208 research outputs found
Remote Sensing and Local Knowledge of Hydrocarbon Exploitation: The Case of Bovanenkovo, Yamal Peninsula, West Siberia, Russia
The capacity of satellite imagery to detect anthropogenic impacts on land cover was assessed for the Bovanenkovo gas field on the Yamal Peninsula in northwest Siberia, which contains some of the worldâs largest untapped gas deposits. The region is also the homeland of nomadic Nenets reindeer herders, whose annual migration between the tree line and the northern tundra exposes them to impacts associated with exploration and production activities. These range from physical obstructions, such as roads, railways, and pipelines, to direct and indirect ecological impacts, such as changes in vegetation and hydrology. Nenetsâ perceptions of their territories encompass changes in the quantity and quality of terrestrial and freshwater habitats and campsites that have been used seasonally for centuries. Industrial impacts on land cover were examined at spatial scales from very detailed to coarse. Very-high-resolution Quickbird-2 imagery revealed the most impacts, but could not detect items like trash that reduce the quality of reindeer pastures. ASTER, SPOT, and Landsat imagery were useful at the broader landscape level. A proper assessment of the overall ecological impacts of hydrocarbon exploitation requires a combination of remote sensing and detailed ground-truthing. Ideally, these efforts should combine scientific and local knowledge from both indigenous herders and non-indigenous industrial workers.Lâaptitude de lâimagerie satellitaire Ă dĂ©tecter les incidences anthropogĂšnes sur la couverture vĂ©gĂ©tale a Ă©tĂ© Ă©valuĂ©e dans le cas du champ de gaz naturel de Bovanenkovo, dans la pĂ©ninsule de Yamal situĂ©e dans le nord-ouest de la SibĂ©rie oĂč se trouve un des plus grands gisements de gaz inexploitĂ©s du monde. Les NĂ©nĂštses, ou Ă©leveurs de rennes nomades, Ă©voluent dans cette rĂ©gion et leur migration annuelle entre la limite forestiĂšre et la toundra du nord les met en contact avec les travaux dâexploration et de production du gaz. Il peut sâagir dâobstructions physiques prenant la forme de routes, de chemins de fer et de pipelines ou encore, dâincidences Ă©cologiques directes et indirectes touchant notamment la vĂ©gĂ©tation et lâhydrologie. Les perceptions relatives aux territoires des NĂ©nĂštses concernent des changements en matiĂšre de quantitĂ© et de qualitĂ© des habitats terrestres et dâeau douce ainsi que les lieux de campement qui sont utilisĂ©s dâune saison Ă lâautre depuis des siĂšcles. Les incidences industrielles sur la couverture vĂ©gĂ©tale ont Ă©tĂ© examinĂ©es Ă diverses Ă©chelles spatiales, allant de trĂšs dĂ©taillĂ©e Ă grossiĂšre. Les images de trĂšs haute rĂ©solution obtenues au moyen de Quickbird-2 ont permis de rĂ©vĂ©ler le plus grand nombre dâincidences, mais nâont pas permis de dĂ©tecter des Ă©lĂ©ments tels que les ordures qui avaient pour effet dâamenuiser la qualitĂ© des pĂąturages destinĂ©s aux rennes. Les images obtenues Ă partir dâASTER, de SPOT et de Landsat ont Ă©tĂ© utiles au niveau plus vaste du paysage. LâĂ©valuation adĂ©quate des incidences Ă©cologiques gĂ©nĂ©rales dĂ©coulant de lâexploitation des hydrocarbures nĂ©cessite Ă la fois des outils de tĂ©lĂ©dĂ©tection et le recours Ă des sites tĂ©moins. IdĂ©alement, ces efforts devraient faire appel tant aux connaissances scientifiques que locales, connaissances provenant des Ă©leveurs indigĂšnes et des travailleurs industriels non-indigĂšnes
Constraining the parameter space for the Solar Nebula
If we want to understand planetesimal formation, the only data set we have is
our own Solar System. It is particularly interesting as it is so far the only
planetary system we know of that developed life. Understanding the conditions
under which the Solar Nebula evolved is crucial in order to understand the
different processes in the disk and the subsequent dynamical interaction
