Femtosecond laser ablation-ICP-mass spectrometry analysis of a heavy metallic matrix : determination of platinum group metals and gold in lead fire-assay buttons as a case study

Owing to the shorter time interval during which energy is delivered to the sample material, femtosecond (fs) laser ablation is preferable over nanosecond laser ablation for metallic samples. In this project, the influence of various laser parameters-beam diameter, repetition rate and laser fluence-on the ablation of Pb as a heavy metallic matrix using an infrared (lambda = 795 nm) fs-LA system (150 fs pulse duration) was studied. The merits of Ar and He as carrier gases were compared and as He did not provide a substantial improvement in the limits of detection, while deposition of sample material on the window of the ablation chamber was more pronounced, Ar was selected for all further measurements. The effect on the ICP caused by the introduction of various amounts of sample aerosol was studied by monitoring the signal intensity for Ar-38(+). It was shown that maximizing the amount of sample ablated and thus, the amount of sample aerosol introduced into the ICP, did not result in maximum sensitivity, which was rather obtained under 'compromise' conditions. Subsequently, femtosecond LA-quadrupole-based ICP-mass spectrometry (ICP-MS) was used for the determination of traces of the platinum group metals (PGMs) Rh, Pd, Ru, Ir and Pt and of Au in Pb buttons obtained by fire assay of platiniferous ore reference materials. The signal of Pb-204(+) was used as an internal reference, correcting for variations in the laser ablation and transport efficiencies and in the instrument's sensitivity. The spectral interferences established for some of the target nuclides due to the occurrence of Pb2+ ions were successfully overcome by pressurizing the reaction cell with NH3. Quantification versus a calibration curve constructed on the basis of the results obtained for matrix-matched standards (>99% Pb) provided excellent accuracy, superior to those obtained using nanosecond LA-ICP-MS. Also the limits of detection were improved by a factor ranging between 3 and 10 and are <0.010 mu g g(-1) for the most important PGMs (Rh, Pd, Pt) and Au. Several measures, such as the use of a large ablation cell and housing up to 10 Pb buttons, were taken to increase the sample throughput. In the same context, day-to-day reproducibility of the calibration curve was also examined. When recording a 'fresh' calibration curve every day, the average bias between the experimental results and the corresponding reference values was established to be <2.5% for every target element. When using one calibration curve during three consecutive days, the bias still remains <10%, while the sample throughput is increased and analysis of several tens of buttons per day is feasible (10-15 min total analysis time per sample)

Characterization of the murine cytomegalovirus early transcription unit e1 that is induced by immediate-early proteins

The regulation of murine cytomegalovirus early (E) gene expression was studied in the cell line B25, which is stably transfected with the immediate-early ie1/ie3 gene complex. Infection of B25 cells in the presence of the protein synthesis inhibitor cycloheximide resulted in the expression of some E genes, whereas for the expression of other E genes prior protein synthesis was still mandatory, thus showing differences in the expression requirements of individual E genes. Transcription unit e1, a member of the E genes induced by immediate-early products of the ie1/ie3 gene complex, was characterized. It is located between map units 0.709 and 0.721 of the genome of murine cytomegalovirus strain Smith. A 2.6-kilobase RNA specified in this region is spliced from three exons of 912, 177, and 1,007 or 1,020 nucleotides, which are separated by introns of 93 and 326 nucleotides. The second AUG located in the first exon 119 nucleotides downstream of the 5' cap site is followed by an open reading frame of 990 nucleotides. The predicted polypeptide of 330 amino acids has a calculated molecular mass of 36.4 kilodaltons. Transfection with e1 revealed three antigenically related proteins of 36, 37, and 38 kilodaltons; these proteins probably represent differently modified forms of the predicted protein. These three proteins are phosphorylated and are associated with intranuclear inclusion bodies. A 33-kilodalton protein also derived from e1 was identified as a product of nonspliced transcripts. Comparison of amino acid sequences revealed homology between the murine cytomegalovirus transcription unit e1 and a human cytomegalovirus E transcription unit

Geschützte und gefährdete Pflanzen, Tiere und Landschaften des Landes Sachsen-Anhalt : zu den Abbildungen 2. und 3. Umschlagseite

