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Search Results: 1 - 10 of 461366 matches for " A. Sillanp?? "
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Comparison of the levels of organic, elemental and inorganic carbon in particulate matter in six urban environments in Europe
M. Sillanp??,A. Frey,R. Hillamo,A. S. Pennanen
Atmospheric Chemistry and Physics Discussions , 2005,
Abstract: A series of 7-week sampling campaigns were conducted in urban background sites in the six European cities as follows: Duisburg 4 October–21 November 2002 (autumn), Prague 29 November 2002–16 January 2003 (winter), Amsterdam 24 January–13 March 2003 (winter), Helsinki 21 March–12 May 2003 (spring), Barcelona 28 March–19 May 2003 (spring) and Athens 2 June–21 July 2003 (summer). The campaigns were scheduled to include seasons of local public health concern due to high PM concentrations or findings in previously conducted epidemiological studies. Aerosol samples were collected in parallel with two identical virtual impactors (VI), which divide air PM into two size fractions, PM2.5 and PM2.5-10. The filter samples were analysed with a microbalance, an energy dispersive X-ray fluorescence (ED-XRF), an ion chromatograph (IC) and a thermo-optical carbon analyser (TOA). The PM2.5 and PM2.5-10 campaign means ranged 8.3–29.6 μg m-3 and 5.4–28.7 μg m-3, respectively. The ''wet and cool'' seasons favoured low coarse PM concentration and high fine PM concentration, whereas the spring and summer led to low fine and high coarse PM concentrations. The contribution of particulate organic matter (POM) to PM2.5-10 was highest (27%) in Prague and the lowest (10%) in Barcelona, while those to PM2.5 were generally higher, ranging from 21% in Barcelona to 54% in Prague. The contribution of elemental carbon (EC) to PM2.5-10 were relatively low (1–6%) in all the six European cities but it contributed somewhat higher (5–9%) to PM2.5. The differences are most likely due to variable contributions of local emission sources and seasonal factors such as domestic heating, vehicle exhausts and photochemical reactions. Carbonate, which interferes with carbon analysis by evolving stage at 900°C, was detected in the coarse particles of Athens and Barcelona and it could be separated reliably from OC by a simple integrating method. The calcium carbonate in Athens and Barcelona accounted for 56% and 11% of coarse PM masses, respectively. Carbonate was not found in other cities or in PM2.5. The mean PM2.5 mass portions of five OC thermal fractions (OC1, OC2, OC3, OC4 and OCP) varied in the range 26–33%, 6–10%, 7–10%, 9–22% and 29–50%, respectively, in six cities. The differences in the mass portion profiles were relatively small between the cities.
Organic, elemental and inorganic carbon in particulate matter of six urban environments in Europe
M. Sillanp??,A. Frey,R. Hillamo,A. S. Pennanen
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2005,
Abstract: A series of 7-week sampling campaigns were conducted in urban background sites of six European cities as follows: Duisburg (autumn), Prague (winter), Amsterdam (winter), Helsinki (spring), Barcelona (spring) and Athens (summer). The campaigns were scheduled to include seasons of local public health concern due to high particulate concentrations or findings in previously conducted epidemiological studies. Aerosol samples were collected in parallel with two identical virtual impactors that divide air particles into fine (PM2.5) and coarse (PM2.5-10) size ranges. From the collected filter samples, elemental (EC) and organic (OC) carbon contents were analysed with a thermal-optical carbon analyser (TOA); total Ca, Ti, Fe, Si, Al and K by energy dispersive X-ray fluorescence (ED-XRF); As, Cu, Ni, V, and Zn by inductively coupled plasma mass spectrometry (ICP/MS); Ca2+, succinate, malonate and oxalate by ion chromatography (IC); and the sum of levoglucosan+galactosan+mannosan (∑MA) by liquid chromatography mass spectrometry (LC/MS). The campaign means of PM2.5 and PM2.5-10 were 8.3-29.6 μg m-3 and 5.4-28.7 μg m-3, respectively. The contribution of particulate organic matter (POM) to PM2.5 ranged from 21% in Barcelona to 54% in Prague, while that to PM2.5-10 ranged from 10% in Barcelona to 27% in Prague. The contribution of EC was higher to PM2.5 (5-9%) than to PM2.5-10 (1-6%) in all the six campaigns. Carbonate (C(CO3), that interferes with the TOA analysis, was detected in PM2.5-10 of Athens and Barcelona but not elsewhere. It was subtracted from the OC by a simple integration method that was validated. The CaCO3 accounted for 55% and 11% of PM2.5-10 in Athens and Barcelona, respectively. It was anticipated that combustion emissions from vehicle engines affected the POM content in PM2.5 of all the six sampling campaigns, but a comparison of mass concentration ratios of the selected inorganic and organic tracers of common sources of organic material to POM suggested also interesting differences in source dominance during the campaign periods: Prague (biomass and coal combustion), Barcelona (fuel oil combustion, secondary photochemical organics) and Athens (secondary photochemical organics). The on-going toxicological studies will clarify the health significance of these findings.
