Energy dependence of non-local potentials

Recently a variety of studies have shown the importance of including non-locality in the description of reactions. The goal of this work is to revisit the phenomenological approach to determining non-local optical potentials from elastic scattering. We perform a $\chi^2$ analysis of neutron elastic scattering data off $^{40}$Ca, $^{90}$Zr and $^{208}$Pb at energies $E \approx 5-40$ MeV, assuming a Perey and Buck or Tian, Pang, and Ma non-local form for the optical potential. We introduce energy and asymmetry dependencies in the imaginary part of the potential and refit the data to obtain a global parameterization. Independently of the starting point in the minimization procedure, an energy dependence in the imaginary depth is required for a good description of the data across the included energy range. We present two parameterizations, both of which represent an improvement over the original potentials for the fitted nuclei as well as for other nuclei not included in our fit. Our results show that, even when including the standard Gaussian non-locality in optical potentials, a significant energy dependence is required to describe elastic-scattering data.Comment: 6 pages, 3 figures, accepted by Phys. Rev. C Rapid Communicatio

Phacelia (Phacelia tanacetifolia Benth.) affects soil structure differently depending on soil texture

Aims: We studied the effects of Phacelia tanacetifolia, increasingly used as a cover-crop species in arable agricultural systems, upon soil structural properties in the context of two contrasting soil textures. We hypothesised there would be differential effects of the plants upon soil structure contingent on the texture. Methods: A sandy-loam and a clay soil were destructured by passing through 2 mm sieves, and planted with Phacelia in a replicated pot experiment, with associated unplanted controls. X-ray Computed Tomography was used to visualise and quantify the soil pore networks in 3D. Results: For the sandy-loam soil, there was no impact of plants upon aggregate size distribution porosity, pore connectivity, and pore surface density decreased in the presence of plants, whereas for the clay, there was a significant increase of aggregates <1000 μm, the porosity was constant, the pore-connectivity decreased, and surface density increased in the presence of plants. Conclusions: Plants can impact the structural genesis of soil depending on its inherent textural characteristics, leading to a differential development of pore architecture in different contexts. These results have implications both from an ecological perspective and in terms of the prescription of plants to remediate or condition soil structure in managed systems

The effects of long-term fertilizations on soil hydraulic properties vary with scales

Soil structural alterations instigated by cropping system conversion and fertilization change have been well documented, but how such alterations vary with scale remains elusive. We investigated this based on the Rothamsted long-term wheat experiment (since 1843) in the UK. Triplicate cores 7cm high and 10cm in diameter were taken from plots that have been under different fertilizations and returned to natural woodland for more than one century for imaging with X-ray computed tomography at resolution of 40µm. We then broke each core and sampled three aggregates from it to scan them at resolution of 1.5µm. For each core or aggregate sample, we calculated its pore size distribution, as well as permeability and tortuosity from pore-scale simulations. The results showed that the fertilization change more than 170 years ago reshaped the soil structure but differently between the core scale and aggregate scale. Macro-porosity of the pores (>40µm) in the cores unfertilized or fertilized with inorganic fertilizers were low and poorly connected in the top 10cm of soil, compared to the cores given farmyard manure or in the woodland. In all treatments, the large macropores in the cores were hydraulically anisotropic with their permeability being higher in the horizontal direction than in the vertical direction, whereas the aggregates were comparatively isotropic. The fertilization affected porosity and permeability of macropores at core scale more significantly than those at aggregate scale, and the aggregates fertilized with farmyard manure and in the woodland were more permeable than aggregates in other treatments. It is also found that, compared to no-fertilization or fertilization with complete fertilizers, fertilizing without phosphorus over the past 20 years increased the porosity and permeability of the aggregates but not of the cores. Fertilization with inorganic fertilizers increased tortuosity of the macropores in the cores but not of the intra-aggregates micropores, compared to no-fertilization. Porosity-permeability relationship for aggregates unfertilized or fertilized with inorganic fertilisers follows a power law with R2 > 0.8. In contrast, the permeability of aggregates in farmyard manure and in the woodland trended differently with the porosity. Aggregates and cores responded differently to carbon in that, with soil carbon increasing, the permeability of the aggregates increased asymptotically while the permeability of the cores increased approximately exponentially. Since soil structure is indicators of soil quality and evolves slowly, our results have important implications for understanding how agronomical practice changes reshape soil structure at different scales as well as the long-term consequence for hydrological and biochemical processes

