Boundary Shift Research Articles

Got Wheat?

Got Wheat?

Towards a fully automatic AI framework to calculate voxel‐wise atrophy in the human brain

AbstractBackgroundLongitudinal changes in volume using co‐registration of two serial T1W MRI scans are used as biomarkers to track the development of Alzheimer’s Disease and monitor potential treatment effects. Current methods (e.g., the boundary shift integral, BSI) may be restricted to certain regions or are computationally intensive and slow (e.g., the Advanced Normalization Tools, ANTs).MethodWe present an AI‐based framework to calculate voxel‐wise atrophy in the human brain. Our method features convolutional neural networks for cross‐sectional semantic segmentation and longitudinal pairwise non‐linear registration which does not require subject‐specific optimization. It warps one image to another by minimizing their difference, while preserving topology. Voxel‐wise volume change is estimated using the Jacobian determinant of the warp field, summed within a specified and automatically segmented region of interest in the baseline image. We evaluate our framework in ADNI (40 HC and 40 MCI) and OASIS3 (100 HC and 100 MCI) participants and assess the method’s measures of annualized atrophy in whole brain, ventricles, and hippocampus using common language effect sizes (CLES) and a Mann‐Whitney U‐test. Retest variability is measured in 30 OASIS3 participants with two serial MR scans not more than 13 days apart. We compare results to BSI as well as the same framework but substituting the non‐linear registration part with ANTs.ResultOur algorithm outperforms ANTs in non‐linear registration accuracy with mean (SD) normalized mutual information of 0.746 (0.055) compared to 0.651 (0.052) for ANTs and 0.646 (0.049) with affine registration only. It also has lower retest variability than ANTs (mean variability range is 0.08%‐0.12% and 0.15%‐0.34% for our algorithm and ANTs respectively). Finally, both BSI and our method show significant group difference for whole brain, ventricles, and hippocampus (all p < 0.002, CLES > 0.69) in both datasets, whereas in ANTs there is no significant group effect for hippocampus (p = 0.12) (see Table 1 for all results).ConclusionOur framework produces fast (seconds) and accurate non‐linear registration and voxel‐wise atrophy calculation for two serial MR images. Our calculated atrophy values show sensitivity to clinical diagnosis in cognitively impaired patients, comparable to current state‐of‐the‐art methods.

Spatio-Temporal Characteristics of Dry-Wet Conditions and Boundaries in Five Provinces of Northwest China from 1960 to 2020

The study of dry-wet climate boundaries in the context of climate warming is of great practical significance for improving the environment of ecologically fragile zones and promoting economic and natural sustainable development. In this study, based on the daily meteorological data of 110 stations, using the wetness index, empirical orthogonal function decomposition, regime shift detection test, Fourier power spectrum, and Kriging interpolation, the researchers analyzed the spatiotemporal characteristics of dry-wet conditions and boundaries in five provinces of Northwest China from 1960 to 2020. The results showed that the overall wetness index increased in the past 61 years, but with significant internal differences, among which the western and central climate tended to be warm and wet, and the eastern tended to be warm and dry. The annual wetness index changed abruptly in 1986 with cycles of 3.61 a, 7.11 a and 8.83 a. The mutations occurred correspondingly in spring, summer, autumn, and winter in 1972, 1976, 1983, and 1988, with periods of 3.88 a and 4.92 a, 2.18 a and 2.81 a, 2.15 a, and 2.10 a, respectively. The dry-wet climate boundary has fluctuated markedly since 1960. The extreme arid and arid regions boundary shifted southward and shrank in size until the extreme arid region disappeared in the 2010s. The arid along with semi-arid regions and semi-arid in addition to semi-humid regions boundaries both have two boundary lines, and show the shift of the northwestern boundary to the southeast and the southeastern boundary to the northwest, with the area of the arid together with semi-arid regions shrinking significantly by 5.64%, simultaneously, the area of the semi-humid region area expanding significantly by 84.11%. The boundary of semi-humid and relatively humid regions, and the boundary of relatively humid and humid regions all shifted to the southeast, moreover, the area of the relatively humid region and humid region shrank significantly by 12.08%. The expansion of semi-humid region and the contraction of other climate regions are characteristics of the dry-wet climate variability in five provinces of Northwest China. The area of the three arid climate zones dwindled by 9.61%, and the area of the three humid zones extended by 39.01%. Obviously, the climate inclined to be warm and humid in general.

