bluuebunny/crossref_metadata_2025 huggingface dataset:
Modified attenuated total reflection for the fast and routine electrooptic measurements of nonlinear optical polymer thin films
Authors: Chen Antao , Chuyanov Vadim , Garner Sean , Steier William H. , Dalton Larry R.
Published: February 2023

In the course of developing EO polymers, a convenient and fast method to obtain the electrooptic (EO) coefficients, r33 and r13, is highly desirable. Some of the existing EO measurement techniques such as Fabry-Perot interferometry(1) and ellipsometry(2) require metal deposition and electrode processing for each test sample. Therefore, they are not suited for daily sample testing. Second harmonic generation (SHG) is an indirect method to measure the EO coefficients(3). It is usually performed with 1.064 Nd:YAG laser and encounters difficulties with polymers that contain high µβ chromophores because these chromophores usually have red-shifted absorption peaks that causes the Kleiman symmetry, a fundamental assumption of this technique, to break down. Attenuated total reflection (ATR) can directly measure the EO coefficients with no restriction on the wavelength of the absorption peak. One measurement scan provides the refractive index, the thickness, and an EO coefficient. Typically, the thin film electrode in contact with the test sample is made of Au or Ag in conventional ATR techniques(4). These metal thin films are soft and not durable for repeated measurements. The curve fitting algorithm for data processing(4, 5) is also inconvenient for fast sample evaluation. In this paper, a modified ATR technique for routine EO measurement is presented which does not require electrode preparation for each test sample and uses a simple algorithm for data processing.
Nonlinear absorption in CuPc-SiO2 Composite
Authors: Blanco E. , Litrán R. , Ramírez-del-Solar M. , Aranda F. J. , Rao D.V.G.L.N. , Rao D. Narayana , Akkara J.A. , Nakashima M. , Tripathy S.
Published: February 2023

Recently macrocyclic organic dyes have attracted a lot of attention as possible candidates for applications in optical power limiters and pulse shaping devices. The fundamental requirement for power limiting is that the system must exhibit fluence dependent reverse saturable absorption. Copper Pthalocyanines possess a larger excited state absorption cross section than a ground state absorption cross section. They are thus suitable candidates for limiting applications. Most of the nonlinear optical studies have been done for solutions of the dyes1. For applications such as intracavity pulse shaping devices a solid material is more attractive than a solution2. In this paper we report nonlinear absorption studies of Copper Pthalocyanine, CuPc, in solution in sulfuric acid as well as incorporated in a Silica matrix host. The concentration of the solution was 5.75 x 10-4 Molar. The composite had a concentration of 1 x 10-4 Molar in the sol. Upon drying of the gel we estimate a similar concentration for the composite as in the solution given the reduction in volume. The thickness of the composite is of 4 mm. The solution was held in 1 mm thick spectroscopic grade glass cuvettes. The CuPc/silica composite was obtained by the Sol-gel method from the hydrolysis of tetramethoxysilane (TMOS). The reaction of TMOS with acidic water (pH=2) was promoted by means of 20 kHz ultrasound energy. The resulting gel was kept drying at room temperature for two weeks. We observe marked differences in the linear absorption spectrum of the solution and the composite. These changes are attributable to aggregation of the Copper Pthalocyanine molecules in the pores of the silica matrix as well as to the interaction between the dye molecules and the matrix. The linear absorption spectrum for both samples is shown in Fig. 1.
Electro-optic Modulation Based on Channel Waveguide of Organic Single Crystal Material
Authors: Xu Jianjun , Zhou Ligui , Thakur M.
Published: February 2023

Channel waveguide is the basic element in fabrication of electro-optic modulator for external electro-optic modulation. Using polymer electro-optic materials, channel waveguide device can be comparative easily fabricated, but the main problem for polymer materials is their stability. On the other hand, organic single crystal has excellent stability, the disadvantage of them is the difficulty in processing which limited their application potential. Recently, channel waveguide has been fabricated by direct growth inside the hollow fiber, but those channel waveguides proved to be difficult to fabricate electrode besides the crystal [1]. By combining ideas of growth of crystal from hollow fibre and shear method [2], a new method able to fabricate raised-up channel waveguide of organic crystal was initiated. In this method, solution of organic molecule was introduced between two substrates, one of them has patterned lines on it. Due to the polar interaction between the substrate materials and molecules of the solution, Single crystal channel waveguides were grown along the patterned line on the substrate, the dimension and direction of the crystal materials were controlled by these patterned lines. Fig.1 illustrated the diagram of this method.
Molecular Orientation in Protein Films Deposited on Substrates Coated with Langmuir-Blodgett and Self-Assembled Monolayers
Authors: Edmiston Paul L. , Wood Laurie L. , Lee John E. , Saavedra S. Scott
Published: February 2023

Formation and characterization of organic thin film assemblies intended for use in biomolecular devices, such as biosensors, is currently a very active area of research. We have been investigating techniques for creating macroscopically ordered protein films formed by covalent bonding between a unique site on the protein and an appropriately derivatized substrate surface. Assemblies consisting of heme proteins immobilized on substrates coated with self-assembled monolayers and Langmuir-Blodgett are being examined. Macroscopic film order is probed using a combination of total internal reflectance fluorescence and planar integrated optical waveguide-attenuated total reflection spectroscopies, from which the orientation distribution of heme tilt angles in the protein film is determined.
Modern Design of Unifocal Lenses
Authors: Ahsbahs F. , Mercier J.L.
Published: February 2023

An unifocal ophthalmic lens is an optical system, in which image formation follows the same rules just as in classical optical design applied to zooms or telescopes.

