Vapor Lock Research Articles

Passive Ultrasonic Irrigation Efficacy in the Vapor Lock Removal: Systematic Review and Meta-Analysis.

Passive Ultrasonic Irrigation (PUI) represents one of the most used systems to improve the endodontic irrigants activity. PUI acts increasing the reaction rate of NaOCl, with an increase of dentinal debris and smear layer removal. There is a stronger shear stress and a vapor lock reduction. Aim of this systematic review was to figure out the effects of the PUI on the vapor lock removal, during irrigation. Literature research has been carried out by two reviewers, consulting online databases such as PubMed, EBSCO, and Google Scholar, using keywords like Vapor Lock, Vapour Lock, and Vapor Lock Endodontic. The articles list has been screened based on titles and abstracts, applying eligibility and inclusion criteria. The three articles were eligible for quantitative and statistical analysis, by using RevManager Software Version 5.3. Results show statistical heterogeneity (P=0.08; I2 index=61%) in the vapor lock elimination between the use of PUI and PPI, with an overall Odds Ratio=0.08, CI=95% [0.03;0.25]. PUI resulted to be a useful technique to improve NaOCl activity for vapor lock removal, despite PPI alone using a needle.

Influence of ethyl acetate addition on phase stability and fuel characteristics of hydrous ethanol-gasoline blends

Hydrous ethanol or commercial ethanol is regarded as a promising additive for gasoline. Its low cost and many other advantages, such as increasing the octane number and reduction of harmful emissions, motivate the researchers to investigate its use as an economic octane booster. The most common drawback of using hydrous ethanol as a gasoline additive is the phase separation problem. In this study, the effect of adding ethyl acetate (EA) on the phase stability, distillation curve, vapor pressure, vapor lock index and octane number of hydrous ethanol-gasoline blends was investigated. The reference fuel blends were formulated by mixing hydrous ethanol (96%) with hydrocarbon-based gasoline in different percentages (5, 10, 15 and 20 vol%). For studying the effect of ethyl acetate on the fuel specifications, it was mixed with 15% hydrous ethanol-gasoline blend in different percentage (3, 6, 9 and 12 vol%). The experimental results indicated that ethyl acetate has a good ability to increase the phase stability and the octane number of the hydrous ethanol-gasoline blends without causing adverse impacts on the other studied specifications.

Physiochemical Property Characterization of Hydrous and Anhydrous Ethanol Blended Gasoline

Water removal during the production of bioethanol is highly energy intensive. At the azeotropic point, the mixture can no longer be separated via fractional distillation, so expensive and energy intensive methods are required for further purification. Hence, there is an interest in using hydrous ethanol at the azeotropic point to improve the energy balance of ethanol fuel production. Currently there is a lack of available thermophysical property data for hydrous ethanol gasoline fuel blends. These data are important to understand the effect of water on critical fuel properties and to evaluate the potential of using hydrous ethanol fuels in conventional and optimized spark ignition engines. In this study, gasoline was blended with 10, 15, and 30 vol % of anhydrous and hydrous ethanol. The distillation curve, Reid vapor pressure, vapor lock protection potential, viscosity, density, haze and phase separation points, and lower heating value were measured for each blend, and the results were compared to ASTM D...

Endodontic irrigants: Different methods to improve efficacy and related problems.

Shaping and cleaning a root canal system along with the preservation of the surrounding periodontal tissues are the principal goals of an endodontic treatment. While most of the attention is paid to the mechanical aspects of a root canal treatment, an essential feature of it is the irrigation. All over the years, many materials have been used to clean the root canal of a tooth, and certainly, the sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid solutions are the most used and most reliable ones. Putting them inside of a canal is mostly done using a normal syringe, but many techniques have been involved in this process, including the use of sonic/ultrasonic instruments, the use of shaping files, and even laser, to increase the efficacy of irrigant solutions, especially of NaOCl one. Each one of this technique faces some disadvantages, just as the vapor lock effect and the apical extrusion, and has a different action on features such as the reaction rate and the shear stress of an endodontic irrigant solution. In this narrative review, we describe the different features of many irrigant solutions and the different ways of upgrading their efficacy in the cleaning of a root canal system, with the use of tables to summarize the entire description, and drawing the readers’ attention to a photographic illustration for a better understanding of the topic.

