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1.
Joseph R. Lakowicz Ignacy Gryczynski Henryk Malak Zygmunt Gryczynski 《Photochemistry and photobiology》1996,64(4):632-635
Abstract— We report the observation of two-photon excitation of an organic fluorophore with two different wavelengths, a phenomenon we refer to as two-color two-photon (2C2P) excitation. Ultraviolet emission of p -Merphenyl at 340 nm was observed when the sample was illuminated with both 375 and 750 nm pulses from a picosecond dye laser. The emission of p -terphenyl was about 100-fold and more than 1000-fold less for illumination at only 375 or 750 nm, respectively. Observation of the 2C2P signal required temporal and spatial overlap of the 375 and 750 nm pulses. The amplitude of the signal depended on the polarization of each beam. 2C2P excitation can have applications in fluorescence microscopy and elsewhere when spatially localized excitation is desirable. 相似文献
2.
El. M. Tace A. Charaf I. Fahim M. Moutaabbid A. Kheïreddine F.-E. Ouaalla 《Phosphorus, sulfur, and silicon and the related elements》2013,188(7):1501-1514
Abstract Chemical presparation, thermal behavior, and infrared (IR) studies are discussed for the cyclotriphosphate MnK4(P3O9)2.2H2O and its anhydrous form MnK4(P3O9)2. The total dehydration of MnK4(P3O9)2.2H2O, between 200 and 550 °C, leads to its anhydrous form MnK4(P3O9)2. MnK4(P3O9)2 is a new cyclotriphosphate crystallizing in the rhombohedral system and is stable until its melting point at 560 °C. The thermal behavior of MnK4(P3O9)2.2H2O has been investigated and interpreted by comparison with IR absorption spectrometry and X-ray diffraction experiments. Two different methods, Ozawa and KAS (Kissinger-Akahira-Sunose), were selected in studying the kinetics of thermal behavior of the title compound. Quantum chemical calculations were made for the P3O 3? 9 ion. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT 相似文献
3.
Malak Azmat Ali G. Murtaza Afzal Khan Eman Algrafy Asif Mahmood Shahid M. Ramay 《International journal of quantum chemistry》2020,120(19):e26357
Highly spin-polarized ferromagnetic materials are essential for efficient spintronic devices. Here, 100% spin-polarized compounds Rb2TaZ6 (Z = Cl, Br) studied via density functional theory are reported. These compounds show stability in the ferromagnetic phase with cubic symmetry and half metallic behavior, thereby exhibiting a nonzero direct band gap in the spin-down channel and zero band gap in the spin-up configuration. The Ta-d sates contribute mainly to the net magnetic moments as explained by the crystal field theory and density of states. High Curie temperatures of 960.35 and 1021.74 K for Ra2TaCl6 and Rb2TaBr6, along with maximum spin polarizability, make these compounds favorable for efficient spintronic applications. 相似文献
4.
Hassan Artail Abdelkarim Ajami Tania Saouma Malak Charaf 《Wireless Communications and Mobile Computing》2016,16(14):1956-1971
This paper presents a faulty node detection approach for wireless sensor networks that aggregate measurement data on their way toward the sink (base station). The approach is based on the idea of commanding sensor nodes on the aggregation paths to temporarily stop including their readings in the received aggregated readings from their upstream neighbors. The scheme is dependent on the ability of the sink to detect faulty nodes through changes in the received aggregated readings at the sink using a Markov Chain Controller (MCC). The algorithm that is run in the sink uses the MCC to assign a state to each sensor node based on transitions that are triggered by receiving aggregated path readings, and accordingly deduces the nodes that may be faulty. The experimental results show at least 98% detection rate at the cost of reasonable detection delays and generated wireless network traffic. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
5.
Neural networks are often used to model nonlinear dynamic systems. The role of neural networks in the structure used in this paper is to approximate static nonlinear relations. To complete the nonlinear dynamic model a dynamic subsystem can add to the static nonlinearity in various forms. Various modelling procedures, however, exhibit a wide range of errors in estimating or predicting the model output. The paper discusses the sensitivity of modelling with respect both to the discretization and structural considerations in sampled data systems. As a tool for the sensitivity analysis equivalent input-output structures are introduced. The aim of the paper is to explain the relationships between the modelling error and the approximation error and to show how to reduce sensitivity by choosing proper system structure. 相似文献
6.
