A critical assessment of high-temperature dynamic mechanical testing of metals

Determination of the mechanical properties of materials under the combined effects of high-temperatures and high strain-rates has been an important and challenging issue. A strategy has been proposed and evaluated recently towards this purpose in which a heating cell with accurate temperature control is synchronized with the split Hopkinson pressure bar (SHPB) system. This strategy allows pre-heating the specimen to desired temperatures before arrival of the stress wave and provides an experimental technique for the measurement of dynamic mechanical properties of materials at high-temperatures. Since its advent, this method has gained increasing interest in the community of dynamic mechanical testing owing to its ease of manipulation. However, a couple of critical problems should be addressed to validate the experimental results. Among the problems, a crucial one is associated with the temperature change in the heated specimen upon its contact with the relatively cold bars. In this paper, experiments were designed to determine the influence of cold-contact-time (CCT) on the temperature variation within the specimen. The experiments were conducted on Ti700 alloy at strain-rates of ∼10⁴ s⁻¹ and at temperatures from 20 to 800 °C. The results show that the CCT does have a strong effect on the experimental results. Based on the experimental results and our analyses, we believe that the data can faithfully reflect the material behavior if CCT is shorter than 50 ms. While in most systems without the heating cell being synchronized with the SHPB system, the typical CCT is about 500 ms, and therefore the experimental data cannot be taken as representing the material behavior.     

Calculating correlated color temperatures across the entire gamut of daylight and skylight chromaticities

Natural outdoor illumination daily undergoes large changes in its correlated color temperature (CCT), yet existing equations for calculating CCT from chromaticity coordinates span only part of this range. To improve both the gamut and accuracy of these CCT calculations, we use chromaticities calculated from our measurements of nearly 7000 daylight and skylight spectra to test an equation that accurately maps CIE 1931 chromaticities x and y into CCT. We extend the work of McCamy [Color Res. Appl. 12, 285-287 (1992)] by using a chromaticity epicenter for CCT and the inverse slope of the line that connects it to x and y. With two epicenters for different CCT ranges, our simple equation is accurate across wide chromaticity and CCT ranges (3000-10(6) K) spanned by daylight and skylight.     

Considerations in development of CCT diagrams for complex ferritic materials

A recent literature review of available data for the bainitic creep strength enhanced ferritic steel grade 23 revealed significant variations among available continuous cooling transformation (CCT) diagrams. Substantial differences in these diagrams were noted with respect to the observed transformation products, reported transformation temperatures and the data provided with the CCT diagram. While it is recognised that grade 23 is a complex material exhibiting up to three transformations on-cooling from austenitisation, there does not seem to be a standardised or uniform procedure for the development of CCT diagrams for such metallurgically diverse materials. This paper details development of a CCT diagram for this material through integration of results from thermal analysis, hardness measurements and microstructural observations.     

Scaling laws for folding native protein structures

We propose a nucleation hypothesis for protein folding. Based on this hypothesis, we have designed a new nearest-neighbor method for the prediction of protein secondary structures, in which the reliability of each prediction is estimated based on sequence conservation and clustering in the databases of known structures. We have found that predictions with higher reliability scores were indeed correlated with a higher predictive accuracy. We also found that by selecting the top 20% of residues based on reliability scores as nucleation residues, a clear pattern emerged where hydrophobic amino acids were largely buried and hydrophilic amino acids were more exposed. This was consistent with the widely accepted HP-model for protein folding. These results were true for several databases, such as PDBSELECT (<25% sequence homology), SCOP-ASTRAL (<25% sequence homology), and SCOP-ASTRAL unique fold classes, with 1300, 3956, and 762 proteins, respectively. Therefore, it is conceivable that the nucleation residues function not only as initiation sites for folding, but also as the core residues playing a primary role in determining the protein (thermodynamic) stability. The occurrence of these two functions on one set of amino acid residues in a protein is perhaps from the result of biological evolution. Finally, we have found power law behaviors in our results, whose scaling properties were modeled using polymer physics and critical phenomena. It is concluded that proteins behave like a real chain. A new physical picture for protein folding derived from our nucleation hypothesis has been described, in which there are two continuous phase transitions corresponding to the two stages of protein folding: one is nucleation and the other collapse. By determining the critical exponents of these two-phase transitions, it has been found that the nucleation process has a spatial dimension of d=3 while the collapse process of d=2.     

