Topographic Constraints Research Articles

Heat flux and topography constraints on thermochemical structure below North China Craton regions and implications for evolution of cratonic lithosphere

AbstractThe eastern North China Craton (NCC) has undergone extensive reactivation during the Mesozoic and Cenozoic, while the western NCC has remained stable throughout its geological history. Geophysical and geochemical observations, including heat flux, surface topography, crustal and lithospheric thicknesses, and volcanism, show significant contrast between the eastern and western NCC. These observations provide constraints on thermochemical structure and reactivation process of the eastern NCC, thus helping understand the dynamic evolution of cratonic lithosphere. In this study, we determined the residual topography for the NCC region by removing crustal contribution to the topography. We found that the residual topography of the eastern NCC region is generally 0.3–0.9 km higher than the western NCC. We computed a large number of two‐dimension thermochemical convection models for gravitational instability of cratonic lithosphere and quantified surface heat flux and topography contrasts between stable and destabilized parts of cratonic lithosphere. These models consider different chemical buoyancy (i.e., buoyancy number B) and viscosity for the cratonic lithosphere. Our models suggest that to explain the difference in heat flux (25–30 mW/m2) and residual topography (0.3–0.9 km) between the eastern and western NCC regions, the buoyancy number B is required to be ~0.3–0.4. This range of B implies that as much as 50% of the original cratonic lithospheric material remains in the present‐day eastern NCC lithosphere and its underlying shallow mantle and that the new lithosphere in the eastern NCC may be a mixture of the relics of old craton materials and the normal mantle.

Inhibitors of HIV-1 maturation: Development of structure–activity relationship for C-28 amides based on C-3 benzoic acid-modified triterpenoids

We have recently reported on the discovery of a C-3 benzoic acid (1) as a suitable replacement for the dimethyl succinate side chain of bevirimat (2), an HIV-1 maturation inhibitor that reached Phase II clinical trials before being discontinued. Recent SAR studies aimed at improving the antiviral properties of 2 have shown that the benzoic acid moiety conferred topographical constraint to the pharmacophore and was associated with a lower shift in potency in the presence of human serum albumin. In this manuscript, we describe efforts to improve the polymorphic coverage of the C-3 benzoic acid chemotype through modifications at the C-28 position of the triterpenoid core. The dimethylaminoethyl amides 17 and 23 delivered improved potency toward bevirimat-resistant viruses while increasing C24 in rat oral PK studies.

Implications for constructed wetlands to mitigate nitrate and pesticide pollution in agricultural drained watersheds

In the context of subsurface drainage, the mitigation of agricultural pollutants means intercepting water flows using green infrastructures such as constructed wetlands (CWs). First, based on a scientific review, this paper analyses how efficiently CWs can remove nitrate and pesticides from the runoff in drained agricultural watersheds. Average efficiency ranges from 20 to 90% and from 40 to 90% for pesticides and nitrate respectively. The main processes involved are based on microbiological activities, for which hydraulic residence time is a key factor. In order to successful implementation of such a wetland system, hydrological diagnosis of water flow and pollutant transfer at different watershed scales should be provided. Typically, the transport and transformation of pollutants shows clear seasonality depending on the application of nitrate (throughout the whole year) and pesticides (only after application periods).We suggest two interception strategies based on field experiments. The “on-stream” strategy means the establishment of free water surface (FWS) CWs directly on streams/ditches and the interception of all drainage flows: a solution suitable for nitrate removal. The “off-stream” strategy requires the establishment of CWs outside of streams/ditches, whereas interception targets only the most polluted water flow, for instance during the period after pesticide application, requiring farmer's involvement.Suggestions are also made for FWS CW design (a geotechnical survey, topography constraints, etc.) respecting ecological engineering concepts. A following size range is proposed: 76m3 per drained hectare, equivalent to 1% of the upstream area, given a maximum water depth of 0.8m. Nevertheless, CWs must be considered as a complementary tool dedicated to transfer reduction, and as part of broader actions aimed at reducing pollutant loading at the plot scale.