Acidification is a common method for preserving dissolved organic matter (DOM) in natural water samples until sophisticated laboratory analyses can be performed. However, little is known about the effects of this practice on the composition and optical properties of DOM. In this study, the effects of acidification on DOM in porewater samples collected from the RL IV bog system of the Glacial Lake Agassiz Peatlands in northern Minnesota were characterized. Molecular composition was determined by ultrahigh resolution mass spectrometry and optical properties by UV absorption and three-dimensional fluorescence spectroscopy. Excitation–emission matrix fluorescence spectroscopy results indicate that the fluorescence properties of the peatland porewater DOM were sensitive to pH and that the observed changes were fluorophore dependent. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed the appearance of newly formed, oxygen-rich compounds upon acidification. The extent to which these oxygen-rich compounds were formed was also dependent on the composition of the DOM. 相似文献
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8.
Henryk Malak Ignacy Gryczynski Jonathan D. Dattelbaum Joseph R. Lakowicz 《Journal of fluorescence》1997,7(2):99-106
We observed the emission of l,6-diphenyl-l,3,5-hexatriene (DPH) when excited with the fundamental output of a fs Ti:sapphire
laser at 860 nm. The emission spectra of DPH were identical to that observed for one-photon excitation at 287 nm. The dependence
of the DPH emission intensity on laser power was cubic, indicating three-photon excitation of DPH at 860 nm. At a shorter
wavelength of 810 nm, the dependence on laser power was quadratic, indicating a two-photon process. At an intermediate wavelength
of 830 nm the mode of excitation was a mixture of two- and three-photon excitation. At 830 nm the anisotropy is no longer
a molecular parameter, and the mode of excitation and anisotropy of DPH depends on laser power. Frequency-domain anisotropy
decays of DPH in triacetin revealed the same rotational correlation times for two- and three-photon excitation. However, the
time 0 anisotropy of DPH was larger for three-photon excitation than for two-photon excitation. Steady-state anisotropy data
for DPH-labeled membranes revealed the same transition temperature for one- and three-photon excitation. These anisotropy
data indicate that membrane heating was not significant with three-photon excitation and that three-photon excitation may
thus be of practical usefulness in fluorescence spectroscopy and microscopy of membranes. 相似文献
9.
Saba Hemmati Mohammad Yousefi Mirmehdi Hashemi Salehi Mahdis Amiri Malak Hekmati 《应用有机金属化学》2020,34(8):e5653
This paper develops a green method for in situ decorated of palladium nanoparticles over Fe3O4 nanoparticles, by utilizing Strawberry fruit extract and ultrasound irradiations, with no use of any toxic reducing agent. The structure's characterization is represented via diverse analytical methods such as FT-IR, FE-SEM, TEM, WDX, ICP, EDS and XXPS. Catalytic efficiency of magnetic Fe3O4@Strawberry/Pd nanocatalyst is investigated in production of different biphenyls with good turnover frequencies (TOF) and turnover numbers (TON) through Suzuki coupling reactions. Furthermore, the catalyst could be recovered and reused 7 runs without considerable palladium leaching or alteration in its performance. 相似文献
10.
Targeted drug delivery is a promising approach to overcome the limitations of classical chemotherapy. In this respect, Imatinib‐loaded chitosan‐modified magnetic nanoparticles were prepared as a pH sensitive system for targeted delivery of drug to tumor sites by applying a magnetic field. The proposed magnetic nanoparticles were prepared through modification of magnetic Fe3O4 nanoparticles with chitosan and Imatinib. The structural, morphological and physicochemical properties of the synthesized nanoparticles were determined by different analytical techniques including energy‐dispersive X‐ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), Fourier‐transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HR‐TEM), vibrating sample magnetometry (VSM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). UV/visible spectrophotometry was used to measure the Imatinib contents. Thermal stability of the prepared particles was investigated and their efficiency of drug loading and release profile were evaluated. The results demonstrated that Fe3O4@CS acts as a pH responsive nanocarrier in releasing the loaded Imatinib molecules. Furthermore, the Fe3O4@CS/Imatinib nanoparticles displayed cytotoxic effect against MCF‐7 breast cancer cells. Results of this study can provide new insights in the development of pH responsive targeted drug delivery systems to overcome the side effects of conventional chemotherapy. 相似文献