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21.
T. Čtvrtníčková F. J. Fortes L. M. Cabalín V. Kanický J. J. Laserna 《Surface and interface analysis : SIA》2009,41(9):714-719
The potential of a double pulse (DP) excitation scheme for in‐depth characterization of ceramic samples using laser induced breakdown spectrometry (LIBS) has been demonstrated. For this purpose, two Q‐switched Nd:YAG lasers in orthogonal configuration were employed, the first one to ablate the sample (1064 nm) and the second one (532 nm) to excite the ablated material. Light emission was collected by a spectrograph and detected by an intensified charge‐coupled device (CCD) detector. Optimal conditions such as relative laser beam positions, laser pulse energies, inter‐pulse separation and CCD delay time were studied. Depth profiles were evaluated on the basis of various elemental compositions in both layers of ceramic samples. The depth resolution with DP configuration was improved by almost twofold as compared to the single‐pulse approach. The reproducibility of the depth profiles is also twice better with double pulse LIBS. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Rubio E Merino I García AB Cabal MP Ribas C Bayod-Jasanada M 《Magnetic resonance in chemistry : MRC》2005,43(4):269-282
New spiro-piperidylrifamycin derivatives are presented. These compounds were synthesized from the reaction of 3-amino-4-iminorifamycin S and enantiomerically pure 4-piperidones, which generate diasteroisomeric rifabutin analogues with a new stereocentre at the spiranic carbon. The (1)H and (13)C NMR spectra of these new compounds, and also the configuration of the new stereogenic centres, were assigned using 2D NMR spectroscopic techniques. A preliminary study of the (1)H and (13)C NMR spectra of the starting compounds rifamycin S, 3-amino-4-iminorifamycin S and the related rifabutin was also carried out and as a result, their previously published (13)C NMR data were corrected. 相似文献
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The hydrophobic-hydrophilic character of a series of microporous activated carbons was explored as a key factor in competitive
adsorption of a non-polar compound from liquid phase. The selectivity of the carbon surface towards naphthalene was explored
by performing the adsorption isotherms in water, cyclohexane and heptane. Solvent polarity and adsorbent hydrophobic character
were found to strongly influence the adsorption capacity of naphthalene. In aqueous media, despite the non-polar character
of the adsorbate, surface acidity lowered adsorption capacity. This is attributed to the competition of water from the adsorption
sites, via H-bonding with surface functionalities and the formation of hydration clusters that reduce the accessibility and
affinity of naphthalene to the inner pore structure. In organic media the uptake decreased due to competition of the hydrophobic
solvent for the active sites of the carbon and to solvation effects. This competitive effect of the solvent is minimized in
oxidized carbons as opposed to the trend obtained in aqueous solutions. The results confirmed that although adsorption of
naphthalene strongly depends on the narrow microporosity of the adsorbent, competitive adsorption of the solvent for the active
sites becomes important. 相似文献
27.
Jiann‐Kuan Luo Maria‐Paz Cabal Ronald F. Federspiel Raymond N. Castle 《Journal of heterocyclic chemistry》2001,38(1):137-140
A previously unknown heterocyclic ring system, naphtho[2′,1′:4,5]thieno[2,3‐c]naphtho[2,1‐f]quinoline ( 14 ), was synthesized via oxidative photocyclization of 3‐chloro‐N‐(2‐phenanthryl)naphtho[1,2‐b]‐thiophene‐2‐carboxamide ( 9 ). Further elaboration of the lactam 10 yielded the unsubstituted ring system 14 . Structural confirmation of compound 14 was accomplished by a total assignment of its 1H and 13C nmr spectra utilizing the concerted two‐dimensional nmr spectroscopic methods. 相似文献
28.
MP Janawadkar R Baskaran R Nagendran K Gireesan N Harishkumar Rita Saha L S Vaidhyanathan J Jayapandian Y Hariharan TS Radhakrishnan 《Pramana》2002,58(5-6):1159-1164
A program has been developed and initiated at the Indira Gandhi Centre for Atomic Research (IGCAR) for the utilization of
SQUID sensors in various application areas. DC SQUID sensors based on Nb-AlO
x
-Nb Josephson junctions have been designed and developed inhouse along with associated flux-locked loop (FLL) electronics.
A compact low field SQUID magnetometer insertible in a liquid helium storage dewar has also been developed inhouse and is
in use. Efforts to build a high field SQUID magnetometer, SQUID-DAC system, are in progress. A planar gradiometric DC SQUID
sensor for non-destructive evaluation (NDE) application to be used in relatively unshielded environment has been designed
and developed. An easily portable NDE cryostat with a small lift-off distance, to be used in external locations has been designed
and tested. The magnetic field produced by a given two-dimensional current density distribution is inverted using the Fourier
transform technique. 相似文献
29.
MP Blencowe 《Contemporary Physics》2013,54(4):249-264
Nanoelectromechanical systems (NEMS) are nano-to-micrometer scale mechanical resonators coupled to electronic devices of similar dimensions. NEMS show promise for fast, ultrasensitive force microscopy and for deepening our understanding of how classical dynamics arises by approximation to quantum dynamics. This article begins with a survey of NEMS and then describes certain aspects of their classical dynamics. In particular, we show that for weak coupling the action of the electronic device on the mechanical resonator can be effectively that of a thermal bath, this despite the device being a driven, far-from-equilibrium system. 相似文献