Crystallization Characteristics of CaO-Al2O3-Based Mold Flux and Their Effects on In-Mold Performance during High-Aluminum TRIP Steels Continuous Casting

Crystallization behaviors of the newly developed lime-alumina-based mold fluxes for high-aluminum transformation induced plasticity (TRIP) steels casting were experimentally studied, and compared with those of lime-silica-based mold fluxes. The effects of mold flux crystallization characteristics on heat transfer and lubrication performance in casting high-Al TRIP steels were also evaluated. The results show that the crystallization temperatures of lime-alumina-based mold fluxes are much lower than those of lime-silica-based mold fluxes. Increasing B2O3 addition suppresses the crystallization of lime-alumina-based mold fluxes, while Na2O exhibits an opposite effect. In continuous cooling of lime-alumina-based mold fluxes with high B2O3 contents and a CaO/Al2O3 ratio of 3.3, faceted cuspidine precipitates first, followed by needle-like CaO center dot B2O3 or 9CaO center dot 3B(2)O(3)center dot CaF2. In lime-alumina-based mold flux with low B2O3 content (5.4 mass pct) and a CaO/Al2O3 ratio of 1.2, the formation of fine CaF2 takes place first, followed by blocky interconnected CaO center dot 2Al(2)O(3) as the dominant crystalline phase, and rod-like 2CaO center dot B2O3 precipitates at lower temperature during continuous cooling of the mold flux. In B2O3-free mold flux, blocky interconnected 3CaO center dot Al2O3 precipitates after CaF2 and 3CaO center dot 2SiO(2) formation, and takes up almost the whole crystalline fraction. The casting trials show that the mold heat transfer rate significantly decreases near the meniscus during the continuous casting using lime-alumina-mold fluxes with higher crystallinity, which brings a great reduction of surface depressions on cast slabs. However, excessive crystallinity of mold flux causes poor lubrication between mold and solidifying steel shell, which induces various defects such as drag marks on cast slab. Among the studied mold fluxes, lime-alumina-based mold fluxes with higher B2O3 contents and a CaO/Al2O3 ratio of 3.3 show comparatively improved performance.open113133sciescopu

Evaluation of Matusita Equation and Its Modified Expression for Determining Activation Energy Associated with Melt Crystallization

Both the Matusita equation and the modified Matusita equation for estimating the activation energy associated with non-isothermal crystallization were critically evaluated. The derivation for melts crystallization on cooling indicates that, unlike for the crystallization that occurs on heating, the term 1 - exp (-Delta G/RT) in the basic rate equation of crystal growth and the term depending on the initial temperature of the cooling process cannot be neglected. It is demonstrated that both the Matusita equation and its modified expression are only valid to estimate the activation energy associated with the crystallization that occurs on heating, but are inapplicable for the melt crystallization that occurs on cooling. It is suggested that the isoconversional methods of Friedman and Vyazovkin should be alternative to determine effective activation energy for melt crystallization that occurs on cooling.open1133sciescopu

Crystallization Kinetics and Mechanism of CaO-Al2O3-Based Mold Flux for Casting High-Aluminum TRIP Steels

Non-isothermal crystallization of the newly developed lime-alumina-based mold fluxes was investigated using differential scanning calorimetry. The crystallization kinetic parameters were determined by Ozawa equation, the combined Avrami-Ozawa equation, and the differential iso-conversional method of Friedman. It was found that Ozawa method failed to describe the non-isothermal crystallization behavior of the mold fluxes. The Avrami exponent determined by the combined Avrami-Ozawa equation indicates that the crystallization of cuspidine occurs through bulk nucleation and reaction-controlled three-dimensional growth, and then transforms to reaction-controlled two-dimensional growth at the crystallization later stage in lime-alumina-based mold fluxes with higher B2O3 content. For the mold fluxes with lower B2O3 content (10.8 mass pct), the crystallization of cuspidine is bulk nucleation and reaction-controlled two-dimensional growth at the crystallization primary stage followed by a diffusion-controlled two-dimensional growth process. The crystallization of CaF2 in mold flux originates from bulk nucleation and diffusion-controlled three-dimensional growth, which then transforms to two-dimensional growth. FE-SEM observations support these kinetic analysis results. The effective activation energy for cuspidine crystallization in the mold flux with higher B2O3 and Na2O contents increases as the crystallization progresses, and then decreases at the relative degree of crystallinity greater than 60 pct. The transition point of this trend approximately corresponds to the relative degree of crystallinity at which the crystallization mode of cuspidine transforms. For the mold fluxes with lower B2O3 and Na2O contents, the effective activation energy for cuspidine formation varies monotonically with the increase in the relative degree of crystallinity.open11149sciescopu

Effect of SiO2 on the Crystallization Behaviors and In-Mold Performance of CaF2-CaO-Al2O3 Slags for Drawing-Ingot-Type Electroslag Remelting

