31 research outputs found
Black Stork Back: Species distribution model predictions of potential habitats for Black Stork Ciconia nigra in Sweden
Increased understanding of the need to save endangered and locally extinct species has led to restoration or preservation of populations through reintroductions. Reintroduction of a species is worthwhile if the prerequisites for existence at the historical location have improved. Thus, background information about the habitat requirements of a target species is important for introduction programmes to be successful. The Black Stork Ciconia nigra was lost as a breeding species in Sweden during the 20th century, but recent observations and reports of potential breeding indicate that habitat conditions for Black Stork in Sweden may have improved. In this study, we used species characteristics and references to identify habitats in Sweden suitable for potential reintroduction of Black Stork. We identified several suitable areas in the former distribution range of this species in southern Sweden. Seven Swedish counties contained more than 18â% suitable habitat within their total area, with highest proportions in Jönköping County (25.8â%), Blekinge County (23.9â%), VĂ€stra Götaland County (22.1â%) and Kronoberg County (20.7â%). We suggest these areas to be made the primary targets for Black Stork reintroduction in Sweden
2-Substituted agelasine analogs : synthesis and biological activity, and structure and reactivity of synthetic intermediates
2-Substituted N-methoxy-9-methyl-9H-purin-6-amines were synthesized either from their corresponding 6-chloro-9-methyl-9H-purines or 2-chloro-N-methoxy-9-methyl- 9H-purin-6-amine. Great diversity in the amino/imino tautomeric ratios was observed and calculated based on 1H NMR. The tautomers were identified by 1D and 2D 1H, 13C, and 15N NMR techniques, and showed significant variation both in 13C and 15N shift values. Comparison of the tautomeric ratios with Hammett F values revealed that as the field/inductive withdrawing abilities of the 2-substituent increased, the ratio of amino:imino tautomers was shifted toward the amino tautomer. Computational chemistry exposed the significance of hydrogen bonding between solvent and the compound in question to reach accurate predictions for tautomeric ratios. B3LYP/def2-TZVP density functional theory (DFT) calculations resulted in quantitatively more accurate predictions than when employing the less expensive BP86 functional. N-7-Alkylation of the 2-substituted N-methoxy-9-methyl-9H-purin-6- amines showed that when the field/inductive withdrawing ability of the 2-substituent reached a certain point the reactivity drastically dropped. This correlated with the atomic charges on N-7 calculated using a natural bond orbital (NBO) analysis. Biological screening of the final 2-substituted agelasine analogs indicated that the introduction of a methyl group in the 2-position is advantageous for antimycobacterial and antiprotozoal activity, and that an amino function may improve activity against several cancer cell lines
A Triple Protostar System Formed via Fragmentation of a Gravitationally Unstable Disk
Binary and multiple star systems are a frequent outcome of the star formation
process, and as a result, almost half of all sun-like stars have at least one
companion star. Theoretical studies indicate that there are two main pathways
that can operate concurrently to form binary/multiple star systems: large scale
fragmentation of turbulent gas cores and filaments or smaller scale
fragmentation of a massive protostellar disk due to gravitational instability.
Observational evidence for turbulent fragmentation on scales of 1000~AU has
recently emerged. Previous evidence for disk fragmentation was limited to
inferences based on the separations of more-evolved pre-main sequence and
protostellar multiple systems. The triple protostar system L1448 IRS3B is an
ideal candidate to search for evidence of disk fragmentation. L1448 IRS3B is in
an early phase of the star formation process, likely less than 150,000 years in
age, and all protostars in the system are separated by 200~AU. Here we
report observations of dust and molecular gas emission that reveal a disk with
spiral structure surrounding the three protostars. Two protostars near the
center of the disk are separated by 61 AU, and a tertiary protostar is
coincident with a spiral arm in the outer disk at a 183 AU separation. The
inferred mass of the central pair of protostellar objects is 1 M,
while the disk surrounding the three protostars has a total mass of 0.30
M_{\sun}. The tertiary protostar itself has a minimum mass of 0.085
M. We demonstrate that the disk around L1448 IRS3B appears susceptible
to disk fragmentation at radii between 150~AU and 320~AU, overlapping with the
location of the tertiary protostar. This is consistent with models for a
protostellar disk that has recently undergone gravitational instability,
spawning one or two companion stars.Comment: Published in Nature on Oct. 27th. 24 pages, 8 figure
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
FrÄn entreprenör till företagsledare : Entreprenörens rollförÀndring under tillvÀxt
Forskare och entreprenörer har lÀnge försökt förstÄ fenomenet entreprenörskap och tillvÀxt. Genom att studera framgÄngsrika entreprenörer har ett flertal modeller för tillvÀxt vuxit fram, men fÄ berör entreprenörers roll i företagen. I början fyller entreprenören ett flertal roller samtidigt. I takt med att företaget vÀxer delegeras dessa uppgifter till andra för att entreprenören ska kunna fokusera pÄ företagsledning. För entreprenörer Àr detta dock ofta en komplicerad förÀndringsprocess som mÄnga misslyckas med. För att öka förstÄelsen för hur förÀndringen frÄn entreprenör till företagsledare ser ut i verkligheten undersöker studien hur entreprenörers arbetsuppgifter och ansvarsfördelning förÀndrats frÄn nystartat företag till etablering. Studien anvÀnder ett kvalitativt tillvÀgagÄngssÀtt för att utveckla och utmana det befintliga teoretiska ramverket. I en inledande litteraturstudie operationaliseras förvÀntade förÀndringar i arbetsuppgifter och ansvarsfördelning till en analysmodell. Denna anvÀnds sedan för analys utav extensiva intervjuer med tre svenska entreprenörer, vars respektive företag haft en hög tillvÀxt under 2000-talet, samt idag har över 500 anstÀllda och en Ärlig omsÀttning om minst 120 MSEK. Resultatet visar hur entreprenörer genom medvetenhet och förberedelser kan undvika förvÀntade kriser och utmaningar, och att det kan finnas behov av nya modeller för tillvÀxt i entreprenörsföretag