Concept Of Optical Basicity Research Articles

Effects of alkali ions on luminescence and scintillation performance of Ce3+ doped phosphate glasses for radiation detection

The luminescence and scintillation properties of Ce3+ doped alkali phosphate glasses 56P2O5:8Gd2O3:5Al2O3:1CeBr3:30XCl (PGAC:X, X = Li/Na/K/Rb/Cs) were studied for their potential applications in gamma and alpha detection. In the Fourier Transform Infrared Spectroscopy (FTIR), X-ray Luminescence (XRL), Photoluminescence (PL), and transmittance spectra, the red shift was found and explained by the concept of optical basicity. Broad Ce3+ emission and energy transfer from Gd3+ to Ce3+ were observed in XRL and PL measurements. Scintillation performance was studied by irradiating the samples under 137Cs gamma and 241Am alpha sources. The fast, intermediate, and slow decay components under gamma and alpha excitation were found around 30, 200 and 3000 ns, respectively. The decay time increased slightly from PGAC:Li to PGAC:Cs, indicating the less effective transition from Gd3+ to Ce3+. The alpha decay time was longer than the gamma decay time, revealing the Pulse Shape Discrimination (PSD) capability of the glasses for particle identification. The XRL intensity reduced significantly from PGAC:Li to PGAC:Cs samples did not reflect the scintillation tendency. By successfully detecting gamma and alpha scintillation signals, the scintillation performance of all samples was found to be similar. In general, all samples can be used for gamma and alpha detection. Using Rb+ or Cs+ ions is favorable in terms of high density and light yield, while Li+ ions enhance the transmittance and homogeneity. Furthermore, a correlation between P–O–H groups within the glass matrix and scintillation performance was also observed.

Electronic polarizability in silicate glasses by comparison of experimental and theoretical optical basicities

AbstractThe concept of optical basicity proposed by Duffy has been recognized as an extremely important issue in science and technology of glasses. In this article, the refractive index (no)‐based optical basicity Λ(no) of some binary and ternary silicate glasses was evaluated using the Lorentz–Lorenz formula, and the discrepancy between the values of Λ(no) and the theoretically calculated optical basicity Λth was analyzed to understand more deeply the electronic polarizability in binary and ternary silicate glasses. A suitable value of the optical basicity for each oxide predicting a good quantitative composition dependence of optical basicity in a given glass system was proposed. The suitable value of SiO2 for the prediction of the optical basicity of silicate glasses is Λ(SiO2 glass) = 0.53, which is larger than the value of Λ(SiO2 oxide) = 0.48 being used in the calculation of Λth so far. Other suitable values such as Λ(Al2O3 glass) = 0.62 and Λ(TiO2 glass) = 1.04 were proposed. The relationship between the optical basicity and coordination structure in some oxides in silicate glasses was discussed.

Why Do Relative Intensities of Charge Transfer and Intra-4f Transitions of Eu3+ Ion Invert in Yttrium Germanate Hosts? Unravelling the Underlying Intricacies from Experimental and Theoretical Investigations.