Losartan to slow the progression of mild-to-moderate Alzheimer’s disease through angiotensin targeting: the RADAR RCT

Background Medications that modify the renin–angiotensin system may reduce Alzheimer’s disease pathology and reduce the rate of disease progression. Objective This study investigated whether taking the antihypertensive drug losartan, in addition to normal care, would slow the progression of Alzheimer’s disease when compared with a placebo. Design A double-blind multicentre randomised controlled trial, after a 4-week open-label phase, with follow-up at 14 days and at 3, 6, 9 and 12 months. The primary outcome was based on measured imaging differences in brain volume between baseline and 12 months. Setting Twenty-three NHS hospital trusts across England, Scotland and Northern Ireland. Participants Patients diagnosed with mild-to-moderate Alzheimer’s disease were eligible to participate if they met the following criteria: (1) aged ≥ 55 years; (2) a Mini Mental State Examination score of 15–28; (3) a modified Hachinski Ischaemic Score of ≤ 5; (4) a previous computerised tomography, single-photon emission computed tomography or magnetic resonance imaging scan consistent with a diagnosis of Alzheimer’s disease; (5) a study companion who was willing to participate in the study; and (6) capacity to consent for themselves. Patients were ineligible if they were (1) taking or intolerant to renin–angiotensin system-related medications, (2) unlikely to undergo magnetic resonance imaging or (3) unlikely to complete the trial protocol. People who had blood pressure outside the normal ranges, defined cardiovascular issues, impaired liver or renal function, or a primary neurodegenerative disease that was not Alzheimer’s disease were also excluded, as were women who had not reached menopause and were unwilling to take relevant protocol-specific safety precautions. Intervention The intervention was either 100 mg of overencapsulated losartan (Teva Pharmaceuticals Industries Ltd, Petah Tikva, Israel) daily or a matched placebo for 12 months. Main outcome measures Difference in brain atrophy, represented by measurement of whole-brain volume before and following 12 months of treatment post randomisation, was measured using volumetric MRI and determined by boundary shift interval analysis. Secondary outcomes included changes in rates of Alzheimer’s disease progression (as assessed using the ADAS-Cog, Mini Mental State Examination and Neuropsychiatric Inventory), the volume of white matter hyperintensities, cerebral blood flow (assessed by magnetic resonance imaging), blood pressure, magnetic resonance imaging measures of atrophy and association with measures of cognitive decline, and drug compliance and tolerability. Results A total of 261 participants entered the open-label phase, of whom 211 were randomised to the intervention (n = 105) or placebo (n = 106) arms. Of the 197 people (93%) who completed the study, 81% (n = 171) had a valid primary outcome. The difference in brain volume between arms was consistent with chance (–2.79 ml, 95% confidence interval –6.46 to 0.89 ml; p = 0.19), and there was no evidence of benefit for any of the secondary outcome measures. Limitations Our study had 82% power to detect treatment-based changes and, as a result, may have been underpowered or, more likely, the intervention, which may not have crossed the blood–brain barrier as much as expected, may have been given too late or for an insufficient amount of time in the disease process to influence the outcomes. Conclusions Losartan administered over 12 months did not alter brain atrophy in Alzheimer’s disease. Future work Other related ‘sartans’ could be tested in patient groups with mild cognitive impairment and for longer to fully test this hypothesis. Trial registration Current Controlled Trials ISRCTN93682878 and EudraCT 2012-003641-15. Funding This project was funded by the Efficacy and Mechanism Evaluation (EME) programme, a Medical Research Council and National Institute for Health Research (NIHR) partnership. This will be published in full in Efficacy and Mechanism Evaluation; Vol. 8, No. 19. See the NIHR Journals Library website for further project information.

