Average Leak Research Articles

Advanced Autonomous Welding for Refabrication and Follow-On Testing of Previously Irradiated Nuclear Fuel

The performance of follow-on experiments using irradiated nuclear fuel at any point in its lifecycle is a critical step in understanding phenomena and behavior. Transient experiments with high-burnup fuel can deepen the understanding of fuel fragmentation, relocations, and dispersal under loss-of-coolant accidents. An advanced autonomous welding process to refabricate commercial fuel rods inside a hot cell was created and tested to enable flexible experiment approaches on fuels irradiated in commercial and test reactors. Irradiated light water reactor fuel test pins from experiments performed at the Advanced Test Reactor (ATR) at Idaho National Laboratory were used to demonstrate the refabrication process. The welding process was found to be sensitive to welding parameters but flexible such that multiple passes could be performed on the same location until a hermetic weld was obtained. The refabrication of rodlets and successful welds was also found to be sensitive to the preparation of the irradiated cladding and endcaps. Thorough defueling of the fuel at the weld location and proper sizing of the endcaps and backing material mitigated these issues. The use of strategically located heat sinks in contact with the cladding and endcap materials also increased welding and refabrication success. For this work, the test pins were sectioned to remove the original endcaps and fuel was removed from both ends of each rodlet. The reassembly of the rodlets was then completed in four steps, which included the press fitting of new endcaps, the circumferential welding of rodlet endcaps to the cladding, rodlet pressurization in a pressure chamber, and seal welding the rodlet under pressure. The integrity of the refabricated rodlets was then verified via helium leak checking inside a vacuum chamber. The advanced welding system is capable of refabricating rodlets up to 380 mm in length, and repressurizing them up to 15 500 kPa. The refabricated lengths of the rodlets used in this work ranged from 149 to 165 mm and the refabricated fuel stack heights ranged from 70.4 to 79.8 mm. The rodlets were pressurized with argon to an average pressure of 3617 kPa, and the average leak rate after refabrication was 6.7∙10−8∙cm3∙s−1.

Characteristics of Volatile Organic Compound Leaks from Equipment Components: A Study of the Pharmaceutical Industry in China

Leak detection and repair (LDAR) plays an important role in controlling the fugitive emission of volatile organic compound (VOC) from chemical enterprises. At present, many policies and standards issued in China have set clear requirements for implementing LDAR in the pharmaceutical industry. In this study, the LDAR work of nine typical pharmaceutical enterprises was selected for analysis to allow investigation of the characteristics of VOC emissions from leaking equipment components. Some suggestions for controlling VOC are proposed to provide a reference for managing the fugitive emissions of VOC from pharmaceutical enterprises. The results showed that the number of equipment components used by the pharmaceutical enterprises ranged from several thousand to more than 20,000, which is lower than that in oil refining and coal chemical enterprises. The predominant leaky component was the flange, which accounted for 56.31% of the total, followed by connectors (21.51%) and valves (18.53%). Light liquid medium components accounted for the largest proportion of equipment (52.83%) on average, followed by gas medium components (45.52%, on average). Heavy liquid medium components, which are rarely used in pharmaceuticals, accounted for only 1.65%. The average leak ratio of the components in the pharmaceutical industry was approximately 0.99%. The leak ratio of the open-ended line was much higher than that of other types of components, reaching an average of 5.00%, while that value was only 0.92% for the flange, despite the numbers and proportion of them that were in use. The total annual VOC leakage from the nine pharmaceutical enterprises studied in this work was 20.11 tons, with an average of 2.23 tons per enterprise and an average of 0.22 kg/a per equipment component. Flanges, connectors, and valves were the top three contributors to leakage, generating 39.17%, 38.72%, and 16.79% of the total, respectively, and a total proportion of 94.68%. Although the number of pumps accounted for only 0.15% of the components, it generated 1.94% of the leakage. In terms of different production processes, the greatest unit product leakage came from the bulk production of chemicals used for pharmaceuticals, reaching 0.085 t/a. The production from traditional Chinese medicine enterprises was the lowest (0.011 t/a), which was only 12.80% of the leakage from the bulk production of chemicals for drugs. The leakage of VOC from the equipment components in the nine enterprises was reduced, to varying degrees, using LDAR. The overall reduction ratio was between 23.55% and 67.72%, with an average of 44.02%. The reduction in leakage was relatively significant after the implementation of LDAR; however, there is still room for improvement. Pharmaceutical enterprises should improve their implementation of LDAR and reduce VOC leakage by reducing the number of inaccessible components used and increasing the repair ratio of leaky components. Controlling the source of component leakage, which should be emphasized, can be realized by cutting down the number of components used, adopting low-leakage equipment, and putting anti-leakage measures in place.

