bluuebunny/crossref_metadata_2025 huggingface dataset:
Ocular Component Correlates of Tonic Accommodation
Authors: Mutti Donald O. , Zadnik Karla , Adams Anthony J.
Published: February 2023

Tonic accommodation (TA) and its adaptation have attracted considerable interest in recent years as putative risk factors for myopia (Ebenholtz, 1983) and TA is currently under investigation in prospective studies of adults (McBrien and Adams, 1989). TA has been widely studied as a function of refractive error. Maddock et al. (1981) found that emmetropes had significantly higher TA values than high myopes. McBrien and Millodot (1987) extended the classification of refractive error in their analysis, differentiating between late and early onset myopes. They found that while early onset myopes and emmetropes did not differ in TA, hyperopes had significantly higher and late onset myopes significantly lower levels of TA. Rosner and Rosner (1989) have demonstrated that the relationship between TA and refractive error in children is similar to that found in adults, with hyperopes having the highest levels of TA, followed by emmetropes, and myopes the lowest values. Correlation coefficients (r) between refractive error and TA have ranged from 0.61 (data on night myopia and refractive error from Irving (1957), 0.48 (Maddock et al., 1981), to 0.24 (McBrien and Millodot, 1987). Regression was not performed on the data from children in Rosner and Rosner (1989).
An interferometric null method for measuring the power distribution across concentric varifocal contact lenses
Authors: Charman W. N. , Plakitsi A.
Published: February 2023

In recent years a miscellany of axially symmetric, varifocal, simultaneous-vision, soft contact lenses has been produced in an attempt to give presbyopes adequate vision over a range of object distances1-4. Although details of the individual designs vary, all use at least one aspheric surface to give a smooth variation in power from the centre to the edge of the optic zone of the lens.
NON-COHERENT METHODS OF INVESTIGATING NEURAL RESOLUTION IN PERIPHERAL VISION
Authors: Thompson Caroline M , Drasdo Neville
Published: February 2023

Although it has long been accepted (Campbell and Green, 1965) that optical degradation contributed to the limitation of performance in central vision, opinion has been divided on its effects in the periphery (Charman, 1983). At first acquaintance this seems surprising because beyond 30 degrees from the point of fixation substantial amounts of oblique astigmatism are known to occur (Ferry, Rand, and Hardy, 1931; Millodot and Lamont, 1974) and lateral chromatic aberration has been considered to be a major contributor.
Theories of the Stiles-Crawford Effect: Waveguiding Properties of Photoreceptors
Authors: Lakshminarayanan Vasudevan
Published: February 2023

Since the discovery of Stiles and Crawford in 1933 that visual sensitivity is greatest for light entering the center of the eye pupil,1 our knowledge of photoreceptor optics has grown tremendously. Photoreceptor optics can be defined as the study of the consequences of light propagation within photoreceptor cells. The retina is a complex optical processing system whose properties play an essential role in visual information processing. The photoreceptors behave as light collectors which capture the incident light and channel the electromagnetic energy to the sites of visual absorption. During this process, the photoreceptors act as classical waveguide (or fiber optic) elements, and the retina can be thought of as an enormous fiber optic bundle. Certain aspects of the behavior of the fiber optic bundle are reflected by the psychophysically determined Stiles Crawford effect or function (SCE). The reader is referred to the literature for further details on the SCE and photoreceptor optics2-4. It is the purpose of this paper to critically review the various theories that have been proposed to explain the SCE. More recent work on certain aspects of waveguiding in photoreceptors will be presented.
The Apertures of Human Cone Photoreceptors
Authors: Williams David R.
Published: February 2023

A key optical parameter of the retina is the cone aperture, which determines the ability of single cone photoreceptors to collect photons. The cone aperture is difficult to measure anatomically in part because of the possibility of histological artifact and also because it is not clear how the functional aperture relates to the physical dimensions of the photoreceptor, such as the diameter of the inner segment. I will describe some psychophysical experiments performed in collaboration with Walter Makous, Donald MacLeod, and Bing Chen (Chen et al., in press; MacLeod et al., 1992) that provide new estimates of the cone aperture in the living human eye.
The Effect of Transverse Chromatic Aberration on Spatio-Temporal Thresholds
Authors: Faubert Jocelyn , Simonet Pierre , Gresset Jacques
Published: February 2023

The advent of thinner ophthalmic lenses has required higher refractive indices. Lower constringence levels associated with higher refractive indices result in increased transverse chromatic aberrations (TCA).
Opto/Acoustic Microscopy
Authors: Bray R. C. , Quate C. F. , Williams C. C.
Published: February 2023

In our work, we have been emphasizing the use of focused beams — both optical and acoustic — as a method for obtaining high resolution images. We work with acoustics in the microwave range and use our set-up for the acoustic microscope to receive the thermally generated signal. Mechanical scanning is used to form the raster pattern. With a cavity-dumped laser which provides us with 25 microsecond pulse at repetition rates of 1 MHz, we are able to record the image in a few seconds.
Determination of Trace Nd Species in Water using Laser-Induced Photoacoustic Spectroscopy
Authors: Raine B.C. , Brown S.D.
Published: February 2023

