Evaluation of selected chemical processes for production of low-cost silicon, phase 3

A Process Development Unit (PDU), which consisted of the four major units of the process, was designed, installed, and experimentally operated. The PDU was sized to 50MT/Yr. The deposition took place in a fluidized bed reactor. As a consequences of the experiments, improvements in the design an operation of these units were undertaken and their experimental limitations were partially established. A parallel program of experimental work demonstrated that Zinc can be vaporized for introduction into the fluidized bed reactor, by direct induction-coupled r.f. energy. Residual zinc in the product can be removed by heat treatment below the melting point of silicon. Current efficiencies of 94 percent and above, and power efficiencies around 40 percent are achievable in the laboratory-scale electrolysis of ZnCl2

Hydrodynamic lift on bound vesicles

Bound vesicles subject to lateral forces such as arising from shear flow are investigated theoretically by combining a lubrication analysis of the bound part with a scaling approach to the global motion. A minor inclination of the bound part leads to significant lift due to the additive effects of lateral and tank-treading motions. With increasing shear rate, the vesicle unbinds from the substrate at a critical value. Estimates are in agreement with recent experimental data.Comment: 9 pages, one figur

Wrinkling of microcapsules in shear flow

Elastic capsules can exhibit short wavelength wrinkling in external shear flow. We analyse this instability of the capsule shape and use the length scale separation between the capsule radius and the wrinkling wavelength to derive analytical results both for the threshold value of the shear rate and for the critical wave-length of the wrinkling. These results can be used to deduce elastic parameters from experiments.Comment: 4 pages, 2 figures, submitted to PR

Development of radiometal automated laboratory workbench

Introduction Radiometals are finding more and more applications in molecular imaging and targeted therapy. For PET imaging, all the novel radiometals are directly or indirectly produced on cyclotrons. Key step in their production is achieving proper radionuclidic, radiochemical and chemical purity, as well as high specific activity. Automation of the process enhances reproducibility, shortens necessary operations and decreases radiation burden. We have, therefore, developed universal radio-metal automated laboratory workbench (RALW) that is focused on separation processes from solid and liquid (solution) targets via solid phase extraction (SPE). Material and Methods RALW is versatile platform for separation, formulation and simple labeling processes. The following FIG. 1 displays its basic scheme. RALW´s main parts are: two reactors, two selec-tors, peristaltic pump, 3/2 way valves, and separation column. Prime reactor R1 is designed to carry out several functions. It can transport solid target material from shielding container to process position, or handle liquid target filling. In both cases, the reactor is leakagefree up to 5 bars. There are 4 positions available to bring solvents to the reactor 1 or applying on a SPE column according to the separation sequence with use of peristaltic pump. Smart software allows for collecting defined fractions leaving the column, e.g. enriched target matrix and the desired radionuclide, by monitoring activity profile and controlling the splitting valves. The system also minimizes losses during transport of the solvents/fractions to the reactor R2 and the software also controls final volume settings (activity concentration) of the product. Up to three positions are available for bringing solvents/solutions to the reactor R2 for formulation or simple labeling steps like chelation. The system’s hardware is driven by a PLC and I/O cards. The PLC is placed outside the module to avoid radiation damage. The module, PLC and host PC communicate via an Ethernet cable. This solution significantly reduced number of cables connecting the module with other component in the control chain. The PLC is controlled via host PC equipped with userfriendly interface. Results and Conclusion The presented RPLW system is rather versatile tool for separation of metal radionuclides and simple postprocessing (formulation/labelling) of the product in stable environment and easy control mechanisms. The RPLW operating prototype is shown on the FIG. 2

Reconstructing the global topology of the universe from the cosmic microwave background

If the universe is multiply-connected and sufficiently small, then the last scattering surface wraps around the universe and intersects itself. Each circle of intersection appears as two distinct circles on the microwave sky. The present article shows how to use the matched circles to explicitly reconstruct the global topology of space.Comment: 6 pages, 2 figures, IOP format. To be published in the proceedings of the Cleveland Cosmology and Topology Workshop 17-19 Oct 1997. Submitted to Class. Quant. Gra

First measurements of the flux integral with the NIST-4 watt balance

In early 2014, construction of a new watt balance, named NIST-4, has started at the National Institute of Standards and Technology (NIST). In a watt balance, the gravitational force of an unknown mass is compensated by an electromagnetic force produced by a coil in a magnet system. The electromagnetic force depends on the current in the coil and the magnetic flux integral. Most watt balances feature an additional calibration mode, referred to as velocity mode, which allows one to measure the magnetic flux integral to high precision. In this article we describe first measurements of the flux integral in the new watt balance. We introduce measurement and data analysis techniques to assess the quality of the measurements and the adverse effects of vibrations on the instrument.Comment: 7 pages, 8 figures, accepted for publication in IEEE Trans. Instrum. Meas. This Journal can be found online at http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=1

Mobility and Diffusion of a Tagged Particle in a Driven Colloidal Suspension

We study numerically the influence of density and strain rate on the diffusion and mobility of a single tagged particle in a sheared colloidal suspension. We determine independently the time-dependent velocity autocorrelation functions and, through a novel method, the response functions with respect to a small force. While both the diffusion coefficient and the mobility depend on the strain rate the latter exhibits a rather weak dependency. Somewhat surprisingly, we find that the initial decay of response and correlation functions coincide, allowing for an interpretation in terms of an 'effective temperature'. Such a phenomenological effective temperature recovers the Einstein relation in nonequilibrium. We show that our data is well described by two expansions to lowest order in the strain rate.Comment: submitted to EP