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Search Results: 1 - 10 of 201993 matches for " Joel N Gilmer "
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A pneumatic power harvesting ankle-foot orthosis to prevent foot-drop
Robin Chin, Elizabeth T Hsiao-Wecksler, Eric Loth, Géza Kogler, Scott D Manwaring, Serena N Tyson, K Alex Shorter, Joel N Gilmer
Journal of NeuroEngineering and Rehabilitation , 2009, DOI: 10.1186/1743-0003-6-19
Abstract: The PhAFO was constructed from a two-part (tibia and foot) carbon composite structure with an articulating ankle joint. Ankle motion control was accomplished through a cam-follower locking mechanism actuated via a pneumatic circuit connected to the bellow pump and embedded in the foam sole. Biomechanical performance of the prototype orthosis was assessed during multiple trials of treadmill walking of an able-bodied control subject (n = 1). Motion capture and pressure measurements were used to investigate the effect of the PhAFO on lower limb joint behavior and the capacity of the bellow pump to repeatedly generate the required pneumatic pressure for toe clearance.Toe clearance during swing was successfully achieved during all trials; average clearance 44 ± 5 mm. Free ankle motion was observed during stance and plantarflexion was blocked during swing. In addition, the bellow component repeatedly generated an average of 169 kPa per step of pressure during ten minutes of walking.This study demonstrated that fluid power could be harvested with a pneumatic circuit built into an AFO, and used to operate an actuated cam-lock mechanism that controls ankle-foot motion at specific periods of the gait cycle.Foot-drop is a condition where the foot does not effectively clear the ground due to weak or absent ankle dorsiflexors which results in a steppage-type gait pattern. Steppage gait is a compensatory walking pattern for foot-drop that is characterized by increased knee and hip flexion during the swing phase to insure that the toe clears the ground during walking. The cause of foot-drop can be neurological and/or muscular in origin due to a multitude of pathologies [1]. A common treatment intervention is the use of an ankle-foot orthosis (AFO) that supports the ankle and foot to preclude foot-drop. This study presents a novel self-contained power harvesting ankle-foot orthosis that controls the unwanted plantarflexion movements associated with foot-drop and permits free ankle
Plasminogen interaction with Trypanosoma cruzi
Almeida Laura,Vanegas Gilmer,Calcagno Marina,Concepción Juan Luis
Memórias do Instituto Oswaldo Cruz , 2004,
Abstract: The ability of Trypanosoma cruzi to interact with plasminogen, the zimogenic form of the blood serin protease plasmin, was examined. Immunohistochemistry studies revealed that both forms, epimastigotes and metacyclic trypomastigotes, were able to fix plasminogen in a lysine dependant manner. This interaction was corroborated by plasminogen activation studies. Both forms of the parasite enhanced the plasminogen activation by tissue-type plasminogen activator.The maximal enhancements obtained were 15-fold and 3.4-fold with epimastigotes and metacyclic trypomastigotes, respectively, as compared to plasminogen activation in absence of cells. Ligand-blotting analysis of proteins extracted with Triton X-114 from a microsomal fraction of epimastigotes revealed at least five soluble proteins and one hydrophobic protein able to bind plasminogen.
On the Density of Happy Numbers
Justin Gilmer
Mathematics , 2011,
Abstract: The happy function $H: \mathbb{N} \rightarrow \mathbb{N}$ sends a positive integer to the sum of the squares of its digits. A number $x$ is said to be happy if the sequence $\{H^n(x)\}^\infty_{n=1}$ eventually reaches one. A basic open question regarding happy numbers is what bounds on the density can be proved. This paper uses probabilistic methods to reduce this problem to experimentally finding suitably large intervals containing a high (or low) density of happy numbers as a subset. Specifically we show that $\bar{d} > .18577$ and $\underline{d} < .1138$. We also prove that the asymptotic density does not exist for several generalizations of happy numbers.