Controls on turbidite sedimentation: Insights from a quantitative approach of submarine channel and lobe architecture (Late Quaternary Congo Fan)

The role of internal and external forcing of sedimentation in turbidite systems remains a subject of debate. Here we propose new insights from the quantitative analysis of architectural parameters of the Congo Axial Fan.Fifty-two channel-levee-lobe systems, spanning the last ca. 200 ka, are visible on the seafloor, most of them having slightly elongated lobe complexes at their termination. Volumes of lobe complexes (usually 3–196 km3) are highly variable in time and space. The cumulative volume of the lobe complexes represents approximately 30% of the volume of the Axial Fan.The Axial Fan is sequentially divided into periods of increasing/decreasing channel lengths and basinward/landward migrations of avulsion points, representing successive prograding/retrograding architectural patterns called architectural cycles. These cycles are either symmetrical saw toothed and bell-shaped with progressive progradation and retrogradation phases, or asymmetrical, with long-lasting progradation phases and abrupt retrogradation phases that correspond to channel avulsions occurring high up on the fan.Our study points to the interplay between internal and external factors controlling the architecture of the Congo Axial Fan. The local topographic constraint is a major factor in the fan's stacking pattern. However, cyclic evolution of the architecture reveals major shifts in the deposition site that are linked to very upfan avulsion events. These events are interpreted to be driven by external factors (e.g. climate and/or eustatic sea-level change) that were able to drastically increase and/or coarsen the sediment supply to the fan.

Growth Type and Functional Trajectories: An Empirical Study of Urban Expansion in Nanjing, China.

Drawing upon the Landsat satellite images of Nanjing from 1985, 1995, 2001, 2007, and 2013, this paper integrates the convex hull analysis and common edge analysis at double scales, and develops a comprehensive matrix analysis to distinguish the different types of urban land expansion. The results show that Nanjing experienced rapid urban expansion, dominated by a mix of residential and manufacturing land from 1985 to 2013, which in turn has promoted Nanjing’s shift from a compact mononuclear city to a polycentric one. Spatial patterns of three specific types of growth, namely infilling, extension, and enclave were quite different in four consecutive periods. These patterns result primarily from the existing topographic constraints, as well as government-oriented urban planning and policies. By intersecting the function maps, we also reveal the functional evolution of newly-developed urban land. Moreover, both self-enhancing and mutual promotion of the newly developed functions are surveyed over the last decade. Our study confirms that the integration of a multi-scale method and multi-perspective analysis, such as the spatiotemporal patterns and functional evolution, helps us to better understand the rapid urban growth in China.

The Barents Sea frontal zones and water masses variability (1980–2011)

Abstract. The polar front separates the warm and saline Atlantic Water entering the southern Barents Sea from the cold and fresh Arctic Water located in the north. These water masses can mix together (mainly in the center of the Barents Sea), be cooled by the atmosphere and receive salt because of brine release; these processes generate dense water in winter, which then cascades into the Arctic Ocean to form the Arctic Intermediate Water. To study the interannual variability and evolution of the frontal zones and the corresponding variations of the water masses, we have merged data from the International Council for the Exploration of the Sea and the Arctic and Antarctic Research Institute and have built a new database, which covers the 1980–2011 period. The summer data were interpolated on a regular grid. A probability density function is used to show that the polar front splits into two branches east of 32° E where the topographic constraint weakens. Two fronts can then be identified: the Northern Front is associated with strong salinity gradients and the Southern Front with temperature gradients. Both fronts enclose the denser Barents Sea Water. The interannual variability of the water masses is apparent in the observed data and is linked to that of the ice cover. The frontal zones variability is found by using data from a general circulation model. The link with the atmospheric variability, represented here by the Arctic Oscillation, is not clear. However, model results suggest that such a link could be validated if winter data were taken into account. A strong trend appears: the Atlantic Water (Arctic Water) occupies a larger (smaller) volume of the Barents Sea. This trend amplifies during the last decade and the model study suggests that this could be accompanied by a northwards displacement of the Southern Front in the eastern part of the Barents Sea. The results are less clear for the Northern Front. The observations show that the volume of the Barents Sea Water remains nearly unchanged, which suggests a northwards shift of the Northern Front to compensate for the northward shift of the Southern Front. Lastly, we noticed that the seasonal variability of the position of the front is small.

