bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow Imaging
Authors: Clemens Noel T. 
Published: October 2003

AbstractImaging has a long history in fluid mechanics and has proven critical to the investigation of nearly every type of flow of interest in science and engineering. A less than exhaustive list of flows where imaging has been successfully applied would include flows that are creeping, laminar, turbulent, reacting, high‐temperature, cryogenic, rarefied, supersonic, and hypersonic. The wide range of applications for flow imaging is demonstrated by the recent development of techniques for imaging at micro‐ and macroscales.Traditionally, flow imaging has been synonymous with “flow visualization,” which usually connotes that only qualitative information is obtained. Owing to the complex and often unpredictable nature of fluid flows, flow visualization remains one of the most important tools available in fluid mechanics research.Most imaging in fluid mechanics research involves planar imaging, where the flow properties are measured within a two‐dimensional cross section of the flow. This is most often accomplished by illuminating the flow using a thin laser light sheet, and then recording the scattered light using a digital camera. The laser light is scattered from either molecules or particles in the flow. The primary emphasis of this article is on this type of planar laser imaging because it remains the cornerstone of quantitative imaging in fluid mechanics research. Furthermore, planar imaging is often a building block for more complex 3‐D imaging techniques. Quantitative imaging is substantially more challenging than simple visualization because a greater degree of knowledge and effort are required before the researcher can ensure that the spatial distribution of the flow property of interest is faithfully represented in the image. The first part of this article discusses some of the most important issues that need to be addressed in quantitative flow imaging. The article ends with a brief survey of primarily planar imaging techniques that have been developed. This survey will not be able to discuss all, or even most, of the techniques that have been developed, but hopefully readers will gain an appreciation for the wide range of techniques that can be applied to their flow problems.
Holography
Authors: Jeong Tung H. 
Published: October 2003

AbstractIn an attempt to correct the spherical aberration of the electron microscope, Dennis Gabor gave birth to the basic concepts ofholographyin 1948, for which he was awarded the Nobel Prize in physics in 1971.However, it was not until after the invention of the laser and further contributions by E. N. Leith and J. Upatnieks and independently by Yu. N. Denisyuk that holography was developed to the present stage.In this chapter, concentration is on optical holography, although the concepts involved are applicable to any type of coherent waves. In particular, the recording and reconstruction of the wavefronts of a three‐dimensional object is analyzed. These analyses are applicable to hybrid developments to be summarized.Generally, the process ofholographycan be defined as the recording of the interference pattern between two mutually coherent radiation fields on a two‐ or three‐dimensional medium. The result is said to be ahologram. It is a complex diffraction grating. When one of the fields is directed at the hologram, the diffraction reconstructs the wavefronts of the other field.Holography can be studied and appreciated at many levels. It is sufficiently simple for those without a technical background to produce beautiful works of art. Indeed, it can now be pursued at the same level as photography. A graphic model is presented which offers intuitive understanding of volume holograms.
Lidar
Authors: Argall P. S. , Sica R. J. 
Published: October 2003

AbstractLight detection and ranging (lidar) is a technique in which a beam of light is used to make range‐resolved remote measurements. A lidar emits a beam of light, that interacts with the medium or object under study. Some of this light is scattered back toward the lidar. The backscattered light captured by the lidar's receiver is used to determine some property or properties of the medium in which the beam propagated or the object that caused the scattering.The lidar technique operates on the same principle as radar; in fact, it is sometimes called laser radar. The principal difference between lidar and radar is the wavelength of the radiation used. Radar uses wavelengths in the radio band whereas lidar uses light, that is usually generated by lasers in modern lidar systems. The wavelength or wavelengths of the light used by a lidar depend on the type of measurements being made and may be anywhere from the infrared through the visible and into the ultraviolet. The different wavelengths used by radar and lidar lead to the very different forms that the actual instruments take.The major scientific use of lidar is for measuring properties of the earth's atmosphere, and the major commercial use of lidar is in aerial surveying and bathymetry (water depth measurement). Lidar is also used extensively in ocean research and has several military applications, including chemical and biological agent detection.Atmospheric lidar relies on the interactions, scattering, and absorption, of a beam of light with the constituents of the atmosphere. Depending on the design of the lidar, a variety of atmospheric parameters may be measured, including aerosol and cloud properties, temperature, wind velocity, and species concentration.This article covers most aspects of lidar as it relates to atmospheric monitoring. Particular emphasis is placed on lidar system design and on the Rayleigh lidar technique.
Neutron Imaging, Radiography, andCT
Authors: Smith Graham C. 
Published: October 2003

