Pressure induced electronic topological transition in Sb2S3

Pressure induced electronic topological transitions in the wide band gap semiconductor Sb2S3 (Eg = 1.7-1.8 eV) with similar crystal symmetry (SG: Pnma) to its illustrious analog, Sb2Se3, has been studied using Raman spectroscopy, resistivity and the available literature on the x-ray diffraction studies. In this report, the vibrational and the transport properties of Sb2S3 have been studied up to 22 GPa and 11 GPa, respectively. We observed the softening of phonon modes Ag(2), Ag(3) and B2g and a sharp anomaly in their line widths at 4 GPa. The resistivity studies also shows an anomaly around this pressure. The changes in resistivity as well as Raman line widths can be ascribed to the changes in the topology of the Fermi surface which induces the electron-phonon and the strong phonon-phonon coupling, indicating a clear evidence of the electronic topological transition (ETT) in Sb2S3. The pressure dependence of a/c ratio plot obtained from the literature showed a minimum at ~ 5 GPa, which is consistent with our high pressure Raman and resistivity results. Finally, we give the plausible reasons for the non-existence of a non-trivial topological state in Sb2S3 at high pressures.Comment: 24 pages, 6 Figures, 2 tables submitted for publicatio

Sorgoleone release from sorghum roots shapes the composition of nitrifying populations, total bacteria, and archaea and determines the level of nitrification

Sorgoleone is a secondary sorghum metabolite released from roots. It has allelopathic properties and is considered to inhibit ammonia-oxidizing archaea (AOA) and bacteria (AOB) responsible for the rate-limiting step (ammonia oxidation) in nitrification. Low activity of these microorganisms in soil may contribute to slow down nitrification and reduce nitrogen loss via denitrification and NO3 − leaching. The potential nitrification rate (PNR) and the composition of microbial communities were monitored in rhizosphere soil to investigate the growth effect sorghum on biological nitrification inhibition (BNI). A greenhouse pipe experiment was conducted using sorghum lines IS20205 (highsorgoleone release ability), IS32234 (medium-sorgoleone release ability), 296B (low-sorgoleone release ability), and a control (no plants) combined with fertilization application of 0 or 120 kg N ha−1. We applied nitrogen as ammonium sulfate at 16 days (20 N), 37 days (40 N), and 54 days (60 N). We collected soil solutions at 7.5 cm depths every 3 days and measured the pH and nitrate levels. At 1 and 2.3 months, we sampled the bulk and rhizosphere soils and roots in the 0–10 cm, 10–30 cm, and 30–80 cm depths to determine NO2, mineral N, total N, total C, sorgoleone, the composition of AOA, AOB, and total bacteria and archaea. Sorgoleone was continuously released throughout the 2.3 months’ growth and was significantly higher in IS20205, followed by IS32234 then 296B, which showed shallow levels. The IS2020 5rhizosphere showed lower NO2 and nitrate levels and significant inhibition of AOA populations. However, we did not find significant differences in the abundance of AOB between plant treatments. Multivariate analysis and Spearman’s correlations revealed that sorgoleone as well as environmental factors such as soil pH, soil moisture, NO3 −-N, and NH4 +- N shape the composition of microbial communities. This study demonstrated that the release of higher amounts of sorgoleone has great potential to inhibit the abundance of AOA and soil nitrification. The breeding of sorghum lines with the ability to release higher amounts of sorgoleone could be a strategic way to improve the biological nitrification inhibition during cultivation

Patterns of osmotic adjustment in pigeonpea — its importance as a mechanism of drought resistance

Osmotic adjustment (OA) is considered as an important physiological mechanism of drought adaptation in many crop plants. The present investigation was aimed at assessing the importance of OA in improving productivity under drought. Using two automated rain-out shelters, 26 extra-short-duration pigeonpea [Cajanus cajan (L.) Millsp.] genotypes were grown with irrigation during the growth period or with water deficit imposed from flowering until maturity. Mean leaf Ψs100 (60–92 DAS) under drought correlated significantly (r2=0.72**; n=26) to the mean OA (60–92 DAS) and contributed 72% of the genotypic variation in OA. Significant genotypic variation was observed in the initiation of OA, the duration of OA and the degree of OA. Based on the measured OA at 72, 82, and 92 days after sowing (DAS), genotypes were grouped into five different clusters. Genotypic differences in total dry matter production under drought were positively associated with OA at 72 DAS (r2=0.36**, n=26). Significant positive relationship between OA at 72 DAS and grain yield under drought was found (r2=0.16*; n=26). However, OA towards the end of pod filling phase, i.e. at 92 DAS, had a significant negative relationship with grain yield under drought (r2=0.21*; n=26). Genotypic differences in grain yield under drought was best explained using stepwise multiple regression to account for differences in OA at 72, 82, and 92 DAS (r2=0.41**; n=78). The degree of OA at 72 and 82 DAS contributed positively to the grain yield, whereas OA at 92 DAS contributed negatively to this relationshi

