A comparison of conventional compression plates and locking compression plates using cantilever bending in an ilial fracture model.

OBJECTIVES: The purpose of this study was to compare the stiffness, yield load, ultimate load at failure, displacement at failure, and mode of failure in cantilever bending of locking compression plates (LCP) and dynamic compression plates (DCP) in an acute failure ilial fracture model. Our hypothesis was that the LCP would be superior to the DCP for all of these biomechanical properties. METHODS: Ten pelves were harvested from healthy dogs euthanatized for reasons unrelated to this study and divided into two groups. A transverse osteotomy was performed and stabilized with either a 6-hole DCP applied in compression or a 6-hole LCP. Pelves were tested in cantilever bending at 20 mm/min to failure and construct stiffness, yield load, ultimate load at failure, displacement at failure, and mode of failure were compared. RESULTS: The mean stiffness of DCP constructs (193 N/mm [95% CI 121 - 264]) and of LCP constructs (224 N/mm [95% CI 152 - 295]) was not significantly different. Mean yield load of DCP constructs (900 N [95% CI 649 -1151]) and of LCP constructs (984 N [95% CI 733 -1235]) was not significantly different. No significant differences were found between the DCP and LCP constructs with respect to mode of failure, displacement at failure, or ultimate load at failure. CLINICAL SIGNIFICANCE: Our study did not demonstrate any differences between DCP and LCP construct performance in acute failure testing in vitro.

Spinal fracture and luxation in dogs and cats: a retrospective evaluation of 95 cases.

The purpose of this retrospective study was to review cases of spinal fractures or luxations (SFL) treated with various modalities in order to describe fracture location, neurological status, treatment, outcome and complications in a patient population at a single centre. The medical records of dogs and cats that had been diagnosed with a SFL between C1 and L7 between January 1995 and June 2005 were reviewed in order to collect pertinent data. Ninety-five cases were included in this study. The severity of spinal cord injury was graded on a scale from 0 to 5. Vehicular trauma was the most common cause of SFL. Spinal fractures were localized between C1-C5 in 10 cases, C6-T2 in one case, T3-L3 in 54 cases, L4-L7 in 36 cases. Thirty patients that were euthanatized without treatment had a median neurological score of 5. Twenty-eight patients, all of which had motor function, were treated conservatively and there was not any change in their median neurological grade at the time of discharge. Thirty-seven patients had surgery, 27 of which were non ambulatory. Thirty-five of 37 were stabilized using pins and/or screws and PMMA or various other techniques. The median neurological grade of surgically treated patients improved by one point between the time of initial diagnosis and discharge. Implant removal was performed in five cases. The patients that were treated with pins and/or screws and PMMA were significantly more improved than conservatively managed patients at the time of discharge, although the surgically treated patients were hospitalized significantly longer than the conservatively managed patients. Our results suggest that dogs that retain pain sensation prior to surgery have a good prognosis for functional recovery. In this study, the dogs that were treated conservatively retained purposeful movement and had a good prognosis for recovery.

Stiffness of modified Type 1a linear external skeletal fixators.

Modifications of a Type 1a external skeletal fixator (ESF) frame were evaluated by alternately placing transfixation pins on opposite sides of the connecting rod (Type 1a-MOD) or by placing additional connecting rods on either of the two inside (Type 1a-INSIDE) or two outside (Type 1a-OUTSIDE) transfixation pins. The objective of this study was to evaluate the stiffness of these modifications in terms of axial compression (AC), cranial-caudal bending (CCB), and medial-lateral bending (MLB). We hypothesized that these designs would allow significant increase in unilateral frame stiffness, over Type 1a, without proportional increase in frame complexity or technical difficulty of application. All of the ESF frames were constructed using large IMEX SKtrade mark clamps, 3.2 mm threaded fixation pins, 9.5 mm carbon fibre connecting rods and Delrin rods as bone models. Nine, eight pin frames of each design were constructed, and subjected to repetitive non-destructive loading forces (AC, CCB, MLB) using a materials testing machine. Frame construct stiffness for each force (AC, CCB, MLB) was derived from load-deformation curve analysis and displayed in N/mm. Data revealed the 1a-MOD and 1a-OUTSIDE constructs had significantly increased stiffness in CCB and AC as compared to the Type 1a constructs while all of the modified constructs were significantly stiffer in MLB than the Type 1a constructs.

Absorption Cross Section of Moderately Conducting Disks at 35 GHz.

Absorption cross-sectional measurements and model predictions of 25 disks with moderate electrical conductivity were made. The disk radii span part of the resonance region, and their thicknesses are an order of magnitude less than the skin depth. A photoacoustic apparatus, with a 35-GHz microwave source, was used to measure the absorption cross sections. The disks tend to be more absorbing when they are edge-on rather than broadside to the incident microwaves. Also they absorb most efficiently near a size parameter of 1. Model predictions generally agree with the measured magnitudes and trends in the data.

Parametric study of the absorption cross section for a moderately conducting thin cylinder.

Asystem has been developed to measure the absorption cross section for a single carbon fiber at 35 GHz as a functio of length, orientation, and diameter. Typical lengths of the fibers considered ranged from 1 to 20 mm, and diameters ranged from 3 to 8 µm. The results were compared with the modified integra equation calculations of Waterman and Pedersen that describe the scattering and absorption behavior for a wire of finite length and conductivity. Good agreement was found for all lengths, orientations, and diameters studied.

Trans-spectral absorption and scattering of electromagnetic radiation by diesel soot.

