Theoretical modelling of the m.i.s.s structure in one and two dimensions

In this thesis, a 1-D computer model of MISS operation is described. This is then used to characterise the qualitative behaviour of the MISS for changes in its structural parameters. The modelled device is assumed to have a four layer MInp structure, commonly used by both theorists and experimentalists. Derived from this 1-D model is a quantitative description of switching in the three layer MIS diode, using a heavily doped (lO(^17)cm(^-3)) n-type substrate. Results are then presented describing its behaviour for changes in fabrication parameters. The computer model of MISS functioning is extended into quasi 2-D by incorporating current spreading in the pn region of the device. Using this, the effect of changes in metal top contact area on device behaviour are explained, with the model providing an accurate quantitative description of these effects for thick oxide (30A) devices. The stability of the MISS as a circuit element is examined in its negative impedance region. A simple equivalent circuit model is produced, and calculated values for negative differential capacitance and negative differential resistances from the quasi 2-D MISS and MIS diode models are used to characterise device behaviour in this region. Within the work a number of accepted terms and ideas are challenged, with their uses being either redefined or discarded. This has been found to be necessary because of the scope of the work presented, which covers such a large range of device parameters

Circulation, hydrography, and transport over the summit of Axial Seamount, a deep volcano in the Northeast Pacific

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 5404–5422, doi:10.1002/2016JC012464.A numerical model of ocean flow, hydrography, and transport is used to extrapolate observations of currents and hydrography and infer patterns of material flux in the deep ocean around Axial Seamount, a destination node of NSF's Ocean Observatories Initiative's Cabled Array. Using an inverse method, the model is made to approximate measured deep ocean flow around this site during a 35 day time period in the year 2002. The model is then used to extract month-long mean patterns and examine smaller-scale spatial and temporal variability around Axial. Like prior observations, model month-long mean currents flow anticyclonically around the seamount's summit in toroidal form with maximum speeds at 1500 m depth of 10–11 cm/s. As a time mean, the temperature (salinity) anomaly distribution takes the form of a cold (briny) dome above the summit. Passive tracer material continually released at the location of the ASHES vent field exits the caldera primarily through its southern open end before filling the caldera. Once outside the caldera, the tracer circles the summit in clockwise fashion, fractionally reentering the caldera over lower walls at its north end, while gradually bleeding southwestward during the modeled time period into the ambient ocean. A second tracer release experiment using a source of only 2 day duration inside and near the CASM vent field at the northern end of the caldera suggests a residence time of the fluid at that locale of 8–9 days.WHOI as a postdoctoral scholar2018-01-0

Defining the word “seamount”

Author Posting. © Oceanography Society, 2010. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 23, 1 (2010): 20-21.The term seamount has been defined many times (e.g., Menard, 1964; Wessel, 2001; Schmidt and Schmincke, 2000; Pitcher et al., 2007; International Hydrographic Organization, 2008; Wessel et al., 2010) but there is no “generally accepted” definition. Instead, most definitions serve the particular needs of a discipline or a specific paper

DuraSeal Exact is a safe adjunctive treatment for durotomy in spine: Postapproval study

Study designA nonrandomized, two-armed prospective study.ObjectiveWater-tight dural closure is paramount to the prevention of cerebrospinal fluid (CSF) leakage and associated complications. Synthetic polyethylene glycol (PEG) hydrogel has been used as an adjunct to sutured dural repair; however, its expansion postoperatively is a concern for neurological complications. A low-swell formulation of PEG sealant was introduced as DuraSeal Exact Spine Sealant System (DESS). A Post-Approval Study was performed primarily to evaluate the safety and efficacy of DESS for spinal dural repair compared to current alternatives, in a large patient population, reflecting a real-world practice.MethodsA total of 36 sites in the United States enrolled 429 patients treated with DESS as an adjunct to dural repair in the spinal sealant group and 406 patients treated with all other modalities in the control arm, from October 2011 to June 2016. The primary endpoint was the incidence of CSF leak within 90 days of operation. The secondary endpoints evaluated were deep surgical site infection and neurological serious adverse events.ResultsThe CSF leakage in the DESS group (6.6%) was not significantly different from the control group (6.5%) (p = .83), and there was no significant difference in the time to first leak. The two groups had no significant differences in deep surgical site infection (1.6% versus control 2.1%, p = .61) or proportion of subjects with neurological serious adverse events (2.9% versus control 1.6%, p = .516).ConclusionsDuraSeal Exact Spinal Sealant is safe when compared to current alternatives for spinal dural repair

Seamount sciences : quo vadis?

