Bathymetry Based Modeling of Subaxial Magma Flows Under the Mid-Atlantic Ridge, 0 to 30° N

Fracture patterns of the Mid-Atlantic Ridge (MAR) provide evidence of tectonic forces related to divergence and magma upwelling at the ridge axis. In this study, we focus on the MAR from 0 to 30° N, where the N-S ridge exhibits slow spreading rates (2-4 cm/yr) and pronounced axial topography. Ridge segments and transform faults identified in bathymetry data were analyzed for strike orientation and axial depth profiles. Azimuths of transform faults and ridge segments exhibit increasing clockwise rotation with latitude, and all have left lateral displacement. Bathymetric sampling along ridge segments occurred at 9 km intervals with 20 km sampling radii, producing axial lithostatic pressure gradients. One-dimensional magma flows parallel to the ridge axis at 10 and 50 km depths were modeled using Darcy’s law based on published parameters and calculated gradients. Subaxial magma velocities of up to 4 cm/yr were predicted for horizontal flow at depth and are comparable in magnitude to upwelling rates in published literature. Average flow magnitudes (n = 422) within the melt generation region are predicted at 0.8 and 0.2 cm/yr for 10 and 50 km depths respectively. Flow velocities up to five times higher are expected with this model in the high-porosity boundary layer below the solidus. The Coriolis parameter would affect the movement of the flows predicted by our model and may be linked to rotational patterns observed at the MAR. Future research of magma migration below divergent margins would benefit from incorporating axial lithostatic load variations as a driver of flow

Extreme heat increases stomatal conductance and drought-induced mortality risk in vulnerable plant species

Tree mortality during global-change-type drought is usually attributed to xylem dysfunction, but as climate change increases the frequency of extreme heat events, it is necessary to better understand the interactive role of heat stress. We hypothesized that some drought-stressed plants paradoxically open stomata in heatwaves to prevent leaves from critically overheating. We experimentally imposed heat (>40°C) and drought stress onto 20 broadleaf evergreen tree/shrub species in a glasshouse study. Most well-watered plants avoided lethal overheating, but drought exacerbated thermal damage during heatwaves. Thermal safety margins (TSM) quantifying the difference between leaf surface temperature and leaf critical temperature, where photosynthesis is disrupted, identified species vulnerability to heatwaves. Several mechanisms contributed to high heat tolerance and avoidance of damaging leaf temperatures—small leaf size, low leaf osmotic potential, high leaf mass per area (i.e., thick, dense leaves), high transpirational capacity, and access to water. Water-stressed plants had smaller TSM, greater crown dieback, and a fundamentally different stomatal heatwave response relative to well-watered plants. On average, well-watered plants closed stomata and decreased stomatal conductance (gs) during the heatwave, but droughted plants did not. Plant species with low gs, either due to isohydric stomatal behavior under water deficit or inherently low transpirational capacity, opened stomata and increased gs under high temperatures. The current paradigm maintains that stomata close before hydraulic thresholds are surpassed, but our results suggest that isohydric species may dramatically increase gs (over sixfold increases) even past their leaf turgor loss point. By actively increasing water loss at high temperatures, plants can be driven toward mortality thresholds more rapidly than has been previously recognized. The inclusion of TSM and responses to heat stress could improve our ability to predict the vulnerability of different tree species to future droughts

The impact of a history of child abuse on cognitive performance:a cross-sectional study in older patients with a depressive, anxiety, or somatic symptom disorder

Background: Child abuse is a major global burden with an enduring negative impact on mental and physical health. A history of child abuse is consistently associated with worse cognitive performance among adults; data in older age groups are inconclusive. Since affective symptoms and cognitive functioning are interrelated among older persons, a synergistic effect can be assumed in patients with affective symptoms who also have suffered from child abuse. This study examines the association between a history of child abuse and cognitive performance in such patients. Methods: Cross-sectional data were collected from the ‘Routine Outcome Monitoring for Geriatric Psychiatry & Science’ project, including 179 older adults (age 60–88 years) with either a unipolar depressive, any anxiety, or somatic symptom disorder referred to specialized geriatric mental health care. A history of physical, sexual, and psychological abuse, and emotional neglect was assessed with a structured interview. Cognitive functioning was measured with three paper and pencils tests (10-words verbal memory test, Stroop Colour-Word test, Digit Span) and four tests from the computerized Cogstate Test Battery (Detection Test, Identification Test, One Card Learning Test, One Back Test). The association between a history of child abuse and cognitive performance was examined by multiple linear regression analyses adjusted for covariates. Results: Principal component analyses of nine cognitive parameters revealed four cognitive domains, i.e., visual-verbal memory, psychomotor speed, working memory and interference control. A history of child abuse was not associated with any of these cognitive domains. However, when looking at the specific types of child abuse separately, a history of physical abuse and emotional neglect were associated with poorer interference control. A history of physical abuse was additionally associated with better visual-verbal memory. Conclusions: The association between a history of child abuse and cognitive performance differs between the different types of abuse. A history of physical abuse might particularly be a key determinant of cognitive performance in older adults with a depressive, anxiety, or somatic symptom disorder. Future studies on the impact of these disorders on the onset of dementia should take child abuse into account. Trial registration: ROM-GPS is registered at the Dutch Trial Register (NL6704 at www.trialregister.nl)

