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•RGO/Au nano-composite was synthesized by a one step solvothermal approach.•The nano composite modified electrode was applied for ultra trace determination Hg.•A protocol has been ...developed for the determination of p-methoxy phenol.•The composite material was applied for the decomposition of p-methoxy phenol.
A facile, one-step solvothermal approach has been utilized for the synthesis of a reduced graphene oxide/Au nanocomposite (RGO/Au) material. Deposition of Au nanoparticles (AuNPs) on the surface of reduced graphene oxide sheets has been realized by a simple reduction of Au precursors and graphite oxide (GO) in ethylene glycol (EG), without using any additional reductants and surfactants. The morphology of the RGO/Au nanocomposite was thoroughly examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The morphology of the RGO/Au nanocomposite was characterized by HRTEM and 20nm was the average size of the AuNPs obtained. The performance of the RGO/Au nanocomposite has been investigated in the application of the Hg determination at the trace/ultra trace level using differential pulse anodic stripping voltammetry. The composite material was also applied for the determination of p-methoxy phenol (PMP) and, most importantly, it was observed that the material was suitable for the decomposition of PMP by the electrochemical oxidation process. The three sigma detection limits for Hg2+ and PMP were obtained as 0.25μgL−1 and 0.64μM, respectively. The applicability of the RGO/Au nanocomposite was further extended to determine Hg2+ in soil samples. Chronoamperometric tests were carried out to investigate the performance of modified and unmodified electrodes in the decomposition of PMP by the electrochemical oxidation route.
A series of Sm and Mn co-doped nanoparticles are synthesized through ethylene glycol assisted sol–gel route to study the impact of both rare earth ions and Mn on the structural, magnetic and low ...temperature electronic behaviour in LaFeO
3
. The Rietveld analysis of X-ray diffraction data shows a single phase nature of the nanoparticle with distorted orthorhombic crystal structure. The unit cell volume reduces with increasing Mn, is due to the ionic radii differences between the cations which cause crystal lattice contraction because of the distortion of Fe/MnO
6
octahedra. Mostly, particles are agglomerated with an average particle size of 38.5 nm. From the XPS spectra, the existence of multivalence state of both Fe and Mn are obtained. This multiple state of transition metal ions along with Sm are expected to play a major role in the magnetic interactions and other related properties. A drastic magnetic disorder phase is acquired by the modified systems at low temperature as compared to the pure G-Type LaFeO
3
. Furthermore, the modified nanoparticle shows a colossal dielectric response (> 10
3
at 100 Hz) and the obtained dielectric relaxation follows mostly non-Debye type which is further confirmed through explicit modulus spectra analysis. From the impedance, modulus and ac-conductivity analysis, the conduction processes in the modified systems reveal a possible N-type and P-type polaronic conduction for both the grain and grain boundary.
Merits of atomic cascade computations Fritzsche, S.; Sahoo, A. K.; Sharma, L. ...
The European physical journal. D, Atomic, molecular, and optical physics,
06/2024, Letnik:
78, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Atomic cascades refer—first and foremost—to the stepwise de-excitation of excited atoms owing to the emission of electrons or photons. Apart from dedicated experiments at storage rings and ...synchrotrons, such cascades frequently occur in astro and plasma physics, material research, surface science and at various places elsewhere. In addition, moreover, “atomic cascades” have been found a useful concept for modeling atomic behavior under different conditions, for instance, when dealing with the photoabsorption of matter, the generation of synthesized spectra, or for determining a rather wide class of (plasma) rate coefficients. We here compile and discuss several atomic cascades (schemes) that help predict cross sections, rate coefficients, electron and photon spectra, or ion distributions. We also demonstrate how readily these schemes have been implemented within JAC, the Jena Atomic Calculator. Emphasis is placed on the classification of atomic cascades and their (quite) natural breakdown into cascade
computations
, to deal with the electronic structure and transition amplitudes of atoms and ions, as well as the cascade
simulation
of those properties and spectra, that are experimentally accessible. As an example, we show and discuss the computation of dielectronic recombination plasma rate coefficients for beryllium-like gold ions. The concept of atomic cascades and its implementation into JAC can be applied for most ions across the periodic table and will facilitate the modeling and interpretation of many forthcoming observations.