The crystallization characteristics of CaF2-CaO-Al2O3 slags with varying amounts of SiO2 were experimentally studied. The effects of slag crystallization behaviors on the horizontal heat transfer and lubrication performance in drawing-ingot-type electroslag remelting (ESR) were also evaluated in terms of as-cast ingots surface quality and drawing-ingot operation. The results show that increasing SiO2 addition from 0 to 6.8 mass pct strongly suppresses the crystallization of ESR type CaF2-CaO-Al2O3 slags. The crystallization temperature of the studied slags decreases with the increase in SiO2 addition. The liquidus temperatures of the slags also show a decreasing trend with increasing SiO2 content. In CaF2-CaO-Al2O3-(SiO2) slags, faceted 11CaO center dot 7Al(2)O(3)center dot CaF2 crystals precipitate first during continuous cooling of the slag melts, followed by the formation of CaF2 at lower temperatures. 11CaO center dot 7Al(2)O(3)center dot CaF2 was confirmed to be the dominant crystalline phase in the studied slags. CaF2-CaO-Al2O3 slags with a small amount of SiO2 addition are favorable for providing sound lubrication and horizontal heat transfer in mold for drawing-ingot-type ESR, which consequently bring the improvement in the surface quality of ESR ingot and drawing-ingot operating practice as demonstrated by plant trials.open11108sciescopu

Kinetics of Isothermal Melt Crystallization in CaO-SiO2-CaF2-Based Mold Fluxes

A kinetic study for isothermal melt crystallization of CaO-SiO2-CaF2-based mold fluxes with different basicity of 0.94 and 1.34 has been carried out systematically by DSC measurements. The kinetic parameters were determined by Johnson-Mehl-Avrami equation. The average Avrami exponent of cuspidine (3CaO center dot 2SiO(2)center dot CaF2) crystallization for mold flux of lower basicity (0.94) is calculated to be 3.1, implying that the crystallization mode is instantaneous nucleation followed by 3-dimensional growth. For the mold flux of higher basicity (1.34), the average Avrami exponent of cuspidine equals to 3.4, strongly suggesting that the growth is still 3 dimensional but the nucleation should be continuous. It was found that the effective crystallization rate constant for both mold fluxes increases as the crystallization temperature decreases, showing that the crystallization rate could be governed by nucleation rate. The negative effective activation energy indicates an anti-Arrhenius behavior for crystallization of the mold fluxes studied. Therefore, it is concluded that the melt crystallization for the commercial mold fluxes will be determined by thermodynamics of nucleation which is relevant to degree of undercooling. The morphology of cuspidine crystals observed by SEM agreeds well with the isothermal crystallization kinetics results.open1173sciescopu

Comparison of primary care experiences among adults in general outpatient clinics and private general practice clinics in Hong Kong

Abstract. Background. The main goal of Hong Kong's publicly-funded general outpatient clinics (GOPCs) is to provide primary medical services for the financially vulnerable. The objective of the current study was to compare the primary care experiences of GOPC users and the users of care provided by private general practitioners (GPs) in Hong Kong via a territory-wide telephone survey. Methods. One thousand adults in Hong Kong aged 18 and above were interviewed by a telephone survey. The modified Chinese translated Primary Care Assessment Tool was used to collect data on respondents' primary care experience. Results. Our results indicated that services provided by GOPC were more often used by female, older, poorer, chronically-ill and less educated population. GOPC participants were also more likely to have visited a specialist or used specialist services (69.7% vs. 52.0%; p < 0.001), although this difference in utilization of specialist services disappeared after adjusting for age (55.7% vs. 52.0%, p = 0.198). Analyses were also performed to asses the relationship between healthcare settings (GOPCs versus private GPs) and primary care quality. Private GP patients achieved higher overall PCAT scores largely due to better accessibility (Mean: 6.88 vs. 8.41, p < 0.001) and person-focused care (Mean: 8.37 vs. 11.69, p < 0.001). Conclusions. Our results showed that patients primarily receiving care from private GPs in Hong Kong reported better primary care experiences than those primarily receiving care from GOPCs. This was largely due to the greater accessibility and better interpersonal relationships offered by the private GPs. As most patients use both GOPCs and private GPs, their overall primary care experiences may not be as different as the findings of this study imply. © 2010 Wong et al; licensee BioMed Central Ltd.link_to_subscribed_fulltex

A role for core planar polarity proteins in cell contact-mediated orientation of planar cell division across the mammalian embryonic skin

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. © The Author(s) 2017. Supplementary information accompanies this paper at doi:10.1038/s41598-017-01971-2.The question of how cell division orientation is determined is fundamentally important for understanding tissue and organ shape in both healthy or disease conditions. Here we provide evidence for cell contact-dependent orientation of planar cell division in the mammalian embryonic skin. We propose a model where the core planar polarity proteins Celsr1 and Frizzled-6 (Fz6) communicate the long axis orientation of interphase basal cells to neighbouring basal mitoses so that they align their horizontal division plane along the same axis. The underlying mechanism requires a direct, cell surface, planar polarised cue, which we posit depends upon variant post-translational forms of Celsr1 protein coupled to Fz6. Our hypothesis has parallels with contact-mediated division orientation in early C. elegans embryos suggesting functional conservation between the adhesion-GPCRs Celsr1 and Latrophilin-1. We propose that linking planar cell division plane with interphase neighbour long axis geometry reinforces axial bias in skin spreading around the mouse embryo body.Peer reviewe

