Influence of oxygenation time on crack growth in titanium alloy under cyclic bending

The paper contains the results of tests on the fatigue crack growth in Ti–6Al–4V titanium alloy. Plane specimens of 4 mm in thickness with a unilateral notch were used. An analysis of crack growth was carried out for specimens without and after 2 and 4 h oxygenation process as well as fatigue crack growth rate was determined. From the test results it appears that the fatigue crack growth in the specimens without thermo-chemical treatment differs from the fatigue crack growth in the specimens after oxygenation. It has been also found that the applied surface treatment increases fatigue life of the considered alloy.Досліджено втомний ріст тріщин у титановому сплаві Ti–6Al–4V у вихідному стані та після високотемпературного насичення киснем на плоских зразках товщиною 4 mm з одностороннім боковим надрізом за навантаження згином. Виконано фрактографічний аналіз особливостей втомного росту тріщини і визначено її швидкість для різних станів металу: у вихідному та після 2 і 4 h насичення киснем. Виявлено, що хімікотермічна обробка впливає на втомний ріст тріщини, при цьому підвищується втомна довговічність.Исследован усталостный рост трещин в титановом сплаве Ti–6Al–4V в исходном состоянии и после высокотемпературного насыщения кислородом на плоских образцах толщиной 4 mm с односторонним боковым надрезом при нагружении изгибом. Проведен фрактографический анализ особенностей усталостного роста тещин и определена её скорость для разных состояний металла: в исходном и после 2 и 4 h насыщения кислородом. Выявлено, что химико-термическая обработка влияет на усталостный рост трещин, при этом повышается усталостная долговечность

Correlation of laser velocimeter measurements over a wing with results of two prediction techniques

The flow field at the center line of an unswept wing with an aspect ratio of eight was determined using a two dimensional viscous flow prediction technique for the flow field calculation, and a three dimensional potential flow panel method to evaluate the degree of two dimensionality achieved at the wing center line. The analysis was made to provide an acceptable reference for comparison with velocity measurements obtained from a fringe type laser velocimeter optics systems operating in the backscatter mode in the Langley V/STOL tunnel. Good agreement between laser velocimeter measurements and theoretical results indicate that both methods provide a true representation of the velocity field about the wing at angles of attack of 0.6 and 4.75 deg

Laser velocimeter survey about a NACA 0012 wing at low angles of attack

An investigation was conducted in the Langley V/STOL tunnel with a laser velocimeter to obtain measurements of airflow velocities about a wing at low angles of attack. The applicability of the laser velocimeter technique for this purpose in the V/STOL tunnel was demonstrated in this investigation with measurement precision bias calculated at -1.33 percent to 0.91 percent and a random uncertainty calculated at + or - 0.47 percent. Free stream measurements were obtained with this device and compared with velocity calculations from pitot static probe data taken near the laser velocimeter measurement location. The two measurements were in agreement to within 1 percent. Velocity measurement results about the centerline at 0.6 degrees angle of attack were typically those expected. At 4.75 degrees, the velocity measurements indicated that a short laminar separation bubble existed near the leading edge with an oscillating shear layer

Extreme Learning Machine for land cover classification

This paper explores the potential of extreme learning machine based supervised classification algorithm for land cover classification. In comparison to a backpropagation neural network, which requires setting of several user-defined parameters and may produce local minima, extreme learning machine require setting of one parameter and produce a unique solution. ETM+ multispectral data set (England) was used to judge the suitability of extreme learning machine for remote sensing classifications. A back propagation neural network was used to compare its performance in term of classification accuracy and computational cost. Results suggest that the extreme learning machine perform equally well to back propagation neural network in term of classification accuracy with this data set. The computational cost using extreme learning machine is very small in comparison to back propagation neural network.Comment: 6 pages, mapindia 2008 conferenc

Lost in plasmids: next generation sequencing and the complex genome of the tick-borne pathogen Borrelia burgdorferi