Significant structural evolution of a long-term fallow soil in response to agricultural management practices requires at least 10 years after conversion at the aggregate level

Agricultural practices can have significant effects on the physical and biological properties of soil. The aim of this study was to understand how the physical structure of a compromised soil, arising from long-term bare-fallow management, was modified by adopting different field management practices. We hypothesised that changing agricultural practice from bare-fallow to arable or grassland would influence the modification of pore structure via an increase in porosity, pore connectivity, and a more homogenous distribution of pore sizes; and that this change exerts a rapid development of soil structure following conversion. Soil aggregates (< 2 mm) collected in successive years from field plots subjected to three contrasting managements were studied; viz. bare-fallow, bare-fallow converted to arable, and bare-fallow converted to grassland. Soil structure was assessed by X-ray Computed Tomography on the aggregates at 1.5 µm resolution, capturing detail relevant to soil biophysical processes. The grassland system increased porosity, diversity of pore sizes, pore-connectivity and pore-surface density significantly over the decade following conversion. However, measured at this resolution, the development of most of these metrics of soil structure required approximately 10 years post-conversion to show a significant effect. The arable system did not influence soil structural development significantly. Only the pore size distribution was modified in grassland in a shorter time frame (2 years post-conversion). Hence development of the soil structural characteristics appears to require at least a decadal timescale following conversion to grassland

Soil as an Extended Composite Phenotype of the Microbial Metagenome

We use a unique set of terrestrial experiments to demonstrate how soil management practises result in emergence of distinct associations between physical structure and biological functions. These associations have a significant effect on the flux, resilience and efficiency of nutrient delivery to plants (including water). Physical structure determining the air-water balance in soil as well as transport rates is influenced by nutrient and physical interventions. Contrasting emergent soil structures exert selective pressures upon the microbiome metagenome. These selective pressures are associated with the quality of organic carbon inputs, the prevalence of anaerobic microsites and delivery of nutrients to microorganisms attached to soil surfaces. This variety results in distinctive gene assemblages characterising each state. The nature of the interactions provide evidence that soil behaves as an extended composite phenotype of the resident microbiome, responsive to the input and turnover of plant-derived organic carbon. We provide new evidence supporting the theory that soil-microbe systems are self-organising states with organic carbon acting as a critical determining parameter. This perspective leads us to propose carbon flux, rather than soil organic carbon content as the critical factor in soil systems, and we present evidence to support this view

Cover crop species have contrasting influence upon soil structural genesis and microbial community phenotype

Cover crops (plants grown in an agricultural rotation between cash crops) can significantly improve soil quality via sequestering carbon, retaining nutrients, decreasing soil erosion, and maintaining belowground biodiversity. However, little is known about the effects of such plants upon soil structure. The aim of the study was to assess the impact of four species typically used as cover crops and which have contrasting root architecture (viz. clover, black oat, phacelia, tillage radish) on soil structural genesis and the associated modification of microbial community structure in a clay soil. The four plant species were grown in a replicated pot experiment with sieved soil (<2 mm), with unplanted soil as control for 8 weeks. X-ray Computed Tomography was used to quantify the formation of pore networks in 3D and phospholipid fatty acid analysis was performed to characterise the microbial community phenotype. Black oats developed a greater soil-pore connectivity than the other species throughout the growth period, whereas phacelia decreased both the porosity and pore-connectivity. The microbial community phenotype under phacelia was notably different from the other species, with a greater proportion of fungal markers. Thus, different plant species have differential effects upon soil structural genesis and microbial community phenotype, which provides evidence that certain species may be more suitable as cover crops in terms of soil structural conditioning depending upon specific contexts

Treatment of chronic hepatitis C in patients unresponsive to interferon. Interest of re-treatment combining interferon induction therapy and ribavirin (a multicenter pilot study)

Aim About 45% of patients with chronic hepatitis C are unresponsive to the present reference treatment combining pegelated interferon plus ribavirin; before pegylated interferon was available the non-response rate was around 60%. This open multicenter pilot study, initiated before pegylated interferon became available, was designed to evaluate, in patients unresponsive to interferon monotherapy, the rate of biological and virological response and side-effects of the ribivirin- alpha 2b interferon combination. Methods The combination protocol was ribavirin (1 to 1.2 g/d) plus alpha 2b interferon at induction doses (9 MU/d the first week; 4.5 MU/d the eleven following weeks; 3 MU/2 days the 36 following weeks). Results Among the 27 included patients, 17 (63%) were viremia-negative (PCR) after 12 weeks of treatment, 9 (33%) were complete responders (undetectable viremia and normal transaminases) at the end of treatment (48 weeks) and of follow-up (72 weeks). Patients with non-1, non-4 genotypes who derived full benefit from this therapeutic strategy (6/7 (86%) were complete responders: 4/5 with genotype 3 and 2/2 with genotype 5). Quality-of-life was impaired during treatment, especially during the first 12 weeks of high-dose interferon therapy. Conclusion While waiting for new therapeutic possibilities, these good results suggest interferon induction at the beginning of treatment remains a valid option

