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The interaction of multiple injections in a diesel engine facilitates a complex interplay between freshly introduced fuel, previous combustion products, and overall combustion. To improve understanding of the relevant processes, high-speed Planar Laser-Induced Fluorescence (PLIF) with 355-nm excitation of formaldehyde and Polycyclic Aromatic Hydrocarbon (PAH) soot precursors is applied to multiple injections of n-dodecane from Engine Combustion Network Spray D, characterized by a converging 189-μm nozzle. High-speed schlieren imaging is applied simultaneously with 50-kHz PLIF excitation to visualize the spray structures, jet penetration, and ignition processes. For the first injection, formaldehyde (as an indicator of low-temperature chemistry) is first found in the jet periphery, after which it quickly propagates through the center of the jet, towards the jet head prior to high-temperature ignition. At second-stage ignition, downstream formaldehyde is consumed rapidly and upstream formaldehyde develops into a quasi-steady structure for as long as the momentum flux from the injector continues. Since the first injection in this work is relatively short, differences to a single long injection are readily observed, ultimately resulting in high-temperature combustion and PAH structures appearing farther upstream after the end of injection. For the second injection in this work, the first formaldehyde signal is significantly advanced because of the entrained high-temperature combustion products, and an obvious premixed burn event does not occur. The propensity for combustion recession after the end of the first injection changes significantly with ambient temperature, thereby affecting the level of interaction between the first- and second injection.

International audience; In a collaborative effort to identify key aspects of heavy-duty diesel injector behavior, the Engine Combustion Network (ECN) Spray C and Spray D injectors were characterized in three independent research laboratories using constant volume pre-burn vessels and a heated constant-pressure vessel. This work reports on experiments with nominally identical injectors used in different optically accessible combustion chambers, where one of the injectors was designed intentionally to promote cavitation. Optical diagnostic techniques specifically targeted liquid-and vapor-phase penetration, combustion indicators, and sooting behavior over a large range of ambient temperatures-from 850 K to 1100 K. Because the large-orifice injectors employed in this work result in flame lengths that extend well beyond the optical diagnostics' field-of-view, a novel method using a characteristic volume is proposed for quantitative comparison of soot under such conditions. Further, the viability of extrapolating these measurements downstream is considered. The results reported in this publication explain trends and unique characteristics of the two different injectors over a range of conditions and serve as calibration targets for numerical efforts within the ECN consortium and beyond. Building on agreement for experimental results from different institutions under inert conditions, apparent differences found in combustion indicators and sooting behavior are addressed and explained. Ignition delay and soot onset are correlated and the results demonstrate the sensitivity of soot formation to the major species of the ambient gas (i.e., carbon dioxide, water, and nitrogen in the pre-burn ambient versus nitrogen only in the constant pressure vessel) when holding ambient oxygen volume percent constant.

Large-Eddy Simulations (LES) of a gasoline spray, where the mixture was ignited rapidly during or after injection, were performed in comparison to a previous experimental study with quantitative flame motion and soot formation data [SAE 2020-01-0291] and an accompanying Reynolds-Averaged Navier–Stokes (RANS) simulation at the same conditions. The present study reveals major shortcomings in common RANS combustion modeling practices that are significantly improved using LES at the conditions of the study, specifically for the phenomenon of rapid ignition in the highly turbulent, stratified mixture. At different ignition timings, benchmarks for the study include spray mixing and evaporation, flame propagation after ignition, and soot formation in rich mixtures. A comparison of the simulations and the experiments showed that the LES with Dynamic Structure turbulence were able to capture correctly the liquid penetration length, and to some extent, spray collapse demonstrated in the experiments. For early and intermediate ignition timings, the LES showed excellent agreement to the measurements in terms of flame structure, extent of flame penetration, and heat-release rate. However, RANS simulations (employing the common G-equation or well-stirred reactor) showed much too rapid flame spread and heat release, with connections to the predicted turbulent kinetic energy. With confidence in the LES for predicted mixture and flame motion, the predicted soot formation/oxidation was also compared to the experiments. The soot location was well captured in the LES, but the soot mass was largely underestimated using the empirical Hiroyasu model. An analysis of the predicted fuel–air mixture was used to explain different flame propagation speeds and soot production tendencies when varying ignition timing.

