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- Volume 43, 2013
Annual Review of Materials Research - Volume 43, 2013
Volume 43, 2013
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Computational Approaches for the Dynamics of Structure Formation in Self-Assembling Polymeric Materials
Vol. 43 (2013), pp. 1–34More LessPolymeric materials can assemble into a multitude of intricate nanoscale morphologies whose free energy differs by only a fraction of the thermal energy per molecule. Such small free-energy differences pose a challenge for modeling and simulation but also offer exciting opportunities to direct the assembly of such materials into morphologies that do not correspond to those of equilibrium bulk structures. Over the past decade, significant progress has been achieved in our ability to guide their self-assembly through the use of confinement, topographical or chemical patterns, and electric fields. In contrast, approaches to guide self-assembly by tailoring the dynamics of structure formation have received less attention. This review discusses opportunities and challenges of recently developed computational strategies to predict the dynamics of self-assembly of polymeric materials on the basis of the underlying free-energy landscape.
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Density Functional Theory Models for Radiation Damage*
Vol. 43 (2013), pp. 35–61More LessDensity functional theory models developed over the past decade provide unique information about the structure of nanoscale defects produced by irradiation and about the nature of short-range interaction between radiation defects, clustering of defects, and their migration pathways. These ab initio models, involving no experimental input parameters, appear to be as quantitatively accurate and informative as the most advanced experimental techniques developed for the observation of radiation damage phenomena. Density functional theory models have effectively created a new paradigm for the scientific investigation and assessment of radiation damage effects, offering new insight into the origin of temperature- and dose-dependent response of materials to irradiation, a problem of pivotal significance for applications.
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Electronic-Structure Theory of Organic Semiconductors: Charge-Transport Parameters and Metal/Organic Interfaces
Vol. 43 (2013), pp. 63–87More LessWe focus this review on the theoretical description, at the density functional theory level, of two key processes that are common to electronic devices based on organic semiconductors (such as organic light-emitting diodes, field-effect transistors, and solar cells), namely charge transport and charge injection from electrodes. By using representative examples of current interest, our main goal is to introduce some of the reliable theoretical methodologies that can best depict these processes. We first discuss the evaluation of the microscopic parameters that determine charge-carrier transport in organic molecular crystals, i.e., electronic couplings and electron-vibration couplings. We then examine the electronic structure at interfaces between an organic layer and a metal or conducting oxide electrode, with an emphasis on the work-function modifications induced by the organic layer and on the interfacial energy-level alignments.
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Phase-Field Model for Microstructure Evolution at the Mesoscopic Scale
Vol. 43 (2013), pp. 89–107More LessThis review presents a phase-field model that is generally applicable to homogeneous and heterogeneous systems at the mesoscopic scale. Reviewed first are general aspects about first- and second-order phase transitions that need to be considered to understand the theoretical background of a phase field. The mesoscopic model equations are defined by a coarse-graining procedure from a microscopic model in the continuum limit on the atomic scale. Special emphasis is given to the question of how to separate the interface and bulk contributions to the generalized thermodynamic functional, which forms the basis of all phase-field models. Numerical aspects of the discretization are discussed at the lower scale of applicability. The model is applied to spinodal decomposition and ripening in Ag-Cu with realistic thermodynamic and kinetic data from a database.
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Reactive Potentials for Advanced Atomistic Simulations
Vol. 43 (2013), pp. 109–129More LessThis article reviews recent advances in the development of reactive empirical force fields or potentials. In particular, we compare two widely used reactive potentials with variable-charge schemes that are desirable for multicomponent or multifunctional systems: the ReaxFF (reactive force field) and charge-optimized many-body (COMB) potentials. Several applications of these approaches in atomistic simulations that involve metal-based heterogeneous systems are also discussed.
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Simulating Mechanical Behavior of Ceramics Under Extreme Conditions
Vol. 43 (2013), pp. 131–156More LessThe mechanical behavior of ceramics in extreme environments can be qualitatively different from that observed at ambient conditions and at typical loading rates. For instance, during shock loading the fracture of ceramics is not controlled by the largest flaw. Computer simulations play an increasingly important role in understanding and predicting material behavior, in particular under conditions in which experiments might be challenging or expensive. Here, we review the strengths and limitations of simulation techniques that are most commonly used to model the mechanical behavior of ceramics. We discuss specific application areas of simulations, focusing on the effects of high strain rate, confined deformation volume, altered material chemistry, and high temperature. We conclude by providing examples of future opportunities for modeling studies in this field.