The geometrical model is sufficient, in most cases, for predicting the images, so the designer has to cope with classical chromatic and geometric aberrations.

We will describe the philosophy of the modern software tools for automatic optical design by optimization, which are the unique way to design complex aspheric modern lenses.
Some Non-Conventional Types of Varifocal Spectacle Lens
Authors: Fowler C W , Pateras E S
Published: February 2023

The origins of varifocal spectacle lenses go hack a long way, the patent of Aves (1907) Being generally accepted, as the first practical design of lens. Varifocals as we know them today Began with the Varilux design from Bernard Maitenaz in the late nineteen-fifties. The original Varilux demonstrated three main features:

1) Stable distance power over the upper half of the lens.

2) Starting near the mid point of the lens, a narrow central progressive power corridor leads into a stable reading area at the bottom of the lens.

3) Complete 'invisibility' of the power zones giving rise to a single vision type appearance.
Binocular Vision Under Impaired Viewing Conditions
Authors: Rassow Bernhard , Wesemann Wolfgang
Published: February 2023

During the past few years spectacle lens manufacturers have been remarkably successful in improving the optical properties of progressive lenses. However these lenses still have astigmatic, prismatic and other refractive errors in the peripheral area of the narrow transitional middle corridor. These problems are tolerated in the interest of the more important aim of correcting the presbyopic eye with one lens for all distances. The errors manifest themselves as magnification differences, image distortions, image tilts and reduced visual acuity. During the development of new progressive lenses, manufacturers have tried to make the increase of these errors as smooth as possible. However, there are still quite a few questions open concerning the physiological effects of refractive errors associated with these lenses. For example, it has still not been determined to which extent the unwelcome side effects may impair fusion and binocular vision and which errors may be tolerated. Another important question which has evoked discussion is whether the binocular system reacts differently to equal optical impairments as compared to different impairments presented to both eyes.
Design Approaches for Bifocal IOL’s and CL's
Authors: Wesemann Wolfgang F.
Published: February 2023

While the number of contact lens wearers in the US doubled in the past decade, to 22 million, the growth rate has slowed down during the last years, because the average age of the contact lens population is increasing. It can be expected that, over the next several years, the typical contact lens wearing patient will be of presbyopic age. Therefore, a number of marketing analysts believe that the future of the contact lens market lies in the presbyopic patient (Wall Street Journal, 1989).
The Crystalline Lens
Authors: Campbell Melanie C.W.
Published: February 2023

Visual performance is influenced in many ways by the crystalline lens, too many to do justice to here. This paper will be restricted to a discussion of how the crystalline lens influences the optical quality of the image on the retina.
Optical Properties of the Bovine Lens Before, During and After the Induction of Cold Cataract
Authors: Sivak J.G. , Stuart D.D. , Weerheim J.A.
Published: February 2023

Introduction The induction of cataracts by reducing temperature has proven to be an attractive experimental paradigm for scientists involved in in vitro cataract research because of the speed and simplicity of the method and because cold cataracts are usually reversible (Bon, 1959; Zigman and Lerman, 1964; Lerman and Zigman, 1967). In general, cold cataracts can be induced in mammalian lenses by cooling to temperatures below 10°C but above freezing (Lerman and Zigman, 1967; Siezen et al., 1985; Uga et al., 1986). Age and species differences in the development of cold cataract have led to efforts to identify the responsible protein (Lerman and Zigman, 1967). However, uncertainty exists as to whether cold cataracts are due to a specific lens protein or to disruption of supramolecular protein organization (Lowenstein and Bettelheim, 1979; Ondruska and Hanson, 1983). The principle function of the lens is to focus or assist the cornea to focus light on the retina. While changes in lens transparency in vitro have been measured photometrically (Dragomirescu et al., 1983) little attention has been paid to lens refraction function in in vitro cataract research. We have developed a computer operated scanning laser system capable of measuring subtle changes in lens focal length and transmittance during long-term organ culture (Sivak et al., 1986). This method has been used to monitor lens damage produced by a variety of chemical agents as well as UV-B radiation (Sivak et al., 1990, 1991; Stuart et al., 1990). This study represents an effort to use the laser scanning system to measure bovine lens focal and relative transmittance characteristics before, during and after cold cataractogenesis.
Automated Refraction
Authors: Guyton David L.
Published: February 2023

Approximately twenty automated refractors are now available, including manual objective refractors, automatic retinoscopes, and remote-controlled refractors. Problems from alignment, irregular refraction and instrument accommodation are still not fully solved.
Progressive Addition Lenses - What Comes Next?
Authors: Fowler Colin
Published: February 2023

