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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Removal of Retrievable Self-Expandable Metallic Tracheobronchial Stents: An 18-Year Experience in a Single Center

PurposeThe purpose of the study was to retrospectively evaluate the technical outcomes of removal of retrievable self-expandable metallic stents (REMSs) and identify predictors of technical failure in 81 patients with benign and malignant tracheobronchial strictures.Materials and MethodsA total of 98 REMSs were removed under fluoroscopic guidance in 81 patients with benign (n = 48) or malignant (n = 33) tracheobronchial strictures. Primary and secondary technical success rates and complication rate were evaluated. Technical outcomes with regard to underlying diseases were also evaluated. Logistic regression models were constructed to identify predictors of primary technical success.ResultsPrimary and secondary technical success rates were 86.7 and 94.9 %, respectively. Stent removal-related complication rate was 7.1 % (7/98) and all were bleeding after stent removal. All bleeding complications were minor and managed conservatively. Primary technical success rate for benign strictures was significantly lower compared with that for malignant strictures (80.9 vs. 97.1 %, P = 0.029), but secondary technical success rate (93.7 vs. 97.1 %, P = 0.652) did not differ between the two groups. Granulation tissue formation was identified as an independent predictor of primary technical success (odds ratio 0.249, 95 % CI 0.071–0.874, P = 0.030).ConclusionRemoval of REMSs in patients with benign and malignant tracheobronchial strictures is safe and technically feasible. Bronchoscopic guidance may be required when the removal using a hook wire fails. The presence of granulation tissue was the negative predictor of primary technical success.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Transjugular Intrahepatic Portosystemic Shunt Using the New Gore Viatorr Controlled Expansion Endoprosthesis: Prospective, Single-Center, Preliminary Experience

Objectives: To evaluate short-term clinical efficacy, complications and possible passive stent expansion of transjugular intrahepatic portosystemic shunt (TIPS) creation using the new controlled expansion ePTFE covered stent (VCX), for portal hypertension complications. Methods: Between 7/2016 and 3/2018, 75 patients received TIPS using VCX. Thirty-nine patients with VCX dilated with an 8-mm angioplasty balloon underwent computed tomography (CT) study during follow-up and CT data were used to measure stent diameter. The CT measurement technique was validated by ex vivo experiment. Results: TIPS indications were: refractory ascites (n = 45), variceal bleeding (n = 22), other (n = 8). Mean follow-up was 5.8 months (± 4.5, range 1–20). In 69 patients, TIPS was dilated to 8 mm of diameter reaching the hemodynamic target of a portosystemic pressure gradient (PSG) < 12 mmHg. In six patients, not reaching the hemodynamic target the stent was dilated to 10 mm of diameter during the same session with a final PSG < 12 mmHg. Overall clinical success was achieved in 66/75 (88%) patients (80% in refractory ascites, 95% variceal bleeding, 100% other). Grade II–III encephalopathy was observed in five patients (6%). TIPS revision with stent dilatation to 10 mm was performed in seven patients: in three patients with ascites persistence, without evidence of stent dysfunction and in four patients for stent stenosis. One patient underwent stent reduction. Fourteen patients (18%) died during follow-up of causes not related to TIPS. Five patients (6%) underwent liver transplant. No passive stent expansion was detected by CT measurements. Conclusion: VCX for TIPS creation retains its diameter over a short-term period and is associated with a good clinical outcome with a reasonably low complication rate.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Prognostic Impact of External Beam Radiation Therapy in Patients Treated With and Without Extended Surgery and Intraoperative Electrons for Locally Recurrent Rectal Cancer: 16-Year Experience in a Single Institution

