Focused ion beam (FIB) microscopy is used to form an image similar to that formed in a conventional scanning electron microscope (SEM), but with greatly enhanced grain contrast due to the use of a primary ion beam as opposed to a beam of primary electrons as found in the SEM. In addition, by increasing the current of the positively charged gallium ion beam, it can be used as a precision, essentially stress‐free milling machine on a scale of tens of nanometres to several hundred microns. In this paper, the application of FIB microscopy to the study of crack profiles is reported. Samples of a Grade 448 (X‐65) pipeline steel were cyclically loaded in a dilute simulated groundwater solution of near neutral pH. Cracks that initiated on these samples were imaged in plan view and were locally cross‐sectioned using a high‐current focused gallium ion beam at different locations along the cracks. Samples were then tilted in situ to permit imaging of the crack profile, the grain structures around the crack tip and accurate measurement of the crack depth using the same ion beam at lower currents. The transgranular crack path and other microstructural features associated with crack development were clearly illustrated, and crack aspect ratio (depth/length) could be obtained. The capability of the FIB for enhanced imaging of grain structures, combined with its precision‐sectioning capability, make it a novel new tool for the study of cracks.
Various methods are described for the elimination of infectious viruses from activated prothrombin complex concentrates (aPCCs) and for the analysis of the final products (AUTOPLEX T and FEIBA VH). Viruses of concern in human plasma-derived products are enveloped (hepatitis B and C, cytomegalovirus, Epstein-Barr virus, and human immunodeficiency virus [HIV]) and nonenveloped (hepatitis A and parvovirus B19). Donated blood used for AUTOPLEX T is screened for antihepatitis C, HBsAg, anti-HIV types 1 and 2, and p24 antigen. Plasma pools utilized for raw materials are also tested by PCR for HIV and hepatitis C virus. Partial virus inactivation and partitioning are achieved by purification of the aPCC. Further reduction of virus infectivity is accomplished by lyophilization and dry-heat treatment. Each step undergoes virus elimination validation studies in which a relevant sample is 'spiked' with the appropriate virus or model virus. The total reduction in virus from raw material to final product can then be calculated. For AUTOPLEX T the cumulative log10 reduction factors for several viruses vary from 4.2 to 14.3. This ensures an exceptionally high margin of safety. Definitive evidence for product safety was obtained by clinical observation of treated patients. The viral inactivation process of AUTOPLEX T involves a four-tier viral safety program, including Cohn alcohol fractionation and dry-heat treatment, in place of the two-stage vapour-heating process for FEIBA.
Current knowledge of the conditions leading to generation of environments that cause stress corrosion cracking (SCC) of high-pressure pipelines was reviewed, and a database of references was compiled. In addition to the surface preparation of the steel pipe and the type of coating that is used, the level of cathodic protection (CP) reaching the pipe surface and the partial pressure of CO2 in the ground water are important factors. The balance between the level of CP reaching the surface and the CO2 partial pressure in the ground water is critical in determining the pH at the steel surface, and hence, whether high-pH SCC, near-neutral-pH SCC, or neither, occurs. Corrosion at pits and other localized sites may be a part of the SCC pre-initiation process. Under ground water conditions that simulate those of near-neutral-pH SCC, hydrogen enters and permeates line pipe steels. The findings of a review on conditions that lead to generation of stress corrosion cracking environments is presented in this report. The literature citations have been organized using Reference Manager, a searchable database of references. About 1,600 citations to references available in the literature as well as to industry reports are listed in the Reference Manager, covering all aspects of stress corrosion cracking, including issues relevant to generation of environments that cause SCC, such as coatings. Selected items from the Reference Manager database are listed in the Appendix of this report.
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