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151.
Francisco Álvarez Christopher White Ashvin Kumar Narayana Swamy Evgeny Shafirovich 《Proceedings of the Combustion Institute》2013,34(2):2245-2252
Combustion of lunar regolith mixed with energetic additives is a potential method for production of construction materials in future moon missions. Recently, self-sustained combustion in the mixtures of JSC-1A lunar regolith and magnesium has been demonstrated. However, the concentration of magnesium in those mixtures was as high as 26 wt%. Note that magnesium must be either transported from Earth or recovered from lunar minerals or used structures. The present paper focuses on the minimization of magnesium content in JSC-1A/Mg mixtures. The mixtures were compacted into pellets and ignited in argon environment. Initial attempts to decrease magnesium concentration resulted in the observations of a spinning combustion wave at 23 wt% Mg. The observed spin combustion involved periodical motion of two counterpropagating hot spots along a helical path on the sample surface. These observations, including features such as formation of a faster hot spot after collision of the counterpropagating spots, confirm theoretical predictions for spin combustion in solid–solid mixtures. High-energy mechanical milling of JSC-1A in a planetary ball mill significantly increased its reactivity and improved combustion of its mixtures with magnesium. Mixtures of the obtained powder (the median diameter of about 3 μm) with 26 wt% Mg exhibit easy ignition and vigorous combustion. The minimum concentration of magnesium required for self-sustained propagation of a planar combustion front is as low as 13 wt%. 相似文献
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Increased bone water content resulting from repetitive patellofemoral joint overloading has been suggested to be a possible mechanism underlying patellofemoral pain (PFP). To date, it remains unknown whether persons with PFP exhibit elevated bone water content. The purpose of this study was to determine whether recreational runners with PFP exhibit elevated patella water content when compared to pain-free controls. Ten female recreational runners with a diagnosis of PFP (22 to 39 years of age) and 10 gender, age, weight, height, and activity matched controls underwent chemical-shift-encoded water-fat magnetic resonance imaging (MRI) to quantify patella water content (i.e., water-signal fraction). Differences in bone water content of the total patella, lateral aspect of the patella, and medial aspect of the patella were compared between groups using independent t tests. Compared with the control group, the PFP group demonstrated significantly greater total patella bone water content (15.4 ± 3.5% vs. 10.3 ± 2.1%; P = 0.001), lateral patella water content (17.2 ± 4.2% vs. 11.5 ± 2.5%; P = 0.002), and medial patella water content (13.2 ± 2.7% vs. 8.4 ± 2.3%; P < 0.001). The higher patella water content observed in female runners with PFP is suggestive of venous engorgement and elevated extracellular fluid. In turn, this may lead to an increase in intraosseous pressure and pain. 相似文献
154.
Radu Cazan Christopher Geppert Wilfried N?rtersh?user Rodolfo Sánchez 《Hyperfine Interactions》2010,196(1-3):177-189
Sympathetic cooling by laser cooled Mg ions has been proposed as a method for fast cooling of highly charged ions to a very low temperature. The paper describes the construction of the solid state laser system at 279.63 nm required for laser cooling of the Mg ions. The laser system is composed of a fiber laser at 1,118.54 nm and two successive second harmonic generation (SHG) ring cavities for frequency quadrupling. In the first SHG cavity, non-critical phase matching of a lithium triborate (LBO) crystal is used for doubling from 1,118.54 to 559.27 nm. The second SHG cavity uses critical phase matching of a β-barium borate (BBO) crystal for doubling from 559.27 to 279.63 nm. With the aid of Boyd–Kleinmann theory, optimum experimental parameters are calculated and used for an efficient SHG. Besides this, the paper intends to be a shortcut for practical applications of the Boyd–Kleinmann theory for SHG. 相似文献
155.
Cornelius von Morze Douglas A.C. Kelley Timothy M. Shepherd Suchandrima Banerjee Duan Xu Christopher P. Hess 《Magnetic resonance imaging》2010
Ventral and rostral regions of the brain are of emerging importance for the MRI characterization of early dementia, traumatic brain injury and epilepsy. Unfortunately, standard single-shot echo planar diffusion-weighted imaging of these regions at high fields is contaminated by severe imaging artifacts in the vicinity of air–tissue interfaces. To mitigate these artifacts and improve visualization of the temporal and frontal lobes at 7 T, we applied a reduced field-of-view strategy, enabled by outer volume suppression (OVS) with novel quadratic phase radiofrequency (RF) pulses, combined with partial Fourier and parallel imaging methods. The new acquisition greatly reduced the level of artifacts in six human subjects (including four patients with early symptoms of dementia). 相似文献
156.
The fine structures of the (ν1 + ν2) and (ν2 + ν3) combination bands of ozone in the 5.7-μm region have been recorded and analyzed. The two vibrational states are coupled through Coriolis and second-order distortion terms. The interaction has been treated by the numerical diagonalization of the secular determinant for the two coupled states. With the centrifugal distortion parameters fixed to the ground state values, the following constants have been obtained: ν1 + ν2 = 1796.266, A110 = 3.6104, B110 = 0.44145, , ν2 + ν3 = 1726.526, A011 = 3.5537, B011 = 0.43982, , Y13 = ?0.466, and X13 = ?0.010 cm?1. In addition, the following anharmonic constants have been obtained: x12 = ?7.821 and x23 = ?16.494 cm?1. The value of the dipole moment ratio, , is 1.30 ± 0.10. 相似文献
157.
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160.
Duc-Truc Pham Philip Clements Christopher J. Easton John Papageorgiou Bruce L. May 《Supramolecular chemistry》2013,25(6):510-519
This study shows that stereochemical factors largely determine the extent to which 6-(4′-t-butylphenylamino)-naphthalene-2-sulphonate, BNS? and its dimer, (BNS? )2, are complexed by β-cyclodextrin, βCD, and a range of linked βCD dimers. Fluorescence and 1H NMR studies, respectively, show that BNS? and (BNS? )2 form host–guest complexes with βCD of the stoichiometry βCD.BNS? (10? 4 K 1 = 4.67 dm3 mol? 1) and βCD.BNS2 2 ? (10? 2 K 2′ = 2.31 dm3 mol? 1), where the complexation constant K 1 = [βCD.BNS? ]/([βCD][BNS? ]) and K 2′ = [βCD. (BNS? )2]/([βCD.BNS? ][BNS? ]) in aqueous phosphate buffer at pH 7.0, I = 0.10 mol dm3 at 298.2 K. (The dimerisation of BNS? is characterised by 10? 2 K d = 2.65 dm3 mol? 1.) For N,N-bis((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)succinamide, 33βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)-N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2su, N,N-bis(6A-deoxy-6A-β-cyclodextrin)succinamide, 66βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)-N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2ur, and N,N-bis(6A-deoxy-6A-β-cyclodextrin)urea, 66βCD2ur, the analogous 10? 4 K 1 = 11.0, 101, 330, 29.6 and 435 dm3 mol? 1 and 10? 2 K 2′ = 2.56, 2.31, 2.59, 1.82 and 1.72 dm3 mol? 1, respectively. A similar variation occurs in K 1 derived by UV–vis methods. The factors causing the variations in K 1 and K 2 are discussed in conjunction with 1H ROESY NMR and molecular modelling studies. 相似文献