Accurate determination of stability constants for actinides is necessary for prediction of transport properties of nuclear waste. Since solubilities are generally low, these stability constants must be determined in dilute solution. We have used cw and pulsed laser-induced photoacoustic spectroscopy to study trace neodymium (III) in water and in aqueous carbonate media; the coordination chemistry of Nd(III) is similar to that of many actinide species, so that Nd(III) is a good model system.
Photoacoustic Detection of Surface and Bulk Absorptions in a Standing Wave
Authors: Bertrand Lionel , Monchalin Jean-Pierre
Published: February 2023

High power lasers require optical components with extremely low bulk and surface absorptions. A method which allows to determine separately these two contributions for a transmitting window is necessary if one wants to improve the material preparation and the polishing technique. When the surface is coated it is also important to be able to measure the intrinsic absorption of the coating material and the absorption occuring at the interfaces.
Photoacoustic Spectroscopy of Metals and Metglasses+)
Authors: Heihoff K. , Pelzl J. , Croitoru N. , Cornaz P.
Published: February 2023

Metallic compounds are optically opaque in the infrared and visible wavelength region. Due to their high reflectivity R, only a small part (1-R) of the incident light intensity Io is absorbed in the material. With regard to the optical detection, the experimental conditions are very similar to those of transparent materials, where PAS has become a promising technique. The present work is concerned with PA studies of the optical reflectivity of amorphous metallic compounds. Here we report on first results obtained at 10K and at room temperature from some metglasses and noble metals; the latter have been used as reference materials.
Absorption Measurement of Optical Fiber by Photoacoustic Method
Authors: Huard S. , Chardon D.
Published: February 2023

Optical fibers are good materials for photo-acoustic investigation. First, their very low absorption limits optical measurements and second the Rayleigh diffused light, often greater than absorbed light, appears as a background. In optical communication range (0.8, 1-3 μm) it is well known that pure absorption is very low and even unmeasurable; nevertheless at other wavelengths such studies by photoacoustic methods are interesting to know the concentration of ions like OH-. On another point of view, if other optical ranges are considered (UV for example) absorption is not negligeable and must be known. But in this case the diffused Rayleigh light is very important (Power varies as λ−4).
An Investigation of Polyester-Cotton Textiles using Photoacoustic Spectroscopy
Authors: Castleden S.L. , Ashworth C.M.
Published: February 2023

The conventional procedure used for the quantitative analysis of components in commercial textile products involves separation by dissolution of one of the individual components in a suitable solvent followed by a gravimetric determination. The British Standard method for the analysis of polyester-cotton mixtures involves the use of hot, concentrated sulphuric acid to dissolve the cotton component, allowing the mass of polyester to be determined (1). Other methods proposed for this determination include the use of sodium hydroxide (2) to dissolve the cotton and tetrachloroethane (3), 1,1,1,3,3,3-hexa-fluoropropan-2-ol (4), or ethanolamine (5) to dissolve the polyester. Although the precision and accuracy of these gravimetric procedures are advantageous the period of time necessary to perform each analysis is rather great and hazardous chemical reagents must be used.
Self-supporting Carbon Glass Films: A PAS Reference Sample
Authors: Coufal H.
Published: February 2023

Photoacoustics, being an effect due to optical and thermal processes within a sample, require reference samples with well-defined spectroscopic, thermal and geometric properties.
Fourier Transform Infrared Photoacoustic Studies of the Chemistry of Organometallic Species Supported on Silica and Alumina Powders
Authors: Kinney John B. , Staley Ralph H.
Published: February 2023

The chemistry of supported cobalt, platinum, chromium, and titanium organometallics has been investigated using a Nicolet Model 7199 Fourier Transform Infrared Spectrometer with photo-acoustic detection. Studies in each system include attachment to high surface area silica and/or alumina powder supports and thermal and/or photochemical reactions with various reagents and molecules. Emphasis is on the behavior of these systems as catalysts.
Nonlinear Photoacoustic Spectroscopy
Authors: Van Stryland Eric W. , Woodall Milton , Soileau M. J. , Williams William E.
Published: February 2023

The capabilities of the photoacoustic technique to measure small absorptivities is now well documented. This capability is now being exploited to measure nonlinear absorption in a variety of materials. The potentials of this new non-linear spectroscopic techniques are just beginning to be realized. Preliminary experiments have shown the ability to separate linear and nonlinear absorption in solids,1 several nonlinear processes in gases have been observed,2 and Raman and two-photon spectra of liquids have been obtained.3,4 All indications are that nonlinear photoacoustic spectroscopy, NLPAS, will be as fruitful a field as linear photoacoustic spectroscopy has been in the past.
Accuracy of Photon Correlation Measurements on Nonergodic Samples
Authors: Schätzel Klaus
Published: February 2023

Typical photon correlation experiments estimate temporal correlation functions of scattered light intensity as time averages. This procedure yields the desired ensemble averages as long as the detected light constitutes an ergodic stochastic process. Fortunately, this condition is met for most scattering experiments, particularly for measurements on fluid samples. But there are two notable exceptions, glasses and gels. Such systems have been recognized as nonergodic samples. Their most characteristic feature are large fluctuations in measured intercepts produced by minor changes of detector position or sample orientation. Three different schemes were proposed to construct valid and reproducible dynamic structure factor data for nonergodic samples [1-3]. This paper discusses their relative merits in terms of statistical accuracy and applicability.
Characterization of Microemulsions in Supercritical Fluids by Photon Correlation Spectroscopy
Authors: Kalhan Sanjay , Gulari Esin
Published: February 2023

