bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tissue Engineering: An Overview
Authors: Kohn Joachim 
Published: August 2016

When trying to identify the beginnings of “tissue engineering” as a defined scientific field, the first major scientific meeting devoted to “tissue engineering” comes to mind. This meeting took place in 1988 at Granlibakken, Lake Tahoe, California. When looking through the proceedings of this meeting, one can see that many of the fundamental challenges of tissue engineering, still unresolved today, were articulated back at that time. As practiced today, the field of tissue engineering is based on a blending of engineering principles in the materials sciences with the principles of cell and tissue biology to create functional replacements for aged, traumadamaged, or diseased human tissues and organs.The driving force behind the field of “tissue engineering” is the desire to replace defective human tissue with artificial substitutes to improve the quality of human life. This desire is not unique to our times but can be traced back several thousand years. The earliest reports of the use of artificial materials in wound healing are contained in the Edgar Smith papyrus. This historic document mentions the use of sutures and woundclosure devices around 4000 B.C. and the use of metals in bone repair around 2000 B.C. In ancient times, Native Americans apparently used silk and hair as suture materials.In 1900 natural tissues like amnion and placenta were suggested as skin replacements, an approach that was obviously doomed to fail due to immunological reactions. The general lack of understanding of the immune response at the beginning of this century forced researchers and clinicians to abandon attempts to use natural tissues as medical implants and contributed to a focus on synthetic materials. Advances in metallurgy facilitated the introduction of metals for bone reconstruction and dental prosthesis, and the large number of casualties during World War I resulted in the establishment of stainless steel and other metals as the preferred orthopedic implant materials.
In SituMaterial Transformations in Tissue Engineering
Authors: Hubbell Jeffrey A. 
Published: August 2016

Novel applications exist for biomedical materials that can undergo transitions in material propertiesin situ—that is, at the site of implantation in the body. Such transitions in polymeric biomaterials can be accomplished by crosslinking a materialin situ, by heating or cooling to induce thermal transitions, and by precipitating polymer from solutionin situ. This article will point out the need for materials that can be induced to undergo such transitions in situ and will describe selected tissue-engineering approaches that have been employed for this purpose.Delivering materials to the body in one form and utilizing them in another form after a transition at the site of implantation has, generally speaking, two potential advantages: (1) the ability to match the morphology of a material implant to a complex tissue shape and (2) the ability to deliver a large device through a small hole in the body. With respect to the former motivation, tissue shapes in the body have an enormous range of complexity: a region of a blood vessel—for example with a curved central axis, a diameter that varies along the length, an eccentric diseased plaque, and numerous side branches. One could develop a variety of implant shapes—arterial stents in this example (for use in structurally supporting arteries after balloon angioplasty, thereby creating a larger cross section for blood flow above the diseased plaque)—and then select the most appropriate implant shape after detailed imaging of the tissue site. One can alternatively attempt to employ some material transformation to deliver a precursor to the final shape of the implant, utilizing the tissue shape to obtain the proper final implant morphology. With regard to the second motivation, it may be desirable to deliver a large object through a small hole, utilizing material transformations. Advances in surgery have focused on manipulating (cutting, coagulating, suturing, stapling) large tissue sites through small holes in the body via minimally invasive surgery. Using such approaches, it has become possible to perform many complex surgical procedures in the joints, abdominopelvic cavity, thoracic cavity, and nasal sinuses, for example, using surgical instruments that are manipulated through surgical access holes less than 1 cm in diameter. Even procedures as complex as coronary-artery bypass surgery have been performed in this way. It still remains generally impossible however to implant devices in the body through such holes unless these implants are very small. If such devices were for example able to be delivered as liquids and then shaped into devices at the implant site, such minimally invasive surgical-device placement could be envisioned.
Binders in Paintings
Authors: Newman Richard 
Published: August 2016

Many naturally occurring adhesive materials have been used throughout history to bind pigments in paintings. A number of synthetic materials have been added to these during the twentieth century.Availability and tradition can influence the choice of binders made by artists. Probably the most widely used medium throughout history, animal glue, is also the most easily obtained. Glues made from the connective tissues or skins of local animals were major media in ancient Egyptian painting and in Chinese and Japanese painting, as well as in many other cultures throughout world history. In many cases, a variety of natural binders were available, and additional factors influenced the choice of binder by a culture. Different media have highly variable properties that affect how they are used in painting. Among these properties are solubility, the transparency or depth of color that is obtainable with a given pigment, and handling properties–how the paint flows, how quickly it dries, whether it can be applied in very thick and very thin layers, etc. Knowledge of the media utilized in paintings can help us understand the intentions of artists. Medieval European painting can be used as an example.
Polymer Chains Under Strong Flow: Stems and Flowers
Authors: Brochard-Wyart F. , Buguin A. 
Published: August 2016