The dominant intensity of parity-forbidden intra-4f transitions of europium(III) over O → Eu charge-transfer band (CTB) intensity is against common perceptions, yet this trend is observed in many germanate hosts and has not been rationalized so far. In search of a plausible explanation for this unusual trend, present work reports an experimental and theoretical investigations in conjunction on two sibling germanate host, namely, Y2GeO5 and Y2Ge2O7 having dopant Eu3+ in their respective YO7 polyhedra. Whereas for Y2GeO5:Eu3+, the CTB is more intense than the intra-4f transitions in the excitation spectrum, in the case of Y2Ge2O7:Eu3+, the relative intensities of CTB and intra-4f transitions are reversed. Comparative structural analysis reveals that Eu3+ present in YO7 of Y2GeO5 has a greater number of tetra-coordinated oxygen (Otetra) and yttrium atom as first and second neighbors, respectively (Eu3+-Otetra-Y3+ linkages). Conversely, in Y2Ge2O7 host, the Eu3+ ion mostly has tricoordinated oxygen (Otri) as its nearest neighbor and germanium ions next to Otri (Eu3+-Otri-Ge4+ linkage). Theoretical calculations reveal that while Y2GeO5:Eu has Otetra(4Y) dominating at the Fermi level and the 4f state of Eu3+ remains inert toward mixing, in Y2Ge2O7:Eu, the Fermi level has major contribution from Otri(2Y + 1Ge) with significant mixing with 4f states of Eu. The dominant control of Eu3+-Otri-Ge4+ linkages in geometrical and electronic structure of Y2Ge2O7:Eu owing to the GeO4 surrounding has been attributed to relative poor intensity of O → Eu CTB. Siege of Eu3+ by GeO4 and subsequent occurrence of Eu3+-Otri-Ge4+ linkages play a dual role: First, it induces electronic rigidity to hinder excitation of electron at bridging (Otri) oxygen by highly charged small Ge4+ cation; second, the covalent character in Eu-O bond is achieved by intermixing of Eu's 4f and Otri 2p orbital which facilitates relaxing of the parity-selection rule thus enhancing the probability of intra-4f transitions. The inferences drawn remain valid when extrapolated to other inorganic oxides having EuOx polyhedra surrounded by covalent units like PO4, SiO4, etc. and have a prevailing number of low-coordinated oxygen atoms and highly charged small cation in the first and second coordination shells, respectively. The optical basicity concept is also found to endorse our explanation. These remarkable generic inferences will pave the rational way for designing efficient phosphors for solid-state lighting.

Anion polarizabilities in oxynitride glasses. Establishing a common optical basicity scale.

Inspired by the work of John Duffy on optical basicity of oxyfluoride glasses, we apply here the concept of optical basicity to oxynitride systems. While in the original work of Duffy and Ingram the basicity of a medium could be probed by s2 ions like Pb2+, the low energy intrinsic absorption edge of nitride-containing systems does not allow the use of such probe ions. This study uses therefore experimental data on refractive index and density of alkaline earth and rare earth containing silicate oxynitride glasses, prepared by the authors or taken from the literature. In addition, literature reports on experimental or calculated refractive index, density and polarizability data are used to compare pure nitride systems, e.g. bulk or thin film materials that are either crystalline or glassy. We compare simple and complex nitride systems with their oxygen counterparts, by calculating their optical basicity using the chemical composition as well as the established relationship between optical basicity, Λ, and electronic polarizability in oxide systems. Our results on oxynitride systems are in good agreement with Duffy's previous work on oxyfluoride glasses and indicate that the optical basicity varies for the isoelectronic anions in nitrides, oxides and fluorides (N3-:O2-:F-) of a cation Mm+ as follows: Λ(MFm) = 1/2Λ(M2Om) = 1/3Λ(M3Nm). Using this relation for CaO, for which the optical basicity was set as unity by Duffy and Ingram, one has Λ(CaF2) = 0.50, Λ(CaO) = 1.00 and Λ(Ca3N2) = 1.50. The optical basicity of complex nitrides can therefore be calculated by the same method established for oxides using the equivalent fractions and the basicity of the constituent nitrides. The relationship between nitride polarizability αN and basicity Λ(nitride) was found to be linear, with Λ(nitride) = 0.39αN- 0.14 where αN is given in Å3.

