bluuebunny/crossref_metadata_2025 huggingface dataset:
MORPHIX: Resolving sample identification bias in morphometrics analysis with a supervised machine learning package
Authors: Mohseni Nima , Elhaik Eran
Published: March 2024

Evolutionary biologists, primarily anatomists and ontogenists, employ modern geometric morphometrics to quantitatively analyse physical forms (e.g., skull morphology) and explore relationships, variations, and differences between samples and taxa using landmark coordinates. The standard approach comprises two steps, Generalised Procrustes Analysis (GPA) followed by Principal Component Analysis (PCA). PCA projects the superimposed data produced by GPA onto a set of uncorrelated variables, which can be visualised on scatterplots and used to draw phenetic, evolutionary, and ontogenetic conclusions. Recently, the use of PCA in genetic studies has been challenged. Due to PCA’s central role in morphometrics, we sought to evaluate the standard approach and claims based on PCA outcomes. To test PCA’s accuracy, robustness, and reproducibility using benchmark data of the crania of five papionin genera, we developed MORPHIX, a Python package containing the necessary tools for processing superimposed landmark data with classifier and outlier detection methods, which can be further visualised using various plots. We discuss the case of
Homo Nesher Ramla
, an archaic human with a questionable taxonomy. We found that PCA outcomes are artefacts of the input data and are neither reliable, robust, nor reproducible as field members may assume and that supervised machine learning classifiers are more accurate both for classification and detecting new taxa. Our findings raise concerns about PCA-based findings in 18,000 to 32,900 studies. Our work can be used to evaluate prior and novel claims concerning the origins and relatedness of inter- and intra-species and improve phylogenetic and taxonomic reconstructions.
Neural encoding of multiple motion speeds in visual cortical area MT
Authors: Huang Xin , Ghimire Bikalpa , Chakrala Anjani Sreeprada , Wiesner Steven
Published: March 2024

Segmenting objects from each other and their background is critical for vision. The speed at which objects move provides a salient cue for segmentation. However, how the visual system represents and differentiates multiple speeds is largely unknown. Here we investigated the neural encoding of multiple speeds of overlapping stimuli in the primate visual cortex. We first characterized the perceptual capacity of human and monkey subjects to segment spatially overlapping stimuli moving at different speeds. We then determined how neurons in the motion-sensitive, middle-temporal (MT) cortex of macaque monkeys encode multiple speeds. We made a novel finding that the responses of MT neurons to two speeds of overlapping stimuli showed a robust bias toward the faster speed component when both speeds were slow (≤ 20°/s). The faster-speed bias occurred even when a neuron had a slow preferred speed and responded more strongly to the slower component than the faster component when presented alone. The faster-speed bias emerged very early in neuronal response and was robust over time and to manipulations of motion direction and attention. As the stimulus speed increased, the faster-speed bias changed to response averaging. Our finding can be explained by a modified divisive normalization model, in which the weights for the speed components are proportional to the responses of a population of neurons elicited by the individual speeds. Our results suggest that the neuron population, referred to as the weighting pool, includes neurons that have a broad range of speed preferences. As a result, the response weights for the speed components are determined by the stimulus speeds and invariant to the speed preferences of individual neurons. Our findings help to define the neural encoding rule of multiple stimuli and provide new insight into the underlying neural mechanisms. The faster-speed bias would benefit behavioral tasks such as figure-ground segregation if figural objects tend to move faster than the background in the natural environment.
The Geometric Basis of Epithelial Convergent Extension
Authors: Brauns Fridtjof , Claussen Nikolas H. , Wieschaus Eric F. , Shraiman Boris I.
Published: March 2024

Shape changes of epithelia during animal development, such as convergent extension, are achieved through concerted mechanical activity of individual cells. While much is known about the corresponding large scale tissue flow and its genetic drivers, key open questions regard the cell-scale mechanics, e.g. internal vs external driving forces, and coordination, e.g. bottom-up self-organization vs top-down genetic instruction. To address these questions, we develop a quantitative, model-based analysis framework to relate cell geometry to local tension in recently obtained timelapse imaging data of gastrulating
Drosophila
embryos. This analysis provides a systematic decomposition of cell shape changes and T1–rearrangements into internally driven, active, and externally driven, passive, contributions. Specifically, we find evidence that germ band extension is driven by active T1 processes that self-organize through positive feedback acting on tensions. More generally, our findings suggest that epithelial convergent extension results from controlled transformation of internal force balance geometry which we quantify with a novel quantification tool for local tension configurations.
High-resolution awake mouse fMRI at 14 tesla
Authors: Hike David , Liu Xiaochen , Xie Zeping , Zhang Bei , Choi Sangcheon , Zhou Xiaoqing Alice , Liu Andy , Murstein Alyssa , Jiang Yuanyuan , Devor Anna , Yu Xin
Published: March 2024