Leakage estimation in water networks based on the BABE and MNF analyses: a case study in Gavankola village, Iran

Abstract Calculating the water loss and leakage in the water distribution networks (WDNs) is performed for various reasons such as monitoring and optimizing, active control, estimating economical damage, and predicting the demand in the network development plans. In this research, two leakage calculation methods including Background and Bursts Estimates (BABE) and minimum night flow (MNF) have been evaluated for a rural network in the north of Iran with a high non-revenue water (NRW) percentage of 47%. Initially, the data related to the inlet flow rate of the network and the average pressure at zone was measured using ultrasonic flow meters and pressure transmitter, respectively. Then, remote data loggers collected these data. With the water loss analyses based on the BABE method (annually) and based on the MNF technique (every 10 minutes), the average leak was found to be 1.45 and 1.105 Lit/s, respectively. Also, according to hydraulic and consumption conditions, the highest frequency of MNF occurrence was observed at 00:00 and 05:00. Moreover, the effects of legitimate night-time consumption (LNC) and leakage exponent (N) were evaluated. The results indicate that determining the LNC, especially in the networks in which the domestic customers use private tanks, is significantly important.

Experimental measurements and theoretical simulation of sodium combustion aerosol leakage through capillaries

In severe accident of Sodium cooled Fast Reactors, containment would be pressurized due to release of radioactive materials and sodium which will form aerosols. These aerosols are released to environment through various leak pathways of containment (cracks, penetrations etc.). The time evolution of these aerosols hovered inside containment and its leakage is very much important for the realistic assessment of environmental source term. In this paper, studies regarding sodium aerosol leakage through capillaries as a function of pressure, aerosol concentration, humidity and dimensions of capillary are reported. Total leaked and plugged mass of aerosol and average leak rates are determined for various experimental conditions. A theoretical model representing the transport of aerosols through capillaries is developed, verified with the measured values and reasonable agreement is found. This work will aid in better understanding of phenomena important for the leakage of radioactive aerosol through cracks developed in severe accident of reactor.

A Novel Silver-Based Braze Sealant for Metal-Supported Solid Oxide Fuel Cells Applications

A proprietary Ag-Ge-Si braze system was developed by INER for use as high-temperature sealing materials for MS-SOFCs applications. For cross-sectional microstructures observation, filler/interconnect brazed joints revealed that there were evident inter-diffusion between the brazing filler and interconnect. Fe-Cr-Si phase was observed at the interface after brazing at elevated temperatures. As for the tensile and shear strength of interconnect joints, the results showed that the optimal joint strength were about 70 and 47 MPa, respectively after brazing at 850 °C for 30 min. The leak rates for the filler/interconnect brazed joints were tested respectively under the conditions of thermal aging (750 °C for 1,000 hours in He/air) and thermal cycling (200-750 °C for 30 cycles, 10 °C/min in He/air). Results indicated that the average leak rates are in the range of 10-5~10-4 mbar∙l/s/cm and the interface of Ag-Ge-Si/interconnect joints still remained rigidly contacted, meeting the hermetic requirements for the MS-SOFCs applications.

