Dynamics of particle clouds in ambient currents with application to open-water sediment disposal

CIVINS (Civilian Institutions) Thesis documentOpen-water sediment disposal is used in many applications around the world, including land reclamation, dredging, and contaminated sediment isolation. Timely examples include the land reclamation campaign currently underway in Singapore and the Boston Harbor Navigation Improvement Project. Both of these projects required the precise dumping of millions of cubic meters of purchased sediment, in the former example, and dredged material (both clean and contaminated), in the latter example. This shows the significant economic and environmental interests in the accurate placement of sediment, which requires knowledge of how particle clouds behave in ambient currents. Flow visualization experiments were performed in a glass-walled recirculating water channel to model open-water sediment disposal by releasing particles quasi-instantaneously into the channel with ambient currents. For releases at the surface, criteria were developed to characterize ambient currents as weak, transitional, or strong as a function of particle size. In weak ambient currents, particle clouds advected downstream with a velocity equal to the ambient current, but otherwise the behavior and structure was similar to that in quiescent conditions. The parent cloud's entrainment coefficient (alpha) increased with decreasing particle size and elevation above the water surface, between values of 0.10 and 0.72, but for most experiments, the range was less significant (0.11 to 0.24). A substantial portion of the mass initially released, up to 30%, was not incorporated into the parent cloud and formed the trailing stem. This was also heavily dependent on the initial release variables, with the greatest sensitivity on particle size. The loss of sediment during descent, defined as the fraction of mass missing a designated target with a radius equal to the water depth, was quantified and found to increase sharply with current speed.http://archive.org/details/dynamicsofpartic109454945CIVINSApproved for public release; distribution is unlimited

Dynamics of particle clouds in ambient currents with application to open-water sediment disposal

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 255-259).Open-water sediment disposal is used in many applications around the world, including land reclamation, dredging, and contaminated sediment isolation. Timely examples include the land reclamation campaign currently underway in Singapore and the Boston Harbor Navigation Improvement Project. Both of these projects required the precise dumping of millions of cubic meters of purchased sediment, in the former example, and dredged material (both clean and contaminated), in the latter example. This shows the significant economic and environmental interests in the accurate placement of sediment, which requires knowledge of how particle clouds behave in ambient currents. Flow visualization experiments were performed in a glass-walled recirculating water channel to model open-water sediment disposal by releasing particles quasi-instantaneously into the channel with ambient currents. For releases at the surface, criteria were developed to characterize ambient currents as "weak," "transitional," or "strong" as a function of particle size. In "weak" ambient currents, particle clouds advected downstream with a velocity equal to the ambient current, but otherwise the behavior and structure was similar to that in quiescent conditions. The parent cloud's entrainment coefficient (??) increased with decreasing particle size and elevation above the water surface, between values of 0.10 and 0.72, but for most experiments, the range was less significant (0.11 to 0.24). A substantial portion of the mass initially released, up to 30 %, was not incorporated into the parent cloud and formed the trailing stem. This was also heavily dependent on the initial release variables, with the greatest sensitivity on particle size. The "loss" of sediment during descent, defined as the fraction of mass missing a designated target with a radius equal to the water depth, was quantified and found to increase sharply with current speed. The cloud number (Nc), which relates the particle settling velocity to a characteristic thermal descent velocity, provides a basis for scaling laboratory results to the real world and formulating guidelines to reduce the losses that could result from open-water sediment disposal.by Robert James Gensheimer, III.S.M

The Use of Preoperative Prophylactic Systemic Antibiotics for the Prevention of Endopthalmitis in Open Globe Injuries:A Meta-Analysis

