Vapor Lock Research Articles

Comparative Evaluation of Different Methods of Activation of Chelating Solution for Smear Layer Removal in the Apical Portion of the Root Canal Using a Scanning Electron Microscopy: An In Vitro Study.

Background The smear layer has an adverse effect on the sealing of root canals during obturation, and it is the main reason for the failure of root canal treatment.Root canal irrigation using a conventional irrigation system is ineffective for smear layer removal, especially from the apical third region, where mostlateral canals are present. For successful endodontic treatment, the smear layer should be removed from the apical third region using an effective irrigation activation system. Aim This study aimed to compare smear layer removal by conventional irrigation, XP Endo Finisher (XPF), endoactivator (EA), passive ultrasonic activation, and root canal brushusing 17% ethylenediaminetetraacetic acid (EDTA) as a chelating solution and 5.25% sodium hypochlorite after chemomechanical preparation, using scanning electron microscopy (SEM). Method A total of 50 extracted human mandibular single canal premolars with mature roots were selected for this study. Samples were decoronated to obtain a standard working length (WL) of 15 mm. Canal patency was achieved using a 10 k file. Samples were sealed with sticky wax to obtain the vapor lock effect. Biomechanical preparation is done till F3. The samples were divided into five groups according to the final irrigation activation protocol: Group 1, control group; group 2, XPF; group 3, EA; group 4, passive ultrasonic irrigation (PUI); and group 5,, root canal brush. Samples were divided into two equal halves longitudinally. Each sample was analyzed for a smear layer under SEM at 2000x magnification. Statistical analysis was done using the one-way Anova "F" test and Tukey's post-hoc test. Results Group 3 showed the least presence of a smear layer, followed by groups 4, 2, 5, and 1. All the groups exhibited highly significant differences between each other (p < 0.001). Group B shows no significant difference with groups C, D, and E. Group C shows no significant difference with groups D and E. Group D shows no significant difference with group E. Conclusion The EA removes the smear layer effectively as compared with other groups. All the irrigation activation system shows the presence of smear layer. No activation systems were able to remove the smear layer completely.

Design and Development of Vapor Lock Detection to Prevent Brake System Failure

Traffic accidents in Indonesia often occur due to failure on the braking system. The results of the KNKT investigation show that there are three phenomena that most often cause brake system failure, namely brake fading, a decrease in the volume of compressed air and vapor lock. The aim of this research is to conduct experimental studies and develop designs for vapor lock detection devices to prevent failure in the braking system. Experimental studies on vapor lock characteristics were carried out through observations and measurements of boiling points and bubbles (the beginning of vapor lock) in the brake fluid heating process with various variations in water content. Experiments on vapor lock characteristics show that increasing the percentage of water content in the brake fluid has an effect on reducing the boiling point of the brake fluid and an empirical equation is produced to predict the boiling point of the brake fluid based on the percentage of water content in it. Apart from that, we have successfully developed a design for a vapor lock detection device to prevent failure in the braking system which is equipped with a water cooler brake system to prevent the temperature from reaching the boiling point of the brake fluid.

CBCT-Based Assessment of Vapor Lock Effects on Endodontic Disinfection

Background: The phenomenon of vapor lock, characterized by the formation of gas bubbles, poses challenges in achieving effective cleaning and debridement during endodontic treatments. This study aimed to evaluate the presence of vapor lock and to quantify its volume in the root canal system. Methods: Ten single-rooted teeth were selected, and their root canals were shaped using the Protaper Next system and irrigated with 5% NaOCl and 17% EDTA. Then, the canals were irrigated with a solution made of contrast medium (8 M cesium chloride solution) mixed in equal proportions with 5% sodium hypochlorite. CBCT scans were performed to analyze the presence and volume of bubbles in different canal thirds. Statistical analysis was conducted to compare the number of bubbles and the percentage of space occupied by them. Results: The results demonstrated the presence of vapor lock in all treated teeth, with a higher concentration of gas bubbles in the apical canal third. The formation of gas bubbles hindered the cleaning and debridement procedures, particularly in the apical region. Conclusions: This study provides evidence of the occurrence of vapor lock and highlights the importance of enhancing the cleaning phase in endodontic treatments to minimize bubble formation or eliminate them once formed. These findings contribute to a better understanding of the challenges posed by vapor lock and suggest avenues for optimizing endodontic procedures.