(INVITED) Eu3+ activated molybdates – Structure property relations

Eu3+ activated phosphors have been a subject of scientific investigation for more than 100 years. Various host materials have been employed, among which molybdate hosts play an important role. They offer an array of advantageous properties such as high critical activator concentrations, facile solid state synthesis and excitation via the Mo6+/O2− charge transfer (CT) transition. This review paper discusses the basics of Eu3+ luminescence and presents the most important properties and synthesis conditions of various Eu3+ activated molybdates. Furthermore, relations between the crystallographic structure of the host and the optical properties of Eu3+ are shown. The point symmetry of the Eu3+ doping site can be determined from specific features of the Eu3+ emission spectrum and the number of crystallographic sites can be estimated. The concept of optical basicity is discussed in regard to the spectral position of the Mo6+/O2− charge transfer band. The influence of the CT band on the thermal quenching properties and consequently the photoluminescence efficiency of Eu3+ is investigated. Disadvantages of molybdates as phosphor host materials are discussed as well, such as the formation of Mo5+ defect states.

Rosalind Franklin's X-ray photo of DNA as an undergraduate optical diffraction experiment

Rosalind Franklin's X-ray diffraction patterns of DNA molecules rendered the important clue that DNA has the structure of a double helix. The most famous X-ray photograph, Photo 51, is still printed in most Biology textbooks. We suggest two optical experiments for undergraduates that make this historic achievement comprehensible for students by using macromodels of DNA and visible light to recreate a diffraction pattern similar to Photo 51. In these macromodels, we replace the double helix both mathematically and experimentally with its two-dimensional (flat) projection and explain why this is permissible. Basic optical concepts are used to infer certain well-known characteristics of DNA from the diffraction pattern.

Viscous characteristics and modelling of CaO–Al2O3-based mould flux with B2O3 as a substitute for CaF2

ABSTRACTFollowing a series of laboratory studies on the development of fluoride-free or low-fluoride CaO–Al2O3-based mould flux for continuous casting of high-aluminium steel, the viscosity properties of CaO–Al2O3-based mould flux with B2O3 as a substitute for CaF2 were investigated using the rotating cylinder method. It was found that B2O3 behaved in a similar manner to CaF2 in changing the viscosity of the flux system. From calculations of the viscous activation energies, it was found that similar changes in the concentrations of CaF2 and B2O3 resulted in almost the same changes in activation energy. A viscosity prediction model was developed using the optical basicity concept as an indicator of melt behaviour. Predicted viscosity values showed good agreement with measurements reported in the literature.

Cerium/aluminum correlation in aluminosilicate glasses and optical silica fiber preforms

Optical, structural properties and redox were studied for Ce-bearing silicate and aluminosilicate glasses and Ce-activated silica (SiO2) fiber preforms, by X-ray Absorption, Raman and Photoluminescence Spectroscopy.The introduction of Al2O3 in Ce-bearing silicate glass strongly stabilizes reduced species in agreement with the optical basicity concept and additionally induces modifications in the Ce3+ surrounding. In Al-free silica preforms, depending on the collapsing conditions, the Ce3+/ΣCe ratio has the highest variability (Ce3+/ΣCe=0.7–0.85±0.07), whereas in Al-bearing fiber preforms, Al codoping induces a strong stabilization of Ce3+ species, despite the collapsing atmosphere.Al presence induces modifications on Ce local environment, and thus variations of the distance between Ce3+ and its ligands, and/or to variations of the covalency of the bonds. Absorption bands in the UV region, ascribed to Charge-transfer (CT) bands, in our samples, occur only for low amount of Ce4+ (Ce3+/ΣCe>0.85±0.07). Indeed, in silicate and aluminosilicate glasses the higher amount of Ce4+ does not give rise to UV absorption bands ascribed to CT processes, whereas, in fiber preforms, Ce3+ species can induce the trapping of hole centers, and enhance the photoluminescence efficiency. More generally, these results enhance our understanding of REE structural and chemical roles in amorphous materials and increase our knowledge for technical applications.

