Atomic Weights of the Elements 2009Dedicated to Prof. Kevin J. R. Rosman, expert scientist, former member of IUPAC’s Commission on Isotopic Abundances and Atomic Weights and IUPAC’s Subcommittee for Isotopic Abundance Measurement, and analytical thinker—a long-time friend of and contributor to the Commission on Isotopic Abundances and Atomic Weights

2016 ◽  
Author(s):  
Michael E. Wieser ◽  
Tyler B. Coplen
Keyword(s):  
Isotopic Abundance ◽  
Long Time ◽  
Isotopic Abundances ◽  
Analytical Thinker

Paleobiological Implications of the Isotopic Signatures (13C,15N) of Fossil Mammal Collagen in Scladina Cave (Sclayn, Belgium)

1997 ◽  
Vol 48 (3) ◽  
pp. 370-380 ◽  
Author(s):  
Hervé Bocherens ◽  
Daniel Billiou ◽  
Marylène Patou-Mathis ◽  
Dominique Bonjean ◽  
Marcel Otte ◽  
...  
Keyword(s):  
Trophic Position ◽  
Brown Bear ◽  
Extraction Process ◽  
Vegetarian Diet ◽  
Isotopic Abundance ◽  
Preliminary Screening ◽  
Isotopic Signatures ◽  
Extant Species ◽  
Isotopic Abundances

An isotopic investigation of upper Pleistocene mammal bones and teeth from Scladina cave (Sclayn, Belgium) demonstrated the very good quality of collagen preservation. A preliminary screening of the samples used the amount of nitrogen in whole bone and dentine in order to estimate the preserved amount of collagen before starting the extraction process. The isotopic abundances of fossil specimens from still-extant species are consistent with their trophic position. Moreover, the15N isotopic abundance is higher in dentine than in bone in bears and hyenas, a phenomenon already observed in modern specimens. These results demonstrate that the isotopic compositions of samples from Scladina cave can be interpreted in ecological terms. Mammoths exhibit a high15N isotopic abundance relative to other herbivores, as was the case in Siberian and Alaskan samples. These results suggest distinctive dietary adaptations in herbivores living in the mammoth steppe. Cave bears are clearly isotopically different from coeval brown bears, suggesting an ecological separation between species, with a pure vegetarian diet for cave bear and an omnivorous diet for brown bear.

scholarly journals Single-Ion Deconvolution of Mass Peak Overlaps for Atom Probe Microscopy

2017 ◽  
Vol 23 (2) ◽  
pp. 300-306 ◽  
Author(s):  
Andrew J. London ◽  
Daniel Haley ◽  
Michael P. Moody
Keyword(s):  
Kinetic Energy ◽  
Point Cloud ◽  
Atom Probe ◽  
Resolving Power ◽  
Isotopic Abundance ◽  
Mass Peak ◽  
Peak Overlap ◽  
Mass Resolving Power ◽  
Charge Spectrum ◽  
Isotopic Abundances

AbstractDue to the intrinsic evaporation properties of the material studied, insufficient mass-resolving power and lack of knowledge of the kinetic energy of incident ions, peaks in the atom probe mass-to-charge spectrum can overlap and result in incorrect composition measurements. Contributions to these peak overlaps can be deconvoluted globally, by simply examining adjacent peaks combined with knowledge of natural isotopic abundances. However, this strategy does not account for the fact that the relative contributions to this convoluted signal can often vary significantly in different regions of the analysis volume; e.g., across interfaces and within clusters. Some progress has been made with spatially localized deconvolution in cases where the discrete microstructural regions can be easily identified within the reconstruction, but this means no further point cloud analyses are possible. Hence, we present an ion-by-ion methodology where the identity of each ion, normally obscured by peak overlap, is resolved by examining the isotopic abundance of their immediate surroundings. The resulting peak-deconvoluted data are a point cloud and can be analyzed with any existing tools. We present two detailed case studies and discussion of the limitations of this new technique.

scholarly journals Isotopic Abundances in Comets

1987 ◽  
Vol 120 ◽  
pp. 461-467
Author(s):  
V. Vanysek
Keyword(s):  
Stable Isotopes ◽  
Chemical Composition ◽  
Solar Nebula ◽  
Isotopic Ratio ◽  
Point Of View ◽  
Isotopic Ratios ◽  
Isotopic Abundance ◽  
Light Elements ◽  
Small Bodies ◽  
Isotopic Abundances

It is belived that the unprocessed material of the solar nebula may be preserved in comets. Thus the data concerning the chemical composition and the abundance of stable isotopes in these primitive bodies are of some importance in cosmological and cosmogonical context. Although the isotopic abundance in the small bodies of the Solar System are poorly known, owing to the forthcoming Halley fly-by missions, the discussion as whether or not the comets have preserved the cosmic isotopic ratio in their nuclei became more relevant. From this point of view expected data of the cosmologically and cosmogonically significant isotopic ratios of stable isotopes of the light elements in comets are discussed.

