Mass balance and 3D model of PAHs in Boston's inner harbor

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1998.Includes bibliographical references (leaves 192-199).by Ricardo N. Petroni, Peter H. Israelsson.M.Eng

Studies of Lagrangian modeling techniques with applications to deep ocean carbon sequestration

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references.This thesis consists of four separate studies which explore the use of random walk particle tracking (RWPT) in simulating environmental mass transport. Two of the studies also consider the efficacy and marine impact of ocean CO2 sequestration by direct injection. The first study compares RWPT to two other simple Lagrangian techniques (forward and backward Gaussian puff tracking) to simulate mixing beyond the near field of a pollutant discharge. RWPT is found to be more accurate, but also more computationally expensive, thus motivating hybrid approaches where Lagrangian calculations transition to Eulerian schemes in the far field. The second study considers 1D RWPT when strong gradients in ambient diffusivity exist. For step profiles, the work of past investigators is unified and extended, and the Thomson et al. (1997) particle reflection approach is recommended. For piecewise linear profiles, a novel and efficient particle reflection with probability translation approach is proposed. The third study implements RWPT to emulate the tracer transport of an ocean general circulation model (OGCM) using the OGCM's flow and diffusivity fields. A high level of agreement between RWPT and OGCM results is achieved. Particle reflection with probability translation successfully handled sharply varying vertical diffusivities. However, precisely mimicking OGCM calculations proved difficult due to complications in specifying the subgrid scale variation of isopycnal slope and diffusivity in steeply sloped or convectively unstable regions, and in accurately implementing the Gent-McWilliams eddy-induced transport.(cont.) Further development is recommended to resolve spurious upwelling occurring mainly in the Southern Ocean. The utility of RWPT is demonstrated by calculating domain-wide CO2 sequestration efficiencies using a novel book-keeping method. Additional RWPT benefits to oceanographic investigation are also proposed. The fourth study updates the Auerbach et al. (1997) and Caulfield et al. (1997) joint assessment of acute environmental impact to zooplankton resulting from ocean CO2 discharges. Acute toxicity data are used to estimate the cumulative harm accrued by passive organisms drifting through idealized CO2 plumes generated by three promising discharge methods. Results suggest that discharges can be engineered to largely avoid acute impacts, and that ocean carbon sequestration should not be dismissed on the basis of environmental impact alone.by Peter Hampus Israelsson.Ph.D

International Collaboration on CO2 Sequestration

On December 4, 1997, the US Department of Energy (USDOE), the New Energy and Industrial Technology Development Organization of Japan (NEDO), and the Norwegian Research Council (NRC) entered into a Project Agreement for International Collaboration on CO{sub 2} Ocean Sequestration. Government organizations from Japan, Canada, and Australia, and a Swiss/Swedish engineering firm later joined the agreement, which outlined a research strategy for ocean carbon sequestration via direct injection. The members agreed to an initial field experiment, with the hope that if the initial experiment was successful, there would be subsequent field evaluations of increasingly larger scale to evaluate environmental impacts of sequestration and the potential for commercialization. The evolution of the collaborative effort, the supporting research, and results for the International Collaboration on CO{sub 2} Ocean Sequestration were documented in almost 100 papers and reports, including 18 peer-reviewed journal articles, 46 papers, 28 reports, and 4 graduate theses. These efforts were summarized in our project report issued January 2005 and covering the period August 23, 1998-October 23, 2004. An accompanying CD contained electronic copies of all the papers and reports. This report focuses on results of a two-year sub-task to update an environmental assessment of acute marine impacts resulting from direct ocean sequestration. The approach is based on the work of Auerbach et al. [6] and Caulfield et al. [20] to assess mortality to zooplankton, but uses updated information concerning bioassays, an updated modeling approach and three modified injection scenarios: a point release of negatively buoyant solid CO{sub 2} hydrate particles from a moving ship; a long, bottom-mounted diffuser discharging buoyant liquid CO{sub 2} droplets; and a stationary point release of hydrate particles forming a sinking plume. Results suggest that in particular the first two discharge modes could be successfully designed to largely avoid zooplankton mortality. Sub-lethal and ecosystem effects are discussed qualitatively, but not analyzed quantitatively

Evaluation of the environmental viability of direct injection schemes for ocean carbon sequestration

Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2008.Includes bibliographical references (p. 143-159).This thesis evaluates the expected impact of several promising schemes for ocean carbon sequestration by direct injection of CO2, and serves as an update to the assessment by Auerbach et al. (1997) and Caulfield et al. (1997) of water quality impacts and the induced mortality to zooplankton. The present work extends the methodology used in the earlier studies, incorporates recent acute CO2 toxicity data on marine organisms, and considers three revised discharge approaches: a point release of negatively buoyant CO2 hydrate particles from a moving ship; a long, bottom-mounted diffuser discharging buoyant liquid CO2 droplets; and a stationary point release of hydrate particles forming a sinking plume. Results suggest that it is possible with present technology to engineer discharge configurations which achieve sufficient dilution to largely avoid acute impacts. Sub-lethal and ecosystem effects are discussed qualitatively, but not analyzed quantitatively. The analysis suggests that, as a temporary climate change mitigation strategy, ocean carbon sequestration by direct injection should not be dismissed on the basis of environmental impact alone. With minor modification, this thesis will also serve as the final chapter of the author's Ph.D. thesis to be submitted in 2008 to the MIT Department of Civil and Environmental Engineering.by Peter Hampus Israelsson.S.M

