bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal variation in depth to water table and hydrochemistry in three raised bogs and their laggs in coastal British Columbia, Canada
Authors: Howie S. A. , van Meerveld H. J.
Published: December 2012

Abstract. The laggs of three raised bogs in coastal British Columbia were studied in 2010–2012 to determine the temporal variation in depth to water table and hydrochemistry. The lagg is an integral, but rarely studied, part of a raised bog that helps to maintain the water mound in the bog and provides a buffer for runoff from adjacent mineral areas. Depth to water table measurements in 25 piezometers displayed similar annual fluctuations, with the highest water table in winter and the lowest at the end of summer. The smallest fluctuations in depth to water table were recorded closest to the bog centre, and the largest fluctuations in the laggs and adjacent mineral soil sites. Removal of a mature forest stand on one of the study transects resulted in a "watering-up" of the lagg site; the mean water level between August and November increased by 8 cm from 2010 to 2011, and by up to 27 cm during the driest time of the year. pH, pH-corrected electrical conductivity, and Na+ and Mg2+ concentrations varied little during the study period, whereas Ca2+, K+, Cl−, and DOC concentrations and acidity were more variable.
The Performance of Carbon Fibre Composites as ICCP Anodes for Reinforced Concrete Structures
Authors: Van Nguyen Chinh , Lambert Paul , Mangat Pal , O’Flaherty Fin , Jones Graeme
Published: December 2012

Cathodic protection has been proven to be one of the most widely applicable and cost-effective solutions for tackling steel corrosion in reinforced concrete. In this study, the possible use of carbon fibre composites, which are primarily used to strengthen concrete members, has been investigated as impressed current cathodic protection anodes. Carbon fibre anodes have been assessed in both concrete and calcium hydroxide solution. Two bonding mediums incorporating epoxy and geopolymer have also been investigated. The results demonstrate that epoxy resin can be used for bonding carbon fibre fabric anodes to reinforced concrete structures while geopolymer is more effective for bonding carbon fibre reinforced polymer (CFRP) rod into preformed grooves in the concrete surface. The dissolution of carbon fibre anode appears to stablise after a period of time, dependent upon the size and shape of the anode and applied voltage and current. Based on the present results, a maximum current density of 128 mA/m2 of reinforcing steel area is recommended for the operation of CFRP fabric anode and 64 mA/m2 of reinforcing steel area for that of CFRP rod anode.
Metastable Metal Hydrides for Hydrogen Storage
Authors: Graetz Jason
Published: December 2012

The possibility of using hydrogen as a reliable energy carrier for both stationary and mobile applications has gained renewed interest in recent years due to improvements in high temperature fuel cells and a reduction in hydrogen production costs. However, a number of challenges remain and new media are needed that are capable of safely storing hydrogen with high gravimetric and volumetric densities. Metal hydrides and complex metal hydrides offer some hope of overcoming these challenges; however, many of the high capacity “reversible” hydrides exhibit a large endothermic decomposition enthalpy making it difficult to release the hydrogen at low temperatures. On the other hand, the metastable hydrides are characterized by a low reaction enthalpy and a decomposition reaction that is thermodynamically favorable under ambient conditions. The rapid, low temperature hydrogen evolution rates that can be achieved with these materials offer much promise for mobile PEM fuel cell applications. However, a critical challenge exists to develop new methods to regenerate these hydrides directly from the reactants and hydrogen gas. This spotlight paper presents an overview of some of the metastable metal hydrides for hydrogen storage and a few new approaches being investigated to address the key challenges associated with these materials.
Dialysis Efficiency of AN69, a Semisynthetic Membrane Not Well Suited for Diffusion
Authors: Herrera-Gutiérrez M. E. , Seller-Pérez G. , Arias Verdu D. , Jironda-Gallegos C. , Martín-Velázquez M. , Quesada-García G.
Published: December 2012

AN69 membrane is not suited for diffusion, with an suggested limit at 25 mL/min dialysate flow rate. When prescribing continuous hemodialysis this threshold must be surpassed to achieve. We designed a study aimed to check if a higher dose of dialysis could be delivered efficiently with this membrane. Ten ICU patients under continuous hemodiafiltration with 1.4 m2 AN69 membrane were included and once a day we set the monitor to exclusively 50 mL/min dialysate flow rate and 250 mL/min blood flow rate and after 15 minutes measured dialysate saturation for urea, creatinine, and -microglobulin. We detected that urea saturation of dialysate was nearly complete () for at least 40 hours, while creatinine saturation showed a large dispersion () and did not detect any relation for these variables with time, blood flow, or anticoagulation regime. Saturation of -microglobulin was low () and decreased discretely with time (, ) and significantly with TMP increases (, ). In our experience AN69 membrane shows a better diffusive capability than previously acknowledged, covering efficiently the range of standard dosage for continuous therapies. Creatinine is not a good marker of the membrane diffusive capability.
Barriers to the Uptake of Concurrent Engineering in the Nigerian Construction Industry
Authors: Aniekwu Nathaniel Anny , Igboanugo Anthony C.
Published: December 2012

