Eine Apparatur zur Messung natürlicher 4C-Aktivitäten

Aufbau, Arbeitsweise und Eigenschaften einer Apparatur, mit der naturliche ^l4C-Aktiviäten in Grund- und Oberflächenwässern gemessen werden können, werden beschrieben.

Die Messung erfordert 3 Arbeitsschritte: Probenahme, Synthese von Benzol, welches dann den Probenkohlenstoff enthält, und Messung der ¹⁴C-Aktivität in einem Flüssigkeitsszintillationszähler.

Die Apparatur kann zur Datierung von Wasserproben im Altersbereich zwischen 200 und 37000 a verwendet werden.     

Beispiele für die Anwendung der 15N-Tracertechnik in der Düngungsforschung mit emissionsspektrometrischen Analysenverfahren (NOI-5; Isonitromat-5200)

Es werden Varianten der Probenchemie für ¹⁵N-Bilanzexperimente in der Düngungsforschung vorgestellt, die den Erfordernissen des Isonitromat-5200 und des NOI-5 angepaßt sind. Die skizzierten Methoden umfassen die destillative Präparation markierter N-Mengen (0,1–1 mg) aus Bodenextrakten, verbunden mil einem Zvsatz unmatkierter N-Mengen bei der Titration sowie eine für den Routinebetrieb geeignete N-Bestimmung in nicht angereicherten Pflanzenaufschlüssen mit dem Isonitromat-5200 als ¹⁵N-Verdünnungsanalyse. Weiterhin werden einfache apparative Varianten zur Bestimmung von sog. Gasförmigen Düngersticksloffverlusten durch Denitrifizierung in gasdichten Kammern dargestellt.

Durch ¹⁵N-Analyse von Luftproben über ¹⁵N-angereicherten natürlichen Bodenmonolithen mit dem NOI-5 können unmittelbar die vom Dünger freigesetzten N₂ und N₂O-Mengen bestimmt werden. Bei Spezialversuchen in stickstofffreier Neon(He)-Atmosphäre können gebildete N₂-, NO- und N₂O-Spuren (um 1 Vol. %)nach gaschromatographischer Trennung (auf Perapak-Q) individuell am NOI-5 gemessen werden. Unter Verwendung von CO₂-Trägergas werden die N-Komponenten in einem Azotometer isoliert und mit Hilfe eines Dosierhahnes, dessen Volumen den geforderten Gasdruck garantiert, in Entladungsrohre überführt.     

Schnell-Methode zur Umsetzung von Kohlenwasserstoffen zu Wasserstoff für die Isotopenanalyse

Es wird eine weiterentwickeltes, isotopenanalytisches Verfahren zur probenchemischen Umsetzung von Kohlenwasserstoffen mit Chromium zu Wasserstoff bei 1300 K vorgestellt. Die erzielten Testergebnisse zeigen anhand der gemessenen δD-Werte, daβ Quarzöfen bei diesen Temperaturen noch keine die Isotopenmeβwerte beeinflussende Diffusion von Wasserstoff durch die Wandung zulassen. Auβerdem erfolgte die Reaktion nahezu spontan und vollständig, was die Methode zeitlich sehr effektiv macht.

A modified isotope analytical method is presented for the chemical reaction of hydrocarbons with chromium at 1300 K to form hydrogen. The test results obtained (i.e. the measured δD-values) show that at this temperature quartz heating tubes do not allow hydrogen to diffuse through the wail, which fact would influence the isotopic composition. Furthermore the reaction proceeds nearly spontaneously and quantitatively, which yields an effective method, especially with respect to time.     

Deterministic joint remote preparation of arbitrary multi-qudit states

In this Letter, we put forward a new nontrivial three-step strategy for joint remote preparation of arbitrary two-qudit states (JRSP) in a deterministic manner from a spatially separated multi-sender to one receiver. The scheme is then extended to the arbitrary multi-qudit case. In our schemes, various partially entangled GHZ-like states with arbitrary complex parameters are used as the quantum channels. It overcomes state preparation failure leading to the loss of valuable quantum channel resource and ensures the prepared data available for the remote terminals under extreme conditions such as limited number of quantum channels and limited quantum information processing technologies.     