High-resolution awake mouse functional magnetic resonance imaging (fMRI) remains challenging despite extensive efforts to address motion-induced artifacts and stress. This study introduces an implantable radio frequency (RF) surface coil design that minimizes image distortion caused by the air/tissue interface of mouse brains while simultaneously serving as a headpost for fixation during scanning. Furthermore, this study provides a thorough acclimation method used to accustom animals to the MRI environment minimizing motion-induced artifacts. Using a 14 T scanner, high-resolution fMRI enabled brain-wide functional mapping of visual and vibrissa stimulation at 100 µm×100 µm×200 µm resolution with a 2 s per frame sampling rate. Besides activated ascending visual and vibrissa pathways, robust blood oxygen level-dependent (BOLD) responses were detected in the anterior cingulate cortex upon visual stimulation and spread through the ventral retrosplenial area (VRA) with vibrissa air-puff stimulation, demonstrating higher-order sensory processing in association cortices of awake mice. In particular, the rapid hemodynamic responses in VRA upon vibrissa stimulation showed a strong correlation with the hippocampus, thalamus, and prefrontal cortical areas. Cross-correlation analysis with designated VRA responses revealed early positive BOLD signals at the contralateral barrel cortex (BC) occurring 2 s prior to the air-puff in awake mice with repetitive stimulation, which was not detected using a randomized stimulation paradigm. This early BC activation indicated a learned anticipation through the vibrissa system and association cortices in awake mice under continuous exposure of repetitive air-puff stimulation. This work establishes a high-resolution awake mouse fMRI platform, enabling brain-wide functional mapping of sensory signal processing in higher association cortical areas.
Root cap cell corpse clearance limits microbial colonization in Arabidopsis thaliana
Authors: Charura Nyasha , Llamas Ernesto , De Quattro Concetta , Vilchez David , Nowack Moritz K , Zuccaro Alga
Published: March 2024

Programmed cell death occurring during plant development (dPCD) is a fundamental process integral for plant growth and reproduction. Here, we investigate the connection between developmentally controlled PCD and fungal accommodation in Arabidopsis thaliana roots, focusing on the root cap-specific transcription factor ANAC033/SOMBRERO (SMB) and the senescence-associated nuclease BFN1. Mutations of both dPCD regulators increase colonization by the beneficial fungus Serendipita indica, primarily in the differentiation zone. smb-3 mutants additionally exhibit hypercolonization around the meristematic zone and a delay of S. indica-induced root-growth promotion. This demonstrates that root cap dPCD and rapid post-mortem clearance of cellular corpses represent a physical defense mechanism restricting microbial invasion of the root. Additionally, reporter lines and transcriptional analysis revealed that BFN1 expression is downregulated during S. indica colonization in mature root epidermal cells, suggesting a transcriptional control mechanism that facilitates the accommodation of beneficial microbes in the roots.
Differential functions of the dorsal and intermediate regions of the hippocampus for optimal goal-directed navigation in VR space
Authors: Hwang Hyeri , Jin Seung-Woo , Lee Inah
Published: March 2024

Goal-directed navigation requires the hippocampus to process spatial information in a value-dependent manner, but its underlying mechanism needs to be better understood. Here, we investigated whether the dorsal (dHP) and intermediate (iHP) regions of the hippocampus differentially function in processing place and its associated value information. Rats were trained in a place-preference task involving reward zones with different values in a visually rich virtual reality environment where two-dimensional navigation was possible. Rats learned to use distal visual scenes effectively to navigate to the reward zone associated with a higher reward. Inactivation of both dHP and iHP with muscimol altered the efficiency and precision of wayfinding behavior, but iHP inactivation induced more severe damage, including impaired place preference. Our findings suggest that the iHP is more critical for value-dependent navigation toward higher-value goal locations.
Introduction
Authors:   Department of Folkloristics, Estonian Literary Museum, Estonia, Anisimov Nikolai
Published: March 2024

The idea for this publication was born in 2021, when I discovered that Maria Pavlovna Nikonova, from my own village, in addition to her many well-known talents (she has in- knowledge of depth traditional rituals and customs, sings folk songs very well, and we could pursue the list of her achievements), kept a diary of her observations, of her emotions and of the events around her. As I am a folklorist, and of course, her fellow villager, it was extraordinarily interesting and valuable, a unique phenomenon in the Udmurt traditional culture.
scAnnoX: an R package integrating multiple public tools for single-cell annotation
Authors: Huang Xiaoqian , Liu Ruiqi , Yang Shiwei , Chen Xiaozhou , Li Huamei
Published: March 2024

Background

Single-cell annotation plays a crucial role in the analysis of single-cell genomics data. Despite the existence of numerous single-cell annotation algorithms, a comprehensive tool for integrating and comparing these algorithms is also lacking.

Methods

This study meticulously investigated a plethora of widely adopted single-cell annotation algorithms. Ten single-cell annotation algorithms were selected based on the classification of either reference dataset-dependent or marker gene-dependent approaches. These algorithms included SingleR, Seurat, sciBet, scmap, CHETAH, scSorter, sc.type, cellID, scCATCH, and SCINA. Building upon these algorithms, we developed an R package named scAnnoX for the integration and comparative analysis of single-cell annotation algorithms.