It is the consensus of scholars that the productivity of the construction industry is very low when compared with other industries. Concurrent Engineering (CE), which has a primary goal of reducing the total time from designing a product to releasing it into the market, while creating better designs as well, has been identified as one of the concepts that has yielded effective adaptation in the construction industry. An exploratory survey was used to identify 63 variables with the capacity to influence the uptake of Concurrent Engineering in Nigeria and was used to design a questionnaire, which was distributed to 50 stratified construction industry stakeholders. A statistical software package (STATISTI-XL) was used to analyse the severity index of each variable, in order to establish the importance of each variable in influencing the uptake of Concurrent engineering and also to compute the Kendall's coefficient of concordance, which assess the levels of agreement among the judges on the consistency of the rankings. A Kendall's coefficient of concordance of W=0.57365 was recorded. A lack of awareness emerged as the most important barrier against the integration of this concept into the Nigerian construction industry. The top five variables are all human factors that can be ameliorated by proper education.
Outsourcing in Healthcare through Process Modularization – A Lean Perspective
Authors: Guimarães Cristina Machado , de Carvalho José Crespo
Published: December 2012

Looking for efficiency, quality and profitability gains, healthcare organizations are adopting outsourcing solutions in the attempt of “doing more with less”. Seeking for cost reduction, risk mitigation, adapting to quick changes without compromising internal resources, these organizations also take big risks in control and flexibility variables. In order to understand how healthcare organizations find the best value equation combining internal and external resources in a modular service conception, a case study on a start-up Long-term Care unit with innovative format, great levels of customization and following an outsourcing strategy, was carried out.

The main conclusion, among others, is that in ambitious start-ups, having speed of entrance as the conditioning factor, a process orientation and management approach may offer a clear view of the gains related with trade-off decisions regarding time and cost (agility) and cost and quality (Leanness) ie, decisions under the “leagile” paradigm.

This study contributes for a wider understanding of the “leagile” concept associated to an outsourcing operational strategy. Additionally, it also provides new insights to the concept of modularity in services settings in a complex service as healthcare.
Concise Review: In Search of Unlimited Sources of Functional Human Pancreatic Beta Cells
Authors: Scharfmann Raphael , Rachdi Latif , Ravassard Philippe
Published: December 2012

It is well-established that insulin-producing pancreatic beta cells are central in diabetes. In type 1 diabetes, beta cells are destroyed by an autoimmune mechanism, whereas in type 2 diabetes, there is a decrease in functional beta-cell mass. In this context, studying beta cells is of major importance. Beta cells represent only 1% of total pancreatic cells and are found dispersed in the pancreatic gland. During the past decades, many tools and approaches have been developed to study rodent beta cells that efficiently pushed the field forward. However, rodent and human beta cells are not identical, and our knowledge of human beta cells has not progressed as quickly as our understanding of rodent beta cells. We believe that one of the reasons for this inefficient progress is the difficulty of accessing unlimited sources of functional human pancreatic beta cells. The main focus of this review concerns recent strategies to generate new sources of human pancreatic beta cells.
Chronic Heart Failure: We Are Fighting the Battle, but Are We Winning the War?
Authors: Atherton John J.
Published: December 2012

Heart failure represents an end-stage phenotype of a number of cardiovascular diseases and is generally associated with a poor prognosis. A number of organized battles fought over the last two to three decades have resulted in considerable advances in treatment including the use of drugs that interfere with neurohormonal activation and device-based therapies such as implantable cardioverter defibrillators and cardiac resynchronization therapy. Despite this, the prevalence of heart failure continues to rise related to both the aging population and better survival in patients with cardiovascular disease. Registries have identified treatment gaps and variation in the application of evidenced-based practice, including the use of echocardiography and prescribing of disease-modifying drugs. Quality initiatives often coupled with multidisciplinary, heart failure disease management promote self-care and minimize variation in the application of evidenced-based practice leading to better long-term clinical outcomes. However, to address the rising prevalence of heart failure and win the war, we must also turn our attention to disease prevention. A combined approach is required that includes public health measures applied at a population level and screening strategies to identify individuals at high risk of developing heart failure in the future.
Dyes, Environmental Analysis ofUpdate based on the original article by J. Riu and D. Barceló,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd
Authors: Pérez Sandra , Riu Josep , Barceló Damià
Published: December 2012

An overview of current analytical methodologies for the determination of dyes in environmental samples is presented. Analytical methods involving liquid chromatography (LC) and mass spectrometry (MS) are reviewed. The combination of capillary electrophoresis (CE) with MS as a new alternative for the analysis and confirmation of polar compounds (and particularly the sulfonated azo dyes) in environmental samples is also discussed. Finally, the extraction and preconcentration of dyes from water samples involving various solid‐phase extraction (SPE) protocols are presented. Recent findings in the occurrence of some dyes in the aquatic environment have also been included.
Clustering and Classification of Analytical DataUpdate based on the original article by Barry K. Lavine,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.
Authors: Lavine Barry K. , Mirjankar Nikhil
Published: December 2012

Clustering and classification are the major subdivisions of pattern recognition. Using these techniques, samples can be classified according to a specific property through measurements indirectly related to a property of interest (e.g. the type of fuel responsible for an underground spill). An empirical relationship or classification rule is developed from a set of samples for which the property of interest and the measurements are known. The classification rule can then be used to predict the property in samples that are not part of the original training set. The set of samples for which the property of interest and the measurements are known is called the training set. The set of measurements that describe each sample in the data set is called a pattern. The determination of the property of interest by assigning a sample to its respective category is called recognition, hence the term pattern recognition.

