bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Influencing the Uptake Rate of Passive Adsorbent Dosimeters Used in the Man-in-Simulant-Test
Authors: Ormond R. Bryan , Barker Roger , Beck Keith , Thompson Donald , Deaton Shawn
Published: January 2013

The passive adsorbent dosimeter (PAD) is a critical component in the man-in-simulant-test (MIST). It is the only approved device for use in determining the localized and systemic protection factors for chemical protective ensembles. In MIST evaluation protocols, PADs are placed on test subjects underneath the protective suit, and then the test subject is exposed to a known concentration of methyl salicylate (MeS), a warfare agent simulant. The purpose of the PADs is to collect the MeS vapors that enter the suit at seams, closures, or interfaces between the protective suit and gloves, boots, or the breathing apparatus. Given this key role, it is imperative that the diffusive uptake rates associated with the PADs are characterized. It is equally important to fully understand the factors influencing these rates. This research investigates two different categories of influential factors: the variation in adsorption rates associated with the simulant concentration and exposure time, and the relation to the effect of the time and temperature of the PAD's storage prior to extraction and analysis. For the first study, PADs were exposed, in the full scale MIST Facility at North Carolina State University, to concentrations ranging from 15 to 100 mg/m3 for exposure times ranging from 1 min to 2 h in duration. In the second study, the effect of the storage time prior to analysis was determined by exposing PADs at a set condition and varying the amount of time before the PADs were extracted. In order to assess the effects of storage temperature on the uptake rate, PADs were exposed and stored at temperatures ranging from below −30°C to 4°C. The findings of this research help identify and explain a possible source of differences that have been observed in MIST results at different testing sites. This work also provides a deeper understanding of the characteristics of the PADs themselves.
Developing a Thermal Sensor for Use in the Fingers of the PyroHands Fire Test System
Authors: Hummel Alexander , Barker Roger , Lyons Kevin , Deaton A. Shawn , Morton-Aslanis John
Published: January 2013

This paper describes a thermal sensor developed for use in the fingers of the PyroHands Fire Test System. The PyroHands Fire Test System measures the thermal protective performance of gloves in laboratory controlled flash fire exposures. The development of the finger sensor presented several challenges; the first was that it required that a small thermal sensor fit into the finger of an anthropometrically designed hand. It was also important to ensure that the thermal sensor accurately measured heat flux incident on the finger. This required showing that the unidirectional heat flux measured by the sensor was unaffected by heat impinging on the sides and back of the finger. An experimental study was conducted in order to investigate the effects of lateral heating on sensor operation. Additional verification of the thermal sensor was provided via the use of computer-aided design models to predict the temperature rise beneath gloves during PyroHands tests.
Interlaboratory Study of ASTM F2731, Standard Test Method for Measuring the Transmitted and Stored Energy of Firefighter Protective Clothing Systems
Authors: Deuser L. , Barker R. , Deaton A. S. , Shepherd A.
Published: January 2013

This paper describes an interlaboratory study conducted using ASTM F2731, Standard Test Method for Measuring the Transmitted and Stored Energy of Firefighter Protective Clothing Systems. Five replications of six different composites representative of firefighting turnout gear materials were tested at six different laboratories equipped to conduct the test. Data collected were used to predict the time to second degree burn for each of the turnout composite test specimens. Statistical analysis showed good agreement between test sites. This interlaboratory study confirmed the repeatability and reliability of ASTM F2731, a test method used to measure an important property associated with the thermal protective performance of firefighter turnout materials.
Bearing Thermal Conductance Measurement Test Method and Experimental Design
Authors: Takeuchi Yoshimi R. , Davis Sean E. , Eby Matthew A. , Fuller Jerry K. , Taylor Donald L. , Rosado Michael J.
Published: January 2013

Bearings are used in a number of spacecraft applications, ranging from minimal motion devices, such as pointing mechanisms, to high-speed components, such as control moment gyroscopes and reaction and momentum wheels. Terrestrial applications include pumps, axles, and tooling. Heat-transfer modes for rotational systems in a vacuum environment differ from their terrestrial counterpart. In space, with the absence of air, heat transfer consists of radiation from the rotating system and conductance through the bearings themselves. Depending on the application, conductance could dominate the effects on bearing temperatures and thermal gradients. Accurate thermal predictions are important because they can drive life and performance requirements. To accurately predict bearing temperatures, basic bearing thermal conductance data was needed. However, bearing thermal conductance tends to be the most significant unknown in a rotational system in the space environment. To address this shortcoming, this paper explores a new vacuum test rig designed to measure bearing conductance under simulated operational conditions. Experimental variables include control of the bearing rotational speed, applied axial load, and average bearing temperature and temperature gradient via an applied heat source/heat sink mechanism. All tests are conducted in vacuum. The experimental variables studied herein allowed parametric studies to be conducted under controlled thermal and mechanical conditions, permitting the exploration of the influences of those operational variables on bearing thermal conductance. This paper will describe the test method, the use of uncertainty analysis to design the experiment, and a verification study.
Steel and Hybrid Spacecraft Ball-Bearing Thermal Conductance Comparisons
Authors: Takeuchi Yoshimi R. , Davis Sean E. , Eby Matthew A.
Published: January 2013

