Initial Leakage Rate Research Articles

Simulation evaluation of a single-photon laser methane remote sensor for leakage rate monitoring.

We propose a novel methane leakage rate remote sensor that combines a single-photon avalanche diode detector with a near-infrared 1653.7 nm low-power laser. The proposed M sequence and triangle wave signal modulation method simultaneously realizes the detection of methane leakage and target point clouds. Innovatively, the sensor's methane concentration and leakage rate quantification ability were simulated by combining the Gaussian plume diffusion model and the Risley prism. The effects of the prism rotation ratio, wind speed, leakage rate, atmospheric stability (AS), target reflectivity, signal averaging period, and concentration spatial interpolation method on leakage rate are discussed. When plume methane concentrations reduce from 10,000 to 500 ppm·m, the relative concentration bias rise from 1% to 30%, the absolute concentration bias is approximately 100 ppm·m. Two spatial concentration interpolation methods introduced leakage rate bias ranging from 6%-25%. For a low AS, the leakage rate bias under the cubic interpolation method was small (approximately 1.6%). In addition, when the initial leakage rate increased from 100 to 1,000 mg/s, the leakage rate bias was approximately 20% smaller.

Potential influences of leakage through a high permeability path on shallow aquifers in compressed air energy storage in aquifers

The potential leakage influences of compressed air energy storage in aquifers, especially on the overlying shallow aquifer environment, need more attention, but there is still a lack of relevant studies. In this research, a coupled wellbore-reservoir underground anticline model is simulated using T2Well/EOS3. Two-phase non-Darcy flows, different from the multiphase Darcy flow in porous media, are considered in both the central working wellbore and a highly permeable leakage path. In an anticline, the results show that the leakage rate will decline and reach a relatively steady state as the cycles continue. The final continuous small periodic oscillations of leakage rate occur with a hysteresis effect with respect to cycle injection-production. When air leakage occurs in the initial gas bubble process, it gradually disappears and gets replaced by brine leakage. A decrease in the reservoir permeability can result in a larger initial leakage rate, but a smaller rate and fluctuation during the cycle process. However, in a horizontal reservoir, strong gas fingering increases the risk of air leakage, which, once occurs, can last during the rest of the process. This research can deepen the understanding of the leakage process and help evaluate and prevent incidents of environmental contamination in gas storage in aquifers.

Deflation and collapse of air-supported membrane structures

Air-supported membrane structures are widely used in stadiums, malls, and museums. The stiffness and shape of such structures are dependent on the pressure difference between the indoor and outdoor environments. As the leakage of indoor air may lead to the collapse of the structure, it is necessary to study the deflation deformation process, including the properties that can cause air-supported membrane structures to collapse. In this study, a rectangular air-supported membrane structure is fabricated using a PVC-coated polyester fabric membrane with dimensions of 38 m × 20 m × 7 m, and a leakage experiment is performed. The relationship between the initial leakage area and the pressure difference is obtained, and a new algorithm to determine the equivalent initial leakage rate is proposed. A collapse test is then conducted, with results illustrating that there are two distinct phases of collapse. There is a quick drop in the pressure difference in the first phase, whereas the pressure difference declines rather slowly in the second phase. Computational formulae for collapse and escape times are established, and finally, a quasi-equilibrium status-based algorithm to determine the collapse time of air-supported structures is proposed. Using the new algorithm, several main parameters that influence the collapse of air-supported structures are studied, including the cables, initial pressure, and leakage area. Results show that the initial pressure has a minimal effect on the collapse of structures, while excessive cables accelerate the process of collapse.