Background: Borrelia (B.) burgdorferi sensu lato, including the tick-transmitted agents of human Lyme borreliosis, have particularly complex genomes, consisting of a linear main chromosome and numerous linear and circular plasmids. The number and structure of plasmids is variable even in strains within a single genospecies. Genes on these plasmids are known to play essential roles in virulence and pathogenicity as well as host and vector associations. For this reason, it is essential to explore methods for rapid and reliable characterisation of molecular level changes on plasmids. In this study we used three strains: a low passage isolate of B. burgdorferi sensu stricto strain B31(-NRZ) and two closely related strains (PAli and PAbe) that were isolated from human patients. Sequences of these strains were compared to the previously sequenced reference strain B31 (available in GenBank) to obtain proof-of-principle information on the suitability of next generation sequencing (NGS) library construction and sequencing methods on the assembly of bacterial plasmids. We tested the effectiveness of different short read assemblers on Illumina sequences, and of long read generation methods on sequence data from Pacific Bioscience single-molecule real-time (SMRT) and nanopore (Oxford Nanopore Technologies) sequencing technology. Results: Inclusion of mate pair library reads improved the assembly in some plasmids as did prior enrichment of plasmids. While cp32 plasmids remained refractory to assembly using only short reads they were effectively assembled by long read sequencing methods. The long read SMRT and nanopore sequences came, however, at the cost of indels (insertions or deletions) appearing in an unpredictable manner. Using long and short read technologies together allowed us to show that the three B. burgdorferi s.s. strains investigated here, whilst having similar plasmid structures to each other (apart from fusion of cp32 plasmids), differed significantly from the reference strain B31-GB, especially in the case of cp32 plasmids. Conclusion: Short read methods are sufficient to assemble the main chromosome and many of the plasmids in B. burgdorferi. However, a combination of short and long read sequencing methods is essential for proper assembly of all plasmids including cp32 and thus, for gaining an understanding of host- or vector adaptations. An important conclusion from our work is that the evolution of Borrelia plasmids appears to be dynamic. This has important implications for the development of useful research strategies to monitor the risk of Lyme disease occurrence and how to medically manage it

The effects of beta-blockers on dobutamine-atropine stress echocardiography: early protocol versus standard protocol

BACKGROUND: To study the effects of Beta-blockers during Dobutamine Stress Echocardiography (DSE) comparing the hemodynamic benefits of an early administration of atropine in patients taking or not Beta-blockers. METHODS: One hundred and twenty-one patients were submitted to dobutamine stress echocardiography for the investigation of myocardial ischemia. The administration of atropine was randomized into two groups: A or B (early protocol when atropine was administered at 10 and 20 mcg/kg/min of dobutamine, respectively) and C (standard protocol with atropine at 40 mcg/kg/min of dobutamine). Analysis of the effects of Beta-blockers was done regarding the behavior pattern of heart rate and blood pressure, test time, number of conclusive and inconclusive (negative sub-maximum test) results, total doses of atropine and dobutamine, and general complications. RESULTS: Beta-blocked patients who received early atropine (Group A&B) had a significantly lower double product (p = 0.008), a higher mean test time (p = 0.010) and required a higher dose of atropine (p = 0.0005) when compared to the patients in this group who were not Beta-blocked. The same findings occurred in the standard protocol (Group C), however the early administration of atropine reduced test time both in the presence and absence of this therapy (p = 0.0001). The patients with Beta-blockers in Group A&B had a lower rate of inconclusive tests (26%) compared to those in Group C (40%). Complications were similar in both groups. CONCLUSION: The chronotropic response during dobutamine stress echocardiography was significantly reduced with the use of Beta-blockers. The early administration of atropine optimized the hemodynamic response, reduced test time in patients with or without Beta-blockers and reduced the number of inconclusive tests in the early protocol