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Uncertainty Quantification in Multiscale Simulation of Materials: A Prospective
Vol. 43 (2013), pp. 157–182More LessSimulation has long since joined experiment and theory as a valuable tool to address materials problems. Analysis of errors and uncertainties in experiment and theory is well developed; such analysis for simulations, particularly for simulations linked across length scales and timescales, is much less advanced. In this prospective, we discuss salient issues concerning uncertainty quantification (UQ) from a variety of fields and review the sparse literature on UQ in materials simulations. As specific examples, we examine the development of atomistic potentials and multiscale simulations of crystal plasticity. We identify needs for conceptual advances, needs for the development of best practices, and needs for specific implementations.
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Nanoscale Hard X-Ray Microscopy Methods for Materials Studies*
Vol. 43 (2013), pp. 183–211More LessThis review discusses recent progress in the development of hard X-ray microscopy techniques for materials characterization at the nanoscale. Although the utility of traditionally ensemble-based X-ray techniques in materials research has been widely recognized, the utility of X-ray techniques as a tool for local characterization of nanoscale materials properties has undergone rapid development in recent years. Owing to a confluence of improvements in synchrotron source brightness, focusing optics fabrication, detection, and data analysis, nanoscale X-ray imaging techniques have moved beyond proof-of-principle experiments to play a central role in synchrotron user programs worldwide with high-impact applications made to materials science questions. Here, we review the current state of synchrotron-based, hard X-ray nanoscale microscopy techniques—including 3D tomographic visualization, spectroscopic elemental and chemical mapping, microdiffraction-based structural analysis, and coherent methods for nanomaterials imaging—with particular emphasis on applications to materials research.
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Nonlinear Optical Microscopy of Single Nanostructures
Libai Huang, and Ji-Xin ChengVol. 43 (2013), pp. 213–236More LessWe review recent advances in nonlinear optical (NLO) microscopy studies of single nanostructures. NLO signals are intrinsically sensitive to the electronic, vibrational, and structural properties of such nanostructures. Ultrafast excitation allows for mapping of energy relaxation pathways at the single-particle level. The strong nonlinear response of nanostructures makes them highly attractive for applications as novel NLO imaging agents in biological and biomedical research. NLO modalities based on harmonic generation, multiphoton photoluminescence, four-wave mixing, and pump-probe processes are discussed in detail.
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Real-Time, Subwavelength Terahertz Imaging
F. Blanchard, A. Doi, T. Tanaka, and K. TanakaVol. 43 (2013), pp. 237–259More LessThe fields of biosensing, nanospectroscopy, and plasmonics have great potential for near-field terahertz (THz) technology. In this work, we demonstrate that electro-optic (EO) imaging combined with the brightness of recently developed intense THz sources permits the imaging of subwavelength-size samples without compromising spatial resolution or acquisition time. We report on recent advances in this field and current achievements in optimizing spatial resolution and acquisition time. Near-field imaging demonstrations on field enhancement in metallic-based resonators and metamaterials are also discussed. This development will accelerate our comprehension of subwavelength light-matter interactions at THz frequencies and enable new spectroscopic applications.
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Superresolution Multidimensional Imaging with Structured Illumination Microscopy
Vol. 43 (2013), pp. 261–282More LessThe resolution of an optical microscope is fundamentally limited by diffraction. In a conventional wide-field fluorescence microscope, the resolution limit is at best 200 nm. However, modern superresolution methods can bypass this limit. Pointillistic imaging techniques like PALM (photoactivated localization microscopy) and STORM (stochastic optical reconstruction microscopy) do so by precisely localizing each individual molecule in a sample. In contrast, STED uses the stimulated emission process driven to saturation to dramatically reduce the size of the region in the sample that is capable of spontaneously emitting fluorescence. Structured illumination microscopy (SIM) illuminates the sample with a pattern, typically the image of a grating. This computationally removes the out-of-focus blur, a method known as optical sectioning SIM. Furthermore, frequency mixing of the illumination pattern with the sample caused by the moiré effect results in a downmodulation of fine sample detail into the frequency-support region of the detection optical transfer function. High-resolution SIM achieves typically a twofold lateral resolution enhancement. This is further improved by exploiting a nonlinear sample response to the illumination light in SIM. Recent developments of the method allow fast, multicolor, and three-dimensional high-resolution live-cell imaging.
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Vesicle Photonics
Vol. 43 (2013), pp. 283–305More LessAmphiphiles, under appropriate conditions, can self-assemble into nanoscale thin membrane vessels (vesicles) that encapsulate and hence protect and transport molecular payloads. Vesicles assemble naturally within cells but can also be artificially synthesized. In this article, we review the mechanisms and applications of light-field interactions with vesicles. By being associated with light-emitting entities (e.g., dyes, fluorescent proteins, or quantum dots), vesicles can act as imaging agents in addition to cargo carriers. Vesicles can also be optically probed on the basis of their nonlinear response, typically from the vesicle membrane. Light fields can be employed to transport vesicles by using optical tweezers (photon momentum) or can directly perturb the stability of vesicles and hence trigger the delivery of the encapsulated payload (photon energy). We conclude with emerging vesicle applications in biology and photochemical microreactors.
