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排序方式: 共有166条查询结果,搜索用时 312 毫秒
21.
Jean-Louis Luche 《Ultrasonics sonochemistry》1994,1(2):S111-S118
Examples of sonochemical reactions occuring under heterogeneous conditions are discussed with respect to their mechanism. The activation of a metal surface involves complex phenomena, in which parameters of importance seem to be the hardness and the adhesion of the passivating layer. Some considerations are given on the probable link between sonochemistry and tribochemistry. 相似文献
22.
Jocelyn Freitas Bennaton 《Journal of Mathematical Analysis and Applications》1985,110(2):364-383
This paper concerns discrete time Galerkin approximations to the solution of the filtering problem for diffusions. Two families of schemes approximating the unnormalized conditional density, respectively, in an “average” and in a “pathwise” sense, are presented. L2 error estimates are derived and it is shown that the rate of convergence is linear in the time increment or linear in the modulus of continuity of the sample path. 相似文献
23.
The recent discovery of superior semicircular canal (SC) dehiscence syndrome as a clinical entity affecting both the auditory and vestibular systems has led to the investigation of the impact of a SC opening on the mechanics of hearing. It is hypothesized that the hole in the SC acts as a "third window" in the inner ear which shunts sound-induced stapes volume velocity away from the cochlea through the opening in the SC. To test the hypothesis and to understand the third window mechanisms the middle-ear input admittance and sound-induced stapes velocity were measured in chinchilla before and after surgically introducing a SC opening and after patching the opening. The extent to which patching returned the system to the presurgical state is used as a control criterion. In eight chinchilla ears a statistically significant, reversible increase in low-frequency middle-ear input admittance magnitude occurred as a result of opening the SC. In six ears a statistically significant reversible increase in stapes velocity was observed. Both of these changes are consistent with the hole creating a shunt pathway that increases the cochlear input admittance. 相似文献
24.
The use of microwave-assisted extraction has gained wide acceptance as a powerful tool for the recovery of environmental contaminants
and their subsequent analysis. This paper reviews the historical and fundamental basis of the technology. It also provides
a cursory review of the current state-of-the-art and literature (2000–2006) in the area of environmental analysis in addition
to providing a critical review of the level of efforts being devoted to its further development.
MAP is a Trademark of Her Majesty the Queen in Right of Canada as represented by the Minister of the Environment. 相似文献
25.
Dutton JL Tindale JJ Jennings MC Ragogna PJ 《Chemical communications (Cambridge, England)》2006,(23):2474-2476
The reaction of SeCl4 with the ubiquitous tert-butyl-substituted diazabutadiene ligand results in the isolation of a rare example of a 1,2,5-selenadiazolium cation, representing a novel route to Se-N ring formation; these heterocycles can be derivatised at selenium, which has led to the identification of a short Se...N secondary bonding interaction. 相似文献
26.
Abstract The molybdate‐bearing mineral szenicsite, Cu3(MoO4)(OH)4, has been studied by Raman and infrared spectroscopy. A comparison of the Raman spectra is made with those of the closely related molybdate‐bearing minerals, wulfenite, powellite, lindgrenite, and iriginite, which show common paragenesis. The Raman spectrum of szenicsite displays an intense, sharp band at 898 cm?1, attributed to the ν1 symmetric stretching vibration of the MoO4 units. The position of this particular band may be compared with the values of 871 cm?1 for wulfenite and scheelite and 879 cm?1 for powellite. Two Raman bands are observed at 827 and 801 cm?1 for szenicsite, which are assigned to the ν3(E g ) vibrational mode of the molybdate anion. The two MO4 ν2 modes are observed at 349 (B g ) and 308 cm?1 (A g ). The Raman band at 408 cm?1 for szenicsite is assigned to the ν4(E g ) band. The Raman spectra are assigned according to a factor group analysis and are related to the structure of the minerals. The various minerals mentioned have characteristically different Raman spectra. 相似文献
27.
Joshua S. Santana Jocelyn T. L. Gamler Sara E. Skrabalak 《Particle & Particle Systems Characterization》2019,36(9)
Microreactors for nanoparticle (NP) synthesis offer advantages over batch reactions in terms of scale‐up and integration with online analyses. Herein, two microreactors (i.e., a duo‐microreactor) are integrated to achieve sequential reactions for the synthesis of bimetallic NPs with architectural control. The generality of the duo‐microreactor is shown with the synthesis of branched Pd‐Pt NPs and core@shell Pd@Au NPs, both achieved by synthesizing Pd nanocubes in the first part of the duo‐microreactor and then using those nanocubes downstream as seeds for Pt or Au deposition. Control of the dimensions of these NPs is further demonstrated and achieved by tailoring metal precursor concentrations inline. This microreactor methodology is anticipated to be applicable to other bimetallic NP systems. 相似文献
28.