Progressive addition spectacle lenses (PALs) are now an integral part of spectacle lens dispensing. The first design is attributed Aves (1907), and used two aspheric surfaces of revolution. This design was characteristic of a number which appeared later, such as the Omnifocal (Volk and Weinberg, 1962), in that the power progressed continuously down the whole aperture of the lens. The main problem with this is at distance, where the lack of a large stabilised reading zone could be a considerable visual handicap to the wearer. A further problem with the Aves type of design is that using two aspheric surfaces would make the incorporation of prescription cylinders extremely difficult.
Design of a Research-oriented Simultaneous Recording System for the Lens Accommodation and the Pupillary Movement
Authors: Watanabe Takeru Ken , Nakamura Fukuzo , Yanagaki Hidenori , Kondo Yasuyuki , Koike Nobuyuki , Inoue Takamichi
Published: February 2023

We have designed an apparatus which can simultaneously record the refractive state and the pupillary dynamics of the eye. Our purpose is to build a reliable, measurement-oriented instrument for vision research that can be used for both human and animal experiments. Scope and requirements toward such design will be summarized as: i) simple optical configuration; ii) simultaneous, complete synchronous detection of lens accommodation and pupil size; iii) feasibility covering a full range of pupil dilation and constriction; iv) facility of computer interface for automated measurement; and v) versatility for physiological and psychophysical applications.
The Effect of The Eye’s Chromatic Aberration on Coaxial Photorefractive Patterns: A Geometrical Optical Analysis
Authors: Campbell Melanie C.W. , Bobier W.R. , McCreary C.R. , Power A.M. , Yang K.
Published: February 2023

Photorefractive methods provide rapid photographic measures of the refractive and accommodative states of infants and young children whose brief attention spans and limited cooperation reduce the effectiveness of more traditional methods such as retinoscopy and autorefraction. Three photographic methods have been designed: orthogonal1,2, isotropic2,3 and eccentric4,5,6. In all three methods, light from a small flash source set near the aperture of a camera lens is reflected from the eye and photographed as a pattern of light whose extent varies with the refractive error and pupil size of the eye. In the past, complicated ray traces, using detailed optical specifications of the camera system, were required to determine the theoretical relationship between the blur size and the refractive error. The authors have developed a novel geometrical optical analysis for all three methods in which the pattern is defined at the plane of focus of the camera. Because this plane is conjugate with the detector plane of the camera, the predicted size of the pattern can be determined simply by measuring the magnification of an object located at the camera’s plane of focus. This does not require knowledge of the optical design of the camera lens.
Quantitative Model of Corneal Astigmatism from Topographic Data
Authors: Raasch Thomas W.
Published: February 2023

Considerable attention in recent years has been directed towards the development of technology for the measurement of corneal topography. These developing techniques have significant applications in contact lens design and fitting, refractive manipulations of the cornea, and in the clinical and laboratory study of corneal diseases (Maguire and Bourne, 1989; McDonnell et al, 1989). There is a great deal of information contained in the typical representations of corneal data from commercial photokeratoscopes, and one of the more common presentation formats is a color coded map of corneal refractive power (Bogan et al, 1990; Maguire et al, 1987). This type of representation is useful, but quantitative representations of this information promise to enhance the utility of photokeratoscopy (Dingeldein et al, 1989). This paper describes a method for summarizing the information generated by photokeratoscopes. This method is particularly applicable to the description of astigmatism, and offers a new technique for conceptualizing and quantifying irregular astigmatism.
The Mechanisms that Prevent Aliasing in the Visual System
Authors: Williams David R.
Published: February 2023

The human retina discretely samples the visual scene with spatial arrays of sampling elements such as photoreceptors and ganglion cell receptive fields. These sampling operations potentially render the human visual system susceptible to aliasing; if the retinal image changes too rapidly over distances comparable to the spacing between sample points, the visual system can make errors in reconstructing the visual scene. Aliasing can be seen when interference fringes of sufficiently high spatial frequency are imaged on the cone mosaic (reviewed in Williams, in press). Subtle aliasing effects can also be seen when viewing conventional high contrast, high spatial frequency gratings in the periphery (e.g. Smith and Cass, 1987; Thibos, Walsh, and Cheney, 1987; Galvin and Williams, submitted). However, aliasing is remarkably difficult to observe under most normal viewing conditions. Many mechanisms have been suggested as offering the visual system protection against aliasing at various locations across the visual field. This talk will assemble the available evidence in order to weigh the the effectiveness of these proposed mechanisms.
Presbyopia: A Closer Look
Authors: Kaufman Paul L.
Published: February 2023

Presbyopia, the age-related loss of accommodative amplitude, is the most common ocular affliction in the world. Loss of accommodative amplitude begins in the second decade of life, so that the ability to accommodate is completely lost by the age of 50 to 55 years. While this condition is correctable by various optical means, its cost in devices and lost productivity is substantial.1 The pathophysiology of presbyopia remains unclear, and dysfunction of every component of the accommodative mechanism has been proposed. The invasive techniques required to answer some of the most critical questions cannot be used in the living human, and subprimate species either do not accommodate or accommodate by very different mechanisms.2
Predicting Astigmatism After Cataract Surgery Using a Neural Network
Authors: Severns M. L. , Lakshminarayanan V. , Smith P.
Published: February 2023