Improved design and parameter optimisation of the transmission mechanism of a tobacco stalk pull‐out crusher

In order to eliminate the plug stem phenomenon and reduce the transmission power consumption of the self-developed integrated tobacco stalk pull-out crusher transmission mechanism when the culms are pulled out at high speed in the field, based on the analysis of the reasons of plug stem, a new rubber-type roller pair transmission mechanism with easy disassembly and adjustable spacing was designed. Through the force analysis, the mathematical model of the force, deformation and transmission power of the tobacco stalk during the extrusion and transportation phase was obtained, and the test platform of the tobacco stalk pull-out crusher transmission mechanism was built to carry out the orthogonal rotation combination test. The test results show that the optimal working parameter combination within the range of test factors is: the roller speed is 530 r/min, the II pair of roller spacing is 90 mm, the III pair of roller spacing is 30 mm, and the tobacco stalk feeding rate is 1.5 s/n. At this time, the plugging rate of stem is 2.22%, the transmission power consumption is 645 W, and the actual average leak stalk rate obtained by repeating 10 tests under this parameter is 3.33%, and the actual transmission power consumption is 684 W, the actual plugging rate of stem and transmission power are basically consistent with the optimized values, indicating that the improved design structure is reasonable, and the established regression model is basically reliable.

Localization of fugitive methane emission from natural gas distribution network of Titas Gas

Abstract The aim of this paper is to localize the fugitive leaks from the above ground facilities of the existing system of Titas Gas (TG) after developing mathematical model for fugitive emission. Soap screening techniques and Gasurveyor 500 series instrument were used in this study for detecting potential leaks. Leaked gas was quantified using either Hi-Flow gas sampler or bagging measurements system. The results show that the respective potential gas leaking point of City Gate Station (CGS), commercial Regulating and Metering Station (RMS), industrial RMS, residential RMS and Town Bordering Station (TBS)/ District Regulating Station (DRS) are scrubber dump valve (average leak rate 217.00 L/min), insulating point (average leak rate 4.04 L/min), tube fitting connector (average leak rate 8.00 L/min), connector (average leak rate 1.55 L/min) and pressure relief valve (average leak rate 437.92 L/min). Fugitive methane emission can be reduced by stopping leaks of fittings or components having high KLeak value.

A low feed-through 3D vacuum packaging technique with silicon vias for RF MEMS resonators

This paper presents a wafer-level three-dimensional (3D) vacuum packaging technique for radio frequency microelectromechanical systems (RF MEMS) resonators. A Sn-rich Au–Sn solder bonding is employed to provide a vacuum encapsulation as well as electrical conductions. Vertical silicon vias are micro-fabricated by glass reflow process. The optimized grounding, via pitch, and all-round shielding effectively reduce feed-through capacitance. Thus the signal-to-background ratios (SBRs) of the transmission signals increase from 17 dB to 20 dB, and the quality factor (Q) values of the packaged resonators go from around 8000 up to more than 9500. The measured average leak rate and shear strength are (2.55 ± 0.9) × 10−8 atm-cc s−1 and 42.53 ± 4.19 MPa, respectively. Furthermore, thermal cycling test between −40 °C and 100 °C and high temperature storage test at 150 °C show that the resonant-frequency drifts are less than ±7 ppm. In addition, the SBRs and the Q values have no obvious change after the tests. The experimental results demonstrated that the proposed encapsulation technique is well suited for the applications of RF MEMS devices.

A zero-level vacuum encapsulation technique with less parasitic effect for VHF MEMS resonators

This paper presents a zero-level vacuum encapsulation technique with the development of effective parasitic optimization methods for VHF MEMS resonator. Sn-rich Au-Sn solder bonding is used to achieve vacuum hermeticity packaging with high shear strength. The measured average leak rate and shear strength are (2.2±0.9)×10−8atm-ccs−1 and 40.65±8.25MPa among 12 packaged chips, respectively. An equivalent circuit model of the packaged resonator is established to analyze the parasitic effect caused by encapsulation. A significant reduction of the parasitic effect is achieved via grounding sealing ring, and decreasing parasitic capacitances between the sealing ring and signal feedthroughs. The measured frequency spectrum of a packaged resonator is not distorted by parasitic effect, which is well consistent with the simulation result. Besides, the Q value of the resonator increases from 6400 to 10,300, as well as the transmission gain at harmonic peak from −73.92dB to −70.36dB due to an excellent electrical performance of the encapsulation structure and a high vacuum in this packaging cavity.