Supercritical fluids (SCFs) as solvents have properties that provide unique advantages. A SCF is a gas heated above its critical temperature and compressed beyond its critical pressure and it possesses both liquid-like and gas-like properties. It is possible to vary these properties in a continuous fashion by changing the temperature and pressure without going through a phase separation. It has been demonstrated that inverse microemulsions can be formed in SCFs. The solubilization capacity, critical micelle concentration, and the strength of micellemicelle interactions depend strongly on the density of the continuous phase.
Speckle Fluctuations and Their Use as Probes of Dense Random Media
Authors: Yodh Arjun G.
Published: February 2023

There is a rich variety of systems in nature which are essentially dense aggregations of particle-like structures whose positions vary randomly in space and time. Unfortunately because the particles often scatter light strongly, progress in our understanding of fluctuating, random media has been limited to very dilute systems. Recently, a number of researchers have developed and applied a new spectroscopy to study the properties of colloidal suspensions which multiply scatter light [1]. This method, called diffusing-wave spectroscopy (DWS), exploits the diffusive nature of light transport in strongly scattering media to relate temporal intensity fluctuations of the scattered light to average particle motion. In contrast to traditional quasi-elastic light scattering methods, DWS probes particle motion in dense, strongly scattering colloids and over length scales much shorter than the wavelength of light (<10Å).
Coherent Backscattering and Laser Feedback Microscopy
Authors: Bearden Alan
Published: February 2023

Laser Feedback Interferometry — It is well known in the laser field that laser light re-entering a laser cavity can produce interference, in some cases sufficient to produce chaotic effects even to the extent of extinguishing laser action [1]. What is less well known is that it is possible to use controlled re-entry light as the basis for laser interferometry where the laser acts simultaneously as light source, detector, amplifier, and interferometer reference and measuring arm [2-5]. If a target surface, which may be a mirror or a diffuse reflector, intercepts the laser beam and coherent laser light is retro-reflected (back-scattered) back into the laser cavity resonant mode (i.e., TEMoo), interference occurs with the circulating energy [6-8] affecting the intensity of the laser. Milliwatt He-Ne lasers, with an emission wavelength of 632.8nm, typically incorporate end mirrors of >98% reflectivity. With a specular reflector as target, intensity modulations of ≤30% are observed and interferometric information (phase and amplitude) is readily measured with diffuse targets and back-scattered light intensities as low as 10-6% of the incident beam intensity [9,10]. One useful model of this effect, called laser-feedback interferometry, is to regard the emergent-end mirror and the target surface as two “mirrors” forming a Fabry-Perot etalon; therefore, displacement of the target (mirror) produces changes in the effective reflectivity of the laser-end mirror pair resulting in modulation of the laser cavity-resonator properties.
Imaging Through a Strong Scattering Medium Using Nonlinear Optical Field Cross-Correlation Techniques
Authors: Bashkansky M. , Reintjes J.
Published: February 2023

There are certain applications where it is desirable to image an object embedded in, or hidden behind, a scattering medium. An example in the medical field would be transillumination of human tissue1,2. Among other potential applications one could consider imaging through any highly scattering medium like clouds or plastics. The obstacle to overcome is the multiply scattered light obscuring the image of the object. Several techniques have been employed to solve this problem. All of them are relying on the fact that the highly scattered light is delayed in time with respect to the less scattered light. The forward scattered component of the light transmits more spatial information about the hidden object. Using very short laser pulses(typically less than a few ps) and time gating one can filter out the scattered light which arrives at the detector later in time. Various time-gating schemes have been used including fast gated electronic amplifier2, fast streak camera3, optical shutters using Kerr effect4, holography with either short5 or long6 broadband laser pulses, and a number of nonlinear-optical techniques7,8,9. Often submillimeter spatial resolution is desired which requires the use of subpicosecond lasers with the gating techniques. It is desirable to extend the hidden object imaging to longer laser pulses that are readily available with commercial lasers today. For example, with longer pulses, higher energies per pulse can be used within the ANSI exposure limits for human tissue. This can significantly reduce the requirements on image collection. Recently a technique called Chrono-Coherent Imaging6 (CCI) was developed, where the short coherence length of a long pulse duration broadband light source is used for gating. The light is split in two beams, where one of the beams illuminates the object. The interference between the two beams is recorded on the film as a holographic image. One of the disadvantages of this method is the degradation of the holographic image due to the scattered light which is also incident on the film. In addition, it is not a real-time imaging technique.
Inclusions in a Micron Sized Electrodynamically Levitated Droplet
Authors: Bronk Burt V. , Smith Michael J. , Arnold Steve
Published: February 2023

