Effective hydrogen diffusivities of AISI 304 stainless steel with Ni or Au coating

Metallic coatings which provide a hydrogen diffusion barrier are thought to reduce hydrogen assisted cracking on stainless steel. The influence of a metallic layer on the hydrogen migration of AISI 304 stainless steel was investigated using a commercial electroplating layer of Ni and Au on a thin stainless steel coupon. Phase identification was performed using an X-ray diffractometer to determine the average thicknesses, measured from back-scattered scanning electron images. Regarding the ASTM G148-97 practice, the effective hydrogen diffusivities of AISI 304 austenitic stainless steel, nickel and gold were measured as 7.07 × 10-13, 2.72 × 10-14 and 9.64 × 10-16 m2 × s-1, respectively. In this work, a gold layer was found to be most effective for the prevention of hydrogen diffusion when compared with untreated and Ni-plated 304 stainless steel.

Selection of Bacteriophages to Control In Vitro 24 h Old Biofilm of Pseudomonas aeruginosa Isolated from Drinking and Thermal Water

Pseudomonas aeruginosa is an opportunistic pathogen that causes public healthcare issues. In moist environments, this Gram-negative bacterium persists through biofilm-associated contamination on surfaces. Bacteriophages are seen as a promising alternative strategy to chemical biocides. This study evaluates the potential of nine lytic bacteriophages as biocontrol treatments against nine environmental P. aerginosa isolates. The spot test method is preliminarily used to define the host range of each virus and to identify their minimum infectious titer, depending on the strain. Based on these results, newly isolated bacteriophages 14.1, LUZ7, and B1 are selected and assessed on a planktonic cell culture of the most susceptible isolates (strains MLM, D1, ST395E, and PAO1). All liquid infection assays are achieved in a mineral minimum medium that is much more representative of real moist environments than standard culture medium. Phages 14.1 and LUZ7 eliminate up to 90% of the PAO1 and D1 bacterial strains. Hence, their effectiveness is evaluated on the 24 h old biofilms of these strains, established on a stainless steel coupon that is characteristic of materials found in thermal and industrial environments. The results of quantitative PCR viability show a maximum reduction of 1.7 equivalent Log CFU/cm2 in the coupon between treated and untreated surfaces and shed light on the importance of considering the entire virus/host/environment system for optimizing the treatment.

PSI-9 Validation of environmental swabbing to detect Senecavirus A in feed

Senecavirus A (SVA) is an emerging virus impacting the U.S. swine herd. Environmental swabbing can help better detect the probability of feed contamination than product testing, but the detection of SVA by swabs has not yet been validated. Therefore, the objective of this experiment was to validate standardized swabbing techniques for detection of SVA. A secondary objective was to determine if a freeze/thaw cycle impacted detectable RNA. This experiment was a 3×4×2 factorial, with 3 forms (inoculum, feed, or swab), 4 doses (0, 10^3, 10^5, or 10^7 TCID50/mL SVA), and 2 storage methods (analyzed initially vs. after a freeze/thaw cycle). One mL SVA was added to 16 g of swine feed. One g reserved, and remaining 15 g spread over a 10 cm×10 cm stainless steel coupon and incubated for 15 minutes. Feed was removed, but residual feed dust remained. Next, surfaces were swabbed, swabs vortexed, and supernatants collected. Samples were split, with one set analyzed initially, and another frozen at -20°C for 7 days, then thawed and analyzed. Results are expressed as threshold cycle (Ct) from qRT-PCR analysis. There were 4 replicates per treatment. There was a sample type×SVA dose interaction (P < 0.0001; Table 1). Feed samples were approximately 8 Ct higher than the inoculum, and swab samples were approximately 4 Ct higher than feed. As expected, SVA level impacted (P < 0.0001) detectable SVA RNA. Finally, a freeze/thaw cycle did not impact (P = 0.846) detectable SVA RNA compared to samples that were analyzed immediately. In summary, this research validated that an environmental swab can be used to detect SVA in feed, however with approximately 4 Ct lower than analyzing feed samples directly. Furthermore, the limit of detection of SVA in environmental swabs appears to be near 10^3 TCID50/mL. Finally, samples can be frozen prior to analysis without impacting detectable SVA RNA.