Drought increases heat tolerance of leaf respiration in Eucalyptus globulus saplings grown under both ambient and elevated atmospheric [CO₂] and temperature

Climate change is resulting in increasing atmospheric [CO₂], rising growth temperature (T), and greater frequency/severity of drought, with each factor having the potential to alter the respiratory metabolism of leaves. Here, the effects of elevated atmospheric [CO₂], sustained warming, and drought on leaf dark respiration (R(dark)), and the short-term T response of R(dark) were examined in Eucalyptus globulus. Comparisons were made using seedlings grown under different [CO₂], T, and drought treatments. Using high resolution T-response curves of R(dark) measured over the 15-65 °C range, it was found that elevated [CO₂], elevated growth T, and drought had little effect on rates of R(dark) measured at T <35 °C and that there was no interactive effect of [CO₂], growth T, and drought on T response of R(dark). However, drought increased R(dark) at high leaf T typical of heatwave events (35-45 °C), and increased the measuring T at which maximal rates of R(dark) occurred (Tmax) by 8 °C (from 52 °C in well-watered plants to 60 °C in drought-treated plants). Leaf starch and soluble sugars decreased under drought and elevated growth T, respectively, but no effect was found under elevated [CO₂]. Elevated [CO₂] increased the Q₁₀ of R(dark) (i.e. proportional rise in R(dark) per 10 °C) over the 15-35 °C range, while drought increased Q₁₀ values between 35 °C and 45 °C. Collectively, the study highlights the dynamic nature of the T dependence of R dark in plants experiencing future climate change scenarios, particularly with respect to drought and elevated [CO₂].This work was funded by the Australian Research Council (ARC FT0991448, DP1093759, and CE140100008, to OKA; and DP0879531, to DTT). This project is supported by funding from the Australian Government Department of Agriculture, Fisheries and Forestry under its Forest Industries Climate Change Research Fund programme. Support for the renovation of the Hawkesbury Forest Experiment tree chambers to improve T and humidity control of the WTC was provided as part of an initiative of the Australian Government through the Education Investment Fund supporting research infrastructure

Sub-dekahertz ultraviolet spectroscopy of 199Hg+

Using a laser that is frequency-locked to a Fabry-Perot etalon of high finesse and stability, we probe the 5d10 6s 2S_1/2 (F=0) - 5d9 6s 2D_5/2 (F=2) Delta-m_F = 0 electric-quadrupole transition of a single laser-cooled 199Hg+ ion stored in a cryogenic radio-frequency ion trap. We observe Fourier-transform limited linewidths as narrow as 6.7 Hz at 282 nm (1.06 X 10^15 Hz), yielding a line Q = 1.6 X 10^14. We perform a preliminary measurement of the 5d9 6s2 2D_5/2 electric-quadrupole shift due to interaction with the static fields of the trap, and discuss the implications for future trapped-ion optical frequency standards.Comment: 4 pages, 4 figures, submitted for publicatio

Small Mercury Ion Clock for On-board Spacecraft Navigation

I.Small Ion Clock Approach and Heritage: a) No lasers, uwave cavities, cryogenics, atomic beams, etc. b) Ions are electrically shuttled between separate optical and microwave traps. II. Each trap is optimized for its task: quadrupole for optical state selection; multi-pole for microwave clock. a) Very good stability shown in USNO. Timescale running "open loop." III. "Open loop" operation means no self-measurements of frequency offsets: (Zeeman, ion temperature,... etc.) a) Fewer parts and procedures, produces stable output continuously. IV. Ion clock is not so sensitive to temperature fluctuations a) Measured u:nshielded temperature coefficient of few 10(exp -15) per C. b) No bulky temperature isolation needed

Verdieping bewaken en beveiligen, editie juli 2023 (2/2023)

De ‘Verdieping Bewaken en Beveiligen’ brengt verdieping aan op actuele gebeurtenissen en ontwikkelingen gerelateerd aan het stelsel Bewaken en Beveiligen. Deze Verdieping wordt aangeboden aan experts die werkzaam zijn bij de stelselpartners en de ketenpartners van het stelsel. Daarnaast wordt dit product aangeboden aan geïnteresseerden in een bredere kring rond het stelsel, waaronder academici, journalisten en politici.Security and Global Affair

TRY plant trait database - enhanced coverage and open access

Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

The fate of carbon in a mature forest under carbon dioxide enrichment

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1 5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration6. Although evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth3 5, it is unclear whether mature forests respond to eCO2 in a similar way. In mature trees and forest stands7 10, photosynthetic uptake has been found to increase under eCO2 without any apparent accompanying growth response, leaving the fate of additional carbon fixed under eCO2 unclear4,5,7 11. Here using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responded to four years of eCO2 exposure. We show that, although the eCO2 treatment of +150 parts per million (+38 per cent) above ambient levels induced a 12 per cent (+247 grams of carbon per square metre per year) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone accounting for half of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on ubiquitous CO2 fertilization as a driver of increased carbon sinks in global forests. © 2020, The Author(s), under exclusive licence to Springer Nature Limited