bluuebunny/crossref_metadata_2025_split huggingface dataset:
Groundwater Protection
Authors: Stauffer Fritz 
Published: September 2009

AbstractDespite all the technical, legal, and social difficulties, and the costs, which arise or which could arise from restoring contaminated groundwater, it is obvious that the timely protection of the groundwater environment is preferable. National regulations define the framework for the protection of aquifers and especially drinking water wells. On the one hand, there are existing or planned activities, which represent hazards or risks for a particular groundwater environment, and, on the other hand, the aquifers exhibit a certain degree of vulnerability to a wide range of chemical and biological pollutants. Accordingly, the basic steps toward the protection of groundwater environments are (i) characterization of the site under consideration, (ii) assessment of the existing and potential groundwater contaminations or contamination risks, (iii) evaluation of the use of groundwater of the site, and (iv) evaluation and implementation of the groundwater protection measures.
Ecohydrological Optimality
Authors: Schymanski Stanislaus J. , Kleidon Axel , Roderick Michael L. 
Published: September 2009

Abstract
Hydrological systems are governed by an incredible wealth of interactive processes, ranging from small‐scale processes within the soil domain such as unsaturated flow, bioturbation, and root water uptake to large‐scale feedbacks between the water balance and the global atmospheric circulation. Optimality approaches aim toward a simpler and more general representation of hydrological systems. As the hydrology of land is strongly affected by the presence of vegetation, these optimality approaches generally need to be explored in the context of how purely hydrological processes are linked to ecological processes. This article summarizes the different optimality assumptions that have been used to describe ecohydrological processes and how these are related to each other. Most approaches can be classified as either physical or ecological optimality. A range of examples are given for applying optimality approaches at various temporal and spatial scales, ranging from the scale of individual leaves and how they control water loss in relation to carbon uptake to the larger scale attributes of vegetation types, ecosystem properties, and river basin networks. The article concludes with a discussion of the usefulness of optimality approaches and their advantages as well as their disadvantages and the need for improvement.
Field‐Portable Instrumentation for Gas and Vapor Samples
Authors: Thompson Cyril V. , Goedert Michel G. 
Published: September 2009

AbstractThe analysis of gas and vapors in the field is an important part of the environmental characterization and remediation process. The purpose of this article is to familiarize the reader with some of the analytical instrumentation currently used to determine the composition of gaseous samples. Although this section deals with portable instruments, on‐site measurements warrant a brief mention. These measurements are often conducted with conventional analytical instruments operating from recreational vehicles. The samples have to be collected and transported to the instrument, and the first part of this article gives an overview of some of the techniques, such as canister and solid adsorbents, used for this purpose. Identification of compounds collected on‐site or directly in the field can be done by gas chromatography (GC) and mass spectrometry (MS). A more comprehensive description of these laboratory‐based techniques is found in a previous version of this article. An important part of the portable section covers direct‐reading instruments such as gas sensors, electrochemical devices, ionization detectors, and colorimetric detectors. These instruments provide a limited amount of information and, most of the time, require prior knowledge of the content of the sample. However, they are small, portable, and cheaper than laboratory analytical instruments and therefore they have found a market. Portable instruments include miniaturized gas chromatographs and mass spectrometers. These instruments do not offer the high performance of their laboratory counterparts, but they give more information about the sample than direct‐reading instruments. The next step in process measurement sophistication is to combine these techniques. The most popular hyphenated technique is coupling of a gas chromatograph with a mass spectrometer, but there are also powerful and lesser‐known techniques such as GC combined with ion mobility spectrometry (IMS). IMS has found a market in military applications for the detection of chemical warfare agents. It offers less resolution than MS but operates at atmospheric pressure and is therefore truly portable. When combined with GC, it offers some interesting features which are described later.
Nuclear Magnetic Resonance, Imaging of Polymers
Authors: Blümler Peter , Hafner Siegfried 
Published: September 2009

