2,847 research outputs found
Giant Magnetic Moments of Nitrogen Stabilized Mn Clusters and Their Relevance to Ferromagnetism in Mn Doped GaN
Using first principles calculations based on density functional theory, we
show that the stability and magnetic properties of small Mn clusters can be
fundamentally altered by the presence of nitrogen. Not only are their binding
energies substantially enhanced, but also the coupling between the magnetic
moments at Mn sites remains ferromagnetic irrespective of their size or shape.
In addition, these nitrogen stabilized Mn clusters carry giant magnetic moments
ranging from 4 Bohr magnetons in MnN to 22 Bohr magnetons in Mn_5N. It is
suggested that the giant magnetic moments of Mn_xN clusters may play a key role
in the ferromagnetism of Mn doped GaN which exhibit a wide range (10K - 940K)
of Curie temperatures
Magnetotransport properties of a polarization-doped three-dimensional electron slab
We present evidence of strong Shubnikov-de-Haas magnetoresistance
oscillations in a polarization-doped degenerate three-dimensional electron slab
in an AlGaN semiconductor system. The degenerate free carriers
are generated by a novel technique by grading a polar alloy semiconductor with
spatially changing polarization. Analysis of the magnetotransport data enables
us to extract an effective mass of and a quantum
scattering time of . Analysis of scattering processes helps
us extract an alloy scattering parameter for the AlGaN material
system to be
A C-Function For Non-Supersymmetric Attractors
We present a c-function for spherically symmetric, static and asymptotically
flat solutions in theories of four-dimensional gravity coupled to gauge fields
and moduli. The c-function is valid for both extremal and non-extremal black
holes. It monotonically decreases from infinity and in the static region
acquires its minimum value at the horizon, where it equals the entropy of the
black hole. Higher dimensional cases, involving -form gauge fields, and
other generalisations are also discussed.Comment: References adde
Response analysis of cracked structure subjected to transit mass – a parametric study
This work is focused on determining the response of a multi-cracked structure in the presence of different types of cracks vibrated due to a transit mass. The open transverse and inclined edge cracks of random crack depth are present at various locations of the cracked structure. The mass is moving on the beam at the different critical speeds of the structure. Runge-Kutta fourth order method is employed to evaluate the response of the structure numerically. The significance of different factors like the magnitude of the moving mass, moving speed, crack depth, crack inclination angle and their effects on the response of the deteriorated structure are investigated. Numerical analyses with numerous examples are carried out and validated the results with finite element analysis (FEA) and experimental investigations
An all-electron density functional theory study of the structure and properties of the neutral and singly charged M-12 and M-13 clusters: M = Sc-Zn
The electronic and geometrical structures of the M 12 and M 13 clusters where M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn along with their singly negatively and positively charged ions are studied using all-electron density functional theory within the generalized gradient approximation. The geometries corresponding to the lowest total energy states of singly and negatively charged ions of V13, Mn12, Co12, Ni 13, Cu 13, Zn 12, and Zn 13 are found to be different from the geometries of the corresponding neutral parents. The computed ionizationenergies of the neutrals, vertical electron detachment energies from the anions, and energies required to remove a single atom from the M 13 and M 13 + clusters are in good agreement with experiment. The change in a total spin magnetic moment of the cation or anion with respect to a total spin magnetic moment of the corresponding neutral is consistent with the one-electron model in most cases, i.e., they differ by ±1.0 μ B. Exceptions are found only for Sc12 −, Ti12 +, Mn12 −, Mn12 +, Fe12 −, Fe13 +, and Co12 +
Cyanobacteria and Algae-Derived Bioactive Metabolites as Antiviral Agents: Evidence, Mode of Action, and Scope for Further Expansion; A Comprehensive Review in Light of the SARS-CoV-2 Outbreak
COVID-19—a severe acute respiratory syndrome disease caused by coronavirus 2 (SARS-CoV-2)—has recently attracted global attention, due to its devastating impact, to the point of being declared a pandemic. The search for new natural therapeutic drugs is mandatory, as the screening of already-known antiviral drugs so far has led to poor results. Several species of marine algae have been reported as sources of bioactive metabolites with potential antiviral and immunomodulatory activities, among others. Some of these bioactive metabolites might be able to act as antimicrobial drugs and also against viral infections by inhibiting their replication. Moreover, they could also trigger immunity against viral infection in humans and could be used as protective agents against COVID-In this context, this article reviews the main antiviral activities of bioactive metabolites from marine algae and their potential exploitation as anti-SARS-CoV-2 drugs
Preliminary investigation of the antioxidant, anti-diabetic, and anti-inflammatory activity of Enteromorpha intestinalis extracts
Marine algae are a promising source of potent bioactive agents against oxidative stress, diabetes, and inflammation. However, the possible therapeutic effects of many algal metabolites have not been exploited yet. In this regard, we explored the therapeutic potential of Enteromorpha intestinalis extracts obtained from methanol, ethanol, and hexane, in contrasting oxidative stress. The total phenolic (TPC) and flavonoids (TFC) content were quantified in all extracts, with ethanol yielding the best values (about 60 and 625 mg of gallic acid and rutin equivalents per gram of extract, respectively). Their antioxidant potential was also assessed through DPPH•, hydroxyl radical, hydrogen peroxide, and superoxide anion scavenging assays, showing a concentration-dependent activity which was greater in the extracts from protic and more polar solvents. The α-amylase and α-glucosidase activities were estimated for checking the antidiabetic capacity, with IC50 values of about 3.8 μg/mL for the methanolic extract, almost as low as those obtained with acarbose (about 2.8 and 3.3 μg/mL, respectively). The same extract also showed remarkable anti-inflammatory effect, as determined by hemolysis, protein denaturation, proteinase and lipoxygenase activity assays, with respectable IC50 values (about 11, 4, 6, and 5 μg/mL, respectively), also in comparison to commercially used drugs, such as acetylsalicylic acid
Mitochondrial ATPase 6/8 genes to infer the population genetic structure of silver pomfret fish Pampus argenteus along the Indian waters
Silver pomfret, Pampus argenteus is an economically important seafood species. The fishery
resource of pomfret in Indian waters shows a dwindling catch since the last few years and the
pomfrets caught were mostly undersized which calls for immediate attempts for management
of resources. An accurate definition of population structure is important for management of
this species. The genetic stock structure of P. argenteus distributed along Indian coast was
identified using analysis of 842 bp of complete ATPase 6/8 genes of mitochondrial DNA.
Altogether, 83 silver pomfret (P. argenteus) collected from 4 locations along Indian coast
(Gujarat, Kerala, Tamil Nadu and West Bengal) were sequenced. Twenty four haplotypes were
identified among 83 individuals with haplotype diversity (0.87) and nucleotide diversity
(0.0025). The significant pair-wise FST and AMOVA values, between samples from West Bengal
(east coast) and other locations along the west coast (Gujarat and Kerala) indicated the
occurrence of distinct population structure in silver pomfret along the coast
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