Atomic mechanism of near threshold fatigue crack growth in vacuum as a basis for understanding environmental effects

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Characteristics of buried paleo-channels in the Western South Yellow Sea during the Late Last Glaciation

Istraživanja o evoluciji paleolitskih korita u obalnim područjima važna su za konstrukcije podmorskog inženjerstva i za otkrivanje promjena u globalnom paleolitskom okruženju. Stoga je za istraživanje značajki paleo-korita tijekom kasnog posljednjeg ledenog doba u zapadnom Južnom Žutom moru primijenjena digitalna metoda analize terena i ArcGis funkcija porijekla rijeke, analizirani su plitki stratigrafski seizmički profili visoke rezolucije i osnovni podaci, a rabljene su empirijske formule rijeke za određivanje riječnih svojstava i struktura. Rezultati pokazuju da je drevni riječni sustav tijekom kasnog posljednjeg ledenog doba grebena Južnog Žutog mora podijeljen na paleo-Žutu (Huanghe) i paleo-Yangtze (Changjiang) rijeku. Paleo-korita blizu 33°N pripadaju paleo-Yangtze rijeci i uglavnom teku od istoka do sjeveroistoka. Paleo-korita oko 35°N i 123,5°E dio su paleo-Žute rijeke. U usporedbi s paleo-Žutom rijekom, paleo-Yangtze rijeka inklinira horizontalnom premiještanju, ima veću prodornu moć i veću količinu vode. Na temelju metode širine nagiba sustav paleo-Žute rijeke može se smatrati uglavnom krivudavim dok je sustav paleo-Yangtze rijeke uglavnom sustav račvaste (braided) rijeke. Pronađene su značajne razlike između paleo-Yangtze rijeke i paleo-Žute rijeke. Značajke podzemnih paleo-korita tijekom kasnog posljednjeg ledenog doba mogu biti korisne u predviđanju popratne moguće opasnosti kod podvodnih konstrukcija i otkrivanju promjena paleookruženja u grebenu Južnog Žutog mora.Studies on the evolution of paleo-channels in coastal areas are important for submarine engineering construction and to reveal changes in the global paleoenvironment. Thus, to explore the characteristics of paleo-channels during the late Last Glaciation in the western South Yellow Sea, digital terrain analysis method and ArcGis river extraction function were employed, high-resolution shallow stratigraphic seismic profiles and core data were analysed, and river empirical formulas were used to determine river properties and river patterns. Results indicate that the ancient river system during the late Last Glaciation of the South Yellow Sea shelf is divided into paleo-Yellow (Huanghe) and paleo-Yangtze (Changjiang) Rivers. The paleo-channels near 33°N belong to the paleo-Yangtze River, and generally flow from east to northeast. The paleo-channels around 35°N and 123,5°E are part of the paleo-Yellow River. Compared with the paleo-Yellow River, the paleo-Yangtze River is prone to horizontal migration and has higher penetration depths and discharge. Based on the slope-width method, the paleo-Yellow River system can be considered mainly as a meandering river, whereas the paleo-Yangtze River system is largely a braided river. Remarkable differences are found between the paleo-Yangtze River and the paleo-Yellow River. The characteristics of buried paleo-channels during the late Last Glaciation can be useful in predicting the incident potential hazard of submarine engineering and in revealing the paleoenvironment changes in the South Yellow Sea shelf

Clinical application of a fully automated blood collection robot and its assessment of blood collection quality of anticoagulant specimens

Background and objectivesTo investigate the application of intelligent puncture blood collection robots in anticoagulated blood specimens, the satisfaction of subjects with the two blood collection methods, and the feasibility of intelligent blood collection devices to replace manual blood collection methods in clinical work.Materials and methodsA total of 154 volunteers from Zhongshan Hospital Fudan University were recruited to compare the test results of anticoagulant blood samples between blood collection robot and manual blood collection, a questionnaire was used to inquire about the volunteers’ feelings about the two blood collection methods; the blood collection data of 6,255 patients willing to use the robot for blood collection were collected to analyze the success rate of blood collection.ResultsThe blood collection robot is superior to manual specimen collection in terms of volume and pain of specimen collection, and the puncture success rate is 94.3%. The anticoagulated blood specimens collected by the robot had 11 indexes statistically different from the results of manual blood collection, but the differences did not affect the clinical diagnosis and prognosis.ConclusionThe intelligent robotic blood collection is less painful and has better acceptance by patients, which can be used for clinical anticoagulated blood specimen collection

