Field Measurements of Terrestrial and Martian Dust Devils

Surface-based measurements of terrestrial and martian dust devils/convective vortices provided from mobile and stationary platforms are discussed. Imaging of terrestrial dust devils has quantified their rotational and vertical wind speeds, translation speeds, dimensions, dust load, and frequency of occurrence. Imaging of martian dust devils has provided translation speeds and constraints on dimensions, but only limited constraints on vertical motion within a vortex. The longer mission durations on Mars afforded by long operating robotic landers and rovers have provided statistical quantification of vortex occurrence (time-of-sol, and recently seasonal) that has until recently not been a primary outcome of more temporally limited terrestrial dust devil measurement campaigns. Terrestrial measurement campaigns have included a more extensive range of measured vortex parameters (pressure, wind, morphology, etc.) than have martian opportunities, with electric field and direct measure of dust abundance not yet obtained on Mars. No martian robotic mission has yet provided contemporaneous high frequency wind and pressure measurements. Comparison of measured terrestrial and martian dust devil characteristics suggests that martian dust devils are larger and possess faster maximum rotational wind speeds, that the absolute magnitude of the pressure deficit within a terrestrial dust devil is an order of magnitude greater than a martian dust devil, and that the time-of-day variation in vortex frequency is similar. Recent terrestrial investigations have demonstrated the presence of diagnostic dust devil signals within seismic and infrasound measurements; an upcoming Mars robotic mission will obtain similar measurement types

Applications of electrified dust and dust devil electrodynamics to Martian atmospheric electricity

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kVm-1 to 100 kVm-1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m-1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)-MicroARES (Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ measurements

Rain Impact on a Curved Surface High-rise Building

ABSTRACT: A Particle Tracking Method is used in conjunction with steady state simulations to determine the trajectories and the impact of rain drops on the curved façade of a high-rise building. The simulation is performed for the upper part of the building comprising a detailed louver system. Rain is trapped at relative high rates on the roof and the penthouse, with Local Intensity Factors (LIF's) of the order of 1. The upper parapets and upper floors get a fair amount of wetting with LIF's of the order of 0.6. The wetting decreases downwards reaching values of 0.2 to 0.25 at the level of the louver system

What are the factors that predict outcome at relapse after previous esophagectomy and adjuvant therapy in high-risk esophageal cancer?

OBJECTIVES: The present study investigated factors affecting outcome at relapse after previous surgery and adjuvant chemoradiation (crt) in high-risk esophageal cancer patients. PATIENTS AND METHODS: From 1989 to 1999, we followed high-risk resected esophageal cancer patients who had completed postoperative crt therapy. Patients who relapsed with a disease-free interval of less than 3 months were treated with palliative crt when appropriate. Patients with a disease-free interval of 3 months or more were treated with best supportive care. Post-recurrence survival was estimated using the Kaplan-Meier technique, and statistical comparisons were made using log-rank chi-square tests and Cox regression. RESULTS: Of the 69 patients treated with adjuvant crt after esophagectomy, 46 experienced recurrence. Median time to relapse was 28 months (range: 0.1-40 months). Among the 46 relapsed patients, median age was 61 years (range: 37-82 years), and 42 were men. At the initial staging, 44 of 46 were node-positive; 31 of 46 had adenocarcinoma. In 33 of 46, post-esophagectomy resection margins were clear. Median follow-up after recurrence was 30.5 months (range: 1.3-100 months). Median overall survival after recurrence was 5.8 months, and the 12-month, 24-month, and 36-month survival rates were 20%, 10%, and 5% respectively. Of the prognostic factors analyzed, only resection margin status and interval to recurrence were statistically significant for patient outcome in univariate and multivariate analysis. Patients who had positive resection margins and who relapsed 12 or fewer months after surgery and adjuvant crt had a median post-recurrence overall survival of 0.85 months as compared with 6.0 months in other patients (more than 12 months to relapse, or negative resection margins, or both; log-rank p = 0.003). CONCLUSIONS: Resection margin status and interval to disease relapse are significant independent prognostic factors for patient outcome after adjuvant crt therapy

Post-Operative Extended Volume External Beam Radiation Therapy in High Risk Esophageal Cancer Patients: A Prospective Experience

Background and purpose: Extended volume external beam radiation therapy (RT) following esophagectomy is controversial. This prospective study evaluates the feasibility of extended volume RT treatment in high-risk esophagectomy patients with cervical anastomosis receiving post–operative combined chemo-radiation therapy. Patients and methods: From 2001-2006, 15 patients with resected esophageal cancer were prospectively accrued to this pilot study, to evaluate the adverse effects of extended volume RT. Eligibility criteria were pathologically proven esophageal malignancy, T3-4, N0-1, disease amenable to surgical resection and esophagectomy with or without resection margin involvement. Patients with distant metastases (M1) and patients treated with previous RT were excluded. All 15 patients received four cycles of 5-fluorouracil-based chemotherapy. External beam RT utilized conformal computerized tomography (CT) planning, with multi-field arrangement tailored to the pathological findings with clinical target volume encompassing the primary tumour bed and anastomotic site in the neck. The radiation therapy dose was 50.40Gy at 1.8Gy per fraction, delivered concurrently with the third cycle of chemotherapy. Outcomes were disease-free survival (DFS) and overall survival (OS), calculated by Kaplan–Meier method. Treatment-related toxicities were assessed using NCI-CTC Grading System. Results: There were 10 male and 5 female patients. The median age was 64 years (ranging 48 to 80 years). The TNM stages included one T3N0, two T2N1, eleven T3N1 and one T4N1. The histopathology included 5 adenocarcinomas and 10 squamous cell carcinomas. Resection margins were clear in 10 patients. The median follow up time was 19 months (range: 3.5-53.4 months). Delay in chemotherapy occurred in 20% of patients and dose reduction was required in 13.3% of patients prior to radiation therapy. During the concurrent chemo-radiation therapy phase, 20% and 6.6% had chemotherapy delay and dose reduction, respectively. No patient experienced treatment related acute and chronic esophagitis of \u3e Grade 2. Disease recurrence occurred in 40% (6/15) and the median time to relapse was 24 months. There was no tumour recurrence at the anastomotic site. The median DFS and OS rate were 23 months and 21 months, respectively. Conclusion: Extended volume external beam radiation therapy encompassing the tumour bed and the anastomotic site is feasible and safe after esophagectomy. These findings support proceeding with a larger trial to assess its efficacy in patients with high-risk esophageal cancer