between (proto-)planets, once the gas disk is gone. Protoplanetary disks
provide a plethora of different parameters to explore. The question is whether
this parameter space can be constrained, allowing simulations to reproduce the
Solar System. Models and observations of planet formation provide constraints
on the initial planetesimal mass in certain regions of the Solar Nebula. By
making use of pebble flux-regulated planetesimal formation, we perform a
parameter study with nine different disk parameters like the initial disk mass,
initial disk size, initial dust-to-gas ratio, turbulence level, and more. We
find that the distribution of mass in planetesimals in the disk depends on the
planetesimal formation timescale and the pebbles' drift timescale. Multiple
disk parameters can influence pebble properties and thus planetesimal
formation. However, it is still possible to draw some conclusions on potential
parameter ranges. Pebble flux-regulated planetesimal formation seems to be very
robust, allowing simulations with a wide range of parameters to meet the
initial planetesimal constraints for the Solar Nebula. I.e., it does not
require a lot of fine tuning.Comment: A&A accepte
Correlating electronic and magnetic coupling in large magnetic molecules via scanning tunneling microscopy
Contains fulltext :
175413.pdf (publisher's version ) (Open Access)7 p
ELISA - Experimental Large Italian Seismic Array
The Italian Seismic Network (ISN) operated by the INGV consists of more than 200 seismic stations and has recently been upgraded by some dozen broadband seismic stations (Nanometrics Trident 24 bit digitizers, Trillium seismometers). Real time data acquisition at Central Data Analysis Centre at the INGV-Rome is realized by satellite data transmission (Libra VSAT)
FUNCTIONALIZED SILICON-COMPOUNDS WITH OMEGA-TETRAMETHYL AND OMEGA-PENTAMETHYLCYCLOPENTADIENYLALKYL LIGANDS - MOLECULAR-COMPONENTS FOR THE PREPARATION OF METALLIC POLYMERS
Jutzi P, Heidemann T, Neumann B, Stammler H-G. Funktionalisierte Siliciumverbindungen mit [omega]-Tetramethyl- und [omega]-Pentamethylcyclopentadienylalkyl-Liganden: Molekulare Bausteine zur Darstellung von Metall-haltigen Polymeren. Journal of Organometallic Chemistry. 1994;472(1-2):27-38.Peralkylierte Cyclopentadien-Systeme des Typs Me5C5(CH2)3Si(Me)mY3-m, die ĂŒber eine Alkyliden-Spacergruppe mit einer funktionalisierten Silan-Einheit verknĂŒpft sind, sind auf zwei verschiedenen Wegen synthetisiert worden. Als Beispiel fĂŒr den ersten Weg wird die Synthese des Disiloxans [Me5C5CH2)3Si(Me)2]2O (2) beschrieben, welches ausgehend von der Iodverbindung [I(CH2)3Si(Me)2]2O (1) durch Umsetzung mit Me5C5K dargestellt werden kann. Das Trichlorsilan Me5C5(CH2)3SiCl3 (4), als Synthesebeispiel fĂŒr den zweiten Weg, ist ĂŒber Hydrosilylierung von 1-Prop-2-enyl-1,2,3,4,5-pentamethylcyclopenta-2,4-dien (3) zugĂ€nglich. Beide Synthesewege sind auch zur Darstellung der teilweise alkylierten Cyclopentadiensysteme des Typs Me4HC5(CH2)3Si(Me)mY3-m geeignet. So fĂŒhren die Umsetzungen der [omega]-Iodalkyl-triethoxysilane I(CH2)nSi(OEt)3 (n = 1, 2, 3) mit Me4HC5K zu den entsprechenden [omega]-(Tetramethylcyclopentadienyl)alkyl-triethoxysilanen 5â7. Verbindungen 5â7 liegen als Isomerengemische vor; das VerhĂ€ltnis zwischen den Isomeren, die ein allylstĂ€ndiges oder ein vinylstĂ€ndiges Wasserstoffatom am Cyclopentadienring aufweisen, ist abhĂ€ngig von der SpacerlĂ€nge. Isomerengemische der 4-(Tetramethylcyclopentadienyl)butyl-silane des Typs Me4HC5(CH2)4Si(Me)mCl3-m (m = 1, 2, 3) (8â10) mit ausschlieĂlich allyistĂ€ndigem Wasserstoffatom am Cyclopentadienring können durch Hydrositylierung von 1-But-3-enyl-2,3,4,5-tetramethyleyclopentadien dargestellt werden. Die am Siliciumatom funktionalisierten Verbindungen 2 und 4â10 können weiter derivatisiert werden. An ausgewĂ€hlten Beispielen wird die Hydrolyse, die Alkoholyse, die reduktive Kupplung, die Heterogenisierung und die