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261.
Two new cembrane diterpenes (+)-polydactylide (1) and (+)-7alpha,8beta-dihydroxydeepoxysarcophine (2) together with (+)-sarcophine (3) and (+)-sarcophytoxide (4) have been isolated from the soft coral Sinularia polydactyla. The new cembrane diterpene (-)-7beta-hydroxy-8alpha-methoxydeepoxysarcophine (5) has been obtained from the soft coral Sarcophyton trocheliophorum and the known briarane diterpene briaexcavatolide W (6) from the gorgonian coral Briareum sp.The structures were determined primarily by NMR spectroscopy. The assignment of NMR signals was performed by means of (1)H-(1)H COSY, ROESY, HMQC and HMBC experiments. 相似文献
262.
Gold catalysts: nanoporous gold foams 总被引:1,自引:0,他引:1
Zielasek V Jürgens B Schulz C Biener J Biener MM Hamza AV Bäumer M 《Angewandte Chemie (International ed. in English)》2006,45(48):8241-8244
263.
Alexander D Bruce J Zuhlke C Koch B Rudebusch R Deogun J Hamza H 《Optics letters》2006,31(13):1957-1959
We present the operation of an optical device that exhibits diodelike properties based on two adjacent layers of quantum dots (QDs) encased in a fiber-optic jacket. The possibility of a multilayered device is also discussed. A significant change in the emission spectrum of CdSe/ZnS core-shell QDs was observed when excited by the input laser and the fluorescence of other CdSe/ZnS core-shell QDs. The output of the diode can be taken to be either the incoming laser wavelength of light similar to a conventional diode, or the output may be considered to be one of the QD fluorescence wavelengths. Current work has applications in biological fluorescence monitors and sensors as well as in telecommunications applications. 相似文献
264.
We report the use of M-mode swept source optical coherence tomography (SS-OCT) for measuring sodium chloride (NaCl) salt concentrations
in liquid phantoms and in drawn whole blood based on temporal dynamics of light scattering. The Brownian motion of scattering
particle is affected due to the change in viscosity of liquid. An autocorrelation function was determined from the power spectrum
of SS-OCT signal and then was fit by mono and double exponential function to obtain decorrelation time. These translational
decorrelation times corresponding to translational diffusion coefficients enabled us to find the controlled viscosity of the
medium. The viscosities of the media were compared with literature values and a fair/excellent agreement was observed. Thus,
the technique has ability to quantify the salt levels in terms of viscosity in nonflowing medium suspensions and many research
routes necessary to determine its potential for in-vivo applications. 相似文献
265.
We present the optical properties of a new type of photonic crystal (PC) named star-shaped PC (STAR-PC) with anomalous equi-frequency contours. Intentionally introducing low-symmetry in the primitive unit cell gives rise to progressively tilting flat contours, which are observed in the fifth band of the transverse magnetic mode. Due to the intrinsic dispersive feature of the proposed PCs, i.e. tilted self-collimation, the incident signal with different wavelengths can be successfully separated in a spatial domain without introducing any corrugations or complexities inside the structure. We show numerical investigations of wavelength selective characteristic of the proposed PC structure in both time and frequency domains. The STAR-PC approach can be considered a good candidate for the wavelength division applications in the design of compact photonic integrated circuits. For the purpose of wavelength separation implementations, the proposed structure may operate within the wavelength interval of 1484.5–1621.5 nm with a broad bandwidth of 8.82%. The corresponding inter-channel crosstalk value is as low as ?19 dB and the calculated transmission efficiency is above 97%. 相似文献
266.
Bezza Abdeslam Ouennoughi Yasmina Bouzerafa Brahim Aggoun Djouhra Bezzi Hamza López Daniel Fernández-García Marta Ourari Ali 《Research on Chemical Intermediates》2018,44(11):6831-6846
Research on Chemical Intermediates - Poly(4-vinylpyridine) crosslinked by 2 % divinylbenzene was partially quaternized (20 % monomer equivalents) by a bidentate Schiff base nickel... 相似文献
267.