It has been known for years that there are post-operative changes in corneal curvature following cataract surgery. This is due to flattening of the corneal meridian at right angles to the incision. Usually, the incision is made above the cornea, and hence there is a post-operative flattening of the vertical meridian with resultant induced astigmatism. This is an integral element in the refractive correction of the pseudophake.
Visual Acuity Impaired by Prisms of Various Power
Authors: Rassow Bernhard
Published: February 2023

The prismatic power of spectacle lenses always causes colour fringes, which reduce the visual acuity in the periphery of the lens.
SOLAR RADIATION AND PERIPHERAL CORNEAL DISEASE.
Authors: Kwok L. Stephen , Coroneo Minas T.
Published: February 2023

The etiology of pterygium and their preponderance at the nasal limbus is unknown. Solar radiation exposure has been implicated (Fig. 1), but its role is controversial.
CHANGE IN FOVEAL ACUITY WITH LIGHT LEVEL: OPTICAL FACTORS
Authors: Coletta Nancy J. , Clark Helmi K.
Published: February 2023

An observer's ability to discriminate fine spatial detail worsens under dim illumination. The change in spatial acuity with illumination is probably caused by several factors, including the physical nature of light and the optical and neural properties of the visual system. In this study, we examined the effect of the eye's optics on the decrease in spatial acuity at low light levels.
Normal Variation in the Stiles-Crawford Effect Peak Location and Rho value*
Authors: Applegate Raymond A. , Lakshminarayanan Vasudevan
Published: February 2023

At the Topical Meeting on the Noninvasive Assessment of the Visual System January 26-28, 1987 at Incline Village, Nevada, we presented normative data on the foveal Stiles-Crawford effect (SCE) peak location for the largest sample of single eyes for single individuals ever tested and compared our results to those of other studies reported in the literature1. In this paper we honor the 60th anniversary of the discovery of the SCE2 by extending our analysis to include SCE rho (ρ) values and a more extensive comparison of our results to results reported in the literature.
Light Transmission and Reflection in Ocular Media
Authors: Lakshminarayanan V. , Lemus T. , Zaleski E.
Published: February 2023

The propagation of light in biological media is of considerable experimental and theoretical interest. Whenever there is an abrupt interface between two otherwise linear, isotropic and locally homogeneous media (with different refractive indices) the incident light will undergo transmission and reflection. The amount, spectral distribution and polarization characteristics of light reaching the retina are modified due to the transmittance characteristics of light; this could be due to reflection, absorption and scattering in any of the ocular media structures. This plays a major role in basic and clinical psychophysical studies.
Monochromatic Aberrations in Accommodated Eyes
Authors: Lu Chengwan , Munger Rejean , Campbell Melanie C. W.
Published: February 2023

Aberrations of an optical system are a function of the conjugate position of the object and image planes. An added factor in considering aberrations as a function of accommodation in the human eye is the changing shape and gradient refractive index of the lens. Present schematic eye models cannot accurately predict aberrations in the human eye1. Some with aspheric surfaces or gradients2 succeed in predicting average spherical aberration on axis for the unaccommodated or fully accommodated states but none predicts the changes for intermediate states or the frequent presence of coma in the eye1.
Transverse Chromatic Aberration of an Ophthalmic Lens Degrades Visual Performance more than Dioptric Defocus
Authors: Simonet Pierre , Faubert Jocelyn , Gresset Jacques
Published: February 2023

The development of ophthalmic lenses in the last few years is characterized by the use of aspheric surfaces for a flattering of base curve and by the use of high refractive index materials. The design of aspheric lenses allows a good control of peripheral monochromatic aberrations. Recent studies (Simonet et al., 1992; Gresset et al., 1993) have shown that oblique astigmatism and mean oblique power error are generally not greater than ±0.50D for an ocular rotation of 300. However such a dioptric defocus affects visual performance measured by contrast sensitivity function (Charman, 1979; Marmor and Gawande, 1988).
Physics of Signal Production in Enclosed-Cell Photoacoustic Spectroscopy of Condensed Matter
Authors: McDonald F. Alan , Wetsel Grover C.
Published: February 2023

Much interest has been shown in recent years in the application of the photoacoustic effect to the spectroscopy of condensed matter using the enclosed-cell, microphone-detection (ECMD) configuration. This paper is concerned with: (1) a review of what is known about the photoacoustic effect in condensed matter from a theoretical perspective, and (2) consideration of the extent to which theory has been experimentally verified.
Application of Photoacoustic Spectroscopy to Combustion Diagnostics
Authors: Tennal K. , Salamo G. J. , Gupta R.
Published: February 2023

In this paper we report on a new application of photoacoustic spectroscopy: Minority species concentration measurements inside a combustion region. As a proof of principle, we have applied the photoacoustic technique to the measurement of NO2 concentration in a flat-flame burner. Because of the sensitivity of this technique, it has the potential of developing into a very powerful combustion diagnostic tool.
The Continuing Search for One Photon State Selective Vibrational Chemistry
Authors: Lishan David G. , Hammond George S. , Reddy K. V. , Leonard Jack E.
Published: February 2023