AbstractNuclear magnetic resonance (NMR) imaging is a noninvasive technique, which is based on the phenomenon of NMR. The resonance frequencies of the nuclear spins can be made spatially dependent by introducing a magnetic‐field gradient into the NMR experiment. The acquired NMR signal is thus spatially encoded and a spin‐density image of the sample can be reconstructed.While originally developed for medical applications, NMR imaging is now increasingly applied for materials investigations. The main advantages of the technique are its nondestructivity, which allows processes to be investigated in situ, and the possibility of introducing NMR spectroscopic information and relaxation contrast into the NMR images. The limitations, on the other hand, are the relatively low sensitivity and the broad NMR lines of polymers, both of which limit the spatial resolution. Whereas the latter can be dealt with by suitable methods, the sensitivity ultimately restricts the achievable spatial resolution of conventional NMR imaging techniques to about (10 µm)3. NMR imaging therefore must not be considered as a competitor of other microscopic techniques such as electron microscopy but as a characterization technique that provides supplementary information. Examples illustrating all these aspects are given in this article.
Glow Discharge Optical Spectroscopy and Mass Spectrometry
Authors: Steiner Robert E. , Barshick Christopher M. , Bogaerts Annemie 
Published: September 2009

AbstractOptical (atomic absorption spectroscopy, AAS; atomic emission spectroscopy, AES; atomic fluorescence spectroscopy, AFS; and optogalvanic spectroscopy) and mass spectrometric (magnetic sector, quadrupole mass analyzer, QMA; quadrupole ion trap, QIT; Fourier transform ion cyclotron resonance, FTICR; and time‐of‐flight, TOF) instrumentation are well suited for coupling to the glow discharge (GD).The GD is a relatively simple device. A potential gradient (500–1500 V) is applied between an anode and a cathode. In most cases, the sample is also the cathode. A noble gas (e.g. Ar, Ne, and Xe) is introduced into the discharge region before power initiation. When a potential is applied, electrons are accelerated toward the anode. As these electrons accelerate, they collide with gas atoms. A fraction of these collisions are of sufficient energy to remove an electron from a support gas atom, forming an ion. These ions are, in turn, accelerated toward the cathode. These ions impinge on the surface of the cathode, sputtering sample atoms from the surface. Sputtered atoms that do not redeposit on the surface diffuse into the excitation/ionization regions of the plasma where they can undergo excitation and/or ionization via a number of collisional processes.GD sources offer a number of distinct advantages that make them well suited for specific types of analyses. These sources afford direct analysis of solid samples, thus minimizing the sample preparation required for analysis. The nature of the plasma also provides mutually exclusive atomization and excitation processes that help to minimize the matrix effects that plague so many other elemental techniques. Unfortunately, the GD source functions optimally in a dry environment, making analysis of solutions more difficult. These sources also suffer from difficulties associated with analyzing nonconducting samples.In this article, first, the principles of operation of the GD plasma are reviewed, with an emphasis on how those principles relate to optical spectroscopy and mass spectrometry. Basic applications of the GD techniques are considered next. These include bulk analysis, surface analysis, and the analysis of solution samples. The requirements necessary to obtain optical information are addressed following the analytical applications. This section focuses on the instrumentation needed to make optical measurements using the GD as an atomization/excitation source. Finally, mass spectrometric instrumentation and interfaces are addressed as they pertain to the use of a GD plasma as an ion source.GD sources provide analytically useful gas‐phase species from solid samples. These sources can be interfaced with a variety of spectroscopic and spectrometric instruments for both quantitative and qualitative analysis.
Silica Gel and its Derivatization for Liquid Chromatography
Authors: Neue Uwe D. 
Published: September 2009