Effects of melting temperature and composition on spectroscopic properties of Er^3+-doped bismuth glasses

The spectroscopic properties (SPs) of bismuth glasses are strongly influenced by the preparation conditions. Here, we studied the effects of melting temperature and concentration ratio of Bi2O3 to SiO2 on the SPs of Er3+ doped Bi2O3-B2O3-SiO2 bismuth glasses. We have shown that the low melting temperature is preferable to achieve large and broad gain of Er3+ ions. When melted at high temperatures, however, the glasses get darkened which is against the application of these materials for optical fiber amplifiers. On the other hand, we have also shown that a compromise has to be made between the laser gain and threshold regarding the optimum concentration ratio of Bi2O3 to SiO2. Theoretical radiative transition rate and quantum efficiency of the 1.55 μm emission of Er3+ have been obtained by Judd-Ofelt (JO) fitting. The variation of the JO parameters characterizing the local chemical environments around Er3+ can be explained based on the concept of optical basicity.

Application of Cues, Prompts, Probes, Questions and Gestures (CPPQG) in Physics Teaching and Learning

This study was an action research using cues, prompts, probes, gestures and questioning strategy to remediate some learning difficulties of students in some physics concepts. This was done by collecting both quantitative and qualitative data using teacher constructed test. Pre-test, was used to assess students' prior knowledge and post-test to determine the final state of the learners. A sample of 40 Level 200 Geography Education students of the Department of Science Education, Modibbo Adama University of Technology, Yola, Nigeria, participated in the study. The data collected were analysed using descriptive statistics, percentages, paired sample t- test and the correlation statistic. The results obtained showed an improvement in students' understanding of basic concepts in optics, heat and mechanics. Students performed relatively better in optics (80% of the students) scoring 45% and higher; followed by thermal physics (heat) (70 %) and mechanics (50%). The post-test mean score was higher than the pre-test. Also, paired sample t-test was significant at 0.05 alpha level and df of 39. Similarly, a moderately high and significant correlation coefficient of 0.70 was calculated between the pre and post test scores. Based on the findings, it is recommended that teachers should integrate CPPQG into all forms of physics instruction in today's changing world of technologies. This is a major way to make its learning interesting to the average learner who ordinarily may not be able to make the kind of connections expected in maximizing physics teaching and learning.

2ZrO2·Y2O3Thermal Barrier Coatings Resistant to Degradation by MoltenCMAS: Part I, Optical Basicity Considerations and Processing

The higher operating temperatures in gas‐turbine engines enabled by thermal barrier coatings (TBCs) engender new materials issues,vizsilicate particles (sand, volcanic ash, fly ash) ingested by the engine melt on the hotTBCsurfaces and form calcium–magnesium–alumino–silicate (CMAS) glass deposits. The moltenCMASglass degradesTBCs, leading to their premature failure. In this context, we have used the concept of optical basicity (OB) to provide a quantitative chemical basis for the screening ofCMAS‐resistantTBCcompositions, which could also be extended to environmental barrier coatings (EBCs). By applyingOBdifference considerations to various majorTBCcompositions and two types of importantCMASs—desert sand and fly ash—the 2ZrO2·Y2O3solid solution (ss)TBCcomposition, with the potential for highCMAS‐resistance, is chosen for this study. Here, we also demonstrate the feasibility of processing of 2ZrO2·Y2O3(ss) air‐plasma sprayed (APS)TBCusing commercially developed powders. The resultingTBCs with typicalAPSmicrostructures are found to be single‐phase cubic fluorite, having a thermal conductivity <0.9 W·(m·K)−1at elevated temperatures. The accompanying PartIIpaper presents results from experiments and analyses of high‐temperature interactions between 2ZrO2·Y2O3(ss)APS TBCand the two types ofCMASs.