Effect of surface roughness on susceptibility of Escherichia coli biofilm to benzalkonium chloride

The inherent natural tendency of bacteria to adhere and form biofilm on both biotic and abiotic surfaces and the consequential resistance to antimicrobial treatments remained a major concerned to humanity. The surface roughness of the sand blasted and cleaned stainless steel (type 304) substrates were measured using 3D measuring laser microscope before biofilm were developed on different surface roughness under continuous nutrient supply. The effect of benzalkonium chloride (BKC) as antibacterial agent on the biofilms was investigated. A concentration of 5 mg/mL BKC exert no pronounced effect on the biofilm formed on the three surfaces as compared to the 10 mg/mL and 20 mg/mL that removed approximately 50% of the cells from the respective surfaces. Conversely, the overall effect of the three concentrations tested were significantly higher (p ≤ 0.05) on the stainless steel coupon with the least average surface roughness of 0.38 ± 1.5 µm. These observations support the hypothesis that surface profile is one of the factors that influence biofilm susceptibility to antibacterial agents and reinforced the wide spread observation that microorganisms living as biofilm tends to be resistance to antimicrobial treatment especially at lower concentrations of 5 mg/mL.

The Effect of Current Density on the NiCu Coating Synthesized by Electroplating

In this paper, the NiCu alloy coatings were electroplated on the 304 stainless steel coupon. The XRD was used to identify the phase structure of the as-prepared products. The SEM and EDS were used to observe the surface morphology of the as-prepared coatings and the atomic composition of the as-prepared coatings, respectively. The influences of the current density on the as-plated NiCu coatings are systematically researched. It was found that the moderate current density is beneficial to the compactness of the coatings. The content of the copper decreased and that of the nickel increased with the increasing of the current density. When the current density is smaller than 40 mA/cm2, the contents of nickel and copper vary apparently. When the current density is larger than 40 mA/cm2, the contents of nickel and copper vary slightly. That means the copper is more easily deposited at low current density and the nickel is more easily deposited at high current density.

The Effect of Temperature on the NiCu Coating Prepared by Electroplating

In this paper, the NiCu alloy coatings were electroplated on the 304 stainless steel coupon. The XRD was used to identify the phase structure of the as-prepared products. The SEM and EDS were used to observe the surface morphology of the as-prepared coatings and the atomic composition of the as-prepared coatings, respectively. The influences of the temperature on the as-plated NiCu coatings are systematically researched. It was found that the lower of the temperature, the more compact of the coatings. With the increasing of the temperatures, the content of the nickel decrease and that of the copper increase. When the temperature is lower than 35 °C the contents of nickel and copper do not vary apparently. When the temperature is larger than 40 °C, there are significant increases of the copper content while apparent decreases of the nickel content.

The Influence of pH Value on the NiCu Coating Synthesized by Electroplating

In this paper, the NiCu alloy coatings were electroplated on the 304 stainless steel coupon. The XRD was used to identify the phase structure of the as-prepared products. The SEM and EDS were used to observe the surface morphology of the as-prepared coatings and the atomic composition of the as-prepared coatings, respectively. The influences of the pH value on the as-plated NiCu coatings are systematically researched. It was found that the weak acid environment was beneficial to the deposition of nickel copper alloy. With the increasing of the pH value, the content of the copper decrease and that of nickel increase.

A Novel Optical Technique for Measuring the Coefficient of Restitution of Microparticle Impacts in a Forced Flowfield

Erosion and deposition in gas turbine engines are functions of particle/wall interactions and Coefficient of Restitution (COR) is a fundamental property of these interactions. COR depends on impact velocity, angle of impact, temperature, particle composition, and wall material. The current study attempts to characterize the fundamental behavior of sand at different impact angles. A PIV system is used in the Virginia Tech Aerothermal Rig to measure velocity trajectories of microparticles. A novel method is used that solves for impact velocity in a forced flowfield by numerical methods. Two sizes of Arizona Test Dust and one of Glass beads are impacted into a 304 Stainless Steel coupon. Free jet velocity is 27m/s at room temperature. Impact angle varies from almost 90 to 25 degrees depending on particle. Mean results compare favorably with trends established in literature. This utilization of this technique to measure COR of microparticle sand will help develop a computational model and serve as a baseline for further measurements at elevated, engine representative air and wall temperatures.

Removal of Listeria monocytogenes Biofilms with Bacteriophage P100†

Listeria monocytogenes is an important foodborne pathogen with a persistent ability to form biofilm matrices in the food processing environments. In this study, we have determined the ability of bacteriophage P100 to reduce L. monocytogenes cell populations under biofilm conditions by using 21 L. monocytogenes strains representing 13 different serotypes. There were considerable differences in the ability of various strains of L. monocytogenes to form biofilms, with strains of serotype 1/2a showing maximum biofilm formation. Irrespective of the serotype, growth conditions, or biofilm levels, the phage P100 treatment significantly reduced L. monocytogenes cell populations under biofilm conditions. On the stainless steel coupon surface, there was a 3.5- to 5.4-log/cm2 reduction in L. monocytogenes cells by phage treatment. These findings illustrate that phage P100 is active against a wide range of L. monocytogenes strains in biofilm conditions.