Search

Sialylated N-glycan isomers with α2-3 or α2-6 linkage(s) have distinctive roles in glycoproteins, but are difficult to distinguish. Wild-type (WT) and glycoengineered (mutant) therapeutic glycoproteins, cytotoxic T lymphocyte-associated antigen-4-immunoglobulin (CTLA4-Ig), were produced in Chinese hamster ovary cell lines; however, their linkage isomers have not been reported. In this study, N-glycans of CTLA4-Igs were released, labeled with procainamide, and analyzed by liquid chromatography-tandem mass spectrometry (MS/MS) to identify and quantify sialylated N-glycan linkage isomers. The linkage isomers were distinguished by comparison of 1) intensity of the N-acetylglucosamine ion to the sialic acid ion (Ln/Nn) using different fragmentation stability in MS/MS spectra and 2) retention time-shift for a selective m/z value in the extracted ion chromatogram. Each isomer was distinctively identified, and each quantity (>0.1%) was obtained relative to the total N-glycans (100%) for all observed ionization states. Twenty sialylated N-glycan isomers with only α2-3 linkage(s) in WT were identified, and each isomer's sum of quantities was 50.4%. Furthermore, 39 sialylated N-glycan isomers (58.8%) in mono- (3 N-glycans; 0.9%), bi- (18; 48.3%), tri- (14; 8.9%), and tetra- (4; 0.7%) antennary structures of mutant were obtained, which comprised mono- (15 N-glycans; 25.4%), di- (15; 28.4%), tri- (8; 4.8%), and tetra- (1; 0.2%) sialylation, respectively, with only α2-3 (10 N-glycans; 4.8%), both α2-3 and α2-6 (14; 18.4%), and only α2-6 (15; 35.6%) linkage(s). These results are consistent with those for α2-3 neuraminidase-treated N-glycans. This study generated a novel plot of Ln/Nn versus retention time to distinguish sialylated N-glycan linkage isomers in glycoprotein.

Background: The identification of N-glycans in plant glycoproteins or plant-made pharmaceuticals is essential for understanding their structure, function, properties, immunogenicity, and allergenicity (induced by plant-specific core-fucosylation or xylosylation) in the applications of plant food, agriculture, and plant biotechnology. N-glycosidase A is widely used to release the N-glycans of plant glycoproteins because the core-fucosylated N-glycans of plant glycoproteins are hydrolyzed by N-glycosidase A but not by N-glycosidase F. However, the efficiency of N-glycosidase A activity on plant glycoproteins remains unclear. Objective: To elucidate the efficient use of N-glycosidases to identify and quantify the N-glycans of plant glycoproteins, the identification of released N-glycans by N-glycosidase F and their relative quantities with a focus on unidentified N-glycans by N-glycosidase A in plant glycoproteins, Phaseolus vulgaris lectin (PHA) and horseradish peroxidase (HRP), were investigated. Methods: Liquid chromatography–tandem mass spectrometry was used to analyze and compare the N-glycans of PHA and HRP treated with either N-glycosidase A or F under denaturing conditions. The relative quantities (%) of each N-glycan (>0.1%) to the total N-glycans (100%) were determined. Results: N-glycosidase A and F released 9 identical N-glycans of PHA, but 2 additional core-fucosylated N-glycans were released by only N-glycosidase A, as expected. By contrast, in HRP, 8 N-glycans comprising 6 core-fucosylated N-glycans, 1 xylosylated N-glycan, and 1 mannosylated N-glycan were released by N-glycosidase A. Moreover, 8 unexpected N-glycans comprising 1 core-fucosylated N-glycan, 4 xylosylated N-glycans, and 3 mannosylated N-glycans were released by N-glycosidase F. Of these, 3 xylosylated and 2 mannosylated N-glycans were released by only N-glycansodase F. Conclusion: These results demonstrated that N-glycosidase A alone is insufficient to release the N-glycans of all plant glycoproteins, suggesting that to identify and quantify the released N-glycans of the plant glycoprotein HRP, both N-glycosidase A and F treatments are required.