For pattern recognition analysis, each sample is represented as a data vectorx = (x1,x2,x3,xj, …,xp), where componentxjis a measurement, e.g. the area of thejth peak in a chromatogram. Each sample is considered as a point in a p‐dimensional measurement space. The dimensionality of the space corresponds to the number of measurements that are available for each sample. A basic assumption is that distance between pairs of points in this measurement space is inversely related to the degree of similarity between the corresponding samples. Points representing samples from one class will cluster in a limited region of the measurement space distant from the points corresponding to the other class. Pattern recognition (i.e. clustering and classification) is a set of methods for investigating data represented in this manner, to assess its overall structure, which is defined as the overall relation of each sample to every other in the data set.
Chiral Separations by High‐Performance Liquid ChromatographyUpdate based on the original article by Timothy J. Ward and Tanya M. Oswald,Encyclopedia of Analytical Chemistry, © 2000, John Wiley & Sons, Ltd.
Authors: Ward Timothy J. , Ward Karen D.
Published: December 2012

The word ‘chiral’ is derived from the Greek word ‘cheir’, which means hand. Chiral molecules are molecules that are related to each other in the same way that a left hand is related to a right hand. These molecules are mirror images of each other and are nonsuperimposable. Chiral separations traditionally have been considered among the most difficult of all separations because enantiomers have identical chemical and physical properties in an achiral environment. In this article, we focus on techniques used in high‐performance liquid chromatography (HPLC). Most chiral separations by HPLC are accomplished via direct resolution using a chiral stationary phase (CSP). In this technique, a chiral resolving agent is bound or immobilized to an appropriate support to make a CSP, and the enantiomers are resolved by the formation of temporary diastereomeric complexes between the analyte and the CSP.

Various types of CSPs have been developed, including polysaccharide‐based, cyclodextrin‐based, cyclofructan‐based, macrocyclic antibiotic‐based, protein‐based, Pirkle‐type, and ligand‐exchange CSPs. The most commercially common CSPs, polysaccharide‐based phases, consist of derivatized cellulose and amylose coated on silica gel and a new generation of polysaccharide‐based phases, which is immobilized through covalent bonding to a silica gel. Generally, analytes separated using the cyclodextrins require the formation of an inclusion complex between the analyte and the cyclodextrin. Separation is most favorable when the analyte also interacts with the mouth of the cyclodextrin molecule via hydrogen bonding to the functional groups present. The cyclofructan‐based CSPs are the newest development in chiral HPLC columns and are now available commercially. These bonded CSPs show excellent enantioselectivity toward all types of primary amines as well as other varieties of compounds. Numerous analytes have been separated using the macrocyclic antibiotic‐based CSPs, which can also be derivatized to alter their selectivity. Protein‐based CSPs comprise a number of commercially available columns. The protein‐based CSPs resemble the bonded macrocyclic antibiotic CSPs in many ways; however, the macrocyclic antibiotic CSPs are more stable and have greater capacities than the protein‐based CSPs. The Pirkle‐type CSPs typically use nonpolar organic mobile phases and often require derivatization of the analyte to add a π‐acid or π‐basic moiety, or both, to achieve separation. Ligand‐exchange phases are used with aqueous buffer mobile phases in which enantiomers are separated based on the differences in their charge and ionization constants. Limitations of ligand‐exchange separations are that only ionized analytes can be resolved using this technique and the copper‐salt‐containing mobile phases used absorb in the ultraviolet (UV) region, decreasing detection sensitivity.
Particle Size Determination for Process Analysis
Authors: Redman Terry P.
Published: December 2012

Particles and droplets are critical in the determination of product quality and process efficiency in the manufacture of a wide range of chemical, pharmaceutical, and biological products. Processes such as crystallization and precipitation, homogenization and emulsification, polymerization, and fermentation are based on the detailed understanding, optimization, and control of particles, droplets, and bubbles.

This article distinguishes between in situ particle system characterization (PSC) and traditional off‐line particle size analysis (PSA), and explains how the broader view of PSC is better suited to optimization and control of complex multiphase processes.