scholarly journals Isotopic Abundances and Atomic Weights: IUPAC Commission II.1 Today

2019 ◽  
Vol 41 (1) ◽  
pp. 24-26
Author(s):  
Juris Meija
Keyword(s):  
Periodic Table ◽  
Atomic Weight ◽  
Scientific Merit ◽  
Long Time ◽  
Isotopic Abundances ◽  
Iupac Commission

Abstract It is hard to imagine IUPAC without the Periodic Table, and in turn, without atomic weights. As IUPAC celebrates its centennial, its oldest body, the Commission on Isotopic Abundances and Atomic Weights (CIAAW) turns 120. The parent Commission was formed in March 1899 and its inaugural task was to decide the atomic weight standard: should it be based on hydrogen or oxygen? Although the issue was settled in favor of oxygen, when the CIAAW formally joined the IUPAC in 1919, the question of the atomic weight scale was back for debate suggesting that many issues before this Commission transcend their scientific merit. In fact, many view the Periodic Table and changes therein as a part of larger cultural fabric of science so any changes are likely to be debated for a long time.

Atomic weights of the elements 1999 (IUPAC Technical Report)

2001 ◽  
Vol 73 (4) ◽  
pp. 667-683 ◽  
Author(s):  
Tyler B. Coplen
Keyword(s):  
Isotopic Composition ◽  
Scientific Community ◽  
Atomic Weight ◽  
Atomic Mass ◽  
Isotopic Abundance ◽  
Technical Report ◽  
Relative Atomic Mass ◽  
Isotopic Abundances

The biennial review of atomic-weight, Ar(E), determinations and other cognate data have resulted in changes for the standard atomic weights of the following elements: elementFromTonitrogen14.006 74 ± 0.000 0714.0067 ± 0.0002 sulfur32.066 ± 0.00632.065 ± 0.005 chlorine35.4527 ± 0.000935.453 ± 0.002germanium72.61 ± 0.0272.64 ± 0.01 xenon131.29 ± 0.02131.293 ± 0.006 erbium167.26 ± 0.03167.259 ± 0.003 uranium238.0289 ± 0.0001238.028 91 ± 0.000 03 Presented are updated tables of the standard atomic weights and their uncertainties estimated by combining experimental uncertainties and terrestrial variabilities. In addition, this report again contains an updated table of relative atomic-mass values and half-lives of selected radioisotopes. Changes in the evaluated isotopic abundance values from those published in 1997 are so minor that an updated list will not be published for the year 1999.Many elements have a different isotopic composition in some nonterrestrial materials. Some recent data on parent nuclides that might affect isotopic abundances or atomic-weight values are included in this report for the information of the interested scientific community.

200kv superconducting cryo electron microscope

1987 ◽  
Vol 45 ◽  
pp. 642-643
Author(s):  
M. Iwatsuki ◽  
Y. Kokubo ◽  
Y. Harada ◽  
J. Lehman
Keyword(s):  
Electron Microscope ◽  
Structure Analysis ◽  
Organic Materials ◽  
Strong Interactions ◽  
Specimen Preparation ◽  
Great Effort ◽  
Electron Microscopic ◽  
Crystal Fields ◽  
Special Skill ◽  
Long Time

In recent years, the electron microscope has been significantly improved in resolution and we can obtain routinely atomic-level high resolution images without any special skill. With this improvement, the structure analysis of organic materials has become one of the interesting targets in the biological and polymer crystal fields.Up to now, X-ray structure analysis has been mainly used for such materials. With this method, however, great effort and a long time are required for specimen preparation because of the need for larger crystals. This method can analyze average crystal structure but is insufficient for interpreting it on the atomic or molecular level. The electron microscopic method for organic materials has not only the advantage of specimen preparation but also the capability of providing various information from extremely small specimen regions, using strong interactions between electrons and the substance. On the other hand, however, this strong interaction has a big disadvantage in high radiation damage.

A Stationary Solution of High-Energy Electron Reflection (HEER) for An Arbitrary Surface

1990 ◽  
Vol 48 (2) ◽  
pp. 374-375
Author(s):  
YIQUN MA
Keyword(s):  
Stationary Solution ◽  
High Energy ◽  
Bloch Wave ◽  
Dynamical Theory ◽  
High Energy Electron ◽  
Bulk Materials ◽  
Periodic Surface ◽  
Electron Transmission ◽  
Electron Reflection ◽  
Long Time

For a long time, the development of dynamical theory for HEER has been stagnated for several reasons. Although the Bloch wave method is powerful for the understanding of physical insights of electron diffraction, particularly electron transmission diffraction, it is not readily available for the simulation of various surface imperfection in electron reflection diffraction since it is basically a method for bulk materials and perfect surface. When the multislice method due to Cowley & Moodie is used for electron reflection, the “edge effects” stand firmly in the way of reaching a stationary solution for HEER. The multislice method due to Maksym & Beeby is valid only for an 2-D periodic surface.Now, a method for solving stationary solution of HEER for an arbitrary surface is available, which is called the Edge Patching method in Multislice-Only mode (the EPMO method). The analytical basis for this method can be attributed to two important characters of HEER: 1) 2-D dependence of the wave fields and 2) the Picard iteractionlike character of multislice calculation due to Cowley and Moodie in the Bragg case.