Results

The development of the scAnnoX software package provides a cohesive framework for annotating cells in scRNA-seq data, enabling researchers to more efficiently perform comparative analyses among the cell type annotations contained in scRNA-seq datasets. The integrated environment of scAnnoX streamlines the testing, evaluation, and comparison processes among various algorithms. Among the ten annotation tools evaluated, SingleR, Seurat, sciBet, and scSorter emerged as top-performing algorithms in terms of prediction accuracy, with SingleR and sciBet demonstrating particularly superior performance, offering guidance for users. Interested parties can access the scAnnoX package at https://github.com/XQ-hub/scAnnoX.
Lasers, Industrial Use of
Authors: Roessler David M. , Steen Wiliam M.
Published: August 2007

Lasers are capable of generating large and controllable quantities of optical energy and delivering it at intensities sufficient to produce permanent changes in materials. This new form of industrial energy has led to a wide range of laser‐based manufacturing processes, such as cutting, welding, surface treatment, bending, cleaning, rapid prototyping, direct casting, and so on. Although these form the focus of this section, it must be noted that there are many other industrial applications that are not covered here, ranging from communications and compact disc players to medicine and metrology. Although laser‐materials processing has developed and grown rapidly in the last few decades, it is still far from being a mature technology. New lasers continue to be developed as do new applications.
Atmospheric Optics
Authors: Bohren Craig F.
Published: August 2007

Colors of the sky and colored displays in the sky are mostly a consequence of selective scattering by molecules or particles, absorption usually being irrelevant. Molecular scattering selective by wavelength—incident sunlight of some wavelengths being scattered more than others—but the same in any direction at all wavelengths gives rise to the blue of the sky and the red of sunsets and sunrises. Scattering by particles selective by direction—different in different directions at a given wavelength—gives rise to rainbows, coronas, iridescent clouds, the glory, sun dogs, halos, and other ice‐crystal displays. The size distribution of these particles and their shapes determine what is observed, water droplets and ice crystals, for example, resulting in distinct displays.

To understand the variation and color and brightness of the sky as well as the brightness of clouds requires coming to grips with multiple scattering: scatterers in an ensemble are illuminated by incident sunlight and by the scattered light from each other. The optical properties of an ensemble are not necessarily those of its individual members.

Mirages are a consequence of the spatial variation of coherent scattering (refraction) by air molecules, whereas the green flash owes its existence to both coherent scattering by molecules and incoherent scattering by molecules and particles.
Charged‐particle Optics
Authors: Nolen Jerry A. , Portillo Mauricio
Published: August 2007

The emphasis of this article is on the common fundamentals and techniques on which the wide variety of different beam‐optical devices are based. It should give the reader the necessary background to understand the principles of the actual devices described elsewhere in more advanced treatments. Along with the qualitative description of the basic building blocks of charged particle beam optics, enough selected references to monographs and research reports are given to guide the interested reader towards more in‐depth studies. Relatively few references to original research papers are given, but extensive bibliographies are included in the listed review articles and textbooks. Topics introduced include: single‐particle motion of charged particles in electric and magnetic fields, sources of charged particles, beam handling and transport, magnetic and electric deflection systems, aberrations of charged particle optical systems, and the mathematics of matrix methods for charged particle optical simulation.
Data Storage, Optical
Authors: Milster Tom D.
Published: August 2007

In its most general definition, optical data storage is simply using light as a tool to store and retrieve data. Optical data storage is found in popular consumer products. Compact Discs (CDs), Digital Versatile Discs (DVDs), and MiniDiscs (MDs), are all forms of optical data storage. More advanced forms of optical data storage include high‐speed devices and library products. All optical data storage devices use optical principles to achieve high data density, rugged packaging, reliable information retrieval, and cost‐effective production. There are many forms of optical storage media and many types of optical systems used to scan data. This chapter discusses the basic principles of optical data storage, types of commercial optical media available in 2003, several performance parameters, and some interesting prospects for future systems.
Electromagnetic Radiation: Emission and Propagation
Authors: Ford George W.
Published: August 2007

The basic phenomena of classical electromagnetic radiation are described. After a brief introduction of the equations of Maxwell and Lorentz for electromagnetism in vacuum, the general theory of integration of these equations is discussed. Applications include the Larmor formula for radiation by a Hertzian dipole, radiation by a confined source, multipole radiation, radiation by an arbitrarily moving point charge, synchrotron radiation, and radiation reaction. The Maxwell equations of electromagnetism in the presence of matter are then introduced together with a brief discussion of their integration. Waves in isotropic and anisotropic material media are described together with their propagation in layered media and waveguides. Applications include radiation by a dipole above a half‐space, Cherenkov radiation, and energy loss by charged particles traversing matter.
Electro‐optic Imaging
Authors: Kürbitz Gunther
Published: August 2007

