2,132 research outputs found

    Nonlethal Weapons, Noncombatant Immunity, and the Principle of Participatory Liability

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    AVIRIS spectra of California wetlands

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    Spectral data gathered by the AVIRIS from wetlands in the Suisun Bay area of California on 13 October 1987 were analyzed. Spectra representing stands of numerous vegetation types (including Sesuvium verrucosum, Scirpus acutus and Scirpus californicus, Xanthium strumarium, Cynadon dactylon, and Distichlis spicata) and soil were isolated. Despite some defects in the data, it was possible to detect vegetation features such as differences in the location of the chlorophyll red absorption maximum. Also, differences in cover type spectra were evident in other spectral regions. It was not possible to determine if the observed features represent noise, variability in canopy architecture, or chemical constituents of leaves

    Focus on fourier transform ion cyclotron resonance mass spectrometry

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    Israel: Bioethics in a Jewish-Democratic State

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    Unlike most Western nations, Israel does not recognize full separation of church and state but seeks instead a gentle fusion of Jewish and democratic values. Inasmuch as important religious norms such as sanctity of life may clash with dignity, privacy, and self-determination, conflicts frequently arise as Israeli lawmakers, ethicists, and healthcare professionals attempt to give substance to the idea of a Jewish-democratic state. Emerging issues in Israeli bioethics—end-of-life treatment, fertility, genetic research, and medical ethics during armed conflict—highlight this conflict vividly

    Charge remote fragmentation of fatty acids cationized with alkaline earth metal ions

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    AbstractFatty acids can be collisionally activated as [M - H + Cat]+, where Cat is an alkaline earth metal, by using tandem mass spectrometry. High-energy collisional activation induces charge remote fragmentation to give structural information. In the full scan mass spectra molecular ions are easily identified, particularly when barium is used as a cationizing agent; ions are shifted to a higher mass, lower chemical noise region of the mass spectrum. Moreover, the isotopic pattern of barium is characteristic, and the high mass defect of barium allows an easy separation of the cationized analyte from any remaining interfering ions (chemical noise), provided medium mass-resolving power is available. An additional advantage is that most of the ion current is localized in [M - H + Cat]+ species. Structural analysis of fatty acids can be performed when the sample size is as low as 1 ng

    Fragmentation Mechanisms of Oxofatty Acids Via High-Energy Collisional Activation

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    AbstractUpon high-energy collisional activation, oxofatty-acid ions undergo fragmentations to produce a unique pattern of product ions by which the position of the ketone is revealed. The reactions occurring in the vicinity of the ketone, which are the subject of this article, produce a spectral pattern that is not symmetrical. Although cleavages of α, β, and γ C–C bonds occur on the side proximal to the charge site, giving α, β, and γ ions, respectively, there is only a γ′ ion formed on the side distal to the charge site. The resulting lack of symmetry seemingly contradicts the concept that the reactions are independent of the charge (i.e., that they are charge remote). To eliminate any interaction between the charge and the reaction site, oxofatty acids were linked to glycyrrhetic acid, a steroid with a rigid polycyclic system. The fragmentation pattern remains the same, indicating that the effect does not depend on charge but rather on the ketone. Isotopic labeling and MS/MS/MS studies confirm that the fragmentations of C–C bonds in the vicinity of the ketone are complex, charge-remote processes. Formation of [M − H − H2O]− and [M − H − CO2]− anions and the ion that is formed by homolytic cleavage of the β bond at the side distal to the charge, however, are charge directed

    Multistep tandem mass spectrometry for sequencing cyclic peptides in an ion-trap mass spectrometer

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    AbstractCollisionally activated decomposition (CAD) of a protonated cyclic peptide produces a superposition spectrum consisting of fragments produced following random ring opening of the cyclic peptide to give a set of acylium ions (or isomeric equivalents) of the same m/z. Assignment of the correct sequence is often difficult owing to lack of selectivity in the ring opening. A method is presented that utilizes multiple stages of CAD experiments in an electrospray ion-trap mass spectrometer to sequence cyclic peptides. A primary acylium ion is selected from the primary product-ion spectrum and subjected to several stages of CAD. Amino-acid residues are sequentially removed, one at each stage of the CAD, from the C-terminus, until a b2 ion is reached. Results are presented for seven cyclic peptides, ranging in sizes from four to eight amino-acid residues. This method of sequencing cyclic peptides eliminates ambiguities encountered with other MS/MS approaches. The power of the strategy lies in the capability to execute several stages of CAD upon a precursor ion and its decomposition products, allowing the cyclic peptide to be sequenced in an unambiguous, stepwise manner
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