Nano-mechanical properties of Fe-Mn-Al-C lightweight steels

High Al Low-density steels could have a transformative effect on the light-weighting of steel structures for transportation and achieving the desired properties with the minimum amount of Ni is of great interest from an economic perspective. In this study, the mechanical properties of two duplex low-density steels, Fe-15Mn-10Al-0.8C-5Ni and Fe-15Mn-10Al-0.8C (wt.%) were investigated through nano-indentation and simulation through utilization of ab initio formalisms in Density Functional Theory (DFT) in order to establish the hardness resulting from two critical structural features (ߢ-carbides and B2 intermetallic) as a function of annealing temperature (500 − 1050 ℃) and the addition of Ni. In the Ni-free sample, the calculated elastic properties of kappa-carbides were compared with those of the B2 intermetallic Fe3Al − L12, and the role of Mn in the kappa structure and its elastic properties were studied. The Ni-containing samples were found to have a higher hardness due to the B2 phase composition being NiAl rather than FeAl, with Ni-Al bonds reported to be stronger than the Fe-Al bonds. In both samples, at temperatures of 900 ℃ and above, the ferrite phase contained nano-sized discs of B2 phase, wherein the Ni-containing samples exhibited higher hardness, attributed again to the stronger Ni-Al bonds in the B2 phase. At 700 ℃ and below, the nano-sized B2 discs were replaced by micrometre sized needles of kappa in the Ni-free sample resulting in a lowering of the hardness. In the Ni-containing sample, the entire alpha phase was replaced by B2 stringers, which had a lower hardness than the Ni-Al nano-discs due to a lower Ni content in B2 stringer bands formed at 700 ℃ and below. In addition, the hardness of needle-like kappa-carbides formed in alpha phase was found to be a function of Mn content. Although it was impossible to measure the hardness of cuboid kappa particles in gamma phase because of their nano-size, the hardness value of composite phases, e.g. gamma + kappa was measured and reported. All the hardness values were compared and rationalized by bonding energy between different atoms

Information resource preferences by general pediatricians in office settings: a qualitative study

BACKGROUND: Information needs and resource preferences of office-based general pediatricians have not been well characterized. METHODS: Data collected from a sample of twenty office-based urban/suburban general pediatricians consisted of: (a) a demographic survey about participants' practice and computer use, (b) semi-structured interviews on their use of different types of information resources and (c) semi-structured interviews on perceptions of information needs and resource preferences in response to clinical vignettes representing cases in Genetics and Infectious Diseases. Content analysis of interviews provided participants' perceived use of resources and their perceived questions and preferred resources in response to vignettes. RESULTS: Participants' average time in practice was 15.4 years (2–28 years). All had in-office online access. Participants identified specialist/generalist colleagues, general/specialty pediatric texts, drug formularies, federal government/professional organization Websites and medical portals (when available) as preferred information sources. They did not identify decision-making texts, evidence-based reviews, journal abstracts, medical librarians or consumer health information for routine office use. In response to clinical vignettes in Genetics and Infectious Diseases, participants identified Question Types about patient-specific (diagnosis, history and findings) and general medical (diagnostic, therapeutic and referral guidelines) information. They identified specialists and specialty textbooks, history and physical examination, colleagues and general pediatric textbooks, and federal and professional organizational Websites as information sources. Participants with access to portals identified them as information resources in lieu of texts. For Genetics vignettes, participants identified questions about prenatal history, disease etiology and treatment guidelines. For Genetics vignettes, they identified patient history, specialists, general pediatric texts, Web search engines and colleagues as information sources. For Infectious Diseases (ID) vignettes, participants identified questions about patients' clinical status at presentation and questions about disease classification, diagnosis/therapy/referral guidelines and sources of patient education. For ID vignettes, they identified history, laboratory results, colleagues, specialists and personal experience as information sources. CONCLUSION: Content analysis of office-based general pediatricians' responses to clinical vignettes provided a qualitative description of their perceptions of information needs and preferences for information resource for cases in Genetics and Infectious Diseases. This approach may provide complementary information for discovering practitioner's information needs and resource preferences in different contexts

AXR1-ECR1 and AXL1-ECR1 heterodimeric RUB-activating enzymes diverge in function in Arabidopsis thaliana

