422 research outputs found
The generalized gradient approximation kernel in time-dependent density functional theory
A complete understanding of a material requires both knowledge of the excited
states as well as of the ground state. In particular, the low energy
excitations are of utmost importance while studying the electronic, magnetic,
dynamical, and thermodynamical properties of the material. Time-Dependent
Density Functional Theory (TDDFT), within the linear regime, is a successful
\textit{ab-initio} method to access the electronic charge and spin excitations.
However, it requires an approximation to the exchange-correlation (XC) kernel
which encapsulates the effect of electron-electron interactions in the
many-body system. In this work we derive and implement the spin-polarized XC
kernel for semi-local approximations such as the adiabatic Generalized Gradient
Approximation (AGGA). This kernel has a quadratic dependence on the wavevector,
{\bf q}, of the perturbation, however the impact of this on the electron energy
loss spectra (EELS) is small. Although the GGA functional is good in predicting
structural properties, it generality overestimates the exchange spin-splitting.
This leads to higher magnon energies, as compared to both ALDA and experiment.
In addition, interaction with the Stoner spin-flip continuum is enhanced by
AGGA, which strongly suppresses the intensity of spin-waves.Comment: 11 pages, 7 figure
Effet de la salinité sur la croissance et la production de biomasse de deux provenances de Jatropha curcas L. cultivés en serre
La salinisation des sols est un processus important de dĂ©gradation des sols. Ce phĂ©nomĂšne ne cesse de prendre de lâampleur. Il affecte la croissance et le rendement des cultures. Lâutilisation dâespĂšces Ă usages multiples telle que Jatropha curcas L. et capable de se dĂ©velopper dans ces milieux est dâune importance capitale. Cette Ă©tude a portĂ© sur lâeffet de diffĂ©rentes concentrations de NaCl (0 g/l, 2 g/l, 4 g/l, 8 g/l, 16 g/l et 35 g/l) pendant une durĂ©e de 42 jours sur des jeunes plants de deux provenances (Nioro et Kaffrine) de Jatropha curcas L en condition de serre vitrĂ©e. La tolĂ©rance des deux provenances par rapport aux diffĂ©rentes concentrations de NaCl a Ă©tĂ© Ă©tudiĂ©e en tenant compte des paramĂštres de croissance et de rendement. Les rĂ©sultats ont montrĂ© que la hauteur des tiges, le diamĂštre au collet, la biomasse sĂšche des parties aĂ©riennes et des parties racinaires Ă©valuĂ©s Ă la fin de lâexpĂ©rience varient en fonction du niveau du stress salin. Les deux provenances ont montrĂ© une tolĂ©rance Ă la salinitĂ© manifestĂ©e par la rĂ©duction dâun appareil aĂ©rien et racinaire important. La provenance Nioro prĂ©sente une croissance des organes aĂ©riens plus importante que celle de Kaffrine. Cependant, la provenance Kaffrine produit plus de biomasse sĂšche aĂ©rienne. Cette diffĂ©rence se situe au niveau de la quantitĂ© de biomasse sĂšche apportĂ©e par les tiges.Mots clĂ©s : Stress salin, croissance, biomasse, Jatropha curcas L., provenance
Economic dynamics of tissue cultured strawberry (FragariaĂ ananassa) under the influence of integrated plant nutrients in humid sub tropical hills of North Eastern India
Satisfactory and sustainable level of agricultural production can be achieved by combined application of inorganic fertilizers with organic manures, bio-fertilizers, bio-regulators and vermicompost. A field experiment was conducted during 2010-12 at experimental farm, Department of Horticulture, Aromatic and Medicinal Plants, Mizoram University, Aizawl, India, to find out the profitability of tissue cultured strawberry (Fragaria Ă ananassa Duch.) (cv. Festival) cultivation by using various integrated plant nutrient system (IPNS) combining inorganic fertilizers with organic manures, bio-fertilizers and bio-regulators. The response of IPNS on economics of strawberry indicated that the overall cost of cultivation as well as economics of strawberry production was significantly influenced by integration of various components. Among the different treatments, the highest expenditure of Rupees 2 077 576.83/ha was incurred in 100% RDF + vermicompost as against the lowest in control. With respect to the income, the highest net income of Rupees 7 298 119.27/ha was obtained in 75 % RDF + vermicompost + Azospirillum + PSB + 50 ppm GA3+50 ppm BA. The same treatment also recorded the highest cost benefit ratio of 1: 3.51
Economic analysis of tissue cultured banana (Musa Ă paradisiaca) production under the influence of integrated nutrient management
An experiment was conducted to evaluate various integrated nutrient management packages to evaluate the yield, quality and economics of banana (Musa Ă paradisaca L.) cultivation during 2008-2010. The response of INM on economics of tissue cultured banana cv. Grand Naine indicated that the overall cost of cultivation as well as economics of banana production was significantly influenced by integration of biofertilizers, organic manure and inorganic fertilizers. Among the different treatments, highest expenditure of âč 264 110.00 per ha was incurred in 100% RDF + VAM + Azospirillum + PSB + Trichoderma harzianum. However, the same treatment recorded the highest gross as well as net income. In spite of maximum cost of cultivation, the highest cost benefit ratio of 4.22:1 was also recorded in this treatment, followed by 75% RDF +VAM + Azospirillum + PSB + Trichoderma harzianum
Thawing Versus. Tracker Behaviour: Observational Evidence
Currently there is a variety of scalar field models to explain the late time
acceleration of the Universe. This includes the standard canonical and
non-canonical scalar field models together with recently proposed Galileon
scalar field models. One can divide all these scalar field models into two
broad categories, namely the thawing and the tracker class. In this work we
investigate the evidence for these models with the presently available
observational data using the Bayesian approach. We use the Generalized
Chaplygin Gas (GCG) parametrization for dark energy equation of state (EoS) as
it gives rise to both the thawing and tracking behaviours for different values
of the parameters. Analysis of the observational data does not give any clear
evidence for either thawing or tracking behaviour within the context of
background cosmology, However, if we consider the evolution of inhomogenities
and analyze the data in this context then there is a significant evidence in
favour of thawing behaviour.Comment: 6 Pages, three eps figures, new material added, new references added.