Adequate vitamin B12 and folate status of Norwegian vegans and vegetarians

Plant-based diets may increase the risk of vitamin B12 deficiency due to limited intake of animal-source foods, while dietary folate increases when adhering to plant-based diets. In this cross-sectional study, we evaluated the B12 and folate status of Norwegian vegans and vegetarians using dietary B12 intake, B12- and folic acid supplement use, and biomarkers (serum B12 [B12], plasma total-homocysteine [tHcy], plasma-methylmalonic acid [MMA], and serum-folate). Vegans (n=115) and vegetarians (n=90) completed a 24-hour dietary recall and a food-frequency questionnaire and provided a non-fasting blood sample. cB12, a combined indicator for evaluation of B12 status, was calculated. B12 status were adequate in both vegans and vegetarians according to the cB12 indicator, however 4% had elevated B12. Serum B12, tHcy, MMA concentrations and the cB12 indicator (overall median: 357pmol/L, 9.0µmol/L, 0.18µmol/L, 1.30 (cB12)) did not differ between vegans and vegetarians, unlike for folate (vegans: 25.8nmol/L, vegetarians: 21.6nmol/L, p=0.027). Serum B12 concentration <221pmol/L, was found in 14% of all participants. Vegetarians revealed the highest proportion of participants below the RDI of 2 µg/day including supplements (40 vs. 18%, p<0.001). Predictors of higher serum B12 concentrations were average daily supplement use and older age. Folate deficiency (<10 nmol/L) was uncommon overall (<2.5%). The combined indicator cB12 suggested that none of the participants was B12 depleted, however low serum B12 concentration was found in 14% of the participants. Folate concentrations were adequate, indicating adequate folate intake in Norwegian vegans and vegetarians.publishedVersionPaid open acces

Effect of suture technique on the occurrence of incisional hernia after elective midline abdominal wall closure: study protocol for a randomized controlled trial

Background: Based on a recent meta-analysis, a continuous suture technique with a suture to wound length ratio of at least 4: 1, using a slowly absorbable monofilament suture material, is recommended for primary median laparotomy closure. Incisional hernia, which develops in 9 to 20% of patients, remains the major complication of abdominal wall closure. Current clinical data indicate that the incidence of incisional hernias increases by 60% between the first and the third year after median laparotomy, implicating that a follow-up period of 1 year postoperatively is too short with regard to this common complication. Trauma to the abdominal wall can be reduced by improvements in suture technique as well as suture material. Several factors, such as stitch length, suture tension, elasticity, and tensile strength of the suture material are discussed and currently under investigation. A Swedish randomized controlled trial showed a significant reduction in the incisional hernia rate by shortening the stitch length. However, a non-elastic thread was used and follow-up ended after 12 months. Therefore, we designed a multicenter, international, double-blinded, randomized trial to analyze the influence of stitch length, using an elastic, extra-long term absorbable monofilament suture, on the long term clinical outcome of abdominal wall closure. Methods: In total, 468 patients undergoing an elective, median laparotomy will be randomly allocated to either the short stitch or the long stitch suture technique for abdominal wall closure in a 1: 1 ratio. Centers located in Germany and Austria will participate. The primary endpoint measure is the incisional hernia rate 1 year postoperatively, as verified by ultrasound. The frequency of short term and long term complications as well as costs, length of hospital stay and patients' quality of life (EQ-5D-5 L) will be considered as secondary parameters. Following hospital discharge, patients will be examined after 30 days and 1, 3, and 5 years after surgery. Discussion: This study will provide further evidence on whether a short stitch suture technique in combination with an elastic, extra-long term absorbable monofilament suture can prevent incisional hernias in the long term, compared with the long stitch suture technique

Space-based research in fundamental physics and quantum technologies

Space-based experiments today can uniquely address important questions related to the fundamental laws of Nature. In particular, high-accuracy physics experiments in space can test relativistic gravity and probe the physics beyond the Standard Model; they can perform direct detection of gravitational waves and are naturally suited for precision investigations in cosmology and astroparticle physics. In addition, atomic physics has recently shown substantial progress in the development of optical clocks and atom interferometers. If placed in space, these instruments could turn into powerful high-resolution quantum sensors greatly benefiting fundamental physics. We discuss the current status of space-based research in fundamental physics, its discovery potential, and its importance for modern science. We offer a set of recommendations to be considered by the upcoming National Academy of Sciences' Decadal Survey in Astronomy and Astrophysics. In our opinion, the Decadal Survey should include space-based research in fundamental physics as one of its focus areas. We recommend establishing an Astronomy and Astrophysics Advisory Committee's interagency ``Fundamental Physics Task Force'' to assess the status of both ground- and space-based efforts in the field, to identify the most important objectives, and to suggest the best ways to organize the work of several federal agencies involved. We also recommend establishing a new NASA-led interagency program in fundamental physics that will consolidate new technologies, prepare key instruments for future space missions, and build a strong scientific and engineering community. Our goal is to expand NASA's science objectives in space by including ``laboratory research in fundamental physics'' as an element in agency's ongoing space research efforts.Comment: a white paper, revtex, 27 pages, updated bibliograph