Injection of a CO2-Reactive Solution for Wellbore Annulus Leakage Remediation

Driven by concerns for safe storage of CO2, substantial effort has been directed on wellbore integrity simulations over the last decade. Since large scale demonstrations of CO2 storage are planned for the near-future, numerical tools predicting wellbore integrity at field scale are essential to capture the processes of potential leakage and assist in designing leakage mitigation measures. Following this need, we developed a field-scale wellbore model incorporating (1) a de-bonded interface between cement and rock, (2) buoyancy/pressure driven (microannulus) flow of brine and CO2, (3) CO2 diffusion and reactivity with cement and (4) chemical cement-rock interaction. The model is aimed at predicting leakage through the microannulus and specifically at assessing methods for CO2 leakage remediation. The simulations show that for a low enough initial leakage rate, CO2 leakage is self-limiting due to natural sealing of the microannulus by mineral precipitation. With a high leakage rate, CO2 leakage results in progressive cement leaching. In case of sustained leakage, a CO2 reactive solution can be injected in the microannulus to induce calcite precipitation and block the leak path. The simulations showed full clogging of the leak path and increased sealing with time after remediation, indicating the robustness of the leakage remediation by mineral precipitation.

Results of Sleeve Gastrectomy in Germany—Data on Nationwide Survey on Quality Assurance in Bariatric Surgery in Germany

Background: Since January 1st of 2005, the situation of bariatric surgery is being analyzed in Germany. The data is registered prospectively in cooperation with the Institute of Quality Assurance in Surgery at the Otto-von-Guericke University Magdeburg. Methods: The data is registered through an online database which includes all information for primary and revision bariatric procedures as well as yearly follow-up. Participation in the quality assurance study is optional. All certificated centers have to participate at the survey. Results: From January 2006 to December 2009, 1478 sleeve gastrectomies (SG) were performed at 45 hospitals. The number of procedures has increased from 126 in 2007 to 933 in 2009. The main complication is leakage of the staple-line. Initial leakage rate was 7% in 2007. Leakage rate dropped down to 2.3% in 2008 and 2.5% in 2009. Mean age of patients was 43.1 years and mean BMI was 52.83 kg/m2. Age and BMI were significantly higher in patients with SG than in all other patients undergoing bariatric surgery. Conclusion: SG is a common and hype bariatric procedure in Germany, but postoperative complication rate is high. Data on the long-term effect of SG on weight loss and amelioration of comorbidities need to be evaluated. More detailed analyzes are necessary to establish the position of SG in the bariatric surgery. Further studies should also include examinations on long-term complications and redo-procedure after SG.

Thermal cycle stability of Al 2O 3-based compressive seals for planar intermediate temperature solid oxide fuel cells

Al 2O 3-based compressive seals were fabricated by tape casting with Al 2O 3 and 0–30 wt% aluminum powders, and their sealing effectiveness, thermal cycle stability between 200 and 750 °C and applicability in planar intermediate temperature solid oxide fuel cells were evaluated. The results indicate that increasing the aluminum content from 0 to 30 wt% in the seals decreases the leakage rate and increases the thermal cycle stability under various inlet gas (N 2) pressures of 3.5, 7.0 and 10.5 kPa. Especially, with the seal containing 30 wt% of aluminum (ACS3), the initial leakage rate was below 0.03 sccm cm −1 under an inlet pressure of 10.5 kPa, and the leakage rates during 96 thermal cycles were below 0.04 sccm cm −1 under the same inlet gas pressure. The interfaces in the interconnect/seal/cell assembly with the ACS3 seal retained integrity after 50 thermal cycles, demonstrating the applicability of the Al 2O 3-based compressive seals in the planar intermediate temperature SOFCs.