Carbon, nutrient and metal controls on phytoplankton concentration and biodiversity in thermokarst lakes of latitudinal gradient from isolated to continuous permafrost

Shallow thaw (thermokarst) lakes abundant in regions of permafrost-affected peatlands represent important sources of carbon dioxide and methane emission to the atmosphere, however the quantitative parameters of phytoplankton communities which control the C cycle in these lakes remain poorly known. This is especially true considering the roles of permafrost, hydrochemical composition of lakes, lake sizes and season as major governing factors on phytoplankton abundance and biodiversity. In this work, we quantified phytoplankton characteristics of 27 thermokarst lakes (sizes ranging from 115 m2 to 1.24 km2) sampled in spring, summer and autumn across a permafrost gradient (isolated, sporadic, discontinuous and continuous zone) in the Western Siberia Lowland (WSL). The biodiversity indices were highest during all seasons in lakes of the continuous permafrost zone and rather similar in lakes of isolated, sporadic and discontinuous permafrost zone. Considering all seasons and permafrost zones, the biomass and cell number of phytoplankton correlated with Dissolved Organic Carbon (DOC), phosphate, and some metal micro-nutrients (Ni, Zn). The strongest correlations were observed for Cyanophycea during summer, with pH, Ni, Cu, Zn, Sr, Ba (cell number) and Cu, Zn, Ba (biomass), and during autumn, with DOC, K, Cr, Cu, Zn, Ba, Cd, Pb (biomass). Using a substituting space for time approach for climate warming and permafrost thaw and suggesting a shift in permafrost boundaries northward, we foresee an increase in cell number and biomass in continuous permafrost zone in spring and summer, and a decrease in phytoplankton abundance in the discontinuous and sporadic permafrost zones. The biodiversity of phytoplankton in the continuous permafrost zone might decrease whereas in other zones, it may not exhibit any sizably change. However, in case of strong deepening of the active layer down to underlaying mineral horizons, and the release of some limiting nutrients (Si, P) due to enhanced connectivity of the lake with groundwater, the share of cyanobacteria and diatoms may increase.

Safety and efficacy of losartan for the reduction of brain atrophy in clinically diagnosed Alzheimer's disease (the RADAR trial): a double-blind, randomised, placebo-controlled, phase 2 trial

SummaryBackgroundDrugs modifying angiotensin II signalling could reduce Alzheimer's disease pathology, thus decreasing the rate of disease progression. We investigated whether the angiotensin II receptor antagonist losartan, compared with placebo, could reduce brain volume loss, as a measure of disease progression, in clinically diagnosed mild-to-moderate Alzheimer's disease.MethodsIn this double-blind, multicentre, randomised controlled trial, eligible patients aged 55 years or older, previously untreated with angiotensin II drugs and diagnosed (National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association criteria) with mild-to-moderate Alzheimer's disease, and who had capacity to consent, were recruited from 23 UK National Health Service hospital trusts. After undergoing a 4-week, open-label phase of active treatment then washout, participants were randomly assigned (1:1) oral over-encapsulated preparations of either 100 mg losartan (after an initial two-dose titration stage) or matched placebo daily for 12 months. Randomisation, minimised by age and baseline medial temporal lobe atrophy score, was undertaken online or via pin-access service by telephone. Participants, their study companions, and study personnel were masked to group assignment. The primary outcome, analysed by the intention-to-treat principle (ie, participants analysed in the group to which they were randomised, without imputation for missing data), was change in whole brain volume between baseline and 12 months, measured using volumetric MRI and determined by boundary shift interval (BSI) analysis. The trial is registered with the International Standard Randomised Controlled Trial Register (ISRCTN93682878) and the European Union Drug Regulating Authorities Clinical Trials Database (EudraCT 2012–003641–15), and is completed.FindingsBetween July 22, 2014, and May 17, 2018, 261 participants entered the open-label phase. 211 were randomly assigned losartan (n=105) or placebo (n=106). Of 197 (93%) participants who completed the study, 171 (81%) had complete primary outcome data. The mean brain volume (BSI) reduction was 19·1 mL (SD 10·3) in the losartan group and 20·0 mL (10·8) in the placebo group. The difference in total volume reduction between groups was –2·29 mL (95% CI –6·46 to 0·89; p=0·14). The number of adverse events was low (22 in the losartan group and 20 in the placebo group) with no differences between treatment groups. There was one treatment-related death per treatment group.Interpretation12 months of treatment with losartan was well tolerated but was not effective in reducing the rate of brain atrophy in individuals with clinically diagnosed mild-to-moderate Alzheimer's disease. Further research is needed to assess the potential therapeutic benefit from earlier treatment in patients with milder cognitive impairment or from longer treatment periods.FundingEfficacy and Mechanism Evaluation Programme (UK Medical Research Council and National Institute for Health Research).

