Tree Damage in Mechanized Uneven-aged Selection Cuttings

201

Epithermal Neutron Beam Interference with Cardiac Pacemakers

Peer reviewe

Environmental conditions and host plant origin override endophyte effects on invertebrate communities

v2011okpka pka ks

Keräsienijuurisymbioosin vaikutus kasvien suolastressiin

Tiivistelmä. Maaperän suolaantuminen on merkittävä ympäristöongelma. Erityisen suuri merkitys on ihmisen toiminnan aiheuttamalla suolaantumisella, joka on usein kytköksissä keinokastelun ongelmiin. Etenkin maaperään kertyvä natriumkloridi voi heikentää merkittävästi maaperän laatua. Tulevaisuudessa ilmastonmuutos tulee pahentamaan suolaantumisen vaikutuksia entisestään. Maaperän liiallinen suolaantuminen johtaa kasveissa suolastressiin, joka vahingoittaa esimerkiksi solukoiden entsyymejä, kalvorakenteita ja fotosynteesikoneistoa. Lopulta suolastressi voi johtaa lehtien viherkatoon, ennenaikaiseen vanhenemiseen ja solukuolemaan. Keräsienet ovat tärkeitä kasvien liittolaisia suolastressin negatiivisten vaikutusten ehkäisemisessä. Keräsienijuurisymbioosi hyödyttää merkittävästi kasviosakasta erilaisten stressitekijöiden sietämisessä. Toisaalta keräsienijuurisymbioosi on välttämätön myös lähes kaikille keräsienilajeille. Keräsienet muodostavat kasvin kortikaalisolujen sisälle keräsiä tiiviiksi yhteydeksi kasviosakkaan ja sieniosakkaan välille. Osakkaiden välillä tapahtuu monipuolista signalointia esimerkiksi ravinteidenvaihdon, kasvihormonien ja mekaanisten ärsykkeiden avulla. Suolastressin seurauksena kasvien ravinteidenotto vaikeutuu ja ionisuhteet häiriintyvät. Toisaalta myös maaperän osmoottinen potentiaali muuttuu suolaantumisen seurauksena, mikä vaikeuttaa kasvin nestetasapainon säätelyä. Keräsienijuurisymbioosin on havaittu auttavan kasvia etenkin riittävässä fosforinsaannissa. Toisaalta keräsienijuuri auttaa kasvia ylläpitämään normaaleja ionisuhteita yhteyttämissolukossa, jossa ionisuhteiden muutokset voivat johtaa vakaviin haittoihin. Keräsienijuurellisissa kasveissa on myös havaittu merkkejä parantuneesta nestetasapainon säätelystä. Keräsienet parantavat lisäksi maaperän laatua erittämällä partikkeleita yhteen sitovaa glomaliinia. Suolastressin pitkittyminen johtaa yleensä hapetusstressiin eli solukoita vaurioittavien happiradikaalien ylimäärään. Kasveilla on onneksi käytössään antioksidatiivisia yhdisteitä, joiden määrää keräsienijuuren on havaittu parantavan. Hapetusstressin ehkäisy suojaa kasvin yhteyttämiskoneistoa vaurioilta. Keräsienijuurellisten kasvien fotosynteesin onkin havaittu olevan usein tehokkaampaa kuin sienijuurettomilla kasveilla. Toisaalta sienijuuri voi vaikuttaa positiivisesti myös ilmarakojen johtokykyyn, mikä mahdollistaa riittävän hiilidioksidin saatavuuden. Tehostuneen fotosynteesin avulla keräsienijuurellinen kasvi voi kasvattaa biomassaansa tehokkaasti, mikä itsessään kertoo kasvin parantuneesta yleiskunnosta

Evaluation of semantic web ontologies for modelling art collections

© 2017, Springer International Publishing AG. The need for organising, sharing and digitally processing Cultural Heritage (CH) information has led to the development of formal knowledge representation models (ontologies) for the CH domain. Based on RDF and OWL, the standard data model and ontology language of the Semantic Web, ontologies such as CIDOC-CRM, the Europeana Data Model and VRA, offer enhanced representation capabilities, but also support for inference, querying and interlinking through the Web. This paper presents the results of a small-scale evaluation of the three most commonly used CH ontologies, with respect to their capacity to fulfil the data modelling requirements of art collections