In vacuum, bearing temperatures are primarily governed by two properties: bearing thermal conductance, which governs the overall heat transfer through the bearing, and heat generation, which is caused by the frictional mechanical losses during bearing motion. Both quantities need to be known for accurate bearing thermal predictions in a vacuum environment. The heat generation term, which is related to torque multiplied by rotational speed, is the better known of the two quantities. Information on bearing thermal conductance; on the other hand, tends to be more poorly quantified, and thus will be the focus of this paper. A comparison will be made between the thermal conductance of all-steel and hybrid bearings containing silicon nitride ceramic balls inside steel races. Thermal conductance is a function of various operational conditions, such as rotational speed, temperature, mechanical loading and presence of lubricant. The exact effects the aforementioned variables have on bearing thermal conductance will be explored in more detail for both bearing types. Results indicate that, for a given bearing size and geometry, bearing thermal conductance is most strongly influenced by the presence and amount of liquid lubricant and state of motion. Both all-steel and hybrid bearings react to these variables in a comparable manner.
Application of Test Methods for Use in Limestone Selection for Wet Flue Gas Desulfurization
Authors: Brown Shannon R. , DeVault Richard F. , Williams Paul J.
Published: January 2013

Industry standard test methods for determination of limestone composition and reactivity are crucial for ensuring adequate performance of limestone force-oxidized (LSFO) wet flue gas desulfurization (WFGD) absorber units. To determine if a limestone will provide design level performance and/or meet contract specifications, it is tested with regard to composition and reactivity. Essential parameters for the composition are the fraction of CaCO3, MgCO3, and inerts. ASTM Method C1271 (XRF), a combination of ASTM Method C25, Section 22 for CO2, ASTM Method C25, Section 17 for CaO, and ASTM Method C25, Section 18 for MgO or TGA, are widely accepted for such determination. Such procedures are commonly incorporated within contract guarantee language and unit performance test plans. In contrast, an industry standard procedure for limestone reactivity is presently unavailable, with different OEMs and many suppliers having their own tests. An ASTM Task group is presently addressing this need, drafting a test method for limestone reactivity that may become the industry standard. Herein is discussed usage of the ASTM test methods C1271 and C25 as well as TGA for limestone compositional analysis and a comparison of some methods presently available for limestone reactivity testing for use in WFGD.
Tennessee Lime-Fly Ash-Stabilized Base Using a High Loss-on-Ignition Fly Ash
Authors: Crouch L. K. , Dillon Sarah , Knight Marcus L.
Published: January 2013

The objective of the research was to determine if fly ash not meeting ASTM C618 can be used successfully in an aggregate-lime fly ash-stabilized base course (ALFASB). The Tennessee Dept. of Transportation (TDOT) Specification 312 for ALFASB includes hydrated lime, fly ash, and TDOT grading C limestone in percentages by dry weight of the total mix of 3.5, 11, and 85.5, respectively. The moisture content of the mix was determined by AASHTO T99. Hydrated lime is required to meet ASTM C977. Fly ash is required to meet ASTM C593 with several exceptions. TDOT grading C limestone was produced by blending No. 57 and limestone screenings. TDOT 312 requires an average compressive strength of 6.5-MPa (950-psi) for three specimens and no individual compressive strength less than 5.5-MPa (800-psi) after 28 days of curing at 37.8°C (100°F). Two different fly ashes were obtained: the control had a loss-on-ignition (LOI) of 1.6 %; the variable had an LOI of 8 %. Twenty-four (8 × 3) compressive strength specimens were fabricated for each set of materials. The only differences were fly ash and optimum moisture contents. The average compressive strength and coefficient of variation were 8.71-MPa (1263-psi) and 5.7 % for the control and 8.41-MPa (1219-psi) and 3.2 % for the variable, respectively. Each individual specimen met the compressive strength requirement for each fly ash. Sixteen (8 × 2) modulus of elasticity specimens were fabricated for each set of materials. The average static modulus of elasticity (estimated with ASTM C469) was 20.68-GPa (3000-ksi) and 15.81-GPa (2294-ksi) for the control and variable, respectively. These results indicate that a very high LOI fly ash can be useful as a stabilizing agent when used in combination with hydrated lime.
Determination of Metals in Lime and Limestone Using Automated Borate Fusions for ICP-OES
Authors: Pitre Janice , Bédard Mélanie , Hineman Aaron
Published: January 2013

