921 research outputs found
National Implementation Measures
No full textYesArticle IV of the Biological and Toxin Weapons Convention sets out the obligation for
States Parties to implement the BTWC through appropriate national measures. Although
some States have enacted such legislation, others have not and the Aum Shinrikyo incident in
Tokyo in March 1995 underlined the importance of appropriate penal legislation both to
implement the BTWC (and the Chemical Weapons Convention) and to criminalise any
development, production, stockpiling or acquisition of such weapons for terrorist or criminal
purposes. This Briefing Paper reviews the development of the language relating to Article IV
of the BTWC by the four Review Conferences, notes the requirements of the Chemical
Weapons Convention and then addresses the opportunity provided by the Ad Hoc Group
negotiations to strengthen the BTWC through stronger implementation measures
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
Oxidation mechanisms of \u3b2-NiAl + Zr determined by SIMS
No full textThe oxidation mechanisms of single crystal Zr-doped \u3b2-NiAl from 800 to 1200 \ub0C were determined using primarily secondary ion mass spectrometry (SIMS) imaging and depth profiling. High spatial resolution SIMS imaging provides a means for critically assessing the effects of diffusion through the boundaries of the various morphologies of \u3b1-Al2O3 scales that form on \u3b2-NiAl. Transient oxidation occurs by outward Al diffusion through transition Al2O3 scales, \u3b8-Al2O3 in this case, for temperatures from 800 to 1100 \ub0C. Steady-state oxidation occurs by counter-diffusion of oxygen inward and both Al and Zr outward through boundaries in the \u3b1-Al2O3 ridge morphology.Peer reviewed: YesNRC publication: Ye
Interrogation of Biological Samples by ToF-SIMS
No full textMass spectrometry is a very versatile and important technique in analytical chemistry. From atomic bombs to Alzheimer’s disease, after a century of improvements and developments there are now countless applications for mass spectrometry in research and industry. One important branch within the field is imaging mass spectrometry as it combines chemical and location specific information.
Lipids, the main building blocks of cell membranes, are found in all living, cellular organisms. They are a diverse group of molecules, fulfilling structural and signal transduction functions. Right at the interface between the extra and intracellular environment, they are an important means of fast communication, they build a barrier to keep the cell alive, can promote cell death or indicate cellular changes in general. As different parts of organisms fulfil different functions, so is the distribution of lipids within organisms highly heterogeneous, indicating that each lipid has a role to play at its specific location.
To study the distribution of lipids, imaging time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a well suited technique as it has a high sensitivity for detecting lipids and can detect lipid distributions on a sub-cellular scale in biological samples. As with any technique, ToF-SIMS has some drawbacks, for example it can be highly destructive so analysed lipids are fragmented and the molecular information is lost, there is a trade-off between spatial resolution and molecular information and the signal detected depends highly on the ionisation efficiency of different species, as well as their surroundings, which can skew the results. ToF-SIMS is a vacuum technique which presents challenges for biological sample handling and every analysis is only as good as the sample that is analysed.
To improve upon those aspects, getting more intact molecules at higher resolutions, improving sample preparation, work towards understating matrix effects and study the overall applicability of ToF-SIMS for biological samples was the scope of this thesis
Differentiation of light-dye effects in the microcirculation
No full textActivation of photosensitive compounds has been used in the treatment of tumors and as a technique to study various microcirculatory phenomena. This technique may be accompanied by deleterious effects which may complicate interpretations of experimental results. However, the relevant physiological mechanisms that induce toxicity and the light doses needed to produce different toxic reactions have not been well defined. In the current study, the rat cremaster muscle preparation was used with in vivo fluorescent television microscopy and subsequently with electron and light microscopy to evaluate toxic reactions of light activation of fluorescein isothiocyanate. The most sensitive photoactive reactions were macromolecular leakage and platelet activation, occurring with 120 J/cm2 activation energy. Macromolecular leakage was at least partially restricted by perivenular and pericapillary pericytes and there was no morphological damage with this light dose. Since macromolecular leakage was significantly inhibited by pretreatment with diphenhydramine or Compound 48/80, it is in part due to the release of histamine from tissue mast cells. 