Conclusion changed. Accepted for publication MNRA
Deviation From \Lambda CDM With Cosmic Strings Networks
In this work, we consider a network of cosmic strings to explain possible
deviation from \Lambda CDM behaviour. We use different observational data to
constrain the model and show that a small but non zero contribution from the
string network is allowed by the observational data which can result in a
reasonable departure from \Lambda CDM evolution. But by calculating the
Bayesian Evidence, we show that the present data still strongly favour the
concordance \Lambda CDM model irrespective of the choice of the prior.Comment: 15 Pages, Latex Style, 4 eps figures, Revised Version, Accepted for
publication in European Physical Journal
Perceptions of change in the environment caused by the COVID-19 pandemic: implications for environmental policy
COVID-19 lockdown measures have impacted the environment with both positive and negative effects. However, how human populations have perceived such changes in the natural environment and how they may have changed their daily habits have not been yet thoroughly evaluated. The objectives of this work were to investigate (1) the social perception of the environmental changes produced by the COVID-19 pandemic lockdown and the derived change in habits in relation to i) waste management, energy saving, and sustainable consumption, ii) mobility, iii) social inequalities, iv) generation of noise, v) utilization of natural spaces, and, vi) human population perception towards the future, and (2) the associations of these potential new habits with various socio-demographic variables. First, a SWOT analysis identified strengths (S), weaknesses (W), opportunities (O), and threats (T) generated by the pandemic lockdown measures. Second, a survey based on the aspects of the SWOT was administered among 2370 adults from 37 countries during the period from February to September 2021. We found that the short-term positive impacts on the natural environment were generally well recognized. In contrast, longer-term negative effects arise, but they were often not reported by the survey participants, such as greater production of plastic waste derived from health safety measures, and the increase in e-commerce use, which can displace small storefront businesses. We were able to capture a mismatch between perceptions and the reported data related to visits to natural areas, and generation of waste. We found that age and country of residence were major contributors in shaping the survey participants ÂŽanswers, which highlights the importance of government management strategies to address current and future environmental problems. Enhanced positive perceptions of the environment and ecosystems, combined with the understanding that livelihood sustainability, needs to be prioritized and would reinforce environmental protection policies to create greener cities. Moreover, new sustainable jobs in combination with more sustainable human habits represent an opportunity to reinforce environmental policy
Bacterial Distribution in the Rhizosphere of Wild Barley under Contrasting Microclimates
Background: All plants in nature harbor a diverse community of rhizosphere bacteria which can affect the plant growth. Our samples are isolated from the rhizosphere of wild barley Hordeum spontaneum at the Evolution Canyon (âECâ), Israel. The bacteria which have been living in close relationship with the plant root under the stressful conditions over millennia are likely to have developed strategies to alleviate plant stress. Methodology/Principal Findings: We studied distribution of culturable bacteria in the rhizosphere of H. spontaneum and characterized the bacterial 1-aminocyclopropane-1-carboxylate deaminase (ACCd) production, biofilm production, phosphorus solubilization and halophilic behavior. We have shown that the H. spontaneum rhizosphere at the stressful South Facing Slope (SFS) harbors significantly higher population of ACCd producing biofilm forming phosphorus solubilizing osmotic stress tolerant bacteria. Conclusions/Significance: The long-lived natural laboratory âEC â facilitates the generation of theoretical testable and predictable models of biodiversity and genome evolution on the area of plant microbe interactions. It is likely that the bacteria isolated at the stressful SFS offer new opportunities for the biotechnological applications in our agro-ecologica
- âŠ