The determination of metals in lime samples by inductively coupled plasma coupled with optical emission spectroscopy (ICP-OES) is not difficult to perform in itself, but a single dissolution method that can include all raw, finished, and waste products involved in lime production would be very appealing to many because of increased productivity factors. The proposed method describes an easy way to determine the concentration of elements of interest (Al, Ca, Fe, Mg, Mn, Si, and Ti) contained in raw materials, finished products, as well as waste products used and produced in common lime industries using borate fusions. This automated borate fusion method is designed to obtain the full dissolution of common lime products, such as limestone, dolomite, calcium hydroxide, and residues, without the need of using harsh acids or extensive sample dissolution techniques. The significance of this research resides in the simplicity of the method, its speed (complete sample dissolution in less than 12 min), automation, and the absence of harsh acids. Furthermore, this technique does not require highly skilled operators.
Testing Pozzolanic Hydraulic Limes (PHLs) With ASTM C1707-09: Suggestions for Improved Conditions of Tests
Authors: Gibson Robin R.
Published: January 2013

The development of efficient, high performance, and porous pure hydraulic limes is an important target for the construction industry with regard to delivering sustainable and easy-to-use materials with a CO2-absorbing free lime content that has the potential to create binders with overall low CO2 emissions. Although lime mortar technology predates cement mortars, lime mortar characterization for national standards currently utilizes know-how derived from cement standards, with a particular focus on ASTM C778–06 sand, volumetric ratios of raw materials, and predetermined water content cured under high relative humidity in order to deliver comparative compressive strength information. We propose several modifications to ASTM C1707-09 that will allow the comparison of pozzolanic hydraulic limes (PHLs) under reproducible conditions in order to provide helpful and robust data, for both the manufacturer and the end user. The proposals are applicable to both new and existing products. These proposals are supported by performance data from the use of a commercial PHL and comparative natural hydraulic limes.
Developing a New Test Method for Determining Free Moisture in Hydrated Lime by Thermogravimetric Analysis (Moisture Balance)
Authors: Thomson Margaret L. , Vernaci Joe , Houghton Melanie
Published: January 2013

Experimental studies were conducted in order to establish a technique for determining the free moisture content of hydrated lime using a thermogravimetric balance (moisture meter) method. The first step was to develop a calibration curve for different moisture levels using sodium tartrate dihydrate, first with dried limestone and then with calibrated weights. Sodium tartrate dihydrate has a moisture content of 15.65 ± 0.05 wt. % at 120°C. Testing was completed at 120°C, 150°C, and 180°C in order to determine whether there was a significant difference in results at the different temperatures. There was a 0.2 % discrepancy in the value of the free moisture between the lowest and the highest temperature, providing a good base from which to recommend further development of the test method.
Measuring and Visualizing Tire–Pavement Noise Using On-Board Sound Intensity
Authors: Rasmussen Robert Otto , Sohaney Richard C.
Published: January 2013

The Concrete Pavement Surface Characteristics Program (CPSCP) has recently developed guidelines and practices for reducing tire– pavement noise. The primary means for doing this is via measurements using the on-board sound intensity (OBSI) technique. OBSI measures tire-pavement noise at the source utilizing specialized microphones mounted to the outside of a vehicle, near the tire–pavement interface. Measurements are performed while the vehicle drives across the pavement being evaluated. To facilitate innovation, specifications have been developed based on an end-result approach. In this paper, a means for how to measure OBSI is provided, along with a means to interpret the as-constructed quality through visualization techniques. With it, the spatial variability of tire-pavement noise, as measured using OBSI, can be readily determined.
Case Studies Using Falling Weight Deflectometer Data with Mechanistic-empirical Design and Analysis
Authors: Pierce Linda M. , Smith Kurt D. , Bruinsma Jim E. , Sivaneswaran Nadarajah
Published: January 2013

The need to accurately characterize the structural condition of existing pavements has increased with the recent development, release, and ongoing implementation of the Mechanistic-Empirical Pavement Design Guide (MEPDG), developed under National Cooperative Highway Research Program Project No. 1-37A. A number of different material inputs are required in the procedure, and it is important that these be adequately characterized and defined so that competent structural designs can be developed. The analysis of deflection data collected with a falling weight deflectometer (FWD) provides a quick and reliable way of characterizing many of the parameters of the existing pavement layers. This paper summarizes how deflection data are incorporated into the MEPDG and describes two case studies, one with a flexible pavement and one with a rigid pavement. Significant findings and recommendations from the evaluated flexible pavement case study include the following: surface-down cracking is critical in the design of the hot mix asphalt (HMA) overlay, correction factors should be used for adjusting backcalculated layer moduli to laboratory determined values, and an FWD testing frequency of 30 Hz should be used for estimating the existing HMA modulus. For rigid pavements, the case study found that the thinnest overlay produced from the MEPDG was a bonded Portland cement concrete (PCC) overlay, whereas the HMA overlay was unreasonably thick. Within the design procedure, the manually entered k-value is used for unbonded and bonded jointed plain concrete pavements but does not appear to be used by the program in the HMA overlay design. The backcalculated dynamic (or static) elastic modulus should be used for the PCC layer, and the dynamic k-value should be used for the supporting layers. The backcalculated k-value representing the composite stiffness of all layers beneath the slab does not appear to have a significant influence on the design thickness for the pavement structure analyzed.
Measurement and Geometric and Functional Characterization of Pavement Texture
Authors: Rasmussen Robert Otto , Sohaney Richard C.
Published: January 2013