Interactions of Novel, Nonhemolytic Surfactants with Phospholipid Vesicles

PEG-12-acyloxystearates constitute a novel class of pharmaceutical solubilizers and are synthesized from polyethylene glycol and 12-hydroxystearic acid, which has been esterified with a second acyl chain. The hemolytic activity of these surfactants decreases drastically with increasing pendant acyloxy chain length, and surfactants with an acyloxy chain of 14 carbon atoms or more are essentially nonhemolytic. In this paper, the interactions of PEG-12-acyloxystearates (acyloxy chain lengths ranging from 8 to 16 carbon atoms) with phosphatidylcholine vesicles, used as a model system for erythrocyte membranes, were studied in search of an explanation for the large variations in hemolytic activity. Surfactant-induced alterations of membrane permeability were investigated by studying the leakage of vesicle-entrapped calcein. It was found that all of the surfactants within the series interact with the vesicle membranes and cause slow leakage at elevated surfactant concentrations, but with large variations in leakage kinetics. The initial leakage rate decreases rapidly with increasing pendant acyloxy chain length. After prolonged incubation, on the other hand, the leakage is not a simple function of acyloxy chain length. The effect of the surfactants on membrane integrity was also investigated by turbidity measurements and cryo-transmission electron microscopy. At a surfactant/lipid molar ratio of 0.4, the vesicle membranes are saturated with surfactant. When the surfactant/lipid molar ratio is further increased, the vesicle membranes are progressively solubilized into mixed micelles. The rate of this process decreases strongly with increasing acyloxy chain length. When comparing the results of the different experiments, it can be concluded that there is no membrane permeabilization below saturation of the vesicle membranes. The large variations in the kinetics suggest that several steps are involved in the mechanism of leakage induced by PEG-12-acyloxystearates and that their relative rates vary with acyloxy chain length. The slow kinetics may in part be explained by the low critical micelle concentrations (CMCs) exhibited by the surfactants. The CMCs were found to be in the range of 0.003-0.025 microM.

Seismic response and failure modes for a water storage structure - A case study

The present paper deals with the seismic response analysis and the evaluation of most likely failure modes for a water storage structure. For the stress analysis, a 3-D mathematical model has been adopted to represent the structure appropriately. The structure has been analyzed for both static and seismic loads. Seismic analysis has been carried out considering the hydrodynamic effects of the contained water. Based on the stress analyses results, the most likely failure modes viz. tensile cracking and compressive crushing of concrete for the various structural elements; caused by the seismic event have been investigated. Further an attempt has also been made to quantify the initial leakage rate and average emptying time for the structure during seismic event after evaluating the various crack parameters viz. crack-width and crack-spacing at the locations of interest. The results are presented with reference to peak ground acceleration (PGA) of the seismic event. It has been observed that, an increase in PGA would result in significant increase in stresses and crack width in the various structural members. Significant increase in initial leakage rate and decrease in average emptying time for the structure has also been observed with the increase in PGA.

Seismic response and fragility analysis of a water storage structure

Stress analysis of a water storage structure has been carried out for static and seismic loading. Based on the stress analyses results, assessment of most likely failure modes for the structure caused by seismic event has been carried out. An attempt has been made to quantify the initial leakage rate and average emptying time for the structure during seismic event after evaluating the various crack parameters, viz., crack-width and crack-spacing at the locations of interest. Finally, the seismic fragility of the structure is developed as families of conditional probability curves plotted against peak ground acceleration (PGA) parameter at the location of interest considering the randomness and uncertainty associated with various parameters that could affect the seismic structural response.

The antibacterial effects of terpene alcohols on Staphylococcus aureus and their mode of action

The study was made of the antibacterial effects of three terpene alcohols on Staphylococcus aureus, focusing on the leakage of K+ ions and toxicity over time. The leakage of K+ ions was monitored continuously with a K+-electrode. Our results suggested that the terpene alcohols, namely, farnesol, nerolidol and plaunotol might act on cell membranes. The rank order of effectiveness, farnesol>nerolidol>plaunotol, was the same in the toxicity assay and in the examination of the leakage of K+ ions, when we considered the initial rate and the amount of leaked K+ ions. The rank order agreed with the results of a growth-inhibition assay reported previously. The antibacterial activity reflected the initial rate of leakage of K+ ions, suggesting that damage to cell membranes might be one of the major modes of action of these terpene alcohols. The results also demonstrated that the initial rate of leakage and the amount of leaked K+ ions are useful as indices of the antibacterial activities of hydrophobic compounds.

The antibacterial effects of terpene alcohols on Staphylococcus aureus and their mode of action

The study was made of the antibacterial effects of three terpene alcohols on Staphylococcus aureus, focusing on the leakage of K + ions and toxicity over time. The leakage of K + ions was monitored continuously with a K +-electrode. Our results suggested that the terpene alcohols, namely, farnesol, nerolidol and plaunotol might act on cell membranes. The rank order of effectiveness, farnesol > nerolidol > plaunotol, was the same in the toxicity assay and in the examination of the leakage of K + ions, when we considered the initial rate and the amount of leaked K + ions. The rank order agreed with the results of a growth-inhibition assay reported previously. The antibacterial activity reflected the initial rate of leakage of K + ions, suggesting that damage to cell membranes might be one of the major modes of action of these terpene alcohols. The results also demonstrated that the initial rate of leakage and the amount of leaked K + ions are useful as indices of the antibacterial activities of hydrophobic compounds.