Identification and Characterization of the Neisseria gonorrhoeae MscS-Like Mechanosensitive Channel.

Mechanosensitive channels are ubiquitous in bacteria and provide an essential mechanism to survive sudden exposure to a hypo-osmotic environment by the sensing and release of increased turgor pressure. No mechanosensitive channels have thus far been identified and characterized for the human-specific bacterial pathogen Neisseria gonorrhoeae In this study, we identified and characterized the N. gonorrhoeae MscS-like mechanosensitive channel (Ng-MscS). Electrophysiological analyses by the patch clamp method showed that Ng-MscS is stretch activated and contains pressure-dependent gating properties. Further mutagenesis studies of critical residues forming the hydrophobic vapor lock showed that gain-of-function mutations in Ng-MscS inhibited bacterial growth. Subsequent analysis of the function of Ng-MscS in N. gonorrhoeae by osmotic down-shock assays revealed that the survival of Ng-mscS deletion mutants was significantly reduced compared with that of wild-type strains, while down-shock survival was restored upon the ectopic complementation of mscS Finally, to investigate whether Ng-MscS is important for N. gonorrhoeae during infections, competition assays were performed by using a murine vaginal tract infection model. Ng-mscS deletion mutants were outcompeted by N. gonorrhoeae wild-type strains for colonization and survival in this infection model, highlighting that Ng-MscS contributes to in vivo colonization and survival. Therefore, Ng-MscS might be a promising target for the future development of novel antimicrobials.

A review of phase separation issues in aviation gasoline fuel and motor gasoline fuels in aviation

In an attempt to bring in sustainable energy resources into the current combustibles mix, recent European legislations make obligatory the addition of biogenic fuels into traditional fossil gasoline. The preferred biogenic fuel, for economic reasons, is predominantly ethanol. Even though likened to fossil gasoline constituents, ethanol has a dissimilar chemical formulation that may lead to a potentially hazardous physicochemical phenomenon, particularly in the presence of water. Owing to increased financially driven propensity to utilize motor vehicle gasoline as aviation gasoline fuel, this may result in potentially hazardous situations, specifically in running smaller or compact General Aviation aircraft. The potential risks posed by ethanol admixtures in aircraft are phase separation and carburettor icing. Gasoline mixed with ethanol is also prone to an increased vulnerability to vapor lock that happens when fuel turns into vapor in the fuel pumps due to high temperatures and lessened ambient pressure at high altitudes. This article provides a literature review on phase separation issues in aviation gasoline fuel and motor gasoline fuels in aviation.

Optimal working fluid charge and degradation thresholds for a closed-circuit intermediate natural circulation heat transport loop

The study derives the optimal working fluid charge of a closed-circuit intermediate natural circulation heat transport loop based on the passive residual heat removal system (PRHRS) of SMART (System-integrated Modular Advanced ReacTor). The study finds that efficient natural circulation flow and heat transfer regimes can be maintained in a narrow band of working fluid charge mass owing to the small secondary side volume of the once-through helical-coil steam generator design of SMART. Overcharging condition is a severe passive system degradation mode that quickly leads to system failure. Overcharging is characterized by sustained two-phase flow instabilities, mainly liquid slugging in the hot leg of the PRHRS, and an increased operating pressure of the PRHRS coupled with a compensating increase in the operating pressure of the reactor coolant system (RCS). Increased pressures maintain the required temperature differential across the steam generator tubes and heat sink heat exchanger to achieve a prescribed quasi-steady state heat removal rate capacity. Undercharging condition is a benign degradation mode relative to overcharging and is characterized by a slow upward drift of the RCS pressure and temperature of the liquid water entering the primary side of the steam generator. Only the undercharged case of a completely dry steam generator secondary side leads to PRHRS failure-to-start via vapor lock.