Application of neural networks for the prediction of continuous cooling transformation diagrams

In the paper the method of forecasting of Continuous Cooling Transformation (CCT) diagrams for steels by the use of neural networks has been presented. Input data are chemical composition and austenitising temperature. Results of calculation of neural networks consist of temperature of the beginning and the end of transformation in the function of cooling rate, the participation of the structural components and the hardness of steel cooled from austenitising temperature with a fixed rate. Presented quantities enable to draw the CCT diagram. The model presented in the paper enables the analysis of the influence of the chemical composition and austenitising temperature on CCT diagrams. In order to work out the methods, the set of experimental data worked out on the basis of information available in the literature consisting of 400 CCT diagrams made for constructional and machinable steels were used.     

A novel bioactive three-dimensional β-tricalcium phosphate/chitosan scaffold for periodontal tissue engineering

The development of suitable bioactive three-dimensional scaffold for the promotion of cellular proliferation and differentiation is critical in periodontal tissue engineering. In this study,porous β-tricalcium phosphate/chitosan composite scaffolds were prepared through a freeze-drying method. These scaffolds were evaluated by analysis of microscopic structure, porosity, and cytocompatibility. The gene expression of bone sialoprotein (BSP) and cementum attachment protein (CAP) was detected with RT-PCR after human periodontal ligament cells (HPLCs) were seeded in these scaffolds. Then cell–scaffold complexes were implanted subcutaneously into athymic mice. The protein expression of alkaline phosphatase (ALP) and osteopontin (OPN) was detected in vivo. Results indicated that composite scaffolds displayed a homogeneous three-dimensional microstructure; suitable pore size (120 μm) and high porosity (91.07%). The composite scaffold showed higher proliferation rate than the pure chitosan scaffold, and up-regulated the gene expression of BSP and CAP. In vivo, HPLCs in the composite scaffold not only proliferated but also recruited vascular tissue ingrowth. The protein expression of ALP and OPN was up-regulated in the composite scaffold. Therefore, it was suggested that the composite scaffold could promote the differentiation of HPLCs towards osteoblast and cementoblast phenotypes.     

THE FRACTURE BEHAVIOUR OF A CENTRE CRACKED TENSILE SPECIMEN

Abstract— This paper reviews the stress intensity factor, limit load, compliance and J-integral functions for a centre cracked tensile (CCT) specimen available in the literature. Compliance and J-integral functions are derived from the optimum stress intensity factor and limit load solutions. The functions are compared with the results obtained from two-dimensional finite element analyses of the specimen.
The finite element results have confirmed the accuracy of the compliance and limit load functions available in the literature and suggest that the unloading compliance technique, based on crack mouth opening displacement, could be developed for a CCT specimen. Non-linear finite element analyses have shown that J can be estimated from the measured load versus load-point displacement behaviour providing a/W ≥ 0.5     

Numerical sensitivity analysis of welding-induced residual stress depending on variations in continuous cooling transformation behavior

The usage of continuous cooling transformation (CCT) diagrams in numerical welding simulations is state of the art. Nevertheless, specifications provide limits in chemical composition of materials which result in different CCT behavior and CCT diagrams, respectively. Therefore, it is necessary to analyze the influence of variations in CCT diagrams on the developing residual stresses. In the present paper, four CCT diagrams and their effect on numerical calculation of residual stresses are investigated for the widely used structural steel S355J2+N welded by the gas metal arc welding (GMAW) process. Rather than performing an arbitrary adjustment of CCT behavior, four justifiable data sets were used as input to the numerical calculation: data available in the Sysweld database, experimental data acquired through Gleeble dilatometry tests, and TTT/CCT predictions calculated from the JMatPro and Edison Welding Institute (EWI) Virtual Joining Portal software. The performed numerical analyses resulted in noticeable deviations in residual stresses considering the different CCT diagrams. Furthermore, possibilities to improve the prediction of distortions and residual stress based on CCT behavior are discussed.     

