3D optical coherence tomography as new tool for microscopic investigations of nucleate boiling on heated surfaces

Boiling phenomena are an important aspect in security and efficiency for technical applications with high heat flux like nuclear reactors. This study presents optical coherence tomography (OCT) as a novel modality for three-dimensional and two-dimensional time resolved imaging of nucleate boiling on heated surfaces on a microscopic scale with high spatial (<10 μm) and temporal (>25 frames per second) resolution. Within this study, a borosilicate glass plate coated with an optically transparent and electrically conductive indium tin oxide (ITO) layer with a thickness of approximately 100 nm was used as heating surface. The combination of these two properties allows optical inspection of the nucleate boiling from the backside by OCT focused on the formation, growth and detachment of single bubbles. We demonstrated for the first time that OCT is an excellent tool to acquire two-dimensional and three-dimensional images of the base of vapor bubbles from the backside of the heated surface. The acquired images allow for instance the temporally resolved measurement of the bubble diameter, diameter of the bubble base and the contact angle. Exploiting the phase information of the acquired OCT signal stacks allows imaging the movement of the bubble surrounding fluid. We think that OCT will provide many new insights into the boiling phenomena at the bubble base. The recent enhancement of the acquisition rates of OCT systems will facilitate four-dimensional imaging of single bubble evaporation procedures in the nearer future.     

Effects of modality change on health-related quality of life

Patients with end‐stage renal disease (ESRD) requiring renal replacement have impaired health‐related quality of life (HRQoL), and there is general consensus that HRQoL improves with successful transplant and evidence of improvement with frequent hemodialysis. This study reports changes in HRQoL associated with changes in treatment modality to daily hemodialysis (DHD) and transplant among patients requiring renal replacement. This cohort study had assessments at baseline and 6‐month following modality change. Subjects were nondiabetic individuals receiving conventional hemodialysis who (a) remained on conventional hemodialysis (n = 13), (b) changed to daily hemodialysis (DHD) (n = 10), or (c) received a living donor transplant (n = 20). Thirty‐four healthy controls were assessed once for comparison. HRQoL was measured using the Kidney Disease Quality of Life Instrument. The Physical Functioning and Physical Composite Scale scores were primary outcomes. Transplantation resulted in significant improvements in six of eight generic scales and the physical composite scale (PCS). Those changing to DHD had significant improvements in Physical Function and PCS scales. Those remaining on dialysis remained lower than controls on all scales except for Vitality; the transplant group remained lower than controls only on the Vitality and General Health scales. Transplant resulted in significant improvements in four of the seven disease‐specific scales (symptoms, effects, and burden of kidney disease, work). DHD resulted in improvements in the effects of kidney disease. Modality change to transplant results in significant improvement in HRQoL, achieving levels similar to controls. Change to daily hemodialysis improves only select HRQoL domains and remains low in disease‐specific domains.     

Prospective reciprocal relations between physical activity and depression in female adolescents.

Objective: Although an inverse correlation between physical activity and depression among adolescents has been found in research, this relation has seldom been examined prospectively. Thus, we tested whether physical activity reduces risk for future escalations in depression and whether depression decreases likelihood of future change in physical activity. Method: Data from a longitudinal study involving annual assessments of 496 adolescent girls (mean age = 13 years, SD = 0.73) followed over a 6-year period were analyzed to address these questions. Results: Using analyses that controlled for several covariates, we found that physical activity significantly reduced risk for future increases in depressive symptoms and risk for onset of major–minor depression. Further, depressive symptoms and major–minor depression significantly reduced future physical activity. However, predictive effects were modest for both. Conclusions: Results support a bidirectional relation between exercise and depression and imply that interventions that increase physical activity may reduce risk for depression among this high-risk population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feasibility study of plasma sprayed Al2O3 coatings as diffusion barrier on CFC components

Carbon fibre reinforced carbon (CFC) materials are increasingly applied as sample carriers in modern furnaces. Only their tendency to react with different metals at high temperatures by C-diffusion is a disadvantage, which can be solved by application of diffusion barriers. Within this study the feasibility of plasma sprayed Al₂O₃ coatings as diffusion barrier was studied. Al₂O₃ coatings were prepared by air plasma spraying (APS). The coatings were investigated in terms of their microstructure, bonding to CFC substrates and thermal stability. The results showed that Al₂O₃ could be well deposited onto CFC substrates. The coatings had a good bonding and thermal shock behavior at 1060°C. At higher temperature of 1270°C, crack network formed within the coating, showing that the plasma sprayed Al₂O₃ coatings are limited regarding to their application temperatures as diffusion barrier on CFC components.     