AbstractThe discovery of the neutron occurred in 1932, and the first neutron diffraction experiments were performed in the late 1940s. As usage progressively increased, the neutron has become a key probe in many fields of science, and sources around the world are now oversubscribed by experimenters. The European Spallation Source (ESS), and the Spallation Neutron Source (SNS), in the United State are new, high‐intensity sources under development that attest to the importance of neutrons as a probe. Because they are uncharged, neutrons are one of the most difficult particles to detect. Only a few elements in nature have a high affinity for neutron interaction. This article is organized as follows. The fundamental reactions upon which all neutron detection relies are described. Then a series of sections describe the main techniques of neutron detection and imaging: gas‐based, scintillator based, semiconductor‐based, film and image plates, and microchannel plates. In these sections, a few applications are noted. The section next to last focuses on neutron radiography/tomography, for which scintillator detectors and image plates are the primary imaging techniques. Some important reviews from recent literature for imaging techniques and for radiography are given. Techniques for (nonimaging) neutron detection have also recently been reviewed.
Stereo and 3‐DDisplay Technologies
Authors: McAllister David F. 
Published: October 2003

AbstractRecently, there have been rapid advancements in 3‐D techniques and technologies. Hardware has improved and become considerably cheaper, making real‐time and interactive 3‐D available to the hobbyist, as well as to the researcher. There have been major studies in areas such as molecular modeling, photogrammetry, flight simulation, CAD, visualization of multidimensional data, medical imaging, teleoperations such as remote vehicle piloting and remote surgery, and stereolithography. In computer graphics, the improvements in speed, resolution, and economy make interactive stereo an important capability. Old techniques have been improved, and new ones have been developed. True 3‐D is rapidly becoming an important part of computer graphics, visualization, virtual‐reality systems, and computer gaming. Numerous 3‐D systems are granted patents each year, but very few systems move beyond the prototype stage and become commercially viable. Here, the salient 3‐D systems are treated.First, the major depth cues that one uses to determine depth relationships among objects in a scene are described.The history of 3‐D displays and an overview of technologies follow. Details are given on the viewing devices required. Large formats, such as IMAX are discused. Autostereoscopic displays with us viewing devices are discussed.
Cathode Ray Tube Display Technology
Authors: Barbin Robert L. , Poulos Anthony S. 
Published: October 2003

AbstractThe invention of the cathode ray tube (CRT) is generally ascribed to Karl Ferdinand Braun in 1897. His tube was the first to combining the basic functions of today's CRTs: electron source, focusing, deflection, acceleration, phosphor screen, and a sealed mechanical structure.The basic components of a CRT used for color displays are electron gun, deflection yoke, phosphor screen, shadow mask, and glass bulb. There are many performance measures that can be used to characterize the quality of CRT displays. Some of the more important parameters and quantify the performance levels typically obtained in color television applications are described.The design of a CRT typically starts with the selection of several basic parameters: screen size, deflection angle, and panel contour. These parameters are usually established by engineering and sales and allow a workable and manufacturable product to be delivered to the customer market.Essentially all of today's direct view color CRTs use tricolor electron guns, which generate three electron beams, one to illuminate each of the primary phosphor colors. These generally use common grids for the three guns in which each of the grids have three apertures, one for each of the three electron beams. The cathodes are separated so that each of the three beams can be electrically modulated.
Optical Image Formation
Authors: Mouroulis Pantazis 
Published: October 2003

Abstract

For the greatest part of human history, visible light has been the only image forming medium. And until recently, visual telescopes and microscopes comprised the vast majority of image forming instruments. The image formation principles examined in this article derive from such venerable ancestry but are broader in their application. Whereas visible wavelengths span a range of less than 2 : 1 in the electromagnetic (EM) spectrum, the contents of this article can find application in devices operating across a wavelength range of ∼10
6
, from nanometers to millimeters. However, the middle part of that range, from about 100 nm to about 10 µm, contains practically all of the devices that are classified as optical instruments, and those are our main concern here.

The simplest device for whole‐field imaging is the pinhole camera. It comprises a square or rectangular box that has a small opening on one side.

The projection of the pinhole on the image plane, taken as approximately the same size as the pinhole itself, provides the
resolution limit
of the pinhole camera. Image details smaller than the pinhole size cannot be resolved. Any close examination of pinhole camera images reveals considerable blur. Thus, the pinhole camera has two fundamental problems: inferior resolution and a dim image.