This article deals with electro‐optical means to see in nonvisible spectral regions and at very low light levels and to produce visible imagery. The wavelength regions covered range from UV (200 nm to 400 nm) to the thermal IR (8 µm to 14 µm). The visible spectrum band from 350 nm to 750 nm is covered only insofar, as very low light levels are concerned, that is, the use of image‐intensifier systems is required. For every waveband, the physical properties of the scene and the atmosphere as well as the corresponding technologies to transform the scene under consideration into a visible representation are described. That includes optics, detectors, and cooling systems (if required). Performance parameters for the systems are described as far as available.
Ellipsometry
Authors: Collins Robert W.
Published: August 2007

Ellipsometry is an optical measurement technique that involves generating a monochromatic or quasimonochromatic light beam in a known polarization state and reflecting it from a sample having a planar, specularly reflecting surface. By measuring the polarization state of the reflected beam, the ellipsometric angles (ψ, Δ) can be determined, and upon detailed analysis, these angles yield information about the sample. Such information includes the optical properties, that is, the index of refraction and extinction coefficient, for a bulk sample or the thickness and optical properties for one or more thin films on the sample surface having plane‐parallel interfaces. For an isotropic sample, the angles (ψ, Δ) are defined by tanψexp(iΔ) = rp/rs, whererpandrsare the complex amplitude reflection coefficients for linear p and s polarization states, for which the electric field vibrates parallel and perpendicular to the plane of incidence, respectively. Several variations of the ellipsometry experiment have been developed. In spectroscopic ellipsometry (SE), (ψ, Δ) are measured continuously versus the wavelength of the light beam, and in real‐time ellipsometry (RT‐E), (ψ, Δ) are measured continuously versus time at fixed wavelength. The latter two modes can be combined to yield real‐time SE (RT‐SE), utilizing an instrument with a linear photodiode array for parallel detection at many wavelengths simultaneously. In imaging ellipsometry (IE), (ψ, Δ) are measured over a two‐dimensional (2‐D) area of a nonuniform sample surface using an instrument with a 2‐D charge‐coupled device (CCD) as the detection system. The most widely used instruments for SE and RT‐SE span the spectral range from the ultraviolet (200–300 nm) to the near infrared (800 nm). Over this spectral range, the optical properties deduced from SE provide information on the processes of absorption and dispersion originating from the valence electrons in semiconductors and dielectrics and from the conduction electrons in metals. Specialized SE equipment designed for the infrared range can be more effective for chemical identification of thin films, based on the absorption processes originating from the vibrational modes of chemical bonds.
Filters, Optical
Authors: Dobrowolski J.A.
Published: August 2007

This article reviews the performance of optical filters for the 0.005 to 1000 µm spectral region. The filters described operate in transmitted or reflected light and are intended for use in free‐space optics. The theory of two or more filters placed in series or in parallel is presented. The effect of surface reflections on the performance of the filters is discussed. Optical filters can be based on many different physical principles. Brief explanations are given of the modes of operation of filters based on absorption, reflection, interference in thin films, holography, scattering, diffraction, and interference of polarized light. The principal advantages and disadvantages of filters based on these phenomena are discussed. Filters can also be classified according to the functions that they are intended to perform. In this article the following generic filter types are considered: antireflection coatings, neutral attenuators, narrow band, medium‐band and wideband reflectors, short‐ and long‐wavelength cutoff filters, narrowband transmission filters, rejection filters, neutral‐ and color‐selective beam splitters and correction or gain flattening filters. For each of the above filter types, spectral transmittance or reflectance curves are presented that correspond to representative filters based on a number of the above‐mentioned physical principles. Information is provided on how to specify the performance of the various filter types.
Holography
Authors: Leith Emmett N.
Published: August 2007

Holography, a method of photography that produces highly realistic images, fully three‐dimensional, with the normal parallax relations of the actual object, is described. Basics of the theory are presented from both a mathematical and a physical viewpoint. Various areas of application are given, including three‐dimensional displays, complex spatial filtering, hologram interferometry for nondestructive testing and metrology, product authentication and counterfeiting security, holographic optical elements, and imaging through inhomogeneities using holographic phase conjugation. The various forms of white light viewable holograms are described, including the Denisyuk or volume type, the Benton or rainbow type, and the integral type. The diffractive properties of holograms are analyzed, including Bragg diffraction, i.e., diffraction from a volume hologram. The construction of commercial display holograms is discussed. The present state of commercial and artistic holography is discussed, along with expected future developments.
Information Processing, Optical
Authors: Javidi Bahram , Horner Joseph L.
Published: August 2007

This article presents a brief review of the fundamentals of optical information processing. We discuss optical information processing techniques, materials and devices for optical processing, optical pattern recognition, optical security, optical neural computing, and optical memory. Optical image processing algorithms and architectures as well as basic hardware concepts such as the fundamentals of optical spatial light modulators are reviewed.
Interconnections, Optical
Authors: Matsumoto Takao , Trewhella Jean
Published: August 2007

