bluuebunny/crossref_metadata_2025 huggingface dataset:
Tissue-Engineering Approaches for Central and Peripheral Nervous-System Regeneration
Authors: Borkenhagen Markus , Aebischer Patrick
Published: August 2016

The nervous system of the human body can be divided into two parts: the central and the peripheral nervous system. While the central nervous system (CNS) includes the brain and the spinal cord, the peripheral nervous system (PNS) consists of all the nerve branches exiting the spinal cord or brain stem that process information from our environment to the CNS and vice versa. The main extension that passes all incoming information to the next neuron or a peripheral target is called an axon. Axons can be as long as 1 meter, as in the case of axons sending electrical signals to the toes. All incoming information is received by smaller structures called dendrites. Axons are wrapped with glial cells, Schwann cells in the PNS, and oligodendrocytes in the CNS. These cells are responsible for the deposition of myelin, a powerful insulator. Each glial cell is covering an axonal segment of about 1-2 mm. An unmyelinated gap separates two glial cells. Action potentials are generated at those gaps. This electrical signal jumps from one unmyelinated gap to the next, giving rise to conduction velocities as fast as 1 m/s. In the PNS, axons are grouped together into fascicles, consisting of a layer of connective tissue surrounding bundles of axons. Several of these fascicles form a peripheral nerve surrounded by another connective tissue layer named epineurium. The epineurium is responsible for the integrity of the overall structure of a peripheral nerve. While the PNS shows regenerative capabilities, this is in general not the case for the CNS. The mechanisms explaining the poor regeneration capabilities of the CNS have started to be elucidated. The expression of inhibitory molecules in the mammalian-adult nervous system seems to be an essential component in the inherent lack of CNS regeneration. Examples for possible applications of materials systems addressing certain issues of PNS and CNS regeneration are presented in the following sections.
A Path to Nanolithography
Authors: Cerrina F. , Marrian C.
Published: August 2016

It is yet unclear what type of new devices, if any, will replace the metaloxide field effect transistor in the sub 0.1-μm domain. Since in any case, the development of quantum-effect devices requires smaller and smaller dimensions for operation above temperatures of a few milliKelvin, we can safely assume that high-resolution patterning steps will always be required to manufacture the devices themselves. Alternative approaches (such as the use of self-assembling systems) have not yet reached a convincing level of demonstration. Furthermore we can assume that the complexity of the circuits will continue to increase because this is the true driving force of miniaturization. In order to process large amounts of information in a short amount of time, the processing circuit must be correspondingly complex. Hence the future quantum devices will continue the development pattern of modern electronics, leading to the fabrication of large chips with very small devices—that is, exceedingly large processing power. The apparent insatiability of our appetites for more memory and processing makes this prediction an almost certain evolution of the current technology.
Materials Performance in a Radiation Environment
Authors: Clinard Frank W.
Published: August 2016

An important part of materials science is the study of the behavior of materials under difficult environmental conditions. Some operating conditions have been traditional objects of study—for example, high temperatures and corrosive atmospheres. The study of materials in radiation environments gained particular significance after the advent of nuclear reactors, and radiation has joined the list of insults to which materials are subjected. Technological applications that involve significant levels of radiation include but are not limited to fission reactors, proposed fusion reactors, nuclear waste, ion accelerators, and spacecraft, with types of radiation encompassing thermal and fast neutrons, light and heavy ions, and energetic photons. More detailed information on applications and accompanying radiation fields appears in the articles published in this issue of MRS Bulletin and in the references listed under Further Reading.

The four theme articles in this issue focus on radiation effects in four families of materials commonly used in radiation environments: metals, ceramics, graphite and carbon-based materials, and polymers.
Radiation Damage in Metallic Materials
Authors: Ullmaier H.
Published: August 2016

Radiation-damage research started with the installation of the first nuclear reactors in the United States. In 1946 Wigner pointed out that energetic neutrons would displace atoms from their regular lattice sites and thus change the properties of irradiated materials—a prediction that was soon confirmed experimentally. Most of these changes are unfavorable for the performance of materials, justifying the influence of radiation being referred to as “radiation damage.”

Since radiation-induced materials degradation can have a drastic impact on the safe and economic operation of present fission reactors and, probably even more, on future fusion reactors, radiation-damage research comprised a large part of the research-and-development programs for nuclear materials. As a result of this effort, a broad database is now available, and materials have been developed that fulfill practically all requirements being encountered in present nuclear technology.