A long deoxyribose-nucleic-acid (DNA) molecule can be seen directly under an optical microscope if it is suitably decorated by fluorescent dyes. This makes it possible to see how a long chain responds to external forces f. The conformation of a uniformly stretched chain has been discussed by Pincus. Under a force f, acting on the two free ends, the chain configuration is modified only above a scale length ξ = kT/f where T is temperature and k is Boltzmann's constant. The chain (Figure 1a), containing N monomers, can be pictured as a string of blobs of size ξ containing g monomers with ξ = gva, where a is the monomer size (v = 1/2 in a θ solvent: the chain is ideal, v = 3/5 in a good solvent). The end-to-end distance is L = (N/g)ξ, that is,For DNA, which is a semirigid chain, ideal behavior has been observed for chain lengths up to 20 μm when f is small. At higher f ( ≅ 100 pN), Cluzel et al. found a structural phase transition, corresponding to a plateau in the curve f versus elongation. Going even further, one reaches the break point.Another method to stretch DNA is based on optical tweezers. Here one end of the DNA is attached to a bead of glass of high polarizability, which is attracted by a region of large (optical) electric field. This was used by the Stanford group: In one series of experiments, they observed the conformations of the chain, pulled at one end by a constant force f. The friction on monomers are cumulative, and the tension along the chain is not uniform—it increases from the free end to the tethered end.
Material Matters
Authors: Oversby Virginia M. 
Published: August 2016

The use of nuclear fission to generate power results in waste materials that can be hazardous to people and to other life forms, particularly in the first few hundred years after the wastes are created. There is a worldwide consensus that the management of these wastes must not place undue burdens on future generations. In some countries, the opinion is openly stated that those who enjoyed the benefits of the power that produced the wastes must be responsible for taking care of the wastes. Opinions diverge when discussion turns to the question of whether the wastes will always be a liability or eventually become an asset.Another point of consensus is that at least some of the radioactive wastes should be disposed of by a method that securely isolates them from the accessible environment of plant, animal, and human life until the radioactivity levels have decayed to levels similar to those found in natural environments. Different countries take different positions on the details of what the activity level might be that constitutes the end of moral responsibility for the wastes, but the general position is basically the same worldwide. I explore some concerns about how disposal containers and waste repositories might be marked with suitable identification. In particular, I examine whether the message to be conveyed by the markings needs to change with time and with the entity examining the objects, and whether we can design markers that will convey this potentially variable message.
Blue-Green Light-Emitting Diodes and Violet Laser Diodes
Authors: Nakamura Shuji 
Published: August 2016

Short-wavelength-emitting devices, such as blue laser diodes (LDs) and light-emitting diodes (LEDs), are currently sought for a number of applications, including full-color electroluminescent displays, laser printers, read-write laser sources for high-density information storage on magnetic and optical media, and sources for undersea optical communications. For these purposes, II–VI materials such as ZnSe and SiC, and III–V-nitride semiconductors such as GaN have been investigated intensively for a long time. However it was impossible to obtain high-brightness (over 1 cd) blue LEDs and reliable LDs. Much progress has been achieved recently on green LEDs and LDs using II–VI-based materials. The short lifetimes prevent II–VI-based devices from commercialization at present. The short lifetime of these II-VI-based devices may be caused by the crystal defects at a density of 103/cm2 because one crystal defect would cause the propagation of other defects leading to failure of the devices. Another wide-bandgap material for blue LEDs is SiC. The brightness of SiC blue LEDs is only between 10 mcd and 20 mcd because of the indirect bandgap of this material.On green LEDs, the external quantum efficiency of conventional, green GaP LEDs is only 0.1% due to the indirect bandgap of this material. The peak wavelength is 555 nm (yellowish green). As another material for green emission devices, AlInGaP has been used. The present performance of green AlInGaP LEDs is an emission wavelength of 570 nm (yellowish green) and maximum external quantum efficiency of 1%.
Radiation Effects in Ceramics
Authors: Pells G.P. 
Published: August 2016

