132,160 research outputs found
Synthesis of furanosesquiterpenoid natural products
No full textThe effect of addition of a catalytic quantity of a crown ether in the reaction of a phosphonate anion with a carbonyl compound (Wadsworth-Emmons reaction) has been studied and found to greatly facilitate this reaction. This modification of the Wadsworth-Emmons reaction, using a catalytic amount of 15-crown-5, has been employed in the synthesis of the naturally occurring furanosesquiterpene Pallescensin-E. The structure of this compound has been confirmed by comparison of its spectral data with that of the synthesised isomer, 4,l0-dihydro-7,8-dimethyl 10H-benzof4,5Jcycloheptafl,2-bJ furan.Homosesquirosefuran, an analogue of the naturally occurring furanosesquiterpene Sesquirosefuran, has been synthesised via the dianion of methylacetoacetate.An approach to the synthesis of Pinguisone (a component of the essential oil of the liverwort Aneura pinguis)has been attempted employing two Diels-Alder reactions to generate the four cis-methyl groups found in the natural product.In a study of the reaction of n-(2-methylallyl)nickel bromide complex with a range of epoxides, this complex was found not only to react with reactive epoxides (e.g. styrene epoxide) but also with less reactive propylene epoxide.Substrates for possible intramolecular n-allylnickel cyclisation to generate an a-methylene-6-valerolactone ring system have been prepared
SIMS imaging in neurobiology and cell biology
No full textSecondary ion mass spectrometry (SIMS) has been increasingly recognized as a powerful technique for visualizing molecular architectures in the fields of neurobiology and cell biology. There are two main platforms of SIMS, namely ToF-SIMS and nanoscale SIMS (nanoSIMS), which are capable of imaging different types of biomolecules with resolution at the single cell and organelle level, respectively. In this review, we focus on the fundamental aspects of SIMS, as well as on the current ongoing instrumental developments of this technology. Selective applications of SIMS in neurobiological and cell biological research are provided to demonstrate its strengths, limitations, and future potential in the field. We add several examples of correlative imaging techniques that combine SIMS with other technologies, while highlighting the current trend for comprehensive and specific bio-imaging
Überlegene Tiefenauflösung von Indium in (Al, In, Ga) N-Strukturen
No full textS.661-664The (Al, Ga, In) N material system has recently found much interest for microelectronic and optoelectronic devices. Heterostructures of this system have been used to fabricate green to ultraviolet fight emitting diodes and lasers. SIMS depth profiling has been indispensible for the analysis of the component profiles to characterize the device structure. Depth profiles of fine InGaN/GaN multilayer structures were recorded by SIMS. In this paper, the energy dependence of the depth resolution of In in InGaN/GaN quantum well (QW) structures is investigated taking roughness effects into account. The depth resolution is compared with the corresponding data in the arsenide material system by investigation of InGaAs/GaAs QWs
Experience of an information aid for newly diagnosed multiple sclerosis patients: a qualitative study on the SIMS-Trial.
No full textBackground The SIMS-Trial (ISRCTN81072971) proved the effectiveness, in terms of patient's knowledge and care satisfaction, of an add-on information aid (personal interview with a physician using a navigable CD and take-home booklet) in 120 newly diagnosed patients with multiple sclerosis (MS) from five Italian centres.
Objective To scrutinize the experience of SIMS-Trial participants in order to gain better understanding of the effectiveness of the information aid and its components.
Design We performed (i) nine individual semi-structured interviews with a purposeful sample of SIMS-Trial patients who received the information aid, (ii) focus group meeting (FGM) with the physicians who conducted the personal interview, and (iii) FGM with patients' caring neurologists.
