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Radioactive tracer techniques, coupled with chemical analysis by paper chromatography, became important in biochemical research in the late 1940’s, and today many investigations into intermediary and other aspects of metabolism rely on these methods. Soon after the marriage of chromatography to the use of tracers, various instruments were constructed which were able simultaneously to locate the positions of radioactive compounds on paper chromatograms and to determine the amount of radioactivity in each separated compound. Such devices are now available commercially in many different designs, and are intended for the scanning and counting of one-dimensional chromatograms only.

If one is faced with the problem of determining the distribution of radioactivity in a paper chromatogram, there are several assay techniques available. The chromatogram may be scanned in a strip counter and the radioactivity estimated by measuring areas under each peak or by use of an electronic integrator [1]. The paper strip can also be cut into appropriate sections and the radioactivity of each section determined under a Geiger counter. Depending on the thickness of the paper, the counting efficiency of these techniques is in the range of 3–10%. More serious than the inefficiency is the variation in efficiency, which makes quantitation difficult.

In radiography picture forming involves either fluoroscopy or registration on special photographic film. Images can also be recorded on photographic paper, Polaroid film and paper, and on various color films; however, such applications are exceptional.

X-ray fluorescence analysis has been successfully applied to the determination of qualitative and quantitative compositions of very minute amounts of sample. The ratios of major components may be determined unequivocally in microgram amounts. The substance is concentrated in the middle of a filter paper, mylar foil, or a similar carrier. In order to lower the effects of background radiation, small filter paper disks may be used which are just large enough to carry the amount of liquid that is to be analyzed. The filter paper disks are held in the proper position by thin mylar or tape strips which are clamped into the sample holder. The liquid may also be dried directly on a mylar strip. Usually, linear calibration curves result. Qualitative and quantitative analysis of smallest amounts of sample is applied successfully in mineralogy and metallurgy; furthermore, x-ray fluorescence provides a simple and reliable identification of heavy metal-containing compounds in the analysis of paper chromatograms. Properly designed devices make possible aperturing of the primary x-ray radiation to a beam of 100μ in diameter which allows one to scan individual areas in metal and ore sections, as well as in welding and soldering products, point by point. Reference to the literature is made in the following sections.

A major feature of the Brunel Symposium was an exhibition of on-line equipment operating either from a local computer or over telephone lines to a remote backup processor. Manufacturers also presented lecture-demonstrations on applications of their systems, and participants were able to see and operate the graphic equipment.

Cigarette filters began gaining acceptance in the early 1950’s and their use has grown steadily since that time. In 1965, filter-tip cigarettes accounted for 46% of total world output.1 By 1970, this figure had increased to about 60%. The increased use of cigarette filters has been accompanied by a marked change in filter performance requirements, and the quest for cigarette filters with improved performance properties has led many investigators to a study of the fundamental principles of cigarette smoke filtration.

Within the last 3 yr. there has been a very rapid increase in the usage of urea as a high grade fertilizer, animal feed supplement, and raw material for certain resins. The low-cost production of urea in large quantities has been widely studied by chemical engineers, and a number of processes have been developed, both in this country and abroad, which reflect considerable sophistication in engineering technology and in the use of specialized alloys to meet the corrosion problems encountered in the reactions required to produce urea.

For the most part oceanographers are physicists, chemists, geologists, biologists and engineers who have turned their interests toward problems in the seas. Consequently their use of computers for scientific research closely parallels that of their solid-earth counterparts. In so far as analysis of data is concerned we can not distinguish the work of the clay mineralogist who obtains his samples from deep sea cores from that of the mineralogist who obtains his from a well in driest Kansas.

This discussion will be concentrated almost exclusively on the toxic effects of microscopic algae, i.e., phytoplankton. Table I (1) shows a simplified diagramatic scheme of the interrelationship of algae and plankton. The form our contribution will take is not that of a report of an original laboratory study. Rather it will be a digestion and distillation of what has gone before, as seen from a medical perspective.

Nuclear technology interacts with laser technology in two ways. Lasers may be used for generation of nuclear energy in connection with laser triggered thermonuclear fusion reactions or nuclear energy may be used to excite lasers. This paper is concerned with the latter possibility. The ultimate goal is to directly convert fission energy, the largest part of which is the kinetic energy of charged particles (fission fragments), into laser light. Historically this idea is almost as old as the laser itself. Papers dealing with this subject began to appear around 1961. A review of this earlier work is given in [1].