PSC goes beyond traditional off‐line PSA, to provide real‐time, in‐process measurements of the rate and degree of change in particles and particle structures as they exist in the actual process environment. In situ process analytical methods can also significantly reduce measurement errors associated with off‐line sampling and sample preparation. This facilitates improved process development through direct real‐time monitoring of the particles and droplets as they exist and change in process. Process‐analytical‐based understanding contributes to faster methods of optimization and results in more consistent scale‐up. Real‐time monitoring and control of the particle system in the manufacturing environment is also used as a tool to help assure product quality.
Nanoparticles in Environmental Waters, Determination of
Authors: Sanchis Josep , Farre Marinella , Barcelo Damia
Published: December 2012

Nanomaterials of different chemical composition, physicochemical properties, and origins are emitted to the environment because of their wide use and incidental emission. Water suspended aggregates in the nanorange can be processed with conventional wastewater treatments, but their efficiency seems to vary according to the characteristics of the aggregates. Moreover, even in the best case scenario, certain amounts of nanomaterials are likely to be present in the effluent flows at trace concentrations. Sewage water disposal together with other processes, such as the atmospheric deposition and the direct spillage risk, make the water environment particularly susceptible to the introduction of these new compounds and carry ecological and health consequences that should be assessed.

Studying the behavior of nanoparticles in water environments of ecological relevance is a crucial step toward a proper assessment of the ecotoxicological effects, distribution patterns, and persistence of nanomaterials in the water environment.
Wavelength‐Dispersive
X
‐Ray Fluorescence Analysis: Part
II
Authors: Jenkins Ron , Kuczumow Andrzej
Published: December 2012

Wavelength‐dispersive X‐ray fluorescence (WD‐XRF) is a recently well‐grounded technique, with unbeaten application in some significant fields: metallurgy, geological analysis, and forensic science. Up to now, the method was rather conservative in construction systems and rate of the progress. Wavelength‐dispersive X‐ray spectrometry is characterized by very good spectral resolution for photon energies below 5 keV; total stability of devices in operations, both repeatable and long‐lasting; excellent quantitation; and clear peak shapes enabling chemical speciation. WD‐XRF systems operate by sequential elemental analysis. The classical version of method is suffering from very low rate of transforming of supplied energy in the final photons, what has effect on the significant cost of device and operation. Now, the progress is going. New multilayer interference mirrors (MIM) are replacing older multilayers, improving the spectral resolution of the structures mentioned and they are applied for analysis of very light elements. Also recently, the combinations of polycapillary half‐lenses, full lenses, or doubly curved crystals (DCCs) enable to overcome the essential drawback of old versions: some new devices became lightweight, with small consumption of energy, with the ability of focusing the exciting beam. All the progress widens the possibility of speciation analyses. New unexpected fields grew, e.g. the trials of quantitative differentiation of species in biology, by the use of multielemental analyses what should complement traditional Linnaean systematics.
Atmospheric Aerosols, Analysis of
Authors: Smichowski Patricia , Gómez Darío R.
Published: December 2012

The increasing concern about air pollution and climate change has attracted the interest of researchers for assessing the presence, as well as the health and environmental impacts, of a diversity of atmospheric pollutants including airborne particles. Primary particles are introduced into the atmosphere through a variety of processes including natural and anthropogenic sources, while secondary particles are formed in the atmosphere by physical and chemical transformations. Airborne particles consist of a mixture of materials generally complex, which can contain organic and inorganic compounds and biological material. The determination of the chemical composition of aerosols is a challenging task for analytical chemists. Their contribution for understanding the role that different chemical components play in the source identification, transport, health impacts, and radiative properties of airborne particulate matter (APM) has been, and still is, crucial for the advance of atmospheric chemistry. For obtaining reliable results, the expertise for selecting adequate, sensitive, and selective analytical techniques for the determination of ions, metals, metalloids, carbonaceous, and organic compounds is of prime importance. This article focuses on the main analytical techniques employed for the determination of inorganic components of atmospheric aerosols.
Methods for the Determination of Arsenic Speciation in Rice: A Review
Authors: Wang Zhongwen , Forsyth Don
Published: December 2012

Arsenic contamination is an emerging environmental problem. A number of incidents around the world have been reported as a result of exposure to arsenic. Although most of the incidents reported are due to exposure from groundwater, contaminated well water, and occupational exposures, in recent years, research on arsenic exposure from food sources has increased. Recent research trends of studying arsenic in rice has captured the public's attention because elevated arsenic levels were found in rice and rice products available in the market place. This emerging issue prompted governments, academic, and private laboratories to develop and implement methods for the analysis of arsenic speciation in rice and rice products. The purpose of this article is to provide a general overview of the existing analytical methods that are used to extract and measure arsenic species in rice. Sample preparation, extraction methods, separation methods, detection methods, and other alternative methods are reviewed. Considerations regarding quality control procedures, such as certified reference material (CRM), speciation stability, etc., are also discussed.
Firearms: Glass Penetration and Damage
Authors: Heard Brian J.
Published: December 2012

This article includes an examination of the effect various missiles have on various types of glass; the deflection from the missile's original path caused by glass and the identification of bullet calibre and type; and how to differentiate between the damage caused by various bullet types from that caused by other objects such as sharp stones. Case examples are given where appropriate.
Glass: Types and Substitutes
Authors: Heard Brian J.
Published: December 2012

The basic types of glass with their use and properties are reviewed. Also included are some of the more recent developments in glass construction including “one‐way glass”, whereby shots can be fired through the glass in one direction and not the other and “spinel ceramic glass”, a type of transparent armor far more resistant to penetration than normal bullet‐resistant glass.
Death Penalty and Age
Authors: Salekin Karen L. , Allen Rebecca S. , Wood Mary E.
Published: December 2012