The development of the quadrupole levitation balance, has led spectroscopic studies of the characteristics of levitated micron-sized droplets(1-7). Experiments not available for other systems arise with this "world's smallest test-tube". In one example it was shown that very high-Q modes occuring for electromagnetic radiation in these nearly perfect spheres permits highly efficient transfer of energy between molecules seperated by distances far larger than those characteristic for Foerster transfer(8). In another application, the possibility of using a sufficiently small droplet consisting of a non-fluorescent solvent as host with one or a few fluorescent molecules present was shown to allow detection of the presence of a single molecule of rhodamine(9).
Probing Turbulence with Homodyne Photon-Correlation Spectroscopy
Authors: Goldburg W. I. , Måløy K. J.
Published: February 2023

Before photon correlation spectroscopy was used in condensed matter physics, and all measurements were made in the frequency domain, it was recognized by Bourke et al.[1] that turbulence could be studied by light scattering. The frequency of light scattered by a single seed particle moving with velocity v(t) in the flowing fluid, will be Doppler shifted by an amount (k) • v(r(t)), where k is the scattering vector. If the fluid contains not one particle but two, a photodetector will register the beat frequency Ω of these two Doppler shifts, and the photocurrent will be modulated at a frequency Ω = k·δv, where δv = [v(r) –v(r + ℓ), where the two particles are separated by the ℓ. The intensity itself, will then be, within a multiplicative constant, I(t) = 1 + cosΩt. Since k is of the order of 105 cm–1. In a water tunnel one might encounter velocity differences of the order of 10 cm/sec, if ℓ is a few mm or less. In this case Ω–1 will be of the order of 1 µsec, a characteristic time that falls in the range of present-day correlators. Of course, a seeded turbulent fluid will contain many particle pairs. If they are present at random positions in turbulent or laminar flow, the seed particles will give a pairwise contribution to I(t), and will cause the the scattered intensity to fluctuate ain time in a random fashion[2].
Algebraic Solution To The Master Equation For A Quantized Cavity Mode With Initial Squeezed State
Authors: Schmitt H. A. , Mufti A.
Published: February 2023

There are numerous examples in physics that can be modeled by the interaction between a small system of interest and a reservoir. The interaction typically leads to the irreversible decay of the system variables. As the system evolves into an equilibrium state, various parameters such as mean values, probabilities, and variances change until the final steady state is reached. The evolution of a system coupled to a reservoir with a short memory is often described by a master equation for the reduced density operator of the system. Master equations are important in physics because of their generality and hence wide range of applicability [1].
Study of the Noise of Correlation and Structure Functions
Authors: Lorusso G.F. , Capozzi V. , Minafra A.
Published: February 2023

The influence of the noise of the statistical estimator used for the interpretation of Dynamic Light Scattering (DLS) measurements on the information available from experiments has been discussed by several authors [1,2]. The knowledge of the behaviour of noise of the used statistical estimator permits an improvement of the accuracy of DLS measurements.
Burst Digital Correlator as LDV Signal Processor
Authors: Ikeda Yuji , Shimazu Masaki , Nakajima Tsuyoshi
Published: February 2023

Current LDV techniques have been employed in undertaking the challenge to the understand complex physical phenomena of flow velocity and turbulence characteristics such as those found in engines, turbomachinery, near wall, and combustion equipment. Especially, it is very important to distinguish turbulence and fluctuation in order to understand the cyclic variation. An optical fiber linked LDV (FLDV) has been developed to flows to which could hardly be made y the conventional LDV access, but the performance of the FLDV has not been enough for in- cylinder flow. The LDV system should be optimized not only for optics but also for signal processing. In shear flow regions such as step-back flow and recirculating flow, there are very large velocity gradient regions where high spatial resolution of the measurement volume is required. When the size of the measurement volume decreases, the fringe spacing has to be small to ensure a minimum fringe number, which induces an increase in the detected frequency. Furthermore, having a large memory with a high data rate is also required to analyze the in- cylinder flows and oscillating flow. In order to overcome these problems and for further LDV applications, the LDV processor should be developed, whose performance is characterized by wide bandwidth, low SN ratio, high data rate, large memory, and real time monitoring.
Prospects for a 1 ns Digital Correlator
Authors: Dove W T , Sampson D D , Jackson D A
Published: February 2023

Conventional multichannel digital correlators are based on electronic shift register delays and logic gate multipliers. Due to problems of low skew clock distribution over a large number of channels and power consumption, they are typically restricted to bandwidths of 50 MHz. We recently reported a successful implementation1 of a fibre-optic-based digital correlator2 which has the potential to exceed 500 MHz bandwidths. Fig. 1 shows a schematic diagram of the prototype correlator.
Photon Correlation and Scattering as Inverse Problems
Authors: Pike E R
Published: February 2023

A powerful mathematical and computational technique for the solution of a number of experimental inverse problems, described by an underlying first-kind Fredholm equation has been under development by several groups in recent years. The programme had its origins in original theoretical work by McWhirter and Pike [1] in which, for the first time, the inverse Laplace transform was solved by ‘information theory’ techniques. These techniques have been greatly generalised by the use of the theory of singular systems which provide exact ‘Fourier’ orthonormal bases for the description of experimental data and reconstructed continuous object solutions of the data processing problem.
Time-of-flight Velocimetry: Bias and Robustness
Authors: Rose Bjarke , Imam Husain , Lading Lars , Hanson Steen G.
Published: February 2023