Development of free-energy-based models for chaperonin containing TCP-1 mediated folding of actin

A free-energy-based approach is used to describe the mechanism through which chaperonin-containing TCP-1 (CCT) folds the filament-forming cytoskeletal protein actin, which is one of its primary substrates. The experimental observations on the actin folding and unfolding pathways are collated and then re-examined from this perspective, allowing us to determine the position of the CCT intervention on the actin free-energy folding landscape. The essential role for CCT in actin folding is to provide a free-energy contribution from its ATP cycle, which drives actin to fold from a stable, trapped intermediate I₃, to a less stable but now productive folding intermediate I₂. We develop two hypothetical mechanisms for actin folding founded upon concepts established for the bacterial type I chaperonin GroEL and extend them to the much more complex CCT system of eukaryotes. A new model is presented in which CCT facilitates free-energy transfer through direct coupling of the nucleotide hydrolysis cycle to the phases of actin substrate maturation.     

A comparative study of two advanced spraying techniques for the deposition of biologically active enzyme coatings onto bone-substituting implants

Surface modification of implant materials with biomolecule coatings is of high importance to improve implant fixation in bone tissue. In the current study, we present two techniques for the deposition of biologically active enzyme coatings onto implant materials. The well-established thin film ElectroSpray Deposition (ESD) technique was compared with the SAW-ED technique that combines high-frequency Surface Acoustic Wave atomization with Electrostatic Deposition. By immobilizing the enzyme alkaline phosphatase (ALP) onto implant surfaces, the influence of both SAW-ED and ESD deposition parameters on ALP deposition efficiency and ALP biological activity was investigated. ALP coatings with preserved enzyme activity were deposited by means of both the SAW-ED and ESD technique. The advantages of SAW-ED over ESD include the possibility to spray highly conductive protein solutions, and the 60-times faster deposition rate. Furthermore, significantly higher deposition efficiencies were observed for the SAW-ED technique compared to ESD. Generally, it was shown that protein inactivation is highly dependent on both droplet dehydration and the applied electrical field strength. The current study shows that SAW-ED is a versatile and flexible technique for the fabrication of functionally active biomolecule coatings.     

Critical cooling rate for the glass formation of ferromagnetic Fe40Ni40P14B6 alloy

Bulk ferromagnetic amorphous Fe-Ni-P-B alloys in rod shape were formed by a rapid solidification technique. The largest amorphous specimen prepared had a diameter of ∼ 2.5 mm and the corresponding cooling rate for the glass formation of this alloy system in our experiment can be estimated to be around 492.4 K/s by the method of finite-difference numerical calculation. This value is on the same order of magnitude as the critical cooling rate R_c of Fe₄₀Ni₄₀P₁₄B₆ alloy estimated by the method of constructing the continuous-cooling-transformation (CCT) curve. It is indicated that the heterophase impurities have been eliminated well in our experiment.     

Gene expressions of Collagen type I,ALP and BMP-4 in osteo-inductive BCP implants show similar pattern to that of natural healing bones

Osteo-inductive materials give rise to ectopic bone formation in vivo either in muscles or in subcutaneous tissue. However, the underlying molecular mechanism is totally unclear. To investigate the expression pattern of bone related genes in osteo-inductive materials, we performed quantitative PCR (qPCR) to detect the expressions of type I collagen, alkaline phosphatase (ALP) and bone morphogenetic protein 4 (BMP-4) in biphasic calcium phosphate (BCP) ceramics implanted in dorsal muscle of dogs. Bone formation in mandibular alveolus defects served as controls showing the expression patterns of these genes in natural healing bones. Histological examinations were performed to show the bone formation in osteo-inductive BCP implants. Data of qPCR indicated that all tested genes had a similar expression pattern with two peaks during the bone formation either in BCP implants or natural healing bones. Type I collagen and ALP were expressed at lower levels with delayed peak in BCP implant than that in natural healing bone. Higher BMP-4 expression level was detected in BCP ceramic implant than in natural healing bone at all the time points. These results demonstrated that expression patterns of bone-related genes in the inductive bone formation are similar to that of natural healing bone formation. As these three genes are important parameters for osteoblast activity in bone formation, our data provide clue to uncover the molecular mechanism of bone formation in osteo-inductive materials.     

