William K. Witherow

Preliminary investigations into solutal flow about growing tetragonal lysozyme crystals

Abstract A series of preliminary experiments were done to investigate solutal flow about growing lysozyme crystals and its effects. Density gradient driven flow as observed using a schlieren optical system. Crystals used ranged from 0.3 to 1.72 mm across the (110) face, and protein concentrations were from 3.7 to 23.7 mg/ml ( C sat = 1.2 mg/ml at 18°C). The convective plume velocities were found to be from 10 to 50 μm/s, which correlated with those predicted to occur based upon a diffusive-convective model. When micro-crystals of lysozyme ( .5 mm) crystals in the terminal phases of a typical crystal growth procedure.

Holographic particle-image velocimetry in the first International Microgravity Laboratory aboard the Space Shuttle Discovery.

In January 1992 the Space Shuttle Discovery carried the first International Microgravity Laboratory into Earth orbit for eight days. One of the many experiments carried out during the orbit was a combined study of triglycine sulfate crystal growth from solution and fluid-particle-dynamics studies in microgravity. Optical diagnostics included holocameras to provide concentration measurements and three-dimensional particle tracking. More than 1000 holograms that were recorded in space have been analyzed since the flight, providing a wide range of interesting conclusions about microgravity, crystal growth, and particle dynamics. This paper focuses on the results of holographic particle-image velocimetry experiments and provides an excellent example, along with new techniques, for exploiting holography for particle and flow diagnostics.

A High Resolution Holographic Particle Sizing System

This paper will review briefly the requirements of holography with respect to particle sizing techniques. A holographic construction system and the appropriate reconstruction system will be discussed regarding their characteristics and performance (i.e. system resolution, magnification, system aberration and correction of aberrations, and maximum total test volume). The capabilities of a commercial particle sizing system used to obtain particle sizes and distribution information from reconstructed holograms will be described and characterized. It will be shown that by using the methods described, high resolution throughout large test volumes can be achieved.

Preliminary observations of the effect of solutal convection on crystal morphology

Abstract Studies to examine the effects of solutal convection on crystal morphology using sucrose as a model system were initiated. Aspect ratios, defined as the width of the {100} face over the width of the {001} face, were determined for oriented crystals which were grown with either the {001} or the {100} face perpendicular to the convective flow. The dependence of the crystal morphology on orientation is much greater for crystals grown with one face occluded than for crystals grown suspended in solution. Many factors appear to interact in a complex fashion to influence crystal morphology.

Algorithm for phase-difference measurement in phase-shifting interferometry

A phase-shifting algorithm is proposed and experimentally demonstrated for phase-difference analysis. The method involves only three steps, the original and two equal in amount but unknown phase steps for each stage. Only six frames of data are thus sufficient for the phase-difference analysis between two stages. Real-time holographic interferometry with a concentration change in a sugar-water solution in a test cell is presented for experimental verification.

Coarsening of three-dimensional droplets by two-dimensional diffusion: part I. Experiment

An experimental study of diffusional coarsening, or Ostwald ripening, in a liquid-liquid two-phase system is described. An experiment performed at its isopycnic point, 42°C, allowed observations for the long times required to investigate coarsening. A holographic technique was instrumental in this work. Holograms takenin situ permit investigation of details regarding both the influence of local environmental conditions on individual droplet size histories and measurement of global averages. This study utilized a 100 μm pathlength test cell. The discrete phase was nucleated on one wall of the cell. This configuration resembles island formation in thin film growth. Observation of Ostwald ripening over a period of 1×107 s (∼4 mo.) reveals that droplet number decays as t−0.733 and the average radius increases as t−0.247, in the asymptotic limit. This shows good agreement with theoretical predictions for diffusional growth of spherical caps on a two-dimensional substrate which is a valid approximation for the geometry of this experiment. Part I of this paper describes the experimental results. Part II discusses a numerical model for droplet growth in a comparison with the experimental results.

Results and further experiments using Spacelab holography

Spacelab 3 provided the platform for the first extensive application of holography in space. Holograms of excellent quality were recorded during the flight, providing information on the solution growth of triglycine sulfate crystals under microgravity conditions. The suppression of convection and the development of a symmetric concentration depletion region around each crystal were clearly shown. Crystal growth was governed by diffusion mass transport across the depletion region. The successful performance of the holographic unit has prompted NASA to schedule a slightly modified version for reflight on IML-1; opportunities now exist for other investigators to use this facility.

Determination of refractive properties of fluids for dual-wavelength interferometry

Methods to calculate the refractive properties of solutions at different wavelengths are described by using experimental data at just two wavelengths. The properties are the refractive index and its gradients with temperature and concentration. Cauchys equation is used to determine the refractive indices. The gradients versus temperature and concentration are then determined by using the Murphy-Alpert and the Lorentz-Lorenz equation, respectively. Finally, the particular case of a triglycine sulfate aqueous solution is considered as an example. The approach should provide the desired information for fringe analysis when dual-wavelength holographic or other interferometry is used for solving heat and mass transfer problems in fluids during crystal-growth experiments.

Recent Advances in Photonic Devices for Optical Super Computing

The twentieth century has been the era of semiconductor materials and electronic technology while this millennium is expected to be the age of photonic materials and optical technology. Optical technology has led to countless optical devices that have become indispensable in our daily lives in storage area networks (SANs) [1], parallel processing [2,3], optical switches [4,5], all-optical data networks [6], holographic storage devices [7] and biometric devices at airports [8].

Reconstruction techniques of holograms from Spacelab 3

Fluid transport effects in a ground-based laboratory are fairly well known. Bouyancy driven transport occurs when there is a local density change in the fluid. In a low-g environment these density changes become less important, and other transport mechanisms dominate. To better understand fluid flows in a low-g environment, a fluid experiment system (FES) was designed to fly aboard the Shuttle orbiter in Spacelab. The FES is a holographic system designed for acquisition of the maximum amount of data from an experiment. The FES flew for the first time in May 1985 on Spacelab 3 for investigation of triglycine sulfate (TGS) crystal growth in low-g. This paper describes the FES optical system. The reconstruction techniques of the holograms are examined in detail, and the multiuser and reflight capabilities are discussed. Proposed future experiments are mentioned.