Topic:This study reports the effect of systemic prophylactic antibiotics (and their route) on the risk of endophthalmitis after open globe injury. Clinical relevance:Endophthalmitis is a major complication of open globe injury, it can lead to rapid sight loss in the affected eye. The administration of systemic antibiotic prophylaxis is common practice in some health care systems, although there is no consensus on their use. PubMed, CENTRAL, Web of Science, CINAHL and Embase were searched. This was completed 6th July 2021 and updated 10th Dec 2022. We included randomised and non-randomised prospective studies which reported the rate of post-open globe injury endophthalmitis, when systemic pre-operative antibiotic prophylaxis (via the oral or intravenous route) was given. The Cochrane Risk of Bias tool and ROBINS-I tool were used for assessing the risk of bias. Where meta-analysis was performed results were reported as odds ratio. PROSPERO registration: CRD42021271271. Three studies were included. One prospective observational study compared outcomes of patients who had received systemic or no systemic pre-operative antibiotics. The endophthalmitis rates reported were 3.75% and 4.91% in the systemic and no systemic pre-operative antibiotics groups, a non-significant difference (p = 0.68). Two randomised controlled trials were included (1,555 patients). The rates of endophthalmitis were 17 events in 751 patients (2.26%) and 17 events in 804 patients (2.11%) in the oral antibiotics and intravenous (+/- oral) antibiotics groups, respectively. Meta-analysis demonstrated no significant differences between groups (OR 1.07 [95% confidence interval 0.54 – 2.12]). The incidences of endophthalmitis after open globe injury were low with and without systemic antibiotic prophylaxis, although high risk cases were excluded in the included studies. When antibiotic prophylaxis is considered, there is moderate evidence that oral antibiotic administration is non-inferior to intravenous

The Risk of Sympathetic Ophthalmia Associated with Open-Globe Injury Management Strategies:A Meta-analysis

Topic: Sympathetic ophthalmia (SO) is a sight-threatening granulomatous panuveitis caused by a sensitizing event. Primary enucleation or primary evisceration, versus primary repair, as a risk management strategy after open-globe injury (OGI) remains controversial.Clinical Relevance: This systematic review was conducted to report the incidence of SO after primary repair compared with that of after primary enucleation or primary evisceration. This enabled the reporting of an estimated number needed to treat.Methods: Five journal databases were searched. This review was registered with International Prospective Register of Systematic Reviews (identifier, CRD42021262616). Searches were carried out on June 29, 2021, and were updated on December 10, 2022. Prospective or retrospective studies that reported outcomes (including SO or lack of SO) in a patient population who underwent either primary repair and primary enucleation or primary evisceration were included. A systematic review and meta-analysis were carried out in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Random effects modelling was used to estimate pooled SO rates and absolute risk reduction (ARR).Results: Eight studies reporting SO as an outcome were included in total. The included studies contained 7500 patients and 7635 OGIs. In total, 7620 OGIs met the criteria for inclusion in this analysis; SO developed in 21 patients with OGI. When all included studies were pooled, the estimated SO rate was 0.12% (95% confidence interval [CI], 0.00%–0.25%) after OGI. Of 779 patients who underwent primary enucleation or primary evisceration, no SO cases were reported, resulting in a pooled SO estimate of 0.05% (95% CI, 0.00%–0.21%). For primary repair, the pooled estimate of SO rate was 0.15% (95% CI, 0.00%–0.33%). The ARR using a random effects model was −0.0010 (in favour of eye removal; 95% CI, −0.0031 [in favor of eye removal] to 0.0011 [in favor of primary repair]). Grading of Recommendations, Assessment, Development, and Evaluations analysis highlighted a low certainty of evidence because the included studies were observational, and a risk of bias resulted from missing data.Discussion: Based on the available data, no evidence exists that primary enucleation or primary evisceration reduce the risk of secondary SO.Financial Disclosure(s): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article

Safety of Nivolumab Added to Chemoradiation Therapy Platforms for Intermediate and High-Risk Locoregionally Advanced Head and Neck Squamous Cell Carcinoma: Radiation Therapy Oncology Group Foundation 3504.

