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Near-infrared spectroscopy (NIRS) is an emerging diffuse optical imaging tool with both clinical and academic applications such as functional brain imaging, breast cancer detection, and cerebral health monitoring. Due to its non-invasiveness, high spatial and temporal resolution, and portability, it has been rapidly growing in popularity over the last 40 years. The technique relies on near-infrared light to measure optical properties { scattering and absorption { which can then be used to infer details of the underlying tissue physiology. Diffuse correlation spectroscopy (DCS) is a complimentary optical technique that relies on long-coherence laser light, also in the near-infrared range, to measure dynamical properties of a medium { in the biomedical context, blood ow. While NIRS and DCS can be used in conjunction to provide even more powerful information, they require separate instrumentation, resulting in reduced portability and difficulty in bedside monitoring. In brain imaging applications, both NIRS and DCS suer from confounds due to layers surrounding the brain, such as the scalp and skull. While this issue has been addressed in NIRS using time-resolved instrumentation known as time-domain (TD) NIRS, it has been largely ignored in the context of DCS. In this work, we demonstrate a novel time-domain diffuse correlation spectroscopy (TD-DCS) technique embodied in a single instrument capable of simultaneously measuring optical and dynamical properties. Along with maintaining portability, the instrument reduces error by directly measuring the absorption and scattering values necessary for precise ow estimation, and removes a major confounding factor by suppressing unwanted signal from superficial layers through time-gating. We describe the construction of the first instrument prototype and demonstrate the depth resolution proof-of-concept with measurements of multi-layer media. We further discuss the theoretical considerations of modeling the light interaction with tissue, necessary for reliable estimates.
The proliferation of harmful phytoplankton in marine ecosystems can cause massive fish kills, contaminate seafood with toxins, impact local and regional economies and dramatically affect ecological balance. Real-time observations are essential for effective short-term operational forecasting, but observation and modelling systems are still being developed. This volume provides guidance for developing real-time and near real-time sensing systems for observing and predicting plankton dynamics, including harmful algal blooms, in coastal waters. The underlying theory is explained and current trends in research and monitoring are discussed.Topics covered include: coastal ecosystems and dynamics of harmful algal blooms; theory and practical applications of in situ and remotely sensed optical detection of microalgal distributions and composition; theory and practical applications of in situ biological and chemical sensors for targeted species and toxin detection; integrated observing systems and platforms for detection; diagnostic and predictive modelling of ecosystems and harmful algal blooms, including data assimilation techniques; observational needs for the public and government; and future directions for research and operations.
Time-correlated Single Photon Counting has been written in the hope that by relating the authors' experiences with a variety of different single photon counting systems, they may provide a useful service to users and potential users of this formidably sensitive technique. Of all the techniques available to obtain information on the rates of depopulation of excited electronic singlet states of molecular species, monitoring of fluorescence provides, in principle, the simplest and most direct measure of concentration. This volume comprises eight chapters, with the first focusing on the time dependence and applications of fluorescence. Succeeding chapters go on to discuss basic principles of the single photon counting lifetime measurement; light sources; photomultipliers; electronics; data analysis; nanosecond time-resolved emission spectroscopy; time dependence of fluorescence anisotropy. This book will be of interest to practitioners in the field of chemistry.
"This book is about Broadband Dielectric Spectroscopy as a Modern Analytical Technique"--
This comprehensive and topical volume presents a number of significant advances on many fronts in this area of research, particularly emphasizing current and future biomedical applications of electromagnetic fields.
The document is a tutorial Monograph describing various aspects of time and frequency (T/F). Included are chapters relating to elemental concepts of precise time and frequency; basic principles of quartz oscillators and atomic frequency standards; historical review, recent progress, and current status of atomic frequency standards; promising areas for developing future primary frequency standards; relevance of frequency standards to other areas of metrology including a unified standard concept; statistics of T/F data analysis coupled with the theory and construction of the NBS atomic time scale; an overview of T/F dissemination techniques; and the standards of T/F in the USA. The Monograph addresses both the specialist in the field as well as those desiring basic information about time and frequency. The authors trace the development and scope of T/F technology, its improvement over periods of decades, its status today, and its possible use, applications, and development in days to come.
Fluorescence methods are being used increasingly in biochemical, medical, and chemical research. This is because of the inherent sensitivity of this technique. and the favorable time scale of the phenomenon of fluorescence. 8 Fluorescence emission occurs about 10- sec (10 nsec) after light absorp tion. During this period of time a wide range of molecular processes can occur, and these can effect the spectral characteristics of the fluorescent compound. This combination of sensitivity and a favorable time scale allows fluorescence methods to be generally useful for studies of proteins and membranes and their interactions with other macromolecules. This book describes the fundamental aspects of fluorescence. and the biochemical applications of this methodology. Each chapter starts with the -theoreticalbasis of each phenomenon of fluorescence, followed by examples which illustrate the use of the phenomenon in the study of biochemical problems. The book contains numerous figures. It is felt that such graphical presentations contribute to pleasurable reading and increased understand ing. Separate chapters are devoted to fluorescence polarization, lifetimes, quenching, energy transfer, solvent effects, and excited state reactions. To enhance the usefulness of this work as a textbook, problems are included which illustrate the concepts described in each chapter. Furthermore, a separate chapter is devoted to the instrumentation used in fluorescence spectroscopy. This chapter will be especially valuable for those perform ing or contemplating fluorescence measurements. Such measurements are easily compromised by failure to consider a number of simple principles.
This text begins by describing the basic principles and diagnostic applications of optical techniques based on detecting and processing the scattering, fluorescence, FT IR, and Raman spectroscopic signals from various tissues, with an emphasis on blood, epithelial tissues, and human skin. The second half of the volume discusses specific imaging technologies, such as Doppler, laser speckle, optical coherence tomography (OCT), and fluorescence and photoacoustic imaging.