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Introduction Femoral neurovascular injury is an uncommon, but potentially devastating complication following surgical approaches to the hip. The intraoperative misplacement of the anterior acetabular retractor is the most commonly cited mechanism for this injury yet there is no gold standard for a proper insertion location in the literature We examined the course of the femoral neurovasculature about the hip to identify safest location for retractor insertion and furthermore demographic populations who are at-risk for injury due to a decreased distance between the hip joint and the femoral neurovasculature. Methods A total of 100 non-pathologic hip magnetic resonance imaging (MRI) studies from adult patients were included. Patients were chosen at random from our medical center's digital radiographic archive and their demographic data recorded. Mean distances between the anterior acetabular wall and the femoral artery were measured at three axial levels (acetabular dome, superior iliopectineal ridge, and inferior iliopectineal ridge). Results Our data showed the femoral neurovascular structures pass closer in proximity to the acetabular wall as they progress distally about the hip. An average direct separation distance of 40.1 mm was seen at the acetabular dome while measurements at the inferior iliopectineal ridge demonstrated an average distance of 20.5 mm. Additionally, statistically significant (p 45 years-old, Discussion By undertaking a large-scale MRI evaluation of the femoral neurovasculature about the hip, not only were we able to approximate the location of the femoral neurovascular bundle as it passes the hip joint, but also the safest location for insertion of anterior acetabular retractors at the level of the acetabular dome or above in close proximity to the bony cortex. Additional care should be taken placing retractors in patients when demographic risk factors including female gender, age >45 years old, stature

During the 1980s, when satellite communication systems and applications experienced significant growth, the Federal Communications Commission (FCC) in the U.S. recognized that special regulations were required for the licensing and operation of VSAT systems in order to maintain efficient use of the radio spectrum and geostationary orbit (GSO) and to expedite the authorization of VSAT networks featuring large numbers of earth-stations. The FSS allocated frequency bands, which are used extensively by domestic satellite communication systems in the U.S. and throughout Region 2, are in the 4–6 GHz and 12–14 GHz bands. In order to satisfy the heavy demand in the U.S. for fixed satellite services in these bands, the FCC devised an orbit plan of two degrees spacing between satellites in the relevant portion of the GSO. In a co-coverage environment, the two most important technical factors for controlling interference between neighbouring satellite systems are (1) earth-station antenna discrimination and (2) cross-polarization. Since VSAT systems, by definition, use very small aperture terminals with relatively low levels of antenna discrimination, it was necessary to establish limits for transmit power flux densities and the minimum size of antennas. These limits, based on compatible operation at two-degree satellite orbit separations, evolved into VSAT standards for the U.S. domestic satellite industry. To expedite the licensing of large numbers of VSAT terminals, conforming systems were given ‘blanket authorizations’ for all VSATs in a network. This paper traces the history of the development of VSAT standards in the U.S. and discusses the technical considerations which were used in these developments. A brief review of receive-only (RO) terminals is also provided.

BioMEMS are compact devices that use microfabrication to miniaturize benchtop instrumentation. Due to the requirement for uniform temperature distributions over restricted areas, thermal isolation, and faster heating and cooling rates in a limited space, thermal management is a key to ensuring successful performance of BioMEMS devices. The continuous flow polymerase chain reactor (CFPCR) is a compact BioMEMS device that is used to amplify target DNA fragments using repeated thermal cycling. The temperature distribution on the backside of a micro CFPCR was measured using thermochromic liquid crystals and an infrared camera. In the liquid crystal experiment, the performance of a 5 mm thick polycarbonate micro CFPCR with thin film heaters attached directly to the bottom polycarbonate surface over each temperature zone was studied. Natural convection was used as a cooling mechanism. The temperature distribution in the renaturation zone was dependent on the positions of the feedback thermocouples in each zone. Three different thermocouple configurations were assessed and the liquid crystal images showed that a best case 3.86°C temperature difference across the zone, leading to a 20% amplification efficiency compared to a commercial thermal cycler [5]. The device was modified to improve the temperature distribution: a thinner substrate, 2 mm, reduced the thermal capacitance; grooves were micro-milled in the backside to isolate each temperature zone; and three separate copper heating stages, combining the thin film heaters with copper plates, applied uniform temperatures to each zone [10]. Infrared camera images showed that the temperature distributions were distinct and uniform with a ±0.3 °C variations in each temperature zone, improving amplification efficiency to 72%. Good thermal management for PCR amplification can’t only increase its reliability and yield efficiency, but also accelerate the entire analytical process.Copyright © 2007 by ASME