Accurate non-contact velocity measurement of a moving surface is an important quantity in online manufacturing. We have investigated a system employing the principle of Laser Time-of-flight Velocimetry (LTV) to measure the velocity of moving solid surfaces (Fig. 1). The LTV system is based on determining the time it takes for a scattering element to travel from one illuminated region to another. The spacing between the two regions is known and the estimated velocity along the direction connecting the two spots is then simply given by the ratio of the spacing to the measured time-of-flight1. The time-of-flight is measured by a correlation scheme.
Viscosity Measurements By Dynamic Light Scattering Using A Novel Scattering Cell
Authors: Will Stefan , Leipertz Alfred
Published: February 2023

Dynamic light scattering (DLS) has proven as a successful technique both for the determination of various thermophysical properties of fluids [1][2] and for particle size analysis [3][4]. A useful special application of characterising fluids by DLS is the measurement of the dynamic viscosity [5][6].
Chaos in Light Scattering
Authors: Ngo Dat , Videen Gorden , Dalling Robert H.
Published: February 2023

Traditionally, chaos has been associated with a system’s trajectory in phase space or with the evolution of the system’s parameters through time. Previous investigations into chaotic scattering from electromagnetic radiation were undertaken by Jensen1 who studied the trajectory of light rays inside a stadium-shaped cylinder, and by Doron et al.2 who investigated microwave scattering from an elbow-shaped horn. In this presentation, we submit for what we believe to be the first time, a novel system whereby chaos can arise from the partial summation of an otherwise convergent infinite series.
Investigation of turbulent flow characteristics by Homodyne Correlation Spectroscopy
Authors: Chopra S. , Bhat S.K.P. , Razdan A.K.
Published: February 2023

Homodyne Correlation Spectroscopy (HCS) is a very useful technique for studying the flow characteristics of fluid turbulence where the intensity of the laser light scattered from small seeded particles is detected and processed in the time domain by means of fast digital correlators. The intensity auto correlation function g(τ) of the scattered light measured by these correlators is sensitive to the relative velocity fluctuations V(R,t) between pairs of seed particles in the flow separated by a distance R thereby characterizing the spatial characteristics of the flow. It has been shown both numerically and experimentally that turbulent flow is intermittent in nature [1], The intermittent effects are characterized by increasingly non-Gaussian statistics of velocity differences or velocity gradients in the flow for smaller and smaller scales of turbulence. It is predicted that the deviation from gaussian statistics is due to the presence of small scale coherent structures [1] and inactive regions [2] in the turbulent flow field. We have recently [3] employed the HCS technique to experimentally verify our theoretical model for the probability distribution function P(V(R,t)) of relative velocity fluctuations V(R,t) and the present work highlights some of our results in the light of above predictions regarding the intermittent nature of turbulence.
160-Channel 0.5-nanosecond Hybrid Digital Correlator Based Upon Fiber Optic Delay Lines
Authors: Podoleanu Adrian GH. , Jackson David A.
Published: February 2023

In order to implement digitally the correlation function, three operations are needed: delay, multiplication and averaging. The hybrid architecture of a multichannel fiber optic digital correlator (MFODC) shown in Fig. 1 implements the delays using optical fibres and coaxial cables, the multiplication using AND gates and the averaging by repeating the measurements and collecting the data using high speed high capacity counters. The main advantage of this architecture as proposed in [1] and demonstrated in the first 8 channel 10 ns MFODC [2] is that it eliminates the clock distribution, which is a major impediment in increasing the speed of electronic correlators. Using shift registers and clock distribution, the commercially available electronic multichannel correlators have lag times no less than 5 ns.
Quasielastic light scattering spectroscopy of blood serum: diagnostics of diseases and demarcation of risk groups
Authors: Noskin V.A. , Ivanova M.A. , Klopov N.V. , Lebedev A.D. , Noskin L.A. , Noskin V.A. , Pavlov M. Yu.
Published: February 2023

It is well known that in subfractional compound of blood serum (or plasma) numerous shifts with correlated character specific for a particular nature of the disease may arise during diseases varying by etiopathogenesis. A large arsenal of electrophoresis, chromatography and sedimentary methods is used in clinics-laboratory practice for diagnostics of the character of subfractional shifts. Without discussing diagnostic informational capacity of each method in use we could observe just a few principal difficulties: 1. Each method identifies a nature of ingredients of blood plasma/serum in a quite narrow interval of their molecular sizes. 2. A large amount of blood is necessary for making most part of investigations. 3. Hard and long preparation procedures are being used for making investigations. 4. Full information on subfractional compound of biological fluid may be got only with combined use of the methods mentioned above.
Is the Shape of Phase for Globular Proteins Universal?
Authors: Muschol Martin , Banish Michael R. , Thomas Bill R. , Rosenberger Franz
Published: February 2023