Polykondensationsreaktion nĂ€her untersucht. So erhĂ€lt man das Silanol 12 und das Disiloxan 13, die Alkoxysilane 14â17, das Disilan 18 und die funktionalisierten Kieselgele 19â20. Verbindungen 2, 4â10 und 12â20 dienen als âPoolâ zur Darstellung von Ăbergangsmetall-Derivaten. Beispielsweise wird die DicarbonylâCobalt-Verbindung 21 durch Umsetzung von 8 mit Co2(CO)8 gebildet. Reaktion von 16 mit K und FeCl2 liefert das Ferrocen-Derivat 22. Die [eta]4-gebundenen Pt(II)- und Pd(II)-Komplexe 23â27 können durch Umsetzung der funktionalisierten Si---O-Verbindungen 2, 13, und 19â20 mit [PtCl2(Ethylen)]2 oder PdCl2(PhCN)2 erhalten werden.Peralkylated cyclopentadiene systems of the type Me5C5(CH2)3Si(Me)mY3-m, which possess cyclopentadiene units connected with a functionalized silane fragment by an alkylidene spacer group, are prepared via two routes. As an example of the first route, the disiloxane [Me5C5(CH2)3Si(Me)2]2O (2) has been synthesized from the corresponding iodo compound [I(CH2)3Si(Me)2]2O (1) by reaction with Me5C5K. The trichlorosilane Me5C5(CH2)3SiCl3 (4), as an example of a compound prepared via the second route, has been isolated after hydrosilylation of 1-prop-2-enyl-1,2,3,4,5-pentamethylcyclopenta-2,4-diene (3) with HSiCl3. Both synthetic methods are also suitable for the preparation of partly alkylated cyclopentadiene systems of the type Me4HC5(CH2)nSi(Me)mY3-m. Thus the omega-iodoalkyltriethoxysilanes I(CH2)nSi(OEt)3 (n = 1, 2, 3) react with Me4HC5K to give the corresponding omega-(tetramethyl-cyclopentadienyl)alkyl-triethoxysilanes 5-7. Compounds 5-7 consist of a mixture of isomers; the ratio between isomers having an allylic or vinylic hydrogen atom at the cyclopentadiene ring depends on the spacer length. Isomeric mixtures of the 4-(tetramethyl-cyclopentadienyl)butyl-silanes of the type Me4HC5(CH2)4Si(Me)mCl3-m (M = 1, 2, 3) (8-10) with an allylic hydrogen atom at the cyclopentadiene ring have been prepared by hydrosilylation of 1-but-3-enyl-2,3,4,5-tetramethylcyclopentadiene. The silane fragment in the alkylated cyclopentadiene systems 2 and 4-10 can be modified further. As examples hydrolysis, alcoholysis, reductive coupling, heterogenisation and polycondensation reactions are described. Following theses procedures the corresponding silanol 12 and disiloxane 13 have been prepared as well as the alkoxysilanes 14-17, the disilane 18 and the functionalized silicagels 19 and 20. Compounds 2, 4-10 and 12-20 serve as a ''pool'' for the preparation of transition metal complexes. The dicarbonyl cobalt compound 21 has been synthesized by reaction of 8 with CO2(CO)8. Reaction of 16 with K and FeCl2 gives the corresponding ferrocene derivative 22. The eta4-bound Pt(II) and Pd(II)-complexes 23-27 have been prepared by reaction of the functionalized Si-O-compounds 2, 13, and 19-20 with [PtCl2(Ethylen)]2 and PdCl2(PhCN)2, respectively
Millimeter emission in photoevaporating disks is determined by early substructures
[abridged]Photoevaporation and dust-trapping are individually considered to
be important mechanisms in the evolution and morphology of protoplanetary
disks. We studied how the presence of early substructures affects the evolution
of the dust distribution and flux in the millimeter continuum of disks that are
undergoing photoevaporative dispersal. We also tested if the predicted
properties resemble those observed in the population of transition disks. We
used the numerical code Dustpy to simulate disk evolution considering gas
accretion, dust growth, dust-trapping at substructures, and mass loss due to
X-ray and EUV (XEUV) photoevaporation and dust entrainment. Then, we compared
how the dust mass and millimeter flux evolve for different disk models. We find
that, during photoevaporative dispersal, disks with primordial substructures
retain more dust and are brighter in the millimeter continuum than disks
without early substructures, regardless of the photoevaporative cavity size.