Agrarian legacies and innovations in the Nabataean territory

The Nabataeans, a nomadic people inhabiting the southern Near East from the end of the 4th century BC, are mainly known for their trade activities along the Incense Road. Recent scientific advances have shown the importance of agro-pastoral activities within the Nabataean kingdom. However, few studies have addressed the identification of the existing agrosystems and the kinds of associated plant production. This paper focuses on agrarian plant resources exploited in the Nabataean territory by analysing the carpological and anthracological data from four sites (Bosra, Dharih, Petra, Hegra) presented Nabataean and Roman layers dated between the 2nd century BC and the end of the 3rd century AD. The results obtained show the existence of farming systems combining annual and perennial crops, responding efficiently to different economic needs (including food, technical raw materials and fuel). Fruit trees were important and their distribution mainly correlated with climate and topographic constraints. Semi-arid sites developed Mediterranean agroforestry systems while the only arid area site developed an oasis agrosystem. Crop production was directly inherited from preceding periods while the presence of cotton in the Hegra oasis reflects innovative agricultural and technical processes probably related to Nabataean trade activities.

Potential sea-level rise from Antarctic ice-sheet instability constrained by observations.

Large parts of the Antarctic ice sheet lying on bedrock below sea level may be vulnerable to marine-ice-sheet instability (MISI), a self-sustaining retreat of the grounding line triggered by oceanic or atmospheric changes. There is growing evidence that MISI may be underway throughout the Amundsen Sea embayment (ASE), which contains ice equivalent to more than a metre of global sea-level rise. If triggered in other regions, the centennial to millennial contribution could be several metres. Physically plausible projections are challenging: numerical models with sufficient spatial resolution to simulate grounding-line processes have been too computationally expensive to generate large ensembles for uncertainty assessment, and lower-resolution model projections rely on parameterizations that are only loosely constrained by present day changes. Here we project that the Antarctic ice sheet will contribute up to 30 cm sea-level equivalent by 2100 and 72 cm by 2200 (95% quantiles) where the ASE dominates. Our process-based, statistical approach gives skewed and complex probability distributions (single mode, 10 cm, at 2100; two modes, 49 cm and 6 cm, at 2200). The dependence of sliding on basal friction is a key unknown: nonlinear relationships favour higher contributions. Results are conditional on assessments of MISI risk on the basis of projected triggers under the climate scenario A1B (ref. 9), although sensitivity to these is limited by theoretical and topographical constraints on the rate and extent of ice loss. We find that contributions are restricted by a combination of these constraints, calibration with success in simulating observed ASE losses, and low assessed risk in some basins. Our assessment suggests that upper-bound estimates from low-resolution models and physical arguments (up to a metre by 2100 and around one and a half by 2200) are implausible under current understanding of physical mechanisms and potential triggers.

Interactions between Inhibitory Interneurons and Excitatory Associational Circuitry in Determining Spatio-Temporal Dynamics of Hippocampal Dentate Granule Cells: A Large-Scale Computational Study.

This paper reports on findings from a million-cell granule cell model of the rat dentate gyrus that was used to explore the contributions of local interneuronal and associational circuits to network-level activity. The model contains experimentally derived morphological parameters for granule cells, which each contain approximately 200 compartments, and biophysical parameters for granule cells, basket cells, and mossy cells that were based both on electrophysiological data and previously published models. Synaptic input to cells in the model consisted of glutamatergic AMPA-like EPSPs and GABAergic-like IPSPs from excitatory and inhibitory neurons, respectively. The main source of input to the model was from layer II entorhinal cortical neurons. Network connectivity was constrained by the topography of the system, and was derived from axonal transport studies, which provided details about the spatial spread of axonal terminal fields, as well as how subregions of the medial and lateral entorhinal cortices project to subregions of the dentate gyrus. Results of this study show that strong feedback inhibition from the basket cell population can cause high-frequency rhythmicity in granule cells, while the strength of feedforward inhibition serves to scale the total amount of granule cell activity. Results furthermore show that the topography of local interneuronal circuits can have just as strong an impact on the development of spatio-temporal clusters in the granule cell population as the perforant path topography does, both sharpening existing clusters and introducing new ones with a greater spatial extent. Finally, results show that the interactions between the inhibitory and associational loops can cause high frequency oscillations that are modulated by a low-frequency oscillatory signal. These results serve to further illustrate the importance of topographical constraints on a global signal processing feature of a neural network, while also illustrating how rich spatio-temporal and oscillatory dynamics can evolve from a relatively small number of interacting local circuits.

