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1.
Umakanta Tripathy R. Justin Rajesh Prem B. Bisht A. Subrahamanyam 《Journal of Chemical Sciences》2002,114(6):557-564
The excited state absorption cross-section of 5,5′-dichloro-11-diphenyl-amino-3,3′-diethyl-10, 12-ethylinethiatricarbocyanine
perchlorate (IR140) have been measured by using a single beam transmission technique. Z-scan experiments have been used to find out a few nonlinear
parameters. The excited state relaxation times have also been measured by using laser induced transient grating (LITG) technique. 相似文献
2.
Four selected Amaranthus tricolor cultivars were grown under four irrigation regimes (25, 50, 80, and 100% field capacity) to evaluate the mechanisms of growth and physiological and biochemical responses against drought stress in randomized complete block design with three replications. Drought stress led to decrease in total biomass, specific leaf area, relative water content (RWC), photosynthetic pigments (chlorophyll a, chlorophyll b, chlorophyll ab), and soluble protein and increase in MDA, H2O2, EL, proline, total carotenoid, ascorbic acid, polyphenols, flavonoids, and antioxidant activity. However, responses of these parameters were differential in respect to cultivars and the degree of drought stresses. No significant difference was observed in control and LDS for most of the traits. The cultivars VA14 and VA16 were identified as more tolerant to drought and could be used for further evaluations in future breeding programs and new cultivar release programs. Positively significant correlations among MDA, H2O2, compatible solutes, and non-enzymatic antioxidant (proline, TPC, TFC, and TAC) suggested that compatible solutes and non-enzymatic antioxidant played vital role in detoxifying of ROS in A. tricolor cultivar. The increased content of ascorbic acid indicated the crucial role of the ASC–GSH cycle for scavenging ROS in A. tricolor. 相似文献
3.
This paper proposes a new robust nonlinear \(\mathscr {H}_{\infty }\) state feedback (NHSF) controller for an autonomous underwater vehicle (AUV) in steering plane. A three-degree-of-freedom nonlinear model of an AUV has considered for developing a steering control law. In this, the energy dissipative theory is used which leads to form a Hamilton–Jacobi–Isaacs (HJI) inequality. The nonlinear \(\mathscr {H}_{\infty }\) control algorithm has been developed by solving HJI equation such that the AUV tracks the desired yaw angle accurately. Furthermore, a path following control has been implemented using the NHSF control algorithm for various paths in steering plane. Simulation studies have been carried out using MATLAB/Simulink environment to verify the efficacies of the proposed control algorithm for AUV. From the results obtained, it is concluded that the proposed robust control algorithm exhibits a good tracking performance ensuring internal stability and significant disturbance attenuation. 相似文献
4.
The migration and diffusion modulated excitation energy transfer has been studied in a new dye pair 7-diethylamino-4-methylcoumarin (donor) to 3,3'-dimethyloxacarbocyanine iodide (acceptor) by steady-state and picosecond time-resolved spectroscopy. To reduce the artifact of self-absorption, at high donor concentrations, the time-resolved studies have been carried out in thin films of polyvinyl alcohol (solid matrix) and in methanol (liquid phase) at front-face geometry of excitation. The Forster-type (nonradiative) energy transfer [Discuss. Faraday Soc. 27, 7 (1959)] takes place directly from donor to acceptor in case of solid matrix, while Yokota-Tanimoto model [J. Phys. Soc. Jpn. 22, 779 (1967)] for diffusion has been found to be operating in the liquid phase. It has been found here that the high interaction strength between donor and acceptor molecules as compared to that among donors masks the effect of energy migration and diffusion at high donor concentrations. The rate and efficiency of energy transfer increase with increasing the acceptor concentration. This has been confirmed by the study of acceptor kinetics. 相似文献
5.
We analyse the low temperature subband electron mobility in a Ga0.5In0.5P/GaAs quantum well structure where the side barriers are delta-doped with layers of Si. The electrons are transferred from
both the sides into the well forming two dimensional electron gas (2DEG). We consider the interface roughness scattering in
addition to ionised impurity scattering. The effect of screening of the scattering potentials by 2DEG on the electron mobility
is analysed by changing well width. Although the ionized impurity scattering is a dominant mechanism, for small well width
the interface roughness scattering happens to be appreciable. Our analysis can be utilized for low temperature device applications.
相似文献
6.
Radio frequency plasma enhanced chemical vapor based ZnO thin film deposition on glass substrate: A novel approach towards antibacterial agent 总被引:1,自引:0,他引:1
Jagannath PanigrahiDebadhyan Behera Ipsita MohantyUmakanta Subudhi Bijan B. NayakBhabani S. Acharya 《Applied Surface Science》2011,258(1):304-311
In the present study, the structural, optical and antibacterial properties of ZnO thin films are reported. ZnO thin films are deposited on borosilicate glass substrates by radio frequency plasma enhanced chemical vapor deposition (PECVD) using oxygen as process gas. The crystallinity of the deposited films is improved upon annealing at 450 °C in air for 1.5 h and the polycrystalline nature of the films is further confirmed by selected area electron diffraction. The particle size of the annealed film (thickness 476 nm) is found to be ∼34 nm from the transmission electron microscopic observation. Energy dispersive X-ray spectrum indicates the stoichiometric deposition of ZnO films. The films are highly transparent (transmittance >85%) in the visible region of electromagnetic spectrum. The films exhibit excellent antibacterial effect towards the growth of Escherichia coli and Pseudomonas aeruginosa. 相似文献
7.