Pavement texture is defined by the irregularities on a pavement surface that deviate from an ideal, perfectly flat surface. Texture influences many aspects of road safety and comfort, including friction, smoothness, splash and spray, rolling resistance, and numerous others. The focus of this paper is on techniques to measure and analyze texture, particularly that which influences tire-pavement noise and friction. Standards for characterizing texture geometrically are described, and techniques that describe texture in terms of its influence on functional performance are explored.
The Use of Hydrated Lime in Concrete as a Cement Replacement: Effect on Compressive Strength
Authors: Holland Nancy L. , Nichols Anne B. , Nichols John M.
Published: January 2013

Hydrated lime can be used as a cement replacement in concrete. There are, as there have always been, two critical issues with this type of cement replacement: the change in physical properties with respect to compressive strength, and the cost analysis of the alternatives. The first stage of this research looks at the change in compressive strength of a standard concrete mix when hydrated lime is substituted for cement. The results from this research show a linear decline in strength with a linear increase in the relative percentage of hydrated lime replacement of cement. A cost analysis will be addressed at a later date as the research progresses.
Simplified Deflection-based Probabilistic Technique for Network-level Pavement Analysis
Authors: Carvalho Regis , Stubstad Richard , Wiser Larry , Selezneva Olga
Published: January 2013

The concept of a pavement management system (PMS) was developed following the successful AASHTO Road Test, in the 1950s, when pavement performance was characterized as “the necessary information to compare design alternatives and expectations over the service life of both flexible and rigid pavement structures.” A link was established between performance and the activities of planning, designing, constructing, and maintaining pavements, and the concept of a “PMS” was defined accordingly. Currently, surface distress and roughness measurements are the main components in determining a pavement's existing condition in a PMS. The structural condition, although capable of providing important information on how the pavement will perform in the future (rate of deterioration, types and severity of expected distresses, etc.), is not widely used. Reasons for this lack of presence in a system-wide PMS are mostly related to time-consuming analyses and the need for an experienced analyst. This paper presents the development of simplified, deflection-based analytical techniques that provide rapid, automated screening of pavement's structural capacity for inclusion in a network-level PMS. The approach is based on stochastic-logistic modeling commonly used in reliability engineering. Data from the Long-Term Pavement Performance database was used to develop appropriate models, which relate the expected future performance to deflection-based parameters extracted analytically from falling weight deflectometer deflection basins and site-specific conditions such as climate and traffic. It is of paramount importance to consider the existing structural capacity of pavements together with pavement distresses in order to predict future pavement conditions more accurately and thus successfully fulfill the overall goals of the original concept of “pavement management.”
Validation of the Performance of Pervious Concrete in a Field Application with Finite Element Analysis
Authors: Alam Md. Ashraful , Haselbach Liv , Cofer William F.
Published: January 2013

Pervious concrete is a paving material that has a number of stormwater and other environmental benefits. Most current applications of pervious concrete are in residential streets, parking lots, driveways, and sidewalks, and it is being considered for shoulders and more high volume applications. Characterizations of stress distribution and deflection patterns in pervious concrete systems may be useful parameters in the structural design of these high volume uses. Pervious concrete panels with tandem axle dual wheel loads were analyzed using finite element analysis. The wheel position was considered in the corner, center, and edge of the pavement. The critical stresses obtained from the analyses were compared against experimental tensile and compressive strengths obtained from samples from a field application for various pervious concrete layer thicknesses, and additional experimental data. It was found that pervious concrete panels of sufficient thickness have adequate strength to support the applied wheel loads. To compare the long term performance when subjected to cyclic loading, the critical tensile stresses for various pavement thicknesses were compared with pavement condition index (PCI) rating data obtained from a field application reflecting pavement performance of approximately 131,000 cycles of an 80 kN single-axle load. For this particular field application, it was found that, for cyclic loading, the required thickness of the pervious concrete layer was approximately 40 %–80 % higher compared with that for the static loading condition.
Ignition Testing by Fracture of Oil- and Particle-Contaminated Aluminum Pipes in High Pressure Oxygen at Ambient and Elevated Temperature
Authors: Meilinger Matthias
Published: January 2013

Aluminum and its alloys are the preferred material in air separation units (ASUs) and are submitted to strict cleanliness requirements to avoid combustion reactions in oxygen. Linde Engineering Division has investigated the role of particle contamination for the ignition of aluminum pipes in high pressure oxygen. Tests were carried out with oil coated aluminum pipes in combination with a particle contamination. Accumulations of following particle types were tested: molecular sieve 13X, filter deposits (rust), perlite, quartz sand, and aluminum swarf. The contaminated pipes were pressurized with oxygen up to 150 bar and fractured in a hydraulic apparatus. The conditions and probability of an ignition reaction compared with oiled pipes without particles were of interest. Additionally, similar high pressure tests with a mixture of liquid and gaseous oxygen were performed. A combination of oil and particles enhanced the probability of an ignition at elevated temperatures. The results indicated that temperature is the dominating factor for an oil ignition, not the oxygen pressure. At room temperature, an oil/aluminum ignition could never be initiated. The results give a good understanding regarding the mechanism of an aluminum ignition and help to clarify causes of damage in the ASU industry.
Fire Without Cause of an Oxygen Component With an Aluminum Seal
Authors: Tillack T. , Binder C. , Brock T. , Treisch N. , Dielforder P.
Published: January 2013