Effects of Thyroxine Exposure on Osteogenesis in Mouse Calvarial Pre-Osteoblasts

The incidence of craniosynostosis is one in every 1,800-2500 births. The gene-environment model proposes that if a genetic predisposition is coupled with environmental exposures, the effects can be multiplicative resulting in severely abnormal phenotypes. At present, very little is known about the role of gene-environment interactions in modulating craniosynostosis phenotypes, but prior evidence suggests a role for endocrine factors. Here we provide a report of the effects of thyroid hormone exposure on murine calvaria cells. Murine derived calvaria cells were exposed to critical doses of pharmaceutical thyroxine and analyzed after 3 and 7 days of treatment. Endpoint assays were designed to determine the effects of the hormone exposure on markers of osteogenesis and included, proliferation assay, quantitative ALP activity assay, targeted qPCR for mRNA expression of Runx2, Alp, Ocn, and Twist1, genechip array for 28,853 targets, and targeted osteogenic microarray with qPCR confirmations. Exposure to thyroxine stimulated the cells to express ALP in a dose dependent manner. There were no patterns of difference observed for proliferation. Targeted RNA expression data confirmed expression increases for Alp and Ocn at 7 days in culture. The genechip array suggests substantive expression differences for 46 gene targets and the targeted osteogenesis microarray indicated 23 targets with substantive differences. 11 gene targets were chosen for qPCR confirmation because of their known association with bone or craniosynostosis (Col2a1, Dmp1, Fgf1, 2, Igf1, Mmp9, Phex, Tnf, Htra1, Por, and Dcn). We confirmed substantive increases in mRNA for Phex, FGF1, 2, Tnf, Dmp1, Htra1, Por, Igf1 and Mmp9, and substantive decreases for Dcn. It appears thyroid hormone may exert its effects through increasing osteogenesis. Targets isolated suggest a possible interaction for those gene products associated with calvarial suture growth and homeostasis as well as craniosynostosis. © 2013 Cray et al

Parametric pattern selection in a reaction-diffusion model

We compare spot patterns generated by Turing mechanisms with those generated by replication cascades, in a model one-dimensional reaction-diffusion system. We determine the stability region of spot solutions in parameter space as a function of a natural control parameter (feed-rate) where degenerate patterns with different numbers of spots coexist for a fixed feed-rate. While it is possible to generate identical patterns via both mechanisms, we show that replication cascades lead to a wider choice of pattern profiles that can be selected through a tuning of the feed-rate, exploiting hysteresis and directionality effects of the different pattern pathways

Adaptive Immunity against Leishmania Nucleoside Hydrolase Maps Its C-Terminal Domain as the Target of the CD4+ T Cell–Driven Protective Response

Nucleoside hydrolases (NHs) show homology among parasite protozoa, fungi and bacteria. They are vital protagonists in the establishment of early infection and, therefore, are excellent candidates for the pathogen recognition by adaptive immune responses. Immune protection against NHs would prevent disease at the early infection of several pathogens. We have identified the domain of the NH of L. donovani (NH36) responsible for its immunogenicity and protective efficacy against murine visceral leishmaniasis (VL). Using recombinant generated peptides covering the whole NH36 sequence and saponin we demonstrate that protection against L. chagasi is related to its C-terminal domain (amino-acids 199–314) and is mediated mainly by a CD4+ T cell driven response with a lower contribution of CD8+ T cells. Immunization with this peptide exceeds in 36.73±12.33% the protective response induced by the cognate NH36 protein. Increases in IgM, IgG2a, IgG1 and IgG2b antibodies, CD4+ T cell proportions, IFN-γ secretion, ratios of IFN-γ/IL-10 producing CD4+ and CD8+ T cells and percents of antibody binding inhibition by synthetic predicted epitopes were detected in F3 vaccinated mice. The increases in DTH and in ratios of TNFα/IL-10 CD4+ producing cells were however the strong correlates of protection which was confirmed by in vivo depletion with monoclonal antibodies, algorithm predicted CD4 and CD8 epitopes and a pronounced decrease in parasite load (90.5–88.23%; p = 0.011) that was long-lasting. No decrease in parasite load was detected after vaccination with the N-domain of NH36, in spite of the induction of IFN-γ/IL-10 expression by CD4+ T cells after challenge. Both peptides reduced the size of footpad lesions, but only the C-domain reduced the parasite load of mice challenged with L. amazonensis. The identification of the target of the immune response to NH36 represents a basis for the rationale development of a bivalent vaccine against leishmaniasis and for multivalent vaccines against NHs-dependent pathogens