bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scattering and Absorption of γ‐Rays and Thermalization and Disappearance of Neutrons
Authors: Borsaru M. 
Published: September 2006

AbstractNuclear techniques are widely used in geological and mineral applications. Owing to the high penetration of γ‐radiation and neutrons, nuclear techniques have found many applications, including well logging, bulk analysis and on‐stream analysis. The first part of this article presents the physics of the interaction of γ‐rays and neutrons with matter. Applications based on these interactions to well logging for oil, uranium, coal and iron ore are presented in the second part of the article. Applications based on the natural radioactivity of rocks are also covered.
β‐Particle Emitters, Determination of
Authors: Caprette David R. 
Published: September 2006

Abstract

Radioisotopes have unstable nuclei that decay in a statistically predictable manner with the release of radiation in the form of particles or electromagnetic waves. In β‐decay “fast electrons” called β‐particles are released, which have a spectrum of kinetic energies ranging from near zero to a characteristic maximum (E

max

). E

max

can vary by orders of magnitude among different types of emitters. The low mass of β‐particles causes them to lose energy quickly through molecular collisions, producing excitation of valence electrons, ionization of atoms, and in some cases specialized radiation (bremsstrahlung and

$\widehat{\hbox{C}}\hbox{erenkov}$

radiation, and Compton scattering). Detection of β‐particle emissions is complicated by the wide range of possible energies and the weakness of some emissions, so that a single type of detector is inadequate for the analysis of radiation from all β‐particle emitters.

Detectors are characterized by a sensitive volume in which particles interact with matter to produce a signal, an example of which is the emission of photons. The signal can produce a continuous current or a pulse. In pulse mode it is desirable to choose a detector such that the pulse is proportional to the energy of the particle, giving the instrument the property of energy discrimination. This property permits spectral analysis and methods of quantitation that are based in part on energy spectra. Liquid scintillation counting (LSC) is the most accurate and widely used method for detecting low‐energy β‐particles. Usually the information obtained by LSC must be corrected for signal loss due to absorption of incident particles or emitted photons. This signal loss is called quenching. For quantitation of low‐energy β‐radiation, quench corrections are usually made using the sample channels ratio (SCR) or an external standard method. All such calculations are subject to error and derived values are subject to the compounding of precision error during mathematical manipulation of the data.
Scintillation counting with organic crystal detectors is the method of choice for high‐energy β‐particle emitters. Gas‐filled detectors are of limited value for β‐particle detection, although windowless proportional counters are appropriate for detection of low‐energy particles, especially in gaseous form. When neither energy discrimination nor precise quantitation is required, Geiger–Müller counters are acceptable for high‐energy β‐particle detection. They can detect all but the least energetic of low‐energy emitters, although Geiger–Müller counters are not practical for the analysis of activity from such emitters because the signal is very weak, and the energies from incident particles are frequently absorbed before reaching the sensitive volume. Silicon‐barrier semiconductors support energy discrimination and are of value for some applications. Visual imaging with photographic film is used for localization of β‐particle emitter activity, as in labeling of biological tissues or macromolecules.
γ‐Spectrometry, High‐Resolution, for Radionuclide Determination
Authors: Toivonen Harri I.K. , Nikkinen Mika T. 
Published: September 2006

