Use Of Larger Particles Research Articles

Obtaining Vortex Formation in Blood Flow by Particle Tracking: Echo-PV Methods and Computer Simulation

Micrometer-sized particles are widely introduced as fluid flow markers in experimental studies of convective flows. The tracks of such particles demonstrate a high contrast in the optical range and well illustrate the direction of fluid flow at local vortices. This study addresses the theoretical justification on the use of large particles for obtaining vortex phenomena and its characterization in stenotic arteries by the Echo Particle Velocimetry method. Calcite particles with an average diameter of 0.15 mm were chosen as a marker of streamlines using a medical ultrasound device. The Euler–Euler model of particle motion was applied to simulate the mechanical behavior of calcite particles and 20 µm aluminum particles. The accuracy of flow measurement at vortex regions was evaluated by computational fluid dynamics methods. The simulation results of vortex zone formation obtained by Azuma and Fukushima (1976) for aluminum particles with the use of the optical velocimetry method and calcite particles were compared. An error in determining the size of the vortex zone behind of stenosis does not exceed 5%. We concluded that the application of large-size particles for the needs of in vitro studies of local hemodynamics is possible.

The impact of deproteinized bovine bone particle size on histological and clinical bone healing outcomes in the augmented sinus: A randomized controlled clinical trial.

The effect of different deproteinized bovine bone mineral (DBBM) particle sizes on bone healing in maxillary sinus floor augmentation remains unclear. This study compared the newly formed tissue and angiogenesis-related bone healing after sinus floor augmentation using large or small DBBM particles. Overall 32 patients were randomly divided into two groups using either large (1-2 mm) or small (0.25-1 mm) DBBM particles for sinus floor augmentation. After 6months, the mineralized tissue volume was calculated using micro-computed tomography (micro-CT) analysis. The newly formed tissue composition was histomorphometrically analyzed. Angiogenesis was also examined by means of vascular endothelial growth factor (VEGF) expression. Implant failure and marginal bone loss were measured at a 1-year follow-up. Statistical analysis was performed using independent samples t-test. Micro-CT analysis demonstrated that grafting with large particles resulted in higher bone volume (6.99 ± 2.72 mm3 , p=0.002) and Bone Volume/Tissue Volume (0.25 ± 0.1, p=0.03) compared with small particles (3.76 ± 1.83 mm3 and 0.14 ± 0.13, respectively). Small particles showed higher non-mineralized tissue volume (26.31 mm3 ) compared with large particle group (17.4 ± 5.34 mm3 ) with p=0.001. The histological data revealed significantly higher area of newly formed bone (32.15% ± 14.04% for the large particle and 15.99% ± 14.12% for the small particle groups, p=0.004). Likewise, non-mineralized tissue was significantly greater in the small particle group (66.48% ± 20.97%) compared with the large particle group (44.36%, p=0.016). Moreover, use of large particles resulted in a significantly higher VEGF staining intensity score and VEFG positive cells. No implant failure was recorded in both groups, while no difference was found in terms of marginal bone loss at the 1-year follow-up. Sinus floor augmentation using large DBBM particles resulted in more angiogenesis expression, higher bone volume, and new bone formation at 6months after sinus augmentation. However, clinical outcomes with regards to implant placement were similar in both groups.

Insitu gasification – chemical looping combustion of large coal and biomass particles: Char conversion and comminution

Utilization of large solid fuel particles in fluidized bed – Chemical Looping Combustion (CLC) has the benefits of reduced energy penalty related to carbon capture. When large fuel particles (mm-sized) are used, comminution plays a vital role in the fuel conversion rate, characteristics of ash, inventory loading and thus in the effective design of CLC systems. The present work deals with the conversion of char of large fuel particles and char fragmentation phenomenon in the insitu-gasification CLC environment. Three different coals and a woody biomass in the size range of + 8–25 mm are tested at three different bed temperatures (800 to 950 °C) in a hematite-based batch CLC unit, using steam as the fluidizing/gasification agent. The char conversion time is found to increase by 60 to 170% when particle size changes from 8 to 25 mm and reduced by 42 to 86% with the increase in bed temperature. Regardless of fuel type and feed size, the inception of char fragmentation is noticed in the very first quarter of conversion indicating its significant influence on the char burnout time. A minimum critical char size exists below which char weakening does not yield breakage, whose values vary between 4.4 and 14.2 mm depending on fuel type and feed size. Fuel type is found to be the prime influencer of char conversion time and fragmentation phenomena. This study recommends the use of large particles of all fuels up to 25 mm in CLC systems without any prior size reduction, except the high-ash coals.