Influence of needle design and irrigation depth in the presence of vapor lock: A computational fluid dynamics analysis in human oval roots with apical ramification.

This paper aims to study the removal of a vapor lock located in the apical ramification of an oval distal root of a human mandibular molar, simulating different needles and irrigation depths with computational fluid dynamic. A geometric reconstruction of the micro-CT of the molar shaped up to a WaveOne Gold Medium instrument was used. A vapor lock located in the apical 2 mm was incorporated. Geometries with positive pressure needles (side-vented [SV], flat or front-vented [FV] and notched [N]) and the EndoVac microcannula (MiC) were created to run the simulations. Irrigation key parameters (flow pattern, irrigant velocity, apical pressure, wall shear stress) and vapor lock removal were compared among the different simulations. Each needle behaved differently that is, FV removed the vapor lock from one ramification and had the highest apical pressure and shear stress values; SV removed the vapor lock in the main root canal but not in the ramification and reached the lowest apical pressure from the positive pressure needles; N was not able to completely remove the vapor lock and showed low apical pressure and shear stress; MiC removed the vapor lock from one ramification, had negative apical pressure and the lowest maximum shear stress. The main conclusion is that none of the needles showed complete removal of vapor lock. MiC, N, and FV were able to partially remove the vapor lock from one out of the three ramifications. However, SV needle was the only simulation that showed high shear stress with low apical pressure.

Impact of Adding Bioethanol and Dimethyl Carbonate on Gasoline Properties

Bioethanol and dimetyl carbonate (DMC) are considered alternative fuels and additives to the synthesis compounds used now, since bioethanol is a biofuel and dimethyl carbonate (DMC) is non-toxic, biodegradable and can be produced in a cleaner way. In this study, the effect of adding dimethyl carbonate (DMC) and ethanol to gasoline on the volatility was investigated. The volatility was the main goal of this research but also, the effect on the antiknock properties was studied. Mixtures of gasoline with DMC or with bioethanol were prepared in different proportions of additive: 3%, 6% and 9% v/v. Additionally, mixtures with 3% v/v ethanol plus 3% or 6% v/v DMC, and3% DMC plus 6% v/v ethanol were prepared. For the volatility evaluation, the ASTM distillation curve and vapor pressure of these mixtures were determined experimentally in order to predict the performance of the resulting fuels. When adding oxygenated compounds, the increase in vapor pressure was proportional to the additive quantity. Additionally, modifications of the ASTM distillation curves were observed, with these indicating the formation of minimum boiling point azeotropes and the corresponding increase in volatility, with good effect on the ease of ignition in the engine. Based on the experimental results, the vapor lock index VLI, drivability index DI and vapor–liquid ratio temperature T(V/L=20) were calculated to quantify the volatility. The experimental results showed that gasoline mixtures with these oxygenated compounds show a significant increase in antiknock properties. Thus, for mixtures with ethanol, the research octane number (RON) increases by up to 2.2 units and the motor octane number (MON) increases by up to 1.2 units. Gasoline mixtures with DMC have another behavior: RON increased by up to 1.5 units, while the MON value increased by up to 2.5 units. For an initial gasoline with RON = 94.7 and MON 84.7, these increases are important and make the difference by exceeding the RON = 95 limit. Adding dimethyl carbonate to gasoline–ethanol blends improves the sensitivity of the fuel.