Both of these problems are resolved by introducing a lens in place of the pinhole.
For any nonideal lens, the focal spot size depends on the specific construction of the lens, as well as on the object and image size or the angle at which rays strike the lens. When these realistic considerations are taken into account, it is found that increasing the lens size beyond a certain point normally leads to an increase in spot size or requires a complicated lens construction.
The subject of this article is a more detailed appreciation of the contents and implications of the above. The necessary background for much of this material is that of a first‐year college physics course. Specifically, some familiarity is assumed with the elementary concepts of a thin lens and its focal length/points and the basic concepts of wave optics. In addition to that, a proper understanding of the image formation concepts in a later section assumes some familiarity with the basic mathematics of Fourier transformations. Although some basic material of Fourier theory is reviewed in the Appendix, it is primarily useful as a refresher for those who already know something about the topic. However, a reader unfamiliar with such mathematics should still be able to appreciate that material because it is largely self‐contained, although significantly compressed through omission of most mathematical proofs. A deliberate attempt has also been made to provide simple physical arguments for most equations, and many illustrations have been included. Clearly, for a detailed understanding, the reader must resort to the references given.
Electron Microscopes
Authors: Dyck Dirk Van , Amelinckx S. 
Published: October 2003

AbstractIn past decades, electron microscopy has matured to an indispensable tool for materials and biomedical research. Numerous are the Nobel Prizes for research work in which electron microscopy revealed crucial evidence. Despite the very small wavelength of the electrons, it has only recently been possible to visualize individual atoms. The reason for this is that magnetic lenses inevitably suffer from aberrations that, contrary to glass lenses in a light microscope, cannot easily be corrected. Recently the problem of compensating the spherical aberration has become solved on the research level.When individual atoms, the building blocks of nature, can be revealed, electron microscopy enters into a new era. Indeed, then it becomes possible to determine the atomic structure of matter quantitatively and accurately, even for objects for which only limited prior knowledge is available. Although the goal is not yet achieved, the progress is very encouraging. In the future, as materials science evolves into materials design, and mesostructures into nanostructures, the role of electron microscopy will become even more important.In recent years one has also seen the development of related techniques such as scanning transmission electron microscopy (STEM), electron holography, ptychography, and add‐on techniques that use complementary information such as X‐ray analysis (EDX), and energy filtering. There is now a growing tendency to incorporate all these techniques into one versatile instrument under full computer control, where they are all considered as different ways to obtain complementary information, mainly of chemical nature.The development of scanning electron microscopy (SEM) has taken place parallel to that of TEM. The SEM is conceptually simpler than the TEM. With the aid of magnetic lenses, the electron beam is focused into a small point that is scanned over the surface of the object. The backscattered electrons, or other secondary signals, can then be detected and synchronously displayed on a cathode‐ray‐tube (CRT) screen. The SEM is relatively easy to use and does not require extensive specimen preparation and is also less expensive than the TEM. On the other hand, it can only be used to study the surface area and, because of the beam spread in the object, its resolution is rather limited and quantitative interpretation of the images is more difficult.
Magnetic Resonance Imaging
Authors: Prost Robert W. 
Published: October 2003

AbstractImaging of materials that contain nuclei of nonzero spin values has become a valuable tool in science, medicine, and industry. The principal use of MRI is to create an image of the distribution of certain physical properties of a substance, whether in the fluid‐filled rock surrounding an oil well, soil, food‐processing, industrial process control or a human subject. These physical properties imaged include the chemistry of the material, its fluidity, its interactions with other materials in the molecular‐level neighborhood, and even the flow of liquids within the object. Magnetic resonance phenomena occur on a timescale that is short relative to many chemical reactions and can often be used to investigate the kinetics of chemical reactions.Many different elements are amenable to investigation by magnetic resonance, but the sensitivity of MR is poor. As a result of this insensitivity, magnetic resonance is not suited to detecting of chemical moities of less than millimolar quantities. For the same reason, gases are largely unsuitable to investigation by magnetic resonance, except for hyperpolarized gases3He and129Xe.All solid or liquid objects, that bear suitable nuclei can be imaged. However, spins within solid materials lose their signal on a very short timescale. This brevity of signal lifetime makes imaging quite difficult, yet not impossible.Examples of nuclei that bear a magnetic moment, or nonzero spin include hydrogen, helium‐3, xenon‐129, phosphorus, lithium, fluorine, carbon‐13 and sodium‐23.An important and recent use of the MR phenomenon is in medical imaging. The reason for the success of MRI in medical imaging is fourfold. The first is the abundance of hydrogen in the human body. Hydrogen nuclei in the brain are about 70 Molar in concentration which is much higher than any other material that can be detected by NMR. The second is that the hydrogen is distributed in the organs in a way which allows using the MR signal to create images. The third is that imaging of hydrogen produces exquisitely detailed images of internal organ structure. The fourth is the functional data that can be extracted. These data include molecular diffusion, distribution of chemical moieties, flow, flow in the capillary bed, oxygen utilization, magnetization transfer rates, and disruption of the blood–brain barrier.Basic MRI physics, imaging processing and k‐space, endogenous image contract and other mechanisms are discussed.
Anticipation and repeat expansion in bipolar disorder
Authors: O'Donovan Michael , Jones Ian , Craddock Nick 
Published: October 2003

