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Currently there are no validated clinical methods to assess liver preservation injury. In this work we use high frequency ultrasound integrated backscatter (HFUIB) to assess liver damage in different experimental models of liver ischemia. The ultimate goal of this work is to provide a non-invasive tool to assess organ suitability for transplantation. To examine the effects of liver ischemia at different temperatures, livers from Wistar rats are surgically excised, immersed in phosphate buffer saline (PBS) and stored at 4 and 20°C for 24h. To mimic organ preservation, livers are excised, flushed with University of Wisconsin (UW) solution and stored at 4°C for 24h. Preservation injury is simulated by not flushing livers with UW solution. Ultrasound images and corresponding radio frequency data are collected over the ischemic periods. No significant increase in HFUIB is measured for the livers prepared using standard preservation conditions. For all other ischemia models, the HFUIB increases by 4-9 dBr demonstrating kinetics dependent on storage conditions. HFUIB increase is associated with liver tissue injury. The results provide a possible framework for using high frequency imaging to non-invasively assess liver preservation injury.

Spatial Correlation of Flow Induced Temperature Gradients During Tissue Heating with Vascular Geometry using CT Angiography: Implications for Thermal Therapy

1. INTRODUCTION Thermal models are used in hyperthermia to predict temperature distributions for treatment and applicator optimization. It is known that blood flow can significantly influence temperature profiles but an accurate description of this effect is unknown. Two models that have been used to model microvascular effects are the Pennes Bioheat Transfer Equation (BHTE) and the Effective Thermal Conductivity Equation (ETCE) [1], while an advection term is used in combination with the above to model large vessel effects [2]. The purpose of this work is to compare model predictions in an experimental system and to critically examine the effects of thermally significant vessels.

Changes in magnetic resonance (MR) signals during interstitial microwave heating are reported, and correlated with simultaneously acquired temperature readings from three fiber-optic probes implanted in a polyacrylamide gel phantom. The heating by a MR-compatible microwave antenna did not interfere with simultaneous MR image data acquisition. MR phase-difference images were obtained using a fast two-dimensional-gradient echo sequence. From these images the temperature-sensitive resonant frequency of the1H nuclei was found to decrease approximately by 0.008 ppm/°C. The method and results presented here demonstrate that noninvasive MR-temperature imaging can be performed simultaneously with interstitial microwave thermal treatment.

Assessing the proportion of biological cells in a volume of interest undergoing structural changes, such as cell death, using high-frequency ultrasound~20–100 MHz!, requires the development of a theoretical model of scattering by any arbitrary cell ensemble. A prerequisite to building such a model is to know the scattering by a single cell in different states. In this paper, a simple model for the high-frequency acoustic scattering by one cell is proposed. A method for deducing the backscatter transfer function from a single, subresolution scatterer is also devised. Using this method, experimental measurements of backscatter from homogeneous, subresolution polystyrenemicrospheres and single, viable eukaryotic cells, acquired across a broad, continuous range of frequencies were compared with elastic scattering theory and the proposed cell scattering model, respectively. The resonant features observed in the backscatter transfer function of microspheres were found to correspond accurately to theoretical predictions. Using the spacing of the major spectral peaks in the transfer functions obtained experimentally, it is possible to predict microsphere diameters with less than 4% error. Such good agreement was not seen between the cell model and the measured backscatter from cells. Possible reasons for this discrepancy are discussed

We describe the design of an intense, pulsed, repetitive, neutral beam based on magnetically insulated diode technology for injection into ITER for spectroscopic measurements of thermalizing alpha particle and thermal helium density profiles, ion temperature, plasma rotation, and low Z impurity concentrations throughout the confinement region. The beam is being developed to enhance low signal-to-noise ratios expected with conventional steady-state ion beams because of severe beam attenuation and intense bremsstrahlung emission. A 5 GW (e.g., 100 keV, 50 kA) 1 μs duration beam would increase the charge exchange recombination signal by 103 compared to a conventional 5 MW beam.