Below some critical temperature Tc aqueous solutions of hen-egg white lysozyme (HEWL) exhibit a phase-separation into two liquid phases with largely differing protein concentrations [1,2]. Similar observations were made with γ-crystalline [3], a bovine lens protein. In both cases, this phase separation is metastable since it occurs under crystallization conditions. The implication of this metastable separation for the determination of advantageous crystallization conditions has received little attention. Using static light scattering, we determined the transition temperature of the liquid-liquid phase separation vs. protein concentration, cp, at salt concentrations typically used in crystallization experiments. We have also qualitatively investigated concanavalin A and apoferritin solutions for such phase transitions. Together with earlier solubility data, the light scattering results define the phase behavior of lysozyme solutions. These and the prior observations suggest a universal character of globular protein phase diagrams, and provide a rational underpinning for the empirically established narrow range of crystallization conditions.
Two-step dispersion profiles for WDM soliton transmission
Authors: Forysiak W. , Devaney J. F. L. , Smith N. J. , Doran N. J.
Published: February 2023

In periodically amplified, wavelength-division multiplexed (WDM) soliton transmission systems, collisions between solitons in different channels result in permanent shifts of their central frequencies. The resulting effect is a timing jitter in the soliton arrival times, which limits the system performance. In this paper, we study the reduction of these frequency shifts by stepwise dispersion profiling of the transmission fibre. In particular, we use the analysis in Ref. [1] to calculate the residual frequency shifts due to two-step dispersion profiles as a function of collision position. We compare the performance of various two-step profiles, and identify a new, optimum profile for the reduction of collision-induced jitter in WDM soliton systems.
Study of Chain Formation and Chain Dynamics in a dilute Magnetorheological Fluid
Authors: Hagenbüchle Martin , Liu Jing
Published: February 2023

Magnetorheological fluids (MR fluids) attracted much interest in recent years [1]. This is due to both their potential applications such as valves, clutches, brakes, and dampers [2] and the fact that they provide a good model system of a complex fluid where the particle-particle interaction is anisotropic. MR fluids consist of micron- or submicron-sized, magnetizable particles which are dispersed in a suitable solvent. We used a monodisperse ferrofluid emulsion as a model MR fluid, i.e. in our case the particles are ferrofluid droplets and the solvent is water. With no magnetic field applied the droplets are not magnetic and behave basically like hard spheres. In this state the MR fluid is a free flowing liquid with a consistency similar to that of the solvent alone. Application of an external magnetic field induces a dipole moment in each droplet. The dipole-dipole interaction between the particles causes the formation of chains and columns of particles along the field lines provided the interaction energy exceeds the thermal energy. In concentrated suspensions the structure formation occurs on a time scale of milliseconds and causes the fluid to respond to shear forces perpendicular to the field direction with a considerable yield stress and a dramatically increased viscosity [3].
The Structure and Dynamics of Hard Sphere Colloidal Crystals under Micro-Gravity with Quasi-Elastic Light Scattering
Authors: Zhu J.X. , Chaikin P.M. , Min Li , Russel W.B. , Meyer W.V. , Rogers Richard B.
Published: February 2023

We use quasi-elastic light scattering to study the structure and dynamics of concentrated hard sphere colloidal suspensions in microgravity. The hard sphere system is the simplest and the most fundamental model system in condensed matter physics. At low volume fractions, ϕ < 0.494, the system is in a disordered state. At ϕ greater than 0.494, the system becomes ordered. Ground based studies of the crystalline phase are subject to sedimentation due to gravity. This paper reports the first experiment of a series planned for microgravity, the NASA Colloidal Order-Disorder Transition (CDOT) project conducted in the glovebox of the Second United States Microgravity Laboratory (USML2) which flew on board space shuttle Columbia from October 20 to November 5 in 1995. A detailed hardware description will be given by another paper. This paper is concerned with the scientific aspects of the experiments.
Laser Light Scattering of Polymer Solutions
Authors: Chu Benjamin
Published: February 2023

Laser light scattering (LLS), small angle x-ray scattering (SAXS) and small angle neutron scattering (SANS) are complementary techniques.1 Together they become unmatched among the physical methods which can investigate the structure and dynamics of polymeric materials over a large range of length and time scales. The unique features of LLS are its ability to determine not only molecular weight, size and internal motions of polymers in solution or of colloids in suspension, but also the size distribution. The applications of LLS to polymer physics and colloid science have been extensive and noteworthy, especially in particle size analysis. In this lecture, three unique examples on (1) Teflon solution characterization,2 (2) coil-to-globule transition3, and (3) supramolecular formation of block copolymers in selective solvents4 are presented.
Application of Dynamic Light Scattering to Aggregation and Gelation
Authors: Martin James E.
Published: February 2023

In the last several years there has been considerable interest in the structure of aggregates and gels, in large part due to the high interest in the fractal geometry these objects exhibit. Of course, light scattering is commonly used to determine fractal dimensions, so it is natural enough to run the scattered field into an autocorrelator to find out what the dynamics are up to. This seemingly innocent move is the first step in a long journey into the unusual dynamical behaviors exhibited by these fractal systems. Since the dynamics of aggregates and gels are quite different, it will be helpful to discuss them sequentially.
Determination of the Time Dependence of Periodical Optical Signals by Correlation Spectroscopy
Authors: Vossmerbäumer C. , Schweiger G.
Published: February 2023