Designers of direct-injection compression-ignition engines use a variety of strategies to improve the fuel/charge-gas mixture within the combustion chamber for increased efficiency and reduced pollutant emissions. Strategies include the use of high fuel-injection pressures, multiple injections, small injector orifices, flow swirl, long-ignition-delay conditions, and oxygenated fuels. This is the first journal publication on a new mixing-enhancement strategy for emissions reduction: ducted fuel injection. The concept involves injecting fuel along the axis of a small cylindrical duct within the combustion chamber, to enhance the mixture in the autoignition zone relative to a conventional free-spray configuration (i.e., a fuel spray that is not surrounded by a duct). The results described herein, from initial proof-of-concept experiments conducted in a constant-volume combustion vessel, show dramatically lower soot incandescence from ducted fuel injection than from free sprays over a range of charge-gas conditions that are representative of those in modern direct-injection compression-ignition engines.

Soot onset in n-dodecane sprays is investigated both experimentally, by means of high-speed imaging data from the Sandia spray combustion vessel, and numerically, using the conditional moment closu...

An n-dodecane spray flame (Spray A from Engine Combustion Network) was simulated using a δ function combustion model along with a dynamic structure large eddy simulation (LES) model to evaluate its performance at engine-relevant conditions and to understand the transient behavior of this turbulent flame. The liquid spray was treated with a traditional Lagrangian method and the gas-phase reaction was modeled using a δ function combustion model. A 103-species skeletal mechanism was used for the n-dodecane chemical kinetic model. Significantly different flame structures and ignition processes are observed for the LES compared to those of Reynolds-averaged Navier − Stokes (RANS) predictions. The LES data suggests that the first ignition initiates in a lean mixture and propagates to a rich mixture, and the main ignition happens in the rich mixture, preferably less than 0.14 in mixture fraction space. LES was observed to have multiple ignition spots in the mixing layer simultaneously while the main ignition initiates in a clearly asymmetric fashion. The temporal flame development also indicates the flame stabilization mechanism is auto-ignition controlled. Soot predictions by LES present much better agreement with experiments compared to RANS, both qualitatively and quantitatively. Multiple realizations for LES were performed to understand the realization to realization variation and to establish best practices for ensemble-averaging diesel spray flames. The relevance index analysis suggests that an average of 5 and 6 realizations can reach 99% of similarity to the target average of 16 realizations on the mixture fraction and temperature fields, respectively. However, more realizations are necessary for the hydroxide (OH) and soot mass fractions due to their high fluctuations.

Global sensitivity analysis was conducted on Spray A of the Engine Combustion Network’s (ECN) experimental conditions across different combustion vessels from different institutions. The main objective was to understand the influence of differences in boundary conditions on specific targets of interest. A list of experimental initial, boundary, and injection conditions with uncertainty ranges were identified for three different ambient conditions for these combustion vessels. Five targets including the liquid length, vapor penetration length, ignition delay, lift-off length, and soot mass in the domain were extracted from hundreds of 3D computational fluid dynamics (CFD) simulations by simultaneously perturbing all the uncertain variables. Each target was analyzed using a global sensitivity analysis (GSA) method and the relative importance of different variables towards specific targets was identified. The uncertainty in the fuel temperature was found to have a profound influence on the liquid length, however, the influence on vapor penetration length, ignition delay, and lift-off length, was rather subtle. Small uncertainties in the initial turbulence level and nozzle diameter was observed to have a significant influence on the vapor penetration. Variables sensitive to ignition delay also showed similar sensitivity to flame lift-off length. The soot mass in the domain was observed to have a closer correlation with the liquid length at least for higher ambient temperature conditions.

Key trace minerals greatly strengthen teeth The outer layers of teeth are made up of nanowires of enamel that are prone to decay. Gordon et al. analyzed the composition of tooth enamel from a variety of rodents at the nanometer scale (see the Perspective by Politi). In regular and pigmented enamel, which contain different trace elements at varying boundary regions, two intergranular phases—magnesium amorphous calcium phosphate or a mixed-phase iron oxide—control the rates of enamel demineralization. This suggests that there may be alternative options to fluoridation for strengthening teeth against decay. Science , this issue p. 746 ; see also p. 712