Besides this applied work, extensive fundamental research on radiation effects has been carried out because physicists soon recognized that bombardment with energetic particles offered a unique method to create controlled populations of defects in solids. Whereas the cross-linking between basic and applied research was rather weak in the early stages, a convergence of the two branches has been clearly noticeable during the last decade. This welcome development occurred for a variety of reasons. Examples are the need to employ simulation irradiations in cases where no prototypic devices exist (fusion reactors, high-power spallation neutron sources) and the increasing application of ion-beam techniques in microelectronics, thin-film technology, and metallurgy where the damage produced by the implanted ions needs clarification.
Irradiation of Plastics: Damage and Gas Evolution
Authors: Evans D. , Crook M.A.
Published: August 2016

There have been many studies (see for instance Reference 1) directed at quantifying the effects of ionizing radiation on polymers. Mainly these studies have focused on assessing the degradation of mechanical properties. In addition to changes in mechanical properties, a mixture of gases results from the irradiation of polymeric compounds. The amount of gas produced is related to the total absorbed dose while the type of gas is independent of dose and is related only to polymer structure. For many polymers, hydrogen is the major component in the gaseous mixture but polyesters and anhydride-cured epoxide resins are a notable exception.

Some problems associated with radiation damage may be further complicated when the irradiation temperature is in the cryogenic range. When materials are irradiated at low temperatures (<150 K), the release of volatile degradation products is delayed and occurs—possibly very rapidly and exceeding normal diffusion rates—only when the polymer is warmed. The rapid release of gaseous degradation products could occur as a result of warming a superconducting magnet that has been resin bonded and irradiated at low temperatures during operation. Radiation damage-related problems may be summarized as follows: (1) changes in short-term mechanical properties, (2) production of gases and low-molecular-weight species, and (3) longer term and geometrical effects (unknown) of trapped gases on electrical and mechanical properties.

This article considers mechanisms of radiation-induced damage and relates the chemical structure of the polymer to the rate of damage accumulation. Changes in electrical properties measured on irradiated polymers are generally small, and mechanical damage is generally more significant than changes in electrical characteristics. However all such reports are a result of electrical measurements on thin films and do not consider the effects of trapped gases on long-term electrical properties in bulk specimens.
Order and Surface Processes in III-V Semiconductor Alloys
Authors: Stringfellow G.B.
Published: August 2016

Semiconductor alloys have become increasingly useful during the last four decades because, through the use of alloys, the properties of semiconductors can be tailored by varying the composition to precisely match the requirements for specific electronic and photonic devices. In addition the use of alloys allows the production of special structures, such as quantum wells, that require rapid changes in bandgap energy during growth. This has led to so-called “bandgap engineering,” in which device designers and epitaxial growers are working together to produce structures having virtually atomic-scale dimensions.
Hard Carbon Coatings: The Way Forward
Authors: Neuville Stephan , Matthews Allan
Published: August 2016

Since the first reports by Aisenberg and Chabot in 1971 indicating the possibility of producing hard amorphous (so-called diamondlike) carbon (DLC) films, many experimental and theoretical research results have been published outlining the properties and film growth mechanisms of these films deposited by a variety of techniques. Polycrystalline and even quasimonocrystalline diamond thin films have also been produced, thus providing a wide range of wear and corrosion properties. The difference between these materials and graphite led to a prediction of rapid market growth for hard carbon. However this has not materialized. A large number of carbonbased films have been produced with differences in hardness, elasticity, friction coefficient, optical and electronic bandgap, electrical and thermal conductivity, and thermal stability. In addition these materials can show very different practical adhesion properties, which depend also on the substrate material and composition. Cost, deposition rate and temperature, geometry, and size of the coating chamber are additional variables. As a result, many of these materials can only be used for a limited range of applications. It is now possible to better understand the suitability of various coatings and the causes of the early failures that occurred through unsuitable material choices. This improved understanding should allow improvements in the performance and reliability of hard carbon films and perhaps trigger the kind of market growth that was originally foreseen but failed to materialize.
The Manuel Lujan Jr. Neutron Scattering Center
Authors: Roberts Joyce A.
Published: August 2016

In October 1986, the neutron scattering facility at Los Alamos National Laboratory became a national user facility and a formal user program was initiated in 1988. In July 1989, this facility was dedicated as the Manuel Lujan Jr. Neutron Scattering Center (Lujan Center) in honor of the long-term Congress representative from New Mexico. The Lujan Center, part of the Los Alamos Neutron Science Center (LANSCE), is a pulsed spallation neutron source equipped with time-of-flight neutron-scattering spectrometers for condensed-matter research. Neutron scattering is a powerful technique for probing the microscopic structure of condensed matter. The energies and wavelengths of thermal neutrons closely match typical excitation energies and interatomic distances in solids and liquids. Because neutrons have no charge, they penetrate bulk samples of material to give precise information on the positions and motions of individual atoms. The magnetic moment of a neutron interacts with unpaired electrons, making neutrons ideal for probing microscopic magnetic properties. Because neutron-scattering cross sections do not vary monotonically with the atomic number of the scattering nucleus, neutrons and x-rays can provide complementary structural information. This technique is particularly effective for structural problems in polymer and biological studies because hydrogen and deuterium scatter neutrons strongly but with different cross sections.
Defects in Liquid-Crystalline Polymers
Authors: Kléman M.
Published: August 2016