Once the photoevaporative cavity opens, the estimated fluxes for the disk
models that are initially structured are comparable to those found in the
bright transition disk population (), while
the disk models that are initially smooth have fluxes comparable to the
transition disks from the faint population (), suggesting a link between each model and population. Our models
indicate that the efficiency of the dust trapping determines the millimeter
flux of the disk, while the gas loss due to photoevaporation controls the
formation and expansion of a cavity, decoupling the mechanisms responsible for
each feature. In consequence, even a planet with a mass comparable to Saturn
could trap enough dust to reproduce the millimeter emission of a bright
transition disk, while its cavity size is independently driven by
photoevaporative dispersal.Comment: Accepted for publication in A&
Partnership for International Development: FinlandâArgentina Conference on Circular Economy and Bioeconomy with Emphasis on Food Sovereignty and Sustainability
A joint collaboration between the Cuarto region of Argentina championed by the National University of Rio Cuarto and the Arctic Centre of the University of Lapland, Finland organised a conference on several topics that are related to food sovereignty, sustainability, circular economy and bioeconomy. The efficient utilisation of natural resources in both regions is an important theme in meeting the sustainable development goals agenda. Hence, this partnership between the partner institutions will lead to the cocreation of knowledge. The topics were multidisciplinary, and the discussion focussed on research and teaching opportunities for institutions in both countries. The experts from both countries will continue to engage on the possibility of promoting the research agenda in these important areas.EEA Marcos JuĂĄrezFil: Raheem, Dele. University of Lapland. Arctic Centre; FinlandiaFil: Soltermann, Arnaldo T. Universidad Nacional de RĂo Cuarto. Departamento de QuĂmica; ArgentinaFil: Tamiozzo, Laura Virginia. Instituto Nacional de TecnologĂa Agropecuaria (INTA). EstaciĂłn Experimental Agropecuaria Marcos JuĂĄrez. Agencia de ExtensiĂłn Rural RĂo Cuarto; ArgentinaFil: Cogo, Ariel. Instituto Nacional de TecnologĂa Agropecuaria (INTA). EstaciĂłn Experimental Agropecuaria Ărea Metropolitana de Buenos Aires. Agencia De ExtensiĂłn Rural LujĂĄn; ArgentinaFil: FavĂ©n, Leena. Centria University of Applied Sciences. RDI Chemistry and Bioeconomy; FinlandiaFil: Punam, Noor Jahan. University of Lapland. Arctic Centre; FinlandiaFil: Sarmiento, Claudio R. Universidad Nacional de RĂo Cuarto. Departamento de QuĂmica; ArgentinaFil: Rainosalo, Egidija. Centria University of Applied Sciences. RDI Chemistry and Bioeconomy; FinlandiaFil: Picco, Franco. Cooperative Initia Limited; ArgentinaFil: Morla, Federico. Universidad Nacional de RĂo Cuarto. Departamento de QuĂmica; ArgentinaFil: Nilson, Armando. Universidad Nacional de RĂo Cuarto. Departamento de QuĂmica; ArgentinaFil: Stammler-Gossmann, Anna. University of Lapland. Arctic Centre; Finlandi
Long-Term Trends and Role of Climate in the Population Dynamics of Eurasian Reindeer
Temperature is increasing in Arctic and sub-Arctic regions at a higher rate than anywhere else in the world. The frequency and nature of precipitation events are also predicted to change in the future. These changes in climate are expected, together with increasing human pressures, to have significant impacts on Arctic and sub-Arctic species and ecosystems. Due to the key role that reindeer play in those ecosystems, it is essential to understand how climate will affect the region's most important species. Our study assesses the role of climate on the dynamics of fourteen Eurasian reindeer (Rangifer tarandus) populations, using for the first time data on reindeer abundance collected over a 70-year period, including both wild and semi-domesticated reindeer, and covering more than half of the species' total range. We analyzed trends in population dynamics, investigated synchrony among population growth rates, and assessed the effects of climate on population growth rates. Trends in the population dynamics were remarkably heterogeneous. Synchrony was apparent only among some populations and was not correlated with distance among population ranges. Proxies of climate variability mostly failed to explain population growth rates and synchrony. For both wild and semi-domesticated populations, local weather, biotic pressures, loss of habitat and human disturbances appear to have been more important drivers of reindeer population dynamics than climate. In semi-domesticated populations, management strategies may have masked the effects of climate. Conservation efforts should aim to mitigate human disturbances, which could exacerbate the potentially negative effects of climate change on reindeer populations in the future. Special protection and support should be granted to those semi-domesticated populations that suffered the most because of the collapse of the Soviet Union, in order to protect the livelihood of indigenous peoples that depend on the species, and the multi-faceted role that reindeer exert in Arctic ecosystems
X-ray photoemission electron microscopy for the study of semiconductor materials
Photoemission Electron Microscopy (PEEM) using X-rays is a novel combination of two established materials analysis techniques--PEEM using UV light, and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. This combination allows the study of elemental composition and bonding structure of the sample by NEXAFS spectroscopy with a high spatial resolution given by the microscope. A simple, two lens, 10 kV operation voltage PEEM has been used at the Stanford Synchrotron Radiation Laboratory and at the Advanced Light Source (ALS) in Berkeley to study various problems including materials of interest for the semiconductor industry. In the present paper the authors give a short overview over the method and the instrument which was used, and describe in detail a number of applications. These applications include the study of the different phases of titanium disilicide, various phases of boron nitride, and the analysis of small particles. A brief outlook is given on possible new fields of application of the PEEM technique, and the development of new PEEM instruments
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