Purpose: Interpersonal competence, a key competence for patient-centered care by nurses, should be understood. Therefore, factors influencing the interpersonal competence of nursing students should be identified to explore and enhance their interpersonal relationships during the undergraduate educational curriculum for nursing educators. In this study factors influencing interpersonal competence, especially on self-assertiveness and empathy in nursing students were identified and analysed.Methods: A cross-sectional study design was used for the study in two Korean nursing colleges with similar baccalaureate nursing curricula. A total of 251 nursing students from freshman to senior year completed a questionnaire to measure related factors that were assumed to influence nursing students’ interpersonal competence. Data were collected from October 11~31, 2016. Study variables included self-assertiveness, empathy, interpersonal competence, and socio-demographic status. Multiple regression analysis was used for data analysis.Results: Nursing students’ interpersonal competence was explained by personality (β=.22), self-assertiveness (β=.16) and empathy (β=.38). The explanatory power of these predictors was 26.8% (p

Phospholipase D6 (PLD6) plays pivotal roles in mitochondrial dynamics and spermatogenesis, but the cellular and subcellular localization of endogenous PLD6 in testis germ cells is poorly defined. We examined the distribution and subcellular localization of PLD6 in mouse testes using validated specific anti-PLD6 antibodies. Ectopically expressed PLD6 protein was detected in the mitochondria of PLD6-transfected cells, but endogenous PLD6 expression in mouse testes was localized to the perinuclear region of pachytene spermatocytes, and more prominently, to the round (Golgi and cap phases) and elongating spermatids (acrosomal phase); these results suggest that PLD6 is localized to the Golgi apparatus. The distribution of PLD6 in the round spermatids partially overlapped with that of the cis-Golgi marker GM130, indicating that the PLD6 expression corresponded to the GM130-positive subdomains of the Golgi apparatus. Correlative light and electron microscopy revealed that PLD6 expression in developing spermatids was localized almost exclusively to several flattened cisternae, and these structures might correspond to the medial Golgi subcompartment; neither the trans-Golgi networks nor the developing acrosomal system expressed PLD6. Further, we observed that PLD6 interacted with tesmin, a testis-specific transcript necessary for successful spermatogenesis in mouse testes. To our knowledge, these results provide the first evidence of PLD6 as a Golgi-localized protein of pachytene spermatocytes and developing spermatids and suggest that its subcompartment-specific distribution within the Golgi apparatus may be related to the specific functions of this organelle during spermatogenesis.

In this study, we examined the effect of deformation twins and dislocation cell structures on the fatigue properties of the CoCrFeMnNi high-entropy alloy using rotational bending fatigue tests. The dislocation cell structures and deformation twins were generated by prestraining the CoCrFeMnNi high-entropy alloy at room temperature (27 °C) and a cryogenic temperature (− 196 °C), respectively. To eliminate the effect of different material strengths on fatigue behavior, the tensile strengths of the specimens evaluated in the fatigue tests were kept similar by controlling the prestraining under room and cryogenic temperatures. The results of the rotational bending fatigue tests revealed that the CoCrFeMnNi high-entropy alloy prestrained at room temperature exhibited higher fatigue resistance and fatigue limit than the specimen prestrained at a cryogenic temperature. A small quantity of large micro-voids was formed at the triple junction of the grain boundaries in the specimen prestrained at room temperature, whereas a large quantity of small micro-voids was formed in the region where the deformation twins intersected the grain boundaries in the specimen prestrained at a cryogenic temperature. Therefore, it is concluded that the different aspects of micro-void formation affected the crack initiation and, consequently, the fatigue properties of the room and cryogenic temperature-prestrained alloys.