The Tertiary uplift of the Eromanga Basin over PELs 5&6 (SA) and ATP 259P (Queensland), has significantly complicated depth-porosity relationships in the important oil-bearing Hutton Sandstone, as well as altering migration pathways. Because seismic reflection data in the Eromanga Basin are focused on the lower part of the succession, they are not suitable for imaging and mapping the Tertiary unconformities. In this study, an estimate of the magnitude of Tertiary uplift across the acreage has been made by cross-plotting interval velocity and depth for the lithologically homogenous Cretaceous marine shales near the top of the succession. Deviations from a depth-velocity baseline fitted to data from the basin depocentres have enabled quantification of uplift. The uplift estimates have been used to produce pre-uplift depth structure maps which can be used to map pre-uplift hydrocarbon migration pathways. Maximum burial depth can also be calculated, providing a better predictor of porosity in the Hutton Sandstone than present burial depth.

BACKGROUND AND AIMS: Previous studies have shown that silica in grass leaves defends them against small herbivores, which avoid high-silica grasses and digest them less efficiently. This study tested the idea that silica can reduce digestibility by preventing the mechanical breakdown of chlorenchyma cells. METHODS: Both the percentage of total chlorophyll liberated from high- and low-silica grass leaves by mechanical grinding and the chlorophyll content of locust faeces were measured. KEY RESULTS: High-silica grasses released less chlorophyll after grinding and retained more after passing through the gut of locusts, showing that silica levels correlated with increased mechanical protection. CONCLUSIONS: These results suggest that silica may defend grasses at least in part by reducing mechanical breakdown of the leaf, and that mechanical protection of resources in chlorenchyma cells is a novel and potentially important mechanism by which silica protects grasses.

A combination of toxicity tests, chemical analyses, and Toxicity Identification Evaluations (TIEs) were used to investigate receiving water toxicity in the Calleguas Creek watershed of southern California. Studies were conducted from 1995 through 1999 at various sites to investigate causes of temporal variability of toxicity throughout this system. Causes of receiving water toxicity varied by site and species tested. Investigations in the lower watershed (Revolon Slough, Santa Clara Drain, Beardsley Wash) indicated that toxicity of samples to the cladoceran Ceriodaphnia dubia was due to elevated concentrations of the organophosphate pesticide chlorpyrifos, while causes of intermittent toxicity to fathead minnows (Pimephales promelas) and the alga Selanastrum capricornutum were less clear. Investigations at sites in the middle and upper reaches of the watershed (Arroyo Simi and Conejo Creek) indicated that the pesticide diazinon was the probable cause of receiving water toxicity to Ceriodaphnia. Elevated ammonia was the cause of toxicity to fathead minnows in the upper watershed sites. Results of these and previous studies suggest that biota are impacted by degraded stream quality from a variety of point and non-point pollution sources in the Calleguas Creek watershed. Water quality resource manager's efforts to identify contaminant inputs and implement source control will be improved with the findings of this study.

Mean sediment quality guideline quotients (mean SQGQs) were developed to represent the presence of chemical mixtures in sediments and are derived by normalizing a suite of chemicals to their respective numerical sediment quality guidelines (SQGs). Mean SQGQs incorporate the number of SQGs exceeded and the degree to which they are exceeded and are used for comparison with observed biological effects in the laboratory or field. The current research makes it clear, however, that the number and type of SQGs used in the derivation of these mean quotients can influence the ability of mean SQGQ values to correctly predict acute toxicity to marine amphipods in laboratory toxicity tests. To determine the optimal predictive ability of mean SQGQs, a total of 18 different chemical combinations were developed and compared. The ability of each set of mean SQGQs to correctly predict the presence and absence of acute toxicity to amphipods was determined using three independent databases (n = 605, 2753, 226). Calculated mean SQGQ values for all chemical combinations ranged from 0.002 to 100. The mean SQGQ that was most predictive of acute toxicity to amphipods is calculated as SQGQ1 = ((sigma ([cadmium]/4.21 )([copper]/270)([lead]/ 12.18)([silver]/1.77)([zinc]/ 410)([total chlordane]/6)([dieldrin]/8)([total PAHoc]/1,800)([total PCB]/400))/9). Both the incidence and magnitude of acute toxicity to amphipods increased with increasing SQGQI values. To provide better comparability between regions and national surveys, SQGQ1 is recommended to serve as the standard method for combination of chemicals and respective SQGs when calculating mean SQGQs.

