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1.
We present exact numerical results for a symmetric layered medium (prism/Ag film/nonlinear dielectric/Ag film/prism) where
the middle dielectric slab is assumed to have a saturation-type nonlinearity. We show bistable behaviour in the power dependence
of the reflectivity ofp-polarized light under the condition when coupled surface modes are excited in the structure. Moreover, we study the effect
of saturation on the bistable behaviour to show that multivalued character is inhibited by saturation effects. The field distributions
corresponding to the minimum reflectivity states of the nonlinear structure are also presented. 相似文献
2.
Vineet Kumar Rai 《Applied physics. B, Lasers and optics》2007,88(2):297-303
The dependence of temperature on the fluorescence lifetime and fluorescence intensity ratio using Stark sublevels and thermally
coupled (close lying) levels in triply ionized rare earth ions, doped into a variety of glasses and fibers, have been reviewed.
Also, it is claimed that not only for the two closely lying levels of triply ionized rare earth ion of the same kind, but
also for two different triply ionized rare earth ions, having their excited levels very close to each other, may be used to
monitor the temperature.
PACS 42.70.Ce 相似文献
3.
B. S. Narwade P. G. Gawali Rekha Pande G. M. Kalamse 《Journal of Chemical Sciences》2005,117(6):673-676
Dielectric constant (ε’) and dielectric loss (ε") of n-propyl alcohol (PA), ethylenediamine (EDA) and their binary mixtures,
for different mole fractions of ethylenediamine have been experimentally measured at 11.15 GHz microwave frequency. Values
of density (ρ), viscosity (η) and square refractive index (n
D
2
) of binary mixtures as well as those of pure liquids are reported. Excess square refractive index, viscosity and activation
energy of viscous flow have also been estimated. These parameters have been used to explain the formation of complexes in
the system. 相似文献
4.
Summary Copper(II) forms a stable colourless complex with thiourea. This property has been utilized to develop a Spectrophotometric method for the determination ofg quantities of thiourea. The complex absorbs in ultraviolet region and the determinations are carried out at 250 nm. The method permits the determination of thiourea from 10–60g with error not exceeding ± 1.0%.
Zusammenfassung Kupfer(II) bildet mit Thioharnstoff eine farblosa Komplexverbindung, die sich auf Grund ihrer Absorption bei 250 nm zur spektrophotometrischen Bestimmung von Mikrogrammengen Thioharnstoff eignet. 10 bis 60g Thioharnstoff lassen sieh mit einem Fehler von höchstens ± 1,0% bestimmen.相似文献
5.
6.
Summary A direct titrimetric method for the estimation of iron(III) has been developed, which involves the adjustment of concentration of iron(III) andPh, dilution, addition of 1 ml of 2% indicator solution and titration with EDTA (30° to 35° C). It is based on the fact that the iron(III) forms a blue coloured complex which is destroyed at the 11 molar ratio making the end-point of the titration. Quantity of iron(III) as small as 23.2 mg can be titrated accurately when present in a volume of 100 ml. Study of interferences revealed that quite a number of elements like Be2+, Mg2+, Ca2+, Sr2+, Ba2+, UO2
2+ and Mn2+ does not interfere, whereas much interference is caused by Cu2+, Zn2+, Pb2+, Fe2+, Co2+, Ni2+, ZrO2+, V02+, Al3+, Cr3+, Ti4+, Ce4+ and Th4+. The method proposed for iron(III) is selective and should be of considerable use in many cases.Part III: See Z. analyt. Chem. 167, 332 (1959). 相似文献
7.
