2100. Over the next 20 years we find decadal changes in Î14C of â30â° to +5â° in the upper 2 km of the ocean, which should be detectable with continued hydrographic surveys. Our simulations can help in planning future observations, and they provide a baseline for investigating natural or anthropogenic changes in ocean circulation using ocean Î14C observations and models
Changes in Oceanic Radiocarbon and CFCs Since the 1990s
Anthropogenic perturbations from fossil fuel burning, nuclear bomb testing, and chlorofluorocarbon (CFC) use have created useful transient tracers of ocean circulation. The atmospheric 14C/C ratio (â14C) peaked in the early 1960s and has decreased now to preâindustrial levels, while atmospheric CFCâ11 and CFCâ12 concentrations peaked in the early 1990s and early 2000s, respectively, and have now decreased by 10%â20%. We present the first analysis of a decade of new observations (2007 to 2018â2019) and give a comprehensive overview of the changes in ocean â14C and CFC concentration since the WOCE surveys in the 1990s. Surface ocean â14C decreased at a nearly constant rate from the 1990â2010s (20â°/decade). In most of the surface ocean â14C is higher than in atmospheric CO2 while in the interior ocean, only a few places are found to have increases in â14C, indicating that globally, oceanic bomb 14C uptake has stopped and reversed. Decreases in surface ocean CFCâ11 started between the 1990 and 2000s, and CFCâ12 between the 2000â2010s. Strong coherence in model biases of decadal changes in all tracers in the Southern Ocean suggest ventilation of Antarctic Intermediate Water was enhanced from the 1990 to the 2000s, whereas ventilation of Subantarctic Mode Water was enhanced from the 2000 to the 2010s. The decrease in surface tracers globally between the 2000 and 2010s is consistently stronger in observations than in models, indicating a reduction in vertical transport and mixing due to stratification
Using games to develop number sense in early grade maths clubs
Background:Â South African learners face the double disadvantage of living in low socio-economic conditions with access to few resources and attending schools with challenging learning conditions. Mathematics performance reflects such conditions with extreme performance gaps between wealthier and poorer learners. The need for early intervention is increasingly acknowledged.
Aim:Â In this conceptual article, we draw out the features of mathematics games that can be used to develop learnersâ foundational number sense that will impact their learning trajectories.
Setting:Â Based on our experience in working with learners from low socio-economic backgrounds in after-school mathematics clubs, we propose that these are opportune spaces for intervention.
Methods:Â Drawing both on the research literature and our experience, we exemplify and discuss key features of mathematics games and argue why these are important to support the development of number sense.
Results:Â We argue that to meaningfully develop young learnersâ number sense, activities need to be sufficiently engaging to retain their interest and be presented in a manner that club practitioners, who might not be teachers, are able to facilitate. Drawing on our experiences of designing and running mathematics clubs, we discuss why components like built-in checks, readily available resources, connection to calculation strategies and transferability to home settings are important design features.
Conclusion:Â Particular design features are important to enable maths games to support learnersâ development of efficient and effective calculation strategies.
Contribution:Â This article contributes a framework of key features for effective use of games to develop mental mathematics strategies for number sense
Temporal Aspects of Endogenous Pain Modulation During a Noxious Stimulus Prolonged for 1 Day
Background
This study investigated (a) if a prolonged noxious stimulus (24âhr topical capsaicin) in healthy adults would impair central pain inhibitory and facilitatory systems measured as a reduction in conditioned pain modulation (CPM) and enhancement of temporal summation of pain (TSP) and (b) if acute pain relief or exacerbation (cooling and heating the capsaicin patch) during the prolonged noxious stimulus would affect central pain modulation. Methods
Twentyâeight participants (26.2 ± 1.0 years; 12 women) wore a transdermal 8% capsaicin patch on the forearm for 24 hr. Data were collected at baseline (Day 0), 1 hr, 3 hr, Day 1 (postâcapsaicin application) and Day 3/4 (postâcapsaicin removal) that included capsaicinâevoked pain intensity, heat pain thresholds (HPTs), TSP (10 painful cuff pressure stimuli on leg) and CPM (cuff pressure pain threshold on the leg prior vs. during painful cuff pressure conditioning on contralateral leg). After 3 hr, cold (12°C) and heat (42°C) stimuli were applied to the capsaicin patch to transiently increase and decrease pain intensity. Results
Participants reported moderate pain scores at 1 hr (2.5 ± 2.0), 3 hr (3.7 ± 2.4), and Day 1 (2.4 ± 1.8). CPM decreased 3âhr postâcapsaicin (p = .001) compared to Day 0 and remained diminished while the capsaicin pain score was reduced (0.4 ± 0.7, p \u3c .001) and increased (6.6 ± 2.2, p \u3c .001) by patch cooling and heating. No significant differences occurred for CPM during patch cooling or heating compared to initial 3HR; however, CPM during patch heating was reduced compared with patch cooling (p = .01). TSP and HPT did not change. Conclusions
This prolonged experimental pain model is useful to provide insight into subacute pain conditions and may provide insight into the transition from acute to chronic pain. Significance
During the early hours of a prolonged noxious stimulus in healthy adults, CPM efficacy was reduced and did not recover by temporarily removing the ongoing pain indicating a less dynamic neuroplastic process
Designing optimal greenhouse gas observing networks that consider performance and cost
Emission rates of greenhouse gases (GHGs) entering into the atmosphere can be
inferred using mathematical inverse approaches that combine observations from
a network of stations with forward atmospheric transport models. Some
locations for collecting observations are better than others for constraining
GHG emissions through the inversion, but the best locations for the inversion
may be inaccessible or limited by economic and other non-scientific factors.