Graphical abstract
Efficient, cost effective and easy to use tools are needed for site specific management of soils for increasing the crop productivity. Currently nutrient management recommendations for rice in the ...study are typically uniform without consideration of spatial heterogeneity of nutrient content in soil. This study has emphasized the use of management zones (MZs) as an efficient method for variable application of fertilizers. Rajnagar Block of Kendrapada District in India was selected as the study area for the present study and 225 soil samples were collected on 1.5kilometer grids. Soil samples were analyzed for pH, electrical conductivity, soil organic carbon, available nitrogen, available phosphorous, available potassium DTPA extractable micronutrients i.e., iron, zinc, copper, and manganese. Spatial variability of these soil properties was analyzed and spatial distribution maps were generated using geostatistics and ordinary kriging technique. Further, principal component analysis and fuzzy c-means clustering algorithm were performed to delineate the management zones based on optimum clusters identified using fuzzy performance index (FPI) and normalized classification entropy (NCE). The results revealed that the optimum number of MZs for this study area was three and there was heterogeneity in soil nutrients in three MZs. The delineated MZs provide a basis of information for site-specific fertilizer management in the rice cultivated fields in the study area.
•Spatial variability of soil properties was quantified using geostatistics.•Fuzzy clustering was used to divide study area into three management zones (MZs).•There was heterogeneity in soil nutrients in three MZs.•MZs may be an efficient method for variable application of fertilizers in rice.
ABSTRACT
We report on the detection of pulsations of three pulsating subdwarf B stars observed by the Transiting Exoplanet Survey Satellite (TESS) satellite and our results of mode identification in ...these stars based on an asymptotic period relation. SB 459 (TIC 067584818), SB 815 (TIC 169285097), and PG 0342 + 026 (TIC 457168745) have been monitored during single sectors resulting in 27 d coverage. These data sets allowed for detecting, in each star, a few tens of frequencies that we interpreted as stellar oscillations. We found no multiplets, though we partially constrained mode geometry by means of period spacing, which recently became a key tool in analyses of pulsating subdwarf B stars. Standard routine that we have used allowed us to select candidates for trapped modes that surely bear signatures of non-uniform chemical profile inside the stars. We have also done statistical analysis using collected spectroscopic and asteroseismic data of previously known subdwarf B stars along with our three stars. Making use of high precision trigonometric parallaxes from the Gaia mission and spectral energy distributions we converted atmospheric parameters to stellar ones. Radii, masses, and luminosities are close to their canonical values for extreme horizontal branch stars. In particular, the stellar masses are close to the canonical one of 0.47 M⊙ for all three stars but uncertainties on the mass are large. The results of the analyses presented here will provide important constrains for asteroseismic modelling.
This work reports the tailoring of optical and magnetic properties in Sb-doped SnO
2
nanoparticles (NPs), i.e., Sn
1-x
Sb
x
O
2
(x = 0.0, 0.03, 0.06, 0.09) synthesized by gel-combustion technique. ...The structural properties of these nanoparticles are investigated by the X-ray diffraction (XRD) technique. Detailed structural analysis shows the crystallization of all these NPs in tetragonal rutile structure, as observed in pristine SnO
2
without any trace of the secondary phase. Nevertheless, the incorporation of Sb dopant was found to increase the lattice constant systematically. Investigation of surface morphology by scanning electron microscopy and particle size by transmission electron microscopy also indicates a systematic increase in the grain size and particle size with Sb doping. Intriguingly, bandgap and room-temperature ferromagnetism (RTFM) are found to be sensitive to particle size and oxygen vacancies. UV–visible absorption, Fourier transform infrared, photoluminescence, and X-ray photoelectron spectroscopic measurements are carried out to explore the underlying physical mechanisms. Besides, the increase in RTFM and decrease in the bandgap witnessed in Sb-doped SnO
2
NPs can be exploited for magneto-optic and spintronic devices.
Recent observations and numerical simulations have profoundly established that the C:N:P ratios in the ocean deviate from the canonical Redfield Ratio (106:16:1). Physical and biogeochemical ...processes have been hypothesized to be responsible for this deviation. However, a paucity of concurrent observations on biogeochemical and physical parameters have barred us to understand their exact role on the C:N:P ratios. For this purpose, we have sampled the Bay of Bengal for its C, N, and P contents in the organic and inorganic pools from 5 to 2000 m depth at eight stations (five coastal and three open ocean) during boreal spring 2019. Mesoscale anticyclonic eddies were identified at two of the sampling stations, where nutrient concentrations were lower in the top layer (5 m to the depth of chlorophyll maximum) compared to those at the non-eddy stations. Mean (NO
3
−
+NO
2
−
):PO
4
3−
ratio was lower at the anticyclonic eddy stations compared to that at the non-eddy stations in the top layer. Yet C:N:P ratios in the particulate and dissolved organic matter in the top layer were the same at anticyclonic eddy and non-eddy stations. Overall the mean C:N:P ratios were 249:39:1 in particulate organic matter and 2338:146:1 in dissolved organic matter in the top layer. Biological N
2
fixation was not a driver in controlling the N:P ratio of the export flux and the subsurface water nutrient ratios during spring. Although the Bay of Bengal receives large riverine influx, its influence in changing the C:N:P ratios was small during this study.