AC insulation property of fluorocarbon in thermal induced two-phase flow by self-heating electrode

Although it has been found that the insulating characteristics of thermal induced two-phase flow changes with pressure and heat power, its breakdown mechanism has not been clarified so far. In order to obtain actual working conditions of two-phase flow state of fluorocarbon, a special apparatus with self-heating electrodes has been manufactured to study AC breakdown voltage (BDV) under different pressure, electrode gap distance and heating density. The experimental data outline that the variation of breakdown voltage vs. heat density is an elongated "Z" shaped curve: Breakdown voltage maintains the liquid value in the Invariant Interval, and drops sharply in the Converting Interval, finally reduces to gas value and maintains in the Maintaining Interval. It is pointed out that the steep converting of BDV is closely related to the change of flow pattern and bubble generation on heating electrode surface. And the threshold of converting point is highly consistent with the peak of electrode surface overheating AT, therefore it can be used as an excellent signal to detect the BDV converting. An electric field model is established based on bubble thermodynamics to explain the discharge mechanism of "vapor lock" effect, offering a theoretical minimum limit of BDV value in the thermal induced two-phase flow, which provides a useful guide to design the insulation subjected to various high voltages.

Reaction Control Thruster Thermal Design for a Mission to Mercury

This paper describes two novel methods used to reduce the prefiring injector temperatures of thrusters on the sun-facing side of a spacecraft designed for a mission to Mercury. The Mercury Transfer Module is the propulsion module that takes the European Space Agency’s BepiColombo mission to the planet Mercury. It contains a bipropellant chemical propulsion system and a xenon-based electric propulsion system. It was predicted that, within a certain distance from the sun, the high solar loads and large internal waste heat from the electric propulsion would cause vapor lock to occur on the sun-facing hydrazine thrusters at the start of firing, rendering their performance unpredictable and inefficient. The paper reports on the development of a method to increase the emissivity of the nozzles via sandblasting and on the development of a special copper collar for directly removing heat from the injector. The design and analysis are reported, along with results from a dedicated thruster-level high solar flux thermal test and a full spacecraft-level thermal test using a flight-representative thruster to which the modifications as described in this paper. The two techniques are shown to enable unrestricted use of the thrusters all the way to Mercury.

LPG 직분사 엔진의 다운사이징 효과 및 시동성 개선을 위한 연료 제어시스템 최적화에 관한 연구

The new 1.4 L turbocharged LPG direct injection (T-LPDI) engine is presented in this paper to improve the fuel efficiency of the vehicles installed with the 2.0 L LPG port fuel injection (LPI) engine, while maintaining the performance as a downsizing concept for the new engine platform development. Firstly, the return type high pressure LPG fuel supply system is designed and mounted in the new 1.4 L T-LPDI engine. As a result, this new engine shows a much better WOT performance and approximately 8 % of improved fuel economy level, as compared to the 2.0 L LPI vehicle. Secondly, the LPDI engine specific optimized design for high pressure fuel components and fuel injection control strategies are proposed and evaluated in order to overcome the restartability problem in a heat-soaked condition called the vapor lock phenomenon. Consequently, these experimental results illustrate a great potential for the developed 1.4 L T-LPDI engine as a possible substitute for the 2.0 L LPI engine.