Physical Risk Assessment for Urban Water Supply in a Developing Country: A Case of Mega City Dhaka

Water supply access in many developing countries is yet to fulfill Millennium Development Goals. Many local governments are incapable of managing their water resources either due to funding constrains or lack of adequate work force. This often results into poor services with low quality, insufficient and inconsistent delivery of water, leakage and wastage creating water shortages. The water stress resulting from urbanization is more acute in terms of Dhaka city due to its capital city-centric development strategies attracting rural-urban migration, which have resulted into an unplanned horizontal and vertical expansion of the city without having facilities for relevant infrastructures. Therefore, it is important to carry out a risk assessment on existing water supply distribution systems to address the challenges of frequent leaks contributing to cross contamination and system loss arising from unplanned development and aging of pipes. The objective of this study is to identify the physical risk for various zones under Dhaka City based on existing distribution systems and its susceptibility to leakage. The assessment requires analyses of distribution system, its length, number of leaks in the pipes detected every month, population density, number of consumers, characteristics of areas whether industrial or residential areas, low lying and vulnerable to flooding. The study finds that Zone IV possesses a very high risk due to an average leak of 93 per month with 1,571,960 people are exposed to vulnerability while Zone II, III, V, VI having average monthly leaks of 39, 36, 26, and 34 respectively are high risk zones.

Modification of Layer Structures of Superconducting Tunnel Junctions to Improve X-ray Energy Resolution

The layer structure of a Nb/Al-based superconducting tunnel junction (STJ) X-ray detector was modified to improve the energy resolution (\(\Delta E\)) of STJ X-ray detectors by suppressing the recombination of excited quasiparticles in the electrodes. A 100-pixel array of 100 \(\times \) 100 \(\upmu \)m STJs with a symmetric layer structure of Nb (300 nm)/Al-AlO\(_{x}\)(70 nm)/Al (70 nm)/Nb (300 nm) was fabricated. Fabrication yields of the 100 pixels were more than 90 %. The average leak current of the STJ array was 8 nA. The mean \(\Delta E\) of the STJ array was 6.7 \(\pm \) 1.0 eV for 400 eV X-rays. This \(\Delta E\) is the best value reported for Nb/Al STJs.

Processing of 8YSZ and CGO thin film electrolyte layers for intermediate- and low-temperature SOFCs

An extensive experimental investigation has been carried out in order to prepare novel thin film electrolytes for enhanced SOFCs. Methods of producing ultra-thin 8 mol% Y2O3-doped ZrO2 (8YSZ) electrolytes (<1μm) and thin 10 mol% Gd2O3-doped CeO2 (10CGO) electrolytes (∼1μm) are presented. The method deposits such thin dense films onto a highly porous anode substrate. As opposed to conventional powder deposition techniques, the method involves depositing a dispersion of nanoparticles to achieve a thin-film mesoporous layer. After sintering at 1400°C, the deposited mesoporous layer becomes a dense thin film with a thickness of ∼1μm or even thinner. Such thicknesses are significantly below the limit currently achievable with powder deposition techniques (∼10μm). The electrolyte layer thickness is comparable to the thicknesses found in micro-SOFCs, but here conventional macroporous SOFC substrates are used. Of considerable importance is the use of a spin-coating process, due to its simplicity and the potential ease of further scaling-up. Results from SEM and leakage tests confirmed that the thin-film electrolytes are homogeneous and have a low number of defects after sintering at 1400°C. The average leak rate for air was 1–2×10−5mbarls−1cm−2 for the 8YSZ electrolyte and 10−4mbarls−1cm−2 for the 10CGO electrolyte.