Der Mittelspecht ist eine der wenigen endemischen Vogelarten in Europa, deren Verbreitung sich auf Mittel- und Südeuropa erstreckt und nur wenige Ausläufer nach Asien bildet. Er gilt deshalb als Charakterart des europäischen Laubwaldes. Wegen der Zurückdrängung dieser Vegetationsform und der Umwandlung der verbliebenen Reste in Koniferenforste ist sein Areal deutlich geschrumpft. Der Stinkende Gänsefuß (Chenopodium vulvaria) gehört sicher nicht zu jenen Arten mit denen breite Bevölkerungsschichten emotional für die Belange des Naturschutzes begeistert werden können. Sie ist aber ein deutlicher Indikator für den Nutzungswandel im ländlichen Siedlungsbereich

Interpolation by spline spaces on classes of triangulations

We describe a general method for constructing triangulations &#916; which are suitable for interpolation by Srq(&#916;),

Studies on the Morphogenesis of Murine Cytomegalovirus

Two modes of assembly of murine cytomegalovirus (MCMV) were observed in cultured mouse embryo fïbroblasts, generating two morphologically different types of viral particles: monocapsid virions and multicapsid virions. The assembly of nucleocapsids appeared to be the same for both types of morphogenesis. Three successive stages of intranuclear capsid formation could be distinguished: capsids with electron-lucent cores, coreless capsids, and capsids with dense cores. Some of the capsids were enveloped at the inner nuclear membrane to form monocapsid virions, which were first detectable in the perinuclear cisterna. Other capsids left the nucleus via nuclear pores and usually entered cytoplasmic capsid aggregates that received an envelope by budding into extended cytoplasmic vacuoles, thereby forming multicapsid virions. Since the formation of multicapsid virions is not restricted to cell culture conditions and also occurs in vivo in immunosuppressed mice, multicapsid virions may play a role in the pathogenesis of cytomegalovirus infection

Monitoring of Thermokarst Lake Changes and Coastal Dynamics in Permafrost Landscapes of the East Siberian Sea Region Using High Resolution Imagery and DEM Data

The coastal region bordering the East-Siberian Sea is covered by ice-rich Yedoma deposits, which are extremely vulnerable to thaw in the course of climate warming in the high latitudes. Widespread permafrost degradation throughout the Arctic resulted in relief changes on ground-ice-cored Yedoma uplands. In order to track dynamics of these processes in the Kolyma lowland tundra at Cape Maly Chukochy (N 72.08°, E 159.9°), we used a set of very high resolution remote sensing imagery (GeoEye and historical airphotos) which were compared with DEM data (TanDEM-X and derived from WorldView-2). Analysis of meteorological data have put observed changes into the context of warming and wetting trends. Yedoma uplands represent flat bogged areas featuring a high number of thermokarst ponds with an average size of 5-10 in diameter. Our image dataset revealed a doubling in the number and areal coverage of ponds from 1972 to 2009 and a further twofold increase until 2013, while thermokarst lakes that formed within Yedoma deposits increased by 7-10 %, being partially in agreement with studies conducted elsewhere in the Arctic. Coastal erosion rates from 1972 until 2013 were high and 1,5 m per year on average. We used the areal extend of thermokarst mounds (baydzherakhs) on Yedoma slopes as indicator for ground ice melt and our estimates show a baydzherakhs coverage increase of 20 % by 2013. All these changes highlight the activation and acceleration of permafrost degradation on Yedoma uplands in response to increasing air temperatures and precipitation in the East-Siberian Sea coastal region

Pricing Web Services

This paper focuses on the challenges associated with composing and pricing web services. We present the results of an online experiment, where subjects were confronted with a variety of choices and decisions relating to web service markets and service composition. Our analysis shows that people expect the price of a composite web service to be lower than the sum of the prices of the elementary services, that is, users are not willing to pay for aggregation by a third party. To obtain a viable business model for composite web services, non-standard pricing mechanisms, such as auctions and negotiations, possibly supported by electronic agents, have to be taken into consideration. Usage-based pricing schemes, combined with an option to switch to a flat subscription, seem most appropriate to penetrate the developing market for web services.Peer Reviewe