The time dependence of a periodical signal is determined by measuring its autocorrelation function and its counting rate distribution. The method is applied to the investigation of highly periodical concentration fluctuations observed in the mixing zone of a triple jet containing CO2 and air.
Photon-Correlation Laser Velocimetry in Reciprocating-Engine Research
Authors: Fansler Todd D.
Published: February 2023

Following a detailed review of practical aspects of photon-correlation laser-Doppler velocimetry, automotive applications are surveyed with emphasis on broad experimental and interpretive concerns common to unsteady flows and confined environments. Such situations typically permit only limited optical access and thereby place a premium on efficient operation with weak (single-photon) signals in the presence of considerable noise. Fast, robust data-acquisition and -reduction techniques that minimize user intervention are described. The survey of automotive applications concentrates on turbulent in-cylinder flow fields and combustion, but briefly includes wind-tunnel and soot-sizing measurements.
Use of Burst-Triggered Correlation for Laser Anemometry Measurement in Turbomachinery
Authors: Jones D. G. , Wiseall S. S.
Published: February 2023

The application of burst-triggered correlation to the processing of laser doppler anemometry signals is described, and some measurement results in a compressor presented.
Miniature Instrumentation for Photon Correlation Experiments
Authors: Brown Robert G. W.
Published: February 2023

Traditional optical systems for photon correlation laser anemometry and spectroscopy have relied upon physically large and fairly expensive lasers, "bulk-optics" such as lenses of a few inches diameter, large mechanical mounts etc and carefully selected, fragile and bulky photon-counting photomultiplier detectors. In some cases experimental fluid dynamics at a desired position in a flow, perhaps deep inside complex machinery, is physically impossible or very difficult. Similar problems exist with photon correlation spectroscopy, eg., heterodyne experiments. We have investigated and characterized various optical and electro-optical components with the aim of replacing existing photon correlation laser anemometry and spectroscopy techniques in miniaturized form, and with significant cost reduction.
Light Scattering From Fractal Colloid Aggregates
Authors: Lindsay H. M. , Lin M. Y. , Weitz D. A. , Ball R. C. , Klein R. , Meakin P.
Published: February 2023

We present a detailed description of both static and dynamic light scattering from fractal colloid aggregates. By properly including the effects of rotational diffusion, we can account for the shape of the autocorrelation functions measured by photon correlation spectroscopy (PCS). We show that the first cumulants measured as a function of time and scattering wavevector can be scaled into a single master curve. The shape of this curve is critically dependent on the details of the aggregation process and aggregate structure, and we use this to demonstrate the universality of colloid aggregation.
Dynamic Light Scattering from Long-Range Density Correlations in a Nonequilibrium Liquid
Authors: Law B. M. , Gammon R. W. , Sengers J. V.
Published: February 2023

We have performed small-angle Rayleigh scattering measurements in toluene removed far from equilibrium by a large stabilizing temperature gradient. The experiments demonstrate the existence of long-range density correlations through a strong enhancement of the thermal fluctuations and they also reveal a negative contribution at shorter-time scales from the viscous fluctuations in agreement with the theoretical predictions. The experiments confirm that both effects vary with (∇T)2/q4, where ∇T is the temperature gradient and q the wave number of the fluctuations.
On-Line Liquid Chromatography Detection by Photon Correlation Spectroscopy
Authors: Carr R. J. G. , Stansfield A. G. , Rarity J. , Brown R. G. W. , Clarke D. J. , Atkinson T.
Published: February 2023

Photon Correlation Spectroscopy has been applied to the routine monitoring of proteins eluting off liquid chromatographic separation systems. The technique has been configured as an on-line, in situ detector capable of remote analyses using fibre optic technology. Analyses of flowing protein samples has been demonstrated and its use in process biochemistry as a quality assurance monitor is discussed.
Exciton Interaction in GaAs-GaAlAs Superlattice
Authors: Hulin D. , Migus A. , Antonetti A. , Mysyrowicz A. , Gibbs H.M. , Peyghambarian N. , Morkoç H. , Masselink W.T.
Published: February 2023

A blue shift of the exciton line has been recently observed1 in MQWS (53 Å GaAs-53 Å GaAlAs) after femtosecond excitation. This shift has been proved to originate from the presence of large number of excitons in the system, either directly created by resonant pumping or due at longer delay to the pairing of the electrons and holes initially created by band to band excitation at low temperature. This blue shift has not been reported in the bulk material GaAs. This effect being related to the sample structure, it is important to know whether the two-dimensional confinement within a well is the only origin of this new type of exciton interaction or if the superlattice type of the sample has to play a role. Experiments have been performed in MQWS with different barrier and well thicknesses, ranging from the case of thick barriers (in order to minimize the interactions between the wells) to the case where excitonic wave functions overlap over neighboring wells. The experimental results demonstrate the influence of the superlattice structure- A model is developped which takes into account the difference between the bulk material isolated wells and superlattices.
Ultrafast Traveling-Wave Light Modulators with Reduced Velocity Mismatch
Authors: Izutsu Masayuki , Haga Hiroshi , Sueta Tadasi
Published: February 2023

