Clues to starburst evolution: The tale of dense gas     

Susanne Hüttemeister  Susanne Aalto 《Astrophysics and Space Science》2003,284(2):877-880

The dense gas tracers HNC and CN prove to be detectable in sensitive single dish studies of infrared luminous starburst galaxies. Their line intensity with respect to both the standard tracer of molecular gas, CO, and the dense, starforming component, HCN, varies significantly. This opens a new, extinction-free window into the investigation of the properties and the evolutionary stage of starbursts. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

The Anthropocene: is there a geomorphological case?     

Antony G. Brown  Stephen Tooth  Richard C. Chiverrell  James Rose  David S. G. Thomas  John Wainwright  Joanna E. Bullard  Varyl R. Thorndycraft  Rolf Aalto  Peter Downs 《地球表面变化过程与地形》2013,38(4):431-434

The ‘Anthropocene’, as used to describe the interval of recent Earth history during which humans have had an ‘overwhelming’ effect on the Earth system, is now being formally considered as a possible new geological Epoch. Such a new geological time interval (possibly equivalent to the Pleistocene Epoch) requires both theoretical justification as well as empirical evidence preserved within the geological record. Since the geological record is driven by geomorphological processes that produce terrestrial and near‐shore stratigraphy, geomorphology has to be an integral part of this consideration. For this reason, the British Society for Geomorphology (BSG) has inaugurated a Fixed Term Working Group to consider this issue and advise the Society on how geomorphologists can engage with debates over the Anthropocene. This ESEX Commentary sets out the initial case for the formalisation of the Anthropocene and a priori considerations in the hope that it will stimulate debate amongst, and involvement by, the geomorphological community in what is a crucial issue for the discipline. The Working Group is now considering the practical aspects of such a formalization including the relative magnitude problem, the boundary problem and the spatial diachrony of ‘anthropogenic geomorphology’. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Trace metal and geochemical variability during 5,500 years in the sediment of Lake Lehmilampi,Finland     

Anna Augustsson  Pasi Peltola  Bo Bergbäck  Timo Saarinen  Eeva Haltia-Hovi 《Journal of Paleolimnology》2010,44(4):1025-1038

A high-resolution geochemical profile from a 5,500-year-old sediment core of Lake Lehmilampi in eastern Finland was analyzed to study long-term trends and variability in element concentrations and accumulation rates. The accumulation rates of all studied elements followed the same trend, responding to changes in the total sedimentation rate. Concentration profiles differed among elements and showed considerable variation over time. Principal components analysis (PCA) was used on the concentration data to identify groups of elements that have similar geochemical controls. The first principal component was influenced by changes in mineral matter accumulation, and it incorporated elements that are associated with stable allochthonous minerals (such as Mg, K, Cs, Rb, Li, Ti and Ga), as well as elements in forms that become diluted when mineral matter increases (e.g., S, Fe and Mn). The second and third principal components showed that a large proportion of the variance was accounted for by elements with continuously increasing or decreasing concentrations related to pedogenetical development of the catchment soil. In the case of Hg, Pb and Cd, however, accumulation rates increased faster at the surface than is simply accounted for by changes in total sedimentation rates. For Cu, Cr, Ni and Zn, concentrations increased over the past 150 years, but there were no indications of a significant addition due to atmospheric deposition. These elements had more variable concentrations before the mid nineteenth century than after, as did elements that are often used for normalization. These findings suggest that lake sediments may not properly reflect the history of atmospheric metal deposition in remote areas.  相似文献   

RAT J1953+1859: a dwarf nova discovered through high amplitude QPOs in quiescence     

Gavin Ramsay  Pasi Hakala  Thomas Barclay  Peter Wheatley  George Marshall  Harry Lehto  Ralf Napiwotzki  Gijs Nelemans  Stephen Potter  Ian Todd 《Monthly notices of the Royal Astronomical Society》2009,398(3):1333-1338

We report the discovery of an accreting binary, RAT J1953+1859, made during the RApid Temporal Survey (RATS) on the Isaac Newton Telescope. It showed high amplitude (0.3 mag) quasi-periodic oscillations on a time-scale of ∼20 min. Further observations made using the Nordic Optical Telescope showed it to be ∼4 mag brighter than in the discovery images. These photometric observations, together with radial velocity data taken using the William Herschel Telescope, point to an orbital period of ∼90 min. These data suggest that RAT J1953+1859 is a dwarf novae of the SU UMa type. What makes RAT J1953+1859 unusual is that it is the first such system to be discovered as a result of high amplitude QPOs during quiescence. This suggests that high-cadence wide-field surveys could be another means to discover cataclysmic variables as a result of their short period variability.  相似文献   

Could Ornamental Plants Serve as Passive Biomonitors in Urban Areas?     

