603 research outputs found
The Memory Metal Minimal Access Cage: A New Concept in Lumbar Interbody Fusion—A Prospective, Noncomparative Study to Evaluate the Safety and Performance
Study Design/Objective. A single-centre, prospective, non-comparative study of 25 patients to evaluate the performance and safety of the Memory Metal Minimal Access Cage (MAC) in Lumbar Interbody Fusion. Summary of Background Data. Interbody fusion cages in general are designed to withstand high axial loads and in the meantime to allow ingrowth of new bone for bony fusion. In many cages the contact area with the endplate is rather large leaving a relatively small contact area for the bone graft with the adjacent host bone. MAC is constructed from the memory metal Nitinol and builds on the concept of sufficient axial support in combination with a large contact area of the graft facilitating bony ingrowth and ease in minimal access implantation due to its high deformability. Methods. Twenty five subjects with a primary diagnosis of disabling back and radicular leg pain from a single level degenerative lumbar disc underwent an interbody fusion using MAC and pedicle screws. Clinical performance was evaluated prospectively over 2 years using the Oswestry Disability Index (ODI), Short Form 36 questionnaire (SF-36) and pain visual analogue scale (VAS) scores. The interbody fusion status was assessed using conventional radiographs and CT scan. Safety of the device was studied by registration of intra- and post-operative adverse effects. Results. Clinical performance improved significantly (P < .0018), CT scan confirmed solid fusion in all 25 patients at two year follow-up. In two patients migration of the cage occurred, which was resolved uneventfully by placing a larger size at the subsequent revision. Conclusions. We conclude that the Memory Metal Minimal Access Cage (MAC) resulted in 100% solid fusions in 2 years and proved to be safe, although two patients required revision surgery in order to achieve solid fusion
NHI Toetsing, Ontwikkeling en toepassing van methode voor toetsing van NHI 2.1 inclusief vergelijking met NHI 2.0.
Dit rapport beschrijft de achtergrond van de methode om NHI2.1 te toetsen aan de criteria die opgesteld zijn door Rijkswaterstaat Waterdienst geldend voor 2010 en bevat de resultaten van die toetsing en de vergelijking met resultaten van NHI2.0. Volgens de criteria is de berekende aan en afvoer van oppervlakte water verbeterd. Op enkele belangrijke meetpunten van de oppervlaktewaterverdeling zijn signifinante verbeteringen te zien
Probing photo-ionization: simulations of positive streamers in varying N2:O2 mixtures
Photo-ionization is the accepted mechanism for the propagation of positive
streamers in air though the parameters are not very well known; the efficiency
of this mechanism largely depends on the presence of both nitrogen and oxygen.
But experiments show that streamer propagation is amazingly robust against
changes of the gas composition; even for pure nitrogen with impurity levels
below 1 ppm streamers propagate essentially with the same velocity as in air,
but their minimal diameter is smaller, and they branch more frequently.
Additionally, they move more in a zigzag fashion and sometimes exhibit a
feathery structure. In our simulations, we test the relative importance of
photo-ionization and of the background ionization from pulsed repetitive
discharges, in air as well as in nitrogen with 1 ppm O2 . We also test
reasonable parameter changes of the photo-ionization model. We find that photo-
ionization dominates streamer propagation in air for repetition frequencies of
at least 1 kHz, while in nitrogen with 1 ppm O2 the effect of the repetition
frequency has to be included above 1 Hz. Finally, we explain the feather-like
structures around streamer channels that are observed in experiments in
nitrogen with high purity, but not in air.Comment: 12 figure
Probing background ionization: Positive streamers with varying pulse repetition rate and with a radioactive admixture
Positive streamers need a source of free electrons ahead of them to
propagate. A streamer can supply these electrons by itself through
photo-ionization, or the electrons can be present due to external background
ionization. Here we investigate the effects of background ionization on
streamer propagation and morphology by changing the gas composition and the
repetition rate of the voltage pulses, and by adding a small amount of
radioactive Krypton 85.
We find that the general morphology of a positive streamer discharge in high
purity nitrogen depends on background ionization: at lower background
ionization levels the streamers branch more and have a more feather-like
appearance. This is observed both when varying the repetition rate and when
adding Krypton 85, though side branches are longer with the radioactive
admixture. But velocities and minimal diameters of streamers are virtually
independent of the background ionization level. In air, the inception cloud
breaks up into streamers at a smaller radius when the repetition rate and
therefore the background ionization level is higher. When measuring the effects
of the pulse repetition rate and of the radioactive admixture on the discharge
morphology, we found that our estimates of background ionization levels are
consistent with these observations; this gives confidence in the estimates.