A tantalizing goal, the unambiguous demonstration of state selective chemistry, is being actively pursued by several research groups.1 Bond selective chemistry has promise for the production of unique chemical species. First it must be shown that nonstatistical rates of reactions can be induced. Progress in this field has been moderately encouraging in that the systems studied are suggestive of small rate enhancements. The best case observed is the isomerization of allylisocyanide to allycyanide by Reddy and Berry.2 This unimolecular reaction was initiated with a single photon corresponding to the energy of a C-H overtone stretching vibration. The three different C-H bonds were excited with varying quanta and a direct correlation between the bond excited and the rate of isomerization was observed. When the isomerization rates are compared to the theoretical "thermal" expectations (RRKM) it is concluded that the overtone vibrational energy has not been throughly redistributed on the time scale for reaction.
Photoacoustic analysis of chemical reactions: H-D exchange in the system H2S - D2S
Authors: Kadibelban R. , Hess P.
Published: February 2023

A pulsed TEA CO2 laser is used as excitation source in the photoacoustic experiments. The apparatus is equipped with two nearly identical photoacoustic cells in tandem. The first cell, filled with a constant pressure of absorbing gas is used as a reference to monitor the laser power. The second cell is the reaction and analysis chamber. The signals from the home-made microphones are preamplified and fed into a Biomation 8100 transient recorder. A Tracor TN-1710 digital analyser, together with a floppy disk system and a teletype, are employed for further signal processing. The photoacoustic signal from the second cell is divided by the signal obtained from the reference cell. The analysis of the acoustic signals is performed by integrating the peaks corresponding to the first two pressure pulses. This procedure is compared with an amplitude analysis of the acoustic signal.
Photothermal Deflexion Fourier Transform Spectroscopy : A Tool for High Sensitivity Absorption and Dichroism Measurements
Authors: Fournier D. , Boccara A.C. , Badoz J.
Published: February 2023

Fig. 1 shows an absorption spectrum taken on our apparatus for a single crystal. The resolution is 16 cm−1, and only a few minutes are necessary to cover a spectral range extending from the near UV to the medium infrared. The source is not a complex and expensive "multi-laser system" but a cheap 250 watt quartz halogen lamp.
New Aspects of Buffer Gas Effects in Resonant Spectrophones
Authors: Johnson Ralph H. , Thomas Launey J. , Gerlach Robert , Amer Nabil M.
Published: February 2023

In studies of gas phase photoacoustic spectroscopy, the gas whose spectrum is being investigated is generally one of several present in the sample, and often only in trace amounts. The response of the spectrophone is determined by the characteristics of the sample gas as a whole, and depends on the various thermal and molecular relaxational properties of the gases present. In particular, for an acoustically resonant spectrophone, important characteristics will include the sound velocity, heat capacity, thermal conductivity, viscosity, and the energies and relaxation times of the molecular vibrations. The sound velocity determines the resonant frequencies of the cavity, while the other parameters govern the loss mechanisms that determine the quality factors of the resonances, and also cause small shifts in the resonant frequencies. In an earlier study,1 the resonant frequencies and quality factors of acoustical resonances were determined for various buffer gases at atmospheric pressure, and the results were compared to theoretical predictions2 based on classical surface viscous and thermal losses. Significant discrepancies were observed for all non-noble gases.3 It is the goal of this work to investigate the pressure dependent behavior of the spectrophone, and to incorporate molecular relaxation effects into the theoretical interpretation of that behavior. We have made a number of extensions and improvements in experimental and analytical technique. The spectrophone used was a stainless steel cylinder polished to a 1/3 micron surface finish to guarantee well defined boundary layers whose losses could be calculated accurately from theory. The spectrophone and vacuum system were bakeable to reduce impurity effects due to outgassing. Whereas in the earlier experiment a large concentration of the optically absorbing component (9000 ppm of CH4) was used, we kept the absorber concentration small (50 ppm of C2H4) so as not to disturb the properties of the buffer gas. Use of an electro-optic modulator system allowed access to modes at much higher frequencies, thus enabling the study of lighter gases. We have measured the resonant frequency and quality factor as a function of pressure from atmopsheric pressure down to 10 torr or lower for each buffer gas. Data analysis consisted largely of nonlinear least squares curve fitting of the resonant response curves, which gave more accurate determinations of the resonant frequency and Q than the half power point method used in the previous experiment.
A Discussion of Particle Size Effects in Photoacoustic Spectroscopy
Authors: Ashworth C.M. , Castleden S.L. , Kirkbright G.F. , Spillane D.E.M.
Published: February 2023

For some time the particle size of the sample has been noticed to affect the magnitude and quality of the photoacoustic signal observed (1,2,3). These effects have become increasingly significant as attempts have been made to obtain quantitative results in applying photoacoustic spectroscopy to the analysis of real samples. It can be demonstrated easily that a sample containing a wide range of particle size produces a photoacoustic signal with a significantly worse signal-to-noise ratio than does a sample containing only a narrow range of particle size.
Evidence for Thermal Wave Interference in Thin Particulate Carbon Samples
Authors: Bennett C. A. , Patty R. R.
Published: February 2023