Impact of Particle Size on Droplet Coalescence in Solid-Stabilized High Internal Phase Emulsions.

High internal phase emulsions (HIPEs) comprise highly faceted droplets separated by thin films of fluid. Though surfactants are traditionally used in formulating HIPEs, growing interest in solid-stabilized HIPEs calls for a better understanding of how particles may affect the coalescence of droplets at high volume fractions of the dispersed phase. In this study, we address the effect of particle size on this issue. Using confocal microscopy, we examine the microstructures of four different solid-stabilized emulsion series and quantify droplet coalescence in each. We show that, systematically, HIPEs stabilized with smaller particles show a greater propensity for film rupture and the presence of partially coalesced droplets, whereas the use of larger particles results in a higher fraction of bridged particle monolayers between neighboring droplets. This result is in contrast with the behavior of dilute emulsions, where the use of smaller particles has been shown to impart greater stability against droplet coalescence. Utilizing a simple model of film rupture, we rationalize our experimental findings in the context of the capillary pressure profile within a solid-stabilized liquid film, and show that bridged monolayer formation is directly linked to improved film stability at high volume fractions of the dispersed phase. Therefore, particle size can impact the stability of solid-stabilized HIPEs by influencing their propensity for monolayer formation.

Doing more with less: Evaluation of the use of high linear velocities in preparative supercritical fluid chromatography

The evaluation of higher than typical linear velocities is discussed for supercritical fluid chromatographic purifications on the preparative scale. SFC separation efficiency suffers far less at high linear velocities than HPLC by the rapid mass transfer of analytes carried by compressed CO2 through the stationary phase. The technique is discussed using chiral test compounds and columns. In many cases, running at high linear velocities can yield significant time savings and decreased consumption of mobile phase solvent, while also lowering energy consumption. Within the practical limitations of commercial instrumentation, using 20 μm particles can aid in achieving higher linear velocities not attainable with smaller 5 μm particles, particularly when running with high percentages of organic co-solvent. Use of larger particles for the stationary phase also lowers the associated column cost. These benefits can yield an overall purification process that is more productive and environmentally friendly.

Pyrolysis of Cynara cardunculus L. samples – Effect of operating conditions and bed stage on the evolution of the conversion

The effect of different parameters on the pyrolysis of Cynara cardunculus L. was studied through an innovative technique based on a precision scale, capable of measuring the time evolution of the biomass samples mass during their thermochemical conversion process while moving freely inside a fluidized bed. A silica sand bed reactor, operated under different values of excess gas velocity and reactor temperature, was employed to hold the pyrolysis reaction of cardoon particles of three different size ranges. The pyrolysis was accelerated for higher excess gas velocities, obtaining pyrolysis times as short as 17.3 s for experiments conducted under bubbling fluidized bed regimes, compared to 185.9 s required to complete the pyrolysis of the same sample in a fixed bed configuration. Similarly, the effect of increasing the reactor temperature promoted faster heating rates across the fuel samples, especially under fixed bed configurations, for which the pyrolysis time is reduced from 321.7 s to 132.0 s when increasing the bed temperature from 450 to 650 °C. Regarding the biomass particle size, small sizes are preferred to minimize the conduction thermal resistance inside the fuel particles and, thus, reduce pyrolysis times and increase volatile yields for the pyrolysis in a bubbling fluidized bed reactor. The opposite result was found when the pyrolysis took place in non-bubbling beds, where the use of larger particles is beneficial to accelerate the biomass pyrolysis reaction.

Combining pressurized liquids with ultrasound to improve the extraction of phenolic compounds from pomegranate peel (Punica granatum L.)