Results Patients' experience with the information aid was positive as it enhanced their understanding of their disease, being viewed as a guided tour of their medical condition. The physicians who conducted the personal interviews were also positive in their overall evaluation but noted an initial difficulty in using the CD. The caring neurologists had limited direct experience of the aid, and their views were confined to utility of the information aid in general. All participants considered the combination of personal interview, CD navigation and take-home booklet essential, but urged a more flexible scheduling of the personal interview. It also emerged that
some content required revision and that the aid was unsuitable for patients with primary progressive MS
ToF-SIMS and XPS study of ancient papers
No full textThe surface composition of 18th century papers was investigated by means of ToF-SIMS and XPS. The aim of the present study was to explore the possibility of using these surface sensitive methods to obtain information which can help to determine the manufacturing process, provenance and state of conservation of ancient papers. The ToF-SIMS results indicate that the analyzed papers were sized by gelatin and that alum was added as hardening agent. The paper sheets produced in near geographical areas but in different paper mills exhibit a similar surface composition and morphology of the fibers as shown by the ToF-SIMS measurements. The ToF-SIMS and the XPS results indicate that a significant fraction of the cellulose fibers is not covered by the gelatin layer. This was observed for the ancient papers and for a modern handmade paper manufactured according to the old recipes. (C) 2010 Elsevier B.V. All rights reserved
A Semantic Similarity Measure for the SIMS Framework
No full textThe amount of currently available digital information grows rapidly. Relevant information is often spread over different information sources. An efficient and flexible framework to allow users to satisfy ef- fectively their information needs is required. The work presented in this paper describes SIMS (Semantic Information Management System), a ref- erence architecture for a framework performing semantic annotation, search and retrieval of information from multiple sources. The work pre- sented in this paper focuses on a specific SIMS module, the SIMS Semantic Content Navigator, proposing an algorithm and the related implementa- tion to calculate a semantic similarity measure inside an OWL ontology. This measure is based on ontology structure and on the information pro- vided by attributes and relations that are defined inside the ontology. This work is the result of a collaborative effort between the DINFO (Depart- ment of Computer Science and Engineering) and the research team of En- gineering - Ingegneria Informatica
Dynamic SIMS Application for Characterization of Advanced Doping Schemes in Semiconductors
No full textSecondary ion mass spectrometry has been the main technique to characterize depth distributions of dopant atoms in Silicon for more than 30 years, following the rapid technological developments in complementary metal oxide semiconductor (CMOS) miniaturization. In fact, SIMS arose among other analytical techniques because of its excellent detection limits (<ppm), depth resolution, and relatively high analytical throughput with great reproducibility/ repeatability. A virtuous circle was established between technological solutions able to provide shallower dopant distributions and SIMS instrumentation improvements. In particular, the constant reduction of junction depths required a continuous optimization of depth resolution and reduction of the sputtering initial transient width, both achievable mainly by reducing the impact energy of primary ions. Phenomena as ion beam induced topography and high concentration quantification needed to be addressed in order to grant the level of accuracy required by CMOS technology, but overall SIMS followed CMOS doping technology up to the last decade. Nowadays, new challenges are posed by the switching from planar transistors to tridimensional nanometric devices like FinFET or Trigate transistors. It is thus harder to assume that phenomena of dopant diffusion or precipitation observed in ‘SIMS-measurable’ un-patterned samples are identical in structures only few ten’s of nanometers thick. Analytical technics like atom probe tomography are gaining space in dopant characterization and it is worth asking what application field is left to SIMS.