AbstractHigh‐resolution γ‐spectrometry is a nondestructive assay method that gives low detection limits for many radioactive nuclides. γ‐Spectrometers use an electric field to collect the free charge carriers, electrons and holes, in a semiconductor detector. Modern detectors are based on high‐purity germanium (HPGe). The material properties of germanium containing extremely low concentrations of impurity atoms are excellent at low temperature (77 K) for creating and collecting charges in the sensitive region of the detector. The major components of the spectrometer are the detector, cooling system, shielding system, signal processing unit, and analysis software. The charge created at the detector is directly proportional to the energy deposited in the detector by the radiation. The weak charge pulse is transformed, shaped and amplified to a voltage pulse, which is then converted to digital form. A multichannel analyzer (MCA) collects and stores the spectrum, which comprises counts partitioned among different channels according to energy dissipated in the detector. The spectrum contains peaks that can be unequivocally associated with certain radionuclides. Peak areas are proportional to the activity of the nuclide. Meticulous calibrations are required to operate the instrument properly. Software plays a major role in the analysis of the spectra, and interactive human work and artificial intelligence, i.e. an expert system, are needed to handle complex cases. Stable elements can be analyzed through neutron activation and subsequent γ‐spectrometric determination. γ‐Spectrometry is not a sensitive method for radionuclides that have a long half‐life (≫30 years).
Neutron Activation Analysis in the Determination of Very Long‐Lived Radionuclides
Authors: Rosenberg Rolf J. 
Published: September 2006

Abstract

This article describes the use of neutron activation analysis (NAA) for the quantitative determination of very long‐lived radionuclides in the environment and nuclear waste. Because of its sensitivity and isotope specificity NAA is used for the determination of a few radionuclides with half‐lives of the order of 10
4
years or longer. The detection limits for some nuclides are lower than those obtainable with most kinds of mass spectrometry. The method has a substantial freedom from systematic errors.

The benefit of NAA, compared with direct radiometric measurement of the parent nuclide, is based on the fact that neutron activation may produce radionuclides with shorter half‐lives and higher specific activities than those of the parent nuclides. An especially significant improvement is obtained when a γ‐emitting nuclide is produced from a nuclide which only emits β‐particles.

There are a few long‐lived radionuclides which need to be determined because they are produced in nuclear fuel, and may pose a hazard in the final disposal of nuclear waste. Of these possible applications, the determination of
99
Tc,
129
I,
135
Cs and
237
Np is described here. NAA has proven to be the most sensitive method to determine
129
I and a useful method to determine
237
Np in environmental samples. Therefore, NAA can be recommended as an analytical method for these nuclides, when a research reactor is available.
Speciation of Radionuclides in the Environment
Authors: Salbu Brit 
Published: September 2006

AbstractTo obtain information on physicochemical forms of radionuclides in the environment, speciation techniques should be applied in situ, at‐site or in laboratories shortly after sample collection. Among speciation techniques for radionuclides in waters, combined in situ ultrafiltration and exchange chromatography are most promising as radionuclides species are fractionated with respect to nominal molecular mass and change properties simultaneously. However, the fractionation and characterization of chemically well‐defined low molecular mass (LMM) species in waters is still a challenge. Surface analytical techniques (e.g. electron microscopy) are useful for characterizing colloids and particles with respect to structure and radionuclide distribution. Recent development within synchrotron‐based X‐ray microbeam techniques allows detailed information of crystallographic structure (micro‐X‐ray diffraction (μ‐XRD)), oxidation states (micro‐X‐ray absorption near‐edge spectroscopy (μ‐XANES)) andvolumedistribution (μ‐XANES tomography) of particle‐associated radionuclides on the micrometer scale. Information on radionuclides reversibly or irreversibly associated with solid surfaces (binding mechanisms) is attained by different extraction techniques, while dynamic tracer experiments can provide information on the kinetics involved.
Inorganic Systems, Thermal Analysis Applications to
Authors: Gallagher Patrick K. 
Published: September 2006

Abstract
Thermoanalytical techniques can be used to characterize a wide range of inorganic materials and processes concerning them. The topics covered involve the measurement of thermal properties, phase equilibria, chemical analysis, and the study of solid‐state reactivity. Examples are selected to include applications to metals, ceramics, minerals and a variety of inorganic compounds. Applications to processes such as catalysis, crystal growth, and synthesis are described.
The principle techniques chosen for these purposes are associated with the measurement of different properties as a function of temperature and time. Thermogravimetry (TG), thermomagnetometry (TM), and evolved gas analysis (EGA) are based on changes in weight and analysis of the materials evolved or consumed. Differential thermal analysis (DTA) and differential scanning calorimetry (DSC) are concerned with changes in temperature and heat capacity. Thermodilatometry (TD) measures changes in length or volume. Examples illustrating the use of each of these techniques are described.
X‐Ray Techniques: Overview
Authors: Jenkins Ron 
Published: September 2006