The properties of imperfections (or defects) of the atomic or molecular order in condensed matter can be conveniently described under two headings: (1) Topological properties—Defects break a specific symmetry of the ordered system at a local scale, that is, along a point defect, a line defect (a dislocation or a disclination), or a surface defect (a wall). (2) Elastic properties—Defects are sources of two types of distortions of the order: long-range distortions, which depend crucially on the broken symmetry but also on the material constants, and short-range distortions in the “core” region of the defect where the order parameter of the ordered phase is broken. These distortions are irreversible in the sense that defects appear during plastic deformation (in solids) or rheological flow (in liquid crystals).

To illustrate this classification, let us recall the example of dislocation lines in solids. These defects break translational symmetries (henceforth a dislocation is defined topologically by the translation b it breaks, the so-called Burgers vector). They are at the origin of rather weak, long-range, internal distortions and stresses that depend on the elastic constants (in the region of the good crystal) and rather strong, short-range distortions and stresses in the “core” region, implying a complete rearrangement of the molecular order. These stresses are different in the static and dynamic states, and the shape of the dislocation line, as well as its size, etc., depend on the history of the sample.

In this article, we will focus on defects in liquid-crystalline polymers. A synthetic polymer that displays mesomorphic order (intermediate between crystalline and liquid) is usually made of units that are themselves mesogenic and that align coherently when in contact.
Morphology and Dynamic Interaction of Defects in Polymer Liquid Crystals
Authors: O'Rourke Mary Jane E. , Thomas Edwin L.
Published: August 2016

The liquid crystal phase is an anisotropic mesophase, intermediate in order between the liquid and crystal phases. Liquid crystals have less translational order than crystals and more rotational order than isotropic liquids. The liquid crystal phase does not support finite shear stresses and thus behaves like a fluid. Molecules that display a liquid crystal phase are referred to as mesogenic. Mesogenic molecules exhibit shape anisotropy: either large length to diameter ratio (needlelike) or large diameter to thickness ratio (disklike). Because of their shape anisotropy, all liquid crystals display orientational order of their molecular axes.

Until 1956, all known examples of liquid crystals were low molecular weight compounds. Robinson was the first to identify liquid crystallinity in a liquid crystalline polymer (LCP) as the explanation for “a birefringent solution” of a polymeric material, poly-y-benzyl-L-glutamate, in chloroform, previously observed by Elliott and Ambrose. Chemists soon discovered that LCPs may be readily synthesized by covalently stitching small mesogenic units (e.g., rigid monomers) together into a chain using short flexible spacers. Mainchain or sidechain liquid crystal polymers may be formed (Figure 1). An example of a polymer molecule possessing a liquid crystal phase is shown in Figure 2. Liquid crystals may be thermotropic, where liquid crystallinity is exhibited over a range of temperatures, or lyotropic, where nonmesogenic solvent molecules are present in addition to the mesogens, and liquid crystallinity is observed over a range of concentrations as well.
A Non-Periodic Lattice Model for Crystals inNephila clavipesMajor Ampullate Silk
Authors: Thiel Brad L. , Viney Christopher
Published: August 2016

Defects play a significant role in determining the physical and thermodynamic behaviors of a material. This precept can be especially helpful when one attempts to interpret the engineering properties of a biological material in the context of its complex, hierarchical microstructure. An excellent example of an impressive engineering material used by nature is silk, which has a composite microstructure assembled from one or more protein polymers. Spiders, aided by several million years of evolution, have succeeded in producing a polymer fiber [major ampullate silk (MAS)] with a strength-to-weight ratio exceeding that of nearly all synthetic materials. Even the exceptions—specialty fibers such as carbon, silica, and some variants of Kevlar—pale in comparison when toughness (energy required to bring about failure) is taken into account; they are relatively brittle and lack the viscoelastic extensibility of MAS. When one considers that spiders produce this naturally biodegradable material under ambient conditions and with an aqueous solvent, the feat becomes even more impressive. It is clear that the spider could be an excellent instructor in both polymer processing and microstructural design.

where the α-carbon is bonded to a functional “R” group that distinguishes the monomer as being one of the 20 commonly occurring natural a-amino acids.
Adhesion of Polymers
Authors: Brown Hugh R.
Published: August 2016

The adhesion of a polymer to itself, to a different polymer, or to an inorganic material can often be one of its most important properties. Adhesives are normally polymers, but then so are nonstick coatings. Clearly, polymer adhesion can vary from very strong to extremely weak. Adhesion is a sufficiently complex and broad area that there are a range of approaches to its understanding. My approach here is one that attempts to bridge between the mechanics of crack propagation and the atomic-scale processes that occur at a crack tip. I will not be concerned with the details of the interface chemistry and its modification. The interface chemical approach is very useful in many practical situations but is often very specific to particular systems. Adhesion (or perhaps its inverse) can be considered a failure property. We can only measure the adhesion between two items by breaking the joint between them. I will be mainly concerned with failure by crack propagation using a fracture-mechanics approach.