N-glycans in glycoproteins can affect physicochemical properties of proteins; however, some reported N-glycan structures are inconsistent depending on the type of glycoprotein or the preparation methods.To obtain consistent results for qualitative and quantitative analyses of N-glycans, N-glycans obtained by different preparation methods were compared for two types of mammalian glycoproteins.N-glycans are released by peptide-N-glycosidase F (PF) or A (PA) from two model mammalian glycoproteins, bovine fetuin (with three glycosylation sites) and human IgG (with a single glycosylation site), and labeled with a fluorescent tag [2-aminobenzamide (AB) or procainamide (ProA)]. The structure and quantity of each N-glycan were determined using UPLC and LC-MS/MS.The 21 N-glycans in fetuin and another 21 N-glycans in IgG by either PF-ProA or PA-ProA were identified using LC-MS/MS. The N-glycans in fetuin (8-13 N-glycans were previously reported) and in IgG (19 N-glycans were previously reported), which could not be identified by using the widely used PF-AB, were all identified by using PF-ProA or PA-ProA. The quantities (%) of the N-glycans (0.1 %) relative to the total amount of N-glycans (100 %) obtained by AB- and ProA-labeling using LC-MS/MS had a similar tendency. However, the absolute quantities (pmol) of the N-glycans estimated using UPLC and LC-MS/MS were more efficiently determined with ProA-labeling than with AB-labeling. Thus, PF-ProA or PA-ProA allows for more effective identification and quantification of N-glycans than PF-AB in glycoprotein, particularly bovine fetuin. This study is the first comparative analysis for the identification and relative and absolute quantification of N-glycans in glycoproteins with PF-ProA and PA-ProA using UPLC and LC-MS/MS.

Electrodeposition is widely used in the refinery, manufacture, and coating of metals and alloys. Electrodeposition is a complicated process with many factors, such as deposition potential, current density, electrolyte composition and concentration, convection, additives, and temperature, can have significant impacts on the phase composition, morphology, and particle size of the deposited metals/alloys, thus consequentially impacting the physical and chemical properties of the deposited parts. In the past, a recipe for a particular metal/alloy electrodeposition is commonly established through trial-and-error tests, which is very time consuming. Here we report our recent efforts trying to build a quantitative and predictive model based on ex situ and in situ experimental characterizations of electrodeposition processes. To build the model, we chose copper as the model material for electrodeposition. A few electrochemical cells which have different geometries and dimensions and provide non-uniform current density distributions were designed and used. Through variation of the electrode placement and cell geometry, the current density distribution on the working electrode in the electrodeposition process can be tuned. The amount and growth rate of the deposited Cu layer in various electrochemical cells and under different deposition conditions (such as different potential, electrolyte concentration or physical location) were experimentally measured with using carefully calibrated and normalized X-ray diffraction (XRD) data. A multi-physics multi-scale model was developed to quantify the distribution of the current density and the growth rate of deposited Cu at different locations. The experimentally measured data was used to verify and improve the model. The results showed that the model can accurately predict the distribution of the current density with given nominal deposition potential or current, and thus predict the growth rate of the deposited Cu phase. The success of this model offers hopes to rationally design the deposition of metals and alloys to replace conventional trial-and-error method. The impact of different deposition substrates, additives, electrolyte concentrations will also be discussed. Proof-of-concept experiments also demonstrated that this rational design method can be applied to the design of electrodeposition of alloys, offering a much broader range of potential applications.

Sialylated and core-fucosylated N-glycans in human transferrin (HTF) are used as glycan biomarkers due to their increased or decreased characteristics in certain diseases. However, their absolute quantities remain unclear. In this study, N-glycans of HTF were identified by UPLC and LC-MS/MS using fluorescence tags [2-aminobenzamide (AB) and procainamide (ProA)] and columns [HILIC and anion exchange chromatography-HILIC (AXH)]. The structures of 14 (including five core-fucosylated) N-glycans in total comprising two non-, six mono-, four di-, and two tri-sialylated N-glycans were identified. The quantities (%) of each N-glycan relative to the total N-glycans (100%) were obtained. HILIC and AXH were better for peak identification and separability except for desialylation, respectively. Specifically, sialylated (in ProA-HILIC and ProA-AXH by UPLC or LC-MS/MS) and core-fucosylated (in AB-HILIC and ProA-AXH by UPLC) N-glycans were efficiently identified. Seven neuraminidase-treated (including three core-fucosylated) N-glycans were efficiently identified in ProA-AXH, even their poor separation. Additionally, ProA-AXH was more efficient for the estimation of the absolute quantities of N-glycans from the results of fluorescence intensity (by UPLC) and relative quantity (by LC-MS/MS). These results first demonstrate that ProA is useful for identifying and quantifying sialylated, core-fucosylated, and neuraminidase-treated desialylated N-glycans in HTF using AXH by UPLC and LC/MS.

