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11.
We use an unrestricted self-consistent Hartree-Fock approach to calculate the nature of doping states in the three-band Hubbard model. It turns out that for physically relevant parameter values one hole is localized within a small spin-polarized region where five Cu spins are aligned in the same direction. The spin polarization and binding energy between these spinpolaronic states are investigated as a function of different parameters including a Holstein-type electron-phonon coupling on the Cu sites. At higher doping concentration we observe the occurrence of afmon states where the holes are localized in a ring-shaped area. Inside this ring the antiferromagnetic order parameter has inverse sign with respect to the residual antifer-romagnetically ordered plane. 相似文献
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E Ernst 《Canadian Metallurgical Quarterly》1995,7(4):259-263
Complementary therapies are frequently used by cancer patients, yet the area is a minefield of hazards and hopes. A distinction between cure and care seems helpful. There are no effective complementary cures and most options that are promoted carry a distinct and, in certain cases, fatal risk. Complementary cancer care is more acceptable and there are options that can be shown to ease suffering. Vis a vis the popularity of complementary cancer treatments, the lack of scientific evidence for most therapies seems unacceptable. The call for more rigorous research is loud and clear. 相似文献
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Ernst Pöppel 《Informatik-Spektrum》2002,73(6):427-437
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Industrial Oxo Synthesis with Immobilised Catalyst. The use of water-soluble catalysts represents a significant advance in homogeneous catalysis; “immobilisation” of the catalyst in a second immiscible liquid phase has the effect of “heterogenisation” and allows the advantages of heterogeneous processing (long lifetimes, straightforward technology) to the combined with those of the homogeneous mode (gentle reaction conditions, high activity and selectivity). In particular, the decisive advantage of homogeneous catalysts, viz. the wide range of variation of their steric and electronic properties which can be adapted to the specific reaction at hand, can be exploited for tailoring highly effective catalysts. Moreover, the mode of action of these homogeneous catalysts remains understandable as a model and under the reaction conditions chosen – in complete contrast to the case of many heterogeneous catalytic systems. The first successful industrial application of water-soluble catalysts was in the oxo process of Ruhrchemie/Rhǒne Poulenc. The following article reports on ten years' experience with this process and the HRh(CO)[P(msulphophenyl-Na)3]3 catalyst. 相似文献
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Depression is one of the most common reasons for using complementary and alternative therapies. The aim of this article is to provide an overview of the evidence available on the treatment of depression with complementary therapies. Systematic literature searches were performed using several databases, reference list searching, and inquiry to colleagues. Data extraction followed a predefined protocol. The amount of rigorous scientific data to support the efficacy of complementary therapies in the treatment of depression is extremely limited. The areas with the most evidence for beneficial effects are exercise, herbal therapy (Hypericum perforatum), and, to a lesser extent, acupuncture and relaxation therapies. There is a need for further research involving randomized controlled trials into the efficacy of complementary and alternative therapies in the treatment of depression. 相似文献
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Wolfgang Luf und Ernst Brandl 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1988,186(4):327-332
Zusammenfassung Zur Bestimmung der Annatto-Farbstoffe Norbixin und Bixin in Käse wird eine derivativspektroskopische und eine HPLC-Methode vorgeschlagen. Beide Methoden kommen mit einer raschen und einfachen Probenaufbereitung aus, da eine Abtrennung von-Carotin und Fett nicht erforderlich ist. Die Probenaufbereitung besteht aus einer Extraktion der Farbstoffe mit Aceton, Filtration, Eindampfen des Extraktes, Entfernen von Restwasser durch Zusats von einigen Millimetern absolutem Alkohol und anschließendem Eindampfen, Aufnehmen in Chloroform/Eisessig (99,5 + 0,5) für die Derivativspektroskopie bzw. Aceton für die HPLC. Die derivativspektroskopische Methode erlaubt sowohl die qualitative Analyse (Nachweisgrenze unter 0,67 mg/kg abhängig vom natürlichen-Carotingealt), als auch eine Quantifizierung. Sie kann deshalb sowohl als Screeningmethode zur Kontrolle der rigorosen österreichischen Vorschriften, als auch zur Kontrolle der Einhaltung von Höchstwerten verwendet werden und zeichnet sich weiters durch eine kurze Analysenzeit (75 s) und geringem Materialaufwand aus. Die HPLC-Methode gestattet einerseits eine Auftrennung der Komponenten Norbixin und Bixin als auch eine separate quentitative Erfassung der in Schnittkäse anzutreffenden Carotinoide wie-Carotin,-Apo-8-Carotinal und-Apo-8-Carotinsäureethylester (Nachweisgrenze für Norbixin und Bixin 0,2 mg/kg). Die dafür erforderliche Analysenzeit beträgt 20 min. Die HPLC-Methode wird für Bestätigungszwecke bei Vorliegen geringer Bixin-Norbixinkonzentrationen bzw. als Alternative vorgeschlagen.
Detection of annatto dye-stuffs, norbixin and bixin, in cheese by means of derivative spectroscopy and high performance liquid chromatography (HPLC)
Summary A derivative spectroscopic method and a HPLC-method are described for the determination of the annatto dye-stuffs, norbixin and bixin, in cheese. Both methods enable a simple and quick sample preparation since the separation of-carotene and fat is not required. The sample preparation step consists of extraction with acetone, filtration, evaporation of the extract and separation of water residues by the addition of a few milliliters of absolute ethanol. This is followed by evaporation and extraction of the residual solution with chloroform/acetic acid (99.5 + 0.5) for the derivative spectroscopic method or with acetone for the HPLC method. The qualitative detection (detection limit greater than 0.67 mg/kg, depending on the genuine-carotene content) as well as the quantitative determination is possible by means of the derivative spectroscopic method. Therefore, this technique may be used within the rigorous Austrian regulation or for controlling the quantities and limits of annatto dye-stuffs in cheese, if its application is allowed. The method also has the advantage of quick detection (only 75 s) and saving of material used. The HPLC method allows for the separation and quantification of norbixin and bixin as well as the other carotenoids such as-carotene,-apo-8-carotenal and-apo-8-carotenoic acid — ethylester, which may also be found in varieties of cheese (detection limit of norbixin and bixin: 0.2 mg/kg). The time required for the separation of the above mentioned substances is 20 min and the HPLC method is proposed for the confirmation of low concentrations of these substances.相似文献