To evaluate the ocular penetration of ISV-304 (ketorolac tromethamine) formulated in DuraSite(®) or DuraSite(®) 2 compared to Acular LS(®) (0.4% ketorolac ophthalmic solution) in rabbits.The left eye of rabbits received a single topical instillation of either ISV-304 (0.2% and 0.4% ketorolac) in DuraSite, ISV-304 (0.2% and 0.4% ketorolac) in DuraSite 2, or Acular LS. At predetermined time points, aqueous humor (AH) levels of ketorolac were measured by HPLC-MS/MS, and Cmax, Tmax, and AUC0.25-24h were determined.The highest mean concentration of ketorolac was achieved in ISV-304 (0.4%) formulated in DuraSite 2 with a Cmax value of 1889 ± 884 ng/mL, compared to Cmax values for ISV-304 (0.4%) formulated in DuraSite (1212 ± 435 ng/mL) or Acular LS (275 ± 83 ng/mL). ISV-304 (0.2%) formulations also achieved higher AH Cmax values (801 ± 205 ng/mL and 1077 ± 415 ng/mL) compared to Acular LS. There was a significant increase in drug exposure in the ISV-304 (0.4%) formulated in DuraSite 2 or DuraSite formulations with AUC0.25-24h values 6836 ng/mL*h and 5684 ng/mL*h, respectively, compared to Acular LS with an AUC0.25-24h value of 1424 ng/mL*h. ISV-304 (0.2%) formulations also had high AUC0.25-24h values (3241 ng/mL*h and 4490 ng/mL*h), which were a 2.3-3.2-fold increase over the Acular LS AUC0.25-24h value.DuraSite and DuraSite 2 delivery systems markedly improved the ketorolac ocular pharmacokinetic parameters in rabbits. DuraSite formulations may lessen the side effects associated with topical nonsteroidal anti-inflammatory drug use by maintaining efficacy with a reduced dosing regimen and reduced active ingredient.

Based on recent research within optically accessible engines and combustion chambers, conceptual models for low-temperature combustion (LTC) diesel engines are proposed. To provide a reference to which the LTC conceptual models may be compared, an established conceptual model framework for conventional diesel combustion is first reviewed and updated. Then, based on multiple optical diagnostic observations and homogeneous reactor simulations using detailed chemical kinetic mechanisms, extensions to the existing conceptual model are proposed. The LTC conceptual models are not intended to describe all LTC strategies, but rather a common subset of low-load, single-injection, partially premixed compression ignition conditions that are diluted by exhaust-gas recirculation to oxygen concentrations in the range of 10–15%. The models describe the spray formation, vaporization, mixing, ignition, and pollutant formation and destruction mechanisms that are consistent with experimental observations and modeling predictions for LTC diesel engines. Two separate subcategories are offered for either heavy-duty, large-bore or for light-duty, small-bore engines. Relative to the existing conventional diesel conceptual model, the features of the LTC conceptual models include longer liquid-fuel penetration, an extended ignition delay that allows more premixing of fuel, a more distinct and temporally extended two-stage ignition, more spatially uniform second-stage ignition, reduced and altered soot formation regions, and increased overmixing leading to incomplete combustion.

For better understanding of soot formation and oxidation processes in a bio-diesel spray flame, morphology, microstructure and size of soot particles directly sampled in a spray flame fuelled with soy-methyl ester were investigated using high-resolution transmission electron microscope (HRTEM). The soot samples were taken at different axial locations in the spray flame, 40, 50 and 70 mm from the injector nozzle, which correspond to soot formation, peak, and oxidation zones, respectively. The bio-diesel spray flame was achieved in a constant volume combustion chamber under a diesel-like high pressure and temperature condition (6.7 MPa, 1000 K). Density, diameter of primary particles and radius of gyration of soot aggregates directly sampled onto the TEM grids in the flame reached a peak at 50 mm from the injector nozzle and was lower or smaller at 40 and 70mm.

The ignition, soot formation, and end of combustion transients of n-heptane and #2 diesel jets were investigated in an optically accessible constant-volume combustion vessel under high exhaust-gas recirculation (EGR) environments. A wide range of EGR levels were simulated by systematically decreasing the ambient oxygen concentration from 21 to 8 per cent, while holding other experimental conditions constant. Characteristics of the effect of EGR on the ignition transient include: development of a cool flame early after injection for all EGR levels, an increase in the premixed-burn (high-temperature combustion) ignition delay inversely proportional to ambient oxygen concentration, ([O2]−1), and lower apparent heat-release rates during the premixed-burn with increasing EGR. The timing of soot formation is strongly dependent upon EGR, and the time between ignition and the first soot formation increases with decreasing ambient oxygen concentration. Soot-forming fuel jets are shown to become soot-free at high-EGR conditions by reducing the injection duration to be less than the soot formation time, but longer than the ignition delay time (negative ignition dwell). While past studies show success in reducing soot formation when the injection duration is less than the ignition delay (positive ignition dwell), this result shows that high EGR can suppress soot formation even with negative ignition dwell, thereby permitting higher-load operation by using longer injection durations. At the end of injection, increasing EGR presents difficulties in completing combustion because of the lower ambient oxygen concentration. Despite eventually reaching the same pressure rise (i.e., combustion efficiency) more time is required for the higher EGR conditions to mix fuel with sufficient oxygen to complete combustion.

