Deriving soil hydraulic parameters in a high spatial resolution for a heterogeneous agricultural field-site

Providing information about the structure of the subsurface plays an important role for setting up soil hydraulic models, which are in turn an important prerequisite for ecosystem modelling approaches. Because soils often show a high within-field heterogeneity in terms of texture, stone content, and bulk density, they may also exhibit a wide range of hydraulic properties in the field. During water stress periods and especially on agricultural fields, which are characterized by uniform vegetation, the occurrence of a within-field heterogeneity in terms of soil hydraulic properties can be observed as it affects the different water status of the plants. The patterns of visible plant water stress and areas of low apparent electrical conductivities measured by electromagnetic induction measurements (EMI) often coincide, for e.g. within sugar beet cropped fields. Such observations have also been made beforehand at the current study site; an agricultural field (2.7 ha) that is situated in an area developed by fluvial processes. To account for this, the current approach included a sampling campaign on a field with 70 drilling locations for texture and organic carbon analyses. Furthermore, soil water retention functions and saturated hydraulic conductivity were determined at 20 sampling locations. Our approach for ecosystem modelling is based on 4 m² grid cells over the whole study site. To consider within-field heterogeneity in the ecosystem model, soil hydraulic parameters were predicted for each grid cell, whereby different approaches such as spatial interpolation, Miller-Miller scaling, and the use of pedotransfer functions were taken into account to identify the most appropriate approach

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

Standard‐space atlas of the viscoelastic properties of the human brain

Standard anatomical atlases are common in neuroimaging because they facilitate data analyses and comparisons across subjects and studies. The purpose of this study was to develop a standardized human brain atlas based on the physical mechanical properties (i.e., tissue viscoelasticity) of brain tissue using magnetic resonance elastography (MRE). MRE is a phase contrast-based MRI method that quantifies tissue viscoelasticity noninvasively and in vivo thus providing a macroscopic representation of the microstructural constituents of soft biological tissue. The development of standardized brain MRE atlases are therefore beneficial for comparing neural tissue integrity across populations. Data from a large number of healthy, young adults from multiple studies collected using common MRE acquisition and analysis protocols were assembled (N = 134; 78F/ 56 M; 18–35 years). Nonlinear image registration methods were applied to normalize viscoelastic property maps (shear stiffness, μ, and damping ratio, ξ) to the MNI152 standard structural template within the spatial coordinates of the ICBM-152. We find that average MRE brain templates contain emerging and symmetrized anatomical detail. Leveraging the substantial amount of data assembled, we illustrate that subcortical gray matter structures, white matter tracts, and regions of the cerebral cortex exhibit differing mechanical characteristics. Moreover, we report sex differences in viscoelasticity for specific neuroanatomical structures, which has implications for understanding patterns of individual differences in health and disease. These atlases provide reference values for clinical investigations as well as novel biophysical signatures of neuroanatomy. The templates are made openly available (github.com/mechneurolab/mre134) to foster collaboration across research institutions and to support robust cross-center comparisons

SiGamal: A supersingular isogeny-based PKE and its application to a PRF

We propose two new supersingular isogeny-based public key encryptions: SiGamal and C-SiGamal. They were developed by giving an additional point of the order $2^r$ to CSIDH. SiGamal is similar to ElGamal encryption, while C-SiGamal is a compressed version of SiGamal. We prove that SiGamal and C-SiGamal are IND-CPA secure without using hash functions under a new assumption: the P-CSSDDH assumption. This assumption comes from the expectation that no efficient algorithm can distinguish between a random point and a point that is the image of a public point under a hidden isogeny. Next, we propose a Naor-Reingold type pseudo random function (PRF) based on SiGamal. If the P-CSSDDH assumption and the CSSDDH$^*$ assumption, which guarantees the security of CSIDH that uses a prime $p$ in the setting of SiGamal, hold, then our proposed function is a pseudo random function. Moreover, we estimate that the computational costs of group actions to compute our proposed PRF are about $\sqrt{\frac{8T}{3\pi}}$ times that of the group actions in CSIDH, where $T$ is the Hamming weight of the input of the PRF. Finally, we experimented with group actions in SiGamal and C-SiGamal. The computational costs of group actions in SiGamal-512 with a $256$-bit plaintext message space were about $2.62$ times that of a group action in CSIDH-512

Cardiac Alterations in Human African Trypanosomiasis (T.b. gambiense) with Respect to the Disease Stage and Antiparasitic Treatment

In Human African Trypanosomiasis (HAT), neurological symptoms dominate and cardiac involvement has been suggested. Because of increasing resistance to the available drugs for HAT, new compounds are desperately needed. Evaluation of cardiotoxicity is one parameter of drug safety, but without knowledge of the baseline heart involvement in HAT, cardiologic findings and drug-induced alterations will be difficult to interpret. The electrocardiogram (ECG) is a tool to evaluate cardiac involvement and the risk of arrythmias. We analysed the ECG of 465 HAT patients and compared them with the ECG of 61 healthy volunteers. In HAT patients the QTc interval was prolonged. This comprises a risk of fatal arrhythmias if new drugs with antiarrhythmic potential will be used. Further, repolarization changes and low voltage were more frequent than in healthy controls. This could be explained by an inflammation of the heart. Treatment of HAT was associated with appearance of repolarization changes but not with a QTc prolongation. These changes appear to be associated with the disease, but not with a specific drug. The main conclusion of this study is that heart involvement is frequent in HAT and mostly well tolerated. However, it can become relevant, if new compounds with antiarrhythmic potential will be used

Cyclic AMP and fructose-2,6-bisphosphate stimulated in vitro phosphorylation of yeast fructose-1,6-bisphosphatase.

Phosphorylation of purified yeast fructose-1,6-bisphosphatase was studied using purified preparations from yeast of two different cyclic AMP-independent protein kinases and a cyclic AMP-dependent protein kinase. Incorporation of 32P into fructose-1,6-bisphosphatase could be demonstrated only with the cyclic AMP-dependent protein kinase. Phosphorylation of fructose-1,6-bisphosphatase was stimulated by 3 μM fructose-2,6-bisphosphate and inhibited by 1 mM 5′-AMP