Is the use of antibiotic-impregnated external ventricular drainage beneficial in the management of iatrogenic ventriculitis?

Profound evidence substantiates significantly reduced risk of catheter-related infections with prophylactic use of rifampin- and clindamycin-impregnated silicone catheters (Bactiseal(®), Codman Johnson & Johnson, Raynham, MA, USA) for external ventricular drainage (EVD). However, whether Bactiseal(®)-EVD (B-EVD) influences the treatment of EVD-related ventriculitis remains controversial.

Integration of external and internal dosimetry in Switzerland

Individual monitoring regulations in Switzerland are based on the ICRP60 recommendations. The annual limit of 20 mSv for the effective dose applies to the sum of external and internal radiation. External radiation is monitored monthly or quarterly with TLD, DIS or CR-39 dosemeters by 10 approved external dosimetry services and reported as H(p)(10) and H(p)(0.07). Internal monitoring is done in two steps. At the workplace, simple screening measurements are done frequently in order to recognise a possible incorporation. If a nuclide dependent activity threshold is exceeded then one of the seven approved dosimetry services for internal radiation does an incorporation measurement to assess the committed effective dose E(50). The dosimetry services report all the measured or assessed dose values to the employer and to the National Dose Registry. The employer records the annually accumulated dose values into the individual dose certificate of the occupationally exposed person, both the external dose H(p)(10) and the internal dose E(50) as well as the total effective dose E = H(p)(10)+E(50). Based on the national dose registry an annual report on the dosimetry in Switzerland is published which contains the statistics for the total effective dose, as well as separate statistics for external and internal exposure.

Effect of external electric field on hydrogen adsorption over activated carbon separated by dielectric materials

Energy crisis and worldwide environmental problem make hydrogen a prospective energy carrier. However, storage and transportation of hydrogen in large quantities at small volume is currently not practical. Lots of materials and devices have been developed for storage hydrogen, but to today none is able to meet the DOE targets. Activated carbon has been found to be a good hydrogen adsorbent due to its high surface area. However, the weak van der Waals force between hydrogen and the adsorbent has limited the adsorption capacity. Previous studies have found that enhanced adsorption can be obtained with applied electric field. Stronger interaction between the polarized hydrogen and the charged sorbents under high voltage is considered as the reason. This study was initiated to investigate if the adsorption can be further enhanced when the activated carbon particles are separated with a dielectric coating. Dielectric TiO2 nanoparticles were first utilized. Hydrogen adsorption measurements on the TiO2-coated carbon materials, with or without an external electric field, were made. The results showed that the adsorption capacity enhancement increased with the increasing amount of TiO2 nanoparticles with an applied electric field. Since the hydrogen adsorption capacity on TiO2 particles is very low and there is no hydrogen adsorption enhancement on TiO2 particles alone when electric field is applied, the effect of dielectric coating is demonstrated. Another set of experiments investigated the behavior of hydrogen adsorption over TiO2-coated activated carbon under various electric potentials. The results revealed that the hydrogen adsorption first increased and then decreased with the increase of electric field. The improved storage was due to a stronger interaction between charged carbon surface and polarized hydrogen molecule caused by field induced polarization of TiO2 coating. When the electric field was sufficient to cause considerable ionization of hydrogen, the decrease of hydrogen adsorption occurred. The current leak detected at 3000 V was a sign of ionization of hydrogen. Experiments were also carried out to examine the hydrogen adsorption performances over activated carbon separated by other dielectric materials, MgO, ZnO and BaTiO3, respectively. For the samples partitioned with MgO and ZnO, the measurements with and without an electric field indicated negligible differences. Electric field enhanced adsorption has been observed on the activated carbon separated with BaTiO3, a material with unusually high dielectric constant. Corresponding computational calculations using Density Functional Theory have been performed on hydrogen interaction with charged TiO2 molecule as well as TiO2 molecule, coronene and TiO2-doped coronene in the presence of an electric field. The simulated results were consistent with the observations from experiments, further confirming the proposed hypotheses.

