267,774 research outputs found
Application and Use of Multivariate Control Charts In a BTA Deep Hole Drilling Process
No full textDeep hole drilling methods are used for producing holes with a high length-to-diameter ratio, good surface finish and straightness. The process is subject to dynamic disturbances usually classified as either chatter vibration or spiralling. In this paper, we will focus on the application and use of multivariate control charts to monitor the process in order to detect chatter vibrations. The results showed that chatter is detected and some alarm signals occurs at time points which can be connected to physical changes of the process. --
Toxic dinoflagellates and marine mammal mortalities : proceedings of an expert consultation held at the Woods Hole Oceanographic Institution
No full textOn May 8 and 9, 1989, a consultation of experts was convened at the Woods Hole
Oceanographic Institution to discuss the possible link between natural biotoxins and recent mass mortalities of humpback whales and bottlenose dolphins along the eastern coast of the United States. The focus was on the possible role of dinoflagellate toxins in these events. The objectives of the meeting were to review and assess the existing evidence and to recommend research priorities and needs.Funding was provided by NOAA, National Marine Fisheries Service, Woods Hole Oceanographic
Institution Coastal Research Center through a grant from the Andrew W. Mellon Foundation and the Woods Hole Oceanographic Institution Sea Grant Program under Grant NA86-D-SW90 (Project R/B - 92 and M/O-2)
Trapping black hole remnants
No full textLarge extra dimensions lower the Planck scale to values soon accessible. The production of TeV mass black holes at the LHC is one of the most exciting predictions. However, the final phases of the black hole's evaporation are still unknown and there are strong indications that a black hole remnant can be left. Since a certain fraction of such objects would be electrically charged, we argue that they can be trapped. In this paper, we examine the occurrence of such charged black hole remnants. These trapped remnants are of high interest, as they could be used to closely investigate the evaporation characteristics. Due to the absence of background from the collision region and the controlled initial state, the signal would be very clear. This would allow to extract information about the late stages of the evaporation process with high precision
Abstracts of papers submitted in 1982 for publication, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
No full textThis Summary of Abstracts contains all abstracts submitted
for publication during calendar year 1981 by the staff and students
of the Woods Hole Oceanographic Institution. Because some of the
abstracts may not be published in the journal to which they have
been submitted initially, we have purposely omitted identifying the
journals. The volume is intended to be informative, but not a
bibliography
Faunal biogeography, community structure, and genetic connectivity of North Atlantic seamounts
No full textSubmitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2008The mechanisms of faunal dispersal across ocean basins are key unknowns toward
understanding of the modern biogeography and biodiversity of deep-sea fauna.
Seamounts are considered to play a defining role in faunal evolution, acting as regional
centers of speciation, “stepping-stones” for dispersal, and/or refugia for deep-sea
populations. The overarching goal of this dissertation was to examine the role of
seamounts in structuring marine biodiversity and biogeography. This study focused on
North Atlantic seamounts, specifically the New England seamount chain, the Corner Rise
seamounts, and Muir seamount, areas damaged and threatened by deep-sea fisheries and
currently a focus of conservation efforts. Videographic analyses of biological community
structure revealed distinct faunal assemblages, dominated by the Porifera, Cnidaria, and
Echinodermata and structured by geographic region, depth regions (with apparent
taxonomic breaks at 1300 m, 2300 m, and 2600 m), and substrate type (including
natural/anthropogenic and abiotic substrates and biotic substrates). Amongst these
assemblages, seven highly specific coral host- invertebrate associate relationships were
identified. To investigate whether or not these broad community patterns were
discernible at a genetic level, the 16S mtDNA gene was utilized as a genetic “barcode”
within the Class Ophiuroidea, through which 22 putative species were identified,
including four target species (Asteroschema clavigera, Ophiocreas oedipus,
Ophioplinthaca abyssalis, and Ophioplinthaca chelys) for subsequent population genetic
studies. Analyses of mitochondrial 16S and COI gene sequences revealed evidence for
recent population expansion and estimates of recent high gene flow across all four
species throughout the North Atlantic seamount region. However, genetic differentiation
within populations of A. clavigera and O. chelys within seamount regions was significant,
suggesting that historical diversification has been mediated by a long-distance dispersal
mechanism that homogenizes this genetic signal on a regional scale. In addition,