Sediment quality was assessed in San Francisco Bay, California, USA, using a two-tiered approach in which 111 sites were initially screened for sediment toxicity. Sites exhibiting toxicity were then resampled and analyzed for chemical contamination, recurrent toxicity, and, in some cases, benthic community impacts. Resulting data were compared with newly derived threshold values for each of the metrics in a triad-based weight-of-evidence evaluation. Sediment toxicity test results were compared with tolerance limits derived from reference site data, benthic community data were compared with threshold values for a relative benthic index based on the presence and abundance of pollution-tolerant and -sensitive taxa, and concentrations of chemicals and chemical mixtures were compared with sediment quality guideline-based thresholds. A total of 57 sites exceeded threshold values for at least one metric, and each site was categorized based on triad inferences. Nine sites were found to exhibit recurrent sediment toxicity associated with elevated contaminant concentrations, conditions that met program criteria for regulatory attention. Benthic community impacts were also observed at three of these sites, providing triad evidence of pollution-induced degradation. Multi- and univariate correlations indicated that chemical mixtures, heavy metals, chlordanes, and other organic compounds were associated with measured biological impacts in the Bay. Toxicity identification evaluations indicated that metals were responsible for pore-water toxicity to sea urchin larvae at two sites. Gradient studies indicated that the toxicity tests and benthic community metrics employed in the study predictably tracked concentrations of chemical mixtures in Bay sediments.

A number of methods have been employed to determine the statistical significance of sediment toxicity test results. To allow consistency among comparisons, regardless of among-replicate variability, a protocol-specific approach has been used that considers protocol performance over a large number of comparisons. Ninetieth-percentile minimum significant difference (MSD) values were calculated to determine a critical threshold for statistically significant sample toxicity. Significant toxicity threshold values (as a percentage of laboratory control values) are presented for six species and nine endpoints based on data from as many as 720 stations. These threshold values are useful for interpreting sediment toxicity data from large studies and in eliminating cases where statistical significance is assigned in individual cases because among-replicate variability is small.

Sediment quality in the Los Angeles and Long Beach Harbor area of southern California, USA, was assessed from 1992 to 1997 as part of the California State Water Resources Control Board's Bay Protection and Toxic Cleanup Program and the National Oceanic and Atmospheric Administration's National Status and Trends Program. The assessment strategy relied on application of various components of the sediment quality triad, combined with bioaccumulation measures, in a weight-of-evidence approach to sediment quality investigations. Results of bulk-phase chemical measurements, solid-phase amphipod toxicity tests, pore-water toxicity tests with invertebrate embryos, benthic community analyses (presented as a relative benthic index), and bioaccumulation measures indicated that inner harbor areas of this system are polluted by high concentrations of a mixture of sediment-associated contaminants and that this pollution is highly correlated with toxicity in laboratory experiments and degradation of benthic community structure. While 29% of sediment samples from this system were toxic to amphipods (Rhepoxynius abronius or Eohaustorius estuarius), 79% were toxic to abalone embryos (Haliotis rufescens) exposed to 100% pore-water concentrations. Statistical analyses indicated that amphipod survival in laboratory toxicity tests was significantly correlated with the number of crustacean species and the total number of species measured in the benthos at these stations. Triad measures were incorporated into a decision matrix designed to classify stations based on degree of sediment pollution, toxicity, benthic community degradation, and, where applicable, tissue concentrations in laboratory-exposed bivalves and feral fish.