I will first consider the general question of the effects of bulk mechanical properties on adhesion and then describe some recent work on fracture mechanics of biomaterial interfaces as it relates to polymer glasses. I will then change the focus to the scale of the polymer chain to consider local processes involved in adhesion.
High-Temperature Applications of Intermetallic Compounds
Authors: Pope David P. , Darolia Ram
Published: August 2016

One of the greatest challenges currently facing the materials community is the need to develop a new generation of materials to replace Ni-based superalloys in the hot sections of gas-turbine engines for aircraft-propulsion systems. The present alloys, which have a Ni-based solid-solution matrix surrounding Ni3Al-based precipitates, are currently used at temperatures exceeding 1100°C, which is over 80% of the absolute melting temperature. Since Ni3Al melts at 1395°C and Ni at 1453°C, it is clear that significantly higher operating temperatures, with the attendant improvements in efficiency and thrust-to-weight ratio, can only be attained by the development of an entirely new materials system. This problem is a primary reason for the current high level of interest in high-temperature intermetallic compounds.

The development of such a material system has important implications for national defense and for spin-offs to civilian technology, as well as for the economy and balance of payments. Obviously it would be a boon to any economy to have these new materials developed domestically, as was the case in the United States for the currently used single-crystal technology applied to Ni-based superalloys. As an example, the aerospace industry is one area where the United States is still the undisputed world leader, with net exports of $29 billion in 1989, twice that of any other U.S. industry.
Plasma Processing of Advanced Materials
Authors: Collins George , Rej Donald J.
Published: August 2016

A plasma, commonly referred to as the “fourth state of matter,” is an ensemble of randomly moving charged particles with a sufficient particle density to remain, on average, electrically neutral. While their scientific study dates from the 19th century, plasmas are ubiquitous, comprising more than 99% of the known material universe. The term “plasma” was first coined in the 1920s by Irving Langmuir at the General Electric Company after the vague resemblance of a filamented glow discharge to a biological plasma.

Plasmas are studied for many reasons. Physicists analyze the collective dynamics of ions and electron ensembles, utilizing principals of classical electromagnetics, and fluid and statistical mechanics, to better understand astrophysical, solar, and ionospheric phenomenon, and in applied problems such as thermonuclear fusion. Electrical engineers use plasmas to develop efficient lighting, and high-power electrical switchgear, and for magneto-hydrodynamic (MHD) power conversion. Aerospace engineers apply plasmas for attitude adjustment and electric propulsion of satellites. Chemists, chemical engineers, and materials scientists routinely use plasmas in reactive ion etching and sputter deposition. These methods are commonplace in microelec tronics since they allow synthesis of complex material structures with submicron feature sizes. A substantial portion of the multi-billion-dollar market for tooling used to manufacture semiconductors employs some form of plasma process. When compared with traditional wet-chemistry techniques, these dry processes result in minimal waste generation. Plasmas are also useful in bulk processing—for example as thermal sprays for melting materials.

While the quest for controlled thermonuclear fusion dominated much of plasma research in the 1960s and 1970s, in the last 20 years it has been the application of plasmas to materials processing that has provided new challenges for many plasma practitioners. It is not surprising that the guest editors and several of the authors for this issue of MRS Bulletin come from a fusion plasma-physics background.
Modification of Polymeric Surfaces With Plasmas
Authors: Coates Don M. , Kaplan Stephen L.
Published: August 2016

As adaptable as polymeric materials are in their many applications to our daily lives, the need exists to tailor the polymer surfaces to provide even more flexibility in regard to their uses. Plasma treatments offer an unprecedented spectrum of possible surface modifications to enhance polymers, ranging from simple topographical changes to creation of surface chemistries and coatings that are radically different from the bulk polymer. Furthermore plasma treatments are environmentally friendly and economical in regard to their use of materials.