In a landmark decision, the Supreme Court of the United States banned the execution of offenders who were under the age of 18 years at the time of their offense. In their 5–4 opinion, the Court stated that there had been a growing national consensus against the death penalty for youthful offenders, and noted their belief that these offenders were less culpable for their actions because of deficits in decision‐making ability, impulse control, and maturity. Of interest, in 2006, the Court declined to hear a case that addressed the constitutionality of the death penalty for aged prisoners (i.e.,Allen v. Ornoski). For many years, it has been recognized that the process of aging is associated with changes in cognitive abilities that may negatively impact flexibility of thought, perspective taking, decision making, and memory. It can be readily seen that these deficits, like those associated with youth, may put the aged prisoner in a position in which the imposition of capital punishment violates the Eighth Amendment of the United States Constitution. To date however, this issue has not been heard by the Supreme Court.
Materials Science
Authors: Anderson Robert N.
Published: December 2012

The discipline of materials engineering and science spans the physical and chemical makeup of materials, as well as the strength, toughness, and other mechanical properties that are critical to taking appropriate decisions in product design, the relationships between and among materials, and, finally, the analysis of actual or potential failures. This discussion of materials engineering and science will explain the most important terms and concepts used when describing and investigating materials failures. It will discuss some common failure modes for the four classes of materials: metals, ceramics/glasses, polymers, and composites. Failure analysis procedures, including methods of testing and microscopic examination, will be discussed. A list of useful materials science and engineering references is provided for further background reading.
Wood
Authors: Cowell Anthony M.
Published: December 2012

Wood and wood products are used universally. The forensic analysis of wood can be important in both criminal and civil cases. The distribution and variation of timber sources are described and ecological factors are reviewed. Timber can be identified by its origin, DNA, appearance, growth rings, and microscopic structure. Wood products such as paper, cardboard, and fiberboard retain some of the natural traits of the timber source. Such traits include fiber length and fiber width, which are critical to the engineering performance of the final product. Forensic analysis of fiber length is an invaluable tool for identifying and comparing wood‐based samples. A method for analyzing fiber length is described. This consists of the maceration of timber samples followed by the analysis of fiber length distribution. Methods using DNA profiling are also described.
Alcohol: Interaction with Other Drugs
Authors: Brick John
Published: December 2012

Prescription medications as well as over‐the‐counter medications are widely used. Many of these medications have psychoactive effects when used alone, but in combination with ethyl alcohol, a common toxicological factor in forensic evaluations, may result in pharmacokinetic and pharmacodynamic interactions. This article reviews the use of and pharmacological interactions between alcohol and analgesics, antibiotics, anticoagulants, anticonvulsants, antidepressants, antidiabetics, antihistamines, antipsychotics, cardiovascular medications, other alcohols, statins, opiates, sedatives, and stimulants. The importance of individual characteristics, experimental design, and drug interactions is discussed in the context of forensic evaluations.
Catalysis of Organic Processes by Metal Phenolates
Authors: Serra Maria Silva , Murtinho Dina M. B.
Published: December 2012

Transition metal catalysts with phenolates as ligands constitute an extensive class of complexes with application in a great variety of catalytic transformations.Because phenol groups can be sterically and electronically modified by the introduction of substituents with different characteristics, the door is opened to a myriad of catalysts with characteristics of reactivity and selectivity for promoting innumerous transformations of synthetic interest in organic chemistry. Metal phenolates have therefore become essential participants in catalytic organic synthesis, including catalytic asymmetric synthesis. Oxidations of alkenes, sulfides, alcohols and alkanes, additions of trimethylsilylcyanide, diorganozincs and nitroalkanes to CO and CN bonds and Diels–Alder reactions are some examples of the types of reactions that are promoted by these catalysts.

This chapter provides an overview of recent advances in the catalysis of organic processes by metal phenolates, with emphasis on the last decade.
Molecular Capsules Based on Metal Complexes with Resorcin[4]arenes and Pyrogallol[4]arenes
Authors: Deakyne Carol A. , Fowler Drew A. , Atwood Jerry L.
Published: December 2012

Metal‐organic nanocapsules (MONCS) have generated widespread interest in recent years because of potential applications in a number of areas, including catalysis, pharmaceutical delivery and information storage. The focus of this chapter is metal complexes for which upper rim hydroxyl groups of resorcin[4]arenes or pyrogallol[4]arenes are ligated to the metal. The stereostructures of the arene macrocycles are discussed in terms of the effect of the R group on the thermodynamic stability of the crown conformation preferred for capsule formation. Studies on hydrogen‐bonded capsules that led to the development of the MONCS are described. Finally, the structures and properties of the MONCs are compared and contrasted with respect to choice of macrocycle, metal, R group, guest, and size.
NMR of Organoselenium and Organotellurium Compounds
Authors: Panda Arunashree , Singh Harkesh B.
Published: December 2012