The combination of ultrasound and pressurized liquid extraction (UAPLE) was evaluated for the extraction of phenolic compounds from pomegranate peels (Punica granatum L.). The influence of several variables of the process on extraction yield, including solvent type (water, ethanol + water 30, 50 and 70% v:v), temperature (50–100 °C), ultrasound power (0–800 W at the generator, or 0–38.5 W at the tip of the probe), mean particle size (0.68 and 1.05 mm), and number of cycles (1–5), were analyzed according to the yield of 20 different phenolic compounds. The most suitable temperatures for the extraction of phenolic compounds using water were from 70 to 80 °C. In general, 100 °C was not adequate since the lowest extraction yields were observed. Results suggested that ultrasound had a greater impact on extraction yields using large particles and that intermediate ultrasound power (480–640 W at the generator, or 23.1–30.8 W at the tip of the probe) produced the best results. Using small particles (0.68 mm) or large particles (1.05 mm), extraction with ultrasound was 1 cycle faster. Ultrasound may have offset the negative effect of the use of large particles, however, did not increase the yield of phenolic compounds in any of the cases studied after five cycles. Additionally, the continuous clogging problems observed with small particles were avoided with the use of large particles, which combined with ultrasound allowed consistent operation with good intra and inter-day reproducibility (>95%). Using samples with large particle size, the best extraction conditions were achieved with water extraction solvent, 70 °C extraction temperature, ultrasound power at 480 W, and 3 cycles, yielding 61.72 ± 7.70 mg/g. UAPLE demonstrated to be a clean, efficient and a green alternative for the extraction of phenolic compounds from pomegranate peels. These findings indicate that UAPLE has a great potential to improve the extraction of bioactive compounds from natural products.

Fuel Cell Performance and Durability of Intermetallic Oxygen Reduction Catalysts

Platinum-based alloy catalysts for the oxygen reduction reaction (ORR) continue to be the industry standard for fuel cell applications, but improvements are needed to increase ORR activity and durability. Despite extensive study, the effects of structure and composition on real world performance and durability in fuel cells are poorly understood. Most research to date has examined random alloy structures, but preliminary results from intermetallic catalysts, especially intermetallic tetragonal structured catalysts, have indicated that superior performance and durability can be achieved through creation of ordered intermetallic structures. Results so far indicate that the degree of ordering is a critical parameter in determining intermetallic catalyst activity and durability, with fully-ordered face-centered tetragonal (fct) FePt catalysts exhibiting substantially improved activity and durability compared to partially ordered phases [1]. Most work on intermetallic nanocatalysts reported so far has been based on ex situ testing methods that use an idealized aqueous electrochemistry environment. While these ex situ methods are inexpensive and convenient, they do not reliably predict performance and durability in real fuel cells. Therefore, rigorous catalyst testing in fuel cells is needed to build understanding of the relationship between catalyst properties and fuel cell performance and durability. In our earlier work, we observed the instability of the intermetallic surface accompanied by substantial iron and performance loss after subjecting to the DOE catalyst AST (30,000 trapezoidal cycles between 0.6 and 0.95 V with 0.5 s rise time) in operating fuel cells. However, when the surface was chemically modified towards a Pt rich surface on the fct core, the stability was significantly improved (Figure 1). Initial results depicted indicate that Pt-on-fct-FePt can have performance comparable or even better than a baseline commercial Pt/C, despite the use of larger particles (5-7 nm for fct-FePt/C vs. 2-3 nm for Pt/C). Notably, the Pt-on-fct-FePt exhibits lower loss of performance following the 30,000 cycle AST. Ongoing work seeks to focus on optimizing the surface structure of fct-FePt and fct-CoPt intermetallic nanoparticle catalysts such that a synergistic effect between the surface and core can be established, i.e., a stable Pt surface that protects the fct-core that is thin enough to benefit from the geometric and electronic effects from the core. Fig. 1. Fuel cell polarization behavior of Pt/C and fct-FePt/C before and after the 30,000 cycle AST. H2/air, 80°C, 100% RH, 150 kPaabs, 0.1 mgPt/cm2. References Q. Li et al., "New Approach to Fully Ordered fct-FePt Nanoparticles for Much Enhanced Electrocatalysis in Acid," Nano Lett. 2015, 15, 2468−2473. Acknowledgements This research is sponsored by the Fuel Cell Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy. Figure 1