Direct imaging of charge transfer

1996 ◽  
Vol 54 ◽  
pp. 680-681
Author(s):  
Yimei Zhu ◽  
J. Tafto
Keyword(s):  
Charge Transfer ◽  
Electron Diffraction ◽  
Scattering Amplitude ◽  
High Temperature Superconductors ◽  
Charge Carriers ◽  
Image Charge ◽  
Net Charge ◽  
Long Time ◽  
Electron Holes ◽  
First Time

The electron holes confined to the CuO2-plane are the charge carriers in high-temperature superconductors, and thus, the distribution of charge plays a key role in determining their superconducting properties. While it has been known for a long time that in principle, electron diffraction at low angles is very sensitive to charge transfer, we, for the first time, show that under a proper TEM imaging condition, it is possible to directly image charge in crystals with a large unit cell. We apply this new way of studying charge distribution to the technologically important Bi2Sr2Ca1Cu2O8+δ superconductors.Charged particles interact with the electrostatic potential, and thus, for small scattering angles, the incident particle sees a nuclei that is screened by the electron cloud. Hence, the scattering amplitude mainly is determined by the net charge of the ion. Comparing with the high Z neutral Bi atom, we note that the scattering amplitude of the hole or an electron is larger at small scattering angles. This is in stark contrast to the displacements which contribute negligibly to the electron diffraction pattern at small angles because of the short g-vectors.

Microstructural characterization of plasma-processed Ti-Al metal matrix composites

1989 ◽  
Vol 47 ◽  
pp. 552-553
Author(s):  
M. G. Burke ◽  
M. N. Gungor ◽  
M. A. Burke
Keyword(s):  
High Temperature ◽  
Titanium Aluminide ◽  
Plasma Processing ◽  
Microstructural Characterization ◽  
High Temperature Strength ◽  
Matrix Composites ◽  
Intermetallic Matrix ◽  
Long Time ◽  
Strength And Stiffness ◽  
Intermetallic Matrix Composites

Intermetallic matrix composites are candidates for ultrahigh temperature service when light weight and high temperature strength and stiffness are required. Recent efforts to produce intermetallic matrix composites have focused on the titanium aluminide (TiAl) system with various ceramic reinforcements. In order to optimize the composition and processing of these composites it is necessary to evaluate the range of structures that can be produced in these materials and to identify the characteristics of the optimum structures. Normally, TiAl materials are difficult to process and, thus, examination of a suitable range of structures would not be feasible. However, plasma processing offers a novel method for producing composites from difficult to process component materials. By melting one or more of the component materials in a plasma and controlling deposition onto a cooled substrate, a range of structures can be produced and the method is highly suited to examining experimental composite systems. Moreover, because plasma processing involves rapid melting and very rapid cooling can be induced in the deposited composite, it is expected that processing method can avoid some of the problems, such as interfacial degradation, that are associated with the relatively long time, high temperature exposures that are induced by conventional processing methods.

Gum arabic helps prepare better lacey polymer films for specimen support in electron microscopy

1993 ◽  
Vol 51 ◽  
pp. 240-241
Author(s):  
Shailesh R. Sheth ◽  
Jayesh R. Bellare
Keyword(s):  
Electron Microscopy ◽  
Polymer Films ◽  
Gum Arabic ◽  
Complete Removal ◽  
Ammonium Bromide ◽  
Release Agent ◽  
Astigmatism Correction ◽  
Long Time ◽  
Micro Holes ◽  
Cetyl Trimethyl Ammonium

Specimen support and astigmatism correction in Electron Microscopy are at least two areas in which lacey polymer films find extensive applications. Although their preparation has been studied for a very long time, present techniques still suffer from incomplete release of the film from its substrate and presence of a large number of pseudo holes in the film. Our method ensures complete removal of the entire lacey film from the substrate and fewer pseudo holes by pre-treating the substrate with Gum Arabic, which acts as a film release agent.The method is based on the classical condensation technique for preparing lacey films which is essentially deposition of minute water or ice droplets on the substrate and laying the polymer film over it, so that micro holes are formed corresponding to the droplets. A microscope glass slide (the substrate) is immersed in 2.0% (w/v) aq. CTAB (cetyl trimethyl ammonium bromide)-0.22% (w/v) aq.

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