It is common, even for high pressure service, for most of the components in oxygen systems to contain nonmetallic materials. The risk of an oxygen fire is low if the design of the component and its metallic and non-metallic materials are properly selected. From a safety point of view, it is obvious that a component made completely of metal with metallic seals should have a lower risk of fire. However, during a test series performed at the outdoor test site of the German Federal Institute for Materials Research and Testing (BAM), “BAM Test Site Technical Safety,” an oxygen component burned out that contained metallic seals only. In the test, a bursting metallic diaphragm produces a single pressure shock at a specified oxygen pressure. In the incident, an aluminum diaphragm with a thickness of 1.5 mm was used at a burst pressure of 171 bar. At first, investigations at BAM focused on the question of whether a bursting aluminum diaphragm is able to ignite a bulk metal. Stress rupture tests were performed on this particular aluminum. A high-speed infrared camera helped reveal information on the temperature rise in the rupture zone. Furthermore, other possible ignition sources such as contamination or flow friction were considered, also. This paper discusses the results of the investigation, and it tries to answer the question of whether aluminum sheet materials increase the fire risk in oxygen components.
Safe for Oxygen but Not for Oxygen-Enriched Gas Mixtures in SCUBA Diving
Authors: Tillack T. , Binder C. , Hesse O. , Lehné S. , Ciscato W.
Published: January 2013

In a market study, more than 60 representative cylinder valves that are used in SCUBA diving were tested for burn-out safety according to the current standard ISO 10297 [2006, “Transportable Gas Cylinders—Cylinder valves—Specification and Type Testing,” International Standards Organization, Geneva, Switzerland]. This standard requires that oxygen cylinder valves have to be pressure-surge tested to prove their ignition resistance. After testing, the samples are disassembled and the nonmetallic materials shall not show any traces of ignition for the valve to pass the test. This is usually done by visual inspection. The existing pass–fail criteria, however, cause problems sometimes when the test results have to be interpreted or are not sufficient to ensure a safe use of the valve. This market study reveals what changes a non-metallic material may show after pressure-surge testing. It also shows the influence of the different design geometries in the seat area on the nonmetallic materials. After testing, some nonmetallic materials do not show any distinct traces of ignition or combustion. Only a change in color, notable surface deterioration, and loss of material is visible. Occasionally, the valve is no longer gas-tight, although no traces of ignition can be detected. However, according to the standard, the valve has passed the test. This paper provides various reasons why the pass–fail criteria of the oxygen pressure surge need to be more tightened. This applies not only to the current version of the standard ISO 10297, but for any standard that requires performance of the pressure-surge test for oxygen components.
Flammability Evaluation of Metals in Piping Configurations Under Flowing Conditions: Hollow-Vessel Promoted Ignition Test
Authors: Ridlova Martina , Rostaing Jean-Christophe , Colson Alain , Longuet Olivier
Published: January 2013

The industry experienced burn-through and failure of large oxygen piping systems corresponding to geometry and flow pattern conditions very different from the ASTM G124 Promoted Ignition Test standard. In Air Liquide's hollow-vessel promoted ignition test, puncturing ignition is effected by a pyrotechnic promoter inserted into the wall of a hollow structure confining high-pressure gaseous oxygen. This is in strong contrast to a rod burning vertically in static atmosphere. The critical flow of oxygen through the breach both supplies efficiently oxygen to the peripheral burning front and blows out the formed oxides, so that combustion propagates with the breach diameter expanding. The facility can supply approximately 9000 Nm3/h oxygen, maintaining the internal pressure at the breach, similar to the case of a real-life piping accident. The final extension of the breach is studied as a function of pressure from 2.8 to 40 barg (40 to 580 psi). Even at the lowest pressure, self-sustained radial propagation is unambiguously evidenced from initial diameter close to promoter size. However, the breach extension indicative of the severity of damages, is, on average, scaled to pressure, and, moreover, substantially larger for carbon steel. Also at highest pressure (30–40 barg), local flow patterns at the breach-like turbulence, recycling, and swirling of strongly heated oxygen tend to enhance metal combustion. It is further observed that increasing the burning metal wall thickness (e.g., from 5.5 mm to 12.5 mm) enhances the burning intensity and aggravates damages. Results give a different vision and understanding regarding the flammability of stainless steel compared to ASTM G124 standard where larger rod section is found to have a mitigating effect.
Situational Non-Flammable Control Valves for Oxygen Service
Authors: Dobinson Chris , Nelson Peter , Steinberg Ted
Published: January 2013

