Vapor Lock Research Articles

A Comparative Study of Biofilm Removal with Hand, Rotary Nickel-Titanium, and Self-Adjusting File Instrumentation Using a Novel In Vitro Biofilm Model

IntroductionThis study sought to present a standardized biofilm model in extracted teeth with an artificial apical groove to quantify the efficacy of hand, rotary nickel-titanium, and self-adjusting file (SAF) instrumentation in biofilm bacteria removal. MethodsThirty-six extracted single-rooted teeth with oblong canals were selected. Each tooth was split longitudinally, and a 0.2-mm-wide groove was placed in the apical 2 to 5 mm of the canal. After growing mixed bacteria biofilm inside the canal under an anaerobic condition, the split halves were reassembled in a custom block, creating an apical vapor lock. Teeth were randomly divided into 3 treatment groups (n = 10 per group) using the K-file, ProFile (Dentsply Tulsa Dental Products, Tulsa, OK), and the SAF (ReDent-Nova, Ra'anana, Israel). Irrigation consisted of 10 mL 3% NaOCl and 4 mL 17% EDTA. Six teeth received no treatment. Areas inside and outside the groove were examined using a scanning electron microscope. ResultsThe scanning electron microscope showed a consistently thick layer of biofilm grown in the canals of the control group after 4 weeks. Within the groove, a smaller area remained occupied by bacteria after the use of the SAF compared with the ProFile and the K-file (3.25%, 19.25%, and 26.98%, respectively; P < .05). For all groups, significantly more bacteria were removed outside the groove than inside (P < .05). No statistical differences were found outside the groove (P > .05). ConclusionsAlthough all techniques equally removed bacteria outside the groove, the SAF reduced significantly more bacteria within the apical groove. No technique was able to remove all bacteria. This biofilm model represents a potentially useful tool for the future study of root canal disinfection.

Transient paralysis from carbon dioxide angiography in a patient after four-vessel endovascular thoracoabdominal aortic aneurysm repair

Contrast angiography with carbon dioxide (CO2) is frequently used in patients with renal dysfunction or iodinated contrast allergies, as CO2 is nonallergenic, nontoxic, and rapidly absorbed in the blood. However, when delivered intra-arterially, there is a possibility that CO2 may create a vapor lock with resultant transient ischemia. We describe a case of suspected CO2 embolus to the iliolumbar artery after iliac artery stenting resulting in immediate loss of bilateral lower extremity motor and sensory function. After placement of a spinal drain and elevation of mean arterial blood pressure, the patient had complete return of sensation with improvement in motor function.

Effect of Maintaining Apical Patency on Irrigant Penetration into the Apical Two Millimeters of Large Root Canals: An In Vivo Study

IntroductionFactors such as complex root canal anatomy and the vapor lock phenomenon have been shown to limit the penetration of irrigating solutions into the apical third in both in vivo and in vitro studies involving small and wide canals. Hence, the aim of this study was to determine whether the use of a patency file is related to the presence of a radiopaque irrigating solution in the apical 2 mm of large human root canals. MethodsForty-three large human root canals were randomly divided into 2 groups. Apical patency was maintained in 1 group (P, n = 22) during shaping and cleaning procedures with a no. 10 K-file 1 mm beyond the working length (WL) but not in the other group (no patency [NP], n = 21). In both groups, the canals were shaped with the K3 system. Irrigation was performed with 1 mL of a solution prepared with a radiopaque contrast medium and 5.25% sodium hypochlorite. Digital images were taken, and 2 calibrated readers determined the presence or absence of the irrigating solution in the apical 2 mm of the root canals. ResultsThere were significantly more canals with irrigant in the apical 2 mm when apical patency was maintained with a no. 10- Kfile 1 mm beyond the WL than when apical patency was not maintained throughout the cleaning and shaping procedures (P = .04). ConclusionsMaintaining apical patency improves the delivery of irrigants into the apical third of large human root canals.