RELATED TO UBIQUITIN (RUB) modification of CULLIN (CUL) subunits of the CUL-RING ubiquitin E3 ligase (CRL) superfamily regulates CRL ubiquitylation activity. RUB modification requires E1 and E2 enzymes that are analogous to, but distinct from, those activities required for UBIQUITIN (UBQ) attachment. Gene duplications are widespread in angiosperms, and in line with this observation, components of the RUB conjugation pathway are found in multiples in Arabidopsis. To further examine the extent of redundancy within the RUB pathway, we undertook biochemical and genetic characterizations of one such duplication event- the duplication of the genes encoding a subunit of the RUB E1 into AUXIN RESISTANT1 (AXR1) and AXR1-LIKE1 (AXL1). In vitro, the two proteins have similar abilities to function with E1 C-TERMINAL-RELATED1 (ECR1) in catalyzing RUB1 activation and RUB1-ECR1 thioester formation. Using mass spectrometry, endogenous AXR1 and AXL1 proteins were found in complex with 3HA-RUB1, suggesting that AXR1 and AXL1 exist in parallel RUB E1 complexes in Arabidopsis. In contrast, AXR1 and AXL1 differ in ability to correct phenotypic defects in axr1-30, a severe loss-of-function AXR1 mutant, when the respective coding sequences are expressed from the same promoter, suggesting differential in vivo functions. These results suggest that while both proteins function in the RUB pathway and are biochemically similar in RUB-ECR1 thioester formation, they are not functionally equivalent

Improving mechanical properties of alginate hydrogel by reinforcement with ethanol treated polycaprolactone nanofibers

Hydrogels offer interesting possibilities in various biomedical applications, including tissue regeneration, drug delivery, and cell therapy, due to excellent biocompatibility and good nutrient and oxygen transportation abilities. However, most of these applications require improvements in mechanical properties and functionalization. In this study, a novel technique for fabricating 3D nanofiber-reinforced hydrogel composites is described as a means of enhancing the strength and durability of hydrogels. The method is based on the layer-by-layer electrospinning of nanofibers on an evenly spread, thin hydrogel solution. A coaxial nozzle was introduced for electrospinning highly wettable ethanol-treated nanofibers. This process enhanced the compatibility between the nanofiber reinforcements and the hydrogel matrix. The compressive strength and stiffness of the resulting nanofiber-reinforced hydrogel composites were enhanced to similar to 221% and similar to 434% compared to the pure hydrogel, respectively. Moreover, the equilibrium modulus was increased by a factor of nearly 1.73 when the volume fraction of nanofibers was 0.085. It was demonstrated that a 3D nanofiber-reinforced hydrogel composite could be fabricated without the cumbersome stacking of hydrogel-coated fiber meshes. Furthermore, the mechanical properties of the reinforced composites can be modulated by adjusting the volume fraction of nanofibers. (c) 2012 Elsevier Ltd. All rights reserved.X112318sciescopu

Temperature-dependent nanomorphology-performance relations in binary iridium complex blend films for organic light emitting diodes

Understanding the mechanism responsible for the temperature-dependent performances of emitting layers is essential for developing advanced phosphorescent organic light emitting diodes. We described the morphological evolution occurring in PVK:Ir(ppy)(3) binary blend films, with respect to thermal annealing up to 300 degrees C, by coupling atomic force microscopy and transmission electron microscopy. In particular, in situ temperature-dependent experimental characterization was performed to directly determine the overall sequence of morphological evolution occurring in the films. The device thermally annealed at 200 degrees C exhibits a noticeable enhancement in the performances, compared to the devices in the as-processed state and to the devices annealed at 300 degrees C. Our approaches reveal that the Ir(ppy)(3) molecules, with a needle-like structure in the as-processed state, were aggregated, and thus diffused into PVK without a morphological change at the temperature regime between 150 degrees C and 200 degrees C. Moreover, both network-like and droplet patterns existed in the devices annealed at 300 degrees C, which was beyond the glass temperature of PVK, leading to a profound increase in the surface roughness. The observed pattern formation is discussed in terms of viscoelastic phase separation. Based on our experimental findings, we propose that the performances of the devices are significantly controlled by the diffusion of dopant molecules and the morphological evolution of the host materials in binary blend systems.1122sciescopu

Short-term evaluation of electromagnetic field pretreatment of adipose-derived stem cells to improve bone healing

An electromagnetic field is an effective stimulation tool because it promotes bone defect healing, albeit in an unknown way. Although electromagnetic fields are used for treatment after surgery, many patients prefer cell-based tissue regeneration procedures that do not require daily treatments. This study addressed the effects of an electromagnetic field on adipose-derived stem cells (ASCs) to investigate the feasibility of pretreatment to accelerate bone regeneration. After identifying a uniform electromagnetic field inside a solenoid coil, we observed that a 45Hz electromagnetic field induced osteogenic marker expression via bone morphogenetic protein, transforming growth factor , and Wnt signalling pathways based on microarray analyses. This electromagnetic field increased osteogenic gene expression, alkaline phosphate activity and nodule formation in vitro within 2weeks, indicating that this pretreatment may provide osteogenic potential to ASCs on three-dimensional (3D) ceramic scaffolds. This pretreatment effect of an electromagnetic field resulted in significantly better bone regeneration in a mouse calvarial defect model over 4weeks compared to that in the untreated group. This short-term evaluation showed that the electromagnetic field pretreatment may be a future therapeutic option for bone defect treatment. Copyright (c) 2012 John Wiley & Sons, Ltd.1142sciescopu