Nitrogen (N) and phosphorus (P) determine the strength of the ocean’s biological carbon (C) pump, and variation in the N:P ratio is key to phytoplankton growth. A fixed C:N:P ratio (106:16:1) in ...organic matter and deep-water nutrients was observed by Alfred C. Redfield. However, recent studies have challenged the concept of the Redfield Ratio, and its veracity remains to be examined in oceanic basins like the Bay of Bengal. For this purpose, we sampled the water in the Bay of Bengal for C, N, and P content in the organic and inorganic pools from the surface to 2000 m. Overall, the C:N:P ratio deviated greatly from the Redfield Ratio. The C:N:P ratio in particulate organic matter varied from 232:25:1 in the top layer (surface to the depth of the chlorophyll maximum) to 966:72:1 in the deep water (300–2000 m). In dissolved organic matter, the ratio varied from 357:30:1 in the top layer to 245:66:1 in the deep water. The N:P ratio in nutrients varied from 3 in the top layer to 12 in the deep water. The nutrient-depleted top layer (average NO₃⁻ + NO₂⁻ ~ 0.7 μmol l−1) with a low N:P ratio coupled with reported low primary production rates in the Bay suggested that the production was N limited. Concurrent N₂ fixation rates were not sufficient to alter the observed C:N:P ratio. Eddies showed a mixed effect on the C:N:P ratio. Our C:N:P ratios in particulate organic matter are comparable to other tropical basins and supports the nutrient supply hypothesis for low latitude ecosystems.
Alzheimer's disease (AD), a deleterious neurodegenerative disorder that impairs memory, cognitive functions and may lead to dementia in late stage of life. The pathogenic cause of AD remains ...incompletely understood and FDA approved drugs are partial inhibitors rather than curative. Most of drugs are synthetic or natural products as galanthamine is an alkaloid obtained from Galanthus spp. Huperzine A, an alkaloid found in Huperzia spp., gingkolides a diterpenoids from Gingko biloba and many ethnobotanicals like Withania somnifera (L.) Dunal., Physostigma venenosum Balf., Bacopa monnieri (L.) Wettst., Centella asiatica (L.) Urb. have been used by traditional Indian, Chinese, and European system of medicines in AD. Clinical significance opioid alkaloid in Papaver somniferum has shown another dimension to this study. Over exploitation of medicinal plants with limited bioactive principles has provided templates to design synthetic drugs in AD e.g. rivastigmine, phenserine, eptastigmine based on chemical structure of physostigmine of Physostigma venenosum Balf. Even ZT-1 a prodrug of Hup A and memogain a prodrug of galantamine has achieved new direction in drug development in AD. All these first-line cholinesterase-inhibitors are used as symptomatic treatments in AD. Single modality of “One-molecule-one-target” strategy for treating AD has failed and so future therapies on “Combination-drugs-multi-targets” strategy (CDMT) will need to address multiple aspects to block the progression of pathogenesis of AD. Besides, cholinergic and amyloid drugs, in this article we summarize proteinopathy-based drugs as AD therapeutics from a variety of biological sources. In this review, an attempt has been made to elucidate the molecular mode of action of various plant products, and synthetic drugs investigated in various preclinical and clinical tests in AD. It also discusses current attempts to formulate a comprehensive CDMT strategy to counter complex pathogenesis in AD.
Information were collected from classical books on medicinal plants, pharmacopoeias and scientific databases like PubMed, Scopus, GoogleScholar, Web of Science and electronic searches were performed using Cochrane Library, Medline and EMBASE. Also published scientific literatures from Elsevier, Taylor and Francis, Springer, ACS, Wiley publishers and reports by government bodies and documentations were assessed.
60 no. of natural and synthetic drugs have been studied with their significant bioactivities. A decision matrix designed for evaluation of drugs for considering to the hypothetic “CDMT” strategy in AD. We have introduced the scoring pattern of individual drugs and based on scoring pattern, drugs that fall within the scoring range of 18–25 are considered in the proposed CDMT. It also highlights the importance of available natural products and in future those drugs may be considered in CDMT along with the qualified synthetic drugs.
A successful validation of the CDMT strategy may open up a debate on health care reform to explore other possibilities of combination therapy. In doing so, it should focus on clinical and molecular relationships between AD and CDMT. A better understanding of these relationships could inform and impact future development of AD-directed treatment strategies. This strategy also involves in reducing costs in treatment phases which will be affordable to a common man suffering from AD.
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