Past work has clearly demonstrated that numerous commonly used metallic materials will support burning in oxygen, especially at higher pressures. An approach to rectify this significant safety problem has been successfully developed and implemented by applying the concept of situational non-flammability. This approach essentially removes or breaks one leg of the conceptual fire triangle, a tool commonly used to define the three things that are required to support burning: a fuel, an ignition source, and an oxidiser. Because an oxidiser is always present in an oxygen system, as are ignition sources, the concept of situational non-flammability essentially removes the fuel leg of the fire triangle by only utilising materials that will not burn at the maximum pressure, for example, that the control valve is to be used in. The utilisation of this approach has lead to the development of a range of oxygen components that are practically unable to burn while in service at their design pressure, thus providing an unparalleled level of first safety while not compromising on the performance or endurance required in the function of these components. This paper describes the concept of situational non-flammability, how it was used to theoretically evaluate designs of components for oxygen service and the outcomes of the actual development, fabrication, and, finally, utilisation of these components in real oxygen systems in a range of flow-control devices.
A Comparison of Fire Reaction Effects of Halogenated Versus Non-Halogenated Non-Metals in High-Pressure Oxygen Components
Authors: Forsyth Bradley S. , Chiffoleau Gwenael J. A. , Odom Greg A. , Newton Barry E.
Published: January 2013

Some high-pressure oxygen-breathing gas components have been transitioning from predominantly halogenated (fluorinated or chlorinated) polymers to non-halogenated materials for seats and seals. The rationale for the material changes was related to reducing the risk associated with production of toxic combustion by-products in the event of a component fire. This paper neither discusses the risks associated with toxicity, nor does it attempt to determine which risk (ignition or toxicity) is preeminent. Rather, examples of fires in components from a component test program are examined to compare the reaction effects for components configured with halogenated and non-halogenated materials. A limited comparison of the test results to actual field fires is also provided. The implications of the ignition and fire effects are discussed.
Rudimentary Cleaning Compared to Level 300A
Authors: Piña Arpin Christina Y. , Stoltzfus Joel
Published: January 2013

A study was performed to characterize the cleanliness level achievable when using a rudimentary cleaning process, and results were compared to JPR 5322.1G Level 300A. While it is not ideal to clean in a shop environment, some situations (e.g., field combat operations) require oxygen system hardware to be maintained and cleaned to prevent a fire hazard, even though it cannot be sent back to a precision cleaning facility. This study measured the effectiveness of basic shop cleaning. Initially, three items representing parts of an oxygen system with maximum operating pressure of 2000 psi were contaminated: a metal plate, valve body, and metal oxygen bottle. The contaminants chosen were representative of materials that could contaminate the system during normal use: oil, lubricant, metal shavings/powder, sand, finger-prints, tape, lip balm, and hand lotion. The cleaning process used hot water, soap, various brushes, gaseous nitrogen, a water nozzle, plastic trays, scouring pads, and a controlled shop environment. Test subjects were classified into three groups: technical professionals having an appreciation for oxygen hazards; professional precision cleaners; and a group with no previous professional knowledge of oxygen or precision cleaning. Three test subjects were in each group, and each was provided with standard cleaning equipment, a cleaning procedure, and one of each of the three test items to clean. The results indicated that the achievable cleanliness level was independent of the technical knowledge or proficiency of the personnel cleaning the items. Results also showed that achieving a Level 300 particle count was more difficult than achieving a Level A nonvolatile residue amount.
Impulsivity and Self-Control during Intertemporal Decision Making Linked to the Neural Dynamics of Reward Value Representation
Authors: Jimura Koji , Chushak Maria S. , Braver Todd S.
Published: January 2013

A characteristic marker of impulsive decision making is the discounting of delayed rewards, demonstrated via choice preferences and choice-related brain activity. However, delay discounting may also arise from how subjective reward value is dynamically represented in the brain when anticipating an upcoming chosen reward. In the current study, brain activity was continuously monitored as human participants freely selected an immediate or delayed primary liquid reward and then waited for the specified delay before consuming it. The ventromedial prefrontal cortex (vmPFC) exhibited a characteristic pattern of activity dynamics during the delay period, as well as modulation during choice, that is consistent with the time-discounted coding of subjective value. The ventral striatum (VS) exhibited a similar activity pattern, but preferentially in impulsive individuals. A contrasting profile of delay-related and choice activation was observed in the anterior PFC (aPFC), but selectively in patient individuals. Functional connectivity analyses indicated that both vmPFC and aPFC exerted modulatory, but opposite, influences on VS activation. These results link behavioral impulsivity and self-control to dynamically evolving neural representations of future reward value, not just during choice, but also during postchoice delay periods.
Individual Differences in White Matter Diffusion Affect Sleep Oscillations
Authors: Piantoni Giovanni , Poil Simon-Shlomo , Linkenkaer-Hansen Klaus , Verweij Ilse M. , Ramautar Jennifer R. , Van Someren Eus J. W. , Van Der Werf Ysbrand D.
Published: January 2013