AbstractThe use of X‐ray methods in the field of materials analysis is now entering its seventh decade. While the broad definition of X‐ray methods covers many techniques based on the scatter, emission and absorption properties of X‐radiation, the two most common are X‐ray fluorescence (XRF) spectrometry and X‐ray powder diffractometry (XRD). When a sample of material is bombarded with energetic radiation (X‐rays, γ‐rays, electrons, protons, etc.) vacancies may arise from the removal of inner orbital electrons. One of the processes by which the atom regains stability is by transference of electrons from outer to inner electron shells. Each of these transitions is accompanied by the emission of an X‐ray photon having an energy equal to the energy difference between the two states. The X‐ray emission wavelengths are characteristic of the atom in question and there is a simple relationship (Moseley's law) between the wavelength of the emission line and the atomic number of the atom. Thus when a sample is made up of many different types of atoms, each atom will produce a series of wavelengths, and all of the contributions add up to become the total X‐ray emission from the sample. XRF is a technique which utilizes the diffracting power of a single crystal, or the proportional characteristics of a photon detector, to separate the polychromatic beam of radiation from the sample into separate wavelengths, thus allowing qualitative and quantitative elemental measurements to be made.A beam of monochromatic radiation may also be scattered when X‐ray photons collide with atomic electrons. Where the scattered wavelengths interfere with one another diffraction of X‐rays occurs. All substances are built up of individual atoms and nearly all substances have some degree of order of periodicity in the arrangement of these atoms. It is the scattering from these periodic arrays that leads to the diffraction effect, and there is a simple relationship (Bragg's law) between the scattering angle, the wavelength of the radiation and the spacings between the planes of atoms. Since the distances between the atomic planes are dependent on the size and distribution of atoms – i.e. the structure of the material, XRD can be used for qualitative and quantitative phase identification.
Ultrafast Diffraction Techniques
Authors: Rousse A. 
Published: September 2006

Abstract

The need for femtosecond time resolution in the analysis of processes governed by atomic motion is well established. In biology, chemistry, and physics different times are of interest, but the shortest relate to the vibration of matter, being typically about 10
−13
s (100 femtoseconds). Time‐resolved experiments are used to monitor time‐dependent processes. Depending on the spectral range of observation, different properties can be studied. Usually, visible or near‐visible radiation provides information on the electronic properties, but atomic motion can be directly monitored only through very short wavelength radiation, such as X‐rays. The electronic changes associated with vibrations in single molecules, liquids or crystal lattices, isomerization and the breaking or formation of chemical bonds, can be monitored by ultrafast optical spectroscopy techniques, but the accompanying ultrafast structural rearrangements cannot be directly observed. In the detailed characterization of structures at the atomic level, X‐ray and electron diffraction is an unparalleled tool, allowing reaction intermediates to be followed.

Synchrotrons have become essential to the study of structures. Nevertheless, the shortest durations attainable with the latest generation of synchrotrons, hold the time resolution of experiments around 50 ps. This article shows how subpicosecond time resolution can be achieved in the analysis of very short‐lived transient structures. The two emerging techniques in subpicosecond time‐resolved X‐ray (electron) diffraction are (1) ultrashort X‐ray (electron) probe pulses, produced through a femtosecond laser system, and (2) fast X‐ray detection during quasicontinuous synchrotron‐produced X‐ray probe illumination.
Wavelength‐Dispersive X‐Ray Fluorescence Analysis
Authors: Jenkins Ron 
Published: September 2006