Beyond 'drinking occasions': Examining complex changes in drinking practices during COVID-19.

Introduction‘Drinking occasions’ are commonly used to capture quantities of alcohol consumed. Yet this standardised terminology brings with it numerous assumptions and epistemological limitations. We suggest that social changes brought on by COVID‐19 restrictions have influenced routines, patterns of time use and drinking practices, highlighting the need to re‐examine how we conceptualise drinking and ‘drinking occasions’ in alcohol research.MethodsThis analysis draws on data gathered from 59 qualitative interviews conducted during the second half of 2020 with Australian drinkers aged 18 and over. The interviews explored how COVID‐19 restrictions impacted daily practices and alcohol consumption patterns.FindingsParticipants spoke about their work, study and social routines changing, which influenced the times, timing and contexts of their drinking practices. We separated these shifts into four overarching themes: shifting of structures shaping drinking; the permeability of drinking boundaries; the extension of drinking occasions; and new contexts for drinking.Discussion and ConclusionCOVID‐19 restrictions have led to shifts in the temporal boundaries and contexts that would otherwise shape people's drinking, meaning drinking practices may be less bound by structures, norms, settings and rituals. The drinking occasions concept, although a simple tool for measuring how much people drink, has not been able to capture these complex developments. This is a timely consideration given that COVID‐19 may have enduring effects on people's lifestyles, work and drinking practices. It may be useful to examine drinking as practice, rather than just an occasion, in order to better contextualise epidemiological studies going forward.

Perceptual adaptation to an artificial accent: Phonetic category shift or expansion?

Listeners can rapidly adapt to a novel accent. For example, following exposure to a speaker whose /f/ sound is ambiguous between [s] and [f], they categorize more sounds along an [s]-[f] phonetic continuum as /f/. Wetested the adaptation mechanism underlying such changes in category structure — do listeners adjust their phonetic boundary for the target sound (category shift), or simply relax their categorization criteria (category expansion)? We trained listeners on a pronunciation containing ambiguous /θ/ [θ / s] and then tested them on categorizing either [θ]-[s] or [θ]-[f] phonetic continua. If listeners simply shift their /θ/ boundary, we predicted an increase in /θ/ responses for the [θ]-[s] continuum, but not [θ]-[f]. By contrast, if listeners expand the category, we predicted a categorization change in both continua, indicating a general broadening of the /θ/ category in phonetic space. Consistent with the boundary shift hypothesis, we found that listeners tested on the [θ]-[s] continua showed a significant increase in proportion of /θ/ responses versus controls [χ2(1) = 4.80, p < 0.05), while those tested on [θ]-[f] did not [χ2(1) = 1.30, p = 0.25). [Work supported by an NSF GRFP Fellowship to YVM.]