The Tank Safety Screening Data Quality Objective (DQO) will be used to classify 149 single shell tanks and 28 double shell tanks containing high-level radioactive waste into safety categories for safety issues dealing with the presence of ferrocyanide, organics, flammable gases, and criticality. Decision rules used to classify a tank as ``safe`` or ``not safe`` are presented. Primary and secondary decision variables used for safety status classification are discussed. The number and type of samples required are presented. A tabular identification of each analyte to be measured to support the safety classification, the analytical method to be used, the type of sample, the decision threshold for each analyte that would, if violated, place the tank on the safety issue watch list, and the assumed (desired) analytical uncertainty are provided. This is a living document that should be evaluated for updates on a semiannual basis. Evaluation areas consist of: identification of tanks that have been added or deleted from the specific safety issue watch lists, changes in primary and secondary decision variables, changes in decision rules used for the safety status classification, and changes in analytical requirements. This document directly supports all safety issue specific DQOs and additional characterization DQO efforts associated with pretreatment and retrieval. Additionally, information obtained during implementation can assist in resolving assumptions for revised safety strategies, and in addition, obtaining information which will support the determination of error tolerances, confidence levels, and optimization schemes for later revised safety strategy documentation.

A new analytic expression for the impulse response of concave radiators is used to compute the transient pressure distributions of phased annular arrays with spherical geometry. The process of phasing the array to achieve variable focusing is treated by summing the delayed impulse responses of the individual annuli. The example of pressure distributions of a five element annular array is treated in detail, and some recommendations are given for practical computer studies.

The stratigraphic succession of formations in the Myall district comprises in ascending order the Bunyah Beds, Wallanbah Formation, Kataway Mudstone, Boolambayte Formation (new names), Nerong Volcanics (E'ngel, 1962), Booti Booti Sandstone, Yagon Siltstone, Koolanock Sandstone, Muirs Creek Conglomerate (new names) and Alum Mountain Volcanics (Engel, 1962). The units range in age from possibly Devonian to possibly Permian, most being Carboniferous. The Mograni (new name), Tugrabakh (Voisey, 1940) and Mayers Flat Limestones (new name) are members of the Wallanbah Formation. The Violet Hill Volcanics (new name) is a member of the Yagon Siltstone. The Burdekins Gap Basalt Member and Lakes Road Rhyolite are members of the Alum Mountain Volcanics. Environments of deposition range from nonmarine (Nerong Volcanics, Alum Mountain Volcanics, Muirs Creek Conglomerate, upper part of Koolanock Sandstone) through shallow marine (Booti Booti Sandstone, lower part of Koolanock Sandstone, calcareous parts of Wall...

Candidate pointing control configurations for a Space Infrared Telescope Facility are examined in terms of fine guidance pointing and large angle slewing accuracies. In particular, the fundamental tradeoff is between a strategy that uses body pointing only, where the entire spacecraft is controlled to null pointing error, or body pointing plus image motion compensation, where a movable secondary mirror is employed to remove high-frequency disturbances and therefore mitigate excitation of flexible body modes. Using known characteristics of available attitude control sensors and actuators, a linear covariance analysis is used to compute rms pointing error, while a time domain simulation is used to compute transient response to specific disturbance torques. It is found that body pointing alone can provide excellent fine pointing accuracy but limits slewing performance. Both slewing performance and disturbance rejection may be significantly improved by a steerable secondary mirror, but the noise level of the attitude sensor under study limits control bandwidth and thus restricts the potential advantages of this approach. It is recommended that improved sensor designs be pursued while enhancing slewing performance by appropriate combination of command profile and control compensation.

Experiments were conducted to develop a sensitive sublethal toxicity test protocol to determine the toxicity of municipal wastewater effluents to larvae of the red abalone Haliotis rufescens. In multiple tests, fertilized abalone embryos were exposed for 48 h to dilutions of a reference toxicant, zinc sulfate, and to dilutions of primary-and secondary-treated effluents. The resulting veliger larvae were examined microscopically for larval shell abnormalities. In a longer flowthrough experiment, abalone were exposed for the entire larval phase, from the two-cell stage through metamorphosis, to compare zinc effects on metamorphosis with zinc effects on short-term larval shell development. Dissolved oxygen, pH, salinity and temperature were measured daily in test solutions, and zinc concentrations were verified by chemical analysis. “No observed effect concentrations” (NOECs) for zinc were 39±2.1 μg l-1 in three 48 h exposures, and 19 μg l-1 for the 9 d exposure through metamorphosis. Median effect concentrations (EC50s) were 68±6.9 μg l-1 in 48 h tests and 50 μg l-1 in the 9 d test. Abalone larvae were affected at lower concentrations of primary than of secondary effluent.