Review: Fuel Volatility Standards and Spark-Ignition Vehicle Driveability

Spark-ignition engine fuel standards have been put in place to ensure acceptable hot and cold weather driveability (HWD and CWD). Vehicle manufacturers and fuel suppliers have developed systems that meet our driveability requirements so effectively that drivers overwhelmingly find that their vehicles reliably start up and operate smoothly and consistently throughout the year. For HWD, fuels that are too volatile perform more poorly than those that are less volatile. Vapor lock is the apparent cause of poor HWD, but there is conflicting evidence in the literature as to where in the fuel system it occurs. Most studies have found a correlation between degraded driveability and higher dry vapor pressure equivalent or lower TV/L = 20, and less consistently with a minimum T50. For CWD, fuels with inadequate volatility can cause difficulty in starting and rough operation during engine warmup. The Driveability Index (DI)-a function of T10, T50, and T90-is well correlated with CWD in hydrocarbon fuels. For ethanol-containing fuels, a correction factor to the DI equation improves the correlation with CWD, although the best value for that factor has still not been determined. Ethanol increases the heat of vaporization. However, this is likely insignificant for E15 and lower concentration fuels.more » The impact of ethanol on driveability is likely due to its direct effect on vapor pressure at cold temperatures. For E51-E83 or flex-fuel blends, ASTM sets a minimum vapor pressure; however, published data suggest that a correction for the amount of ethanol in the fuel is needed to accurately predict CWD, possibly because ethanol has a higher lower-flammability limit.« less

부하증가로 인한 궤도형 장갑차의 엔진꺼짐현상 개선

Currently, there are many kinds of tracked armored vehicles in service and they have encountered various environment and situations. So there are many obstacles to operate them improperly such as an engine stall. The causes of engine stall are an insufficient fueling, a mixture of air-fuel or vapor lock, and load increment which results from a rapid steering or increasing a viscosity of lubricant by low temperature. In this paper, engine stall by load increment due to a rapid steering or increasing of lubricant viscosity on tracked armored vehicles is analyzed, the ways to prevent it are applied, and their degrees of improvement are evaluated.

Properties of the Mechanosensitive Channel MscS Pore Revealed by Tryptophan Scanning Mutagenesis.

Bacterial mechanosensitive channels gate when the transmembrane turgor rises to levels that compromise the structural integrity of the cell wall. Gating creates a transient large diameter pore that allows hydrated solutes to pass from the cytoplasm at rates close to those of diffusion. In the closed conformation, the channel limits transmembrane solute movement, even that of protons. In the MscS crystal structure (Protein Data Bank entry 2oau), a narrow, hydrophobic opening is visible in the crystal structure, and it has been proposed that a vapor lock created by the hydrophobic seals, L105 and L109, is the barrier to water and ions. Tryptophan scanning mutagenesis has proven to be a highly valuable tool for the analysis of channel structure. Here Trp residues were introduced along the pore-forming TM3a helix and in selected other parts of the protein. Mutants were investigated for their expression, stability, and activity and as fluorescent probes of the physical properties along the length of the pore. Most Trp mutants were expressed at levels similar to that of the parent (MscS YFF) and were stable as heptamers in detergent in the presence and absence of urea. Fluorescence data suggest a long hydrophobic region with low accessibility to aqueous solvents, extending from L105/L109 to G90. Steady-state fluorescence anisotropy data are consistent with significant homo-Förster resonance energy transfer between tryptophan residues from different subunits within the narrow pore. The data provide new insights into MscS structure and gating.

Next generation design, development, and evaluation of cryoprobes for minimally invasive surgery and solid cancer therapeutics: in silico and computational studies.

