Reduction of carbon dioxide and organic carbonyls by hydrosilanes catalysed by the perrhenate anion

The simple perrhenate salt [N(hexyl)4][(ReO4)] acts as a catalyst for the reduction of organic carbonyls and carbon dioxide by primary and secondary hydrosilanes. In the case of CO2, this results in the formation of methanol equivalents via silylformate and silylacetal intermediates. Furthermore, the addition of alkylamines to the reaction mixture favours catalytic amine N-methylation over methanol production under certain conditions. DFT analysis of the mechanism of CO2 reduction shows that the perrhenate anion activates the silylhydride forming a hypervalent silicate transition state such that the CO2 can directly cleave a Si–H bond

Orbital Observations of Dust Lofted by Daytime Convective Turbulence

Over the past several decades, orbital observations of lofted dust have revealed the importance of mineral aerosols as a climate forcing mechanism on both Earth and Mars. Increasingly detailed and diverse data sets have provided an ever-improving understanding of dust sources, transport pathways, and sinks on both planets, but the role of dust in modulating atmospheric processes is complex and not always well understood. We present a review of orbital observations of entrained dust on Earth and Mars, particularly that produced by the dust-laden structures produced by daytime convective turbulence called “dust devils”. On Earth, dust devils are thought to contribute only a small fraction of the atmospheric dust budget; accordingly, there are not yet any published accounts of their occurrence from orbit. In contrast, dust devils on Mars are thought to account for several tens of percent of the planet’s atmospheric dust budget; the literature regarding martian dust devils is quite rich. Because terrestrial dust devils may temporarily contribute significantly to local dust loading and lowered air quality, we suggest that martian dust devil studies may inform future studies of convectively-lofted dust on Earth

Planar computer tomography (PCT)

There is an increasing demand on testing various layers of a multi-layer Printed Circuit Board (PCB) assembly. Especially the soldered joints are often the reason for the malfunction of IC board. This problem cannot be solved by 2-dimensional testing devices because of an overlapping of two different components or soldered jounkts at double side assemblies. Also in the case of Ball Grid Arrays (BGAs), only tomographic inspection systems provide the required information. Classical Computer Tomography (CT) reconstruction is based on axial rotation of the inspected object. The planar geometry of PCBs presents a problem with the necessary axial rotation for the inspection of PCB. Lateral planar movement would be better suited than rotation necessary for classical CT. Since the algorithm of Planar Computer Tomography (PCT) is well suited for parallel computers and only a few projections are needed, a significant speed-up will be achieved compared with axial (CT) and other 3D inspection tech niques. As a future extension, it is planned to add the possibility of testing even electronic devices internally because all ICs, which were soldered directly on a PCB, face the risk of being damaged due to the high temperatures of the soldering process. Therefore a final inspection for cracks and delaminations becomes more and more necessary. As a result, resolution and reliability of such testing devices has to be improved significantly

Heterogeneity of nano-sized zeolite crystals

Analytical characterization and evaluation of performance of zeolite catalysts are normally done under the assumption of a homogeneous batch. However, it is known that in the same batch particles of the zeolite ZSM-5 can be very different one from another, regarding their aluminum content and catalytic performance. Here, we quantify the extent of this heterogeneity within a singular synthesis batch of nanocrystalline ZSM-5, through the analysis of single crystalline individua. We found that the overall aluminum content was distributed unequally between two kinds of crystal populations. Cornered crystals contained three times more aluminum than round-shaped crystals. This observation connects morphological differences to the chemical composition of each zeolite crystal for the first time. This finding could provide a means for performance optimization in zeolite synthesis

Mikrosystemtechnisch hergestelltes Sensorsystem zur Klimadatenerfassung (A-Haus). Teilvorhaben: Sensorik und Kalibrierung Abschlussbericht