It is well known that thermal wave interference will affect the photoacoustic signal arising from very thin samples; (1,2) in this report we present experimental evidence for thermal wave interference effects in thin layers of elemental carbon particles which have been deposited on three commonly used filter substrates. Not only are these results important to our present objectives concerning the calibration of an ambient soot monitor, they may be of significance to those engaged in a photoacoustic study of samples which are less than a thermal wavelength in thickness.
Photoacoustic Analysis of Particulate Carbon in the Atmosphere
Authors: McClenny W. A. , Röhl R.
Published: February 2023

Photoacoustics offers a distinctive combination of features that recommends its use in analyzing the visible light absorption properties of particles collected on filters. The technique is nondestructive and responds only to absorbed light. Unloaded Teflon filters of the type used routinely by the USEPA in dichotomous samplers do not absorb visible light so that no pre-loading measurement is necessary. Previous studies of the photoacoustic (PA) response to soot loaded on Teflon filters have shown that: (1) at 100 Hz and 1000 Hz chopping frequencies the PA signal due to soot loading does not saturate even for loadings at which the sample is totally opaque, i.e., βℓ>31; (2) thermal wave interference effects are evident in the photoacoustic analysis of soot samples2; (3) the perturbation of the signal from soot, when typical ambient loadings of (NH4)2SO4 are admixed is considerably less (±10%) than the perturbation that occurs in light transmission measurements.3 Item (1) precludes the use of simplifying assumptions in relating PA response to the light absorption parameter βℓ. Item (2) explains item (1). Item (3) suggests that a calibration curve relating photoacoustic response and soot loading could be used to translate PA readings on ambient samples to elemental carbon content.
Leaf Physiology and Anatomy by Photoacoustics
Authors: Bults Gerard , Horwitz Benjamin A. , Malkin Shmuel , Cahen David
Published: February 2023

Plant leaves are generally composed of about seven to eight layers of cells: an upper epidermis layer, two to three layers of elongated palisade cells, about three layers of spongy cells with large intercellular air spaces and a lower spidermis. The epidermis layers contain pores (stomata) with a mechanism to open or close them, controlled by adjacent guard cells.
The Extended Helmholtz Resonator in Low Temperature Pas
Authors: Pelzl J. , Nordhaus O. , Klein K.
Published: February 2023

A possible way to realize a PA-cell for measurements at variable temperatures is to separate the sample and the microphone chamber. In order to retain large acoustic amplification of the whole arrangement small gas volumes and resonance type acoustic cells are required. In this work we have investigated experimentally and theoretically PA cells which make use of a narrow cylindrical tube to separate the microphone from the sample. This type of construction has already been applied for low and high temperature PAS by several research groups /1,2/. The present approach proceeds from a generalized treatment of the Helmholtz resonator model which takes into acount the retardation effects in the duct. Here we report on theoretical and experimental results obtained in the temperature range between 10 K and 300 K with the cell arrangement sketched in Figure 1. The low temperature cell consists of two chambers V1 ≅ V2 ≅ 700 mm3 and the connecting tube which has an inner diameter of 1,5 mm and a length 1 = 600 mm. Both chambers are supplied with an electret microphone. The whole construction is designed to fit into an optical cryostat. Room temperature measurements were mostly carried out with air.
Absorption Spectra of Crystalline and Amorphous Silicon by Photothermal Deflection Spectroscopy
Authors: Jackson Warren B. , Amer Nabil M. , Fournier Daniele , Boccara A. Claude
Published: February 2023

The nature of the optical absorption in semiconductors at and below the absorption edge is of interest, particularly in the case of amorphous materials. The sensitivity of conventional transmission techniques are limited by the requirement of measuring the difference between two nearly equal signals. Furthermore, such techniques are highly sensitive to scattering. While adequately sensitive, the disadvantages of piezoelectric photoacoustic detection(1) are that it requires a laser as the exciting source, is highly sensitive to scattering, and requires reliable coupling between the transducer and the sample.
The photoacoustic effect at phase-transitions: its dependence on the thermal thickness of the sample
Authors: Korpiun P. , Tilgner R.
Published: February 2023

The thermal properties that are the essential determinants of the PA-signal from a solid or a liquid are the density, the thermal conductivity and the specific heat. At a first-order phase-transition, the latent heat strongly influences the signal. It has been found experimentally that the amplitude runs through a minimum; the phase-angle as a function of temperature shows different patterns /1,2/.
Microemulsion Characterization Using a Fiber Optic Probe
Authors: Ansari Rafat R. , Dhadwal Harbans S. , Cheung H. Michael , Meyer William V.
Published: February 2023

Microemulsions are thermodynamically stable systems in which one phase (e.g. oil) is dispersed into another phase (e.g. water). The globule size of the dispersed phase is normally less than 1 micron. Microemulsion systems are normally transparent when a short chain alcohol is added. Microemulsions have practical value in food industry, cosmetic industry, drug-delivery systems, and enhanced oil recovery. One of the most sought out physical characteristic of a microemulsion system is the globule size in case of a monodisperse system and the globule size distribution in case of a polydisperse system. The conventional techniques of sedimentation, centrifugation, and electrochemical are limited in scope, because they require elaborate calibration procedures and are invasive in nature. The conventional light scattering has the capability of making non-invasive measurements on dilute microemulsion systems, but as discussed later the conventional light scattering instrumentation is practically difficult to use in field operations.
The mean length of light paths in turbid suspensions determined from position dependent volume reflection profiles.
Authors: Bolt R.A. , ten Bosch J.J.
Published: February 2023