Streamer channels generally do not follow the paths of previous discharge
channels for repetition rates of up to 10 Hz. We estimate the effect of
recombination and diffusion of ions and free electrons from the previous
discharge and conclude that the old trail has largely disappeared at the moment
of the next voltage pulse; therefore the next streamers indeed cannot follow
the old trail.Comment: 30 pages, 13 figure
Decreased neuroinflammation correlates to higher vagus nerve activity fluctuations in near-term ovine fetuses: a case for the afferent cholinergic anti-inflammatory pathway?
Motor Nucleus of Vagus---Location. Methods supplementary material: Neuroanatomical approach to locating vagal motor nucleus in fetal sheep brain (PDF 1716 kb
Probing photo-ionization: Experiments on positive streamers in pure gasses and mixtures
Positive streamers are thought to propagate by photo-ionization whose
parameters depend on the nitrogen:oxygen ratio. Therefore we study streamers in
nitrogen with 20%, 0.2% and 0.01% oxygen and in pure nitrogen, as well as in
pure oxygen and argon. Our new experimental set-up guarantees contamination of
the pure gases to be well below 1 ppm. Streamers in oxygen are difficult to
measure as they emit considerably less light in the sensitivity range of our
fast ICCD camera than the other gasses. Streamers in pure nitrogen and in all
nitrogen/oxygen mixtures look generally similar, but become somewhat thinner
and branch more with decreasing oxygen content. In pure nitrogen the streamers
can branch so much that they resemble feathers. This feature is even more
pronounced in pure argon, with approximately 10^2 hair tips/cm^3 in the
feathers at 200 mbar; this density could be interpreted as the free electron
density creating avalanches towards the streamer stem. It is remarkable that
the streamer velocity is essentially the same for similar voltage and pressure
in all nitrogen/oxygen mixtures as well as in pure nitrogen, while the oxygen
concentration and therefore the photo-ionization lengths vary by more than five
orders of magnitude. Streamers in argon have essentially the same velocity as
well. The physical similarity of streamers at different pressures is confirmed
in all gases; the minimal diameters are smaller than in earlier measurements.Comment: 28 pages, 14 figures. Major differences with v1: - appendix and
spectra removed - subsection regarding effects of repetition frequency added
- many more smaller change
TURNING TEENS INTO FOSSILPHILES: CITIZEN SCIENCE AND ADVANCED VISUALIZATION OF PALEONTOLOGY COLLECTIONS
In 2016, the North Carolina Museum of Natural Sciences (NCMNS) received funding from NSF’s Collections in Support of Biological Research Program to launch a new citizen science initiative—FossilPhiles—aimed at improving publically accessible natural history specimen data. The FossilPhiles project supported NCMNS’ ongoing efforts to digitize paleontology collections and provide STEM opportunities for historically underrepresented student populations by engaging middle and high school students in authentic data collection.
Five students were chosen from area schools with underserved populations to digitize highly significant or visually impactful vertebrate, invertebrate, and paleobotanical fossil specimens (e.g., type specimens, rare collections, specimens of high public interest). Students were trained in specimen handling, collections data, and archiving. They collected standard measurement data, photographed specimens in 2D, and constructed 3D photorealistic models using photogrammetry. Over a period of six months, students took over 13,000 photos, documenting 176 specimens in 2D and 137 in 3D. Of these, 124 photos have already been uploaded to the NCMNS’ open-access collections database, accessible through the NCMNS’ website, GBIF, VertNet, and iDigBio. Future project plans include creation of a publicly accessible, interactive portal of the 3D specimen models.
Throughout their internships, FossilPhiles students were provided training and opportunities to communicate their experiences with the broader community. The entirety of the FossilPhiles project took place within the glass-walled Paleontology Research Lab (PRL) in the Nature Research Center of the NCMNS, on view to NCMNS’ ~1 million annual visitors. Additionally, students were regularly engaged with communicating about the project in real-time via social media outlets (e.g., Twitter, blogs), sharing photos of fossils they worked on, facts and skills that they learned, and challenges they overcame. FossilPhiles students also partnered with peers engaged in non-STEM museum internships to promote cross-learning. They collaborated with the NCMNS’ Teen Newsroom program to produce a video interview about their evolving impressions on what it means to be a scientist
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