comparisons of all ophiuroid populations revealed no congruent pattern of historical
migration amongst seamounts, which may also be attributed to the varying levels of host
specificity and reproductive strategy of each ophiuroid species. These results will guide
future studies and conservation efforts to protect seamount communities vulnerable to
deep-sea fishery activities.Financial support was provided by the Ocean Life Institute, Deep-Ocean
Exploration Institute, and Academic Programs Office of the Woods Hole Oceanographic
Institution, the Census of Marine Life for Seamounts (CenSeam) through their mini-grant
program (Grant #12301), the Office of Ocean Exploration, National Oceanic and
Atmospheric Administration (NA05OAR4601054) and the National Science Foundation
(OCE-0624627; OCE-0451983; OCE-0647612)
Internal limiting membrane peeling versus no peeling for idiopathic full-thickness macular hole: a pragmatic randomized controlled trial
No full text<p>Purpose: To determine whether internal limiting membrane (ILM) peeling is effective and cost effective compared with no peeling in patients with idiopathic stage 2 or 3 full-thickness maculay hole (FTMH).</p>
<p>Methods: This was a pragmatic multicenter randomized controlled trial. Eligible participants from nine centers were randomized to ILM peeling or no peeling (1:1 ratio) in addition to phacovitrectomy, including detachment and removal of the posterior hyaloid and gas tamponade. The primary outcome was distance visual acuity (VA) at 6 months after surgery. Secondary outcomes included hole closure, distance VA at other time points, near VA, contrast sensitivity, reading speed, reoperations, complications, resource use, and participant-reported health status, visual function, and costs.</p>
<p>Results: Of 141 participants randomized in nine centers, 127 (90%) completed the 6-month follow-up. Nonstatistically significant differences in distance visual acuity at 6 months were found between groups (mean difference, 4.8; 95% confidence interval [CI], −0.3 to 9.8; P = 0.063). There was a significantly higher rate of hole closure in the ILM-peel group (56 [84%] vs. 31 [48%]) at 1 month (odds ratio [OR]) at 1 month (odds ratio [OR, 6.23; 95% CI, 2.64–14.73; P < 0.001) with fewer reoperations (8 [12%] vs. 31 [48%]) performed by 6 months (OR, 0.14; 95% CI, 0.05–0.34; P < 0.001). Peeling the ILM is likely to be cost effective.</p>
<p>Conclusions: There was no evidence of a difference in distance VA after the ILM peeling and no-ILM peeling techniques. An important benefit in favor of no ILM peeling was ruled out. Given the higher anatomic closure and lower reoperation rates in the ILM-peel group, ILM peeling seems to be the treatment of choice for idiopathic stage 2 to 3 FTMH.</p>
Hole dangling-bond capture cross-sections in a-Si:H
No full textIt is demonstrated that the occupation statistics for a Gaussian distribution of dangling bond states may account for the measured variation of hole mobility-lifetime values in hydrogenated amorphous silicon as the Fermi energy is systematically varied by doping from about 0.55 eV to 1.05 eV below the conduction band edge. An assessment of how the deduced dangling bond parameters may be influenced by underlying doping effects suggests that the minimum cross-section ratio for hole capture into charged (sh-) and neutral (sh0) dangling bond states requires that sh-/sh0 = 5. The capture of holes is consequently dominated by charged dangling bonds provided the Fermi energy lies within the upper half of the band-gap. Both sh- and sh0 are observed to depend upon temperature (T) as sh ? T-ß which may indicate the presence of tunnelling transitions between valence band tail states and dangling bonds
The aggregation of clay minerals and marine microalgal cells : physicochemical theory and implications for controlling harmful algal blooms
No full textSubmitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2001In recent years, the use of clay minerals has emerged as one of the most promising
strategies for directly controlling harmful algal blooms (HABs). Its principle is based on
the mutual aggregation of algal cells and mineral particles, leading to the formation of
large flocs that rapidly settle to the ocean floor. This work investigated the effectiveness
of various domestic clays against a number of bloom-forming species from the United
States. Twenty-five clays were tested against the dinoflagellate, Karenia brevis (formerly
Gymnodinium breve), and the chrysophyte, Aureococcus anophagefferens. In general,
the highest removal efficiencies (RE > 90% at 0.25 g rl of clay) against K. brevis were
found using montmorillonite, bentonite and phosphatic clays (i.e. a product of phosphate
mining containing large amounts of montmorillonite). The RE of phosphatic clays
remained high (> 80%) even at 0.03 g rl. Kaolinite and zeolite were mostly ineffective
against K. brevis. Removal with clay exceeded those for alum, polyaluminum chloride
(PAC) and several other polymeric flocculants by a factor of two. However, the combination
of phosphatic clay and PAC (at 5 mg rl) decreased the amount of clay needed to
maintain 80% RE by one order of magnitude. Cell viability and recovery remained high
when clay loading stayed below 0.03 g rl with or without resuspension of the sediment.