Effects of a Flaxseed-Derived Lignan Supplement in Type 2 Diabetic Patients: A Randomized, Double-Blind, Cross-Over Trial

Flaxseed consumption has been shown to improve blood lipids in humans and flaxseed-derived lignan has been shown to enhance glycemic control in animals. The study aimed to investigate the effect of a flaxseed-derived lignan supplement on glycemic control, lipid profiles and insulin sensitivity in type 2 diabetic patients.This was a randomized, double-blind, placebo-controlled, cross-over trial and it was conducted between April and December 2006 in Shanghai, China. Seventy-three type 2 diabetic patients with mild hypercholesterolemia were enrolled into the study. Patients were randomized to supplementation with flaxseed-derived lignan capsules (360 mg lignan per day) or placebo for 12 weeks, separated by an 8-week wash-out period. HbA1c, lipid profiles, insulin resistance index and inflammatory factors were measured. Sixty-eight completed the study and were included in the analyses. The lignan supplement significantly improved glycemic control as measured by HbA(1c) (-0.10+/-0.65 % vs. 0.09+/-0.52 %, P = 0.001) compared to placebo; however, no significant changes were observed in fasting glucose and insulin concentrations, insulin resistance and blood lipid profiles. Urinary excretion of lignan metabolites (enterodiol and enterolactone) was significantly higher after the lignan supplement intervention compared to baseline (14.2+/-18.1 vs. 1.2+/-2.4 microg/mL, P<0.001). Data also suggested minimal competition between lignan and isoflavones for bioavailability when measured by the excretion concentrations.Daily lignan supplementation resulted in modest, yet statistically significant improvements in glycemic control in type 2 diabetic patients without apparently affecting fasting glucose, lipid profiles and insulin sensitivity. Further studies are needed to validate these findings and explore the efficacy of lignans on type 2 diabetes.ClinicalTrials.gov NCT00363233

The Association of Depressive Symptoms with Inflammatory Factors and Adipokines in Middle-Aged and Older Chinese

Studies in Western populations find that depression is associated with inflammation and obesity. The present study aimed to evaluate the relation of depressive symptoms with inflammatory factors and adipose-derived adipokines in middle-aged and older Chinese.Data were from 3289 community residents aged 50-70 from Beijing and Shanghai who participated in the Nutrition and Health of Aging Population in China project. Depressive symptoms were defined as a Center for Epidemiological Studies of Depression Scale (CES-D) score of 16 or higher. Plasma concentrations of C-reactive protein (CRP), interleukin-6 (IL-6), adiponectin, resistin, plasminogen activator inhibitor-1 (PAI-1) and retinol binding protein 4 (RBP4) were measured. Of the 3289 participants, 312 (9.5%) suffered from current depressive symptoms. IL-6 level was higher in participants with depressive symptoms compared to their counterparts in the crude analyses (1.17 vs. 1.05 pg/mL, p = 0.023) and this association lost statistical significance after multiple adjustments (1.13 vs. 1.10 pg/mL, p = 0.520). Depressive symptoms were not associated with increased mean levels of any other inflammatory factors or adipokines in the unadjusted or adjusted analyses.We found no evidence that depressive symptoms were associated with inflammatory factors and adipokines in the middle-aged and older Chinese populations. Prospective studies and studies in clinically diagnosed patients are needed to confirm our results and clarify the relation of depression with inflammatory factors and adipokines