Dynamic Movement of Intracanal Gas Bubbles during Cleaning and Shaping Procedures: The Effect of Maintaining Apical Patency on Their Presence in the Middle and Cervical Thirds of Human Root Canals—An In Vivo Study

Introduction The vapor lock effect has been shown to limit the penetration of irrigating solutions into the apical third of root canals both in vivo and in vitro; however, little attention has been given to gas bubbles in the remainder of the root canal system. Methods Seventy-one human root canals were randomly divided into 4 groups. Apical patency was maintained in 2 groups in both small (PS) (n = 21) and big canals (PB) (n = 15) during shaping and cleaning procedures with a 10 K-file 1 mm beyond working length but not in the other 2 groups: no patency, small canals (NPS) (n = 19) and no patency, big canals (NPB) (n = 16). Irrigation was performed with 1 mL of a solution prepared with a radiopaque contrast medium and sodium hypochlorite 5.25%. Digital images were taken, and a calibrated reader determined the presence or absence of gas bubbles in the middle and cervical thirds of the root canal system. Results When a patency file was not used, 40% of the root canals presented gas bubbles; when a patency file was used, 25% of the cases exhibited gas bubbles. Conclusions The presence of gas bubbles in the middle and cervical thirds of the root canal system during cleaning and shaping procedures is a common finding regardless of whether a patency file was used, although maintaining apical patency significantly leads to minimizing the presence of gas bubbles in big canals ( P < .05).

Discontinuation of the Plastic Bag Delivery System for Carbon Dioxide Angiography Will Increase Radiocontrast Nephropathy and Life-Threatening Complications

AJR:197, November 2011 pure CO2 may have contaminants, such as rust, methane, and particulate matter. We recommend using a disposable aluminum or a stainless steel cylinder that has not been previously used and has been individually tested for purity. Some of the cylinders available for anesthesia may contain 80% oxygen and 20% CO2. If CO2 cylinders are purchased from other vendors, they should be tested for purity with a mass spectrometer (usually available in anesthesia departments) or using an inexpensive chemical reagent tube (Colorimetric Gas Detector Tube, Sensidyne). If an excessive volume of CO2 is injected into the venous side of the circulation, blood will be displaced from the right heart and pulmonary artery, resulting in a vapor lock phenomenon and possibly cardiac arrest. If excessive amounts are injected into the arterial system, there can be reflux into unwanted areas, such as the cerebral or coronary circulation, which might be lethal. Again, the cylinder should never be connected directly to the patient because even with the plastic bag system CO2 could rapidly flow into the vascular circulation. If the syringe is filled directly from the cylinder, the pressurized CO2 will expand in the vessel causing reflux into the adjacent vessel and discomfort to the patient. No system should include stopcocks, which could be inadvertently malpositioned, or additional 3-way stopcocks to fill the plastic bag system. The 1500-mL bag contains more than enough volume for most diagnostic and interventional procedures. If the bag is filled only to atmospheric pressure (flaccid), the amount of CO2 aspirated into the syringe is always accurate in volume. A closed airtight system is absolutely necessary because the partial pressure difference between the syringe CO2 and room air will result in rapid diffusion of room air into the syringe if the stopcock is left open [4]. Any system with stopcocks should not be used because the stopcock could be left open Discontinuation of the Plastic Bag Delivery System for Carbon Dioxide Angiography Will Increase Radiocontrast Nephropathy and Life-Threatening Complications

Renewable Oxygenate Blending Effects on Gasoline Properties

The oxygenates ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol (isobutanol), 1-pentanol, 3-methyl-1-butanol (isopentanol), methyl levulinate, ethyl levulinate, butyl levulinate, 2-methyltetrahydrofuran (MTHF), 2-methylfuran (MF), and 2,5-dimethylfuran (DMF) were blended in three gasoline blendstocks for oxygenate blending (BOBs) at levels up to 3.7 wt % oxygen. Chemical and physical properties of the blends were compared to the requirements of ASTM specification D4814 for spark-ignited engine fuels to determine their utility as gasoline extenders. Vapor pressure, vapor lock protection, distillation, density, octane rating, viscosity, and potential for extraction into water were measured. Blending of ethanol at 3.7% oxygen increased vapor pressure by 5–7 kPa as expected. 2-Propanol slightly increased vapor pressure in the lowest-volatility BOB, while all other oxygenates caused a reduction in vapor pressure of up to 10 kPa. Coefficients for the Wilson equation were fitted to the ...

Siphoning—a weighty topic

Will a siphon work in a gravitational field without an atmosphere, such as on the Moon or in an evacuated bell jar? Sure it will. A siphon depends on gravity and not on atmospheric pressure. Of course, you have to assume a liquid that will not vaporize in a vacuum and cause a vapor lock.If you are siphoning water into a lake or gasoline out of a fuel tank, atmospheric pressure is a necessary condition to prevent vapor lock of those volatile liquids, but the pressure does not cause the siphon’s operation.© 2011 American Institute of Physics.

