Search results for "thesis"
showing 10 items of 4193 documents
A novel approach to β-decay: PANDORA, a new experimental setup for future in-plasma measurements
2022
International audience; Theoretical predictions as well as experiments performed at storage rings have shown that the lifetimes of β-radionuclides can change significantly as a function of the ionization state. In this paper we describe an innovative approach, based on the use of a compact plasma trap to emulate selected stellar-like conditions. It has been proposed within the PANDORA project (Plasmas for Astrophysics, Nuclear Decay Observation and Radiation for Archaeometry) with the aim to measure, for the first time in plasma, nuclear β-decay rates of radionuclides involved in nuclear-astrophysics processes. To achieve this task, a compact magnetic plasma trap has been designed…
Molecular evolution of aphids and their primary (Buchnera sp.) and secondary endosymbionts: Implications for the role of symbiosis in insect evolution
2001
Aphids maintain an obligate, endosymbiotic association with Buchnera sp., a bacterium closely related to Escherichia coli. Bacteria are housed in specialized cells of organ-like structures called bacteriomes in the hemocoel of the aphid and are maternally transmitted. Phylogenetic studies have shown that the association had a single origin, dated about 200-250 million years ago, and that host and endosymbiont lineages have evolved in parallel since then. However, the pattern of deepest branching within the aphid family remains unsolved, which thereby hampers an appraisal of, for example, the role played by horizontal gene transfer in the early evolution of Buchnera. The main role of Buchner…
Non-conventional synthesis and photophysical studies of platinum(ii) complexes with methylene bridged 2,2′-dipyridylamine derivatives
2019
Methylene bridged 2,2′-dipyridylamine (dpa) derivatives and their metal complexes possess outstanding properties due to their inherent structural flexibility. Synthesis of such complexes typically involves derivatization of dpa followed by coordination on metals, and may not always be very efficient. In this work, an alternative synthetic approach, involving the derivatization step after – rather than prior to – coordination of dpa on metal center, is proposed and applied to synthesis of a number of platinum(II) complexes with substituted benzyldi(2-pyridyl)amines. Comparison with the more conventional synthetic route reveals greater efficiency and versatility of the proposed approach. The …
Facile and efficient chemical functionalization of aliphatic polyesters by cross metathesis
2016
International audience; An effective preparation of new tailor-made macromolecular materials via a combination of two (atom-efficient) catalytic transformations is reported. First, new aliphatic polyesters with alternated composition have been prepared using a salen aluminum catalyst system. Next, the pendant vinyl moieties in those copolymers have been selectively transformed into various functional groups by metathesis in the presence of homogeneous Grubbs catalysts. The latter metathesis reaction has been optimized in terms of catalytic activity and selectivity, to define the conditions for an effective and safe procedure that does not affect the macromolecular architecture. All polymer …
Silseskwioksany i ich zastosowanie w syntezie materiałów polimerowych
2015
Artykuł stanowi przegląd literatury dotyczącej syntezy oraz charakterystyki materiałów polimerowych zawierających silseskwioksany (POSS). Przedstawiono metody otrzymywania hybrydowych materiałów polimerowych z udziałem funkcjonalizowanych POSS na drodze click chemistry, polikondensacji, poliaddycji, metatezy z otwarciem pierścienia ipolimeryzacji rodnikowej zarówno konwencjonalnej, jak i kontrolowanej (ATRP).
Restricciones y capacidades para la acción climática: un análisis en empresas de economías con debilidades institucionales
2023
Indagamos porqué las empresas se comprometen con acciones contra el cambio climático (ACC). Primero estudiamos un efecto macro de las interacciones entre la configuración institucional que externaliza la FDI y las instituciones locales. La FDI externalizará positivamente las instituciones de origen cuando proviene de economías de mercado más coordinadas, mientras que las instituciones locales juegan diversos roles y contrarrestan los efectos negativos de la FDI de otro origen. Luego estudiamos la complementación positiva entre las fachadas organizativas —frentes simbólicos— sobre algunos recursos de la empresa. Finalmente se relacionan las acciones más sustantivas con la ampliación de los l…
Are habitat loss, predation risk and climate related to the drastic decline in a Siberian flying squirrel population? A 15 year study
2014
To devise effective conservation actions, it is important to know which factors are associated with the population parameters of a declining population. Using mark–recapture methods, we estimated the annual population size, growth rate and survival probability of an ear-tagged flying squirrel population over a 15-year period in a 4,500 ha study area in western Finland. The species is considered vulnerable, but detailed knowledge concerning population sizes or trends is lacking. The population parameters and changes therein were regressed against habitat availability, an indicator of predation pressure, and mean winter temperature (an indicator of climate change), to reveal potential reasons…
Priming effect increases with depth in a boreal forest soil
2016
Abstract Climate warming increases labile carbon (C) inputs to soil through increased photosynthesis and C allocation belowground. This could counterintuitively lead to losses of soil C via priming effects (PE): the stimulation of soil organic matter (SOM) decomposition caused by labile C addition. Systematic quantification of PEs in different ecosystems is needed. We measured PEs of free-living soil microbes in different layers of a boreal forest soil, and found that the relative magnitude of the PE increased with soil depth. The relationship between relative PE and the added glucose amount also depended on the soil layer. Our results indicate that the decomposition of SOM in deeper soil l…
Synthesis and Antitumor Evaluation of Menthone-Derived Pyrimidine-Urea Compounds as Potential PI3K/Akt/mTOR Signaling Pathway Inhibitor.
2022
A series of novel menthone derivatives bearing pyrimidine and urea moieties was designed and synthesized to explore more potent natural product-derived antitumor agents. The structures of the target compounds were confirmed by FTIR, NMR, and HRMS. The in vitro antitumor activity was tested by standard methyl thiazolytetrazolium assay and showed that 4i, 4g, 4s, and 4m are the best compounds with IC50 values of 6.04 ± 0.62µM, 3.21 ± 0.67µM, 19.09 ± 0.49µM, and 18.68 ± 1.53µM, against Hela, MGC-803, MCF-7, and A549, respectively. The results of the preliminary action mechanism studies showed that compound 4i, the representative compound, could induce cell apoptosis in Hela cells in a dose-dep…