Author Posting. © Oceanography Society, 2010. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 23, 1 (2010): 212-213.Seamounts are fascinating natural ocean laboratories that inform us about fundamental planetary and ocean processes, ocean ecology and fisheries, and hazards and metal resources. The more than 100,000 large seamounts are a defining structure of global ocean topography and biogeography, and hundreds of thousands of smaller ones are distributed throughout every ocean on Earth

The prediction, verification, and significance of flank jets at mid-ocean ridges

Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 1 (2012): 277–283, doi:10.5670/oceanog.2012.26.One aspect of ocean flow over mid-ocean ridges that has escaped much attention is the capacity of a ridge to convert oscillatory flows into unidirectional flows. Those unidirectional flows take the form of relatively narrow jets hugging the ridge's flanks. In the Northern Hemisphere, the jets move heat and dissolved and particulate matter poleward on the west and equatorward on the east of north-south trending ridges. Recent measurements and a model of flow at the East Pacific Rise at 9–10°N show that these ridge-parallel flows can extend 10–15 km horizontally away from the ridge axis, reach from the seafloor to several hundreds of meters above ridge crest depth, and have maximum speeds in their cores up to 10 cm s–1. Because of their along-ridge orientation and speed, the jets can significantly affect the transport of hydrothermal vent-associated larvae between vent oases along the ridge crest and, possibly, contribute to the mesoscale stirring of the abyssal ocean. Because jet-formation mechanisms involve oscillatory currents, ocean stratification, and topography, the jets are examples of "stratified topographic flow rectification." Ridge jets have parallels in rectified flows at seamounts and submarine banks.JWL is supported by the National Oceanic and Atmospheric Administration (NOAA) Pacific Marine Environmental Laboratory and by NOAA Vents Program. The work of other authors has been supported by National Science Foundation through grants OCE-0424953 and OCE-0425361, LADDER (LArval Dispersion along the Deep East pacific Rise)

Active positioning of vent larvae at a mid-ocean ridge

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 92 (2013): 46-57, doi:10.1016/j.dsr2.2013.03.032.The vertical position of larvae of vent species above a mid-ocean ridge potentially has a strong effect on their dispersal. Larvae may be advected upward in the buoyant vent plume, or move as a consequence of their buoyancy or active swimming. Alternatively, they may be retained near bottom by the topography of the axial trough, or by downward swimming. At vents near 9°50’N on the axis of the East Pacific Rise, evidence for active larval positioning was detected in a comparison between field observations of larvae in the plankton in 2006 and 2007 and distributions of non-swimming larvae in a two-dimensional bio-physical model. In the field, few vent larvae were collected at the level of the neutrally buoyant plume (~75 m above bottom); their relative abundances at that height were much lower than those of simulated larvae from a near-bottom release in the model. This discrepancy was observed for many vent species, particularly gastropods, suggesting that they may actively remain near bottom by sinking or swimming downward. Near the seafloor, larval abundance decreased from the ridge axis to 1000 m off axis much more strongly in the observations than in the simulations, again pointing to behavior as a potential regulator of larval transport. We suspect that transport off axis was reduced by downward-moving behavior, which positioned larvae into locations where they were isolated from cross-ridge currents by seafloor topography, such as the walls of the axial valley – which are not resolved in the model. Cross-ridge gradients in larval abundance varied between gastropods and polychaetes, indicating that behavior may vary between taxonomic groups, and possibly between species. These results suggest that behaviorally mediated retention of vent larvae may be common, even for species that have a long planktonic larval duration and are capable of long-distance dispersal.We gratefully acknowledge the support of NSF grants OCE-0424953 and OCE-0525361, which funded the Larval Dispersal on the Deep East Pacific Rise (LADDER) project. WHOI provided additional support to LSM as an Ocean Life Fellow, to DJM as the Holger Jannasch Chair for Excellence in Oceanography, and to JRL as the Edward W. and Betty J. Scripps Senior Scientist Chair. JWL was supported by the National Oceanic and Atmospheric Administration’s (NOAA) Vents Program and by NOAA’s Pacific Marine Environmental Laboratory

