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P D Edmonds

Publications and source records attributed to P D Edmonds.

At least 19 recordsLinked to original sources
PubMed2001

High-resolution x-ray imaging of a globular cluster core: compact binaries in 47Tuc.

We have obtained high-resolution (approximately 1") deep x-ray images of the globular cluster 47Tucanae (NGC 104) with the Chandra X-ray Observatory to study the population of compact binaries in the high stellar density core. A 70-kilosecond exposure of the cluster reveals a centrally concentrated population of faint (Lx approximately 10(30-33) ergs per second) x-ray sources, with at least 108 located within the central 2' x 2.5' and greater, similar half with Lx approximately 10(30.5) ergs per second. All 15 millisecond pulsars (MSPs) recently located precisely by radio observations are identified, though 2 are unresolved by Chandra. The x-ray spectral and temporal characteristics, as well as initial optical identifications with the Hubble Space Telescope, suggest that greater, similar50 percent are MSPs, about 30 percent are accreting white dwarfs, about 15 percent are main-sequence binaries in flare outbursts, and only two to three are quiescent low-mass x-ray binaries containing neutron stars, the conventional progenitors of MSPs. An upper limit of about 470 times the mass of the sun is derived for the mass of an accreting central black hole in the cluster. These observations provide the first x-ray "color-magnitude" diagram for a globular cluster and census of its compact object and binary population.

Journal Article↗
PubMed1996

Ultrasound tissue characterization of breast biopsy specimens: expanded study.

Tissue classification by examining sets of ultrasound parameters is an elusive goal. We report analysis of measurements of ultrasound speed, attenuation and backscatter in the range 3 to 8 MHz in breast tissues at 37 C. Statistical discriminant analysis and neural net analysis were employed. Data were acquired from 24 biopsy and 7 mastectomy specimens. Best separation of the classes normal, benign, and malignant occurred in the 18 cases where two tissue classes were present in the same specimen and parameters were corrected for within-patient mean; then 85-90% of cases in test sets were correctly classified. Most errors comprised misclassified benign cases. The neural net was comparable to discriminant analysis and slightly superior in separating normal and malignant classes.

Breast↗
PubMed1992

Conservation of bactericidal activity in ultrasound-exposed murine peritoneal phagocytic cells.

Murine peritoneal exudate cells (PEC), predominantly macrophages, were insonated in vitro with burst-mode ultrasound and assayed for their ability to phagocytose and kill Staphylococcus aureus. PEC were exposed at 37 degrees C in rotating tubes to 1-MHz, burst-mode (10 ms on, 10 ms off) ultrasound at 3.7 +/- 0.2 W/cm2 ISPTA (7.4 +/- 0.4 W/cm2 ISPBA) for 150 s. Bactericidal activity was assayed at 1, 2, and 3 h after exposure and subsequent 37 degrees C incubation with the bacteria for 20 min. In these experiments, which comprised 17 treated and 7 sham-treated control samples, there was no significant difference in results between treated and control samples (p > 0.29).

Animals↗
PubMed1992

Conservation of receptor expression and phagocytic activity of murine macrophages exposed to various ultrasonic regimens in vitro.

Murine peritoneal macrophages insonated in vitro at 37 degrees C were assayed for impairment of adhesion to and spreading on glass coverslips, expressions of Fc gamma and C3b receptors, and phagocytosis. Insonation conditions were typical for exposures by B-mode imaging equipment and approximated the most severe exposures anticipated in use of pulsed Doppler equipment. In no case were the assay results for insonated samples significantly different from those for the sham-exposed controls.

Animals↗
PubMed1991

Ultrasound tissue characterization of breast biopsy specimens.

Results of measurements of ultrasound speed and absorption coefficients in the range 3 to 8 MHz in breast tissues at 37 C are reported and analyzed in attempts to identify a set of ultrasound parameters capable of discriminating normal, benign, and malignant tissues. We analyzed 118 tissue regions, comprising 47 normal, 55 benign, and 16 malignant by straight-line fitting of frequency dependence of attenuation. Data for ten additional regions, for a total of 128, became available and were added to the cohort when we subsequently fitted quadratic curves. Sound speed consistently emerged as the variable with greatest discriminating power, particularly for separating normal from benign and malignant tissue. Great difficulty was encountered in discriminating benign from malignant, even when the jackknife technique was used. More success was found with classification and regression trees (CART), although results were sensitive to assigned misclassification costs. Best results from straight-line fits were obtained when discriminating malignant from combined normal/benign data after randomly assigning 75 percent of the data to the learning set and 25 percent to the test set. Then, 23 out of 25 normal/benign and 4 out of 4 malignant cases in the test set were correctly classified. With quadratic fitting, best results were obtained in the three-class case--the false positive rate for malignancy was reduced to zero in the learning (0/31) and test (0/10) sets. Nevertheless, the false negative rate increased to 13 out of 31 (42 percent) in the learning set, while attaining zero (0/4) in the test set.

