Hitchcock on Hitchcock, Volume 1

Hitchcock, Alfred; Gottlieb, Sidney

doi:10.1525/9780520960947

Cited by 8 publications

(9 citation statements)

References 0 publications

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“…Spectra at each image pixel or particular regions of interest in the sample image were extracted from the “stack,” which is a collection of images recorded at multiple, closely spaced photon energies across the absorption edge. Data treatment was performed with aXis2000 code developed at McMaster University . NEXAFS spectra at the Eu M V,IV edges were recorded from stack images and normalized (intensity and energy) with respect to the most intense M V peak at 1130.6 eV.…”

Section: Methodsmentioning

confidence: 99%

How Do Radionuclides Accumulate in Marine Organisms? A Case Study of Europium with Aplysina cavernicola

Maloubier

Shuh

Minasian

et al. 2016

Environ. Sci. Technol.

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In the ocean, complex interactions between natural and anthropogenic radionuclides, seawater, and diverse marine biota provide a unique window through which to examine ecosystem and trophic transfer mechanisms in cases of accidental dissemination. The nature of interaction between radionuclides, the marine environment, and marine species is therefore essential for better understanding transfer mechanisms from the hydrosphere to the biosphere. Although data pertaining to the rate of global transfer are often available, little is known regarding the mechanism of environmental transport and uptake of heavy radionuclides by marine species. Among marine species, sponges are immobile active filter feeders and have been identified as hyperaccumulators of several heavy metals. We have selected the Mediterranean sponge Aplysina cavernicola as a model species for this study. Actinide elements are not the only source of radioactive release in cases of civilian nuclear events; however, their physicochemical transfer mechanisms to marine species remain largely unknown. We have targeted europium(III) as a representative of the trivalent actinides such as americium or curium. To unravel biological uptake mechanisms of europium in A. cavernicola, we have combined radiometric (γ) measurements with spectroscopic (time-resolved laser-induced fluorescence spectroscopy, TRLIFS, and X-ray absorption near-edge structure, XANES) and imaging (transmission electron microscopy, TEM, and scanning transmission X-ray microscopy, STXM) techniques. We have observed that the colloids of NaEu(CO)·nHO formed in seawater are taken up by A. cavernicola with no evidence that lethal dose has been reached in our working conditions. Spectroscopic results suggest that there is no change of speciation during uptake. Finally, TEM and STXM images recorded at different locations across a sponge cross section, together with differential cell separation, indicate the presence of europium particles (around 200 nm) mainly located in the skeleton and toward the outer surface of the sponge.

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Section: Methodsmentioning

confidence: 99%

How Do Radionuclides Accumulate in Marine Organisms? A Case Study of Europium with Aplysina cavernicola

Maloubier

Shuh

Minasian

et al. 2016

Environ. Sci. Technol.

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“…Although MS is often considered blind to chirality, diastereomers, such as epimeric isomers, may sometimes be differentiated by MS/MS based on unique fragmentation patterns associated with each stereochemical configuration. 36,38,[63][64][65] Amster and coworkers showed that the C5 uronic acid stereochemistry near the reducing end in HS tetrasaccharides may be determined by EDD MS/MS, based on the differential ratio (DR), DR=log (1/3((∑(B 3 ,Y 1 ,C 2 ,Z 2 )/(∑(Y 2 , 1,5 X 2 ))), where a positive DR value is associated with GlcA and a negative value with IdoA. 36 Even though this strategy cannot be directly applied to determine the epimeric configuration in the compounds studied here, because of the difference in the chain length, charge state and the fragmentation method employed, the DR value may still be used for differentiation.…”

Section: Gated-tims Netd Ms/ms Analysis Of Highly Sulfated Dp6 Isomersmentioning

confidence: 99%

Characterization and Quantification of Highly Sulfated Glycosaminoglycan Isomers by Gated-Trapped Ion Mobility Spectrometry Negative Electron Transfer Dissociation MS/MS

Wei

Tang

et al. 2019

Anal. Chem.

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Glycosaminoglycans (GAGs) play vital roles in many biological processes, and are naturally present as complex mixtures of polysaccharides with tremendous structural heterogeneity, including many structural isomers. Mass spectrometric analysis of GAG isomers, in particular highly sulfated heparin (Hep) and heparan sulfate (HS), is challenging because of their structural similarity and facile sulfo losses during analysis. Herein, we show that highly sulfated Hep/HS isomers may be resolved by gated-trapped ion mobility spectrometry (gated-TIMS) with negligible sulfo losses. Subsequent negative electron transfer dissociation (NETD) tandem mass spectrometry (MS/MS) analysis of TIMS-separated Hep/HS isomers generated extensive glycosidic and cross-ring fragments for confident isomer differentiation and structure elucidation. The high mobility resolution and preservation of labile sulfo modifications afforded by gated-TIMS MS analysis also allowed relative quantification of highly sulfated heparin isomers. These results show that the gated-TIMS-NETD MS/MS approach is useful for both qualitative and quantitative analysis of highly sulfated Hep/HS compounds in a manner not possible with other techniques.

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“…Data analysis was performed using software aXis2000. 47 AFM AFM maps were acquired with a MultiMode Nanoscope V AFM (Veeco Metrology Group) in contact mode using Pt/Ir coated Si tips with a cantilever spring constant of 0.2 N/m and nominal radius of 12 nm (Bruker, SCM--PIC).…”

Section: Txm--nexafsmentioning

confidence: 99%

Spatially resolved TiOx phases in switched RRAM devices using soft X-ray spectromicroscopy

Carta

Hitchcock

Guttmann

et al. 2016

Sci Rep

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Reduction in metal-oxide thin films has been suggested as the key mechanism responsible for forming conductive phases within solid-state memory devices, enabling their resistive switching capacity. The quantitative spatial identification of such conductive regions is a daunting task, particularly for metal-oxides capable of exhibiting multiple phases as in the case of TiOx. Here, we spatially resolve and chemically characterize distinct TiOx phases in localized regions of a TiOx–based memristive device by combining full-field transmission X-ray microscopy with soft X-ray spectroscopic analysis that is performed on lamella samples. We particularly show that electrically pre-switched devices in low-resistive states comprise reduced disordered phases with O/Ti ratios around 1.37 that aggregate in a ~100 nm highly localized region electrically conducting the top and bottom electrodes of the devices. We have also identified crystalline rutile and orthorhombic-like TiO2 phases in the region adjacent to the main reduced area, suggesting that the temperature increases locally up to 1000 K, validating the role of Joule heating in resistive switching. Contrary to previous studies, our approach enables to simultaneously investigate morphological and chemical changes in a quantitative manner without incurring difficulties imposed by interpretation of electron diffraction patterns acquired via conventional electron microscopy techniques.

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Hitchcock on Hitchcock, Volume 1

Cited by 8 publications

References 0 publications

How Do Radionuclides Accumulate in Marine Organisms? A Case Study of Europium with Aplysina cavernicola

How Do Radionuclides Accumulate in Marine Organisms? A Case Study of Europium with Aplysina cavernicola

Characterization and Quantification of Highly Sulfated Glycosaminoglycan Isomers by Gated-Trapped Ion Mobility Spectrometry Negative Electron Transfer Dissociation MS/MS

Spatially resolved TiOx phases in switched RRAM devices using soft X-ray spectromicroscopy

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