The characteristic oscillations of the sleeping brain, spindles and slow waves, show trait-like, within-subject stability and a remarkable interindividual variability that correlates with functionally relevant measures such as memory performance and intelligence. Yet, the mechanisms underlying these interindividual differences are largely unknown. Spindles and slow waves are affected by the recent history of learning and neuronal activation, indicating sensitivity to changes in synaptic strength and thus to the connectivity of the neuronal network. Because the structural backbone of this network is formed by white matter tracts, we hypothesized that individual differences in spindles and slow waves depend on the white matter microstructure across a distributed network. We recorded both diffusion-weighted magnetic resonance images and whole-night, high-density electroencephalography and investigated whether individual differences in sleep spindle and slow wave parameters were associated with diffusion tensor imaging metrics; white matter fractional anisotropy and axial diffusivity were quantified using tract-based spatial statistics. Individuals with higher spindle power had higher axial diffusivity in the forceps minor, the anterior corpus callosum, fascicles in the temporal lobe, and the tracts within and surrounding the thalamus. Individuals with a steeper rising slope of the slow wave had higher axial diffusivity in the temporal fascicle and frontally located white matter tracts (forceps minor, anterior corpus callosum). These results indicate that the profiles of sleep oscillations reflect not only the dynamics of the neuronal network at the synaptic level, but also the localized microstructural properties of its structural backbone, the white matter tracts.
Sortilin and SorLA Display Distinct Roles in Processing and Trafficking of Amyloid Precursor Protein
Authors: Gustafsen Camilla , Glerup Simon , Pallesen Lone Tjener , Olsen Ditte , Andersen Olav M. , Nykjær Anders , Madsen Peder , Petersen Claus Munck
Published: January 2013

The development and progression of Alzheimer's disease is linked to excessive production of toxic amyloid-β peptide, initiated by β-secretase cleavage of the amyloid precursor protein (APP). In contrast, soluble APPα (sAPPα) generated by the α-secretase is known to stimulate dendritic branching and enhance synaptic function. Regulation of APP processing, and the shift from neurotrophic to neurotoxic APP metabolism remains poorly understood, but the cellular localization of APP and its interaction with various receptors is considered important. We here identify sortilin as a novel APP interaction partner. Like the related APP receptor SorLA, sortilin is highly expressed in the CNS, but whereas SorLA mainly colocalizes with APP in the soma, sortilin interacts with APP in neurites. The presence of sortilin promotes α-secretase cleavage of APP, unlike SorLA, which inhibits the generation of all soluble products. Also, sortilin and SorLA both bind and mediate internalization of sAPP but to different cellular compartments. The interaction involves the 6A domain of APP, present in both neuronal and non-neuronal APP isoforms. This is important as sAPP receptors described so far only bind the non-neuronal isoforms, leaving SorLA and sortilin as the only receptors for sAPP generated by neurons. Together, our findings establish sortilin, as a novel APP interaction partner that influences both production and cellular uptake of sAPP.
Neuroestrogens Rapidly Regulate Sexual Motivation But Not Performance
Authors: Seredynski Aurore L. , Balthazart Jacques , Christophe Virginie J. , Ball Gregory F. , Cornil Charlotte A.
Published: January 2013

Estrogens exert pleiotropic effects on reproductive traits, which include differentiation and activation of reproductive behaviors and the control of the secretion of gonadotropins. Estrogens also profoundly affect non-reproductive traits, such as cognition and neuroprotection. These effects are usually attributed to nuclear receptor binding and subsequent regulation of target gene transcription. Estrogens also affect neuronal activity and cell-signaling pathways via faster, membrane-initiated events. How these two types of actions that operate in distinct timescales interact in the control of complex behavioral responses is poorly understood. Here, we show that the central administration of estradiol rapidly increases the expression of sexual motivation, as assessed by several measures of sexual motivation produced in response to the visual presentation of a female but not sexual performance in male Japanese quail. This effect is mimicked by membrane-impermeable analogs of estradiol, indicating that it is initiated at the cell membrane. Conversely, blocking the action of estrogens or their synthesis by a single intracerebroventricular injection of estrogen receptor antagonists or aromatase inhibitors, respectively, decreases sexual motivation within minutes without affecting performance. The same steroid has thus evolved complementary mechanisms to regulate different behavioral components (motivation vs performance) in distinct temporal domains (long- vs short-term) so that diverse reproductive activities can be properly coordinated to improve reproductive fitness. Given the pleiotropic effects exerted by estrogens, other responses controlled by these steroids might also depend on a slow genomic regulation of neuronal plasticity underlying behavioral activation and an acute control of motivation to engage in behavior.
Phenotyping the Function of TRPV1-Expressing Sensory Neurons by Targeted Axonal Silencing
Authors: Brenneis Christian , Kistner Katrin , Puopolo Michelino , Segal David , Roberson David , Sisignano Marco , Labocha Sandra , Ferreirós Nerea , Strominger Amanda , Cobos Enrique J. , Ghasemlou Nader , Geisslinger Gerd , Reeh Peter W. , Bean Bruce P. , Woolf Clifford J.
Published: January 2013