PRODUCTION OF GASOLINE COMPONENTS IN ASEAN REFINERIES AND EFFECTS OF THE STRICTER FUEL QUALITY REQUIREMENT

Intensive implementation of the blue sky program in many countries imposed the use of reformulated gasoline with a very sophisticated specification. Motor gasoline is essentially a complex mixture of hydrocarbons distilled between 40 and 220 C, which consist of distillate fraction of crude oils and the conversion products of crude oil fractions. Small amounts of additives are also used to enhance various aspects of the performance of gasoline. In ASEAN refineries, over 740 MBPSD of feed- stock is processed which produce about 512 MBPSD of gasoline components. About 96 percent of the amount is processed in 39 units of the heterogeneous catalytic processes: i.e. cracking. reforming and isomerization, and the other 4 percent in 4 units of homogeneous catalytic processes: L.e. alkylation and polymerization. Volatility, octane number, hydroegtys4 com: position and impurity content are the most determinant criteria of the gasoline. In most spark-ignition internal combustion engines, the fuel is metered in liquid form through the carburettor or fuel injector, and is mixed with air and partially vaporized before entering the cylinders of the engine. Consequently. volatility, is and extremely important characteristic with respect to starting, driveability, vapor lock, dilution of engine oil fuel economy, and carburettor icing. To increase the octane level of gasoline an anti knock agent such as tetraethyl lead (TEL) or tetramethyl lead (TML) can also be used. Pres- sures to reduce atmospheric pollution are tending towards the reduction or elimination of lead from gasoline. Lead itself is known to be a poison and its presence in the exhaust gas is undesirable. Leudacts as a catalyst poison of catalytic converter installed to reduce carbon monaxide and hydrocarbon emission. Methyl tertiary butyl ether (MTBE) is one of the alternative to replace lead alkyls, and has been used as antiknock. Unleaded gasoline (ULG) has been introduced since 1990 in ASEAN Countries: The actual penetration of ULG utilization in the first half of 1998 are as follows : Brunei Darussalam 48.9 , Indonesia 0.6 %. Malaysia 80 %, Philippines 17.7 %, Singapore 81 %. and Thailand 100%. The passage of the Clean Air Act Amendment of 1990 in the USA has forced American refiners to install new facilities to comply with stricter specifications for fuels such as gasoline and diesel oil. Various terms in the models address quality of the gasoline blended, sulfur content, and total aromatics and olefins contents, RVP, the Tof distillation range, sulfur content, and oxygenated content. Specifications for the reformulated gasoline and the ASEAN commecial gasoline are presented. Driveability index (DI) has been standardized by ASTM D-4814-98a and in the near future this DI could be recommended in the specification for the reformulated gasoline. Reformu- lated gasoline can be blended from the high quality gasoline components. Volatitity (RVP. T T T and driveability index), octane number (RON, MON and octane distribution), and hydrocarbon compositions of the gasoline components, as well as the refinery configuration to improve the quality of the gasoline components, and the compositions of these improved gasoline components of reformulated gasoline production are briefly discussed in this paper.

Emulsification of waste cooking oil biodiesel blend with hydrogen peroxide to assess tailpipe emissions and performance of a compression ignition engine

AbstractHydrogen peroxide (H2O2) is an excellent oxidant carrier that finds its use in combustion and fuel applications. In the present study, H2O2 (30% assay) is used as an emulsifier in waste cooking oil biodiesel blend (B20) and the emissions and performance in a compression ignition engine are assessed. Along with the neat B20, three blends of B20 with 0.5%, 1%, and 1.5% H2O2 concentrations are used. Increasing the concentration of H2O2 beyond 1.5% resulted in vapor lock in the fuel pump leading to a loss in injection pressure. An increase in the exhaust gas temperature was recorded with the increase in H2O2 concentration due to improved fuel properties, like, cetane number, thermal conductivity, and microexplosions of fuel droplets. However, NOx emissions decreased mainly due to the presence of the hydroperoxyl group from H2O2. Analysis of variance was also carried out to assess the statistical significance of H2O2 on the responses and is seen that the maximum impact of H2O2 was positively influencing brake thermal efficiency (BTE), brake‐specific fuel consumption (BSFC), hydrocarbon (HC), and NOx. Compared with the B20 blend, H2O2 emulsified fuel with a concentration of 1.5% showed a substantial reduction of 53.7%, 28.6%, 14.2%, and 16.2% in the average emissions of CO, HC, smoke, and NOx, respectively. Similarly, 7.9% and 7.1% improvement in the BTE and BSFC is obtained. However, more studies are required to ascertain the NOx reduction mechanism and address issues of fuel vaporization at higher concentrations of H2O2.