AbstractIn this article, we review the preparation and use of silica and hybrid packings and their derivatives in liquid chromatography (LC). First, the properties of the carrier that are important for its application in LC are examined and then bonded phases and coated phases based on silica and hybrid packings are considered. The current state of the art of the preparation of bonded phases and coated phases is surveyed, and the properties that are relevant for the chromatographer are discussed. Owing to the popularity of reversed‐phase liquid chromatography (RPLC), most of the emphasis is placed on phases used in this technique; however, other chromatographic techniques are not ignored. A detailed characterization of reversed‐phase packings is provided.
Nuclear Reaction Spectroscopy
Authors: Trocellier Patrick , Berger Pascal 
Published: September 2009

AbstractAmong ion‐beam‐based analytical methods, direct observation of nuclear reactions induced by highly energetic (Me V domain) charged particles is dedicated to quantitative determination of volumic distributions of light elements fromZ = 1 (H) toZ = 41 (Ga) in the near surface region of solids. In most cases, discrimination between their isotopes is enabled up to37Cl. The incident ions are generally protons, deuterons, helium‐3, or helium‐4 ions. Nuclear reactions induced by heavier ions are rarely used, mostly for hydrogen depth profiling. All these reactions are characterized by the prompt emission of charged particles (protons or helium‐4 ions) and/or γ‐rays. Nuclear reaction analysis (NRA), performed in ion millibeam or microbeam modes, is an efficient complement to charged‐particle‐induced X‐ray emission, Rutherford backscattering spectrometry, and elastic recoil detection methods. Its applications are all intended for either absolute quantification or tracing experiments. They cover a broad panorama from life sciences to cultural heritage artifacts, including metallurgy, Earth sciences, nanotechnology, and material science.
Particle‐InducedX‐Ray Emission (PIXE)
Authors: Mandò Pier A. , Przybyłowicz Wojciech J. 
Published: September 2009

AbstractParticle‐induced X‐ray emission (PIXE) is the most popular among the ion beam analysis (IBA) techniques, which are based on the use of the specimen to be analyzed as a target for a beam of accelerated particles. The detection of the radiation induced by the beam bombardment is then used to discriminate and quantify the presence of the different elements in the specimen. In PIXE, what is exploited is, in particular, the X‐rays emitted from the target, whose energies are characteristic of the emitting atomic species. After a general, simple description of the main features of PIXE, with a short historical overview and a brief comparison to other X‐ray fluorescence (XRF) techniques, the article covers in greater depth all the specific aspects of this technique. The basic aspects of X‐ray emission from the atoms are first recalled; then, the extraction of quantitative compositional data from thin and thick specimens is explained, and a discussion is given of the excellent performance of PIXE in terms of minimum detection limits, and of the factors affecting them. A technical description then follows of how proper beams for PIXE are produced and of the experimental setups commonly used. The X‐ray detector characteristics, the electronics for constructing the energy spectra, and the software processes for their deconvolution, leading to the extraction of quantitative data, are then briefly described. The last section surveys the main analytical applications of PIXE in various fields (environmental monitoring, biomedicine, earth sciences, cultural heritage, and materials analysis), with no intent of exhaustiveness but rather with the purpose of focusing on when and why PIXE may be particularly suitable in each of them.
Magic‐Angle Spinning Solid‐State Nuclear Magnetic Resonance: Application to Structural Biology
Authors: Goldbourt Amir 
Published: September 2009

AbstractThe application of magic‐angle spinning (MAS) solid‐state NMR methods to large‐scale problems in structural biology has seen a significant progress in the last decade. Improved hardware, better sample preparation techniques, and new methodologies have resulted in the ability to solve the three‐dimensional structures of proteins, and to study their dynamic properties, making this method a viable and important tool for understanding the relation between biological processes and protein structure and function. One of the biggest advantages of MAS solid‐state NMR is in the ability to study structures, which are not easily accessible by traditional methods such as X‐ray crystallography and solution NMR. Hence, new classes of important proteins and biological complexes such as membrane proteins, amyloid fibrils and prions, metalloenzymes, and viruses, have all been characterized to various extents. It is expected that the role of MAS solid‐state NMR in structural biology will increase significantly as the number of dedicated research groups rises, and methodologies and hardware further improve.
Quadrupolar Nuclei in Biological Systems
Authors: Wu Gang 
Published: September 2009