PURPOSE: Programmed death-1 immune checkpoint blockade improves survival of patients with recurrent/metastatic head and neck squamous cell carcinoma (HNSCC), but the benefits of addition to (chemo)radiation for newly diagnosed patients with HNSCC remain unknown. METHODS AND MATERIALS: We evaluated the safety of nivolumab concomitant with 70 Gy intensity modulated radiation therapy and weekly cisplatin (arm 1), every 3-week cisplatin (arm 2), cetuximab (arm 3), or alone for platinum-ineligible patients (arm 4) in newly diagnosed intermediate- or high-risk locoregionally advanced HNSCC. Patients received nivolumab from 2 weeks prior to radiation therapy until 3 months post-radiation therapy. The primary endpoint was dose-limiting toxicity (DLT). If ≤2 of the first 8 evaluable patients experienced a DLT, an arm was considered safe. Secondary endpoints included toxicity and feasibility of adjuvant nivolumab to 1 year, defined as all 7 additional doses received by ≥4 of the first 8 evaluable patients across arms. RESULTS: Of 39 patients (10 in arms 1, 3, 4 and 9 in arm 2), 72% had T3-4 tumors, 85% had N2-3 nodal disease, and 67% had \u3e10 pack-years of smoking. There were no DLTs in arms 1 and 2, 1 in arm 3 (mucositis), and 2 in arm 4 (lipase elevation and mucositis in 1 and fatigue in another). The most common grade ≥3 nivolumab-related adverse events were lipase increase, mucositis, diarrhea, lymphopenia, hyponatremia, leukopenia, fatigue, and serum amylase increase. Adjuvant nivolumab was feasible as defined in the protocol. CONCLUSIONS: Concomitant nivolumab with the 4 tested regimens was safe for patients with intermediate- and high-risk HNSCC, and subsequent adjuvant nivolumab was feasible as defined (NCT02764593)

Safety of Nivolumab Added to Chemoradiation Therapy Platforms for Intermediate and High-Risk Locoregionally Advanced Head and Neck Squamous Cell Carcinoma: RTOG Foundation 3504

PurposeProgrammed death-1 immune checkpoint blockade improves survival of patients with recurrent/metastatic head and neck squamous cell carcinoma (HNSCC), but the benefits of addition to (chemo)radiation for newly diagnosed patients with HNSCC remain unknown.Methods and materialsWe evaluated the safety of nivolumab concomitant with 70 Gy intensity modulated radiation therapy and weekly cisplatin (arm 1), every 3-week cisplatin (arm 2), cetuximab (arm 3), or alone for platinum-ineligible patients (arm 4) in newly diagnosed intermediate- or high-risk locoregionally advanced HNSCC. Patients received nivolumab from 2 weeks prior to radiation therapy until 3 months post-radiation therapy. The primary endpoint was dose-limiting toxicity (DLT). If ≤2 of the first 8 evaluable patients experienced a DLT, an arm was considered safe. Secondary endpoints included toxicity and feasibility of adjuvant nivolumab to 1 year, defined as all 7 additional doses received by ≥4 of the first 8 evaluable patients across arms.ResultsOf 39 patients (10 in arms 1, 3, 4 and 9 in arm 2), 72% had T3-4 tumors, 85% had N2-3 nodal disease, and 67% had >10 pack-years of smoking. There were no DLTs in arms 1 and 2, 1 in arm 3 (mucositis), and 2 in arm 4 (lipase elevation and mucositis in 1 and fatigue in another). The most common grade ≥3 nivolumab-related adverse events were lipase increase, mucositis, diarrhea, lymphopenia, hyponatremia, leukopenia, fatigue, and serum amylase increase. Adjuvant nivolumab was feasible as defined in the protocol.ConclusionsConcomitant nivolumab with the 4 tested regimens was safe for patients with intermediate- and high-risk HNSCC, and subsequent adjuvant nivolumab was feasible as defined (NCT02764593)