Plasma processing can be classified into at least four categories that often overlap. These are the following: (1) surface preparation by breakdown of surface oils and loose contaminates, (2) etching of new topographies, (3) surface activation by creation or grafting of new functional groups or chemically reactive, excited metastable species on the surface, and (4) deposition of monolithic, adherent surface coatings by polymerization of monomeric species on the surface. Key features of these processes will be briefly discussed, with a rudimentary introduction to the chemistries involved, as well as examples. Focus is placed on capacitively coupled radio-frequency (rf) plasmas (see Figure 1 in the article by Lieberman et al. in this issue of MRS Bulletin) since they are most commonly used in polymer treatment.
Materials Processing With Thermal Plasmas
Authors: Boulos Maher , Pfender Emil
Published: August 2016

Thermal plasmas in which the plasma state approaches local thermodynamic equilibrium may be produced by high-intensity arcs (current I > 100 A) or by radio-frequency (rf) discharges at high-power densities and at pressures exceeding 10 kPa (0.1 atm). In such plasmas, electron and heavy-particle temperatures are identical, and particle densities are only a function of the temperature (chemical equilibrium).

Thermal-plasma technology has passed through a drastic transition stage from primarily space-related activities in the 1960s to a more and more materials-oriented focus in the 1980s and 1990s, and thermal-plasma processing of materials is now attracting increasing interest for industrial applications.

Thermal-plasma processing of materials however must be viewed in the context of much broader technology trends, some of which are visible today. There is no question that materials and materials processing will be one of the most important technical issues as we approach the turn of the century. This trend will not be restricted to the development of new materials but will also include the refining of materials, the conservation of materials (by hard facing, coating, etc.), and the development of new processing routes that are more energy-efficient, more productive, and less damaging to our environment. Thermal-plasma processing is already playing an important role in these developments. Its potential for developing new materials-related technologies is increasingly recognized, and many research laboratories all over the world are engaged in advancing the frontiers of our knowledge in this exciting field. As a result of these efforts, thermal-plasma processing has emerged as a powerful technology that is finding numerous industrial applications.
Electroceramic Thin Films Part II: Device Applications
Authors: Auciello Orlando , Ramesh Ramamoorthy
Published: August 2016

Ferroelectric thin films have experienced tremendous development in recent years due to the advent of sophisticated film-synthesis techniques and an increase in the understanding of the related materials science and integration of films into various novel devices. Major advances in ferroelectric thin-film synthesis and characterization were addressed last month in the June MRS Bulletin. This volume is dedicated to selective device issues and applications.

Ferroelectric materials can be used to fabricate capacitors for integration into nonvolatile ferroelectric random-access memories (NVFRAMs) and as high di-electric layers for capacitors with high capacitance for manufacturing planar dynamic random-access memories (DRAMs). Ceramic conductors can be applied to ohmic, voltage-dependent, and thermally sensitive resistors; fast-ion conductors; and humidity and gas sensors. Piezoelectricity is being exploited in micromachines such as accelerometers, displacement transducers, and actuators such as those required for inkjet printers, for video-recording head positioning, and for micromachining. Pyroelectricity can be utilized in the fabrication of high-sensitivity room-temperature infrared detectors while electro-optic activity can be used in color-filter devices, displays, image-storage systems, and optical switches for integrated optical systems. These applications of electroceramic thin films are only part of a more extensive list.
Glass Substrates for Flat Panel Displays
Authors: Moffatt Dawne M.
Published: August 2016

One material exists in most types of flat panel displays that are used in high information content applications, from liquid crystal displays to electroluminescent displays. This material is glass, something we all use daily. As a substrate, glass plays a significant role in the manufacture and function of flat panel displays (FPDs). In the case of active-matrix liquid crystal displays (AMLCDs), the semiconductor-based thin-film transistors (TFTs) or diodes are fabricated on the active glass substrate. In addition, AMLCDs require color-filter structures consisting of dyed or pigmented resins built upon the passive plate of an AMLCD cell. For plasma and electroluminescent display panels, the glass provides the surface upon which are deposited phosphors, conductive lines, and dielectrics.

The excellent properties of glass make it the substrate of choice in FPDs. It is the only material that can meet the demanding requirements of high-information-content FPD manufacturing processes and operation. Glass' transparency is an obvious requirement. For all types of displays, the rigidity of glass also plays a important role because it adds overall mechanical integrity and strength.

One of the most important attributes of glass in terms of the display manufacturing process is its thermal stability. Glass substrates, particularly those made of “hard” or high temperature glasses, can be processed at elevated temperatures with minimal deformation. In addition, the dimensional precision required in the alignment of various display components is maintained throughout the specific manufacturing processes.
Observation of Vortices in Superconductors
Authors: Bonevich J.E. , Harada K. , Matsuda T. , Tonomura A.
Published: August 2016

Electron holography was originally proposed as a means of improving the resolution of the transmission electron microscope (TEM). And within the last decade dramatic improvements in coherent field-emission electron sources, coupled with TEM instrumentation, have allowed the promise of holography to come to fruition. These improvements in TEM resolution notwithstanding, it has been the application of holography techniques and coherent-beam imaging to the investigation of magnetic and electric fields that has sparked the interest of materials scientists. Electron holography is a unique tool for probing phenomena in the microscopic world because all the information about the object is contained in the hologram (both the electron wave's amplitude and phase), whereas conventional microscopy records only the intensity. It is in this sensitivity to the phase that materials scientists can observe the true potential of electron holography.