Sustainable Food Security in the Mountains of Pakistan: Towards a Policy Framework

The nature and causes of food and livelihood security in mountain areas are quite different to those in the plains. Rapid socioeconomic and environmental changes added to the topographical constraints have exacerbated the problem of food insecurity in the Hindu Kush-Himalayan (HKH) region. In Pakistan, food insecurity is significantly higher in the mountain areas than in the plains as a result of a range of biophysical and socioeconomic factors. The potential of mountain niche products such as fruit, nuts, and livestock has remained underutilized. Moreover, the opportunities offered by globalization, market integration, remittances, and non-farm income have not been fully tapped. This paper analyzes the opportunities and challenges of food security in Pakistan’s mountain areas, and outlines a framework for addressing the specific issues in terms of four different types of area differentiated by agro-ecological potential and access to markets, information, and institutional services.

Odor recognition in robotics applications by discriminative time-series modeling

Odor classification by a robot equipped with an electronic nose (e-nose) is a challenging task for pattern recognition since volatiles have to be classified quickly and reliably even in the case of short measurement sequences, gathered under operation in the field. Signals obtained in these circumstances are characterized by a high-dimensionality, which limits the use of classical classification techniques based on unsupervised and semi-supervised settings, and where predictive variables can be only identified using wrapper or post-processing techniques. In this paper, we consider generative topographic mapping through time (GTM-TT) as an unsupervised model for time-series inspection, based on hidden Markov models regularized by topographic constraints. We further extend the model such that supervised classification and relevance learning can be integrated, resulting in supervised GTM-TT. Then, we evaluate the suitability of this new technique for the odor classification problem in robotics applications. The performance is compared with classical techniques as nearest neighbor, as an absolute baseline, support vector machine and a recent time-series kernel approach, demonstrating the eligibility of our approach for high-dimensional data. Additionally, we exploit the learning system introduced in this work, providing a measure of the relevance of each sensor and individual time points in the classification process, from which important information can be extracted.

Energy Auditing as a Tool for Outlining Major Inefficiencies: Results from a Real Water Supply System

The application of a novel energy auditing scheme in a real water supply system and its sub-systems to determine major sources of energy inefficiency is presented. This scheme has been consolidated in the Portuguese National Initiative for the management of water-energy losses (www.iperdas.org). Within this initiative, 17 water utilities have carried out energy audits following a two-step procedure: (i) simplified energy auditing and calculation of efficiency metrics for the global system and for sub-systems and (ii) detailed energy auditing for critical sub-systems. The case-study of Águas do Sado water utility is presented to illustrate the application of this approach. This system has 25% of non-revenue waterand consumes 5.5 GWh per year, which is approximately twice the minimum energy required. The analysis of therespective 17 sub-systems has shown that the major inefficiencies are due to topography constraints, to water losses and to the lack of intermediate service pressure levels.

Ocean bottom pressure variability in the Mediterranean Sea and its relationship with sea level from a numerical model

The spatial and temporal scales of variability of ocean bottom pressure (Pb) in the Mediterranean Sea are characterized and their relationship with sea level was assessed using a high resolution eddy-permitting regional ocean model spanning the period 1999–2011. It was found that rapid (periods of a few days) bottom pressure fluctuations are coherent with sea level and are decoupled between the eastern and western basins as a result of topographic constraints. In the longer periods, steric processes gained relevance away from the coast and partially broke the coherence between sea level and Pb, especially on the western basin. Results confirm that sea level changes are predominantly barotropic over most of the basin and at all time scales, except for the annual cycle. Along the coasts sea level fluctuations reflected local steric processes taking place in their vicinity. This effect was stronger on the western basin, whereas the coasts of the Eastern Mediterranean arise as the most suitable proxies for basin wide long term (>60days) mean sea level (or ocean bottom pressure) changes at non-seasonal periods.