A multicenter randomized controlled trial evaluating the effect of small stitches on the incidence of incisional hernia in midline incisions

Contains fulltext : 95575.pdf (publisher's version ) (Open Access)BACKGROUND: The median laparotomy is frequently used by abdominal surgeons to gain rapid and wide access to the abdominal cavity with minimal damage to nerves, vascular structures and muscles of the abdominal wall. However, incisional hernia remains the most common complication after median laparotomy, with reported incidences varying between 2-20%. Recent clinical and experimental data showed a continuous suture technique with many small tissue bites in the aponeurosis only, is possibly more effective in the prevention of incisional hernia when compared to the common used large bite technique or mass closure. METHODS/DESIGN: The STITCH trial is a double-blinded multicenter randomized controlled trial designed to compare a standardized large bite technique with a standardized small bites technique. The main objective is to compare both suture techniques for incidence of incisional hernia after one year. Secondary outcomes will include postoperative complications, direct costs, indirect costs and quality of life. A total of 576 patients will be randomized between a standardized small bites or large bites technique. At least 10 departments of general surgery and two departments of oncological gynaecology will participate in this trial. Both techniques have a standardized amount of stitches per cm wound length and suture length wound length ratio's are calculated in each patient. Follow up will be at 1 month for wound infection and 1 year for incisional hernia. Ultrasound examinations will be performed at both time points to measure the distance between the rectus muscles (at 3 points) and to objectify presence or absence of incisional hernia. Patients, investigators and radiologists will be blinded during follow up, although the surgeon can not be blinded during the surgical procedure. CONCLUSION: The STITCH trial will provide level 1b evidence to support the preference for either a continuous suture technique with many small tissue bites in the aponeurosis only or for the commonly used large bites technique

Low recurrence rate of a two-layered closure repair for primary and recurrent midline incisional hernia without mesh

Background: Incisional hernia is a serious complication after abdominal surgery and occurs in 11-23% of laparotomies. Repair can be done, for instance, with a direct suture technique, but recurrence rates are high. Recent literature advises the use of mesh repair. In contrast to this development, we studied the use of a direct suture repair in a separate layer technique. The objective of this retrospective observational study is to assess the outcomes (recurrences and complications) of a two-layered open closure repair for primary and recurrent midline incisional hernia without the use of mesh. Methods: In an observational retrospective cohort study, we analysed the hospital and outpatient records of 77 consecutive patients who underwent surgery for a primary or recurrent incisional hernia between 1st May 2002 and 8th November 2006. The repair consisted of separate continuous suturing of the anterior and posterior fascia, including the rectus muscle, after extensive intra-abdominal adhesiolysis. Results: Forty-one men (53.2%) and 36 women (46.8%) underwent surgery. Sixty-three operations (81.8%) were primary repairs and 14 (18.2%) were repairs for a recurrent incisional hernia. Of the 66 patients, on physical examination, three had a recurrence (4.5%) after an average follow-up of 2.6 years. The 30-day postoperative mortality was 1.1%. Wound infection was seen in five patients (6.5%). Conclusions: A two-layered suture repair for primary and recurrent incisional hernia repair without mesh with extensive adhesiolysis was associated with a recurrence rate comparable to mesh repair and had an acceptable complication rate

Tension of knotted surgical sutures shows tissue specific rapid loss in a rodent model

<p>Abstract</p> <p>Background</p> <p>Every surgical suture compresses the enclosed tissue with a tension that depends from the knotting force and the resistance of the tissue. The aim of this study was to identify the dynamic change of applied suture tension with regard to the tissue specific cutting reaction.</p> <p>Methods</p> <p>In rabbits we placed single polypropylene sutures (3/0) in skin, muscle, liver, stomach and small intestine. Six measurements for each single organ were determined by tension sensors for 60 minutes. We collected tissue specimens to analyse the connective tissue stability by measuring the collagen/protein content.</p> <p>Results</p> <p>We identified three phases in the process of suture loosening. The initial rapid loss of the first phase lasts only one minute. It can be regarded as cutting through damage of the tissue. The percentage of lost tension is closely related to the collagen content of the tissue (r = -0.424; p = 0.016). The second phase is characterized by a slower decrease of suture tension, reflecting a tissue specific plastic deformation. Phase 3 is characterized by a plateau representing the remaining structural stability of the tissue. The ratio of remaining tension to initial tension of phase 1 is closely related to the collagen content of the tissue (r = 0.392; p = 0.026).</p> <p>Conclusions</p> <p>Knotted non-elastic monofilament sutures rapidly loose tension. The initial phase of high tension may be narrowed by reduction of the surgeons' initial force of the sutures' elasticity to those of the tissue. Further studies have to confirm, whether reduced tissue compression and less local damage permits improved wound healing.</p