The purpose of this study was to compare the ocular pharmacokinetics of experimental solutions of bromfenac in DuraSite(®) to Xibrom™ (bromfenac ophthalmic solution) 0.09%.The bromfenac content was measured in the aqueous humor of 84 Dutch Belted rabbits after a single dose of either 0.045% or 0.09% bromfenac in DuraSite in the left eye and the commercial preparation in the right eye. The drug content in the aqueous humor was measured at 0.5, 1, 2, 4, 8, 12, and 24 h after instillation. In a separate multi-dose study, rabbits received one drop of the 0.09% experimental or commercial preparation, 3 times daily for 14 days. For both experiments the drug content in ocular tissues was analyzed using liquid chromatography atmospheric pressure ionization tandem mass spectrometry.In single-dose experiments, the concentration of bromfenac in the aqueous humor was higher with the experimental preparations than with the commercial solution. The area under the concentration-time curve of 0.045% and 0.09% bromfenac in DuraSite was ∼2 and 4-fold higher than that of commercial bromfenac ophthalmic solution, 0.09%. After multi-dose experiments, ocular tissue concentrations of bromfenac were ∼3 times higher for the experimental than for the commercial formulation.The study demonstrates that the DuraSite topical drug delivery system can deliver bromfenac to various ocular tissues and attain considerably higher concentrations than the commercially available eye drop formulation. The higher aqueous concentration sustained with these experimental formulations could broaden the utility of bromfenac and/or reduce the currently approved dosing frequency of this drug.

This paper presents soot processes of a blend of 23% m-xylene and 77% n-dodecane, which has been selected by several working groups as a surrogate for jet fuel. Fuel sprays were injected into high-temperature, high-pressure ambient conditions that are representative of practical engine combustion. Simultaneous laser extinction (KL) measurement and planar laser-induced incandescence imaging were performed to derive the in situ soot volume fraction. Also, soot particles were extracted from different positions within the reacting jet by means of a thermophoretic probe, and analyzed using transmission electron microscopy (TEM) to clarify the soot structure and its correlation with the measured soot volume fraction. The same measurements were repeated for the conventional jet fuel to understand the overall performance of the selected surrogate fuel. The soot volume fraction results show that, at fixed ambient conditions, the surrogate fuel produces more soot than the conventional jet fuel. The TEM images show that the soot aggregates are more agglomerated, which may not be easily eliminated by in-cylinder oxidation. The total number of primary particles and the mean primary particle size are higher for the surrogate fuel, consistent with the soot volume fraction trend. Considering that there is similar lift-off length between fuels, the differences in soot level and morphology are caused by molecular structure effects, such as a higher aromatic content. The quantitative soot database obtained from the present study offers data for the validation of soot kinetic models, particularly at high temperature and pressure conditions where little fundamental data exist.

Insufficiency fractures occur when physiological loads are applied to bone deficient in mechanical resistance. A better understanding of pelvic mechanics and the effect of bone density alterations could lead to improved diagnosis and treatment of insufficiency fractures. This study aimed to develop and validate a subject-specific three-dimensional (3D) finite element (FE) model of a pelvis, to analyse pelvic strains as a function of interior and cortical surface bone density, and to compare high strain regions with common insufficiency fracture sites. The FE model yielded strong agreement between experimental and model strains. By means of the response surface method, changes to cortical surface bone density using the FE model were found to have a 60 per cent greater influence compared with changes in interior bone density. A small interaction was also found to exist between surface and interior bone densities (< 3 per cent), and a non-linear effect of surface bone density on strain was observed. Areas with greater increases in average principal strains with reductions in density in the FE model corresponded to areas prone to insufficiency fracture. Owing to the influence of cortical surface bone density on strain, it may be considered a strong global (non-linear) indicator for insufficiency fracture risk.

Azithromycin is an azalide class of antibiotic with pharmacodynamics that have made it a valuable agent in the treatment of soft tissue infections. In ophthalmology, oral administration of azithromycin has been proven effective for the treatment of trachoma. However, topical formulations of azithromycin to treat ocular surface infections have been challenging to develop because of the drug's hydrophobicity and instability in aqueous solutions at pH levels that are comfortable in the eye. The design of a polycarbophil polymer-based delivery system for a topical formulation of azithromycin was evaluated for its ability to provide drug stability, comfort, and increased retention of the formulation in the eye.Formulations of 0.5% and 1.0% azithromycin were created in polycarbophil, a lightly cross-linked polyacrylic acid polymer that was adjusted to a viscosity, pH, and osmolality that are suitable for dispensing in the eye.The polycarbophil-based ophthalmic delivery system, DuraSite (InSite Vision, Alameda, CA), helps solubilize azithromycin and retard its degradation in aqueous solution. The formulation was stable at room temperature as well as 5 degrees C. Upon administration of a single drop of 1% azithromycin in DuraSite ophthalmic solution in rabbits' eyes, tear concentrations of azithromycin ranged from 87 to 288 microg/g and high concentrations were sustained for over a 24-h period.Azithromycin can be developed as an eyedrop in an aqueous ocular delivery system for the treatment of ocular surface infections. The ocular delivery system, DuraSite solubilizes azithromycin at a high concentration in an aqueous solution and protects it from degradation during manufacture and storage. The development of azithromycin in this delivery system enhances the antibiotic's usefulness in ophthalmology for the topical treatment of ocular surface bacterial infections and lid margin diseases.