Electromagnetic phenomena in a wide range of materials systems have been observed via electron holography; domain structures in magnetic particles and electric fields in p-n junctions are just two examples. Furthermore, fundamental physical properties, such as the existence of the vector potential predicted by Aharonov-Bohm (the AB effect), have been conclusively demonstrated by electron holography. For more information, interested readers are referred to several reviews of electron holography.
Supramolecular Assemblies of Chromophores in LB Films and Related Media
Authors: Chen Huijuan , Farahat Catie Weiss , Farahat Mohammad S. , Geiger H. Cristina , Leinhos Uwe W. , Liang Kangning , Song Xuedong , Penner Thomas L. , Ulman Abraham , Perlstein Jerry , Law Kock-Yee , Whitten David G.
Published: August 2016

Formation of aggregates has been observed as a general phenomenon for a wide variety of organic molecules, especially aromatic compounds and dyes. Aggregation is most commonly encountered in crystals or in thin films. However, it has been increasingly observed in microheterogenous media or in other situations where high local concentrations occur or where specific orientation is favored. Two limiting types of aggregation have been defined based on the orientation of transition dipoles and their absorption spectral characteristics. These are the “J” aggregate, in which head-to-tail arrangements of transitiondipole moments are characterized by a sharp, intense, red-shifted transition compared to the isolated (solvated) monomer, and the “H” aggregate, where head-to-head (card-pack) orientations are characterized by a blue shift of the prominent transition compared with the monomer. Several treatments have been proposed to correlate the observed spectral shifts with the aggregate structure. For a number of compounds, the association of known x-ray-determined structures with spectral features has supported the theoretical predictions developed by Kasha and Hochstrasser or by Czikkely, Försterling, and Kuhn. The focus of the studies described here has been on aggregation occurring in Langmuir-Blodgett (LB) films and related media, such as bilayer vesicles, which are characterized by an assembly of molecules in an interfacial situation where a polar-nonpolar or water-hydrocarbon boundary should provide a strong organizing influence. In early cases where aggregates were encountered as prominent components of mixed LB films (even when relatively dilute mixtures were used), the phenomenon was usually dismissed as “microcrystallization,” which was considered an unavoidable nuisance and not really due to fundamental intermolecular interactions. More recent studies have shown that aggregation in these media is really a significant molecular phenomenon that shows dependence both on the specific molecules and the topology of the film-forming surfactant. Although some previous investigations have been carried out with different results for various substrates, we have embarked on a study to correlate aggregation behavior for a number of different chromophores incorporated into amphiphilic structures to obtain a general picture of the relative importance of different factors that can control aggregation phenomena.
The Quartz-Crystal-Microbalance Study of Protein Binding on Lipid Monolayers at the Air-Water Interface
Authors: Okahata Y. , Ebara Y. , Sato T.
Published: August 2016

Interactions of proteins with cell membranes are of great interest in studies such as molecular recognition at cell surfaces. A monolayer lipid film at the airwater interface is useful in cell-surface modeling. Studies in binding behavior of proteins from a solution with a lipid monolayer have been reported by using variousin situtechniques: surface-tension measurements, fluorescent-labeling techniques, radio-labeling techniques, fluorescence reflection methods, surface plasmon resonance, and surface-force measurements. These methods have potential applications in the observation of protein bindings. However, they require large, expensive equipment forin situmeasurements and present difficulties for quantitatively obtaining the amount of protein adsorbed and the time frame for both binding and dissociation processes.

In this article, we discuss a new, easyin situtechnique to detect interactions of adsorbed proteins with a phospholipids monolayer through the use of a Langmuir film balance on which a quartz-crystal microbalance (QCM) is horizontally attached to the lipid monolayer from the air phase (see Figure 1). QCMs are known to be very sensitive mass-measuring devices because their resonance frequency decreases with an increase of a given mass on a QCM at the nanogram level. Adsorption and penetration behavior of proteins can be observed quantitatively from the frequency changes (ΔF) of the QCM on the monolayer and the surface-pressure changes (Δπ) of the monolayer responding to the addition of proteins. The amount of adsorbed proteins (Δm) wasalso obtained from the frequency changes after lifting and drying the sample in air.

Recently, QCMs have become popular tools for detection of bioactive compounds such as odorous and bitter substances, and for measurement of protein adsorption, immuno-assays, DNA hybridization, enzyme reactions, and cell growth.
Deterministic Chaos Theory and Its Applications to Materials Science
Authors: Markworth Alan J. , Stringer John , Rollins Roger W.
Published: August 2016

Over the past 30 years or so, some fascinating new developments have taken place in a field that is now called “nonlinear science.” These developments have been of such magnitude that historian Alan Beyerchen concluded “There is every reason to believe that the westernized world is in the early stages of an intellectual transformation of major proportions, perhaps as significant as the emergence of the modern worldview in the fifteenth through seventeenth centuries.”