Cytotoxic T-lymphocyte-associated protein 4-Ig (CTLA4-Ig) produced using Chinese hamster ovary (CHO) cell lines is a fusion protein of CTLA4 and the Fc region of antibody. In the present study, we identified and overexpressed genes capable of increasing sialic acid levels in CTLA4-Ig to develop cell lines using glycoengineering technology. CTLA4-Ig was produced using CHO cells overexpressing N-acetylglucosaminyltransferase (GnT) and α2,6-sialyltransferase (α2,6-ST). The conditions were wild type (WT), overexpression (GnT-IV, GnT-V, and α2,6-ST), and co-overexpression (GnT-IV and α2,6-ST, and GnT-V and α2,6-ST). GnT-IV and GnT-V were transfected into CHO cells to determine tri-antennary structure formation in CTLA4-Ig. CHO

Gastric cancer (GC) is one of the most common causes of cancer-associated death. However, traditional therapeutic strategies have failed to significantly improve the survival of patient with advanced GC. While KRAS mutations have been found in some patients with gastric cancer, an effective therapy to treat KRAS-driven gastric cancer has not been established yet. To provide a rationale for clinical application of kinase inhibitors targeting RAS pathways, we first determined the sensitivity of GC cell lines harboring KRAS mutations or amplification to RAS pathway inhibitors. We found that MAPK pathway inhibitors (MEKi and ERKi) were more effective than AKT inhibitor, suggesting that KRAS-driven gastric cancer cells are dependent on MAPK pathway for survival. Further, we established a KRAS mutant GC cell line with acquired resistance to MEK inhibitors in order to mimic clinical situation of kinase inhibitor resistance. A comprehensive analysis of tyrosine phosphorylation in receptor tyrosine kinases in combination with small molecule chemical library screening revealed upregulated c-MET phosphorylation in this resistance cell line with elevated sensitivity to c-MET TKI (crizotinib) and PI3K/mTOR dual inhibitor (BEZ235). We also showed that migration and invasion of resistant cells were promoted, and crizotinib and BEZ235 could inhibit this malignant phenotype. Overall, our results indicate that prolonged MAPK pathway inhibition could result in acquired resistance which is associated with increased malignant phenotype in KRAS mutant GC and pharmacological targeting c-MET and PI3K/mTOR could overcome this problem.

Bovine submaxillary mucin (BSM) is a natural polymer used in biomaterial applications for its viscoelasticity, lubricity, biocompatibility, and biodegradability. N-glycans are important for mucin stability and function, but their structures have not been fully characterized, unlike that of O-glycans. In this study, BSM N-glycans were investigated using liquid chromatography-tandem mass spectrometry. The microheterogeneous structures of 32 N-glycans were identified, and the quantities (%) of each N-glycan relative to total N-glycans (100%) were obtained. The terminal N-acetylgalactosamines in 12 N-glycans (sum of relative quantities, 27.9%) were modified with mono- (10 glycans) and disulfations (2 glycans). Total concentration of all sulfated N-glycans was 6.1 pmol in BSM (20 &micro, g), corresponding to 25.3% of all negatively charged glycans (sum of present N-glycans and reported O-glycans). No N-glycans with sialylated or phosphorylated forms were identified, and sulfate modification ions were the only negative charges in BSM N-glycans. Mucin structures, including sulfated N-glycans located in the hydrophobic terminal regions, were indicated. This is the first study to identify the structures and quantities of 12 sulfated N-glycans in natural mucins. These sulfations play important structural roles in hydration, viscoelasticity control, protection from bacterial sialidases, and polymer stabilization to support the functionality of BSM via electrostatic interactions.

