In this research the three different FSW joints of Titanium Grade 1 have been performed by using tool made of W25Re alloy with different welding velocity values. In order to investigate the influence ...of FSW process on microstructure of joined material the light microscope observations have been performed on the etched samples. It has been reported that significant grain refinement occurs in the stir zone in all analyzed samples. On the other hand, occurrence of weld defects, such as tunneling defect and kissing bond has been noticed. The microhardness analysis of the cross-section of the obtained joints indicates on microhardness increasing in the stir zone by 40-60 HV0,1 compared to the base material. Peak hardness of stir zone in the researched samples has tendency to decrease along with increasing of welding velocity. The strength of obtained joints was designated in the uniaxial tensile tests and confronted with strength of base material. Despite the occurrence of weld defects the established joints efficiency contains in range 92-94%. It has been stated that Young’s modulus of Titanium Grade 1 FSW joints is 15-19% lower in comparison to the base material. At the same time, no significant influence of FSW on the ductility of material were observed.
We make an attempt to explain brittle propagation of short fatigue cracks in specimens of WT3-1 titanium alloy tested by simultaneous bending and torsion. It is assumed that the fracture process can ...be affected by hydrogen absorbed from the atmosphere and penetrating to the tips of microcracks in the subsurface layer of the material. Higher concentrations of hydrogen observed near the crack lips located near the specimen surface as compared with the bulk of the specimen confirm the assumption that the effect of hydrogen is responsible for the brittle propagation of short fatigue cracks.
We report on a patient with a diagnosed obstructive sleep apnoea syndrome (OSAS) who became pregnant during treatment with the nCPAP (nasal continuous positive airway pressure) apparatus, and gave ...birth. In the literature search we didn't find any similar case report. The present view on OSAS treatment with particular regard to the use of nCPAP is also presented. Through reviewing literature we analysed positive effects of this kind of treatment on mother and fetus. The negative aspects of nCPAP treatment are discussed.
A retrospective analysis of 400 twin and 14 triplet pregnancies at the Department of Obstetrics and Perinatology, University School of Medicine in Lublin, from January 1, 1989 to June 30, 1999 was ...undertaken. A number increase of multiply pregnancies was observed--from 124 in the period 1989-1992 to 181 in the period 1996-1999. A percentage increase of cesarean sections was observed--from 52.42% to 77.34% respectively. The most frequent indications for the cesarean sections were non-vertex presentation of the first twin, threatened intrauterine infection and threatened intrauterine asphyxia.
Preterm birth remains a major cause of perinatal morbidity and mortality. The purpose of the study was to examine factors influencing on the survival and early prognosis of very low birth weight ...premature infants in multiple gestation born at the Department of Obstetrics and Perinatology University School of Medicine in Lublin. Congenital malformations were excluded from the study.
In this retrospective analysis the reduction in the incidence of respiratory distress syndrome in multiple gestation was observed. Survival was significantly correlated to prenatal corticoid prophylaxis, Apgar score and lack of the respiratory distress syndrome. The mortality showed an inverse correlation to birth weight and age of gestation.
A retrospective analysis of 14 triplet pregnancies at the Department of Obstetrics and Perinatology, University School of Medicine in Lublin, from January 1, 1989 to June 30, 1999 was undertaken. All ...pregnancies were ended by cesarean section. No difference in Apgar score and in average birth weight between I, II and III foetus was observed. The mean hospitalisation time for mothers was 32.5 +/- 29.01 days and the mean gestational age at delivery was 32.14 +/- 3.44 weeks. The indication for cesarean section in all cases was triplet pregnancy and additional complications: threatened intrauterine infection, threatened intrauterine asphyxia, abruptio placentae, preterm labour. Perinatal mortality rate was 12.82%.
The presence of fallout137Cs in the boreal forest and the effect of fire in redistributing137Cs were studied in the remote region of Wood Buffalo National Park, N.W.T., Canada. Results of a ...preliminary study of five burned (the fire occurred in 1981) and five unburned stands conducted in 1986 revealed that137Cs concentrations were higher in the surface soil of the burned stands than in the unburned ones. In 1989, a comprehensive study was conducted, in which one burned and one unburned white spruce stand were sampled in greater detail. The latter investigation also revealed a difference in the distribution of137Cs within the burned stand compared to the unburned one. Specifically, in the unburned stand, the highest137Cs concentration was identified in the epiphytic lichens and in the mosses, whereas in the burned stand, the highest concentration was measured in the surface organic soil. These results indicate that fire caused the mobilization of part of the137Cs bound to the above-ground matter and concentrated it in the ash layer of the burned surface soil. An additional ecologically important finding in our study was that significantly lower total137Cs load was observed in the burned stand compared to the unburned one. Hence, our data not only provide evidence that137Cs is being redistributed within the burned stand to the surface soil, but also that part of the137Cs is lost due to fire, presumably contaminating other ecosystems. Volatilization and fly-ash during the fire, and runoff (e.g. from snow melt) after the fire are the most likely mechanisms for the137Cs removal. These findings point to fire as an agent of137Cs secondary contamination for initially unaffected systems, as well as for those previously contaminated.
PDF
