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41.
Hussein Abulkasim Ahmed Farouk Hanan Alsuqaih Walaa Hamdan Safwat Hamad S. Ghose 《Quantum Information Processing》2018,17(11):316
Recently, Wang and Ma (Quantum Inf Process 16(5):130, 2017) proposed two interesting quantum key agreement protocols with a single photon in both polarization and spatial-mode degrees of freedom. They claimed that the privacy of participants’ secret keys in the multiparty case is protected against dishonest participants. However, in this paper, we prove that two dishonest participants can deduce the secret key of an honest one using a fake sequence of single photons, without being detected. Also, we propose an additional security detection process to avoid the security loophole in their protocol. 相似文献
42.
Stabilization of the Reductase Domain in the Catalytically Self‐Sufficient Cytochrome P450BM3 by Consensus‐Guided Mutagenesis 下载免费PDF全文
Prof. Dr. Gloria Saab‐Rincón Hanan Alwaseem Dr. Valeria Guzmán‐Luna Leticia Olvera Prof. Dr. Rudi Fasan 《Chembiochem : a European journal of chemical biology》2018,19(6):622-632
The multidomain, catalytically self‐sufficient cytochrome P450 BM‐3 from Bacillus megaterium (P450BM3) constitutes a versatile enzyme for the oxyfunctionalization of organic molecules and natural products. However, the limited stability of the diflavin reductase domain limits the utility of this enzyme for synthetic applications. In this work, a consensus‐guided mutagenesis approach was applied to enhance the thermal stability of the reductase domain of P450BM3. Upon phylogenetic analysis of a set of distantly related P450s (>38 % identity), a total of 14 amino acid substitutions were identified and evaluated in terms of their stabilizing effects relative to the wild‐type reductase domain. Recombination of the six most stabilizing mutations generated two thermostable variants featuring up to tenfold longer half‐lives at 50 °C and increased catalytic performance at elevated temperatures. Further characterization of the engineered P450BM3 variants indicated that the introduced mutations increased the thermal stability of the FAD‐binding domain and that the optimal temperature (Topt) of the enzyme had shifted from 25 to 40 °C. This work demonstrates the effectiveness of consensus mutagenesis for enhancing the stability of the reductase component of a multidomain P450. The stabilized P450BM3 variants developed here could potentially provide more robust scaffolds for the engineering of oxidation biocatalysts. 相似文献
43.
Yassine Ennaciri Mohammed Bettach Hanan El Alaoui-Belghiti 《The International journal of environmental studies》2020,77(2):297-306
ABSTRACTThe production of phosphoric acid generates an enormous amount of phosphogypsum with emission of toxic fluorine acid gas. To remedy these environmental problems, a novel and a simple procedure permits converting phosphogypsum waste by recycled fluorine acid into valuable products. The obtained results confirm the efficiency of this procedure, which synthesises at room temperature the calcium fluoride in the form of nano-crystalline powder and the ammonium bisulphate salt from the exact stoichiometric proportions of phosphogypsum, hydrofluoric acid and ammonia. The total conversion of phosphogypsum is achieved after reaction time equal to one hour and a half. Generally, this novel procedure offers not only a solution for reducing phosphogypsum waste and fluorine gas emission, but also gives rise to valuable products, useful to industry and agriculture. 相似文献
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Khaled R. Mohamed Hanan H. Beherei Gehan T. El Bassyouni Nahed El Mahallawy 《Materials science & engineering. C, Materials for biological applications》2013,33(7):4126-4132
In the current study, the semiconducting metal oxides such as nano-ZnO and SiO2 powders were prepared via sol–gel technique and conducted on nano-hydroxyapatite (nHA) which was synthesized by chemical precipitation. The properties of fabricated nano-structured composites containing different ratios of HA, ZnO and SiO2 were examined using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. The effect of the variation of ratios between the three components on mechanical, microstructure and in-vitro properties was assessed to explore the possibility of enhancing these properties. The results proved that the mechanical properties exhibited an increment with increasing the ZnO content at the extent of HA. In-vitro study proved the formation and nucleation of apatite onto the surface of the fabricated composites after one week of immersion. It is concluded that HA composites containing SiO2 or SiO2/ZnO content had a suitable mechanical properties and ability to form apatite particles onto the composite surface. Based on bioactivity behavior, Si-HA is more bioactive than pure hydroxyapatite and nano-arrangements will provide an interface for better bone formation. Therefore, these nano-composites will be promising as bone substitutes especially in load bearing sites. 相似文献
47.
Scientific applications represent a dominant sector of compute‐intensive applications. Using massively parallel processing systems increases the feasibility to automate such applications because of the cooperation among multiple processors to perform the designated task. This paper proposes a parallel hidden Markov model (HMM) algorithm for 3D magnetic resonance image brain segmentation using two approaches. In the first approach, a hierarchical/multilevel parallel technique is used to achieve high performance for the running algorithm. This approach can speed up the computation process up to 7.8× compared with a serial run. The second approach is orthogonal to the first and tries to help in obtaining a minimum error for 3D magnetic resonance image brain segmentation using multiple processes with different randomization paths for cooperative fast minimum error convergence. This approach achieves minimum error level for HMM training not achievable by the serial HMM training on a single node. Then both approaches are combined to achieve both high accuracy and high performance simultaneously. For 768 processing nodes of a Blue Gene system, the combined approach, which uses both methods cooperatively, can achieve high‐accuracy HMM parameters with 98% of the error level and 2.6× speedup compared with the pure accuracy‐oriented approach alone. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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This paper studies the problem of interference-free broadcast in wireless ad hoc networks. In particular, we are interested in asymmetric power assignments so that the induced broadcast communication graph is both, energy efficient and has a short collision-free broadcast schedule. We consider both random and deterministic node layouts and develop four different broadcast schemes with provable performance guarantees on three optimization objectives simultaneously: total energy consumption, network lifetime and collision-free schedule length. We also show extensive numerical results which support our findings. 相似文献
50.
Sanaa M. Solyman Noha A.K. Aboul-Gheit Fathia M. Tawfik M. Sadek Hanan A. Ahmed 《Egyptian Journal of Petroleum》2013,22(1):91-99
Catalytic dehydration of methanol to dimethyl ether was carried out over nano-zeolites and their modified samples via ultrasonic technique. Parent H-Beta and Parent H-Mordenite zeolites are used as synthesized and after sonication. H-Mordenite sonicated for 20 and 120 min whereas H-Beta sonicated for 20 min only. The reaction temperature was varied between 100 and 225 °C at three different contact times. The different catalyst samples were characterized using: XRD, FTIR, TEM, SEM and NH3-TPD techniques. The results revealed that sonication of parent zeolite samples affects on the unit cell dimensions and their crystal size. FTIR-spectroscopic analysis indicated that sonication may decrease the pore opening and cause framework structure defects. TEM and SEM micrographs showed that sonication broke-up and re-ordered zeolite crystals with longer time resulted in a different morphology relative to parents and also change the particle size. Sonicated samples have a good performance in methanol dehydration with complete conversion and complete selectivity to dimethyl ether at lower temperature relative to the corresponding parent zeolites. TPD results indicated that the concentration of strong acid sites decreased in sonicated H-Mordenite samples leading to an increase of their catalytic activity and the selectivity to DME. On the other hand, ultrasonic treatment of H-Beta sample decreased its catalytic activity. 相似文献