AbstractRecent advances in solid‐state nuclear magnetic resonance (NMR) methodology and improvement in high‐field NMR instrumentation have generated a new wave of research interests in the application of solid‐state NMR to the study of quadrupolar nuclei in biological systems. These developments now permit increasingly complex biological systems to be probed by direct NMR detection of quadrupolar nuclei. In this article, we describe some recent progress in solid‐state NMR studies of17O (S = 5/2),25Mg (S = 5/2),43Ca (S = 7/2),67Zn (S = 5/2),23Na (S = 3/2), and39K (S = 3/2) nuclei in biological systems with a prognosis for future directions.
Diffusion and Electrophoretic Studies Using Nuclear Magnetic Resonance
Authors: Stilbs Peter 
Published: September 2009

AbstractThe NMR diffusometry methodology and instrumentation currently available is routinely capable of quite fast multicomponent self‐diffusion mapping in solution, providing a quantitative pathway to many analytical applications as well as physicochemical information. A measurement time span of approximately 10 min may suffice, and an accuracy of a few percent or better is normally routinely achievable. Relating the behavior of self‐diffusion coefficients of solution components to, e.g. solution composition changes adds another dimension to the field and a path to quantitative methods for elucidation of, e.g. molecular association or conformational changes even in complex systems. In routine form, the techniques are primarily applicable to liquid systems and use proton (1H) NMR detection. A limited number of nuclei other than protons (primarily2H,7Li,13C,19F,31P) are also amenable for monitoring. Electrophoretic NMR (eNMR) is a related, less exploited technique, which has a more limited applicability than NMR diffusometry, but which can be uniquely useful. Instrumental and methodological advances have lately also opened up the application field to proton‐detected diffusion studies in semisolid systems.
Production of Radionuclides for Tracers
Authors: Alfassi Zeev B. , Groppi F. 
Published: September 2009

AbstractThis chapters deals with production of radionuclides by both neutron bombardment from nuclear reactors and heavy charged accelerated atoms from accelerators. In the case of neutrons, most radionuclides have low specific activity due to the present carrier. The production of carrier‐free radionuclides is described.
Electrochemical Gas Sensors
Authors: Opekar František , Štulík Karel 
Published: September 2009

AbstractFundamental properties and structures of potentiometric and amperometric sensors for detection of compounds in gaseous phase are discussed. The discussion primarily deals with membrane sensors containing liquid electrolytes and solid‐state sensors employing inorganic and solid polymer electrolytes. Applications of gas sensors for detection of compounds in solution are also briefly discussed. Numerous practical examples are listed in tables. The advantages and drawbacks of various detector designs are critically surveyed and the important trends for further development are briefly outlined.
Catalytic Surfaces for Electroanalysis
Authors: Cox James A. , Kulesza Pawel J. 
Published: September 2009

AbstractIn this article, electrochemical determinations based on oxidation or reduction processes that require a catalyst to obtain a current proportional to analyte concentration are described. The scope is restricted to cases where the catalyst is immobilized at the electrode surface. In general, oxidation or reduction of a substance at an electrode surface can be the basis of an analytical method as long as the electron‐transfer reaction occurs in the potential window between redox of the solvent, supporting electrolyte, and/or the electrode material. The need for a catalyst arises because only a small fraction of solutes that are predicted on the basis of standard potentials to undergo redox in an available potential window are electrolyzed in the absence of a catalyst at a sufficient rate to provide an analytically useful current. As described later, the common mode of promotion of the rate of electron transfer is by mediation. A problem that results when immobilized mediators are used is that the potential at which the current is produced is related to the mediator as well as to the analytes; hence, many practical applications of catalytic surfaces involve electrochemical detection after separation by methods such as high‐performance liquid chromatography (HPLC).
The influence of text legibility on eye movements during reading
Authors: Slattery Timothy J. , Rayner Keith 
Published: September 2009