This chapter gives a systematic account of and surveys the available data on77Se and125Te NMR spectra of organochalcogen compounds such as chacogenols, mono and dichalcogenides, chalcogenolates, tetra and hexa substituted chalcogen compounds, chalcogenyl halides, chalcogen‐containing heterocycles and macrocycles, chalcogen‐oxygen/nitrogen compounds, etc. The review is based on the literature from 1985 to 2011 and includes 780 references. The77Se/125Te NMR spectra of organochalcogen compounds reveal expansive chemical shifts (δSe/δTe) leading to sharp sensitivity of these nuclei (Se/Te) to their environment such as solvent, temperature, molecular geometry, ligand backbone, oxidation state, chelate ring size, steric strain, etc. This is well illustrated by the advantageous use of this spectroscopy in the successful determination of the solution state structure of several organochalcogen compounds. It is noted that the125Te and77Se chemical shifts of a large number of structurally similar organotellurium and selenium compounds show linear relationship.
Carbides: Transition‐Metal Solid‐State ChemistryUpdate based on the original article by Walter Lengauer,Encyclopedia of Inorganic ChemistrySecond Edition © 2005, John Wiley & Sons, Ltd.
Authors: Lengauer Walter
Published: December 2012

Basic properties and use of transition‐metal carbides and carbonitrides are presented in this article. Starting from crystal chemistry, bonding, and preparation, the article also briefly discusses analytical chemistry of chemical and physical carbon analysis as well as thermodynamics. Phase diagrams of groups 4, 5, and 6 transition metals with carbon are presented, together with the most important transition‐metal carbonitride systems Ti CN. A large part is devoted to the solid‐state properties because they make carbides and carbonitrides interesting materials for applications. The presentation of these properties includes hardness, thermal properties, conductivities, carbon diffusivity, and elastic properties. Some ternary and quaternary carbonitrides are also discussed. Several of these properties are given as a function of temperature and composition. A variety of examples for bulk application of carbides in modern hardmetal and cermet types are included, such as printed circuit board drills, stone drills, and drills for metal machining with cooling channels, functionally graded surfaces of hardmetals for cutting and milling, and ultra‐hardmetals for water jet cutting nozzles. Layers and diffusion barriers are only briefly addressed.
Metallic Materials Deposition: Metal‐Organic PrecursorsUpdate based on the original article by Charles H. Winter, Wenjun Zheng and Hani M. El‐Kaderi,Encyclopedia of Inorganic ChemistrySecond Edition, © 2005, John Wiley & Sons, Ltd.
Authors: Winter Charles H. , Knisley Thomas J. , Kalutarage Lakmal C. , Zavada Mark A. , Klesko Joseph P. , Hiran Perera T.
Published: December 2012

This review describes metal‐organic precursors for the growth of metal‐containing thin films by chemical vapor deposition (CVD)‐based methods. The major emphasis is on precursors that have been reported since 2004, which corresponds to a time of major growth in this field. Progress in the development of metal‐organic precursors is documented for the main group, lanthanide, and group 4– 11 elements. In the main group elements, there has been considerable research activity directed toward the identification of strontium and barium precursors, due both to the technological importance of mixed oxide phases and the inherent difficulties in obtaining volatile, stable thermally complexes of these large metal ions. Aluminum, gallium, and indium have also been the subject of intense investigation because of the importance of many phases containing these elements. The group 4 and 5 elements titanium, zirconium, hafnium, niobium, and tantalum have been the subject of considerable precursor development activity because of the importance of several mixed oxide phases and the applications of zirconium oxide and hafnium oxide as high‐permittivity gate materials in microelectronic devices. Growth of metal nitride films of these elements has also been an active area of research for use as barrier materials in microelectronic devices. The deposition of copper and other first‐row transition‐metal films from metal‐organic precursors is driven by the urgent need for copper metalization procedures in microelectronics device manufacturing. The atomic layer deposition (ALD) growth of the noble metals ruthenium, rhodium, iridium, palladium, and platinum has been a very active research area. The current state of metal‐organic precursor development is presented for each of these metallic elements.
Alkaline Earth Metals: Organometallic ChemistryUpdate based on the original article by Jacob S. Alexander, Marites Guino‐o, Maria Felisa Zuniga, Roger C. Hahn and Karin Ruhlandt‐Senge,Encyclopedia of Inorganic ChemistrySecond Edition, © 2005, John Wiley & Sons, Ltd.
Authors: Goos Alan G. , Rosado Flores Peter J. , Takahashi Yuriko , Ruhlandt‐Senge Karin
Published: December 2012

The organometallic chemistry of the alkaline‐earth metals has undergone a renaissance during the last 20 years with heavy organoalkaline‐earth metal compounds becoming recognized as an area of organometallic chemistry with significant potential. Intense research efforts have provided a series of synthetic methodologies that provided access to a rapidly growing family of compounds not thought possible only recently. As a result, this improved insight did not only provide the basis for a more detailed understanding of the metal‐ligand bonding characteristics but also paved the way toward a number of applications including uses as diverse as in polymerization initiation, organic synthetic chemistry, catalysis, and materials chemistry. This article summarizes some of the recent, exciting developments in regards to alkaline‐earth organometallics.
Low‐Oxidation‐State Main Group CompoundsUpdate based on the original article by Charles L. B. Macdonald and Bobby D. Ellis,Encyclopedia of Inorganic ChemistrySecond Edition, © 2005, John Wiley & Sons, Ltd.
Authors: Macdonald Charles L.B. , Ellis Bobby D. , Swidan Ala'aeddeen
Published: December 2012