Brake-Disc Holes and Slit Shape Design to Improve Heat Dissipation Performance and Structural Stability

A brake disc decelerates the vehicle through friction with the brake pads. When the brake system is overheated, brake fade can occur, in which the friction coefficient drops significantly. Additionally, an over-heated brake system may cause vapor lock, in which the brake hydraulic fluid is vaporized. These phenomena can lead to the loss of braking power and cause a fatal accident. Therefore, brake systems must have stable braking and heat dissipation performance. Having through-holes and slits on the friction surface of the rotor has been adopted to improve the heat dissipation performance, but the holes become stress points and potentially cause cracks. Therefore, brake systems should be designed to have structural stability as well as good heat dissipation. In this study, finite element (FE) modeling was developed to analyze the structural stability and heat dissipation performance of a brake system, and structural and thermal simulations were performed in ANSYS, a CAE software package. In addition, to minimize concentrated stress and temperature, optimal design of the shape and pattern of holes and slits was carried out using PIAnO, an integrated optimal design software package. The first step of design optimization was performed while considering the shape and pattern of the disc holes and slits as design factors. Among the design factors, those with the largest effects on the objective functions were found and set as new design factors to perform the second step. The designs were compared to existing discs. Through the optimization presented in this paper, it is expected that the performance of the braking system will improve and the life of the brake parts will be increased.

Water Nanoconfined in a Hydrophobic Pore: Molecular Dynamics Simulations of Transmembrane Protein 175 and the Influence of Water Models.

Water molecules within biological ion channels are in a nano-confined environment and therefore exhibit behaviours which differ from that of bulk water. Here, we investigate the phenomenon of hydrophobic gating, the process by which a nanopore may spontaneously de-wet to form a ‘vapour lock’ if the pore is sufficiently hydrophobic and/or narrow. This occurs without steric occlusion of the pore. Using molecular dynamics simulations with both rigid fixed-charge and polarizable (AMOEBA) force fields, we investigate this wetting/de-wetting behaviour in the TMEM175 ion channel. We examine how a range of rigid fixed-charge and polarizable water models affect wetting/de-wetting in both the wild-type structure and in mutants chosen to cover a range of nanopore radii and pore-lining hydrophobicities. Crucially, we find that the rigid fixed-charge water models lead to similar wetting/de-wetting behaviours, but that the polarizable water model resulted in an increased wettability of the hydrophobic gating region of the pore. This has significant implications for molecular simulations of nano-confined water, as it implies that polarizability may need to be included if we are to gain detailed mechanistic insights into wetting/de-wetting processes. These findings are of importance for the design of functionalised biomimetic nanopores (for e.g. sensing or desalination), as well as for furthering our understanding of the mechanistic processes underlying biological ion channel function.