Atomistic modeling of crack tip behavior in ductile materials

125 pagesThis dissertation is composed of three papers and related unpublished work that laid the foundation for the succeeding scientific discoveries. The first two papers detail work intended to illuminate the atomic-scale mechanisms governing the near threshold fatigue crack growth phenomenon. First, by harnessing a concurrent multiscale approach and contemporary computational resources, fatigue crack simulations with cycle counts well beyond those analyzed previously have been performed. The validity of long-hypothesized material separation mechanisms thought to control near threshold fatigue crack growth in vacuum is assessed. Results show that fatigue crack growth arrests after an initial transient period, reconciling reports of crack growth in atomistic simulations at loading amplitudes below experimental crack growth thresholds. It is also observed that sustained crack growth in vacuum only occurs when emitted dislocations return to the crack tip on a slip plane behind its original one, which is resulted from slip trace intersection in the 2D simulated system and is expected to occur in 3D crystals by other additional mechanisms. Second, building upon the concurrent atomistic-continuum multiscale modeling framework, the isolated effect of material dissolution on crack growth is investigated. A series of dissolution simulations are carried out with different loading conditions and dissolution rates. Simulation results and subsequent quantitative analysis suggest that while dissolution is capable of freeing arrested fatigue cracks, the crack tip is always blunted under both static and cyclic loading, implying that dissolution has an overall crack arresting effect, and the dissolution-induced-blunting is found to be independent of the mechanical loading magnitude. Finally, from a standpoint of how state-of-the-art engineering and technology can be applied to other applications in an attempt to directly better the human condition, the third paper details a field work about the assessment of additive manufacturing for increasing sustainability and productivity of smallholder agriculture. This study analyzes and compares different manufacturing approaches from the perspectives of structural performance and cost efficiency and seeks to provide solutions to the mechanical obstacles encountered by smallholder farmers in the field. The acquired data suggests that the material extrusion 3D printing technology is able to provide functional parts more rapidly, accelerating the design cycle, and lowering cost relative to local fabrication routes, while traditional means is proved to be more economical in the case where mechanical performance of the part is the most critical

Scaling up photoautotrophic production of eicosapentaenoic acid (EPA) using microalgae