Hydration properties of mechanosensitive channel pores define the energetics ofgating

Opening of ion channels directly by tension in the surrounding membrane appears to be themost ancient and simple mechanism of gating. Bacterial mechanosensitive channels MscLand MscS are the best-studied tension-gated nanopores, yet the key physicalfactors that define their gating are still hotly debated. Here we present estimations,simulations and experimental results showing that hydration of the pore mightbe one of the major parameters defining the thermodynamics and kinetics ofmechanosensitive channel gating. We associate closing of channel pores with completedehydration of the hydrophobic gate (occlusion by ‘vapor lock’) and formation of twowater–vapor interfaces above and below the constriction. The opening path is theexpansion of these interfaces, ultimately leading to wetting of the hydrophobic pore,which does not appear to be the exact reverse of the closing path, thus producinghysteresis. We discuss specifically the role of polar groups (glycines) buried in narrowclosed conformations but exposed in the open states that change the wettingcharacteristics of the pore lining and stabilize conductive states of the channels.

Effect of Vapor Lock on Root Canal Debridement by Using a Side-vented Needle for Positive-pressure Irrigant Delivery

IntroductionThis study examined the effect of vapor lock on canal debridement efficacy by testing the null hypothesis that there is no difference between a “closed” and an “open” system design in smear layer and debris removal by using a side-vented needle for irrigant delivery. MethodsRoots in the closed system were sealed with hot glue and embedded in polyvinylsiloxane to restrict fluid flow through the apical foramen during cleaning and shaping. For the open system, the apical foramen was enlarged and connected to the external environment via a channel within the polyvinylsiloxane to permit unrestricted fluid flow. Smear and debris scores were evaluated by using scanning electron microscopy and analyzed by using Cochran-Mantel-Haenszel statistic. ResultsNo difference in smear scores was detected between the 2 systems at all canal levels. Significant differences in debris scores between the 2 systems were found at each canal level: coronal (P < .001), middle (P < .001), and apical (P < .001). ConclusionsThe null hypothesis was rejected; presence of an apical vapor lock effect adversely affects debridement efficacy. Thus, studies with unspecified or questionable mechanisms to restrict fluid flow through the apical foramen have to be interpreted with caution.

Flashing flow of superheated jet fuel

Fuel stabilization technologies make it possible to utilize jet fuel to meet the heat sink capability demanded by the high performance jet engines in development. The resultant high fuel temperature creates the danger of vapor lock in the fuel line but also the possibility of utilizing the flash boiling to enhance the spray and mixing characteristics of an aero-engine combustor. To incorporate this new technology into the next generation aero-combustors, we need a quantitative understanding of the effects of this non-equilibrium, or flash vaporization of fuel in the Jet-A family on both the internal flow and the spray. We present the first attempt in simulating the flashing flow of a superheated JP8 fuel using a multi-dimensional transient code which incorporates a multi-component surrogate model to predict the JP8 properties in the superheated regime and resolves the finite flash vaporization rate under realistic flight conditions. Our numerical code was validated against available flashing flow data for water. Our simulations with superheated JP8 showed that, with respect to flow control and risk mitigation, flashing induced choking can occur even when the flow is subsonic – a consequence of the significant and rapid expansion of the two-phase fluid during the flashing process. This restriction on the flow rate, however, can be effectively controlled by adjusting the up-stream pressure. Our simulations also provided the initial conditions for the spray model. It showed that the spray core at the exit of the injector is non-uniform and is in the superheated state of varying degrees. A preliminary analysis of the flash vaporization time scale and the spray core breakup time indicated that the flashing phenomenon will play an important role in the spray breakup processes which will constitute our further works.

Study on the application of DME/diesel blends in a diesel engine

In this paper fuels, based on various DME to diesel ratios are investigated. Physical and chemical properties of DME and diesel display mutual solubility at any ratio. The vapor pressure of DME/diesel blends is lower than that of pure DME at the same temperatures and it decreases with an increase of diesel mass fraction in blends, which is beneficial to the elimination of vapor lock in the fuel supply system on CI engines. Performance, emission and other features of three kinds of DME/diesel blend fuels and diesels are evaluated in a four-cylinder test engine. By taking relative advantages of DME and diesel, the DME/diesel blends could achieve satisfactory properties in lubricity and atomization, which contributed to improvements in spray and combustion characteristics. Simultaneously, smoke emission could be reduced significantly with a little penalty on CO and HC emissions for DME/diesel blended engine at high loads, in comparison to diesel engine. NO x emissions of the engine powered by DME/diesel blends are decreased somewhat. Moreover, the power output would be improved a little and NO x emission could be reduced further if the fuel supply advance angle is retarded appropriately.

