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781.
M. Jasińska A. Nowak J.W. Łukaszewicz G. Śliwiński 《Applied Physics A: Materials Science & Processing》2008,92(1):211-215
The surface discoloration due to laser cleaning was investigated for a historical Gotland sandstone. The difference in discoloration
for cleaning performed in air and in the shielding environment of N2 flowing at low velocities was studied by means of colorimetry and scanning electron microscopy and energy dispersive X-ray
spectroscopy techniques. For ablative removal of the natural as well as artificially applied encrustation a pulsed 1064-nm
laser operated at a fluence of 0.5 J/cm2 was applied. It was observed that the natural colour variations (ΔL*=21; Δb*=23) of the stone can completely screen the laser-induced changes. Under conditions of shielding with nitrogen, darkening
and yellowing slightly stronger than those occurring in the ambient air were revealed for the laser-cleaned, artificially
crusted samples and the effect was independent of the gas-flow velocity. The observed difference confirmed the contribution
of iron oxidation to the laser-induced yellowing and showed that the presence of oxygen in the ambient air affects favourably
the cleaning by supporting removal of a variety of combustible surface remnants and crust components of organic as well as
inorganic origin.
PACS 42.62.-b; 52.70.Kz; 81.65.Cf 相似文献
782.
采用高分离度快速液相色谱(RRLC)测定牛黄解毒片中黄芩苷的含量。色谱柱为Zorbax XDB-C18(4.6×50mm,1.8μm),流动相为甲醇-水-磷酸(45∶55∶0.2),检测波长315nm,流速0.5mL.min-1,柱温为30℃。黄芩苷在0.15—1.35μg(r=0.9999)范围内峰面积与浓度呈良好的线性关系,加样回收率为100.41%,RSD=1.42%。采用高分离度快速液相色谱(RRLC)测定复方牛黄解毒片中黄芩苷的含量,缩短了保留时间,提高了效率,降低了成本。本方法简便、准确,结果稳定。 相似文献
783.
Hanna Rostkowska Leszek Lapinski Maciej J. Nowak 《Journal of Physical Organic Chemistry》2010,23(1):56-66
Monomers of 5‐mercapto‐1,3,4‐thiadiazole‐2‐thione (bismuthiol) were studied using an experimental matrix‐isolation technique as well as by carrying out theoretical quantum chemical calculations. The calculations, performed using the quadratic configuration interaction method with single and double excitations (QCISD)/6‐31++G(d,p)//DFT(B3LYP)/6‐311++G(2d,p), predict that the thione–thiol tautomer of bismuthiol should be significantly (by more than 19 kJ mol?1) more stable than other tautomeric forms. Accordingly, only the signatures of the thione–thiol tautomer were observed in the FT‐IR spectrum of bismuthiol, recorded directly after deposition of an Ar matrix. UV (λ > 320 nm) irradiation induced the conversion of the thione–thiol tautomer into the dithiol form. Analogous investigations were carried out for two related compounds: 5‐methyl‐1,3,4‐thiadiazole‐2‐thione and 5‐methylthio‐1,3,4‐thiadiazole‐2‐thione. For these two species, only the thione tautomeric forms were observed after deposition of Ar matrices. These tautomers were predicted (by QCISD calculations) to be more stable (by at least 19 kJ mol?1) than other tautomeric forms. Upon UV irradiation, the most stable thione forms of these compounds were transformed into the corresponding thiol tautomers. Direct observation of the thione → thiol phototautomeric processes provides a clear proof that intramolecular proton transfer reaction can occur in molecules, such as bismuthiol, in spite of the increased NH···S distance, in comparison to other phototautomerizing species studied so far. All the isomers of the studied compounds (substrates and products of the photoreactions) were identified by comparison of their IR spectra with the spectra calculated at the DFT(B3LYP)/6‐311++G(2d,p) level of theory for possible isomeric structures. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
784.
The electrical properties of CuInSe2 epitaxial layers on (111)A-, (110)-, and (100)-oriented GaAs substrates are investigated. At substrate temperatures Tsub ≧ 820 K the p-type conductivity observed is governed by an acceptor state with an ionization energy of about 110 meV independent of the substrate orientation. At Tsub ≦ 770 K three different acceptor states are found in dependence on the substrate orientation: 390 meV for (111)A-, 110 meV for (110)-, and a very shallow acceptor for (100)-oriented substrates. A possible correlation between these acceptor states and intrinsic defects is proposed. 相似文献
785.
H. Neumann B. Schumann E. Nowak A. Tempel G. Kühn 《Crystal Research and Technology》1983,18(7):895-900
Using CuIn2Se3.5 as source material epitaxial layers are obtained on (111)A- und (100)-oriented GaAs substrates by flash evaporation in the substrate temperature range Tsub = 720—870 K. The composition of the films is between CuInSe2 and CuIn2Se3.5. The structural properties of the films are similar to those for CuInSe2 epitaxial layers and refer to a chalcopyrite-like structure. The films are always p-type conducting but different acceptor states are found in dependence on the substrate temperature. 相似文献
786.
W.-D. Nowak 《Fortschritte der Physik》1986,34(2):57-117
The present situation in deep inelastic lepton-nucleon scattering is reviewed from an experimenter's point of view. After describing, in some detail, the quark-parton model (QPM) predictions the basic ideas of Quantum Chromodynamics (QCD) are illustrated. The perturbative QCD predictions for deep inelastic scattering are summarised discussing also their theoretical uncertainties of today. Past and present experiments on deep inelastic electron and muon scattering are compared regarding their ability to test these predictions. It is shown that all data is in very good agreement with the QPM and fully consistent with perturbative QCD. New results on lepton scattering off nuclei are discussed and confronted to recently invented phenomenological models. 相似文献
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