Lateral external fixation: a new surgical technique for displaced unreducible supracondylar humeral fractures in children

BACKGROUND: Percutaneous Kirschner wire fixation represents the classic treatment for displaced supracondylar humeral fractures in childhood. This type of treatment first requires satisfactory reduction of the fracture. Failure to achieve a satisfactory reduction or inadequate stabilization can result in instability of the fracture fragments, which can result in either an unsatisfactory cosmetic or functional outcome. In our experience, these problems can be overcome with the use of a small lateral external fixator. METHODS: Between 1999 and 2005, thirty-one of 170 Gartland type-III supracondylar humeral fractures were treated with a lateral external fixator. The outcome of treatment was analyzed with regard to limb alignment, elbow movement, cosmetic appearance, and patient satisfaction. RESULTS: In twenty-eight of the thirty-one patients, a satisfactory reduction was achieved with closed methods. All children except one had a normal or good range of movement. The cosmetic result was excellent in all cases. All of the children and their parents stated that they would choose this treatment again. CONCLUSIONS: The use of a small lateral external fixator seems to be a safe alternative for the treatment of displaced supracondylar fractures of the humerus when a closed reduction appears to be unattainable by means of manipulation alone or when sufficient stability is not achieved with standard methods of Kirschner wire fixation.

Effects of combustion-derived ultrafine particles and manufactured nanoparticles on heart cells in vitro

Evidence from epidemiological studies indicates that acute exposure to airborne pollutants is associated with an increased risk of morbidity and mortality attributed to cardiovascular diseases. The present study investigated the effects of combustion-derived ultrafine particles (diesel exhaust particles) as well as engineered nanoparticles (titanium dioxide and single-walled carbon nanotubes) on impulse conduction characteristics, myofibrillar structure and the formation of reactive oxygen species in patterned growth strands of neonatal rat ventricular cardiomyocytes in vitro. Diesel exhaust particles as well as titanium dioxide nanoparticles showed the most pronounced effects. We observed a dose-dependent change in heart cell function, an increase in reactive oxygen species and, for titanium dioxide, we also found a less organized myofibrillar structure. The mildest effects were observed for single-walled carbon nanotubes, for which no clear dose-dependent alterations of theta and dV/dt(max) could be determined. In addition, there was no increase in oxidative stress and no change in the myofibrillar structure. These results suggest that diesel exhaust as well as titanium dioxide particles and to a lesser extent also single-walled carbon nanotubes can directly induce cardiac cell damage and can affect the function of the cells.

Impact of E22 on two-stroke and four-stroke snowmobiles

A push to reduce dependency on foreign energy and increase the use of renewable energy has many gas stations pumping ethanol blended fuels. Recreational engines typically have less complex fuel management systems than that of the automotive sector. This prevents the engine from being able to adapt to different ethanol concentrations. Using ethanol blended fuels in recreational engines raises several consumer concerns. Engine performance and emissions are both affected by ethanol blended fuels. This research focused on assessing the impact of E22 on two-stroke and four-stroke snowmobiles. Three snowmobiles were used for this study. A 2009 Arctic Cat Z1 Turbo with a closed-loop fuel injection system, a 2009 Yamaha Apex with an open-loop fuel injection system and a 2010 Polaris Rush with an open-loop fuel injection system were used to determine the impact of E22 on snowmobile engines. A five mode emissions test was conducted on each of the snowmobiles with E0 and E22 to determine the impact of the E22 fuel. All of the snowmobiles were left in stock form to assess the effect of E22 on snowmobiles currently on the trail. Brake specific emissions of the snowmobiles running on E22 were compared to that of the E0 fuel. Engine parameters such as exhaust gas temperature, fuel flow, and relative air to fuel ratio (λ) were also compared on all three snowmobiles. Combustion data using an AVL combustion analysis system was taken on the Polaris Rush. This was done to compare in-cylinder pressures, combustion duration, and location of 50% mass fraction burn. E22 decreased total hydrocarbons and carbon monoxide for all of the snowmobiles and increased carbon dioxide. Peak power increased for the closed-loop fuel injected Arctic Cat. A smaller increase of peak power was observed for the Polaris due to a partial ability of the fuel management system to adapt to ethanol. A decrease in peak power was observed for the open-loop fuel injected Yamaha.

Dynamic modeling of active regeneration in catalyzed and non-catalyzed diesel particulate filters