Material Removal Mechanism of Additively Manufactured Components Finished using Magnetic Abrasive Finishing

This paper describes the effects of tool deformability, by changing the size of magnetic particles mixed with abrasive, and abrasive type (magnetic abrasive or conventional abrasive) on the material removal mechanism and resulting surface profiles of 316L stainless steel components made by selective laser melting (SLM). The use of large particles (rigid tool) facilitated the removal of material from the peaks of the target surface geometry of the SLM-produced workpiece. The use of small particles (flexible tool) facilitated the removal of material from the target surface along the surface features. The magnetic abrasive gradually removed material from the peaks of the surface features according to the magnetic abrasive contact against the target surface. In contrast, conventional abrasive freely contacted the target surface and removed material from surface according to the magnetic particle contact against the target surface. Magnetic abrasive finishing produces a surface dominated by valleys. In particular, the surface made by the magnetic abrasive showed higher skewness and lower kurtosis than the one made by the conventional abrasive.

Nanoparticle-Modified Magnetic Vortex Dynamics

With a view toward ferromagnetic-resonance-mediated detection of magnetic nanoparticles, we use micromagnetic simulations to study how the stray magnetic field produced by a uniformly magnetized spherical magnetic nanoparticle can modify the vortex gyrotropic resonance. We also show how these modifications depend on the particle's position and size. For small particle sizes, a core confinement effect induced by interaction between the particle's highly localized out-of-plane stray field and the vortex core magnetization can induce large frequency shifts. However, the generation of large shifts via this mechanism relies on the core's trajectory being localized directly below the particle. For larger particles (which generate stronger but less localized stray fields), changes in the gyrotropic frequency result from a combination of wide-scale out-of-plane spin canting and in-plane-field-induced shifting of the vortex core within its anharmonic confining potential. Compared to confinement-driven frequency shifting, the generation of large frequency shifts ( ${\gtrsim }$ 10 MHz) via these latter mechanisms is less dependent on particle positioning and the core orbit radius. The use of large particles, thus, represents a more reliable sensing modality if the particles cannot be guaranteed to align centrally over the disk.

Particle size and lime addiction on properties of wood-cement composites produced by the method of densification by vibro compaction

ABSTRACT: This paper aimed to evaluate the effects of particle size and the use of lime as a pretreatment of Pinus spp wood particles on the production of wood-cement composites by vibro-compaction densification. Specimens for internal bond and static bending were produced with two different particle sizes: G1, particles that pass through a 4mm screen and were retained at 2mm screen, and G2, particles that pass through a 2mm screen and were retained at 0.84mm screen. The use of lime was also tested in two different methods as pretreatment of wood particles: carbonatation of wood particles before being used in the composite mixture; and addition of hydrated lime directly to the composite mixture. Use of larger particles (G1) presented higher values of internal bond and MOR than composites produced with smaller particles (G2). About the pretreatments, the use of hydrated lime resulted in composites with higher density and better internal bond.

A comparison of local phosphorescence detection and fluid dynamic gauging methods for studying the removal of cohesive fouling layers: Effect of layer roughness

The performance of industrial cleaning in place (CIP) procedures is critically important for food manufacture. CIP has yet to be optimised for many processes, in part since the mechanisms involved in cleaning are not fully understood. Laboratory tests have an important role in guiding industrial trials, and this paper introduces and compares two experimental techniques developed for studying CIP mechanisms: local phosphorescence detection (LPD), and scanning fluid dynamic gauging (sFDG).To illustrate the comparison, each technique is used to investigate the influence of soil topology on the cleaning of pre-gelatinised starch-based layers from stainless steel (SS 316) substrates by aqueous NaOH solutions at ambient temperature. The roughness of the soil surface is varied by incorporating zinc sulphide particles with different particle size distributions (range 1–80μm) into the starch suspensions. The soil roughness increased with the use of larger particles, increasing the 3D arithmetic mean roughness (Sa) of the dry layers (range 0.37–3.33μm). Rough layers were cleaned more readily than those containing small inclusions, with a good correlation between the cleaning rates observed during LPD and FDG measurements. The LPD technique, which is an instrumented CIP test, gives a better indication of the cleaning time, while sFDG measurements provide further insight into the removal mechanisms.