AbstractSubjects read passages of text on a video monitor as their eye movements were recorded. In Experiment 1, the passages were presented either in a format (ClearType) designed to display smoother, clearer characters on LCD monitors by eliminating pixilation or in standard format (non‐ClearType). The passages were also presented in three different fonts (Times New Roman, Harrington and Script MT bold) which differed in how easy the letters were to encode. While there were no comprehension differences due to ClearType or font, ClearType led to faster reading, fewer fixations, and shorter fixation durations than non‐ClearType. There were also font differences, with Times New Roman leading to faster reading than the other two fonts. In Experiment 2, we replicated the results that ClearType lead to faster reading than non‐ClearType when subjects read single sentences with high or low frequency target words. Across both experiments, word frequency interacted with presentation format. Copyright © 2009 John Wiley & Sons, Ltd.
Bulk Metallic Glasses with Functional Physical Properties
Authors: Wang W. H. 
Published: September 2009

AbstractIn this review, we report on the formation of a variety of novel, metallic, glassy materials that might well have applications as functional materials. The metallic glasses, with excellent glass‐forming ability, display many fascinating properties and features such as excellent wave‐absorption ability, exceptionally low glass‐transition temperatures (∼35–60 °C) approaching room temperature, ultralow elastic moduli comparable to that of human bone, high elasticity and high strength, superplasticity and polymer‐like thermoplastic formability near room temperature, an excellent magnetocaloric effect, hard magnetism and tunable magnetic properties, heavy‐fermion behavior, superhydrophobicity and superoleophobicity, and polyamorphism, all of which are of interest not only for basic research but also for technological applications. A strategy based on elastic‐moduli correlations for fabrication of bulk metallic glasses (BMGs) with controllable properties is presented. The work has implications in the search for novel metallic glasses with unique functional properties, for advancing our understanding of the nature and formation of glasses, and for extending the applications of the materials.
Controlled Growth of High‐Quality ZnO‐Based Films and Fabrication of Visible‐Blind and Solar‐Blind Ultra‐Violet Detectors
Authors: Du Xiaolong , Mei Zengxia , Liu Zhanglong , Guo Yang , Zhang Tianchong , Hou Yaonan , Zhang Ze , Xue Qikun , Kuznetsov Andrej Yu 
Published: September 2009

AbstractZnO is a wide‐bandgap (3.37 eV at room temperature) oxide semiconductor that is attractive for its great potential in short‐wavelength optoelectronic devices, in which high quality films and heterostructures are essential for high performance. In this study, controlled growth of ZnO‐based thin films and heterostructures by molecular beam epitaxy (MBE) is demonstrated on different substrates with emphasis on interface engineering. It is revealed that ultrathin AlN or MgO interfacial layers play a key role in establishing structural and chemical compatibility between ZnO and substrates. Furthermore, a quasi‐homo buffer is introduced prior to growth of a wurtzite MgZnO epilayer to suppress the phase segregation of rock‐salt MgO, achieving wide‐range bandgap tuning from 3.3 to 4.55 eV. Finally, a visible‐blind UV detector exploiting a double heterojunction of n‐ZnO/insulator‐MgO/p‐Si and a solar‐blind UV detector using MgZnO as an active layer are fabricated by using the growth techniques discussed here.
Epitaxial Growth and Properties of Doped Transition Metal and Complex Oxide Films
Authors: Chambers Scott A. 
Published: September 2009

AbstractThe detailed science and technology of crystalline oxide film growth using vacuum methods is reviewed and discussed with an eye toward gaining fundamental insights into the relationships between growth process and parameters, film and interface structure and composition, and electronic, magnetic and photochemical properties. The topic is approached first from a comparative point of view based on the most widely used growth methods, and then on the basis of specific material systems that have generated very high levels of interest. Emphasis is placed on the wide diversity of structural, electronic, optical and magnetic properties exhibited by oxides, and the fascinating results that this diversity of properties can produce when combined with the degrees of freedom afforded by heteroepitaxy.