Minimization of stress concentration factors in fatigue crack repairs

A numerical study is reported of a repair by flaw removal on a conventional welded joint. The repair profile is optimized with respect to the flaw and joint dimensions in order to minimize the resulting stress concentration factor (SCF). Two dimensional (edge repair) and three dimensional (surface repair) finite element analyses were made for the determination of SCF values and a graphical representation of results is presented. A relation between edge repair and surface repair is obtained and short and long repairs are defined. The weld geometry and repair orientation effects on SCF values are discussed. Finally, implications on using short and long repairs on fatigue initiation and inspection are presented.     

StressProbe - A New Non-contacting Stress Measurement Technique

Abstract:  A new non-contacting stress measurement technique, the StressProbe, based on the piezomagnetic effect has recently come into service. It utilises inducing and sensing coils that are arranged so that an almost linear response to stress is possible. Theoretical work already reported has shown that it can be used for measurement of residual stress, dead loads and cyclic stress. In general, a calibration is needed for the interpretation of StressProbe measurements and this may be obtained from a simple three-point bend or axial load tests. For some metals, the StressProbe response shows hysteresis during a static load–unload test. For these metals, it has been found that using a demagnetisation cycle between each measurement eliminates most of the hysteresis loop. For continuous cyclic loading, this behaviour does not occur.     

Comparison of the bactericidal action of amikacin, netilmicin and tobramycin in free and liposomal formulation against Pseudomonas aeruginosa

Glycoprotein Ibalpha (GP Ibalpha; CD 42b; hereafter GPIBA) is a component of the cell surface receptor for the von Willebrand factor (vWf) on platelets. Immunizations against various platelet surface antigens play a major role in neonatal alloimmune thrombocytopenia and in post-transfusion purpura. Only one antigenic polymorphism in GPIBA has thus far been established: the HPA-2 (Ko) alloantigen system. To screen other polymorphisms in GPIBA systematically, we analyzed the whole coding sequence of the GPIBA gene in 50 Finnish blood donors using the single-strand conformation polymorphism method. In addition to the known polymorphisms, we detected three others. Sequencing of the gene segments carrying the new polymorphisms revealed that none of them changed the predicted amino acid sequence. Polymorphism designated RS was located five base pairs upstream from the initiation codon at position 3064 and had the gene frequency of 16% for R and 84% for S, respectively, in the Finnish population, and it was detectable by the restriction enzyme Hae III. The EF polymorphism was at position 3842 (Asn242) and the gene frequencies were 97% for E and 3% for F. The KL polymorphism was at position 4142 (Arg342) and the gene frequencies were 98% for K and 2% for L. The five polymorphic positions in GPIBA formed altogether six different alleles of the gene. The data suggest that there are only a few variable amino acids in GPIBA.     

Phase I study of the orally administered butyrate prodrug, tributyrin, in patients with solid tumors

Butyrates have been studied as cancer differentiation agents in vitro and as a treatment for hemoglobinopathies. Tributyrin, a triglyceride with butyrate molecules esterified at the 1, 2, and 3 positions, induces differentiation and/or growth inhibition of a number of cell lines in vitro. When given p.o. to rodents, tributyrin produces substantial plasma butyrate concentrations. We treated 13 patients with escalating doses of tributyrin from 50 to 400 mg/kg/day. Doses were administered p.o. after an overnight fast, once daily for 3 weeks, followed by a 1-week rest. Intrapatient dose escalation occurred after two courses without toxicity greater than grade 2. The time course of butyrate in plasma was assessed on days 1 and 15 and after any dose escalation. Grade 3 toxicities consisted of nausea, vomiting, and myalgia. Grades 1 and 2 toxicities included diarrhea, headache, abdominal cramping, nausea, anemia, constipation, azotemia, lightheadedness, fatigue, rash, alopecia, odor, dysphoria, and clumsiness. There was no consistent increase in hemoglobin F with tributyrin treatment. Peak plasma butyrate concentrations occurred between 0.25 and 3 h after dose, increased with dose, and ranged from 0 to 0.45 mM. Peak concentrations did not increase in three patients who had dose escalation. Butyrate pharmacokinetics were not different on days 1 and 15. Because peak plasma concentrations near those effective in vitro (0.5-1 mM) were achieved, but butyrate disappeared from plasma by 5 h after dose, we are now pursuing dose escalation with dosing three times daily, beginning at a dose of 450 mg/kg/day.     

The influence of stress reversals on the structure of initially cold-rolled copper

An electron microscope study of initially cold-rolled copper has revealed that cyclic stressing, in the long life region of theS/log (N) curve, can promote room temperature recovery in isolated regions. Examples of polygonisation, subgrain growth and even a recrystallised grain have been detected in specimens possessing predominantly the typical cold-rolled structure. This is envisaged as a preliminary stage allowing eventually the formation of fatigue damage in certain regions.     

Responses to ergometer exercise in a healthy biracial population of children

To determine normal values for the exercise variables heart rate, blood pressure, maximal workload, physical working capacity index, J point displacement, and ST segment slope, we stress tested 405 healthy children. We analyzed the data for four body surface area-determined groups, to discover whether there were any racial differences between healthy white children and black children. There were numerous racial differences in blood pressure, maximal workload, and physical working capacity index; there were no differences in the heart rate values. The incidence of false-positive J point displacement was less than or equal to 3% when the PR isoelectric line method was used. The ST segment slope in healthy children was always greater than zero at maximal exercise. Thus, norms for exercise variables must be expressed in relation to both sex and race. The nomograms presented in this report provide an easy-to-use set of normative data for cycle ergometer stress testing in children.     

Microstructural properties and improvement in photoluminescence thermometry of Mn-activated single-phased Zn–SO–Mn phosphors

Fabrication by sol–gel and study of the physical properties of Mn²⁺ doped Zn₂SiO₄ (Zn–SO–Mn) materials phosphors (heat-treated at 1500 °C) were reported. The morphology, microstructure and size of the particles were resolved by the XRD and TEM techniques. Moreover, PL measurements of the samples phosphors demonstrate a good emission at 576 nm (yellow: ⁴T₁–⁶A₁). The decay kinetics of the emission (yellow: ⁴T₁–⁶A₁) was analyzed (fitting: a single exponential function). After the adjustment, the Zn–SO–Mn samples exhibited that the lifetime is around 13.09 ms. These lifetime are considered as promising values compared to those obtained until now. In fact, these results provide a simple means of obtaining the phosphors have excellent yellow luminescence which is very interesting for several technological applications.