This paper describes a number of methods for recording suboptical wavelength displacements or vibrations of a surface as a linear function of the irradiance of the image of the surface. The methods are an extension of conventional interferometric holography, including time averaged holography of sinusoidal vibration, double pulsed holography of sinusoidal vibrations or general displacements, time averaged holography of linear motion, and real time interferometric holography. The basic concept described here was first presented at the Second International Symposium on Acoustical Holography and published in the proceedings. The theory was later expanded and presented at the Annual Meeting of the Optical Society of America in October 1969. This paper presents the theoretical analysis of linearized subfringe interferometric holography and some experimental results. The theory is expanded to show how this can be used to record acoustical holograms.

As electronic components become smaller and smaller, the mechanical design engineer must devise packaging techniques to assure optimum use of these components. The first paper in this compendium describes precisely how the packaging of digital circuitry for a command storage programmer unit was accomplished. The second paper describes a computer program developed at G.E. to assure an optimum package for this or any similar digital unit. The final product of this combined effort has been a reliable command unit with the impressive circuit density of approximately 1100 transistors, 5000 diodes, 2500 resistors, and 200 capacitors, packaged in 32 separate modules in a total volume of 155 in.3

Although pulsed lasers have been commercially available for only one decade, they have been utilized in chemical analysis as highly monochromatic light sources, as intense, short duration sources for photolysis, and during the last few years, as thermal sources for degradation processes. Pulsed laser energy offers unique properties for the initiation of thermal degradation. Especially sensible is the combination of laser induced thermal degradation with gas chromatography. This paper reviews some applications and experimental possibilities of this new pyrolysis method. It should be noted that only a few papers have appeared on this topic and certainly much still needs to be done to fully characterize the potentialities of this technique.

The recent development of superconducting magnetic bearings of high load-carrying characteristics has led to the design of cryogenic motors which have essentially no internal losses from either mechanical or electrical sources. Small synchronous motors have been operated with the superconducting rotor in liquid helium, helium gas or in high vacuums. This paper will discuss some of the superconducting principles involved in the design of small reversible shaftless motors capable of prolonged high-speed operation while in a high vacuum, Motors of this type offer an unusually high degree of constancy of performance, which makes their use in cryogenic gyroscopes appear attractive, Undoubtedly numerous other applications exist. Only brief reference will be made to the superconducting bearings used in these motors since this subject is discussed in a recent paper by T. A. Buchhold [1] and also by I. Simon [2].

In the last few years several papers have appeared on the effects of ultrasonics on crystallizing substances [1, 2], These papers dealt with polycrystalline materials formed from melts, and did not touch on monocrystals. We give here some data on the effects of ultrasonics on monocrystals of potash alum.

The first part of this paper reports progress to date on an experimental investigation of the feasibility of applying holographic techniques to acoustical imaging to obtain three-dimensional images of opaque objects as encountered in nondestructive testing. Equipment was fabricated to make acoustical holograms of objects in water. Acoustical holograms were recorded by mechanically scanning an acoustical point transducer over the water’s surface in a TV-like raster. The acoustic frequency was 5 MHz. The resulting holograms were then used to make visible images. Holograms of objects examined in water, where the ultrasonic wavelength was 0.3 mm, show image detail smaller than 1 mm. A variety of acoustical holograms and their corresponding images (including one of a hole in an aluminum block) are presented and discussed. The second part of this paper presents a simplified theoretical analysis of these acoustical holograms. The effects of nonlinearities, sampling rates and pulse duration, coherent sound, and wavelength scaling on the acoustical image are discussed. The problem of three-dimensional visualization of the acoustical image is considered in detail. The third part of this paper discusses some potential uses of acoustical holographic techniques in nondestructive testing.

It is the purpose of this paper to survey the fields described in the title. We do not intend a catalogue of available equipment: microscope and photographic equipment manufacturers will, no doubt, be delighted to supply interested people with full details of their products. Rather, it is our purpose to comment on the generality of what is available and on the techniques which this equipment make possible in the examination of structures of all kinds. The paper is divided into six sections which deal respectively with the microscope, the camera, illumination, lenses, the recording medium and some special techniques.

The techniques of liquid surface acoustical holography have proven to be very effective and useful in applications to industrial testing and biomedical imaging. The most useful images have been produced by focused image techniques, that is, by using acoustic lenses to focus the image into the hologram. Because liquid surface holography has usually been illustrated by use of images focused into the hologram, there has been an erroneous but growing belief that liquid surfaces are not effective in forming true holograms capable of imaging outside the hologram plane. Although published papers (1,2,3) provide evidence that this belief is incorrect, further evidence at this time may be useful and will be presented in this paper.