Understanding Northeastern US Alpine Mountains: Context, Causal Agents of Treeline, and Meteorology to Approximate Their Response to Climate Change

Understanding climate change and air pollution impacts on the northeastern region's restricted alpine ecosystems is complex. Reduced in size and spatial distribution post deglaciation, these alpine ecosystems survived the Hypsithermal warming period with less change than lower-elevation ecosystems. They are low for their latitude and below physiologically limited treeline. More-recent data support and expand on earlier researchers' hypotheses that wind and moisture, not temperature, explains the continued existence of alpine ecosystems in the Northeast. Shifts in species composition and abundance may occur, but frequency of free troposphere exposure, wind, clouds, and rime-icing events, and related topographic, aspect, and microhabitat may maintain resistance to major alpine-treeline ecotone boundary shifts in this century. Under scenarios assuming high levels of emission of greenhouse gases, future predictions become less clear.

Lineage-Specific Variation in IR Boundary Shift Events, Inversions, and Substitution Rates among Caprifoliaceae s.l. (Dipsacales) Plastomes.

Caprifoliaceae s.l. plastid genomes (plastomes) show that one inversion and two inverted repeat boundary shifts occurred in the common ancestor of this family, after which the plastomes are generally conserved. This study reports plastome sequences of five additional species, Fedia cornucopiae, Valeriana fauriei, and Valerianella locusta from the subfamily Valerianoideae, as well as Dipsacus japonicus and Scabiosa comosa from the subfamily Dipsacoideae. Combined with the published plastomes, these plastomes provide new insights into the structural evolution of plastomes within the family. Moreover, the three plastomes from the subfamily Valerianoideae exhibited accelerated nucleotide substitution rates, particularly at synonymous sites, across the family. The patterns of accD sequence divergence in the family are dynamic with structural changes, including interruption of the conserved domain and increases in nonsynonymous substitution rates. In particular, the Valeriana accD gene harbors a large insertion of amino acid repeat (AAR) motifs, and intraspecific polymorphism with a variable number of AARs in the Valeriana accD gene was detected. We found a correlation between intron losses and increased ratios of nonsynonymous to synonymous substitution rates in the clpP gene with intensified positive selection. In addition, two Dipsacoideae plastomes revealed the loss of the plastid-encoded rps15, and a potential functional gene transfer to the nucleus was confirmed.

Academic Reform in Fractured Disciplines \u2013 On the Interaction of Bologna, New-Public-Management and the Dynamics of Disciplinary Development

At the intersection of science studies and higher education research, this contribution looks at the way in which the requirements of universities as organizations release development dynamics in academic disciplines and it analyses the interaction between discipline and organization. We will analyse German educational science, bearing in mind it is an example of disciplines that are fractured and consequently have little consensus in terms of fundamental theories and basic concepts. Firstly, we take on a quantitative approach and analyse the changes in degree courses at the structural level and the symbolic boundaries or conceptual distinctions following the transition to the Bachelor and Master system. Secondly, we take a close look at the negotiating processes and practices, as well as at the disciplinary orientations that determine these boundary shifts, using a qualitative approach that focuses on the actors. In group discussions with representatives of the German educational science at different universities it stood out that actors involved in course design are compelled to find an equilibrium between the demands of the discipline and those of the organization, and do so in very different ways. Finally, we discuss the extent to which close interaction between higher education reforms and academic disciplines can be figured out, particularly for disciplines seen as fractured and which do not have consensual common disciplinary standards.