H-alpha monitoring of OJ 287 in 2005-08
K. Nilsson,L. O. Takalo,H. J. Lehto,A. Sillanp??
Physics , 2010, DOI: 10.1051/0004-6361/201014198
Abstract: We present the results of H-alpha monitoring of the BL Lac object OJ 287 with the VLT during seven epochs in 2005-08. We were able to detect five previously undetected narrow emission lines, 6548,6583[NII], 6563H-alpha$ and 6716,6731[SII] during at least one of the epochs and a broad H-alpha feature during two epochs. The broad H-alpha luminosity was a factor ~10 lower in 2005-08 than in 1984 when the line was previously detected and a factor ~10 lower than what is observed in quasars and Seyfert galaxies at the same redshift. The data are consistent with no change in the position or luminosity of the H-alpha line in 2005-08. The width of the H-alpha line was 4200 +- 500 km/s, consistent with the width in 1984.
Dynamics of the Inductive Single-Electron Transistor
Mika A. Sillanp??,Leif Roschier,Pertti J. Hakonen
Physics , 2004,
Abstract: Using a classical equation of motion, dynamics of the phase is analyzed in the Inductive Single-Electron Transistor (L-SET) which is a promising new system suitable for quantum measurement with ultimate sensitivity and low back-action. In a regime of nonlinear dynamics, a shift of the oscillator resonant frequency is discovered which has a direct analogy to the switching of a dc-biased Josephson junction into voltage state. Results are reviewed for the predicted charge sensitivity, and it is shown that a performance challenging the best rf-SETs is foreseeable with the new device.
Morphology-Controlled Synthesis of ZnxCd1-xS Solid Solutions: An Efficient Solar Light Active Photocatalyst for the Degradation of 2,4,6-Trichlorophenol  [PDF]
Rengaraj Selvaraj, Kezhen Qi, Sathish Babu Soundra Pandian, Mohammed A. Meetani, Bushra Al Wahaibi, Haider Al Lawati, Salma M. Z. Al Kindy, Younghun Kim, Mika Sillanp??