A comparative study of urban expansion in Beijing, Tianjin and Shijiazhuang over the past three decades

Detailed comparative studies on spatiotemporal patterns of both urbanized area and urban expansion over a relatively long timeframe are rare. Here, we compared spatiotemporal patterns of urbanization in three major cities (i.e., Beijing, Tianjin and Shijiazhuang) in the Jing-Jin-Ji Urban Agglomeration using multi-temporal Landsat MSS, TM, and ETM+ images data of circa 1980, 1990, 1995, 2000, 2005 and 2010 integrated with Geographic Information System (GIS) techniques and landscape analysis approaches. A multi-scale analysis on the landscape responses to urban expansion from regional landscape to city and within city levels was performed. Results showed that urban area in Beijing, Tianjin and Shijiazhuang has expanded from 801km2, 795km2 and 682km2 to 2452km2, 3343km2 and 1699km2, increasing annually at 3.7%, 4.7% and 3.2%, respectively. Spatially, Beijing, Tianjin and Shijiazhuang have presented a mononuclear concentric polygon pattern, a double-nucleated polygon-line pattern, a sectorial point pattern, respectively, resulting primarily from their respective topographic constraints as well as urban planning and policy. Landscape responses to urban expansion varied with time and scale investigated, suggesting a general understanding on landscape metrics at regional or city level may fail to reveal detailed within city landscape dynamics under the impacts of urban expansion. The Jing-Jin-Ji Urban Agglomeration faces a great challenge to manage trades-offs between narrowing down intra-regional disparity and maintaining regional economic and ecological benefits.

The ancient water system at the Upper city of Hasankeyf, Turkey

In this paper, the water distribution system at the Upper city of a well-preserved medieval town of Hasankeyf near the Tigris is questioned and its relation to the urban settlement pattern is assessed. The discussions are based on the cistern-intensive and available canal data collected within the residential borders of the Upper city in 2005. Being the third level features of the water system, the cisterns the majority of which are now attributable to the “conical, small and individual” typology, have shown that they were actively operated through the open rock-cut canals which were fed by the backbone of the distribution network—namely the siphon system, until recent times. Although a considerable number of converted cisterns hallmark shifts in the function of the water system and the changing conjectures over time, the blue prints of such a big “hydro-design” reveal the competence of semi-arid occupational environments in Upper Mesopotamia in showing how to cope with the topographical constraints and climatic disadvantages and turn these into an opportunity through the efficient use of terrain along with a carefully designed settlement area. That the Upper city now offers numerous water features makes this piece of land quite a representative of the regional works and shows the apex of the perception of ancient technology achieved with the siphon that could have been launched in the Roman era, and the state of art of planning ancient natural and man-made habitats.

New Reconstruction of Antarctic Near-Surface Temperatures: Multidecadal Trends and Reliability of Global Reanalyses*,+

Abstract A reconstruction of Antarctic monthly mean near-surface temperatures spanning 1958–2012 is presented. Its primary goal is to take advantage of a recently revised key temperature record from West Antarctica (Byrd) to shed further light on multidecadal temperature changes in this region. The spatial interpolation relies on a kriging technique aided by spatiotemporal temperature covariances derived from three global reanalyses [the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim), Modern-Era Retrospective Analysis for Research and Applications (MERRA), and Climate Forecast System Reanalysis (CFSR)]. For 1958–2012, the reconstruction yields statistically significant annual warming in the Antarctic Peninsula and virtually all of West Antarctica, but no significant temperature change in East Antarctica. Importantly, the warming is of comparable magnitude both in central West Antarctica and in most of the peninsula, rather than concentrated either in one or the other region as previous reconstructions have suggested. The Transantarctic Mountains act for the temperature trends, as a clear dividing line between East and West Antarctica, reflecting the topographic constraint on warm air advection from the Amundsen Sea basin. The reconstruction also serves to highlight spurious changes in the 1979–2009 time series of the three reanalyses that reduces the reliability of their trends, illustrating a long-standing issue in high southern latitudes. The study concludes with an examination of the influence of the southern annular mode (SAM) on Antarctic temperature trends. The results herein suggest that the trend of the SAM toward its positive phase in austral summer and fall since the 1950s has had a statistically significant cooling effect not only in East Antarctica (as already well documented) and but also (only in fall) in West Antarctica.

Topographic NMF for data representation.