Preparation of TiO2-carbon surface composites with high photoactivity by supercritical pretreatment and sol-gel processing

TiO₂-carbon surface (TCS) composites were prepared by pretreatment of a sealing substrate in supercritical carbon dioxide using paraffin as a plugging agent, and sol-gel processing using tetrabutyl orthotitanate as a precursor. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectrum (XPS), optical absorption spectroscopy and nitrogen absorption. The photoactivity of TCS was checked by monitoring the decomposition of methylene blue (MB) in aqueous solution under UV irradiation. The results indicated that compared with TC prepared only by the sol-gel method, the small nanosize TiO₂ particles are well dispersed on carbon surface with large amount of micropores and high Eg values, meanwhile TCS have high Ti³⁺ concentration due to supercritical pretreatment providing a amount of carbon on the composite surface with interfacial energy effects, which controls the growth of TiO₂ nanoparticles, baffles the agglomeration of TiO₂ nanoparticles and easily produces Ti³⁺ ions. These are reasons why TCS has a higher efficiency of decomposing MB than TiO₂-carbon (TC) composites and pure TiO₂. Additional, it is also attributed to the fact that TCS produce a high concentration of organic compounds near TiO₂ in comparison with TC and pure TiO₂, because their surface area are greater than that of TC and pure TiO₂.     

Remote preparation of an entangled two-qubit state with three parties

We present a scheme for probabilistic remote preparation of an entangled two-qubit state with three parties from a sender to either of two receivers. The quantum channel is composed of a partially entangled two-qubit state and a partially entangled three-qubit state. We calculate the successful total probabilities of the scheme in general and particular cases, respectively. We also calculate total classical communication cost in a general case and two particular cases, respectively.     

2，5─哌嗪二酮与α，β─不饱和醛反应研究

综合运用了多种波谱学方法及化学手段确证并归属了２，５－哌嗪二酮与α，β－不饱和醛在超声波分散金属钾及双季铵盐作用下反应产物的立体化学与核磁共振信号，为研究这个反应提供了有用的信息．     

Efficient epoxidation over cyanocobalamine containing SBA-15 organic-inorganic nanohybrids

SBA-15 mesoporous silica is synthesized using triblock copolymer P123 surfactant and chemically modified by aminopropyl, thiol, ammonium and sulfonic acid functional groups. Functionalization is performed via post synthesize method using 3-aminopropyltriethoxysilane (APTES) or 3-mercatopropyl trimethoxysilane (MPTMS) precursor. The as synthesized mesoporous systems are applied for immobilization of cyanocobalamine. Functionalization effectively improves sorption properties of the supports, while different functional groups exert different effects. The organic-inorganic mesoporous materials are characterized via X-ray diffraction (XRD), nitrogen adsorption and desorption, transmission electron microscopy (TEM), FT-IR and inductively coupled plasma-optical emission (ICP). The newly synthesized systems exhibit high catalytic activity for heterogeneous epoxidation of cyclooctene in presence of hydrogen peroxide. Reaction conditions are optimized, effect of functional groups on performance of the catalysts is taken into consideration and reusability of the designed heterogeneous systems is studied. Systems with chemically modified supports are shown to be more efficient and stable catalysts however; chemical nature of functional groups plays a crucial role.     

Microwave-assisted synthesis of SrFe12O19 hexaferrites

Ultra-fine and homogeneous SrFe₁₂O₁₉ hexaferrites were synthesized by a microwave-assisted calcination route. The calcined precursors were prepared by a sol-gel auto-combustion method using Fe(NO₃)₃·9H₂O, Sr(NO₃)₂ and citric acid as starting materials. The structures, powder morphology and magnetic properties of the products were characterized by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer. The results showed that microwaves are helpful to reduce the calcination temperature and shorten the calcination time. The ferrites with saturation magnetization, remanence and intrinsic coercivity of 54.80 emu/g, 29.52 emu/g and 5261 Oe, respectively, were obtained in samples calcined at 800 °C for 80 min.