Jagannath Panigrahi Bijan B. Nayak Debadhyan Behera Umakanta Subudhi Bhabani S. Acharya 《Applied Physics A: Materials Science & Processing》2012,108(3):577-585
Nano ZnO thin films were deposited on thin Al foils by a rf glow discharge plasma method in which sublimed zinc acetate vapor (precursor) reacted with oxygen plasma inside a low-pressure reactor. The films were microstructurally characterized using XRD, TEM, FESEM, optical reflectance and micro-Raman spectroscopy methods. In view of the good scope of ZnO coating in food packaging, the antibacterial activity in the ZnO thin films was studied by exposing the films to E. coli and P. aeruginosa for up to 8 h. Bacterial cell inhibition of up to 98–99 % was observed in the thin films. 相似文献
8.
Umakanta Sarker Md. Golam Rabbani Shinya Oba Wagdy M. Eldehna Sara T. Al-Rashood Nada M. Mostafa Omayma A. Eldahshan 《Molecules (Basel, Switzerland)》2022,27(9)
The underutilized Amaranthus leafy vegetables are a unique basis of pigments such as β-cyanins, β-xanthins, and betalains with radical scavenging capacity (RSC). They have abundant phytonutrients and antioxidant components, such as pigments, vitamins, phenolics, and flavonoids. Eight selected genotypes (four genotypes from each species) of underutilized Amaranthus leafy vegetables were evaluated for phytonutrients, pigments, vitamins, phenolics, flavonoids, and antioxidants in a randomized complete block design under ambient field conditions with three replicates. The studied traits showed a wide range of variations across eight genotypes of two species of Amaranthus leafy vegetables. The highest fat, β-xanthins, K, dietary fiber, Mg, β-cyanins, Mn, chlorophyll ab, Zn, TP, TF, betalains, chlorophyll a content, and (RSC) (DPPH) and RSC (ABTS+) were obtained from A. tricolor accessions. Conversely, the highest protein, Cu, carbohydrates, Ca, and chlorophyll b content were obtained from A. lividus accessions. The highest dry matter, carotenoids, Fe, energy, and ash were obtained from A. tricolor and A. lividus. The accession AT2 confirmed the highest vit. C and RSC (DPPH) and RSC (ABTS+); AT5 had the highest TP content; and AT12 had the highest TF content. A. tricolor accessions had high phytochemicals across the two species, such as phytopigments, vitamins, phenolics, antioxidants, and flavonoids, with considerable nutrients and protein. Hence, A. tricolor accessions can be used as high-yielding cultivars comprising ample antioxidants. The correlation study revealed that vitamin C, pigments, flavonoids, β-carotene, and phenolics demonstrated a strong RSC, and showed a substantial contribution to the antioxidant potential (AP) of A. tricolor. The investigation exposed that the accessions displayed a plentiful origin of nutritional values, phytochemicals, and AP with good quenching ability of reactive oxygen species (ROS) that provide enormous prospects for nourishing the mineral-, antioxidant-, and vitamin-threatened community. 相似文献
9.
Transient absorptions, which can be assigned to the triplet—triplet absorptions of excimers, have been observed from fluid solutions of α,α-dinaphthylalkanes. The temporal characteristics of the absorptions are identical to those of the emission previously assigned to excimer phosphorescence. Analysis of the monomer and the excimer absorptions indicate that the kinetics of formation and decay of the triplet excimer can be represented by a simple consecutive reaction scheme: 3M* → 3D* → 1M. 相似文献
10.
Umakanta Tripathy 《Optics Communications》2006,261(2):353-358
With picosecond pulses at the wavelength of 532 nm, we have determined the optical nonlinear refractive and absorptive parameters of the dye N,N′-bis(2,5-di-tert-butylphenyl)-3,4,9,10-perylenedicarboximide (DBPI) by a single closed-aperture (CA) Z-scan technique. This technique uses a theoretical model that elucidates the refractive and absorptive optical nonlinearity present simultaneously in the CA Z-scan profile. The observed remarkable red shift in the absorption spectrum of the dye in the acidic medium as compared to that in the polar medium has been used to vary the optical density at a single frequency. We find that the effect of saturable absorption (SA) is complete at higher concentrations. The effect of reverse saturable absorption (RSA) is dominating in dilute concentrations. The observed variations in the excited state refractive cross-section (σr) with the concentration and the energy have been attributed to the contributions of higher order nonlinearity along with the existing third-order nonlinearity. 相似文献