Leakage of K + ions from Staphylococcus aureus in response to tea tree oil

The leakage of K + ions from Staphylococcus aureus in response to tea tree oil (TTO) was investigated with an ion-selective electrode. The amount of leaked K + ions and the rate of leakage of K + ions induced by TTO were dependent on the concentration of TTO. Measurements of initial rates required less time than measurements of total amounts and provided an index of the interaction between TTO and the cell membrane. Thus, the initial rate of leakage might be a more useful measure of the antibacterial activity of TTO than the total amount.

Physiochemical characterization of the nisin-membrane interaction with liposomes derived from Listeria monocytogenes.

Mechanistic information about the bacteriocin nisin was obtained by examining the efflux of 5(6)-carboxy-fluorescein from Listeria monocytogenes-derived liposomes. The initial leakage rate (percentage of efflux per minute) of the entrapped dye was dependent on both nisin and lipid concentrations. At all nisin concentrations tested, 5(6)-carboxyfluorescein efflux plateaued before all of the 5(6)-carboxyfluorescein was released (suggesting that pore formation was transient), but efflux resumed when more nisin was added. Isotherms for the binding of nisin to liposomes constructed on the basis of the Langmuir isotherm gave an apparent binding constant of 6.2 x 10(5)M(-1) at pH 6.0. The critical number of nisin molecules required to induce efflux from liposomes at pH 6.0 was approximately 7,000 molecules per liposome. The pH affected the 5(6)-carboxyfluorescein leakage rates, with higher pH values resulting in higher leakage rates. The increased leakage rate observed at higher pH values was not due to an increase in the binding affinity of the nisin molecules towards the liposomal membrane. Rather, the critical number of nisin molecules required to induce activity was decreased (approximately 1,000 nisin molecules per liposome at pH 7.0). These data are consistent with a poration mechanism in which the ionization state of histidine residues in nisin plays an important role in membrane permeabilization.

Capillary leakage of a macromolecular MRI agent, carboxymethyldextran-Gd-DTPA, in the liver: pharmacokinetics and imaging implications.

Capillary leakage of a macromolecular contrast agent, Carboxymethyl Dextran-Gd-DTPA (CMD-Gd-DTPA) was characterized in a highly permeable system, the liver, to assess its potential as a blood pool marker. Its elimination kinetics in hepatic lymph were compared in nephrectomized rabbits with that of a tracer of extra cellular fluid space, Gd-DOTA. Four parameters were defined: volume of distribution, normalized initial leakage rate (ILRn), maximum ratio of lymph and plasma concentrations (max Cl/Cp), and the time to obtain this maximum ratio. The effect of this leakage was studied on MR images by comparing liver contrast enhancement after injection and after almost total removal of the contrast agent from the blood by exchange transfusion. Capillary leakage of CMD-Gd-DTPA was detected in lymph. Compared to Gd-DOTA, it was slower (ILRn = 0.36 10(-5) l min-1 for CMD-Gd-DTPA and ILRn = 2.6 10(-5) l min-1 for Gd-DOTA), less abundant (max Cl/Cp was 80% for CMD-Gd-DTPA and 100% for Gd-DOTA). Liver enhancement remained stable, which indicated that the leakage did not modify the enhancement induced by the intravascular fraction of the contrast agent. These results obtained in a highly permeable capillary model indicate that this agent can be used as a selective blood pool enhancer.

Peptide inhibitors of enveloped virus infection inhibit phospholipid vesicle fusion and Sendai virus fusion with phospholipid vesicles.