The synthesis and chemistry of compounds containing groups 1, 2, and 13‐15 elements in unusually low oxidation states or valence states is presented. In general, the oxidation or valence state of an element influences the chemistry of the compounds in which the atom is found. For the main group elements, compounds containing elements in lower‐than‐usual oxidation or valence states exhibit significantly different structural features, modes of bonding, and chemistry than is observed for compounds containing the element in a more typical oxidation state. The elements of the s‐block form a limited number of low‐oxidation‐state compounds and the elements of groups 16‐18 are generally found in the lowest available oxidation state. Thus, this article provides an overview of the following classes of low‐valent main group species: the chemistry of group 2 elements in the +1 oxidation state, the chemistry of group 13 elements in oxidation states lower than +3, the chemistry of group 14 elements in oxidation states lower than +2, and the chemistry of the group 15 elements in oxidation states lower than +3. Numerous exemplary modes of reactivity are presented, and the utility of some low‐oxidation‐state compounds as catalysts or precursors to materials is acknowledged.
Lanthanides: Electronic Structure
Authors: de Bettencourt‐Dias Ana
Published: December 2012

The electronic structure of the lanthanides is discussed here. The configurations of the elements as well as of the ions in the oxidation states +II, +III, and +IV are presented. The lifting of the degeneracy of the electronic levels of the +III ions due to electron‐electron interactions, spin–orbit coupling, and crystal field effects is discussed.
Lanthanides: Variable Valency
Authors: Platt Andrew W.G.
Published: December 2012

The reasons for the restricted range of oxidation states of lanthanides are explained with emphasis on the relative unimportance of covalent bonding. The stability of the +2 and +4 oxidation states of the metals is discussed in terms of the thermodynamics of their formation and decomposition reactions in the solid state and in solution. Stability of Ln
IV
and Ln
II
in the solid state is assessed with respect to decomposition to Ln
III
and disproportionation to Ln
III
and Ln
0
, respectively. The thermodynamic instability of all Ln
IV
and Ln
II
species in aqueous solution is explained by appropriate redox potentials. The kinetic stability for some Ce
IV
and Tb
IV
species in aqueous solution is discussed and the variation of oxidizing ability of Ce
IV
as a function of counterion outlined. Redox data in nonaqueous systems are briefly discussed.
Lanthanides: Group Trends
Authors: Platt Andrew W.G.
Published: December 2012

Trends in the properties of lanthanide metals and some of their compounds are outlined. The correlation of properties as a function of atomic number and as a function of total orbital angular momentum is discussed. The trends in metallic properties such as metallic radii and chemical reactivity are discussed and explanations of the trends given. The lanthanide contraction and its consequences on the structures adopted by simple salts and coordination complexes are summarized and representative examples given. The variations of a number of important thermochemical properties such as enthalpies of vaporization of the metals, hydration enthalpies, and entropies of the Ln
3+
ions and enthalpies of formation of halides and oxides are outlined and discussed. The relationship of the stability of complexes as a function of atomic number and angular momentum
L
are described with representative examples of halide, aminocarboxylate, and carboxylate complexes.
Lanthanides: Comparison to 3d Metals
Authors: Cotton Simon A.
Published: December 2012

Lanthanides superficially resemble the 3 d transition metals, for example, in forming coloured compounds, but there are significant differences. Their reactivity is greater, resembling the Group II elements such as magnesium, reflecting the large negative reduction potentials of the ions. Unlike the 3 d metals, their chemistry is largely of one oxidation state; this is due to large reduction potentials for the oxidation states related by one‐electron reductions common in 3 d chemistry. The lack in 4f chemistry of the very high oxidation states familiar in the 3 d transition series can be linked with the unwillingness of the 4f metals to form strong Ln O double bonds, while the lack of significant variation in the third ionization energyI3is an important factor in maintaining the +3 oxidation state at the end of the lanthanide series. Lanthanide complexes are relatively labile, in the absence of polydentate ligands; one result of this is that certain oxidation states cannot be stabilized by suitable choice of ligand, as with 3 d metals. The lanthanides are developing a rich and complex organometallic chemistry. Unlike the transition metals, little or no use is made of π‐acceptor ligands. One consequence of this is that the organometallics isolated are largely determined by steric factors, rather than the electronic factors embodied in the 18‐electron rule applicable in transition metal chemistry. Very unstable carbonyls are only found at low temperatures, but there are sandwich compounds stabilized by very bulky π‐arenes. In contrast with the 3 d metals, where spin‐orbit coupling is weak and ligand fields strong, the converse applies to the 4f metals. This is again a consequence of the shielding of the 4f orbitals, so that 4f electrons are relatively unperturbed by the ligands. Optical spectra are characterized by weak but very sharp transitions, while the magnetic moments are usually well described by predictions using the Russell‐Saunders coupling scheme for the ground state.
Lanthanides: Carboxylates
Authors: Lu Jia‐sheng , Wang Ruiyao
Published: December 2012

