Chemical composition, mass size distribution and source analysis of long-range transported wildfire smokes in Helsinki

Special episodes of long-range transported particulate (PM) air pollution were investigated in a one-month field campaign at an urban background site in Helsinki, Finland. A total of nine size-segregated PM samplings of 3- or 4-day duration were made between August 23 and September 23, 2002. During this warm and unusually dry period there were two (labelled P2 and P5) sampling periods when the PM2.5 mass concentration increased remarkably. According to the hourly-measured PM data and backward air mass trajectories, P2 (Aug 23-26) represented a single, 64-h episode of long-range transported aerosol, whereas P5 (Sept 5-9) was a mixture of two 16- and 14-h episodes and usual seasonal air quality. The large chemical data set, based on analyses made by ion chromatography, inductively coupled plasma mass spectrometry, X-ray fluorescence analysis and smoke stain reflectometry, demonstrated that the PM2.5 mass concentrations of biomass signatures (i.e. levoglucosan, oxalate and potassium) and of some other compounds associated with biomass combustion (succinate and malonate) increased remarkably in P2. Crustal elements (Fe, Al, Ca and Si) and unidentified matter, presumably consisting to a large extent of organic material, were also increased in P2. The PM2.5 composition in P5 was different from that in P2, as the inorganic secondary aerosols (NO3-, SO4(2-), NH4+) and many metals reached their highest concentration in this period. The water-soluble fraction of potassium, lead and manganese increased in both P2 and P5. Mass size distributions (0.035-10 microm) showed that a large accumulation mode mainly caused the episodically increased PM2.5 concentrations. An interesting observation was that the episodes had no obvious impact on the Aitken mode. Finally, the strongly increased concentrations of biomass signatures in accumulation mode proved that the episode in P2 was due to long-range transported biomass combustion aerosol.     

Pareto optima of isostatic trusses

Multicriterion optimization of elastic stress limited isostatic trusses is considered and a numerical method for determining the Pareto optimal set of the problem is developed. The weight of the structure and some chosen nodal displacements are taken as design criteria, and member areas are used as design variables. The corresponding bicriterion problem with weight and one displacement in the objective function is solved exactly, and this result is used as a basis of the proposed method. By introducing certain parameters, each joined with one displacement criterion, the Pareto optimal solutions of the general problem may be obtained with any accuracy. Two examples are given to illustrate the method.     

Local Oscillator Generation Circuit for Direct Conversion Transmitter

In this paper a fully monolithic on-chip local oscillator signal generation circuit is presented for eliminating the negative effect of coupling between bond-wires, package pins and output and input lines of the power amplifier output to the local oscillator input for direct conversion transmitters. The proposed circuit generates the local oscillator signal at frequencies 1710–1785 GHz which is harmonically uncorrelated from two input signals at 464 MHz and 1792–2088 MHz. The required building blocks are a frequency divider, a mixer and an active band-pass filter. Fully monolithic high frequency band-pass filters have not been available until recently, and the designed circuit is in fact one of the first applications reported for MMIC active filters in cellular phones. The circuit is designed with a 0.5 m GaAs MESFET technology and the performance is verified with on-chip measurements.     

Vortex Pinning to a Solid Sphere in Helium II

We report here the results of a computer simulation of quantized vortex pinning in He II at 0 K in the simple situation where a single sphere and a rectilinear vortex are considered. Our simulation shows that a vortex nearby a sphere is captured due to a velocity field produced by the sphere, exciting Kelvin waves. The dependence of the “pinning” on temperature is investigated as well. Finally, the possibility of pinning in PIV experiments, which visualize superfluid turbulence, is discussed.     

CFD evaluation of hydrogen risk mitigation measures in a VVER-440/213 containment

In the PHARE project “Hydrogen Management for the VVER440/213” (HU2002/000-632-04-01), CFD (Computational Fluid Dynamics) calculations using GASFLOW, FLUENT and CFX were performed for the Paks NPP (Nuclear Power Plant), modelling a defined severe accident scenario which involves the release of hydrogen. The purpose of this work is to demonstrate that CFD codes can be used to model gas movement inside a containment during a severe accident. With growing experience in performing such analyses, the results encourage the use of CFD in assessing the risk of losing containment integrity as a result of hydrogen deflagrations. As an effective mitigation measure in such a situation, the implementation of catalytic recombiners is planned in the Paks NPP. In order to support these plans both unmitigated and recombiner-mitigated simulations were performed. These are described and selected results are compared. The codes CFX and FLUENT needed refinement to their models of wall and bulk steam condensation in order to be able to fully simulate the severe accident under consideration.Several CFD codes were used in parallel to model the same accident scenario in order to reduce uncertainties in the results.Previously it was considered impractical to use CFD codes to simulate a full containment subject to a severe accident extending over many hours. This was because of the expected prohibitive computing times and missing physical capabilities of the codes. This work demonstrates that, because of developments in the capabilities of CFD codes and improvements in computer power, these calculations have now become feasible.     