In Vitro Evaluation of a Micro-Doppler Catheter for Detection and Aspiration of Venous Air Emboli

Venous air embolism (VAE) is a potentially fatal complication of surgery when open veins at a surgical site are exposed to ambient air pressure which exceeds the pressure in the venous system. Common techniques of detecting VAE are precordial Doppler monitoring and transesophogeal echocardiography. Precordial Doppler monitoring has poor accuracy and transesophogeal echocardiography is expensive and user-intensive. In both methods, a separate catheter must be inserted into the vena cava so that an embolus may be aspirated if it is detected. We created a micro-Doppler assembly using two ceramic transducers fitted over a 5.8F multiorifice central venous catheter. This micro-Doppler catheter (MDC) was tested in vitro using a static tank and an artificial vena cava (AVC). The MDC was also tested for acoustic pressure and current leakage in the static tank and for heat generation and cavitation in the AVC. The MDC was able to detect bubbles more than 2 mm in diameter with 100% accuracy. A blinded observer was able to identify the onset of vapor lock in 10 of 10 trials. The same observer was able to terminate vapor lock in 10 of 10 trials. The acoustic pressures measured were <1.8 MPa. There was no increase in temperature in the AVC over 24 h and there was no evidence of cavitation in the AVC over 4 h. We have created a MDC that can detect air emboli and relieve vapor lock in a simulated vena cava and atrium. This catheter could be placed percutaneously in the vena cava. Based on the measurements of acoustic pressure, temperature in the AVC and lack of cavitation in the AVC, the device appears to be safe for use in humans. More studies are required to determine if the catheter could be used to detect and aspirate VAE during surgeries where VAE is likely, such as sitting craniotomy.

Discharge on boiling in a channel: Effect of channel geometry on the performance characteristics of determining metals in a liquid flow by atomic emission spectrometry

Discharge on boiling in a channel was studied as a new atomization and excitation source for spectrochemical analysis in a flow of electrolyte solutions. The discharge arises between the liquid walls of a vapor lock formed in the channel of a dielectric membrane because of the rapid Joule heating of the liquid in the channel. The effect of channel geometry on the reproducibility of the integrated light intensity was studied. The background radiation spectrum was measured over the range 220–900 nm, and the possibility of determining alkali and alkaline earth metals in a flow was studied. The parameters of linear calibration equations and the detection limits for these metals are given.

Improvements in the Measurement of Distillation Curves. 1. A Composition-Explicit Approach

The distillation (or boiling) curve of a complex fluid is a critically important indicator of the bulk behavior or response of the fluid. For this reason, the distillation curve, usually presented graphically as the boiling temperature against the volume fraction distilled, is often cited as a primary design and testing criterion for liquid fuels, lubricants, and other important industrial fluids. While the distillation curve gives a direct measure of fluid volatility fraction by fraction, the information the curve contains can be taken much further; there are numerous engineering and application-specific parameters that can be correlated to the distillation curve. When applied to liquid motor fuels, for example, one can estimate engine starting ability, drivability, fuel system icing and vapor lock, the fuel injector schedule, and fuel autoignition, etc. It can be used in environmental applications as a guide for blending virgin stock with reclaimed oil, guiding the formulation of product that will be suitable in various applications. Moreover, the distillation curve can be related to mutagenicity and the composition of the pollutant suite. It is therefore desirable to enhance or extend the usual approach to distillation curve measurement to allow optimal information content. In this paper, we present several modifications to the measurement of distillation curves that provide (1) temperature and volume measurement(s) of low uncertainty and, most important, (2) a composition-explicit data channel in addition to the usual temperature−volume relationship. This latter modification is achieved with a new sampling approach that allows precise qualitative as well as quantitative analyses of each fraction, on the fly. The analysis is done by gas chromatography coupled with specific or universal detectors. This second modification is the most significant change, since it is composition that is the most important underlying parameter that governs curve shape.

Pater familias.

Pater familias.

Gas-Based Vascular Imaging

Intravascular injection of contrast solutions is the de facto standard method for diagnosis of vaso-occlusive disease. However, these agents have osmolar, chemotoxic, and anaphylactic risks. Use of gas as a contrast medium has significant potential to avoid these recognized limitations of conventional contrast media solutions. Additionally, automated intravascular injection of various gases may enable novel imaging approaches with different imaging modalities (computed tomography [CT], ultrasound, magnetic resonance imaging [MRI], and others). This potential can be conceptualized and tested for vascular applications based on the following underlying principles: (a) Gases can be injected through smaller and less traumatic access systems than liquids. (b)Gases can transit smaller vascular conduits than liquids. (c) Highly soluble gases (such as CO2) can be imaged as a bolus, which provides negative contrast by displacing the blood column. (d)Even poorly soluble gases can be safely introduced intravascularly if the injection mode permits dispersion in the fluid phase and avoids formation of macrobubbles that could cause vapor lock. Appropriate gas–fluid (blood) boluses can be imaged if the gases have special properties such as high molecular weight (eg, xenon) for density imaging, or affect magnetic properties (eg, hyperpolarized gases such as xenon, helium, argon, or oxygen) for MRI.