We present a method to design an optimal GHG observing network in the
presence of multiple objectives that may be in conflict with each other. As a
demonstration, we use our method to design a prototype network of six
stations to monitor summertime emissions in California of the potent GHG
1,1,1,2-tetrafluoroethane (CH<sub>2</sub>FCF<sub>3</sub>, HFC-134a). We use a
multiobjective genetic algorithm to evolve network configurations that seek
to jointly maximize the scientific accuracy of the inferred HFC-134a
emissions and minimize the associated costs of making the measurements. The
genetic algorithm effectively determines a set of "optimal" observing
networks for HFC-134a that satisfy both objectives (i.e., the Pareto
frontier). The Pareto frontier is convex, and clearly shows the tradeoffs
between performance and cost, and the diminishing returns in trading one for
the other. Without difficulty, our method can be extended to design optimal
networks to monitor two or more GHGs with different emissions patterns, or to
incorporate other objectives and constraints that are important in the
practical design of atmospheric monitoring networks
Future changes in ÎŽ 13 C of dissolved inorganic carbon in the ocean
Emissions of carbon dioxide from fossil fuel combustion are reducing the ratio 13C/12C, ÎŽ13C, in atmospheric urn:x-wiley:23284277:media:eft2900:eft2900-math-0001 and in the carbon in the ocean and terrestrial biosphere that exchanges with the atmosphere on timescales of decades to centuries. Future changes to fossil fuel emissions vary across different scenarios and may cause decreases of more than 6â° in atmospheric ÎŽ13urn:x-wiley:23284277:media:eft2900:eft2900-math-0002 between 1850 and 2100. The effects of these potential changes on the three-dimensional distribution of ÎŽ13C in the ocean has not yet been investigated. Here, we use an ocean biogeochemical-circulation model forced with a range of Shared Socioeconomic Pathway (SSP)-based scenarios to simulate ÎŽ13C in ocean dissolved inorganic carbon from 1850 to 2100. In the future, vertical ÎŽ13C gradients characteristic of the biological pump are reduced or reversed, relative to the preindustrial period, with the reversal occurring in higher emission scenarios. For the highest emission scenario, SSP5-8.5, surface ÎŽ13C in the centre of Pacific subtropical gyres falls from 2.2â° in 1850 to -3.5â° by 2100. In lower emission scenarios, ÎŽ13C in the surface ocean decreases but then rebounds. The relationship between anthropogenic carbon (Cant) and ÎŽ13C in the ocean shows a larger scatter in all scenarios, suggesting that errors in ÎŽ13C-based estimates of Cant may increase in the future. These simulations were run with fixed physical forcing and ocean circulation, providing a baseline of predicted ÎŽ13C. Further work is needed to investigate the impact of climate-carbon cycle feedbacks on ocean ÎŽ13C changes
Standardized image quality for 68Ga-DOTA-TATE PET/CT
Background: Positron emission tomography (PET) imaging with 68Gallium labeled somatostatin analogues (68Ga-DOTA-SSA) plays a key role in neuroendocrine tumor management. The impact of patient size on PET image quality is not well known for PET imaging with 68Ga-DOTA-SSA. The aim of this study is to propose a dose regimen based on patient size that optimizes image quality and yields sufficient image quality for diagnosis. Methods: Twenty-one patients (12 males, 9 females) were prospectively included for 68Gallium-DOTA-Tyr3-Octreotate (68Ga-DOTA-TATE) PET/CT, which was acquired in whole body list mode using 6 min per bed position (mbp). The list-mode events were randomly sampled to obtain 1 to 6 mbp PET reconstructions. For semi-quantitative assessment of image quality, the signal-to-noise ratio (SNR) was measured in the liver. The SNR normalized (SNRnorm) for admini
Requirement of a Membrane Potential for the Posttranslational Transfer of Proteins into Mitochondsria
Posttranslational transfer of most precursor proteins into mitochondria is dependent on energization of the mitochondria. Experiments were carried out to determine whether the membrane potential or the intramitochondrial ATP is the immediate energy source. Transfer in vitro of precursors to the ADP/ATP carrier and to ATPase subunit 9 into isolated Neurospora mitochondria was investigated. Under conditions where the level of intramitochondrial ATP was high and the membrane potential was dissipated, import and processing of these precursor proteins did not take place. On the other hand, precursors were taken up and processed when the intramitochondrial ATP level was low, but the membrane potential was not dissipated. We conclude that a membrane potential is involved in the import of those mitochondrial precursor proteins which require energy for intracellular translocatio
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