Limestone particle size and artificial light for laying hens in the second laying cycle

The experiment was conducted to evaluate the effects of limestone particle size and the use of artificial light for laying hens in the second laying cycle. We used 240 Hisex White laying hens at 82 weeks of age in a completely randomized design in a 5 × 2 factorial arrangement, resulting in 10 treatments with 4 replicates of 6 birds. The variables were the five particle sizes obtained by increasing the proportion of thick limestone (0, 25, 50, 75 and 100%) compared with thin limestone and two lighting programs: with and without artificial light. Limestone particle size and light did not affect performance or egg quality. However, there were changes in bird feeding schedule throughout the day as a response to the lighting program. Bone quality, density and mineral content of the tibia were not affected by the treatments, but limestone particle size had a quadratic effect of on bone deformity and strength, obtaining maximum inclusion points with 63% and 59% of thick limestone, respectively. The use of large particles of limestone in the diet and the use of a lighting program does not influence the performance and quality of the eggs of laying hens in the second production cycle, but the use of a proportion of 63.3 g of average particle size (0.60 mm) replacing the fine limestone (0.23 mm) per 100 g of total limestone added to the diet improves bone quality in these birds.

J043024 低圧コールドスプレー法を用いた色素増感太陽電池用T102皮膜の開発([J043-02]厚膜形成技術と厚膜の機械特性評価(2))

In order to make a dye-sensitized solar (DSC) cell, a Low-pressure Cold Spray (LCS) technique is used to make Ti02 film in this study. In our previous study, it was successful that dense and more than 15μm thick TiO_2 film can be obtained by the LCS. However, in the case of the DSC, the dense film is not good for power generation. It is better to obtain films with pores, high cohesive force, and suitable thickness. Therefore, the aim of this study is to make the porous and thick film, which was controlled by mixture TiO_2 powder with large and small diameters. It was made that several mixture TiO_2 powders with different proportion of large and small powders, and then a film was coated by the LCS. Moreover, the influence on the deposition efficiency and the film thickness in repetition film coating were evaluated. As a result, it is successful to make porous TiO_2 films controlled by proportion of large and small powder contents. And, it was made clear that use of small particles indicated high deposition efficiency. On the other hand, use of large particles indicated low deposition efficiency. Finally, the battery properties of the film made by the LCS was evaluated. As a result, conversion efficiencies of the film made by the LCS were less than 1% in any mixture ratio, because of inhomogeneous porosity. However, the LCS becomes an effective tool for making films for the DSC.

Superselective Particle Embolization Enhances Efficacy of Radiofrequency Ablation: Effects of Particle Size and Sequence of Action

To evaluate the effects of particle size and course of action of superselective bland transcatheter arterial embolization (TAE) on the efficacy of radiofrequency ablation (RFA). Twenty pigs were divided into five groups: group 1a, 40-μm bland TAE before RFA; group 1b, 40-μm bland TAE after RFA; group 2a, 250-μm bland TAE before RFA; group 2b, 250-μm bland TAE after RFA and group 3, RFA alone. A total of 40 treatments were performed with a combined CT and angiography system. The sizes of the treated zones were measured from contrast-enhanced CTs on days 1 and 28. Animals were humanely killed, and the treated zones were examined pathologically. There were no complications during procedures and follow-up. The short-axis diameter of the ablation zone in group 1a (mean ± standard deviation, 3.19 ± 0.39 cm) was significantly larger than in group 1b (2.44 ± 0.52 cm; P = 0.021), group 2a (2.51 ± 0.32 cm; P = 0.048), group 2b (2.19 ± 0.44 cm; P = 0.02), and group 3 (1.91 ± 0.55 cm; P < 0.001). The greatest volume of ablation was achieved by performing embolization with 40-μm particles before RFA (group 1a; 20.97 ± 9.65 cm(3)). At histology, 40-μm microspheres were observed to occlude smaller and more distal arteries than 250-μm microspheres. Bland TAE is more effective before RFA than postablation embolization. The use of very small 40-μm microspheres enhances the efficacy of RFA more than the use of larger particles.