Control method for brake vapor lock in automobiles

Our basic idea for brake vapor lock is founded on our previously published theories, in which the phenomenon is caused by the bubble growth in the braking equipment. The restraining method for the vapor lock is to shift the fluid inlet point for disk brake, to the point of the air bleed screw. In this report, we confirmed the effect of this method after braking tests using a passenger car. For example, the brake fluid pressure in the braking device could be gained, even if the fluid temperature rises over the fluid boiling point.

Quench energies and stagnant normal zones in cryostable magnets

In a cryostable magnet cooled by pool boiling helium, an area with deteriorated heat transfer, such as a vapor lock, can locally destroy stability in the winding. When a thermal disturbance occurs in this area, depending on its energy and the size of the area, it can: (a) lead to recovery of the superconducting state; (b) develop into a local steady normal zone; or (c) create an ever-growing stagnant zone. The stagnant zone is characterized by an uncontrollable temperature growth in the center, reaching hundreds of K in several minutes, while its fronts slowly advance into cryostable regions. It represents the most probable quench scenario in a cryostable magnet and should be considered as a main target for a quench protection system. Classification of different normal zones in a cryostable winding with a vapor lock is presented. Criteria are derived which determine regions of existence of steady and stagnant zones in conductors with nonlinear properties and heat transfer. Critical sizes of the uncooled area are defined, and quench energies are calculated for copper and aluminum stabilized conductors.

The Formation and Behavior of Vapor Lock"Pressure Seals and Associated Hydrocarbon Accumulations in Geologically Young Basins: ABSTRACT"

The Formation and Behavior of Vapor Lock"Pressure Seals and Associated Hydrocarbon Accumulations in Geologically Young Basins: ABSTRACT"

CO2 Digital Angiography: A Safer Contrast Agent for Renal Vascular Imaging?

Although the new nonionic contrast agents are safer than ionic agents, renal insufficiency and even death still occur occasionally. Therefore, we have explored the use of carbon dioxide (CO2) as an alternative angiographic contrast agent used in combination with digital subtraction angiography. Clinical observations have been made in over 800 patients. The images obtained are of equivalent diagnostic quality compared with those using conventional iodinated contrast agents. Recent advances in imaging, including “stacking,” provide images comparable with iodinated contrast. Very small vessels, equivalent to third-order branches of the renal artery, can be imaged satisfactorily with CO2. Occasional studies with CO2 yield information not apparent with iodinated contrast agents, including excellent visualization of arteriovenous shunts, collateral circulations, malignant tumors, and minute amounts of arterial bleeding. Many of the advantages and disadvantages of CO2 derive from its special physical and chemical properties. The advantages include no allergic potentiation and no renal metabolism of CO2, because CO2 is cleared by the lungs and does not recirculate. Other advantages include delivery by very small catheters because of the low viscosity of CO2, minimal discomfort on injection, and very low cost. However, the low-density and compressibility of CO2 poses some special problems. Imaging requires digital subtraction angiography with electronic enhancement and injections require an experienced investigator and, ideally, a dedicated CO2 injector. The dedicated C02 injector provides calculated, controlled dosing and rates for injection, while excluding the possibility of air contamination. The buoyancy of CO2 inhibits good filling of dependent vessels. Accordingly, CO2 does not normally produce good nephrographic images, although proximal renal arteries are normally shown clearly. Experimental studies in dogs, whose renal arteries have been injected repeatedly with very large doses of CO2, demonstrate only transient changes in renal blood flow and no endothelial cell damage. However, these studies also showed clearly that renal ischemia can occur due to a “vapor lock” phenomenon if the kidney is positioned vertically above the injection site, and recurrent injections are given without time for absorption of the arterially delivered CO2 boluses. Uncontrolled studies in over 800 patients have confirmed that CO2 likely has a very low renal toxicity. At the University of Florida, CO2 is the radiologic contrast agent of choice in patients with renal insufficiency, especially those with diabetes mellitus, and in those with pre-existing allergy to iodinated contrast agents. Further controlled clinical studies are required to define the true clinical utility and safety of CO2 compared with conventional radiologic contrast agents.