scholarly journals Gamma radiation sterilization of N95 respirators leads to decreased respirator performance

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0248859
Author(s):  
Haedi E. DeAngelis ◽  
Anne M. Grillet ◽  
Martin B. Nemer ◽  
Maryla A. Wasiolek ◽  
Don J. Hanson ◽  
...  
Keyword(s):  
Gamma Radiation ◽  
Electrostatic Potential ◽  
Particle Filtering ◽  
Performance Testing ◽  
Field Measurements ◽  
The United States ◽  
Filtration Efficiency ◽  
Radiation Sterilization ◽  
Potential Measurement ◽  
N95 Respirators

In response to personal protective equipment (PPE) shortages in the United States due to the Coronavirus Disease 2019, two models of N95 respirators were evaluated for reuse after gamma radiation sterilization. Gamma sterilization is attractive for PPE reuse because it can sterilize large quantities of material through hermetically sealed packaging, providing safety and logistic benefits. The Gamma Irradiation Facility at Sandia National Laboratories was used to irradiate N95 filtering facepiece respirators to a sterilization dose of 25 kGy(tissue). Aerosol particle filtration performance testing and electrostatic field measurements were used to determine the efficacy of the respirators after irradiation. Both respirator models exhibited statistically significant decreases in particle filtering efficiencies and electrostatic potential after irradiation. The largest decrease in capture efficiency was 40–50% and peaked near the 200 nm particle size. The key contribution of this effort is correlating the electrostatic potential change of individual filtration layer of the respirator with the decrease filtration efficiency after irradiation. This observation occurred in both variations of N95 respirator that we tested. Electrostatic potential measurement of the filtration layer is a key indicator for predicting filtration efficiency loss.

Effects of sterilization modes on the mechanical strengths of plaster of paris implants

1989 ◽  
Vol 47 ◽  
pp. 890-891
Author(s):  
K. Cowden ◽  
B. Giammara ◽  
T. Devine ◽  
J. Hanker
Keyword(s):  
Gamma Radiation ◽  
Calcium Sulfate ◽  
Significant Loss ◽  
Potassium Sulfate ◽  
Limiting Factors ◽  
Radiation Sterilization ◽  
Plaster Of Paris ◽  
Hardness Tester ◽  
Dry Heat ◽  
Calcium Sulfate Hemihydrate

Plaster of Paris (calcium sulfate hemihydrate, CaSO4. ½ H2O) has been used as a biomedical implant material since 1892. One of the primary limiting factors of these implants is their mechanical properties. These materials have low compressive and tensile strengths when compared to normal bone. These are important limiting factors where large biomechanical forces exist. Previous work has suggested that sterilization techniques could affect the implant’s strength. A study of plaster of Paris implant mechanical and physical properties to find optimum sterilization techniques therefore, could lead to a significant increase in their application and promise for future use as hard tissue prosthetic materials.USG Medical Grade Calcium Sulfate Hemihydrate Types A, A-1 and B, were sterilized by dry heat and by gamma radiation. Types A and B were additionally sterilized with and without the setting agent potassium sulfate (K2SO4). The plaster mixtures were then moistened with a minimum amount of water and formed into disks (.339 in. diameter x .053 in. deep) in polyethylene molds with a microspatula. After drying, the disks were fractured with a Stokes Hardness Tester. The compressive strengths of the disks were obtained directly from the hardness tester. Values for the maximum tensile strengths σo were then calculated: where (P = applied compression, D = disk diameter, and t = disk thickness). Plaster disks (types A and B) that contained no setting agent showed a significant loss in strength with either dry heat or gamma radiation sterilization. Those that contained potassium sulfate (K2SO4) did not show a significant loss in strength with either sterilization technique. In all comparisons (with and without K2SO4 and with either dry heat or gamma radiation sterilization) the type B plaster had higher compressive and tensile strengths than that of the type A plaster. The type A-1 plaster however, which is specially modified for accelerated setting, was comparable to that of type B with K2SO4 in both compressive and tensile strength (Table 1).

Modular Bridge Expansion Joints for Lacey V. Murrow Floating Bridge

1997 ◽  
Vol 1594 (1) ◽  
pp. 163-171 ◽  
Author(s):  
John A. Van Lund ◽  
Mark R. Kaczinski ◽  
Robert J. Dexter
Keyword(s):  
Fatigue Strength ◽  
Fatigue Cracking ◽  
Field Measurements ◽  
The United States ◽  
Limit States ◽  
Expansion Joints ◽  
Lake Washington ◽  
Floating Bridge ◽  
Modular Bridge Expansion Joints ◽  
Washington State Department

