ProP Is Required for the Survival of Desiccated Salmonella enterica Serovar Typimurium Cells on a Stainless Steel Surface

Consumers trust commercial food production to be safe, and it is important to strive to improve food safety at every level. Several outbreaks of food-borne disease have been caused by Salmonella strains associated with dried food. Currently we do not know the mechanisms used by Salmonella enterica serovar Typhimurium to survive in desiccated environments. The aim of this study was to discover the responses of S. Typhimurium ST4/74 at the transcriptional level to desiccation on a stainless steel surface and to subsequent rehydration. Bacterial cells were dried onto the same steel surfaces used during the production of dry foods, and RNA was recovered for transcriptomic analysis. Subsequently, dried cells were rehydrated and were again used for transcriptomic analysis. A total of 266 genes were differentially expressed under desiccation stress compared with a static broth culture. The osmoprotectant transporters proP, proU, and osmU (STM1491 to STM1494) were highly upregulated by drying. Deletion of any one of these transport systems resulted in a reduction in the long-term viability of S. Typhimurium on a stainless steel food contact surface. The proP gene was critical for survival; proP deletion mutants could not survive desiccation for long periods and were undetectable after 4 weeks. Following rehydration, 138 genes were differentially expressed, with upregulation observed for genes such as proP, proU, and the phosphate transport genes (pstACS). In time, this knowledge should prove valuable for understanding the underlying mechanisms involved in pathogen survival and should lead to improved methods for control to ensure the safety of intermediate-and low-moisture foods. © 2013, American Society for Microbiology.

Properties of Super-Hydrophobic Copper and Stainless Steel Meshes: Applications in Controllable Water Permeation and Organic Solvents/Water Separation

The wettability and hydrophobicity of super-hydrophobic (SH) meshes is greatly influenced by their topographic structures, chemical composition and coating process. In this study, the properties of copper and stainless steel meshes, coated with super-hydrophobic electrolessly deposited silver were investigated. A new method to test the pressure resistance of super-hydrophobic mesh was applied to avoid any deformation of mesh. Results showed that SH copper mesh and SH stainless steel meshes with the same pore size have almost the same contact angle and the same hydrophobicity. SH copper mesh with a pore size of 122 μm can resist water pressure of 4900 Pa and a decrease of pore size of mesh can increase the pressure resistance of SH copper mesh. The SH copper mesh modified with 0.1 M HS(CH2)10COOH solution in ethanol has a controllable water permeation property by simply adjusting the pH of water solution. SH copper mesh shows super-oleophilicity with organic solvents and so with a water contact angle of 0° and it can be an effective tool for organic solvents/water separation. The separation efficiency of SH copper mesh for separating mixtures of organic solvent and water can be as high as 99.8%.

Oxygen Reduction Reaction on Metal-Terminated MnCr2O4 Nano-octahedron Catalyzing MnS Dissolution in an Austenitic Stainless Steel

To understand pitting corrosion in stainless steel is very important, and a recent work showed that the MnS dissolution catalyzed by MnCr2O4{111} is a starting point of pit g. This demonstrates the need to understand the oxygen reduction reaction (ORR) on MnCr2O4{111}, which is the other half-reaction to complete pitting corrosion. In this study, the adsorption behaviors of all oxygen-containing species on MnCr2O4{111}, which has several possible terminations, are explored via density functional theory calculations. It is found that O-2 adsorbs on MnCr2O4{111) surfaces very strongly. Many possible reactions are investigated and the favored reaction mechanism of ORR is determined. The interactions between O-2 and H2O on the two metal-terminated MriCr(2)O(4){111} are found to be different according to the atomic configurations of the two surfaces. All the calculated results suggest that ORR can readily occur on the MnCr2O4{111} surfaces.