Remediating Some Learning Difficulties of L200 Science Education Students of Modibbo Adama University of Technology in Some Physics Concepts Using Multiple Representations

Academic performance and achievement of students is highly dependent on the approach of presenting information and how it is received. This study was an action research using the problem-solving strategy to find out the effect of multiple representations-based instruction on students’ performance in some physics concepts. This was done by collecting both qualitative and quantitative data with two instruments, pre-test, to assess students’ prior knowledge and post-test to determine the final state of the learners. A sample of 40 L200 Geography Education students of the Department of Science Education, Modibbo Adama University of Technology took part in the study. Descriptive statistics were used to analyze the data collected. The results obtained showed an improvement in students’ achievement on basic concepts in optics, heat and mechanics. Students performed relatively better in optics (80% of the students) scoring 45% and above of the marks; followed by thermal physics (heat) (70%) and mechanics (50%). Also, effect size of 0.41calculated to see effectiveness of the treatment confirmed the improvement in the students’ performance. This study suggests that it is possible to use multiple representations in physics instruction to motivate and sustain students’ interest in the subject, especially those with limited physics’ knowledge to apply the laws and formulae learnt to calculate and solve problems

A stratified study of students’ understanding of basic optics concepts in different contexts using two‐tier multiple‐choice items

A large scale study involving 1786 year 7–10 Korean students from three school districts in Seoul was undertaken to evaluate their understanding of basic optics concepts using a two‐tier multiple‐choice diagnostic instrument consisting of four pairs of items, each of which evaluated the same concept in two different contexts. The instrument, which proved to be reliable, helped identify several context‐dependent alternative conceptions that were held by about 25% of students. At the same time, students’ performance on the diagnostic test correlated with the location of the schools, students’ achievement in school science and their attitudes to science learning. However, students’ grade levels had limited influence on their understanding of basic concepts in optics as measured by the instrument.

Dysprosium (III)-doped novel silicate glasses

Dysprosium-doped optical materials are currently becoming a matter of interest mainly for their utilisation in the MIR spectral region. We report here on specially designed dysprosium-doped silicate glasses, whose optical properties were characterised by VIS and NIR measurements of their absorption and transmission spectra. The planar waveguides were fabricated in these glasses employing Ag + and K + ion exchange (IE), and their optical properties were ascertained by dark mode spectroscopy. The chemical compositions of the exchanged layers were determined using electron microscope analysis (EMA), where the effect of the bivalent glass modifiers (such as Ca 2+, Mg 2+ and Zn 2+ and their mixtures) in the glass matrix on the properties of the exchanged layers – both chemical (with different permeabilities of the matrix for diffusing ions) and optical (waveguiding) were examined. The role of bivalent modifiers in the permeability of the glasses has been described and explained on the basis of the concept of optical basicity. The relations yielding a guideline to specify the contributions of the particular modifiers to the resultant depths of the IE layers have been suggested as well.

The Coordination Number of Silicon in Silicon−Oxygen Compounds: The Special Case of 6-Fold Coordination in Thaumasite

In most silicon-oxygen compounds, the silicon atom is 4-fold coordinated. Exceptionally, silicon is found in 6-fold coordination, as in the mineral thaumasite, which also may be formed in the degradation, and sometimes subsequent weakening, of certain concretes. The connection between coordination number and chemical bonding in oxidic compounds generally is explored using the optical basicity concept to estimate the extent of negative charge provided by oxide(-II) donor atoms in the coordination sphere. A correlation is established between this charge and the heat of formation of silicate (per oxide(-II) atom), which indicates that reduction in charge decreases thermodynamic stability. Calculations for thaumasite show that 4-fold coordination would provide a very small charge, but that 6-fold provides a charge comparable with that for stable 4-fold coordinated silicates such as K2Si2O5.

A guided tour into subcellular colocalization analysis in light microscopy

It is generally accepted that the functional compartmentalization of eukaryotic cells is reflected by the differential occurrence of proteins in their compartments. The location and physiological function of a protein are closely related; local information of a protein is thus crucial to understanding its role in biological processes. The visualization of proteins residing on intracellular structures by fluorescence microscopy has become a routine approach in cell biology and is increasingly used to assess their colocalization with well-characterized markers. However, image-analysis methods for colocalization studies are a field of contention and enigma. We have therefore undertaken to review the most currently used colocalization analysis methods, introducing the basic optical concepts important for image acquisition and subsequent analysis. We provide a summary of practical tips for image acquisition and treatment that should precede proper colocalization analysis. Furthermore, we discuss the application and feasibility of colocalization tools for various biological colocalization situations and discuss their respective strengths and weaknesses. We have created a novel toolbox for subcellular colocalization analysis under ImageJ, named JACoP, that integrates current global statistic methods and a novel object-based approach.