The Lacey V. Murrow Bridge (LVM Bridge) is a 2013-m-long floating bridge on Interstate 90 across Lake Washington in Seattle, Washington. Single-support-bar, swivel-joist modular bridge expansion joint systems are located at each end of the bridge between the shore approach spans and the floating pontoons. These joints were designed for 960 mm of longitudinal movement as well as horizontal and vertical rotations caused by wind, wave, temperature, and changes in lake level elevation. A similar joint in an adjacent floating bridge had experienced premature fatigue cracking at welded attachment details because of low fatigue strength. For the LVM Bridge the joint components were fatigue tested and designed by using fatigue limit-states loads, resulting in welded attachment details with improved fatigue strength. In addition, a stiffer center beam and reduced center-beam span lengths produced lower fatigue stress ranges. Joint movements and rotations, fatigue design methodology, results of dynamic analyses, field measurements of the dynamic response, and construction details are described. The total cost of the LVM joints was 1 percent of the final bridge cost. The Washington State Department of Transportation required a 5-year guarantee for the LVM joints. These are the largest modular bridge expansion joints in the United States to be tested and designed for fatigue.

Performance Testing of Coal Fired Power Plants

2007 ◽  
Author(s):  
Shane E. Powers ◽  
William C. Wood
Keyword(s):  
Power Plant ◽  
Power Plants ◽  
Performance Test ◽  
Model Development ◽  
Performance Testing ◽  
The United States ◽  
Plant Performance ◽  
Cycle Performance ◽  
Test Program

With the renewed interest in the construction of coal-fired power plants in the United States, there has also been an increased interest in the methodology used to calculate/determine the overall performance of a coal fired power plant. This methodology is detailed in the ASME PTC 46 (1996) Code, which provides an excellent framework for determining the power output and heat rate of coal fired power plants. Unfortunately, the power industry has been slow to adopt this methodology, in part because of the lack of some details in the Code regarding the planning needed to design a performance test program for the determination of coal fired power plant performance. This paper will expand on the ASME PTC 46 (1996) Code by discussing key concepts that need to be addressed when planning an overall plant performance test of a coal fired power plant. The most difficult aspect of calculating coal fired power plant performance is integrating the calculation of boiler performance with the calculation of turbine cycle performance and other balance of plant aspects. If proper planning of the performance test is not performed, the integration of boiler and turbine data will result in a test result that does not accurately reflect the true performance of the overall plant. This planning must start very early in the development of the test program, and be implemented in all stages of the test program design. This paper will address the necessary planning of the test program, including: • Determination of Actual Plant Performance. • Selection of a Test Goal. • Development of the Basic Correction Algorithm. • Designing a Plant Model. • Development of Correction Curves. • Operation of the Power Plant during the Test. All nomenclature in this paper utilizes the ASME PTC 46 definitions for the calculation and correction of plant performance.

The wildland - urban interface fire problem - current approaches and research needs

2010 ◽  
Vol 19 (2) ◽  
pp. 238 ◽  
Author(s):  
William E. Mell ◽  
Samuel L. Manzello ◽  
Alexander Maranghides ◽  
David Butry ◽  
Ronald G. Rehm
Keyword(s):  
Wildland Fire ◽  
Fire Suppression ◽  
Economic Cost ◽  
Field Measurements ◽  
The United States ◽  
Test Methods ◽  
Wildland Urban Interface ◽  
Fuel Treatment ◽  
Treatment Techniques ◽  
Exposure Conditions

Wildfires that spread into wildland–urban interface (WUI) communities present significant challenges on several fronts. In the United States, the WUI accounts for a significant portion of wildland fire suppression and wildland fuel treatment costs. Methods to reduce structure losses are focussed on fuel treatments in either wildland fuels or residential fuels. There is a need for a well-characterised, systematic testing of these approaches across a range of community and structure types and fire conditions. Laboratory experiments, field measurements and fire behaviour models can be used to better determine the exposure conditions faced by communities and structures. The outcome of such an effort would be proven fuel treatment techniques for wildland and residential fuels, risk assessment strategies, economic cost analysis models, and test methods with representative exposure conditions for fire-resistant building designs and materials.

scholarly journals High concentrations of coarse particles emitted from a cattle feeding operation

2011 ◽  
Vol 11 (16) ◽  
pp. 8809-8823 ◽  
Author(s):  
N. Hiranuma ◽  
S. D. Brooks ◽  
J. Gramann ◽  
B. W. Auvermann
Keyword(s):  
United States ◽  
Particulate Matter ◽  
Chemical Properties ◽  
Field Measurements ◽  
The United States ◽  
Water Soluble ◽  
Size Distributions ◽  
Cattle Feeding ◽  
High Concentrations ◽  
Organic Particles