720 J/cm2 reduced the red blood cell column in the venules by over 50% due to platelet thrombus formation, an effect that was accentuated by pretreatment with indomethacin. This suggests an inhibitory role of prostaglandins in platelet thrombus formation. In addition, 720 J/cm2 caused endothelial and smooth muscle cell swelling and ruptures, gap formation, and leukocyte and protein accumulation in the vessel walls.LR: 20061115; PUBM: Print; JID: 0165035; 0 (Prostaglandins); 0 (Receptors, Histamine); 3326-32-7 (Fluorescein-5-isothiocyanate); 506-32-1 (Arachidonic Acid); 58-73-1 (Diphenhydramine); EC 1.14.99.1 (Prostaglandin-Endoperoxide Synthases); ppublishSource type: Electronic(1
Morphology of the toxin-producing diatom Nitzschia-pungens Grunow forma multiseries Hasle
No full textThe toxin-producing diatom Nitzschia pungens Grunow forma multiseries Hasle from three toxic blooms in two Prince Edward Island estuaries, spanning 1987-89, was studied using light and electron microscopy. Cell ultrastructure of N. pungens is, in general, similar to that of other species of Nitzschia and other diatoms. Important features include prominent peripheral, polarized nucleoli (numbering one or two) and imperforate poroids, present on inner valves and girdle bands. Cell division is usually synchronous for all cells in a filament with respect to polarity and time. Postdivisional elongation of the filament appears to involve a "slide-by" process whereby sibling cells slide by each other along their opposed valve faces and then stop, becoming fused by their overlapping tips. The raphe is probably involved in this, as well as in filament and cell motility. Observations of particle motion along the cell raphe suggest the existence of a motility apparatus such as microcilia which would facilitate locomotion, intercellular coordination, and the postdivisional slide-by process. No bacteria or other organisms were observed associated with field samples of toxic N. pungens f. multiseries. This supports a view that domoic acid production is autonomous.Source type: Electronic(1
Accuracy and reproducibility of coral Sr/Ca SIMS timeseries in modern and fossil corals
No full text© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sayani, H., Cobb, K., Monteleone, B., & Bridges, H. Accuracy and reproducibility of coral Sr/Ca SIMS timeseries in modern and fossil corals. Geochemistry, Geophysics, Geosystems, 23(9), (2022): e2021GC010068, https://doi.org/10.1029/2021gc010068.Coral strontium-to-calcium ratios (Sr/Ca) provide quantitative estimates of past sea surface temperatures (SST) that allow for the reconstruction of changes in the mean state and climate variations, such as the El Nino-Southern Oscillation, through time. However, coral Sr/Ca ratios are highly susceptible to diagenesis, which can impart artifacts of 1–2°C that are typically on par with the tropical climate signals of interest. Microscale sampling via Secondary Ion Mass Spectrometry (SIMS) for the sampling of primary skeletal material in altered fossil corals, providing much-needed checks on fossil coral Sr/Ca-based paleotemperature estimates. In this study, we employ a set modern and fossil corals from Palmyra Atoll, in the central tropical Pacific, to quantify the accuracy and reproducibility of SIMS Sr/Ca analyses relative to bulk Sr/Ca analyses. In three overlapping modern coral samples, we reproduce bulk Sr/Ca estimates within ±0.3% (1σ). We demonstrate high fidelity between 3-month smoothed SIMS coral Sr/Ca timeseries and SST (R = −0.5 to −0.8; p < 0.5). For lightly-altered sections of a young fossil coral from the early-20th century, SIMS Sr/Ca timeseries reproduce bulk Sr/Ca timeseries, in line with our results from modern corals. Across a moderately-altered section of the same fossil coral, where diagenesis yields bulk Sr/Ca estimates that are 0.6 mmol too high (roughly equivalent to −6°C artifacts in SST), SIMS Sr/Ca timeseries track instrumental SST timeseries. We conclude that 3–4 SIMS analyses per month of coral growth can provide a much-needed quantitative check on the accuracy of fossil coral Sr/Ca-derived estimates of paleotemperature, even in moderately altered samples.We'd also like to thank Yolande Berta and Georgia Tech's Center for Nanostructure Characterization for providing access to their SEM facilities, and the Khaled bin Sultan Living Ocean Foundation and The Nature Conservancy for financial and logistical support for field excursions to Palmyra. Funding for this work was provided by the National Science Foundation (Award Numbers 1502832 and 2002458 to K.M.C) and the National Oceanic and Atmospheric Administration (Award Number: NA11OAR4310165 to K.M.C)
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