Effects of three modes of respironics auto CPAP machines in patients with OSAHS

Introduction The effective treatment of for obstructive sleep apnea (OSA) is continuous positive airway pressure (CPAP). It is considered to be the gold standard treatment for moderate and severe OSA. However, compliance is the main challenge in CPAP usage because of lack of comfort. New technology has been tried to look for different modes to improve comfort ability of CPAP usage. Philips Respironics has designed productive algorithms that maintain effective therapy at minimal pressures. These modes are C-Flex and A- Flex: A-Flex makes each breath more comfortable at inhalation and exhalation. It provides flow- based pressure relief at the beginning of the exhalation. C-Flex makes sleep therapy more comfortable by reducing pressure at the beginning exhalation and returning to therapeutic pressure just before inhalation. OBJECTIVE: we aimed to differentiate the effects of three modes (A-Flex, C-Flex and 0- Flex) on CPAP compliance and comfort ability for randomized OSA patients. Materials and methods Randomized patients men and women who applied full-night Polysomnography in sleep lab,Clinical physiology Department,Sultan Qaboos University Hospital were diagnosed as moderate to severe obstructive sleep apneas. Auto CPAP Respironics machine was prescribed to these patients. This machine has two different pressure relief technologies (modes). These modes were breathing cycles (A-Flex and C-Flex). Comfort ability of CPAP was assessed using Visual Analogue Scale (VAS),AHI pre and post CPAP titration, O 2 desaturation pre and post CPAP titration, average leak and Epworth Sleepiness scale (ESS) to evaluate sleep pre and post of CPAP use. And compliance was assessed by usage (hours). Results Data were collected from 100 (60 males & 40 females) with average age of 30–60 years old and diagnosed as moderate to severe OSA with mean AHI of 52/h & SD of 33.2. Patients who had treated with A-flex showed more comfort ( P = 0.02) using VAS compared to patients who had treated with C-flex and 0-flex modes. There was no difference in AHI and CPAP pressure among all modes. Conclusion The study showed that A-flex is more comfortable to patients compared to other modes of auto CPAP treatment. Acknowledgements department of clinical physiology, Sultan Qaboos University Hospital.

Air Leak during CPAP Titration as a Risk Factor for Central Apnea

Emergence of central sleep apnea has been described in the setting of continuous positive airway pressure (CPAP) initiation. The underlying mechanism is unclear; however, we postulate that air leak washing out anatomical dead space is a contributing factor. Data were obtained from 310 patients with obstructive sleep apnea (OSA) who underwent either split-night or full-night CPAP titration during January to July of 2009. The majority (n = 245) underwent titration with a nasal mask. Average total leak and maximum total leak were measured at therapeutic CPAP level. Unintentional leak was calculated by subtracting manufacturer-defined intentional leak from maximum leak. SUBJECTS WERE DIVIDED INTO TWO GROUPS: central apnea index (CAI) during titration < 5/hour and ≥ 5/hour. The groups were similar in terms of gender, age, BMI, and AHI. The CAI < 5 group had a median average leak of 45.5 L/min (IQR 20.8 L/min) versus 51.0 L/min (IQR 21.0 L/min) with CAI ≥ 5 (p = 0.056). Maximum leak was 59.5 L/min (IQR 27.0 L/min) with CAI < 5 and 75.0 L/min (IQR 27.8 L/min) with CAI ≥ 5 (p = 0.003). In the subset of subjects titrated using a nasal mask, median average leak was 42.0 L/min (IQR 17.0) in the CAI < 5 group and 50.0 L/min (IQR 16.8) in the CAI ≥ 5 group (p = 0.001). In the CAI < 5 group, median maximum leak was 57.0 L/min (IQR 23.0) versus 74.5 L/min (IQR 24.3) in the CAI ≥ 5 group (p < 0.001). Leak during CPAP titration is associated with the development of acute central apnea; these data may have mechanistic and therapeutic implications for complex apnea. A commentary on this article appears in this issue on page 1193.

New single use supraglottic airway device with non-inflatable cuff and gastric tube channel.

To assess ventilatory characteristics and airway complications associated with the use of I-gel in patients undergoing gynaecological surgeries. Experimental study. Department of Anaesthesiology, Surgical Intensive Care Unit and Pain Management, Civil Hospital, Dow University of Health Sciences, Karachi, from July 2008 to June 2009. One hundred adult female patients aged 15 - 75 years, ASA-I and II scheduled for elective gynaecologic surgical procedures under general anaesthesia with controlled ventilation were included in this study. After insertion of device, ease of insertion, time of insertion, peak airway pressure, leak pressure were noted. After proper placement of device, gastric tube was also passed in every patient. Pharyngolaryngeal morbidities (sore throat, dysphagia, dysphonia, neck pain and coughing at 1 hour and 24 hours postoperatively) were also noted. I-gel was inserted in the first attempt in 92% patients while second attempt was required in 8% of patients. Average time of insertion was 9.68 ± 2.69 seconds. Average leak pressure of 22.48 ± 2.07 cm H2O. After removal of I-gel no blood staining was found on any device. Coughing was noted in 6% patients after removal of device and mild sore throat was noted in only one patient after 24 hours of surgery. I-gel is a simple and easy to use supraglottic airway device. Its insertion do not require laryngoscopy and airway can be maintained in very short time in adult female patients.

