Scott Taylor

Design and Implementation of a Facility for Discovering New Scintillator Materials

We describe the design and operation of a high-throughput facility for synthesizing thousands of inorganic crystalline samples per year and evaluating them as potential scintillation detector materials. This facility includes a robotic dispenser, arrays of automated furnaces, a dual-beam X-ray generator for diffractometry and luminescence spectroscopy, a pulsed X-ray generator for time response measurements, computer-controlled sample changers, an optical spectrometer, and a network-accessible database management system that captures all synthesis and measurement data.

A novel MPTP primate model of Parkinson's disease: neurochemical and clinical changes

Positron emission tomography (PET) and the dopamine (DA) metabolism tracer, [18F]6-fluoro-L-m-tyrosine (FMT) were used to evaluate the relationship between DA metabolism and the clinical stage of parkinsonism monkeys following either unilateral ICA MPTP infusion or unilateral ICA MPTP infusion and subsequent varying sequential systemic doses of MPTP. Clinical stage corresponded to PET measures of striatal DA metabolism, showing the usefulness of the overlesioned hemiparkinsonian monkey as a stable model of various stages of Parkinsons disease (PD).

Genome-free Viral Capsids as Carriers for Positron Emission Tomography Radiolabels

PurposeWe have developed a modular synthetic strategy to append imaging agents to a viral capsid.ProceduresThe hollow protein shell of bacteriophage MS2 (mtMS2) was labeled on its inside surface with [18F]fluorobenzaldehyde through a multistep bioconjugation strategy. An aldehyde functional group was first attached to interior tyrosine residues through a diazonium coupling reaction. The aldehyde was further elaborated to an alkoxyamine functional group, which was then condensed with n.c.a. [18F]fluorobenzaldehyde. Biodistribution of the radioactive MS2 conjugates was subsequently evaluated in Sprague–Dawley rats.ResultsRelative to fluorobenzaldehyde, fluorine-18-labeled MS2 exhibited prolonged blood circulation time and a significantly altered excretion profile. It was also observed that additional small molecule cargo installed inside the capsids did not alter the biodistribution.ConclusionsThese studies provide further insight into the pharmacokinetic behavior of nanomaterials and serve as a platform for the future development of targeted imaging and therapeutic agents based on mtMS2.

Serotonin transporter inhibitors : Synthesis and binding potency of 2'-methyl- and 3'-methyl-6-nitroquipazine

Racemic 2-methyl- and 3-methyl-6-nitroquipazine ligands were selected as targets, synthesized and evaluated at the serotonin transporter employing an in vitro competitive inhibition assay with [3H]paroxetine and rat cortical membrane. The 2-methyl-6-nitroquipazine was found to be 50 times more potent than the 3-methyl-substituted counterpart and of comparable potency to the known high affinity agent 5-iodo-6-nitroquipazine.

Systematic Search for New Lanthanum Scintillators

The objective of this work is the discovery of new lanthanum scintillators for ambient-temperature gamma-ray spectroscopy. Increasing the number of known scintillator materials increases the potential for producing crystals with good energy resolution in larger sizes and at lower cost than those currently available. Through solid-state reactions we have synthesized 20 microcrystalline lanthanum samples in undoped form and doped with 1% Ce3+. We used X-ray diffraction to verify the crystal phase, pulsed X-ray excitation to measure the luminosity and decay time of the scintillation light, and optical excitation to measure the emission wavelength. In undoped form, many materials exhibit slow charge transfer emission within polyatomic anionic groups and, in one case, fast core-valence emission. In doped form, the lanthanum oxyhalides (LaOCl, LaOBr and LaOI) and one lanthanum phosphate (CsLa(PO3)4) showed bright and fast emission characteristic of cerium activation.

Performance of an Integrated, General-Purpose Networked Data Acquisition System

This paper describes a general-purpose real-time software system developed for a broad range of networked data acquisition and process control applications. Performance of the software on DEC LSI-11 and VAX computers, Ethernet, and CAMAC is presented, including measuremnents of network transfer rates, data acquisition rates, and interrupt response times.

Radiotracer medical imaging technologies applied to environmental remediation systems

We demonstrate an alternate application of high-sensitivity radiotracer imaging technologies developed for nuclear medical imaging. There are several available radioisotopes, namely 51Cr and 99mTc, that are particularly appealing for studying environmental remediation techniques, notably for modeling toxic element runoff through the soil near former nuclear facilities such as the Hanford reactors in Washington state (USA). 52Cr (stable) and 99Tc (2.3×106 year half-life) are important reactor-generated contaminants that have entered the groundwater. There are numerous studies being conducted to model transport of these compounds in different types of soil such as sand, clay, dirt and gravel. The speed and character of contaminant transport through medium depends on chemical composition of the particles, chemical composition of water, physical properties of the medium (particle size, homogeneity, temperature) and on content of different types of microorganisms. Measurements are typically performed by flowing water containing 52Cr or 99Tc through sediment columns (tubes a few cm in diameter and 0.5-1 meter long) and monitoring the in-and out- flows of contaminants. We will support the effort to develop different methods of reducing the contaminant transport speed by using SPECT imaging to study transport of the singlephoton emitting surrogates 51Cr and 99mTc. By quantitatively imaging the contaminant distribution in the sediment column as a function of time, a much richer set of data can be obtained. We will compare contaminant transport in various media under different conditions including standard diffusion and flow at different speeds and volumes. Experimental work will be supplemented with theoretical analysis and modeling of transport processes, including studies of diffusion and chemical exchange using a standard multi-compartment model. In this conference record, we present the results of two studies of technetium 99m transport in hydrated sand, including both planar and tomographic SPECT images of the columns acquired at different conditions.

Parallel processing and real-time data acquisition

A detailed description of a low-cost, very-high-performance data-acquisition front-end processor is given. The front-end processor, called the transputer foundation module, is built around the Inmos transputer, an ideally suited real-time parallel processor. Special-purpose digital signal processing hardware is combined with the transputer foundation module to form a high-power, flexible data acquisition and processing system. The transputer foundation module can concurrently perform data acquisition, reduction, and high-speed transfer. One such system is capable of acquiring data at burst rates of 40 MB/s and performing 2000 and 1024-point complex FFTs (fast Fourier transforms) per second. >

Operating Applications of a Networked Data Acquisition System

This paper describes operating applications of a networked data acquisition computer system which has met the needs of researchers in a variety of scientific disciplines. The network software system, called IRANET (Interfield Research Associates Network Software System), has been effectively used in nuclear physics, plasma physics, aeronautical engineering, and semiconductor processing laboratories.