The first part of this paper will be a discussion of some of the physical limitations encountered in far infrared spectroscopy using the echellette grating monochromator with filters to separate orders. An inclusive discussion of the methods of far infrared spectroscopy using gratings and filters will be omitted because these methods are well known and used in hundreds of laboratories. In about the past 5 years such spectroscopic systems have become available from instrument manufacturers. The last part of the paper will describe some less common systems using interferometric equipment. There will be an account of some new detectors which can be applied to far infrared spectroscopy.

A recent paper in this annual series has presented the development of a new gas bearing for cryogenic expansion turbines [1]. Because of space restrictions, it was not possible to consider a theoretical analysis of this new gas bearing. This paper provides such an analysis.

The pulsed magnetic fields encountered in synchrotrons, accelerators, and the proposed Tokamak fusion experiment require intermediate energy storage to reduce the large fluctuations in power demand. Only superconducting coils are expected to be economical at sizes required for reactors. The challenge of switching energy between inductors has produced many solutions, none of which is without drawbacks. This paper defines performance parameters, compares the various schemes, and proposes an ideal system with optimal response. A companion paper proposes a modified rotating coil system to approximate the optimal design.

The normal procedure for a quantitative measurement of two phases with an X-ray diffractometer is to scan or count the intensities of two diffraction peaks and then to calculate the ratio of the two phases using an appropriate equation. This paper will describe an improved method of quantitatively measuring two phases in a sample. The diffractometer, which was constructed by Philips Electronics Instruments, consists of two fixed scintillation counters mounted at the Seeman-Bohlin focusing positions for the two desired diffraction lines. Each counter is preceded by a lithium fluoride curved crystal monochromator. The output from each counter feeds to a separate scaler which can be arranged to gate both scalers at a preselected number of counts. At this point a tape printer prints out the counts for both scalers. These counts are then related to the proportions of each phase present by an appropriate equation. Most of the electronics are solid-state designs. This paper will describe the instrumentation and show how it can be used to measure rapidly and precisely the ratio of anatase to rutile in a titanium dioxide system. The savings in time over the conventional method can be as much as 100 to 1.

The automation of pharmaceutical analysis was seriously undertaken in 1957 when a system and methodology for the automated analysis of streptomycin and penicillin were presented at the 132nd Annual Meeting of the American Chemical Society in New York City. Since then a wealth of literature in the form of individual papers and monographs of conferences at the New York Academy of Sciences and elsewhere have testified both to the need for and concern of the scientific community to provide better analytical procedures and means to the control of and manufacture of pharmaceutical products. In the past fourteen years, changes for the better in the analysis of pharmaceutical products have been enacted by the U. S. Pharmacopoeia, i.e., single tablet assays. In addition, the pharmaceutical drug manufacturers have developed and improved upon analytical procedures and adapted many of these for increased productivity and quality control in their laboratories. Several papers in the past have indicated that these newer concepts can provide information on drugs and their effects upon living matters, as well as to elicit information on the mechanisms by which they exert their action in the animal body and on the normal metabolic processes of microorganisms and parasites. The above will be discussed and reviewed.

This paper deals with computer data structures. These data structures can be represented by directed graph structures and the purpose of this paper is to show how methods and techniques of graph theory can then be used to process these graphs. A viewpoint is taken that a basic tree structure exists in a general data structure. If this tree structure can be extracted, or identified during the creation of the data structure, then it can be used to make comparisons with other basic tree structures. An algorithm to find the greatest common structure of two trees is presented. If a cost function is associated with the arcs of a graph structure, then a minimum cost tree can be derived. This has application in minimizing data retrieval times and in minimizing page swapping in data structure paging systems. Arbitrary relations among data can also be represented by a graph and its matrices. It is shown that, by means of standard operations on these matrices, operations can be performed on these relations to derive further relations and logical data associations. A general model builder system, with which some of the above ideas will be investigated, is briefly mentioned.