This chapter gives an overview on the synthetic and the structural chemistry of rare earth carboxylates, including monocarboxylates and polycarboxylates. The synthesis, coordination modes and geometries, and solid‐state structures are discussed. Special efforts have been made to review the types of the structures and the controls over their syntheses.
Lanthanides: β‐Diketonate Compounds
Authors: Wang Ke‐Zhi
Published: December 2012

This chapter first outlines the types of β‐diketones recently reported for lanthanide coordination complexes, followed by summaries of some representative examples of β‐diketonate lanthanide complexes. Special attention has been paid to the fascinating world of single‐crystal X‐ray structures of these complexes.
Lanthanides: Complexes with Multidentate Ligands
Authors: Yang Xiaoping , Jones Richard A. , Wong Wai‐Kwok
Published: December 2012

The synthesis, crystal structures, and photophysical properties of 25 polynuclear lanthanide complexes and lanthanide coordination polymers based on six multidentate “salen”‐style Schiff‐base ligands are described in this chapter. Most of these lanthanide complexes exhibit interesting “multidecker,” cage‐like, or polymeric structures. In these complexes, the multidentate Schiff‐base ligands can efficiently sensitize the emissions from lanthanide ions by serving as antennas that absorb excitation light and transfer the energy to the lanthanide centers. With the lanthanide ions encapsulated by chromophoric Schiff‐base ligands and shielded from solvent molecules, which can quench the emissions of lanthanide ions, those lanthanide complexes which have multidecker and cage‐like structures show improved luminescence properties.
Lanthanides: Aryl Compounds
Authors: Cotton Simon A.
Published: December 2012

Simple phenyls are only known for scandium and the later lanthanides, obtained as solvates [Ln(C
6
H
5
)
3
(THF)
3
] (Ln = Ho, Er, Tm, Lu) and [La(C
6
H
5
)
3
(THF)
2
] (Ln = Lu, Sc), which have octahedral and trigonal bipyramidal structures, respectively. These appear to oligomerize on heating, thus the lanthanides do not form unsolvated molecular phenyls. The only unsolvated species are the anions [Li(THF)
4
] [Ln(2,6‐dimethylphenyl)
4
] (Ln = Yb, Lu). Monophenyls such as [Gd(C
6
H
5
)Cl
2
(THF)
4
] can be made using a deficit of phenyl lithium in the synthesis, but with very bulky aryl groups 2,6‐dimesitylphenyl (Dmp) and 2,6‐di(1‐naphthyl)phenyl (Dnp), steric effects prevent the introduction of more than one aryl in the compounds [Y(Dmp)Cl
2
(THF)
3
], [Ln(Dmp)Cl
2
(THF)
2
] (Ln = Sc, Yb), and [DnpLnCl
2
(THF)
2
] (Ln = Y, Tm, Yb), which have adopted five‐ and six‐coordinate structures.
Lanthanides: Tetravalent Inorganic
Authors: Sroor Farid M.A. , Edelmann Frank T.
Published: December 2012

This chapter gives an overview on the chemistry of tetravalent lanthanide compounds, especially those of tetravalent cerium. Following a brief introduction, it covers the tetrahalides, dioxides, and other lanthanides(IV) salts. Coordination compounds of cerium in the oxidation state +4 include halogeno complexes and complexes of oxo acids, β‐diketonates and related Schiff‐base complexes, as well as porphyrinates and related complexes.
Lanthanides: Molecular Magnetic Materials
Authors: Wang Bing‐Wu , Gao Song
Published: December 2012

Rare earths are important magnetic carriers in the construction of molecular magnetic materials. In this chapter, we introduce the essential concepts and magnetic properties of molecular magnetic materials containing rare earths. For weak exchange‐coupling interactions between rare earth ions and other spin carriers, only a few magnetic ordering systems are briefly described in terms of their magnetic properties and geometry structures. Considerable attention is focused on the low‐dimensional magnetic compound with slow relaxation of magnetization behavior. Quantum tunneling and the relaxation mechanism are also briefly introduced in the section on magnetic relaxation.
Lanthanides: Superconducting Materials
Authors: Dos santos‐García Antonio J. , Alario‐Franco Miguel Á. , Sáez‐Puche Regino
Published: December 2012

Since the discovery of superconductivity in mercury by the Dutch physicist Heike Kamerlingh Onnes a century ago, in 1911, hundreds of superconducting materials including elements, intermetallic compounds, molecular and nonmolecular solids are now known. Among these, the rare earth element seems to play an important role in the synthesis and magnetic properties of the so‐called high‐temperature superconductors. In spite of the efforts made in the developing of a theory that fully explains this amazing phenomenon, there is no consensus among scientists yet. However, this fact has not represented a barrier for the developing of superconducting materials in films, wires, etc. that allows one to use them for many applications. This article is an overview and an introduction to superconductivity and superconducting materials.