Microstructure, mechanical properties and chemical degradation of brazed AISI 316 stainless steel/alumina systems

The main aims of the present study are simultaneously to relate the brazing parameters with: (i) the correspondent interfacial microstructure, (ii) the resultant mechanical properties and (iii) the electrochemical degradation behaviour of AISI 316 stainless steel/alumina brazed joints. Filler metals on such as Ag–26.5Cu–3Ti and Ag–34.5Cu–1.5Ti were used to produce the joints. Three different brazing temperatures (850, 900 and 950 °C), keeping a constant holding time of 20 min, were tested. The objective was to understand the influence of the brazing temperature on the final microstructure and properties of the joints. The mechanical properties of the metal/ceramic (M/C) joints were assessed from bond strength tests carried out using a shear solicitation loading scheme. The fracture surfaces were studied both morphologically and structurally using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). The degradation behaviour of the M/C joints was assessed by means of electrochemical techniques. It was found that using a Ag–26.5Cu–3Ti brazing alloy and a brazing temperature of 850 °C, produces the best results in terms of bond strength, 234 ± 18 MPa. The mechanical properties obtained could be explained on the basis of the different compounds identified on the fracture surfaces by XRD. On the other hand, the use of the Ag–34.5Cu–1.5Ti brazing alloy and a brazing temperature of 850 °C produces the best results in terms of corrosion rates (lower corrosion current density), 0.76 ± 0.21 μA cm−2. Nevertheless, the joints produced at 850 °C using a Ag–26.5Cu–3Ti brazing alloy present the best compromise between mechanical properties and degradation behaviour, 234 ± 18 MPa and 1.26 ± 0.58 μA cm−2, respectively. The role of Ti diffusion is fundamental in terms of the final value achieved for the M/C bond strength. On the contrary, the Ag and Cu distribution along the brazed interface seem to play the most relevant role in the metal/ceramic joints electrochemical performance.

Rapid automated method for on-site determination of sulfadiazine in fish farming: a stainless steel veterinary syringe coated with a selective membrane of PVC serving as a potentiometric detector in a flow-injection-analysis system

Sulfadiazine is an antibiotic of the sulfonamide group and is used as a veterinary drug in fish farming. Monitoring it in the tanks is fundamental to control the applied doses and avoid environmental dissemination. Pursuing this goal, we included a novel potentiometric design in a flow-injection assembly. The electrode body was a stainless steel needle veterinary syringe of 0.8-mm inner diameter. A selective membrane of PVC acted as a sensory surface. Its composition, the length of the electrode, and other flow variables were optimized. The best performance was obtained for sensors of 1.5-cm length and a membrane composition of 33% PVC, 66% onitrophenyloctyl ether, 1% ion exchanger, and a small amount of a cationic additive. It exhibited Nernstian slopes of 61.0 mV decade-1 down to 1.0×10-5 mol L-1, with a limit of detection of 3.1×10-6 mol L-1 in flowing media. All necessary pH/ionic strength adjustments were performed online by merging the sample plug with a buffer carrier of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, pH 4.9. The sensor exhibited the advantages of a fast response time (less than 15 s), long operational lifetime (60 days), and good selectivity for chloride, nitrite, acetate, tartrate, citrate, and ascorbate. The flow setup was successfully applied to the analysis of aquaculture waters. The analytical results were validated against those obtained with liquid chromatography–tandem mass spectrometry procedures. The sampling rate was about 84 samples per hour and recoveries ranged from 95.9 to 106.9%.

Simulation on the process of fatigue crack initiation in a martensitic stainless steel

Die vorliegende Arbeit beschäftigt sich mit der Computersimulation des Rissinitiierungsprozesses für einen martensitischen Stahl, der der niederzyklischen Ermüdung unterworfen wurde. Wie auf der Probenoberfläche beobachtet wurde, sind die Initiierung und das frühe Wachstum dieser Mikrorisse in hohem Grade von der Mikrostruktur abhängig. Diese Tatsache wurde in mesoskopischen Schädigungsmodellen beschrieben, wobei die Körner als einzelne Kristalle mit anisotropem Materialverhalten modelliert wurden. Das repräsentative Volumenelement (RVE), das durch einen Voronoi-Zerlegung erzeugt wurde, wurde benutzt, um die Mikrostruktur des polykristallinen Materials zu simulieren. Spannungsverteilungen wurden mit Hilfe der Finiten-Elemente-Methode mit elastischen und elastoplastischen Materialeigenschaften analysiert. Dazu wurde die Simulation zunächst an zweidimensionalen Modellen durchgeführt. Ferner wurde ein vereinfachtes dreidimensionales RVE hinsichtlich des sowohl dreidimensionalen Gleitsystems als auch Spannungszustandes verwendet. Die kontinuierliche Rissinitiierung wurde simuliert, indem der Risspfad innerhalb jedes Kornes definiert wurde. Die Zyklenanzahl bis zur Rissinitiierung wurde auf Grundlage der Tanaka-Mura- und Chan-Gleichungen ermittelt. Die Simulation lässt auf die Flächendichten der einsegmentige Risse in Relation zur Zyklenanzahl schließen. Die Resultate wurden mit experimentellen Daten verglichen. Für alle Belastungsdehnungen sind die Simulationsergebnisse mit denen der experimentellen Daten vergleichbar.