Purpose: To analyze prognostic factors associated with survival in patients after intraoperative electrons containing resective surgical rescue of locally recurrent rectal cancer (LRRC). Methods and Materials: From January 1995 to December 2011, 60 patients with LRRC underwent extended surgery (n=38: multiorgan [43%], bone [28%], soft tissue [38%]) or nonextended (n=22) surgical resection, including a component of intraoperative electron-beam radiation therapy (IOERT) to the pelvic recurrence tumor bed. Twenty-eight (47%) of these patients also received external beam radiation therapy (EBRT) (range, 30.6-50.4 Gy). Survival outcomes were estimated by the Kaplan-Meier method, and risk factors were identified by univariate and multivariate analyses. Results: The median follow-up time was 36 months (range, 2-189 months), and the 1-year, 3-year, and 5-year rates for locoregional control (LRC) and overall survival (OS) were 86%, 52%, and 44%; and 78%, 53%, 43%, respectively. On multivariate analysis, R1 resection, EBRT at the time of pelvic rerecurrence, no tumor fragmentation, and non-lymph node metastasis retained significance with regard to LRR. R1 resection and no tumor fragmentation showed a significant association with OS after adjustment for other covariates. Conclusions: EBRT treatment integrated for rescue, resection radicality, and not involved fragmented resection specimens are associated with improved LRC in patients with locally recurrent rectal cancer. Additionally, tumor fragmentation could be compensated by EBRT. Present results suggest that a significant group of patients with LRRC may benefit from EBRT treatment integrated with extended surgery and IOERT.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS1985

Accelerators for critical experiments involving single-particle upset in solid-state microcircuits

Charged-particle interactions in microelectronic circuit chips (integrated circuits) present a particularly insidious problem for solid-state electronic systems due to the generation of soft errors or single-particle event upset (SEU) by either cosmic rays or other radiation sources. Particle accelerators are used to provide both light and heavy ions in order to assess the propensity of integrated circuit chips for SEU. Critical aspects of this assessment involve the ability to analytically model SEU for the prediction of error rates in known radiation environments. In order to accurately model SEU, the measurement and prediction of energy deposition in the form of an electron-hole plasma generated along an ion track is of paramount importance. This requires the use of accelerators which allow for ease in both energy control (change of energy) and change of ion species. This and other aspects of ion-beam control and diagnostics (e.g., uniformity and flux) are of critical concern for the experimental verification of theoretical SEU models.

Zoutendyk, J. A.↗
DOE OSTI2015

X-rays only when you want them: Optimized pump–probe experiments using pseudo-single-bunch operation

Laser pump–X-ray probe experiments require control over the X-ray pulse pattern and timing. Here, the first use of pseudo-single-bunch mode at the Advanced Light Source in picosecond time-resolved X-ray absorption experiments on solutions and solids is reported. In this mode the X-ray repetition rate is fully adjustable from single shot to 500 kHz, allowing it to be matched to typical laser excitation pulse rates. Suppressing undesired X-ray pulses considerably reduces detector noise and improves signal to noise in time-resolved experiments. In addition, dose-induced sample damage is considerably reduced, easing experimental setup and allowing the investigation of less robust samples. Single-shot X-ray exposures of a streak camera detector using a conventional non-gated charge-coupled device (CCD) camera are also demonstrated.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Re-evaluating cloud chamber constraints on depositional ice growth in cirrus clouds – Part 1: Model description and sensitivity tests

Abstract. Ice growth from vapor deposition is an important process for the evolution of cirrus clouds, but the physics of depositional ice growth at the low temperatures (<235 K) characteristic of the upper troposphere and lower stratosphere is not well understood. Surface attachment kinetics, generally parameterized as a deposition coefficient αD, control ice crystal habit and also may limit growth rates in certain cases, but significant discrepancies between experimental measurements have not been satisfactorily explained. Experiments on single ice crystals have previously indicated the deposition coefficient is a function of temperature and supersaturation, consistent with growth mechanisms controlled by the crystal's surface characteristics. Here we use observations from cloud chamber experiments in the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) aerosol and cloud chamber to evaluate surface kinetic models in realistic cirrus conditions. These experiments have rapidly changing temperature, pressure, and ice supersaturation such that depositional ice growth may evolve from diffusion limited to surface kinetics limited over the course of a single experiment. In Part 1, we describe the adaptation of a Lagrangian parcel model with the Diffusion Surface Kinetics Ice Crystal Evolution (DiSKICE) model (Zhang and Harrington, 2014) to the AIDA chamber experiments. We compare the observed ice water content and saturation ratios to that derived under varying assumptions for ice surface growth mechanisms for experiments simulating ice clouds between 180 and 235 K and pressures between 150 and 300 hPa. We found that both heterogeneous and homogeneous nucleation experiments at higher temperatures (>205 K) could generally be modeled consistently with either a constant deposition coefficient or the DiSKICE model assuming growth on isometric crystals via abundant surface dislocations. Lower-temperature experiments showed more significant deviations from any depositional growth model, with different ice growth rates for heterogeneous and homogeneous nucleation experiments.

54 ENVIRONMENTAL SCIENCES↗