Although progress has been made in optical interconnections, electrical interconnections continue to dominate most of the hierarchical interconnect layers that comprise computer systems. (The delay in the industry's move to optics is largely due to the continued improvements in electrical links, most notably the addition of equalization schemes [1].) The challenges faced by electrical interconnections [2] are described along with a presentation of the potential benefits optical interconnections afford. Commercial success for optical interconnections has largely been in rack‐to‐rack links, where the distances are great enough to require the low loss advantages of optical transmission. Further work on optical schemes for each layer of interconnection hierarchy, rack to rack, board to board, and intraboard is presented. These schemes can be broken into two general types of guided wave solutions that use fibers or waveguides as transmission media and free‐space solutions, which require only the optical elements. Advantages and examples of links using each type are described. It is shown that free‐space optical interconnections board to board can reduce wiring congestion dramatically over electrical or guided wave approaches, which force all interconnections to pass between the boards through the backplane. The density achievable can be further improved by employing 3D interconnection arrangements which are discussed in the intraboard examples. Optical interconnection will gradually penetrate from the outer levels of the systems to the inner as the technology matures, but all of these interesting possibilities will remain possibilities unless future areas of study include focus on low cost, small size for high density and high reliability of optical interconnections and devices.
Lasers, Semiconductor
Authors: Ogasawara Nagaatsu , Ito Ryoichi
Published: August 2007

Following a brief history of semiconductor lasers, this article describes their operation principles in relation to their device structures and materials. Their fundamental operation characteristics, including the static, spectral, and dynamic aspects, are then presented. Finally, the current state of the art in semiconductor laser technology is described by reviewing up‐to‐date devices incorporating new structures and new functions.
Light and Lighting Systems
Authors: Bullough John D. , Rea Mark S.
Published: August 2007

Lighting is the application of visually effective optical radiation. This chapter provides the reader with some basic information about lighting terminology and technologies (lamps, ballasts, luminaires, and controls), and the results of recent research on the effective use of lighting. This article supplements the articles on
COLOR VISION
;
COLORIMETRY
;
OPTICAL RADIATION SOURCES AND STANDARDS
; and
PHYSIOLOGICAL OPTICS
.
Monochromators
Authors: Margaritondo Giorgio , Staehli Jean‐Louis
Published: August 2007

An overview on monochromators for electromagnetic radiation is presented. Instruments working in the infrared, visible, and ultraviolet spectral regions and for soft and hard X rays are briefly described, starting from the fundamental concepts and definitions. The major advantages, difficulties, and limits of the different designs are mentioned. An important part of the article is devoted to the very widely used grating monochromators.
Motion Picture and Video Lenses
Authors: Hope Thomas W. , Laikin Milton
Published: August 2007

The origin of the motion picture lens is traced to the modern state of the art. Motion picture camera lenses of all types are detailed with schematics. Image formation, effective focal length, photometry, depth of field, image aberrations, antireflection, stray‐light reduction, and camera formats are explained. Projection lenses are examined by prime and anamorphic lenses with details of wide‐screen systems. Video camera lenses and types are studied by the following, commercial and consumer plus projectors from consumer to high‐end. The article concludes with video conferencing and security/surveillance camera lenses.
Nonlinear Optics
Authors: Flytzanis Christos
Published: August 2007

We present an unified overview and classification of the main nonlinear optical effects and the underlying nonlinear optical interactions. The physical origin of these effects is analyzed and related to material features and their behavior, their characteristics and efficiency are discussed in terms of the nonlinear propagation equations. Some aspects related to nonlinear optical materials and devices are presented and connections with quantum optics, nonlinear spectroscopy and optoelectronics are stressed.
Optical Coatings
Authors: Macleod Angus
Published: August 2007

Optical coatings consist of thin uniform layers of material over a surface. Interference effects combine with the intrinsic properties of the materials to modify the specular properties of the surface without altering its power. Antireflection coatings reduce reflection losses, high‐reflectance coatings increase the reflectance, others divide or combine light beams perhaps according to their wavelength or direction, some are purely decorative, and there are many others of different types.
Optical Components and Systems
Authors: Litfin Gerd , Schuhmann Rainer
Published: August 2007

This article gives an overview of geometrical optics and includes the most important formulas as well as a few optical systems of general interest.

It describes the main optical components such as lenses, mirrors, plane plates, prisms, fibers, and thin films and their influence on light beams as light propagation and polarization. The principles of reflection and refraction are discussed as well as the optical imaging based on first‐order optics. The basic formulas are given.

The discussion on plano‐optics considers the spectral properties of filters and prisms, the change of image orientation by a single prism and prism systems, beam splitting, and polarization effects due to birefringence of crystal components. Total internal reflection can guide light in optical fibers. Different fiber types are described.

Besides single components as best‐form lenses and doublets, only multielement optical systems can meet the requirements of different imaging applications. Therefore, a selection of well‐known optical systems considering their main properties is described. This includes camera lenses, microscopes, and more sophisticated optical systems as well as a short side‐glance on the requirements of interferometers that cannot be described by the geometrical optics approach.