AbstractWhen an element is bombarded by high‐energy particles, orbital electrons may be ejected creating inner orbital atomic vacancies. These vacancies may be filled by transition of outer level electrons giving rise to characteristic X‐radiation. X‐ray fluorescence spectrometry provides the means of the identification of an element by measurement of its characteristic X‐ray emission wavelength of energy. The method allows the quantization of a given element by first measuring the emitted characteristic line intensity and then relating this intensity of element concentration. While the roots of the method go back to the early part of this century, where electron excitation systems were employed, it is only during the last 30 years or so that the technique has gained major significance as a routine means of elemental analysis. Wavelength‐dispersive spectrometers employ diffraction by a single crystal to separate characteristic wavelengths emitted by the sample. Today, nearly all commercially available X‐ray spectrometers use the fluorescence excitation method and employ a sealed X‐ray tube as the primary excitation source. The first commercial X‐ray spectrometer became available in the early 1950s and although these earlier spectrometers operated only with an air path, they were able to provide qualitative and quantitative information on all elements above atomic number 22 (titanium). Later versions allowed use of helium or vacuum paths that extended the lower atomic number cut‐off to around atomic number 9 (fluorine). X‐ray detectors used include the flow counter, the scintillation counter and the Si(Li) detector.The X‐ray method has good overall performance characteristics. In particular, the speed, accuracy and versatility of X‐ray fluorescence are the most important features among the many that have made it the method of choice in over 30 000 laboratories all over the world. Most wavelength‐dispersive spectrometers fall into two broad categories – single channel and multichannel. Single channel spectrometers are typically employed for both routine and nonroutine analysis of a wide range of products, including ferrous and nonferrous alloys, oils, slags and sinters, ores and minerals, thin films, and so on. These systems are very flexible but relative to multichannel spectrometers are somewhat slow. The multichannel wavelength‐dispersive instruments are used almost exclusively for routine, high‐throughout analysis where the great need is for fast accurate analysis, but where flexibility is of no importance.Interelement (matrix) effects often complicate quantitative analysis by X‐ray fluorescence. However, a wide selection of methods is now available for minimizing these effects, allowing excellent accuracy to be obtained in many cases. Detection limits are achievable down to the low parts per million (ppm) range and it is possible to obtain reasonable responses from as little as a few milligrams of material.
Gravimetry
Authors: Widmer M. 
Published: September 2006

Abstract
Gravimetry is one of the oldest techniques of quantitative analysis. In gravimetry, the analyte is precipitated as a stoichiometrically defined compound. After collecting and drying, the precipitate is weighed on an analytical balance and the analyte is determined from the mass and the known stoichiometry of the analytes in the precipitated compound. Although many instrumental methods have superseded gravimetry it is a very important method for standardization processes. Since calibration is inherent in the relative molecular masses and the stoichiometry of the chemical reaction, it represents one of the few primary methods.
As a closely related method, electrogravimetry is also considered. In electrogravimetry the analyte is deposited on a metal, for example a platinum electrode, by electrolysis with a controlled current and its mass is evaluated from the weight difference of the electrode before and after electrolysis. Electroseparation of two analytes is feasible by judicious choice of the electrode potential.
Quality Assurance in Analytical Chemistry
Authors: Fischbacher Christoph 
Published: September 2006

Abstract
Analytical methods have to meet certain quality requirements, so that the results are credible and can be used with confidence for regulatory, economic and research decisions. Analytical quality assurance (QA) contains preventive action and comprises planning steps, quality control (QC), quality assessment, documentation and quality improvement. All factors leading to the analytical result have to be controlled, clearly described and documented. Furthermore, the analytical result should be linked to the sample and related to reference materials (RMs) or measurement standards by an unbroken chain of traceability. Two elements are needed in order to achieve this goal: internal QA measures comprise elements performed by the laboratory, such as method validation and documentation and the use of RMs, external QA relates to performance evaluation by persons outside the laboratory, such as proficiency tests and accreditation.
Titrimetry
Authors: Widmer (Deceased) M. 
Published: September 2006