Dendritic Cell-Mediated, DNA-Based Vaccination Against Hepatitis C Induces the Multi-Epitope-Specific Response of Humanized, HLA Transgenic Mice

Hepatitis C virus (HCV) is the etiologic agent of chronic liver disease, hepatitis C. Spontaneous resolution of viral infection is associated with vigorous HLA class I- and class II-restricted T cell responses to multiple viral epitopes. Unfortunately, only 20% of patients clear infection spontaneously, most develop chronic disease and require therapy. The response to chemotherapy varies, however; therapeutic vaccination offers an additional treatment strategy. To date, therapeutic vaccines have demonstrated only limited success. Vector-mediated vaccination with multi-epitope-expressing DNA constructs alone or in combination with chemotherapy offers an additional treatment approach. Gene sequences encoding validated HLA-A2- and HLA-DRB1-restricted epitopes were synthesized and cloned into an expression vector. Dendritic cells (DCs) derived from humanized, HLA-A2/DRB1 transgenic (donor) mice were transfected with these multi-epitope-expressing DNA constructs. Recipient HLA-A2/DRB1 mice were vaccinated s.c. with transfected DCs; control mice received non-transfected DCs. Peptide-specific IFN-γ production by splenic T cells obtained at 5 weeks post-immunization was quantified by ELISpot assay; additionally, the production of IL-4, IL-10 and TNF-α were quantified by cytokine bead array. Splenocytes derived from vaccinated HLA-A2/DRB1 transgenic mice exhibited peptide-specific cytokine production to the vast majority of the vaccine-encoded HLA class I- and class II-restricted T cell epitopes. A multi-epitope-based HCV vaccine that targets DCs offers an effective approach to inducing a broad immune response and viral clearance in chronic, HCV-infected patients

The effectiveness of pre-contoured titanium alloy rods in inducing thoracic kyphosis after sequential spinal releases in an in vitro biomechanical model

PurposeEvaluate the ability of pre-contoured rods to induce thoracic kyphosis (TK) in human cadaveric spines and determine the effectiveness of sequential surgical adolescent idiopathic scoliosis (AIS) release procedures.MethodsSix thoracolumbar (T3-L2) spine specimens were instrumented with pedicle screws bilaterally (T4–T12). Over correction using pre-contoured rods was performed for intact condition and Cobb angle was measured. Rod radius of curvature (RoC) was measured pre- and post-reduction. The process was repeated following sequential release procedures of (1) interspinous and supraspinous ligaments (ISL); (2) ligamentum flavum; (3) Ponte osteotomy; (4) posterior longitudinal ligament (PLL); and (5) transforaminal discectomy. Cobb measurements determined the effective contribution of release on TK and RoC data displayed effects of reduction to the rods.ResultsThe intact TK (T4–12) was 38.0° and increased to 51.7° with rod reduction and over correction. Each release resulted in 5°–7°of additional kyphosis; the largest releases were ISL and PLL. All releases resulted in significant increases in kyphosis compared to intact with rod reduction and over correction. Regionally, kyphosis increased ∼2° for each region following successive releases. Comparing RoC before and after reduction showed significant 6° loss in rod curvature independent of release type.ConclusionKyphosis increased in the thoracic spine using pre-contoured and over corrected rods. Subsequent posterior releases provided a substantial, meaningful clinical change in the ability to induce additional kyphosis. Regardless of the number of releases, the ability of the rods to induce and over correct kyphosis was reduced following reduction