Adenofibroma↗
PubMed1991

Apparatus for ultrasound tissue characterization of excised specimens.

Apparatus is described for measurement of sound speed and ultrasound attenuation coefficients by the substitution technique in the frequency range 3 to 8 MHz. Phase-cancellation artifacts leading to overestimation of attenuation coefficients are avoided by use of an acoustoelectric transducer. Specimens confined by polystyrene windows can be interrogated by focused ultrasound beams at selected locations spaced on a grid of 3 x 3 mm voxels. Pulse time of flight is measured with an accuracy of 30 ns, yielding sound speeds accurate to +/- 6.7 m/s, for samples 10 mm thick. Uncertainties in measured insertion losses range from 0.1 dB in low-loss (10 dB) specimens to 0.5 dB in high-loss (25 dB) specimens.

Algorithms↗
PubMed1989

Effects of ultrasound exposure in vitro on neuroblastoma cell membranes.

Mechanisms of action of ultrasound on cell membranes were studied on two murine C1300 neuroblastoma cell lines of minimum genetic diversity. Cavitation was established in rotating polystyrene centrifuge tubes by 1 MHz cw ultrasound; exposure time was 5 minutes. NS20Y and N2A cells exposed in suspension responded similarly by 86Rb+ transport and Na+-K+-ATPase activity assays, but differently by trypan blue dye exclusion and lysis assays. This indicates similar overall damage to the cell membranes, despite use of trypsin to release N2As only. Primary evidence of damage was lysis of NS20Ys and permeabilization of N2As. These results indicate that the same ultrasound exposure conditions can produce different effects in cells that differ in their membrane properties.

Animals↗
PubMed1988

Protein synthesis by neuroblastoma cells is enhanced by exposure to burst-mode ultrasound cavitation.

We observed enhancement of protein synthesis, compared to control cells, 24 h after exposing C1300 neuroblastoma cells (N2A) in rotating tubes at 37 degrees C to 1-MHz ultrasound tone bursts [1:1; durations from 6 to 600 ms; 3.4 W/cm2 spatial-peak burst-average intensity; 5 min total treatment duration (on + off periods)]. Protein synthesis was measured by uptake of 3H-leucine and normalized for cell proliferation by measured uptake of 14C thymidine. The similarity between results for enhanced cavitation-stimulated iodine-release reported by Ciaravino and our results for cellular protein synthesis suggests that cavitation causes this biological effect.

Acoustics↗
PubMed1986

Acoustic emission as a measure of exposure of suspended cells in vitro.

Cell viability, survival, and growth of C1300 mouse neuroblastoma cells were assayed by trypan blue dye exclusion, clonogenesis, and culturing, respectively, after exposure in suspension to therapeutic levels of ultrasound (1 MHz; continuous wave; spatial peak intensity 0.9, 1.7, and 2.6 W/cm2; 5 min at 37 degrees C). Acoustic emission from the cavitating cell suspensions was recorded as the rms value of the half-harmonic and noise components combined. Cell viability and survival appeared better correlated with acoustic emission than with spatial peak intensity, implying that acoustic emission may provide a more direct measure of insult to the cells in a cavitating field than the incident intensity. Biological assay results of growth were well correlated with spatial peak intensity but not with acoustic emission levels, which seems to imply that for this end point incident intensity is a more directly interacting parameter than cavitational activity, provided however that the latter is present. Further refinement of the technique for measuring acoustic emission from cell suspensions should permit separate measurements of the half-harmonic and noise components. When thus refined, it may provide the means to demonstrate cavitational action without resorting to additional experiments to suppress cavitation.

Acoustics↗
PubMed1986

Interlaboratory comparison of ultrasonic attenuation and speed measurements.