AbstractAnticipation is the phenomenon whereby a disease becomes more severe and/or presents with earlier onset as it is transmitted down through generations of a family. The only known mechanism for true anticipation is a class of mutations containing repetitive sequences exemplified by the pathogenic trinucleotide repeat. Studies of bipolar disorder (BPD) are consistent with the presence of anticipation and, by inference, the possibility that trinucleotide repeats contribute to this disorder, although it is possible that these data are the result of methodological problems. On the assumption that anticipation in BPD may be real, several surveys of the genome of BPD probands for large trinucleotide repeats have been conducted, as have studies of many repeat‐containing candidate genes. No pathogenic triplet repeat has yet been unambiguously implicated. © 2003 Wiley‐Liss, Inc.
Family, twin, and adoption studies of bipolar disorder
Authors: Smoller Jordan W. , Finn Christine T. 
Published: October 2003

AbstractFamily, twin, and adoption studies have been essential in defining the genetic epidemiology of bipolar disorder over the past several decades. Family studies have documented that first‐degree relatives of affected individuals have an excess risk of the disorder, while twin studies (and to a lesser extent, adoption studies) suggest that genes are largely responsible for this familial aggregation. We review these studies, including the magnitude of familial risk and heritability estimates, efforts to identify familial subtypes of bipolar disorder, and the implications of family/genetic data for validating nosologic boundaries. Taken together, these studies indicate that bipolar disorder is phenotypically and genetically complex. © 2003 Wiley‐Liss, Inc.
The neurobiology of bipolar disorder
Authors: Berns Gregory S. , Nemeroff Charles B. 
Published: October 2003

AbstractThe neurobiology of bipolar disorder is reviewed. Bipolar disorder is associated with alterations in central nervous system (CNS) function from the level of large‐scale brain circuits to intracellular signal transduction mechanisms. Because of the broad spectrum over which these abnormalities appear, the causative effects are most likely present in the lowest common denominator of all of these systems. Current evidence points to subtle alterations in signal transduction that reverberate downstream both intra‐ and extracellularly to produce the symptoms of bipolar disorder. © 2003 Wiley‐Liss, Inc.
Fortschritte bei der Synthese anorganischer Nanoröhren und Fulleren‐artiger Nanopartikel
Authors: Tenne Reshef 
Published: October 2003

AbstractWie Graphit sind Nanopartikel aus anorganischen Verbindungen mit zweidimensionaler lamellarer Struktur wie MoS2 gegen Faltung instabil und können daher Nanoröhren und Fulleren‐artige Strukturen, auch anorganische Fullerene oder IFs genannt, liefern. Für solche Nanomaterialien wurde eine Reihe von Anwendungen vorgeschlagen. So ließen sich IF‐WS2‐Nanopartikel als festes Schmiermittel und als Teil tribologischer Oberflächen nutzen. Weitere Anwendungen von IFs für Fasern mit hoher Zugfestigkeit, als Wasserstoffspeicher, für wiederaufladbare Batterien, in der Katalyse und in der Nanotechnologie werden diskutiert. Dieser Kurzaufsatz beleuchtet einige der neuesten Entwicklungen bei der Synthese anorganischer Nanoröhren und Fulleren‐artiger Strukturen. Des Weiteren werden strukturelle Gesichtspunkte und Eigenschaften von IFs kurz diskutiert, in denen sie sich von den lamellaren Materialien als solchen unterscheiden.
Synthetic Expanded Porphyrin Chemistry
Authors: Sessler Jonathan L. , Seidel Daniel 
Published: October 2003

AbstractExpanded porphyrins are synthetic analogues of the porphyrins, and differ from these and other naturally occurring tetrapyrrolic macrocycles by containing a larger central core with a minimum of 17 atoms, while retaining the extended conjugation features that are a hallmark of these quintessential biological pigments. The result of core expansion is to produce systems with novel spectral and electronic features, interesting and, often unprecedented, cation‐coordination properties, and, in many cases, an ability to bind anions in certain protonation states. Also adding to the appeal of expanded porphyrins is their central role in addressing issues of aromaticity. In many cases, they also display structural features, such as decidedly nonplanar “figure‐eight” motifs, that have no antecedents in the chemistry of porphyrins or related macrocyclic compounds. In this Review, the various synthetic approaches now being employed to produce expanded porphyrins as well as their various applications‐related aspects are discussed.