Avni A. Argun Ashley M. Banks Gwendolynne Merlen Linda A. Tempelman Michael F. Becker Thomas Schuelke Badawi M. Dweik 《Analytica chimica acta》2013
A series of Boron-Doped Diamond (BDD) ultramicroelectrode arrays were fabricated and investigated for their performance as electrochemical sensors to detect trace level metals such as cadmium. The steady-state diffusion behavior of these sensors was validated using cyclic voltammetry followed by electrochemical detection of cadmium in water and in human urine to demonstrate high sensitivity (>200 μA ppb−1 cm−2) and low background current (<4 nA). When an array of ultramicroelectrodes was positioned with optimal spacing, these BDD sensors showed a sigmoidal diffusion behavior. They also demonstrated high accuracy with linear dose dependence for quantification of cadmium in a certified reference river water sample from the U.S. National Institute of Standards and Technology (NIST) as well as in a human urine sample spiked with 0.25–1 ppb cadmium. 相似文献
268.
Exploration of structural,optical, and photoluminescent properties of (1-x)NiCo2O4/xPbS nanocomposites for optoelectronic applications
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The (1-x)NiCo2O4/xPbS (0≤ x≤ 0.2) nanocomposite samples are synthesized using the hydrothermal and thermolysis procedures. The different phases developed in the obtained nanocomposite samples are accurately determined using the x-ray diffraction technique equipped with a line-detector. The percentage of the formed phases (NiCo2O4 (NCO), PbS, PbSO4), structural and microstructure parameters are determined using Rietveld quantitative phase analysis. The transmission electron microscope (TEM) images and Rietveld analysis reveal almost isotropic particle size in the nano range with a very narrow size distribution. The obtained phase percentage of PbS and PbSO4 are smaller than nominated values (x) suggesting dissolving of some Pb and S ions into NCO which is then confirmed by the analysis of Fourier-transform infrared (FTIR) spectra of nanocomposite samples. The absorption spectra are modified upon doping NCO with PbS. The optical band gaps of the nanocomposites increase as the amount of PbS augments. The effect of alloying on extinction coefficient, refractive index, dielectric constant, optical conductivity, the intensity, and emitted color from the photoluminescence of the nanocomposite samples are also studied. The refractive index value of NCO and NCO-PbS nanocomposite samples exhibit normal dispersions. The photoluminescent measurements reveal that the NCO-PbS nanocomposites can emit a violet color. The improvement in the values of the nonlinear optical (NLO) parameters of pristine NCO at high frequencies or the nanocomposite samples at low frequencies, are made them used in NLO photonic devices. 相似文献
269.
Khasawneh MA Elwy HM Hamza AA Fawzi NM Hassan AH 《Molecules (Basel, Switzerland)》2011,16(9):7510-7521
Leptadenia pyrotechnica Forssk is a traditional medicinal herb used for treatment of inflammatory diseases and cancer. In this research, the aqueous ethanolic crude extract of Leptadenia pyrotechnica aerial parts, along with its ethyl acetate, n-butanol and water partitioning fractions were evaluated for their antioxidant capacity, polyphenolic content, anti-inflammatory and anti-cancer properties. The total antioxidant capacity was estimated by the FRAP, DPPH, ABTS and β-carotene bleaching assays.The ethyl acetate fraction exhibited the highest polyphenolic content (252.27 mg gallic acid/g) and the best antioxidant activity (1.2, 0.57, 0.45 mmol ascorbic acid equivalent/g in the FRAP, ABTS and DPPH assays, respectively). Furthermore, the same extract showed appreciable anti-inflammatory via lipoxygenase (LOX) inhibitory activity (IC?? = 1.41 μg/mL). Moreover, the ethyl acetate fraction also showed the strongest cytotoxic effect (IC?? = 43.16 μg/mL) against MCF-7 human breast cancer cell line. These results suggest that this plant may be considered an interesting source of compounds with antioxidant, anti-inflammatory and anti-cancer properties for therapeutic, nutraceutical and functional food applications. 相似文献
270.
Galal Hamza Elgemeie Shahinaz Hassan Sayed 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):465-473
A novel and efficient method for the synthesis of a new variety of novel N -arylsulfonylamino derivatives of biheterocycles by the reaction of N -cyanoaceto-arylsulphonylhydrazides with f , g -unsaturated nitriles. The synthetic potential of the method is demonstrated. \centerline{\epsfbox{:art:s-fig-01a.eps}\hspace*{2pc}\epsfbox{:art:s-fig-01b.eps}\hspace*{2pc}\epsfbox{:art:s-fig-01c.eps}} 相似文献