Ionic−Covalent Character of Metal and Nonmetal Oxides

The acid-base properties of oxidic media are quantified in terms of the optical basicity concept, which serves to correlate many properties with chemical constitution. Optical basicity values, Lambda, have been assigned to 25 oxides such that they relate to Lambda for crystalline CaO being taken as unity. Since Lambda for an oxide is proportional to the degree of negative charge borne by the oxide-(-II) atom or ion, it follows that optical basicity should go hand-in-hand with the ionic/covalent nature of the cation-oxide-(-II) bonding. Unfortunately, this assumption produces many anomalies and trends that do not fit normal inorganic trends. The problem is resolved by adjusting the influence of ionic forms to the bonding by taking into account the heats of formation. In contrast to the (Pauling) electronegativity treatment of oxides, this procedure allows assignment of percentage ionicity to the bonding, and the trends in these in the Periodic Table are as expected for inorganic oxides.

A large-active-area light-blocking based switch for people with disability

This paper proposes a force-free large-active-area light-blocking based switch structure. Our key approach is based on a combination of three basic optical concepts: optical beam shaping (S) that converts an incident optical beam into a diverging sheet of light beam across a desired active area, optical beam floating (F) that allows the sheet of light beam float above the desired active area and optical beam blocking (B) for checking the appearance of an obstruction in space over the touching zone. By adding electronic filters for post processing, unwanted optical noises can also be suppressed. Our SFB-based optical sensor prototype using two light emitting diodes, two plastic cylindrical lenses and eight photoreceivers shows an active area of 27 mm × 29 mm with a measured 23.5-dB electrical on/off ratio. A 100% active area is achieved for a ≥9-mm diameter obstruction. In addition, our SFB-based optical sensor can be operated under a typical 300 lx and a high illumination of 2000 lx without sensor malfunction, verifying that it is suitable for indoor use. So far, 10 sets of our SFB-based optical sensors have been deployed for disabled students to comfortably turn on/off computers for more than 9 months without showing sensor failure.

Optical basicity, interpreted by means of Ce 3+ 5d level spectroscopy in ionic crystals

The concept of optical basicity based on spectroscopy of Tl +, Pb 2+, and Bi 3+ energy levels in oxidic media like glasses and molten salts will be tested against information and theoretical knowledge available on Ce 3+ in oxide ionic crystals. The redshift of the 4f → 5d transition of Ce 3+ does not provide a basis for determining optical basicity. It will be shown that the proper basis is provided by the shift of the whole 5d configuration. Reasons why optical basicity can be based on the redshift of the 1S 0 → 3P 1 transition in Tl +, Pb 2+, and Bi 3+ will be discussed. The theory on the centroid shift in Ce 3+ provides new insights in the relation between optical basicity and physical properties like anion polarizability and refractive index. An alternative method to calculate optical basicity from the chemical composition of a compound will be proposed both for oxide and fluoride compounds.