On Witten multiple zeta-functions associated with semisimple Lie algebras IV

In our previous work, we established the theory of multi-variable Witten zeta-functions, which are called the zeta-functions of root systems. We have already considered the cases of types $A_2$, $A_3$, $B_2$, $B_3$ and $C_3$. In this paper, we consider the case of $G_2$-type. We define certain analogues of Bernoulli polynomials of $G_2$-type and study the generating functions of them to determine the coefficients of Witten's volume formulas of $G_2$-type. Next we consider the meromorphic continuation of the zeta-function of $G_2$-type and determine its possible singularities. Finally, by using our previous method, we give explicit functional relations for them which include Witten's volume formulas.Comment: 22 pag

Importance of Canopy Attributes in Determining Dry Matter Accumulation of Pigeonpea under Contrasting Moisture Regimes

Using two automated rain-out shelters, 6 genotypes of pigeon peas (Cajanus cajan) were grown under well-watered conditions or with water deficit imposed from flowering until maturity at the ICRISAT Asia Center, India. Water deficit significantly decreased the cumulative intercepted photosynthetically active radiation (CIR). The relationship between biomass accumulation and CIR was linear and water deficit affected the slope of the relationship (i.e., radiation use efficiency, RUE) (b = 1.92 g MJ sup(-1) for well watered vs. 1.43 g MJ sup(-1) for water deficit). Genotypes differed in RUE under well watered (1.70-2.19 g MJ sup(-1)) and moisture deficit (1.30-1.66 g MJ sup(-1)) conditions. Genotypic variation in canopy attributes was significant. Leaf area duration significantly correlated with crop growth rate (CGR) only under well watered conditions. Cumulative intercepted radiation and RUE accounted for nearly 99% of the genotypic variation in CGR under both moisture regimes, of which RUE alone contributed nearly 90%. Variation among genotypes in CIR alone did not explain the differences in dry matter accumulation under either moisture regime. Only RUE explained more than 90% of the genotypic variation in CGR and 70% in total dry matter under both moisture regimes. The results indicated that RUE is critical in determining pigeonpea productivity under well-watered and moisture-deficit regimes

Further insights into underlying mechanisms for the release of biological nitrification inhibitors from sorghum roots

Background Sorghum roots release two categories of biological nitrification inhibitors (BNIs) – hydrophilic-BNIs and hydrophobic-BNIs. Earlier research indicated that rhizosphere pH and plasma membrane (PM) H+ATPase are functionally linked with the release of hydrophilic BNIs, but the underlying mechanisms are not fully elucidated. This study is designed to reveal further insights into the regulatory mechanisms of BNIs release in root systems, using three sorghum genetic stocks. Methods Sorghum plants were grown in a hydroponic system with pH of nutrient solutions ranging from 3.0 ̴ 9.0. Pharmacological agents [(fusicoccin and vanadate) and anion-channel blockers (−niflumic acid (NIF) and anthracene-9-carboxylate (A9C)] were applied to root exudate collection solutions; BNI activity was determined with luminescent Nitrosomonas europaea bioassay. Sorgoleone levels in root exudates and H+ excretion from roots were determined. Two-phase partitioning system is used to isolate root plasma membrane (PM) and H+ ATPase activity was determined. Results A decrease in rhizosphere pH improved the release of hydrophilic-BNIs from roots of all the three sorghum genotypes, but had no effect on the release of hydrophobic-BNIs. Hydrophobic-BNI activity and sorgoleone levels in root-DCM wash are positively correlated. Fusicoccin promoted H+extrusion and stimulated the release of hydrophilic-BNIs. Vanadate, in contrast, suppressed H+ extrusion and lowered the release of hydrophilic-BNIs. Anion-channel blockers did not inhibit the release of hydrophilic BNIs, but enhanced H+-extrusion and hydrophilic-BNIs release. Conclusion Rhizosphere pH has a major influence on hydrophilic-BNIs release, but not on the release of hydrophobic-BNIs. The low rhizosphere pH stimulated PM-H+ ATPase activity; H+-extrusion is closely coupled with hydrophilic-BNIs release. Anion-channel blockers stimulated H+ extrusion and hydrophilic-BNIs release. Our results indicate that some unknown membrane transporters are operating the release of protonated BNIs, which may compensate for charge balance when transport of other anions is suppressed using anion-channel blockers. A new hypothesis is proposed for the release of hydrophilic-BNIs from sorghum roots

Potential for biological nitrification inhibition to reduce nitrification and N2O emissions in pasture crop-livestock systems