Linearized subfringe interferometric holography, described in Chapter 4, has been used for detection and recording in an acoustical holography system which is presently under development at McDonnell Douglas Corporation. This paper describes the laboratory system used to test the feasibility of the concept and to work out some of the problems associated with this technique. Acoustical hologram movies have been recorded at 16 frames per second, with each frame being recorded in 6 microseconds from a 100microsecond burst of sournd. Each movie frame is the recording of a complete acoustical hologram of 30-cm aperture at a sound frequency of 1 MHz. With a sound wavelength of 1.5 mm we have resolved about 2.5 mm and imaged objects less than 1 mm. The threedimensional image volume is about a 30-cm cube. There is no acoustic lens in the system and thus the resolution is limited by the 30-cm aperture of the acoustic hologram. We have resolved about 1.5 times the Rayleigh limit.

The Malvern-Birmingham groups have conducted light scattering experiments on liquid helium in a number of different regimes: Rayleigh and Brillouin scattering from superfluid mixtures of 3He-4He,1 from normal and superfluid 4He,2 second-order Raman scattering from 4He above the λ-point,3 and total intensity measurements close to the λ-line.4 This paper describes the spectroscopic equipment used in recent studies and the results of attenuation and velocity measurements of first sound close to the λ-line at elevated pressure and a frequency close to 1 GHz. These latter results relate well in their general form with previous measurements at SVP and show a velocity minimum and attenuation maximum several millidegrees below the λ-point.

This paper summarizes recent contributions to the understanding of the structure and the reorientation kinetics of various impurity-defect complexes in alkaline earth fluroides. For the most part the relevant investigations involve relaxation of electric polarization as revealed by the ionic thermo-current (ITC) method on CaF2, SrF2 and BaF2 crystals doped with a variety of trivalent rare earth (RE3+) ions. In the absence of contaminating oxygen the extra positive charge is compensated by an interstitial fluoride ion (Fi -) which except at elevated temperature forms a complex with the In CaF2 the (dominant form of the complex as revealed by EPR and ITC is tetragonal with the Fi - located in the nearest neighboring interstitial site (Type I complex). In BaF2 the dominant form is trigonal with the situated in a next nearest site along a ‹111› direction (Type II complex). In SrF2 both Type I and Type II complexes are clearly evident in the ITC relaxation peak structure. In a crystal of CaF2:Gd3+ treated to introduce oxygen the Type I relaxation at 131 K is replaced almost quantitatively by a new peak at 166 K. Comparison with EPR behavior reveals that the new peak is associated with the relaxation of the CaF2:Gd3+O4 complex (Type T1) which had been previously identified by ENDOR.

In a previous paper (1) we showed that RNase in pure aqueous solution is strongly adsorbed on Sepharose and Biogel. To determine the conformational changes of the enzyme due to binding to the gel, two different ESR-spin labelled RNase preparations were investigated. The advantage of the ESR technique over UV, fluorescence and CD or NMR techniques is its indifference to turbidity or opacity. Thus, heterogeneous mixtures and suspensions of solid particles in water can be investigated. RNase was reacted with N-4-(2.2.6.6-tetra-methyl-l-oxyl-piperidinyl) bromacetamide once on the active site at pH 5.5 (RNase I), and once on the enzyme surface, in borate buffer at pH 8.5 (RNase II).

One of the peculiarities observed in laser produced deuterium plasmas is the correlation of neutron production with increased reflectivity of the laser light, the creation of a second elevated temperature of a few keV, and the generation of a fast group of plasma with 20 keV ions. Besides the very complex questions of the plasma dynamics characterized by nonlinear changes in the collision frequency, parametric instabilities, anomalous absorption and nonlinear forces, in this paper special mechanism is treated where the nonlinear ponderomotive forces are calculated for the field of an obliquely incident standing wave, generating a motion along the planes of the nodes of this standing wave, parallel or antiparallel to the direction of the plane of incidence. The electric vector of the light has to be parallel to the plane of incidence. These forces vanish at perpendicular incidence and are due to the longitudinal component of the electric vector of the wave. The forces cause a maximum laminar motion for angles of incidence of 25°. The motion needs a mean free path less than the thickness of the layers. The limitation toward turbulent motion is given. Laser intensitites around 1013 W/cm2 can build up striated jets with ion energies of a few keV. This model could explain a not purely thermonuclear generation of fusion neutrons and is consisted with a number of observations.

This paper discusses a new technique for obtaining an acoustical hologram using optical holography. Temporal modulation in the form of phase modulation and Doppler upshifting is used in the reference beam of the optical system. This allows recording of the amplitude and phase of sound waves impinging on a mirror interface. The advantages and disadvantages of this system technique are discussed.