Phospholipase D6 (PLD6) plays pivotal roles in mitochondrial dynamics and spermatogenesis, but the cellular and subcellular localization of endogenous PLD6 in testis germ cells is poorly defined. We examined the distribution and subcellular localization of PLD6 in mouse testes using validated specific anti-PLD6 antibodies. Ectopically expressed PLD6 protein was detected in the mitochondria of PLD6-transfected cells, but endogenous PLD6 expression in mouse testes was localized to the perinuclear region of pachytene spermatocytes, and more prominently, to the round (Golgi and cap phases) and elongating spermatids (acrosomal phase); these results suggest that PLD6 is localized to the Golgi apparatus. The distribution of PLD6 in the round spermatids partially overlapped with that of the cis-Golgi marker GM130, indicating that the PLD6 expression corresponded to the GM130-positive subdomains of the Golgi apparatus. Correlative light and electron microscopy revealed that PLD6 expression in developing spermatids was localized almost exclusively to several flattened cisternae, and these structures might correspond to the medial Golgi subcompartment; neither the trans-Golgi networks nor the developing acrosomal system expressed PLD6. Further, we observed that PLD6 interacted with tesmin, a testis-specific transcript necessary for successful spermatogenesis in mouse testes. To our knowledge, these results provide the first evidence of PLD6 as a Golgi-localized protein of pachytene spermatocytes and developing spermatids and suggest that its subcompartment-specific distribution within the Golgi apparatus may be related to the specific functions of this organelle during spermatogenesis.

We present a hybrid Visible-Light Communication (VLC) and Radio-Frequency (RF) communication system based on an open-source platform, which is integrated at the Medium-Access-Control (MAC) layer. Downlink data transmissions of the system use VLC with a commercially available lighting source, and uplink transmissions use RF. An auxiliary, low-power infra-red (IR) control channel is also implemented on the uplink to transmit acknowledgement signals for VLC data packets. We experimentally demonstrate that the system has low latency, and can achieve end-to-end TCP/IP throughput comparable to single antenna, 20 MHz 802.11 links when operated in isolation, and provide a 70% increase in total throughput when operating concurrently and in the same channel as a legacy 802.11 TCP/IP link. We also show that the RF signals of our system can achieve fair usage of the RF spectrum with an independent 802.11 network with UDP transmissions. In addition to addressing some practical challenges of implementing hybrid, asymmetric VLC-RF systems, our system is open-source, and requires no custom components and can serve as a reference for researchers who wish to construct and analyze hybrid VLC-RF systems.

To deploy a novel wireless sensor platform in non-urban area, great consideration must be taken on its powering system. This paper describes an autonomous power generation system in extreme weather such as winter cold, summer heat, and other natural events. The system was designed to apply to the Waggle Stack. The Waggle platform, a research project from Argonne National Laboratory is one of the most practical autonomous nodes allowing for the collection of environmental data in an urban area. Previous work on Waggle’s power system stopped at a limitation of 3.17 hours of operation when all modules were on. Our power system lasted for 8 hours which is 2.5 times as long as the previous one. This paper examines the power system to provide continuous power and remain operational 24 x 7 x 365, regardless of the environmental conditions.By measuring the system’s performance through state-of-charge checking of the battery in this project, we tested the improved structure of the power system.

This paper investigates the relationship between CEO age and firm innovation measured as innovation productivity (i.e., the number of patent applications) and innovation scope (i.e., technological proximity). Using a sample of 11,194 firm-year observations from the Korean stock markets for the sample period of 2002−2016, we document that a firm’s innovation productivity or innovation scope decreases in CEO age. We also report that younger CEOs in IT firms are more likely to participate in firm innovation than those in non-IT firms. Our main results are robust in Tobit, Poisson, and negative binomial regressions, in specification of CEO-fixed effect models, and in estimating new sample constructed by a propensity score matching. Taken together, younger CEOs in IT firms may be more motivated to signal their innovativeness to the market to be regarded as outstanding innovators or adventurous innovators, which supports managerial signaling hypothesis for young CEOs.