Application of factor analysis in the determination of vapor lock tendency in aviation gasolines/motor gasoline/blends and the compatibility as alternatives in naturally aspirated aviation engines

The danger of vapour lock, generation of vapor bubbles inside the aircraft fuel system, needs a well-documented understanding to establish safe operating confines at existing fuel temperature and pressures. The aim of the research is specifically to make contributions in the direction of the present scientific studies of UL aviation gasoline initiatives in piston aircrafts, globally specifically aiming on the vapor locking tendencies of aviation fuels, motor fuels and the blends and comparing the results both experimentally and statistically. Chemical and physical properties of the fuels were tested and categorised based on hydrocarbon types and properties. Study considered nine variables for vapor lock. Twenty-three aviation fuels from various literatures were collected, model equations derived, and respective comprehensive factor scores were calculated. The model was applied to the 14 fuels in this study and their respective comprehensive factor scores were calculated and ranked from the best to worst. The temperature of the gasoline as it approaches the carburettor was experimentally derived for comparative analysis with the comprehensive factor scores. Results showed that Kaiser’s Measure of Sampling Adequacy (MSA) measure of sampling adequacy value is 0.728. Four common factors and their cumulative variance proportion of rotation sums of squared loadings has reached 95.530%. Based on the loadings of the rotated components, PC1 has strong significant correlation with VL index of value 0.917. Among the aviation rated fuels, for vapor lock tendency UL 82, UL 87, SWIFT UL 102, SWIFT Binary Blend and 100 SF have the highest factor score. Fuels AVGAS 100LL (D910), AVF1, AVF2, AVF4, AVGAS, Leaded 91/98, and UL 94 exhibited very poor vapor lock tendencies. RON 98 exhibited the best VL protection among all the tested fuels in this study with ccomprehensive factor scores of 0.126166 and the best experimental temperature of the gasoline as it approaches the carburettor was also exhibited by RON 98. The findings showed that RON 98 able to outperform the commercial AVGAS in terms of vapor locking characteristics.

Effect of cyclohexanol on phase stability and volatility behavior of hydrous ethanol-gasoline blends

Biofuels can contribute to reducing greenhouse gas emissions and bridging the gap between production and consumption. Ethanol is a renewable source of energy. It can reduce oil dependence and also can be appropriately used in gasoline as a blend. The high cost of dry ethanol has turned the researcher's attention to the more economic hydrous ethanol. However many works were focused on its impact on the engine performance and the exhaust emissions; few works were interested in the phase stability of those blends. This work aims to study the impact of blending cyclohexanol (CH) into hydrous ethanol-gasoline blends as a stabilizing agent. Four dual-alcohol (E5-3CH, E10-3CH, E15-3CH, and E20-3CH) blends were investigated besides their single hydrous ethanol (E0, E5, E10, E15, and E20) blends. The tests involved; water tolerance, distillation curve, and vapor pressure. Vapor lock protection potential, the area under the distillation curve (AUDC), and the area due to azeotrope formation (ADAF) were calculated. The obtained results show that cyclohexanol significantly increases the water tolerance of hydrous ethanol-gasoline blends. The blends of E5 and E10 which were separated at 30 °C converted into miscible and clear samples when they were blended with 3 vol% of cyclohexanol. These samples can also tolerate additional water. For E20, the addition of 3 vol% of cyclohexanol increased the water tolerance by about six times. Also, it was found that cyclohexanol does not have any negative effect on the volatility properties of the fuel blends. It was found that blending CH into the hydrous ethanol blends causes a significant increase in the AUDC and consequently, the area due to azeotrope formation (ADAF) decrease.