Ceramics are inorganic, nonmetallic materials, a class that includes solids with both crystalline and glassy (i.e., aperiodic) atomic structures. This article will emphasize radiation effects in conventional refractory oxide ceramics and glasses that display high-temperature strength, chemical inertness, and high electrical resistivity. The introduction to this issue cites various radiation environments to which materials may be exposed; a number of these environments receive mention in this article. However emphasis here is on giving the reader an overview of damage mechanisms and of the changes in key physical properties (optical, thermal, electrical, and mechanical) that can affect the behavior of these materials. The broad subject of radiation-damage phenomena in ceramics has recently been reviewed by Hobbs et al.Even at low doses of energetic radiation, whether particulate or electromagnetic, isolated atomic-level defects may be generated and can offer the potential to induce changes in physical properties. However for some applications such as fission reactors, fusion reactors (now in the conceptual design stages), and high-energy accelerators, one must deal with high fluences capable of generating relatively large damage aggregates such as dislocation loops and voids. Thus one must understand the evolution of damage microstructures from point defects to aggregates in both model materials and engineering ceramics. Even when induced changes are only electronic in nature, the effects on some properties (e.g., electrical conductivity) can be dramatic. In the following sections, evolution of the damage state and consequent changes in key properties are described, with some attention to the often critical role of impurities.
The Microstructure of Metalorganic-Chemical-Vapor-Deposition GaN on Sapphire
Authors: Hersee S.D. , Ramer J.C. , Malloy K.J. 
Published: August 2016

The group-III-N materials (GaN and its related alloys, InGaN and AlGaN) are a rapidly emerging family of compound semiconductors that have great potential for a wide range of optoelectronics and electronics applications.GaN-based blue light-emitting diodes (LEDs) are commercially available and can already be found in full-color, billboard-size displays in major cities in Japan. Achievement of continuous-wave (cw) laser operation at blue wavelengths will lead to the commercialization of these coherent sources probably within the next few years. Like other semiconductor lasers, these devices can be manufactured relatively cheaply (eventually for a few dollars), and they are expected to replace current ($1,000 and up) ultraviolet and blue-laser sources in medical spectroscopy, high-density information storage, and in projection displays.This article reviews the key role of the crystal structure of GaN grown on sapphire, which is currently the most widely used substrate. We trace the origin of this crystal structure from nucleation and show how it evolves as growth proceeds. We show that the final GaN film is an ordered polycrystal (rather than a single crystal), in which the individual grains are of high crystalline quality but are “tilted” and “twisted” with respect to one another. We conclude by speculating on how this microstructure may explain the unusual optical and electrical properties of GaN.
Polymerization and Properties of Polymer-Stabilized Ferroelectric Liquid Crystals
Authors: Bowman Christopher N. , Guymon C. Allan 
Published: August 2016

The following is based on the presentation made by Christopher N. Bowman, recipient of the MRS Outstanding Investigator Award, at the 1997 MRS Spring Meeting.I would like to focus on our recent work involving photopolymerizations of monomers in a liquid-crystalline environment. This work is one of the many aspects of photopolymerizations that we are focusing on at the University of Colorado. In particular this effort concentrates on understanding the influence of a liquid-crystalline medium and monomer segregation on polymerization behavior and polymer structure. These studies are of considerable importance for polymer-stabilized ferroelectric liquid crystals (FLCs) because of the enormous potential impact on the area.I will briefly introduce liquid crystals (LCs), FLCs, and photopolymerizations. I will then discuss the observed electrooptic properties and how these properties change as the LC phase during polymerization is varied. Finally I will address how polymerization kinetics are affected by the LC phase and monomer segregation. This discussion will include results from x-ray diffraction, polarized infrared spectroscopy, and differential scanning calorimetry experiments.
Spectroscopic Characterization of Polymer Surfaces
Authors: Zhuang Hengzhong , Gardella Joseph A. 
Published: August 2016