Small hydrophobic peptides that are capable of inhibiting Sendai virus infection of cells (Richardson, C. D., Scheid, A., and Choppin, P. W. (1980) Virology 105, 205-222) are also capable of inhibiting membrane fusion in a pure lipid vesicle system. Large unilamellar vesicles of N-methyl dioleoylphosphatidylethanolamine containing encapsulated 1-aminonaphthalene-3,6,8-trisulfonic acid and/or p-xylene bis (pyridinium bromide) were formed by extrusion. Vesicle fusion (contents mixing) and leakage were then monitored with the 1-aminonaphthalene-3,6,8-trisulfonic acid/p-xylene bis(pyridinium bromide) fluorescence assay. Sendai virus fusion with lipid vesicles was measured by following the relief of fluorescence quenching of virus labeled with octadecylrhodamine B chloride, a lipid mixing assay for fusion. The efficiency with which the peptides carbobenzoxy-D-Phe-L-PheGly, carbobenzoxy-L-Phe-L-Tyr, and carbobenz-oxy-Gly-L-Phe inhibit fusion of N-methyl dioleoyl-phosphatidylethanolamine large unilamellar vesicles directly paralleled their previously known effectiveness in blocking virus infectivity of cultured cells. In addition, above a certain concentration threshold, the inhibitory peptides decreased the initial rate of leakage from lipid vesicles. The inhibition by these peptides of virus-vesicle fusion followed the same order of potency as for vesicle-vesicle fusion. The observation of the same relative potency of these peptides toward inhibition of virus-cell infection, and virus-vesicle and vesicle-vesicle membrane fusion suggested that these peptides inhibited virus-cell infection by inhibiting the ability of the virus to fuse with the cell. Furthermore, these results suggest that the mechanism of inhibition of all three fusion events may have steps in common.

Modulation of membrane fusion by membrane fluidity: temperature dependence of divalent cation induced fusion of phosphatidylserine vesicles.

We have investigated the temperature dependence of the fusion of phospholipid vesicles composed of pure bovine brain phosphatidylserine (PS) induced by Ca2+ or Mg2+. Aggregation of the vesicles was monitored by 90 degrees light-scattering measurements, fusion by the terbium/dipicolinic acid assay for mixing of internal aqueous volumes, and release of vesicle contents by carboxyfluorescein fluorescence. Membrane fluidity was determined by diphenylhexatriene fluorescence polarization measurements. Small unilamellar vesicles (SUV, diameter 250 A) or large unilamellar vesicles (LUV, diameter 1000 A) were used, and the measurements were done in 0.1 M NaCl at pH 7.4. The following results were obtained: (1) At temperatures (0-5 degrees C) below the phase transition temperature (Tc) of the lipid, LUV (PS) show very little fusion in the presence of Ca2+, although vesicle aggregation is rapid and extensive. With increasing temperature, the initial rate of fusion increases dramatically. Leakage of contents at the higher temperatures remains limited initially, but subsequently complete release occurs as a result of collapse of the internal aqueous space of the fusion products. (2) SUV (PS) are still in the fluid state down to 0 degree C, due to the effect of bilayer curvature, and fuse rapidly in the entire temperature range from 0 to 35 degrees C in the presence of Ca2+. The initial rate of leakage is low relative to the rate of fusion. At higher temperatures (15 degrees C and above), subsequent collapse of the vesicles' internal space causes complete release.(ABSTRACT TRUNCATED AT 250 WORDS)

Postirradiation Permeability of Escherichia coli Cells

Escherichia coli cells that have been subjected to gamma irradiation show leakage of components. Those associated with DNA appear in the medium with no lag. The absence of lag is observed even for cells in which the tracer label is far from the polymerase, indicating that the enzyme causing DNA degradation is probably not the polymerase. A temperature-sensitive mutant that does not synthesize DNA at temperatures above 42°C nevertheless shows leakage. The amount, but not the initial rate of leakage, is oxygen-dependent. Leakage after a lag of 40 minutes is observed in many, but not all, strains. This is general, indicating a considerable impairment of the permeability barrier. The strain dependence, temperature dependence, and lack of oxygen sensitivity strongly suggest that the delayed permeability is associated with the induction of a defective prophage. Leakiness in all cells occurs at long times after irradiation. We suggest that this is due to a developing imbalance in enzyme content due to radiation ...