However, cell mortality approached 100% with 0.50 g rl even with daily resuspension.
Between 0.10 and 0.25 g rl, K. brevis survival and recovery depended on the interplay of
clay loading, the frequency of resuspension, and duration of contact prior to the first
resuspension event. For A. anophagefferens, the RE did not exceed 40% for any clay at
0.25 g rl even in combination with coagulants and flocculants. The highest removal was
achieved by thoroughly mixing the clay slurry (e.g. phosphatic clay) into the cell culture.
The RE by phosphatic clay varied significantly in a survey consisting of 17 different
species from five algal classes. Moreover, the removal trends varied substantially
with increasing cell concentration. For example, cell removal increased with increasing
clay loading and cell concentration for K. brevis. However, RE dropped below 70%
when cell concentration was < 1000 cell ml-1 for clay loadings up to 0.50 g rl. This
suggested that a critical number of organisms should be present for clays to remain effective.
Similarly, enhanced removal with increasing cell concentration was also found in
Akashiwo sanguinea (formerly Gymnodinium sanguineum), Heterosigma akashiwo and
Heterocapsa triquetra. In the six remaining species, RE initially increased then decreased,
or RE remained constant as more cells were treated. The removal pattern among the
species at comparable cell numbers did not correlate with the cross-sectional area (R2 =
0.23), swimming speed (R2 = 0.04), or a type of cell covering (i.e. theca, silica frustule).
However, when the total collision frequency coefficients were calculated (including
collisions due to cell motility) over the interval when clays were < 50 μm, these values
correlated well with the empirical RB's for the flagellated species (R2 = 0.90). These
results suggested that collisions due to cell motility may be important during the early
stages of aggregation when clay sizes are relatively small (i.e. near the surface where the
clay layer is initially added).
The electrophoretic mobility (EPM) of marine microalgae displayed a small range
of negative values. While the values were smaller that those reported from freshwater
species, these results confirmed earlier assumptions that marine species carry a negative
charge like their freshwater counterparts. In addition, these results also revealed that the
stabilities of cell suspensions in seawater are not controlled by charge neutralization.
However, these measurements did not provide direct information on why one species was
more readily removed over another by a given clay mineral (e.g. phosphatic clay).
The EPM of clays in freshwater also exhibited predictable negative values, with
montmorillonites showing the highest stability and phosphatic clays the lowest. Kaolinite
and zeolite displayed a range of intermediate values. These differences vanished when
the clays were suspended in natural seawater (29.6 salinity), reducing the surface charge
to a small range of negative values. This effect occurred even at 1116 of the final salinity
(1.85 salinity). Viewed alone, these results did not provide direct information on why
one clay mineral worked better than another against a given algal species (e.g. K. brevis).
Kinetic and modelling experiments using K. brevis and three minerals revealed
some distinct patterns in aggregation and settling among the clays, including how they
removed the organisms. After dispersing on the surface, phosphatic clays aggregated
quickly by virtue of low stability (low EPM). Cell removal coincided with the onset of
settling. Also, kaolinite aggregated quickly and was controlled by size as well as stability.
However, cell removal followed clay settling over 40 min, after which cell removal
decreased yielding only 46% RE. Bentonite aggregated slowly over 90 min due to its
high stability (high EPM), but produced a number of large voluminous flocs that steadily
removed the algae. The sinking rate of flocs increased as cells became incorporated, but
the onset of settling was delayed when cells were present in phosphatic clay and kaolinite
due to a predicted reduction in aggregate density. The process of kinetics and sedimentation
were modelled using first order equations for all mineral-algae combinations.