Sabina Rossini Oliva  Pasi Rautio 《Journal of Atmospheric Chemistry》2004,49(1-3):137-148

A search for cheap and efficient method to monitor atmospheric particulates in city centres has raised new interest to measure foliar element concentrations after the role of particulate pollution for respiratory illnesses was discovered. Leaf samples of Golden dewdrop (Duranta repens L.) collected in Palermo (South of Italy) between 1998 and 2000 were analysed to study the possible use of this shrub as a passive biomonitor for atmospheric pollution in urban areas. Concentrations of Ba, Cd, Cu, Fe, Mg, Mn, Pb and Zn were determined from leaf samples collected from six sampling sites representing either (a) areas of high traffic density or (b) areas not directly affected by the city traffic (e.g. gardens). Most of the elements showed a significant temporal variation but no consistent trends could be seen, i.e. the highest (or lowest) values were not detected consistently at some particular time of the year. Furthermore temporal changes were of same magnitude in polluted versus less polluted areas; no statistically significant interaction between pollution level and collection period was detected. Pollution level (traffic density) was the primary factor to explain spatial variation only in the case of foliar Mg concentrations. On the other hand, variation in foliar concentrations between sampling sites (irrespective of the pollution level) was large. Our results suggest that particulate deposition needs to be quite high before spatial segregation can be done on the basis of foliar element concentrations.  相似文献   

Finite element seepage flow nets     

J. Aalto 《国际地质力学数值与分析法杂志》1984,8(3):297-303

A variational principle and the corresponding finite element equations for determination of the stream function for soil seepage problems is given using the standard finite element potential solution as data. The procedure is very simple and independent of the element type employed. Generalization of the method to multiply connected domains is included.  相似文献   

The defining characteristics of intermediate polars – the case of three-candidate systems     

Gavin Ramsay  Peter J. Wheatley  A. J. Norton  Pasi Hakala  Darren Baskill 《Monthly notices of the Royal Astronomical Society》2008,387(3):1157-1162

Intermediate polars (IPs) are a group of cataclysmic variables (CVs) which are thought to contain white dwarfs which have a magnetic field strength in the range ∼0.1–10 MG. A significant fraction of the X-ray sources detected in recent deep surveys has been postulated to consist of IPs. Until now two of the defining characteristics of IPs have been the presence of high (and complex) absorption in their X-ray spectra and the presence of a stable modulation in the X-ray light curve which is a signature of the spin period, or the beat period, of the accreting white dwarf. Three CVs, V426 Oph, EI UMa and LS Peg, have characteristics which are similar to IPs. However, there has been only tentative evidence for a coherent period in their X-ray light curve. We present the results of a search for coherent periods in XMM–Newton data of these sources using an autoregressive analysis which models the effects of red noise. We confirm the detection of a ∼760 s period in the soft X-ray light curve of EI UMa reported by Reimer et al. and agree that this represents the spin period. We also find evidence for peaks in the power spectrum of each source in the range 100–200 s which are just above the 3σ confidence level. We do not believe that they represent genuine coherent modulations. However, their X-ray spectra are very similar to those of known IPs. We believe that all three CVs are bona fide IPs. We speculate that V426 Oph and LS Peg do not show evidence for a spin period since they have closely aligned magnetic and spin axes. We discuss the implications that this has for the defining characteristics of IPs.  相似文献   

RApid Temporal Survey (RATS) – II. Followup observations of four newly discovered short-period variables     

Gavin Ramsay  Ralf Napiwotzki  Pasi Hakala  Harry Lehto 《Monthly notices of the Royal Astronomical Society》2006,371(2):957-962

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Hygroscopic properties of aerosol particles in the north‐eastern Atlantic during ACE‐2     

Erik Swietlicki  Jingchuan Zhou  David S. Covert  Kaarle Hämeri  Bernhard Busch  Minna Väkeva  Ulrike Dusek  Olle H. Berg  Alfred Wiedensohler  Pasi Aalto  Jyrki Mäkelä  Bengt G. Martinsson  Giorgos Papaspiropoulos  Besim Mentes  Göran Frank  Frank Stratmann 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):201-227

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Metallic mineral deposits in the Nordic countries     

Paer Weihed Pasi Eilu Rune B. Larsen Henrik Stendal Mikko Tontti 《《幕》》2008,31(1):125-132

The Nordic countries, including Greenland, have a long tradition in mining. Documented mining dates back to the 8th century AD. Today this region is the most important metallic mining district of the European Union. Metals are produced from active mines in all countries except Iceland and related industries are thriving in all countries.
Important ore deposit types include： volcanogenic massive sulphide deposits （Cu, Zn, Pb, Au, Ag）, orogenic gold deposits （Au）, layered intrusions （Ni, PGE, Ti±V）, intrusive hosted Cu-Au, apatite-Fe deposits, Cr- and anorthosite hosted Ti deposits. Besides these well- documented deposits, new kinds of deposits are being explored, e.g., iron oxide-copper-gold （IOCG）, shale-hosted Ni-Zn-Cu and different types of uranium deposits.  相似文献