Influence of ZrO2 particles on the optical properties of pc-LEDs

Experimental and modeling progress and results aiming to increase the color uniformity of hemisphere-type pcW-LEDs are proposed. By adding micrometric zirconia particles, the light scattering is enhanced, that induces a decrease of phosphor necessary to obtain a specific CCT. The optical model is able to determine the optical properties (CCT, angular CCT distribution, chromaticity and packaging efficiency) in a hemisphere LED for various amount of YAG-phosphor and ZrO₂-zirconia particles. Based on previous process, the work is in the first step to fit the effective radius and refractive index that will be implemented in the optical model. In the second step, the optical model is compared with the experimental measurement to determine the absorption coefficient and conversion efficiency of a package of silicone resin containing phosphor and zirconia. Finally, the model, confirmed by selected experimental results, allows determining the optical properties of any king of package that lead to a CCT emission ranging from 4500 K to 6500 K. The analysis of these data is interpreted by comparing, for a specific CCT, the phosphor loss, the packaging efficiency and the angular distribution of CCT. The results show that if the effort is targeted on one of the previous parameters, there is always a counterpart on the other ones. Increasing the color uniformity will induce to decrease the packaging efficiency.     

Satellite and satellite subsystems reliability: Statistical data analysis and modeling

Reliability has long been recognized as a critical attribute for space systems. Unfortunately, limited on-orbit failure data and statistical analyses of satellite reliability exist in the literature. To fill this gap, we recently conducted a nonparametric analysis of satellite reliability for 1584 Earth-orbiting satellites launched between January 1990 and October 2008. In this paper, we extend our statistical analysis of satellite reliability and investigate satellite subsystems reliability. Because our dataset is censored, we make extensive use of the Kaplan–Meier estimator for calculating the reliability functions. We derive confidence intervals for the nonparametric reliability results for each subsystem and conduct parametric fits with Weibull distributions using the maximum likelihood estimation (MLE) approach. We finally conduct a comparative analysis of subsystems failure, identifying the “culprit subsystems” that drive satellite unreliability. The results here presented should prove particularly useful to the space industry for example in redesigning subsystem test and screening programs, or providing an empirical basis for redundancy allocation.     

The inducible expression of the long pentraxin PTX3 in osteoblast-like MC 3T3-E1 cells by E. coli lipopolysaccharide

In this study, we have found that Escherichia coli lipopolysaccharide (LPS) could induce the expression of pentraxin 3 (PTX3) mRNA in osteoblast-like cells (MC 3T3-E1) dose dependently. The relation between this expression and alkaline phosphatase (ALP), mitogen-activated protein kinases (MAPKs), and nuclear factor kappa B (NF-κB) was also analyzed. The results show that the mRNA expression of PTX3 was related to that of ALP. It was also related to the mRNA expression of ERK-1 and p38 but not JNK-1 and NF-κB. These results suggest that ERK-1 and p38 are involved in the regulation of PTX3 expression and PTX3 promotes the differentiation of MC 3T3-E1 cells in response to LPS.     

SIFs of CCT plate repaired with single‐sided composite patch

Constant amplitude load fatigue tests are performed to obtain crack propagation data for LF2‐aluminium centre crack tension (CCT) plates un‐repaired and repaired with single‐sided composite patches. Then, the James–Anderson method, an experimental method, is used to obtain the stress intensity factor (SIF) formula for the repaired CCT plates with carbon–fibre composite patches. At last, crack propagation life prediction and finite element (FE) calculation are carried out to validate the experimental SIF formula. It is shown that the present SIF formula can exactly predict the fatigue‐crack propagation life of the patched CCT plates and is close to the FE results, which implies the effectivity of the experimental SIF formula in the present paper.     