Abstract
In a titration, the analyte reacts with a reagent added as a solution of known concentration. The standard solution added from a buret is called a titrant. The volume of the titrant required to react completely with the analyte is measured as the volume at the equivalence point. The notions titrimetry and volumetry have the same meaning. Only well‐defined stoichiometric reactions are applied. No additional calibration is necessary, i.e. titrimetric methods are primary methods. Indication of the equivalence point can be carried out by visual indicators or instrumental methods.
Acidimetric and alkalimetric titrations can be described by Brønsted's theory of strong and weak acids and bases. Theoretical titration curves for reactions of strong or weak acids (bases) with strong bases (acids) are demonstrated. Extremely weak electrolytes can be titrated in the presence of precipitating, oxidizing or complexing agents.
Determinations of metal ions are feasible by means of complexometric titrations. The theory of complexometry, including coupled chemical equilibria, can be derived from the fundamentals of complex‐formation reactions in aqueous solutions. Applications are important for analyzing individual metal ions, mainly for their standardization, or for determining the hardness of water.
With regard to the instrumental indications of a titration, the potentiometric, amperometric and conductometric principles are outlined. Amperometric titrations of metal ions are performed with one polarizable electrode. The use of two polarizable electrodes (biamperometry) is especially important to determine the water content of organic solvents.
Traceability in Analytical Chemistry
Authors: Adams Freddy 
Published: September 2006

Abstract
This article describes the concepts of traceability for chemical measurements (in chemical analysis) as they are defined at present, and their relation to analytical chemistry. Traceability concerns the direct or indirect linkage of analytical results to the international metric system of units [Système International (SI)], thereby showing a way to achieving comparability in chemical analysis. The metrological concepts to do this, as they have been developed up to the present, are critically evaluated. They concern the units in which analytical results should be expressed and the tools, such as primary reference methods and primary standards, certified reference materials (CRMs) and other reference materials (RMs), that can be used to increase the accuracy of results of analysis.
Absorption and Ingestion Toxicology
Authors: Sen Pranab K. 
Published: September 2006

Abstract
Absorption and ingestion toxicology relates to the prevalence of ambient toxins, their intake process by human being through skin (epidermal) absorption or ingestion as foods, drinks, or drugs (narcotic or not) either taken orally or by injection, biological/neurological/behavioral reactions, related molecular and carcinogenic developments, and resulting health hazards.
Agroforestry
Authors: Lund H. Gyde 
Published: September 2006

Abstract
Agroforestry is a collective name for land‐use systems and practices for the deliberate growing of trees and crops on the same piece of land. In its broadest interpretation, agroforestry can include the planting of trees and shrubs around a farmstead for beauty and shade, or the management of public forests for timber and livestock grazing, mushroom and berry production, or fisheries. Key in all definitions of agroforestry is that the trees are grown deliberately for a purpose, along with the plants and/or animals, and that they are not merely remnants left over from land clearing or conversion.
A
merican
S
tatistical
A
ssociation, Section on Statistics and the Environment
Authors: Nussbaum Barry D. 
Published: September 2006

Abstract

The objective of the Section on Statistics & the Environment of the American Statistical Association is to serve as the focal point for Association members with special interests in the following areas:

Application and interpretation of statistics in disciplines related to the environment.

Development of improved statistical theory, concepts, and procedures for application to problems of the environment.

Improvement of training in environmental statistics.
Atmospheric Dispersion: Chemistry
Authors: Builtjes P.J.H. 
Published: September 2006

Abstract
Most trace gases and particles that are brought into the atmosphere are not inert, i.e. are passive. They are chemically, or physically, transformed in the atmosphere, and are removed from the atmosphere by dry deposition – reaction with the surface – and wet deposition – taken up in water‐droplets (rain‐out) or removed by falling droplets (wash‐out). The environmental impacts of the effects of chemistry relative to atmospheric dispersion are presented in this article by considering different spatial scales, namely local, regional and global.