Several studies have been done concerning the length of light paths in turbid materials [1]..[4]. Most of these studies deal with propagation of short pulses through the medium, requiring the use of pulsed lasers. In [2] the length of light paths was determined for the case of transmission of (collimated) light through a turbid suspension, using relatively simple equipment and added quantities of absorber. We used a technique based upon adding absorber to determine the mean length of light paths in the case of volume reflection in a turbid medium, as a function of distance to the point of illumination.
Determination of the Dynamic Viscosity of Selected Transparent Liquids Using Dynamic Light Scattering
Authors: Will S. , Kraft K. , Leipertz A.
Published: February 2023

Dynamic light scattering has been used successfully for the determination of various thermophysical properties of fluids, e.g., thermal diffusivity, sound velocity and binary diffusion coefficient. The applicability to measuring dynamic viscosities has been shown, e.g., by Brunson and Byers [1]. Basis of the measurement is the Stokes-Einstein formula

Here, η is the viscosity required and d is the hydrodynamic diameter of the spherical particles suspended. Viscosity measurements preferrably make use of monodisperse particles. Thus no integration over particle sizes is necessary. The particle diffusion coefficient D and the modulus q of the scattering vector of the optical arrangement form the decay constant in the autocorrelation function measured, τc = (2q2D)−1. From this value η can be determined for known temperature T.
Laser Light Scattering Spectroscopy Combined With Brewster Angle Microscopy: nCB and Polymer Monolayers
Authors: Tseng C.S. , Tin P. , de Mul M. , Meyer W.V. , Lando J.B. , Mann J.A.
Published: February 2023

Brewster Angle Microscopy (BAM) is a powerful tool to image the structure of monomolecular films1,2. Laser Light Scattering Spectroscopy (LLSS) is used to measure the surface visco-elastic coefficients
Ke=G¯+K¯ and
KV=η¯+ζ¯ as a function of surface density. In addition, since the surface pressure vs. surface density is known, the isotherm compressibility vs. surface density can be estimated. These numbers will be compared for the liquid crystal, nCB systems that collapse to multilayers reversibly and for certain polymer systems to be used as alignment layers in liquid crystal video display applications. The footprints of the incident beams for BAM and LLSS are superposed so the Ke, Kv coefficients can be associated with the morphology displayed by the BAM image. The BAM images show that convective transport is usually present unless the monolayer is very rigid. In many cases the monolayer in the footprint of the laser beams is not either homogeneous or isotropic. Indeed, the molecular director may be aligned in domains and there can be a distribution of defects all observable by BAM. This fact must be taken into account when interpreting LLSS autocorrelation functions. Since the grating technique is used with normal incidence, it is easy to make measurements with LLSS as a function of direction on the surface by simply rotating the grating. Experimental techniques and results will be discussed. We conclude that LLSS data is incomplete for monomolecular films unless BAM images of the footprint are also recorded. Two literature references to BAM images of nCB from our group follow.
Colloid Aggregation Kinetics in Opaque Petroleum Mixtures
Authors: Yudin I.K. , Nikolaenko G.L. , Gorodetsky E.E. , Kosov V.I.
Published: February 2023

The general problem of enhancing the oil recovery is directly connected with the problem of decreasing the viscosity of the crude oil. The complex colloid-like structures are responsible for the viscosity of oil. Asphaltenes are the main surfactant components of a heavy oil fraction, capable of forming the colloid structures. The content of asphaltenes in different crude oils varies in a wide range and accounts for 25-30 % of weight. The study of asphaltene aggregation kinetics is a reliable way for investigation of colloid properties of crude oil [1]. We studied this process in toluene/heptane mixtures using the photon correlation spectroscopy (PCS).
Investigation of internal motions of high-molecular DNA by Dynamic Light Scattering
Authors: Ivanova M.A. , Ivanova M.A. , Arutyunyan A. V. , Lomakin A. V. , Noskin V.A.
Published: February 2023

Dynamic Light Scattering (DLS) is widely used to study the internal dynamics of biological and synthetic macromolecules. In our internal dynamics investigations we used the approach advanced by Akcasu et al. [1,2]. It consists in obtaining the dynamic characteristics of random coils using the calculations of the first cumulants. We compared the angular dependence of the first cumulant predicted theoretically with that obtained experimentally. We observed the first cumulant transition from the asymptotic for good solvent to the asymptotic for Θ condition in the intermediate q region.
All-optical Regenerative Memory
Authors: Poustie A. J. , Blow K. J. , Manning R. J.
Published: February 2023