There has recently been considerable interest in the “laser absorption waves” (LAW) which accompany laser-induced breakdown in a gas. The breakdown region is observed to grow in time, propagating up the beam towards the laser(1). It is the purpose of this paper to summarize and put into perspective our current understanding of the mechanisms by which this propagation of the breakdown region occurs.

This paper provides an overview of superconducting materials for nonspecialists in this currently very active field of research. Several new classes of materials have emerged in the past two or three years, and some of them offer promise of higher critical temperatures—although new records have not yet been achieved. Several of the hydrides of the transition metals have recently been found to be superconducting, for example, thorium hydride, Th4H 15, discovered by Satterthwaite and co-workers1 at the University of Illinois. Hydrogen has also been introduced into palladium by ion implantation; the system becomes superconducting close to 10°K.2 Another interesting class of superconductors involves layer compounds, such as tantalum disulfide, which were shown to have very interesting asymmetric superconducting characteristics by Geballe and co-workers at Stanford.3 Recently Matthias and coworkers4 have discovered a new ternary group, typified by LiTiS2, in which critical temperatures as high as 17°K have already been achieved. All these materials are discussed elsewhere in this volume and we shall not elaborate on them here.

Many flow configurations of engineering significance involve free turbulent mixing. In this paper we discuss some of the characteristics of this phenomenon, and the possibility of using Raman scattering to examine its detailed behavior.

A scanning laser acoustic microscope that simultaneously produces acoustic and optical images of a specimen has already been described.(1,2,3) This paper reports recent developments regarding improving the resolution and regarding operating the microscope in the “interference” mode. The principle of operation of the acoustic microscope is based upon optically measuring the localized dynamic displacements of a mirrored surface which are caused by incident sound waves that are scattered from an object.(4) For further details concerning the basic instrument the reader is referred to the literature cited above.

Since the double resonance effect in molecules was first observed in 1955 with an ammonia-beam maser at 24 GHz, it has been investigated as a tool for microwave and radiofrequency spectroscopy. The recent development of infrared lasers has made the infrared- microwave double resonance experiment feasible by using the vibration-rotation transitions in molecules. Previous works on double resonance were reviewed1 in 1971, and they are not shown in this paper.

The purpose of this paper is to contribute to the mathematical treatment of hierarchies of decision-making systems as given e.g. by Mesarovic e.a. in [1]. This will be done by making explicit in the formalization of the relevant concepts a few aspects which in [1] were supposed to be implicitly understood, and had to be kept in mind to distinguish hierarchies from other kinds of systems. Although the intended meaning in [1] seems to be fairly clear it is advantageous to push the formalization further, first because then we will have to keep in mind less than before and secondly because we are forced to keep to what we had in mind and eventually may observe whether the thing we had in mind was adequate to our purpose.

For many materials immersed in either liquid 3He or liquid 4He the low-temperature thermal boundary resistance is found to vary approximately as 1/T 3. This behavior is often discussed in terms of the acoustic mismatch theory1 in which phonons are assumed responsible for transferring thermal energy between the solid and the liquid helium. At least one system has been found for which the phonon resistance is not the limiting low-temperature resistance. That system is cerium magnesium nitrate (CMN) immersed in liquid 3He, for which the very low-temperature thermal boundary resistance is found experimentally to vary linearly with the temperature2 and to decrease in the presence of a small magnetic field.3 This resistance has been discussed4,5 in terms of thermal energy exchange via a surface magnetic coupling between the cerium spins of the CMN and the 3He nuclear spins. In this paper we present data which suggest that the thermal boundary resistance between Pt and liquid 3He is qualitatively different from the phonon and magnetic boundary resistances mentioned above.

An ultrasonic holography system with a moving source and an electronic reference is studied, where anamorphic holograms are recorded due to the relative movements of the source, object and receiver. In this paper a technique to reconstruct images from such anamorphic holograms using a cylindrical lens is proposed and a theoretical analysis is conducted. An experiment using a one-dimensional receiver array is done to examine the theoretical discussion.

This paper suggests that superconductors with very high critical fields and critical currents may be constructed from refractory superconductors by preparing them in granular form.

In this paper we would like to consider the production of metastable systems by means of ion implantation into a substrate held at liquid helium temperature. This technique has the great advantage that one can fabricate nearly all types of alloy systems. In most cases the thermal energy at 4 K is sufficiently low to prevent the diffusion and the clustering of the implanted atoms. The investigation of such metastable alloys is very interesting with respect to their superconducting properties. As long as the electron-phonon interaction is the only known interaction producing superconductivity, it is believed that the highest transition temperatures can only be achieved in such “highly sophisticated” metastable alloys.