Two‐temperature stage biphasic CO2–H2O pretreatment of lignocellulosic biomass at high solid loadings

Most biomass pretreatment processes for monosaccharide production are run at low-solid concentration (<10 wt%) and use significant amounts of chemical catalysts. Biphasic CO(2) -H(2) O mixtures could provide a more sustainable pretreatment medium while using high-solid contents. Using a stirred reactor for high solids (40 wt%, biomass water mixture) biphasic CO(2)-H(2) O pretreatment of lignocellulosic biomass allowed us to explore the effects of particle size and mixing on mixed hardwood and switchgrass pretreatment. Subsequently, a two-temperature stage pretreatment was introduced. After optimization, a short high-temperature stage at 210°C (16 min for hardwood and 1 min for switchgrass) was followed by a long low-temperature stage at 160°C for 60 min. Glucan to glucose conversion yields of 83% for hardwood and 80% for switchgrass were obtained. Total molar sugar yields of 65% and 55% were obtained for wood and switchgrass, respectively, which consisted of a 10% points improvement over those obtained during our previous study despite a 10-fold increase in particle size. These yields are similar to those obtained with other major pretreatment technologies for wood and within 10% of major technologies for switchgrass despite the absence of chemical catalysts, the use of large particles (0.95 cm) and high solid contents (40 wt%).

Development of a Laboratory-Scale System for Hybrid Rocket Motor Testing

DOI: 10.2514/1.47521 Theresultsofeffortstoestablishalaboratory-scalesetupforhot-firetestingofamodularhybridrocketmotorand experimental evaluation of the effect of several additives on the regression rates of hydroxyl-terminated– polybutadiene-based fuels are presented. Supercharged nitrous oxide was used as the oxidizer in all tests. The main objectivesofthereportedtest-programphasewerethedesignandbuildupoftheexperimentalfacilityandtosortout, by hot-fire tests, various fuel compositions with respect to the fuel regression rate and combustion–extinction ability at oxidizer shutoff. The cartridge-loaded fuel grains had an initial circular port diameter of 42 mm, a length of 400 mm, and a web thickness of 15 mm. Five fuel composition families with various additive contents of fine ammoniumperchlorate,polystyrene,andaburning-ratecatalystweretested.Thefuelregressionrateincreasedwith the increase in the ammonium perchlorate portion, but combustion extinguishment was not possible with high ammonium perchlorate content. A significant enhancement of the regression rate of up to 3:5 mm=s at an average oxidizer mass flux of about 140 kg=m 2 s (0:2 lbm=in 2 s) was obtained with the addition of both fine ammonium perchlorate and large particles of polystyrene. Full combustion extinguishment and multipulse operation with an insignificant effect on the regression rate was demonstrated by the use of large particles of polystyrene additive and no addition of ammonium perchlorate.

Pebble abrasion during fluvial transport: Experimental results and implications for the evolution of the sediment load along rivers

In actively eroding landscapes, fluvial abrasion modifies the characteristics of the sediment carried by rivers and consequently has a direct impact on the ability of mountain rivers to erode their bedrock and on the characteristics and volume of the sediment exported from upland catchments. In this experimental study, we use a novel flume replicating hydrodynamic conditions prevailing in mountain rivers to investigate the role played by different controlling variables on pebble abrasion during fluvial transport. Lithology controls abrasion rates and processes, with differences in abrasion rates exceeding two orders of magnitude. Attrition as well as breaking and splitting are efficient processes in reducing particle size. Mass loss by attrition increases with particle velocity but is weakly dependent on particle size. Fragment production is enhanced by the use of large particles, high impact velocities and the presence of joints. Based on our experimental results, we extrapolate a preliminary generic relationship between pebble attrition rate and transport stage (τ*/τ*c), where τ* = fluvial Shields stress and τ*c = critical Shields stress for incipient pebble motion. This relationship predicts that attrition rates are independent of transport stage for (τ*/τ*c) ≤ 3 and increase linearly with transport stage beyond this value. We evaluate the extent to which abrasion rates control downstream fining in several different natural settings. A simplified model predicts that the most resistant lithologies control bed load flux and fining ratio and that the concavity of transport‐limited river profiles should rarely exceed 0.25 in the absence of deposition and sorting.