МІЖ ПРИРОДНИМ ТА ШТУЧНИМ: АНТРОПОЛОГІЧНИЙ ВИМІР

Pankiv O. V. Between natural and artificial: anthropological dimension. – Article.Modern technological progress, in particular bio-, nano-, neurotechnology, informatization, not only determines the development of society, but also affects the worldview of a person and introduces new values. The presence of the latest technologies and their widespread implementation gives a sense of new opportunities. The article concerns the problem of human’s ability to change wildlife in its various forms (from the environment to various modifications of the human body). The purpose and direction of such changesas well as possible modifications lead to a number ofethical questions about the degree of responsibility and possible risks. In particular, special attention is paid to the activities of DIY-science communities, which due to the freedom, accessibility and effectiveness of research and experiments, on the one hand, promote development, however on the other – can be a source of bio-crime and bio-terrorism. In this article, based on the appeal to such interdisciplinary areas as artificial life (ALife), synthetic biology (SynBio), attention is drawn to the shift of the traditional boundary between the natural and the artificial, life and technology. The article also introduces thoughts of modern researchers on the future of mankind during the implementation of the post- and transhumanist project as the liberation from the power of physical nature and the transformation into a creature with superpowers. Of concern are new technological perspectives that threaten the transformation of man into an object of the technosphere, and human life into a component of engineering. The outlined problem is expressed both, in the ontological aspect in the definition of being, and in the epistemological aspect, which concerns the understanding of living systems, as well as ethical as problems of the consequences of the creation of living systems. Both, general scientific and philosophi- cal methods are used in the study, namely, the ana- lysis, synthesis, phenomenological, hermeneutic, andcomparative.

Paradigm shifts in boundary and border studies: disclosing geopolitical assumptions

ABSTRACT This article argues that four paradigm shifts have unfolded in boundary and border studies from the delimitation of the Durand line as the Indo-Afghan frontier. Three subsequent paradigm shifts relate to cooperative management of the Canada–US border after WW1, cultural hybridization across the Mexico-US border since the 1980s, and current networked assemblage of EU’s external border. The paradigm-shift framework connects conceptual advancements in boundary making and border studies with the geopolitical prominence of given borders. The article claims that scholars draw ideal types from the paradigmatic borders of their times, either by accepting or contesting the values anchored in them.

Effects of Cognitive Load on the Categorical Perception of Mandarin Tones.

Purpose This study investigated the effect of cognitive load (CL) on the categorical perception (CP) of Mandarin lexical tones to discuss the application of the generalized pulse-skipping hypothesis. This hypothesis assumes that listeners might miss/skip temporal pulses and lose essential speech information due to CL, which consequently affects both the temporal and spectral dimensions of speech perception. Should CL decrease listeners' pitch sensitivity and impair the distinction of tone categories, this study would support the generalized pulse-skipping hypothesis. Method Twenty-four native Mandarin-speaking listeners were recruited to complete a dual-task experiment where they were required to identify or discriminate tone stimuli while concurrently memorizing six Chinese characters or graphic symbols. A no-load condition without a memory recall task was also included as a baseline condition. The position of categorical boundary, identification slope, between- and within-category discrimination, and discrimination peakedness were compared across the three conditions to measure the impact of CL on tone perception. The recall accuracy of Chinese characters and graphic symbols was used to assess the difficulty of memory recall. Results Compared with the no-load condition, both load conditions showed a boundary shift to Tone 3, shallower identification slope, poorer between-category discrimination, and lower discrimination peakedness. Within-category discrimination was negatively affected by CL in the graphic symbol condition only, not in the Chinese character condition. Conclusions CL degraded listeners' sensitivity to subtle fundamental frequency changes and impaired CP of Mandarin lexical tones. This provides support for the generalized pulse-skipping hypothesis. Besides, the involvement of lexical information modulated the effect of CL.

Northwestward shift of the northern boundary of the East Asian summer monsoon during the mid-Holocene caused by orbital forcing and vegetation feedbacks

The East Asian summer monsoon (EASM) northern boundary is a critical indicator of EASM variations. Movement of the boundary is modulated by both the EASM and the mid-latitude westerlies. Here, we use the Earth system model EC-Earth to quantify the contribution of orbital forcing and vegetation feedbacks in modulating the movement of EASM northern boundary. The results show that the simulated EASM northern boundary during the mid-Holocene shifts by a maximum of ∼213 km northwestward due to orbital forcing. When the model was coupled with a dynamic vegetation module LPJ-GUESS, the northern boundary shifts further northwestward by a maximum of ∼90 km, indicating the importance of vegetation feedbacks.During the mid-Holocene, temperature increased in the mid-latitude during the boreal summer due to insolation, leading to increased meridional air temperature differences (MTDs) over the region north of 45°N and to decreased MTDs to the south. The changes in the temperature gradient weakened the East Asian Westly Jet (EAWJ) and displaced it northward, resulting in an earlier transition of the Meiyu stage and a more prolonged Midsummer stage. The northward movement of EAWJ, combined with the enhanced southerly moisture flow from South China, caused more precipitation in North China and eventually to a northwestward shift of the northern boundary of the EASM. The coupled dynamic vegetation module LPJ-GUESS simulated more grassland and less forest over Northeast Asia during the mid-Holocene. The increased surface albedo tended to lower the temperature in the region, and further enhanced the MTDs in mid-latitude East Asia, leading to the further northward movement of the EAWJ and a northwestward shift of the EASM northern boundary. Although the simulated vegetation distribution in several regions may be not accurate, it reflects the substantial contribution of climate-vegetation interaction on modulating the EASM.