Review of Flow visualization , edited by A. J. Smits and T. T. Lim

Flow visualization is perhaps the oldest investigative tool in fluid mechanics and hydraulics. Remarkable insights into fluid flow, such as those made by Leonardo da Vinci, were obtained over time using this straightforward method. The advent of the digital revolution in modern times transformed these essentially qualitative techniques to strong quantitative ones. Among the distinctive advantages of flow visualization over the other experimental approaches is that they are essentially nonintrusive. In recent years, twoor three-dimensional vector and associated scalar-flow quantities have become available through continued and sophisticated technological development. Currently, the modern flow visualization instruments gain continuously spatial and temporal capabilities such that they are increasingly complementing the data obtained by Computational Fluid Dynamics ~CFD!, another offspring of the digital revolution. The rapid, intensive, and extensive evolution of the flow visualization techniques in past decades, did not allow fast assimilation of the techniques in current laboratory practice. The need of evaluation, validation, and dissemination of the benefits of these techniques was continuously felt during these decades. From this respect, the publication of this book is valuable and timely. The book consists of twelve chapters covering a large range of flow visualization techniques including new methods not widely covered in the technical literature ~e.g., molecular tagging velocimetry, thermo-chromic liquid crystals, threeand four-dimensional ~inclusive of time! imaging!. The contributing authors are leading scientific authorities with extensive expertise in the presented techniques. Chapter 1 familiarizes the reader with the interpretation of flow patterns with a strong emphasis on the significance of the critical points. The relationships between tensor invariants and streamline patterns are explained in detail using comprehensive illustrations and theoretical derivations. It is also shown that a combination of invariants can be used to detect local vortices from the three-dimensional velocity information obtained by CFD. Chapter 2 discusses the well-known hydrogen bubble technique, initially developed for visualizing organized turbulent structures in turbulent boundary layers. The configuration of the bubble-generating systems, probes, lighting procedures, and the limitations of the method are briefly described. Chapter 3 describes another traditional experimental approach, namely visualization using dye and smoke. The use of the technique is separately described in accordance with the working fluid used in the experiments, i.e., water or air. Special attention is given to the capturing of the visualized information. Chapters 4 and 5 treat two newer techniques based on laser light interaction with atoms or molecules contained in the flows. Chapter 4, dealing with Molecular Tagging Velocimetry ~MTV!, first introduces the reader to the particularities of the photochromic materials. Similarly, Chapter 5 familiarizes the reader with the underlying principles of the planar-laser imaging. LaserInduced Fluorescence ~LIF! and Planar-Doppler Velocimetry ~PDV! are subsequently described in this chapter. Results obtained with the above mentioned methods are illustrated in the last parts of Chapters 4 and 5. Chapter 6 describes Digital Particle-Image Velocimetry ~DPIV!, one of the most innovative flow diagnostic technologies in contemporary fluid mechanics. Following a brief description of the measurement principle involved, post-processing methods, and a valuable section on the sources of errors associated with DPIV measurements are presented. Given the widespread use of the DPIV, even for largescale flows, such as Fig. 1 shows for a river cross section, the application section of this chapter could have been more generous. Chapters 7 and 8 are associated with surface measurement technologies. These methods have evolved considerably in recent years. Surface temperature sensing techniques using thermochromic Liquid Crystals ~LCs! are concisely described in Chapter 7. Examples of LC application to boundary layer heat transfer processes are illustrated at the end of the chapter. Surface pressure and surface shear stress measurements made with the aid of a special coating technology are detailed in Chapter 8. Pressuresensitive paint ~PSP!, shear-sensitive liquid crystal coating ~SSLCC!, and Fringe-Imaging Skin-Friction Interferometry ~FISF! are extensively documented. Practical means to achieve proper lighting, calibration, and data reduction methods are described for each of the methods. Well-illustrated examples support the importance of these methods to nonintrusively measure the pressure distribution and shear stresses in practical aerodynamics and experimental fluid mechanics. Chapter 9 introduces the reader to the visualization methods for compressible flows. A comprehensive introduction to basic optical concepts related to the subsequent described techniques makes this chapter selfcontained. Practical configurations and results obtained with Shadowgraph, Schlieren, Interferometers, and Holography are succinctly presented at the end of the chapter. Chapter 10 and 11 concern 3and 4D flow measurement methods. These quite complex techniques are the most recent developments of the experimental methods technologies and continue