Lattice distortions in a sawtooth chain with Heisenberg and Ising bonds

An exactly solvable model of the sawtooth chain with Ising and Heisenberg bonds and with coupling to lattice distortion for Heisenberg bonds is considered in the magnetic field. Using the direct transfer-matrix formalism an exact description of the thermodynamic functions is obtained. The ground state phase diagrams for all regions of parameters values containing phases corresponding to the magnetization plateaus at $M=0,1/4$ and 1/2 have been obtained. Exact formulas for bond distortions for various ground states are presented. A novel mechanism of magnetization plateau stabilization corresponding to $M=1/4$ state is reported.Comment: 16 pages, 12 figure

Nucleation of Al3Zr and Al3Sc in aluminum alloys: from kinetic Monte Carlo simulations to classical theory

Zr and Sc precipitate in aluminum alloys to form the compounds Al3Zr and Al3Sc which for low supersaturations of the solid solution have the L12 structure. The aim of the present study is to model at an atomic scale this kinetics of precipitation and to build a mesoscopic model based on classical nucleation theory so as to extend the field of supersaturations and annealing times that can be simulated. We use some ab-initio calculations and experimental data to fit an Ising model describing thermodynamics of the Al-Zr and Al-Sc systems. Kinetic behavior is described by means of an atom-vacancy exchange mechanism. This allows us to simulate with a kinetic Monte Carlo algorithm kinetics of precipitation of Al3Zr and Al3Sc. These kinetics are then used to test the classical nucleation theory. In this purpose, we deduce from our atomic model an isotropic interface free energy which is consistent with the one deduced from experimental kinetics and a nucleation free energy. We test di erent mean-field approximations (Bragg-Williams approximation as well as Cluster Variation Method) for these parameters. The classical nucleation theory is coherent with the kinetic Monte Carlo simulations only when CVM is used: it manages to reproduce the cluster size distribution in the metastable solid solution and its evolution as well as the steady-state nucleation rate. We also find that the capillary approximation used in the classical nucleation theory works surprisingly well when compared to a direct calculation of the free energy of formation for small L12 clusters.Comment: submitted to Physical Review B (2004

Cardiac investigations in sudden unexpected death in DEPDC5-related epilepsy

Objective: Germline loss-of-function mutations in DEPDC5, and in its binding partners (NPRL2/3) of the mammalian target of rapamycin (mTOR) repressor GATOR1 complex, cause focal epilepsies and increase the risk of sudden unexpected death in epilepsy (SUDEP). Here, we asked whether DEPDC5 haploinsufficiency predisposes to primary cardiac defects that could contribute to SUDEP and therefore impact the clinical management of patients at high risk of SUDEP. Methods: Clinical cardiac investigations were performed in 16 patients with pathogenic variants in DEPDC5, NPRL2, or NPRL3. Two novel Depdc5 mouse strains, a human HA-tagged Depdc5 strain and a Depdc5 heterozygous knockout with a neuron-specific deletion of the second allele (Depdc5c/−), were generated to investigate the role of Depdc5 in SUDEP and cardiac activity during seizures. Results: Holter, echocardiographic, and electrocardiographic (ECG) examinations provided no evidence for altered clinical cardiac function in the patient cohort, of whom 3 DEPDC5 patients succumbed to SUDEP and 6 had a family history of SUDEP. There was no cardiac injury at autopsy in a postmortem DEPDC5 SUDEP case. The HA-tagged Depdc5 mouse revealed expression of Depdc5 in the brain, heart, and lungs. Simultaneous electroencephalographic–ECG records on Depdc5c/− mice showed that spontaneous epileptic seizures resulting in a SUDEP-like event are not preceded by cardiac arrhythmia. Interpretation: Mouse and human data show neither structural nor functional cardiac damage that might underlie a primary contribution to SUDEP in the spectrum of DEPDC5-related epilepsies. ANN NEUROL 2022;91:101–11