The size of cytoplasmic lipid droplets varies between tumour cell lines of the nervous system: a 1H NMR spectroscopy study

Object

Cytoplasmic lipid droplets (LDs) are dynamic cellular organelles; their accumulation is associated with several cellular processes, such as cell proliferation, apoptosis and necrosis. ¹H Nuclear Magnetic Resonance (NMR) spectroscopy detects resonances from lipids present in cytoplasmic (LDs); an understanding of the relationship between LD characteristics and NMR lipid signals is important.

Materials and methods

In this study, five nervous system cancer cell lines were investigated. Nile red staining was used to measure the diameter of LDs. High-resolution magic angle spinning NMR (HR-MAS) was performed on harvested cell pellets to quantify the patterns of lipid signals.

Results

LDs were present in all five cell lines with different morphology. An average LD diameter of approximately 0.2???m was found in all cell types. Diameter of the largest LDs varied across the cell lines. The intensity of NMR lipid signals varied greatly between cell types, and a good correlation was found between total volume of LDs and the proton NMR lipid signal intensity at 0.9 and 1.3?ppm.

Conclusion

The correlation implied that little NMR signal is detected from LDs of diameters less than approximately 0.34???m, most likely due to restriction of rotational motion of the lipids.     

Rapid removal of lead and cadmium from water by specific lactic acid bacteria

Cadmium and lead are highly toxic metals. People are exposed to them primarily through food and water. Available conventional methods (precipitation, flocculation, ion exchange, and membrane filtration) for removal of these metals from water at low concentrations are claimed to be expensive and inefficient. Different microbes have been proposed to be an efficient and economical alternative in heavy metal removal from water. In this work, specific lactic acid bacteria (LAB) were assessed for their ability to remove cadmium and lead from water. Significant removal was observed, and it was found to be metal and bacterial strain specific. Removal was a fast, metabolism-independent surface process. It was also strongly influenced by pH, indicating that ion exchange mechanisms could be involved. The most effective metal removers were Bifidobacterium longum 46, Lactobacillus fermentum ME3 and Bifidobacterium lactis Bb12. The highest maximum cadmium and lead removal capacities of 54.7 mg metal/g and 175.7 mg/g dry biomass, respectively, were obtained with B. longum 46.     

In vitro studies toward noninvasive glucose monitoring with optical coherence tomography

We use optical coherence tomography (OCT) to measure glucose-induced changes in Intralipid and in mouse skin samples in vitro. Mouse skin samples are cultured in a CO2 incubator before measurements are made with different amounts of added glucose concentrations. The results show that the glucose-induced changes in the OCT slope value vary between 20% and 52%/30 mM glucose in different mouse skin samples. This change is much larger than the change in 2% Intralipid (2.1%/30 mM) and in 5% Intralipid (0.86%/30 mM). Hence the results show that OCT has potential to monitor glucose-induced changes in tissues in vitro.     

Size Distribution Measurement of Carbonaceous Particulate Matter Using a Low Pressure Impactor with Quartz Fiber Substrates

The collection characteristics of a small deposit area low pressure impactor (SDI) were studied in order to employ the impactor for size distribution measurements of carbonaceous matter. In this work, the SDI was calibrated for soft and porous quartz substrate material in a series of laboratory experiments. The collection efficiency curves were measured by using monodisperse dioctyl sebacate particles and by applying two different detection methods. One method was based on the detection of current carried by charged test particles, and the other measured number concentrations of particles in bipolar charge equilibrium by two condensation particle counters. Concerning the particle size corresponding to a 50% collection efficiency (D ₅₀ ), significant shifts toward smaller particle sizes were found for the quartz fiber substrates compared with the flat plates. Also the shapes of the collection efficiency curves differed considerably: quartz substrate gave less steep curves than plain impaction plates. The new calibration was applied to field data from urban and rural sites. Compared with the original calibration of the SDI, the new calibration changed the measured size distributions of organic and elemental carbon. In addition, a reasonable size-segregated mass closure was achieved by combining data from thermal-optical analysis and ion-chromatography.