Chemical data quantify Deepwater Horizon hydrocarbon flow rate and environmental distribution

Detailed airborne, surface, and subsurface chemical measurements, primarily obtained in May and June 2010, are used to quantify initial hydrocarbon compositions along different transport pathways (i.e., in deep subsurface plumes, in the initial surface slick, and in the atmosphere) during the Deepwater Horizon oil spill. Atmospheric measurements are consistent with a limited area of surfacing oil, with implications for leaked hydrocarbon mass transport and oil drop size distributions. The chemical data further suggest relatively little variation in leaking hydrocarbon composition over time. Although readily soluble hydrocarbons made up ∼25% of the leaking mixture by mass, subsurface chemical data show these compounds made up ∼69% of the deep plume mass; only ∼31% of the deep plume mass was initially transported in the form of trapped oil droplets. Mass flows along individual transport pathways are also derived from atmospheric and subsurface chemical data. Subsurface hydrocarbon composition, dissolved oxygen, and dispersant data are used to assess release of hydrocarbons from the leaking well. We use the chemical measurements to estimate that (7.8 ± 1.9) × 10(6) kg of hydrocarbons leaked on June 10, 2010, directly accounting for roughly three-quarters of the total leaked mass on that day. The average environmental release rate of (10.1 ± 2.0) × 10(6) kg/d derived using atmospheric and subsurface chemical data agrees within uncertainties with the official average leak rate of (10.2 ± 1.0) × 10(6) kg/d derived using physical and optical methods.

Positive Airway Pressure Initiation: A Randomized Controlled Trial to Assess the Impact of Therapy Mode and Titration Process on Efficacy, Adherence, and Outcomes

(1) To determine the efficacy of automatically adjusted positive airway pressure (APAP) with a comfort feature (A-Flex) at reducing apneas and hypopneas in participants with moderate to severe OSA. (2) To determine the relative difference between A-Flex, continuous positive airway pressure (CPAP), and APAP-derived optimal pressure for CPAP (CPAP(APAP)) on adherence to treatment. (3) To determine the relative difference between APAP with A-Flex, CPAP, and CPAP(APAP) on long-term change in functional outcomes. Randomized, double-blinded, 3-arm, multicenter trial. University and Veterans Affairs medical centers. 168 participants were randomized, and 140 completed the 180-day study. (1) A-Flex; (2) CPAP; (3) APAP for 14 days and then switched to CPAP at a fixed pressure. Apnea-hypopnea indices, average and minimum oxygen saturation, time spent < 90% were significantly poorer for A-Flex vs. CPAP at the initiation of study treatment; with the exception of minimum oxygen saturation, these differences were absent at 180 days. A-Flex had lower average leak values at both 3 and 6 months. There were no significant differences between groups in major efficacy, adherence, and outcome (subjective sleepiness, objective vigilance, blood pressure, quality of life) measures. No differences between groups in attitudes toward use were observed at 3 or 6 months; participant ratings for CPAP were significantly higher than A-Flex on treatment satisfaction and benefit, but not different for sleep quality and mask comfort. We found that A-Flex shows equivalency, but non-superiority (except for average leak values), in efficacy, adherence, and functional outcomes compared to CPAP after either 3 or 6 months. Positive Pressure Treatment of Obstructive Sleep Apnea, http://www.clinicaltrials.gov, NCT00636181.