A TQFT for Wormhole cobordisms over the field of rational functions
Patrick Gilmer
Mathematics , 1995,
Abstract: We consider a cobordism category whose morphisms are punctured connect sums of $S^1 \times S^2$'s (wormhole spaces) with embedded admissibly colored banded trivalent graphs. We define a TQFT on this cobordism category over the field of rational functions in an indeterminant $A.$ For $r$ large, we recover, by specializing $A$ to a primitive 4rth root of unity, the Witten-Reshetikhin-Turaev TQFT restricted to links in wormhole spaces. Thus, for $r$ large, the $r$th Witten-Reshetikhin-Turaev invariant of a link in some wormhole space, properly normalized, is the value of a certain rational function at $e^{\frac{\pi i}{2r}}.$ We relate our work to Hoste and Przytycki's calculation of the Kauffman bracket skein module of $S^1 \times S^2.$
Invariants for 1-dimensional cohomology classes arising from TQFT
Patrick Gilmer
Mathematics , 1995,
Abstract: Let $(V,Z)$ be a Topological Quantum Field Theory over a field $f$ defined on a cobordism category whose morphisms are oriented $n+1$-manifolds perhaps with extra structure. Let $(M,\chi)$ be a closed oriented $n+1$-manifold $M$ with this extra structure together with $\chi \in H^1(M).$ Let $M_{\infty}$ denote the infinite cyclic cover of $M$ given by $\chi.$ Consider a fundamental domain $E$ for the action of the integers on $M_{\infty}$ bounded by lifts of a surface $\Sigma$ dual to $\chi,$ and in general position. $E$ can be viewed as a cobordism from $\Sigma$ to itself. We give Turaev and Viro's proof of their theorem that the similarity class of the non-nilpotent part of $Z(E)$ is an invariant. We give a method to calculate this invariant for the $(V_p,Z_p)$ theories of Blanchet,Habegger, Masbaum and Vogel when $M$ is zero framed surgery to $S^3$ along a knot K. We give a formula for this invariant when $K$ is a twisted double of another knot. We obtain formulas for the quantum invariants of branched covers of knots, and unbranched covers of 0-surgery to $S^3$ along knots.
Plasminogen interaction with Trypanosoma cruzi
Almeida, Laura;Vanegas, Gilmer;Calcagno, Marina;Concepción, Juan Luis;Avilan, Luisana;
Memórias do Instituto Oswaldo Cruz , 2004, DOI: 10.1590/S0074-02762004000100011
Abstract: the ability of trypanosoma cruzi to interact with plasminogen, the zimogenic form of the blood serin protease plasmin, was examined. immunohistochemistry studies revealed that both forms, epimastigotes and metacyclic trypomastigotes, were able to fix plasminogen in a lysine dependant manner. this interaction was corroborated by plasminogen activation studies. both forms of the parasite enhanced the plasminogen activation by tissue-type plasminogen activator.the maximal enhancements obtained were 15-fold and 3.4-fold with epimastigotes and metacyclic trypomastigotes, respectively, as compared to plasminogen activation in absence of cells. ligand-blotting analysis of proteins extracted with triton x-114 from a microsomal fraction of epimastigotes revealed at least five soluble proteins and one hydrophobic protein able to bind plasminogen.
The Disk-Halo Connection and Where Has All The Gas Gone?