Particulate matter (PM) emissions standards set by the US Environmental Protection Agency (EPA) have become increasingly stringent over the years. The EPA regulation for PM in heavy duty diesel engines has been reduced to 0.01 g/bhp-hr for the year 2010. Heavy duty diesel engines make use of an aftertreatment filtration device, the Diesel Particulate Filter (DPF). DPFs are highly efficient in filtering PM (known as soot) and are an integral part of 2010 heavy duty diesel aftertreatment system. PM is accumulated in the DPF as the exhaust gas flows through it. This PM needs to be removed by oxidation periodically for the efficient functioning of the filter. This oxidation process is also known as regeneration. There are 2 types of regeneration processes, namely active regeneration (oxidation of PM by external means) and passive oxidation (oxidation of PM by internal means). Active regeneration occurs typically in high temperature regions, about 500 - 600 °C, which is much higher than normal diesel exhaust temperatures. Thus, the exhaust temperature has to be raised with the help of external devices like a Diesel Oxidation Catalyst (DOC) or a fuel burner. The O2 oxidizes PM producing CO2 as oxidation product. In passive oxidation, one way of regeneration is by the use of NO2. NO2 oxidizes the PM producing NO and CO2 as oxidation products. The passive oxidation process occurs at lower temperatures (200 - 400 °C) in comparison to the active regeneration temperatures. Generally, DPF substrate walls are washcoated with catalyst material to speed up the rate of PM oxidation. The catalyst washcoat is observed to increase the rate of PM oxidation. The goal of this research is to develop a simple mathematical model to simulate the PM depletion during the active regeneration process in a DPF (catalyzed and non-catalyzed). A simple, zero-dimensional kinetic model was developed in MATLAB. Experimental data required for calibration was obtained by active regeneration experiments performed on PM loaded mini DPFs in an automated flow reactor. The DPFs were loaded with PM from the exhaust of a commercial heavy duty diesel engine. The model was calibrated to the data obtained from active regeneration experiments. Numerical gradient based optimization techniques were used to estimate the kinetic parameters of the model.

External auditory canal cholesteatoma: reassessment of and amendments to its categorization, pathogenesis, and treatment in 34 patients

OBJECTIVE: External auditory canal cholesteatoma (EACC) is a rarity. Although there have been numerous case reports, there are only few systematic analyses of case series, and the pathogenesis of idiopathic EACC remains enigmatic. STUDY DESIGN: In a tertiary referral center for a population of 1.5 million inhabitants, 34 patients with 35 EACC (13 idiopathic [1 bilateral] and 22 secondary) who were treated between 1994 and 2006 were included in the study. RESULTS: EACC cardinal symptoms were longstanding otorrhea (65%) and dull otalgia (12%). Focal bone destruction in the external auditory canal with retained squamous debris and an intact tympanic membrane were characteristic. Only 27% of the patients showed conductive hearing loss exceeding 20 dB. Patients with idiopathic EACC had lesions typically located on the floor of the external auditory canal and were older, and the mean smoking intensity was also greater (p < 0.05) compared with patients with secondary EACC. The secondary lesions were assigned to categories (poststenotic [n = 6], postoperative [n = 6], and posttraumatic EACC [n = 4]) and rare categories (radiogenic [n = 2], postinflammatory [n = 1], and postobstructive EACC [n = 1]). In addition, we describe 2 patients with EACC secondary to the complete remission of a Langerhans cell histiocytosis of the external auditory canal. Thirty of 34 patients were treated surgically and became all free of recurrence, even after extensive disease. DISCUSSION: For the development of idiopathic EACC, repeated microtrauma (e.g., microtrauma resulting from cotton-tipped applicator abuse or from hearing aids) and diminished microcirculation (e.g., from smoking) might be risk factors. A location other than in the inferior portion of the external auditory canal indicates a secondary form of the disease, as in the case of 2 patients with atypically located EACC after years of complete remission of Langerhans cell histiocytosis, which we consider as a new posttumorous category and specific late complication of this rare disease.

Computational study of internal and external condensing flows and experimental synthesis to investigate their attainability and stability in ground-based and space-based environments

This doctoral thesis presents the computational work and synthesis with experiments for internal (tube and channel geometries) as well as external (flow of a pure vapor over a horizontal plate) condensing flows. The computational work obtains accurate numerical simulations of the full two dimensional governing equations for steady and unsteady condensing flows in gravity/0g environments. This doctoral work investigates flow features, flow regimes, attainability issues, stability issues, and responses to boundary fluctuations for condensing flows in different flow situations. This research finds new features of unsteady solutions of condensing flows; reveals interesting differences in gravity and shear driven situations; and discovers novel boundary condition sensitivities of shear driven internal condensing flows. Synthesis of computational and experimental results presented here for gravity driven in-tube flows lays framework for the future two-phase component analysis in any thermal system. It is shown for both gravity and shear driven internal condensing flows that steady governing equations have unique solutions for given inlet pressure, given inlet vapor mass flow rate, and fixed cooling method for condensing surface. But unsteady equations of shear driven internal condensing flows can yield different “quasi-steady” solutions based on different specifications of exit pressure (equivalently exit mass flow rate) concurrent to the inlet pressure specification. This thesis presents a novel categorization of internal condensing flows based on their sensitivity to concurrently applied boundary (inlet and exit) conditions. The computational investigations of an external shear driven flow of vapor condensing over a horizontal plate show limits of applicability of the analytical solution. Simulations for this external condensing flow discuss its stability issues and throw light on flow regime transitions because of ever-present bottom wall vibrations. It is identified that laminar to turbulent transition for these flows can get affected by ever present bottom wall vibrations. Detailed investigations of dynamic stability analysis of this shear driven external condensing flow result in the introduction of a new variable, which characterizes the ratio of strength of the underlying stabilizing attractor to that of destabilizing vibrations. Besides development of CFD tools and computational algorithms, direct application of research done for this thesis is in effective prediction and design of two-phase components in thermal systems used in different applications. Some of the important internal condensing flow results about sensitivities to boundary fluctuations are also expected to be applicable to flow boiling phenomenon. Novel flow sensitivities discovered through this research, if employed effectively after system level analysis, will result in the development of better control strategies in ground and space based two-phase thermal systems.