For the high-speed and wideband operation, the traveling-wave structure has been developed for guided-wave modulators. Applying the asymmetric stripline as electrodes, the frequency response of the LiNbO3 waveguide modulators has been smoothed over. The operation bandwidth has been expanded up to 18 GHz[1] and a temporal pulse waveform less than 50 ps created by the modulator has already been observed by the streak camera[2].
Subpicosecond Response Times from Ion Bombarded InP
Authors: Downey P. M.
Published: February 2023

Picosecond photoconductivity studies of 3He
+
bombarded Fe-doped InP have demonstrated free carrier lifetimes and mobilities of 6 ps and 600 cm2/Vs, respectively[1]. This result compares very favorably with the 10 ps response time and mobility less than 20 cm2/Vs observed in oxygen irradiated silicon-on-sapphire[2]. Even when compared to proton irradiated GaAs sampling gates[3] the He bombarded InP photoconductors demonstrate over an order of magnitude higher peak electrical transmission with comparable sampling apertures and optical pulse energies. Radiation damaged InP appears then to be the more promising material for achieving ultrashort response times and optimum photoconducting sensitivity. In this paper we explore the extent to which the free carrier response time can be reduced by increasing the radiation dose in ion bombarded InP photoconductors. Subpicosecond response times are demonstrated for InP photoconducting sampling gates, but the required radiation doses are found to severely compromise the device sensitivity.
Picosecond Josephson Logic Gates for Degital LSIs
Authors: Sone Jun-ich , Tsai Jaw-Shen , Abe Hiroyuki
Published: February 2023

This paper will discuss the realized and projected picosecond logic speed of Resistor Coupled Josephson Logic for LSI applications. The 4b x 4b parallel multiplier, developed very recently by using 5-μm lead alloy technology, demonstrates a multiplication time as small as 280 picoseconds. The averaged logic delay per gate is 21 picoseconds in this multiplier. The advancement in Josephson IC fabrication technology, on the other hand, has shown the possibility for fabricating 1-μm minimum line width Josephson LSI. The projested logic delay per gate of densely packed 1-μm RCJL LSI will be less than 10 picoseconds.
Time-domain Measurements for Silicon Integrated Circuit Testing Using Photoconductors
Authors: Eisenstadt W. R. , Hammond R. B. , Bowman D. , Dutton R. W.
Published: February 2023

Picosecond time-domain measurements of silicon integrated circuit interconnects were successfully performed using photoconductors integrated on-chip. Both bulk silicon and thin-film polycrystalline silicon photoconductors were studied. Standard integrated circuit fabrication techniques followed by shadow-masked, ion-beam irradiation were used to create photoconductor/interconnect structures. Starting materials used were 70 ft-cm n-type wafers and 16 Ω-cm p-type wafers. A subpicosecond pulsed laser system excited the photoconductors to produce and sample picosecond pulses on the Si substrate.
The Role of Ultrashort Optical Pulses in High Speed-Electronics
Authors: Shank C. V.
Published: February 2023

As the speed of electronic and optoelectronic devices moves into the picosecond time domain, optical techniques have the potential of an ever increasing importance in analyzing both device performance and the physical processes necessary for understanding high-speed operation. Optical methods have the advantage of ultrashort time resolution that exceeds all other high-speed measurement techniques. The state of ultrashort optical techniques is reviewed and the areas where these methods are likely to have an important impact are discussed.
Picosecond Processes in Carrier Transport Theory*
Authors: Ferry D. K.
Published: February 2023

High-electric-field transport has been studied for some three decades. In recent years it has become of much more interest due to the advent of semiconductor devices on the micrometer and submicrometer dimensional scale. Theoretically, such hot-carrier transport has been discussed primarily in terms of the Boltzmann equation. However, semiconductor transport in high electric fields is a classical example of a far-from-equlibrium system. On the short-time scales appropriate to the submicrometer dimensions, the Boltzmann equation ceases to have general validity, and more exact approaches have been sought.
Picosecond Time Resolved Photoemission Study of the InP (110) Surface
Authors: Bokor J. , Haight R. , Stark J. , Storz R. H. , Freeman R. R. , Bucksbaum P. H.
Published: February 2023

Angle resolved ultraviolet photoemission spectroscopy (ARUPS) is a powerful and well established tool for the study of bulk and surface electron states in solids. We report the first demonstration of picosecond time-resolved ARUPS. The technique was used to study the dynamics of electrons photoexcited by a 50 picosecond visible laser pulse on a cleaved InP (110) surface.
Properties of GaAlAs/GaAs Quantum Well Heterostructures Grown by Metalorganic Chemical Vapor Deposition
Authors: Bumham R. D. , Streifer W. , Paoli T. L. , Thornton R. L. , Smith D. L.
Published: February 2023

The existence of the heterojunction and the recent development of methods for growing a variety of epitaxial ultrathin III-V semiconductor layers (wider-gap or narrower-gap, doped or undoped, abrupt or graded) enables the fabrication of sophisticated quantum-well heterostructures. In the past few years, one of these techniques, metalorganic chemical vapor deposition (MO-CVD), has become increasingly popular as a consequence of its versatility and economy. The chemistry of MO-CVD growth of III-V compounds was pioneered by Manasevit as early as 19681; however, it was Dupuis and Dapkus in 19772 who demonstrated that high quality GaAlAs/GaAs heterostructure lasers can be grown by MO-CVD.