Furthermore, a section on optical bench systems summarizes the necessary support of optics by mechanical components. This includes bench profiles and structural systems using the micro bench.
Optical Instrumentation
Authors: Hoeschen Dietmar , Mirandé Werner
Published: August 2007

Optical instrumentation is based on phenomena caused by optical radiation. In this article, optical radiation is limited to a wavelength range between 200 nm and 50 µm. After a short survey about the historical development of optical instrumentation, phenomena resulting from the various characteristics of optical radiation, as for instance, a wave or a particle, are considered. Based on the wavelength character, optical instrumentation used for interferometry, colorimetry, spectroscopy, diffraction, imaging, and optical frequency standards is treated. The interaction of optical radiation with matter is used in refractometry, in polarimetry, for studying matter with ultrashort pulses of radiation, and for processing matter with radiation of high‐energy density. Finally, the particle character is considered to be used for fields such as radiometry and energy conversion.
Optical Radiation Sources and Standards
Authors: Diedrich Jonathan , Dodds John
Published: August 2007

Artificial visible and near‐visible electromagnetic radiation is produced and characterized in several different ways. From incandescent light bulbs and gas‐discharge lamps to LEDs and lasers, light sources have been evolving for years. This chapter describes the various ways that light is produced as well as standardized. The first section discusses some of the different types of sources of radiation. Illustrated along with the different sources are examples of their uses. With all these sources, standardization and calibration are very important. The second section will discuss how, along with improved technology, the methods and procedures used to realize standards have evolved. Discussed is the evolution of radiation standards leading to the current method of realizing them. In addition, we discuss the methods used to calibrate optical devices using these standards.
Photochemistry
Authors: Stevenson Kenneth L. , Horváth Ottó
Published: August 2007

This article presents a systematic introduction to theoretical and experimental aspects of photochemistry, along with typical examples and applications. It gives a survey of photochemical laws and fundamental principles of photophysics and photochemistry, including multiphoton processes that occur at high light intensity laser irradiation. Descriptions of experimental techniques are given for both continuous irradiation and flash photolysis, including laser spectroscopy and femtochemistry. Detailed discussions of the important theories and representative reactions in the photochemistry of organic, inorganic, and coordination compounds are also presented. Finally, some of the more significant roles photochemistry plays in nature and in modern life, such as photosynthesis, information storage, and phototherapy, are briefly introduced.
Photography, Digital
Authors: Kriss Michael A.
Published: August 2007

Digital photography, with the advent of reasonably priced mega‐pixel digital cameras and high quality inkjet printers, is starting to challenge conventional, silver halide based imaging systems in the profitable consumer markets. This article is designed to provide a systematic review of all the technologies required to support digital photography. The digital imaging chain provides the flow and structure for reviewing the important imaging technologies including camera optics, imaging sensors and architectures, sensor speed, color reproduction, compression, image processing and digital hardcopy. In addition to the evaluation of individual imaging technologies, a systematic, system‐wide image quality assessment is provided that takes into account image quality (sharpness) and the most common image artifacts associated with digital photography.
Photonics
Authors: King Terence A.
Published: August 2007

Photonics concerns the generation, transmission, manipulation, and interactions of light and its applications in many varied areas in research, industry, and everyday life. This general overview of photonics draws special attention to the development of laser sources, semiconductor optics, fiber optics, and photonic techniques such as ultrafast pulse generation. The wide range of applications is reviewed with particular attention to information technology and optical communications, optical information storage, displays, sensors, and industrial applications. The rapidly growing field of applications in biophotonics and biomedical optics is also emphasized with new techniques of optical coherence tomography (OCT) and optical trapping.
Sensors, Optical
Authors: Haus Jörg , Schaefer Roland
Published: August 2007

In terms of dynamic range and noise, optical sensors have great advantages over their electronic or mechanical counterparts. In addition, the noncontact nature of all optical measurements avoids influences of the sensor on the measured value and, thus, measurement‐introduced systematic errors. This article gives an introduction to the components found in all kinds of optical sensors: light sources, detectors, and optical elements. On the basis of this optoelectronic toolbox, sensors for the measurement of various physical and chemical quantities are described.
Spectroscopy, Laser
Authors: Inguscio Massimo , Sasso Antonio
Published: August 2007

The high intensity, high spectral purity, and short‐pulse duration of laser sources have opened a new era in laser spectroscopy. Many sophisticated spectroscopic techniques have been developed during the last decades. They have allowed the investigation of the structure of atoms and molecules with great detail, making it possible to test fundamental quantum mechanics theories. Moreover, laser spectroscopy represents a very diffused tool in many other fields. A wide range of applications concern not only free atoms and molecules but also plasma physics and solid‐state physics and many other interdisciplinary fields such as chemistry, biology, and medicine. Laser spectroscopy is till now a very fascinating field of research continuously in evolution: the new techniques of laser cooling have allowed the production of condensates of atoms that represent a new state of the matter only recently explored.
Spectroscopy, Photoacoustic
Authors: Harren Frans J. M. , Laarhoven Lucas J. J.
Published: August 2007