Joel N. Bregman
Physics , 2009,
Abstract: The wealth of data in the past decades, and especially in the past 15 years has transformed our picture of the gas around the Milky Way and other spiral galaxies. There is good evidence for extraplanar gas that is a few kpc in height and is seen in all gaseous phases: neutral; warm atomic; and hot, X-ray emitting gas. This medium is seen not only around the Milky Way, but other spiral galaxies and it is related to the star formation rate, so it is likely produced by the activity in the disk through a galactic fountain. More extended examples of halo gas are seen, such as the HVC around the Milky Way and around M31. This gas is typically 10-20 kpc from the galaxy and is not seen beyond 50 kpc. This gas is most likely being accreted. A hot dilute halo (1E6 K) is present with a similar size, although its size is poorly determined. An ongoing controversy surrounds the relative amounts of outflow from the disk and accretion onto galaxies such as the Milky Way. There is good evidence for accretion of cold material onto the Milky Way and other galaxies, but it is not clear if there is enough to modify the gas content and star formation properties in the disk. The reservoir of accretion material is as yet unidentified. Some of these findings may be related to the issue that galaxies are baryon-poor: their baryon to dark matter ratio is well below the cosmological value. The absence of baryons may be due to extremely violent outflow events in the early stages of galaxy formation. We may be able to understand this stage of galaxy evolution by applying our deepening understanding of our local disk-halo environment.
The Missing Baryons in the Milky Way and Local Group
Joel N. Bregman
Physics , 2009,
Abstract: The Milky Way and all other galaxies are missing most of their baryons in that the ratio of the known baryonic mass to the gravitating mass (within the virial radius), is several times less than the cosmic ratio determined from WMAP. This implies that either the baryons never fell into galaxies or that powerful galactic winds removed most of the baryons. It is possible to discriminate between these two pathways if we can discover the missing baryons and measure its properties: spatial distribution; temperature; and metallicity. The missing baryons from galaxies are expected to have temperatures of 1-3E6 K, so X-ray observations are required. In this white paper, we show how X-ray observations, obtained with a facility such as IXO, can be used to identify and study these elusive baryons.
The Cosmic Web of Baryons
Joel N. Bregman
Physics , 2009,
Abstract: Only about 10% of the baryons in the universe lie in galaxies as stars or cold gas, with the remainder predicted to exist as a dilute gaseous filamentary network known as the Cosmic Web. Some of this gas is detected through UV absorption line studies, but half of the gas remains undetected. Growth of structure simulations suggest that these "missing" baryons were shock heated in unvirialized cosmic filaments to temperatures of 10^5.5-10^7 K, and that the gas is chemically enriched by galactic superwinds. Most of the gas in this temperature regime can be detected only by X-ray observations through absorption and emission from the He-like and H-line ions of C, N, and O. This white paper shows that an X-ray telescope such as IXO can test the most central predictions of the Cosmic Web: the distribution of gas mass with temperature; the dynamics of the gas and its relationship to nearby galaxies; and the topology of the Cosmic Web material.
Mass Loss From Planetary Nebulae in Elliptical Galaxies
Joel N. Bregman,Joel R. Parriott
Physics , 2009, DOI: 10.1088/0004-637X/699/2/923
Abstract: Early-type galaxies possess a dilute hot (2-10E6 K) gas that is probably the thermalized ejecta of the mass loss from evolving stars. We investigate the processes by which the mass loss from orbiting stars interacts with the stationary hot gas for the case of the mass ejected in a planetary nebula event. Numerical hydrodynamic simulations show that at first, the ejecta expands nearly symmetrically, with an upstream bow shock in the hot ambient gas. At later times, the flow past the ejecta creates fluid instabilities that cause about half of the ejecta to separate and the other half to flow more slowly downstream in a narrow wake. When radiative cooling is included, most of the material in the wake (>80%) remains below 1E5 K while the separated ejecta is hotter (1E5-1E6 K). The separated ejecta is still less than one-quarter the temperature of the ambient medium and the only way it will reach the temperature of the ambient medium is through turbulent mixing (after the material has left the grid). These calculations suggest that a significant fraction of the planetary nebula ejecta may not become part of the hot ambient material. This is in contrast to our previous calculations for continuous mass loss from giant stars in which most of the mass loss became hot gas. We speculate that detectable OVI emission may be produced, but more sophisticated calculations will be required to determine the emission spectrum and to better define the fraction of cooled material.
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