We describe a novel all-optical regenerative memory where the data pattern is re-imposed onto a separate pulse train after each circulation of an optical fibre delay line. Optical memory is envisaged to be an important function in future ultrahigh-speed photonic networks and processing systems. For example, memory allows 100Gbit/s packets [1] to be buffered and queued for subsequent processing of the data and memory is also an intrinsic function for bit-serial optical computing systems [2]. Several types of optical memory have already been demonstrated such as passive [3,4] and active [5] recirculating fibre loops. In these configurations, the stability of the data pattern depends on being able to retime the optical pulses within the loop since it acts like a long transmission line [6]. In this paper the memory architecture is similar to the optoelectronic scheme described in reference [7].
CW Fiber Optical Parametric Amplifier with Net Gain and Wavelength Conversion Efficiency Greater than One
Authors: Yang F. S. , Marhic M. E. , Kazovsky L. G.
Published: February 2023

In order to be useful in a wide range of communication applications, fiber optical parametric amplifiers (OPA’s) and wavelength converters should operate on a cw basis. Furthermore, conversion efficiency Gi should be greater than or equal to one, in order to avoid the substantial signal-to-noise ratio degradation which occurs if Gi ≪ 1. Currently silica-based fibers have the best characteristics for making fiber OPA’s. However, owing to the relative weakness of the third-order nonlinear susceptibility in such fibers, amplification by fiber OPA’s requires a high pump power and/or a large fiber length. Pulsed amplification has been reported by a number of groups. CW fiber parametric amplification with a 17 dBm pump has been reported, but with a gain insufficient to overcome fiber loss [1].
A Compact Laser Light Scattering Instrument for Microgravity Research
Authors: Rogers Richard B. , Meyer William V. , Turner Walter , Zhu Jixiang , Chaikin Paul M. , Russel William B.
Published: February 2023

NASA has developed a compact and versatile laser light scattering instrument for microgravity research. This instrument was used in the first experiment to gather data on the behavior of hard sphere systems in a reduced gravity environment. The Colliodal Disorder - Order Transition (CDOT) experiment took place aboard the Space Shuttle Columbia as part of the Second United States Microgravity Laboratory (USML-2) which flew from October 20 to November 5, 1995. This paper will describe the instrument and how it was employed in the CDOT experiment. The detailed results of the experiment will be the subject of another paper.
Heterodyne QELS Instrument LCS-03
Authors: Lebedev A.D. , Kapshin Yu.S. , Lomakin A. V. , Noskin V.A. , Patsekin V.P.
Published: February 2023

There are two major varieties of the photon correlation technique:
homodyne and heterodyne [1,2]. Heterodyne design of
optical scheme is required in studies of the directed motion. This
design is commonly used for Doppler velocimetry, in electrophoretic
light scattering for instance. The homodyne method is generally less
concentration sensitive, has 2 times worse signal to shot noise ration
and gives data which are much more difficult to analyze, especially in
the case of scattering on polydisperse solutions with very broad
particle size distribution.
Dynamic and Static Light Scattering Studies of Binary Fluids in Silica Gels*
Authors: Frisken B.J. , Cannell David S.
Published: February 2023

Studies of binary fluids in silica gels are motivated by questions related to the effect of quenched disorder on critical phenomena.1 We have been involved in a series of both light2 and neutron3 scattering studies investigating these systems.
Measurement of Diesel Exhaust Particles in a Dilution Tunnel by Photon Correlation Spectroscopy
Authors: Lhuissier N. , Nazih A. , Weill M. E.
Published: February 2023

The soot particles generated by a Diesel car exhaust have been sized by P.C.S.in a dilution tunnel for various loads. Due to the very heterogeneous composition of the particles population on-line measurements were not possible. So we have chosen to record a set of successive correlograms. The choice of the correlograms having to be regrouped before processing is based upon the total count number received during an experiment. They are displayed on a histogram or a Henry line. The necessary K 7027 software modifications are briefly described.
Fluorescence Photobleaching Recovery Measurements of Facilitated Diffusion
Authors: Pike E. R. , Gould H. J. , Watanabe F.
Published: February 2023

The feasibility of a direct measurement of sliding of proteins along a DNA chain by the fluorescence photobleaching recovery technique is demonstrated. The results obtained with a protein, histone H1, provides a firm basis for the understanding of the "facilitated diffusion" mechanism by which site-specific DNA binding proteins are thought to find efficiently their unique loci.
Features of Diffusing Wave Spectroscopy
Authors: Pine D. J. , Weitz D. A. , Chaikin P. M. , Herbolzheimer E.
Published: February 2023

Photon correlation spectroscopy is extended to strongly multiply scattering systems by assuming that the transport of light is diffusive. A simple model is developed which accounts for different sample geometries, scattering configurations, absorption, and sample polydispersity. Experimental data are found to be in excellent agreement with the predictions. The dependence on geometry provides an important experimental control over the length and time scales probed.
Reduction of Electron-Phonon Scattering Rates by Total Spatial Quantization
Authors: Reed M.A. , Bate R.T. , Duncan W.M. , Frensley W.R. , Shih H.D.
Published: February 2023

The physics of spatially quantized systems has been the subject of intense investigation since the introduction of MBE and MOCVD. Quantum wells have been exhaustively examined since the seminal works of Dingle et al1. More recently, studies on quantum wires2 have yielded interesting new properties. Here, we present data on a completely spatial quantized system that shows unique photoluminescence structure resulting from an electron or hole phonon scattering bottleneck.