In this presentation, an overview of the SIMS application to dopant characterization in the last 10 years will be given through a summary of results collected from specific analytical cases, mainly focused on n-type dopants in Si. In particular, results obtained applying sub-keV primary beam impact energies will be summarized and examples of quantitative depth profiling will be reported for shallow distributions in silicon showing what application margins are left to SIMS and which strength points can still represent an added value of the technique. Plasma ion immersion implantation (PIII) samples will be reported as ultimate case of application of SIMS and results will be discussed with respect to other analytical techniques
Determining the order of deposition of natural latent fingerprints and laser printed ink using chemical mapping with secondary ion mass spectrometry
No full textTime-of-flight secondary ion mass spectrometry (ToF-SIMS) chemical mapping was used to investigate the order of deposition of natural latent fingerprints and laser printed ink on paper. This feasibility study shows that sodium, potassium and C3H5 positive ions were particularly abundant endogenous components of the natural fingerprints and also present in the paper examined, but were mostly absent in the laser printed ink. Mapping of these ions enables the observation of friction ridges from latent prints on the ink surface, only when a fingerprint was deposited above the layer of ink. As a demonstration of proof of concept, blind testing of 21 samples from three donors resulted in a 100% success rate. The sensitivity of this technique was investigated within this trial through the examination of up to fifth depletion fingerprints and ageing of up to 28 days. Migration of fingerprint and paper components to the ink surface, although observed with increased ageing time, was not found to compromise determination of the deposition sequence
N omega-nitro-L-arginine methyl ester inhibits inflammatory liver injury induced by interleukin-2
No full textAdministration of interleukin-2 (IL-2) for treatment of metastatic disease often results in inflammatory liver injury. Previous studies have implicated increased leukocyte and platelet adhesion and enhanced nitric oxide production as causative factors in the development of IL-2-induced hepatic injury. This study investigated the capacity of N omega-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthesis inhibitor, to limit IL-2-induced hepatic edema and hepatocellular damage in mice. Using hepatic intravital microscopy, we also examined the effects of L-NAME on IL-2-induced increases in leukocyte and platelet adhesion. Administration of IL-2 increased leukocyte and platelet adhesion in post-sinusoidal venules and decreased hepatic perfusion. Cotreatment with L-NAME had no effect on leukocyte adhesion but increased platelet-endothelial adhesion and microvascular thrombosis. Chronic IL-2 treatment induced hepatic edema and hepatocellular injury. However, coadministration of L-NAME attenuated IL-2-induced edema and completely inhibited hepatocellular damage. These findings suggest that nitric oxide may play a central role in IL-2-induced inflammatory liver injury.LR: 20061115; PUBM: Print; JID: 8405628; 0 (Enzyme Inhibitors); 0 (Interleukin-2); 10102-43-9 (Nitric Oxide); 50903-99-6 (NG-Nitroarginine Methyl Ester); EC 1.14.13.39 (Nitric Oxide Synthase); EC 2.6.1.1 (Aspartate Aminotransferases); EC 2.6.1.2 (Alanine Transaminase); ppublishSource type: Electronic(1
Different approaches to soil monitoring: comparison between national soil information monitoring systems (N-SIMS) and LUCAS soil
No full textInternational audienceThe EU Soil Strategy for 2030 and the Proposal for a Directive on Soil Monitoring and Resilience aim to achieve healthy soils by 2050. This information is currently provided at European level by LUCAS soil survey and nationally through monitoring networks (N-SIMS) developed individually by each member state with different approaches. In this context, integrating data from diverse sources (i.e. LUCAS soil and N-SIMS) is essential.Under the EJPSOIL programme, twelve countries employed a common methodology to compare their N-SIMS to LUCAS Soil in terms of sampling strategy and representativeness of land use and soil types. This analysis revealed significant disparities in monitoring strategies, including variations in sampling design, monitored land cover, and sampling depth. While most N-SIMS and LUCAS Soil used a stratified random sampling design, some N-SIMS employed a regular grid approach. Sampling depth varied across countries, with some using fixed depth intervals and others opting for soil horizons sampling, while LUCAS Soil sampled topsoil at 0–20 cm depth (0-30cm in LUCAS 2022). Site density was generally higher in N-SIMS than in LUCAS Soil, with some cases exhibiting a difference of one order of magnitude. The significant increase in the number of sites in the LUCAS Soil 2022 campaign partially filled this gap. The spatial distribution of N-SIMS appeared more homogeneous than LUCAS Soil, especially in countries like France and Spain where N-SIMS followed a grid-based system and in regions with extensive mountainous areas systematically excluded by LUCAS Soil.Comparisons of site proportions in different soil types or land cover classes indicated that N-SIMS results were more aligned with the current estimated proportions (calculated by using Corinne Land Cover and WRB, respectively) compared to LUCAS Soil. However, both methods exhibited significant variations from current estimated proportions. This work underscores differences in sampling protocols andrepresentativeness among N-SIMS and between N-SIMS and LUCAS Soil. This is a preparatory work towards the soil properties comparisons among soil monitoring programs
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