Romanian Academy

About: Romanian Academy is a archive organization based out in Bucharest, Romania. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 3662 authors who have published 10491 publications receiving 146447 citations. The organization is also known as: Academia Română & Societatea Literară Română.

Targeted drugs by olefin metathesis: piperidine-based iminosugars

Abstract: Examining advances in the class of natural and non-natural piperidine azasugars, important therapeutic agents and potent glycosidase inhibitors, this review looks at syntheses applying olefin metathesis as a highly efficient key step and gateway strategy for discovery of better iminosugar leads for treatment of widespread affections like viral and metabolic diseases. Amply illustrated is how ring-closing metathesis (RCM and RCEYM), promoted by commercial ruthenium alkylidene catalysts, manage to construct the common tetrahydropyridine core while cross-metathesis (CM), starting from this generic scaffold, provides general access to families of novel azasugars. Special consideration is given to high-profile iminosugar drugs of this class (1-deoxynojirimycin and congeners, adenophorine, fagomine, isofagomine and some of their N- and C-substituted analogues) stressing upon newest trends for enhancing biological activity and modulating previously unexploited targets in multispecific therapies.

Recent changes in global drylands: Evidences from two major aridity databases

Abstract: Drying of terrestrial areas is a critical issue in our era of climate change. However, there is limited knowledge on the current spatial status of drylands, which can be assessed using updated and more rigorous data than information used in the initial dryland estimations. Here we investigate the current extent of drylands globally, continentally and nationally by analysing one of the most recent aridity database (1950–2000 period) and compare statistically, for the first time, with the initial dryland estimations (1951–1980). Using diachronic analysis between the databases, we found that drylands are currently almost 4% larger worldwide than expected and cover 45.4% of the Earth's land surface. This net increase of global dryland areas is due to the expansion of arid (+3.4%) and semi-arid (+0.9%) areas, whilst hyper-arid zones decreased (−0.8%) and dry sub-humid areas remained stable. Except for Europe and South America, all continents have experienced a net expansion of arid environments in the recent climate database. Our findings show that Asia is home to the world's largest increases in dryland areas, where China alone accounts for almost one third of the new lands exposed to aridity worldwide. The Earth's drier conditions can generally be attributed to climate changes occurring after 1980. Our results highlight large-scale drying processes and therefore the exacerbation of land degradative conditions at low and middle latitudes. Also, our findings signal the danger of triggering certain positive feedbacks in global warming, considering the newly-identified drylands migration towards higher latitudes in North America and Asia, which can modify the albedo and destabilize the large carbon pools in permafrost, peatlands or boreal forests.

Magnetic changes observed in the formation of two filaments in a complex active region: Trace and MSDP observations

Abstract: This paper is focused on the formation of two filaments in a complex center of decaying active regions (AR 8329 and AR 8326), located in the northern hemisphere. The observations were obtained in Hα by the Multi-channel Subtractive Double Pass spectrograph (MSDP mounted on the German telescope VTT in Tenerife) and EUV lines with TRACE (Transition Region And Corona Explorer). High Doppler shifts are found to be related to the ends of filament segments where canceling magnetic fields are also located (as seen on magnetograms from Big Bear Solar Observatory). At these locations, velocities along the line of sight, derived by using a cloud model method reach −20 km s−1, the segments of filaments merge and frequently a time-related sub-flare is observed by TRACE. The chirality of the filament segments has been determined by different methods: the segments of dextral chirality join together and form a long dextral filament, and a single filament of sinistral chirality forms end to end with the dextral filament but does not merge with it. Assuming a model of twisted flux tube for filament material, we suggest that the dextral filament has negative helicity and a relationship between its formation and the close by sunspot with the same sign of helicity.