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241.
242.
A general detailed analysis of the nonlinear generation of localized fields due to the existence of a strong pump field inside an inhomogeneous plasma has been performed taking into account the effects of relativistic and nonlocal nonlinearities on the structure of the plasma resonance region. The nonlinear Schrödinger equation describing the localized fields is investigated. A generalized dispersion relation is obtained to study the modulational instabilities in different cases. 相似文献
243.
Mohamed P. Abdel-megeed 《光谱学快报》2013,46(4):291-306
The electronic absorption spectra of a series of 4-aryl-azopyridylpyrazolones were investingated in different organic solvents of different polarities. The ir-spectra analysis suggested the presence of enol-azo and hydrazono-keto tautomeric structures. The 1H-nmr-spectra of these compounds were analysed and assigned in term of these proposed tautomeric structures. An additional proof of this finding was given by mass spectral fragmentation analyses. 相似文献
244.
Theoretical analysis of the radiation effect on transient behavior of an optoelectronic integrated device composed of a heterojunction phototransistor and a light emitting diode is studied theoretically. First, the transient behavior and the rise time of this device before radiation are investigated based on the frequency response of the constituent devices and the optical feedback inside the device. Second, the effect of neutron irradiation flux on the transient behavior of this device is theoretically studied. The results show that, by increasing the optical feedback inside the device, the rise time in the amplification mode is increased along with an increasing output, while that in the switching mode can be reduced effectively, and the neutron irradiation reduces the transient response and the rise time in both the amplification and switching modes. This type of model can be exploited as optical amplifier, optical switching device, and other applications. 相似文献
245.
Patrick M. Tchepmo Djomegni Emile F. Doungmo Goufo Subrata K. Sahu Mohamed Mbehou 《Natural Resource Modeling》2019,32(4)
A model is proposed to understand the dynamics in a food chain (one predator‐two prey). Unlike many approaches, we consider mutualism (for defense against predators) between the two groups of prey. We investigate the conditions for coexistence and exclusion. Unlike Elettreby's (2009) results, we show that prey can coexist in the absence of predators (as expected since there is no competition between prey). We also show the existence of Hopf bifurcation and limit cycle in the model, and numerically present bifurcation diagrams in terms of mutualism and harvesting. When the harvest is practiced for profit making, we provide the threshold effort value that determines the profitability of the harvest. We show that there is zero profit when the constant effort is applied. Below (resp. above) , there will always be gain (resp. loss). In the case of gain, we provide the optimal effort and optimal steady states that produce maximum profit and ensure coexistence. Recommendations for resource managers As a result of our investigation, we bring the following to the attention of management:
- 1. In the absence of predators, different groups of prey can coexist if they mutually help each other (no competition among them).
- 2. There is a maximal effort to invest in order to gain profit from the harvest. Above , the investment will result in a loss.
- 3. In the case of profit from harvest, policy makers should recommend the optimal effort to be applied and the optimal stock to harvest. This will guarantee maximum profit while ensuring sustainability of all species.
246.
Mohamed Elagawany Nehal F. Farid Bahaa Elgendy Esraa H. Abdelmomen Nada S. Abdelwahab 《Biomedical chromatography : BMC》2019,33(9)
An efficient, economic and high yielding method was described for the synthesis of baclofen (BAC) pharmacopoeial impurities (impurity A and impurity B) which can be used for gram‐scale synthesis. Furthermore, a novel ecofriendly thin‐layer chromatographic TLC–densitometric method was established and validated for the determination of BAC and its synthesized impurities. The developed TLC–densitometric method is based on the chromatographic separation using TLC plates (60 F254) using a green mobile phase of ethyl acetate–methanol–ammonia solution, 33% (8:2:0.1, by volume) with UV scanning at 220 nm. The proposed method was validated with respect to International Conference on Harmonization guidelines. The validated method was successfully applied for determination of BAC in pure form and in its commercial dosage form. Additionally, the greenness profile of the developed method was evaluated and compared with those of the reported chromatographic methods. The developed method was found to be superior to the published methods, being environmentally benign. 相似文献
247.
Fanny Danton Dr. Mohamed Othman Dr. Ata Martin Lawson Dr. Ján Moncol Dr. Alina Ghinet Prof. Benoît Rigo Prof. Adam Daïch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(24):6113-6118
An efficient domino transformation using a phenyliodine(III) diacetate (PIDA)/I2 combination towards Morin 1,4-thiazine compounds has been developed starting from N,S-acetals. The latter leads to “one-step” regioselective methylene insertion without the need for traditional sulfoxide intermediates in good yields. The reaction involves easily accessible N,S-acetals obtained from cost-effective basic ketones and cysteamine as starting materials. This process ultimately leads to 1,4-thiazines related to natural product and fused derivatives necessary for further QSAR study. 相似文献
248.
Agamy Adel Mohamed Ahmed M. 《International Journal of Wireless Information Networks》2021,28(1):134-146
International Journal of Wireless Information Networks - Wireless access networks need to deliver a satisfactory level of Quality of Service (QoS) to their subscribers. The service quality can be... 相似文献
249.
Abduraouf Alamer Mohamed Abdurhman Yan Zhang Guoan Zhang Shuai Wang 《Analytical and bioanalytical chemistry》2015,407(26):8129-8136
250.