9,090 research outputs found
The Effectiveness Of Two Types Of Visual Aid Treatments On Eye Movement Performance Of Educationally Handicapped Pupils In The Elementary School
The study was designed to test the effectiveness of two visual aid treatments: Controlled Reader and Tachistoscopic-X machines on educationally handicapped students in elementary school. In addition, this study was conducted to test the effectiveness of such an instructional program on efficient eye-movements on the educationally handicapped student during the reading act
Chiral microstructures (spirals) fabrication by holographic lithography
We present an optical interference model to create chiral microstructures
(spirals) and its realization in photoresist using holographic lithography. The
model is based on the interference of six equally-spaced circumpolar linear
polarized side beams and a circular polarized central beam. The pitch and
separation of the spirals can be varied by changing the angle between the side
beams and the central beam. The realization of the model is carried out using
the 325 nm line of a He-Cd laser and spirals of sub-micron size are fabricated
in photoresist.Comment: 6 page
Cooperative Carbon Dioxide Adsorption in Alcoholamine- and Alkoxyalkylamine-Functionalized Metal-Organic Frameworks.
A series of structurally diverse alcoholamine- and alkoxyalkylamine-functionalized variants of the metal-organic framework Mg2 (dobpdc) are shown to adsorb CO2 selectively via cooperative chain-forming mechanisms. Solid-state NMR spectra and optimized structures obtained from van der Waals-corrected density functional theory calculations indicate that the adsorption profiles can be attributed to the formation of carbamic acid or ammonium carbamate chains that are stabilized by hydrogen bonding interactions within the framework pores. These findings significantly expand the scope of chemical functionalities that can be utilized to design cooperative CO2 adsorbents, providing further means of optimizing these powerful materials for energy-efficient CO2 separations
Polarization gaps in spiral photonic crystals
We studied the optical properties of a dielectric photonic crystal structure
with spirals arranged in a hexagonal lattice. The dielectric constant of the
material is 9 and the filling ratio is 15.2%. We found that this kind of
structure exhibits a significant polarization gap for light incident along the
axis of the spirals. The eigenmodes inside the polarization gap are right-hand
(left-hand) circularly polarized depending on the whether the spirals are
left-handed (right-handed). The transmission spectrum of a slab of such a
structure has been calculated and matches well with the analysis of the
eigenmodes.Comment: 6 pages, 7 figure
Vortices and the entrainment transition in the 2D Kuramoto model
We study synchronization in the two-dimensional lattice of coupled phase
oscillators with random intrinsic frequencies. When the coupling is larger
than a threshold , there is a macroscopic cluster of
frequency-synchronized oscillators. We explain why the macroscopic cluster
disappears at . We view the system in terms of vortices, since cluster
boundaries are delineated by the motion of these topological defects. In the
entrained phase (), vortices move in fixed paths around clusters, while
in the unentrained phase (), vortices sometimes wander off. These
deviant vortices are responsible for the disappearance of the macroscopic
cluster. The regularity of vortex motion is determined by whether clusters
behave as single effective oscillators. The unentrained phase is also
characterized by time-dependent cluster structure and the presence of chaos.
Thus, the entrainment transition is actually an order-chaos transition. We
present an analytical argument for the scaling for small
lattices, where is the threshold for phase-locking. By also deriving the
scaling , we thus show that for small , in
agreement with numerics. In addition, we show how to use the linearized model
to predict where vortices are generated.Comment: 11 pages, 8 figure
Laparoscopic Assisted Fusion of the Lumbosacral Spine: A Biomechanical and Histologic Analysis of the Open Versus Laparoscopic Technique in an Animal Model
Study Design. An animal model for laparoscopic lumbosacral fusion.
Objectives. To compare the biomechanical and histologic results of open to laparoscopic lumbosacral discectomy and fusion in an animal model.
Background Data. Early clinical reports of laparoscopic lumbosacral fusions are encouraging, but animal experiments have not been reported.
Methods. Ten pigs (50-80 kg) were divided into two groups. Group 1 underwent an open anterior lumbosacral discectomy and fusion at L7-S1 using autologous bone graft and a titanium MOSS (DePuy Motech) cage. Group 2 was identical to Group 1 except that a laparoscopic technique was used. The animals were killed at 3 months, and the lumbosacral spines were harvested for biomechanical and histologic testing.
Results. Estimated blood loss and average length of operation, respectively, for the two groups were: Group 1, 50 mL, 2 hours 50 minutes; and Group 2, 40 mL, 3 hours 40 minutes. There were no perioperative or postoperative complications in either group. Motion analysis results showed less motion in lateral bending, flexion, and extension than in the intact specimen in both groups. Tensile testing showed that the stiffness was significantly greater in the open group than in the laparoscopic group (P \u3c 0.004). Histologic examination showed a less extensive discectomy and less bone growth in the implant in the laparoscopic group. Inadequate decortication of end-plates occurred in two animals who underwent laparoscopy.
Conclusions. Although lumbosacral discectomy and implant insertion can be performed using the laparoscopic technique, the construct may not have the same biomechanical strength as that attained with the open procedure. Laparoscopic-assisted lumbosacral fusion surgery requires additional investigation before it is widely used in clinical situations
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