Agriculture and livestock production systems are two major emitters of greenhouse gases. Methane with a GWP (global warming potential) of 21, and nitrous oxide (N2O) with a GWP of 300, are largely emitted from animal production agriculture, where livestock production is based on pasture and feed grains. The principal biological processes involved in N2O emissions are nitrification and denitrification. Biological nitrification inhibition (BNI) is the natural ability of certain plant species to release nitrification inhibitors from their roots that suppress nitrifier activity, thus reducing soil nitrification and N2O emission. Recent methodological developments (e.g. bioluminescence assay to detect BNIs in plant root systems) have led to significant advances in our ability to quantify and characterize the BNI function. Synthesis and release of BNIs from plants is a highly regulated process triggered by the presence of NH4 + in the rhizosphere, which results in the inhibitor being released precisely where the majority of the soil-nitrifier population resides. Among the tropical pasture grasses, the BNI function is strongest (i.e. BNI capacity) in Brachiaria sp. Some feed-grain crops such as sorghum also have significant BNI capacity present in their root systems. The chemical identity of some of these BNIs has now been established, and their mode of inhibitory action on Nitrosomonas has been characterized. The ability of the BNI function in Brachiaria pastures to suppress N2O emissions and soil nitrification potential has been demonstrated; however, its potential role in controlling N2O emissions in agro-pastoral systems is under investigation. Here we present the current status of our understanding on how the BNI functions in Brachiaria pastures and feed-grain crops such as sorghum can be exploited both genetically and, from a production system's perspective, to develop low-nitrifying and low N2O-emitting production systems that would be economically profitable and ecologically sustainabl

Nitrogen Management in Grasslands and Forage-Based Production Systems–Role of Biological Nitrification Inhibition (BNI)

Nitrogen (N), being the most critical and essential nutrient for plant growth, largely determines the productivity in both extensive- and intensive- grassland systems. Nitrification and denitrification processes in the soil are the primary drivers generating reactive-N: NO3-, N2O, and NO, and is largely responsible for N-loss and degradation of grasslands. Suppressing nitrification can thus facilitate the retention of soil-N to sustain long-term productivity of grasslands and forage-based production systems. Certain plants can suppress soil nitrification by releasing inhibitors from roots, a phenomenon termed ‘biological nitrification inhibition’ (BNI). Recent methodological developments (e.g. bioluminescence assay to detect BNIs from plant-root systems) led to significant advances in our ability to quantify and characterize BNI function in pasture grasses. Among grass-pastures, BNI-capacity is strongest in low-N adapted grasses such as Brachiaria humidicola and weakest in high-N environment grasses such as Italian ryegrass (Lolium perenne) and B. brizantha. The chemical identity of some of the BNIs produced in plant tissues and released from roots has now been established and their mode of inhibitory action determined on nitrifying bacteria Nitrosomonas. Synthesis and release of BNIs is a highly regulated and localized process, triggered by the presence of NH4+ in the rhizosphere, which facilitates the release of BNIs close to soil-nitrifier sites. Substantial genotypic variation is found for BNI-capacity in B. humidicola, which opens the way for its geneticmanipulation. Field studies suggest that Brachiaria grasses suppress nitrification and N2O emissions from soil. The potential for exploiting BNI function (from a genetic improvement and a system perspective) to develop production systems that are low-nitrifying, low N2O-emitting, economically efficient and ecologically sustainable, will be the subject of discussion

Pathogenicity of highly pathogenic avian H5N1 influenza A viruses isolated from humans between 2003 and 2008 in northern Vietnam

Vietnam is one of the countries most affected by highly pathogenic H5N1 influenza A viruses. To evaluate the potential pathogenicity in mammals of H5N1 viruses isolated from humans in Vietnam, we determined the sequences of all eight genes of 22 human isolates collected between 2003 and 2008 and compared their virulence in mice. The isolates were classified into clade 1 and clade 2.3.4 and differed in pathogenicity for mice. Whilst lysine at position 627 of PB2 (PB2-627K) is a critical virulence determinant for clade 2.3.4 viruses, asparagine at position 701 of PB2 and other unknown virulence determinants appear to be involved in the high pathogenicity of clade 1 viruses, warranting further studies to determine the factors responsible for the high virulence of H5N1 viruses in mammals

Strategies for Improving Drought Resistance in Grain Legumes

This review distills recent information on drought resistance characteristics of grain legumes with a view toward developing appropriate genetic enhancement strategies for water-limited environments. First, the possible adaptations that allow grain legumes to better cope with drought stress are summarized. It is suggested that there are considerable gains to be made in increasing yield and yield stability in environments characterized by terminal drought stress by further exploiting drought escape, by shortening crop duration. Many traits conferring dehydration avoidance and dehydration tolerance are available, but integrated traits, expressing at a higher level of organization, are suggested to be more useful in crop improvement programs. Possible genetic improvement strategies are outlined, ranging from empirical selection for yield in droughted environments to a physiological genetic approach. It is suggested that in view of recent advances in understanding drought resistance mechanisms, the latter strategy is becoming more feasible. It is concluded that use of this recently derived knowledge in a systematic manner can lead to significant gains in yield and yield stability of the world's major grain legumes, as they are mainly grown (and will continue to be grown) under rain-fed conditions