Stress corrosion cracking behaviour of stainless steels with respect to their use in architecture,part 2: corrosion in the passive state

Unexpected failures of 18/10 CrNi and 17/12/2 CrNiMo steels in indoor swimming pool atmospheres made it necessary to reinvestigate chloride stress corrosion cracking of stainless steels with respect to their use in arcitecture. A preceding paper presented inwestigations into stress corrosion cracking (SCC) in the active state of corrosion; the present paper deals with SCC In the passive state. The investigations showed that – in contrast to general opinion – stress corrosion cracking in the passive state can occur at temperatures well below 50°C in 18/10 CrNi and 17/12/2 CrNiMo steels, provided the corrosive medium has an extremely high chloride concentration. Other factors such as stress level, pH value or type of kation only exert a subordinate influence. Especially the high alloy austenitic steels 1.4439 and 1.4539 proved SCC-resistant under such conditions at ambient temperatures. Electrolytes with critical chloride concentrations may develop when deposits containing chlorides of sufficiently high solubility (e.g. MgCI₂, CaCl₂) are exposed to an atmoshere with critical, i.e. comparatively low humidity. Such conditions are evidently met only under very specific circumstances such as may occur in indoor swimming pools. In other structures where stainless steels have been used for decades without such damage having occurred to date, these critical conditions appear generally not to be reached.     

Efficiency of low-temperature adsorptive hydrogen storage systems

This study presents a thermodynamic analysis of adsorptive hydrogen storage systems at cryogenic temperatures, focusing mainly on the efficiency of the storage system. Four different operation modes, differing in the process used to release the hydrogen and the availability of cooling during storage time, are examined. A sensitivity analysis was performed to determine the dependency of the efficiency on several input parameters including storage time, enthalpy of adsorption, energy required for cooling, and system size. It can be concluded that the energetic efficiency of the hydrogen storage system not considering production and usage steps ranges from 65 to 81% for short storage times, depending on the energy effort and hydrogen losses of the applied operation mode. The storage time has the most noticeable impact on efficiency and cryo-adsorptive hydrogen storage is not suitable for long storage times due to the increasing cooling effort or hydrogen losses. For short storage times e.g. hours, cooling during storage time may be omitted due to the low hydrogen losses.     

Recent Advances in Experimental Techniques for Flow and Mass Transfer Analyses in Thermal Separation Systems

Modelling flow and mass transfer of thermal separation equipment constitutes one of the most challenging tasks in fluids process engineering. The difficulty of this task comes from the multiscale multiphase flow phenomena in rather complex geometries. Both analysis of flow and mass transfer on different scales as well as validation of models and simulation results require advanced experimental and measurement techniques. As a follow-up to intensive discussions during the 2019 Tutzing Symposium “Separation Units 4.0” a wide set of available modern experimental technologies is presented.     

Antibiotic treatment of metritis in dairy cows—A meta-analysis

The objective of this meta-analysis was to assess the efficacy of the treatment of bovine metritis with common antibiotic and nonantibiotic treatment options. Acute puerperal metritis, a systemic and potentially painful illness with rectal temperature >39.5°C and signs of toxemia due to an infection of the uterus, occurs within 21 d after parturition. Because of the infectious nature, antibiotics are considered beneficial for the treatment of acute puerperal metritis. Each use of an antimicrobial drug, however, is associated with selective pressure for eventual emergence of resistant bacteria. The 23 trials evaluated in the course of a previously conducted systematic review were the basis for meta-analytic investigations. Selected trials were screened regarding their eligibility for the following investigations: (1) comparison of different antibiotic treatments with respect to metritis prevalence at time of re-examination, (2) efficacy of ceftiofur treatment with respect to metritis prevalence at time of re-examination, (3) comparison of efficacy of antibiotic versus nonantibiotic drugs with respect to metritis prevalence at time of re-examination, and (4) equivalence assessment of treatment effects on reproductive performance measures. Where at least 3 trials had investigated the same outcome variable and met the inclusion criteria (inclusion of a control or reference group diagnosed with metritis; reporting means and standard deviation in case of continuous data), meta-analytic investigations were carried out. Due to a shortage of comparable studies, we could not conduct investigations (1) and (3). Ceftiofur treatment of 828 metritic cows was associated with a decrease in the prevalence of metritis following treatment in comparison to 804 untreated cows. In conclusion, meta-analytic investigations uncovered a need for more high-quality studies. Furthermore, a positive effect of the most commonly used antibiotic drug, ceftiofur, for the treatment of bovine metritis could be shown. A comparison with other antibiotic or nonantibiotic treatment options could not be made.     

Short communication: Meta-analysis on therapy of bovine endometritis with prostaglandin F2α—An update

The objective of the study was to update a prior meta-analysis on the efficacy of the treatment of bovine endometritis with PGF_2α. Clinical endometritis in cattle is defined as the presence of a purulent or mucopurulent vaginal discharge after 20 or 26 d, respectively, postpartum. Although the prevalence and impact of this disease are well known, the questions of whether and how to treat endometritis are still controversially discussed. Hence, to ensure timeliness of scientific results, we updated an existing meta-analysis published in 2013 that showed no treatment effect of PGF_2α in cases of bovine endometritis. As in the prior meta-analysis, a comprehensive literature search was conducted. After applying specific inclusion and exclusion criteria, 3 trials remained that could be added to the 6 trials in the initial meta-analysis. Data for each trial were analyzed using the meta-analysis software Review Manager (version 5.3; The Nordic Cochrane Centre, Copenhagen, Denmark). Estimated effect sizes of PGF_2α were calculated on calving to first service interval (CFSI) and calving to conception interval (CCI). As revealed by the initial meta-analysis, PGF_2α treatment still had no effect on both reproductive parameters. Heterogeneity remained substantial for CFSI and CCI and even increased for CCI compared with the initial meta-analysis. Subgroup analysis, however, did not reveal a source of heterogeneity. In updating the meta-analysis, publication bias for trials reporting CCI became even more pronounced, suggesting that studies with higher standard error (i.e., usually smaller studies) that reported a prolonging effect on CCI after a PGF_2α treatment were less likely to be published. Finally, although the number of trials published on the chosen topic and their comparability are still limited, this update of our meta-analysis now provides results that are based on approximately twice the number of included cows. The overall outcome, however, has not substantially changed and a positive effect of a PGF_2α treatment in case of clinical endometritis could not be shown. Therefore, we do not recommend a treatment of bovine endometritis with PGF_2α as a means to improve reproductive performance.