Abstract. Housing roughly 10 million head of cattle in the United States alone, open air cattle feedlots represent a significant but poorly constrained source of atmospheric particles. Here we present a comprehensive characterization of physical and chemical properties of particles emitted from a large representative cattle feedlot in the Southwest United States. In the summer of 2008, measurements and samplings were conducted at the upwind and downwind edges of the facility. A series of far-field measurements and samplings was also conducted 3.5 km north of the facility. Two instruments, a GRIMM Sequential Mobility Particle Sizer (SMPS) and a GRIMM Portable Aerosol Spectrometer (PAS), were used to measure particle size distributions over the range of 0.01 to 25 μm diameter. Raman microspectroscopy was used to determine the chemical composition of particles on a single particle basis. Volume size distributions of dust were dominated by coarse mode particles. Twenty-four hour averaged concentrations of PM10 (particulate matter with a diameter of 10 μm or less) were as high as 1200 μg m−3 during the campaign. The primary constituents of the particulate matter were carbonaceous materials, such as humic acid, water soluble organics, and less soluble fatty acids, including stearic acid and tristearin. A significant fraction of the organic particles was present in internal mixtures with salts. Basic characteristics such as size distribution and composition of agricultural aerosols were found to be different than the properties of those found in urban and semi-urban aerosols. Failing to account for such differences may lead to errors in estimates of aerosol effects on local air quality, visibility, and public health.

sorbed dose must be measured by placing dose meters into the carriers, as described in Section V. If all of the gamma radiation coming from the 60Co source were absorbed by the irradiated goods, the radiation facility would have % irradiation efficiency. This is of course impossible because some of the radiation will be absorbed by the concrete shielding, by the carrier metal, and by the water below the source rack. Well-designed gamma facilities have an efficiency of about 30%. Designs differ­ ent from that shown in Figure 3 may use tote boxes on a conveyor belt instead of carriers hanging from a monorail, or the carriers may move around the source in a double loop instead of a single loop. Storage of the radioactive source in air in a concrete-shielded or lead-shielded cask instead of the water pool is also possible but is not often practiced. The outside appearance of a gamma irradiation facility is not much different from that of any other small or medium size industrial plant. A view of the first irradiation plant in the United States designed exclusively for the processing of foods (1) is shown in Figure 4. In principle, a 137Cs irradiator operates exactly like a 60Co irradiator. Some­ what less concrete shielding (1.2 m) is needed because the 0.66 MeV gamma rays of ,37Cs are less penetrating than the 1.33 MeV of Co. The longer half-life of

1995 ◽  
pp. 33-33
Keyword(s):  
United States ◽  
Gamma Radiation ◽  
Half Life ◽  
The United States ◽  
Conveyor Belt ◽  
Radioactive Source ◽  
Industrial Plant ◽  
Medium Size ◽  
Double Loop ◽  
60Co Source

scholarly journals Experimental and field verifications of radial gates as flow measurement structures

2021 ◽  
Author(s):  
Hossein Khalili Shayan ◽  
Javad Farhoudi ◽  
Alireza Vatankhah
Keyword(s):  
Field Measurements ◽  
The United States ◽  
Data Series ◽  
Flow Conditions ◽  
Flow Limit ◽  
Before And After ◽  
Energy And Momentum ◽  
Extensive Experimental Data ◽  
Radial Gate ◽  
Discharge Curves

Abstract Radial gates are common structures in irrigation projects. This paper presents some theoretical-based equations for explicit estimation of the discharge from the radial gate under free and submerged flow conditions using Energy and Momentum (E-M) principles. The proposed equations were calibrated using extensive experimental data collected from the literature and this study for three types of radial gates under free and submerged flow conditions. The submergence threshold of radial gates is concluded, based on the concepts of hydraulic jump and the intersection of free and submerged head-discharge curves. The results indicated that the error in estimating the discharge increases under transition ( − 2.5 ≤ Sr% ≤ + 2.5), gate lip (1 < y0/w ≤ 2), and high submerged (yt/y0 ≥ 0.95) flow conditions. However, in these flow limit conditions, the discharge error can be considerably decreased by adjusting the tailwater depth to flow depth just after the gate and using the energy equation for the sections before and after the gate. The efficiency of the proposed methods was evaluated based on the data series from field measurements of radial gates in 29 check structures at irrigation canals in the United States and Iran. The results showed that the discharge could be estimated using the proposed equations in field conditions with acceptable accuracy.

scholarly journals Sterilization of N95 Respirators via Gamma Radiation: Comparison of Post-sterilization Efficacy.

2020 ◽  
Author(s):  
Paul Thelen ◽  
Anne Grillet ◽  
Martin Nemer ◽  
Haedi De Angelis ◽  
Maryla Olszewska-Wasiolek ◽  
...  
Keyword(s):  
Gamma Radiation ◽  
N95 Respirators
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