Purpose: The pharmacokinetics of a 2% ocular solution of azithromycin in DuraSite was evaluated in rabbits to determine whether the PK/PD parameters support a once-a-day for three-day therapeutic regimen against bacterial conjunctivitis. Materials and Methods: Mean levels of azithromycin were determined in tears, bulbar conjunctiva, cornea, and plasma following a single drop of 2% azithromycin. The levels were determined by HPLC-MS. Results: Concentrations of azithromycin peaked at 30 minutes. At the end of 24 hours, ocular tissue concentrations exceeded the MIC breakpoint for the most common causative pathogens of bacterial conjunctivitis by at least 7-fold. Conclusion: The PK/PD profile of 2% azithromycin suggests efficacy against common causative bacteria with just one dose per day for three days.

The mechanisms affecting lift-off stabilization at diesel conditions were investigated by laser-igniting a diesel fuel jet upstream of its natural lift-off position. Single-nozzle fuel sprays penetrating into all optically accessible constant-volume chamber were ignited using laser-induced plasma formation both prior to natural autoignition or after a quasi-steady lift-off length was established. Fuel sprays ignited readily, with reaction kernels growing ill connected regions. After laser-ignition, the lift-off persists upstream of the natural lift-off position for a Substantial period of time indicating that upstream ignition has a strong influence on lift-off stabilization. While not discounting the role of flame propagation downstream of the ignition event, these results show that upstream ignition sites call start a chain of events that effectively controls lift-off. Lift-off eventually returns to its natural position, but only after injection times that are too long for practical engines. The time of return to the natural position depends upon the relative distance of the laser-ignition site to the natural lift-off length. A theory for fuel jet lift-off stabilization based oil flame propagation into pure fuel-ambient reactant streams fails to predict the long upstream stabilization away from the natural lift-off length because turbulent velocities are higher ill upstream regions of the fuel jet. Likewise, upstream lift-off stabilization by autoignition Of pure reactants (no mixing with combustion products) fails because of cooler temperatures and shorter residence times. A potential mechanism explaining the transient lift-off response to laser-ignition is offered based on turbulent mixing with high-temperature combustion products found at the jet edges. Published by Elsevier Inc. on behalf of The Combustion Institute.

To analyze the effect of azithromycin 1% ophthalmic solution in DuraSite (InSite Vision, Inc, Alameda, California, USA) on bacterial conjunctivitis.Prospective, randomized, vehicle-controlled, parallel-group, double-masked multicenter clinical study.Eligible male or female participants with a clinical diagnosis of acute bacterial conjunctivitis were randomized to either 1% azithromycin in DuraSite or vehicle for five days. Infected eyes were dosed twice daily on days 1 and 2 and once daily on days 3 through 5. Conjunctival cultures were obtained at baseline, visit 2 (day 3 or 4), and visit 3 (day 6 or 7). The primary end point was clinical resolution of signs and symptoms (rating of zero on ocular discharge, bulbar and palpebral injection) at visit 3. Efficacy measures were clinical resolution and bacterial eradication as evaluated in the per-protocol population. Safety was assessed by adverse events, slit-lamp findings, and ophthalmoscopy.Two hundred and seventy-nine participants (n = 130, 1% azithromycin in DuraSite; n = 149, vehicle), age one to 96 years, were evaluated for efficacy. Clinical resolution with azithromycin ophthalmic solution was statistically significant compared with that of vehicle (P = .030) at visit 3. Bacterial eradication rates with azithromycin ophthalmic solution reached 88.5% at visit 3 (P.001) and included some pathogens resistant to azithromycin in vitro. Overall, adverse event rates were similar in both treatment groups.Azithromycin 1% ophthalmic solution in DuraSite showed statistically significant differences in clinical resolution and bacterial eradication rates when compared with vehicle. Because it was well tolerated in this population, it may be a viable treatment option for children and adults with bacterial conjunctivitis.