After a short introduction and description of particular features of the equipment used, attention is centered on applications. Solids, surfaces, and solutions have been studied by photoacoustic spectroscopy; recent work is quoted. Gas‐phase investigations are discussed with emphasis on trace gas detection. Especially, applications in plant physiology and microbiology are considered.
Spectroscopy,Raman
Authors: Edwards Howell G. M.
Published: August 2007

This article describes the origins of Raman scattering and the important parameters upon which its application depends, in particular, its dependence upon molecular species concentration, molecular and crystal orientation, polarizability changes, and the wavelength and power densities of the laser excitation. The instrumentation used to record Raman spectra from the ultraviolet to the near‐infrared regions of the electromagnetic spectrum and the minimization of sample fluorescence is reviewed. Finally, some current applications of Raman spectroscopy to the characterization of materials are highlighted in the fields of biomedical diagnostics, archaeological science, art history, industrial process control, environmental science, and astrobiology. The interdisciplinarity of modern Raman‐spectroscopic technique applications is illustrated by the efforts now being made in the miniaturization of Raman spectrometers for planetary exploration as part of instrumentation suites on robotic landers—projects that bring together teams of chemists, applied spectroscopists, biologists, physicists, astronomers, space scientists, and astrobiologists.
Stereoscopy
Authors: Claus Michael , Knupfer Klaus
Published: August 2007

This article covers the principles of stereoscopic imaging and measurements. It explains stereoscopic image‐generation techniques and the available methods of stereoimage display. 3D measurements in stereoimages and the related mathematics are explained, together with required hardware equipment and software. The generation of products such as digital elevation models, orthophotos and semiautomatic produced maps, resulting from the 3D measurements, is explained.
Nanoparticle Coating for Advanced Optical, Mechanical and Rheological Properties
Authors: Hakim L. F. , King D. M. , Zhou Y. , Gump C. J. , George S. M. , Weimer A. W.
Published: August 2007

Primary titania nanoparticles were coated with ultrathin alumina films using Atomic Layer Deposition (ALD). The deposited films were highly uniform and conformal with an average growth rate of 0.2 nm per coating cycle. The alumina films eliminated the surface photocatalytic activity of titania nanoparticles, while maintained their original extinction efficiency of ultraviolet light. Deposited films provided a physical barrier that effectively prevented the titania surface from oxidizing organic material whereas conserving its bulk optical properties. Parts fabricated from coated powders by pressureless sintering had a 13 % increase in surface hardness over parts similarly fabricated from uncoated particles. Owing to its homogeneous distribution, the secondary alumina phase suppressed excessive grain growth. Alumina films completely reacted during sintering to form aluminum titanate composites, as verified by XRD. Coated particles showed a pseudoplastic behavior at low shear rates due to modified colloidal forces. This behavior became similar to the Newtonian flow of uncoated nanoparticle slurries as the shear rate increased. Suspensions of coated particles also showed a decreased viscosity relative to the viscosity of uncoated particle suspensions.
Organic Thin‐Film Photovoltaic Cells Based on Oligothiophenes with Reduced Bandgap
Authors: Uhrich C. , Schueppel R. , Petrich A. , Pfeiffer M. , Leo K. , Brier E. , Kilickiran P. , Baeuerle P.
Published: August 2007

The best polymeric solar cells reported so far are based on a so‐called bulk heterojunction of a polythiophene as donor and a soluble fullerene derivative as acceptor. However, these cells still suffer from an unsatisfying photovoltage, typically below 0.7 V. Here, we show that we can achieve higher photovoltages using a new terthiophene end‐capped with electron withdrawing dicyanovinyl groups (DCV3T) that increase both the ionization energy and even more strongly the electron affinity of the compound. The new material is tested in cells using a photoactive heterojunction to separate the excitons generated in the oligomer and a p‐doped wide‐gap transport layer. The solar cells show an open circuit voltage of up to 1.04 V and a broad spectral sensitivity band ranging from 420 nm to 650 nm. Solar cells based on such oligothiophenes are promising candidates for stacked organic solar cells tailored to the sun‐spectrum. Moreover, we present first examples of a new concept for organic solar cells: By blending DCV3T with fullerene C60, an enhanced generation of triplet excitons on the oligomer can be achieved via a back and forth transfer of excitons (ping‐pong‐effect).
Facile Synthesis of Nanostructured Carbon through Self‐Assembly between Block Copolymers and Carbohydrates
Authors: Rodriguez A. T. , Li X. , Wang J. , Steen W. A. , Fan H.
Published: August 2007