Finally, phosphatic clays demonstrated the ability to selectively remove K. brevis
in a mixed culture with the dinoflagellate, Prorocentrum micans, or the diatom, Skeletonema
costatum. While the RE's were generally comparable to individual cultures, the RE
of either species increased in the presence of the other, especially for K. brevis. Similar
results were observed in mesocosm studies using a natural assemblage during a Karenia
bloom. In fact, the RE of K. brevis were higher than would be predicted from single species
laboratory studies given its low initial concentration.
Overall, this research demonstrated the effectiveness of clay treatment against a
number of HAB species in the U.S. This work also provided new insights into the aggregation
phenomenon between minerals and living algal cells by focusing on the physical
(cell size), chemical and behavioral (i.e. motility) properties of both particle types, the
effect of particle concentration, and the aggregation kinetics of the clay-algae system.This work has been funded by the following: EPA Grant CR827090, Florida Institute
of Phosphate Research Grant 99-03-138, Florida Fish and Wildlife Conservation
Commission, Contracts MR266, 99157 and Purchase Order No. S7701 615727, Sholley
Foundation, and the Cove Point Foundation. Scholarships to the author were provided by
the Ford Foundation, and the Education Office of the Woods Hole Oceanographic Institution
Clinical and cost-effectiveness of internal limiting membrane peeling for patients with idiopathic full thickness macular hole. Protocol for a Randomised Controlled Trial : FILMS (Full-thickness macular hole and Internal Limiting Membrane peeling Study)
No full textBackground: A full-thickness macular hole (FTMH) is a common retinal condition associated with impaired vision. Randomised controlled trials (RCTs) have demonstrated that surgery, by means of pars plana vitrectomy and post-operative intraocular tamponade with gas, is effective for stage 2, 3 and 4 FTMH. Internal limiting membrane (ILM) peeling has been introduced as an additional surgical manoeuvre to increase the success of the surgery; i.e. increase rates of hole closure and visual improvement. However, little robust evidence exists supporting the superiority of ILM peeling compared with no-peeling techniques. The purpose of FILMS (Fullthickness macular hole and Internal Limiting Membrane peeling Study) is to determine whether ILM peeling improves the visual function, the anatomical closure of FTMH, and the quality of life of patients affected by this disorder, and the cost-effectiveness of the surgery.
Methods/Design: Patients with stage 2–3 idiopathic FTMH of less or equal than 18 months duration (based on symptoms reported by the participant) and with a visual acuity ≤ 20/40 in the study eye will be enrolled in this FILMS from eight sites across the UK and Ireland. Participants will be randomised to receive combined cataract surgery (phacoemulsification and intraocular lens implantation) and pars plana vitrectomy with postoperative intraocular tamponade with gas, with or without ILM peeling. The primary outcome is distance visual acuity at 6 months. Secondary outcomes include distance visual acuity at 3 and 24 months, near visual acuity at 3, 6, and 24 months, contrast sensitivity at 6 months, reading speed at 6 months, anatomical closure of the macular hole at each time point (1, 3, 6, and 24 months), health related quality of life (HRQOL) at six months, costs to the health service and the participant, incremental costs per quality adjusted life year (QALY) and adverse events.
Discussion: FILMS will provide high quality evidence on the role of ILM peeling in FTMH surgery.
Trial registration: This trial is registered with Current Controlled Trials ISRCTN number 33175422 and Clinical Trials.gov identifier NCT00286507.Chief Scientist Office, Scotland (project ref no CZH/4/235), NHS GrampianPeer reviewedPublisher PD
Lightly strained germanium quantum wells with hole mobility exceeding one million
No full textWe demonstrate that a lightly strained germanium channel (ϵ / / = - 0.41 %) in an undoped Ge/Si0.1Ge0.9 heterostructure field effect transistor supports a two-dimensional (2D) hole gas with mobility in excess of 1 × 10 6 cm2/Vs and percolation density less than 5 × 10 10 cm-2. This low disorder 2D hole system shows tunable fractional quantum Hall effects at low densities and low magnetic fields. The low-disorder and small effective mass (0.068 m e) defines lightly strained germanium as a basis to tune the strength of the spin-orbit coupling for fast and coherent quantum hardware. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.QCD/Scappucci LabBUS/TNO STAFFQN/Veldhorst La
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