Climate-controlled root zone parameters show potential to improve water flux simulations by land surface models

The root zone storage capacity (Sr) is the maximum volume of water in the subsurface that can potentially be accessed by vegetation for transpiration. It influences the seasonality of transpiration as well as fast and slow runoff processes. Many studies have shown that Sr is heterogeneous as controlled by local climate conditions, which affect vegetation strategies in sizing their root system able to support plant growth and to prevent water shortages. Root zone parameterization in most land surface models does not account for this climate control on root development and is based on lookup tables that prescribe the same root zone parameters worldwide for each vegetation class. These lookup tables are obtained from measurements of rooting structure that are scarce and hardly representative of the ecosystem scale. The objective of this research is to quantify and evaluate the effects of a climate-controlled representation of Sr on the water fluxes modeled by the Hydrology Tiled ECMWF Scheme for Surface Exchanges over Land (HTESSEL) land surface model. Climate-controlled Sr is estimated here with the “memory method” (MM) in which Sr is derived from the vegetation's memory of past root zone water storage deficits. Sr,MM is estimated for 15 river catchments over Australia across three contrasting climate regions: tropical, temperate and Mediterranean. Suitable representations of Sr,MM are implemented in an improved version of HTESSEL (Moisture Depth – MD) by accordingly modifying the soil depths to obtain a model Sr,MD that matches Sr,MM in the 15 catchments. In the control version of HTESSEL (CTR), Sr,CTR is larger than Sr,MM in 14 out of 15 catchments. Furthermore, the variability among the individual catchments of Sr,MM (117–722 mm) is considerably larger than of Sr,CTR (491–725 mm). The climate-controlled representation of Sr in the MD version results in a significant and consistent improvement of the modeled monthly seasonal climatology (1975–2010) and interannual anomalies of river discharge compared with observations. However, the effects on biases in long-term annual mean river discharge are small and mixed. The modeled monthly seasonal climatology of the catchment discharge improved in MD compared to CTR: the correlation with observations increased significantly from 0.84 to 0.90 in tropical catchments, from 0.74 to 0.86 in temperate catchments and from 0.86 to 0.96 in Mediterranean catchments. Correspondingly, the correlations of the interannual discharge anomalies improve significantly in MD from 0.74 to 0.78 in tropical catchments, from 0.80 to 0.85 in temperate catchments and from 0.71 to 0.79 in Mediterranean catchments. The results indicate that the use of climate-controlled Sr,MM can significantly improve the timing of modeled discharge and, by extension, also evaporation fluxes in land surface models. On the other hand, the method has not been shown to significantly reduce long-term climatological model biases over the catchments considered for this study.</p

Passwords and the evolution of imperfect authentication

Theory on passwords has lagged practice, where large providers use back-end smarts to survive with imperfect technology.This is the author accepted manuscript. The final version is available from ACM via http://dx.doi.org/10.1145/269939

The quest to replace passwords: A framework for comparative evaluation of web authentication schemes

Abstract—We evaluate two decades of proposals to replace text passwords for general-purpose user authentication on the web using a broad set of twenty-five usability, deployability and security benefits that an ideal scheme might provide. The scope of proposals we survey is also extensive, including password management software, federated login protocols, graphical password schemes, cognitive authentication schemes, one-time passwords, hardware tokens, phone-aided schemes and biometrics. Our comprehensive approach leads to key insights about the difficulty of replacing passwords. Not only does no known scheme come close to providing all desired benefits: none even retains the full set of benefits that legacy passwords already provide. In particular, there is a wide range from schemes offering minor security benefits beyond legacy passwords, to those offering significant security benefits in return for being more costly to deploy or more difficult to use. We conclude that many academic proposals have failed to gain traction because researchers rarely consider a sufficiently wide range of real-world constraints. Beyond our analysis of current schemes, our framework provides an evaluation methodology and benchmark for future web authentication proposals. Keywords-authentication; computer security; human computer interaction; security and usability; deployability; economics; software engineering. I

Correlation of carotid artery reactivity with cardiovascular risk factors and coronary artery vasodilator responses in asymptomatic, healthy volunteers.

OBJECTIVES: Carotid artery reactivity (CAR%), involving carotid artery diameter responses to a cold pressor test (CPT), is a noninvasive measure of conduit artery function in humans. This study examined the impact of age and cardiovascular risk factors on the CAR% and the relationship between CAR% and coronary artery vasodilator responses to the CPT. METHODS: Ultrasound was used to measure resting and peak carotid artery diameters during the CPT, with CAR% being calculated as the relative change from baseline (%). We compared CAR% between young (n = 50, 24 ± 3 years) and older participants (n = 44, 61 ± 8 years), and subsequently assessed relationships between CAR% and traditional cardiovascular risk factors in 50 participants (44 ± 21 years). Subsequently, we compared left anterior descending (LAD) artery velocity (using transthoracic Doppler) with carotid artery diameter (i.e. CAR%) during the CPT (n = 33, 37 ± 17 years). RESULTS: A significantly larger CAR% was found in young versus older healthy participants (4.1 ± 3.7 versus 1.8 ± 2.6, P < 0.001). Participants without cardiovascular risk factors demonstrated a higher CAR% than those with at least two risk factors (2.9 ± 2.9 versus 0.5 ± 2.9, P = 0.019). Carotid artery diameter and LAD velocity increased during CPT (P < 0.001). Carotid diameter and change in velocity correlated with LAD velocity (r = 0.486 and 0.402, P < 0.004 and 0.02, respectively). CONCLUSION: Older age and cardiovascular risk factors are related to lower CAR%, while CAR% shows good correlation with coronary artery responses to the CPT. Therefore, CAR% may represent a valuable technique to assess cardiovascular risk, while CAR% seems to reflect coronary artery vasodilator function