The surface science of polymer materials has recently grown to a dynamic field, largely because of application in such areas as composite materials, wetting, coatings, adhesion, friction, and biocompatibility. The synthesis of new polymer materials, resulting in desired polymer-surface structures and composition, has become more sophisticated and is driving the development of new spectroscopic probes and continuing evolution of more established methods.A good example of how instrumentation development has led to better applications in polymer-surface science is to follow the growth of studies using x-ray photoelectron spectroscopy (XPS)—also called electron spectroscopy for chemical analysis (ESCA). ESCA is now routinely used to obtain surface composition of polymers, and to follow processing steps and degradation chemistry. Advances in instrumentation have driven many of these more sophisticated applications.Nevertheless, to improve the understanding of polymer-surface chemistry, more information is needed about surface structure with further sophistication, at a higher level of precision. For example, the knowledge of orientation and subsequent reactive availability of functional groups and of monomer ar rangement along a chain in copolymers and intrachain interactions is important. Macromolecular chain arrangement, termination, branching, and micromorphological information (i.e., domain size and distribution), molecular-weight distributions at or near the surface (in comparison with the average, bulk distribution), and higher degrees of spatial resolution in all three dimensions are all important in determining sophisticated surface structure-property relationships. To approach this level of structural and reactivity information at surfaces and interfaces, evolution of established methods and development of new methods must both be accomplished.
Film as a Composite Material
Authors: Fleischer Cathy A. , Bauer Charles L. , Massa Dennis J. , Taylor Jeffrey F. 
Published: August 2016

Since its development over 150 years ago, silver-halide imaging has retained a central role in the imaging world, despite advances in electronic imaging over the last five to 10 years. At present the high cost of electronic cameras and printing systems prohibits their widespread general use. Nevertheless digital electronic features are now being incorporated into silver-halide-based imaging systems. Development of new films that incorporate magnetic-storage capability into conventional silver-halide film, as well as smaller cameras and tighter winding radii, put more stringent requirements on the physical performance of the final silver-halide-based product.For many years, advances in silver-halide imaging focused on improved photographic emulsions, providing improvements in resolution, color balance, and latitude. Advances in the photographic emulsions resulted from particle shape and morphology control of the silver-halide crystal, as well as new sensitizing dyes, couplers, and other image-modifying addenda that provided increases in speed and quality. Literature on the “science of photography” and “photographic materials and processes” emphasizes silver-halide chemistry and the function of sensitizing dyes and couplers in color photography as they impact film latitude, resolution, color balance, etc., with minor mention of the support materials and properties. Literature on support characteristics and physical properties is limited.
Materials for Flat-Panel Displays
Authors: Im James S. , Chiang Anne 
Published: August 2016

Flat-panel displays (FPDs) will soon become ubiquitous products in our homes, workplaces, and a number of places in between. Familiar display applications pioneered by the venerable cathode-ray tube (CRT) will progressively utilize a number of different FPDs. Flat-panel displays will also initiate and pioneer new applications, as was the case with notebook computers and personal digital assistants.The future proliferation of FPDs can no longer be doubted for two simple reasons. First, such devices help us cope with this already information-saturated society. Second, the technological momentum and financial commitment needed for FPDs to take hold are already irreversibly set in place. It is the insatiable current and near-future demand that are pulling the field, and that are fueling a flurry of research and development activities. The display market has grown in size from tens of millions of dollars only a decade ago to a nearly ten-billion-dollar industry. This market growth is expected to continue at a brisk pace during the next decade.This of course is in no way bad news for materials scientists and engineers. We nearly always benefit from development of new and complex products. It is in regard to these rather incipient but advanced manufacturing technologies where we often encounter challenging, relevant, and interesting materials problems. The better we address these obstacles during these early and therefore critical times, the more successful the FPD technology will be in fulfilling the potential opportunities that lie ahead.
Materials Issues in Magnetic-Disk Performance
Authors: Doerner Mary F. , White Richard L. 
Published: August 2016

The continued exponential growth in areal density for longitudinal magnetic-recording devices places ever more stringent demands on disk performance. The design of materials and processes must provide the required advances in technology. The magnetic properties are controlled through the choice of underlayers, magnetic alloys, and the deposition processes that control crystallographic orientation and magnetic isolation between grains. The requirement of lower head-disk spacing places increasing stress on the tribological performance of the disks, controlled by a very thin overcoat and lubricant layer. This article reviews the various materials issues relevant to magnetic-disk technology.The major obstacle for achieving high areal density in thin-film media is transition noise. This noise arises from the zig-zag transition boundaries that occur due to cooperative switching of the magnetic grains. Both exchange coupling between grains and magnetostatic interactions cause magnetic-cluster sizes larger than the grain size. The goal is to magnetically isolate the grains and keep the grain size small. As the dimensions of the bit cell shrink, smaller grain size is required to obtain enough grains per bit cell to maintain the required signal-to-noise ratio (SNR). In the 10–40-Gbits/in.2 areal-density range, the issue of thermal stability of small (<10 nm), isolated grains needs to be addressed.In addition to good SNR, a narrow transition width is needed in order to pack the transitions closer together. The objective is to minimize interactions between transitions to reduce nonlinear amplitude loss and superlinear noise.