Continued development of a detailed model of arc discharge dynamics

Using a previously developed set of codes (SEMC, CASCAD, ACORN), a parametric study was performed to quantify the parameters which describe the development of a single electron indicated avalanche into a negative tip streamer. The electron distribution function in Teflon is presented for values of the electric field in the range of four-hundred million volts/meter to four billon volts/meter. A formulation of the scattering parameters is developed which shows that the transport can be represented by three independent variables. The distribution of ionization sites is used to indicate an avalanche. The self consistent evolution of the avalanche is computed over the parameter range of scattering set

The NBS: Processing/Microstructure/Property Relationships in 2024 Aluminum Alloy Plates

As received plates of 2024 aluminum alloy were examined. Topics covered include: solidification segregation studies; microsegregation and macrosegregation in laboratory and commercially cast ingots; C-curves and nondestructive evaluation; time-temperature precipitation diagrams and the relationships between mechanical properties and NDE measurements; transmission electron microscopy studies; the relationship between microstructure and properties; ultrasonic characterization; eddy-current conductivity characterization; the study of aging process by means of dynamic eddy current measurements; and Heat flow-property predictions, property degradations due to improve quench from the solution heat treatment temperature

Computerized system for translating a torch head

The system provides a constant travel speed along a contoured workpiece. It has a driven skate characterized by an elongated bed, with a pair of independently pivoted trucks connected to the bed for support. The trucks are mounted on a contoured track of arbitrary configuration in a mutually spaced relation. An axially extensible torch head manipulator arm is mounted on the bed of the carriage and projects perpendicular from the midportion. The torch head is mounted at its distal end. A real-time computerized control drive subsystem is used to advance the skate along the track of a variable rate for maintaining a constant speed for the torch head tip, and to position the torch axis relative to a preset angle to the workpiece

Histotripsy Effects on the Bladder Trigone: Functional and Histologic Consequences in the Canine Model

Background: Histotripsy is an extracorporeal therapeutic ultrasound (US) technology, where high-amplitude acoustic energy is applied to targeted tissue. Previous research has demonstrated the feasibility, safety, and effectiveness of histotripsy tissue homogenization and debulking of the prostate in the canine model. Before translating this technology for human use, it is prudent to examine the susceptibility of critical periprostatic structures to cavitation injury in the event of histotripsy mistargeting. In this study, we sought to characterize the tissue effects and biologic response of directly treating the bladder trigone with histotripsy. Materials and Methods: In eight anesthetized canines, 750,000 histotripsy pulses were applied uniformly across a 2?1.5-cm area encompassing the bladder trigone and ureteral orifices. Prostate and bladder trigone were harvested immediately after treatment (2 subjects) or at 14 days (6 subjects). Flexible cystourethroscopy, US imaging, and creatinine levels were obtained at intervals until harvest, 14 days after treatment. In one control subject, harvested at 2 days, the same treatment algorithm was applied to the prostate. Results: Transrectal US imaging revealed a cavitation bubble cloud on the surface of the bladder trigone and progressive development of tissue edema during treatment. Flexible cystourethroscopy immediately after treatment confirmed edema and erythema of the trigone. In the six subjects survived 2 weeks after treatment, one incidence of transient, self-limited ureteral obstruction was noted based on hydronephrosis and creatinine levels. At harvest, ureteral orifices were confirmed patent by passage of a guide wire. Histologic evaluation revealed hemorrhage acutely with mild localized fibrosis at 14 days. Conclusions: In this study, designed along the lines of a worst-case, destructive testing scenario, direct targeting of the bladder trigone with supratherapeutic histotripsy failed to induce significant tissue damage or clinical complication. These results are reassuring and will guide treatment strategy in upcoming human clinical trials of histotripsy treatment for benign prostatic hyperplasia.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140374/1/end.2013.0234.pd

Treatment technology for leachate from faecal sludge drying beds

The use of planted drying beds for faecal sludge treatment is effective for solid-liquid separation, but the leachate produced requires further treatment prior to discharge or reuse. This study investigates the potential of a new and low-cost solution for leachate treatment