The decay of solvated electrons in various aqueous solutions was studied using a stroboscopic pulse radiolysis technique with a time resolution of 24 psec. High concentrations of solutes such as H2O2, acetone, CdCl2, NaNO2, and NaNO3 decreased the initial solvated electron yield, while high acid concentrations did not. Reasons for this reduction in yield are discussed, and the conclusion reached is that the scavengers must be reacting with a precursor to the solvated electron. We believe that this precursor is probably a low‐energy electron which reacts prior to solvation.

Radium implantation has long been established as a good method for treating cancer in the anterior two-thirds of the tongue and, to a lesser extent, for other lesions of the buccal mucosa. Its advantages for healing with minimal scarring and minimal irradiation of salivary tissue are well known. The tongue lends itself well to implantation with rigid radium needles but these sources are more difficult to apply to other sites in the mouth where lesions may be confined by adjacent structures or present on curved surfaces to which the rigid sources cannot conform. For these and other reasons, in the past ten years many experiments with other radioactive sources which may be used in place of radium have been attempted. This brief paper discusses the use of tantalum 182 in the treatment of lesions of the integument generally, and of the buccal mucosa in particular. Isotopes for Interstitial Implants In recent years, many centres have been experimenting with artificial radioactive isotopes in interstitial impla...

Observations of the solvated electron in water and the common aliphatic alcohols have been made in the time region ∼ 20–350 psec. Molar concentrations of acid have been used to scavenge eaq− and k(eaq−+Haq+) has been measured as (1.2 ± 0.2) × 1010 liter/mole·sec for [Haq+] from 0.5 to 5.0M. The factors limiting the time response of our picosecond pulse radiolysis system are discussed. The time of formation of esol− is estimated to be less than 10 psec for all solvents studied. The yield of solvated electrons in alcohols has been measured to be approximately one‐third of the yield in water at picosecond times.

Rate constants for reactions of the hydrated electron with a wide range of compounds, including simple salts and amino acids, have been measured in the time region 20–350 psec. In nearly all cases the second‐order rate constant for reaction with the hydrated electron did not change in the concentration range studied. However, the measured rate constant was in general different to that obtained in dilute solutions, and this was attributed to incomplete formation of the ionic atmosphere around the hydrated electron before reaction. Apart from the hydronium ion, Haq+, nearly all compounds decreased the initial hydrated electron yield: in all cases this decrease showed an exponential dependence on concentration. Compounds most efficient at decreasing the hydrated electron yield were cystine and cadmium salts, in both cases 0.39 mole/liter being needed to reduce the initial yield to 37%. The ability to reduce the initial yield showed no direct correlation with the corresponding hydrated electron rates. This an...

The solvation time of the electron in water and various alcohols is estimated as about 10 ps or faster1. In the same experiments the existence and reactions of a precursor to the solvated electron, the dry electron, were described2,3. In alcoholic glasses the solvated electron spectrum shifts from the infrared to the visible region with time due to dielectric relaxation4,5. The first direct observation of the solvation process was made by Baxendale and Wardman using cold, but still liquid, alcohols6. They measured the decay of a species in the infrared and the concomitant formation of the relaxed solvated electron at 500 nm. The aim of the present work has been to obtain information in the range 210 to 277 K to give, in conjunction with Baxendale's data7, good values for the solvation times and activation energies of the process from extrapolation of the Arrhenius plot to room temperature.

Because of the short wavelength of ultrasound beams, they can be effectively focussed so that improved temperature profiles at depths in the body can be achieved. These are also unusual properties of these intense ultrasound beams that have the potential of enhancing effects.