State of Art of Using Biofuels in Spark Ignition Engines

Biofuels are receiving increased scientific attention, and recently different biofuels have been proposed for spark ignition engines. This paper presents the state of art of using biofuels in spark ignition engines (SIE). Different biofuels, mainly ethanol, methanol, i-butanol-n-butanol, and acetone, are blended together in single dual issues and evaluated as renewables for SIE. The biofuels were compared with each other as well as with the fossil fuel in SIE. Future biofuels for SIE are highlighted. A proposed method to reduce automobile emissions and reformulate the emissions into new fuels is presented and discussed. The benefits and weaknesses of using biofuels in SIE are summarized. The study established that ethanol has several benefits as a biofuel for SIE; it enhanced engine performance and decreased pollutant emissions significantly; however, ethanol showed some drawbacks, which cause problems in cold starting conditions and, additionally, the engine may suffer from a vapor lock situation. Methanol also showed improvements in engine emissions/performance similarly to ethanol, but it is poisonous biofuel and it has some sort of incompatibility with engine materials/systems; its being miscible with water is another disadvantage. The lowest engine performance was displayed by n-butanol and i-butanol biofuels, and they also showed the greatest amount of unburned hydrocarbons (UHC) and CO emissions, but the lowest greenhouse effect. Ethanol and methanol introduced the highest engine performance, but they also showed the greatest CO2 emissions. Acetone introduced a moderate engine performance and the best/lowest CO and UHC emissions. Single biofuel blends are also compared with dual ones, and the results showed the benefits of the dual ones. The study concluded that the next generation of biofuels is expected to be dual blended biofuels. Different dual biofuel blends are also compared with each other, and the results showed that the ethanol–methanol (EM) biofuel is superior in comparison with n-butanol–i-butanol (niB) and i-butanol–ethanol (iBE).

Experimental study on the transient behaviors of mechanically pumped two-phase loop with a novel accumulator for thermal control of space camera payload

Mechanically pumped two-phase loop (MPTL) shows a promising prospect in thermal control of space camera payload. However, transient behaviors of MPTL caused by start-up and heat sources load-on/off are rarely reported. In the present study, one MPTL setup was designed and constructed to reveal them. Particularly, a novel two-phase thermal-controlled accumulator integrating with passive cooling was designed and employed to replace the traditional accumulator. The obtained test data, including the temperatures, pressures and mass flow-rate, were invited to analyze the dynamic behaviors of MPTL during the whole processes, the dynamic behaviors of accumulator, and the coupled heat and mass transfer processes between main loop and the accumulator. Vapor lock took place during the phase changing process and leaded to oscillations of flow resistance and mass flow-rate. During processes of heat sources load-on and load-off, two oscillations of temperature and pressure in the accumulator were both needed for the MPTL returning to stable. Meanwhile, fluctuation patterns at these two processes were opposite. Lowering the pump speed decreased the stable temperatures of evaporator, flow resistance as well as the mass flow rate. An average temperature decrease of 0.43 °C was presented after changing the pump speed from 26,700 r/min to 20,000 r/min.

자동차 브레이크액 누유에 따른 발화 위험성 연구

The brake fluid plays an important role in braking device. It increases the water content and lowers the boiling point and the flash point, as the travel distance is increased. The possibility of vapor lock and the risk of fire is also increased. The brake fluid leakage due to the solenoid failure in the ABS module, which is a main component of the brake system, can be ignited by the circuit board terminal trekking short circuit. It has been confirmed that the leaked brake fluid caused by overheating of the drum and the disc due to repetition of braking can be ignited even in the case of short-circuit spark and high-temperature metal contact. Also, the leakage and the injected brake fluid due to the cylinder failure of the disc and the drum brake are ignited by overheating due to braking repetition.

Differences in apical vapor lock formation after sodium hypochlorite irrigation with and without surfactant using two needle types

Background: Endodontic irrigation with 5.25% sodium hypochlorite (NaOCl) solution using single side-vented and double side-vented needles is commonly used. Surfactant is added to reduce high surface tension of the NaOCl solution. Apical vapor lock, or air entrapment inside closed-end root canal system, lowers the efficacy of irrigants. Thus, the irrigants are hindered in penetrating the root canal system and can lead to risk of reinfection. Objective: The objective is to analyze the difference of 5.25% NaOCl solution with and without surfactant using two types of irrigation needle in the formation of apical vapor lock. Methods: Forty lower premolars were prepared and randomly divided into four groups (n = 10 per group) then irrigated with 5.25% NaOCl solution with and without surfactant using a single side-vented or double side-vented needle. Contrast medium was added so that the measurement of the apical vapor lock could be performed using a digital radiograph. Analysis was done with two-way analysis of variance and the Tukey method. Results: 5.25% NaOCl solution with a single side-vented needle showed a significant difference from 5.25% NaOCl solution with a double side-vented needle. 5.25% NaOCl solution with a surfactant using a single side-vented needle showed a significant difference from 5.25% NaOCl solution using a double side-vented needle, likewise NaOCl 5.25% using double side-vented needle group from NaOCl 5.25% with surfactant using single side-vented needle group. Conclusion: Minimal formation of an apical vapor lock resulted from the use of 5.25% NaOCl solution with a surfactant using a single side-vented needle.

