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81.
Using a cosmological black hole model proposed recently, we have calculated the quasi-local mass of a collapsing structure
within a cosmological setting due to different definitions put forward in the last decades to see how similar or different
they are. It has been shown that the mass within the horizon follows the familiar Brown–York behavior. It increases, however,
outside the horizon again after a short decrease, in contrast to the Schwarzschild case. Further away, near the void, outside
the collapsed region, and where the density reaches the background minimum, all the mass definitions roughly coincide. They
differ, however, substantially far from it. Generically, we are faced with three different Brown–York mass maxima: near the
horizon, around the void between the overdensity region and the background, and another at cosmological distances corresponding
to the cosmological horizon. While the latter two maxima are always present, the horizon mass maxima is absent before the
onset of the central singularity. 相似文献
82.
The viability and a number of morphological properties of in situ astrocytes of rat spinal cord cultures including changes in surface area and migration of both cell body and nucleus were investigated at magnetic field intensities comparable to those currently used for magnetic resonance imaging. Viability of rat spinal astrocytes was studied after up to 72 hours of 2.1T static magnetic field exposure. Surface areas and two-dimensional centroids of both soma and nucleus after 2 hours of magnetic field exposure were determined and compared with those of the same cells before magnetic field exposure. Cell membrane ruffling was quantified using fractal analysis. 相似文献
83.
Hamid Reza Shaterian Asghar Hosseinian Majid Ghashang 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):3136-3144
Herein, we describe a green procedure for the one-pot preparation of 1,8-dioxo-octahydroxanthene derivatives by condensation of dimedone and substituted benzaldehydes in the presence of FeCl 3 -SiO 2 as an efficient and heterogeneous catalyst under microwave irradiation and thermal conditions. This method has the advantages of high yields, cleaner reactions, efficient and cost-effective method, simple methodology, short reaction times, easy workup, and greener conditions. 相似文献
84.
Ali Ramazani Ali Morsali Bijan Ganjeie Ali Reza Kazemizadeh Ebrahim Ahmadi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2439-2442
Abstract Selenourea reacts with dialkyl acetylenedicarboxylates in acetone to form 1:1 adducts, which undergo a cyclization reaction to produce alkyl Z-2-(2-amino-4-oxo-1,3-selenazol-5(4H)-yliden) acetates in fairly good yields. The reaction is completely stereoselective. 相似文献
85.
Ali Ramazani Ali Reza Kazemizadeh Bijan Ganjeie Ebrahim Ahmadi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2569-2572
Tiourea reacts with dialkyl acetylenedicarboxylates in solventless conditions to form 1:1 adducts, which undergo a cyclization reaction to produce alkyl Z-2-(2-amino-4-oxo-1,3-thiazol-5(4H)-yliden)acetates in fairly good yields. The stereochemistry of the ethyl Z-2-(2-amino-4-oxo-1,3-thiazol-5(4H)-yliden)acetate was established by the use of X-ray single crystal structure analysis. The reaction is completely stereoselective. 相似文献
86.
Abdolreza Iraj Mansouri Zahra Hassani Mohammad Reza Islami 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1753-1758
2-Aminobenzoic acids or 4-aminobenzoic acid react with dimethyl acetylenedicarboxylate/triphenylphosphine in less than 20 min at 15–25°C to produce new organic phosphorus compounds in good to excellent yields. The conversion occurs with selective N- over O-alkylation of the amino group and isolation of the products is accomplished simply by filtration. 相似文献
87.
Mohammad Hossein Keshavarz Somayeh Moradi Bahman Ebrahimi Saatluo Hadi Rahimi Ali Reza Madram 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1453-1463
A novel general method is introduced to predict deflagration temperature of organic energetic compounds containing at least –NNO2, –ONO2, or –CNO2 groups. Deflagration temperature is an important safety parameter in working with dangerous energetic compounds and their environmental problems. It is shown that the contribution of some molecular structure parameters can be used to interpret thermal decomposition of an energetic compound. For 86 energetic materials (corresponding to 102 measured values) with different molecular structures, the new correlation has the root mean square (rms) and the average deviations of 23.8 and 19.0 K, respectively. The new method is also tested for some energetic compounds with complex molecular structures, e.g., two new organic energetic molecules N,N′-bis(1,2,4-triazol-3yl)-4,4′-diamino-2,2′,3,3′,5,5′,6,6′-octanitroazobenzene (BTDAONAB) and 2,4,6-trinitrophloroglucinol. 相似文献
88.
Reza Ojani Jahan-Bakhsh Raoof Akbar Khanmohammadi Ebrahim Zarei 《Journal of Solid State Electrochemistry》2013,17(1):63-68
The widely utilization of phenol and its derivatives such as 3-nitrophenol (3-NP) has led to the worldwide pollution in the environment. In this study, Ti/TiO2 photoelectrode was prepared with anodic oxidation of Ti foil electrode and then the photoelectrocatalytic (PEC) degradation of 3-NP was performed via this electrode, comparing with photocatalytic (PC), electrooxidation and direct photolysis by ultraviolet light. A significant photoelectrochemical synergetic effect in 3-NP degradation was observed on the Ti/TiO2 electrode and rate constant for the PEC process of Ti/TiO2 electrode was about three times as high as its PC degradation process. 3-NP concentration monitoring was carried out with differential pulse voltammetry. Results showed that PEC degradation has highest effect on concentration decreasing of 3-NP at solution and degraded it about 38 %, while other processes degradation efficiencies were about 4, 7, and 12 % for electrooxidation, direct photolysis and photocatalytic degradation, respectively. Finally, effects of solution pH and applied potential on degradation efficiency were studied and results showed that optimum pH for degradation is equal 4.00 and optimum potential is 1.2 V vs. Ag|AgCl|KCl (3M) reference electrode. 相似文献
89.
Mahdi Tohidian Seyed Reza Ghaffarian Seyed Emadodin Shakeri Erfan Dashtimoghadam Mohammad Mahdi Hasani-Sadrabadi 《Journal of Solid State Electrochemistry》2013,17(8):2123-2137
Nanocomposite membranes based on polyelectrolyte complex (PEC) of chitosan/phosphotungstic acid (PWA) and different types of montmorillonite (MMT) were prepared as alternative membranes to Nafion for direct methanol fuel cell (DMFC) applications. Fourier transform infrared spectroscopy (FTIR) revealed an electrostatically fixed PWA within the PEC membranes, which avoids a decrease in proton conductivity at practical condition. Various amounts of pristine as well as organically modified MMT (OMMT) (MMT: Cloisite Na, OMMT: Cloisite 15A, and Cloisite 30B) were introduced to the PEC membranes to decrease in methanol permeability and, thus, enhance efficiency and power density of the cells. X-ray diffraction patterns of the nanocomposite membranes proved that MMT (or OMMT) layers were exfoliated in the membranes at loading weights of lower than 3 wt.%. Moreover, the proton conductivity and the methanol permeability as well as the water uptake behavior of the manufactured nanocomposite membranes were studied. According to the selectivity parameter, ratio of proton conductivity to methanol permeability, the PEC/2 wt.% MMT 30B was identified as the optimum composition. The DMFC performance tests were carried out at 70 °C and 5 M methanol feed and the optimum membrane showed higher maximum power density as well as acceptable durability compared to Nafion 117. The obtained results indicated that owing to the relatively high selectivity and power density, the optimum nanocomposite membrane could be considered as a promising polyelectrolyte membrane (PEM) for DMFC applications. 相似文献