Status report of the JYFL-ECR ion sources

"Ion beam cocktails" are mixtures of ions with near-identical charge-to-mass ratios. In conjunction with the JYFL-ECRIS, the K130-cyclotron acts as a mass analyzer: the switch from one ion to another within the same cocktail is simple and fast. In the case of the first ion beam cocktail, the oxygen and argon gases were mixed into the gas feed line. At the same time the magnesium and iron ion beams were produced using the MIVOC method. Magnesocene and ferrocene compounds were both mixed into the MIVOC chamber. This capability is especially useful in the study of single event effects (SEE) in space electronics. All gaseous elements from H to Xe can be produced. The non-gaseous elements produced so far are C, Mg, Al, Si, S, Ca, Ti, Cr, Fe, Co, Ni, Cu, Zn and Ge. A major technical modification since the construction (in 1990) of the JYFL-ECRIS was made in January 98: a negatively biased disc replaces now the first plasma stage. After a couple of months experience with the modified source the change was found to be towards a correct direction. The source is now much easier to use and the good operating conditions are well repeated. A real advantage is the new magnetic field settings which are practically the same for all kind of beams, gaseous and solids. Due to the requirements of ion beams with higher charges and heavier elements than the present JYFL-ECRIS can produce, JYFL decided to begin a design and construction project of a new ECR ion source, called as ECRIS 2. The project aims to a source that is based mainly on the design of the 14 GHz AECR-U source at the LBNL. Some modifications made into the similar source under construction at the NSCL/MSU will be utilized here. The new source will be installed horizontally in the basement of the ECRIS laboratory. It requires a new beam-line from the source to the cyclotron injection line, since the old vertically located JYFL-ECRIS will be preserved in operation. The new source is planned to be operational during the year 2000

New approaches to model and study social networks

We describe and develop three recent novelties in network research which are particularly useful for studying social systems. The first one concerns the discovery of some basic dynamical laws that enable the emergence of the fundamental features observed in social networks, namely the nontrivial clustering properties, the existence of positive degree correlations and the subdivision into communities. To reproduce all these features we describe a simple model of mobile colliding agents, whose collisions define the connections between the agents which are the nodes in the underlying network, and develop some analytical considerations. The second point addresses the particular feature of clustering and its relationship with global network measures, namely with the distribution of the size of cycles in the network. Since in social bipartite networks it is not possible to measure the clustering from standard procedures, we propose an alternative clustering coefficient that can be used to extract an improved normalized cycle distribution in any network. Finally, the third point addresses dynamical processes occurring on networks, namely when studying the propagation of information in them. In particular, we focus on the particular features of gossip propagation which impose some restrictions in the propagation rules. To this end we introduce a quantity, the spread factor, which measures the average maximal fraction of nearest neighbors which get in contact with the gossip, and find the striking result that there is an optimal non-trivial number of friends for which the spread factor is minimized, decreasing the danger of being gossiped.Comment: 16 Pages, 9 figure

Measuring the spin of the primary black hole in OJ287

The compact binary system in OJ287 is modelled to contain a spinning primary black hole with an accretion disk and a non-spinning secondary black hole. Using Post Newtonian (PN) accurate equations that include 2.5PN accurate non-spinning contributions, the leading order general relativistic and classical spin-orbit terms, the orbit of the binary black hole in OJ287 is calculated and as expected it depends on the spin of the primary black hole. Using the orbital solution, the specific times when the orbit of the secondary crosses the accretion disk of the primary are evaluated such that the record of observed outbursts from 1913 up to 2007 is reproduced. The timings of the outbursts are quite sensitive to the spin value. In order to reproduce all the known outbursts, including a newly discovered one in 1957, the Kerr parameter of the primary has to be $0.28 \pm 0.08$. The quadrupole-moment contributions to the equations of motion allow us to constrain the `no-hair' parameter to be $1.0\:\pm\:0.3$ where 0.3 is the one sigma error. This supports the `black hole no-hair theorem' within the achievable precision. It should be possible to test the present estimate in 2015 when the next outburst is due. The timing of the 2015 outburst is a strong function of the spin: if the spin is 0.36 of the maximal value allowed in general relativity, the outburst begins in early November 2015, while the same event starts in the end of January 2016 if the spin is 0.2Comment: 12 pages, 6 figure