A simple and direct wet chemistry method is reported to simultaneously synthesize nanostructured carbon films and particles through self‐assembly of poly(styrene)‐poly(4‐vinylpyridine) (PS‐P4VP) and carbohydrate precursors (turanose, raffinose, glucose, etc.) in two fabrication processes—spin‐coating and aerosol processing. Starting with a homogeneous solution containing PS‐P4VP and carbohydrates, evaporation of solvent during either spin‐coating or an aerosol process leads to the formation of ordered mesostructured films and particles. High temperature treatment in argon atmosphere removes PS fragments, carbonizes carbohydrates and partial PVP fragments, and results in ordered nanoporous carbon films and particles. SEM, TEM, and GISAXS characterization indicates that these nanostructured carbon materials exhibit large nanopores (> 20 nm), controlled 1–3 dimensional structures, and controlled surface chemistry. Nitrogen sorption isotherms and electrochemistry characterization indicates the accessibility of the carbon nanopores to both gas phase and aqueous phase. Results suggest that the nanostructured carbon films and particles can be tuned through solvent annealing, precursor concentration, and choice of block copolymers used. These carbon materials present varied practical applications for sorption and separation, sensors, electrode materials, etc.
Towards an Understanding of Nanoparticle–Chiral Nematic Liquid Crystal Co‐Assembly
Authors: Payne J. C. , Thomas E. L.
Published: August 2007

The fabrication of a one‐dimensional photonic crystal without time‐reversal and space‐inversion symmetries was pursued. Theoretical studies predict that such a system would exhibit unusual optical properties, including indirect photonic bandgaps and backward wave propagating eigenmodes. Such a system can be created experimentally by combing magnetooptical nanoparticles with a chiral nematic liquid crystal. The manner in which nanoparticles co‐assemble with a chiral nematic liquid crystal was investigated. It was determined that the addition of nanoparticles to a 5CB‐COC system disrupts the system's helical structure. This disruption lowers the system's phase transition temperatures and inhibits the system's ability to form reflectivity peaks.
Solvent Dependent Shape and Magnetic Properties of Doped ZnO Nanostructures
Authors: Clavel G. , Willinger M.‐G. , Zitoun D. , Pinna N.
Published: August 2007

This study reports on a new solution phase synthesis leading to cobalt and manganese doped ZnO which have been theoretically predicted ferromagnetic at room temperature. The solvothermal synthesis involving the reaction of zinc and cobalt acetate or manganese oleate with benzyl alcohol leads to pure inorganic nanoparticles that are diluted magnetic semiconductors. The addition of an inert solvent, that is used in order to control the amount of benzyl alcohol, drastically influences the particles morphology and strongly affects the magnetic behaviors. Cobalt doped particles are paramagnetic or ferromagnetic depending on the synthesis conditions. In order to exclude the formation of secondary phases and/or metal clusters and to understand the role of the solvent on the magnetic properties, the local structure of Co2+ and Mn2+ in the wurtzite ZnO matrix were characterized by XRD, UV‐visible diffuse reflectance and electron paramagnetic resonance.
Printable All‐Organic Electrochromic Active‐Matrix Displays
Authors: Andersson P. , Forchheimer R. , Tehrani P. , Berggren M.
Published: August 2007

All‐organic active matrix addressed displays based on electrochemical smart pixels made on flexible substrates are reported. Each individual smart pixel device combines an electrochemical transistor with an electrochromic display cell, thus resulting in a low‐voltage operating and robust display technology. Poly(3,4‐ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) served as the active material in the electrochemical smart pixels, as well as the conducting lines, of the monolithically integrated active‐matrix display. Different active‐matrix display addressing schemes have been investigated and a matrix display fill factor of 65 % was reached. This is achieved by combining a three‐terminal electrochemical transistor with an electrochromic display cell architecture, in which an additional layer of PEDOT:PSS was placed on top of the display cell counter electrode. In addition, we have evaluated different kinds of electrochromic polymer materials aiming at reaching a high color switch contrast. This work has been carried out in the light of achieving a robust display technology that is easily manufactured using a standard label printing press, which forced us to use the fewest different materials as well as avoiding exotic and complex device architectures. Together, this yields a manufacturing process of only five discrete patterning steps, which in turn promise for that the active matrix addressed displays can be manufactured on paper or plastic substrates in a roll‐to‐roll production procedure.
Efficient Deep‐Blue Organic Light‐Emitting Diodes: Arylamine‐Substituted Oligofluorenes
Authors: Gao Z. Q. , Li Z. H. , Xia P. F. , Wong M. S. , Cheah K. W. , Chen C. H.
Published: August 2007

Novel deep‐blue‐light‐emitting diphenylamino and triphenylamino end‐capped oligofluorenes were synthesized by double palladium‐catalyzed Suzuki cross‐coupling of dibromo‐oligofluorene with the corresponding boronic acid as a key step. These oligofluorenes exhibit deep‐blue emission (λemmax = 429–432 nm), low and reversible electrochemical oxidation (highest occupied molecular orbital = 5.15–5.20 eV), high fluorescence quantum yield (ΦFL = 0.61–0.93), and good thermal properties (glass‐transition temperature, Tg = 99–195 °C and decomposition temperature, Tdec > 450 °C). Remarkably, saturated deep‐blue organic light‐emitting diodes, made from these oligofluorenes as dopant emitters, have been achieved with excellent performance and maximum efficiencies up to 2.9 cd A–1 at 2 mA cm–2 (external quantum efficiency of 4.1 %) and with Commission Internationale de l'Éclairage (x,y) coordinates of (0.152,0.08), which is very close to the National Television System Committee standard blue.