Influence of Strain Rate,Temperature, Plastic Strain,and Microstructure on the Strain Rate Sensitivity of Automotive Sheet Steels

This work identifies the influence of strain rate, temperature, plastic strain, and microstructure on the strain rate sensitivity of automotive sheet steel grades in crash conditions. The strain rate sensitivity m has been determined by means of dynamic tensile tests in the strain rate range 10^?3–200 s^?1 and in the temperature range 233–373 K. The dynamic flow curves have been tested by means of servohydraulic tensile testing. The strain rate sensitivity decreases with increasing plastic strain due to a gradual exhausting of work hardening potential combined with adiabatic softening effects. The strain rate sensitivity is improved with decreasing temperature and increasing strain rate, according to the thermally activated deformation mechanism. The m‐value is reduced with increasing strength level, this decrease being most pronounced for steels with a yield strength below 400 MPa. Solid solution alloying with manganese, silicon, and especially phosphorous elements lowers the strain rate sensitivity significantly. Second phase hardening with bainite and martensite as the second constituent in a ferritic matrix reduces the strain rate sensitivity of automotive sheet steels. A statistical modeling is proposed to correlate the m‐value with the corresponding quasistatic tensile flow stress.     

Particle In-Flight and Coating Properties of Fe-Based Feedstock Materials Sprayed with Modern Thermal Spray Systems

New developments in the field of thermal spraying systems (increased particle velocities, enhanced process stability) are leading to improved coatings. Innovations in the field of feedstock materials are supporting this trend. The combination of both has led to a renaissance of Fe-based feedstocks. Using modern APS or HVOF systems, it is now possible to compete with classical materials for wear and corrosion applications like Ni-basis or metal-matrix composites. This study intends to give an analysis of the in-flight particle and spray jet properties achievable with two different modern thermal spraying systems using Fe-based powders. The velocity fields are measured with the Laser Doppler Anemometry. Resulting coatings are analyzed and a correlation with the particle in-flight properties is given. The experiments are accompanied by computational fluid dynamics simulations of spray jet and particle velocities, leading to a comprehensive analysis of the achievable particle properties with state-of-the-art HVOF and APS systems.     

Failure probability prediction based on condition monitoring data of wind energy systems for spare parts supply

The feasibility of maintenance processes relies on the availability of spare parts. Spare part inventory planning is capital intensive. It is based on demand forecasting, which possesses a high potential in reducing inventories. Even if condition monitoring systems are installed in technical systems, condition monitoring information is barely used to predict the failure probability of units. Therefore, an enhanced forecast model, which integrates SCADA information, has been developed. This leads to more accurate spare part demand forecasts. The approach presented in the paper is based on data mining, the proportional hazards model (PHM) and a binomial distribution. It has been validated with maintenance data of wind energy systems.     

Two‐photon laser scanning microscopy as a useful tool for imaging and evaluating macrophage‐, IL‐4 activated macrophage‐ and osteoclast‐based In Vitro degradation of beta‐tricalcium phosphate bone substitute material

Two‐photon microscopy is an innovative technology that has high potential to combine the examination of soft and hard tissues in vitro and in vivo. Calcium phosphates are widely used substitutes for bone tissue engineering, since they are degradable and consequently replaced by newly formed tissue. It is well known that osteoclasts are responsible for the resorption processes during bone remodelling. We hypothesize that also macrophages are actively involved in the resorption process of calcium phosphate scaffolds and addressed this question in in vitro culture systems by two‐photon laser scanning microscopy. Beta‐tricalcium phosphate specimens were incubated with (1) macrophages, (2) interleukin‐4 activated macrophages, and (3) osteoclasts for up to 21 days. Interestingly, macrophages degraded beta‐tricalcium phosphate specimens in an equivalent fashion compared to osteoclasts and significantly more than IL‐4 activated macrophages. An average of ～32% of the macrophages was partially filled with ceramic material while this was 18% for osteoclasts and 9% for IL‐4 activated macrophages. For the first time by applying two‐photon microscopy, our studies show the previously unrecognized potential of macrophages to phagocytose ceramic material, which is expected to have implication on osteoconductive scaffold design. Microsc. Res. Tech. 77:143–152, 2014. © 2013 Wiley Periodicals, Inc.