Histotripsy of Rabbit Renal Tissue in Vivo: Temporal Histologic Trends

Background and Purpose: Histotripsy is defined as noninvasive, nonthermal, mechanical (cavitational) tissue ablation. We previously demonstrated the predictable acute tissue effects of histotripsy in rabbit kidney and other tissues. We sought to characterize the appearance and natural history of renal tissue after histotripsy. Materials and Methods: Following Institutional Animal Care Committee approval, the left kidneys of 29 rabbits were treated with 60,000 750-kHz, 15-cycle bursts of ultrasound energy from an 18-element phased-array transducer at a 1-kHz pulse-repetition frequency. The treated kidneys were harvested at 0, 1, 2, 7, 21, or 60 days; fixed in Formalin; then prepared for microscopic analysis with hematoxylin and eosin and trichrome stains. Results: For kidneys harvested acutely (day 0), a contiguous area of finely disrupted tissue was observed containing no recognizable cells or cellular components. Along the boundary of architectural disruption, a border several tubules wide contained cells that were not visibly disrupted but appeared damaged (pyknotic nuclei). At subsequent time intervals, an inflammatory response developed in association with a steadily decreasing area of cellular and architectural disruption. By day 60, only a small fibrous scar persisted adjacent to a wedge of tubular dilation and fibrosis underlying a surface-contour defect. Conclusions: Histotripsy produces mechanical fractionation of cellular and architectural structures. The resultant acellular material appears to be readily reabsorbed within 60 days in the rabbit. This may prove to be a significant advantage for imaging assessment of residual tumor after ablation of renal malignancy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63123/1/end.2007.9915.pd

Histotripsy of the Prostate in a Canine Model: Characterization of Post-Therapy Inflammation and Fibrosis

Introduction: Histotripsy is a nonthermal, noninvasive, pulsed ultrasound technology that homogenizes tissue within the targeted volume. From previous experiments, it appeared that the resultant fibrotic response from histotripsy was limited compared with the typical tissue response seen after thermoablation. The objective of this study was to characterize the inflammatory response and quantify patterns of collagen deposition 6 weeks after in vivo canine prostate histotripsy. Methods: Histotripsy was applied to the left half of eight canine prostates to produce an intraparenchymal zone of tissue homogenization. Six weeks after treatment, prostates were harvested, sectioned, and stained with hematoxylin and eosin for histologic evaluation, CD3, CD20, and Mac387 immunohistochemistry to characterize the inflammatory components, and picrosirius red staining to identify collagen. Results: Seven of eight treated prostates exhibited only minimal residual inflammation. Visual microscopic analysis of picrosirius red slides revealed a band of dense collagen (0.5?mm wide) immediately adjacent to the cavity produced by histotripsy. This was surrounded by a second band (1?mm wide) of less dense collagen interspersed among glandular architecture. A lobar distribution of epithelial atrophy and basal cell hyperplasia reminiscent of periurethral glands and ducts was apparent surrounding the margin of the treatment cavities. Tissue loss (-31%) was apparent on the treated side of all prostates while four demonstrated a net decrease in collagen content. Conclusions: In vivo histotripsy of canine prostate produced a decrease in prostate volume coupled with a limited inflammatory and fibrotic response. A narrow (1.5?mm) band of fibrosis around the empty, reepithelialized treatment cavity was observed 6 weeks after treatment. In four cases, an overall reduction in collagen content was measured. Further studies are planned to correlate these histologic findings with alteration in mechanical tissue properties and to explore histotripsy strategies for treatment of benign prostatic hyperplasia that optimize tissue volume removal with minimization of fibrosis.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140079/1/end.2014.0585.pd