Radiological imaging is essential to the appropriate management of patients with bone metastasis; however, there have been no widely accepted guidelines as to the optimal method for quantifying the potential impact of skeletal lesions or to evaluate response to treatment. The current inability to rapidly quantify the response of bone metastases excludes patients with cancer and bone disease from participating in clinical trials of many new treatments as these studies frequently require patients with so-called measurable disease. Computed tomography (CT) can provide excellent skeletal detail with a sensitivity for the diagnosis of bone metastases. The purpose of this study was to establish an objective method to quantitatively characterize disease in the bony spine using CT-based segmentations. It was hypothesized that histogram analysis of CT vertebral density distributions would enable standardized segmentation of tumor tissue and consequently allow quantification of disease in the metastatic spine. Thirty two healthy vertebral CT scans were first studied to establish a baseline characterization. The histograms of the trabecular centrums were found to be Gaussian distributions (average root-mean-square difference=30 voxel counts), as expected for a uniform material. Intrapatient vertebral level similarity was also observed as the means were not significantly different (p>0.8). Thus, a patient-specific healthymore » vertebral body histogram is able to characterize healthy trabecular bone throughout that individual's thoracolumbar spine. Eleven metastatically involved vertebrae were analyzed to determine the characteristics of the lytic and blastic bone voxels relative to the healthy bone. Lytic and blastic tumors were segmented as connected areas with voxel intensities between specified thresholds. The tested thresholds were {mu}-1.0{sigma}, {mu}-1.5{sigma}, and {mu}-2.0{sigma}, for lytic and {mu}+2.0{sigma}, {mu}+3.0{sigma}, and {mu}+3.5{sigma} for blastic tissue where {mu} and {sigma} were taken from the Gaussian characterization of a healthy level within the same patient. The ideal lytic and blastic segmentation thresholds were determined to be {mu}-{sigma} and {mu}+2{sigma}, respectively. Using the optimized thresholds to segment tumor tissue, a quantitative characterization of disease is possible to calculate tumor volumes, disease severity, and temporal progression or treatment effect. Our proposed histogram-based method for characterizing spinal metastases shows great potential in extending the quantitative capacity of CT-based radiographic evaluations.« less

Quantitative assessment of metastatic disease in bone is often considered immeasurable and, as such, patients with skeletal metastases are often excluded from clinical trials. In order to effectively quantify the impact of metastatic tumor involvement in the spine, accurate segmentation of the vertebra is required. Manual segmentation can be accurate but involves extensive and time-consuming user interaction. Potential solutions to automating segmentation of metastatically involved vertebrae are demons deformable image registration and level set methods. The purpose of this study was to develop a semiautomated method to accurately segment tumor-bearing vertebrae using the aforementioned techniques. By maintaining morphology of an atlas, the demons-level set composite algorithm was able to accurately differentiate between trans-cortical tumors and surrounding soft tissue of identical intensity. The algorithm successfully segmented both the vertebral body and trabecular centrum of tumor-involved and healthy vertebrae. This work validates our approach as equivalent in accuracy to an experienced user.

The effect of exhaust-gas recirculation (EGR) on the equivalence ratio of premixed-burn mixture in diesel combustion was investigated experimentally. The ambient oxygen concentration was systematically decreased from 21% to 10% in a constant-volume combustion vessel to simulate EGR effects in engines. Pressure measurements and time-resolved imaging of high-temperature chemiluminescence were used to characterize the temporal and spatial ignition and premixed burn characteristics of n-heptane diesel jets. With increasing EGR, ignition delay increases and the location of premixed burn occurs further downstream from the nozzle. Subsequent to first ignition, high temperature reactions stabilize at a quasi-steady lift-off length, showing that lift-off is a bounding parameter for determining premixed-burn region. The equivalence ratio of the fuel–ambient mixture in the premixed-burn region was measured using planar laser Rayleigh scattering. Fuel–oxygen mass distribution functions show that more mass is mixed into the premixed-burn region with increasing EGR, but the equivalence ratio of this mixture is the same. The study shows that an increasing ignition delay with increasing EGR does not necessarily decrease the equivalence ratio as would be desired for reducing soot formation in low-temperature combustion engines. However, measures to improve fuel–ambient mixing, such as shortened injection durations coupled to long ignition delay, could decrease equivalence ratio.