Food insecurity is one of the major challenges that the world faces today. Improving food security is about not only ending hunger but also ensuring easy, affordable access to nutritious, healthy food for all people. The importance of adequate consumption of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is well recognized. EPA and DHA are essential omega-3 fatty acids that must obtained from the diet. Producing sufficient amounts of EPA and DHA to meet the global demand from their conventional sources – fish – is becoming increasingly challenging due to population growth and overfishing. To bridge the supply gap of EPA and DHA via sustainable means, the idea of sourcing these nutrients directly from their natural primary producers – microalgae – has emerged. The overarching aim of this thesis was to develop a scalable bioprocess that used photoautotrophic microalgae to produce EPA. Such a strategy would offer the advantages of not requiring arable land or potable water, thus would avoid competition with existing food production techniques for these resources. Currently, commercial production of microalgal EPA is hindered by the process economics. One of the major hurdles is the difficulties of growing EPA-producing microalgae efficiently at large scales, hence the development of scalable, cost-effective production processes is needed. In this research, three broad avenues were taken: (1) identification of suitable strains, (2) optimization of the process operation and (3) optimization of the bioreactor design. Microorganisms used for industrial applications need to have certain characteristics. A key metric is high product accumulation under realistic settings, others include robust growth and consistent performance in industrial systems as well as tolerance to changes in the growth conditions. Systematic evaluations using these industrial metrics have not been done for screening EPA-producing microalgae. To address this gap, a screening procedure was conducted to quantify the EPA productivity for a range of microalgae in both 300 mL flask and 5 L flat-panel photobioreactor cultures. It was found that results from the flask screening offered poor predictions of performance in photobioreactors, suggesting a need for improved screening tools, such as scale-down simulators, for selecting industrial microalgal species. In the photobioreactor cultures Phaeodactylum tricornutum displayed the highest EPA productivity, which was approximately an order of magnitude higher than those of the other species tested. The results demonstrated the potential of P. tricornutum for large scale production of EPA. To further evaluate the suitability of P. tricornutum for scaled-up production, the effects of two key environmental factors, temperature and salinity, on the EPA production of P. tricornutum were examined in photobioreactors. It was found that P. tricornutum could tolerate relatively wide ranges of temperature (13-27 °C) and salinity (35-50 g L-1); within these ranges its EPA content was approximately constant at 5% of the dry biomass weight. These results illustrate the robustness of P. tricornutum which is an obvious advantage from the perspective of industrial production. A comprehensive nutritional analysis was also performed for the biomass of P. tricornutum. In addition to being a good source of EPA, P. tricornutum biomass was also rich in protein (45% of dry weight), iron and vitamin B12. The nutritional information here could serve as a starting point for the formulation of P. tricornutum into food products. With P. tricornutum being identified as a suitable species, improving the EPA productivity was the next step in the process development. The use of reliable computational models could greatly facilitate the identification of optimal operating strategies, with fewer laborious, time-consuming experiments required. This research demonstrated the development of a model for the EPA production of P. tricornutum, which was the first to predict the biomass and EPA productivities along with the EPA concentrations in the biomass and fatty acid fraction for microalgae. The model was built on a kinetic modelling framework where the system behaviour was simulated using a set of ordinary differential equations, with the integrated effect of light and nitrogen availability being accounted for. This mathematically simple model was able to produce satisfactory predictions for different reactor geometries and scales (5 L flat-panel and 50 L cylindrical reactors), light path lengths (5 cm and 19 cm) as well as operating modes (batch and repeated-batch), with the model-data mismatches being typically less than 20%. Using this model, an optimized repeated-batch strategy was developed. Implementation of this strategy over four repeated cycles led to 50% and 20% increases in the biomass and EPA productivities, respectively. The results demonstrated the usefulness of this model as a tool in the scale-up, design and optimization of microalgal EPA production. Another avenue for improving process productivity is developing better reactor designs. A major challenge in improving the performance of photoautotrophic cultures is delivering light into high-cell-density cultures. Using Computational Fluid Dynamics (CFD) with Lagrangian particle tracking, this work examined means of improving the frequency at which the microalgal cells were transported between the light and dark zones, something that was recognized as a way for improving light delivery but has not been sufficiently evaluated under industrially relevant conditions. Different superficial gas velocities (0.6-6.0 cm s-1), reactor diameters (0.14-0.29 m), internal structure designs (split-cylinder airlift, segmental baffles, disc-and-doughnut baffles) and sparger configurations (asymmetrical and oscillatory spargers) were investigated for their effect on the hydrodynamics in 50 L bubble column photobioreactors. It was found that the frequency increased linearly with the superficial gas velocities but did not vary appreciably with the reactor diameter within the tested range. The frequency could be increased by 160% and 50% by the installation of segmental baffles and disc-and-doughnut baffles, respectively; In comparison, using the alternative sparger configurations had smaller effect (within ±30%) on the frequency. The work also developed a modelling approach that predicted the biomass accumulation of P. tricornutum using the simulation results from Lagrangian particle tracking. To the best of the author’s knowledge, this was the first method that could predict the effect of different reactor designs and operating conditions (e.g. superficial gas velocity on algal biomass growth). The model simulation results, together with the reactor hydrodynamics simulated by CFD, could be used to guide the design of more light-efficient photobioreactors. In summary, this thesis presented research in three directions of the development and optimization of a scalable process for producing EPA using photoautotrophic microalgae. Substantial, novel experimental data about the EPA productivity under industrially relevant conditions was generated for a range of species. For the first time a modelling approach was developed which provided accurate predictions of the biomass, EPA and total fatty acid concentrations. This model was found to work for a range of reactor designs, scales and operating conditions, and the approach developed here could be readily applied to other microalgal processes. Finally, the kinetic model was coupled with the results from CFD simulations to develop a novel modelling tool that can be used for the in-silico design of improved photobioreactor designs. Taken together the results from this work are a substantial step towards addressing the challenges in scaling-up microalgal EPA production. Successful scale-up of microalgae EPA production is key in ensuring people have a sustainable, affordable source of EPA