Botulinum toxins for the prevention of migraine in adults

BackgroundMigraine occurs in around 15% of adults and is ranked as the seventh most disabling disease amongst all diseases globally. Despite the available treatments many people suffer prolonged and frequent attacks which have a major impact on their quality of life. Chronic migraine is defined as 15 or more days of headache per month, at least eight of those days being migraine. People with episodic migraine have fewer than 15 headache days per month. Botulinum toxin type A has been licensed in some countries for chronic migraine treatment, due to the results of just two trials.ObjectivesTo assess the effects of botulinum toxins versus placebo or active treatment for the prevention or reduction in frequency of chronic or episodic migraine in adults.Search methodsWe searched CENTRAL, MEDLINE & MEDLINE in Process, Embase, ClinicalTrials.gov and World Health Organization International Clinical Trials Registry (to December 2017). We examined reference lists and carried out citation searches on key publications. We sent correspondence to major manufacturers of botulinum toxin.Selection criteriaRandomised, double‐blind, controlled trials of botulinum toxin (any sero‐type) injections into the head and neck for prophylaxis of chronic or episodic migraine in adults. Eligible comparators were placebo, alternative prophylactic agent or different dose of botulinum toxin.Data collection and analysisTwo review authors independently selected trials and extracted data. For continuous outcomes we used mean change data when available. For dichotomous data we calculated risk ratios (RRs). We used data from the 12‐week post‐treatment follow‐up time point. We assessed the evidence using GRADE and created two 'Summary of findings' tables.Main resultsDescription of trialsWe found 90 articles describing 28 trials (4190 participants), which were eligible for inclusion. The longest treatment duration was three rounds of injections with three months between treatments, so we could not analyse long‐term effects. For the primary analyses, we pooled data from both chronic and episodic participant populations. Where possible, we also separated data into chronic migraine, episodic migraine and ‘mixed group’ classification subgroups. Most trials (21 out of 28) were small (fewer than 50 participants per trial arm). The risk of bias for included trials was low or unclear across most domains, with some trials reporting a high risk of bias for incomplete outcome data and selective outcome reporting.Botulinum toxin versus placeboTwenty‐three trials compared botulinum toxin with placebo. Botulinum toxin may reduce the number of migraine days per month in the chronic migraine population by 3.1 days (95% confidence interval (CI) ‐4.7 to ‐1.4, 4 trials, 1497 participants, low‐quality evidence). This was reduced to ‐2 days (95% CI ‐2.8 to ‐1.1, 2 trials, 1384 participants; moderate‐quality evidence) when we removed small trials.A single trial of people with episodic migraine (N = 418) showed no difference between groups for this outcome measure (P = 0.49).In the chronic migraine population, botulinum toxin reduces the number of headache days per month by 1.9 days (95% CI ‐2.7 to ‐1.0, 2 trials, 1384 participants, high‐quality evidence). We did not find evidence of a difference in the number of migraine attacks for both chronic and episodic migraine participants (6 trials, N = 2004, P = 0.30, low‐quality evidence). For the population of both chronic and episodic migraine participants a reduction in severity of migraine rated during clinical visits, on a 10 cm visual analogue scale (VAS) of 3.3 cm (95% CI ‐4.2 to ‐2.5, very low‐quality evidence) in favour of botulinum toxin treatment came from four small trials (N = 209); better reporting of this outcome measure from the additional eight trials that recorded it may have improved our confidence in the pooled estimate. Global assessment and quality‐of‐life measures were poorly reported and it was not possible to carry out statistical analysis of these outcome measures. Analysis of adverse events showed an increase in the risk ratio with treatment with botulinum toxin over placebo 30% (RR 1.28, 95% CI 1.12 to 1.47, moderate‐quality evidence). For every 100 participants 60 experienced an adverse event in the botulinum toxin group compared with 47 in the placebo group.Botulinum toxin versus other prophylactic agentThree trials studied comparisons with alternative oral prophylactic medications. Meta‐analyses were not possible for number of migraine days, number of headache days or number of migraine attacks due to insufficient data, but individually trials reported no differences between groups for a variety of efficacy measures in the population of both chronic and episodic migraine participants. The global impression of disease measured using Migraine Disability Assessment (MIDAS) scores were reported from two trials that showed no difference between groups. Compared with oral treatments, botulinum toxin showed no between‐group difference in the risk of adverse events (2 trials, N = 114, very low‐quality evidence). The relative risk reduction (RRR) for withdrawing from botulinum toxin due to adverse events compared with the alternative prophylactic agent was 72% (P = 0.02, 2 trials, N = 119).Dosing trialsThere were insufficient data available for the comparison of different doses.Quality of the evidenceThe quality of the evidence assessed using GRADE methods was varied but mostly very low; the quality of the evidence for the placebo and active control comparisons was low and very low, respectively for the primary outcome measure. Small trial size, high risk of bias and unexplained heterogeneity were common reasons for downgrading the quality of the evidence.Authors' conclusionsIn chronic migraine, botulinum toxin type A may reduce the number of migraine days per month by 2 days compared with placebo treatment. Non‐serious adverse events were probably experienced by 60/100 participants in the treated group compared with 47/100 in the placebo group. For people with episodic migraine, we remain uncertain whether or not this treatment is effective because the quality of this limited evidence is very low. Better reporting of outcome measures in published trials would provide a more complete evidence base on which to draw conclusions

Attentional guidance by salient feature singletons depends on intertrial contingencies.

Evidence that salient feature singletons guide attention only when the target and the singleton frequently coincide has been taken to suggest that selection of singletons is under top-down control: Observers strategically use an attentional set sensitive to the singleton being a target. Changing the singleton-target (or singleton-distractor) coincidence also changes the opportunity for facilitative and disruptive intertrial effects to occur. The authors show that benefits and costs associated with certain singletons depend at least partly on the preceding trial type. Results are in line with dimensional weighting and perceptual priming accounts, which propose a (semi-) automatic transfer of dimensional activity from one trial to the next. Results also indicate that priming is set independently for each dimension