The effect of entropy on the strengths of the disordered and ordered phases was investigated. Cost effective AlCoxCrFeNi (x = 0, 0.25, 0.5, 0.75, and 1) high-entropy alloys were fabricated reducing Co content. The strength was considerably reduced when the Co content was zero. This was attributed to the low hardness of the A2 phase due to reduced configurational entropy compared with quinary system. On the other hand, the ordered B2 phase showed the opposite tendency. This result shows that the configurational entropy causes opposing effects on disordered and ordered phases, and the importance of considering the effect of entropy on each phase when the number of elements changed, and an alloy is composed of two or more phases, in particular, having BCC structure.

This work investigated edge-cracking behavior of equiatomic CoCrFeMnNi high-entropy alloy during hot rolling at rolling temperatures 500 ≤ TR ≤ 1000 °C. Edge cracks did not form in the material rolled at 500 °C, but widened and deepened into the inside of plate as TR increased from 500 °C. Edge cracks were most severe in the material rolled at 1000 °C. Mn–Cr–O type non-metallic inclusion and oxidation were identified as major factors that caused edge cracking. The inclusions near edge region acted as preferential sites for crack formation. Connection between inclusion cracks and surface cracks induced edge cracking. Rolling at TR ≥ 600 °C generated distinct inclusion cracks whereas they were not serious at TR = 500 °C, so noticeable edge cracks formed at TR ≥ 600 °C. At TR = 1000 °C, significant oxidation occurred at the crack surface. This accelerated edge crack penetration by embrittling the crack tip, so severe edge cracking occurred at TR = 1000 °C.

The ultrafine-grained (UFG) structure (∼100 nm) of CoCrFeMnNi high-entropy alloy was achieved using cryogenic multi-pass caliber rolling at 77 K to impose less deformation (e = 1) compared to severe plastic deformation (SPD, e > 4). Highly increased twinning activity at 77 K caused the grain interiors to fragment significantly, so UFG structure could be induced without imposing SPD. Intersected twin morphology and secondary twins played a key role in twinning-induced grain refinement to achieve UFG structure. The processed material showed an exceptional high yield strength of ∼1.5 GPa with a reasonable fracture elongation of ∼10% at room temperature.

We present a simplified constitutive model, based on the dominant deformation mechanisms, to capture the mechanical behavior of magnesium. This approach takes into account (1) the accumulation and annihilation of 〈 a 〉 and 〈 c + a 〉 dislocations, (2) the volume fraction of extension twins, and (3) two material domains — the parent region and the twinned region. We first show that the model successfully captures the material responses of single crystal magnesium under different loading conditions. We then extend the model for application to a polycrystalline magnesium alloy. The results provide a simple and straightforward approximate model for magnesium and its alloys under various loading conditions.

The intermediate strain rate tensile behaviors of a CoCrFeMnNi high-entropy alloy were investigated. Dislocation slips combined with deformation twinning dominated the initial stage of deformation. A phonon drag mechanism became evident after necking; this extended post-elongation gave rise to a ductility superior to that displayed at a static strain rate.

Commercialization of TWinning Induced Plasticity (TWIP) steels has been delayed because of deteriorated surface quality, delayed fracture, and liquid metal embrittlement in spite of their excellent tensile properties. In order to complement these drawbacks, TWIP/low-carbon (LC) steel clad sheets were fabricated by hot rolling, and their dynamic tensile properties were measured by a Hopkinson tensile bar. In all TWIP/LC clad sheets, TWIP/LC interfaces were well bonded without pores or voids by mechanical and metallurgical bonding. Thanks to well-activated dynamic Hall-Petch effect in the TWIP steel region of the clad sheets, the dynamic strength and ductility of the clad sheets were higher than quasi-static ones because the twin formation was more activated under the dynamic loading. They were also considerably higher than those calculated by a rule of mixtures because the interfacial area took most of dynamic applied tensile stress and strain. The present TWIP/LC clad sheets covered wide ranges of excellent dynamic tensile strength and ductility ( e.g ., 792–1076 MPa and 50–57%, respectively) by controlling the volume fraction of TWIP region, which can readily discover new applications for automotive structural steel sheets.