A comparative analysis of dielectric, rheological and thermophysical behaviour of ethylene vinyl acetate/BaTiO3 composites

Dielectric, rheological and thermal behaviours of ethylene vinyl acetate/barium titanate sphere (EVA/BaTiO3) composite materials were investigated in this work. Several composites were prepared for different volume concentrations (from 5% to 49%) and for two types of spheres sizes d: d = 9 µm and d = 105 µm. We show that the use of larger particles allows an increase of dielectric permittivity and thermal conductivity, particularly at high filler concentrations. A comparison between the thermal, dielectric and rheological behaviours of the composites is also reported in this paper. A linear dependence of the relative variation of thermal conductivity and dielectric permittivity, on the one hand, and thermal conductivity and Newtonian viscosity, on the other, was shown.

Use of the Oak Ridge National Laboratory Tungsten-188/Rhenium-188 Generator for Preparation of the Rhenium-188 HDD/Lipiodol Complex for Trans-Arterial Liver Cancer Therapy

This work describes the installation, use, and quality control (QC) of the alumina-based tungsten-188 ((188)W)/rhenium-188 ((188)Re) generators provided by the Oak Ridge National Laboratory (ORNL). In addition, methods used for concentration of the (188)Re-perrhenate bolus and preparation of (188)Re-labeled HDD (4-hexadecyl-2,2,9,9-tetramethyl-4,7-diaza-1,10-decanethiol) for trans-arterial administration for therapy of nonresectable liver cancer also are described. The (188)W/(188)Re generator has a long useful shelf-life of several months and is a convenient on-site (188)Re production system. (188)Re has excellent therapeutic and imaging properties (T(1/2) 16.9 hours; E(betamax) 2.12 MeV; 155-keV gamma ray, 15%) and is cost effectively obtained on demand by saline elution of the generator. The clinical efficacy of a variety of (188)Re-labeled agents has been demonstrated for several therapeutic applications. Because of the favorable physical properties of (188)Re, several (188)Re-labeled agents are being developed and evaluated for the treatment of nonresectable/refractory liver cancer. (188)Re-labeled HDD has been the most widely studied of these agents for this application and has been introduced into clinical trials at a number of institutions. The trans-arterial administration of (188)Re-labeled agents for treatment of inoperable liver cancer requires use of high-level (1-2 Ci) (188)W/(188)Re generators. The handling of such high levels of (188)Re imposes radiological precautions normally not encountered in a radiopharmacy and adequate care and ALARA (ie, "As Low As Reasonably Achievable") principles must be followed. The ORNL generator provides consistently high (188)Re yields (>75%) and low (188)W parent breakthrough (<10(-3)%) over an extended shelf-life of several months. However, the high elution volumes (20-40 mL for 1-2 Ci generators) can require concentration of the (188)Re bolus by postelution passage through silver cation chloride trapping columns used in the cost-effective tandem cation/anion column system. The silver column removes the high levels of chloride anion as insoluble AgCl, thus allowing subsequent specific trapping of the perrhenate anion on the small (QMA SeaPak) anion column. This method permits subsequent elution of (188)Re-perrhenate with a small volume of saline, providing a very high activity-concentration solution. Because the (188)Re-specific volume-activity concentration continually decreases with time, the tandem system is especially effective method for extending the useful generator shelf-life. Low elution flow rates (<1 mL/min) minimize any high back pressure which may be encountered during generator/tandem column elution when using tightly packed, small-particle-size commercial columns. In-house preparation of silver cation columns is recommended since the chloride trapping capacity is essentially unlimited, it is inexpensive and not limited in availability to any one supplier, and back pressure can be eliminated by the use of larger particles. Methods for the preparation of (188)Re-HDD have been optimized and this agent can be obtained in high yield (80%).