Continuous flow polymerase chain reaction (CFPCR) devices are compact reactors suitable for microfabrication and the rapid amplification of target DNAs. For a given reactor design, the amplification time can be reduced simply by increasing the flow velocity through the isothermal zones of the device; for flow velocities near the design value, the PCR cocktail reaches thermal equilibrium at each zone quickly, so that near ideal temperature profiles can be obtained. However, at high flow velocities there are penalties of an increased pressure drop and a reduced residence time in each temperature zone for the DNA/reagent mixture, potentially affecting amplification efficiency. This study was carried out to evaluate the thermal and biochemical effects of high flow velocities in a spiral, 20 cycle CFPCR device. Finite element analysis (FEA) was used to determine the steady-state temperature distribution along the micro-channel and the temperature of the DNA/reagent mixture in each temperature zone as a function of linear velocity. The critical transition was between the denaturation (95°C) and renaturation (55°C-68°C) zones; above 6 mm/s the fluid in a passively-cooled channel could not be reduced to the desired temperature and the duration of the temperature transition between zones increased with increased velocity. The amplification performance of the CFPCR as a function of linear velocity was assessed using 500 and 997 base pair (bp) fragments from λ-DNA. Amplifications at velocities ranging from 1 mm/s to 20 mm/s were investigated. Alternative design of PCR was investigated. Shuttle PCR has a single straight channel and a DNA plug, driven by electrokinetic flow, will move forward and backward in the microchannel to achieve the repetitive thermal cycles. Thermal performance, independent insulated temperature blocks, and molecular and thermal diffusion were evaluated.

Two types of Microfluidic bioanalytical systems were designed and fabricated in polymer substrates using the LIGA process. A continuous flow polymerase chain reaction (CFPCR) Microfluidic device was fabricated in polycarbonate (PC), which utilized isothermal zone and shuttling the sample through each zone to achieve amplification. A 20-cycle PCR amplification of a fragment of a plasmid DNA template was achieved in 5.3 min. The results were comparable to those obtained in commercial laboratory-scale PCR system. The second system consisted of a microchip contating a low-density array assembled into the Microfluidic channel, which was hot-embossed in poly(methyl methacrylate) (PMMA). The detection of low-abundant mutations in gene fragments (K-ras) that carry point mutations with high diagnostic value for colorectal cancer was successfully performed. The array accessed microfluidics in order to enhance the kinetic associated with hybridization.

A continuous flow polymerase chain reaction (CFPCR) system was designed, fabricated from molded polycarbonate, and tested. Finite element modeling was used to simulate the thermal and Microfluidic response of the system. The mold insert for the initial prototypes was fabricated using the X-ray LIGA microfabrication process and device components produced by hot embossing polycarbonate. Commercial thin film heaters under PID control were used to supply the necessary heat flux to maintain the steady-state temperatures in the PCR. The simulated transient temperature response at start up was compared to the experimental response. The simulated steady state temperature profile along the channel generated by the finite element analysis was compared to the experimental temperature profile displayed by liquid crystals. Experimental and simulated results were within 5% of each other, validating the thermal design of the CFPCR device.

Continuous flow polymerase chain reaction (CFPCR) devices are compact reactors suitable for microfabrication and the rapid amplification of target DNAs. For a given reactor design, the amplification time can be reduced simply by increasing the flow velocity through the isothermal zones of the device; for flow velocities near the design value, the PCR cocktail reaches thermal equilibrium at each zone quickly, so that near ideal temperature profiles can be obtained. However, at high flow velocities there are penalties of an increased pressure drop and a reduced residence time in each temperature zone for the DNA/reagent mixture, that potentially affect amplification efficiency. This study was carried out to evaluate the thermal and biochemical effects of high flow velocities in a spiral, 20 cycle CFPCR device. Finite element analysis (FEA) was used to determine the steady-state temperature distribution along the micro-channel and the temperature of the DNA/reagent mixture in each temperature zone as a function of linear velocity. The critical transition was between the denaturation (95 degrees C) and renaturation (55 degrees C-68 degrees C) zones; above 6 mm s(-1) the fluid in a passively-cooled channel could not be reduced to the desired temperature and the duration of the temperature transition between zones increased with increased velocity. The amplification performance of the CFPCR as a function of linear velocity was assessed using 500 and 997 base pair (bp) fragments from lambda-DNA. Amplifications at velocities ranging from 1 mm s(-1) to 20 mm s(-1) were investigated. The 500 bp fragment could be observed in a total reaction time of 1.7 min (5.2 s cycle(-1)) and the 997 bp fragment could be detected in 3.2 min (9.7 s cycle(-1)). The longer amplification time required for detection of the 997 bp fragment was due to the device being operated at its enzyme kinetic limit (i.e., Taq polymerase deoxynucleotide incorporation rate).

We evaluated 39 patients with intraocular disease by magnetic resonance imaging (MRI). Malignant uveal melanoma was considered the likely diagnosis in 25 patients. Seventeen patients underwent surgery, and the histopathologic diagnosis of melanoma was confirmed. The authors observed that uveal melanomas had characteristic MRI features consisting of a relatively high-signal intensity in T1-weighted images and a relatively low-signal intensity in T2-weighted images. These images reflected their inherently relative short T1 and T2 relaxation times. Choroidal lesions elevated more than 3 mm were well visualized on MRIs. MRI also proved valuable for differentiating uveal melanoma from associated subretinal effusion, choroidal hemangioma, choroidal metastasis, and hemorrhagic and serous choroidal detachments.