Cryosurgery is a widely regarded minimally invasive surgery for treatment of various types of cancers. It involves destruction of cancer cells within a limited spatial domain by exposing them to very low temperatures while minimizing injury to surrounding peripheral healthy tissues. Surprisingly, despite increasing demands for cryosurgery, there has been limited innovation in the design of cryoprobes, particularly in solid tumors (e.g., breast, prostate, and lung cancers). For advances in cancer therapeutics, integrative biology research can illuminate the mechanistic interface between a surgical cryoprobe and its tissue site of action. Here, we describe the design and development of three novel low pressure liquid nitrogen (LN2) cryoprobes with different physical dimensions and the parameters that determine their effectiveness experimentally, using water and bio-gel as the phase changing mediums. Smaller diameter low pressure probes produced lesser cryogenic injury. Vapor Separator is found to be an effective means (particularly for smaller diameter probes) to remove the vapor lock in the LN2 low pressure cryoprobes and also to reduce the precooling time. The low pressure LN2 cryoprobes produced lower probe temperatures and consequently larger and faster iceball growth for low cooling loads. Additionally, a numerical code was written in MATLAB based on the Enthalpy method to simulate the bio-heat transfer in a cryosurgical process. The numerical code is validated by analytical solution, laboratory experiments, and data from an in vivo cryosurgery. The developed numerical code is presented herein to illustrate that LN2 cryoprobes capable of producing lower probe temperatures produce more efficient cryosurgical operation by reducing the buffer zone and duration of surgery.This is the first report, to the best of our knowledge, on design of the next generation of LN2 surgical cryoprobes. These new surgical cryoprobes offer potentials for future preclinical and clinical testing in solid cancers.

甲醇–汽油相稳定性与蒸发性及其控制研究进展

随着中国对石油需求量的日益增大，发展车用能源替代品甲醇–汽油显得越来越紧迫，然而目前甲醇–汽油的全面推广和应用还面临一些问题亟待解决解决。本文综述了汽油组分、甲醇含量、水的含量及助溶剂对甲醇–汽油体系稳定性以及蒸发性的影响，对几类助溶剂和降气阻剂的研究现状进行了分析，在此基础上对今后甲醇–汽油的发展方向提出了展望。 With China's growing demand for oil, the development of methanol-gasoline energy alternatives for car becomes more and more urgent, but there are also some problems needed to be solved in methanol-gasoline comprehensive promotion and application. This article reviewed the impact of gasoline component, methanol content, water content and co-solvent on evaporation and stability of methanol-gasoline, and analyzed the research status of co-solvent and vapor lock lowering agent. Based on the review, the development direction of methanol-gasoline was prospected.

Root canal penetration of a sodium hypochlorite mixture using sonic or ultrasonic activation.

The purpose of this ex vivo study was to determine, in "open" and "closed" systems, whether the design has an influence on the penetration length of sodium hypochlorite mixed with a radiopaque contrast medium, measured in millimeters, when delivered using positive pressure (PP) and using sonic (SI) or passive ultrasonic (PUI) activation. Sixty single-rooted teeth were divided into two groups: open and closed systems (n=30). Root canal shaping was performed to a working length of 17 mm. The samples were divided into three sub-groups (n=10) according to irrigant delivery and activation: PP, and SI or PUI activation. By using radiographs, penetration length was measured, and vapor lock was assessed. For the closed group, the penetration distance means were: PP 15.715 (±0.898) mm, SI 16.299 (±0.738) mm and PUI 16.813 (±0.465) mm, with vapor lock occurring in 53.3% of the specimens. In the open group, penetration to 17 mm occurred in 97.6% of the samples, and no vapor lock occurred. Irrigant penetration and distribution evaluation using open and closed systems provide significantly different results. For closed systems, PUI is the most effective in delivering the irrigant to working length, followed by SI.

Development of tartaric esters as bifunctional additives of methanol-gasoline.

BackgroundMethanol has become an alternative fuel for gasoline, which is facing a rapidly rising world demand with a limited oil supply. Methanol-gasoline has been used in China, but phase stability and vapor lock still need to be resolved in methanol-gasoline applications. In this paper, a series of tartaric esters were synthesized and used as phase stabilizers and saturation vapor pressure depressors for methanol-gasoline.ResultsThe results showed that the phase stabilities of tartaric esters for methanol-gasoline depend on the length of the alkoxy group. Several tartaric esters were found to be effective in various gasoline-methanol blends, and the tartaric esters display high capacity to depress the saturation vapor pressure of methanol-gasoline.ConclusionAccording to the results, it can be concluded that the tartaric esters have great potential to be bifunctional gasoline-methanol additives.