These new developments are rooted in work conducted by mathematician Jules Henri Poincaré around the turn of the century. He carried out some calculations regarding planetary orbits and demonstrated the possibility of erratic or “chaotic” dynamical behavior. What is particularly interesting about such behavior is that it is exhibited bydeterministicsystems, that is, systems that have no stochastic (noisy) character of any kind. Little was done with Poincaré's findings until the 1960s when new work in nonlinear science, based on numerical models, led to the discovery of amazingly complex behavior that can be exhibited even by very simple deterministic systems. Since that time, the discipline has grown enormously and has been applied in practically every area of science and engineering, as well as in other diverse areas such as the financial market, political science, economics, and even Adlerian psychology.
Brief Communication: The Effect of Toxic Microbes on Accelerator Performance
Authors: Smart I.M. , Tu U.R. , Sport B.A.
Published: August 2016

The potential of the environment inside evacuated accelerator beam-lines for breeding microbes which are both toxic to users and possess electric or magnetic organs of strength sufficient to deflect soft charged-particle beams has been explored. Unexplained human and accelerator “long-runtime” syndromes plaguing accelerator facilities for many years can be understood from this study. We have artificially bred such organisms and demonstrated that they are the cause of these syndromes. An appropriate microbicide-impregnated antiseptic beampipe liner with good outgassing properties could alleviate the problem.
Science and Techniques Using Pulsed Magnetic Fields
Authors: Franse J.J.M. , Miura N.
Published: August 2016

In this article, we examine materials behavior in the magnetic field region from about 40 T to 500 T using pulsed magnet technology. Examples of materials science using two different pulsed magnet technologies are described in this article.

Semicontinuous Magnets

Since the late 1960s, the University of Amsterdam has operated a semicontinuous magnetic field installation that produces magnetic fields up to 40 T with typical time constants of about one second. The magnet coil is constructed from hard-drawn copper wire with a reinforcement cylinder of maraging steel positioned at roughly one third of the outer diameter. Before operation, the coil is cooled to 30 K by cold neon gas. The power for this installation is taken directly from a 10 kV connection to the public electricity grid. By means of a thyristor-based power control system, highly flexible field-time profiles can be realized: step-wise pulses can be generated with field levels constant within 10−4 during 100 ms; linearly increasing and decreasing fields as well as exponentially ripple-free decreasing fields are other examples of standard field-time profiles. Among the measuring techniques frequently used are magnetization, magneto-transport, quantum oscillations, relaxation phenomena, etc. Temperatures at which experiments can be performed range from 400 mK to room temperature. In the Netherlands, the Amsterdam High Field Facility has recently been combined with the High Magnetic Field Laboratory in Nijmegen, where static magnetic fields up to 30 T are produced in hybrid magnet systems, to form the Amsterdam-Nijmegen Magnet Laboratory (ANML). The high field research of ANML comprises semiconductors, magnetism in transition-metal compounds, heavy-fermion physics, superconductors, organic conductors, and magnetic separation. We present here a few selected topics.
Aqueous Alteration of Nuclear Waste Glasses and Metal Package Components
Authors: Wicks George G. , Lodding Alexander R. , Molecke Martin A.
Published: August 2016

The United States is at an important crossroads in its management of high-level radioactive waste (HLW). It is presently in the process of changing over from a strategy that was developed during World War II, which involves storing HLW in a relatively mobile liquid form, to a strategy of the 1990s, which involves removing and isolating potentially harmful radionuclides and immobilizing them into solid and inert forms, more specifically, borosilicate glass. The resulting waste glass products will then be permanently disposed of by deep burial, within stable geologic formations, where they become one element of a multibarrier waste-isolation system. This barrier system is designed to retain radionuclides so they can be permanently isolated from the public and from the accessible environment. Important contributing factors to the success of this strategy include the excellent stability and technical performance of waste glass forms and the ability of the glass, as well as waste package materials, to retain radionuclides even when exposed to potential leachants within a repository environment.
CulnSe2 and Other Chalcopyrite-Based Solar Cells
Authors: Schock Hans-W.
Published: August 2016

CuInSe2 and related chalcopyrite semiconductors are among the compound semiconductors that have been considered for thin solar cells for about the past 20 years. Recently, high efficiencies close to 17% have been achieved. This result could be the starting point for a new category of solar cells—high-performance thin-film cells—that would combine the high performance of single-crystal cells with possible low-cost thin-film processing.