Effectiveness of Vapor Lock Effect Removal in Endo Training Blocks: Manual Dynamic Agitation versus Passive Ultrasonic Irrigation

Root canal cleaning plays an important role in endodontics. In most cases, root canal cleaning is performed using irrigants, such as sodium hypochlorite or EDTA (ethylenediaminetetraacetic acid). The efficacy of these irrigants may be compromised by different phenomena, such as vapor lock. Different methods can be used to overcome this problem; in this paper, we compare the efficacy of two such methods: manual dynamic agitation (MDA) and passive ultrasonic irrigation (PUI). We shaped 50 endo training blocks, which were divided into two groups of 25 samples each, into MDA or PUI groups. In both groups, the vapor lock was produced by delivering a watery solution using a disposable syringe with a tip-opened needle. Using the MDA technique, vapor lock was removed in 15/25 cases. The PUI technique produced the same results in 17/25 cases, where vapor lock was only reduced, not removed. The MDA method produced an average reduction in vapor lock of 80%, whereas the PUI method yielded a 55% reduction. The differences among groups were assessed through a Mann–Whitney U test, and the results had a p-value of 0.0013, which was considered to be statistically significant. The MDA method was able to effectively remove vapor lock. PUI, however, was only able to reduce but not remove vapor lock.

Hyperbaric treatment of air or gas embolism: current recommendations

Gas can enter arteries (arterial gas embolism, AGE) due to alveolar-capillary disruption (caused by pulmonary over-pressurization, e.g. breath-hold ascent by divers) or veins (venous gas embolism, VGE) as a result of tissue bubble formation due to decompression (diving, altitude exposure) or during certain surgical procedures where capillary hydrostatic pressure at the incision site is subatmospheric. Both AGE and VGE can be caused by iatrogenic gas injection. AGE usually produces stroke-like manifestations, such as impaired consciousness, confusion, seizures and focal neurological deficits. Small amounts of VGE are often tolerated due to filtration by pulmonary capillaries; however VGE can cause pulmonary edema, cardiac "vapor lock" and AGE due to transpulmonary passage or right-to-left shunt through a patient foramen ovale. Intravascular gas can cause arterial obstruction or endothelial damage and secondary vasospasm and capillary leak. Vascular gas is frequently not visible with radiographic imaging, which should not be used to exclude the diagnosis of AGE. Isolated VGE usually requires no treatment; AGE treatment is similar to decompression sickness (DCS), with first aid oxygen then hyperbaric oxygen. Although cerebral AGE (CAGE) often causes intracranial hypertension, animal studies have failed to demonstrate a benefit of induced hypocapnia. An evidence based review of adjunctive therapies is presented.