The mass density normalized absorption and total scattering coefficients have been measured using in situ techniques at selected wavelengths from the visible to approximately 1 cm for soot generated by the open combustion of diesel fuel. Particle morphologies are complex although similar to those of soots of other hydrocarbons and methods of generation. An ellipsoidal model has been applied as an approximation to the often multiconnected, chainlike aerosol and then compared with the measured results. The experimental results show an approximate (lambda)(-1) dependence over more than five decades of wavelength data. There is only general agreement with the simplified calculations in this feature as well as in the magnitude.

Infrared optical properties of diesel smoke plumes.

Far IR optical properties have been measured for smoke from diesel fires. Concentrations of both gaseous and particulate combustion products have been measured and chemical species contributing to the optical effects identified. To obtain these results, a variety of sampling instruments were lofted into large plumes on a mobile and open structure. The smoke plumes of diesel fires have been found to consist largely of carbonaceous material (in fibrous form) and heavy liquid hydrocarbons infused with the expected gaseous products of the combustion process. Strong attenuation at a wavelength of 10.6 microm is found to be due largely to the carbonaceous aerosol. The absorption coefficient is typically ~500 km(-1) at 10 m from the source with a variable but often comparable total scattering coefficient. The extinction coefficient, normalized to the mass density of the aerosol in a unit volume of space, is found to be 1.2 m(2)-g(-1) with an estimated variance of 20%. luctuational spectra of the attenuation follow a form similar to turbulence spectra.

Propagation at 10 microm through smoke produced by atmospheric combustion of diesel fuel.

Absorption and extinction due to the smoke produced by the atmospheric combustion of diesel fuel have been measured using a CO2 laser spectrophone at a wavelength of 10.6 microm. The absorption coefficient normalized to the aerosol mass density is 0.84 +/-0.076 m2/g, and the total scattering coefficient (the difference between the extinction and absorption values) normalized in the same way is 0.15 +/- 0.014 m2/g. The largely fibrous aerosol was found to be 80% carbon, with most of the remainder consisting of hydrocarbons which are comparatively transparent at 10.6 microm and physically resemble the unburned fuel. The normalized coefficients of this study approximate those of diesel automobile effluents. This is not surprising since the aerosol composition and morphology appear to be similar.

Optoacoustic spectroscopy of C2H4 at the 9- and 10-microm C12O216 laser wavelengths.

Absorption coefficients have been measured for ethylene in the 9- and l0-microm range with a photoacoustic spectrophone. Pressure dependency in the 10P C(12)O(2)(16) range was studied for various concentrations of ethylene. Comparisons of the data with other measurements of both atmospheric and pressure-dependent absorption coefficients were also made, and a method for relating ethylene pressure-dependency data on absorption to molecular structure was examined. Typical discrepancies between up to six independent measurements of ethylene absorption were 38.1% at the 10-microm R(20) line, 4.4% at the 10-microm P(18) line, and 18.5% at the 10-microm P(26) laser line.

Absorption spectra of deuterated water at DF laser wavelengths.

Absorption coefficients for deuterated water have been measured at twenty-two deuterium fluoride (DF) laser wavelengths and presented for atmospheric conditions classified as midlatitude-summer (14.3 T water vapor, standard temperature, and pressure). The HDO vapor was produced from a liquid mixture of H(2)O and D(2)O. The proportions of the resulting equilibrium mixture involving these constituents and HDO were calculated using previously measured constants and produced strong HDO absorption at the 3.5-4.1-microm DF laser wavelengths relative to those of the H(2)O and D(2)O vapors. Predicted and measured pressure dependencies at constant mixing ratios are compared for several laser wavelengths having strong HDO absorption. Absorption coefficients are in fairly close agreement with those of the current Air Force Geophysical Laboratory line-by-line model for standard temperature and pressure conditions. At lower total pressures, the comparison is less satisfactory and suggests inaccurate line parameters in the predictive data base.

Experimentally determined relationship between extinction coefficients and liquid water content.

Simultaneous environmental chamber measurements have been made of 10.27-microm extinction coefficients and liquid water content of droplet distributions with sizes spanning those of light to heavy fogs. The measurements yield a linear relation that is nearly independent of droplet size distribution, in agreement with recent calculated results and predictions. Liquid water content varied from 0.01 to 3.3 g/m(3), and droplet size distributions with both single and bimodal differential extinction coefficient curves were included. The spectral variation of the extinction ceofficient between 9.2 and 10.8 microm was also measured. The results are in good agreement with the variation calculated for typical droplet size distributions.

Water vapor continuum absorption in the 3.5-4.0-microm region.

Measurements of water vapor continuum absorption in the 3.5-4.0-microm region are presented. The measurements were made with both long-path absorption cell and spectrophone systems. A deuterium fluoride grating tunable laser was the ir source. Measurements were made at 23 degrees C and 65 degrees C with 14.3 Torr and 65 Torr of water vapor, respectively, buffered to 760-Torr total pressure by an 80/20 mixture of N(2)/O(2). Both natural water and a special sample of deuterium depleted water (one-fiftieth the normal concentration) were used. The 65 degrees C results agree with previous measurements by other workers. The 23 degrees C results indicate a continuum absorption at this temperature about a factor of 2 larger than expected based on the extrapolation scheme and high-temperature data (>/=65 degrees C) of others.

Photoacoustic spectroscopy of NH(3) at the 9-microm and 10-microm (12)C(16)O(2) laser wavelengths.

A spectrophone and a CO(2) laser source were used to determine the absorption coefficients of NH(3) at seventy-seven laser lines in the 00 degrees 1-02 degrees 0 band at 9.4 microm and the 00 degrees 1-10 degrees 0 band at 10.4 microm. The NH(3) was buffered with N(2) to 1 atm at 295 K; its concentration ranged from 30 ppm to 200 ppm. The absorption coefficients and their probable errors are tabulated.