Journal of Environmental Protection (JEP) , 2016, DOI: 10.4236/jep.2016.711132
ZnxCd1-xS solid solutions with controlled morphology have been successfully synthe-sized by a facile solution-phase method. The prepared samples were characterized by X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectra, X-ray photoelec-tron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission elec-tron microscopy (TEM). The photocatalytic activity of ZnxCd1-xS was evaluated in the 2,4,6-trichlorophenol (TCP) degradation and mineralization in aqueous solution under direct solar light illumination. The experiment demonstrated that TCP was effectively degraded by more than 95% with 120 min. The results show that ZnS with Cd doping (ZnxCd1-xS) exhibits the much stronger visible light adsorption than that of pure ZnS, the light adsorption increasing as the Cd2+ doping amount. These results indicate that Cd doping into a ZnS crystal lattice can result in the shift of the valence band of ZnS to a positive direction. It may lead to its higher oxidative ability than pure ZnS, which is important for organic pollutant degradation under solar light irradiation. Further-more, the photocatalytic activity studies reveal that the prepared ZnxCd1-xS nanostructures exhibit an excellent photocatalytic performance, degrading rapidly the aqueous 2,4,6-trichlorophenol solution under solar light irradiation. These results sug-gest that ZnxCd
Childhood Adversities Associated with Eating Disorders Reported by Adults  [PDF]
Veera Sillanp??, Kari Mattila, Markku Sumanen
Health (Health) , 2015, DOI: 10.4236/health.2015.710147
Abstract: Background: It has been suggested that childhood events increase the risk of suffering from an eating disorder (ED) in adolescence or young adulthood. Our study here aimed at investigating whether there was an association between stressful childhood events and eating disorders later in life. Methods: Our population-based study was a part of the HeSSup (The Health and Social Support) postal survey in 2003, a follow-up survey with a random sample of working-aged subjects drawn from the Finnish Population Register in 1998. Participants in this study reported having been suffering from ED (N = 374), while controls (N = 18,639) reported no history of eating disorder in the questionnaire both in 1998 and 2003. The questionnaire included six questions related to childhood adversities. Results: Each childhood stressor increased the risk of developing ED cumulatively (one adversity OR 1.7 versus all six OR 8.3). Intrafamiliar conflicts (OR 2.0), being afraid of a family member (OR 1.5) or long-term illnesses in the family (OR 1.4) increased the ED-risk statistical significantly. Conclusion: Children exposed to stress are more likely to suffer from eating disorders as adults than those not exposed.
Ionospheric conductances derived from satellite measurements of auroral UV and X-ray emissions, and ground-based electromagnetic data: a comparison
A. Aksnes, O. Amm, J. Stadsnes, N. stgaard, G. A. Germany, R. R. Vondrak,I. Sillanp
Annales Geophysicae (ANGEO) , 2005,
Abstract: Global instantaneous conductance maps can be derived from remote sensing of UV and X-ray emissions by the UVI and PIXIE cameras on board the Polar satellite. Another technique called the 1-D method of characteristics provides mesoscale instantaneous conductance profiles from the MIRACLE ground-based network in Northern Scandinavia, using electric field measurements from the STARE coherent scatter radar and ground magnetometer data from the IMAGE network. The method based on UVI and PIXIE data gives conductance maps with a resolution of ~800km in space and ~4.5min in time, while the 1-D method of characteristics establishes conductances every 20s and with a spatial resolution of ~50km. In this study, we examine three periods with substorm activity in 1998 to investigate whether the two techniques converge when the results from the 1-D method of characteristics are averaged over the spatial and temporal resolution of the UVI/PIXIE data. In general, we find that the calculated conductance sets do not correlate. However, a fairly good agreement may be reached when the ionosphere is in a state that does not exhibit strong local turbulence. By defining a certain tolerance level of turbulence, we show that 14 of the 15 calculated conductance pairs during relatively uniform ionospheric conditions differ less than ±30%. The same is true for only 4 of the 9 data points derived when the ionosphere is in a highly turbulent state. A correlation coefficient between the two conductance sets of 0.27 is derived when all the measurements are included. By removing the data points from time periods when too much ionospheric turbulence occurs, the correlation coefficient raises to 0.57. Considering the two very different techniques used in this study to derive the conductances, with different assumptions, limitations and scale sizes, our results indicate that simple averaging of mesoscale results allows a continuous transition to large-scale results. Therefore, it is possible to use a combined approach to study ionospheric events with satellite optical and ground-based electrodynamic data of different spatial and temporal resolutions. We must be careful, though, when using these two techniques during disturbed conditions. The two methods will only give results that systematically converge when relatively uniform conditions exist. Full Article (PDF, 929 KB) Citation: Aksnes, A., Amm, O., Stadsnes, J., stgaard, N., Germany, G. A., Vondrak, R. R., and Sillanp , I.: Ionospheric conductances derived from satellite measurements of auroral UV and X-ray emissions, and ground-based electromagnetic data: a comparison, Ann. Geophys., 23, 343-358, doi:10.5194/angeo-23-343-2005, 2005. Bibtex EndNote Reference Manager XML