We have designed an atomic beam experiment to be performed at low temperature in order to study the scattering of helium atoms at the liquid surface. This work has been partly stimulated by the theoretical papers of Anderson1 and Hyman et al.2 as well as by the experimental work of Johnston and King3. Anderson pointed out that the spectrum of atoms evaporating from the liquid should show a sharp increase in intensity at an energy corresponding to the difference between the atomic binding energy L and the roton minimum Δ. This prediction is made by assuming that inelastic processes at the surface play a minor role in evaporation.

A rotating electrical machine may be manufactured in a few minutes using some copper wire, a battery and a few odds and ends. However, when the power required from a machine is increased, more sophisticated methods are necessary and ultimately the available technology is pushed to its limits. For large direct current motors and generators, the subject of this paper, the limit of power using the conventional design approach is around 10 MW or so and, of course, the use of iron magnetic circuits is essential (we shall see later how essential is the iron if normal temperature materials are employed). The magnetic flux density in the iron may be between land2Tesla depending upon the selected machine geometry, and certainly flux densities much below this level are not much use for rotating electrical machines. It is for this reason that the early superconductors (type 1 superconductors) were of only academic interest to machine designers; the best of them is niobium with a practical working level of less than 0.2 Tesla. It is this fact which explains the absence of superconducting machine development from that historic day in 1911 when superconductivity was discovered to the mid 1960’s when the first machine (in the power range) was manufactured. Superconducting machines became possible with the development of type 2 superconductors, initially with niobium-zirconium, now with niobium-titanium and perhaps in the future niobium-tin. The potential of superconductors to electrical engineers is graphically illustrated in Fig. 1 which compares the current carrying capacities of copper and niobium-titanium.

The mechanical properties of glass-ceramics depend not only on the nature of the precipitated phases and the glassy matrix but also on the microstructure (texture) of the material. It is the aim of this paper to review: a) Experimental techniques available to characterise glassceramics; and, b) Theories correlating their mechanical strength and microstructure.

This paper outlines an approach to the analysis of the stability and instability of large scale interconnected systems. It is shown how one may deduce the dissipativeness or the cyclo-dissipativeness of an interconnected system from the properties of the component subsystems. Thus, after having established the connection between dissipativeness or cyclo-dissipativeness on the one hand, and stability or instability on the other, this leads to a systematic method for analyzing the qualitative behavior of interconnected systems.

Elton (1958) gave as one reason why more complex ecosystems might be expected to be more stable than simpler ones, that simple, two species, ecosystem models tend to be unstable. As May (1971, 1973), has pointed out, such an argument is only valid if it may be shown that more complex ecosystem models, involving more species with a greater degree of food web linkage, exhibit greater stability than simpler ones. Recent studies of ecosystem models (May, 1971, 1973; Gardner and Ashby, 1970), have suggested that this is not the case, in particular May concluded ‘that if we contrast simple few species mathematical models with the analogously simple multispecies models, the latter are in general less stable than the former’. In this paper, the question of stability is examined in a multispecies difference equation model under two contrasting degrees of linkage complexity, in a randomly fluctuating environment.

Magnetic resonances have proved to be a convenient tool to study the problem of local molecular dynamics in liquid crystals, In this paper three different approaches will be presented.

The two-fluid nature of liquid helium II leads to the possibility of several types of wave motion, e.g., first sound, second sound, fourth sound, and the fifth wave mode. First and second sound appear in the bulk liquid. The characters of these wave modes alter materially if helium is bounded by solid walls, e.g., between two plane-parallel plates forming a channel. This paper reports upon the calculation of the properties of wave modes which can exist in such channels.

This paper describes some recent developments in the technology of tunable sources which operate in the near to middle infrared regions. Included among these are external cavity controlled and hydrostatic pressure tuned semiconductor lasers, spin-flip Raman lasers, and nonlinear mixing using tunable and quasitunable laser sources. The spectral linewidth and tuning range of these devices will be discussed with emphasis on their application for high resolution spectroscopy.

The purpose of this paper is to show that Raman scattering excited by a pulsed laser can be used to obtain useful information about both the mean values of gas properties and their fluctuations in a dynamic system. This conclusion is illustrated by data from measurements on a CO2-air jet and a CO2-enriched flame.