An experimental and theoretical investigation of plane-stress fracture of 2024-T351 aluminum alloy

Plane-stress fracture behavior of precracked aluminum alloy

Terästen hapettumiskoejärjestelyn herkkyysanalyysi

Tiivistelmä. Tässä työssä tutkittiin aihionkuumennuksen aikana tapahtuvaa hapettumista. Aihionkuumennuksen aikana teräksenpinta hapettuu ja pinnalle muodostuu oksidikerros. Työn tavoitteena oli selvittää, onko lämpötilalla vaikutusta muodostuvaan oksidikerrokseen. Aihionkuumennuksessa aihiot kuumennetaan lämpötilaan, jossa niitä voidaan muovata valssaimilla. Aihionkuumennus voidaan toteuttaa askelpalkki- ja läpityöntöuuneilla, jotka ovat tavallisesti kaasulämmitteisiä. Vaihtoehtoisia lämmitystapoja ovat sähkölämmitys ja vedyn käyttäminen polttoaineena. Työhön sisältyy hehkutuskokeet sekä valomikroskooppikuvat näytepaloista. Työn neljä hehkutuskoetta toteutettiin pystysuoralla putkiuunilla ja termovaa’alla. Lämpötilan vaikutusta hapettumiseen tarkasteltiin näytteen massanmuutoksen avulla ja oksidikerroksien paksuuksilla. Tuloksena huomattiin lämpötilan nostamisen kasvattavan näytteen massanmuutosnopeutta ja muodostuvan hilseen määrää. Valomikroskooppisuurennuksista nähtiin lämpötilan vaikutus muodostuneen oksidikerroksen paksuuteen

Effect of maternal weight during pregnancy on offspring muscle strength response to resistance training in late adulthood

Purpose: Maternal obesity can unfavorably influence offspring body composition, muscle strength, and possibly muscle's adaptability to training, but the human studies are scarce. Therefore, we aimed to investigate the effect of maternal obesity on offspring muscle strength responses to resistance training intervention in elderly frail women. Materials/methods: Recruited participants were elderly frail women offspring of lean/normal weight mothers (n = 19, mean body mass index (BMI): 22.8 kg/m2, range: 19.9-24.5) or overweight/obese mothers (n = 16, mean BMI: 29.7 kg/m2, range: 28.2-34.2). Information on maternal BMI immediately prior to delivery was collected from the birth registers. All women participated in a 4-month supervised progressive resistance training intervention three times a week for 60 min. Predicted 1-RM of abdominal crunch, hip abduction, leg curl, leg press, seated row, and total strength were measured at baseline and after each month of training. Results: According to rANOVA, strength increased significantly in both groups (p for time 0.072). On average, muscle strength of the women offspring of overweight/obese mothers tended to be lower than in women offspring of lean/normal weight mothers, but the only significant difference was found in leg curl (p = 0.006). No significant differences between the groups were found in relative strength changes from baseline to 4-months. Conclusions: Muscle strength response to supervised resistance training is not modulated by maternal adiposity in late pregnancy in elderly frail female offspring.Peer reviewe

Association between dog ownership and type 2 diabetes in later life : the Helsinki birth cohort study

Dog ownership has been reported to have beneficial effects on physical activity and emotional well-being, both known to reduce the risk for type 2 diabetes (T2D). The aim of this study was to evaluate the association between dog ownership during the whole life course and having T2D in later life. The study subjects consisted of 731 people (307 men and 424 women) from the Helsinki Birth Cohort Study. We assessed dog ownership with questionnaires, for every decade of life as well as current dog ownership. We investigated the associations between dog ownership and T2D with generalised estimating equation models and with generalised linear models. At a mean age of 71.0 (standard deviation [SD] 2.6) years, 13% of the participants had T2D. Dog ownership prior to the clinical examination was not associated with T2D (p >= 0.51). In men, but not in women, current dog owners had greater odds of having T2D compared with the non-owners when adjusted for age when clinically examined, socio-economic status, smoking, leisure-time physical activity, chronic diseases (OR = 3.32, 95% confidence interval 1.25-8.79, p = 0.016). In the age group of people around 70 years, dog ownership is not associated with reduced odds for developing T2D.Peer reviewe