The development of CuInSe2 cells started in 1974, when single-crystal cells with an efficiency of 12% were reported by a group at Bell Laboratories. Soon after, thin-film solar cells were demonstrated by Kazmerski et al. CuInSe2 thin films have been deposited by evaporating the CuInSe2 source material to completion and adding Se from a separate source. It was found that straight-forward evaporation of the compound does not generally lead to films with stoichiometric composition. By coevaporation of the elements, films with any desired composition can be obtained, provided there is appropriate process control. A “bilayer” recipe developed by Boeing, namely combining Cu-rich films and In-rich films, solved the problem of combining larger grains with suitable electronic properties. By this method, the first CuInSe2 thin-film solar cells with an efficiency exceeding 10% conversion efficiency were fabricated.

Alloying CuInSe2 with CuGaSe2 and CuInS2 considerably increases the potential for the innovative development of solar cells from these materials. The energy gaps covered by these alloys range from about 1 eV to about 2.4 eV The possibility of increasing the energy gap and achieving absorber layers with graded bandgaps has many advantages for the application of these materials in thin-film solar cell modules.
III-V Materials for Photovoltaic Applications
Authors: Fraas Lewis M.
Published: August 2016

While there are only two group IV semiconductors, Si and Ge, the III-V material system offers a nearly infinite number of single-crystal semiconducting compounds to choose from. For example, there are nine binary compounds resulting from combining the group III elements Al, Ga, or In with the group V elements P, As, or Sb. From this group, high-performance photovoltaic cells have been made from GaAs, GaSb, and InP. Using ternary III-V compounds, high-performance photovoltaic devices have been made with AlGaAs, GalnAs, GaAsP, and InGaP2. All of the above-cited photovoltaic cells have respectable energy conversion efficiencies of over 15%.

A primary strength associated with the III-V semiconductor material system lies therefore in the diversity of materials to choose from. Thus, a single-crystal III-V compound can be found with almost any bandgap ranging from 0.16 eV for InSb to 2.24 eV for GaP (or 3.5 eV for GaN). But not only can one choose a material with a particular bandgap, one can, more importantly, as a result of tetrahedral covalent bonding, also be assured that that material can be grown as a single crystal with either n- and p-type doping, and that junctions can be formed with nearly ideal rectifying characteristics. The implication this holds for solar cells of ideal diode characteristics is the achievement of theoretical limit open-circuit voltages and fill factors. An additional important feature associated with many of the III-V compounds is the direct-gap photon absorption which translates to a short optical absorption distance, with the result that excited-state carriers in a solar cell are created near the junction.
Iron Sulfide for Photovoltaics
Authors: Dasbach R. , Willeke G. , Blenk O.
Published: August 2016

In recent years, iron sulfide (FeS2), otherwise known as pyrite, has received some attention as a possible candidate for thin-film photovoltaic applications. This interest stems in part from the fact that it has a relatively large absorption coefficient of α > 105 cm−1 for photon energies larger than about 1.3 eV (see Figure 1), such that a thin layer of less than 1,000 Å should effectively absorb the visible part of the solar spectrum. The bandgap of pyrite of 0.95 eV is probably on the borderline of what might still be considered acceptable for a high-efficiency single-junction device, but can be considered ideal in combination with a 1.8 eV material for tandem structures. Another important advantage of this compound semiconductor is that it is composed of cheap, abundant, and non-toxic elements, the latter being of particular importance in times of growing environmental consciousness.

Pyrite is a naturally occurring mineral (also known as “fool's gold” because of its golden color) which shows both n- and p-type conduction. This could indicate possible electronic viability of this material. The study of synthetic crystals has been severely impeded by the fact that pyrite undergoes a peritectic decomposition into the more stable FeS and liquid sulfur at 743°C and that therefore the melt growth of high-purity large single-crystalline material is not possible. Nevertheless, it has been shown that polycrystalline pyrite layers could be prepared with different thin-film preparation techniques (see Table I), such that in principle a cost-effective large-scale application could be envisaged.
Test Structures as a Way to Evaluate Packaging Reliability
Authors: Palmer David W.
Published: August 2016

Electronics packaging has always accounted for about 50% of reliability shortcomings in electronics systems. Materials, processes, and geometries used in microelectronics packaging are quickly evolving to meet the commercial challenge for more reliable, lighter, smaller, cheaper devices, and lower power consumption. Amid the rapid evolution, methodology and metrology to measure package reliability and materials aging properties must be standardized to allow quantitative technology comparisons.

What Is Packaging?

For most purposes packaging can be thought of as everything involved in making an electronics system except the wafer fabrication. For example, all the design, fabrication, assembly, and finishing that goes into interconnecting the integrated circuits, discrete devices, resistors, and capacitors and then interfacing the system to the user is traditionally called “packaging.”