Advances in the miniaturization of devices lead to smaller and cheaper sensors for different applications. Embedded systems also offer the possibility to communicate over standardized interfaces within an electronic network. In this paper we describe, how these technologies can be applied to an intelligent Weather Station not larger than a cup. This Weather Station is e.g. needed for an optimized energy saving management of large buildings in regard of heating and air conditioning. Using modern building management systems, heating of private and office buildings can be optimized for lower energy consumption. These days heating systems are controlled by the input of the outdoor temperature of air measured at the north side of the building. However, the thermal loss of a building is determined by more parameters. Our weather system consists of a solar radiometer, a rain detector (only qualitative), a hygrometer, a thermometer and a wind gauge. All meteorological data are monitored automatically and made available to the building management system over a digital interface like EIB. (orig.)Im Zentrum der betrachteten Loesungsansaetze standen kostenguenstige Loesungen und es musste eine geraetetechnische Ausfuehrung einbezogen werden. Es galt die am Markt vorhandenen dezentralen Wetterstationen der Gebaeudeautomatisierung durch eine kompakte zu ersetzen. Um diese geometrisch moeglichst klein und kompakt gestalten zu koennen, kamen Techniken der Mikrosystemtechnik zum Einsatz. Gegenstand der sensorischen Entwicklung war der Feuchtesensor und der kombinierte Windgeschwindigkeits- und Windrichtungssensor. Beim Feuchtesensor kam eine IDK-Struktur mit feuchteempfindlichem Polyimid zur Anwendung, bei der Windgeschwindigkeitsmessung fand ein 'thermischer Oszillator' seine Verwendung, der ein der Windgeschwindigkeit proportionales digitales Ausgangssignal liefert und bei der Windrichtungsmessung eine vektorielle Analogschaltung. Die Strahlungsleistungsdichtemessung erfolgt bei der realisierten Loesung mit zwei Fotodioden, die eine unterschiedliche spektrale Empfindlichkeit haben. Der Niederschlagssensor ist ein rein digitaler Sensor, mit dem nur das Vorhandensein von Niederschlag erkannt werden kann. Die erforderliche Schaltungsanordnung zur Auswertung des Sensorsignals basiert auf einem Laufzeitvergleich zwischen dem kapazitiven Niederschlagssensor und einem Referenzzweig. Kern des Sensorsystems zur Klimadatenerfassung ist ein Mikrocontroller ADuC 812, in dem die Messwertverarbeitung und die Speicherung der Kalibrierfunktionen erfolgt. Mit Potenzreihen 3. Ordnung wird der nichtlinearen Charakter des Feuchtefuehlers, des Windsensors und der Temperaturmessschaltung hinreichend beschrieben. An die jeweiligen Eingaenge dieses Mikrocontrollers sind die einzelnen Sensoren mit dem zugehoerigen Interface angeschlossen. Dieses fuer die einzelnen klimarelevanten Messgroessen benoetigte Sensorinterface ist aus Gruenden der Kostenminimierung und eines geringen Eigenenergieverbrauchs sehr einfach ausgefuehrt worden. Ueber eine angeschlossene Schnittstelle werden die klimarelevanten Messwerte einheitengerecht gemaess SI ausgegeben. (orig.)Available from TIB Hannover: F02B1922 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Observations of ion cyclotron waves in the solar wind near 0.3 AU

Using 2 Hz magnetic field data from the MESSENGER mission, we have investigated more than 300 strong narrowband ion cyclotron wave (ICW) events at a heliocentric distance of about 0.3 AU during 31 May to 9 June 2008. These nearly circularly polarized transverse waves are observed extensively and discretely in the solar wind, with a median duration of 21 s. They are preferentially observed when the magnetic field is more radial than the ambient solar wind. The waves appear both left-handed and right-handed in the spacecraft frame. Their wave frequencies in the spacecraft frame are generally larger than the local proton cyclotron frequency (f(pc)), with a median of 1.44 f(pc). The wave power spectra do not cutoff at the local f(pc). On the basis of their wave characteristics, we conclude that they are intrinsically left-handed in the solar wind frame and they are generated closer to the Sun and carried out to the spacecraft by the super Alfvenic solar wind. After removing the Doppler shift, the wave frequencies in the solar wind frame are all below the local f(pc), with a median of 0.35 f(pc). The ICWs propagate nearly parallel to the magnetic field, and the median wave amplitude is about 0.73 nT, 3% of the background magnetic field. We compare these observations with earlier Helios observations at 0.3 AU in 1976 and contemporary 1 AU observations