Correlation Between the Resistance to Stress Corrosion Cracking of Steel Tubes of Gas Pipelines with Their Layerwise Texture Inhomogeneity

In the present work, the influence of the tubes texture layering on their resistance to stress-corrosion cracking (SCC) is demonstrated by the example of several main gas pipelines (MGP) constructed of X70 steel tubes of different manufactures and operated under various exploitation conditions. X-ray studies of crystallographic texture and structural characteristics were implemented for external and internal layers of various tubes sections, which were cut out from MGP zones with fixed SCC defects and without them. Correlation between the depth of corrosion cracks and the thickness of the surface layer with sharply differing texture parameters is established. The system data analysis also shows that the presence of the texture component {110} <001> in the tubes surface layers can increase their resistance to the SCC. Keywords: crystallographic texture, structure, texture layering, electron backscattered diffraction, stress corrosion cracking, main gas pipeline, hot rolling

EPIDEMIOLOGICAL FEATURES OF BACTERIAL INFECTIONS IN BONE MARROW TRANSPLANT UNITS

The aim of the study was to identify the epidemiological features of bacterial infections in patients and circulation of epidemiologically significant microorganisms in the bone marrow transplant (BMT) units. Materials and methods. The study was conducted in three BMT departments. To identify the epidemiological features of bacterial infections, a prospective observational study was conducted from 01 April 2014 to 31 August 2014 (91 patients) which included active detection of cases of infection and microbiological examination of patients. In order to detect the circulation of epidemiologically significant microorganisms, point prevalence studies (59 patients, 170 environmental samples) were conducted. To study the role of colonization, microbiological monitoring of patients on admission to the department was carried out, and repeated every week before discharge. Swab samples from skin and mucous membrane of the oral cavity and stool sampleswere included in the monitoring. In total, 639 samples from 50 patients were tested. Results. The study revealed a high incidence of infectious complications in BMT patients (100 cases of bacterial infections in 57 patients: sepsis 30.8 per 100 patients, pneumonia 26.4 per 100 patients, urinary tract infections 32.9 per 100 patients, soft tissue infection 9.9 per 100 patients, catheter-associated bloodstream infection 9.9 per 100 patients). Most infections were caused by Gram-negative bacteria, in particular K. pneumoniae. The onset of disease manifestation was preceded by colonization of the patient with these microorganisms. Fatal outcomes were observed from sepsis and pneumonia caused by K. pneumoniae and/or P. aeruginosa. Sepsis and pneumonia were often associated with cytopenia, RR 2.63 [95% CI 1.52–4.57] p = 0.004 and RR 3.97 [95% CI 2.19–7.19] p < 0.001 respectively. In course of observation, the frequency of colonization of patients with microorganisms susceptible to antibiotics decreased, and colonization with resistant pathogens increased. A series of prevalence studies revealed a constant circulation of VRE in the BMT units with a contacttransmission via household objects. Multidrug-resistant gram-negative microorganisms did not have a constant circulation and appeared sporadically against the background of the constant circulation of susceptible strains of these pathogens. Conclusions. Prospective epidemiological surveillance and microbiological monitoring are required in the BMT units. Widespread contamination of household objects in the environment indicates the need to strengthen the hygienic education of patients and visitors as well as disinfection of these facilities. In addition, we recommend introduction of weekly fecal screening cultures to monitor intestinal colonization of patients with MDRO