Fabrication Flaw Density and Distribution In Repairs to Reactor Pressure Vessel and Piping Welds

The Pacific Northwest National Laboratory is developing a generalized fabrication flaw distribution for the population of nuclear reactor pressure vessels and for piping welds in U.S. operating reactors. The purpose of the generalized flaw distribution is to predict component-specific flaw densities. The estimates of fabrication flaws are intended for use in fracture mechanics structural integrity assessments. Structural integrity assessments, such as estimating the frequency of loss-of-coolant accidents, are performed by computer codes that require, as input, accurate estimates of flaw densities. Welds from four different reactor pressure vessels and a collection of archived pipes have been studied to develop empirical estimates of fabrication flaw densities. This report describes the fabrication flaw distribution and characterization in the repair weld metal of vessels and piping. This work indicates that large flaws occur in these repairs. These results show that repair flaws are complex in composition and sometimes include cracks on the ends of the repair cavities. Parametric analysis using an exponential fit is performed on the data. The relevance of construction records is established for describing fabrication processes and product forms. An analysis of these records shows there was a significant change in repair frequency over the years when these components were fabricated. A description of repair flaw morphology is provided with a discussion of fracture mechanics significance. Fabrication flaws in repairs are characterized using optimized-access, high-sensitivity nondestructive ultrasonic testing. Flaw characterizations are then validated by other nondestructive evaluation techniques and complemented by destructive testing

Irradiation-assisted stress corrosion cracking considerations at temperatures below 288{degree}C

Irradiation-assisted stress corrosion cracking (IASCC) occurs above a critical neutron fluence in light-water reactor (LWR) water environments at 288 C, but very little information exists to indicate susceptibility as temperatures are reduced. Potential low-temperature behavior is assessed based on the temperature dependencies of intergranular (IG) SCC in the absence of irradiation, radiation-induced segregation (RIS) at grain boundaries and micromechanical deformation mechanisms. IGSCC of sensitized SS in the absence of irradiation exhibits high growth rates at temperatures down to 200 C under conditions of anodic dissolution control, while analysis of hydrogen-induced cracking suggests a peak crack growth rate near 100 C. Hence from environmental considerations, IASCC susceptibility appears to remain likely as water temperatures are decreased. Irradiation experiments and model predictions indicate that RIS also persists to low temperatures. Chromium depletion may be significant at temperatures below 100C for irradiation doses greater than 10 displacements per atom (dpa). Macromechanical effects of irradiation on strength and ductility are not strongly dependent on temperature below 288 C. However, temperature does significantly affect radiation effects on SS microstructure and micromechanical deformation mechanisms. The critical conditions for material susceptibility to IASCC at low temperatures may be controlled by radiation-induced grain boundary microchemistry, strain localization due to irradiation microstructure and irradiation creep processes. 39 refs

Amiodarone disrupts cholesterol biosynthesis pathway and causes accumulation of circulating desmosterol by inhibiting 24-dehydrocholesterol reductase

Background We have earlier reported that amiodarone, a potent and commonly used antiarrhythmic drug increases serum desmosterol, the last precursor of cholesterol, in 20 cardiac patients by an unknown mechanism. Objective Here, we extended our study to a large number of cardiac patients of heterogeneous diagnoses, evaluated the effects of combining amiodarone and statins (inhibitors of cholesterol synthesis at the rate-limiting step of hydroxy-methyl-glutaryl CoA reductase) on desmosterol levels and investigated the mechanism(s) by which amiodarone interferes with the metabolism of desmosterol using in vitro studies. Methods and Results We report in a clinical case-control setting of 236 cardiac patients (126 with and 110 without amiodarone treatment) that amiodarone medication is accompanied by a robust increase in serum desmosterol levels independently of gender, age, body mass index, cardiac and other diseases, and the use of statins. Lipid analyses in patient samples taken before and after initiation of amiodarone therapy showed a systematic increase of desmosterol upon drug administration, strongly arguing for a direct causal link between amiodarone and desmosterol accumulation. Mechanistically, we found that amiodarone resulted in desmosterol accumulation in cultured human cells and that the compound directly inhibited the 24-dehydrocholesterol reductase (DHCR24) enzyme activity. Conclusion These novel findings demonstrate that amiodarone blocks the cholesterol synthesis pathway by inhibiting DHCR24, causing a robust accumulation of cellular desmosterol in cells and in the sera of amiodarone-treated patients. It is conceivable that the antiarrhythmic potential and side effects of amiodarone may in part result from inhibition of the cholesterol synthesis pathway.Peer reviewe