Conception, fabrication et performances de bielles en materiau composite (matrice metallique et fibres FP, fibres d'alumine de la societe Du Pont de Nemours)

As a focussed ultrasound beam converges in tissue each point of the wavefront experiences velocity and attenuation fluctuations due to the structure and composition of the tissue at that point. These fluctuations lead to a spreading of the beam at the focal zone and steering effects (1,2) where the whole focal zone is moved off axis. Since beam distortion is directly related to loss of resolution in pulse-echo systems it is important to characterize this phenomenon and establish, if possible, the transducer parameters which maximize system resolution. Using a unique variable aperture, variable focal length ultrasound system, the beam distortion in the focal zone has been studied as a function of f-number (focal length/diameter), intervening tissue type, and intervening tissue thickness. The transducer diameter varied from 11 mm to 50 mm and thus the results apply to both wide aperture and conventional transducers.

A continuous flow, rapid-mixing system has been constructed to measure the degree of radiosensitization or protection observable after incubation of Chinese hamster ovary cells at room temperature for periods from about 5 to 1000 ms with a number of radiation modifiers. In agreement with Adams et al. (1975) full sensitization by oxygen is obtained in only a few tens of milliseconds. Misonidazole (10 mM) sensitizes at very nearly the steady-state level (E.R. approximately 2.3) in about 300 ms. Similarly near maximum sensitization by 10 mM metronidazole is seen within the same period. For large effects to be observed in such short times makes unlikely the involvement of any biochemical modification of either the drug or cells. Radioprotection by 1 M dimethyl suplhoxide reaches about 80% of the equilibrium control value within 850 ms. However, if its mode of action involves scavenging of hydroxyl radicals in competition with cellular components, the necessity for very high concentrations in the immediate region of the cellular target would be expected to require longer diffusion times. Cysteamine (10 mM) shows no evidence of its substantial protective ability even after 850 ms incubation. This molecule, which alone in this group exists as an ion in neutral solution, may encounter considerable difficulty in entering the cells.

Different needs must be considered in the control of localized tumors or disseminated disease when deep heating techniques are used. For localized disease, various electromagnetic microwaves, radiofrequency currents and high-powered ultrasound sources are being used. At the present time, each approach has its own strengths and limitations. Microwave and inductive approaches appear to be useful only for surface lesions. Radiofrequency currents, generated by pairs of plates, give more deeper heating in the body, but excessive heating occurs in fatty layers related to high resistivity of the tissue and sometimes near the edge of the applicators. In an invasive approach, needles are implanted into the tumor and excited by a radiofrequency source. Considerable clinical successes are claimed for local heating of the lesion with this approach, but it is only useful for specific sites of the body. Ultrasound has special advantages for both surface or deep-seated soft tissues due to its flexibility and its ability to focus the beam onto the lesion. However, ultrasound cannot be used in the chest cavity or near bone, and the dosimetry is not defined at present. For disseminated disease, much larger regions, particularly in the chest cavity, can be heated, with the hope that the reduced blood circulation in some tumors can achieve a preferential heating in the lesion. Several microwave and inductive heating approaches are being used or considered in the achievement of this goal.

Several generations of carbonate minerals, kaolinite, and quartz are present in Australian bituminous coals. Petrographic observations show that disseminated, fine-grained kaolinite and quartz are common in the coal. On the basis of oxygen isotope ratios, it appears that the disseminated kaolinite and siderite nodules were precipitated from Permian pore water early in the deposition of peat at calculated temperatures of 16° to 32°C. Secondary cleat-filling kaolinite at Leichhardt colliery in the Bowen Basin has a constant 18O value of around +6, which is consistent with formation from mine water of the present isotopic composition at a temperature of 56°C. Lower temperatures are indicated for secondary kaolinitization in coals of the southern Sydney Basin. Detrital quartz grains and chemical quartz have similar isotopic compositions and therefore cannot be distinguished isotopically. However, the oxygen isotope ratio of disseminated, fine-grained silica is consistent with formation in the brown coal stage at a temperature of 52°C and depth of about 700 m. Secondary carbonates are not readily characterized in terms of isotopic criteria and are best recognized by their mode of occurrence. The ability to distinguish between primary and secondary kaolinite appears to hold promise as a guide to prediction of outbursting conditions in underground coal mines.