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Bionanomaterials and Bioinspired Nanostructures for Selective Vapor Sensing
Vol. 43 (2013), pp. 307–334More LessAt present, monitoring of air at the workplace, in urban environments, and on battlefields; exhaled air from medical patients; air in packaged food containers; and so forth can be accomplished with different types of analytical instruments. Vapor sensors have their niche in these measurements when an unobtrusive, low-power, and cost-sensitive technical solution is required. Unfortunately, existing vapor sensors often degrade their vapor-quantitation accuracy in the presence of high levels of interferences and cannot quantitate several components in complex gas mixtures. Thus, new sensing approaches with improved sensor selectivity are required. This technological task can be accomplished by the careful design of sensing materials with new performance properties and by coupling these materials with the suitable physical transducers. This review is focused on the assessment of the capabilities of bionanomaterials and bioinspired nanostructures for selective vapor sensing. We demonstrate that these sensing materials can operate with diverse transducers based on electrical, mechanical, and optical readout principles and can provide vapor-response selectivity previously unattainable by using other sensing materials. This ability for selective vapor sensing provides opportunities to significantly impact the major directions in development and application scenarios of vapor sensors.
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Electroplating Using Ionic Liquids
Vol. 43 (2013), pp. 335–358More LessElectroplating is a key technology in many large-scale industrial applications such as corrosion-resistant and decorative coatings. Issues with current aqueous processes, such as toxicity of reagents and low current efficiencies, can often be overcome by using ionic liquids, and this approach has turned ionometallurgy into a fast-growing area of research. This review outlines the interactions in ionic liquids that are responsible for the advantageous properties of these solvents in electroplating. It summarizes recent research in which these properties have been analyzed or exploited and highlights fundamental issues in research and technology that need to be addressed.
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Engineering Crystal Morphology
Vol. 43 (2013), pp. 359–386More LessCrystallization is an important separation and particle formation technique in the manufacture of high-value-added products. During crystallization, many physicochemical characteristics of the substance are established. Such characteristics include crystal polymorph, shape and size, chemical purity and stability, reactivity, and electrical and magnetic properties. However, control over the physical form of crystalline materials has remained poor, due mainly to an inadequate understanding of the basic growth and dissolution mechanisms, as well as of the influence of impurities, additives, and solvents on the growth rate of individual crystal faces. Crystal growth is a surface-controlled phenomenon in which solute molecules are incorporated into surface lattice sites to yield the bulk long-range order that characterizes crystalline materials. In this article, we describe some recent advances in crystal morphology engineering, with a special focus on a new mechanistic model for spiral growth. These mechanistic ideas are simple enough that they can be made to work and accurate enough that they are useful.
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Flexoelectric Effect in Solids
Vol. 43 (2013), pp. 387–421More LessFlexoelectricity—the coupling between polarization and strain gradients—is a universal effect allowed by symmetry in all materials. Following its discovery several decades ago, studies of flexoelectricity in solids have been scarce due to the seemingly small magnitude of this effect in bulk samples. The development of nanoscale technologies, however, has renewed the interest in flexoelectricity, as the large strain gradients often present at the nanoscale can lead to strong flexoelectric effects. Here we review the fundamentals of the flexoelectric effect in solids, discuss its presence in many nanoscale systems, and look at potential applications of this electromechanical phenomenon. The review also emphasizes the many open questions and unresolved issues in this developing field.
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Mesoscale Domains and Nature of the Relaxor State by Piezoresponse Force Microscopy
Vol. 43 (2013), pp. 423–449More LessFerroelectric relaxors continue to be one of the most mysterious solid-state materials. Since their discovery by Smolenskii and coworkers, there have been many attempts to understand the properties of these materials, which are exotic, yet useful for applications. On the basis of the numerous experimental data, several theories have been established, but none of them can explain all the properties of relaxors. The recent advent of piezoresponse force microscopy (PFM) has allowed for polarization mapping on the surface of relaxors with subnanometer resolution. This development thus leads to the question of whether the polar nanoregions that contribute to diffuse X-ray scattering and a range of macroscopic properties can be visualized. This review summarizes recent advancements in the application of PFM to a number of ferroelectric relaxors and provides a tentative explanation of the peculiar polarization distributions related to the intriguing physical phenomena in these materials.