Effects of dual-alcohol gasoline blends on physiochemical properties and volatility behavior

Biofuels can contribute to reducing greenhouse gas emissions from the transportation sector. Ethanol is the main additive for gasoline in the United States, and gasoline containing 10 vol% ethanol is the most commonly used transportation fuel. However, the vapor pressure of these blends is significantly higher than gasoline, which contributes to evaporative emissions. One way to circumvent this and other issues is to use a dual-alcohol approach, mixing lower (methanol or ethanol) and higher alcohols with gasoline to obtain a blend with a vapor pressure close to that of the base gasoline. The goal of this study was to evaluate the fuel potential of dual alcohol blends experimentally and theoretically. Ten dual-alcohol blends were tested at blending ratios from 10 to 80 vol%, with methanol and ethanol used as the lower alcohols and iso-butanol and 3-methyl-3-pentanol as the higher alcohols. The corresponding single alcohol-gasoline blends were also evaluated. For each blend, Reid vapor pressure, vapor lock protection potential, distillation curve, lower heating value, kinematic viscosity, and water tolerance at three temperatures were measured. A model of droplet evaporation was also applied to provide insights into the azeotropic volatility behavior and mixing/sooting potential of the blends. The results of this study show that it is advantageous to use dual-alcohol blends containing up to 40 vol% because they have the characteristics necessary for good performance in existing spark-ignition engines, particularly in terms of volatility, kinematic viscosity, and water tolerance. This study is the first to characterize matched vapor pressure, dual-alcohol blends over a wide blending range as drop-in fuels for conventional spark ignition engines. Furthermore, this was the first investigation of the fuel potential of iso-butanol in dual-alcohol blends and of 3-methyl-3-pentanol in single- and dual-alcohol blends.

APICAL VAPOUR LOCK EFFECT -PHENOMENON RELATED TO ENDODONTIC IRRIGATION - A REVIEW.

Complete debridement of the root canal system is a primary requirement for the successful root canal treatment 1. Thus for optimum disinfection , a thorough cleaning and shaping is mandatory ; so the current concept in Endodontics is ‘ Files shape, irrigants clean’2. Even with the use of rotary instrumentation, the nickel-titanium instruments currently available only act on the central body of the canal, leaving canal fins, isthmi, and cul-de-sacs untouched after completion of the preparation. These areas might harbor tissue debris, microbes, and their by-products, which might prevent close adaptation of the obturation material and result in persistent periradicular inflammation 3,4.So the irrigants must be brought into direct contact with the entire canal wall surfaces for effective action, particularly for the apical portions of small root canals. Recently, concern has been expressed about the possible presence of gas bubbles in the apical part of the root canal that could block irrigant penetration and may affect effective debridement.This phenomenon is termed as‘apical vapor lock’5 (AVL). It is also called as Dead Water Zone.

The thermo-mechanical behavior of brake discs for high-speed railway vehicles

The structure of a brake disc is coupled to the axle and rotates together with the wheel. A brake disc is a friction-type device that presses the pad on both sides of the disc. As more of its surface area becomes exposed to the air, it has better heat dissipation than the drum disc. It also has low fade phenomenon or vapor lock phenomenon despite frequent brake operation. In addition, it has the advantage of enabling precise control. But the braking force is obtained by the disc brake system by using the frictional force between the disc and the pad, and the pad is subjected to wear. For high-speed railway vehicles in particular, the wear and tear of the pad occurs more rapidly. This not only shortens the replacement cycle of the pad, but also has the disadvantage of reducing braking efficiency due to the rise in temperature during the initial braking process. Moreover, the heat that occurs will cause thermal distortion, which leads to the occurrence of a hot spot. This results in a reduction of the disc life. Looking comprehensively at the research trends to date it appears that thermal behavior analysis has only been performed thus far in terms of frictional thermal energy between the disc and the pad. Thermomechanical contact characteristics, on the other hand, have yet to be considered. The thermal behavior of the disc is analyzed experimentally using an infrared camera, and the causes of the hot band and hotspot are suggested. This analytical approach can shorten the analysis time, but it can only confirm the temperature distribution achieved by a single braking. While there is a significant difference in temperature distribution according to the actual braking, the analytical approach has solely focused on the hotspot generation mechanism. Therefore, in this study, the authors will use both a dynamometer and a thermographic camera to analyze BPs through a repetitive braking process, and will attempt to verify the cause of thermomechanical movement and BP occurrence through contact analysis of the disc and the pad.