Using simulation to study the folding kinetics of 20-mer poly-phenylacetylene (pPA) oligomers, we find a long time scale trapped kinetic phase in the cumulative folding time distribution. This is demonstrated using molecular dynamics to simulate an ensemble of over 100 folding trajectories. The simulation data are fit to a four-state kinetic model which includes the typical folded and unfolded states, along with an intermediate state, and most surprisingly, a kinetically trapped state. Topologically diverse conformations reminiscent of alpha helices, beta turns, and sheets in proteins are observed, along with unique structures in the form of knots. The nonhelical conformations are implicated, on the basis of structural correlations to kinetic parameters, to contribute to the trapped kinetic behavior. The strong solvophobic forces which mediate the folding process and produce a stable helical folded state also serve to overstabilize the nonhelical conformations, ultimately trapping them. From our simulations, the folding time is predicted to be on the order of 2.5-12.5 mus in the presence of the trapped kinetic phase. The folding mechanism for these 20-mer chains is compared with the previously reported folding mechanism for the pPA 12-mer chains. A linear scaling relationship between the chain length and the mean first passage time is predicted in the absence of the trapped kinetic phase. We discuss the major implications of this discovery in the design of self-assembling nanostructures. 相似文献
8.
Foldamer simulations: novel computational methods and applications to poly-phenylacetylene oligomers
We apply several methods to probe the ensemble kinetic and structural properties of a model system of poly-phenylacetylene (pPA) oligomer folding trajectories. The kinetic methods employed included a brute force accounting of conformations, a Markovian state matrix method, and a nonlinear least squares fit to a minimalist kinetic model used to extract the folding time. Each method gave similar measures for the folding time of the 12-mer chain, calculated to be on the order of 7 ns for the complete folding of the chain from an extended conformation. Utilizing both a linear and a nonlinear scaling relationship between the viscosity and the folding time to correct for a low simulation viscosity, we obtain an upper and a lower bound for the approximate folding time within the range 70 ns相似文献
9.
Ageratum conyzoides L. and Its Secondary Metabolites in the Management of Different Fungal Pathogens
Rubal Chahal Arun Nanda Esra Küpeli Akkol Eduardo Sobarzo-Snchez Ashwani Arya Deepak Kaushik Rohit Dutt Rashmi Bhardwaj Md. Habibur Rahman Vineet Mittal 《Molecules (Basel, Switzerland)》2021,26(10)
Ageratum conyzoides L. (Family—Asteraceae) is an annual aromatic invasive herb, mainly distributed over the tropical and subtropical regions of the world. It owns a reputed history of indigenous remedial uses, including as a wound dressing, an antimicrobial, and mouthwash as well as in treatment of dysentery, diarrhea, skin diseases, etc. In this review, the core idea is to present the antifungal potential of the selected medicinal plant and its secondary metabolites against different fungal pathogens. Additionally, toxicological studies (safety profile) conducted on the amazing plant A. conyzoides L. are discussed for the possible clinical development of this medicinal herb. Articles available from 2000 to 2020 were reviewed in detail to exhibit recent appraisals of the antifungal properties of A. conyzoides. Efforts were aimed at delivering evidences for the medicinal application of A. conyzoides by using globally recognized scientific search engines and databases so that an efficient approach for filling the lacunae in the research and development of antifungal drugs can be adopted. After analyzing the literature, it can be reported that the selected medicinal plant effectively suppressed the growth of numerous fungal species, such as Aspergillus, Alternaria, Candida, Fusarium, Phytophthora, and Pythium, owing to the presence of various secondary metabolites, particularly chromenes, terpenoids, flavonoids and coumarins. The possible mechanism of action of different secondary metabolites of the plant against fungal pathogens is also discussed briefly. However, it was found that only a few studies have been performed to demonstrate the plant’s dosage and safety profile in humans. Considered all together, A. conyzoides extract and its constituents may act as a promising biosource for the development of effective antifungal formulations for clinical use. However, in order to establish safety and efficacy, additional scientific research is required to explore chronic toxicological effects of ageratum, to determine the probability of interactions when used with different herbs, and to identify safe dosage. The particulars presented here not only bridge this gap but also furnish future research strategies for the investigators in microbiology, ethno-pharmacology, and drug discovery. 相似文献
10.