Preoperative Electrocardiograms Patient Factors Predictive of Abnormalities

Background: Age is often the sole criterion for determining the need for preoperative electrocardiograms. However, screening electrocardiograms have not been shown to add value above clinical information. This study was designed to determine whether it is possible to target electrocardiograms ordering to patients most likely to have an abnormality that would affect management and if age alone is predictive of significant electrocardiograms abnormalities. Methods: A list was developed of electrocardiograms abnormalities considered significant enough to impact management, as well as a list of patient factors believed to increase cardiovascular risk. electrocardiograms in all patients over 50 yr of age presenting for preoperative evaluation during a 2-month period were reviewed. Results: A total of 1,149 electrocardiograms were reviewed, with 89 patients (7.8%) having at least one significant abnormality. These patients were compared with a group of 195 patients who had electrocardiograms that did not contain significant abnormalities. Patients at higher risk of having a significantly abnormal electrocardiograms that would potentially affect management were those older than 65 yr of age or who had a history of heart failure, high cholesterol, angina, myocardial infarction, or severe valvular disease. Five patients (0.44%) had an abnormal electrocardiograms in the absence of risk factors. The sensitivity of the model is 87.6%. Conclusion: Age greater than 65 yr remains an independent predictor for significant preoperative electrocardiograms abnormalities. The specific clinical risk factors that were found have a high sensitivity and identified all but 0.44% of patients with electrocardiograms abnormalities that may affect preoperative management

Herbal medicine use during pregnancy in a group of Australian women

BACKGROUND: There are limited data on the extent of women's use of herbal medicines during pregnancy, despite the fact that knowledge of the potential benefits or harms of many of these products is sparse, particularly with respect to their use in pregnancy. We aimed to measure the prevalence of herbal medicine use in a group of pregnant women attending a public tertiary maternity hospital in Melbourne, Australia. Secondary aims were to explore why women took the herbal medicine, where they received advice, what form the supplements took and if they perceived the supplements to be helpful. METHODS: Consecutive pregnant women were approached in the antenatal clinic and the birth centre at around 36–38 weeks gestation. A questionnaire was developed and self-administered in English, as well as being translated into the four most common languages of women attending the hospital: Cantonese, Vietnamese, Turkish and Arabic. Back translation into English was undertaken by different professional translators to verify accuracy of both words and concepts. Data collected included demographic information, model of pregnancy care and herbal supplement use. Descriptive statistics were used initially, with stratified and regression analysis to compare sub-groups. RESULTS: Of 705 eligible women, 588 (83%) agreed to participate. Of these, 88 (15%) completed the questionnaire in a language other than English. Thirty-six percent of women took at least one herbal supplement during the current pregnancy. The most common supplements taken were raspberry leaf (14%), ginger (12%) and chamomile (11%). Women were more likely to take herbal supplements if they were older, tertiary educated, English speaking, non-smokers and primiparous. CONCLUSION: Use of herbal supplements in pregnancy is likely to be relatively high and it is important to ascertain what supplements (if any) women are taking. Pregnancy care providers should be aware of the common herbal supplements used by women, and of the evidence regarding potential benefits or harm

Does maternal exposure to an environmental stressor affect offspring response to predators?

There is growing recognition of the ways in which maternal effects can influence offspring size, physiological performance, and survival. Additionally, environmental contaminants increasingly act as stressors in maternal environments, possibly leading to maternal effects on subsequent offspring. Thus, it is important to determine whether contaminants and other stressors can contribute to maternal effects, particularly under varied ecological conditions that encompass the range under which offspring develop. We used aquatic mesocosms to determine whether maternal effects of mercury (Hg) exposure shape offspring phenotype in the American toad (Bufo americanus) in the presence or absence of larval predators (dragonfly naiads). We found significant maternal effects of Hg exposure and significant effects of predators on several offspring traits, but there was little evidence that maternal effects altered offspring interactions with predators. Offspring from Hg-exposed mothers were 18% smaller than those of reference mothers. Offspring reared with predators were 23% smaller at metamorphosis than those reared without predators. There was also evidence of reduced larval survival when larvae were reared with predators, but this was independent of maternal effects. Additionally, 5 times more larvae had spinal malformations when reared without predators, suggesting selective predation of malformed larvae by predators. Lastly, we found a significant negative correlation between offspring survival and algal density in mesocosms, indicating a role for top-down effects of predators on periphyton communities. Our results demonstrate that maternal exposure to an environmental stressor can induce phenotypic responses in offspring in a direction similar to that produced by direct exposure of offspring to predators