Ionospheric currents estimated simultaneously from CHAMP satelliteand IMAGE ground-based magnetic field measurements: a statisticalstudy at auroral latitudes
P. Ritter, H. Lühr, A. Viljanen, O. Amm, A. Pulkkinen,I. Sillanp
Annales Geophysicae (ANGEO) , 2004,
Abstract: One important contribution to the magnetic field measured at satellite altitude and at ground level comes from the external currents. We used the total field data sampled by the Overhauser Magnetometer on CHAMP and the horizontal magnetic field measurements of the IMAGE ground-based magnetometer network to study the ionospheric Hall current system in the auroral regions. For the CHAMP data a current model consisting of a series of lines and placed at a height of 110km is fitted to the magnetic field signature sampled on the passage across the polar region. The derived current distributions depend, among others, on season and on the local time of the satellite track. At dawn/dusk the auroral electrojets can be detected most clearly in the auroral regions. Their intensity and location are evidently correlated with the A E activity index. For a period of almost two years the results obtained from space and the currents determined from ground-based observations are studied. For the full IMAGE station array a newly-developed method of spherical elementary current systems (SECS) is employed to compute the 2-D equivalent current distribution, which gives a detailed picture of an area covering latitudes 60° – 80° N and 10° – 30° E in the auroral region. Generally, the current estimates from satellite and ground are in good agreement. The results of this survey clearly show the average dependence of the auroral electrojet on season and local time. This is particularly true during periods of increased auroral activity. The correlation coefficient of the results is close to one in the region of sizeable ionospheric current densities. Also the ratio of the current densities, as determined from above and below the ionosphere, is close to unity. It is the first time that the method of Hall current estimate from a satellite has been validated quantitatively by ground-based observations. Among others, this result is of interest for magnetic main field modelling, since it demonstrates that ground-based observations can be used to predict electrojet signatures in satellite magnetic field scalar data. Key words. Ionosphere (auroral Ionosphere; electric fields and currents; ionosphere-magnetosphere interactions)
The CTA Observatory
R. M. Wagner,E. J. Lindfors,A. Sillanp??,S. Wagner,for the CTA Consortium,)
Physics , 2009,
Abstract: In recent years, ground-based very-high-energy (VHE; E>100 GeV) gamma-ray astronomy has experienced a major breakthrough with the impressive astrophysical results obtained mainly by the current generation experiments like H.E.S.S., MAGIC, MILAGRO and VERITAS. The ground-based Imaging Air Cherenkov Technique for detecting VHE gamma-rays has matured, and a fast assembly of inexpensive and robust telescopes is possible. The goal for the next generation of instruments is to increase their sensitivity by a factor >10 compared to current facilities, to extend the accessible gamma-ray energies from a few tens of GeV to a hundred TeV, and to improve on other parameters like the energy and angular resolution (improve the point-spread function by a factor 4-5 w.r.t. current instruments). The Cherenkov Telescope Array (CTA) project is an initiative to build the next generation ground-based gamma-ray instrument, will serve as an observatory to a wide astrophysics community. I discuss the key physics goals and resulting design considerations for CTA, the envisaged technical solutions chosen, and the organizational and operational requirements for operating such a large-scale facility as well as the specific needs of VHE gamma-ray astronomy.
Stamp transferred suspended graphene mechanical resonators for radio-frequency electrical readout
Xuefeng Song,Mika Oksanen,Mika A. Sillanp??,H. G. Craighead,J. M. Parpia,Pertti J. Hakonen
Physics , 2012, DOI: 10.1021/nl203305q
Abstract: We present a simple micromanipulation technique to transfer suspended graphene flakes onto any substrate and to assemble them with small localized gates into mechanical resonators. The mechanical motion of the graphene is detected using an electrical, radio-frequency (RF) reflection readout scheme where the time-varying graphene capacitor reflects a RF carrier at f=5-6 GHz producing modulation sidebands at f +/- fm. A mechanical resonance frequency up to fm=178 MHz is demonstrated. We find both hardening/softening Duffing effects on different samples, and obtain a critical amplitude of ~40 pm for the onset of nonlinearity in graphene mechanical resonators. Measurements of the quality factor of the mechanical resonance as a function of DC bias voltage Vdc indicate that dissipation due to motion-induced displacement currents in graphene electrode is important at high frequencies and large Vdc.
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