EFFECT OF ELECTRICAL DISCHARGE PATTERN ON SPARK IGNITED FLAME KERNEL DEVELOPMENT

Fuel-lean combustion and exhaust gas recirculation (EGR) in spark ignition engines improve engine efficiency and reduce emission. However, flame initiation becomes more difficult in lean and dilute fuel-air mixture with traditional spark discharge. This research proposal will first provide an intensive review on topics related to spark ignition including properties of electrical discharge, flame kernel behavior and spark ignition modeling and simulation. Focus will be laid on electrical discharge pattern effect as it is showing prospect in extending ignition limits in SI engines. An experimental setup has been built with an optically accessible constant volume combustion vessel. Multiple imaging techniques as well as spectroscopy will be applied. By varying spark discharge patterns, preliminary test results are available on consequent flame kernel development. In addition to experimental investigation of spark plasma and flame kernel development, spark ignition modeling with detailed description of plasma channel is also proposed for this study.

Spray characterization under flash boiling conditions of a DI multi-hole injector at high injection pressures in a combustion vessel

Spray characterization under flash boiling conditions was investigated utilizing a symmetric multi-hole injector applicable to the gasoline direct injection (GDI) engine. Tests were performed in a constant volume combustion vessel using a high-speed schlieren and Mie scattering imaging systems. Four fuels including n-heptane, 100% ethanol, pure ethanol blended with 15% iso-octane by volume, and test grade E85 were considered in the study. Experimental conditions included various ambient pressure, fuel temperature, and fuel injection pressure. Visualization of the vaporizing spray development was acquired by utilizing schlieren and laser-based Mie scattering techniques. Time evolved spray tip penetration, spray angle, and the ratio of the vapor to liquid region were analyzed by utilizing digital image processing techniques in MATLAB. This research outlines spray characteristics at flash boiling and non-flash boiling conditions. At flash boiling conditions it was observed that individual plumes merge together, leading to significant contraction in spray angle as compared to non-flash boiling conditions. The results indicate that at flash boiling conditions, spray formation and expansion of vapor region is dependent on momentum exchange offered by the ambient gas. A relation between momentum exchange and liquid spray angle formed was also observed.

DEVELOPMENT OF A PREDICTIVE COMBUSTION MODEL OF A SPARK IGNITED ENGINE WITH GASOLINE DIRECT INJECTION, VARIABLE VALVE TIMING, DURATION AND LIFT TECHNOLOGIES

There is a need by engine manufactures for computationally efficient and accurate predictive combustion modeling tools for integration in engine simulation software for the assessment of combustion system hardware designs and early development of engine calibrations. This thesis discusses the process for the development and validation of a combustion modeling tool for Gasoline Direct Injected Spark Ignited Engine with variable valve timing, lift and duration valvetrain hardware from experimental data. Data was correlated and regressed from accepted methods for calculating the turbulent flow and flame propagation characteristics for an internal combustion engine. A non-linear regression modeling method was utilized to develop a combustion model to determine the fuel mass burn rate at multiple points during the combustion process. The computational fluid dynamic software Converge ©, was used to simulate and correlate the 3-D combustion system, port and piston geometry to the turbulent flow development within the cylinder to properly predict the experimental data turbulent flow parameters through the intake, compression and expansion processes. The engine simulation software GT-Power © is then used to determine the 1-D flow characteristics of the engine hardware being tested to correlate the regressed combustion modeling tool to experimental data to determine accuracy. The results of the combustion modeling tool show accurate trends capturing the combustion sensitivities to turbulent flow, thermodynamic and internal residual effects with changes in intake and exhaust valve timing, lift and duration.