Holocene East African monsoonal variations recorded in wave-dominated clastic paleo-shorelines of Lake Abhe, Central Afar region (Ethiopia & Djibouti)

In tropical Africa, Late Pleistocene-Holocene climatic fluctuations heavily impacted the continental hydro-systems. The timing and magnitude of ‘African Humid Period’ hydrological dynamics (AHP; ~14.8 to ~5.5 ka BP) are not yet fully understood due to the extreme variability in African geomorphic patterns and the complex network of past air convergence boundary shifts. The investigation of the functioning of specific hydro-sedimentary basins is needed to improve our knowledge on the AHP spatial and chronological patterns over the continent. In this paper we present a revised Holocene lake level curve of Lake Abhe: an endorheic basin situated in the Afar Depression at the northern extremity of the East African Rift System (EARS). Located at the boundary of the Red Sea and the Indian and Atlantic Oceans' air moisture mass fluxes, the Lake Abhe watershed represents a system sensitive to changes in Northeast African hydro-climate. Based on numerous littoral lacustrine geomorphic features and 53 related radiocarbon ages on stromatolites and nearshore deposits, we have defined the main Holocene lake highstands proposing a detailed paleo-shoreline record. The first rise in water level is dated to ~11.1 ka cal. BP, while the Maximal Holocene Highstand Shoreline (~420 m a.s.l.) was rapidly reached around ~10 ka cal. BP. Evidence of the impact of the 8.2 ka North Atlantic cooling event is recognized with slow lake level regression until ~8.3 ka cal. BP and with an abrupt drop at ~8 ka cal. BP. The resurgence of humid conditions was recorded from ~7.7 ka cal. BP to ~4.6 ka cal. BP. Radiocarbon ages on littoral materials allow us to propose a Holocene subsidence rate of the Abhe basin axial valley. Furthermore, multiphase sill overflow incisions towards the downstream Hanle basin and transient fluvial connectivity with the upstream Ziway-Shala basin, indicate strong geomorphic controls on lake highstand elevations. In summary, Lake Abhe Holocene fluctuations are the result of combined hydro-climatic, tectonic and local geomorphic controls. However, the confrontation with others East African basins allows us to discuss the transport of moisture masses dynamics into the northern EARS during the Holocene.

Coating recession effects in ceramic composite strength

BN fiber coatings in SiC-SiC composites are vulnerable to oxidation and volatilization at elevated temperature in the presence of water vapor. These processes lead to coating recession in the composite interior with recession fronts starting from matrix cracks and proceeding axially along the fibers. In some operational domains, the main effect of recession is to de-couple the fibers from the matrix, precluding load transfer that would otherwise occur through frictional sliding. Here we present a modelling framework to address effects of coating recession on composite strength. The framework is built upon the characteristic strengths and transfer lengths that govern fiber and matrix fragmentation during tensile loading. Four dominant behavioral domains are identified and analyzed. Recession causes shifts in the domain boundaries and reductions in composite strength. Variations in degraded strength with the extent of recession are interpreted in terms of stress rupture plots. In the regime where recession leads to time-dependent fracture, the composite response is defined by two strengths: (i) the pristine composite strength (governed by the in situ fiber bundle properties) and (ii) a threshold stress below which failure is not predicted to occur (governed by the strength of an equivalent fiber bundle in the absence of a matrix). The time scales are set by the square of the ratio of recession length and the matrix crack spacing, the latter governed by a combination of the matrix strength distribution, interface sliding stress, fiber content and applied stress.

