Деформационное упрочнение начально-изотропных металлов при деформировании по траекториям малой кривизны

На примере стали мартенситного класса исследованы закономерности деформационного упрочнения при нагружении по траекториям, имеющим вид двухзвенных ломаных, которым соответствуют траектории деформирования малой кривизны. Показано, что поверхность нагружения, разделяющая области упругого и упругопластического деформирования, смещается в направлении вектора, который соединяет центр поверхности нагружения и изображающую точку на траектории нагружения, при этом не изменяется форма ее фронтальной части. Зависимость величины смещения центра поверхности нагружения от интенсивности накопленных пластических деформаций описывается кривой, инвариантной к виду траектории нагружения.На прикладі сталі мартенситного класу досліджено закономірності деформаційного зміцнення при навантаженні по траєкторіях, що мають вигляд дволанкових ламаних, яким відповідають траєкторії деформування малої кривини. Показано, що поверхня навантаження, яка розділяє області пружного та пружнопластичного деформування, зміщується у напрямку вектора, який з ’єднує центр поверхні навантаження та відображуючу точку на траєкторії навантаження, при цьому форма фронтальної частини не змінюється. Залежність величини зміщення центра поверхні навантаження від інтенсивності накопичених пластичних деформацій описується кривою, яка є інваріантною відносно траєкторії навантаження.By the example of martensitic steel we study regularities of strain hardening under loading along two-section broken lines corresponding to slightly curved strain paths. It is shown that the loading surface separating domains of elastic and elastoplastic strains (yield surface) is displaced in the direction of a vector connecting the surface center with the loading trajectory image point, while the shape of its frontal part remains unchanged. The yield surface center displacement versus the intensity of accumulated plastic strains is described by a curve invariant to the loading trajectory

Non-AIDS defining cancers in the D:A:D Study-time trends and predictors of survival : a cohort study

BACKGROUND:Non-AIDS defining cancers (NADC) are an important cause of morbidity and mortality in HIV-positive individuals. Using data from a large international cohort of HIV-positive individuals, we described the incidence of NADC from 2004-2010, and described subsequent mortality and predictors of these.METHODS:Individuals were followed from 1st January 2004/enrolment in study, until the earliest of a new NADC, 1st February 2010, death or six months after the patient's last visit. Incidence rates were estimated for each year of follow-up, overall and stratified by gender, age and mode of HIV acquisition. Cumulative risk of mortality following NADC diagnosis was summarised using Kaplan-Meier methods, with follow-up for these analyses from the date of NADC diagnosis until the patient's death, 1st February 2010 or 6 months after the patient's last visit. Factors associated with mortality following NADC diagnosis were identified using multivariable Cox proportional hazards regression.RESULTS:Over 176,775 person-years (PY), 880 (2.1%) patients developed a new NADC (incidence: 4.98/1000PY [95% confidence interval 4.65, 5.31]). Over a third of these patients (327, 37.2%) had died by 1st February 2010. Time trends for lung cancer, anal cancer and Hodgkin's lymphoma were broadly consistent. Kaplan-Meier cumulative mortality estimates at 1, 3 and 5 years after NADC diagnosis were 28.2% [95% CI 25.1-31.2], 42.0% [38.2-45.8] and 47.3% [42.4-52.2], respectively. Significant predictors of poorer survival after diagnosis of NADC were lung cancer (compared to other cancer types), male gender, non-white ethnicity, and smoking status. Later year of diagnosis and higher CD4 count at NADC diagnosis were associated with improved survival. The incidence of NADC remained stable over the period 2004-2010 in this large observational cohort.CONCLUSIONS:The prognosis after diagnosis of NADC, in particular lung cancer and disseminated cancer, is poor but has improved somewhat over time. Modifiable risk factors, such as smoking and low CD4 counts, were associated with mortality following a diagnosis of NADC

The loss of seagrass in cockburn sound, Western Australia. III. The effect of epiphytes on productivity of Posidonia australis Hook. F.

The hypothesis was examined that increased epiphyte growth was responsible for a reduction in seagrass meadows in Cockburn Sound during the discharge of nutrient-rich effluent. One study site was in a deteriorating meadow near an effluent outfall, the other at similar depth in an unaffected meadow in more oceanic water. Seagrass production at the first site was less than that at the second, with 33% lower growth per shoot and 29% less dense meadow. Water at the former site had higher mean concentrations of chlorophyll and phosphate than the latter, but light reaching the seagrass meadows was not significantly different. Epiphyte loads (as dry weight or chlorophyll per unit leaf area) were 2–8 times higher at the former site. Seasonal changes in epiphyte loads were well correlated with periphyton biomass on glass slides or plastic seagrass. Photosynthesis of leaf segments, with and without epiphytes, was measured using an oxygen meter in the laboratory; epiphyte photosynthetic rates were similar to those of periphyton on plastic, expressed per unit chlorophyll. The percentage reduction in light by known periphyton loads was measured, and used to calculate light reduction by epiphytes in the field, which was estimated to be 63% on average at the first site and 15% at the second. Pooling data for sites and seasons, there was a negative log-linear relationship between leaf production and epiphyte load. The observations provide support for the suggestion that seagrass loss in the Sound may be attributed to enhanced epiphyte loads following nutrient enrichment