Roland Gilbert Jocelyn Jalbert Pierre Tétreault Brigitte Morin Yves Denos 《Cellulose (London, England)》2009,16(2):327-338
Recently, the existence of a relation between the rupture of 1,4-β-glycosidic bonds in the cellulose during thermal-ageing of paper/oil systems and the detection of methanol in the oil has been reported for the first time in this journal (Jalbert et al. 2007). The present study addresses the rate constants of the reaction for standard wood kraft papers, two immersed in inhibited naphthenic oil under air (paper/oil weight–volume ratio of 1:18) and one in non-inhibited paraffinic oil under nitrogen (paper/oil weight–volume ratio of 1:30). The isotherms in the range of 60–130 °C show that the initial rate of methanol production markedly increases with temperature and to a lesser extent with the moisture of the specimens (initially between 0.5 and 2.25% (w/w)), similarly to what is noted for the depolymerization through the Ekenstam’s pseudo-zero order model. The Arrhenius expression of the rate constants reveals linear relationships that confirm the dominance of a given mechanism in both cases. A very good agreement is also noted for the activation energy over the entirely paper/oil systems studied (106.9 ± 4.3 and 103.5 ± 3.7 kJ mol?1 for methanol and scissions, respectively). Furthermore, a comparison of the rate constants $ \left( {k_{{{\text{CH}}_{ 3} {\text{OH}}}} /k_{\text{scissions}} } \right) Recently, the existence of a relation between the rupture of 1,4-β-glycosidic bonds in the cellulose during thermal-ageing of paper/oil systems and the detection of methanol in the oil has
been reported for the first time in this journal (Jalbert et al. 2007). The present study addresses the rate constants of the reaction for standard wood kraft papers, two immersed in inhibited
naphthenic oil under air (paper/oil weight–volume ratio of 1:18) and one in non-inhibited paraffinic oil under nitrogen (paper/oil
weight–volume ratio of 1:30). The isotherms in the range of 60–130 °C show that the initial rate of methanol production markedly
increases with temperature and to a lesser extent with the moisture of the specimens (initially between 0.5 and 2.25% (w/w)),
similarly to what is noted for the depolymerization through the Ekenstam’s pseudo-zero order model. The Arrhenius expression
of the rate constants reveals linear relationships that confirm the dominance of a given mechanism in both cases. A very good
agreement is also noted for the activation energy over the entirely paper/oil systems studied (106.9 ± 4.3 and 103.5 ± 3.7 kJ mol−1 for methanol and scissions, respectively). Furthermore, a comparison of the rate constants shows approximately constant values indicating an apparent yield for the methanol of about one-third molecule per every scission
for the tests under air (0.27 ± 0.04 for Clupak HD75 and 0.37 ± 0.14 for Munksj? TH70) and even lower for the ones under N2 (0.12 ± 0.03 for Munksj? E.G.). As expected from a pseudo-zero order model, these values were shown to be consistent with
a similar comparison of the amount of CH3OH and chain-end groups produced under specific time–temperature ageing conditions (168 h at 120 °C). Finally, an additional
test carried out with unaged cellulose in contact with a fresh solution of methanol in oil (cellulose/oil weight–volume ratio
of 1:18) shows that at equilibrium, over 58% of the species is lost from the solution due to penetration into the fibres.
Such results reveal the importance of the species partitioning in establishing the true correspondence between the molecules
of CH3OH produced and the scissions. 相似文献
29.
The resonant excitation of neutron star (NS) modes by tides is investigated as a source of short gamma-ray burst (SGRB) precursors. We find that the driving of a crust-core interface mode can lead to shattering of the NS crust, liberating ~10{46}-10{47} erg of energy seconds before the merger of a NS-NS or NS-black-hole binary. Such properties are consistent with Swift/BAT detections of SGRB precursors, and we use the timing of the observed precursors to place weak constraints on the crust equation of state. We describe how a larger sample of precursor detections could be used alongside coincident gravitational wave detections of the inspiral by Advanced LIGO class detectors to probe the NS structure. These two types of observations nicely complement one another, since the former constrains the equation of state and structure near the crust-core boundary, while the latter is more sensitive to the core equation of state. 相似文献
30.
CVD diamond films: from growth to applications 总被引:3,自引:0,他引:3
The present review provides an up-to-date report on the main potential of CVD diamond films for industrial applications as well as on recent basic research which seeks to understand diamond deposition microwave plasma reactors. This review includes firstly an overview of diamond film applications. Elements which explain variations in diamond film characteristics as a function of synthesis conditions are given. Also experimental results are reported which show variations in diamond characteristics (quality, microstructure, growth rate, growth mechanisms) as four plasma variables (pressure, power, percentage of methane, substrate temperature) are systematically changed. In the second part, we discuss the effects of these variables on local parameters such as electron temperature, gas temperature, carbon-containing species and H-atom densities. Finally, based on these results, relationships between key local parameters and diamond characteristics are established and discussed. 相似文献