Wafer-Level Vacuum Packaging of Micromachined Thermoelectric IR Sensors

In the trend towards low-cost, high-performance, and miniaturization, a wafer-level vacuum package is developed for micromachined thermoelectric infrared (IR) sensor. An IR sensor wafer and a cap wafer are bonded together in a vacuum chamber using Au-Au thermocompression bonding, where the cap wafer not only protects the floating thermopile structure but also selects IR light for the sensor. The device fabrication and Au-Au thermocompression hermetic bonding process as well as the packaged IR sensor characterization is presented in this paper. Experimental results show that the wafer-level vacuum packaged IR sensor has a four times higher responsivity and detectivity than the IR sensor with atmosphere pressure package, which confirms the IR performance improvement due to vacuum packaging. IR microscope image of the packaged device proved that the Au-Au thermocompression bonding process is compatible to the handling of fragile micromachined thermopile structure. Average leak rate and shear strength are, respectively, 3.9 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> atm cc/s and 16.709 Kgf, which shows that the Au-Au thermocompression hermetic bonding is suitable for the wafer-level vacuum packaging of micromachined thermoelectric IR sensor.

The Application ofn-Butyl 2-Cyanoacrylate to Repair CSF Fistulas for 221 Patients who Underwent Transsphenoidal Surgery

The adequate repair of intraoperative CSF leaks during transsphenoidal surgery remains a challenge. The authors describe the application of N-butyl 2-cyanoacrylate (cyanoacrylate) tissue glue for repair of CSF fistulas during transsphenoidal surgery. The authors retrospectively reviewed the records of 221 consecutive patients who underwent transsphenoidal surgery during 1998-2007. Among these patients, 52 (24%) experienced detectable intraoperative CSF leakage. The CSF fistulas were graded on a scale of 1-3, according to the amount of CSF loss and extent of diaphragmatic disruption. 39 patients who had an average leak scale of 1.28 received cyanoacrylate glue to seal the floor. The remaining 13 patients who were not part of this report received other dura sealant substitutes, including Tisseel and Dura Seal, or fat/cartilage grafts without any additional glue material. 4 of 221 patients (2%) who underwent surgery had postoperative CSF fistula. Of the 39 patients who underwent repair of their fistula using fat graft, cartilage/bone buttress and cyanoacrylate reconstruction, 2 (5.13%) developed postoperative CSF fistulas without any other side effects. The average intraoperative leak grade in these 2 patients was 2.00. The authors used cyanoacrylate glue for intraoperative repair of higher grade CSF fistulas. As an adjunct to careful sellar reconstruction, cyanoacrylate glue appears to be effective and safe in preventing postoperative CSF leakage after transsphenoidal surgery.

Exposure to anaesthetic trace gases during general anaesthesia: CobraPLA vs. LMA classic

To prospectively investigate the performance, sealing capacity and operating room (OR) staff exposure to waste anaesthetic gases during the use of the Cobra perilaryngeal airway (CobraPLA) compared with the laryngeal mask airway classic (LMA). Sixty patients were randomly assigned to the CobraPLA or the LMA group. Insertion time, number of insertion attempts and airway leak pressures were assessed after induction of anaesthesia. Occupational exposure to nitrous oxide (N(2)O) and Sevoflurane (SEV) was measured at the anaesthetists' breathing zone and the patients' mouth using a photoacoustic infrared spectrometer. N(2)O waste gas concentrations differed significantly in the anaesthetist's breathing zone (11.7+/-7.2 p.p.m. in CobraPLA vs. 4.1+/-4.3 p.p.m. in LMA, P=0.03), whereas no difference could be shown in SEV concentrations. Correct CobraPLA positioning was possible in 28 out of 30 patients (more than one attempt necessary in five patients). Correct positioning of the LMA classic was possible in all 30 patients (more than one attempt in three patients). Peak airway pressure was higher in the CobraPLA group (16+/-3 vs. 14+/-2 cmH(2)O, P=0.01). The average leak pressure of the CobraPLA was 24+/-4 cmH(2)O, compared with 20+/-4 cmH(2)O of the LMA classic (P<0.001; all values means+/-SD). Despite higher airway seal pressures, the CobraPLA caused higher intraoperative N(2)O trace concentrations in the anaesthetists' breathing zone.