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Nanowire Heterostructures
Vol. 43 (2013), pp. 451–479More LessThe nanoscale diameter and high aspect ratio of nanowires are the foundation of fascinating structure-property relationships derived from confinement, interface effects, and mechanical degrees of freedom. When heterostructures are formed by high-quality growth of dissimilar materials on or within nanowires, the interactions of the low-dimensional components and their interfaces can give rise to electronic, photonic, magnetic, and thermal characteristics that are superior to those of (or unattainable in) planar geometries. This tutorial review provides a brief overview of heterostructures with a semiconductor nanowire as the central component, describes the properties of nanoscale components and interfaces, and distills the advantages that arise from the unique structure-property relationships. A select set of these concepts are further elaborated by highlighting electronic, optoelectronic, and energy-related applications that have successfully exploited these advantages.
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Phosphors for Solid-State White Lighting
Vol. 43 (2013), pp. 481–501More LessSince the mid-1990s, phosphors have played a key role in emerging solid-state white-lighting technologies that are based on combining a III-nitride-based near-UV or blue solid-state light source with downconversion to longer wavelengths. Almost all widely used phosphors comprise a crystalline oxide, nitride, or oxynitride host that is appropriately doped with either Ce3+ or Eu2+. These ions, with [Xe] 4fn5d0 configurations (n = 1 for Ce3+ and 7 for Eu2+) have proximal excited states that are [Xe] 4fn−15d1. Optical excitation into these states and concomitant reemission can be tuned into the appropriate regions of the visible spectrum by the crystal these ions are hosted in. In this article, we review the current needs and key aspects of the conversion process. We describe some currently used families of phosphors and consider why they are suitable for solid-state lighting. Finally, we describe some empirical rules for new and improved host materials.
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Polymer Electrolytes
Vol. 43 (2013), pp. 503–525More LessThis review article covers applications in which polymer electrolytes are used: lithium batteries, fuel cells, and water desalination. The ideas of electrochemical potential, salt activity, and ion transport are presented in the context of these applications. Potential is defined, and we show how a cell potential measurement can be used to ascertain salt activity. The transport parameters needed to fully specify a binary electrolyte (salt + solvent) are presented. We define five fundamentally different types of homogeneous electrolytes: type I (classical liquid electrolytes), type II (gel electrolytes), type III (dry polymer electrolytes), type IV (dry single-ion-conducting polymer electrolytes), and type V (solvated single-ion-conducting polymer electrolytes). Typical values of transport parameters are provided for all types of electrolytes. Comparison among the values provides insight into the transport mechanisms occurring in polymer electrolytes. It is desirable to decouple the mechanical properties of polymer electrolyte membranes from the ionic conductivity. One way to accomplish this is through the development of microphase-separated polymers, wherein one of the microphases conducts ions while the other enhances the mechanical rigidity of the heterogeneous polymer electrolyte. We cover all three types of conducting polymer electrolyte phases (types III, IV, and V). We present a simple framework that relates the transport parameters of heterogeneous electrolytes to homogeneous analogs. We conclude by discussing electrochemical stability of electrolytes and the effects of water contamination because of their relevance to applications such as lithium ion batteries.
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Previous Volumes
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Volume 53 (2023)
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Volume 52 (2022)
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Volume 51 (2021)
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Volume 50 (2020)
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Volume 49 (2019)
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Volume 48 (2018)
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Volume 47 (2017)
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Volume 46 (2016)
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Volume 45 (2015)
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Volume 44 (2014)
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Volume 43 (2013)
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Volume 42 (2012)
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Volume 41 (2011)
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Volume 40 (2010)
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Volume 39 (2009)
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Volume 38 (2008)
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Volume 37 (2007)
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Volume 36 (2006)
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Volume 35 (2005)
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Volume 34 (2004)
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Volume 33 (2003)
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Volume 32 (2002)
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Volume 31 (2001)
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Volume 30 (2000)
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Volume 29 (1999)
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Volume 28 (1998)
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Volume 27 (1997)
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Volume 26 (1996)
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Volume 25 (1995)
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Volume 24 (1994)
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Volume 23 (1993)
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Volume 22 (1992)
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Volume 21 (1991)
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Volume 20 (1990)
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Volume 19 (1989)
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Volume 18 (1988)
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Volume 17 (1987)
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Volume 16 (1986)
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Volume 15 (1985)
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Volume 14 (1984)
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Volume 13 (1983)
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Volume 12 (1982)
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Volume 11 (1981)
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Volume 10 (1980)
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Volume 9 (1979)
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Volume 8 (1978)
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Volume 7 (1977)
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Volume 6 (1976)
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Volume 5 (1975)
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Volume 4 (1974)
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Volume 3 (1973)
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Volume 2 (1972)
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Volume 1 (1971)
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Volume 0 (1932)