薄板坯连铸连轧生产65Mn钢的CCT曲线和淬透性

利用Formaster热膨胀仪和金相法,测定了薄板坯连铸连轧工艺(CSP)生产的高碳高强度65Mn钢的CCT曲线,测得临界点为AC1=719℃,AC3=747℃,Ms=267℃,临界冷却速率为35℃/s。使用扫描电镜和硬度仪分析表明,薄板坯连铸连轧工艺生产的65Mn钢的淬火组织细小均匀,硬度高,比传统工艺生产的65Mn钢的淬透性好。     

Exploring the role of the sharing economy in disasters management

Improvements in information and communications technologies (ICTs) have facilitated the inclusion of the sharing economy (SE) in societies more than ever. In the aftermath of recent disasters, the SE played significant roles to help the affected people and support official responders. However, the literature has not effectively explored these roles, and thus, no framework can support the systematic inclusion of the SE in disasters management. This paper aims to address the gap through a two-stage exploratory research approach. First, we conduct a systematic literature review to identify the extent to which the SE is taken into consideration in disasters. After that, we investigate the role of three Iranian SE-based companies that were involved in the 2019 Iran floods response. We collect empirical data by conducting semi-structured interviews and reviewing official reports.Our findings indicate that very few studies discuss the different roles of the SE in disasters, although SE companies have often provided effective solutions to address critical post-disaster logistics challenges. Four research propositions are presented to describe emerging roles for SE companies. The contribution of our study is twofold. First, our research identifies the different roles that the SE could play in disasters and therefore, brings a new perspective to the literature. Second, the study suggests opportunities for collaboration and partnership models from the point of origin to delivery that can support coordination and logistics in disasters.     

The geography of university scientific production in Europe: an exploration in the field of Food Science and Technology

This paper contributes to the literature on the factors explaining the regional university production of science and its quality in the field of Food Science and Technology (FS&T). We hypothesized that the regional quantity of science generated by universities is shaped not only by the amount of research and development (R&D) funds, as the main mainstream literature suggests, but also by the demand for science at the regional level. Furthermore, given the evolutionary nature of knowledge production, we suggest that the number of publications has a significant effect on the quality of scientific research at the regional level. Drawing on a sample of 48,207 scientific papers in FS&T over the period 1998–2010, we first map and examine the regional distribution of science and its quality across Europe-15. Second, we address our hypotheses by specifying several econometric models to identify the factors affecting the quantity and quality of scientific production. Our results show that the regional demand for FS&T—captured by the regional employment in the food and beverage industry—matters for the generation of science. Additionally, our findings support the hypothesis of a positive and significant effect of the production of papers on the scientific quality at the regional level.     

Anaphylactoid reaction during hemodiafiltration on AN69 membrane in a patient with atypical hemolytic uremic syndrome: A pediatric case report

Reactions associated with hemodiafiltration can be life threatening if not recognized early in the course of dialysis. AN69 (acrylonitrile and sodium methallyl sulfonate copolymer) membrane-associated reactions during hemodialysis have been documented in adult patients receiving angiotensin converting enzyme inhibitors, which are thought to be triggered by the negative charge of the AN69 membrane. Here, we present a 5-month-old girl requiring continuous renal replacement therapy (CRRT) for acute kidney injury secondary to atypical hemolytic uremic syndrome who experienced acute cyanosis, angioedema, tachycardia, and impaired circulation during CRRT. After switching to a different type of hemofiltration membrane, her clinical findings improved and she was able to tolerate hemodialysis. We concluded that she had experienced an anaphylactoid reaction to the AN69 membrane. To our knowledge, this case is the first pediatric case report of AN69 membrane-associated anaphylactoid reaction.