A pilot application of risk-informed methods to establish inservice inspection priorities for nuclear components at Surry Unit 1 Nuclear Power Station. Revision 1

As part of the Nondestructive Evaluation Reliability Program sponsored by the US Nuclear Regulatory Commission, the Pacific Northwest National Laboratory has developed risk-informed approaches for inservice inspection plans of nuclear power plants. This method uses probabilistic risk assessment (PRA) results to identify and prioritize the most risk-important components for inspection. The Surry Nuclear Power Station Unit 1 was selected for pilot application of this methodology. This report, which incorporates more recent plant-specific information and improved risk-informed methodology and tools, is Revision 1 of the earlier report (NUREG/CR-6181). The methodology discussed in the original report is no longer current and a preferred methodology is presented in this Revision. This report, NUREG/CR-6181, Rev. 1, therefore supersedes the earlier NUREG/CR-6181 published in August 1994. The specific systems addressed in this report are the auxiliary feedwater, the low-pressure injection, and the reactor coolant systems. The results provide a risk-informed ranking of components within these systems

Integration of NDE Reliability and Fracture Mechanics

The Pacific Northwest Laboratory is conducting a four-phase program for measuring and evaluating the effectiveness and reliability of in-service inspection (lSI} performed on the primary system piping welds of commercial light water reactors (LWRs). Phase I of the program is complete. A survey was made of the state of practice for ultrasonic rsr of LWR primary system piping welds. Fracture mechanics calculations were made to establish required nondestrutive testing sensitivities. In general, it was found that fatigue flaws less than 25% of wall thickness would not grow to failure within an inspection interval of 10 years. However, in some cases failure could occur considerably faster. Statistical methods for predicting and measuring the effectiveness and reliability of lSI were developed and will be applied in the "Round Robin Inspections" of Phase II. Methods were also developed for the production of flaws typical of those found in service. Samples fabricated by these methods wilI be used in Phase II to test inspection effectiveness and reliability. Measurements were made of the influence of flaw characteristics {i.e., roughness, tightness, and orientation) on inspection reliability. These measurernents, as well as the predictions of a statistical model for inspection reliability, indicate that current reporting and recording sensitivities are inadequate

From DNA sequence to application: possibilities and complications

The development of sophisticated genetic tools during the past 15 years have facilitated a tremendous increase of fundamental and application-oriented knowledge of lactic acid bacteria (LAB) and their bacteriophages. This knowledge relates both to the assignments of open reading frames (ORF’s) and the function of non-coding DNA sequences. Comparison of the complete nucleotide sequences of several LAB bacteriophages has revealed that their chromosomes have a fixed, modular structure, each module having a set of genes involved in a specific phase of the bacteriophage life cycle. LAB bacteriophage genes and DNA sequences have been used for the construction of temperature-inducible gene expression systems, gene-integration systems, and bacteriophage defence systems. The function of several LAB open reading frames and transcriptional units have been identified and characterized in detail. Many of these could find practical applications, such as induced lysis of LAB to enhance cheese ripening and re-routing of carbon fluxes for the production of a specific amino acid enantiomer. More knowledge has also become available concerning the function and structure of non-coding DNA positioned at or in the vicinity of promoters. In several cases the mRNA produced from this DNA contains a transcriptional terminator-antiterminator pair, in which the antiterminator can be stabilized either by uncharged tRNA or by interaction with a regulatory protein, thus preventing formation of the terminator so that mRNA elongation can proceed. Evidence has accumulated showing that also in LAB carbon catabolite repression in LAB is mediated by specific DNA elements in the vicinity of promoters governing the transcription of catabolic operons. Although some biological barriers have yet to be solved, the vast body of scientific information presently available allows the construction of tailor-made genetically modified LAB. Today, it appears that societal constraints rather than biological hurdles impede the use of genetically modified LAB.