Specific somatosensations may be processed by different subsets of primary afferents. C-fibers expressing heat-sensitive TRPV1 channels are proposed, for example, to be heat but not mechanical pain detectors. To phenotype in rats the sensory function of TRPV1+afferents, we rapidly and selectively silenced only their activity, by introducing the membrane-impermeant sodium channel blocker QX-314 into these axons via the TRPV1 channel pore. Using tandem mass spectrometry we show that upon activation with capsaicin, QX-314 selectively accumulates in the cytosol only of TRPV1-expressing cells, and not in control cells. Exposure to QX-314 and capsaicin induces in small DRG neurons a robust sodium current block within 30 s. In sciatic nerves, application of extracellular QX-314 with capsaicin persistently reduces C-fiber but not A-fiber compound action potentials and this effect does not occur in TRPV1−/−mice. Behavioral phenotyping after selectively silencing TRPV1+sciatic nerve axons by perineural injections of QX-314 and capsaicin reveals deficits in heat and mechanical pressure but not pinprick or light touch perception. The response to intraplantar capsaicin is substantially reduced, as expected. During inflammation, silencing TRPV1+axons abolishes heat, mechanical, and cold hyperalgesia but tactile and cold allodynia remain following peripheral nerve injury. These results indicate that TRPV1-expressing sensory neurons process particular thermal and mechanical somatosensations, and that the sensory channels activated by mechanical and cold stimuli to produce pain in naive/inflamed rats differ from those in animals after peripheral nerve injury.
Defense-Like Behaviors Evoked by Pharmacological Disinhibition of the Superior Colliculus in the Primate
Authors: DesJardin Jacqueline T. , Holmes Angela L. , Forcelli Patrick A. , Cole Claire E. , Gale John T. , Wellman Laurie L. , Gale Karen , Malkova Ludise
Published: January 2013

Stimulation of the intermediate and deep layers of superior colliculus (DLSC) in rodents evokes both orienting/pursuit (approach) and avoidance/flight (defense) responses (Dean et al., 1989). These two classes of response are subserved by distinct output projections associated with lateral (approach) and medial (defense) DLSC (Comoli et al., 2012). In non-human primates, DLSC has been examined only with respect to orienting/approach behaviors, especially eye movements, and defense-like behaviors have not been reported. Here we examined the profile of behavioral responses evoked by activation of DLSC by unilateral intracerebral infusions of the GABAAreceptor antagonist, bicuculline methiodide (BIC), in nine freely moving macaques. Across animals, the most consistently evoked behavior was cowering (all animals), followed by increased vocalization and escape-like behaviors (seven animals), and attack of objects (three animals). The effects of BIC were dose-dependent within the range 2.5–14 nmol (threshold dose of 4.6 nmol). The behaviors and their latencies to onset did not vary across different infusion sites within DLSC. Cowering and escape-like behaviors resembled the defense-like responses reported after DLSC stimulation in rats, but in the macaques these responses were evoked from both medial and lateral sites within DLSC. Our findings are unexpected in the context of an earlier theoretical perspective (Dean et al., 1989) that emphasized a preferential role of the primate DLSC for approach rather than defensive responses. Our data provide the first evidence for induction of defense-like behaviors by activation of DLSC in monkeys, suggesting that the role of DLSC in responding to threats is conserved across species.
Short-Term Plasticity Explains Irregular Persistent Activity in Working Memory Tasks
Authors: Hansel David , Mato German
Published: January 2013

Persistent activity in cortex is the neural correlate of working memory (WM). In persistent activity, spike trains are highly irregular, even more than in baseline. This seemingly innocuous feature challenges our current understanding of the synaptic mechanisms underlying WM. Here we argue that in WM the prefrontal cortex (PFC) operates in a regime of balanced excitation and inhibition and that the observed temporal irregularity reflects this regime. We show that this requires that nonlinearities underlying the persistent activity are primarily in the neuronal interactions between PFC neurons. We also show that short-term synaptic facilitation can be the physiological substrate of these nonlinearities and that the resulting mechanism of balanced persistent activity is robust, in particular with respect to changes in the connectivity. As an example, we put forward a computational model of the PFC circuit involved in oculomotor delayed response task. The novelty of this model is that recurrent excitatory synapses are facilitating. We demonstrate that this model displays direction-selective persistent activity. We find that, even though the memory eventually degrades because of the heterogeneities, it can be stored for several seconds for plausible network size and connectivity. This model accounts for a large number of experimental findings, such as the findings that have shown that firing is more irregular during the persistent state than during baseline, that the neuronal responses are very diverse, and that the preferred directions during cue and delay periods are strongly correlated but tuning widths are not.