The two-stage Lagrangian (TSL) reacting-jet model of Broadwell and Lutz is applied to n-heptane fuel jets to understand soot formation at diesel engine operating conditions. The model employs a diffusion-flame reactor and homogeneous core reactor with jet entrainment rates determined by empirical correlations. Detailed chemical kinetics, consisting of 696 species and 3224 reactions, are used for predictions of n-heptane oxidation and soot precursor formation up to seven-ring polycyclic aromatic hydrocarbons. Boundary conditions are based on realistic diesel operating conditions, mixing rates, and flame lift-off lengths. TSL soot precursor simulations are compared with closed-reactor (Senkin) predictions over a range of temperatures and equivalence ratios. Results show that the equivalence ratio-temperature region of soot precursor formation varies from the closed-reactor predictions and depends upon parameters such as ambient oxygen concentration, injection pressure, nozzle orifice size, and flame lift-off. The lack of a unique equivalence ratio-temperature region for soot precursor formation implies that the soot formation process depends upon the equivalence ratio-temperature path followed during jet mixing, and the residence time along the path.

Soot formation in the region downstream of the lift-off length of diesel fuel jets was investigated in an optically accessible constant-volume combustion vessel under quiescent-type diesel engine conditions. Planar laser-induced incandescence and line-of-sight laser extinction were used to determine the location of the first soot formation during mixing-controlled combustion. OH chemiluminescence imaging was used to determine the location of high-heat-release reactions relative to the soot-forming region. The primary parameters varied in the experiments were the sooting propensity of the fuel and the amount of fuel-air premixing that occurs upstream of the lift-off length. The fuels considered in order of increasing sooting propensity were: an oxygenated fuel blend (T70), a blend of diesel cetane-number reference fuels (CN80), and a #2 diesel fuel (D2). Fuel-air mixing upstream of the lift-off length was varied by changing ambient gas and injector conditions, which varied either the lift-off length or the air entrainment rate into the fuel jet relative to the fuel injection rate. Results show that soot formation starts at a finite distance downstream of the lift-off length and that the spatial location of soot formation depends on the fuel type and operating conditions. The distance from the lift-off length to the location of the first soot formation increases as the fuel sooting propensity decreases (i.e. in the order D2 < CN80 < T70). At the baseline operating conditions, the most upstream soot formation occurs at the edges of the jet for D2 and CN80, while for T70 the soot formation is confined to the jet central region. When conditions are varied to produce enhanced fuel-air mixing upstream of the lift-off length in D2 fuel jets, the initial soot formation shifts towards the fuel jet centre and eventually no soot is formed. For all experimental conditions, the observed location of soot formation relative to the heat-release location (lift-off) suggests that soot formation occurs in a mixture of combustion products originating from partially premixed reactions and a diffusion flame. The results also imply that soot precursor formation rates depend strongly on fuel type in the region between the lift-off length and the first soot formation.

Measurements of soot distributions in fuel jets injected into high-temperature, high-pressure diesel-like operating conditions were made in an optically accessible constant-volume combustion vessel. A laser-extinction technique was used to make quantitative measurements of path-length-averaged soot volume fraction. Flame luminosity and planar laser-induced incandescence imaging were used to visualize the sooting region of the fuel jet. Flame lift-off lengths were also measured and used in the interpretation and analysis of the soot measurements. Fuel was injected with a common-rail diesel fuel injector equipped with a single 100-μm-diameter orifice. The fuel used was #2 diesel fuel. The matrix of experimental conditions included ambient gas temperatures from 850 to 1300 K, ambient gas densities from 7.3 to 30.0 kg/m3, and injection pressures from 43 to 184 MPa. The results show that peak soot level in a fuel jet increases with increasing ambient gas temperature, with the increase scaling linearly with temperature. However, near the tip of the flame, the soot levels decrease with increasing ambient temperature, indicating significantly higher soot oxidation rates in the flame-tip region at higher temperatures. The results also show that the peak soot level in a fuel jet increases with increasing ambient gas density and decreasing injection pressure. The increase with increasing ambient density is nonlinear with respect to density. The increase with decreasing injection pressure is linear with decreasing injection velocity (or the square root of the pressure drop across the injector orifice). Overall, the trends observed in diesel fuel jet soot closely correlate with the cross-sectional average equivalence ratio at the lift-off length, with soot levels decreasing as the equivalence ratio decreases (i.e., as more air entrainment and mixing of fuel and air occur upstream of the lift-off length).

As more techniques sensitive to the effects of poor effort are validated, clinicians are faced with the choice of which techniques to use and what to do in the case of discrepancies. We compared th...

SUMMARY The MMPI-2 is one of the most widely used instruments in forensic neuropsychology. Unlike most tests, it has the advantage of containing validity scales that assist the examiner in determining the level of cooperation of the examinee. Scales that provide information for evaluating the validity of an MMPI-2 profile include VRIN, TRIN, L, F, K, F -K, FB, F(p), FBS (Fake Bad Scale), Total Obvious -Subtle, Ds, Dsr, and Ego Strength. This article discusses research available when considering the applicability of these procedures in the context of challenges to their scientific reliability and validity in legal proceedings, according to the standards set forth in Daubert v. Merrell Dow Pharmaceuticals, Inc.