In this study, dynamic tensile tests were conducted on TWinning Induced Plasticity (TWIP) and low-carbon (LC) steel sheets at a strain rate of 1500–2000/s by using a split Hopkinson tensile bar, and deformation mechanisms related with improvement of dynamic tensile properties were investigated by a digital image correlation (DIC) technique. The dynamic tensile strength was higher than the quasi-static tensile strength in both TWIP and LC sheets, while the dynamic elongation was same to the quasi-static elongation in the TWIP sheet and was much lower than the quasi-static elongation in the LC sheet. According to the DIC results of the dynamically tensioned TWIP sheet, the homogeneous deformation occurred before the necking at the strain of 47.4%. This indicated that the dynamic deformation processes were almost similar to the quasi-static ones as the TWIP sheet was homogeneously deformed in the initial and intermediate deformation stages. This could be explained by deformation mechanisms including twinning, in consideration of favorable effect of increased twinning on tensile properties under the dynamic loading. On the other hand, the dynamically tensioned LC sheet was rapidly deformed and fractured as the necking was intensified in a narrow strain-concentrated region. The present DIC technique is an outstanding method for detailed dynamic deformation analyses, and provides an important idea for practical safety analyses of automotive steel sheets.

In this study, TWIP-cored three-layer steel sheets containing thin surface layers of low-carbon (LC) or interstitial-free (IF) steel were fabricated by solid-state hot-roll-bonding followed by cold-rolling. Interfaces were well bonded without any pores or voids, which indicated a successful fabrication of the TWIP-cored sheets. According to the tensile test results, both strength and elongation of TWIP-cored sheets increased proportionally with the volume fraction of TWIP-cored region, and were well matched with strength and elongation calculated by a rule of mixtures. However, yield point (YP) was observed in most of TWIP-cored sheets as well as mono-layer TWIP and LC sheets. After the sheets were quenched from 830 °C, the YP disappeared because the dislocation density was greatly increased by effects of thermal stresses formed during the rapid cooling. A bainitic microstructure, which was generally characterized by the continuous yielding, was formed along TWIP/LC or TWIP/IF interfaces, and also beneficially influenced to the elimination of YP. These TWIP-cored sheets covered a wide range of yield and tensile strength and ductility levels requiring in automotive steel sheets by controlling the volume fraction of TWIP-cored region, and thus present new applications to multi-functional automotive steel sheets.

As automotive steels require high impact resistance for absorbing impact energy upon vehicle body collision, detailed investigation of dynamic deformation behavior of TWinning Induced Plasticity (TWIP) steels is essentially needed. Here we show a plausible explanation of improving dynamic tensile properties by investigating deformation mechanisms using transmission electron microscopy and electron back-scatter diffraction analyses of interrupted tensile specimens. According to microstructural evolution results, slip mechanisms change from wavy slip to (planar+wavy) slip with increasing strain rate. With respect to twinning, the transition occurs from stacking faults to primary twins with increasing strain under quasi-static loading, while twinning becomes more activated under dynamic loading. Due to favorable effects of increased planar slip and twinning on tensile properties, the TWIP steel shows higher strength and similar ductility under dynamic loading. Our results demonstrate desirable applications of the TWIP steel to automotive steel sheets demanding excellent safety requirement of vehicle body.

Step-wise deformations are applied to pure copper along uniaxial direction or multiaxial directions in three conditions of speed and temperature: static and room temperature, dynamic and room temperature, or dynamic and low temperature. Through examinations of total 36 deformation stages, the influences of strain rate, temperature, and deformation direction on microstructural evolution and mechanical properties are investigated. According to the results, the deformation mechanism at extreme conditions (high strain rate and low temperature) changes from only dislocation slip to dislocation slip and deformation twinning. Although deformation-direction change has no significant effect on the final mechanical properties and total dislocation densities measured from X-ray diffraction results, the evolutions of grain-boundary misorientation and geometrically necessary dislocations (GNDs) are clearly influenced. The trend of microstructural evolution, i.e. larger grain size and lower GND densities by multi-axial deformation than the uniaxial case, is reversed when twinning occurred. Based on the results, we suggest four evolution models: uniaxial or multi axial cases with dislocation slip, or with dislocation slip and deformation twining. Even if the homogenous and almost fully twinned microstructure producing improved mechanical strength was obtained by applying the extreme deformations, poor ductility of the processed specimen were observed.