A set of test samples, all containing ultrasonically equivalent tissue-mimicking material, was produced and measurements of ultrasonic speed and ultrasonic attenuation coefficients were made at seven laboratories using various techniques. The ultrasonic speed values agree well with one another, having a spread of about 0.3 per cent; thus, speed values for tissue parenchyma appearing in the literature are likely to be accurate. Values of ultrasonic attenuation coefficients agree fairly well with one another, with differences between individual values and the group mean of generally less than 20 per cent of the group mean.

Humans↗
PubMed1982

The molecular basis of ultrasonic absorption by proteins.

This article reviews significant advances in understanding the basis for the magnitude of ultrasonic absorption in proteins and related biological materials. Carstensen and Schwan's accurate and extensive measurements on blood and hemoglobin solutions provided the initial experimental data; these were augmented by data from measurements on aqueous solutions of gelatin, bovine serum albumin, lysozyme, various polypeptides, and amino acids. The initial frequency range of 1-10 MHz was expanded to 0.035-1000 MHz; temperature and pH dependences of absorption were studied. Theoretical approaches included consideration of the relative motion of blood cells in plasma, perturbation of water structure around macromolecules, solvation of charged entities, proton-transfer reactions, and helix-coil transitions. Proton-transfer reactions between amino and carboxylic groups and water proved to be largely responsible for the observed peaks in pH dependence of absorption coefficient; the peaks occurred in the basic and acidic regions corresponding to the pKs for titration of these groups. Such reactions could not account for the magnitude of absorption at physiological pH because only histidine titrated in this range. Extensive analysis, using relaxation theory, and measurements have shown that the proton transfer reaction between the imidazole group of histidine and hydrogen phosphate ion (in solution) provides sufficient volume change for significant ultrasonic absorption at physiological pH. Excellent agreement between theory and experiment was found with the peptide bacitracin in phosphate buffer solutions. By generalizing these results to the case of a protein, Slutsky wt al estimated maximum values of frequency-dependent absorption coefficients for "typical tissue" and found them to be correct to order of magnitude, even exceeding observed values in soft tissues in some instances, instead of being far too small as was always the case in the past. Thus, in principle, adjustment of parameters, such as pK values, could bring theory and experiment into agreement for the first time.

Animals↗
PubMed1980

Effects of ultrasound on the mouse exposed at different stages of gestation: acute studies.

At five stages of gestation, mice were exposed dorsally to ultrasonic irradiation at 1 W/cm2 (spatial and temporal average), 2 MHz, and 34 and 37 degrees C (temperature at beginning of exposure). The results indicated that ultrasonic exposure up to at least 100 s is not hazardous to a pregnant mouse or its offspring in utero under the conditions of our experiment. Thresholds for both undesirable and lethal effects on the dam and its embryos or fetuses appeared between 100 and 200 s. Temperature rises in the uterus to more than 40 degrees C and similarity of results obtained with continuous-wave and burst modes of irradiation suggest a thermal mechanism as one cause of these effects. Preliminary conclusions are that thresholds for both tissue damage to the dam and deleterious effects on pregnancy were similar; however, they occurred at spatial average intensity and exposure levels far in excess of those used in clinical diagnostic medicine.

Animals↗
PubMed1980

Toxicity of ultrasound in mice: neonatal studies.

Pregnant mice were exposed to ultrasound (continuous wave, 2 MHz) on Day 8 of gestation to determine effects on the progeny. The most significant finding was a decrease in mean uterine weight of the female progeny. The thresholds for this effect were 140 s at 0.5 W/cm2 and 60 s at 1 W/cm2, which were below the thresholds previously reported for other effects in mice. We suggest that this indicates a delay or impairment of maturation of the mice exposed in utero. Exposure of the dams to spatial average intensity of 1 W/cm2 for 40 and 60 s had no effect on body weight of the progeny, compared with sham-treated controls. In this experiment the body weights of progeny from sham-treated controls were significantly lower than those from untreated controls on Days 10, 17, and 25 of age. After exposure in utero to 0.5 W/cm2 for 180 s, statistically significant decreases in mean body weights of the neonates were observed, but only on Day 25 of age, in both sexes compared with sham-treated controls. At necropsy at Day 25 of age, neonatal organ weights relative to body weights were not significantly affected for the thymus in either sex or for the seminal vesicles and tests ion comparison with sham-treated controls.

Animals↗