Effect of DEM-smoothing and -aggregation on topographically-based flow directions and catchment boundaries

It is generally assumed that, in humid climates, the groundwater table is a subdued copy of the surface topography. However, the general groundwater table is unlikely to be affected by the microtopography as seen in high-resolution Digital Elevation Models (DEMs). So far, there has been little guidance on the best resolution DEM to use to determine the shape of the water table or the direction of shallow groundwater flow in headwater catchments. We, therefore, looked at the effects of DEM-smoothing and -aggregation on the calculated flow directions and derived catchment boundaries, and identified areas and landscape features for which the calculated flow directions are particularly sensitive to DEM smoothing or aggregation. For > 40 % of the area of the Krycklan study catchment, the calculated flow directions depend strongly on the degree of smoothing or aggregation of the DEM. The four main landscape features for which DEM smoothing or aggregation strongly affected the calculated flow directions were: local slopes in the opposite direction of the general slope, flat areas, ridges, and incised streambanks. To determine the effects of the changing flow directions on the derived catchment boundaries for the smoothed and aggregated DEMs, we calculated the drainage area for 40 locations, representing the outlets of catchments of varying sizes. The shape and size of the catchments of first-order streams were most affected by the processing of the DEM. These streams were often almost completely smoothed out during the DEM preprocessing steps. These shifts in catchment boundaries and drainage area would have a large effect on the water balance. This study thus highlights the need to carefully consider the effects of DEM smoothing or -aggregation on the calculated flow directions and drainage areas.

The Sargasso Sea Commission: An Evolving New Paradigm for High Seas Ecosystem Governance?

The Sargasso Sea is to be found within the North Atlantic Subtropical Gyre. Its borders are the major ocean currents. These boundaries shift with these currents, but there is a core area that covers approximately 2 million square nautical miles situated around the Bermuda archipelago, the majority of which is beyond the national jurisdiction of any State. Ten governments have now signed the 2014 Hamilton Declaration on Collaboration for the Conservation of the Sargasso Sea, which mandated the Government of Bermuda to appoint the members of the Sargasso Sea Commission—the first such body to take on a stewardship role for a high seas ecosystem. The Commission has committed to working with the existing international organizations with jurisdictional competences over a myriad of high seas activities. This paper will examine the work of the Commission and lessons learned over the past decade; it will discuss its possible role as a “boundary spanning” organization and look forward to its future in the light of recent grants from the Global Environment Facility (GEF) and the Fonds Francais pour l’Environnement Mondial (FFEM).

Phase diagram of the two-dimensional dipolar Heisenberg model with Dzyaloshinskii-Moriya interaction and Ising anisotropy

We study phase transitions in the two-dimensional Heisenberg model with Dzyaloshinskii-Moriya interaction, Ising anisotropy $\ensuremath{\eta}$, and dipolar interaction under zero and finite magnetic fields $H$. For three typical strengths (zero, weak, and strong) of the dipolar interaction, we present the $H\text{\ensuremath{-}}\ensuremath{\eta}$ phase diagrams by estimating order parameters for skyrmion-lattice and helical phases and in-plane magnetization using a Monte Carlo method with an $O(N)$ algorithm. We find in the phase diagrams three types of skyrmion-lattice phases, i.e., two square lattices and a triangular lattice, helical phases with diagonal and vertical (or horizontal) stripes, a canted ferromagnetic phase, and a polarized ferromagnetic phase. The effect of the dipolar interaction varies the types of the skyrmion and helical phases in a complex manner. The dipolar interaction also expands the regions of the ordered phases accompanying shifts of the phase boundaries to the positive $H$ and $\ensuremath{\eta}$ directions and causes an increase of the density of skyrmions and shortening of the pitch length (stripe width) of helical structures. We discuss the details of the features of the phase transitions.