Nonnegative matrix factorization (NMF) is a useful technique to explore a parts-based representation by decomposing the original data matrix into a few parts-based basis vectors and encodings with nonnegative constraints. It has been widely used in image processing and pattern recognition tasks due to its psychological and physiological interpretation of natural data whose representation may be parts-based in human brain. However, the nonnegative constraint for matrix factorization is generally not sufficient to produce representations that are robust to local transformations. To overcome this problem, in this paper, we proposed a topographic NMF (TNMF), which imposes a topographic constraint on the encoding factor as a regularizer during matrix factorization. In essence, the topographic constraint is a two-layered network, which contains the square nonlinearity in the first layer and the square-root nonlinearity in the second layer. By pooling together the structure-correlated features belonging to the same hidden topic, the TNMF will force the encodings to be organized in a topographical map. Thus, the feature invariance can be promoted. Some experiments carried out on three standard datasets validate the effectiveness of our method in comparison to the state-of-the-art approaches.

How ecosystem services knowledge and values influence farmers' decision-making.

The ecosystem services (ES) concept has emerged and spread widely recently, to enhance the importance of preserving ecosystems through global change in order to maintain their benefits for human well-being. Numerous studies consider various dimensions of the interactions between ecosystems and land use via ES, but integrated research addressing the complete feedback loop between biodiversity, ES and land use has remained mostly theoretical. Few studies consider feedbacks from ecosystems to land use systems through ES, exploring how ES are taken into account in land management decisions. To fill this gap, we carried out a role-playing game to explore how ES cognition mediates feedbacks from environmental change on farmers' behaviors in a mountain grassland system. On a close to real landscape game board, farmers were faced with changes in ES under climatic and socio-economic scenarios and prompted to plan for the future and to take land management decisions as they deemed necessary. The outcomes of role-playing game were complemented with additional agronomic and ecological data from interviews and fieldwork. The effects of changes in ES on decision were mainly direct, i.e. not affecting knowledge and values, when they constituted situations with which farmers were accustomed. For example, a reduction of forage quantity following droughts led farmers to shift from mowing to grazing. Sometimes, ES cognitions were affected by ES changes or by external factors, leading to an indirect feedback. This happened when fertilization was stopped after farmers learned that it was inefficient in a drought context. Farmers' behaviors did not always reflect their attitudes towards ES because other factors including topographic constraints, social value of farming or farmer individual and household characteristics also influenced land-management decisions. Those results demonstrated the interest to take into account the complete feedback loop between ES and land management decisions to favor more sustainable ES management.

A VS30 Map for California with Geologic and Topographic Constraints

Abstract For many earthquake engineering applications, site response is estimated through empirical correlations with the time‐averaged shear‐wave velocity to 30 m depth ( V S 30 ). These applications therefore depend on the availability of either site‐specific V S 30 measurements or V S 30 maps at local, regional, and global scales. Because V S 30 measurements are sparse, a proxy frequently is needed to estimate V S 30 at unsampled locations. We present a new V S 30 map for California, which accounts for observational constraints from multiple sources and spatial scales, such as geology, topography, and site‐specific V S 30 measurements. We apply the geostatistical approach of regression kriging (RK) to combine these constraints for predicting V S 30 . For the V S 30 trend, we start with geology‐based V S 30 values and identify two distinct trends between topographic gradient and the residuals from the geology V S 30 model. One trend applies to deep and fine Quaternary alluvium, whereas the second trend is slightly stronger and applies to Pleistocene sedimentary units. The RK framework ensures that the resulting map of California is locally refined to reflect the rapidly expanding database of V S 30 measurements throughout California. We compare the accuracy of the new mapping method to a previously developed map of V S 30 for California. We also illustrate the sensitivity of ground motions to the new V S 30 map by comparing real and scenario ShakeMaps with V S 30 values from our new map to those for existing V S 30 maps. Online Material: California statewide V S 30 and ShakeMaps for Loma Prieta.

Topographic constraints on the origin of the equatorial ridge on Iapetus

Saturn’s moon Iapetus has an equatorial ridge system, which may be as high as 20km, that may have formed by endogenic forces, such as tectonic and convective forces, or exogenic processes such as debris infall. We use high-resolution topographic data to conduct a topographic analysis of the ridge, which suggests a predominantly triangular morphology, with some ridge face slopes reaching 40°, allowing for an exogenic formation mechanism.