New material for orthopedic implants: Electrochemical study of nickel free P558 stainless steel in minimum essential medium

Nickel, a component of stainless steels (SS) applied in orthopedic implants may cause allergic processes in human tissues P558 nickel free SS was studied to verify its viability as a substitute for stainless steel containing nickel Its performance is compared to ISO 5832-9 and F138 most used nowadays grades in implants fabrications, in minimum essential medium. MEM, at 37 degrees C. Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and ""in vitro"" cytotoxicity were used as techniques. From the electrochemical point of view P558 SS is comparable to ISO 5832-9 SS in MEM It remains passivated until the transpassivation potential, above which generalized corrosion occurs F138 presents pitting corrosion at 370 mV/SCE. The cytotoxicity results showed that P558. ISO 5832-9 and F138 do not present cytotoxic character Therefore, these results suggest that P558 SS can be applied in orthopedic implants (C) 2010 Elsevier BV All rights reserved

Comparative electrochemical study of 5832-9 stainless steel at different media of biological interest

The electrochemical behavior of ISO 5832-9 stainless steel at 37 degrees C in 0.9% NaCl, Ringer Lactate and minimum essential medium (MEM) has been studied, using linear voltammetry, and surface analysis by SEM and EDS. Mechanical and toxicity tests were made. ISO 5832-9 is passivated at corrosion potential (E) and it does not present pitting corrosion on the media studied from to 50 in V above the transpassivation potential (Ei). SEM and EDS analysis have shown that the sample previously immersed in MEM presents a diffirent behavior at 50 in V above El: the manganese oxide inclusions are absent in the surface. E. values and passivation current density values j(pass) changed according to the following. E(corr, RL) < E(corr,NaCl) < E(corr, MEM) and J (MEM) << j(RL) congruent to j(NaCl) The stainless steel was characterized as non toxic in the cytotoxicity assay

The influence of albumin on the anodic dissolution of chromium present in UNSS31254 stainless steel in chloride environment

The influence of bovine serum albumin (BSA) on the anodic dissolution of chromium present in UNS S31254 stainless steel (SS) in 0.15 mol L-1 NaCl at 37.0 +/- 0.5 degrees C has been studied, using anodic potentiostatic polarization curves and optical emission spectroscopy. Electrochemical results have shown that BSA has little effect on the transpassivation potential (E-T) and on the passivation current density values. However on the passivation range, BSA diminishes the intensity of the anodic wave seen at about E=750mV versus SCE attributed to Cr(III)/Cr(VI) oxidation. Optical emission spectroscopy results have shown that BSA prevents the anodic dissolution of chromium to occur and minimizes iron dissolution above the transpassivation potential (E=1160 mV versus SCE). (C) 2007 Elsevier B.V. All rights reserved.

Study of electrochemical behavior of azoles for AISI 430 stainless steel in H(2)SO(4) 1 mol L(-1)

Corrosion is an undesirable process that occurs in metallic materials. Studied was the effect of inhibiting Benzotriazole (BTAH), Benzimidazole (BZM) and Indole in different concentrations-for the stainless steel (SS) AISI 430 in H(2)SO(4) mol The techniques employed this research were: anodic potenciostatic polarisation, electrochemical impedance spectroscopy, optical microscopy and scanning electron microscopy The curves of anodic polarisation showed that BTAH, BZM and Indol act as corrosion inhibitors for 430 SS, at concentrations of 1x10(-3) and 5x10(-4) mol L(-1) but do not inhibit corrosion for concentrations equal to or less than 1x10(-4) mol L(-1). The in-crease of the efficiency in relation to the inhibitory substances studied followed this order: Indol