액체수소용 초저온 고압 피스톤 펌프의 기밀성 향상에 관한 기초연구

As an initial step to develop a liquid hydrogen pump of piston type operated under cryogenic and high pressure, leakage and piston head shape for the piston pump were discussed with temperature and pressure. As the results, the leakage depended on correlation among density, viscosity, clearance area by the low temperature. In order to reduce the leakage, it was found that the air-tightness can be improved by minimizing contact surface between piston and cylinder, and also increasing pressure in-cylinder can reduce piston clearance. Among the proposed piston shapes, D type piston shape had the most air-tightness. D type piston had smaller contact surface than other piston shape and easier expansion of cup shape by pressure. The leakage of D type piston shape was found about 7%, compared with A type piston shape. But it was required that analyze about vapor lock by friction and wear resistance.

Formation and removal of apical vapor lock during syringe irrigation: a combined experimental and Computational Fluid Dynamics approach

(i) To evaluate the effect of needle type and insertion depth, root canal size and irrigant flow rate on the entrapment of air bubbles in the apical part of a root canal (apical vapor lock) during syringe irrigation using experiments and a Computational Fluid Dynamics (CFD) model, (ii) to investigate whether the irrigant contact angle affects bubble entrapment, (iii) to examine if an established vapor lock can be removed by syringe irrigation. Bubble entrapment during irrigation of straight artificial root canals of size 35 or 50 was evaluated by real-time visualizations. The irrigant was delivered by a closed-ended or an open-ended needle positioned at 1 or 3 mm short of working length (WL) and at a flow rate of 0.033-0.260 mL s(-1) . Results were analysed by nonparametric tests at 0.05 significance. Selected cases were also simulated by a two-phase CFD model. A vapor lock was observed in 48% of the cases investigated experimentally. Increasing the apical size, using an open-ended needle, positioning the needle closer to WL and delivering the irrigant at higher flow rate resulted in significantly smaller vapor lock. An increased contact angle resulted in the entrapment of a larger bubble when a low flow rate was used. Both brief insertion of the needle to WL whilst irrigating at a flow rate of 0.083 mL s(-1) and delivering the irrigant at 0.260 mL s(-1) without changing the needle position were capable of removing an established vapor lock. Apical vapor lock may occur under certain conditions, but appears to be easily prevented or removed by syringe irrigation.

Multivariate analysis of the cleaning efficacy of different final irrigation techniques in the canal and isthmus of mandibular posterior teeth

ObjectivesThe aim of this study was to compare the cleaning efficacy of different final irrigation regimens in canal and isthmus of mandibular molars, and to evaluate the influence of related variables on cleaning efficacy of the irrigation systems.Materials and MethodsMesial root canals from 60 mandibular molars were prepared and divided into 4 experimental groups according to the final irrigation technique: Group C, syringe irrigation; Group U, ultrasonics activation; Group SC, VPro StreamClean irrigation; Group EV, EndoVac irrigation. Cross-sections at 1, 3 and 5 mm levels from the apex were examined to calculate remaining debris area in the canal and isthmus spaces. Statistical analysis was completed by using Kruskal-Wallis test and Mann-Whitney U test for comparison among groups, and multivariate linear analysis to identify the significant variables (regular replenishment of irrigant, vapor lock management, and ultrasonic activation of irrigant) affecting the cleaning efficacy of the experimental groups.ResultsGroup SC and EV showed significantly higher canal cleanliness values than group C and U at 1 mm level (p < 0.05), and higher isthmus cleanliness values than group U at 3 mm and all levels of group C (p < 0.05). Multivariate linear regression analysis demonstrated that all variables had independent positive correlation at 1 mm level of canal and at all levels of isthmus with statistical significances.ConclusionsBoth VPro StreamClean and EndoVac system showed favorable result as final irrigation regimens for cleaning debris in the complicated root canal system having curved canal and/or isthmus. The debridement of the isthmi significantly depends on the variables rather than the canals.