Morphological effects of vegetation on the tidal-fluvial transition in Holocene estuaries

Vegetation enhances bank stability and sedimentation to such an extent that it can modify river patterns, but how these processes manifest themselves in full-scale estuarine settings is poorly understood. On the one hand, tidal flats accrete faster in the presence of vegetation, reducing the flood storage and ebb dominance over time. On the other hand flow-focusing effects of a tidal floodplain elevated by mud and vegetation could lead to channel concentration and incision. Here we study isolated and combined effects of mud and tidal marsh vegetation on estuary dimensions. A 2-D hydromorphodynamic estuary model was developed, which was coupled to a vegetation model and used to simulate 100 years of morphological development. Vegetation settlement, growth and mortality were determined by the hydromorphodynamics. Eco-engineering effects of vegetation on the physical system are here limited to hydraulic resistance, which affects erosion and sedimentation pattern through the flow field. We investigated how vegetation, combined with mud, affects the average elevation of tidal flats and controls the system-scale planform. Modelling with vegetation only results in a pattern with the largest vegetation extent in the mixed-energy zone of the estuary, which is generally shallower. Here vegetation can cover more than 50 % of the estuary width while it remains below 10 %–20 % in the outer, tide-dominated zone. This modelled distribution of vegetation along the estuary shows general agreement with trends in natural estuaries observed by aerial image analysis. Without mud, the modelled vegetation has a limited effect on morphology, again peaking in the mixed-energy zone. Numerical modelling with mud only shows that the presence of mud leads to stabilisation and accretion of the intertidal area and a slight infill of the mixed-energy zone. Combined modelling of mud and vegetation leads to mutual enhancement with mud causing new colonisation areas and vegetation stabilising the mud. This occurs in particular in a zone previously described as the bedload convergence zone. While vegetation focusses the flow into the channels such that mud sedimentation in intertidal side channels is prevented on a timescale of decades, the filling of intertidal area and the resulting reduction in tidal prism may cause the infilling of estuaries over centuries

Metabolomic and lipidomic signatures associated with activation of human cDC1 (BDCA3(+)/CD141(+)) dendritic cells

Dendritic cells (DCs) bridge the connection between innate and adaptive immunity. DCs present antigens to T cells and stimulate potent cytotoxic T-cell responses. Metabolic reprogramming is critical for DC development and activation; however, metabolic adaptations and regulation in DC subsets remains largely uncharacterized. Here, we mapped metabolomic and lipidomic signatures associated with the activation phenotype of human conventional DC type 1, a DC subset specialized in cross-presentation and therefore of major importance for the stimulation of CD8(+) T cells. Our metabolomics and lipidomic analyses showed that Toll-like receptor (TLR) stimulation altered glycerolipids and amino acids in cDC1. Poly I:C or pRNA stimulation reduced triglycerides and cholesterol esters, as well as various amino acids. Moreover, TLR stimulation reduced expression of glycolysis-regulating genes and did not induce glycolysis. Conversely, cDC1 exhibited increased mitochondrial content and oxidative phosphorylation (OXPHOS) upon TLR3 or TLR7/8 stimulation. Our findings highlight the metabolic adaptations required for cDC1 maturation.Proteomic

Sandy contourite drift in the late Miocene Rifian Corridor (Morocco):Reconstruction of depositional environments in a foreland-basin seaway

The Rifian Corridor was a seaway between the Atlantic Ocean and the Mediterranean Sea during the late Miocene. The seaway progressively closed, leading to the Messinian Salinity Crisis in the Mediterranean Sea. Despite the key palaeogeographic importance of the Rifian Corridor, patterns of sediment transport within the seaway have not been thoroughly studied. In this study, we investigated the upper Miocene sedimentation and bottom current pathways in the South Rifian Corridor. The planktic and benthic foraminifera of the upper Tortonian and lower Messinian successions allow us to constrain the age and palaeo-environment of deposition. Encased in silty marls deposited at 150–300 m depth, there are (i) 5 to 50 m thick, mainly clastic sandstone bodies with unidirectional cross-bedding; and (ii) 50 cm thick, mainly clastic, tabular sandstone beds with bioturbation, mottled silt, lack of clear base or top, and bi-gradational sequences. Furthermore, seismic facies representing elongated mounded drifts and associated moat are present at the western mouth of the seaway. We interpret these facies as contourites: the products of a westward sedimentary drift in the South Rifian Corridor. The contourites are found only on the northern margin of the seaway, thus suggesting a geostrophic current flowing westward along slope and then northward. This geostrophic current may have been modulated by tides. By comparing these fossil examples with the modern Gulf of Cadiz, we interpret these current-dominated deposits as evidence of late Miocene Mediterranean overflow into the Atlantic Ocean, through the Rifian Corridor. This overflow may have affected late Miocene ocean circulation and climate, and the overflow deposits may represent one of the first examples of mainly clastic contourites exposed on land

Counting points on hyperelliptic curves over finite fields

International audienceWe describe some algorithms for computing the cardinality of hyperelliptic curves and their Jacobians over finite fields. They include several methods for obtaining the result modulo small primes and prime powers, in particular an algorithm à la Schoof for genus 2 using Cantor's division polynomials. These are combined with a birthday paradox algorithm to calculate the cardinality. Our methods are practical and we give actual results computed using our current implementation. The Jacobian groups we handle are larger than those previously reported in the literature