The Siege

A short story written by Chris Muffoletto

Numerical techniques for Fresnel diffraction in computational holography

Optical holography can produce very realistic virtual images due to its capability to properly convey the depth cues that we use to interpret three-dimensional objects. Computational holography is the use of digital representations plus computational methods to carry out the holographic operations of construction and reconstruction. The large computational requirements of holographic simulations prohibit present-day existence of real-time holographic displays comparable in size to traditional two-dimensional displays. Fourier-based approaches to calculate the Fresnel diffraction of light provide one of the most efficient algorithms for holographic computations because this permits the use of the fast Fourier transform (FFT). The limitations on sampling imposed by Fourier-based algorithms have been overcome by the development, in this research, of a fast shifted Fresnel transform. This fast shifted Fresnel transform was used to develop a tiling approach to hologram construction and reconstruction, which computes the Fresnel propagation of light between parallel planes having different resolutions. A new method for hologram construction is presented, named partitioned hologram computation, which applies the concepts of the shifted Fresnel transform and tiling

Application of an airfoil stall flutter computer prediction program to a three-dimensional wing: Prediction versus experiment

An aerodynamic computer code, capable of predicting unsteady and C sub m values for an airfoil undergoing dynamic stall, is used to predict the amplitudes and frequencies of a wing undergoing torsional stall flutter. The code, developed at United Technologies Research Corporation (UTRC), is an empirical prediction method designed to yield unsteady values of normal force and moment, given the airfoil's static coefficient characteristics and the unsteady aerodynamic values, alpha, A and B. In this experiment, conducted in the PSU 4' x 5' subsonic wind tunnel, the wing's elastic axis, torsional spring constant and initial angle of attack are varied, and the oscillation amplitudes and frequencies of the wing, while undergoing torsional stall flutter, are recorded. These experimental values show only fair comparisons with the predicted responses. Predictions tend to be good at low velocities and rather poor at higher velocities

Pyogenic Arthritis of the Facet Joint with Concurrent Epidural and Paraspinal Abscess: A Case Report

Pyogenic arthritis of lumber spinal facet joints is an extremely rare condition. There are only 40 reported cases worldwide. Most cases were associated with history of paravertebral injection, which was not found in our patient. At the time of hospital admission, he had no abnormal magnetic resonance image findings. Two weeks later, he developed pyogenic facet joint arthritis associated with paravertebral and epidural abscess. This report is the first to describe delayed presentation of pyogenic arthritis associated with paravertebral abscess and epidural infection

Decompressive cervical laminectomy and lateral mass screw-rod arthrodesis. Surgical analysis and outcome

<p>Abstract</p> <p>Background</p> <p>This study evaluates the outcome and complications of decompressive cervical Laminectomy and lateral mass screw fixation in 110 cases treated for variable cervical spine pathologies that included; degenerative disease, trauma, neoplasms, metabolic-inflammatory disorders and congenital anomalies.</p> <p>Methods</p> <p>A retrospective review of total 785 lateral mass screws were placed in patients ages 16-68 years (40 females and 70 males). All cases were performed with a polyaxial screw-rod construct and screws were placed by using Anderson-Sekhon trajectory. Most patients had 12-14-mm length and 3.5 mm diameter screws placed for subaxial and 28-30 for C1 lateral mass. Screw location was assessed by post operative plain x-ray and computed tomography can (CT), besides that; the facet joint, nerve root foramen and foramen transversarium violation were also appraised.</p> <p>Results</p> <p>No patients experienced neural or vascular injury as a result of screw position. Only one patient needed screw repositioning. Six patients experienced superficial wound infection. Fifteen patients had pain around the shoulder of C5 distribution that subsided over the time. No patients developed screw pullouts or symptomatic adjacent segment disease within the period of follow up.</p> <p>Conclusion</p> <p>decompressive cervical spine laminectomy and Lateral mass screw stabilization is a technique that can be used for a variety of cervical spine pathologies with safety and efficiency.</p

Paraspinal Abscess Communicated with Epidural Abscess after Extra-Articular Facet Joint Injection

Facet joint injection is considered to be a safe procedure. There have been some reported cases of facet joint pyogenic infection and also 3 cases of facet joint infection spreading to paraspinal muscle and epidural space due to intra-articular injections. To the author's knowledge, paraspinal and epidural abscesses after facet joint injection without facet joint pyogenic infection have not been reported. Here we report a case in which extra-articular facet joint injection resulted in paraspinal and epidural abscesses without facet joint infection. A 50-year-old man presenting with acute back pain and fever was admitted to the hospital. He had the history of diabetes mellitus and had undergone the extra-articular facet joint injection due to a facet joint syndrome diagnosis at a private clinic 5 days earlier. Physical examination showed tenderness over the paraspinal region. Magnetic resonance image (MRI) demonstrated the paraspinal abscess around the fourth and fifth spinous processes with an additional epidural abscess compressing the thecal sac. The facet joints were preserved. The laboratory results showed a white blood cell count of 14.9 × 109 per liter, an erythrocyte sedimentation rate of 52mm/hour, and 10.88mg/dL of C-reactive protein. Laminectomy and drainage were performed. The pus was found in the paraspinal muscles, which was communicated with the epidural space through a hole in the ligamentum flavum. Cultures grew Staphylococcus aureus. Paraspinal abscess communicated with epidural abscess is a rare complication of extra-articular facet joint injection demonstrating an abscess formation after an invasive procedure near the spine is highly possible

Reflections on Designing and Producing an Internet-Based Course

Describes the design and development of an Internet-based distance education class at the University of Northern Iowa. Discusses collaboration with students, basic course design, conceptual and epistemological context of the course, delivery environment, and forms of interaction including electronic mail. (LRW