SUMMARY The Computerized Assessment of Response Bias (CARB) is a forced-choice digit recognition test designed to detect suboptimal performance during a psychological or neuropsychological evaluation. First developed in 1992, CARB has incorporated a number of refinements such as early termination for excellent early performance and analysis of response times and patterns. Patients with moderate or severe brain injury, or neurological disease, easily pass CARB. These groups provide primary validation for the test, along with more recent analogue malingering studies. CARB is sensitive to poor effort or suboptimal performance in patients with a wide variety of diagnoses, including outpatients with mild traumatic brain injuries, pain disorders, fibromyalgia, and depression. When used properly, CARB will likely hold up under Daubert challenges due to its specific focus and purpose, and extensive validation research.

The Word Memory Test (WMT; Green, Allen, & Astner, 1996) contains measures that are very sensitive to exaggeration or poor effort but insensitive to all but the most extreme forms of cognitive impairment. The WMT is unique among symptom validity tests because of its extensive validation in clinical forensic settings, rather than relying on simulation research with healthy volunteers. Effort measured by the WMT predicted 50% of the variance in a total of 30,736 neuropsy-chological test results from 904 consecutive patients involved in com-pensation claims. In group data, WMT-measured effort was sufficient to eliminate or reverse major effects, such as the presence of greater impairment in people with severe versus mild head injuries. The removal of invalid data from people failing the WMT was found to make a major difference to the conclusions of several studies. Properly interpreted, the WMT will meet Daubert challenges.

The structure of a reacting hydrocarbon-air two-stream planar mixing layer was investigated experimentally with non-premixed reactants under pressurized conditions. Propane and dimethyl ether (DME) diluted with argon or nitrogen was used as the fuel stream while heated air was used as the oxidizer. Experiments were performed at a range of Reynolds numbers in both the pre- and post-mixing transition portions of the mixing layer under conditions where the lean reactant (air) was placed in either the high-speed (AHS) or low-speed stream (FHS). The reacting mixing layer was visualized using a combined OH LIF/soot LII technique, wherein the reaction zone and the region of parent fuel entrainment and decomposition were simultaneously imaged. In both AHS and FHS cases at all Reynolds numbers examined, the mixing layer consisted of two regions: a high temperature reaction zone with a laminar appearance found on the oxidizer side of the mixing layer and an ‘internal’ mixing layer in which products mixed with pyrolized fuel in a manner reminiscent of a two-stream non-reacting mixing layer. The location and dynamics of the soot formed within the mixing layer were closely related to the mixing behavior of the large-scale structures. The regions of highest soot volume fraction were found in low temperature regions near the location of raw fuel entrainment. There was no significant broadening of the high-temperature reaction zone or increase in flame area under turbulent conditions due to the lack of dilution of the freestream conditions, unlike previous observations in jet flames. Changes in the inlet streams which affected chemistry did not appear to cause significant changes in the overall mixing layer structure shown in the OH/LII images. However, finite-chemistry effects were discernable with temperature measurements and indicated that reduced product formation was observed with reductions in a characteristic Damkohler number, Da . The point of flame lift-off was shown to occur at Da

This chart review examined the effects of effort on neuropsychological assessment and test performance patterns among genuine and exaggerating patients, with and without neurological findings, as aids to diagnosing symptom exaggeration. The sample consisted of 561 consecutive patients involved in compensation claims. With a flexible neuropsychological test (NPT) battery, the claims were assessed over 2 days. The sample included 303 patients evaluated for traumatic brain injury, 55 patients with neurological disease, and 203 patients assessed for other conditions (eg, depression or chronic pain). An average of 38 ability measures per patient were used to generate an overall NPT domain score. Composite scores were also computed for symptom validity tests, self-report measures of psychiatric symptoms, and memory complaint inventory. Seven NPT cognitive subdomain scores were multiply regressed onto the symptom validity test composite, accounting for 45% of its total variance. Patients were also assigned to Genuine or Exaggerator groups based on symptom validity test performance. The NPT for Exaggerating patients averaged 1.43 standard deviations below that of Genuine patients, suggesting that NPT scores for most Exaggerating patients are underestimates of their true ability. Factor analysis results differed between these groups. As a result, clinicians might avoid falsely identifying genuine patients as exaggerating by incorporating their self-reports of psychiatric symptoms and memory complaints into the diagnostic process.