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51.
Akbar Hossain Milan Skalicky Marian Brestic Sagar Maitra Sukamal Sarkar Zahoor Ahmad Hindu Vemuri Sourav Garai Mousumi Mondal Rajan Bhatt Pardeep Kumar Pradipta Banerjee Saikat Saha Tofazzal Islam Alison M. Laing 《Molecules (Basel, Switzerland)》2021,26(4)
The trace element selenium (Se) is a crucial element for many living organisms, including soil microorganisms, plants and animals, including humans. Generally, in Nature Se is taken up in the living cells of microorganisms, plants, animals and humans in several inorganic forms such as selenate, selenite, elemental Se and selenide. These forms are converted to organic forms by biological process, mostly as the two selenoamino acids selenocysteine (SeCys) and selenomethionine (SeMet). The biological systems of plants, animals and humans can fix these amino acids into Se-containing proteins by a modest replacement of methionine with SeMet. While the form SeCys is usually present in the active site of enzymes, which is essential for catalytic activity. Within human cells, organic forms of Se are significant for the accurate functioning of the immune and reproductive systems, the thyroid and the brain, and to enzyme activity within cells. Humans ingest Se through plant and animal foods rich in the element. The concentration of Se in foodstuffs depends on the presence of available forms of Se in soils and its uptake and accumulation by plants and herbivorous animals. Therefore, improving the availability of Se to plants is, therefore, a potential pathway to overcoming human Se deficiencies. Among these prospective pathways, the Se-biofortification of plants has already been established as a pioneering approach for producing Se-enriched agricultural products. To achieve this desirable aim of Se-biofortification, molecular breeding and genetic engineering in combination with novel agronomic and edaphic management approaches should be combined. This current review summarizes the roles, responses, prospects and mechanisms of Se in human nutrition. It also elaborates how biofortification is a plausible approach to resolving Se-deficiency in humans and other animals. 相似文献
52.
A. Maitra Marina Dan A. K. Sen K. Bhattacharyya C. K. Sarkar 《International Journal of Infrared and Millimeter Waves》1993,14(3):703-713
Distortion of pulses with pulse widths ranging from 0.1 to 1 ns propagating with carrier frequencies in the range 10–100 GHz through rain filled medium has been estimated considering the absorptive and dispersive effects produced by rain drops on the propagation of millimeter waves. It is found that the rain induced broadening or compression can be quite appreciable for very short pulses in the window region of millimeter wave band under intense and extensive raining conditions. 相似文献
53.
In study of polymer-salt complexes usually one is interested in the dc conductivity, which can be extracted from impedance
spectroscopy. However, impedance spectroscopy yields a host of additional information, for example, frequency variation of
the measured admittance or impedance, nature of the Cole-Cole plot and dielectric function. Proper analysis of this information
reveals details of the microstructure and transport processes in the sample. This in turn, will lead to development of better
solid electrolytes with tailor-made properties. The polymer electrolyte PEO-NH4ClO4 shows an interesting variation in its properties in two different regimes, (1) where salt concentration is below ∼ 19 wt.%
and (2) above this concentration. In the present paper we suggest an equivalent circuit incorporating a constant phase element
(CPE), which reproduces the complex admittance behavior at different salt fractions.
Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003. 相似文献
54.
Novel calixsalen-type cavitands have been synthesized using metal-free synthesis from simple and inexpensive materials, such as ethylenediamine and 5,5′-methylene-bis-salicylaldehyde derivatives. The cavitand 1 containing salen functionality recognizes fluoride ion. Fluoride ions switch on fluorescence on binding with the cavitand 1. Substitution on bis-salicylaldehyde part of calixsalen-type cavitand shows change in recognition behavior. On the attachment of electron withdrawing substituent, such as nitro group, the cavitand lost its fluorescence properties but proved to be a better colorimetric probe showing marked color change from pale yellow to red on addition of tetrabutyl ammonium salt of fluoride ion to the solution of cavitand. The nitro substituted cavitand is highly sensitive and selective for fluoride anion and hence is a promising candidate for development of colorimetric chemosensor. The binding of the cavitands with fluoride ion is investigated using 1H NMR-titration experiments. 相似文献
55.
U. K. Yadav T. Maitra I. Singh 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(3):365-370
Thermodynamic properties of the spinless Falicov-Kimball model are studied on a
triangular lattice using numerical diagonalization technique with Monte-Carlo simulation
algorithm. Discontinuous metal-insulator transition is observed at finite temperature.
Unlike the case of square lattice, here we observe that the finite temperature effect is
not able to smear out the discontinuous metal-insulator transition seen in the ground
state. Calculation of specific heat (C
v
)
shows single and double peak structures for different values of parameters like on-site
correlation strength (U), f-electron energy
(E
f
) and temperature. 相似文献
56.
57.
Maitra NT 《The Journal of chemical physics》2006,125(1):014110
We discuss possibilities and challenges for describing correlated electron and nuclear dynamics within a surface-hopping framework using time-dependent density functional theory (TDDFT) for the electron dynamics. We discuss the recent surface-hopping method proposed by Craig et al. [Phys. Rev. Lett. 95, 163001 (2005)] that is based on Kohn-Sham potential energy surfaces. Limitations of this approach arise due to the Kohn-Sham surfaces generally having different gradients than the true TDDFT-corrected ones. Two mechanisms of the linear response procedure cause this effect: we illustrate these with examples. 相似文献
58.
Adiabatic time-dependent density functional theory fails for excitations of a heteroatomic molecule composed of two open-shell fragments at large separation. Strong frequency dependence of the exchange-correlation kernel is necessary for both local and charge-transfer excitations. The root of this is the static correlation created by the step in the exact Kohn-Sham ground-state potential between the two fragments. An approximate nonempirical kernel is derived for excited molecular dissociation curves at large separation. Our result is also relevant when the usual local and semilocal approximations are used for the ground-state potential, as static correlation there arises from the coalescence of the highest occupied and lowest unoccupied orbital energies as the molecule dissociates. 相似文献
59.
[Structure: see text] Chenodeoxycholic acid based PET sensors for alkali metal ions have been immobilized on Merrifield resin and on Tentagel. The fluorescence of the sensor beads is enhanced upon binding the cations. The modular nature of the sensor allows designing different sensors based on this concept. 相似文献
60.
Md. Selim Arpita Sengupta Sadhu Kalyan K. Mukherjea 《Monatshefte für Chemie / Chemical Monthly》2010,40(1):933-938